fix(mcp): disable the chromium sandbox for the bundled browser on linux by yury-s · Pull Request #42490 · microsoft/playwright

Yury Semikhatsky (yury-s) · 2026-09-01T17:31:36Z

Summary

An undefined channel with browserName: 'chromium' resolves to the same downloaded build as the chromium and chrome-for-testing channels, so treat it the same when defaulting chromiumSandbox on linux.

An explicit browserName 'chromium' without a channel launches the same downloaded build as the 'chromium' and 'chrome-for-testing' channels, which has no setuid sandbox helper on linux. Fixes: microsoft#42452

Pavel Feldman (pavelfeldman) · 2026-09-01T17:54:06Z

+    if (process.platform === 'linux') {
+      // Downloaded chromium builds (undefined channel, 'chromium', 'chrome-for-testing') lack the setuid sandbox helper on linux.
+      const { channel } = browser.launchOptions;
+      browser.launchOptions.chromiumSandbox = channel !== undefined && channel !== 'chromium' && channel !== 'chrome-for-testing';


channel !== 'chrome-for-testing' <-- I would kick this out.

It's in the same category. The downloaded builds ship chrome_sandbox, but it's extracted from a zip as -rwxr-xr-x user user and archives can't carry setuid root.

github-actions · 2026-09-01T18:28:25Z

Test results for "MCP"

1 failed
❌ [firefox] › mcp/cli-core.spec.ts:97 › fill @mcp-windows-latest-firefox

8307 passed, 1377 skipped

Merge workflow run.

github-actions · 2026-09-01T18:32:21Z

Hi, I'm the Playwright bot and I took a first look at the CI failure here.

🟢 The one failure is a pre-existing flake — this PR is clear

The single red is [firefox] › mcp/cli-core.spec.ts:97 › fill on mcp-windows-latest-firefox. This PR only changes how chromiumSandbox defaults for downloaded Chromium builds on Linux — it can't affect a Firefox MCP test on Windows. And the same test failed on a non-PR push (SHA d529911d, 2026-07-28) with the identical error, so it predates your change.

Details

Pre-existing flake / infra

[firefox] › mcp/cli-core.spec.ts:97 › fill — Windows-Firefox-only flake. Across the test-results DB this test is green almost everywhere: mcp-windows-latest-firefox 2 failed / 694 runs, and 0 failures on the ubuntu (701 runs) and macOS (707 runs) bots. Crucially, one of those two failures was run 30317255877 on SHA d529911d (a push, not this PR), with the exact same assertion:
```
expect(received).toBe(expected)
Expected: "- textbox [active] [ref=e2]: Hello, world!"
Received: undefined
```
The snapshot occasionally comes back without the filled textbox on Windows-Firefox. This PR touches only packages/playwright-core/src/tools/mcp/config.ts (chromiumSandbox defaulting for chromium/chrome-for-testing/undefined channels on Linux) and a Linux-gated test — nothing in the Firefox fill/snapshot path.

_{Triaged by the Playwright bot - agent run}

## What's New ### 🎉 New Tools - **`browser_webmcp_list` / `browser_webmcp_call`** — List and call the tools a page registers through the [WebMCP](https://webmachinelearning.github.io/webmcp/) API, letting the page do the work instead of driving its UI. When a page has WebMCP tools, the page status reports how many are available ([#42613](microsoft/playwright#42613)). WebMCP is experimental, see [WebMCP in Chrome](https://developer.chrome.com/docs/ai/webmcp) for how to enable it. ### Other Changes - New `--profile-dir-name <name>` option (env `PLAYWRIGHT_MCP_PROFILE_DIR_NAME`) selects the Chrome profile to connect to in extension mode when the extension is installed in several profiles, for example `"Profile 1"` ([#42527](microsoft/playwright#42527)) - Headless browsers launched by the server are now closed after one hour without tool calls; the next tool call launches a new one. Use `--idle-timeout <ms>` (config `timeouts.idle`, env `PLAYWRIGHT_MCP_IDLE_TIMEOUT`) to change the timeout, `0` disables it. Headed and attached browsers are not closed unless a timeout is set explicitly ([#42663](microsoft/playwright#42663), [#42676](microsoft/playwright#42676)) - `--image-responses` accepts `only`: a response that carries an image consists of the image parts alone, without the text part ([#42672](microsoft/playwright#42672)) ## Bug Fixes - `browser_close` returns an error when the browser context is shared (`--shared-browser-context`) instead of breaking the calling client's session. This supersedes the v0.0.80 change that dropped the backend after `browser_close` ([#42495](microsoft/playwright#42495)) - With `--shared-browser-context`, `browser_start_recording` / `browser_stop_recording` (opt-in via `--caps=devtools`) keep each client's recording separate instead of delivering one client's recorded actions to another ([#42622](microsoft/playwright#42622), [#42627](microsoft/playwright#42627)) - The file access check follows symlinks, so a symlink inside the workspace can no longer be used to read or write files outside the allowed roots ([#42628](microsoft/playwright#42628)) - Explicitly named output files in a nested directory (e.g. `sub/shot.png`) no longer fail with `ENOENT`; `browser_file_upload` and `browser_drop` resolve relative paths against the workspace root ([#42540](microsoft/playwright#42540)) - In extension mode with `PLAYWRIGHT_MCP_EXTENSION_TOKEN` set, a connection that never completes (e.g. the token belongs to another Chrome profile) now fails after 30 seconds with a hint instead of hanging the tool call forever ([#42525](microsoft/playwright#42525)) - Disable the Chromium sandbox by default on Linux for the bundled Chromium build, which lacks the setuid sandbox helper ([#42490](microsoft/playwright#42490))

