diff --git a/internal/protocoltest/awsrestjson/api_client.go b/internal/protocoltest/awsrestjson/api_client.go
index 9c9d18af79b..d80d7568eb4 100644
--- a/internal/protocoltest/awsrestjson/api_client.go
+++ b/internal/protocoltest/awsrestjson/api_client.go
@@ -5,7 +5,9 @@ package awsrestjson
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	awshttp "github.com/aws/aws-sdk-go-v2/aws/transport/http"
@@ -16,6 +18,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 )
 
@@ -39,6 +42,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPClient(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -63,6 +68,10 @@ type Options struct {
 	// Configures the events that will be sent to the configured logger.
 	ClientLogMode aws.ClientLogMode
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -83,9 +92,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -113,6 +135,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -165,11 +193,13 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -179,10 +209,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -210,6 +274,21 @@ func addClientUserAgent(stack *middleware.Stack) error {
 	return awsmiddleware.AddSDKAgentKeyValue(awsmiddleware.APIMetadata, "restjsonprotocol", goModuleVersion)(stack)
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/internal/protocoltest/ec2query/api_client.go b/internal/protocoltest/ec2query/api_client.go
index d844b5d9eb6..e237016c5ed 100644
--- a/internal/protocoltest/ec2query/api_client.go
+++ b/internal/protocoltest/ec2query/api_client.go
@@ -5,7 +5,9 @@ package ec2query
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	awshttp "github.com/aws/aws-sdk-go-v2/aws/transport/http"
@@ -16,6 +18,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 )
 
@@ -39,6 +42,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPClient(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -63,6 +68,10 @@ type Options struct {
 	// Configures the events that will be sent to the configured logger.
 	ClientLogMode aws.ClientLogMode
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -83,9 +92,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -113,6 +135,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -165,11 +193,13 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -179,10 +209,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -210,6 +274,21 @@ func addClientUserAgent(stack *middleware.Stack) error {
 	return awsmiddleware.AddSDKAgentKeyValue(awsmiddleware.APIMetadata, "ec2protocol", goModuleVersion)(stack)
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/internal/protocoltest/jsonrpc/api_client.go b/internal/protocoltest/jsonrpc/api_client.go
index 106fb0677b1..04223ab212f 100644
--- a/internal/protocoltest/jsonrpc/api_client.go
+++ b/internal/protocoltest/jsonrpc/api_client.go
@@ -4,7 +4,9 @@ package jsonrpc
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/internal/protocoltest/jsonrpc10/api_client.go b/internal/protocoltest/jsonrpc10/api_client.go
index 5179f18aa1c..286d3049d8c 100644
--- a/internal/protocoltest/jsonrpc10/api_client.go
+++ b/internal/protocoltest/jsonrpc10/api_client.go
@@ -4,7 +4,9 @@ package jsonrpc10
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	awshttp "github.com/aws/aws-sdk-go-v2/aws/transport/http"
@@ -14,6 +16,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 )
 
@@ -37,6 +40,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPClient(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -59,6 +64,10 @@ type Options struct {
 	// Configures the events that will be sent to the configured logger.
 	ClientLogMode aws.ClientLogMode
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -75,9 +84,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -105,6 +127,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -157,11 +185,13 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -171,10 +201,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -202,6 +266,21 @@ func addClientUserAgent(stack *middleware.Stack) error {
 	return awsmiddleware.AddSDKAgentKeyValue(awsmiddleware.APIMetadata, "jsonrpc10", goModuleVersion)(stack)
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/internal/protocoltest/query/api_client.go b/internal/protocoltest/query/api_client.go
index c31a406a709..2bcf4193b8a 100644
--- a/internal/protocoltest/query/api_client.go
+++ b/internal/protocoltest/query/api_client.go
@@ -5,7 +5,9 @@ package query
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	awshttp "github.com/aws/aws-sdk-go-v2/aws/transport/http"
@@ -16,6 +18,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 )
 
@@ -39,6 +42,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPClient(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -63,6 +68,10 @@ type Options struct {
 	// Configures the events that will be sent to the configured logger.
 	ClientLogMode aws.ClientLogMode
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -83,9 +92,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -113,6 +135,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -165,11 +193,13 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -179,10 +209,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -210,6 +274,21 @@ func addClientUserAgent(stack *middleware.Stack) error {
 	return awsmiddleware.AddSDKAgentKeyValue(awsmiddleware.APIMetadata, "queryprotocol", goModuleVersion)(stack)
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/internal/protocoltest/restxml/api_client.go b/internal/protocoltest/restxml/api_client.go
index f302d53aa9a..c91bab45aa6 100644
--- a/internal/protocoltest/restxml/api_client.go
+++ b/internal/protocoltest/restxml/api_client.go
@@ -5,7 +5,9 @@ package restxml
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	awshttp "github.com/aws/aws-sdk-go-v2/aws/transport/http"
@@ -16,6 +18,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 )
 
@@ -39,6 +42,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPClient(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -63,6 +68,10 @@ type Options struct {
 	// Configures the events that will be sent to the configured logger.
 	ClientLogMode aws.ClientLogMode
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -83,9 +92,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -113,6 +135,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -165,11 +193,13 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -179,10 +209,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -210,6 +274,21 @@ func addClientUserAgent(stack *middleware.Stack) error {
 	return awsmiddleware.AddSDKAgentKeyValue(awsmiddleware.APIMetadata, "restxmlprotocol", goModuleVersion)(stack)
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/internal/protocoltest/restxmlwithnamespace/api_client.go b/internal/protocoltest/restxmlwithnamespace/api_client.go
index 2e90b4d5219..310e8190643 100644
--- a/internal/protocoltest/restxmlwithnamespace/api_client.go
+++ b/internal/protocoltest/restxmlwithnamespace/api_client.go
@@ -4,7 +4,9 @@ package restxmlwithnamespace
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	awshttp "github.com/aws/aws-sdk-go-v2/aws/transport/http"
@@ -14,6 +16,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 )
 
