Model comparison
Claude Fable 5.1 vs GPT-6 Astra
GPT-6 Astra is the stronger model overall, scoring 70.8 to 69.0 on the Noometry Index.
Last verified . 51 shared benchmarks.
Summary
- They share 51 benchmarks with published results for both. Claude Fable 5.1 scores higher in 5 categories and GPT-6 Astra in 5 categories; 10 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-6 Astra leads 85.1 to 76.7.
- The biggest single-benchmark swing is MirrorCode: 73.3% for Claude Fable 5.1 and 46.7% for GPT-6 Astra.
- Both cost about the same: $10 input and $50 output per million tokens.
- GPT-6 Astra accepts more context: 1.05M tokens versus 1M.
Side by side
| Claude Fable 5.1 | GPT-6 Astra | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Noometry Index | 69.0 | 70.8 |
| Released | 2026-09-01 | 2026-09-03 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 1.05M |
| Max output | 128K | 128K |
| Input $ / M tokens | $10 | $10 |
| Output $ / M tokens | $50 | $50 |
| Results tracked | 52 | 56 |
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Category by category
Coding Claude Fable 5.1 leads
Claude Fable 5.1: 74.7 (#1), GPT-6 Astra: 73.7 (#2)
| Benchmark | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| FrontierCode | 50.9% | 53.3% |
| LMArena WebDev | 1744 | 1786 |
| FrontierSWE | 56.3% | 65.5% |
| SciCode | 63.1% | 56.5% |
| GSO | 88.2% | 79.4% |
| WeirdML | 92.9% | 93.6% |
| LMArena Coding | 1528 | 1487 |
| MirrorCode | 73.3% | 46.7% |
| ALE-Bench | 2,143 | 2,951 |
| DeepSWE | — | 74.1% |
| CursorBench | 51.8% | — |
Agentic & Tool Use GPT-6 Astra leads
Claude Fable 5.1: 50.7 (#5), GPT-6 Astra: 52.9 (#3)
| Benchmark | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| APEX-Agents | 68.6% | 64.7% |
| Remote Labor Index | 17.9% | 20.8% |
| GDP.pdf | 29.6% | 34.2% |
| Vending-Bench 2 | 5,422 | 15,515 |
| BALROG | — | 68.3% |
Reasoning GPT-6 Astra leads
Claude Fable 5.1: 76.7 (#7), GPT-6 Astra: 85.1 (#1)
| Benchmark | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| ARC-AGI-2 | 90% | 95% |
| NYT Connections (extended) | 90% | 98.1% |
| ARC-AGI-1 | 97.5% | 98.5% |
| CritPt | 31.1% | 31.7% |
| Chess Puzzles | 47% | 72% |
| EBR-Bench | 57.1% | 76.2% |
| LMArena Hard Prompts | 1526 | 1462 |
| Mystery Game Puzzles | 58% | 84% |
| DTBench | 97.6% | 97.3% |
| LMCA | 65.5% | 64.4% |
| Epoch Capabilities Index | 164.7 | 166.45 |
| Bench to the Future 3 | — | 0.14 |
Math GPT-6 Astra leads
Claude Fable 5.1: 89.6 (#4), GPT-6 Astra: 93.5 (#2)
| Benchmark | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| FrontierMath (Tiers 1-3) | 90.2% | 93.7% |
| FrontierMath Tier 4 | 87.8% | 97.6% |
| OTIS Mock AIME 2024-2025 | 100% | 100% |
| ProofBench | 100% | 99% |
| LMArena Math | 1525 | 1465 |
| FrontierMath Erdős | 0% | 2.9% |
Knowledge GPT-6 Astra leads
Claude Fable 5.1: 69.6 (#6), GPT-6 Astra: 75.3 (#1)
| Benchmark | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| Humanity's Last Exam | 46.5% | 54.8% |
| SimpleQA Verified | 70.8% | 75.6% |
| LMArena Expert | 1535 | 1483 |
| GPQA Diamond | — | 95.8% |
| Vectara Hallucination Rate | — | 8.7% |
Multimodal GPT-6 Astra leads
Claude Fable 5.1: 53.9 (#4), GPT-6 Astra: 55.0 (#3)
| Benchmark | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| LMArena Vision | 1318 | 1281 |
| Blueprint-Bench 2 | 41.9% | 49.7% |
| Furniture Assembly | 70% | 80% |
| LMArena Document | 1513 | 1468 |
Multilingual Claude Fable 5.1 leads
Claude Fable 5.1: 59.1 (#3), GPT-6 Astra: 53.7 (#61)
| Benchmark | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| LMArena Non-English | 1507 | 1430 |
| LMArena Chinese | 1586 | 1484 |
| LMArena French | 1525 | 1456 |
| LMArena German | 1500 | 1440 |
| LMArena Japanese | 1543 | 1379 |
| LMArena Korean | 1534 | 1426 |
| LMArena Russian | 1521 | 1436 |
| LMArena Spanish | 1516 | 1407 |
Instruction Following Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#6), GPT-6 Astra: 76.3 (#44)
| Benchmark | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| LMArena Instruction Following | 1517 | 1450 |
Long Context Claude Fable 5.1 leads
Claude Fable 5.1: 46.7 (#20), GPT-6 Astra: 44.5 (#62)
| Benchmark | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| LMArena Longer Query | 1522 | 1456 |
Writing & Preference Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#2), GPT-6 Astra: 75.3 (#7)
| Benchmark | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| LMArena Text | 1510 | 1441 |
| LMArena Creative Writing | 1507 | 1418 |
| EQ-Bench Creative Writing | 2162 | 2173 |
| LMArena Multi-Turn | 1492 | 1448 |
Frequently asked questions
Is Claude Fable 5.1 better than GPT-6 Astra?
GPT-6 Astra is the stronger model overall, scoring 70.8 to 69.0 on the Noometry Index.
Which is cheaper, Claude Fable 5.1 or GPT-6 Astra?
GPT-6 Astra is cheaper. It lists at $10 per million input tokens and $50 per million output tokens; Claude Fable 5.1 lists at $10 and $50.
Is Claude Fable 5.1 or GPT-6 Astra better for coding?
Claude Fable 5.1 scores higher on coding benchmarks: 74.7 versus 73.7 in the Noometry coding category.
Which has the bigger context window?
GPT-6 Astra does, with 1.05M tokens against 1M.
How many benchmarks do Claude Fable 5.1 and GPT-6 Astra share?
51 benchmarks have published results for both models. Claude Fable 5.1 has 52 scored results on Noometry and GPT-6 Astra has 56.