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Mathlib is the community-built mathematics library for the Lean proof assistant, providing formalized definitions and theorems for machine-checked proofs.
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Anthropic published a 13-million-line Lean 4 proof of Fermat's Last Theorem that dozens of Claude agents wrote in 11 days. For teams weighing agents on correctness-critical code, the kernel checks every step, so what humans still review is the statement being proved.
Reality
An interview with Lean's founder says an AI translated C zlib into Lean and proved compress-then-decompress round-trips in about a week. The remaining work is optimization without breaking the proof.
Reality
Anthropic's own account has dozens of agents writing 13 million machine-checked lines in 11 days, about 7% of them dead ends, and only after a Columbia team built the shared to-do list that stopped them duplicating work.
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Kevin Buzzard holds a five-year grant to do the same job by hand. He compiled Anthropic's 13 million lines himself and says the result teaches mathematicians nothing and anyone running agent fleets quite a lot.
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Anthropic says its Claude agents ran autonomously for 11 days to formalise Fermat's Last Theorem in 13 million lines of Lean, a result that rests on a finished human proof and 2 million lines of prior formalisation.
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The build fails unless the theorem rests on exactly Lean's three standard axioms, and an independent kernel written in Rust re-checked more than a million declarations. The eleven-day timeline rests on Anthropic's own account.
Perspective Coverage
3 publishersReality
The Math-AI project turns plain-language mathematics into Lean 4 theorems, then files whatever compiles into a reusable library. The architecture is the claim, not the benchmark.
Reality