diff --git a/client/webpack.config.desktop.js b/client/webpack.config.desktop.js
index 5cd86ff9f340b..f6b11f140e52b 100644
--- a/client/webpack.config.desktop.js
+++ b/client/webpack.config.desktop.js
@@ -83,6 +83,7 @@ module.exports = {
 	],
 	resolve: {
 		extensions: [ '.json', '.js', '.jsx', '.ts', '.tsx' ],
+		mainFields: [ 'calypso:src', 'module', 'main' ],
 		modules: [ __dirname, 'node_modules' ],
 		alias: {
 			config: 'server/config',
diff --git a/client/webpack.config.js b/client/webpack.config.js
index 5903cff178498..38d4576b21944 100644
--- a/client/webpack.config.js
+++ b/client/webpack.config.js
@@ -256,6 +256,7 @@ const webpackConfig = {
 	},
 	resolve: {
 		extensions: [ '.json', '.js', '.jsx', '.ts', '.tsx' ],
+		mainFields: [ 'browser', 'calypso:src', 'module', 'main' ],
 		modules: [ __dirname, 'node_modules' ],
 		alias: Object.assign(
 			{
diff --git a/client/webpack.config.node.js b/client/webpack.config.node.js
index 2e6206851d7ef..f429f56511e0f 100644
--- a/client/webpack.config.node.js
+++ b/client/webpack.config.node.js
@@ -59,6 +59,7 @@ function getMonorepoPackages() {
  *
  * @returns {Array} list of externals
  */
+
 function getExternals() {
 	return [
 		// Don't bundle any node_modules, both to avoid a massive bundle, and problems
@@ -144,6 +145,7 @@ const webpackConfig = {
 	},
 	resolve: {
 		extensions: [ '.json', '.js', '.jsx', '.ts', '.tsx' ],
+		mainFields: [ 'calypso:src', 'module', 'main' ],
 		modules: [ __dirname, path.join( __dirname, 'extensions' ), 'node_modules' ],
 		alias: {
 			'calypso/config': 'server/config',
diff --git a/packages/babel-plugin-transform-wpcalypso-async/jest.config.js b/packages/babel-plugin-transform-wpcalypso-async/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/babel-plugin-transform-wpcalypso-async/jest.config.js
+++ b/packages/babel-plugin-transform-wpcalypso-async/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/calypso-analytics/jest.config.js b/packages/calypso-analytics/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/calypso-analytics/jest.config.js
+++ b/packages/calypso-analytics/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/calypso-build/webpack.config.js b/packages/calypso-build/webpack.config.js
index d563544571c83..22df3672aa2b1 100644
--- a/packages/calypso-build/webpack.config.js
+++ b/packages/calypso-build/webpack.config.js
@@ -132,6 +132,7 @@ function getWebpackConfig(
 		},
 		resolve: {
 			extensions: [ '.json', '.js', '.jsx', '.ts', '.tsx' ],
+			mainFields: [ 'browser', 'calypso:src', 'module', 'main' ],
 			modules: [ 'node_modules' ],
 		},
 		node: false,
diff --git a/packages/calypso-codemods/jest.config.js b/packages/calypso-codemods/jest.config.js
index 38c6fc9e904a8..b704c656adf18 100644
--- a/packages/calypso-codemods/jest.config.js
+++ b/packages/calypso-codemods/jest.config.js
@@ -4,4 +4,5 @@ module.exports = {
 	testMatch: [ '<rootDir>/tests/*/codemod.spec.js' ],
 	setupFiles: [ '<rootDir>/setup-tests.js' ],
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/components/jest.config.js b/packages/components/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/components/jest.config.js
+++ b/packages/components/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/composite-checkout/jest.config.js b/packages/composite-checkout/jest.config.js
index 5c63fbf20b323..3ddfd2808d3de 100644
--- a/packages/composite-checkout/jest.config.js
+++ b/packages/composite-checkout/jest.config.js
@@ -4,4 +4,5 @@ module.exports = {
 	testEnvironment: 'jsdom',
 	globals: { window: { navigator: { userAgent: 'jest' } } },
