Claude produced the first end-to-end machine-checked proof of Fermat's Last Theorem: 13M lines of Lean, 30,300 theorems, 11 days, ~6B output tokens
Anthropic published the result on 2026-09-04: an internal general-purpose research model roughly comparable to Claude Fable 5.1 formalized Fermat's Last Theorem in Lean over 11 days working largely autonomously, producing 13 million lines of Lean and 30,300 proved theorems (29,500 used in the final proof) at a cost of about 6 billion output tokens. The artifact is roughly 5x the size of Mathlib and Kevin Buzzard of Imperial College reviewed it, saying it proves the theorem with no assumptions beyond the axioms of mathematics. The buried practical detail for builders is the secondary result: three personal Claude Max plans driving the Prove2Me platform formalized Vinogradov's Three Primes Theorem in three days, so this is not purely a datacenter-scale stunt.
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