chore: first pass at browser server #36327
Conversation
There was a problem hiding this comment.
Pull Request Overview
This PR introduces a new browser server that manages browser lifecycle and enables sharing between Playwright MCP, VS Code Extension, and CLI clients via HTTP endpoints.
- Adds
/json/listand/json/launchHTTP endpoints toWSServer - Implements
onList/onLaunchinPlaywrightServerwithreuseGrouplogic - Updates CLI to POST to the browser server when
PW_BROWSER_SERVERis set
Reviewed Changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.
Show a summary per file
| File | Description |
|---|---|
| packages/playwright-core/src/server/utils/wsServer.ts | Added HTTP endpoints for listing and launching browsers and JSON body parsing helpers |
| packages/playwright-core/src/remote/playwrightServer.ts | Impl. of onList/onLaunch, tracking non-testing browsers by reuseGroup and exposing WebSocket paths |
| packages/playwright-core/src/remote/playwrightConnection.ts | Added keepBrowser callback to preserve reusable browsers and exported launchOptionsHash |
| packages/playwright-core/src/client/browserType.ts | Adjusted connect overloads to return the correct Browser type |
| packages/playwright-core/src/cli/program.ts | Uses PW_BROWSER_SERVER to POST launch requests, falling back to direct launch |
Comments suppressed due to low confidence (6)
packages/playwright-core/src/server/utils/wsServer.ts:90
- You should validate the parsed
body(e.g. checkbrowserName,launchOptionspresence and types) and return a clear HTTP 400 error when the payload is invalid, instead of letting JSON parsing errors or missing fields throw uncaught exceptions.
const body = await readBodyJSON(request) as LaunchRequest;
packages/playwright-core/src/server/utils/wsServer.ts:82
- Consider adding automated tests to cover the new
/json/listendpoint to verify it returns the expected browser list structure under different conditions.
if (request.method === 'GET' && request.url === '/json/list') {
packages/playwright-core/src/remote/playwrightServer.ts:87
- There is a potential race condition if two launch requests with the same
reuseGrouparrive concurrently: both could skip the existing browser check and launch duplicate browsers. Consider serializing or locking reuseGroup-based launches to prevent duplicates.
if (request.reuseGroup) browser = playwright.allBrowsers().find(b => b.options.name === request.browserName && this._nonTestingBrowsers.get(b)?.reuseGroup === request.reuseGroup);
packages/playwright-core/src/server/utils/wsServer.ts:56
- The
streamnamespace is used here but not imported. Please addimport type { Duplex } from 'stream';(or similar) sostream.Duplexis resolved correctly.
onUpgrade(request: http.IncomingMessage, socket: stream.Duplex): { error: string } | undefined;
packages/playwright-core/src/server/utils/wsServer.ts:58
- The delegate type makes
onClosemandatory but elsewhere you callthis._delegate.onClose?.(). Either makeonCloseoptional in the type or remove the optional chaining in the invocation to keep them consistent.
onClose(): Promise<void>;
packages/playwright-core/src/cli/program.ts:483
- When POSTing JSON, include the
Content-Type: application/jsonheader for clarity and to ensure proper parsing on the server side.
body: JSON.stringify({
This comment has been minimized.
This comment has been minimized.
| onConnection: (request: http.IncomingMessage, url: URL, ws: WebSocket, id: string) => WSConnection; | ||
| onClose?(): Promise<void>; | ||
| onHeaders(headers: string[]): void; | ||
| onList(): any[]; |
There was a problem hiding this comment.
These should be onGet() and onPost() instead. Or, as we usually do, a setRoute() direct call.
| @@ -60,14 +70,30 @@ export class WSServer { | |||
| async listen(port: number = 0, hostname: string | undefined, path: string): Promise<string> { | |||
| debugLogger.log('server', `Server started at ${new Date()}`); | |||
|
|
|||
| const server = createHttpServer((request: http.IncomingMessage, response: http.ServerResponse) => { | |||
| const server = createHttpServer(async (request: http.IncomingMessage, response: http.ServerResponse) => { | |||
| if (request.method === 'GET' && request.url === '/json') { | |||
There was a problem hiding this comment.
I'm not sure this endpoint makes sense for the new server.
| browserName: browser.options.name, | ||
| launchOptions: browser.options.originalLaunchOptions, | ||
| reuseGroup: this._nonTestingBrowsers.get(browser)?.reuseGroup, | ||
| wsPath: this._options.path + '?' + new URLSearchParams({ browserGuid: browser.guid }), |
There was a problem hiding this comment.
I think we'd like different paths for different browsers.
| }, | ||
|
|
||
| onLaunch: async request => { | ||
| if (!this._preLaunchedPlaywright) |
There was a problem hiding this comment.
I feel like the code here should be shared with what PlaywrightConnection does. Overall, the ownership of the browsers should be in a single place, not split between server and connection. Let's land a refactoring beforehand if we need it.
There was a problem hiding this comment.
Based on my understanding of the Server/Connection split, this means that browser ownership should live exclusively in the Server, not in the Connection. Does that match your thinking? Happy land a refactor if you could outline some more.
| }, | ||
|
|
||
| onLaunch: async request => { | ||
| if (!this._preLaunchedPlaywright) |
There was a problem hiding this comment.
Based on my understanding of the Server/Connection split, this means that browser ownership should live exclusively in the Server, not in the Connection. Does that match your thinking? Happy land a refactor if you could outline some more.
Test results for "tests 1"6 flaky39427 passed, 822 skipped Merge workflow run. |
|
Mirroring our offline discussion here:
|
|
revision 2: #36382 |
Adds a first sketch for a browser server that manages the browser lifecycle and facilitates sharing amongst Playwright MCP, the VS Code Extension and CLI clients like
npx playwright openornpx playwright test.GET /json/listgets a list of running browsersPOST /json/launchlaunches a browser, if there's no other browser with the same reuseGroupHere's a demo of interop between VS Code and MCP:
Screen.Recording.2025-06-16.at.15.01.37.mov
You can also do
nxp playwright openwith thePW_BROWSER_SERVERenv var. There's no support in test runner yet.See microsoft/playwright-mcp#554 and microsoft/playwright-vscode#643 for the other side of the demo.