Claude Autonomously Formalizes Fermat’s Last Theorem Proof With 13 Million Lines of Code

Claude produced the first end-to-end, computer-checked proof of Fermat’s Last Theorem over an 11-day period. The multi-agent system wrote 13M lines of Lean code and successfully verified 29,500 intermediate theorems. Anthropic utilized an internal research model comparable to Claude Fable 5.1, burning roughly 6B output tokens. The agents initially lost track of the project state, but succeeded after switching to the open collaborative platform Prove2Me.