chore: reuse browser in server mode (#495)

index.d.ts

@@ -18,6 +18,7 @@
 import type { Server } from '@modelcontextprotocol/sdk/server/index.js';
 import type { Config } from './config';
 import type { Transport } from '@modelcontextprotocol/sdk/shared/transport.js';
+import type { BrowserContext } from 'playwright';
 
 export type Connection = {
   server: Server;
@@ -25,5 +26,5 @@ export type Connection = {
   close(): Promise<void>;
 };
 
-export declare function createConnection(config?: Config): Promise<Connection>;
+export declare function createConnection(config?: Config, contextGetter?: () => Promise<BrowserContext>): Promise<Connection>;
 export {};

package-lock.json

@@ -11,6 +11,7 @@
       "dependencies": {
         "@modelcontextprotocol/sdk": "^1.11.0",
         "commander": "^13.1.0",
+        "debug": "^4.4.1",
         "playwright": "1.53.0-alpha-2025-05-27",
         "zod-to-json-schema": "^3.24.4"
       },
@@ -22,6 +23,7 @@
         "@eslint/js": "^9.19.0",
         "@playwright/test": "1.53.0-alpha-2025-05-27",
         "@stylistic/eslint-plugin": "^3.0.1",
+        "@types/debug": "^4.1.12",
         "@types/node": "^22.13.10",
         "@typescript-eslint/eslint-plugin": "^8.26.1",
         "@typescript-eslint/parser": "^8.26.1",
@@ -354,6 +356,16 @@
         "url": "https://github.com/sponsors/jonschlinkert"
       }
     },
+    "node_modules/@types/debug": {
+      "version": "4.1.12",
+      "resolved": "https://registry.npmjs.org/@types/debug/-/debug-4.1.12.tgz",
+      "integrity": "sha512-vIChWdVG3LG1SMxEvI/AK+FWJthlrqlTu7fbrlywTkkaONwk/UAGaULXRlf8vkzFBLVm0zkMdCquhL5aOjhXPQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/ms": "*"
+      }
+    },
     "node_modules/@types/estree": {
       "version": "1.0.6",
       "resolved": "https://registry.npmjs.org/@types/estree/-/estree-1.0.6.tgz",
@@ -375,6 +387,13 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@types/ms": {
+      "version": "2.1.0",
+      "resolved": "https://registry.npmjs.org/@types/ms/-/ms-2.1.0.tgz",
+      "integrity": "sha512-GsCCIZDE/p3i96vtEqx+7dBUGXrc7zeSK3wwPHIaRThS+9OhWIXRqzs4d6k1SVU8g91DrNRWxWUGhp5KXQb2VA==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@types/node": {
       "version": "22.13.10",
       "resolved": "https://registry.npmjs.org/@types/node/-/node-22.13.10.tgz",
@@ -853,29 +872,6 @@
         "node": ">=18"
       }
     },
-    "node_modules/body-parser/node_modules/debug": {
-      "version": "4.4.0",
-      "resolved": "https://registry.npmjs.org/debug/-/debug-4.4.0.tgz",
-      "integrity": "sha512-6WTZ/IxCY/T6BALoZHaE4ctp9xm+Z5kY/pzYaCHRFeyVhojxlrm+46y68HA6hr0TcwEssoxNiDEUJQjfPZ/RYA==",
-      "license": "MIT",
-      "dependencies": {
-        "ms": "^2.1.3"
-      },
-      "engines": {
-        "node": ">=6.0"
-      },
-      "peerDependenciesMeta": {
-        "supports-color": {
-          "optional": true
-        }
-      }
-    },
-    "node_modules/body-parser/node_modules/ms": {
-      "version": "2.1.3",
-      "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz",
-      "integrity": "sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA==",
-      "license": "MIT"
-    },
     "node_modules/body-parser/node_modules/qs": {
       "version": "6.14.0",
       "resolved": "https://registry.npmjs.org/qs/-/qs-6.14.0.tgz",
@@ -1156,12 +1152,12 @@
       }
     },
     "node_modules/debug": {
-      "version": "4.3.6",
+      "version": "4.4.1",
-      "resolved": "https://registry.npmjs.org/debug/-/debug-4.3.6.tgz",
+      "resolved": "https://registry.npmjs.org/debug/-/debug-4.4.1.tgz",
-      "integrity": "sha512-O/09Bd4Z1fBrU4VzkhFqVgpPzaGbw6Sm9FEkBT1A/YBXQFGuuSxa1dN2nxgxS34JmKXqYx8CZAwEVoJFImUXIg==",
+      "integrity": "sha512-KcKCqiftBJcZr++7ykoDIEwSa3XWowTfNPo92BYxjXiyYEVrUQh2aLyhxBCwww+heortUFxEJYcRzosstTEBYQ==",
       "license": "MIT",
       "dependencies": {
-        "ms": "2.1.2"
+        "ms": "^2.1.3"
       },
       "engines": {
         "node": ">=6.0"
@@ -1826,6 +1822,29 @@
         "express": "^4.11 || 5 || ^5.0.0-beta.1"
       }
     },
+    "node_modules/express/node_modules/debug": {
+      "version": "4.3.6",
+      "resolved": "https://registry.npmjs.org/debug/-/debug-4.3.6.tgz",
+      "integrity": "sha512-O/09Bd4Z1fBrU4VzkhFqVgpPzaGbw6Sm9FEkBT1A/YBXQFGuuSxa1dN2nxgxS34JmKXqYx8CZAwEVoJFImUXIg==",
+      "license": "MIT",
+      "dependencies": {
+        "ms": "2.1.2"
+      },
+      "engines": {
+        "node": ">=6.0"
+      },
+      "peerDependenciesMeta": {
+        "supports-color": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/express/node_modules/ms": {
+      "version": "2.1.2",
+      "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.2.tgz",
+      "integrity": "sha512-sGkPx+VjMtmA6MX27oA4FBFELFCZZ4S4XqeGOXCv68tT+jb3vk/RyaKWP0PTKyWtmLSM0b+adUTEvbs1PEaH2w==",
+      "license": "MIT"
+    },
     "node_modules/fast-deep-equal": {
       "version": "3.1.3",
       "resolved": "https://registry.npmjs.org/fast-deep-equal/-/fast-deep-equal-3.1.3.tgz",
@@ -1930,29 +1949,6 @@
         "node": ">= 0.8"
       }
     },
-    "node_modules/finalhandler/node_modules/debug": {
-      "version": "4.4.0",
-      "resolved": "https://registry.npmjs.org/debug/-/debug-4.4.0.tgz",
-      "integrity": "sha512-6WTZ/IxCY/T6BALoZHaE4ctp9xm+Z5kY/pzYaCHRFeyVhojxlrm+46y68HA6hr0TcwEssoxNiDEUJQjfPZ/RYA==",
-      "license": "MIT",
-      "dependencies": {
-        "ms": "^2.1.3"
-      },
-      "engines": {
-        "node": ">=6.0"
-      },
-      "peerDependenciesMeta": {
-        "supports-color": {
-          "optional": true
-        }
-      }
-    },
-    "node_modules/finalhandler/node_modules/ms": {
-      "version": "2.1.3",
-      "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz",
-      "integrity": "sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA==",
-      "license": "MIT"
-    },
     "node_modules/find-root": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/find-root/-/find-root-1.1.0.tgz",
@@ -3003,9 +2999,9 @@
       }
     },
     "node_modules/ms": {
-      "version": "2.1.2",
+      "version": "2.1.3",
-      "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.2.tgz",
+      "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz",
-      "integrity": "sha512-sGkPx+VjMtmA6MX27oA4FBFELFCZZ4S4XqeGOXCv68tT+jb3vk/RyaKWP0PTKyWtmLSM0b+adUTEvbs1PEaH2w==",
+      "integrity": "sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA==",
       "license": "MIT"
     },
     "node_modules/natural-compare": {
@@ -3713,12 +3709,6 @@
         "node": ">= 0.6"
       }
     },
-    "node_modules/send/node_modules/ms": {
-      "version": "2.1.3",
-      "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz",
-      "integrity": "sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA==",
-      "license": "MIT"
-    },
     "node_modules/serve-static": {
       "version": "2.1.0",
       "resolved": "https://registry.npmjs.org/serve-static/-/serve-static-2.1.0.tgz",

