OK, enough. I'm tired of wondering whether GPT quietly got worse on me and just isn't saying so. To find out if it's my paranoia, I built is-gpt-nerfed: a nerf detector for Codex. Nerfing can happen at three levels, and it checks all three: - Account level: your whole account has been degraded. Every new session gets the worse model. Caught by probing a brand-new session. - Session level: only some of your sessions are degraded. Caught by forking the session ephemerally and fingerprinting the answers, so nothing shows up in Codex. - Request level: only some of your requests are degraded. A single turn quietly sent to a smaller model or a lower reasoning effort. Codex's own records give this away, so this check costs zero tokens. If those records lied, this would be the hardest level to catch. It's also the least likely: switching models mid-session throws away multiple layers of cache, which costs them more compute. It also tells you when you've been quietly moved up to a canary model, like the 5.6 Sol → 6 Sol switch people have been reporting on X.