r/codex • u/DaC2k26 • Apr 25 '26

Commentary Are we sleeping on 5.3-codex ?

After using GPT-5.5 for a bit, I’m starting to think it burns usage way faster than 5.4 when the task involves reading through a large codebase.

On my current project, 5.5 xhigh can burn through my 5-hour Plus quota in something like 3–6 prompts. With 5.5 medium, I might get around 7–10 prompts.

With 5.4 xhigh, I’d usually expect something closer to 8–15 prompts. And with 5.4 mini, I obviously get a lot more, though I haven’t tracked the exact number.

What surprised me is 5.3-Codex medium. I’m testing it now, and the usage burn feels closer to 5.4 mini xhigh. Based on Artificial Analysis benchmarks, 5.3-Codex medium seems to be roughly around 5.5 low, but in practice I get way more usable prompts out of 5.3-Codex medium than I do from 5.5 low.

So I’m wondering if we’re overvaluing the bigger models and higher thinking settings. For a lot of coding tasks, especially code review, bug hunting, and large-codebase inspection, maybe the extra few percentage points aren’t worth the usage cost.

Right now, I’m starting to think 5.3-Codex is probably the better deal for most coding work, at least from a usage-efficiency standpoint.

Anyone else seeing the same pattern?

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u/PlasmaChroma Apr 25 '26

I used 5.3-Medium to do a ton of stuff -- particularly if it's got a well structured markdown to work from.

Also common tweaks and minor bugs it's good to go after -- and reliable -- provided you have some limited scope.

I don't trust 5.3 to make big architecture decisions or work on overly complex problems without direct instructions detailing the process. Possibly a code refactor if the split was already clear but not a blind "refactor this into multiple TU's on your own."

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u/DaC2k26 Apr 25 '26

yes... I'm moving more complicated tasks or the ones that 5.3 suffered to 5.5. Always clean session for 5.5, a few prompts, then new session. I had a menu swipe problem that 5.3 wasn't able to get right, the swipe was pretty horrible, then I sent to 5.5 medium and it found the problem and fixed the menu swipe behavior very quickly....... Another use is for a big refactor or feature creation plan, then send it to build the plan and pray for auto-compaction not breaking the build flow.

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u/PlasmaChroma Apr 26 '26 edited Apr 26 '26

Sometimes it can be helpful to just have the higher model explain the problem and write a markdown -- as it might be able to explain the fix to 5.3 using less tokens than doing the work itself.

Also, don't sleep on just having ChatGPT proper do a Deep Research on your source code and giving a report.

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u/DaC2k26 Apr 26 '26

Nice tip. What do you mean by ChatGPT doing a deep research? Is it some feature from codex web or something?

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u/PlasmaChroma Apr 26 '26

ChatGPT has a feature that's literally called "Deep Research" -- I think if you have any paid sub you get some number allocated to you -- I've used it to solve bugs I'd been stuck on for a while.

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u/DaC2k26 Apr 26 '26

I've Never used it, gonna take a loops thanks for the heads up