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/composite-checkout/webpack.config.demo.js b/packages/composite-checkout/webpack.config.demo.js
index 20c6cf230a5e6..e300562885ea2 100644
--- a/packages/composite-checkout/webpack.config.demo.js
+++ b/packages/composite-checkout/webpack.config.demo.js
@@ -18,7 +18,10 @@ module.exports = {
 			},
 		],
 	},
-	resolve: { extensions: [ '*', '.js', '.jsx' ] },
+	resolve: {
+		extensions: [ '*', '.js', '.jsx' ],
+		mainFields: [ 'browser', 'calypso:src', 'module', 'main' ],
+	},
 	output: {
 		path: path.resolve( __dirname, '/dist/' ),
 		publicPath: '/dist/',
diff --git a/packages/composite-checkout/webpack.config.js b/packages/composite-checkout/webpack.config.js
index ac940d0c1a8c1..a0380fb3f2d45 100644
--- a/packages/composite-checkout/webpack.config.js
+++ b/packages/composite-checkout/webpack.config.js
@@ -27,7 +27,10 @@ module.exports = {
 			},
 		],
 	},
-	resolve: { extensions: [ '*', '.js', '.jsx' ] },
+	resolve: {
+		extensions: [ '*', '.js', '.jsx' ],
+		mainFields: [ 'browser', 'calypso:src', 'module', 'main' ],
+	},
 	output: {
 		path: path.resolve( __dirname, 'dist/' ),
 		publicPath: '/dist/',
diff --git a/packages/data-stores/jest.config.js b/packages/data-stores/jest.config.js
index d48c7a1ad33be..e27cc661b4226 100644
--- a/packages/data-stores/jest.config.js
+++ b/packages/data-stores/jest.config.js
@@ -3,4 +3,5 @@ module.exports = {
 	rootDir: __dirname,
 	setupFiles: [ 'regenerator-runtime/runtime' ],
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/domain-picker/jest.config.js b/packages/domain-picker/jest.config.js
index 03c0eea29f8a5..c930936b55413 100644
--- a/packages/domain-picker/jest.config.js
+++ b/packages/domain-picker/jest.config.js
@@ -6,4 +6,5 @@ module.exports = {
 	globals: {
 		__i18n_text_domain__: 'default',
 	},
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/effective-module-tree/jest.config.js b/packages/effective-module-tree/jest.config.js
index 94c7b33cabe46..25a79abd199f6 100644
--- a/packages/effective-module-tree/jest.config.js
+++ b/packages/effective-module-tree/jest.config.js
@@ -4,4 +4,5 @@ module.exports = {
 	// Node project, no need to transform anything
 	transformIgnorePatterns: [ '<rootDir>/', '/node_modules/' ],
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/eslint-config-wpcalypso/jest.config.js b/packages/eslint-config-wpcalypso/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/eslint-config-wpcalypso/jest.config.js
+++ b/packages/eslint-config-wpcalypso/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/eslint-plugin-wpcalypso/jest.config.js b/packages/eslint-plugin-wpcalypso/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/eslint-plugin-wpcalypso/jest.config.js
+++ b/packages/eslint-plugin-wpcalypso/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/format-currency/jest.config.js b/packages/format-currency/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/format-currency/jest.config.js
+++ b/packages/format-currency/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/format-currency/package.json b/packages/format-currency/package.json
index 964775de3f9d6..c80afcb474294 100644
--- a/packages/format-currency/package.json
+++ b/packages/format-currency/package.json
@@ -4,6 +4,7 @@
 	"description": "JavaScript library for formatting currency",
 	"main": "dist/cjs/index.js",
 	"module": "dist/esm/index.js",
+	"calypso:src": "src/index.js",
 	"sideEffects": false,
 	"repository": {
 		"type": "git",
@@ -29,8 +30,8 @@
 	},
 	"scripts": {
 		"clean": "npx rimraf dist",
-		"prepublish": "yarn run clean",
-		"prepare": "transpile"
+		"build": "transpile",
+		"prepack": "yarn run clean && yarn run build"
 	},
 	"types": "types"
