diff --git a/.github/workflows/copilot-setup-steps.yml b/.github/workflows/copilot-setup-steps.yml
index 473f0bfc8b..e4923fd6bc 100644
--- a/.github/workflows/copilot-setup-steps.yml
+++ b/.github/workflows/copilot-setup-steps.yml
@@ -62,5 +62,13 @@ jobs:
         run: composer install --no-interaction --no-progress
       - name: Build assets
         run: npm run build
-      - name: Install WordPress and start environment
-        run: npm run wp-env start
+      - name: Install WordPress and start environments
+        run: |
+          set -euo pipefail
+          trap 'kill 0' ERR
+
+          npm run wp-env start &
+          npm run wp-env-test start &
+
+          wait -n
+          wait -n
diff --git a/.github/workflows/e2e-test.yml b/.github/workflows/e2e-test.yml
index a7e864803e..df1c122803 100644
--- a/.github/workflows/e2e-test.yml
+++ b/.github/workflows/e2e-test.yml
@@ -57,7 +57,7 @@ jobs:
         run: npx playwright install chromium --with-deps
 
       - name: Install WordPress
-        run: npm run wp-env start
+        run: npm run wp-env-test start
 
       - name: Run tests
         env:
diff --git a/.github/workflows/php-test-plugins.yml b/.github/workflows/php-test-plugins.yml
index 25324e324e..294848e6d3 100644
--- a/.github/workflows/php-test-plugins.yml
+++ b/.github/workflows/php-test-plugins.yml
@@ -85,12 +85,12 @@ jobs:
       - name: Install WordPress
         run: |
           if [ "${{ matrix.coverage }}" == "true" ]; then
-            npm run wp-env start -- --xdebug=coverage
+            npm run wp-env-test start -- --xdebug=coverage
           else
-            npm run wp-env start
+            npm run wp-env-test start
           fi
       - name: Composer Install
-        run: npm run wp-env run tests-cli -- --env-cwd="wp-content/plugins/$(basename $(pwd))" composer install --no-interaction --no-progress
+        run: npm run wp-env-test run cli -- --env-cwd="wp-content/plugins/$(basename $(pwd))" composer install --no-interaction --no-progress
       - name: Update Composer Dependencies
         run: composer update --with-all-dependencies --no-interaction --no-progress
       - name: Install PHPUnit
diff --git a/.gitignore b/.gitignore
index 4f52de6bab..5b8808d022 100644
--- a/.gitignore
+++ b/.gitignore
@@ -32,6 +32,7 @@ nbproject/
 
 build
 .wp-env.override.json
+.wp-env.test.override.json
 *.min.js
 *.min.css
 *.asset.php
diff --git a/.wp-env.json b/.wp-env.json
index 7e0511af4c..2dbd5c790a 100644
--- a/.wp-env.json
+++ b/.wp-env.json
@@ -1,5 +1,6 @@
 {
 	"$schema": "https://schemas.wp.org/trunk/wp-env.json",
+	"testsEnvironment": false,
 	"core": null,
 	"plugins": [
 		"./plugins/optimization-detective",
@@ -13,19 +14,7 @@
 		"./plugins/web-worker-offloading",
 		"./plugins/webp-uploads"
 	],
-	"env": {
-		"development": {
-			"config": {
-				"WP_DEVELOPMENT_MODE": "plugin"
-			}
-		},
-		"tests": {
-			"config": {
-				"FS_METHOD": "direct"
-			},
-			"mappings": {
-				"wp-content/plugins/performance": "."
-			}
-		}
+	"config": {
+		"WP_DEVELOPMENT_MODE": "plugin"
 	}
 }
diff --git a/.wp-env.test.json b/.wp-env.test.json
new file mode 100644
index 0000000000..6df028964c
--- /dev/null
+++ b/.wp-env.test.json
@@ -0,0 +1,26 @@
+{
+	"$schema": "https://schemas.wp.org/trunk/wp-env.json",
+	"testsEnvironment": false,
+	"port": 8889,
+	"core": null,
+	"plugins": [
+		"./plugins/optimization-detective",
+		"./plugins/auto-sizes",
+		"./plugins/dominant-color-images",
+		"./plugins/embed-optimizer",
+		"./plugins/image-prioritizer",
+		"./plugins/performance-lab",
+		"./plugins/speculation-rules",
+		"./plugins/view-transitions",
+		"./plugins/web-worker-offloading",
+		"./plugins/webp-uploads"
+	],
+	"config": {
+		"WP_DEBUG": false,
+		"SCRIPT_DEBUG": false,
+		"FS_METHOD": "direct"
+	},
+	"mappings": {
+		"wp-content/plugins/performance": "."
+	}
+}
diff --git a/AGENTS.md b/AGENTS.md
index 23e8aa05b9..0a973ee2fc 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -38,13 +38,23 @@ This is a monorepo for the WordPress Performance Team, containing a collection o
 
 ### Running a Local Environment
 
-This project uses `@wordpress/env` to create a local development environment.
+This project uses `@wordpress/env` to create local environments. There are two,
+each defined by its own config file and running as fully isolated containers:
 
-* Check if the environment is already running: `npm run wp-env status`
-* Start the environment: `npm run wp-env start`
-* Stop the environment: `npm run wp-env stop`
+* **Development** (for browsing) — `.wp-env.json`, at `http://localhost:8888`.
+* **Tests** (for PHPUnit and E2E) — `.wp-env.test.json`, at `http://localhost:8889`.
 
