Model comparison
Claude Fable 5.1 vs Claude Opus 5.5
Claude Fable 5.1 and Claude Opus 5.5 score almost the same on the Noometry Index (69.0 vs 68.6), so choose on price, context window or the category you care about most.
Last verified . 43 shared benchmarks.
Summary
- They share 43 benchmarks with published results for both. Claude Fable 5.1 scores higher in 4 categories and Claude Opus 5.5 in 6 categories; 6 gaps are clear of the uncertainty.
- The widest gap is in agentic & tool use, where Claude Fable 5.1 leads 50.7 to 45.3.
- The biggest single-benchmark swing is EBR-Bench: 57.1% for Claude Fable 5.1 and 71.4% for Claude Opus 5.5.
- Claude Opus 5.5 is cheaper at $4 / $20 per million input/output tokens, against $10 / $50 for Claude Fable 5.1.
Side by side
| Claude Fable 5.1 | Claude Opus 5.5 | |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Noometry Index | 69.0 | 68.6 |
| Released | 2026-09-01 | 2026-09-22 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 1M |
| Max output | 128K | 128K |
| Input $ / M tokens | $10 | $4 |
| Output $ / M tokens | $50 | $20 |
| Results tracked | 52 | 44 |
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Category by category
Coding Claude Fable 5.1 leads
Claude Fable 5.1: 74.7 (#1), Claude Opus 5.5: 71.9 (#3)
| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 |
|---|---|---|
| FrontierCode | 50.9% | 54.6% |
| CursorBench | 51.8% | 57.8% |
| LMArena WebDev | 1744 | 1813 |
| FrontierSWE | 56.3% | 62.3% |
| SciCode | 63.1% | 66.9% |
| LMArena Coding | 1528 | 1547 |
| MirrorCode | 73.3% | 77.4% |
| ALE-Bench | 2,143 | 2,147 |
| GSO | 88.2% | — |
| WeirdML | 92.9% | — |
Agentic & Tool Use Claude Fable 5.1 leads
Claude Fable 5.1: 50.7 (#5), Claude Opus 5.5: 45.3 (#15)
| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 |
|---|---|---|
| APEX-Agents | 68.6% | 73.5% |
| GDP.pdf | 29.6% | 30.6% |
| Vending-Bench 2 | 5,422 | 9,235 |
| Remote Labor Index | 17.9% | — |
Reasoning Claude Opus 5.5 leads
Claude Fable 5.1: 76.7 (#7), Claude Opus 5.5: 80.2 (#3)
| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 |
|---|---|---|
| ARC-AGI-2 | 90% | 93.3% |
| NYT Connections (extended) | 90% | 88.5% |
| ARC-AGI-1 | 97.5% | 98.5% |
| CritPt | 31.1% | 31.7% |
| EBR-Bench | 57.1% | 71.4% |
| LMArena Hard Prompts | 1526 | 1535 |
| Mystery Game Puzzles | 58% | 71% |
| DTBench | 97.6% | 98.9% |
| LMCA | 65.5% | 68.2% |
| Epoch Capabilities Index | 164.7 | 167.33 |
| Chess Puzzles | 47% | — |
Math Claude Opus 5.5 leads
Claude Fable 5.1: 89.6 (#4), Claude Opus 5.5: 91.8 (#3)
| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 |
|---|---|---|
| FrontierMath (Tiers 1-3) | 90.2% | 91.2% |
| FrontierMath Tier 4 | 87.8% | 95% |
| OTIS Mock AIME 2024-2025 | 100% | 100% |
| ProofBench | 100% | 100% |
| LMArena Math | 1525 | 1506 |
| FrontierMath Erdős | 0% | 2.9% |
Knowledge Claude Fable 5.1 leads
Claude Fable 5.1: 69.6 (#6), Claude Opus 5.5: 66.4 (#10)
| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 |
|---|---|---|
| SimpleQA Verified | 70.8% | 72.2% |
| LMArena Expert | 1535 | 1547 |
| GPQA Diamond | — | 90.6% |
| Humanity's Last Exam | 46.5% | — |
Multimodal Claude Opus 5.5 leads
Claude Fable 5.1: 53.9 (#4), Claude Opus 5.5: 57.8 (#1)
| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 |
|---|---|---|
| LMArena Vision | 1318 | 1321 |
| Blueprint-Bench 2 | 41.9% | 51.2% |
| Furniture Assembly | 70% | 83.3% |
| LMArena Document | 1513 | — |
Multilingual Too close to call
Claude Fable 5.1: 59.1 (#3), Claude Opus 5.5: 59.1 (#2)
| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 |
|---|---|---|
| LMArena Non-English | 1507 | 1507 |
| LMArena Chinese | 1586 | 1588 |
| LMArena French | 1525 | 1514 |
| LMArena Russian | 1521 | 1520 |
| LMArena Spanish | 1516 | 1507 |
| LMArena German | 1500 | — |
| LMArena Japanese | 1543 | — |
| LMArena Korean | 1534 | — |
Instruction Following Too close to call
Claude Fable 5.1: 79.2 (#6), Claude Opus 5.5: 80.0 (#3)
| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 |
|---|---|---|
| LMArena Instruction Following | 1517 | 1537 |
Long Context Too close to call
Claude Fable 5.1: 46.7 (#20), Claude Opus 5.5: 47.1 (#19)
| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 |
|---|---|---|
| LMArena Longer Query | 1522 | 1532 |
Writing & Preference Too close to call
Claude Fable 5.1: 79.2 (#2), Claude Opus 5.5: 78.2 (#3)
| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 |
|---|---|---|
| LMArena Text | 1510 | 1515 |
| LMArena Creative Writing | 1507 | 1533 |
| EQ-Bench Creative Writing | 2162 | 2050 |
| LMArena Multi-Turn | 1492 | 1499 |
Frequently asked questions
Is Claude Fable 5.1 better than Claude Opus 5.5?
Claude Fable 5.1 and Claude Opus 5.5 score almost the same on the Noometry Index (69.0 vs 68.6), so choose on price, context window or the category you care about most.
Which is cheaper, Claude Fable 5.1 or Claude Opus 5.5?
Claude Opus 5.5 is cheaper. It lists at $4 per million input tokens and $20 per million output tokens; Claude Fable 5.1 lists at $10 and $50.
Is Claude Fable 5.1 or Claude Opus 5.5 better for coding?
Claude Fable 5.1 scores higher on coding benchmarks: 74.7 versus 71.9 in the Noometry coding category.
Which has the bigger context window?
Both accept 1M tokens.
How many benchmarks do Claude Fable 5.1 and Claude Opus 5.5 share?
43 benchmarks have published results for both models. Claude Fable 5.1 has 52 scored results on Noometry and Claude Opus 5.5 has 44.