@@ -37,6 +40,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPClient(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -59,6 +64,10 @@ type Options struct {
 	// Configures the events that will be sent to the configured logger.
 	ClientLogMode aws.ClientLogMode
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -75,9 +84,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -105,6 +127,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -157,11 +185,13 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -171,10 +201,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -202,6 +266,21 @@ func addClientUserAgent(stack *middleware.Stack) error {
 	return awsmiddleware.AddSDKAgentKeyValue(awsmiddleware.APIMetadata, "restxmlprotocolnamespace", goModuleVersion)(stack)
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/accessanalyzer/api_client.go b/service/accessanalyzer/api_client.go
index 44a3ab0c94d..65aeb02d209 100644
--- a/service/accessanalyzer/api_client.go
+++ b/service/accessanalyzer/api_client.go
@@ -5,7 +5,9 @@ package accessanalyzer
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/account/api_client.go b/service/account/api_client.go
index a0897068f39..b81392f4a31 100644
--- a/service/account/api_client.go
+++ b/service/account/api_client.go
@@ -4,7 +4,9 @@ package account
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/acm/api_client.go b/service/acm/api_client.go
index c0a80409b38..d322b733399 100644
--- a/service/acm/api_client.go
+++ b/service/acm/api_client.go
@@ -4,7 +4,9 @@ package acm
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/acmpca/api_client.go b/service/acmpca/api_client.go
index c913621ef75..d652f259ada 100644
--- a/service/acmpca/api_client.go
+++ b/service/acmpca/api_client.go
@@ -4,7 +4,9 @@ package acmpca
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/alexaforbusiness/api_client.go b/service/alexaforbusiness/api_client.go
index cb345b016b9..7d7edcaff4c 100644
--- a/service/alexaforbusiness/api_client.go
+++ b/service/alexaforbusiness/api_client.go
@@ -5,7 +5,9 @@ package alexaforbusiness
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/amp/api_client.go b/service/amp/api_client.go
index 570186959c0..26d464ebabf 100644
--- a/service/amp/api_client.go
+++ b/service/amp/api_client.go
@@ -5,7 +5,9 @@ package amp
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/amplify/api_client.go b/service/amplify/api_client.go
index b3b7820d6d0..8e98659b724 100644
--- a/service/amplify/api_client.go
+++ b/service/amplify/api_client.go
@@ -4,7 +4,9 @@ package amplify
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/amplifybackend/api_client.go b/service/amplifybackend/api_client.go
index 7f4e7c0d945..062206a14e2 100644
--- a/service/amplifybackend/api_client.go
+++ b/service/amplifybackend/api_client.go
@@ -4,7 +4,9 @@ package amplifybackend
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/amplifyuibuilder/api_client.go b/service/amplifyuibuilder/api_client.go
index 9d09abc3ddf..5ac28747e0e 100644
--- a/service/amplifyuibuilder/api_client.go
+++ b/service/amplifyuibuilder/api_client.go
@@ -5,7 +5,9 @@ package amplifyuibuilder
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/apigateway/api_client.go b/service/apigateway/api_client.go
index ac94db1a410..a475ed1ebb4 100644
--- a/service/apigateway/api_client.go
+++ b/service/apigateway/api_client.go
@@ -4,7 +4,9 @@ package apigateway
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -16,6 +18,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/apigatewaymanagementapi/api_client.go b/service/apigatewaymanagementapi/api_client.go
index 1ef14f6451f..e823d39bccc 100644
--- a/service/apigatewaymanagementapi/api_client.go
+++ b/service/apigatewaymanagementapi/api_client.go
@@ -4,7 +4,9 @@ package apigatewaymanagementapi
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/apigatewayv2/api_client.go b/service/apigatewayv2/api_client.go
index 9256661e8e2..b4372ed99ff 100644
--- a/service/apigatewayv2/api_client.go
+++ b/service/apigatewayv2/api_client.go
@@ -4,7 +4,9 @@ package apigatewayv2
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/appconfig/api_client.go b/service/appconfig/api_client.go
index c4c2283e37a..eb5e5d50798 100644
--- a/service/appconfig/api_client.go
+++ b/service/appconfig/api_client.go
@@ -4,7 +4,9 @@ package appconfig
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/appconfigdata/api_client.go b/service/appconfigdata/api_client.go
index 9d913425dc6..753f3f7950a 100644
--- a/service/appconfigdata/api_client.go
+++ b/service/appconfigdata/api_client.go
@@ -4,7 +4,9 @@ package appconfigdata
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/appflow/api_client.go b/service/appflow/api_client.go
index 0ec64afa024..44df58906cb 100644
--- a/service/appflow/api_client.go
+++ b/service/appflow/api_client.go
@@ -4,7 +4,9 @@ package appflow
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/appintegrations/api_client.go b/service/appintegrations/api_client.go
index f4ae9bb710d..86b9fe2f32f 100644
--- a/service/appintegrations/api_client.go
+++ b/service/appintegrations/api_client.go
@@ -5,7 +5,9 @@ package appintegrations
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/applicationautoscaling/api_client.go b/service/applicationautoscaling/api_client.go
index e87573caadc..f41f82aa849 100644
--- a/service/applicationautoscaling/api_client.go
+++ b/service/applicationautoscaling/api_client.go
@@ -4,7 +4,9 @@ package applicationautoscaling
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/applicationcostprofiler/api_client.go b/service/applicationcostprofiler/api_client.go
index 5a5297b960b..d80f7b1025e 100644
--- a/service/applicationcostprofiler/api_client.go
+++ b/service/applicationcostprofiler/api_client.go
@@ -4,7 +4,9 @@ package applicationcostprofiler
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/applicationdiscoveryservice/api_client.go b/service/applicationdiscoveryservice/api_client.go
index 0a8000caf0e..fc46b9b6391 100644
--- a/service/applicationdiscoveryservice/api_client.go
+++ b/service/applicationdiscoveryservice/api_client.go
@@ -5,7 +5,9 @@ package applicationdiscoveryservice
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/applicationinsights/api_client.go b/service/applicationinsights/api_client.go
index 821f8d47227..28feff58dc3 100644
--- a/service/applicationinsights/api_client.go
+++ b/service/applicationinsights/api_client.go
@@ -4,7 +4,9 @@ package applicationinsights
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/appmesh/api_client.go b/service/appmesh/api_client.go
index 0a27789e847..a1f08158c84 100644
--- a/service/appmesh/api_client.go
+++ b/service/appmesh/api_client.go
@@ -5,7 +5,9 @@ package appmesh
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/apprunner/api_client.go b/service/apprunner/api_client.go
index aa9ede04fc8..6c2704ac3da 100644
--- a/service/apprunner/api_client.go
+++ b/service/apprunner/api_client.go
@@ -4,7 +4,9 @@ package apprunner
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/appstream/api_client.go b/service/appstream/api_client.go
index 5e7d2d8dcde..f5d64e2e7c2 100644
--- a/service/appstream/api_client.go
+++ b/service/appstream/api_client.go
@@ -4,7 +4,9 @@ package appstream
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/appsync/api_client.go b/service/appsync/api_client.go
index e176d389875..3cb9eb5a2d6 100644
--- a/service/appsync/api_client.go
+++ b/service/appsync/api_client.go
@@ -4,7 +4,9 @@ package appsync
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/athena/api_client.go b/service/athena/api_client.go
index 91212217814..6807056f94e 100644
--- a/service/athena/api_client.go
+++ b/service/athena/api_client.go
@@ -5,7 +5,9 @@ package athena
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/auditmanager/api_client.go b/service/auditmanager/api_client.go
index 29fcebe863a..9d449b2f34a 100644
--- a/service/auditmanager/api_client.go
+++ b/service/auditmanager/api_client.go
@@ -4,7 +4,9 @@ package auditmanager
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/autoscaling/api_client.go b/service/autoscaling/api_client.go
index dcff6e8b9ec..3e55fbe5dd4 100644
--- a/service/autoscaling/api_client.go
+++ b/service/autoscaling/api_client.go
@@ -4,7 +4,9 @@ package autoscaling
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/autoscalingplans/api_client.go b/service/autoscalingplans/api_client.go
index eb7748a7370..98c7e4c1fa6 100644
--- a/service/autoscalingplans/api_client.go
+++ b/service/autoscalingplans/api_client.go
@@ -4,7 +4,9 @@ package autoscalingplans
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/backup/api_client.go b/service/backup/api_client.go
index e612eceabf7..de5735cd31e 100644
--- a/service/backup/api_client.go
+++ b/service/backup/api_client.go
@@ -5,7 +5,9 @@ package backup
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/backupgateway/api_client.go b/service/backupgateway/api_client.go
index 57e3484333e..44c77bc040a 100644
--- a/service/backupgateway/api_client.go
+++ b/service/backupgateway/api_client.go
@@ -4,7 +4,9 @@ package backupgateway
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/batch/api_client.go b/service/batch/api_client.go
index a72364711b4..72d0e60e680 100644
--- a/service/batch/api_client.go
+++ b/service/batch/api_client.go
@@ -4,7 +4,9 @@ package batch
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/braket/api_client.go b/service/braket/api_client.go
index 8015f508356..9d547dcba72 100644
--- a/service/braket/api_client.go
+++ b/service/braket/api_client.go
@@ -5,7 +5,9 @@ package braket
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/budgets/api_client.go b/service/budgets/api_client.go
index 61d8114f547..1dfa5aad153 100644
--- a/service/budgets/api_client.go
+++ b/service/budgets/api_client.go
@@ -4,7 +4,9 @@ package budgets
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/chime/api_client.go b/service/chime/api_client.go
index 3c557703877..25e94342728 100644
--- a/service/chime/api_client.go
+++ b/service/chime/api_client.go
@@ -5,7 +5,9 @@ package chime
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/chimesdkidentity/api_client.go b/service/chimesdkidentity/api_client.go
index 311800a5333..242f64c84bb 100644
--- a/service/chimesdkidentity/api_client.go
+++ b/service/chimesdkidentity/api_client.go
@@ -5,7 +5,9 @@ package chimesdkidentity
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/chimesdkmeetings/api_client.go b/service/chimesdkmeetings/api_client.go
index a389ca3de85..f4984e0ce35 100644
--- a/service/chimesdkmeetings/api_client.go
+++ b/service/chimesdkmeetings/api_client.go
@@ -5,7 +5,9 @@ package chimesdkmeetings
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/chimesdkmessaging/api_client.go b/service/chimesdkmessaging/api_client.go
index 076ee61fdcc..c7a1f0af06b 100644
--- a/service/chimesdkmessaging/api_client.go
+++ b/service/chimesdkmessaging/api_client.go
@@ -5,7 +5,9 @@ package chimesdkmessaging
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/cloud9/api_client.go b/service/cloud9/api_client.go
index d7d60ea97a6..50f7aaeb44e 100644
--- a/service/cloud9/api_client.go
+++ b/service/cloud9/api_client.go
@@ -4,7 +4,9 @@ package cloud9
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/cloudcontrol/api_client.go b/service/cloudcontrol/api_client.go
index f8c3012adbd..faa3f5dc44b 100644
--- a/service/cloudcontrol/api_client.go
+++ b/service/cloudcontrol/api_client.go
@@ -5,7 +5,9 @@ package cloudcontrol
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/clouddirectory/api_client.go b/service/clouddirectory/api_client.go
index 7817f013f4c..02476c1d5da 100644
--- a/service/clouddirectory/api_client.go
+++ b/service/clouddirectory/api_client.go
@@ -4,7 +4,9 @@ package clouddirectory
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/cloudformation/api_client.go b/service/cloudformation/api_client.go
index ff3df5de72c..fe7244d95a2 100644
--- a/service/cloudformation/api_client.go
+++ b/service/cloudformation/api_client.go
@@ -5,7 +5,9 @@ package cloudformation
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/cloudfront/api_client.go b/service/cloudfront/api_client.go
index bdabcd0a6fc..dc408730adc 100644
--- a/service/cloudfront/api_client.go
+++ b/service/cloudfront/api_client.go
@@ -4,7 +4,9 @@ package cloudfront
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/cloudhsm/api_client.go b/service/cloudhsm/api_client.go
index ae1ade94c7f..e244340b97d 100644
--- a/service/cloudhsm/api_client.go
+++ b/service/cloudhsm/api_client.go
@@ -4,7 +4,9 @@ package cloudhsm
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/cloudhsmv2/api_client.go b/service/cloudhsmv2/api_client.go
index 1b540d7e85e..af2f487fe10 100644
--- a/service/cloudhsmv2/api_client.go
+++ b/service/cloudhsmv2/api_client.go
@@ -4,7 +4,9 @@ package cloudhsmv2
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/cloudsearch/api_client.go b/service/cloudsearch/api_client.go
index 9138e32da6a..91a3c03abae 100644
--- a/service/cloudsearch/api_client.go
+++ b/service/cloudsearch/api_client.go
@@ -4,7 +4,9 @@ package cloudsearch
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/cloudsearchdomain/api_client.go b/service/cloudsearchdomain/api_client.go
index fe20221e480..86f82aa1338 100644
--- a/service/cloudsearchdomain/api_client.go
+++ b/service/cloudsearchdomain/api_client.go
@@ -4,7 +4,9 @@ package cloudsearchdomain
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/cloudtrail/api_client.go b/service/cloudtrail/api_client.go
index 22dcd7fc398..95549ea6ba9 100644
--- a/service/cloudtrail/api_client.go
+++ b/service/cloudtrail/api_client.go
@@ -4,7 +4,9 @@ package cloudtrail
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/cloudwatch/api_client.go b/service/cloudwatch/api_client.go
index 8e66303ae92..2b1ef2b7c72 100644
--- a/service/cloudwatch/api_client.go
+++ b/service/cloudwatch/api_client.go
@@ -4,7 +4,9 @@ package cloudwatch
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/cloudwatchevents/api_client.go b/service/cloudwatchevents/api_client.go
index be1d80022f4..f9644c77b0a 100644
--- a/service/cloudwatchevents/api_client.go
+++ b/service/cloudwatchevents/api_client.go
@@ -4,7 +4,9 @@ package cloudwatchevents
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/cloudwatchlogs/api_client.go b/service/cloudwatchlogs/api_client.go
