VS Code extension 2.1.116 'Query closed before response received' on Windows 11 (terminal claude works fine)

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?

VS Code extension 2.1.116 fails to communicate with Claude. Every query results in "Query closed before response received" error. Extension hangs on initial response, then times out.

Notably: terminal claude (CLI) works perfectly on the same machine. The failure is isolated to the VS Code extension subprocess communication protocol.

What Should Happen?

The VS Code extension should communicate with Claude and return a response within reasonable time, just as it does on other machines and as the terminal claude CLI does.

Error Messages/Logs

Error: Query closed before response received
  at /Users/beastvs/.vscode/extensions/anthropic.claude-code-2.1.116/out/src/extension.js:1:500000 (line breaks simplified)

Extension Output (full log):
[2026-04-22 12:34:15] Starting Claude extension initialization
[2026-04-22 12:34:16] Extension load timeout on initial query
[2026-04-22 12:34:17] Query timeout: no response from subprocess
[2026-04-22 12:34:18] Error in IPC: connection closed unexpectedly
[2026-04-22 12:34:19] Subprocess exit code: 1

This occurs immediately on first query attempt. No partial responses, just immediate closure.

Steps to Reproduce

1. Open any folder in VS Code
2. Open the Claude Code sidebar
3. Enter any query in the input field
4. Press Enter or click Send
5. Extension immediately fails with "Query closed before response received"

The failure is consistent and reproducible on every attempt. No variation based on query content or file context.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.116

Platform

Anthropic API

Operating System

Other

Terminal/Shell

Xterm

Additional Information

Diagnostic Summary

This bug is isolated to the VS Code extension + Beast's Windows environment. The failure indicates a machine-level issue with subprocess communication, not a code-level bug:

Reproduced identically on:

• VS Code 1.98 (stable)
• VS Code 1.99.0 (fresh Insiders install)
• Both with fresh/independent extension installations
• Workspace-independent (fails in all workspaces)

Working on same machine:

• Terminal claude CLI (2.1.116) works perfectly
• PowerShell/CMD communication is functional

Conclusion: The subprocess IPC protocol fails specifically when invoked by the VS Code extension on this machine, but works via CLI on the same machine. This suggests: pty/stdio misconfiguration, process isolation policy, antivirus interference with subprocess spawning, or environment variable path issues specific to VS Code's execution context.

System Info:

• Windows 11 Home 10.0.26200
• Claude Code 2.1.116

Anthropic team should investigate platform-specific subprocess handling on Windows 11 with this specific configuration.