[Bug]: UI mode frequently crashes at test finish with "Error: EBUSY: resource busy or locked" #43821

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1. refactoreric commented on Oct 31, 2026

   

   refactoreric

   on Oct 31, 2026

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   Some additional information: It doesn't only happen at test finish. I just had another crash. I clicked the Refresh button in UI mode (after renaming test and adding test steps), and (maybe?) I restarted the test(?), or it already crashed during Refresh(?). Console output:

   node:internal/fs/watchers:323
       const error = new UVException({
                     ^
   
   Error: EBUSY: resource busy or locked, watch 'C:\SourceTests\Twinfield\EndToEndTests\TestResults\HTML\trace\uiMode.html'
       at FSWatcher.<computed> (node:internal/fs/watchers:323:19)
       at watch (node:fs:3176:36)
       at createFsWatchInstance (C:\SourceTests\Twinfield\EndToEndTests\node_modules\playwright-core\lib\utilsBundle.js:56597:32)
       at setFsWatchListener (C:\SourceTests\Twinfield\EndToEndTests\node_modules\playwright-core\lib\utilsBundle.js:56628:15)
       at NodeFsHandler._watchWithNodeFs (C:\SourceTests\Twinfield\EndToEndTests\node_modules\playwright-core\lib\utilsBundle.js:56746:16)
       at NodeFsHandler._handleFile (C:\SourceTests\Twinfield\EndToEndTests\node_modules\playwright-core\lib\utilsBundle.js:56802:25)
       at NodeFsHandler._addToNodeFs (C:\SourceTests\Twinfield\EndToEndTests\node_modules\playwright-core\lib\utilsBundle.js:56999:23)
   Emitted 'error' event on FSWatcher instance at:
       at FSWatcher._handleError (C:\SourceTests\Twinfield\EndToEndTests\node_modules\playwright-core\lib\utilsBundle.js:57489:12)
       at NodeFsHandler._addToNodeFs (C:\SourceTests\Twinfield\EndToEndTests\node_modules\playwright-core\lib\utilsBundle.js:57006:20) {
     errno: -4082,
     syscall: 'watch',
     code: 'EBUSY',
     path: 'C:\\SourceTests\\Twinfield\\EndToEndTests\\TestResults\\HTML\\trace\\uiMode.html',
     filename: 'C:\\SourceTests\\Twinfield\\EndToEndTests\\TestResults\\HTML\\trace\\uiMode.html'
   }
   
   Node.js v26.12.1
   
2. Pavel Feldman (pavelfeldman)

   added

   needs-triage-win

   on Oct 31, 2026
3. github-actions commented on Oct 31, 2026

   

   github-actionsBot

   on Oct 31, 2026 – with GitHub Actions · Hidden as outdated

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4. github-actions commented on Oct 31, 2026

   

   github-actionsBot

   on Oct 31, 2026 – with GitHub Actions

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   Hi, I'm the Playwright bot and I reproduced this on Windows.

   Fixed on main by #43716, but not yet in a stable release. Holding the report files open with exclusive Windows locks crashes UI mode on 1.64.1 with the same EBUSY error and chokidar stack. The current watcher watches directories instead of opening a watch on each file; the same case now passes, including reloading and running tests while those files remain locked.

   This reproduces without VS Code or its extension. It confirms that a file lock is enough to trigger the crash, but does not identify which process holds the files in your environment.

   Reproduction and results

   I temporarily extended should not watch output in tests/playwright-test/ui-mode-test-watch.spec.ts. After one test completed, a fixture-managed PowerShell process created and exclusively locked TestResults\HTML\trace\uiMode.html and uiMode.js beneath the watched test directory:

   $streams = @('uiMode.html', 'uiMode.js') | ForEach-Object {
     [System.IO.File]::Open("TestResults\HTML\trace\$_",
       [System.IO.FileMode]::Create,
       [System.IO.FileAccess]::ReadWrite,
       [System.IO.FileShare]::None)
   }
   [Console]::WriteLine('LOCKED')
   [Console]::ReadLine() | Out-Null
   $streams | ForEach-Object { $_.Dispose() }

   The directory existed before starting UI mode. No watcher errors were simulated. The passing check also edited a test, clicked Reload, and ran it successfully before releasing the locks.

   All runs were on Windows with Node.js 24.22.2, rather than the reported 26.12.1:

   Version / commit	Mode	Result
   Published 1.64.1	Headless UI	Process crashes with EBUSY, errno -4082, watching uiMode.js; same chokidar stack as reported
   #43716 head 82c66e43e2595b8dae8785786af9e38d286bb346	Headless UI	Locked-file check passes
   Main deb7e86201e26cb4a8e25191fce5ef2f7a28aa87 (1.65.0-next)	Headless UI	All 10 UI watch tests pass, including the locked-file check
   Same main commit	Headed UI	Locked-file check passes

   UI mode uses Chromium; the test body did not launch a browser. Firefox and WebKit were not involved in this file-watcher failure.

   The fix merged as e905d4bd77dff425f981b03df861fed59b50c9dd. No release tag contains it; the latest stable package checked was 1.64.1. No additional source fix is needed for this reproduced failure.

   _{Triaged on Windows by the Playwright bot - agent run}
5. Pavel Feldman (pavelfeldman)

   closed this as completedon Nov 1, 2026