Anthropic just had claude spend 11 days producing a verified, machine-checkable proof of fermat…
anthropic just had claude spend 11 days producing a verified, machine-checkable proof of fermat last theorem. the headline isnt math, its that a closed-form proof is now a routine eval.
what gets formalized next is whatever the labs need to claim their model can do.
Context
Anthropic's report of 4 September 2026 describes the first complete computer-checked proof of Fermat's Last Theorem. It says Claude worked largely autonomously over 11 days to write the proof in Lean, at 13 million lines and 29,500 intermediate theorems. It quotes Kevin Buzzard, who led the 2024 Lean effort on the theorem, saying it proves the result with no assumptions other than the axioms of mathematics.
This is Anthropic's own account. Largely autonomous is the report's wording, not fully autonomous, and the checking is Lean's checker plus Buzzard's statement as quoted by Anthropic. The proof's verification and assumptions were not independently audited here. Closed-form proof is the note's wording. That formal proofs become a routine eval, and what gets formalized next, are the author's opinion.
Related work
- Claude formalized Fermat's Last Theorem in 11 days (Forbes) ↗Secondary, dated 7 September 2026, after the note; snippet only.
- Nature report ↗Secondary, dated 7 September 2026; snippet only.
- fermats-last-theorem repository (GitHub) ↗Lean 4 on Mathlib; snippet only.
Watch next
- Independent review of the Lean proof.
Sources
Provenance
The note above is reproduced unedited from the original post, first published on Threads on 5 September 2026 at 09:03 IST. Sources are the papers and datasets the note draws on.
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