Claude Fable 5.1 scores 69.4 on the Respan Index (#4), ahead of Claude Sonnet 5.5 at 68.5 (#6). Claude Fable 5.1 leads on 13 of the 22 benchmarks both report. Claude Sonnet 5.5 is 5.0x cheaper per token at list price.
* Estimated: no published scores in that category. How the Respan Index works
| Furniture Assembly (Epoch AI) |
| 70% |
| 75% |
| LiveBench Agentic Coding (LiveBench) | 66.1% | 56.3% |
| LiveBench Coding (LiveBench) | 86.4% | 91.4% |
| LiveBench Data Analysis (LiveBench) | 80.3% | 78.6% |
| LiveBench Instruction Following (LiveBench) | 73% | 70.5% |
| LiveBench Language (LiveBench) | 89.5% | 83.4% |
| LiveBench Mathematics (LiveBench) | 97% | 96.7% |
| LiveBench Reasoning (LiveBench) | 91.7% | 91.6% |
| Mystery Game Puzzles (Epoch AI) | 58% | 65% |
| OTIS Mock AIME 2024-2025 (Epoch AI) | 100% | 100% |
| SAGE (Vals AI) | 48.5% | 51.8% |
| SimpleQA Verified | 70.8% | 46.5% |
| Terminal-Bench 4.0 (Vals AI) | 58.1% | 64.1% |
| LMArena Agent (LMArena) | 0.1431 | 0.1252 |
| LMArena Elo | 1501 | 1471 |
| LMArena Vision (LMArena) | 1288 | 1268 |
| LMArena WebDev (LMArena) | 1749 | 1786 |
| SimpleBench (SimpleBench) | 86.6% | 75.9% |
Higher is better. Each score links to where it was published.