Codex 5.3 Xhigh > Opus 4.6 in my work to this point.
Hoping for Opus 4.7 or whatever comes next to rectify this as I'm a bit annoyed over having to drop to a lower quality model.
But for the chat, I feel like ChatGPT got worse and worse.
Unless I specifically say "use git", it won't bother using git, apparently saying "configure AGENTS.md to us best practices" isn't enough for it to (at least in this case) use git. If this was isolated I might put that down to bad luck, given the nature of LLMs, but I have been finding Codex uses the wrong approaches all over the place, also stops in the middle of tasks, skips some tasks entirely (sometimes while marking them as done, other times it just doesn't get around to it).
I'd rank the output of Claude as similar to a junior with 1-3 years experience. It's not great, but it's certainly serviceable, a bit of tweaking even shippable. Codex… what I see is more like a student project. Or perhaps someone in the first month of their first job. Even the absolute worst human developers I've worked with after university weren't as bad as Codex, but several of them I'd rank worse than Claude.
Also, I noticed it skips instructions if I steer it with prompts while it is doing stuff instead of queueing my instructions.
OpenAI's 5.3 Codex model on xhigh still makes a huge number of mistakes, somewhere between 25-50% of commits, and it's still terrible at making its own plan, estimating how long tasks will take to complete, and recognising which tasks need to be subdivided*. Claude's model last November was better on both counts, even though it still wasn't IMO ready for true lights-off-no-code-check-needed-vibe-coding, it was making mistakes far less often and was scoping task complexity appropriately.
That said, given xhigh seems to be going through my token allowance far, far slower than on medium, I wouldn't be surprised if it turns out the Codex app itself is vibe coded and has mis-mapped that setting in some weird way. Either that or they've suddenly got a lot more spare capacity because of the boycotts.
* given the METR study, in the planning phase I ask all these models (Codex and Claude) to break down tasks into things that would take a junior developer 1-2 hours, but Codex will estimate 60 minutes for everything from "write 19 lines including comments to stub 3 empty methods in new class" to tasks I'd expect to take a senior 2 days.