chore(extension): reject second http connection (#766)

extension/src/connect.ts

@@ -69,6 +69,7 @@ class ConnectPage {
 
     continueBtn.addEventListener('click', async () => {
       buttonRow.style.display = 'none';
+      this._tabListContainer.style.display = 'none';
       try {
         const selectedTab = this._selectedTab;
         if (!selectedTab) {

src/browserServerBackend.ts

@@ -30,6 +30,8 @@ import type { Tool } from './tools/tool.js';
 export class BrowserServerBackend implements ServerBackend {
   name = 'Playwright';
   version = packageJSON.version;
+  onclose?: () => void;
+
   private _tools: Tool[];
   private _context: Context;
   private _sessionLog: SessionLog | undefined;
@@ -61,6 +63,7 @@ export class BrowserServerBackend implements ServerBackend {
   }
 
   serverClosed() {
+    this.onclose?.();
     void this._context.dispose().catch(logUnhandledError);
   }
 }

src/extension/cdpRelay.ts

@@ -123,8 +123,13 @@ export class CDPRelayServer {
   }
 
   stop(): void {
-    this._closePlaywrightConnection('Server stopped');
-    this._closeExtensionConnection('Server stopped');
+    this.closeConnections('Server stopped');
+    this._wss.close();
+  }
+
+  closeConnections(reason: string) {
+    this._closePlaywrightConnection(reason);
+    this._closeExtensionConnection(reason);
   }
 
   private _onConnection(ws: WebSocket, request: http.IncomingMessage): void {
@@ -141,6 +146,11 @@ export class CDPRelayServer {
   }
 
   private _handlePlaywrightConnection(ws: WebSocket): void {
+    if (this._playwrightConnection) {
+      debugLogger('Rejecting second Playwright connection');
+      ws.close(1000, 'Another CDP client already connected');
+      return;
+    }
     this._playwrightConnection = ws;
     ws.on('message', async data => {
       try {
@@ -311,6 +321,11 @@ class ExtensionContextFactory implements BrowserContextFactory {
     };
   }
 
+  clientDisconnected() {
+    this._relay.closeConnections('MCP client disconnected');
+    this._browserPromise = undefined;
+  }
+
   private async _obtainBrowser(clientInfo: { name: string, version: string }): Promise<playwright.Browser> {
     await this._relay.ensureExtensionConnectionForMCPContext(clientInfo);
     const browser = await playwright.chromium.connectOverCDP(this._relay.cdpEndpoint());

src/extension/main.ts

@@ -22,6 +22,18 @@ import type { FullConfig } from '../config.js';
 
 export async function runWithExtension(config: FullConfig, abortController: AbortController) {
   const contextFactory = await startCDPRelayServer(config.browser.launchOptions.channel || 'chrome', abortController);
-  const serverBackendFactory = () => new BrowserServerBackend(config, contextFactory);
+
+  let backend: BrowserServerBackend | undefined;
+  const serverBackendFactory = () => {
+    if (backend)
+      throw new Error('Another MCP client is still connected. Only one connection at a time is allowed.');
+    backend = new BrowserServerBackend(config, contextFactory);
+    backend.onclose = () => {
+      contextFactory.clientDisconnected();
+      backend = undefined;
+    };
+    return backend;
+  };
+
   await mcpTransport.start(serverBackendFactory, config.server);
 }