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GPT-5.5 Codex reasoning-token clustering may be leading to degraded performance

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Re: GPT-5.5 Codex reasoning-token clustering may be leading to degraded performance

#61

Post by zuzululu »

this explains so much why gpt 5.5 has been so bad lately it was really puzzling why it struggled so much where when it first came out it was one shotting stuff totally amazing, i tried the prompt that will tell you if your plan is degraded:

    codex exec --json --skip-git-repo-check --ephemeral -s read-only --disable memories -m gpt-5.5 -c model_reasoning_effort=high "Do not use external tools. A black bag contains candies with counts: round apple 7, round peach 9, round watermelon 8; star apple 7, star peach 6, star watermelon 4. Shape is distinguishable by touch before drawing; flavor is not. What is the minimum number of candies to draw to guarantee having apple and peach candies of different shapes, i.e. round apple + star peach or round peach + star apple? Give reasoning and final number. The local project dir is irrelevant for this task, do not consult it. "
1. 516, 24

2. 516, 27

3. 516, 12

4. 516, 21

5. 516, 21

This means that the whole time we've been paying for a product that was silently routing to something completely different and inferior from gpt 5.5

Also I read through the github issues and it seems like they closed a previous issue without addressing it ???!!

whooo boy somebody from OpenAI is getting fired over this if not a class action lawsuit is almost guaranteed at this point.

Re: GPT-5.5 Codex reasoning-token clustering may be leading to degraded performance

#62

Post by matco11 »

zenapollo wrote: post #9

I’ve definitely experienced step jumps down in quality on an almost daily basis. I usually used xhigh. The experience of relying on codex’s outstandingly thorough coding earlier in the year has evaporated for me. I’m seeing incredibly stupid implementations intermittently, and have simply switched to Claude until openai takes the issue seriously. As far as i could tell they haven’t taken it seriously for the several…

I have noticed this degradation of 5.5 reliability to what, in my experience, I consider Claude-level of reliability since early June.

My journey dealing with this has been transitioning from 5.5 high to 5.5 xhigh to 5.4 high.

5.4 high has been perfectly reliable for me for the last 3 weeks, and I am happy there.

Occasionally, I run some tasks on 5.5 xhigh to check if it has gone back to being 100% perfectly reliable, but, at this point, I am assuming they are just counting on releasing 5.6 rather than dealing with this reliability issue.

Re: GPT-5.5 Codex reasoning-token clustering may be leading to degraded performance

#63

Post by jiggawatts »

simonw wrote: post #12
siva7 wrote: post #11

I swear some days ago someone here claimed Openai succeeded cutting down their compute cost by half with a breakthrough optimization. So this is it?

That was an article in The Information but it didn't read very well to me, I didn't get the impression the author was enough of a technical expert on how LLMs work to credibly evaluate the claim, which came from an insider rumor: https://www.theinformation.com/newsletters/ai-agenda/openai-... > OpenAI engineers earlier this month told some colleagues they had figured out a way to more than halve the cost of inference…

I bet that since this bug has made headlines, there are some panicked engineers at OpenAI desperately trying to figure out how to fix it without undoing their “magic optimisation”.

Re: GPT-5.5 Codex reasoning-token clustering may be leading to degraded performance

#64

Post by adithyassekhar »

laurels-marts wrote: post #58

I love that Codex is open source and issues like these can surface/be addressed publicly.

I feel openai in general is much more open and real business like compared to anthropic. They’re just a black box.

Re: GPT-5.5 Codex reasoning-token clustering may be leading to degraded performance

#65

Post by mannanj »

HumanOstrich wrote: post #26
jatora wrote: post #22

Earlier quoted context omitted.

The vibe-assumed claude code performance regression, yep. People should stop expecting consistent performance from non-deterministic systems. There is zero empirical corroboration of performance degredation. There has been a step change... in the amount of whining and complaining coders exhibit lately.

If you bother to look at the issue instead of whining and complaining, you will see the evidence.

This reminds me of a time in COVID-health response when certain scientists said their evidence was real evidence and yours was not.

"There's no evidence to prove xyz" then they would say, as your evidence was never as rigorous as theirs. And since they were proclaimed to be the only authorized scientists in the room, by authority of big governing bodies, they were right.

So people will see whatever evidence they want, and whine and complain to dig into their side as tribalistic creatures.

Re: GPT-5.5 Codex reasoning-token clustering may be leading to degraded performance

#66

Post by cute_boi »

adithyassekhar wrote: post #64
laurels-marts wrote: post #58

I love that Codex is open source and issues like these can surface/be addressed publicly.

I feel openai in general is much more open and real business like compared to anthropic. They’re just a black box.

Not only that, OpenAI generally doesn't gaslight compared to the misanthropic team especially Boris, who was constantly claiming there is nothing wrong with Claude Code. And OpenAI is generous with resets.

Re: GPT-5.5 Codex reasoning-token clustering may be leading to degraded performance

#67

Post by rockwotj »

laurels-marts wrote: post #58

I love that Codex is open source and issues like these can surface/be addressed publicly.

But this is model behavior and just a public issue tracker which claude code has just without code? I don’t see how it’s any different than https://github.com/anthropics/claude-code for these issues.

I do appreciate that codex is open source generally, but I don’t think it matters for this class of issue as the model is closed still

Re: GPT-5.5 Codex reasoning-token clustering may be leading to degraded performance

#68

Post by mhitza »

kleton wrote: post #7

Clearly they are batching reasoning inference in a few multiples of 512 tokens as a throughput optimization

My first thought would be an adjustment to a reasoning budget parameter (using llama.cpp as my reference) which would lead to these results. But no way to know precisely without an OpenAI statement.

It could be a very dishonest way of scaling to demand during peak hours. I know that some people already scoff in this topic about the subjective nature of perceived performance of models. But the model seemed less smart when US comes online (at least from my testing over the month of May).

On my company blog post from a few weeks ago I felt the need to point this out because it had a perceptively more consistent pattern during those overlap times. Should have saved the session logs for further analysis https://webesque.agency/blog/2026-06-19-llms.html

Re: GPT-5.5 Codex reasoning-token clustering may be leading to degraded performance

#69

Post by edg5000 »

For me, the encrypted reasoning contents, when looking at the base64 string lengtht, show this effect. However, the server-reported reasoning tokens don't. So I assumed it was part of the encryption and/or obfuscation purely. So I don't think there is a real issue.

This is the biggest downside of GPT; thinking is encrypted, so it's more of a black box than kimi/glm/deepseek. You still get thinking summaries though. It's awkward, but workable.

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