1,000 CLAUDE AGENTS TURNED A 350-YEAR-OLD MATH PROOF INTO COMPUTER CODE IN 30 HOURS

Anthropic released Claude Fable 5.2 and Claude Mythos 5.2 on November 9 — the same underlying model under different safeguards. Fable is open to all users; Mythos goes only to vetted cybersecurity and life-sciences organizations. Both cost $8 per million input tokens and $40 per million output, down from $10 and $50, and generate output up to 30% faster than the 5.1 generation, with a 1 million-token context window.

The showpiece claims are Anthropic's own and still await independent verification: a team of about 1,000 Fable 5.2 agents formalized the proof of Fermat's Last Theorem in Lean in about 30 hours — a computer-checked formalization, not a new proof — the models solved two open problems in black-hole physics and designed three working electronic devices, and Fable 5.2 scored 49.1% on the FrontierCode 2.0 coding benchmark against 32.4% for Fable 5.1. Anthropic says Claude now writes more than 90% of the changes merged into its core codebase, with human guidance.