Anthropic uploads a Lean 4 proof of Fermat's Last Theorem, and it 'smells like Claude'

eldonredwards · x · 2026-09-05

Anthropic has uploaded a Lean 4 formalization of Fermat's Last Theorem. Ethan Mollick notes that even the short proof description — 'names each step and the Lean Theorem that carries it' — strongly resembles Claude's style, suggesting heavy Claude involvement. Formalizing landmark proofs is a marquee test of frontier-model math ability, making this a notable milestone.

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