index 768ac315da9..25909a8a201 100644
--- a/service/cloudwatchlogs/api_client.go
+++ b/service/cloudwatchlogs/api_client.go
@@ -4,7 +4,9 @@ package cloudwatchlogs
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/codeartifact/api_client.go b/service/codeartifact/api_client.go
index fe21458ee14..1108f2d4e52 100644
--- a/service/codeartifact/api_client.go
+++ b/service/codeartifact/api_client.go
@@ -4,7 +4,9 @@ package codeartifact
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/codebuild/api_client.go b/service/codebuild/api_client.go
index 9b7e7072ccc..91622db1d12 100644
--- a/service/codebuild/api_client.go
+++ b/service/codebuild/api_client.go
@@ -4,7 +4,9 @@ package codebuild
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/codecommit/api_client.go b/service/codecommit/api_client.go
index 05b94644813..8000aa02ba3 100644
--- a/service/codecommit/api_client.go
+++ b/service/codecommit/api_client.go
@@ -5,7 +5,9 @@ package codecommit
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/codedeploy/api_client.go b/service/codedeploy/api_client.go
index e06eb13a948..3f74b96fb19 100644
--- a/service/codedeploy/api_client.go
+++ b/service/codedeploy/api_client.go
@@ -4,7 +4,9 @@ package codedeploy
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/codeguruprofiler/api_client.go b/service/codeguruprofiler/api_client.go
index da9b44f7d87..385068f073a 100644
--- a/service/codeguruprofiler/api_client.go
+++ b/service/codeguruprofiler/api_client.go
@@ -5,7 +5,9 @@ package codeguruprofiler
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/codegurureviewer/api_client.go b/service/codegurureviewer/api_client.go
index b54d180ad4c..330acca3889 100644
--- a/service/codegurureviewer/api_client.go
+++ b/service/codegurureviewer/api_client.go
@@ -5,7 +5,9 @@ package codegurureviewer
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/codepipeline/api_client.go b/service/codepipeline/api_client.go
index b8441bf4c95..41f20f4ca1c 100644
--- a/service/codepipeline/api_client.go
+++ b/service/codepipeline/api_client.go
@@ -5,7 +5,9 @@ package codepipeline
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/codestar/api_client.go b/service/codestar/api_client.go
index 50fb4294397..a5207319f6b 100644
--- a/service/codestar/api_client.go
+++ b/service/codestar/api_client.go
@@ -4,7 +4,9 @@ package codestar
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/codestarconnections/api_client.go b/service/codestarconnections/api_client.go
index 491bfb02d25..ee1c888683a 100644
--- a/service/codestarconnections/api_client.go
+++ b/service/codestarconnections/api_client.go
@@ -4,7 +4,9 @@ package codestarconnections
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/codestarnotifications/api_client.go b/service/codestarnotifications/api_client.go
index 9dec52c518a..0c436834785 100644
--- a/service/codestarnotifications/api_client.go
+++ b/service/codestarnotifications/api_client.go
@@ -5,7 +5,9 @@ package codestarnotifications
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/cognitoidentity/api_client.go b/service/cognitoidentity/api_client.go
index e6bda298e87..3ffbd9eeb75 100644
--- a/service/cognitoidentity/api_client.go
+++ b/service/cognitoidentity/api_client.go
@@ -4,7 +4,9 @@ package cognitoidentity
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/cognitoidentityprovider/api_client.go b/service/cognitoidentityprovider/api_client.go
index a45093bd0f3..3996f8c4f21 100644
--- a/service/cognitoidentityprovider/api_client.go
+++ b/service/cognitoidentityprovider/api_client.go
@@ -4,7 +4,9 @@ package cognitoidentityprovider
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/cognitosync/api_client.go b/service/cognitosync/api_client.go
index aff1c509165..716a1659d08 100644
--- a/service/cognitosync/api_client.go
+++ b/service/cognitosync/api_client.go
@@ -4,7 +4,9 @@ package cognitosync
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/comprehend/api_client.go b/service/comprehend/api_client.go
index 449059f04ae..40a03596b26 100644
--- a/service/comprehend/api_client.go
+++ b/service/comprehend/api_client.go
@@ -5,7 +5,9 @@ package comprehend
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/comprehendmedical/api_client.go b/service/comprehendmedical/api_client.go
index b69493fa786..67b7c56a160 100644
--- a/service/comprehendmedical/api_client.go
+++ b/service/comprehendmedical/api_client.go
@@ -5,7 +5,9 @@ package comprehendmedical
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/computeoptimizer/api_client.go b/service/computeoptimizer/api_client.go
index b2400605665..bbb020610c0 100644
--- a/service/computeoptimizer/api_client.go
+++ b/service/computeoptimizer/api_client.go
@@ -4,7 +4,9 @@ package computeoptimizer
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/configservice/api_client.go b/service/configservice/api_client.go
index 9a53484e8d7..a38dd9b9934 100644
--- a/service/configservice/api_client.go
+++ b/service/configservice/api_client.go
@@ -4,7 +4,9 @@ package configservice
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/connect/api_client.go b/service/connect/api_client.go
index 9ae527750cf..02f80c10cf9 100644
--- a/service/connect/api_client.go
+++ b/service/connect/api_client.go
@@ -5,7 +5,9 @@ package connect
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/connectcontactlens/api_client.go b/service/connectcontactlens/api_client.go
index dc36e52bd3e..d33a92059f4 100644
--- a/service/connectcontactlens/api_client.go
+++ b/service/connectcontactlens/api_client.go
@@ -4,7 +4,9 @@ package connectcontactlens
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/connectparticipant/api_client.go b/service/connectparticipant/api_client.go
index 26382553f90..7e329add5c8 100644
--- a/service/connectparticipant/api_client.go
+++ b/service/connectparticipant/api_client.go
@@ -5,7 +5,9 @@ package connectparticipant
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/costandusagereportservice/api_client.go b/service/costandusagereportservice/api_client.go
index 6b6121a19cd..9fc77636269 100644
--- a/service/costandusagereportservice/api_client.go
+++ b/service/costandusagereportservice/api_client.go
@@ -4,7 +4,9 @@ package costandusagereportservice
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/costexplorer/api_client.go b/service/costexplorer/api_client.go
index aa1a0366030..3970de08c96 100644
--- a/service/costexplorer/api_client.go
+++ b/service/costexplorer/api_client.go
@@ -4,7 +4,9 @@ package costexplorer
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/customerprofiles/api_client.go b/service/customerprofiles/api_client.go
index 755e045bf17..3ecb68e193f 100644
--- a/service/customerprofiles/api_client.go
+++ b/service/customerprofiles/api_client.go
@@ -4,7 +4,9 @@ package customerprofiles
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/databasemigrationservice/api_client.go b/service/databasemigrationservice/api_client.go
index 26c6a076844..39f5718b1ef 100644
--- a/service/databasemigrationservice/api_client.go
+++ b/service/databasemigrationservice/api_client.go
@@ -4,7 +4,9 @@ package databasemigrationservice
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/databrew/api_client.go b/service/databrew/api_client.go
index b44a2bacd65..984e18b90b6 100644
--- a/service/databrew/api_client.go
+++ b/service/databrew/api_client.go
@@ -4,7 +4,9 @@ package databrew
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/dataexchange/api_client.go b/service/dataexchange/api_client.go
index 97e3612eb05..d0701715b5b 100644
--- a/service/dataexchange/api_client.go
+++ b/service/dataexchange/api_client.go
@@ -4,7 +4,9 @@ package dataexchange
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/datapipeline/api_client.go b/service/datapipeline/api_client.go
index a8af747d866..4dd58c5329f 100644
--- a/service/datapipeline/api_client.go
+++ b/service/datapipeline/api_client.go
@@ -4,7 +4,9 @@ package datapipeline
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/datasync/api_client.go b/service/datasync/api_client.go
index 303e6293e6f..77210ef534d 100644
--- a/service/datasync/api_client.go
+++ b/service/datasync/api_client.go
@@ -4,7 +4,9 @@ package datasync
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/dax/api_client.go b/service/dax/api_client.go
index 815a27f49ed..61971ad73ed 100644
--- a/service/dax/api_client.go
+++ b/service/dax/api_client.go
@@ -4,7 +4,9 @@ package dax
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/detective/api_client.go b/service/detective/api_client.go
index c64a2eea679..e7915d4ef08 100644
--- a/service/detective/api_client.go
+++ b/service/detective/api_client.go
@@ -4,7 +4,9 @@ package detective
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/devicefarm/api_client.go b/service/devicefarm/api_client.go
index c80899620fe..6f277d2ad37 100644
--- a/service/devicefarm/api_client.go
+++ b/service/devicefarm/api_client.go
@@ -4,7 +4,9 @@ package devicefarm
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/devopsguru/api_client.go b/service/devopsguru/api_client.go
index b33944376ae..e2071356c5c 100644
--- a/service/devopsguru/api_client.go
+++ b/service/devopsguru/api_client.go
@@ -5,7 +5,9 @@ package devopsguru
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/directconnect/api_client.go b/service/directconnect/api_client.go
index 941ecf1afa3..06cfdcd745c 100644
--- a/service/directconnect/api_client.go
+++ b/service/directconnect/api_client.go
@@ -4,7 +4,9 @@ package directconnect
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/directoryservice/api_client.go b/service/directoryservice/api_client.go
index 3e384865aff..fb9cb17c73f 100644
--- a/service/directoryservice/api_client.go
+++ b/service/directoryservice/api_client.go
@@ -4,7 +4,9 @@ package directoryservice
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/dlm/api_client.go b/service/dlm/api_client.go
index be8d8de18c7..b4593b1164a 100644
--- a/service/dlm/api_client.go
+++ b/service/dlm/api_client.go
@@ -4,7 +4,9 @@ package dlm
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/docdb/api_client.go b/service/docdb/api_client.go
index edd3a633c77..977403391b8 100644
--- a/service/docdb/api_client.go
+++ b/service/docdb/api_client.go
@@ -4,7 +4,9 @@ package docdb
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/protocol/query"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -69,6 +74,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -88,9 +97,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -118,6 +140,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -170,12 +198,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -185,10 +215,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -243,6 +307,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/drs/api_client.go b/service/drs/api_client.go
index 6cec3dc8ee8..27fd7615527 100644
--- a/service/drs/api_client.go
+++ b/service/drs/api_client.go
@@ -4,7 +4,9 @@ package drs
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/dynamodb/api_client.go b/service/dynamodb/api_client.go
index 94bce94fa51..bb6b0167b73 100644
--- a/service/dynamodb/api_client.go
+++ b/service/dynamodb/api_client.go
@@ -7,6 +7,7 @@ import (
 	cryptorand "crypto/rand"
 	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -21,6 +22,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"net/url"
 	"strings"
@@ -52,6 +54,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -83,6 +87,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// Allows you to disable the client's validation of response integrity using CRC32
 	// checksum. Enabled by default.
 	DisableValidateResponseChecksum bool
@@ -117,9 +125,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -147,6 +168,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -199,12 +226,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -215,10 +244,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -273,6 +336,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/dynamodbstreams/api_client.go b/service/dynamodbstreams/api_client.go
index 40c54cf8298..46defa4a314 100644
--- a/service/dynamodbstreams/api_client.go
+++ b/service/dynamodbstreams/api_client.go
@@ -4,7 +4,9 @@ package dynamodbstreams
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/ebs/api_client.go b/service/ebs/api_client.go
index 180d11903bd..05d236fc1af 100644
--- a/service/ebs/api_client.go
+++ b/service/ebs/api_client.go
@@ -5,7 +5,9 @@ package ebs
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/ec2/api_client.go b/service/ec2/api_client.go
index 2c87c12b43a..80a488e923b 100644
--- a/service/ec2/api_client.go
+++ b/service/ec2/api_client.go
@@ -5,7 +5,9 @@ package ec2
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/protocol/query"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
@@ -19,6 +21,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -46,6 +49,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -73,6 +78,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -96,9 +105,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -126,6 +148,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -178,12 +206,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -193,10 +223,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -251,6 +315,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/ec2instanceconnect/api_client.go b/service/ec2instanceconnect/api_client.go
index 0126d4d8031..907827f5639 100644
--- a/service/ec2instanceconnect/api_client.go
+++ b/service/ec2instanceconnect/api_client.go
@@ -4,7 +4,9 @@ package ec2instanceconnect
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/ecr/api_client.go b/service/ecr/api_client.go
index 4e274f2714c..92d8d951b82 100644
--- a/service/ecr/api_client.go
+++ b/service/ecr/api_client.go
@@ -4,7 +4,9 @@ package ecr
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/ecrpublic/api_client.go b/service/ecrpublic/api_client.go
index d8e2f569ba5..8dd3ffb77ab 100644
--- a/service/ecrpublic/api_client.go
+++ b/service/ecrpublic/api_client.go
@@ -4,7 +4,9 @@ package ecrpublic
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/ecs/api_client.go b/service/ecs/api_client.go
index 55ae6a0c909..1207ac34b5a 100644
--- a/service/ecs/api_client.go
+++ b/service/ecs/api_client.go
@@ -4,7 +4,9 @@ package ecs
