OpenAI Codex CLI: Lightweight coding agent that runs in your terminal

I tried one task head-to-head with Codex o4-mini vs Claude Code: writing documentation for a tricky area of a medium-sized codebase.

Claude Code did great and wrote pretty decent docs.

Codex didn't do well. It hallucinated a bunch of stuff that wasn't in the code, and completely misrepresented the architecture - it started talking about server backends and REST APIs in an app that doesn't have any of that.

I'm curious what went so wrong - feels like possibly an issue with loading in the right context and attending to it correctly? That seems like an area that Claude Code has really optimized for.

I have high hopes for o3 and o4-mini as models so I hope that other tests show better results! Also curious to see how Cursor etc. incorporate o3.

Claude Code still feels superior. o4-mini has all sorts of issues. o3 is better but at that point, you aren't saving money so who cares.

I feel like people are sleeping on Claude Code for one reason or another. Its not cheap, but its by far the best, most consistent experience I have had.

"gemini 2.5 pro exp" is superior to Claude Sonnet 3.7 when I use it with Aider [1]. And it is free (with some high limit).

[1]https://aider.chat/