## What's New ### 🎉 New Commands - **`webmcp-list` / `webmcp-call`** — List and call the tools a page registers through the [WebMCP](https://webmachinelearning.github.io/webmcp/) API, letting the page do the work instead of driving its UI. When a page has WebMCP tools, the page status reports how many are available ([#42613](microsoft/playwright#42613)). WebMCP is experimental, see [WebMCP in Chrome](https://developer.chrome.com/docs/ai/webmcp) for how to enable it. ### Other Changes - Headless sessions now shut down after one hour without commands, so a session an agent never closed no longer holds a browser; run `open` again to start a new one. Use `open --idle-timeout <ms>` (config `timeouts.idle`, env `PLAYWRIGHT_MCP_IDLE_TIMEOUT`) to change the timeout, `0` disables it. Headed browsers stay open, and attached browsers are only detached when `attach --idle-timeout <ms>` is set ([#42676](microsoft/playwright#42676)) - The skill includes a guide for attaching screenshots and videos to pull requests with `gh --attach` ([#42645](microsoft/playwright#42645)) ## Bug Fixes - Session daemons exit when their control socket is deleted or replaced, instead of staying alive with the browser ([#42454](microsoft/playwright#42454)) - Explicitly named output files in a nested directory (e.g. `screenshot --filename=sub/shot.png`) no longer fail with `ENOENT` ([#42540](microsoft/playwright#42540)) - Video chapters and screencast overlays are no longer hidden behind open dialogs and popovers ([#42642](microsoft/playwright#42642)) - `npx playwright test --debug=cli` works for tests that create more than one browser context and for every test in a worker, not just the first ([#42503](microsoft/playwright#42503)) - With `PLAYWRIGHT_MCP_EXTENSION_TOKEN` set, `attach --extension` fails after 30 seconds with a hint when the extension never connects (e.g. the token belongs to another Chrome profile) instead of hanging forever ([#42525](microsoft/playwright#42525)) - Disable the Chromium sandbox by default on Linux for the bundled Chromium build, which lacks the setuid sandbox helper ([#42490](microsoft/playwright#42490)) ## Upgrading ```bash npm install -g @playwright/cli@0.1.20 ```

fix(mcp): disable the chromium sandbox for the bundled browser on linux

9f286c5

An explicit browserName 'chromium' without a channel launches the same downloaded build as the 'chromium' and 'chrome-for-testing' channels, which has no setuid sandbox helper on linux. Fixes: microsoft#42452

Pavel Feldman (pavelfeldman) reviewed Sep 1, 2026

View reviewed changes

Pavel Feldman (pavelfeldman) approved these changes Sep 1, 2026

View reviewed changes

Yury Semikhatsky (yury-s) merged commit 03a69df into microsoft:main Sep 1, 2026
16 of 17 checks passed

Yury Semikhatsky (yury-s) deleted the fix-42452 branch September 1, 2026 18:08

This was referenced Sep 2, 2026

Track upstream MCP: auto-disable chromium sandbox for bundled Chromium on Linux JustasMonkev/mcp-accessibility-scanner#206

Closed

fix: disable bundled Chromium sandbox on Linux JustasMonkev/mcp-accessibility-scanner#208

Merged

github-actions Bot mentioned this pull request Sep 2, 2026

test(webkit): reenable WebSocket handshake HAR coverage #42513

Merged

This was referenced Sep 14, 2026

chore: mark v0.0.81 microsoft/playwright-mcp#1751

Merged

chore: mark v0.1.20 microsoft/playwright-cli#467

Merged

Navigation Menu

Uh oh!

fix(mcp): disable the chromium sandbox for the bundled browser on linux - #42490

fix(mcp): disable the chromium sandbox for the bundled browser on linux#42490
Yury Semikhatsky (yury-s) merged 1 commit into
microsoft:mainfrom
yury-s:fix-42452

Yury Semikhatsky (yury-s) commented Sep 1, 2026

Uh oh!

Pavel Feldman (pavelfeldman) Sep 1, 2026

Uh oh!

Yury Semikhatsky (yury-s) Sep 1, 2026

Uh oh!

Uh oh!

github-actions Bot commented Sep 1, 2026

Uh oh!

github-actions Bot commented Sep 1, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Uh oh!

Conversation

Yury Semikhatsky (yury-s) commented Sep 1, 2026

Summary

Uh oh!

Pavel Feldman (pavelfeldman) Sep 1, 2026

Choose a reason for hiding this comment

Uh oh!

Yury Semikhatsky (yury-s) Sep 1, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

github-actions Bot commented Sep 1, 2026

Test results for "MCP"

Uh oh!

github-actions Bot commented Sep 1, 2026

🟢 The one failure is a pre-existing flake — this PR is clear

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants