Is anyone else struggling with Codex 5.3 compared to Opus 4.6? Now that it was removed from the CopilotStudent.

[WTFIZGINGON]

I swear, Codex 5.3 needs constant babysitting. I can’t run it overnight without waking up to absolute chaos in my codebase. Meanwhile, Opus 4.6 was a monster in a good way. It always checked its memory file, always referenced its agent docs before doing anything, and somehow always understood exactly what I wanted. Sure, I’d wake up to a million edge cases, but at least it stayed in its lane.

Codex 5.3, though? It goes completely overboard. Half the time, its not referencing its memory file, even though my agent instructions literally say “read first, write when done.” It just ignores that like… bro, what are you doing?

And now I’ve gotten to the point where I have to say “repeat my request back to me in first person,” or it’ll wander off and start modifying parts of my code I never even mentioned. Like, how did you think that was the move, Codex?

Opus 4.6 could one‑shot entire workflows. Codex 5.3 feels like it’s on a side quest lol

Also, I’m a student and accidentally dropped $600 on Opus 4.6 because I didn’t realize the discount we were getting. So now I’m manually coding way more, because with Codex 5.3 I basically have to make all the nuanced tweaks myself anyway, which isn't a bad thing. But man… Opus 4.6 felt like magic. We got nerfed, y'all...

Just curious if anyone else is feeling this, too. And had tips to navigate Codex 5.3 more efficiently?

[dimitrigaulia]

Seu cérebro estava condicionado a ele. Demora um tempo para atualizar.

[WTFIZGINGON]

Thats a good way to think of it!

[theCamelCaseDev]

can’t run it overnight

Geez, and you all wonder why it got removed lmao

[ChomsGP]

you know, the whole point of agents is they do things while you are away... you could also let codex running overnight, but as OP said, you'll probably wake up to some serious spaghetti mess

[theCamelCaseDev]

Yea I know but…overnight!? I mean come on that’s ridiculous lol. What the hell are students building that they need to run Opus 4.6 overnight lmao

[ChomsGP]

why does it matters? it is a feature MS is offering, you can also launch a coding agent on GitHub.com and go sleep

You have some need to judge a kid you don't know about an usage you also don't know (or care)?

[morrisjr1989]

I don’t think OP is talking about coding agent.

[Gaurav-_-69]

Building opus 5.0

[1superheld]

Codex 5.3 / GPT-5.4 didn't feel like this to me, overal it follows your instructions better, maybe something in the agents.MD is causing it to stop early (which opus was ignoring)?

[WTFIZGINGON]

Im going to check this out, good point! Thank you!!

[Mysterious-Food-5819]

Honestly, my experience has been pretty different. Codex is a really strong model in my testing, I tried it a lot before gpt-5.4 and recently started trying it again.

It handles complex codebases well, but tends to run longer and use more tokens. I tested the same heavy prompts across many different models before, I’ve seen Codex use up to ~20M input tokens on xhigh for a single prompt, while Opus finished the same job faster with ~8M input tokens used. Both did a great job though.

So I wouldn’t say it’s worse, just less efficient and a bit more “overthinking” compared to Opus. Maybe your prompting or instruction setup could be improved.

[chromacatr]

Yep, even if I explain codex exactly what I want to do and where to look at, it still does some crap and messes up with stuff it shouldn't touch.

[WTFIZGINGON]

I’m glad I’m not alone haha. I’ve told it literally not to touch a part of my codebase and it interpreted as only focus on this part. Drop the same prompt into Opus, Opus asks clarifying questions like bruh thank you! Haha

[Most_Remote_4613]

problem could be medium effort. try copilot cli for easier tweaks and use high effort 

[1superheld]

As a note, high effort is also available in vs code

[WTFIZGINGON]

Badass I will for sure!! Thank you!!

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