diff --git a/.gitattributes b/.gitattributes
index db8a36b2..4560403d 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -2,3 +2,4 @@
 /.editorconfig export-ignore
 /.gitattributes export-ignore
 /.github export-ignore
+/package.json export-ignore
diff --git a/.github/tests/wpcm.spec.ts b/.github/tests/wpcm.spec.ts
new file mode 100644
index 00000000..de8861e3
--- /dev/null
+++ b/.github/tests/wpcm.spec.ts
@@ -0,0 +1,65 @@
+import { test, expect } from "@playwright/test";
+
+const exampleArticle = "Hello world!";
+const siteTitle = "WPCM Playwright Tests";
+const siteUrl = process.env.SITE_URL || "https://dev-wpcm-playwright-tests.pantheonsite.io";
+
+test("homepage loads and contains example content", async ({ page }) => {
+  await page.goto(siteUrl);
+  await expect(page).toHaveTitle(siteTitle);
+  await expect(page.getByText(exampleArticle)).toHaveText(exampleArticle);
+});
+
+test("WP REST API is accessible", async ({ request }) => {
+  const apiRoot = await request.get(`${siteUrl}/wp-json`);
+  expect(apiRoot.ok()).toBeTruthy();
+});
+
+test("Hello World post is accessible", async ({ page }) => {
+  await page.goto(`${siteUrl}/hello-world/'`);
+  await expect(page).toHaveTitle(`${exampleArticle} – ${siteTitle}`);
+  // Locate the element containing the desired text
+  const welcomeText = page.locator('text=Welcome to WordPress');
+  await expect(welcomeText).toContainText('Welcome to WordPress');
+});
+
+test("validate core resource URLs", async ({ request }) => {
+  const coreResources = [
+    'wp-includes/js/dist/interactivity.min.js',
+    'wp-includes/css/dist/editor.min.css',
+  ];
+
+  for ( const resource of coreResources ) {
+    const resourceUrl = `${siteUrl}/wp/${resource}`;
+    const response = await request.get(resourceUrl);
+    await expect(response).toBeTruthy();
+  }
+});
+
+test("graphql is able to access hello world post", async ({ request }) => {
+  const query = `
+    query {
+      posts(where: { search: "${exampleArticle}" }) {
+        edges {
+          node {
+            title
+          }
+        }
+      }
+    }
+  `;
+
+  const response = await request.post(`${siteUrl}/wp/graphql`, {
+    data: {
+      query: query
+    },
+    headers: {
+      'Content-Type': 'application/json'
+    }
+  });
+
+  const responseBody = await response.json();
+
+  expect(responseBody.data.posts.edges.length).toBeGreaterThan(0);
+  expect(responseBody.data.posts.edges[0].node.title).toBe(exampleArticle);
+});
diff --git a/.github/workflows/playwright.yml b/.github/workflows/playwright.yml
new file mode 100644
index 00000000..f3d7442c
--- /dev/null
+++ b/.github/workflows/playwright.yml
@@ -0,0 +1,113 @@
+name: WordPress (Composer Managed) Playwright Tests
+on:
+  pull_request:
+    types:
+      - opened
+      - reopened
+      - synchronize
+      - ready_for_review
+
+permissions:
+    contents: write
+
+jobs:
+  playwright:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Generate lock files
+        run: |
+          npm install --package-lock-only
+
+      - name: Set up cache for dependencies
+        uses: actions/cache@v4
+        id: cache
+        with:
+          path: |
+            ~/.composer/cache
+            ./vendor
+            ~/.npm
+            ./node_modules
+          key: ${{ runner.os }}-deps-${{ hashFiles( '**/composer.json', '**/package-lock.json' ) }}
+          restore-keys: ${{ runner.os }}-deps-
+
+      - name: Install Composer dependencies
+        if: steps.cache.outputs.cache-hit != true
+        run: composer update --no-progress --prefer-dist --optimize-autoloader
+
+      - name: Install NPM dependencies
+        if: steps.cache.outputs.cache-hit != true
+        run: npm ci
+
+      - name: Install Playwright Browsers
+        run: npx playwright install --with-deps
+
+      - name: Install SSH keys
+        uses: webfactory/ssh-agent@v0.9.0
+        with:
+          ssh-private-key: ${{ secrets.SSH_PRIVATE_KEY }}
+
+      - name: Get latest Terminus release
+        uses: pantheon-systems/terminus-github-actions@v1
+        with:
+          pantheon-machine-token: ${{ secrets.TERMINUS_TOKEN }}
+      - name: Validate Pantheon Host Key
+        run: |
+          echo "Host *.drush.in HostKeyAlgorithms +ssh-rsa" >> ~/.ssh/config
+          echo "Host *.drush.in PubkeyAcceptedKeyTypes +ssh-rsa" >> ~/.ssh/config
+          echo "StrictHostKeyChecking no" >> ~/.ssh/config
+      - name: Log into Terminus
+        run: |
+          terminus auth:login --machine-token=${{ secrets.TERMINUS_TOKEN }}
+
+      - name: Create Site
+        run: |
+          if terminus site:info wpcm-playwright-tests; then
+            echo "Test site already exists, skipping site creation."
+            # If the site exists already, we should switch it to git mode.
+            terminus connection:set wpcm-playwright-tests.dev git -y
+          else
+            terminus site:create wpcm-playwright-tests 'WordPress (Composer Managed) Playwright Test Site' 'WordPress (Composer Managed)' --org=5ae1fa30-8cc4-4894-8ca9-d50628dcba17
+          fi
+
+      - name: Clone the site locally and copy PR updates
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          git config --global user.email "cms-platform+sage-testing@pantheon.io"
+          git config --global user.name "Pantheon WPCM Bot"
+          PR_NUMBER=$(echo ${{ github.event.pull_request.number }})
+          echo "Pull Request Number: ${PR_NUMBER}"
+          COMMIT_MSG=$(gh pr view ${PR_NUMBER} --json commits --jq '.commits[-1] | "\(.messageHeadline) \(.messageBody)"')
+          echo "Commit Message: ${COMMIT_MSG}"
+          terminus local:clone wpcm-playwright-tests
+          cd ~/pantheon-local-copies/wpcm-playwright-tests
+          rsync -a --exclude='.git' ${{ github.workspace }}/ .
+          git add -A
+          git commit -m "Update to latest commit: ${COMMIT_MSG}" || true
+          git push origin master || true
+
+      - name: Status Check
+        run: terminus wp wpcm-playwright-tests.dev -- cli info
+
+      - name: Install WordPress
+        run: |
+          terminus wp wpcm-playwright-tests.dev -- core install --title='WPCM Playwright Tests' --admin_user=wpcm --admin_email=test@dev.null
+          terminus wp wpcm-playwright-tests.dev -- option update permalink_structure '/%postname%/'
+          terminus wp wpcm-playwright-tests.dev -- rewrite flush
+          terminus wp wpcm-playwright-tests.dev -- cache flush
+
+      - name: Install WP GraphQL
+        run: |
+          terminus workflow:wait wpcm-playwright-tests.dev
+          terminus connection:set wpcm-playwright-tests.dev sftp
+          terminus wp wpcm-playwright-tests.dev -- plugin install --activate wp-graphql
+
+      - name: Run Playwright Tests
+        run: npm run test .github/tests/wpcm.spec.ts
+
+      - name: Delete Site
+        if: success()
+        run: terminus site:delete wpcm-playwright-tests -y
diff --git a/package.json b/package.json
new file mode 100644
index 00000000..3842ab81
--- /dev/null
+++ b/package.json
@@ -0,0 +1,12 @@
+{
+  "name": "@pantheon-systems/wordpress-composer-managed",
+  "version": "1.31.0",
+  "description": "Automated testing for WordPress (Composer Managed).",
+  "scripts": {
+    "test": "playwright test --trace on",
+    "report": "playwright show-report"
+  },
+  "devDependencies": {
+    "@playwright/test": "^1.28.0"
+  }
+}
diff --git a/upstream-configuration/scripts/ComposerScripts.php b/upstream-configuration/scripts/ComposerScripts.php
index 07cb923e..7d6828de 100644
--- a/upstream-configuration/scripts/ComposerScripts.php
+++ b/upstream-configuration/scripts/ComposerScripts.php
@@ -55,9 +55,9 @@ public static function applyComposerJsonUpdates(Event $event)
         // is the same as the Pantheon PHP version (which is only major.minor).
         // If they do not match, force an update to the platform PHP version. If they
         // have the same major.minor version, then
-        $platformPhpVersion = static::getCurrentPlatformPhp($event);
-        $pantheonPhpVersion = static::getPantheonPhpVersion($event);
-        $updatedPlatformPhpVersion = static::bestPhpPatchVersion($pantheonPhpVersion);
+        $platformPhpVersion = static::getCurrentPlatformPhp($event) ?? '';
+        $pantheonPhpVersion = static::getPantheonPhpVersion($event) ?? '';
+        $updatedPlatformPhpVersion = static::bestPhpPatchVersion($pantheonPhpVersion) ?? '';
         if ((substr($platformPhpVersion, 0, strlen($pantheonPhpVersion)) != $pantheonPhpVersion) && !empty($updatedPlatformPhpVersion)) {
             $io->write("<info>Setting platform.php from '$platformPhpVersion' to '$updatedPlatformPhpVersion' to conform to pantheon php version.</info>");
             $composerJson['config']['platform']['php'] = $updatedPlatformPhpVersion;
diff --git a/web/app/mu-plugins/filters.php b/web/app/mu-plugins/filters.php
index bcaedb38..b9b3fa7d 100644
--- a/web/app/mu-plugins/filters.php
+++ b/web/app/mu-plugins/filters.php
@@ -96,6 +96,28 @@ function fix_core_resource_urls( string $url ) : string {
 	}
 }
 