package.json

@@ -37,6 +37,7 @@
   "dependencies": {
     "@modelcontextprotocol/sdk": "^1.11.0",
     "commander": "^13.1.0",
+    "debug": "^4.4.1",
     "playwright": "1.53.0-alpha-2025-05-27",
     "zod-to-json-schema": "^3.24.4"
   },
@@ -45,6 +46,7 @@
     "@eslint/js": "^9.19.0",
     "@playwright/test": "1.53.0-alpha-2025-05-27",
     "@stylistic/eslint-plugin": "^3.0.1",
+    "@types/debug": "^4.1.12",
     "@types/node": "^22.13.10",
     "@typescript-eslint/eslint-plugin": "^8.26.1",
     "@typescript-eslint/parser": "^8.26.1",

src/browserContextFactory.ts

@@ -0,0 +1,202 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+
+import debug from 'debug';
+import * as playwright from 'playwright';
+
+import type { FullConfig } from './config.js';
+
+const testDebug = debug('pw:mcp:test');
+
+export function contextFactory(browserConfig: FullConfig['browser']): BrowserContextFactory {
+  if (browserConfig.remoteEndpoint)
+    return new RemoteContextFactory(browserConfig);
+  if (browserConfig.cdpEndpoint)
+    return new CdpContextFactory(browserConfig);
+  if (browserConfig.isolated)
+    return new IsolatedContextFactory(browserConfig);
+  return new PersistentContextFactory(browserConfig);
+}
+
+export interface BrowserContextFactory {
+  createContext(): Promise<{ browserContext: playwright.BrowserContext, close: () => Promise<void> }>;
+}
+
+class BaseContextFactory implements BrowserContextFactory {
+  readonly browserConfig: FullConfig['browser'];
+  protected _browserPromise: Promise<playwright.Browser> | undefined;
+  readonly name: string;
+
+  constructor(name: string, browserConfig: FullConfig['browser']) {
+    this.name = name;
+    this.browserConfig = browserConfig;
+  }
+
+  protected async _obtainBrowser(): Promise<playwright.Browser> {
+    if (this._browserPromise)
+      return this._browserPromise;
+    testDebug(`obtain browser (${this.name})`);
+    this._browserPromise = this._doObtainBrowser();
+    void this._browserPromise.then(browser => {
+      browser.on('disconnected', () => {
+        this._browserPromise = undefined;
+      });
+    }).catch(() => {
+      this._browserPromise = undefined;
+    });
+    return this._browserPromise;
+  }
+
+  protected async _doObtainBrowser(): Promise<playwright.Browser> {
+    throw new Error('Not implemented');
+  }
+
+  async createContext(): Promise<{ browserContext: playwright.BrowserContext, close: () => Promise<void> }> {
+    testDebug(`create browser context (${this.name})`);
+    const browser = await this._obtainBrowser();
+    const browserContext = await this._doCreateContext(browser);
+    return { browserContext, close: () => this._closeBrowserContext(browserContext, browser) };
+  }
+
+  protected async _doCreateContext(browser: playwright.Browser): Promise<playwright.BrowserContext> {
+    throw new Error('Not implemented');
+  }
+
+  private async _closeBrowserContext(browserContext: playwright.BrowserContext, browser: playwright.Browser) {
+    testDebug(`close browser context (${this.name})`);
+    if (browser.contexts().length === 1)
+      this._browserPromise = undefined;
+    await browserContext.close().catch(() => {});
+    if (browser.contexts().length === 0) {
+      testDebug(`close browser (${this.name})`);
+      await browser.close().catch(() => {});
+    }
+  }
+}
+
+class IsolatedContextFactory extends BaseContextFactory {
+  constructor(browserConfig: FullConfig['browser']) {
+    super('isolated', browserConfig);
+  }
+
+  protected override async _doObtainBrowser(): Promise<playwright.Browser> {
+    const browserType = playwright[this.browserConfig.browserName];
+    return browserType.launch(this.browserConfig.launchOptions).catch(error => {
+      if (error.message.includes('Executable doesn\'t exist'))
+        throw new Error(`Browser specified in your config is not installed. Either install it (likely) or change the config.`);
+      throw error;
+    });
+  }
+
+  protected override async _doCreateContext(browser: playwright.Browser): Promise<playwright.BrowserContext> {
+    return browser.newContext(this.browserConfig.contextOptions);
+  }
+}
