11 days, 13 million lines of Lean: Claude formalised Fermat's Last Theorem.
A post claims Claude formalised Fermat's Last Theorem in eleven days, largely autonomously, and that nobody will ever read the proof. Numbers on screen: 30,300, 29,500 and about 6 billion.
- 11 dayslargely autonomous
- 29,500theorems in the proof
- ~6Boutput tokens
- Claude produced a computer-checked proof of Fermat's Last Theorem in 11 days.Anthropic's research post reports the first end-to-end formalisation of the theorem in Lean, produced in 11 days by dozens of Claude agents running a multi-agent workflow. Nature covered it as a milestone for mathematics.Formalizing Fermat's Last Theorem
- The numbers on screen: 30,300 theorems, 29,500 used, about 6 billion.The run proved 30,300 intermediate theorems, 29,500 of which sit in the final proof, wrote about 13 million lines of Lean and used roughly 6 billion output tokens.Formalizing Fermat's Last Theorem
- Nobody will ever read the proof.That is the point of a proof assistant: Lean's small kernel checks every step, so humans read the statement and the kernel's verdict, not 13 million lines. Kevin Buzzard's human-led formalisation project, started in 2024, was expected to take years; the AI run compresses that, it does not replace Andrew Wiles's 1995 proof.
the line to remember
Long-running agent swarms with a hard verifier (here, Lean's kernel) can finish multi-year work in days. The verifier is what makes autonomy safe.
For your product
Where your work has a checker (tests, a compiler, a ledger that must balance, a schema), agents can run for days unattended. Where it does not, they cannot. Build the checker first.
Sources: Formalizing Fermat's Last Theorem (Anthropic) · Anthropic AI 'formalizes' proof of Fermat's last theorem (Nature)