Claude completes 13M-line Lean formalization of Fermat's Last Theorem, largest proof ever
burny_tech · x · 2026-09-06
Anthropic announced that Claude last month completed the first full formalized proof of Fermat's Last Theorem in Lean: over 13 million lines of code, the largest Lean proof ever written, which also machine-verified more than 29,000 prerequisite theorems. Experts had expected the project to take many years.
- FLT was first proven by Sir Andrew Wiles in 1995, 350+ years after the conjecture; formalization enables computer proof assistants to verify the reasoning.
- Per the retweet, the bulk of the work was done by Kevin Buzzard's large team of students and postdocs; the proof is not yet formalized in Heyting arithmetic, and the poster has started building a Heyting arithmetic library for that final step.
- The related repo leanprovercommunity/flt-regular covers FLT for regular primes in Lean.
Related event: Claude Formalizes Fermat's Last Theorem in 11 Days with 13M Lines of Lean(45 posts)→
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