# Claude Fable 5.1 vs Claude Opus 5.5

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

- Canonical page: https://benchlm.ai/compare/claude-fable-5-1-vs-claude-opus-5-5
- Last updated: September 22, 2026

- Shared sourced benchmarks: 16
- HTML indexing: indexable
- Ranking lane: BenchAlign v5

## Quick Verdict

Pick Claude Fable 5.1 if you want the stronger benchmark profile. Claude Opus 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 83.65 to 81.03.
- The clearest category separation is in knowledge, where the averages are 86.1 for Claude Fable 5.1 and 81.8 for Claude Opus 5.5.
- The biggest single benchmark swing is Terminal-Bench 4.0 in Agentic, with scores of 55.80% and 66.40%.
- Claude Opus 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 Opus 5.5 |
|----------|----------|----------|
| Creator | Anthropic | Anthropic |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 1M | 1M |
| Overall Score | 83.65 | 81.03 |
| Benchmarks Covered | 26 | 47 |
| Pricing (input/output) | $10.00 / $50.00 | $4.00 / $20.00 |

## Category Breakdown

### Agentic

- Winner: Claude Opus 5.5
- Claude Fable 5.1 public-lane score: 80 (Supported · #2/157)
- Claude Opus 5.5 public-lane score: 82.9 (Supported · #1/157)

| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 4.0 | 55.80% | 66.40% | Claude Opus 5.5 |
| Terminal-Bench-Science 0.1 | 52.6% | 58.7% | Claude Opus 5.5 |
| OSWorld 2.0 | 41.7% | 48.7% | Claude Opus 5.5 |
| AutomationBench | 31.4% | 40.0% | Claude Opus 5.5 |
| Toolathlon-Verified | 77.8% | 77.8% | Tie |
| Toolathlon Verified Pass@3 | 81.5% | 82.4% | Claude Opus 5.5 |
| Toolathlon Verified Pass³ | 73.1% | 72.2% | Claude Fable 5.1 |
| Toolathlon Verified avg. turns | 23.7 turns | 26.9 turns | Claude Opus 5.5 |
| Terminal-Bench 2.1 (Vals) | 85.0% | Coming soon | Coming soon |
| ApprenticeBench | 72% | Coming soon | Coming soon |
| HLE w/ tools | Coming soon | 67.7% | Coming soon |
| LAB all-pass (Harvey held-out) | Coming soon | 8.3% | Coming soon |
| LAB criterion-pass (Harvey held-out) | Coming soon | 91.2% | Coming soon |

### Coding

- Winner: Claude Fable 5.1
- Claude Fable 5.1 public-lane score: 83.3 (Supported · #1/159)
- Claude Opus 5.5 public-lane score: 80.1 (Supported · #2/159)

| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 | Winner |
|-----------|-----------|-----------|--------|
| Bug Hunt Bench | 43 fixes | Coming soon | Coming soon |
| SWE-bench Pro | 81.2% | 89.9% | Claude Opus 5.5 |
| SWE Multilingual | 89.1% | 93.9% | Claude Opus 5.5 |
| SWE Multimodal | 54.7% | 61.4% | Claude Opus 5.5 |
| DeepSWE | 67.4% | 74.2% | Claude Opus 5.5 |
| FrontierSWE v2 | 56.3% | 62.3% | Claude Opus 5.5 |
| ProgramBench | 87.6% | 91.2% | Claude Opus 5.5 |
| cursorBench32 | 73.4% | Coming soon | Coming soon |
| LiveCodeBench (Vals) | 90.5% | Coming soon | Coming soon |
| cursorBench40 | 51.8% | 57.8% | Claude Opus 5.5 |
| FrontierCode 1.1 Main | Coming soon | 54.4% | Coming soon |
| FrontierCode 1.1 Extended | Coming soon | 63.6% | Coming soon |

### Reasoning

- Winner: Coming soon
- Claude Fable 5.1 public-lane score: 79.4 (#2/17)
- Claude Opus 5.5 public-lane score: 78.5 (#4/17)

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

### Multimodal & Grounded

- Winner: Coming soon
- Claude Fable 5.1 public-lane score: Coming soon
- Claude Opus 5.5 public-lane score: 88.8 (#3/50)

| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 | Winner |
|-----------|-----------|-----------|--------|
| Chartography (tools) | Coming soon | 89.0% | Coming soon |
| Chartography (no tools) | Coming soon | 64.4% | Coming soon |
| BenchCAD Vision2Code (no tools) | Coming soon | 0.730 | Coming soon |
| BenchCAD Vision2Code (tools) | Coming soon | 0.962 | Coming soon |
| Biomedical image analysis | Coming soon | 71.4% | Coming soon |
| OfficeQA | Coming soon | 78.9% | Coming soon |
| OfficeQA Pro | Coming soon | 67.7% | Coming soon |

### Knowledge

- Winner: Coming soon
- Claude Fable 5.1 public-lane score: 86.1 (Supported · #1/189)
- Claude Opus 5.5 public-lane score: 81.8 (Estimated · #4/189)

| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 | Winner |
|-----------|-----------|-----------|--------|
| HLE | 65% | Coming soon | Coming soon |
| HLE w/o tools | 60.9% | 64.4% | Claude Opus 5.5 |
| GPQA Diamond (Vals) | 93.4% | Coming soon | Coming soon |
| MMLU-Pro (Vals) | 92.4% | Coming soon | Coming soon |
| HealthBench (raw) | Coming soon | 68.1% | Coming soon |
| HealthBench (length-adjusted) | Coming soon | 60.6% | Coming soon |
| HealthBench Professional | Coming soon | 65.6% | Coming soon |
| HealthBench Professional (raw) | Coming soon | 77.1% | Coming soon |
| BioMysteryBench (human-solvable) | Coming soon | 89.3% | Coming soon |
| BioMysteryBench (human-difficult) | Coming soon | 50.0% | Coming soon |
| SpatialBench Verified | Coming soon | 72.0% | Coming soon |
| SingleCellBench | Coming soon | 61.2% | Coming soon |
| Morphology-to-molecule matching | Coming soon | 34.0% | Coming soon |
| Medicinal chemistry | Coming soon | 63.5% | Coming soon |
| Protein Design | Coming soon | 60.2% | Coming soon |
| Protein Design library ranking | Coming soon | 56.0% | Coming soon |
| De novo protein-binder design | Coming soon | 82.6% | Coming soon |
| Protocols (troubleshooting) | Coming soon | 73.7% | Coming soon |
| Protocols (understanding) | Coming soon | 69.0% | Coming soon |

### Multilingual

- Winner: Coming soon
- Claude Fable 5.1 public-lane score: Coming soon
- Claude Opus 5.5 public-lane score: Coming soon

| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 | Winner |
|-----------|-----------|-----------|--------|
| GMMLU | Coming soon | 94.3% | Coming soon |
| MILU | Coming soon | 93.1% | Coming soon |

### Mathematics

- Winner: Coming soon
- Claude Fable 5.1 public-lane score: Coming soon
- Claude Opus 5.5 public-lane score: Coming soon

| Benchmark | Claude Fable 5.1 | Claude Opus 5.5 | Winner |
|-----------|-----------|-----------|--------|
| ArXivMath Aug. 2026 (no tools) | Coming soon | 91.2% | Coming soon |
| ArXivMath Aug. 2026 (tools) | Coming soon | 96.9% | Coming soon |

## FAQ

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

The widest category gap is in knowledge, where the averages are 86.1 for Claude Fable 5.1 and 81.8 for Claude Opus 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 Opus 5.5 cover on BenchLM?

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

## Explore More

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