# Claude Fable 5.1 vs Claude Sonnet 5.5

> Side-by-side benchmark comparison for Claude Fable 5.1 and Claude Sonnet 5.5 across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/claude-fable-5-1-vs-claude-sonnet-5-5
- Last updated: September 28, 2026

- Shared sourced benchmarks: 14
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.7

## Quick Verdict

Pick Claude Fable 5.1 if you want the stronger benchmark profile. Claude Sonnet 5.5 only makes more sense when its price, context window, or workload-specific category wins matter more than the overall score.

## Summary

- Claude Fable 5.1 leads overall 82.96 to 80.49.
- The clearest category separation is in agentic, where the averages are 78.8 for Claude Fable 5.1 and 66.1 for Claude Sonnet 5.5.
- The biggest single benchmark swing is Terminal-Bench 4.0 in Agentic, with scores of 55.80% and 70.60%.
- Claude Sonnet 5.5 is the cheaper option on output tokens, which matters if you expect large responses or heavy interactive use.

## Model Snapshot

| Property | Claude Fable 5.1 | Claude Sonnet 5.5 |
|----------|----------|----------|
| Creator | Anthropic | Anthropic |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 1M | 1M |
| Overall Score | 82.96 | 80.49 |
| Benchmarks Covered | 26 | 47 |
| Pricing (input/output) | $10.00 / $50.00 | $2.00 / $10.00 |

## Category Breakdown

### Agentic

- Winner: Claude Fable 5.1
- Claude Fable 5.1 public-lane score: 78.8 (Supported · #2/111)
- Claude Sonnet 5.5 public-lane score: 66.1 (Supported · #10/111)

| Benchmark | Claude Fable 5.1 | Claude Sonnet 5.5 | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 4.0 | 55.80% | 70.60% | Claude Sonnet 5.5 |
| Terminal-Bench-Science 0.1 | 52.6% | 59.9% | Claude Sonnet 5.5 |
| OSWorld 2.0 | 41.7% | Coming soon | Coming soon |
| AutomationBench | 31.4% | Coming soon | Coming soon |
| Toolathlon-Verified | 77.8% | 77.8% | Tie |
| Toolathlon Verified Pass@3 | 81.5% | 85.2% | Claude Sonnet 5.5 |
| Toolathlon Verified Pass³ | 73.1% | 68.5% | Claude Fable 5.1 |
| Toolathlon Verified avg. turns | 23.7 turns | 31.6 turns | Claude Sonnet 5.5 |
| Terminal-Bench 2.1 (Vals) | 85.0% | Coming soon | Coming soon |
| ApprenticeBench | 72% | Coming soon | Coming soon |
| HLE w/ tools | Coming soon | 64.5% | Coming soon |
| DRACO | Coming soon | 87.0% | Coming soon |
| LAB all-pass (Harvey held-out) | Coming soon | 10.0% | Coming soon |
| LAB criterion-pass (Harvey held-out) | Coming soon | 93.1% | Coming soon |
| AutomationBench (Zapier 1.0.6) | Coming soon | 44.7% | Coming soon |

### Coding

- Winner: Directional only
- Claude Fable 5.1 public-lane score: 79.7 (Supported · #2/136)
- Claude Sonnet 5.5 public-lane score: 79.6 (Estimated · #3/136)

| Benchmark | Claude Fable 5.1 | Claude Sonnet 5.5 | Winner |
|-----------|-----------|-----------|--------|
| Bug Hunt Bench | 43 fixes | Coming soon | Coming soon |
| SWE-bench Pro | 81.2% | 81.3% | Claude Sonnet 5.5 |
| SWE Multilingual | 89.1% | 90.3% | Claude Sonnet 5.5 |
| SWE Multimodal | 54.7% | 54.3% | Claude Fable 5.1 |
| DeepSWE | 67.4% | 71.0% | Claude Sonnet 5.5 |
| FrontierSWE v2 | 56.3% | 61.9% | Claude Sonnet 5.5 |
| ProgramBench | 87.6% | 79.7% | Claude Fable 5.1 |
| cursorBench32 | 73.4% | Coming soon | Coming soon |
| LiveCodeBench (Vals) | 90.5% | Coming soon | Coming soon |
| cursorBench40 | 51.8% | 55.5% | Claude Sonnet 5.5 |
| FrontierCode 1.1 Main | Coming soon | 46.2% | Coming soon |
| FrontierCode 1.1 Extended | Coming soon | 59.1% | Coming soon |

### Reasoning

- Winner: Directional only
- Claude Fable 5.1 public-lane score: 81.4 (#3/27)
- Claude Sonnet 5.5 public-lane score: 79.2 (#7/27)

| Benchmark | Claude Fable 5.1 | Claude Sonnet 5.5 | Winner |
|-----------|-----------|-----------|--------|
| ARC-AGI-1 | 97.50% | Coming soon | Coming soon |
| ARC-AGI-2 | 90% | Coming soon | Coming soon |

