diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 56d6af2da..61b13f1e3 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -37,7 +37,7 @@ jobs:
         with:
           php-version: ${{ matrix.php-version }}
           coverage: ${{ matrix.coverage-driver }}
-          ini-values: memory_limit=512M
+          ini-values: memory_limit=512M, xdebug.mode=off
           tools: composer:v2
 
       - name: Get composer cache directory
diff --git a/devTools/Dockerfile b/devTools/Dockerfile
index c2d44757f..c940361ef 100644
--- a/devTools/Dockerfile
+++ b/devTools/Dockerfile
@@ -30,7 +30,7 @@ RUN apk add --no-cache \
         zip
 
 COPY --from=composer:2 /usr/bin/composer /usr/bin/composer
-COPY memory-limit.ini xdebug-coverage.ini ${PHP_INI_DIR}/conf.d/
+COPY memory-limit.ini xdebug.ini ${PHP_INI_DIR}/conf.d/
 
 RUN adduser -h /opt/infection -s /bin/bash -D infection
 
diff --git a/devTools/phpstan-src.neon b/devTools/phpstan-src.neon
index e501eee69..7a709b716 100644
--- a/devTools/phpstan-src.neon
+++ b/devTools/phpstan-src.neon
@@ -28,6 +28,12 @@ parameters:
             path: '../src/Container.php'
             message: '#^Method Infection\\Container::get.*\(\) should return .* but returns object\.$#'
             count: 1
+        -
+            path: '../src/Process/OriginalPhpProcess.php'
+            message: '#Function ini_get is unsafe to use#'
+        -
+            path: '../src/TestFramework/Coverage/CoverageChecker.php'
+            message: '#Function ini_get is unsafe to use#'
     level: max
     paths:
         - ../src
diff --git a/devTools/phpstan-tests.neon b/devTools/phpstan-tests.neon
index a5a2ae67f..1a1ffef74 100644
--- a/devTools/phpstan-tests.neon
+++ b/devTools/phpstan-tests.neon
@@ -26,6 +26,9 @@ parameters:
             message: "#^Variable method call on Infection\\\\Tests\\\\FileSystem\\\\Finder\\\\MockVendor\\.$#"
             count: 1
             path: ../tests/phpunit/FileSystem/Finder/TestFrameworkFinderTest.php
+        -
+            message: '#Function ini_get is unsafe to use#'
+            path: ../tests/phpunit/Process/OriginalPhpProcessTest.php
     level: 4
     paths:
         - ../tests/phpunit
diff --git a/devTools/xdebug-coverage.ini b/devTools/xdebug-coverage.ini
deleted file mode 100644
index cea362e77..000000000
--- a/devTools/xdebug-coverage.ini
+++ /dev/null
@@ -1 +0,0 @@
-xdebug.mode=coverage
diff --git a/devTools/xdebug.ini b/devTools/xdebug.ini
new file mode 100644
index 000000000..9d4987171
--- /dev/null
+++ b/devTools/xdebug.ini
@@ -0,0 +1 @@
+xdebug.mode=off
diff --git a/src/Process/OriginalPhpProcess.php b/src/Process/OriginalPhpProcess.php
index b110563b2..09b62f855 100644
--- a/src/Process/OriginalPhpProcess.php
+++ b/src/Process/OriginalPhpProcess.php
@@ -35,7 +35,12 @@
 
 namespace Infection\Process;
 
+use function array_merge;
 use Composer\XdebugHandler\PhpConfig;
+use Composer\XdebugHandler\XdebugHandler;
+use function extension_loaded;
+use function ini_get as ini_get_unsafe;
+use const PHP_SAPI;
 use Symfony\Component\Process\Process;
 
 /**
@@ -57,8 +62,37 @@ public function start(?callable $callback = null, ?array $env = null): void
         $phpConfig = new PhpConfig();
         $phpConfig->useOriginal();
 
+        if (self::shallExtendEnvironmentWithXdebugMode()) {
+            $env = array_merge($env ?? [], [
+                'XDEBUG_MODE' => 'coverage',
+            ]);
+        }
+
         parent::start($callback, $env ?? []);
 
