GPT-5.5 reasoning tokens cluster at 516, causing wrong answers on coding tasks

GPT-5.5 的推理卡在 516 个 token：模型"想"的那一层会单独坏掉

Developer vguptaa45 audited 390K Codex responses and found GPT-5.5 reasoning cuts off at exactly 516 tokens in 44% of cases, versus 19.8% for GPT-5.4 and 0.34% for GPT-5.2. Truncated runs all produced wrong answers; the same tasks completed with 6,000–8,000 tokens all got correct. The community reproduced it and found adding 'THIS IS HARD' to the prompt bypasses the cutoff, pointing to a budget-classification bug rather than a model capability drop. In the same week, Liquid AI released Antidoom to fix the opposite failure—reasoning models stuck in self-revising doom loops. Both failures live in the reasoning layer, invisible to standard pass-rate evals. The post recommends monitoring reasoning token distributions and not assuming newer models are more stable.

Why it matters: A community audit of 390k Codex responses shows GPT-5.5's reasoning clips at exactly 516 tokens in 44% of coding tasks, all wrong, while full runs get it right. Solid data, reproduced, with a workaround — directly useful signal for AI coders. Not scored higher because it's a s...