Claude formalized Fermat's Last Theorem in 11 days

Mathematicians expected the formalization of Fermat’s Last Theorem to take years. Anthropic says Claude did it in 11 days.

What happened

Working largely autonomously, dozens of Claude agents produced the first end-to-end, computer-checked proof of Fermat’s Last Theorem in Lean, the language mathematicians use to verify logic step by step. The run wrote about 13 million lines of Lean, proved 30,300 intermediate theorems, and followed a simplified version of the Wiles proof. Human input was limited to occasional high-level instructions. The finished proof is more than five times the size of Mathlib, the community library it builds on, and it passes Lean’s checker using just three standard axioms.

Why it matters

A formal proof is not a matter of opinion. It compiles or it does not, and here a machine confirms it compiles. Handing that work to autonomous agents at this scale is a concrete sign of AI doing mathematical labor rather than describing it, even as the proof is, in Anthropic’s own words, likely much longer than it needs to be.