         $phpConfig->usePersistent();
     }
+
+    private static function shallExtendEnvironmentWithXdebugMode(): bool
+    {
+        // Most obvious cases when we don't want to add XDEBUG_MODE=coverage:
+        // - PCOV is loaded
+        // - PHPDBG is in use
+        if (extension_loaded('pcov') || PHP_SAPI === 'phpdbg') {
+            return false;
+        }
+
+        // We also do not need to add XDEBUG_MODE for Xdebug <=3:
+        // it had coverage enabled at all times and it didn't have `xdebug.mode`.
+        if (ini_get_unsafe('xdebug.mode') === false) {
+            return false;
+        }
+
+        // The last case: Xdebug 3+ running inactive.
+        return ini_get_unsafe('xdebug.mode') === '';
+
+        // Why going through all the trouble above? We don't want to enable
+        // Xdebug when there are more compelling choices. In the end the user is
+        // still in control: they can provide XDEBUG_MODE=coverage on their own.
+    }
 }
diff --git a/src/TestFramework/Coverage/CoverageChecker.php b/src/TestFramework/Coverage/CoverageChecker.php
index b2fb2cf62..7266d9bca 100644
--- a/src/TestFramework/Coverage/CoverageChecker.php
+++ b/src/TestFramework/Coverage/CoverageChecker.php
@@ -42,6 +42,7 @@
 use Infection\FileSystem\Locator\FileNotFound;
 use Infection\TestFramework\Coverage\JUnit\JUnitReportLocator;
 use Infection\TestFramework\Coverage\XmlReport\IndexXmlCoverageLocator;
+use function ini_get as ini_get_unsafe;
 use const PHP_EOL;
 use const PHP_SAPI;
 use function Safe\preg_match;
@@ -175,6 +176,7 @@ private function hasCoverageGeneratorEnabled(): bool
             || XdebugHandler::isXdebugActive()
             || extension_loaded('pcov')
             || XdebugHandler::getSkippedVersion() !== ''
+            || ini_get_unsafe('xdebug.mode') !== false
             || $this->isXdebugIncludedInInitialTestPhpOptions()
             || $this->isPcovIncludedInInitialTestPhpOptions();
     }
diff --git a/tests/e2e/Exec_Path/run_tests.bash b/tests/e2e/Exec_Path/run_tests.bash
index 6d3ad8355..9524dc1d8 100755
--- a/tests/e2e/Exec_Path/run_tests.bash
+++ b/tests/e2e/Exec_Path/run_tests.bash
@@ -35,6 +35,7 @@ if [ "$DRIVER" = "phpdbg" ]
 then
     PATH=$PATH:bin phpdbg -qrr vendor/bin/phpunit --coverage-xml=coverage/coverage-xml --log-junit=coverage/junit.xml
 else
+    export XDEBUG_MODE=coverage
     PATH=$PATH:bin php vendor/bin/phpunit --coverage-xml=coverage/coverage-xml --log-junit=coverage/junit.xml
 fi
 
diff --git a/tests/e2e/Provide_Existing_Coverage/run_tests.bash b/tests/e2e/Provide_Existing_Coverage/run_tests.bash
index 44679065f..37394ee54 100755
--- a/tests/e2e/Provide_Existing_Coverage/run_tests.bash
+++ b/tests/e2e/Provide_Existing_Coverage/run_tests.bash
@@ -9,6 +9,7 @@ if [ "$DRIVER" = "phpdbg" ]
 then
     phpdbg -qrr $PHPUNIT
 else
+    export XDEBUG_MODE=coverage
     php $PHPUNIT
 fi
 
diff --git a/tests/e2e/Skip_Initial_Tests/run_tests.bash b/tests/e2e/Skip_Initial_Tests/run_tests.bash
index 035817778..f86032e24 100755
--- a/tests/e2e/Skip_Initial_Tests/run_tests.bash
+++ b/tests/e2e/Skip_Initial_Tests/run_tests.bash
@@ -9,6 +9,7 @@ if [ "$DRIVER" = "phpdbg" ]
 then
     phpdbg -qrr $PHPUNIT
 else
+    export XDEBUG_MODE=coverage
     php $PHPUNIT
 fi
 
