Especially in the CLI, it seems that its so way too eager to start writing code nothing can stop it, not even the best Agents.md.
Asking it a question or telling it to check something doesn‘t mean it should start editing code, it means answer the question. All models have this issue to some degree, but codex is the worst offender for me.
I see people gushing over these codex models but they seem worse than the big gpt models in my own actual use (i.e. I'll give the same prompt to gpt-5.1 and gpt-5.1-codex and codex will give me functional but weird/ugly code, whereas gpt-5.1 code is cleaner)
What has somewhat worked for me atm is to ask to only update an .md plan file and act on the file only, seems to appease its eagerness to write files.
I feel the same. CodexTheModel (why have two things named the same way?!) is a good deal faster than the other models, and probably on the "fast/accuracy" scale it sits somewhere else, but most code I want to be as high quality as possible, and the base models do seem better at that than CodexTheModel.