[BUG] Zombie background task

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?

The background task listed in tasks has the status killed, but it is still running. Output is growing and all.

<img width="2404" height="1188" alt="Image" src="https://github.com/user-attachments/assets/ac3b0e89-ea3d-4037-ab61-23004f16242a" />

What Should Happen?

Claude should correctly show the tasks status.

Error Messages/Logs

Steps to Reproduce

I'm not sure, to be honest, let me know what information might be helpful.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.2

Platform

Anthropic API

Operating System

Other Linux

Terminal/Shell

Other

Additional Information

_No response_