diff --git a/tests/phpunit/AutoReview/ProjectCode/ProjectCodeProvider.php b/tests/phpunit/AutoReview/ProjectCode/ProjectCodeProvider.php
index fac494948..62b91da45 100644
--- a/tests/phpunit/AutoReview/ProjectCode/ProjectCodeProvider.php
+++ b/tests/phpunit/AutoReview/ProjectCode/ProjectCodeProvider.php
@@ -64,7 +64,6 @@
 use Infection\Mutant\DetectionStatus;
 use Infection\Mutation\MutationAttributeKeys;
 use Infection\Mutator\NodeMutationGenerator;
-use Infection\Process\OriginalPhpProcess;
 use Infection\Process\Runner\IndexedProcessBearer;
 use Infection\Process\ShellCommandLineExecutor;
 use Infection\TestFramework\AdapterInstaller;
@@ -100,7 +99,6 @@ final class ProjectCodeProvider
         RunCommand::class,
         Application::class,
         ProgressFormatter::class,
-        OriginalPhpProcess::class,
         ComposerExecutableFinder::class,
         StrykerCurlClient::class,
         MutationGeneratingConsoleLoggerSubscriber::class,
diff --git a/tests/phpunit/Console/E2ETest.php b/tests/phpunit/Console/E2ETest.php
index 71179698d..393e5ac46 100644
--- a/tests/phpunit/Console/E2ETest.php
+++ b/tests/phpunit/Console/E2ETest.php
@@ -145,7 +145,7 @@ public function test_it_runs_on_itself(): void
         }
 
         $output = $this->runInfection(self::EXPECT_SUCCESS, [
-            '--test-framework-options="--exclude-group=' . self::EXCLUDED_GROUP . '"',
+            '--test-framework-options=--exclude-group=' . self::EXCLUDED_GROUP,
         ]);
 
         $this->assertMatchesRegularExpression('/\d+ mutations were generated/', $output);
@@ -331,6 +331,10 @@ private function runInfection(int $expectedExitCode, array $argvExtra = []): str
             $this->markTestSkipped("Infection from within PHPUnit won't run without Xdebug or PHPDBG");
         }
 
+        if ('\\' === DIRECTORY_SEPARATOR) {
+            $this->markTestSkipped('This test can be unstable on Windows');
+        }
+
         /*
          * @see https://github.com/sebastianbergmann/php-code-coverage/blob/7743bbcfff2a907e9ee4a25be13d0f8ec5e73800/src/Driver/PHPDBG.php#L24
          */
diff --git a/tests/phpunit/Process/OriginalPhpProcessTest.php b/tests/phpunit/Process/OriginalPhpProcessTest.php
new file mode 100644
index 000000000..6a7077e5c
--- /dev/null
+++ b/tests/phpunit/Process/OriginalPhpProcessTest.php
@@ -0,0 +1,83 @@
+<?php
+/**
+ * This code is licensed under the BSD 3-Clause License.
+ *
+ * Copyright (c) 2017, Maks Rafalko
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * * Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ *
+ * * Neither the name of the copyright holder nor the names of its
+ *   contributors may be used to endorse or promote products derived from
+ *   this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+declare(strict_types=1);
+
+namespace Infection\Tests\Process;
+
+use function extension_loaded;
+use Infection\Process\OriginalPhpProcess;
+use function ini_get as ini_get_unsafe;
+use const PHP_SAPI;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Process\Process;
+
+final class OriginalPhpProcessTest extends TestCase
+{
+    public function test_it_extends_symfony_process(): void
+    {
+        $process = new OriginalPhpProcess([]);
+
+        $this->assertInstanceOf(Process::class, $process);
+    }
+
+    public function test_it_takes_command_line(): void
+    {
+        $process = new OriginalPhpProcess(['foo']);
+        $this->assertStringContainsString('foo', $process->getCommandLine());
+    }
+
+    /**
+     * @group integration
+     */
+    public function test_it_injects_xdebug_env_vars(): void
+    {
+        $process = new OriginalPhpProcess(['env']);
+        $process->run(null, ['TESTING' => 'test']);
+
+        if (
+            !extension_loaded('pcov') &&
+            PHP_SAPI !== 'phpdbg' &&
+            (
+                ini_get_unsafe('xdebug.mode') === false ||
+                ini_get_unsafe('xdebug.mode') === ''
+            )
+        ) {
+            $this->assertStringContainsString('XDEBUG_MODE=coverage', $process->getOutput());
+        } else {
+            $this->assertStringNotContainsString('XDEBUG_MODE=coverage', $process->getOutput());
+        }
+
+        $this->assertStringContainsString('TESTING=test', $process->getOutput());
+    }
+}