A number theory theorem proposed by Pierre de Fermat in 1637, stating no three positive integers satisfy a^n + b^n = c^n for any integer n greater than two.
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.
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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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OpenAI says tens of thousands of agents solved a 90-year-old problem carrying a $1 million prize. The solution still needs independent verification, and a rival pair of mathematicians has a claim on the credit.
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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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