+
+class CdpContextFactory extends BaseContextFactory {
+  constructor(browserConfig: FullConfig['browser']) {
+    super('cdp', browserConfig);
+  }
+
+  protected override async _doObtainBrowser(): Promise<playwright.Browser> {
+    return playwright.chromium.connectOverCDP(this.browserConfig.cdpEndpoint!);
+  }
+
+  protected override async _doCreateContext(browser: playwright.Browser): Promise<playwright.BrowserContext> {
+    return this.browserConfig.isolated ? await browser.newContext() : browser.contexts()[0];
+  }
+}
+
+class RemoteContextFactory extends BaseContextFactory {
+  constructor(browserConfig: FullConfig['browser']) {
+    super('remote', browserConfig);
+  }
+
+  protected override async _doObtainBrowser(): Promise<playwright.Browser> {
+    const url = new URL(this.browserConfig.remoteEndpoint!);
+    url.searchParams.set('browser', this.browserConfig.browserName);
+    if (this.browserConfig.launchOptions)
+      url.searchParams.set('launch-options', JSON.stringify(this.browserConfig.launchOptions));
+    return playwright[this.browserConfig.browserName].connect(String(url));
+  }
+
+  protected override async _doCreateContext(browser: playwright.Browser): Promise<playwright.BrowserContext> {
+    return browser.newContext();
+  }
+}
+
+class PersistentContextFactory implements BrowserContextFactory {
+  readonly browserConfig: FullConfig['browser'];
+  private _userDataDirs = new Set<string>();
+
+  constructor(browserConfig: FullConfig['browser']) {
+    this.browserConfig = browserConfig;
+  }
+
+  async createContext(): Promise<{ browserContext: playwright.BrowserContext, close: () => Promise<void> }> {
+    testDebug('create browser context (persistent)');
+    const userDataDir = this.browserConfig.userDataDir ?? await this._createUserDataDir();
+
+    this._userDataDirs.add(userDataDir);
+    testDebug('lock user data dir', userDataDir);
+
+    const browserType = playwright[this.browserConfig.browserName];
+    for (let i = 0; i < 5; i++) {
+      try {
+        const browserContext = await browserType.launchPersistentContext(userDataDir, { ...this.browserConfig.launchOptions, ...this.browserConfig.contextOptions });
+        const close = () => this._closeBrowserContext(browserContext, userDataDir);
+        return { browserContext, close };
+      } catch (error: any) {
+        if (error.message.includes('Executable doesn\'t exist'))
+          throw new Error(`Browser specified in your config is not installed. Either install it (likely) or change the config.`);
+        if (error.message.includes('ProcessSingleton') || error.message.includes('Invalid URL')) {
+          // User data directory is already in use, try again.
+          await new Promise(resolve => setTimeout(resolve, 1000));
+          continue;
+        }
+        throw error;
+      }
+    }
+    throw new Error(`Browser is already in use for ${userDataDir}, use --isolated to run multiple instances of the same browser`);
+  }
+
+  private async _closeBrowserContext(browserContext: playwright.BrowserContext, userDataDir: string) {
+    testDebug('close browser context (persistent)');
+    testDebug('release user data dir', userDataDir);
+    await browserContext.close().catch(() => {});
+    this._userDataDirs.delete(userDataDir);
+    testDebug('close browser context complete (persistent)');
+  }
+
+  private async _createUserDataDir() {
+    let cacheDirectory: string;
+    if (process.platform === 'linux')
+      cacheDirectory = process.env.XDG_CACHE_HOME || path.join(os.homedir(), '.cache');
+    else if (process.platform === 'darwin')
+      cacheDirectory = path.join(os.homedir(), 'Library', 'Caches');
+    else if (process.platform === 'win32')
+      cacheDirectory = process.env.LOCALAPPDATA || path.join(os.homedir(), 'AppData', 'Local');
+    else
+      throw new Error('Unsupported platform: ' + process.platform);
+    const result = path.join(cacheDirectory, 'ms-playwright', `mcp-${this.browserConfig.launchOptions?.channel ?? this.browserConfig?.browserName}-profile`);
+    await fs.promises.mkdir(result, { recursive: true });
+    return result;
+  }
+}