 }
diff --git a/packages/i18n-calypso-cli/jest.config.js b/packages/i18n-calypso-cli/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/i18n-calypso-cli/jest.config.js
+++ b/packages/i18n-calypso-cli/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/i18n-calypso/jest.config.js b/packages/i18n-calypso/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/i18n-calypso/jest.config.js
+++ b/packages/i18n-calypso/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/i18n-calypso/package.json b/packages/i18n-calypso/package.json
index 15ff07b1ce196..933ddd4d87afa 100644
--- a/packages/i18n-calypso/package.json
+++ b/packages/i18n-calypso/package.json
@@ -4,6 +4,7 @@
 	"description": "i18n JavaScript library on top of Tannin originally used in Calypso",
 	"main": "dist/cjs/index.js",
 	"module": "dist/esm/index.js",
+	"calypso:src": "src/index.js",
 	"types": "types/index.d.ts",
 	"sideEffects": false,
 	"repository": {
@@ -39,7 +40,7 @@
 	},
 	"scripts": {
 		"clean": "npx rimraf dist",
-		"prepublish": "yarn run clean",
-		"prepare": "transpile"
+		"build": "transpile",
+		"prepack": "yarn run clean && yarn run build"
 	}
 }
diff --git a/packages/load-script/jest.config.js b/packages/load-script/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/load-script/jest.config.js
+++ b/packages/load-script/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/load-script/package.json b/packages/load-script/package.json
index 849a72548dfdb..6711f83dc82c1 100644
--- a/packages/load-script/package.json
+++ b/packages/load-script/package.json
@@ -4,6 +4,7 @@
 	"description": "Async Script Loader.",
 	"main": "dist/cjs/index.js",
 	"module": "dist/esm/index.js",
+	"calypso:src": "src/index.js",
 	"keywords": [
 		"wordpress"
 	],
@@ -28,7 +29,7 @@
 	},
 	"scripts": {
 		"clean": "npx rimraf dist",
-		"prepublish": "yarn run clean",
-		"prepare": "transpile"
+		"build": "transpile",
+		"prepack": "yarn run clean && yarn run build"
 	}
 }
diff --git a/packages/media-library/jest.config.js b/packages/media-library/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/media-library/jest.config.js
+++ b/packages/media-library/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/photon/jest.config.js b/packages/photon/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/photon/jest.config.js
+++ b/packages/photon/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/photon/package.json b/packages/photon/package.json
index 3ddfaef4b8770..ac519f6143111 100644
--- a/packages/photon/package.json
+++ b/packages/photon/package.json
@@ -4,6 +4,7 @@
 	"description": "JavaScript library for the WordPress.com Photon image manipulation service",
 	"main": "dist/cjs/index.js",
 	"module": "dist/esm/index.js",
+	"calypso:src": "src/index.js",
 	"sideEffects": false,
 	"repository": {
 		"type": "git",
@@ -38,7 +39,7 @@
 	},
 	"scripts": {
 		"clean": "npx rimraf dist",
-		"prepublish": "yarn run clean",
-		"prepare": "transpile"
+		"build": "transpile",
+		"prepack": "yarn run clean && yarn run build"
 	}
 }
diff --git a/packages/popup-monitor/package.json b/packages/popup-monitor/package.json
index 29687d84083c0..079af17f98614 100644
--- a/packages/popup-monitor/package.json
+++ b/packages/popup-monitor/package.json
@@ -4,6 +4,7 @@
 	"description": "Utility to facilitate the monitoring of a popup window close action.",
 	"main": "dist/cjs/index.js",
 	"module": "dist/esm/index.js",
+	"calypso:src": "src/index.js",
 	"sideEffects": false,
 	"keywords": [
 		"wordpress",
@@ -29,8 +30,8 @@
 	],
 	"scripts": {
 		"clean": "npx rimraf dist",
-		"prepublish": "yarn run clean",
-		"prepare": "transpile"
+		"build": "transpile",
