AI development company Anthropic announced on 2026-09-04 that its AI, Claude, has completed a proof of Fermat's Last Theorem that can be verified by a computer from start to finish. Working almost autonomously over the course of 11 days, Claude generated approximately 13 million lines of code in the proof assistant system Lean 4 and proved roughly 29,500 intermediate theorems. This is equivalent to more than five times the size of Mathlib, the library used by the mathematics community.

In mathematical proofs, if even a single logical link fails, the conclusion no longer holds. Therefore, computer verification requires rigorous descriptions of minute steps that are often omitted in papers written for humans. This process is known as "formalization," and this project was expected to take several years.

During the process, multiple AI agents divided the tasks of defining concepts and developing intermediate proofs. The development team stated that they achieved success by solving the challenge of project progress management through the introduction of Prove2Me, a collaborative platform for managing dependencies between theorems. The completed proof has been published on GitHub.

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