playwright-cli remoteEndpoint does not forward browserName to run-server

[davzucky]

Summary

The playwright-core remote browser path used by @playwright/cli does not pass browserName when connecting to a raw Playwright run-server endpoint. The remote server then receives no x-playwright-browser header and fails while trying to launch an undefined browser type.

This shows up in @playwright/cli when using browser.remoteEndpoint in .playwright/cli.config.json.

Related user-facing CLI issue: microsoft/playwright-cli#408

Use Case

We run a development container with @playwright/cli installed and a separate Playwright service container running:

npx -y playwright@1.60.0 run-server --port 3456 --host 0.0.0.0

Our E2E tests already use this pattern successfully via @playwright/test and chromium.connect(...). We want @playwright/cli to connect to the same remote browser service via:

{
  "browser": {
    "browserName": "chromium",
    "isolated": true,
    "remoteEndpoint": "ws://playwright:3456/",
    "launchOptions": {
      "channel": "chrome"
    }
  }
}

Actual Behavior

playwright-cli open https://example.com --config=.playwright/cli.config.json fails with:

Cannot read properties of undefined (reading 'launch')

Debug output shows the inner server-side error:

TypeError: Cannot read properties of undefined (reading 'launch')
    at PlaywrightServer._initLaunchBrowserMode

Root Cause

In the remote browser path, createRemoteBrowser(config) calls connectToBrowser() without forwarding config.browser.browserName:

const endpoint = config.browser.remoteEndpoint;
const playwrightObject = playwright;
const browser = await connectToBrowser(playwrightObject, { endpoint });
browser._connectToBrowserType(playwrightObject[browser._browserName], {}, void 0);

But connectToBrowser() only sends the browser type to the server when params.browserName is present:

const nameParam = params.browserName ? { "x-playwright-browser": params.browserName } : {};

Because browserName is omitted, the remote run-server endpoint cannot select a browser type to launch.

Proposed Fix

Pass the configured browser name into connectToBrowser():

 const endpoint = config.browser.remoteEndpoint;
 const playwrightObject = playwright;
-const browser = await connectToBrowser(playwrightObject, { endpoint });
+const browser = await connectToBrowser(playwrightObject, {
+  endpoint,
+  browserName: config.browser.browserName,
+});
 browser._connectToBrowserType(playwrightObject[browser._browserName], {}, void 0);

Local Validation

We patched the installed bundled playwright-core locally with the change above. With:

• @playwright/cli@0.1.11
• matching remote playwright@1.60.0-alpha-1777669338000
• matching browser revision installed in the server container
• browser.isolated: true

the CLI successfully opened the page:

### Browser opened
### Ran Playwright code
await page.goto('https://example.com');

### Page
- Page URL: https://example.com/
- Page Title: Example Domain

browser.isolated: true is still needed because run-server returns a browser without an existing default context, but the undefined launch failure is fixed by forwarding browserName.

[yury-s]

run-server is a not a published API and we don't want to commit to supporting it for launching browsers via playwright-cli open.

In your case the recommended flow is to use launchServer/npx playwright launch-server --browser chromium to launch the browser and then call playwright-cli attach --endpoint <..> to attach to it. The idea is to use attach to remote (not owned by the client, including cdp, remote and extension) browser and use playwright-cli open only when the browser is launched by cli. Will this work for you?

While looking at this issue, we decided to restructure the config and separate remote/cdp/extension configuration from the browser config. While doing this we can also add remoteHeaders similar to cdpHeaders. After that you should be able to configure undocumented x-playwright-browser header for remote connection and that would give you the desired behavior with run-server, while we keep the right to break it in the future.