Model comparison
Claude Fable 5.1 vs GPT-5.5 Pro
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 64.3 on the Noometry Index.
Last verified . 10 shared benchmarks.
Summary
- They share 10 benchmarks with published results for both. Claude Fable 5.1 scores higher in 3 categories and GPT-5.5 Pro in 0 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Fable 5.1 leads 89.6 to 84.0.
- The biggest single-benchmark swing is Chess Puzzles: 47% for Claude Fable 5.1 and 64% for GPT-5.5 Pro.
- Claude Fable 5.1 is cheaper at $10 / $50 per million input/output tokens, against $30 / $180 for GPT-5.5 Pro.
- GPT-5.5 Pro accepts more context: 1.05M tokens versus 1M.
Side by side
| Claude Fable 5.1 | GPT-5.5 Pro | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Noometry Index | 69.0 | 64.3 |
| Released | 2026-09-01 | 2026-04-23 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 1.05M |
| Max output | 128K | 128K |
| Input $ / M tokens | $10 | $30 |
| Output $ / M tokens | $50 | $180 |
| Results tracked | 52 | 14 |
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Category by category
Coding Not comparable
Claude Fable 5.1: 74.7 (#1), GPT-5.5 Pro: —
| Benchmark | Claude Fable 5.1 | GPT-5.5 Pro |
|---|---|---|
| FrontierCode | 50.9% | — |
| CursorBench | 51.8% | — |
| LMArena WebDev | 1744 | — |
| FrontierSWE | 56.3% | — |
| SciCode | 63.1% | — |
| GSO | 88.2% | — |
| WeirdML | 92.9% | — |
| LMArena Coding | 1528 | — |
| MirrorCode | 73.3% | — |
| ALE-Bench | 2,143 | — |
Agentic & Tool Use Not comparable
Claude Fable 5.1: 50.7 (#5), GPT-5.5 Pro: —
| Benchmark | Claude Fable 5.1 | GPT-5.5 Pro |
|---|---|---|
| APEX-Agents | 68.6% | — |
| Remote Labor Index | 17.9% | — |
| GDP.pdf | 29.6% | — |
| Vending-Bench 2 | 5,422 | — |
Reasoning Claude Fable 5.1 leads
Claude Fable 5.1: 76.7 (#7), GPT-5.5 Pro: 73.3 (#10)
| Benchmark | Claude Fable 5.1 | GPT-5.5 Pro |
|---|---|---|
| ARC-AGI-2 | 90% | 84.6% |
| ARC-AGI-1 | 97.5% | 96.5% |
| CritPt | 31.1% | 30.6% |
| Chess Puzzles | 47% | 64% |
| DTBench | 97.6% | 96% |
| LMCA | 65.5% | 53.9% |
| Epoch Capabilities Index | 164.7 | 162.07 |
| SimpleBench | — | 76.9% |
| NYT Connections (extended) | 90% | — |
| EBR-Bench | 57.1% | — |
| LMArena Hard Prompts | 1526 | — |
| Mystery Game Puzzles | 58% | — |
Math Claude Fable 5.1 leads
Claude Fable 5.1: 89.6 (#4), GPT-5.5 Pro: 84.0 (#10)
| Benchmark | Claude Fable 5.1 | GPT-5.5 Pro |
|---|---|---|
| FrontierMath (Tiers 1-3) | 90.2% | 87.7% |
| FrontierMath Tier 4 | 87.8% | 78% |
| OTIS Mock AIME 2024-2025 | 100% | 100% |
| ProofBench | 100% | — |
| LMArena Math | 1525 | — |
| FrontierMath (Feb 2025 set) | — | 52.4% |
| FrontierMath Erdős | 0% | — |
| FrontierMath Tier 4 (v1) | — | 39.6% |
Knowledge Claude Fable 5.1 leads
Claude Fable 5.1: 69.6 (#6), GPT-5.5 Pro: 64.1 (#19)
| Benchmark | Claude Fable 5.1 | GPT-5.5 Pro |
|---|---|---|
| GPQA Diamond | — | 93.9% |
| Humanity's Last Exam | 46.5% | — |
| SimpleQA Verified | 70.8% | — |
| LMArena Expert | 1535 | — |
Multimodal Not comparable
Claude Fable 5.1: 53.9 (#4), GPT-5.5 Pro: —
| Benchmark | Claude Fable 5.1 | GPT-5.5 Pro |
|---|---|---|
| LMArena Vision | 1318 | — |
| Blueprint-Bench 2 | 41.9% | — |
| Furniture Assembly | 70% | — |
| LMArena Document | 1513 | — |
Multilingual Not comparable
Claude Fable 5.1: 59.1 (#3), GPT-5.5 Pro: —
| Benchmark | Claude Fable 5.1 | GPT-5.5 Pro |
|---|---|---|
| LMArena Non-English | 1507 | — |
| LMArena Chinese | 1586 | — |
| LMArena French | 1525 | — |
| LMArena German | 1500 | — |
| LMArena Japanese | 1543 | — |
| LMArena Korean | 1534 | — |
| LMArena Russian | 1521 | — |
| LMArena Spanish | 1516 | — |
Instruction Following Not comparable
Claude Fable 5.1: 79.2 (#6), GPT-5.5 Pro: —
| Benchmark | Claude Fable 5.1 | GPT-5.5 Pro |
|---|---|---|
| LMArena Instruction Following | 1517 | — |
Long Context Not comparable
Claude Fable 5.1: 46.7 (#20), GPT-5.5 Pro: —
| Benchmark | Claude Fable 5.1 | GPT-5.5 Pro |
|---|---|---|
| LMArena Longer Query | 1522 | — |
Writing & Preference Not comparable
Claude Fable 5.1: 79.2 (#2), GPT-5.5 Pro: —
| Benchmark | Claude Fable 5.1 | GPT-5.5 Pro |
|---|---|---|
| LMArena Text | 1510 | — |
| LMArena Creative Writing | 1507 | — |
| EQ-Bench Creative Writing | 2162 | — |
| LMArena Multi-Turn | 1492 | — |
Frequently asked questions
Is Claude Fable 5.1 better than GPT-5.5 Pro?
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 64.3 on the Noometry Index.
Which is cheaper, Claude Fable 5.1 or GPT-5.5 Pro?
Claude Fable 5.1 is cheaper. It lists at $10 per million input tokens and $50 per million output tokens; GPT-5.5 Pro lists at $30 and $180.
Which has the bigger context window?
GPT-5.5 Pro does, with 1.05M tokens against 1M.
How many benchmarks do Claude Fable 5.1 and GPT-5.5 Pro share?
10 benchmarks have published results for both models. Claude Fable 5.1 has 52 scored results on Noometry and GPT-5.5 Pro has 14.