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/efs/api_client.go b/service/efs/api_client.go
index c7660c5a7dc..a7b17c9ea4c 100644
--- a/service/efs/api_client.go
+++ b/service/efs/api_client.go
@@ -5,7 +5,9 @@ package efs
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/eks/api_client.go b/service/eks/api_client.go
index 63f36e5f571..0f10ed89529 100644
--- a/service/eks/api_client.go
+++ b/service/eks/api_client.go
@@ -5,7 +5,9 @@ package eks
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/elasticache/api_client.go b/service/elasticache/api_client.go
index 3b5a3121327..812fe3e0c1a 100644
--- a/service/elasticache/api_client.go
+++ b/service/elasticache/api_client.go
@@ -4,7 +4,9 @@ package elasticache
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/elasticbeanstalk/api_client.go b/service/elasticbeanstalk/api_client.go
index dd62e68f9c6..0191039cd56 100644
--- a/service/elasticbeanstalk/api_client.go
+++ b/service/elasticbeanstalk/api_client.go
@@ -4,7 +4,9 @@ package elasticbeanstalk
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/elasticinference/api_client.go b/service/elasticinference/api_client.go
index ed1322fc8cc..0df707455a6 100644
--- a/service/elasticinference/api_client.go
+++ b/service/elasticinference/api_client.go
@@ -4,7 +4,9 @@ package elasticinference
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/elasticloadbalancing/api_client.go b/service/elasticloadbalancing/api_client.go
index 5f6a55a5767..30cb56f1021 100644
--- a/service/elasticloadbalancing/api_client.go
+++ b/service/elasticloadbalancing/api_client.go
@@ -4,7 +4,9 @@ package elasticloadbalancing
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/elasticloadbalancingv2/api_client.go b/service/elasticloadbalancingv2/api_client.go
index e5691ba35bc..5a8dffb86d7 100644
--- a/service/elasticloadbalancingv2/api_client.go
+++ b/service/elasticloadbalancingv2/api_client.go
@@ -4,7 +4,9 @@ package elasticloadbalancingv2
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/elasticsearchservice/api_client.go b/service/elasticsearchservice/api_client.go
index eb281eb41ca..463bff401c0 100644
--- a/service/elasticsearchservice/api_client.go
+++ b/service/elasticsearchservice/api_client.go
@@ -4,7 +4,9 @@ package elasticsearchservice
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/elastictranscoder/api_client.go b/service/elastictranscoder/api_client.go
index 7eefaef0c5a..04e94433210 100644
--- a/service/elastictranscoder/api_client.go
+++ b/service/elastictranscoder/api_client.go
@@ -4,7 +4,9 @@ package elastictranscoder
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/emr/api_client.go b/service/emr/api_client.go
index 32d7d776571..c47ba4ee21a 100644
--- a/service/emr/api_client.go
+++ b/service/emr/api_client.go
@@ -4,7 +4,9 @@ package emr
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/emrcontainers/api_client.go b/service/emrcontainers/api_client.go
index 14599345160..7ccf5849cb6 100644
--- a/service/emrcontainers/api_client.go
+++ b/service/emrcontainers/api_client.go
@@ -5,7 +5,9 @@ package emrcontainers
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/eventbridge/api_client.go b/service/eventbridge/api_client.go
index 8819268177c..991c6959604 100644
--- a/service/eventbridge/api_client.go
+++ b/service/eventbridge/api_client.go
@@ -4,7 +4,9 @@ package eventbridge
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/evidently/api_client.go b/service/evidently/api_client.go
index b184f799906..b05680e6e76 100644
--- a/service/evidently/api_client.go
+++ b/service/evidently/api_client.go
@@ -4,7 +4,9 @@ package evidently
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/finspace/api_client.go b/service/finspace/api_client.go
index 8feed162ee5..9fe699f9fe2 100644
--- a/service/finspace/api_client.go
+++ b/service/finspace/api_client.go
@@ -6,6 +6,7 @@ import (
 	"context"
 	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -16,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"strings"
 	"time"
@@ -44,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -69,6 +73,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -88,9 +96,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -118,6 +139,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -170,12 +197,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -185,10 +214,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -243,6 +306,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/finspacedata/api_client.go b/service/finspacedata/api_client.go
index 46d9d6d6b22..905ee8c548a 100644
--- a/service/finspacedata/api_client.go
+++ b/service/finspacedata/api_client.go
@@ -7,6 +7,7 @@ import (
 	cryptorand "crypto/rand"
 	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -18,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"strings"
 	"time"
@@ -45,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -72,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -95,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -125,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -177,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -192,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -250,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/firehose/api_client.go b/service/firehose/api_client.go
index 55995909886..649ee17662a 100644
--- a/service/firehose/api_client.go
+++ b/service/firehose/api_client.go
@@ -4,7 +4,9 @@ package firehose
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/fis/api_client.go b/service/fis/api_client.go
index 0d798f8bc2a..bf9d904fd83 100644
--- a/service/fis/api_client.go
+++ b/service/fis/api_client.go
@@ -5,7 +5,9 @@ package fis
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/fms/api_client.go b/service/fms/api_client.go
index 5804b3b2373..7ececf9b547 100644
--- a/service/fms/api_client.go
+++ b/service/fms/api_client.go
@@ -4,7 +4,9 @@ package fms
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/forecast/api_client.go b/service/forecast/api_client.go
index 665041b1d47..7a3cf345c81 100644
--- a/service/forecast/api_client.go
+++ b/service/forecast/api_client.go
@@ -4,7 +4,9 @@ package forecast
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/forecastquery/api_client.go b/service/forecastquery/api_client.go
index 09c37a9df5c..fb693ac43ce 100644
--- a/service/forecastquery/api_client.go
+++ b/service/forecastquery/api_client.go
@@ -4,7 +4,9 @@ package forecastquery
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/frauddetector/api_client.go b/service/frauddetector/api_client.go
index e46e520636c..d5508bc8786 100644
--- a/service/frauddetector/api_client.go
+++ b/service/frauddetector/api_client.go
@@ -4,7 +4,9 @@ package frauddetector
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/fsx/api_client.go b/service/fsx/api_client.go
index dddff0f42a1..387d5095b0f 100644
--- a/service/fsx/api_client.go
+++ b/service/fsx/api_client.go
@@ -5,7 +5,9 @@ package fsx
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/gamelift/api_client.go b/service/gamelift/api_client.go
index f6f1fceaad1..d3fc47ae73f 100644
--- a/service/gamelift/api_client.go
+++ b/service/gamelift/api_client.go
@@ -4,7 +4,9 @@ package gamelift
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/glacier/api_client.go b/service/glacier/api_client.go
index e607783e076..73932894c75 100644
--- a/service/glacier/api_client.go
+++ b/service/glacier/api_client.go
@@ -4,7 +4,9 @@ package glacier
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/globalaccelerator/api_client.go b/service/globalaccelerator/api_client.go
index 79196de6319..d17f1503693 100644
--- a/service/globalaccelerator/api_client.go
+++ b/service/globalaccelerator/api_client.go
@@ -5,7 +5,9 @@ package globalaccelerator
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/glue/api_client.go b/service/glue/api_client.go
index 075243e9d0f..e39ba22b5b8 100644
--- a/service/glue/api_client.go
+++ b/service/glue/api_client.go
@@ -4,7 +4,9 @@ package glue
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/grafana/api_client.go b/service/grafana/api_client.go
index 3605d847d07..eb1d868af6e 100644
--- a/service/grafana/api_client.go
+++ b/service/grafana/api_client.go
@@ -5,7 +5,9 @@ package grafana
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/greengrass/api_client.go b/service/greengrass/api_client.go
index 75a434b6280..577463342ac 100644
--- a/service/greengrass/api_client.go
+++ b/service/greengrass/api_client.go
@@ -4,7 +4,9 @@ package greengrass
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/greengrassv2/api_client.go b/service/greengrassv2/api_client.go
index dc8d6ca6e90..2054622625c 100644
--- a/service/greengrassv2/api_client.go
+++ b/service/greengrassv2/api_client.go
@@ -5,7 +5,9 @@ package greengrassv2
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/groundstation/api_client.go b/service/groundstation/api_client.go
index 86da4af5a49..4707a616b57 100644
--- a/service/groundstation/api_client.go
+++ b/service/groundstation/api_client.go
@@ -4,7 +4,9 @@ package groundstation
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/guardduty/api_client.go b/service/guardduty/api_client.go
index 584769b9909..6638710a637 100644
--- a/service/guardduty/api_client.go
+++ b/service/guardduty/api_client.go
@@ -5,7 +5,9 @@ package guardduty
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/health/api_client.go b/service/health/api_client.go
index 0575dbff056..bdc8f95f618 100644
--- a/service/health/api_client.go
+++ b/service/health/api_client.go
@@ -4,7 +4,9 @@ package health
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/healthlake/api_client.go b/service/healthlake/api_client.go
index b30be495d41..e0f6bd1793e 100644
--- a/service/healthlake/api_client.go
+++ b/service/healthlake/api_client.go
@@ -5,7 +5,9 @@ package healthlake
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/honeycode/api_client.go b/service/honeycode/api_client.go
index 6cc40d95a91..f2f4720a684 100644
--- a/service/honeycode/api_client.go
+++ b/service/honeycode/api_client.go
@@ -4,7 +4,9 @@ package honeycode
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/iam/api_client.go b/service/iam/api_client.go
index 40826b4a0e6..f482c3a1614 100644
--- a/service/iam/api_client.go
+++ b/service/iam/api_client.go
@@ -4,7 +4,9 @@ package iam
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/identitystore/api_client.go b/service/identitystore/api_client.go
index 40b3a3b9eff..a4848a4c041 100644
--- a/service/identitystore/api_client.go
+++ b/service/identitystore/api_client.go
@@ -4,7 +4,9 @@ package identitystore
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/imagebuilder/api_client.go b/service/imagebuilder/api_client.go
index 18198401ee1..da9c5c45335 100644
--- a/service/imagebuilder/api_client.go
+++ b/service/imagebuilder/api_client.go
@@ -5,7 +5,9 @@ package imagebuilder
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/inspector/api_client.go b/service/inspector/api_client.go
index 1d47d8c1132..735635de7c5 100644
--- a/service/inspector/api_client.go
+++ b/service/inspector/api_client.go
@@ -4,7 +4,9 @@ package inspector
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/inspector2/api_client.go b/service/inspector2/api_client.go
index a2f0277ed14..b9ac6571271 100644
--- a/service/inspector2/api_client.go
+++ b/service/inspector2/api_client.go
@@ -5,7 +5,9 @@ package inspector2
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/iot/api_client.go b/service/iot/api_client.go
index 16b66e6751b..495cdea3b05 100644
--- a/service/iot/api_client.go
+++ b/service/iot/api_client.go
@@ -5,7 +5,9 @@ package iot
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/iot1clickdevicesservice/api_client.go b/service/iot1clickdevicesservice/api_client.go
index 316f7739850..6bf632e542d 100644
--- a/service/iot1clickdevicesservice/api_client.go
+++ b/service/iot1clickdevicesservice/api_client.go
@@ -4,7 +4,9 @@ package iot1clickdevicesservice
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/iot1clickprojects/api_client.go b/service/iot1clickprojects/api_client.go
index 032ca767368..2a1fc4baf06 100644
--- a/service/iot1clickprojects/api_client.go
+++ b/service/iot1clickprojects/api_client.go
@@ -4,7 +4,9 @@ package iot1clickprojects
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/iotanalytics/api_client.go b/service/iotanalytics/api_client.go
index dd2ec058633..c58b00423cc 100644
--- a/service/iotanalytics/api_client.go
+++ b/service/iotanalytics/api_client.go
@@ -4,7 +4,9 @@ package iotanalytics
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/iotdataplane/api_client.go b/service/iotdataplane/api_client.go
index 76ab9d9603c..2f602e110de 100644
--- a/service/iotdataplane/api_client.go
+++ b/service/iotdataplane/api_client.go
@@ -4,7 +4,9 @@ package iotdataplane
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/iotdeviceadvisor/api_client.go b/service/iotdeviceadvisor/api_client.go
index ec33531accf..c8f50d3cd6a 100644
--- a/service/iotdeviceadvisor/api_client.go
+++ b/service/iotdeviceadvisor/api_client.go
@@ -4,7 +4,9 @@ package iotdeviceadvisor
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/iotevents/api_client.go b/service/iotevents/api_client.go
index d9f5d002cfa..170e3b10c6e 100644
--- a/service/iotevents/api_client.go
+++ b/service/iotevents/api_client.go
@@ -4,7 +4,9 @@ package iotevents
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/ioteventsdata/api_client.go b/service/ioteventsdata/api_client.go
index a421741634a..8d60b663cd1 100644
--- a/service/ioteventsdata/api_client.go
+++ b/service/ioteventsdata/api_client.go
@@ -4,7 +4,9 @@ package ioteventsdata
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/iotfleethub/api_client.go b/service/iotfleethub/api_client.go
index b05ecfffdef..c9c1cad5355 100644
--- a/service/iotfleethub/api_client.go
+++ b/service/iotfleethub/api_client.go
@@ -5,7 +5,9 @@ package iotfleethub
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/iotjobsdataplane/api_client.go b/service/iotjobsdataplane/api_client.go
index b22f0f93f2c..46e09fac440 100644
--- a/service/iotjobsdataplane/api_client.go
+++ b/service/iotjobsdataplane/api_client.go
@@ -4,7 +4,9 @@ package iotjobsdataplane
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/iotsecuretunneling/api_client.go b/service/iotsecuretunneling/api_client.go
index ef65b0d7980..f86a32ba16f 100644
