Anthropic launches Claude Fable 5.2 and Mythos 5.2, claiming two solved black-hole physics problems
Fable 5.2 is available to all users today, while Mythos 5.2, the same model with fewer safeguards, goes only to vetted organisations; both are up to 30% faster and cost $8/$40 per million tokens.
Why it matters
The 5.2 models follow Fable 5.1 and Mythos 5.1 in September and arrive as Anthropic prepares its IPO. Anthropic's own table puts Fable 5.2 ahead of Opus 5.5, GPT-6 Astra and Gemini 4 Carbon on most tests, including 49.1% on FrontierCode 2.0 and 74.2% on Humanity's Last Exam with tools. It also says the model formalised the proof of Fermat's Last Theorem in 30 hours. These are company-reported results; watch for independent benchmark runs, the system card's safety findings and outside checks of the physics claims.
Key facts
- Fable 5.2 available to all users from 9 Nov 2026
- Mythos 5.2 limited to vetted organisations
- Price: $8 input / $40 output per million tokens
- Up to 30% faster than the 5.1 models
- FrontierCode 2.0: 49.1% at Xhigh effort
- Formalised Fermat's Last Theorem proof in 30 hours (company claim)