-The environment will by default be located at `http://localhost:8888` but this can be overridden by `.wp-env.override.json`.
+The `wp-env-test` script is shorthand for `wp-env --config=.wp-env.test.json`.
+
+* Check if the environments are running: `npm run wp-env status` / `npm run wp-env-test status`
+* Start the environments: `npm run wp-env start` / `npm run wp-env-test start`
+* Stop the environments: `npm run wp-env stop` / `npm run wp-env-test stop`
+
+The `test-php*` and `test-e2e*` scripts run against the tests environment, so
+start it with `npm run wp-env-test start` before running them.
+
+Each environment can be overridden locally (these files are git-ignored):
+`.wp-env.override.json` for development and `.wp-env.test.override.json` for tests.
 
 ## Code Style
 
diff --git a/bin/test-php-watch.sh b/bin/test-php-watch.sh
index 7ddbe3c966..1dbfd13e2d 100755
--- a/bin/test-php-watch.sh
+++ b/bin/test-php-watch.sh
@@ -29,5 +29,5 @@ while true; do
 	echo "Running phpunit tests for $(tput bold)$plugin_slug$(tput sgr0):"
 	# TODO: Interrupt when a change is made while running tests or re-run if change made since tests started running.
 	# Note: This is calling phpunit directly and not the composer script due to extra noise it outputs.
-	npm run wp-env --silent -- run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance -- vendor/bin/phpunit --testsuite "$plugin_slug" "$@"
+	npm run wp-env-test --silent -- run cli --env-cwd=/var/www/html/wp-content/plugins/performance -- vendor/bin/phpunit --testsuite "$plugin_slug" "$@"
 done
diff --git a/package.json b/package.json
index cfd5dcd534..fad9326fec 100644
--- a/package.json
+++ b/package.json
@@ -65,31 +65,32 @@
 		"test-e2e:debug": "wp-scripts test-playwright --config tools/e2e/playwright.config.ts --ui",
 		"test-e2e:auto-sizes": "wp-scripts test-playwright --config tools/e2e/playwright.config.ts --project=auto-sizes",
 		"lint-php": "composer lint:all",
-		"test-php": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:plugins",
+		"test-php": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:plugins",
 		"test-php-watch": "./bin/test-php-watch.sh",
-		"test-php-multisite": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:plugins",
-		"test-php:performance-lab": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:performance-lab",
-		"test-php:auto-sizes": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:auto-sizes",
-		"test-php:dominant-color-images": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:dominant-color-images",
-		"test-php:embed-optimizer": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:embed-optimizer",
-		"test-php:image-prioritizer": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:image-prioritizer",
-		"test-php:optimization-detective": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:optimization-detective",
-		"test-php:speculation-rules": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:speculation-rules",
-		"test-php:view-transitions": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:view-transitions",
-		"test-php:web-worker-offloading": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:web-worker-offloading",
-		"test-php:webp-uploads": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:webp-uploads",
-		"test-php-multisite:performance-lab": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:performance-lab",
-		"test-php-multisite:auto-sizes": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:auto-sizes",
-		"test-php-multisite:dominant-color-images": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:dominant-color-images",
-		"test-php-multisite:embed-optimizer": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:embed-optimizer",
-		"test-php-multisite:image-prioritizer": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:image-prioritizer",
-		"test-php-multisite:optimization-detective": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:optimization-detective",
-		"test-php-multisite:speculation-rules": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:speculation-rules",
-		"test-php-multisite:view-transitions": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:view-transitions",
-		"test-php-multisite:web-worker-offloading": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:web-worker-offloading",
-		"test-php-multisite:webp-uploads": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:webp-uploads",
+		"test-php-multisite": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:plugins",
+		"test-php:performance-lab": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:performance-lab",
+		"test-php:auto-sizes": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:auto-sizes",
+		"test-php:dominant-color-images": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:dominant-color-images",
+		"test-php:embed-optimizer": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:embed-optimizer",
+		"test-php:image-prioritizer": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:image-prioritizer",
+		"test-php:optimization-detective": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:optimization-detective",
+		"test-php:speculation-rules": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:speculation-rules",
+		"test-php:view-transitions": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:view-transitions",
+		"test-php:web-worker-offloading": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:web-worker-offloading",
+		"test-php:webp-uploads": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:webp-uploads",
+		"test-php-multisite:performance-lab": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:performance-lab",
+		"test-php-multisite:auto-sizes": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:auto-sizes",
+		"test-php-multisite:dominant-color-images": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:dominant-color-images",
+		"test-php-multisite:embed-optimizer": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:embed-optimizer",
+		"test-php-multisite:image-prioritizer": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:image-prioritizer",
+		"test-php-multisite:optimization-detective": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:optimization-detective",
+		"test-php-multisite:speculation-rules": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:speculation-rules",
+		"test-php-multisite:view-transitions": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:view-transitions",
+		"test-php-multisite:web-worker-offloading": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:web-worker-offloading",
+		"test-php-multisite:webp-uploads": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:webp-uploads",
 		"update-test-case-snapshots": "bin/update-test-case-snapshots.sh",
 		"wp-env": "wp-env",
+		"wp-env-test": "wp-env --config=.wp-env.test.json",
 		"prepare": "husky"
 	}
 }