Released with 1M token context and 128k output.

Claude quietly removed full thinking traces feature, according to user reports and researcher Ethan Mollick.

Claude Opus 5 released with Fast Mode (2.5x speed) at Opus 4.8 pricing, saving 50% on tokens

Claude Opus 4.8 beats Gemini Pro 5 by 11 points on Fable 5 benchmark

Claude Opus 4.8 achieves 89% task completion and 2.5% harm rate on WorkBench, a dramatic improvement over GPT-4.

Claude Opus 4.8 adds dynamic workflows for agentic coding

GPT-5.5 fully solved TLO enterprise network simulation in 2 of 10 attempts

GPT-5.5 scored 71.4% on AISI expert CTF tasks, matching Claude Mythos Preview

Early user review of GPT-5.5 in Codex highlights major improvements

GPT-5.5 model family achieves leading position on Artificial Analysis Index for cost-performance