Model comparison
Claude Fable 5.1 vs GPT-6 Luna
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 53.3 on the Noometry Index. GPT-6 Luna costs 100× less per token, which makes it the better buy when Claude Fable 5.1's lead doesn't matter for your workload.
Last verified . 40 shared benchmarks.
Summary
- They share 40 benchmarks with published results for both. Claude Fable 5.1 scores higher in 10 categories and GPT-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 48.2.
- The biggest single-benchmark swing is Mystery Game Puzzles: 58% for Claude Fable 5.1 and 7% for GPT-6 Luna.
- GPT-6 Luna is cheaper at $0.10 / $0.50 per million input/output tokens, against $10 / $50 for Claude Fable 5.1.
- GPT-6 Luna accepts more context: 1.05M tokens versus 1M.
Side by side
| Claude Fable 5.1 | GPT-6 Luna | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Noometry Index | 69.0 | 53.3 |
| Released | 2026-09-01 | 2026-09-22 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 1.05M |
| Max output | 128K | 128K |
| Input $ / M tokens | $10 | $0.10 |
| Output $ / M tokens | $50 | $0.50 |
| Results tracked | 52 | 42 |
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Category by category
Coding Claude Fable 5.1 leads
Claude Fable 5.1: 74.7 (#1), GPT-6 Luna: 55.5 (#25)
| Benchmark | Claude Fable 5.1 | GPT-6 Luna |
|---|---|---|
| FrontierCode | 50.9% | 42.4% |
| LMArena WebDev | 1744 | 1581 |
| SciCode | 63.1% | 54.6% |
| LMArena Coding | 1528 | 1439 |
| ALE-Bench | 2,143 | 1,577 |
| DeepSWE | — | 66.6% |
| CursorBench | 51.8% | — |
| FrontierSWE | 56.3% | — |
| GSO | 88.2% | — |
| WeirdML | 92.9% | — |
| MirrorCode | 73.3% | — |
Agentic & Tool Use Claude Fable 5.1 leads
Claude Fable 5.1: 50.7 (#5), GPT-6 Luna: 33.3 (#54)
| Benchmark | Claude Fable 5.1 | GPT-6 Luna |
|---|---|---|
| APEX-Agents | 68.6% | 44.3% |
| GDP.pdf | 29.6% | 23% |
| Remote Labor Index | 17.9% | — |
| Vending-Bench 2 | 5,422 | — |
Reasoning Claude Fable 5.1 leads
Claude Fable 5.1: 76.7 (#7), GPT-6 Luna: 48.2 (#41)
| Benchmark | Claude Fable 5.1 | GPT-6 Luna |
|---|---|---|
| ARC-AGI-2 | 90% | 59.3% |
| NYT Connections (extended) | 90% | 68.7% |
| ARC-AGI-1 | 97.5% | 86.7% |
| CritPt | 31.1% | 19.4% |
| Chess Puzzles | 47% | 31% |
| LMArena Hard Prompts | 1526 | 1411 |
| Mystery Game Puzzles | 58% | 7% |
| DTBench | 97.6% | 90.1% |
| LMCA | 65.5% | 44.5% |
| Epoch Capabilities Index | 164.7 | 156.28 |
| EBR-Bench | 57.1% | — |
Math Claude Fable 5.1 leads
Claude Fable 5.1: 89.6 (#4), GPT-6 Luna: 76.1 (#15)
| Benchmark | Claude Fable 5.1 | GPT-6 Luna |
|---|---|---|
| FrontierMath (Tiers 1-3) | 90.2% | 78.9% |
| FrontierMath Tier 4 | 87.8% | 56.1% |
| OTIS Mock AIME 2024-2025 | 100% | 98.9% |
| ProofBench | 100% | 64% |
| LMArena Math | 1525 | 1416 |
| FrontierMath Erdős | 0% | — |
Knowledge Claude Fable 5.1 leads
Claude Fable 5.1: 69.6 (#6), GPT-6 Luna: 57.0 (#41)
| Benchmark | Claude Fable 5.1 | GPT-6 Luna |
|---|---|---|
| SimpleQA Verified | 70.8% | 41.4% |
| LMArena Expert | 1535 | 1444 |
| GPQA Diamond | — | 90.5% |
| Humanity's Last Exam | 46.5% | — |
Multimodal Claude Fable 5.1 leads
Claude Fable 5.1: 53.9 (#4), GPT-6 Luna: 42.4 (#30)
| Benchmark | Claude Fable 5.1 | GPT-6 Luna |
|---|---|---|
| LMArena Vision | 1318 | 1217 |
| Blueprint-Bench 2 | 41.9% | 31.2% |
| Furniture Assembly | 70% | 44.2% |
| LMArena Document | 1513 | — |
Multilingual Claude Fable 5.1 leads
Claude Fable 5.1: 59.1 (#3), GPT-6 Luna: 50.5 (#117)
| Benchmark | Claude Fable 5.1 | GPT-6 Luna |
|---|---|---|
| LMArena Non-English | 1507 | 1386 |
| LMArena Chinese | 1586 | 1433 |
| LMArena French | 1525 | 1420 |
| LMArena German | 1500 | 1369 |
| LMArena Japanese | 1543 | 1369 |
| LMArena Korean | 1534 | 1360 |
| LMArena Russian | 1521 | 1394 |
| LMArena Spanish | 1516 | 1393 |
Instruction Following Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#6), GPT-6 Luna: 74.3 (#99)
| Benchmark | Claude Fable 5.1 | GPT-6 Luna |
|---|---|---|
| LMArena Instruction Following | 1517 | 1409 |
Long Context Claude Fable 5.1 leads
Claude Fable 5.1: 46.7 (#20), GPT-6 Luna: 43.0 (#111)
| Benchmark | Claude Fable 5.1 | GPT-6 Luna |
|---|---|---|
| LMArena Longer Query | 1522 | 1409 |
Writing & Preference Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#2), GPT-6 Luna: 58.3 (#119)
| Benchmark | Claude Fable 5.1 | GPT-6 Luna |
|---|---|---|
| LMArena Text | 1510 | 1391 |
| LMArena Creative Writing | 1507 | 1363 |
| LMArena Multi-Turn | 1492 | 1396 |
| EQ-Bench Creative Writing | 2162 | — |
Frequently asked questions
Is Claude Fable 5.1 better than GPT-6 Luna?
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 53.3 on the Noometry Index. GPT-6 Luna costs 100× 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-6 Luna?
GPT-6 Luna is cheaper. It lists at $0.10 per million input tokens and $0.50 per million output tokens; Claude Fable 5.1 lists at $10 and $50.
Is Claude Fable 5.1 or GPT-6 Luna better for coding?
Claude Fable 5.1 scores higher on coding benchmarks: 74.7 versus 55.5 in the Noometry coding category.
Which has the bigger context window?
GPT-6 Luna does, with 1.05M tokens against 1M.
How many benchmarks do Claude Fable 5.1 and GPT-6 Luna share?
40 benchmarks have published results for both models. Claude Fable 5.1 has 52 scored results on Noometry and GPT-6 Luna has 42.