Model comparison
Claude Fable 5.1 vs GPT-5.6 Luna
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 54.6 on the Noometry Index. GPT-5.6 Luna costs 44× less per token, which makes it the better buy when Claude Fable 5.1's lead doesn't matter for your workload.
Last verified . 45 shared benchmarks.
Summary
- They share 45 benchmarks with published results for both. Claude Fable 5.1 scores higher in 10 categories and GPT-5.6 Luna 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 47.6.
- The biggest single-benchmark swing is ProofBench: 100% for Claude Fable 5.1 and 60% for GPT-5.6 Luna.
- GPT-5.6 Luna is cheaper at $0.20 / $1.20 per million input/output tokens, against $10 / $50 for Claude Fable 5.1.
- GPT-5.6 Luna accepts more context: 1.05M tokens versus 1M.
Side by side
| Claude Fable 5.1 | GPT-5.6 Luna | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Noometry Index | 69.0 | 54.6 |
| Released | 2026-09-01 | 2026-07-09 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 1.05M |
| Max output | 128K | 128K |
| Input $ / M tokens | $10 | $0.20 |
| Output $ / M tokens | $50 | $1.20 |
| Results tracked | 52 | 52 |
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Category by category
Coding Claude Fable 5.1 leads
Claude Fable 5.1: 74.7 (#1), GPT-5.6 Luna: 54.5 (#28)
| Benchmark | Claude Fable 5.1 | GPT-5.6 Luna |
|---|---|---|
| FrontierCode | 50.9% | 39.8% |
| CursorBench | 51.8% | 35.9% |
| LMArena WebDev | 1744 | 1519 |
| SciCode | 63.1% | 53.6% |
| WeirdML | 92.9% | 60.9% |
| LMArena Coding | 1528 | 1466 |
| ALE-Bench | 2,143 | 1,667 |
| DeepSWE | — | 67.2% |
| FrontierSWE | 56.3% | — |
| GSO | 88.2% | — |
| MirrorCode | 73.3% | — |
Agentic & Tool Use Claude Fable 5.1 leads
Claude Fable 5.1: 50.7 (#5), GPT-5.6 Luna: 34.4 (#45)
| Benchmark | Claude Fable 5.1 | GPT-5.6 Luna |
|---|---|---|
| APEX-Agents | 68.6% | 43% |
| GDP.pdf | 29.6% | 22.7% |
| Vending-Bench 2 | 5,422 | 4,095 |
| Remote Labor Index | 17.9% | — |
| BALROG | — | 45.6% |
Reasoning Claude Fable 5.1 leads
Claude Fable 5.1: 76.7 (#7), GPT-5.6 Luna: 47.6 (#43)
| Benchmark | Claude Fable 5.1 | GPT-5.6 Luna |
|---|---|---|
| ARC-AGI-2 | 90% | 59.5% |
| NYT Connections (extended) | 90% | 69.4% |
| ARC-AGI-1 | 97.5% | 88% |
| CritPt | 31.1% | 20.6% |
| Chess Puzzles | 47% | 40% |
| LMArena Hard Prompts | 1526 | 1451 |
| Mystery Game Puzzles | 58% | 21% |
| DTBench | 97.6% | 89.1% |
| LMCA | 65.5% | 48.5% |
| Epoch Capabilities Index | 164.7 | 156.39 |
| SimpleBench | — | 46.8% |
| Kagi LLM Benchmark | — | 49.1% |
| EBR-Bench | 57.1% | — |
| Surface Evolver Bench | — | 61.9% |
Math Claude Fable 5.1 leads
Claude Fable 5.1: 89.6 (#4), GPT-5.6 Luna: 77.7 (#14)
| Benchmark | Claude Fable 5.1 | GPT-5.6 Luna |
|---|---|---|
| FrontierMath (Tiers 1-3) | 90.2% | 82.1% |
| FrontierMath Tier 4 | 87.8% | 61% |
| OTIS Mock AIME 2024-2025 | 100% | 98.3% |
| ProofBench | 100% | 60% |
| LMArena Math | 1525 | 1458 |
| FrontierMath Erdős | 0% | — |
Knowledge Claude Fable 5.1 leads
Claude Fable 5.1: 69.6 (#6), GPT-5.6 Luna: 58.5 (#34)
| Benchmark | Claude Fable 5.1 | GPT-5.6 Luna |
|---|---|---|
| SimpleQA Verified | 70.8% | 41% |
| LMArena Expert | 1535 | 1478 |
| GPQA Diamond | — | 91.6% |
| Humanity's Last Exam | 46.5% | — |
Multimodal Claude Fable 5.1 leads
Claude Fable 5.1: 53.9 (#4), GPT-5.6 Luna: 42.7 (#28)
| Benchmark | Claude Fable 5.1 | GPT-5.6 Luna |
|---|---|---|
| LMArena Vision | 1318 | 1258 |
| Blueprint-Bench 2 | 41.9% | 22.6% |
| Furniture Assembly | 70% | 42.5% |
| LMArena Document | 1513 | 1457 |
Multilingual Claude Fable 5.1 leads
Claude Fable 5.1: 59.1 (#3), GPT-5.6 Luna: 52.8 (#78)
| Benchmark | Claude Fable 5.1 | GPT-5.6 Luna |
|---|---|---|
| LMArena Non-English | 1507 | 1417 |
| LMArena Chinese | 1586 | 1470 |
| LMArena French | 1525 | 1456 |
| LMArena German | 1500 | 1454 |
| LMArena Japanese | 1543 | 1411 |
| LMArena Korean | 1534 | 1415 |
| LMArena Russian | 1521 | 1428 |
| LMArena Spanish | 1516 | 1448 |
Instruction Following Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#6), GPT-5.6 Luna: 75.6 (#57)
| Benchmark | Claude Fable 5.1 | GPT-5.6 Luna |
|---|---|---|
| LMArena Instruction Following | 1517 | 1437 |
Long Context Claude Fable 5.1 leads
Claude Fable 5.1: 46.7 (#20), GPT-5.6 Luna: 43.9 (#82)
| Benchmark | Claude Fable 5.1 | GPT-5.6 Luna |
|---|---|---|
| LMArena Longer Query | 1522 | 1436 |
Writing & Preference Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#2), GPT-5.6 Luna: 68.0 (#29)
| Benchmark | Claude Fable 5.1 | GPT-5.6 Luna |
|---|---|---|
| LMArena Text | 1510 | 1431 |
| LMArena Creative Writing | 1507 | 1396 |
| EQ-Bench Creative Writing | 2162 | 1829 |
| LMArena Multi-Turn | 1492 | 1434 |
| EQ-Bench 4 | — | 1156 |
Frequently asked questions
Is Claude Fable 5.1 better than GPT-5.6 Luna?
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 54.6 on the Noometry Index. GPT-5.6 Luna costs 44× 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 GPT-5.6 Luna?
GPT-5.6 Luna is cheaper. It lists at $0.20 per million input tokens and $1.20 per million output tokens; Claude Fable 5.1 lists at $10 and $50.
Is Claude Fable 5.1 or GPT-5.6 Luna better for coding?
Claude Fable 5.1 scores higher on coding benchmarks: 74.7 versus 54.5 in the Noometry coding category.
Which has the bigger context window?
GPT-5.6 Luna does, with 1.05M tokens against 1M.
How many benchmarks do Claude Fable 5.1 and GPT-5.6 Luna share?
45 benchmarks have published results for both models. Claude Fable 5.1 has 52 scored results on Noometry and GPT-5.6 Luna has 52.