src/config.ts

@@ -74,8 +74,8 @@ const defaultConfig: FullConfig = {
 type BrowserUserConfig = NonNullable<Config['browser']>;
 
 export type FullConfig = Config & {
-  browser: BrowserUserConfig & {
+  browser: Omit<BrowserUserConfig, 'browserName'> & {
-    browserName: NonNullable<BrowserUserConfig['browserName']>;
+    browserName: 'chromium' | 'firefox' | 'webkit';
     launchOptions: NonNullable<BrowserUserConfig['launchOptions']>;
     contextOptions: NonNullable<BrowserUserConfig['contextOptions']>;
   },

src/connection.ts

@@ -24,11 +24,13 @@ import { packageJSON } from './package.js';
 
 import { FullConfig } from './config.js';
 
-export function createConnection(config: FullConfig): Connection {
+import type { BrowserContextFactory } from './browserContextFactory.js';
+
+export function createConnection(config: FullConfig, browserContextFactory: BrowserContextFactory): Connection {
   const allTools = config.vision ? visionTools : snapshotTools;
   const tools = allTools.filter(tool => !config.capabilities || tool.capability === 'core' || config.capabilities.includes(tool.capability));
 
-  const context = new Context(tools, config);
+  const context = new Context(tools, config, browserContextFactory);
   const server = new McpServer({ name: 'Playwright', version: packageJSON.version }, {
     capabilities: {
       tools: {},

src/context.ts

@@ -14,10 +14,7 @@
  * limitations under the License.
  */
 
-import fs from 'node:fs';
+import debug from 'debug';
-import os from 'node:os';
-import path from 'node:path';
-
 import * as playwright from 'playwright';
 
 import { callOnPageNoTrace, waitForCompletion } from './tools/utils.js';
@@ -28,20 +25,19 @@ import { outputFile } from './config.js';
 import type { ImageContent, TextContent } from '@modelcontextprotocol/sdk/types.js';
 import type { ModalState, Tool, ToolActionResult } from './tools/tool.js';
 import type { FullConfig } from './config.js';
+import type { BrowserContextFactory } from './browserContextFactory.js';
 
 type PendingAction = {
   dialogShown: ManualPromise<void>;
 };
 