### Multimodal & Grounded

- Winner: Not comparable
- Claude Fable 5.1 public-lane score: Coming soon
- Claude Sonnet 5.5 public-lane score: 83.3 (Unranked · 7 rankable rows)

| Benchmark | Claude Fable 5.1 | Claude Sonnet 5.5 | Winner |
|-----------|-----------|-----------|--------|
| Chartography (no tools) | Coming soon | 61.6% | Coming soon |
| Chartography (tools) | Coming soon | 90.2% | Coming soon |
| BenchCAD Vision2Code (no tools) | Coming soon | 0.747 | Coming soon |
| BenchCAD Vision2Code (tools) | Coming soon | 0.963 | Coming soon |
| Biomedical image analysis | Coming soon | 72.2% | Coming soon |
| OfficeQA | Coming soon | 76.9% | Coming soon |
| OfficeQA Pro | Coming soon | 65.6% | Coming soon |

### Knowledge

- Winner: Claude Fable 5.1
- Claude Fable 5.1 public-lane score: 86 (Supported · #3/160)
- Claude Sonnet 5.5 public-lane score: 80.9 (Supported · #6/160)

| Benchmark | Claude Fable 5.1 | Claude Sonnet 5.5 | Winner |
|-----------|-----------|-----------|--------|
| HLE | 65% | Coming soon | Coming soon |
| HLE w/o tools | 60.9% | 56.9% | Claude Fable 5.1 |
| GPQA Diamond (Vals) | 93.4% | Coming soon | Coming soon |
| MMLU-Pro (Vals) | 92.4% | Coming soon | Coming soon |
| HealthBench (raw) | Coming soon | 69.4% | Coming soon |
| HealthBench (length-adjusted) | Coming soon | 65.4% | Coming soon |
| HealthBench Professional (raw) | Coming soon | 77.1% | Coming soon |
| HealthBench Professional | Coming soon | 69.2% | Coming soon |
| BioMysteryBench (human-solvable) | Coming soon | 89.2% | Coming soon |
| BioMysteryBench (human-difficult) | Coming soon | 44.7% | Coming soon |
| SpatialBench Verified | Coming soon | 72.5% | Coming soon |
| SingleCellBench | Coming soon | 59.1% | Coming soon |
| Protein Design | Coming soon | 51.0% | Coming soon |
| Morphology-to-molecule matching | Coming soon | 25.0% | Coming soon |
| Medicinal chemistry | Coming soon | 65.3% | Coming soon |
| Protein Design library ranking | Coming soon | 54.8% | Coming soon |
| De novo protein-binder design | Coming soon | 82.3% | Coming soon |
| Protocols (troubleshooting) | Coming soon | 67.3% | Coming soon |
| Protocols (understanding) | Coming soon | 66.6% | Coming soon |

### Multilingual

- Winner: Not comparable
- Claude Fable 5.1 public-lane score: Coming soon
- Claude Sonnet 5.5 public-lane score: Coming soon

| Benchmark | Claude Fable 5.1 | Claude Sonnet 5.5 | Winner |
|-----------|-----------|-----------|--------|
| GMMLU | Coming soon | 92.1% | Coming soon |
| MILU | Coming soon | 91.6% | Coming soon |

### Mathematics

- Winner: Not comparable
- Claude Fable 5.1 public-lane score: Coming soon
- Claude Sonnet 5.5 public-lane score: Coming soon

| Benchmark | Claude Fable 5.1 | Claude Sonnet 5.5 | Winner |
|-----------|-----------|-----------|--------|
| ArXivMath Aug. 2026 (no tools) | Coming soon | 86.8% | Coming soon |
| ArXivMath Aug. 2026 (tools) | Coming soon | 95.2% | Coming soon |

## FAQ

### Which is better overall, Claude Fable 5.1 or Claude Sonnet 5.5?

Claude Fable 5.1 is ahead overall on BenchLM right now.

### Where is the biggest gap between Claude Fable 5.1 and Claude Sonnet 5.5?

The widest category gap is in agentic, where the averages are 78.8 for Claude Fable 5.1 and 66.1 for Claude Sonnet 5.5.

### How many benchmarks does Claude Fable 5.1 cover on BenchLM?

Claude Fable 5.1 currently has 26 sourced benchmark scores on BenchLM.

### How many benchmarks does Claude Sonnet 5.5 cover on BenchLM?

Claude Sonnet 5.5 currently has 47 sourced benchmark scores on BenchLM.

## Related Comparisons

- [Claude Fable 5.1 vs Claude Fable 5](/compare/claude-fable-vs-claude-fable-5-1)
- [Claude Sonnet 5.5 vs Claude Fable 5](/compare/claude-fable-vs-claude-sonnet-5-5)
- [Claude Fable 5.1 vs GPT-6 Astra](/compare/claude-fable-5-1-vs-gpt-6-astra)
- [Claude Sonnet 5.5 vs GPT-6 Astra](/compare/claude-sonnet-5-5-vs-gpt-6-astra)

## Explore More

- [Claude Fable 5.1 profile](/models/claude-fable-5-1)
- [Claude Sonnet 5.5 profile](/models/claude-sonnet-5-5)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)