--- a/service/iotsecuretunneling/api_client.go
+++ b/service/iotsecuretunneling/api_client.go
@@ -4,7 +4,9 @@ package iotsecuretunneling
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/iotsitewise/api_client.go b/service/iotsitewise/api_client.go
index 885686bf9b0..63e05625237 100644
--- a/service/iotsitewise/api_client.go
+++ b/service/iotsitewise/api_client.go
@@ -5,7 +5,9 @@ package iotsitewise
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/iotthingsgraph/api_client.go b/service/iotthingsgraph/api_client.go
index 701115c2c04..5d5f6d9e393 100644
--- a/service/iotthingsgraph/api_client.go
+++ b/service/iotthingsgraph/api_client.go
@@ -4,7 +4,9 @@ package iotthingsgraph
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/iottwinmaker/api_client.go b/service/iottwinmaker/api_client.go
index d15490143c2..9980a397da6 100644
--- a/service/iottwinmaker/api_client.go
+++ b/service/iottwinmaker/api_client.go
@@ -4,7 +4,9 @@ package iottwinmaker
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/iotwireless/api_client.go b/service/iotwireless/api_client.go
index a2c11473dd1..74ccc1509fd 100644
--- a/service/iotwireless/api_client.go
+++ b/service/iotwireless/api_client.go
@@ -5,7 +5,9 @@ package iotwireless
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/ivs/api_client.go b/service/ivs/api_client.go
index 598db3f0f63..3a7985eb327 100644
--- a/service/ivs/api_client.go
+++ b/service/ivs/api_client.go
@@ -4,7 +4,9 @@ package ivs
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/kafka/api_client.go b/service/kafka/api_client.go
index 7bf5ee3d396..a699217893d 100644
--- a/service/kafka/api_client.go
+++ b/service/kafka/api_client.go
@@ -4,7 +4,9 @@ package kafka
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/kafkaconnect/api_client.go b/service/kafkaconnect/api_client.go
index bfb279bc8b3..fc6356d2dda 100644
--- a/service/kafkaconnect/api_client.go
+++ b/service/kafkaconnect/api_client.go
@@ -4,7 +4,9 @@ package kafkaconnect
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/kendra/api_client.go b/service/kendra/api_client.go
index f499c9bd47c..407d85fd3dd 100644
--- a/service/kendra/api_client.go
+++ b/service/kendra/api_client.go
@@ -5,7 +5,9 @@ package kendra
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/kinesis/api_client.go b/service/kinesis/api_client.go
index 9cc1ecf2079..e4659771ccd 100644
--- a/service/kinesis/api_client.go
+++ b/service/kinesis/api_client.go
@@ -4,7 +4,9 @@ package kinesis
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -169,12 +197,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -184,10 +214,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -242,6 +306,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/kinesisanalytics/api_client.go b/service/kinesisanalytics/api_client.go
index 249edcd801e..72a57baf710 100644
--- a/service/kinesisanalytics/api_client.go
+++ b/service/kinesisanalytics/api_client.go
@@ -4,7 +4,9 @@ package kinesisanalytics
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/kinesisanalyticsv2/api_client.go b/service/kinesisanalyticsv2/api_client.go
index 4086730c560..f073e812c09 100644
--- a/service/kinesisanalyticsv2/api_client.go
+++ b/service/kinesisanalyticsv2/api_client.go
@@ -4,7 +4,9 @@ package kinesisanalyticsv2
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/kinesisvideo/api_client.go b/service/kinesisvideo/api_client.go
index 3d1f087624f..b86217d4795 100644
--- a/service/kinesisvideo/api_client.go
+++ b/service/kinesisvideo/api_client.go
@@ -4,7 +4,9 @@ package kinesisvideo
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/kinesisvideoarchivedmedia/api_client.go b/service/kinesisvideoarchivedmedia/api_client.go
index cf8e31b798e..7f18cb5355c 100644
--- a/service/kinesisvideoarchivedmedia/api_client.go
+++ b/service/kinesisvideoarchivedmedia/api_client.go
@@ -4,7 +4,9 @@ package kinesisvideoarchivedmedia
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/kinesisvideomedia/api_client.go b/service/kinesisvideomedia/api_client.go
index 3edaa11f41d..8d59734d633 100644
--- a/service/kinesisvideomedia/api_client.go
+++ b/service/kinesisvideomedia/api_client.go
@@ -4,7 +4,9 @@ package kinesisvideomedia
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/kinesisvideosignaling/api_client.go b/service/kinesisvideosignaling/api_client.go
index 21e0e36482c..25937232dea 100644
--- a/service/kinesisvideosignaling/api_client.go
+++ b/service/kinesisvideosignaling/api_client.go
@@ -4,7 +4,9 @@ package kinesisvideosignaling
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/kms/api_client.go b/service/kms/api_client.go
index 0bc829e22b9..776862dfc5e 100644
--- a/service/kms/api_client.go
+++ b/service/kms/api_client.go
@@ -4,7 +4,9 @@ package kms
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/lakeformation/api_client.go b/service/lakeformation/api_client.go
index c0d63664a88..b196088a639 100644
--- a/service/lakeformation/api_client.go
+++ b/service/lakeformation/api_client.go
@@ -4,7 +4,9 @@ package lakeformation
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/lambda/api_client.go b/service/lambda/api_client.go
index 770dd4ca943..f074f4fb785 100644
--- a/service/lambda/api_client.go
+++ b/service/lambda/api_client.go
@@ -4,7 +4,9 @@ package lambda
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/lexmodelbuildingservice/api_client.go b/service/lexmodelbuildingservice/api_client.go
index 3aed57b2ec5..18f68c74f46 100644
--- a/service/lexmodelbuildingservice/api_client.go
+++ b/service/lexmodelbuildingservice/api_client.go
@@ -4,7 +4,9 @@ package lexmodelbuildingservice
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/lexmodelsv2/api_client.go b/service/lexmodelsv2/api_client.go
index 1fa3b77b462..8bef83f0e06 100644
--- a/service/lexmodelsv2/api_client.go
+++ b/service/lexmodelsv2/api_client.go
@@ -4,7 +4,9 @@ package lexmodelsv2
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/lexruntimeservice/api_client.go b/service/lexruntimeservice/api_client.go
index 7085144c4d0..1d54ebfdfb4 100644
--- a/service/lexruntimeservice/api_client.go
+++ b/service/lexruntimeservice/api_client.go
@@ -4,7 +4,9 @@ package lexruntimeservice
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/lexruntimev2/api_client.go b/service/lexruntimev2/api_client.go
index 7151f4c188b..74aa0d89128 100644
--- a/service/lexruntimev2/api_client.go
+++ b/service/lexruntimev2/api_client.go
@@ -4,7 +4,9 @@ package lexruntimev2
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -170,12 +198,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -185,10 +215,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -243,6 +307,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/licensemanager/api_client.go b/service/licensemanager/api_client.go
index a09b8714518..ad5368edb39 100644
--- a/service/licensemanager/api_client.go
+++ b/service/licensemanager/api_client.go
@@ -4,7 +4,9 @@ package licensemanager
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/lightsail/api_client.go b/service/lightsail/api_client.go
index 60a6d9401bb..1664f871bf2 100644
--- a/service/lightsail/api_client.go
+++ b/service/lightsail/api_client.go
@@ -4,7 +4,9 @@ package lightsail
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/location/api_client.go b/service/location/api_client.go
index 12f9b642559..a8f3b0f62fe 100644
--- a/service/location/api_client.go
+++ b/service/location/api_client.go
@@ -4,7 +4,9 @@ package location
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/lookoutequipment/api_client.go b/service/lookoutequipment/api_client.go
index 9ccc3594582..2db5ca65cee 100644
--- a/service/lookoutequipment/api_client.go
+++ b/service/lookoutequipment/api_client.go
@@ -5,7 +5,9 @@ package lookoutequipment
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/lookoutmetrics/api_client.go b/service/lookoutmetrics/api_client.go
index efd21ee6616..e24a3a8a683 100644
--- a/service/lookoutmetrics/api_client.go
+++ b/service/lookoutmetrics/api_client.go
@@ -4,7 +4,9 @@ package lookoutmetrics
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/lookoutvision/api_client.go b/service/lookoutvision/api_client.go
index 293b8d102b1..994d8c81c75 100644
--- a/service/lookoutvision/api_client.go
+++ b/service/lookoutvision/api_client.go
@@ -5,7 +5,9 @@ package lookoutvision
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/machinelearning/api_client.go b/service/machinelearning/api_client.go
index ac2042157ee..c51422fede7 100644
--- a/service/machinelearning/api_client.go
+++ b/service/machinelearning/api_client.go
@@ -4,7 +4,9 @@ package machinelearning
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/macie/api_client.go b/service/macie/api_client.go
index 392ba5756d3..5db99984aa6 100644
--- a/service/macie/api_client.go
+++ b/service/macie/api_client.go
@@ -4,7 +4,9 @@ package macie
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/macie2/api_client.go b/service/macie2/api_client.go
index 4ca29964d2b..9ee739b08e3 100644
--- a/service/macie2/api_client.go
+++ b/service/macie2/api_client.go
@@ -5,7 +5,9 @@ package macie2
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/managedblockchain/api_client.go b/service/managedblockchain/api_client.go
index 07005e54c5e..73be8962c70 100644
--- a/service/managedblockchain/api_client.go
+++ b/service/managedblockchain/api_client.go
@@ -5,7 +5,9 @@ package managedblockchain
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/marketplacecatalog/api_client.go b/service/marketplacecatalog/api_client.go
index a8118344300..041b5b60fb2 100644
--- a/service/marketplacecatalog/api_client.go
+++ b/service/marketplacecatalog/api_client.go
@@ -4,7 +4,9 @@ package marketplacecatalog
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/marketplacecommerceanalytics/api_client.go b/service/marketplacecommerceanalytics/api_client.go
index 1b91404b043..a4906f85b32 100644
--- a/service/marketplacecommerceanalytics/api_client.go
+++ b/service/marketplacecommerceanalytics/api_client.go
@@ -4,7 +4,9 @@ package marketplacecommerceanalytics
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/marketplaceentitlementservice/api_client.go b/service/marketplaceentitlementservice/api_client.go
index 9d15c76de37..c66a8ed0598 100644
--- a/service/marketplaceentitlementservice/api_client.go
+++ b/service/marketplaceentitlementservice/api_client.go
@@ -4,7 +4,9 @@ package marketplaceentitlementservice
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/marketplacemetering/api_client.go b/service/marketplacemetering/api_client.go
index a2fb2d1dfa1..e688a8e3157 100644
--- a/service/marketplacemetering/api_client.go
+++ b/service/marketplacemetering/api_client.go
@@ -4,7 +4,9 @@ package marketplacemetering
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/mediaconnect/api_client.go b/service/mediaconnect/api_client.go
index be4d152e32d..77bea9ae2a3 100644
--- a/service/mediaconnect/api_client.go
+++ b/service/mediaconnect/api_client.go
@@ -4,7 +4,9 @@ package mediaconnect
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/mediaconvert/api_client.go b/service/mediaconvert/api_client.go
index 4c1bdd05a7b..f6aa62bc217 100644
--- a/service/mediaconvert/api_client.go
+++ b/service/mediaconvert/api_client.go
@@ -5,7 +5,9 @@ package mediaconvert
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/medialive/api_client.go b/service/medialive/api_client.go
index d86010cdfb2..287b4a82b6d 100644
--- a/service/medialive/api_client.go
+++ b/service/medialive/api_client.go
@@ -5,7 +5,9 @@ package medialive
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/mediapackage/api_client.go b/service/mediapackage/api_client.go
index db77449cfbf..eae2bfe3c07 100644
--- a/service/mediapackage/api_client.go
+++ b/service/mediapackage/api_client.go
@@ -4,7 +4,9 @@ package mediapackage
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/mediapackagevod/api_client.go b/service/mediapackagevod/api_client.go
index 4d602749411..c1346f26fe7 100644
--- a/service/mediapackagevod/api_client.go
+++ b/service/mediapackagevod/api_client.go
@@ -4,7 +4,9 @@ package mediapackagevod
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/mediastore/api_client.go b/service/mediastore/api_client.go
index fba84f951d3..5d89e82ae6b 100644
--- a/service/mediastore/api_client.go
+++ b/service/mediastore/api_client.go
@@ -4,7 +4,9 @@ package mediastore
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/mediastoredata/api_client.go b/service/mediastoredata/api_client.go
index bf3e5a5a087..8a3f32392b8 100644
--- a/service/mediastoredata/api_client.go
+++ b/service/mediastoredata/api_client.go
@@ -4,7 +4,9 @@ package mediastoredata
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/mediatailor/api_client.go b/service/mediatailor/api_client.go
index 1c0f354cb20..0ae04a439cb 100644
--- a/service/mediatailor/api_client.go
+++ b/service/mediatailor/api_client.go
@@ -4,7 +4,9 @@ package mediatailor
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/memorydb/api_client.go b/service/memorydb/api_client.go
index 74adb00bf3d..fbf538e2272 100644
--- a/service/memorydb/api_client.go
+++ b/service/memorydb/api_client.go
@@ -4,7 +4,9 @@ package memorydb
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/mgn/api_client.go b/service/mgn/api_client.go
index 305aa603cde..59f66c4668a 100644
--- a/service/mgn/api_client.go
+++ b/service/mgn/api_client.go
@@ -4,7 +4,9 @@ package mgn
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/migrationhub/api_client.go b/service/migrationhub/api_client.go
index 9f94687cc86..20a95320880 100644
--- a/service/migrationhub/api_client.go
+++ b/service/migrationhub/api_client.go
@@ -4,7 +4,9 @@ package migrationhub
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/migrationhubconfig/api_client.go b/service/migrationhubconfig/api_client.go
index f2015d54ab1..3280fcbb00a 100644
--- a/service/migrationhubconfig/api_client.go
+++ b/service/migrationhubconfig/api_client.go
@@ -4,7 +4,9 @@ package migrationhubconfig
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/migrationhubrefactorspaces/api_client.go b/service/migrationhubrefactorspaces/api_client.go
index 0ab54d9a6c0..759a8c872c0 100644
--- a/service/migrationhubrefactorspaces/api_client.go
+++ b/service/migrationhubrefactorspaces/api_client.go
@@ -5,7 +5,9 @@ package migrationhubrefactorspaces
