Claude Fable 5.1 vs GPT-5.5 Pro
Claude Fable 5.1 
GPT-5.5 Pro Verdict
- Claude Fable 5.1 (high) leads on quality: 72.0 vs 67.1.
- Claude Fable 5.1 (high) is stronger in agents & tools, coding, composite, knowledge, long context, reasoning.
- GPT-5.5 Pro (xhigh) is stronger in maths.
- Claude Fable 5.1 (high) is 3.4× cheaper ($20.00 vs $67.50 per 1M blended).
- Claude Fable 5.1 (high) streams 13.7× faster (55 vs 4 tokens per second).
| Metric | Claude Fable 5.1 (high) | GPT-5.5 Pro (xhigh) |
|---|---|---|
| BenchLeader Index | 72.0 | 67.1 |
| Agents & tools score | 66.6 | – |
| Coding score | 74.1 | – |
| Composite score | 94.0 | – |
| Knowledge score | 83.7 | – |
| Long context score | 68.4 | – |
| Reasoning score | 81.0 | 80.1 |
| Maths score | – | 74.5 |
| Blended price $/M | $20.00 | $67.50 |
| Output speed | 55 tok/s | 4 tok/s |
| Time to first answer | 14.7 s | 3.5 s |
| Context window | 1M | 1.1M |
| FrontierMath Tiers 1–3 | – | 87.7% |
| FrontierMath Tier 4 | – | 78.0% |
| Terminal-Bench | 54.5% | – |
| SciCode | 57.6% | – |
| WeirdML | 92.3% | – |
| APEX-Agents | 44.4% | – |
| AA Intelligence Index | 51.2 | – |
| AA-LCR | 83.7% | – |
| AA-Omniscience | 40.8 | – |
| GPQA Diamond (AA) | 90.6% | – |
| Humanity's Last Exam (AA) | 55.9% | – |
| SciCode (AA) | 58.7% | – |
| ARC-AGI-1 | 96.0% | 95.0% |
| ARC-AGI-2 | 88.8% | 84.2% |
| CritPt | 30.3% | 30.6% |
| GDPval (AA) | 57.5% | – |
| τ²-Bench Banking (AA) | 43.1% | – |
| MirrorCode | 73.3% | – |
| LMCA | – | 53.9% |
| DTBench | – | 96.0% |
| CursorBench | 69.4% | – |
| ALE-Bench | 2143.2 | – |
Data as of 2026-09-19. Best configuration of each model; every score links to its source on the model pages.
Claude Fable 5.1 vs GPT-5.5 Pro: questions
- Is Claude Fable 5.1 better than GPT-5.5 Pro?
- Claude Fable 5.1 (high) leads on quality: 72.0 vs 67.1. The BenchLeader Index combines every independent quality benchmark; Claude Fable 5.1 (high) is ahead overall as of 2026-09-19, but check the category scores for your use.
- Which is cheaper, Claude Fable 5.1 or GPT-5.5 Pro?
- Claude Fable 5.1 is cheaper: $20.00 against $67.50 per million tokens, blended at three input tokens per output token.
- Which is faster, Claude Fable 5.1 or GPT-5.5 Pro?
- Claude Fable 5.1 streams faster: 55 against 4 output tokens per second.
- Which has the larger context window?
- GPT-5.5 Pro accepts more context: 1.1M against 1M tokens.