# Claude Fable 5.1 vs Nemotron 3 Ultra

> Side-by-side benchmark comparison for Claude Fable 5.1 and Nemotron 3 Ultra across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/claude-fable-5-1-vs-nemotron-3-ultra
- Last updated: October 17, 2026

- Shared sourced benchmarks: 8
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.8

## Quick Verdict

Claude Fable 5.1 leads by point estimate. Conditional score ranges do not establish rank confidence. Choose using the category evidence and your own workload tests.

## Summary

- Claude Fable 5.1 has the higher overall point estimate 83.18 to 46.58. Conditional score ranges do not establish rank confidence.
- The clearest category separation is in coding, where the averages are 76.8 for Claude Fable 5.1 and 21.7 for Nemotron 3 Ultra.
- The biggest single benchmark swing is HLE in Knowledge, with scores of 65% and 26.7%.
- Nemotron 3 Ultra 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 | Nemotron 3 Ultra |
|----------|----------|----------|
| Creator | Anthropic | NVIDIA |
| Type | Proprietary | Open Weight |
| Reasoning | Reasoning | Reasoning |
| Context | 1M | 1M |
| Overall Score | 83.18 | 46.58 |
| Benchmarks Covered | 33 | 25 |
| Pricing (input/output) | $10.00 / $50.00 | $0.00 / $0.00 |

## Category Breakdown

### Agentic

- Winner: Claude Fable 5.1
- Claude Fable 5.1 public-lane score: 80.9 (Supported · #2/128)
- Nemotron 3 Ultra public-lane score: 27.7 (Supported · #98/128)

| Benchmark | Claude Fable 5.1 | Nemotron 3 Ultra | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 4.0 | 55.80% | Coming soon | Coming soon |
| Terminal-Bench-Science 0.1 | 52.6% | Coming soon | Coming soon |
| OSWorld 2.0 | 41.7% | Coming soon | Coming soon |
| AutomationBench | 31.4% | Coming soon | Coming soon |
| Toolathlon-Verified | 77.8% | Coming soon | Coming soon |
| Toolathlon Verified Pass@3 | 81.5% | Coming soon | Coming soon |
| Toolathlon Verified Pass³ | 73.1% | Coming soon | Coming soon |
| Toolathlon Verified avg. turns | 23.7 turns | Coming soon | Coming soon |
| Terminal-Bench 2.1 (Vals) | 85.0% | 50.9% | Claude Fable 5.1 |
| ApprenticeBench | 72% | Coming soon | Coming soon |
| CWE-bench v1 | 58.0% | Coming soon | Coming soon |
| MazeBench | 10% | 0% | Claude Fable 5.1 |
| Terminal-Bench 2.1 | Coming soon | 56.4% | Coming soon |
| PinchBench | Coming soon | 90.0% | Coming soon |
| BrowseComp | Coming soon | 44.4% | Coming soon |
| τ³-bench results | Coming soon | 70.9% | Coming soon |
| HLE w/ tools | Coming soon | 37.4% | Coming soon |

### Coding

- Winner: Claude Fable 5.1
- Claude Fable 5.1 public-lane score: 76.8 (Supported · #3/150)
- Nemotron 3 Ultra public-lane score: 21.7 (Supported · #116/150)

| Benchmark | Claude Fable 5.1 | Nemotron 3 Ultra | Winner |
|-----------|-----------|-----------|--------|
| Bug Hunt Bench | 43.0 fixes | Coming soon | Coming soon |
| SWE-bench Pro | 81.2% | Coming soon | Coming soon |
| SWE Multilingual | 89.1% | 67.7% | Claude Fable 5.1 |
| SWE Multimodal | 54.7% | Coming soon | Coming soon |
| DeepSWE | 67.4% | Coming soon | Coming soon |
| FrontierSWE v2 | 56.3% | Coming soon | Coming soon |
| ProgramBench | 87.6% | Coming soon | Coming soon |
| CursorBench 3.2 | 73.4% | Coming soon | Coming soon |
| LiveCodeBench (Vals) | 90.5% | 86.0% | Claude Fable 5.1 |
| CursorBench 4.0 | 51.8% | Coming soon | Coming soon |
| PostTrainBench v1.1 | 40.2% | Coming soon | Coming soon |
| SWE-bench Verified | Coming soon | 71.9% | Coming soon |
| LiveCodeBench v6 | Coming soon | 89.0% | Coming soon |
| SciCode | Coming soon | 44.6% | Coming soon |
| Terminal-Bench 2.1 | Coming soon | 56.4% | Coming soon |
| SWE-bench (Vals) | Coming soon | 69.0% | Coming soon |