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/migrationhubstrategy/api_client.go b/service/migrationhubstrategy/api_client.go
index ec6fa0d3025..c2ea80d0755 100644
--- a/service/migrationhubstrategy/api_client.go
+++ b/service/migrationhubstrategy/api_client.go
@@ -4,7 +4,9 @@ package migrationhubstrategy
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/mobile/api_client.go b/service/mobile/api_client.go
index 9a31eeca0c9..beeda0ebabb 100644
--- a/service/mobile/api_client.go
+++ b/service/mobile/api_client.go
@@ -4,7 +4,9 @@ package mobile
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/mq/api_client.go b/service/mq/api_client.go
index 840d085a24c..7f88b783a73 100644
--- a/service/mq/api_client.go
+++ b/service/mq/api_client.go
@@ -5,7 +5,9 @@ package mq
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/mturk/api_client.go b/service/mturk/api_client.go
index 073b943f166..b97c5a71241 100644
--- a/service/mturk/api_client.go
+++ b/service/mturk/api_client.go
@@ -4,7 +4,9 @@ package mturk
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/mwaa/api_client.go b/service/mwaa/api_client.go
index 3d3dc4c5911..14e655a3323 100644
--- a/service/mwaa/api_client.go
+++ b/service/mwaa/api_client.go
@@ -4,7 +4,9 @@ package mwaa
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/neptune/api_client.go b/service/neptune/api_client.go
index 3ec95e82120..111606e373e 100644
--- a/service/neptune/api_client.go
+++ b/service/neptune/api_client.go
@@ -4,7 +4,9 @@ package neptune
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/protocol/query"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -68,6 +73,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -87,9 +96,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -117,6 +139,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -169,12 +197,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -184,10 +214,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -242,6 +306,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/networkfirewall/api_client.go b/service/networkfirewall/api_client.go
index 4cfa78ee1a5..92bed6a06d5 100644
--- a/service/networkfirewall/api_client.go
+++ b/service/networkfirewall/api_client.go
@@ -4,7 +4,9 @@ package networkfirewall
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/networkmanager/api_client.go b/service/networkmanager/api_client.go
index cc3409e23da..4a2d21516d5 100644
--- a/service/networkmanager/api_client.go
+++ b/service/networkmanager/api_client.go
@@ -5,7 +5,9 @@ package networkmanager
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/nimble/api_client.go b/service/nimble/api_client.go
index cb17a1b7886..c11a0a04711 100644
--- a/service/nimble/api_client.go
+++ b/service/nimble/api_client.go
@@ -5,7 +5,9 @@ package nimble
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/opensearch/api_client.go b/service/opensearch/api_client.go
index e74881c4f9d..cbabd5a1ecf 100644
--- a/service/opensearch/api_client.go
+++ b/service/opensearch/api_client.go
@@ -4,7 +4,9 @@ package opensearch
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/opsworks/api_client.go b/service/opsworks/api_client.go
index c436653ab23..14425b81c1e 100644
--- a/service/opsworks/api_client.go
+++ b/service/opsworks/api_client.go
@@ -4,7 +4,9 @@ package opsworks
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/opsworkscm/api_client.go b/service/opsworkscm/api_client.go
index 0f248c4ea28..d5826a8d860 100644
--- a/service/opsworkscm/api_client.go
+++ b/service/opsworkscm/api_client.go
@@ -4,7 +4,9 @@ package opsworkscm
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/organizations/api_client.go b/service/organizations/api_client.go
index 0ce750bf99e..ab8c103b819 100644
--- a/service/organizations/api_client.go
+++ b/service/organizations/api_client.go
@@ -4,7 +4,9 @@ package organizations
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/outposts/api_client.go b/service/outposts/api_client.go
index 9803e6c1925..93ed40a5223 100644
--- a/service/outposts/api_client.go
+++ b/service/outposts/api_client.go
@@ -4,7 +4,9 @@ package outposts
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/panorama/api_client.go b/service/panorama/api_client.go
index 851f4742618..645ecad0812 100644
--- a/service/panorama/api_client.go
+++ b/service/panorama/api_client.go
@@ -4,7 +4,9 @@ package panorama
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/personalize/api_client.go b/service/personalize/api_client.go
index 2c9ad427c64..6b0ae798763 100644
--- a/service/personalize/api_client.go
+++ b/service/personalize/api_client.go
@@ -4,7 +4,9 @@ package personalize
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/personalizeevents/api_client.go b/service/personalizeevents/api_client.go
index 7b87a501aa7..44fd20902da 100644
--- a/service/personalizeevents/api_client.go
+++ b/service/personalizeevents/api_client.go
@@ -4,7 +4,9 @@ package personalizeevents
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/personalizeruntime/api_client.go b/service/personalizeruntime/api_client.go
index 8576310fb69..fe475fa1182 100644
--- a/service/personalizeruntime/api_client.go
+++ b/service/personalizeruntime/api_client.go
@@ -4,7 +4,9 @@ package personalizeruntime
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/pi/api_client.go b/service/pi/api_client.go
index 307eac2abfe..fe07aeeec96 100644
--- a/service/pi/api_client.go
+++ b/service/pi/api_client.go
@@ -4,7 +4,9 @@ package pi
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/pinpoint/api_client.go b/service/pinpoint/api_client.go
index 5be5d300d71..58105b17a32 100644
--- a/service/pinpoint/api_client.go
+++ b/service/pinpoint/api_client.go
@@ -4,7 +4,9 @@ package pinpoint
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/pinpointemail/api_client.go b/service/pinpointemail/api_client.go
index 8f89c7de9c7..5f3894ac5ab 100644
--- a/service/pinpointemail/api_client.go
+++ b/service/pinpointemail/api_client.go
@@ -4,7 +4,9 @@ package pinpointemail
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/pinpointsmsvoice/api_client.go b/service/pinpointsmsvoice/api_client.go
index 1ffea969245..7072b245c3e 100644
--- a/service/pinpointsmsvoice/api_client.go
+++ b/service/pinpointsmsvoice/api_client.go
@@ -4,7 +4,9 @@ package pinpointsmsvoice
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/polly/api_client.go b/service/polly/api_client.go
index 9a79d7de6b1..c726ef93902 100644
--- a/service/polly/api_client.go
+++ b/service/polly/api_client.go
@@ -4,7 +4,9 @@ package polly
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/pricing/api_client.go b/service/pricing/api_client.go
index 4349b90cfa2..c3f03b4c722 100644
--- a/service/pricing/api_client.go
+++ b/service/pricing/api_client.go
@@ -4,7 +4,9 @@ package pricing
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/proton/api_client.go b/service/proton/api_client.go
index 6d958cc5137..9f8f27011cb 100644
--- a/service/proton/api_client.go
+++ b/service/proton/api_client.go
@@ -5,7 +5,9 @@ package proton
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/qldb/api_client.go b/service/qldb/api_client.go
index 26c0ac3b74c..7608c5b45bf 100644
--- a/service/qldb/api_client.go
+++ b/service/qldb/api_client.go
@@ -4,7 +4,9 @@ package qldb
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/qldbsession/api_client.go b/service/qldbsession/api_client.go
index 3d386a80151..d669c332b7d 100644
--- a/service/qldbsession/api_client.go
+++ b/service/qldbsession/api_client.go
@@ -4,7 +4,9 @@ package qldbsession
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/quicksight/api_client.go b/service/quicksight/api_client.go
index 7d2020e4495..6a0689f8c53 100644
--- a/service/quicksight/api_client.go
+++ b/service/quicksight/api_client.go
@@ -4,7 +4,9 @@ package quicksight
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/ram/api_client.go b/service/ram/api_client.go
index fe568838144..25225a97073 100644
--- a/service/ram/api_client.go
+++ b/service/ram/api_client.go
@@ -4,7 +4,9 @@ package ram
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/rbin/api_client.go b/service/rbin/api_client.go
index ac8290e525e..91582ba688e 100644
--- a/service/rbin/api_client.go
+++ b/service/rbin/api_client.go
@@ -4,7 +4,9 @@ package rbin
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/rds/api_client.go b/service/rds/api_client.go
index 143d13f6779..bd2c3844e27 100644
--- a/service/rds/api_client.go
+++ b/service/rds/api_client.go
@@ -4,7 +4,9 @@ package rds
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/protocol/query"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -69,6 +74,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -88,9 +97,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -118,6 +140,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -170,12 +198,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -185,10 +215,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -243,6 +307,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/rdsdata/api_client.go b/service/rdsdata/api_client.go
index 41a14ca6746..e2b3bc0a511 100644
--- a/service/rdsdata/api_client.go
+++ b/service/rdsdata/api_client.go
@@ -4,7 +4,9 @@ package rdsdata
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/redshift/api_client.go b/service/redshift/api_client.go
index c272628c214..b027f68c3a5 100644
--- a/service/redshift/api_client.go
+++ b/service/redshift/api_client.go
@@ -4,7 +4,9 @@ package redshift
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/redshiftdata/api_client.go b/service/redshiftdata/api_client.go
index 81c586e0399..f666f977c72 100644
--- a/service/redshiftdata/api_client.go
+++ b/service/redshiftdata/api_client.go
@@ -4,7 +4,9 @@ package redshiftdata
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/rekognition/api_client.go b/service/rekognition/api_client.go
index 2ca1f462349..f9963c278cf 100644
--- a/service/rekognition/api_client.go
+++ b/service/rekognition/api_client.go
@@ -4,7 +4,9 @@ package rekognition
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/resiliencehub/api_client.go b/service/resiliencehub/api_client.go
index 90f47c10ec8..94a6e8c485f 100644
--- a/service/resiliencehub/api_client.go
+++ b/service/resiliencehub/api_client.go
@@ -5,7 +5,9 @@ package resiliencehub
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/resourcegroups/api_client.go b/service/resourcegroups/api_client.go
index 31bd8d6a029..621a824a5a0 100644
--- a/service/resourcegroups/api_client.go
+++ b/service/resourcegroups/api_client.go
@@ -4,7 +4,9 @@ package resourcegroups
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/resourcegroupstaggingapi/api_client.go b/service/resourcegroupstaggingapi/api_client.go
index 4a7118600ed..f84918e6744 100644
--- a/service/resourcegroupstaggingapi/api_client.go
+++ b/service/resourcegroupstaggingapi/api_client.go
@@ -4,7 +4,9 @@ package resourcegroupstaggingapi
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/robomaker/api_client.go b/service/robomaker/api_client.go
index fd386046380..3f59a93addc 100644
--- a/service/robomaker/api_client.go
+++ b/service/robomaker/api_client.go
@@ -5,7 +5,9 @@ package robomaker
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/route53/api_client.go b/service/route53/api_client.go
index 631a0379ccf..905b3c01e30 100644
--- a/service/route53/api_client.go
+++ b/service/route53/api_client.go
@@ -4,7 +4,9 @@ package route53
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -16,6 +18,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"strings"
 	"time"
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -68,6 +73,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -87,9 +96,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -117,6 +139,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -169,12 +197,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -184,10 +214,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -242,6 +306,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/route53domains/api_client.go b/service/route53domains/api_client.go
index f14e4a921f0..a5b1bc60be7 100644
--- a/service/route53domains/api_client.go
+++ b/service/route53domains/api_client.go
@@ -4,7 +4,9 @@ package route53domains
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/route53recoverycluster/api_client.go b/service/route53recoverycluster/api_client.go
index 0adfa8838f1..d03e335f0e3 100644
--- a/service/route53recoverycluster/api_client.go
+++ b/service/route53recoverycluster/api_client.go
@@ -4,7 +4,9 @@ package route53recoverycluster
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/route53recoverycontrolconfig/api_client.go b/service/route53recoverycontrolconfig/api_client.go
index d58501955f1..9b1e4b4279e 100644
--- a/service/route53recoverycontrolconfig/api_client.go
+++ b/service/route53recoverycontrolconfig/api_client.go
@@ -5,7 +5,9 @@ package route53recoverycontrolconfig
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/route53recoveryreadiness/api_client.go b/service/route53recoveryreadiness/api_client.go
index 40bef15a63b..a91433ff55b 100644
--- a/service/route53recoveryreadiness/api_client.go
+++ b/service/route53recoveryreadiness/api_client.go
@@ -4,7 +4,9 @@ package route53recoveryreadiness
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/route53resolver/api_client.go b/service/route53resolver/api_client.go
index 49ac37626c5..137ec0261a1 100644
--- a/service/route53resolver/api_client.go
+++ b/service/route53resolver/api_client.go
@@ -5,7 +5,9 @@ package route53resolver
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/rum/api_client.go b/service/rum/api_client.go
index d652e38ca5c..160b1b03a84 100644
--- a/service/rum/api_client.go
+++ b/service/rum/api_client.go
@@ -4,7 +4,9 @@ package rum
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/s3/api_client.go b/service/s3/api_client.go
index c5ab34de2d7..3fcb5310776 100644
--- a/service/s3/api_client.go
+++ b/service/s3/api_client.go
@@ -6,6 +6,7 @@ import (
 	"context"
 	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -22,6 +23,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -49,6 +51,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveHTTPSignerV4a(&options)
@@ -78,6 +82,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// Allows you to disable S3 Multi-Region access points feature.
 	DisableMultiRegionAccessPoints bool
 
