Claude Fable 5.1
ECI#2
164Claude Fable 5.1 is a closed-weights model from Anthropic, released September 1, 2026. It has an ECI score of 164 and ranks 2nd of 247 tracked models. At the time of its release, it ranked 1st of 246 tracked models. At $10/Mtok for input tokens and $50/Mtok for output tokens, it is more expensive per token than similarly-capable models.
Input price$10 / 1M tokens
Output price$50 / 1M tokens
ParametersUnknown
Training computeUnknown
Claude Fable 5.1 vs select alternatives
Reasoning
| Domain | Benchmark | Claude Fable 5.1 | |||
|---|---|---|---|---|---|
ECI scoreBest score 167 | 164 | 163 | 162 | 158 | |
| Ranking | #2 | #3 | #5 | #11 | |
| Games | Chess PuzzlesBest score 72.0% | ||||
Earthborne Rangers (EBR-bench)Best score 76.2% | |||||
Mystery Game PuzzlesBest score 84.0% | |||||
| Mathematics | FrontierMath ErdősBest score 2.9% | ||||
FrontierMath Tiers 1-3 (v2)Best score 93.7% | |||||
FrontierMath Tier 4 (v2)Best score 97.6% | |||||
OTIS Mock AIME 2024-2025Best score 100.0% | |||||
| Software engineering | MirrorCodeBest score 73.3% | ||||
| World knowledge | SimpleQA VerifiedBest score 75.6% |