+/**
+ * Prepopulate GraphQL endpoint URL with default value if unset.
+ * This will ensure that the URL is not changed from /wp/graphql to /graphql by our other filtering unless that's what the user wants.
+ *
+ * @since 1.1.0
+ */
+function prepopulate_graphql_endpoint_url() {
+	$options = get_option( 'graphql_general_settings' );
+
+    // Bail early if options have already been set.
+    if ( $options ) {
+        return;
+    }
+
+    $options = [];
+	$site_path = site_url();
+    $endpoint = ( ! empty( $site_path ) || strpos( $site_path, 'wp' ) !== false ) ? 'graphql' : 'wp/graphql';
+    $options['graphql_endpoint'] = $endpoint;
+    update_option( 'graphql_general_settings', $options );
+}
+add_action( 'graphql_init', __NAMESPACE__ . '\\prepopulate_graphql_endpoint_url' );
+
 /**
  * Drop the /wp, if it exists, from URLs on the main site (single site or multisite).
  *
@@ -106,6 +128,15 @@ function fix_core_resource_urls( string $url ) : string {
  * @return string The filtered URL.
  */
 function adjust_main_site_urls( string $url ) : string {
+	if ( doing_action( 'graphql_init' ) ) {
+		return $url;
+	}
+
+	// Explicit handling for /wp/graphql
+	if ( strpos( $url, '/graphql' ) !== false ) {
+		return $url;
+	}
+
 	// If this is the main site, drop the /wp.
 	if ( is_main_site() && ! __is_login_url( $url ) ) {
 		$url = str_replace( '/wp/', '/', $url );
@@ -157,11 +188,11 @@ function __is_login_url( string $url ) : bool {
 	}
 