@@ -100,6 +108,12 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
 	// Allows you to enable arn region support for the service.
 	UseARNRegion bool
 
@@ -126,9 +140,16 @@ type Options struct {
 	// Signature Version 4a (SigV4a) Signer
 	httpSignerV4a httpSignerV4a
 
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -156,6 +177,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -212,12 +239,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -228,10 +257,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -287,6 +350,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/s3control/api_client.go b/service/s3control/api_client.go
index db075282397..34be84e5a81 100644
--- a/service/s3control/api_client.go
+++ b/service/s3control/api_client.go
@@ -5,7 +5,9 @@ package s3control
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -19,6 +21,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -45,6 +48,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -72,6 +77,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -95,6 +104,12 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
 	// Allows you to enable arn region support for the service.
 	UseARNRegion bool
 
@@ -105,9 +120,16 @@ type Options struct {
 	// field is set it overrides this field value.
 	UseDualstack bool
 
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -135,6 +157,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -187,12 +215,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -203,10 +233,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -261,6 +325,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/s3outposts/api_client.go b/service/s3outposts/api_client.go
index 306535ff155..a0920e85dcd 100644
--- a/service/s3outposts/api_client.go
+++ b/service/s3outposts/api_client.go
@@ -4,7 +4,9 @@ package s3outposts
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/sagemaker/api_client.go b/service/sagemaker/api_client.go
index 3ed0595b432..bcc6d9b5d51 100644
--- a/service/sagemaker/api_client.go
+++ b/service/sagemaker/api_client.go
@@ -5,7 +5,9 @@ package sagemaker
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/sagemakera2iruntime/api_client.go b/service/sagemakera2iruntime/api_client.go
index a9079832011..5b6747e2b72 100644
--- a/service/sagemakera2iruntime/api_client.go
+++ b/service/sagemakera2iruntime/api_client.go
@@ -4,7 +4,9 @@ package sagemakera2iruntime
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/sagemakeredge/api_client.go b/service/sagemakeredge/api_client.go
index 452c86e4991..fc13088555b 100644
--- a/service/sagemakeredge/api_client.go
+++ b/service/sagemakeredge/api_client.go
@@ -4,7 +4,9 @@ package sagemakeredge
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/sagemakerfeaturestoreruntime/api_client.go b/service/sagemakerfeaturestoreruntime/api_client.go
index 7e6f2ba9b96..c58953fa35a 100644
--- a/service/sagemakerfeaturestoreruntime/api_client.go
+++ b/service/sagemakerfeaturestoreruntime/api_client.go
@@ -4,7 +4,9 @@ package sagemakerfeaturestoreruntime
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/sagemakerruntime/api_client.go b/service/sagemakerruntime/api_client.go
index dcc028e20f8..e1d018632f2 100644
--- a/service/sagemakerruntime/api_client.go
+++ b/service/sagemakerruntime/api_client.go
@@ -4,7 +4,9 @@ package sagemakerruntime
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/savingsplans/api_client.go b/service/savingsplans/api_client.go
index d295bc95544..d40a8a880ff 100644
--- a/service/savingsplans/api_client.go
+++ b/service/savingsplans/api_client.go
@@ -5,7 +5,9 @@ package savingsplans
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/schemas/api_client.go b/service/schemas/api_client.go
index 6ab9afce8ba..92168c733bd 100644
--- a/service/schemas/api_client.go
+++ b/service/schemas/api_client.go
@@ -5,7 +5,9 @@ package schemas
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/secretsmanager/api_client.go b/service/secretsmanager/api_client.go
index 9e17bf16356..577e2cf2d33 100644
--- a/service/secretsmanager/api_client.go
+++ b/service/secretsmanager/api_client.go
@@ -5,7 +5,9 @@ package secretsmanager
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/securityhub/api_client.go b/service/securityhub/api_client.go
index 6ea968c8b24..8f10015730f 100644
--- a/service/securityhub/api_client.go
+++ b/service/securityhub/api_client.go
@@ -4,7 +4,9 @@ package securityhub
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/serverlessapplicationrepository/api_client.go b/service/serverlessapplicationrepository/api_client.go
index d8c9d2e6d43..8dc6a084c06 100644
--- a/service/serverlessapplicationrepository/api_client.go
+++ b/service/serverlessapplicationrepository/api_client.go
@@ -4,7 +4,9 @@ package serverlessapplicationrepository
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/servicecatalog/api_client.go b/service/servicecatalog/api_client.go
index 54b30ce7274..f58a8a7e568 100644
--- a/service/servicecatalog/api_client.go
+++ b/service/servicecatalog/api_client.go
@@ -5,7 +5,9 @@ package servicecatalog
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/servicecatalogappregistry/api_client.go b/service/servicecatalogappregistry/api_client.go
index ba4105d9ad2..02887215465 100644
--- a/service/servicecatalogappregistry/api_client.go
+++ b/service/servicecatalogappregistry/api_client.go
@@ -5,7 +5,9 @@ package servicecatalogappregistry
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/servicediscovery/api_client.go b/service/servicediscovery/api_client.go
index be5cb36cae3..9766fd48217 100644
--- a/service/servicediscovery/api_client.go
+++ b/service/servicediscovery/api_client.go
@@ -5,7 +5,9 @@ package servicediscovery
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/servicequotas/api_client.go b/service/servicequotas/api_client.go
index 6bd0dd0de3c..aafa343cd72 100644
--- a/service/servicequotas/api_client.go
+++ b/service/servicequotas/api_client.go
@@ -4,7 +4,9 @@ package servicequotas
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/ses/api_client.go b/service/ses/api_client.go
index ad666c79874..886cd8fae64 100644
--- a/service/ses/api_client.go
+++ b/service/ses/api_client.go
@@ -4,7 +4,9 @@ package ses
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/sesv2/api_client.go b/service/sesv2/api_client.go
index bc2c3db0a3f..e0749aa02f9 100644
--- a/service/sesv2/api_client.go
+++ b/service/sesv2/api_client.go
@@ -4,7 +4,9 @@ package sesv2
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/sfn/api_client.go b/service/sfn/api_client.go
index a392ed72ca5..204dd919a54 100644
--- a/service/sfn/api_client.go
+++ b/service/sfn/api_client.go
@@ -4,7 +4,9 @@ package sfn
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/shield/api_client.go b/service/shield/api_client.go
index f4b645b74c8..b656d857f9f 100644
--- a/service/shield/api_client.go
+++ b/service/shield/api_client.go
@@ -4,7 +4,9 @@ package shield
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/signer/api_client.go b/service/signer/api_client.go
index 21e91b6d9e1..67a6e963a01 100644
--- a/service/signer/api_client.go
+++ b/service/signer/api_client.go
@@ -5,7 +5,9 @@ package signer
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/sms/api_client.go b/service/sms/api_client.go
index 6f8878f589f..f7da2a9282a 100644
--- a/service/sms/api_client.go
+++ b/service/sms/api_client.go
@@ -4,7 +4,9 @@ package sms
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/snowball/api_client.go b/service/snowball/api_client.go
index 2a26cb45d37..9338eca52b1 100644
--- a/service/snowball/api_client.go
+++ b/service/snowball/api_client.go
@@ -4,7 +4,9 @@ package snowball
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/snowdevicemanagement/api_client.go b/service/snowdevicemanagement/api_client.go
index 845af8419d6..90daf720b00 100644
--- a/service/snowdevicemanagement/api_client.go
+++ b/service/snowdevicemanagement/api_client.go
@@ -5,7 +5,9 @@ package snowdevicemanagement
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/sns/api_client.go b/service/sns/api_client.go
index d32d2676926..400e08f0be2 100644
--- a/service/sns/api_client.go
+++ b/service/sns/api_client.go
@@ -4,7 +4,9 @@ package sns
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/sqs/api_client.go b/service/sqs/api_client.go
index eeecc931c50..928acfe4e33 100644
--- a/service/sqs/api_client.go
+++ b/service/sqs/api_client.go
@@ -4,7 +4,9 @@ package sqs
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/ssm/api_client.go b/service/ssm/api_client.go
index a785b03947b..12638107098 100644
--- a/service/ssm/api_client.go
+++ b/service/ssm/api_client.go
@@ -5,7 +5,9 @@ package ssm
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/ssmcontacts/api_client.go b/service/ssmcontacts/api_client.go
index 98d7f225829..e8f5c7c9c37 100644
--- a/service/ssmcontacts/api_client.go
+++ b/service/ssmcontacts/api_client.go
@@ -5,7 +5,9 @@ package ssmcontacts
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/ssmincidents/api_client.go b/service/ssmincidents/api_client.go
index 9373c5702a9..ab374c571a1 100644
--- a/service/ssmincidents/api_client.go
+++ b/service/ssmincidents/api_client.go
@@ -5,7 +5,9 @@ package ssmincidents
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/sso/api_client.go b/service/sso/api_client.go
index 4fed68b6f9d..916291b0811 100644
--- a/service/sso/api_client.go
+++ b/service/sso/api_client.go
@@ -4,7 +4,9 @@ package sso
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/ssoadmin/api_client.go b/service/ssoadmin/api_client.go
index 2607cb86215..2c854f3a0fc 100644
--- a/service/ssoadmin/api_client.go
+++ b/service/ssoadmin/api_client.go
@@ -4,7 +4,9 @@ package ssoadmin
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/ssooidc/api_client.go b/service/ssooidc/api_client.go
index 0f2e100f801..003078fe9f5 100644
--- a/service/ssooidc/api_client.go
+++ b/service/ssooidc/api_client.go
@@ -4,7 +4,9 @@ package ssooidc
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/storagegateway/api_client.go b/service/storagegateway/api_client.go
index 9b269399781..a68df7bf354 100644
--- a/service/storagegateway/api_client.go
+++ b/service/storagegateway/api_client.go
@@ -4,7 +4,9 @@ package storagegateway
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/sts/api_client.go b/service/sts/api_client.go
index 6614d01b007..de29ca55cc9 100644
--- a/service/sts/api_client.go
+++ b/service/sts/api_client.go
@@ -4,7 +4,9 @@ package sts
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/protocol/query"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -69,6 +74,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -88,9 +97,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -118,6 +140,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -170,12 +198,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -185,10 +215,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -243,6 +307,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/support/api_client.go b/service/support/api_client.go
index 71b5174f53f..f1ff740640d 100644
--- a/service/support/api_client.go
+++ b/service/support/api_client.go
@@ -4,7 +4,9 @@ package support
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/swf/api_client.go b/service/swf/api_client.go
index 485ffffa0ca..f443d92c796 100644
--- a/service/swf/api_client.go
+++ b/service/swf/api_client.go
@@ -4,7 +4,9 @@ package swf
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/synthetics/api_client.go b/service/synthetics/api_client.go
index ee19b060b92..d2ecd24e07e 100644
--- a/service/synthetics/api_client.go
+++ b/service/synthetics/api_client.go
@@ -4,7 +4,9 @@ package synthetics
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/textract/api_client.go b/service/textract/api_client.go
index fce4cafdcc1..e96639d35b9 100644
--- a/service/textract/api_client.go
+++ b/service/textract/api_client.go
@@ -4,7 +4,9 @@ package textract
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/timestreamquery/api_client.go b/service/timestreamquery/api_client.go
index adafd4e65a0..f9a8987e7d6 100644
--- a/service/timestreamquery/api_client.go
+++ b/service/timestreamquery/api_client.go
@@ -7,6 +7,7 @@ import (
 	cryptorand "crypto/rand"
 	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -19,6 +20,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"net/url"
 	"strings"
@@ -51,6 +53,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -82,6 +86,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// Allows configuring endpoint discovery
 	EndpointDiscovery EndpointDiscoveryOptions
 
