OpenAI's GPT-5.6 family — Luna ($1/$6), Terra ($2.50/$15), Sol ($5/$30) — hits GA. Sol beats Claude Fable 5 on Agents' Last Exam by 13.1 points.
Simon Willison spent 5.5 hours stress-testing Anthropic's Claude Fable 5. It's a big model with big guardrails — and a new fallback mechanism when safety filters trigger.
Anthropic's Claude Opus 4.8 arrives with improved honesty, better uncertainty flagging, and benchmark leads over GPT-5.5 — and the company actually calls it a minor update.