 	// Check if the URL is a login or admin page
-	if (strpos($url, 'wp-login') !== false || strpos($url, 'wp-admin') !== false) {
+	if ( strpos( $url, 'wp-login' ) !== false || strpos($url, 'wp-admin' ) !== false) {
 		return true;
 	}
 
-	return false
+	return false;
 }
 
 /**
@@ -172,15 +203,31 @@ function __is_login_url( string $url ) : bool {
  * @return string The normalized URL.
  */
 function __normalize_wp_url( string $url ): string {
-    $scheme = parse_url( $url, PHP_URL_SCHEME );
-    $scheme_with_separator = $scheme ? $scheme . '://' : '';
+	// Parse the URL into components.
+	$parts = parse_url( $url );
 
-    // Remove the scheme from the URL if it exists.
-    $remaining_url = $scheme ? substr( $url, strlen($scheme_with_separator ) ) : $url;
+	// Normalize the URL to remove any double slashes.
+	if ( isset( $parts['path'] ) ) {
+		$parts['path'] = preg_replace( '#/+#', '/', $parts['path'] );
+	}
 
-    // Normalize the remaining URL to remove any double slashes.
-    $normalized_url = str_replace( '//', '/', $remaining_url );
+	// Rebuild and return the full normalized URL.
+	return __rebuild_url_from_parts( $parts );
+}
 
-    // Reconstruct and return the full normalized URL.
-    return $scheme_with_separator . $normalized_url;
+/**
+ * Rebuild parsed URL from parts.
+ *
+ * @since 1.1.0
+ * @param array $parts URL parts from parse_url.
+ * @return string Re-parsed URL.
+ */
+function __rebuild_url_from_parts( array $parts ) : string {
+	return trailingslashit(
+		( isset( $parts['scheme'] ) ? "{$parts['scheme']}:" : '' ) .
+        ( isset( $parts['host'] ) ? "{$parts['host']}" : '' ) .
+		( isset( $parts['path'] ) ? untrailingslashit( "{$parts['path']}" ) : '' ) .
+		( isset( $parts['query'] ) ? str_replace( '/', '', "?{$parts['query']}" ) : '' ) .
+		( isset( $parts['fragment'] ) ? str_replace( '/', '', "#{$parts['fragment']}" ) : '' )
+	);
 }