@@ -108,9 +116,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -138,6 +159,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -190,12 +217,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -206,10 +235,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -264,6 +327,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/timestreamwrite/api_client.go b/service/timestreamwrite/api_client.go
index 685a9c060cd..fe0d8754446 100644
--- a/service/timestreamwrite/api_client.go
+++ b/service/timestreamwrite/api_client.go
@@ -6,6 +6,7 @@ import (
 	"context"
 	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +18,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"net/url"
 	"strings"
@@ -49,6 +51,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveEnableEndpointDiscovery(&options)
@@ -78,6 +82,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// Allows configuring endpoint discovery
 	EndpointDiscovery EndpointDiscoveryOptions
 
@@ -100,9 +108,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -130,6 +151,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -182,12 +209,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -198,10 +227,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -256,6 +319,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/transcribe/api_client.go b/service/transcribe/api_client.go
index d95a696e6ce..f589c1ef53f 100644
--- a/service/transcribe/api_client.go
+++ b/service/transcribe/api_client.go
@@ -4,7 +4,9 @@ package transcribe
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/transcribestreaming/api_client.go b/service/transcribestreaming/api_client.go
index c81dbdfdc5a..88a156df916 100644
--- a/service/transcribestreaming/api_client.go
+++ b/service/transcribestreaming/api_client.go
@@ -4,7 +4,9 @@ package transcribestreaming
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -170,12 +198,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -185,10 +215,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -243,6 +307,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/transfer/api_client.go b/service/transfer/api_client.go
index ccf689c088d..cc4116c2802 100644
--- a/service/transfer/api_client.go
+++ b/service/transfer/api_client.go
@@ -4,7 +4,9 @@ package transfer
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/translate/api_client.go b/service/translate/api_client.go
index 29f5555c466..b99f3cf87c2 100644
--- a/service/translate/api_client.go
+++ b/service/translate/api_client.go
@@ -5,7 +5,9 @@ package translate
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/voiceid/api_client.go b/service/voiceid/api_client.go
index 2f8b253bc73..4e775890c12 100644
--- a/service/voiceid/api_client.go
+++ b/service/voiceid/api_client.go
@@ -5,7 +5,9 @@ package voiceid
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/waf/api_client.go b/service/waf/api_client.go
index a6de09d8d78..eeea716c0c9 100644
--- a/service/waf/api_client.go
+++ b/service/waf/api_client.go
@@ -4,7 +4,9 @@ package waf
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/wafregional/api_client.go b/service/wafregional/api_client.go
index 79177caa9ef..e0ef02ab7b4 100644
--- a/service/wafregional/api_client.go
+++ b/service/wafregional/api_client.go
@@ -4,7 +4,9 @@ package wafregional
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/wafv2/api_client.go b/service/wafv2/api_client.go
index df8a314829d..7550a75814d 100644
--- a/service/wafv2/api_client.go
+++ b/service/wafv2/api_client.go
@@ -4,7 +4,9 @@ package wafv2
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/wellarchitected/api_client.go b/service/wellarchitected/api_client.go
index b94e8fdfabc..6d55c009ed6 100644
--- a/service/wellarchitected/api_client.go
+++ b/service/wellarchitected/api_client.go
@@ -5,7 +5,9 @@ package wellarchitected
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/wisdom/api_client.go b/service/wisdom/api_client.go
index dbb1b4a9fac..384591b2db6 100644
--- a/service/wisdom/api_client.go
+++ b/service/wisdom/api_client.go
@@ -5,7 +5,9 @@ package wisdom
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/workdocs/api_client.go b/service/workdocs/api_client.go
index 2e724d0f654..d830152689c 100644
--- a/service/workdocs/api_client.go
+++ b/service/workdocs/api_client.go
@@ -4,7 +4,9 @@ package workdocs
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/worklink/api_client.go b/service/worklink/api_client.go
index b4676f6b85e..3ffd15411a4 100644
--- a/service/worklink/api_client.go
+++ b/service/worklink/api_client.go
@@ -4,7 +4,9 @@ package worklink
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/workmail/api_client.go b/service/workmail/api_client.go
index 4bb3ff8f5e8..7b2ca86e13d 100644
--- a/service/workmail/api_client.go
+++ b/service/workmail/api_client.go
@@ -5,7 +5,9 @@ package workmail
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -43,6 +46,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -70,6 +75,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -93,9 +102,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -123,6 +145,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -175,12 +203,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -190,10 +220,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -248,6 +312,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/workmailmessageflow/api_client.go b/service/workmailmessageflow/api_client.go
index 045cd2af6a5..e557aef2527 100644
--- a/service/workmailmessageflow/api_client.go
+++ b/service/workmailmessageflow/api_client.go
@@ -4,7 +4,9 @@ package workmailmessageflow
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -42,6 +45,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -67,6 +72,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -86,9 +95,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -116,6 +138,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -168,12 +196,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -183,10 +213,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -241,6 +305,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/workspaces/api_client.go b/service/workspaces/api_client.go
index 030037a6c61..d92189207bd 100644
--- a/service/workspaces/api_client.go
+++ b/service/workspaces/api_client.go
@@ -4,7 +4,9 @@ package workspaces
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,
diff --git a/service/workspacesweb/api_client.go b/service/workspacesweb/api_client.go
index 1bc7cc8d3c1..1677223c6f2 100644
--- a/service/workspacesweb/api_client.go
+++ b/service/workspacesweb/api_client.go
@@ -5,7 +5,9 @@ package workspacesweb
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -17,6 +19,7 @@ import (
 	"github.com/aws/smithy-go/middleware"
 	smithyrand "github.com/aws/smithy-go/rand"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -44,6 +47,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	resolveIdempotencyTokenProvider(&options)
@@ -71,6 +76,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -94,9 +103,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -124,6 +146,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -176,12 +204,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -191,10 +221,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -249,6 +313,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func resolveIdempotencyTokenProvider(o *Options) {
 	if o.IdempotencyTokenProvider != nil {
 		return
diff --git a/service/xray/api_client.go b/service/xray/api_client.go
index 5d6da2140d0..14991c5987f 100644
--- a/service/xray/api_client.go
+++ b/service/xray/api_client.go
@@ -4,7 +4,9 @@ package xray
 
 import (
 	"context"
+	"fmt"
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/defaults"
 	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
 	"github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
@@ -15,6 +17,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"net"
 	"net/http"
 	"time"
 )
@@ -41,6 +44,8 @@ func New(options Options, optFns ...func(*Options)) *Client {
 
 	resolveHTTPSignerV4(&options)
 
+	setResolvedDefaultsMode(&options)
+
 	resolveDefaultEndpointConfiguration(&options)
 
 	for _, fn := range optFns {
@@ -66,6 +71,10 @@ type Options struct {
 	// The credentials object to use when signing requests.
 	Credentials aws.CredentialsProvider
 
+	// The configuration DefaultsMode that the SDK should use when constructing the
+	// clients initial default settings.
+	DefaultsMode aws.DefaultsMode
+
 	// The endpoint options to be used when attempting to resolve an endpoint.
 	EndpointOptions EndpointResolverOptions
 
@@ -85,9 +94,22 @@ type Options struct {
 	// failures. When nil the API client will use a default retryer.
 	Retryer aws.Retryer
 
+	// The RuntimeEnvironment configuration, only populated if the DefaultsMode is set
+	// to AutoDefaultsMode and is initialized using config.LoadDefaultConfig. You
+	// should not populate this structure programmatically, or rely on the values here
+	// within your applications.
+	RuntimeEnvironment aws.RuntimeEnvironment
+
+	// The initial DefaultsMode used when the client options were constructed. If the
+	// DefaultsMode was set to aws.AutoDefaultsMode this will store what the resolved
+	// value was at that point in time.
+	resolvedDefaultsMode aws.DefaultsMode
+
 	// The HTTP client to invoke API calls with. Defaults to client's default HTTP
 	// implementation if nil.
 	HTTPClient HTTPClient
+
+	clientInitializedOptions map[struct{}]interface{}
 }
 
 // WithAPIOptions returns a functional option for setting the Client's APIOptions
@@ -115,6 +137,12 @@ func (o Options) Copy() Options {
 	to := o
 	to.APIOptions = make([]func(*middleware.Stack) error, len(o.APIOptions))
 	copy(to.APIOptions, o.APIOptions)
+
+	to.clientInitializedOptions = make(map[struct{}]interface{}, len(o.clientInitializedOptions))
+	for k, v := range o.clientInitializedOptions {
+		to.clientInitializedOptions[k] = v
+	}
+
 	return to
 }
 func (c *Client) invokeOperation(ctx context.Context, opID string, params interface{}, optFns []func(*Options), stackFns ...func(*middleware.Stack, Options) error) (result interface{}, metadata middleware.Metadata, err error) {
@@ -167,12 +195,14 @@ func addSetLoggerMiddleware(stack *middleware.Stack, o Options) error {
 // NewFromConfig returns a new client from the provided config.
 func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 	opts := Options{
-		Region:        cfg.Region,
-		HTTPClient:    cfg.HTTPClient,
-		Credentials:   cfg.Credentials,
-		APIOptions:    cfg.APIOptions,
-		Logger:        cfg.Logger,
-		ClientLogMode: cfg.ClientLogMode,
+		Region:             cfg.Region,
+		DefaultsMode:       cfg.DefaultsMode,
+		RuntimeEnvironment: cfg.RuntimeEnvironment,
+		HTTPClient:         cfg.HTTPClient,
+		Credentials:        cfg.Credentials,
+		APIOptions:         cfg.APIOptions,
+		Logger:             cfg.Logger,
+		ClientLogMode:      cfg.ClientLogMode,
 	}
 	resolveAWSRetryerProvider(cfg, &opts)
 	resolveAWSEndpointResolver(cfg, &opts)
@@ -182,10 +212,44 @@ func NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {
 }
 
 func resolveHTTPClient(o *Options) {
+	var buildable *awshttp.BuildableClient
+
 	if o.HTTPClient != nil {
-		return
+		var ok bool
+		buildable, ok = o.HTTPClient.(*awshttp.BuildableClient)
+		if !ok {
+			return
+		}
+	} else {
+		buildable = awshttp.NewBuildableClient()
+	}
+
+	var mode aws.DefaultsMode
+	if ok := mode.SetFromString(string(o.DefaultsMode)); !ok {
+		panic(fmt.Errorf("unsupported defaults mode constant %v", mode))
+	}
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
 	}
-	o.HTTPClient = awshttp.NewBuildableClient()
+
+	if mode != aws.LegacyDefaultsMode {
+		modeConfig, _ := defaults.GetModeConfiguration(mode)
+
+		buildable = buildable.WithDialerOptions(func(dialer *net.Dialer) {
+			if dialerTimeout, ok := modeConfig.GetConnectTimeout(); ok {
+				dialer.Timeout = dialerTimeout
+			}
+		})
+
+		buildable = buildable.WithTransportOptions(func(transport *http.Transport) {
+			if tlsHandshakeTimeout, ok := modeConfig.GetTLSNegotiationTimeout(); ok {
+				transport.TLSHandshakeTimeout = tlsHandshakeTimeout
+			}
+		})
+	}
+
+	o.HTTPClient = buildable
 }
 
 func resolveRetryer(o *Options) {
@@ -240,6 +304,21 @@ func newDefaultV4Signer(o Options) *v4.Signer {
 	})
 }
 
+func setResolvedDefaultsMode(o *Options) {
+	if len(o.resolvedDefaultsMode) > 0 {
+		return
+	}
+
+	var mode aws.DefaultsMode
+	mode.SetFromString(string(o.DefaultsMode))
+
+	if mode == aws.AutoDefaultsMode {
+		mode = defaults.ResolveAutoDefaultsMode(o.Region, o.RuntimeEnvironment)
+	}
+
+	o.resolvedDefaultsMode = mode
+}
+
 func addRetryMiddlewares(stack *middleware.Stack, o Options) error {
 	mo := retry.AddRetryMiddlewaresOptions{
 		Retryer:          o.Retryer,