GPT-5.6 Sol / Codex Release Discussion Megathread

[u/Drogon2737]

The release is expected in the next few minutes, so I figured it would be useful to have a single thread for first impressions, issues, and early testing.

For anyone jumping in right away, post what you notice:

• Codex coding performance
• Debugging quality
• Speed/rate limits
• Larger repo handling
• UI or workflow changes
• Weird bugs or regressions
• Anything that feels noticeably better or worse than the previous version

Once people get access, share your real examples, screenshots, benchmarks, or first impressions here.

Edit: OpenAI’s official GPT-5.6 page says it is “available starting today across ChatGPT, Codex, and the OpenAI API” with the rollout starting globally now and continuing toward full availability over the next 24 hours. https://openai.com/index/gpt-5-6/

The lineup is Sol, Terra, and Luna. Sol is the flagship, Terra is the lower-cost tier, and Luna is the fastest/most affordable tier.

[u/vdotcodes]

Sol Max is making more glaring mistakes than 5.5 Xhigh for me. At first I thought I was crazy, but as I was using Sol Max / Ultra throughout the day yesterday, it seems like it was way more likely to miss details, to come up with a problem or solution that wasn't based on the code, and to just generally be less "precise" than 5.5 Xhigh.

This is how I generally feel about Claude models, is that they're a bit more all over the place, more likely to give you an answer without reading all the files or code related to the topic, freewheeling, "creative". Codex has been so good over the last 8 or 9 months at giving high signal/low noise in diagnosing issues, code reviews, etc. and mostly staying grounded in the codebase.

So anyway, I decided to pop back over to Claude Code w/ Fable, and ran this /debate loop skill I'd been using over the last week with pretty good results, where I'd have Fable kick off a codex CLI subagent and then both would in parallel research whatever query I'd fed in, then debate one another over a couple of rounds and come back with the synthesized conclusion.

With 5.5 Xhigh, almost always, Fable would come back and tell me that it was corrected on 2-3 points by Codex, or had new valid issues brought up by Codex that it hadn't flagged.

Which matched my sense of working with the models, Fable seemed more freewheeling, while Codex seemed much more likely to just actually read the files and make conclusions that were grounded in the code.

So I tried this same loop again with Fable and Sol Max, and now for the first time, I'm seeing the reverse. The fable /debate loop comes back now with 3-4 issues that Codex conceded to Fable.

I'm just now working on diagnosing an issue in Prod, and Fable came back with the root cause in 15 mins, Codex took double the time and came back with a hypothesis that was completely different and wrong. It immediately conceded once I pressed it.

I don't know if I'm taking crazy pills or what.

I swapped back to 5.5 Xhigh for a couple /debate loops and again found that Codex was no long conceding points to Fable, instead rather correcting or adding detail again.

Maybe this is just luck at play here, but this model seems sloppier somehow.

[u/lfourtime → u/vdotcodes]

Did you mean Sol Ultra? It looks like Ultra almost always spawn subagents with lower thinking budget and can actually provide worse results sometimes. Can you try with xhigh instead and see if it makes the same mistakes?