+		"prepack": "yarn run clean && yarn run build"
 	},
 	"dependencies": {
 		"lodash": "^4.17.15"
diff --git a/packages/request-external-access/jest.config.js b/packages/request-external-access/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/request-external-access/jest.config.js
+++ b/packages/request-external-access/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/request-external-access/package.json b/packages/request-external-access/package.json
index 99f845d56ad99..a1ba9f7dbe4ed 100644
--- a/packages/request-external-access/package.json
+++ b/packages/request-external-access/package.json
@@ -4,6 +4,7 @@
 	"description": "Utility for requesting authorization of sharing services.",
 	"main": "dist/cjs/index.js",
 	"module": "dist/esm/index.js",
+	"calypso:src": "src/index.js",
 	"sideEffects": false,
 	"keywords": [
 		"wordpress",
@@ -30,8 +31,8 @@
 	],
 	"scripts": {
 		"clean": "npx rimraf dist",
-		"prepublish": "yarn run clean",
-		"prepare": "transpile"
+		"build": "transpile",
+		"prepack": "yarn run clean && yarn run build"
 	},
 	"dependencies": {
 		"@automattic/popup-monitor": "^1.0.0"
diff --git a/packages/social-previews/jest.config.js b/packages/social-previews/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/social-previews/jest.config.js
+++ b/packages/social-previews/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/social-previews/package.json b/packages/social-previews/package.json
index 08354a496f60f..8d9445a075b36 100644
--- a/packages/social-previews/package.json
+++ b/packages/social-previews/package.json
@@ -4,6 +4,7 @@
 	"description": "A suite of components to generate previews for a post for both social and search engines",
 	"main": "dist/cjs/index.js",
 	"module": "dist/esm/index.js",
+	"calypso:src": "src/index.js",
 	"sideEffects": [
 		"*.css",
 		"*.scss"
@@ -34,8 +35,8 @@
 	],
 	"scripts": {
 		"clean": "npx rimraf dist",
-		"prepublish": "yarn run clean",
-		"prepare": "transpile && copy-assets"
+		"build": "transpile && copy-assets",
+		"prepack": "yarn run clean && yarn run build"
 	},
 	"dependencies": {
 		"@babel/runtime": "^7.11.1",
diff --git a/packages/tree-select/jest.config.js b/packages/tree-select/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/tree-select/jest.config.js
+++ b/packages/tree-select/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/tree-select/package.json b/packages/tree-select/package.json
index 2b60da2306081..3a435ee99cc3c 100644
--- a/packages/tree-select/package.json
+++ b/packages/tree-select/package.json
@@ -11,6 +11,7 @@
 	"license": "GPL-2.0-or-later",
 	"main": "dist/cjs/index.js",
 	"module": "dist/esm/index.js",
+	"calypso:src": "src/index.js",
 	"sideEffects": false,
 	"repository": {
 		"type": "git",
@@ -29,7 +30,7 @@
 	],
 	"scripts": {
 		"clean": "npx rimraf dist",
-		"prepublish": "yarn run clean",
-		"prepare": "transpile"
+		"build": "transpile",
+		"prepack": "yarn run clean && yarn run build"
 	}
 }
diff --git a/packages/viewport-react/jest.config.js b/packages/viewport-react/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/viewport-react/jest.config.js
+++ b/packages/viewport-react/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/viewport-react/package.json b/packages/viewport-react/package.json
index 391f3fa2fce8b..87a745534c773 100644
--- a/packages/viewport-react/package.json
+++ b/packages/viewport-react/package.json
@@ -4,6 +4,7 @@
 	"description": "React helpers for tracking viewport changes",
 	"main": "dist/cjs/index.js",
 	"module": "dist/esm/index.js",
+	"calypso:src": "src/index.js",
 	"sideEffects": false,
 	"repository": {
 		"type": "git",
