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

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When Claude Code invokes the AskUserQuestion tool, the permission stream closes before a response is received. This causes a JSON parse error (Expected ']') due to malformed tool input JSON, which then surfaces as Unhandled case: [object Object] in the VS Code extension UI. The session becomes unresponsive and shows a stream stall before dying.

What Should Happen?

The AskUserQuestion tool permission prompt should render in the VS Code extension, wait for user input, and return a valid response to the stream without closing prematurely.

Error Messages/Logs

[ERROR] "SyntaxError: SyntaxError: JSON Parse error: Expected ']'
    at <parse> (:0)
    at parse (unknown)
    at jOK (B:/~BUN/root/src/entrypoints/cli.js:175:10088)"

[DEBUG] "AskUserQuestion tool input error: AskUserQuestion failed due to the following issue:
The required parameter `questions` is missing"

[WARN] Streaming completed with 1 stall(s), total stall time: 54.7s

Tool output:
Tool permission request failed: Error: Tool permission stream closed before response received

Steps to Reproduce

1. Open Claude Code in VS Code
2. Start a session with a sufficiently complex or multi-step task
3. Wait for Claude Code to invoke the AskUserQuestion tool (typically happens when it needs clarification mid-task)
4. Observe that the permission prompt does not appear in the extension UI
5. Stream stalls (~15-30s) then closes with "Tool permission stream closed before response received"
6. Extension displays "Unhandled case: [object Object]" in the chat UI

Note: Issue appears intermittent and more likely to occur in longer sessions or after previous stalls.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.92 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

Issue occurs intermittently, more frequently in longer sessions. Stream stall warnings appear in logs before the crash (stream_idle_partial with lastChunkAgeMs=15000+). Session had message_count=420 in one instance. OS: Windows (Bun runtime path B:/~BUN/ visible in stack trace).