Claude completes first end-to-end Lean formal proof of Fermat's Last Theorem

Anthropic said an internal Claude research model, adapting pieces of Kevin Buzzard's Imperial College FLT formalisation project and building on Mathlib, produced a complete computer-checked proof in 11 days using about six billion output tokens. It generated around 13 million lines of Lean and proved some 30,300 intermediate theorems, 29,500 of which were used in the final proof, with only occasional high-level human direction. Buzzard said it relies only on the axioms of mathematics; Anthropic notes the proof is likely much longer than it needs to be.