[BUG] Subagent grep outlives its session, ate 11 GB of RAM

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?

A previous Claude Code session spawned a grep that kept running after the session ended. Found it casually using 38.8% of my RAM (11.4 GB on a 28 GB machine) and 99.9% CPU:

grep -o .\{0,2000\}Your order has been processed.\{0,3000\} ~/.claude/projects/<project>/<session>.jsonl
It was grepping through its own conversation transcript with a huge regex context window, which made it buffer the whole file into memory. Only found it because RAM hit 92% and I went hunting with ps aux.

Child processes from subagents should get cleaned up when the session ends.

Claude Code VS Code extension v2.1.63, Linux

What Should Happen?

Child processes from subagents should get cleaned up when the session ends.

Error Messages/Logs

Steps to Reproduce

1. Use Claude Code in VS Code with subagents over a long session
2. End the session
3. Check ps aux --sort=-%mem — orphaned grep process still running on the session's JSONL transcript
4. Process consumes unbounded RAM (11.4 GB in this case)

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.62 (Claude Code) / Extension 2.1.63

Platform

Anthropic API

Operating System

Other Linux

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_