fix(mcp): close isolated contexts on client disposal

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

@@ -132,14 +132,20 @@ export function decorateMCPCommand(command: Command) {
           },
           disposed: async backend => {
             clientCount--;
-            if (sharedBrowserPromise && clientCount > 0)
+            const browserContext = (backend as BrowserBackend).browserContext;
+            const browser = browserContext.browser();
+            // Decide before awaiting context closure, since client disposals can run concurrently.
+            const shouldKeepBrowser = !!sharedBrowserPromise && clientCount > 0;
+            if (shouldKeepBrowser) {
+              if (config.browser.isolated)
+                await browserContext.close().catch(() => { });
               return;
+            }
 
             testDebug('close browser');
             sharedBrowserPromise = undefined;
-            const browserContext = (backend as BrowserBackend).browserContext;
             await browserContext.close().catch(() => { });
-            await browserContext.browser()?.close().catch(() => { });
+            await browser?.close().catch(() => { });
           }
         };
         await mcpServer.start(factory, config.server);

tests/mcp/http.spec.ts

@@ -20,7 +20,7 @@ import dns from 'dns';
 import { ChildProcess, spawn } from 'child_process';
 import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/streamableHttp.js';
 import { Client } from '@modelcontextprotocol/sdk/client/index.js';
-import { test as baseTest, expect, mcpServerPath, formatLog } from './fixtures';
+import { test as baseTest, expect, mcpServerPath, formatLog, parseResponse } from './fixtures';
 import { inheritAndCleanEnv } from '../config/utils';
 
 import type { Config } from '../../packages/playwright-core/src/tools/mcp/config.d';
@@ -182,6 +182,14 @@ test('http transport browser lifecycle (isolated, multiclient)', async ({ server
   await transport1.terminateSession();
   await client1.close();
 
+  await expect.poll(async () => {
+    const response = parseResponse(await client2.callTool({
+      name: 'browser_run_code_unsafe',
+      arguments: { code: 'page => page.context().browser().contexts().length' },
+    }));
+    return response.result;
+  }).toBe('1');
+
   const transport3 = new StreamableHTTPClientTransport(new URL('/mcp', url));
   const client3 = new Client({ name: 'test', version: '1.0.0' });
   await client3.connect(transport3);