Fermat's Last Theorem in Lean (Anthropic)
Agent teams formalize Fermat's Last Theorem in Lean. Scores measure the weighted proportion of 60 accepted intermediate theorems.
Teams run for 18 hours without internet access. This theorem differs from the earlier large agent team task.
- Made by
- Anthropic
- Released
- November 2026
- Kind
- Formal proofs
- Level
- Research frontier
- Scored
- Checked automatically
- Answers
- Agent task
- Tasks
- Kept private
- Strongest model tested
- Claude Fable 5.2 #1 on the capability index
- Last in a system card
- November 2026
- Last model added
- November 2026
Claude Fable 5.2 leads with 35%
Best score per model as labs report them in their own cards. Labs pick their own settings, so these compare less cleanly than independent runs.
Source: Labs’ model cards
| # | Model | Score | Setting | Date | Source |
|---|---|---|---|---|---|
| 1 | Claude Fable 5.2 | 35% | Nov 2026 | Lab model card |
Scores over time
All the scores we have, one dot each, so a model tested at several settings appears more than once.
Source: Labs’ model cards
Labs report it only in system cards
We read the headline results of 522 launch posts from 52 labs, and none of them list this benchmark. Some system cards do, below.
One system card reports it
Besides launch posts, we read the system cards, model cards and technical reports labs publish with a release. They report far more, including safety and frontier-risk tests.
| Date | Document | Score | As the document writes it | Section |
|---|---|---|---|---|
| Nov 9, 2026 | Claude Fable 5.2 system card | 35 | Fermat's Last Theorem in Lean, 100-agent team, best weighted proof-completion score within 18 hours, mean of three runs, 0.35 converted to 35%. Single agent 0.12. The 1,000-agent result uses an earlier snapshot and is excluded (Section 8.12.3 and Figure 8.12.3.A) | Capabilities |
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