Claude Fable 5.1
ECI#2
165Claude Fable 5.1 is a closed-weights model from Anthropic, released September 1, 2026. It has an ECI score of 165 and ranks 2nd of 251 tracked models. At the time of its release, it ranked 1st of 247 tracked models.
Claude Fable 5.1 vs select alternatives
| Domain | Benchmark | Claude Fable 5.1 | |||
|---|---|---|---|---|---|
ECI scoreBest score 167 | 165 | 164 | 162 | 158 | |
| Ranking | #2 | #3 | #5 | #11 | |
| Games | Chess PuzzlesBest score 72% | ||||
Earthborne Rangers (EBR-bench)Best score 76% | |||||
Mystery Game PuzzlesBest score 84% | |||||
| Mathematics | FrontierMath ErdősBest score 3% | ||||
FrontierMath Tiers 1-3 (v2)Best score 94% | |||||
FrontierMath Tier 4 (v2)Best score 98% | |||||
| Multimodal | Furniture Assembly BenchmarkBest score 83% | ||||
| Software engineering | MirrorCodeBest score 73% | ||||
| World knowledge | SimpleQA VerifiedBest score 76% |
