Claude Fable 5.1 vs GPT-5.5
Claude Fable 5.1 
GPT-5.5 Verdict
- Claude Fable 5.1 (xhigh) leads on quality: 70.3 vs 66.6.
- Claude Fable 5.1 (xhigh) is stronger in coding, composite, knowledge, reasoning.
- GPT-5.5 is stronger in long context, agents & tools, human preference, instruction following, multimodal.
- GPT-5.5 is 1.8× cheaper ($11.25 vs $20.00 per 1M blended).
- GPT-5.5 streams 1.5× faster (88 vs 58 tokens per second).
| Metric | Claude Fable 5.1 (xhigh) | GPT-5.5 |
|---|---|---|
| BenchLeader Index | 70.3 | 66.6 |
| Coding score | 71.3 | 57.3 |
| Composite score | 95.0 | 77.7 |
| Knowledge score | 84.1 | 73.7 |
| Long context score | 68.1 | 68.8 |
| Reasoning score | 76.4 | 69.7 |
| Agents & tools score | – | 68.4 |
| Human preference score | – | 67.6 |
| Instruction following score | – | 73.3 |
| Multimodal score | – | 64.9 |
| Blended price $/M | $20.00 | $11.25 |
| Output speed | 58 tok/s | 88 tok/s |
| Time to first answer | 132.0 s | 62.3 s |
| Context window | 1M | 1.1M |
| Humanity's Last Exam | 46.5% | – |
| Terminal-Bench | – | 84.7% |
| SimpleBench | – | 69.0% |
| SciCode | 60.1% | – |
| Remote Labor Index | – | 6.3% |
| APEX-Agents | – | 38.5% |
| FrontierCode | – | 43.0% |
| Epoch Capabilities Index | – | 159.1 |
| LMArena Text | – | 1477 |
| LMArena Hard Prompts | – | 1498 |
| LMArena Coding | – | 1509 |
| LMArena WebDev | – | 1458 |
| LMArena Vision | – | 1296 |
| LMArena Agent | – | 3 |
| AA Intelligence Index | 53.2 | 38.6 |
| IFBench | – | 75.8% |
| AA-LCR | 83.0% | 84.3% |
| MMMU-Pro | – | 79.9% |
| AA-Omniscience | 42.4 | 20.5 |
| Terminal-Bench Hard | – | 60.6% |
| GPQA Diamond (AA) | 93.4% | 93.5% |
| Humanity's Last Exam (AA) | 58.7% | 45.8% |
| SciCode (AA) | 60.9% | 55.8% |
| τ²-Bench Telecom (AA) | – | 93.9% |
| HiL-Bench | – | 39.7% |
| EQ-Bench 4 | – | 1315 |
| Kagi LLM Benchmark | – | 88.8% |
| ARC-AGI-1 | 96.5% | – |
| ARC-AGI-2 | 90.0% | – |
Data as of 2026-09-09. Best configuration of each model; every score links to its source on the model pages.