### Reasoning

- Winner: Not comparable
- Claude Fable 5.1 public-lane score: 85.2 (#4/28)
- Nemotron 3 Ultra public-lane score: 70.3 (Unranked · 1 rankable row)

| Benchmark | Claude Fable 5.1 | Nemotron 3 Ultra | Winner |
|-----------|-----------|-----------|--------|
| ARC-AGI-1 | 97.50% | Coming soon | Coming soon |
| ARC-AGI-2 | 90% | Coming soon | Coming soon |
| GraphWalks BFS 256K–1M | 65.0% | Coming soon | Coming soon |
| CritPt | Coming soon | 3.1% | Coming soon |
| LongBench v2 | Coming soon | 61.9% | Coming soon |

### Knowledge

- Winner: Directional only
- Claude Fable 5.1 public-lane score: 86.9 (Supported · #2/184)
- Nemotron 3 Ultra public-lane score: 50 (Estimated · #81/184)

| Benchmark | Claude Fable 5.1 | Nemotron 3 Ultra | Winner |
|-----------|-----------|-----------|--------|
| HLE | 65% | 26.7% | Claude Fable 5.1 |
| HLE w/o tools | 60.9% | 26.7% | Claude Fable 5.1 |
| GPQA Diamond (Vals) | 93.4% | 86.1% | Claude Fable 5.1 |
| MMLU-Pro (Vals) | 92.4% | 85.8% | Claude Fable 5.1 |
| GPQA | Coming soon | 87% | Coming soon |
| GPQA-D | Coming soon | 87.0% | Coming soon |
| MMLU-Pro | Coming soon | 86.8% | Coming soon |

### Multilingual

- Winner: Not comparable
- Claude Fable 5.1 public-lane score: Coming soon
- Nemotron 3 Ultra public-lane score: 89.2 (#7/17)

| Benchmark | Claude Fable 5.1 | Nemotron 3 Ultra | Winner |
|-----------|-----------|-----------|--------|
| MMLU-ProX | Coming soon | 83% | Coming soon |

### Instruction Following

- Winner: Not comparable
- Claude Fable 5.1 public-lane score: Coming soon
- Nemotron 3 Ultra public-lane score: 92.1 (#20/148)

| Benchmark | Claude Fable 5.1 | Nemotron 3 Ultra | Winner |
|-----------|-----------|-----------|--------|
| Gray Swan IPI (15 attempts) | 1.0% | Coming soon | Coming soon |
| IFBench | Coming soon | 81.7% | Coming soon |

### Mathematics

- Winner: Not comparable
- Claude Fable 5.1 public-lane score: 96.8 (Unranked · 2 rankable rows)
- Nemotron 3 Ultra public-lane score: Coming soon

| Benchmark | Claude Fable 5.1 | Nemotron 3 Ultra | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath v2 (Tiers 1-3) | 90.175% | Coming soon | Coming soon |
| FrontierMath v2 (Tier 4) | 87.805% | Coming soon | Coming soon |

## FAQ

### Which is better overall, Claude Fable 5.1 or Nemotron 3 Ultra?

Claude Fable 5.1 has the higher overall point estimate. Conditional score ranges do not establish rank confidence.

### Where is the biggest gap between Claude Fable 5.1 and Nemotron 3 Ultra?

The widest category gap is in coding, where the averages are 76.8 for Claude Fable 5.1 and 21.7 for Nemotron 3 Ultra.

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

Claude Fable 5.1 currently has 33 sourced benchmark scores on BenchLM.

### How many benchmarks does Nemotron 3 Ultra cover on BenchLM?

Nemotron 3 Ultra currently has 25 sourced benchmark scores on BenchLM.

## Related Comparisons

- [Claude Fable 5.1 vs Claude Fable 5](/compare/claude-fable-vs-claude-fable-5-1)
- [Nemotron 3 Ultra vs Claude Fable 5](/compare/claude-fable-vs-nemotron-3-ultra)
- [Claude Fable 5.1 vs Claude Opus 5.5](/compare/claude-fable-5-1-vs-claude-opus-5-5)
- [Nemotron 3 Ultra vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-nemotron-3-ultra)

## Explore More

- [Claude Fable 5.1 profile](/models/claude-fable-5-1)
- [Nemotron 3 Ultra profile](/models/nemotron-3-ultra)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)