@@ -30,8 +31,8 @@
 	},
 	"scripts": {
 		"clean": "npx rimraf dist",
-		"prepublish": "yarn run clean",
-		"prepare": "transpile"
+		"build": "transpile",
+		"prepack": "yarn run clean && yarn run build"
 	},
 	"publishConfig": {
 		"access": "public"
diff --git a/packages/viewport/jest.config.js b/packages/viewport/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/viewport/jest.config.js
+++ b/packages/viewport/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/viewport/package.json b/packages/viewport/package.json
index 5956fdbfe136a..f90bd3e844473 100644
--- a/packages/viewport/package.json
+++ b/packages/viewport/package.json
@@ -4,6 +4,7 @@
 	"description": "Vanilla helpers for tracking viewport changes",
 	"main": "dist/cjs/index.js",
 	"module": "dist/esm/index.js",
+	"calypso:src": "src/index.js",
 	"sideEffects": false,
 	"repository": {
 		"type": "git",
@@ -18,8 +19,8 @@
 	"homepage": "https://github.com/Automattic/wp-calypso/tree/HEAD/packages/viewport#readme",
 	"scripts": {
 		"clean": "npx rimraf dist",
-		"prepublish": "yarn run clean",
-		"prepare": "transpile"
+		"build": "transpile",
+		"prepack": "yarn run clean && yarn run build"
 	},
 	"publishConfig": {
 		"access": "public"
diff --git a/packages/webpack-config-flag-plugin/jest.config.js b/packages/webpack-config-flag-plugin/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/webpack-config-flag-plugin/jest.config.js
+++ b/packages/webpack-config-flag-plugin/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/webpack-inline-constant-exports-plugin/jest.config.js b/packages/webpack-inline-constant-exports-plugin/jest.config.js
index b94a8c8661cfe..ec0a18b144880 100644
--- a/packages/webpack-inline-constant-exports-plugin/jest.config.js
+++ b/packages/webpack-inline-constant-exports-plugin/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	preset: '@automattic/calypso-build',
 	rootDir: __dirname,
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/wp-babel-makepot/jest.config.js b/packages/wp-babel-makepot/jest.config.js
index 6e3acfa28109e..9d36966165669 100644
--- a/packages/wp-babel-makepot/jest.config.js
+++ b/packages/wp-babel-makepot/jest.config.js
@@ -2,4 +2,5 @@ module.exports = {
 	rootDir: __dirname,
 	testMatch: [ '<rootDir>/**/test/*.[jt]s?(x)', '!**/.eslintrc.*', '!**/examples/**' ],
 	cacheDirectory: '<rootDir>/../../.cache/jest',
+	resolver: '<rootDir>/../../test/module-resolver.js',
 };
diff --git a/packages/wpcom-proxy-request/package.json b/packages/wpcom-proxy-request/package.json
index a9874a9f3530f..7f96447d9886e 100644
--- a/packages/wpcom-proxy-request/package.json
+++ b/packages/wpcom-proxy-request/package.json
@@ -4,6 +4,7 @@
 	"description": "Proxied cookie-authenticated REST API requests to WordPress.com",
 	"main": "dist/cjs/index.js",
 	"module": "dist/esm/index.js",
+	"calypso:src": "src/index.js",
 	"sideEffects": false,
 	"keywords": [
 		"browser",
@@ -37,8 +38,8 @@
 	"types": "types",
 	"scripts": {
 		"clean": "npx rimraf dist",
-		"prepublish": "npm run clean",
-		"prepare": "transpile"
+		"build": "transpile",
+		"prepack": "yarn run clean && yarn run build"
 	},
 	"dependencies": {
 		"@babel/runtime": "^7.11.1",
diff --git a/packages/wpcom.js/package.json b/packages/wpcom.js/package.json
index 4d9fe4ecfae89..5854154679a82 100644
--- a/packages/wpcom.js/package.json
+++ b/packages/wpcom.js/package.json
@@ -4,12 +4,13 @@
 	"version": "6.0.0",
 	"main": "dist/cjs/index.js",
 	"module": "dist/esm/index.js",
+	"calypso:src": "src/index.js",
 	"author": "Automattic, Inc.",
 	"private": true,
 	"scripts": {
 		"clean": "npx rimraf dist",
-		"prepublish": "yarn run clean",