-type BrowserContextAndBrowser = {
+const testDebug = debug('pw:mcp:test');
-  browser?: playwright.Browser;
-  browserContext: playwright.BrowserContext;
-};
 
 export class Context {
   readonly tools: Tool[];
   readonly config: FullConfig;
-  private _browserContextPromise: Promise<BrowserContextAndBrowser> | undefined;
+  private _browserContextPromise: Promise<{ browserContext: playwright.BrowserContext, close: () => Promise<void> }> | undefined;
+  private _browserContextFactory: BrowserContextFactory;
   private _tabs: Tab[] = [];
   private _currentTab: Tab | undefined;
   private _modalStates: (ModalState & { tab: Tab })[] = [];
@@ -49,9 +45,11 @@ export class Context {
   private _downloads: { download: playwright.Download, finished: boolean, outputFile: string }[] = [];
   clientVersion: { name: string; version: string; } | undefined;
 
-  constructor(tools: Tool[], config: FullConfig) {
+  constructor(tools: Tool[], config: FullConfig, browserContextFactory: BrowserContextFactory) {
     this.tools = tools;
     this.config = config;
+    this._browserContextFactory = browserContextFactory;
+    testDebug('create context');
   }
 
   clientSupportsImages(): boolean {
@@ -296,15 +294,15 @@ ${code.join('\n')}
     if (!this._browserContextPromise)
       return;
 
+    testDebug('close context');
+
     const promise = this._browserContextPromise;
     this._browserContextPromise = undefined;
 
-    await promise.then(async ({ browserContext, browser }) => {
+    await promise.then(async ({ browserContext, close }) => {
       if (this.config.saveTrace)
         await browserContext.tracing.stop();
-      await browserContext.close().then(async () => {
+      await close();
-        await browser?.close();
-      }).catch(() => {});
     });
   }
 
@@ -332,8 +330,10 @@ ${code.join('\n')}
     return this._browserContextPromise;
   }
 
-  private async _setupBrowserContext(): Promise<BrowserContextAndBrowser> {
+  private async _setupBrowserContext(): Promise<{ browserContext: playwright.BrowserContext, close: () => Promise<void> }> {
-    const { browser, browserContext } = await this._createBrowserContext();
+    // TODO: move to the browser context factory to make it based on isolation mode.
+    const result = await this._browserContextFactory.createContext();
+    const { browserContext } = result;
     await this._setupRequestInterception(browserContext);
     for (const page of browserContext.pages())
       this._onPageCreated(page);
@@ -346,72 +346,6 @@ ${code.join('\n')}
         sources: false,
       });
     }
-    return { browser, browserContext };
+    return result;
-  }
-
-  private async _createBrowserContext(): Promise<BrowserContextAndBrowser> {
-    if (this.config.browser?.remoteEndpoint) {
-      const url = new URL(this.config.browser?.remoteEndpoint);
-      if (this.config.browser.browserName)
-        url.searchParams.set('browser', this.config.browser.browserName);
-      if (this.config.browser.launchOptions)
-        url.searchParams.set('launch-options', JSON.stringify(this.config.browser.launchOptions));
-      const browser = await playwright[this.config.browser?.browserName ?? 'chromium'].connect(String(url));
-      const browserContext = await browser.newContext();
-      return { browser, browserContext };
-    }
-
-    if (this.config.browser?.cdpEndpoint) {
-      const browser = await playwright.chromium.connectOverCDP(this.config.browser.cdpEndpoint);
-      const browserContext = this.config.browser.isolated ? await browser.newContext() : browser.contexts()[0];
-      return { browser, browserContext };
-    }
-
-    return this.config.browser?.isolated ?
-      await createIsolatedContext(this.config.browser) :
-      await launchPersistentContext(this.config.browser);
   }
 }
-
-async function createIsolatedContext(browserConfig: FullConfig['browser']): Promise<BrowserContextAndBrowser> {
-  try {
-    const browserName = browserConfig?.browserName ?? 'chromium';
-    const browserType = playwright[browserName];
-    const browser = await browserType.launch(browserConfig.launchOptions);
-    const browserContext = await browser.newContext(browserConfig.contextOptions);
-    return { browser, browserContext };
-  } catch (error: any) {
-    if (error.message.includes('Executable doesn\'t exist'))
-      throw new Error(`Browser specified in your config is not installed. Either install it (likely) or change the config.`);
-    throw error;
-  }
-}
-
-async function launchPersistentContext(browserConfig: FullConfig['browser']): Promise<BrowserContextAndBrowser> {
-  try {
-    const browserName = browserConfig.browserName ?? 'chromium';
-    const userDataDir = browserConfig.userDataDir ?? await createUserDataDir({ ...browserConfig, browserName });
-    const browserType = playwright[browserName];
-    const browserContext = await browserType.launchPersistentContext(userDataDir, { ...browserConfig.launchOptions, ...browserConfig.contextOptions });
-    return { browserContext };
-  } catch (error: any) {
-    if (error.message.includes('Executable doesn\'t exist'))
-      throw new Error(`Browser specified in your config is not installed. Either install it (likely) or change the config.`);
-    throw error;
-  }
-}
-
-async function createUserDataDir(browserConfig: FullConfig['browser']) {
-  let cacheDirectory: string;
-  if (process.platform === 'linux')
-    cacheDirectory = process.env.XDG_CACHE_HOME || path.join(os.homedir(), '.cache');
-  else if (process.platform === 'darwin')
-    cacheDirectory = path.join(os.homedir(), 'Library', 'Caches');
-  else if (process.platform === 'win32')
-    cacheDirectory = process.env.LOCALAPPDATA || path.join(os.homedir(), 'AppData', 'Local');
-  else
-    throw new Error('Unsupported platform: ' + process.platform);
-  const result = path.join(cacheDirectory, 'ms-playwright', `mcp-${browserConfig.launchOptions?.channel ?? browserConfig?.browserName}-profile`);
-  await fs.promises.mkdir(result, { recursive: true });
-  return result;
-}

