Model comparison
Claude Fable 5.1 vs GPT-5.5 Instant
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 42.7 on the Noometry Index.
Last verified . 26 shared benchmarks.
Summary
- They share 26 benchmarks with published results for both. Claude Fable 5.1 scores higher in 9 categories and GPT-5.5 Instant in 0 categories; 9 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Fable 5.1 leads 89.6 to 26.5.
- The biggest single-benchmark swing is FrontierMath Tier 4: 87.8% for Claude Fable 5.1 and 2.4% for GPT-5.5 Instant.
Side by side
| Claude Fable 5.1 | GPT-5.5 Instant | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Noometry Index | 69.0 | 42.7 |
| Released | 2026-09-01 | 2026-05-05 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | — |
| Max output | 128K | — |
| Input $ / M tokens | $10 | — |
| Output $ / M tokens | $50 | — |
| Results tracked | 52 | 27 |
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Category by category
Coding Claude Fable 5.1 leads
Claude Fable 5.1: 74.7 (#1), GPT-5.5 Instant: 44.3 (#74)
| Benchmark | Claude Fable 5.1 | GPT-5.5 Instant |
|---|---|---|
| SciCode | 63.1% | 48.6% |
| LMArena Coding | 1528 | 1433 |
| FrontierCode | 50.9% | — |
| CursorBench | 51.8% | — |
| LMArena WebDev | 1744 | — |
| FrontierSWE | 56.3% | — |
| GSO | 88.2% | — |
| WeirdML | 92.9% | — |
| MirrorCode | 73.3% | — |
| ALE-Bench | 2,143 | — |
Agentic & Tool Use Not comparable
Claude Fable 5.1: 50.7 (#5), GPT-5.5 Instant: —
| Benchmark | Claude Fable 5.1 | GPT-5.5 Instant |
|---|---|---|
| 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 Instant: 24.9 (#155)
| Benchmark | Claude Fable 5.1 | GPT-5.5 Instant |
|---|---|---|
| CritPt | 31.1% | 0% |
| Chess Puzzles | 47% | 12% |
| LMArena Hard Prompts | 1526 | 1426 |
| Epoch Capabilities Index | 164.7 | 142.52 |
| ARC-AGI-2 | 90% | — |
| NYT Connections (extended) | 90% | — |
| ARC-AGI-1 | 97.5% | — |
| EBR-Bench | 57.1% | — |
| Mystery Game Puzzles | 58% | — |
| DTBench | 97.6% | — |
| LMCA | 65.5% | — |
Math Claude Fable 5.1 leads
Claude Fable 5.1: 89.6 (#4), GPT-5.5 Instant: 26.5 (#259)
| Benchmark | Claude Fable 5.1 | GPT-5.5 Instant |
|---|---|---|
| FrontierMath (Tiers 1-3) | 90.2% | 26.3% |
| FrontierMath Tier 4 | 87.8% | 2.4% |
| OTIS Mock AIME 2024-2025 | 100% | 68.1% |
| LMArena Math | 1525 | 1420 |
| ProofBench | 100% | — |
| FrontierMath Erdős | 0% | — |
Knowledge Claude Fable 5.1 leads
Claude Fable 5.1: 69.6 (#6), GPT-5.5 Instant: 48.9 (#74)
| Benchmark | Claude Fable 5.1 | GPT-5.5 Instant |
|---|---|---|
| LMArena Expert | 1535 | 1409 |
| GPQA Diamond | — | 82.5% |
| Humanity's Last Exam | 46.5% | — |
| SimpleQA Verified | 70.8% | — |
Multimodal Claude Fable 5.1 leads
Claude Fable 5.1: 53.9 (#4), GPT-5.5 Instant: 40.0 (#52)
| Benchmark | Claude Fable 5.1 | GPT-5.5 Instant |
|---|---|---|
| LMArena Vision | 1318 | 1250 |
| LMArena Document | 1513 | 1403 |
| Blueprint-Bench 2 | 41.9% | — |
| Furniture Assembly | 70% | — |
Multilingual Claude Fable 5.1 leads
Claude Fable 5.1: 59.1 (#3), GPT-5.5 Instant: 52.8 (#80)
| Benchmark | Claude Fable 5.1 | GPT-5.5 Instant |
|---|---|---|
| LMArena Non-English | 1507 | 1417 |
| LMArena Chinese | 1586 | 1456 |
| LMArena French | 1525 | 1428 |
| LMArena German | 1500 | 1411 |
| LMArena Japanese | 1543 | 1408 |
| LMArena Korean | 1534 | 1392 |
| LMArena Russian | 1521 | 1431 |
| LMArena Spanish | 1516 | 1429 |
Instruction Following Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#6), GPT-5.5 Instant: 74.2 (#100)
| Benchmark | Claude Fable 5.1 | GPT-5.5 Instant |
|---|---|---|
| LMArena Instruction Following | 1517 | 1406 |
Long Context Claude Fable 5.1 leads
Claude Fable 5.1: 46.7 (#20), GPT-5.5 Instant: 43.4 (#96)
| Benchmark | Claude Fable 5.1 | GPT-5.5 Instant |
|---|---|---|
| LMArena Longer Query | 1522 | 1422 |
Writing & Preference Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#2), GPT-5.5 Instant: 61.8 (#85)
| Benchmark | Claude Fable 5.1 | GPT-5.5 Instant |
|---|---|---|
| LMArena Text | 1510 | 1419 |
| LMArena Creative Writing | 1507 | 1419 |
| LMArena Multi-Turn | 1492 | 1433 |
| EQ-Bench Creative Writing | 2162 | — |
Frequently asked questions
Is Claude Fable 5.1 better than GPT-5.5 Instant?
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 42.7 on the Noometry Index.
Is Claude Fable 5.1 or GPT-5.5 Instant better for coding?
Claude Fable 5.1 scores higher on coding benchmarks: 74.7 versus 44.3 in the Noometry coding category.
How many benchmarks do Claude Fable 5.1 and GPT-5.5 Instant share?
26 benchmarks have published results for both models. Claude Fable 5.1 has 52 scored results on Noometry and GPT-5.5 Instant has 27.