-		"prepare": "run-s build:modules build:bundle",
+		"build": "run-s build:modules build:bundle",
+		"prepack": "yarn run clean && yarn run build",
 		"build:modules": "transpile",
 		"build:bundle": "webpack --display errors-only"
 	},
@@ -34,7 +35,8 @@
 	],
 	"browser": {
 		"./dist/cjs/lib/util/fs.js": "./dist/cjs/lib/util/fs-browser.js",
-		"./dist/esm/lib/util/fs.js": "./dist/esm/lib/util/fs-browser.js"
+		"./dist/esm/lib/util/fs.js": "./dist/esm/lib/util/fs-browser.js",
+		"./src/lib/util/fs.js": "./src/lib/util/fs-browser.js"
 	},
 	"dependencies": {
 		"@babel/runtime": "^7.11.1",
diff --git a/test/client/jest.config.js b/test/client/jest.config.js
index a051255bd26c1..3f2921dedb4ca 100644
--- a/test/client/jest.config.js
+++ b/test/client/jest.config.js
@@ -12,6 +12,7 @@ module.exports = {
 	},
 	modulePaths: [ '<rootDir>/../test', '<rootDir>', '<rootDir>/extensions' ],
 	rootDir: '../../client',
+	resolver: '<rootDir>../test/module-resolver.js',
 	testEnvironment: 'node',
 	transformIgnorePatterns: [
 		'node_modules[\\/\\\\](?!flag-icon-css|redux-form|simple-html-tokenizer|draft-js|social-logos|gridicons|calypso)',
diff --git a/test/integration/jest.config.js b/test/integration/jest.config.js
index bf63aa86db00e..1666cfef2776d 100644
--- a/test/integration/jest.config.js
+++ b/test/integration/jest.config.js
@@ -5,6 +5,7 @@ module.exports = {
 	modulePaths: [ '<rootDir>/test', '<rootDir>/client', '<rootDir>/client/extensions' ],
 	rootDir: '../..',
 	testEnvironment: 'node',
+	resolver: '<rootDir>/test/module-resolver.js',
 	testMatch: [
 		'<rootDir>/bin/**/integration/*.[jt]s',
 		'<rootDir>/client/**/integration/*.[jt]s',
diff --git a/test/module-resolver.js b/test/module-resolver.js
new file mode 100644
index 0000000000000..97d84c0d22db8
--- /dev/null
+++ b/test/module-resolver.js
@@ -0,0 +1,32 @@
+/**
+ * Implements a custom resolver that uses `pkg['calypso:src']` isntead of `pkg.main` for packages from the monorepo.
+ *
+ * Doc: https://jestjs.io/docs/en/configuration#resolver-string
+ *
+ * Jest will call this method with the package to be resolved. We'll call back the default resolver but passing
+ * an extra `packageFilter`. The default resolver will call `resolve` (https://www.npmjs.com/package/resolve). That
+ * library will read `package.json` from the requested module and pass it through `packageFilter` to pre-process it
+ * before trying to read the entrypoint.
+ *
+ * If the requested package _name_ is one of the packages we have under `./packages`, we tell the resolver to use `pkg['calypso:src']`
+ * to read the main file.
+ *
+ * @param {string} request The package being requested
+ * @param {*} options Options for the resolver
+ */
+module.exports = ( request, options ) => {
+	return options.defaultResolver( request, {
+		...options,
+		packageFilter: ( pkg ) => {
+			//TODO: when Jest moves to resolver v2, this method will receive a second argument that points to the real package file (ie: no symlink)
+			//We can use it to determine if the package file is within the repo
+			if ( 'calypso:src' in pkg ) {
+				return {
+					...pkg,
+					main: pkg[ 'calypso:src' ] || pkg.module,
+				};
+			}
+			return pkg;
+		},
+	} );
+};
diff --git a/test/server/jest.config.js b/test/server/jest.config.js
index df1d95e59a5a6..0fc4889a67bff 100644
--- a/test/server/jest.config.js
+++ b/test/server/jest.config.js
@@ -4,6 +4,7 @@ module.exports = {
 	rootDir: '../../client',
 	roots: [ '<rootDir>/server' ],
 	testEnvironment: 'node',
+	resolver: '<rootDir>/../test/module-resolver.js',
 	transform: {
 		'\\.[jt]sx?$': 'babel-jest',
 		'\\.(gif|jpg|jpeg|png|svg|scss|sass|css)$': require.resolve(