src/index.ts

@@ -16,10 +16,30 @@
 
 import { Connection, createConnection as createConnectionImpl } from './connection.js';
 import { resolveConfig } from './config.js';
+import { contextFactory } from './browserContextFactory.js';
 
 import type { Config } from '../config.js';
+import type { BrowserContext } from 'playwright';
+import type { BrowserContextFactory } from './browserContextFactory.js';
 
-export async function createConnection(userConfig: Config = {}): Promise<Connection> {
+export async function createConnection(userConfig: Config = {}, contextGetter?: () => Promise<BrowserContext>): Promise<Connection> {
   const config = await resolveConfig(userConfig);
-  return createConnectionImpl(config);
+  const factory = contextGetter ? new SimpleBrowserContextFactory(contextGetter) : contextFactory(config.browser);
+  return createConnectionImpl(config, factory);
+}
+
+class SimpleBrowserContextFactory implements BrowserContextFactory {
+  private readonly _contextGetter: () => Promise<BrowserContext>;
+
+  constructor(contextGetter: () => Promise<BrowserContext>) {
+    this._contextGetter = contextGetter;
+  }
+
+  async createContext(): Promise<{ browserContext: BrowserContext, close: () => Promise<void> }> {
+    const browserContext = await this._contextGetter();
+    return {
+      browserContext,
+      close: () => browserContext.close()
+    };
+  }
 }

src/server.ts

@@ -15,21 +15,27 @@
  */
 
 import { createConnection } from './connection.js';
+import { contextFactory } from './browserContextFactory.js';
 
 import type { FullConfig } from './config.js';
 import type { Connection } from './connection.js';
 import type { Transport } from '@modelcontextprotocol/sdk/shared/transport.js';
+import type { BrowserContextFactory } from './browserContextFactory.js';
 
 export class Server {
   readonly config: FullConfig;
   private _connectionList: Connection[] = [];
+  private _browserConfig: FullConfig['browser'];
+  private _contextFactory: BrowserContextFactory;
 
   constructor(config: FullConfig) {
     this.config = config;
+    this._browserConfig = config.browser;
+    this._contextFactory = contextFactory(this._browserConfig);
   }
 
   async createConnection(transport: Transport): Promise<Connection> {
-    const connection = createConnection(this.config);
+    const connection = createConnection(this.config, this._contextFactory);
     this._connectionList.push(connection);
     await connection.server.connect(transport);
     return connection;

src/transport.ts

@@ -18,6 +18,7 @@ import http from 'node:http';
 import assert from 'node:assert';
 import crypto from 'node:crypto';
 
+import debug from 'debug';
 import { SSEServerTransport } from '@modelcontextprotocol/sdk/server/sse.js';
 import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
 import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
@@ -28,6 +29,8 @@ export async function startStdioTransport(server: Server) {
   await server.createConnection(new StdioServerTransport());
 }
 
