fix(mcp): launch the Chrome profile that has the extension installed (#41939)

extension mode validated that the playwright extension was installed in any of Chrome's profiles under the user data directory, but then launched without `--profile-directory`, meaning it could open a different profile than the one that was checked

when the opened profile lacks the extension, `connect.html` can't load and the connection silently hangs for ~120s

resolve the profile that actually has the extension (preferring the last-used profile from Local State so we don't switch away from the user's session unnecessarily) and pass it as `--profile-directory`

fixes <https://github.com/microsoft/playwright/issues/41916>

packages/playwright-core/src/tools/mcp/cdpRelay.ts

@@ -34,7 +34,7 @@ import ws, { WebSocketServer as wsServer } from 'ws';
 import { ManualPromise } from '@isomorphic/manualPromise';
 import { registry } from '../../server/registry/index';
 
-import { playwrightExtensionId } from '../utils/extension';
+import { findPlaywrightExtensionProfile, playwrightExtensionId } from '../utils/extension';
 import { addressToString } from '../utils/mcp/http';
 import { logUnhandledError } from './log';
 import { ExtensionProtocolV2 } from './cdpRelayV2';
@@ -61,6 +61,7 @@ export class CDPRelayServer {
   private _wsHost: string;
   private _browserChannel: string;
   private _executablePath?: string;
+  private _userDataDir?: string;
   private _cdpPath: string;
   private _extensionPath: string;
   private _wss: WebSocketServer;
@@ -70,10 +71,11 @@ export class CDPRelayServer {
   private _handler: ExtensionProtocolV2;
   private _extensionConnectionPromise = new ManualPromise<void>();
 
-  constructor(server: http.Server, browserChannel: string, executablePath?: string) {
+  constructor(server: http.Server, browserChannel: string, executablePath?: string, userDataDir?: string) {
     this._wsHost = addressToString(server.address(), { protocol: 'ws' });
     this._browserChannel = browserChannel;
     this._executablePath = executablePath;
+    this._userDataDir = userDataDir;
     this._protocolVersion = parseInt(process.env.PLAYWRIGHT_EXTENSION_PROTOCOL ?? protocol.VERSION.toString(), 10);
 
     const sendCommand = (method: string, params: any): Promise<any> => {
@@ -102,14 +104,14 @@ export class CDPRelayServer {
 
   async establishExtensionConnection(clientName: string) {
     debugLogger('Establishing extension connection');
-    this._openConnectPageInBrowser(clientName);
+    await this._openConnectPageInBrowser(clientName);
     debugLogger('Waiting for incoming extension connection');
     await this._extensionConnectionPromise;
     await this._handler.ready();
     debugLogger('Extension connection established');
   }
 
-  private _openConnectPageInBrowser(clientName: string) {
+  private async _openConnectPageInBrowser(clientName: string) {
     const mcpRelayEndpoint = `${this._wsHost}${this._extensionPath}`;
     const url = new URL(`chrome-extension://${playwrightExtensionId}/connect.html`);
     url.searchParams.set('mcpRelayUrl', mcpRelayEndpoint);
@@ -137,9 +139,13 @@ export class CDPRelayServer {
     }
 
     const args: string[] = [];
-    const userDataDir = process.env.PWTEST_EXTENSION_USER_DATA_DIR;
-    if (userDataDir)
-      args.push(`--user-data-dir=${userDataDir}`);
+    const testUserDataDir = process.env.PWTEST_EXTENSION_USER_DATA_DIR;
+    if (testUserDataDir)
+      args.push(`--user-data-dir=${testUserDataDir}`);
+    const userDataDir = testUserDataDir ?? this._userDataDir;
+    const profileDirectory = userDataDir ? await findPlaywrightExtensionProfile(userDataDir) : undefined;
+    if (profileDirectory)
+      args.push(`--profile-directory=${profileDirectory}`);
     if (os.platform() === 'linux' && channel === 'chromium')
       args.push('--no-sandbox');
     args.push(href);

packages/playwright-core/src/tools/mcp/extensionContextFactory.ts

@@ -27,15 +27,16 @@ const debugLogger = debug('pw:mcp:relay');
 
 export async function createExtensionBrowser(channel: string, executablePath: string | undefined, clientName: string): Promise<playwrightTypes.Browser> {
   // Custom executablePath may target a browser in a different filesystem (e.g. Windows chrome.exe from WSL2), so the local profile path is not meaningful.
+  let userDataDir: string | undefined;
   if (!executablePath) {
-    const userDataDir = process.env.PWTEST_EXTENSION_USER_DATA_DIR ?? defaultUserDataDirForChannel(channel);
+    userDataDir = process.env.PWTEST_EXTENSION_USER_DATA_DIR ?? defaultUserDataDirForChannel(channel);
     if (userDataDir && !await isPlaywrightExtensionInstalled(userDataDir))
       throw new Error(`Playwright Extension not found in "${userDataDir}". Install it from ${playwrightExtensionInstallUrl}`);
   }
 
   const httpServer = createHttpServer();
   await startHttpServer(httpServer, {});
-  const relay = new CDPRelayServer(httpServer, channel, executablePath);
+  const relay = new CDPRelayServer(httpServer, channel, executablePath, userDataDir);
   debugLogger(`CDP relay server started, extension endpoint: ${relay.extensionEndpoint()}.`);
 
   try {

packages/playwright-core/src/tools/utils/extension.ts

@@ -22,22 +22,47 @@ export const playwrightExtensionId = 'mmlmfjhmonkocbjadbfplnigmagldckm';
 
 export const playwrightExtensionInstallUrl = `https://chromewebstore.google.com/detail/playwright-extension/${playwrightExtensionId}`;
 
