Claude formalized Fermat's Last Theorem in 11 days.

Anthropic says Claude produced the first complete computer-checked proof of Fermat's Last Theorem in Lean after working largely autonomously for 11 days. The project matters because the proof is inspectable as code: 13 million lines, 30,300 proved theorems, and 29,500 theorems used in the final argument.

The underlying mathematics follows a simplified version of Andrew Wiles's accepted 1995 proof. The new development is the formalization workflow and its machine-checkable artifact. Dozens of Claude agents worked through Prove2Me, which organized theorem dependencies, while Lean checked the compiled result.

The proof repository is public. 12