[BUG] AskUserQuestion permission stream closes before response - "Unhandled case: [object Object]" in VS Code extension

Seeing the same Unhandled case: [object Object] banner on macOS (Claude Code v2.1.141, VS Code 1.95+, Darwin 25.4.0), but with a different root cause in the webview console — not AskUserQuestion / JSON parse, but Monaco editor worker loading.

Worth noting because both stacktraces end at the same React error boundary, so it might be one bug or two — wanted to flag it in case it's useful triage data.

Webview DevTools console (Cmd+Shift+P → "Developer: Open Webview Developer Tools")

Preceded by 6× CSP font-src violations, then:

Could not create web worker(s). Falling back to loading web worker code in main thread, which might cause UI freezes.
You must define a function MonacoEnvironment.getWorkerUrl or MonacoEnvironment.getWorker

Uncaught Error: Cannot read properties of undefined (reading 'toUrl')
TypeError: Cannot read properties of undefined (reading 'toUrl')
at Cv.toUri (index.js:22:12569)
at Cv.asBrowserUri (index.js:22:12022)
at index.js:36:30407
at new Promise (<anonymous>)
at $M.$loadForeignModule (index.js:36:30269)
at index.js:631:7606
at async index.js:1419:6748

This loops hundreds of times until the React error boundary catches it and renders Unhandled case: [object Object] in the chat UI.

Output channel (Anthropic.claude-code.Claude VSCode.log)

The Node side is clean — only routine claude-vscode: tools/list failed (MCP error -32601: Method not found) per prompt, no AskUserQuestion errors, no JSON parse errors. So this is purely webview-side.

Repro

Intermittent, no clear trigger — appears mid-session on long-running tasks. Functionality continues to work (Claude responses still render), banner is cosmetic but persistent until window reload.

Suggested fix direction

Monaco's worker setup needs MonacoEnvironment.getWorker defined for the webview's CSP/sandbox context — the current bundle seems to assume a different host environment. Same place could also tighten the error boundary so unknown error shapes render something less opaque than [object Object].

Happy to provide more logs or test a fix.
Wenn du's posten willst:

gh issue comment 59024 --repo anthropics/claude-code --body-file <PATH>
Soll ich den Text in eine .md-Datei im Repo legen damit du ihn easy posten kannst, oder einfacher: du kopierst direkt von hier rein? Letzteres ist sauberer (kein commit-tauglicher Müll im Repo).

aber claude unterbricht dann die session, wird interrupted, jfi
Wichtige Korrektur — dann ist's kein kosmetisches Problem sondern hard breakage. Let me fix the comment:

Seeing the same Unhandled case: [object Object] banner on macOS (Claude Code v2.1.141, VS Code 1.95+, Darwin 25.4.0), but with a different root cause in the webview console — not AskUserQuestion / JSON parse, but Monaco editor worker loading.

Worth noting because both stacktraces end at the same React error boundary, so it might be one bug or two — wanted to flag it in case it's useful triage data.

Impact

Not just cosmetic — when the banner appears, the active Claude session is interrupted. The stream stops mid-response and the user has to restart or resume. Functionality is not preserved across the error.

Webview DevTools console (Cmd+Shift+P → "Developer: Open Webview Developer Tools")

Preceded by 6× CSP font-src violations, then:

Could not create web worker(s). Falling back to loading web worker code in main thread, which might cause UI freezes.
You must define a function MonacoEnvironment.getWorkerUrl or MonacoEnvironment.getWorker

Uncaught Error: Cannot read properties of undefined (reading 'toUrl')
TypeError: Cannot read properties of undefined (reading 'toUrl')
at Cv.toUri (index.js:22:12569)
at Cv.asBrowserUri (index.js:22:12022)
at index.js:36:30407
at new Promise (<anonymous>)
at $M.$loadForeignModule (index.js:36:30269)
at index.js:631:7606
at async index.js:1419:6748

This loops hundreds of times until the React error boundary catches it and renders Unhandled case: [object Object] in the chat UI, interrupting the in-flight session.

Output channel (Anthropic.claude-code.Claude VSCode.log)

The Node side is clean — only routine claude-vscode: tools/list failed (MCP error -32601: Method not found) per prompt, no AskUserQuestion errors, no JSON parse errors. So this is purely webview-side.

Repro

Intermittent, no clear trigger — appears mid-session on long-running tasks. After the banner, the session is dead and the next prompt starts a fresh stream context.

Suggested fix direction

Monaco's worker setup needs MonacoEnvironment.getWorker defined for the webview's CSP/sandbox context — the current bundle seems to assume a different host environment. Same place could also tighten the error boundary so unknown error shapes render something less opaque than [object Object] instead of killing the session.

Happy to provide more logs or test a fix.

Found 3 possible duplicate issues:

1. https://github.com/anthropics/claude-code/issues/51851
2. https://github.com/anthropics/claude-code/issues/51339
3. https://github.com/anthropics/claude-code/issues/44157

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