[BUG] Bash tool hangs and executes as background tasks in VSCode Copilot harness

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?

Description:

The Bash tool hangs when invoked through the Claude SDK/VSCode Copilot harness. All bash commands are spawned as background tasks instead of executing synchronously and returning output.

Environment:

• Platform: Linux (EL 8.10)
• Claude Code via: VSCode Copilot extension (Claude SDK agent harness)
• Settings: Minimal (only theme and attempted sandbox config)

Actual Behavior:

Every bash command returns immediately with a background task ID instead of executing. The task output file exists but remains empty. No errors appear in VSCode developer console.

Diagnostics:

• File tools (Read, Write, Glob, Grep) work correctly
• Bash tool always hangs, regardless of command
• No console errors in VSCode
• settings.json changes don't help
• Disabling sandbox doesn't help

Related Issues:

#52917, #52910, #52920

What Should Happen?

Bash commands execute synchronously and return output immediately.

Error Messages/Logs

Steps to Reproduce

1. Search for files in this directory beginning with the letter a

Result: Command running in background with ID: [id]. Output is being written to: /tmp/.../tasks/[id].output

Claude Model

Other

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

claude-haiku-4-5-20251001 VIA github.copilot-chat 0.45.1

Platform

Other

Operating System

Other Linux

Terminal/Shell

Other

Additional Information

Using VSCode copilot extension handing off to claude code SDK