Model comparison
Claude Fable 5.1 vs Claude Sonnet 5
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 54.6 on the Noometry Index. Claude Sonnet 5 costs 5.0× less per token, which makes it the better buy when Claude Fable 5.1's lead doesn't matter for your workload.
Last verified . 42 shared benchmarks.
Summary
- They share 42 benchmarks with published results for both. Claude Fable 5.1 scores higher in 10 categories and Claude Sonnet 5 in 0 categories; 10 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Claude Fable 5.1 leads 76.7 to 49.1.
- The biggest single-benchmark swing is FrontierMath Tier 4: 87.8% for Claude Fable 5.1 and 29.3% for Claude Sonnet 5.
- Claude Sonnet 5 is cheaper at $2 / $10 per million input/output tokens, against $10 / $50 for Claude Fable 5.1.
Side by side
| Claude Fable 5.1 | Claude Sonnet 5 | |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Noometry Index | 69.0 | 54.6 |
| Released | 2026-09-01 | 2026-06-29 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 1M |
| Max output | 128K | 128K |
| Input $ / M tokens | $10 | $2 |
| Output $ / M tokens | $50 | $10 |
| Results tracked | 52 | 51 |
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Category by category
Coding Claude Fable 5.1 leads
Claude Fable 5.1: 74.7 (#1), Claude Sonnet 5: 55.5 (#26)
| Benchmark | Claude Fable 5.1 | Claude Sonnet 5 |
|---|---|---|
| FrontierCode | 50.9% | 42.7% |
| CursorBench | 51.8% | 34.1% |
| LMArena WebDev | 1744 | 1541 |
| SciCode | 63.1% | 54.3% |
| GSO | 88.2% | 37.3% |
| WeirdML | 92.9% | 68.8% |
| LMArena Coding | 1528 | 1483 |
| ALE-Bench | 2,143 | 1,463 |
| DeepSWE | — | 53.8% |
| FrontierSWE | 56.3% | — |
| MirrorCode | 73.3% | — |
Agentic & Tool Use Claude Fable 5.1 leads
Claude Fable 5.1: 50.7 (#5), Claude Sonnet 5: 42.8 (#18)
| Benchmark | Claude Fable 5.1 | Claude Sonnet 5 |
|---|---|---|
| APEX-Agents | 68.6% | 54.5% |
| Vending-Bench 2 | 5,422 | 6,378 |
| Remote Labor Index | 17.9% | — |
| GBAEval | — | 65.3% |
| GDP.pdf | 29.6% | — |
| LMArena Search | — | 1194 |
Reasoning Claude Fable 5.1 leads
Claude Fable 5.1: 76.7 (#7), Claude Sonnet 5: 49.1 (#39)
| Benchmark | Claude Fable 5.1 | Claude Sonnet 5 |
|---|---|---|
| NYT Connections (extended) | 90% | 75.1% |
| CritPt | 31.1% | 16.9% |
| Chess Puzzles | 47% | 35% |
| LMArena Hard Prompts | 1526 | 1461 |
| Mystery Game Puzzles | 58% | 35% |
| DTBench | 97.6% | 92.5% |
| LMCA | 65.5% | 50% |
| Epoch Capabilities Index | 164.7 | 156.21 |
| ARC-AGI-2 | 90% | — |
| SimpleBench | — | 60.6% |
| ARC-AGI-1 | 97.5% | — |
| EBR-Bench | 57.1% | — |
| Surface Evolver Bench | — | 60% |
| Bench to the Future 3 | — | 0.14 |
| ForecastBench | — | 61.1 |
Math Claude Fable 5.1 leads
Claude Fable 5.1: 89.6 (#4), Claude Sonnet 5: 66.2 (#27)
| Benchmark | Claude Fable 5.1 | Claude Sonnet 5 |
|---|---|---|
| FrontierMath (Tiers 1-3) | 90.2% | 65.6% |
| FrontierMath Tier 4 | 87.8% | 29.3% |
| OTIS Mock AIME 2024-2025 | 100% | 94.7% |
| ProofBench | 100% | 77% |
| LMArena Math | 1525 | 1467 |
| FrontierMath Erdős | 0% | — |
Knowledge Claude Fable 5.1 leads
Claude Fable 5.1: 69.6 (#6), Claude Sonnet 5: 55.6 (#47)
| Benchmark | Claude Fable 5.1 | Claude Sonnet 5 |
|---|---|---|
| SimpleQA Verified | 70.8% | 33.7% |
| LMArena Expert | 1535 | 1490 |
| GPQA Diamond | — | 90.5% |
| Humanity's Last Exam | 46.5% | — |
Multimodal Claude Fable 5.1 leads
Claude Fable 5.1: 53.9 (#4), Claude Sonnet 5: 42.4 (#31)
| Benchmark | Claude Fable 5.1 | Claude Sonnet 5 |
|---|---|---|
| LMArena Vision | 1318 | 1274 |
| Blueprint-Bench 2 | 41.9% | 24.9% |
| LMArena Document | 1513 | 1466 |
| Furniture Assembly | 70% | — |
Multilingual Claude Fable 5.1 leads
Claude Fable 5.1: 59.1 (#3), Claude Sonnet 5: 53.8 (#55)
| Benchmark | Claude Fable 5.1 | Claude Sonnet 5 |
|---|---|---|
| LMArena Non-English | 1507 | 1431 |
| LMArena Chinese | 1586 | 1477 |
| LMArena French | 1525 | 1460 |
| LMArena German | 1500 | 1440 |
| LMArena Japanese | 1543 | 1422 |
| LMArena Korean | 1534 | 1411 |
| LMArena Russian | 1521 | 1451 |
| LMArena Spanish | 1516 | 1437 |
Instruction Following Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#6), Claude Sonnet 5: 76.3 (#41)
| Benchmark | Claude Fable 5.1 | Claude Sonnet 5 |
|---|---|---|
| LMArena Instruction Following | 1517 | 1452 |
Long Context Claude Fable 5.1 leads
Claude Fable 5.1: 46.7 (#20), Claude Sonnet 5: 44.8 (#55)
| Benchmark | Claude Fable 5.1 | Claude Sonnet 5 |
|---|---|---|
| LMArena Longer Query | 1522 | 1463 |
Writing & Preference Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#2), Claude Sonnet 5: 69.2 (#25)
| Benchmark | Claude Fable 5.1 | Claude Sonnet 5 |
|---|---|---|
| LMArena Text | 1510 | 1442 |
| LMArena Creative Writing | 1507 | 1416 |
| EQ-Bench Creative Writing | 2162 | 1794 |
| LMArena Multi-Turn | 1492 | 1454 |
| EQ-Bench 4 | — | 1236 |
Frequently asked questions
Is Claude Fable 5.1 better than Claude Sonnet 5?
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 54.6 on the Noometry Index. Claude Sonnet 5 costs 5.0× less per token, which makes it the better buy when Claude Fable 5.1's lead doesn't matter for your workload.
Which is cheaper, Claude Fable 5.1 or Claude Sonnet 5?
Claude Sonnet 5 is cheaper. It lists at $2 per million input tokens and $10 per million output tokens; Claude Fable 5.1 lists at $10 and $50.
Is Claude Fable 5.1 or Claude Sonnet 5 better for coding?
Claude Fable 5.1 scores higher on coding benchmarks: 74.7 versus 55.5 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 Sonnet 5 share?
42 benchmarks have published results for both models. Claude Fable 5.1 has 52 scored results on Noometry and Claude Sonnet 5 has 51.