Model comparison
Claude Fable 5.1 vs Nemotron 3.5 Lightning
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 40.0 on the Noometry Index. Nemotron 3.5 Lightning costs 229× less per token, which makes it the better buy when Claude Fable 5.1's lead doesn't matter for your workload.
Last verified . 18 shared benchmarks.
NVIDIASummary
- They share 18 benchmarks with published results for both. Claude Fable 5.1 scores higher in 8 categories and Nemotron 3.5 Lightning in 0 categories; 8 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Fable 5.1 leads 89.6 to 37.5.
- Nemotron 3.5 Lightning is cheaper at $0.05 / $0.20 per million input/output tokens, against $10 / $50 for Claude Fable 5.1.
- Claude Fable 5.1 accepts more context: 1M tokens versus 262K.
- Nemotron 3.5 Lightning has downloadable open weights; the other is API-only.
Side by side
| Claude Fable 5.1 | Nemotron 3.5 Lightning | |
|---|---|---|
| Provider | Anthropic | NVIDIA |
| Noometry Index | 69.0 | 40.0 |
| Released | 2026-09-01 | 2026-08-11 |
| Weights | Proprietary | Open |
| Context window | 1M | 262K |
| Max output | 128K | 262K |
| Input $ / M tokens | $10 | $0.05 |
| Output $ / M tokens | $50 | $0.20 |
| Results tracked | 52 | 18 |
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Category by category
Coding Claude Fable 5.1 leads
Claude Fable 5.1: 74.7 (#1), Nemotron 3.5 Lightning: 40.4 (#141)
| Benchmark | Claude Fable 5.1 | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Coding | 1528 | 1375 |
| FrontierCode | 50.9% | — |
| CursorBench | 51.8% | — |
| LMArena WebDev | 1744 | — |
| FrontierSWE | 56.3% | — |
| SciCode | 63.1% | — |
| GSO | 88.2% | — |
| WeirdML | 92.9% | — |
| MirrorCode | 73.3% | — |
| ALE-Bench | 2,143 | — |
Agentic & Tool Use Not comparable
Claude Fable 5.1: 50.7 (#5), Nemotron 3.5 Lightning: —
| Benchmark | Claude Fable 5.1 | Nemotron 3.5 Lightning |
|---|---|---|
| APEX-Agents | 68.6% | — |
| Remote Labor Index | 17.9% | — |
| GDP.pdf | 29.6% | — |
| Vending-Bench 2 | 5,422 | — |
Reasoning Claude Fable 5.1 leads
Claude Fable 5.1: 76.7 (#7), Nemotron 3.5 Lightning: 26.8 (#127)
| Benchmark | Claude Fable 5.1 | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Hard Prompts | 1526 | 1337 |
| ARC-AGI-2 | 90% | — |
| NYT Connections (extended) | 90% | — |
| ARC-AGI-1 | 97.5% | — |
| CritPt | 31.1% | — |
| Chess Puzzles | 47% | — |
| EBR-Bench | 57.1% | — |
| Mystery Game Puzzles | 58% | — |
| DTBench | 97.6% | — |
| LMCA | 65.5% | — |
| Epoch Capabilities Index | 164.7 | — |
Math Claude Fable 5.1 leads
Claude Fable 5.1: 89.6 (#4), Nemotron 3.5 Lightning: 37.5 (#155)
| Benchmark | Claude Fable 5.1 | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Math | 1525 | 1359 |
| FrontierMath (Tiers 1-3) | 90.2% | — |
| FrontierMath Tier 4 | 87.8% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| ProofBench | 100% | — |
| FrontierMath Erdős | 0% | — |
Knowledge Claude Fable 5.1 leads
Claude Fable 5.1: 69.6 (#6), Nemotron 3.5 Lightning: 37.5 (#154)
| Benchmark | Claude Fable 5.1 | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Expert | 1535 | 1356 |
| Humanity's Last Exam | 46.5% | — |
| SimpleQA Verified | 70.8% | — |
Multimodal Not comparable
Claude Fable 5.1: 53.9 (#4), Nemotron 3.5 Lightning: —
| Benchmark | Claude Fable 5.1 | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Vision | 1318 | — |
| Blueprint-Bench 2 | 41.9% | — |
| Furniture Assembly | 70% | — |
| LMArena Document | 1513 | — |
Multilingual Claude Fable 5.1 leads
Claude Fable 5.1: 59.1 (#3), Nemotron 3.5 Lightning: 44.0 (#180)
| Benchmark | Claude Fable 5.1 | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Non-English | 1507 | 1295 |
| LMArena Chinese | 1586 | 1359 |
| LMArena French | 1525 | 1366 |
| LMArena German | 1500 | 1282 |
| LMArena Japanese | 1543 | 1206 |
| LMArena Korean | 1534 | 1238 |
| LMArena Russian | 1521 | 1253 |
| LMArena Spanish | 1516 | 1345 |
Instruction Following Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#6), Nemotron 3.5 Lightning: 69.6 (#170)
| Benchmark | Claude Fable 5.1 | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Instruction Following | 1517 | 1318 |
Long Context Claude Fable 5.1 leads
Claude Fable 5.1: 46.7 (#20), Nemotron 3.5 Lightning: 39.9 (#165)
| Benchmark | Claude Fable 5.1 | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Longer Query | 1522 | 1314 |
Writing & Preference Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#2), Nemotron 3.5 Lightning: 48.5 (#201)
| Benchmark | Claude Fable 5.1 | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Text | 1510 | 1327 |
| LMArena Creative Writing | 1507 | 1254 |
| EQ-Bench Creative Writing | 2162 | 1280 |
| LMArena Multi-Turn | 1492 | 1328 |
Frequently asked questions
Is Claude Fable 5.1 better than Nemotron 3.5 Lightning?
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 40.0 on the Noometry Index. Nemotron 3.5 Lightning costs 229× 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 Nemotron 3.5 Lightning?
Nemotron 3.5 Lightning is cheaper. It lists at $0.05 per million input tokens and $0.20 per million output tokens; Claude Fable 5.1 lists at $10 and $50.
Is Claude Fable 5.1 or Nemotron 3.5 Lightning better for coding?
Claude Fable 5.1 scores higher on coding benchmarks: 74.7 versus 40.4 in the Noometry coding category.
Which has the bigger context window?
Claude Fable 5.1 does, with 1M tokens against 262K.
How many benchmarks do Claude Fable 5.1 and Nemotron 3.5 Lightning share?
18 benchmarks have published results for both models. Claude Fable 5.1 has 52 scored results on Noometry and Nemotron 3.5 Lightning has 18.