MCP shutdown can terminate unrelated processes with Homebrew pgrep

[bagelcode-jhkim]

What happened?

On macOS, quitting an OmO native session can terminate unrelated processes when Homebrew proctools provides the first pgrep on PATH.

MCP shutdown calls collectProcessTree(), which currently runs pgrep -P <pid> without the required positional pattern. Homebrew pgrep treats that as a system-wide match, so reapProcessTree() can collect and signal PIDs that are not descendants of Senpi.

This matters because a normal /quit can close unrelated terminals, editors, and background services.

Steps to reproduce safely

Do not reproduce this through /quit. The lookup bug can be observed without sending any signals:

sleep 30 & child=$!
/opt/homebrew/bin/pgrep -P $$ | wc -l
/opt/homebrew/bin/pgrep -P $$ .
/usr/bin/pgrep -P $$ .
kill "$child"

On my machine, the patternless Homebrew command returned 798 PIDs and included PID 1. Both commands with the explicit . pattern returned only the actual child.

Expected behavior

Process-tree collection should query only direct children. Passing . as the match-all process-name pattern works with both Homebrew proctools and macOS /usr/bin/pgrep.

I am preparing a minimal fix and regression test.

Version

• omo-ai@5.0.0-0.beta.6
• nested @code-yeongyu/senpi@2026.8.11-4
• Homebrew proctools@0.4pre1
• current main at 20d33e8e46bef8ad38fcf1e99f8196b599741c44

[bagelcode-jhkim]

AI assistance disclosure: This report and the accompanying fix were drafted with Codex. I reproduced the behavior locally against the stated versions and reviewed the commands, diagnosis, and proposed patch.