-export async function isPlaywrightExtensionInstalled(userDataDir: string): Promise<boolean> {
-  // Chrome stores profiles as `Default` and `Profile <N>` subdirs of the user data dir;
-  // the extension may be installed into any of them.
+export async function findPlaywrightExtensionProfile(userDataDir: string): Promise<string | undefined> {
+  const profiles = await listProfileDirectories(userDataDir);
+  const lastUsed = await readLastUsedProfile(userDataDir);
+  const ordered = lastUsed && profiles.includes(lastUsed)
+    ? [lastUsed, ...profiles.filter(profile => profile !== lastUsed)]
+    : profiles;
+  for (const profile of ordered) {
+    if (await isExtensionInstalledInProfile(path.join(userDataDir, profile)))
+      return profile;
+  }
+  return undefined;
+}
+
+async function listProfileDirectories(userDataDir: string): Promise<string[]> {
   let entries: string[];
   try {
     entries = await fs.promises.readdir(userDataDir);
   } catch {
-    return false;
+    return [];
   }
-  for (const entry of entries) {
-    if (entry !== 'Default' && !entry.startsWith('Profile '))
-      continue;
-    if (await isExtensionInstalledInProfile(path.join(userDataDir, entry)))
-      return true;
+  const profiles = entries.filter(entry => entry === 'Default' || /^Profile \d+$/.test(entry));
+  profiles.sort((a, b) => profileRank(a) - profileRank(b));
+  return profiles;
+}
+
+function profileRank(profile: string): number {
+  return profile === 'Default' ? -1 : parseInt(profile.slice('Profile '.length), 10);
+}
+
+async function readLastUsedProfile(userDataDir: string): Promise<string | undefined> {
+  try {
+    const localState = JSON.parse(await fs.promises.readFile(path.join(userDataDir, 'Local State'), 'utf-8'));
+    const lastUsed = localState?.profile?.last_used;
+    return typeof lastUsed === 'string' ? lastUsed : undefined;
+  } catch {
+    return undefined;
   }
-  return false;
+}
+
+export async function isPlaywrightExtensionInstalled(userDataDir: string): Promise<boolean> {
+  return await findPlaywrightExtensionProfile(userDataDir) !== undefined;
 }
 
 async function isExtensionInstalledInProfile(profileDir: string): Promise<boolean> {

tests/extension/extension.spec.ts

@@ -15,6 +15,7 @@
  */
 
 import fs from 'fs/promises';
+import path from 'path';
 
 import { test, testWithOldExtensionVersion, expect, extensionId, clickAllowAndSelect, connectAndNavigate, startWithExtensionFlag } from './extension-fixtures';
 import { utils } from '../../packages/playwright-core/lib/coreBundle';
@@ -248,6 +249,31 @@ test(`custom executablePath skips local extension check`, {
   }).toPass();
 });
 
+test(`launches the profile that has the extension`, {
+  annotation: { type: 'issue', description: 'https://github.com/microsoft/playwright/issues/41916' },
+}, async ({ startClient, server }, testInfo) => {
+  // The extension lives in a non-default profile only; the launch must target that profile via
+  // `--profile-directory`, otherwise Chrome opens the default profile without the extension and the
+  // connection hangs. A fake executable records the launch arguments, so no real browser is needed.
+  const userDataDir = testInfo.outputPath('multi-profile');
+  await fs.mkdir(path.join(userDataDir, 'Default'), { recursive: true });
+  await fs.mkdir(path.join(userDataDir, 'Profile 1', 'Extensions', extensionId), { recursive: true });
+
+  const executablePath = testInfo.outputPath('echo.sh');
+  await fs.writeFile(executablePath, '#!/bin/bash\necho "Custom exec args: $@" > "$(dirname "$0")/output.txt"', { mode: 0o755 });
+
+  const { client } = await startClient({
+    args: [`--extension`, `--executable-path=${executablePath}`],
+    env: { PWTEST_EXTENSION_USER_DATA_DIR: userDataDir },
+  });
+
+  client.callTool({ name: 'browser_navigate', arguments: { url: server.HELLO_WORLD } }).catch(() => {});
+  await expect(async () => {
+    const output = await fs.readFile(testInfo.outputPath('output.txt'), 'utf8');
+    expect(output).toContain(`--profile-directory=Profile 1`);
+  }).toPass();
+});
+
 test(`fails when extension is missing in custom userDataDir`, async ({ startClient, server }) => {
   const userDataDir = test.info().outputPath('empty-profile');