Codex

Codex: OpenAI’s coding agent, working in the same terminal-and-project shape as other agents.

Not the same as ChatGPT in a browser tab

A chat hands you text to paste. Codex works on the repository itself: in the CLI or the IDE extension on your machine, or as a cloud task whose changed files you inspect before you commit or open a pull request.

Where it bites

Codex reads AGENTS.md files before doing any work, and a file closer to your working directory overrides guidance from one higher up. Rules kept in another agent’s instruction file are not what it reads by default, so check which file each agent actually loads when you switch between them.