Codex CLI Zombie Processes Consuming CPU and Temporary Fix with pkill

Tadashi Shigeoka ·  Tue, November 11, 2025

I encountered a phenomenon where my MacBook Pro (Apple M1 Max) CPU was pegged at 100%, causing significant performance degradation. When I checked the Activity Monitor to investigate, I found numerous processes with the familiar name codex.

Temporary Fix for Codex CLI Zombie Processes

The root cause of this issue has not yet been identified, but since leaving it alone affects the overall machine performance, I decided to apply a symptomatic treatment.

The simplest method is to manually force-terminate the problematic processes.

pkill -f codex

Summary

In this article, I introduced the issue of Codex CLI becoming zombie processes that consume CPU, and a temporary workaround using pkill.

This is merely a symptomatic treatment, not a fundamental solution. Since this is likely a bug in Codex CLI itself, I’m considering actions such as investigating related issues on GitHub or compiling and reporting reproduction steps.

If you’re experiencing similar issues, I hope this temporary workaround helps.

That’s all from the Gemba on temporarily dealing with Codex CLI zombie processes using pkill -f codex.

References