An AI Formalized and Verified Fermat’s Last Theorem in 11 Days, a Task Expected to Take Years

An AI Formalized and Verified Fermat’s Last Theorem in 11 Days, a Task Expected to Take Years

Claude did not rediscover the proof. It made the existing one machine-checkable.

13 million lines; 29,500 theorems: AI tackles Fermat's Last Theorem in 11 days

Anthropic says Claude has formalised Fermat's Last Theorem in just 11 days, producing 13 million lines of Lean code and 29,500 intermediate theorems, turning a famous human proof into a computer-checked mathematical proof.

Claude formalizes Fermat's Last Theorem in 11 days, completing the first complete machine-verified proof with 13 million lines of Lean code.

On September 4, 2026, AI development company Anthropic announced that its AI, 'Claude,' had completed a fully machine-verifiable proof of Fermat's Last Theorem. Claude worked almost autonomously for 11 days, generating approximately 13 million lines of code using the proof assistance system 'Lean 4.' Anthropic described this as the first complete machine-verified proof of Fermat's Last Theorem. Formalizing Fermat's Last Theorem \ Anthropic https…