+const testDebug = debug('pw:mcp:test');
+
 async function handleSSE(server: Server, req: http.IncomingMessage, res: http.ServerResponse, url: URL, sessions: Map<string, SSEServerTransport>) {
   if (req.method === 'POST') {
     const sessionId = url.searchParams.get('sessionId');
@@ -46,8 +49,10 @@ async function handleSSE(server: Server, req: http.IncomingMessage, res: http.Se
   } else if (req.method === 'GET') {
     const transport = new SSEServerTransport('/sse', res);
     sessions.set(transport.sessionId, transport);
+    testDebug(`create SSE session: ${transport.sessionId}`);
     const connection = await server.createConnection(transport);
     res.on('close', () => {
+      testDebug(`delete SSE session: ${transport.sessionId}`);
       sessions.delete(transport.sessionId);
       // eslint-disable-next-line no-console
       void connection.close().catch(e => console.error(e));

tests/sse.spec.ts

@@ -15,7 +15,7 @@
  */
 
 import url from 'node:url';
-import { spawn } from 'node:child_process';
+import { ChildProcess, spawn } from 'node:child_process';
 import path from 'node:path';
 import { SSEClientTransport } from '@modelcontextprotocol/sdk/client/sse.js';
 import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/streamableHttp.js';
@@ -26,35 +26,200 @@ import { test as baseTest, expect } from './fixtures.js';
 // NOTE: Can be removed when we drop Node.js 18 support and changed to import.meta.filename.
 const __filename = url.fileURLToPath(import.meta.url);
 
-const test = baseTest.extend<{ serverEndpoint: string }>({
+const test = baseTest.extend<{ serverEndpoint: (args?: string[]) => Promise<{ url: URL, stderr: () => string }> }>({
-  serverEndpoint: async ({}, use) => {
+  serverEndpoint: async ({ mcpHeadless }, use, testInfo) => {
-    const cp = spawn('node', [path.join(path.dirname(__filename), '../cli.js'), '--port', '0'], { stdio: 'pipe' });
+    let cp: ChildProcess | undefined;
-    try {
+    const userDataDir = testInfo.outputPath('user-data-dir');
+    await use(async (args?: string[]) => {
+      if (cp)
+        throw new Error('Process already running');
+
+      cp = spawn('node', [
+        path.join(path.dirname(__filename), '../cli.js'),
+        '--port=0',
+        '--user-data-dir=' + userDataDir,
+        ...(mcpHeadless ? ['--headless'] : []),
+        ...(args || []),
+      ], {
+        stdio: 'pipe',
+        env: {
+          ...process.env,
+          DEBUG: 'pw:mcp:test',
+          DEBUG_COLORS: '0',
+          DEBUG_HIDE_DATE: '1',
+        },
+      });
       let stderr = '';
-      const url = await new Promise<string>(resolve => cp.stderr?.on('data', data => {
+      const url = await new Promise<string>(resolve => cp!.stderr?.on('data', data => {
         stderr += data.toString();
         const match = stderr.match(/Listening on (http:\/\/.*)/);
         if (match)
           resolve(match[1]);
       }));
 
-      await use(url);
+      return { url: new URL(url), stderr: () => stderr };
-    } finally {
+    });
-      cp.kill();
+    cp?.kill('SIGTERM');
-    }
   },
 });
 
