I work in Codex CLI and generally update when I see a new stable version come out. That meant that yesterday, I agreed to the prompt to try gpt-5.1.-codex-max. I stuck with it for an entire day, but by the end it caused so many problems that I switched back to plain gpt-5.1-codex model (bonus for the confusing naming here). codex-max was far too aggressive in making changes and did not explore bugs as deeply as I wished. When I went back to the old model and undid the damage it was a big relief.

That said I suspect many vibe coders in this sub might like it. I think Open AI heard the complaints that their agent was "lazy" and decided to compensate by making it go all out. That did not work for me though. I'm refactoring an enterprise codebase and I need an agent that follows directions, producing code for me to review in reasonable chunks. Maybe the future is agents that follow our individual needs? In the meantime I'm sticking with regular codex, but may re-evaluate in the future.

EDIT: Since people have asked, I ran both models at High. I did not try the Extended Thinking mode that codex-max has. In the past I've had good experiences with regular Codex medium as well, but I have Pro now so generally leave it on high.