which GPT 5 model do you mean?
In the Codex desktop app I see 5.2, 5.3, 5.4 mini, 5.4, and 5.5. All with various reasoning and speed options. but no singular GPT 5.
I havent noticed any lower quality tbh. I have primarily been just using 5.5 and 5.3 for some planning, and they have seemed fine. i know there was some token consumption issues a bit ago, but that seems fine now. But as far as quality goes, I havent seen a drop or downgrade.
Is there any other info or examples you can give that could help troubleshoot this apaprent drop in quality? And also specify which GPT 5.x you mean?