 test('sse transport', async ({ serverEndpoint }) => {
-  const transport = new SSEClientTransport(new URL(serverEndpoint));
+  const { url } = await serverEndpoint();
+  const transport = new SSEClientTransport(url);
   const client = new Client({ name: 'test', version: '1.0.0' });
   await client.connect(transport);
   await client.ping();
-  await client.close();
+});
+
+test('sse transport browser lifecycle (isolated)', async ({ serverEndpoint, server }) => {
+  const { url, stderr } = await serverEndpoint(['--isolated']);
+
+  const transport1 = new SSEClientTransport(url);
+  const client1 = new Client({ name: 'test', version: '1.0.0' });
+  await client1.connect(transport1);
+  await client1.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.HELLO_WORLD },
+  });
+  await client1.close();
+
+  const transport2 = new SSEClientTransport(url);
+  const client2 = new Client({ name: 'test', version: '1.0.0' });
+  await client2.connect(transport2);
+  await client2.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.HELLO_WORLD },
+  });
+  await client2.close();
+
+  await expect(async () => {
+    const lines = stderr().split('\n');
+    expect(lines.filter(line => line.match(/create SSE session/)).length).toBe(2);
+    expect(lines.filter(line => line.match(/delete SSE session/)).length).toBe(2);
+
+    expect(lines.filter(line => line.match(/create context/)).length).toBe(2);
+    expect(lines.filter(line => line.match(/close context/)).length).toBe(2);
+
+    expect(lines.filter(line => line.match(/create browser context \(isolated\)/)).length).toBe(2);
+    expect(lines.filter(line => line.match(/close browser context \(isolated\)/)).length).toBe(2);
+
+    expect(lines.filter(line => line.match(/obtain browser \(isolated\)/)).length).toBe(2);
+    expect(lines.filter(line => line.match(/close browser \(isolated\)/)).length).toBe(2);
+  }).toPass();
+});
+
+test('sse transport browser lifecycle (isolated, multiclient)', async ({ serverEndpoint, server }) => {
+  const { url, stderr } = await serverEndpoint(['--isolated']);
+
+  const transport1 = new SSEClientTransport(url);
+  const client1 = new Client({ name: 'test', version: '1.0.0' });
+  await client1.connect(transport1);
+  await client1.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.HELLO_WORLD },
+  });
+
+  const transport2 = new SSEClientTransport(url);
+  const client2 = new Client({ name: 'test', version: '1.0.0' });
+  await client2.connect(transport2);
+  await client2.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.HELLO_WORLD },
+  });
+  await client1.close();
+
+  const transport3 = new SSEClientTransport(url);
+  const client3 = new Client({ name: 'test', version: '1.0.0' });
+  await client3.connect(transport3);
+  await client3.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.HELLO_WORLD },
+  });
+
+  await client2.close();
+  await client3.close();
+
+  await expect(async () => {
+    const lines = stderr().split('\n');
+    expect(lines.filter(line => line.match(/create SSE session/)).length).toBe(3);
+    expect(lines.filter(line => line.match(/delete SSE session/)).length).toBe(3);
+
+    expect(lines.filter(line => line.match(/create context/)).length).toBe(3);
+    expect(lines.filter(line => line.match(/close context/)).length).toBe(3);
+
+    expect(lines.filter(line => line.match(/create browser context \(isolated\)/)).length).toBe(3);
+    expect(lines.filter(line => line.match(/close browser context \(isolated\)/)).length).toBe(3);
+
+    expect(lines.filter(line => line.match(/obtain browser \(isolated\)/)).length).toBe(1);
+    expect(lines.filter(line => line.match(/close browser \(isolated\)/)).length).toBe(1);
+  }).toPass();
+});
+
+test('sse transport browser lifecycle (persistent)', async ({ serverEndpoint, server }) => {
+  const { url, stderr } = await serverEndpoint();
+
+  const transport1 = new SSEClientTransport(url);
+  const client1 = new Client({ name: 'test', version: '1.0.0' });
+  await client1.connect(transport1);
+  await client1.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.HELLO_WORLD },
+  });
+  await client1.close();
+
+  const transport2 = new SSEClientTransport(url);
+  const client2 = new Client({ name: 'test', version: '1.0.0' });
+  await client2.connect(transport2);
+  await client2.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.HELLO_WORLD },
+  });
+  await client2.close();
+
+  await expect(async () => {
+    const lines = stderr().split('\n');
+    expect(lines.filter(line => line.match(/create SSE session/)).length).toBe(2);
+    expect(lines.filter(line => line.match(/delete SSE session/)).length).toBe(2);
+
+    expect(lines.filter(line => line.match(/create context/)).length).toBe(2);
+    expect(lines.filter(line => line.match(/close context/)).length).toBe(2);
+
+    expect(lines.filter(line => line.match(/create browser context \(persistent\)/)).length).toBe(2);
+    expect(lines.filter(line => line.match(/close browser context \(persistent\)/)).length).toBe(2);
+
+    expect(lines.filter(line => line.match(/lock user data dir/)).length).toBe(2);
+    expect(lines.filter(line => line.match(/release user data dir/)).length).toBe(2);
+  }).toPass();
+});
+
+test('sse transport browser lifecycle (persistent, multiclient)', async ({ serverEndpoint, server }) => {
+  const { url } = await serverEndpoint();
+
+  const transport1 = new SSEClientTransport(url);
+  const client1 = new Client({ name: 'test', version: '1.0.0' });
+  await client1.connect(transport1);
+  await client1.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.HELLO_WORLD },
+  });
+
+  const transport2 = new SSEClientTransport(url);
+  const client2 = new Client({ name: 'test', version: '1.0.0' });
+  await client2.connect(transport2);
+  const response = await client2.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.HELLO_WORLD },
+  });
+  expect(response.isError).toBe(true);
+  expect(response.content?.[0].text).toContain('use --isolated to run multiple instances of the same browser');
+
+  await client1.close();
+  await client2.close();
 });
 
 test('streamable http transport', async ({ serverEndpoint }) => {
-  const transport = new StreamableHTTPClientTransport(new URL('/mcp', serverEndpoint));
+  const { url } = await serverEndpoint();
+  const transport = new StreamableHTTPClientTransport(new URL('/mcp', url));
   const client = new Client({ name: 'test', version: '1.0.0' });
   await client.connect(transport);
   await client.ping();