Model comparison
Aion 3.5 vs Claude Fable 5.1
Claude Fable 5.1 has enough public results to be ranked (#2); Aion 3.5 does not yet, so treat this comparison as directional.
Last verified . 1 shared benchmarks.
Summary
- They share 1 benchmark with published results for both. Aion 3.5 scores higher in 0 categories and Claude Fable 5.1 in 1 category; one gap is clear of the uncertainty.
- The widest gap is in writing & preference, where Claude Fable 5.1 leads 79.2 to 74.9.
- Aion 3.5 is cheaper at $3 / $6 per million input/output tokens, against $10 / $50 for Claude Fable 5.1.
- Claude Fable 5.1 accepts more context: 1M tokens versus 262K.
Side by side
| Aion 3.5 | Claude Fable 5.1 | |
|---|---|---|
| Provider | AionLabs | Anthropic |
| Noometry Index | 58.1 | 69.0 |
| Released | — | 2026-09-01 |
| Weights | Proprietary | Proprietary |
| Context window | 262K | 1M |
| Max output | 33K | 128K |
| Input $ / M tokens | $3 | $10 |
| Output $ / M tokens | $6 | $50 |
| Results tracked | 1 | 52 |
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Category by category
Coding Not comparable
Aion 3.5: —, Claude Fable 5.1: 74.7 (#1)
| Benchmark | Aion 3.5 | Claude Fable 5.1 |
|---|---|---|
| FrontierCode | — | 50.9% |
| CursorBench | — | 51.8% |
| LMArena WebDev | — | 1744 |
| FrontierSWE | — | 56.3% |
| SciCode | — | 63.1% |
| GSO | — | 88.2% |
| WeirdML | — | 92.9% |
| LMArena Coding | — | 1528 |
| MirrorCode | — | 73.3% |
| ALE-Bench | — | 2,143 |
Agentic & Tool Use Not comparable
Aion 3.5: —, Claude Fable 5.1: 50.7 (#5)
| Benchmark | Aion 3.5 | Claude Fable 5.1 |
|---|---|---|
| APEX-Agents | — | 68.6% |
| Remote Labor Index | — | 17.9% |
| GDP.pdf | — | 29.6% |
| Vending-Bench 2 | — | 5,422 |
Reasoning Not comparable
Aion 3.5: —, Claude Fable 5.1: 76.7 (#7)
| Benchmark | Aion 3.5 | Claude Fable 5.1 |
|---|---|---|
| ARC-AGI-2 | — | 90% |
| NYT Connections (extended) | — | 90% |
| ARC-AGI-1 | — | 97.5% |
| CritPt | — | 31.1% |
| Chess Puzzles | — | 47% |
| EBR-Bench | — | 57.1% |
| LMArena Hard Prompts | — | 1526 |
| Mystery Game Puzzles | — | 58% |
| DTBench | — | 97.6% |
| LMCA | — | 65.5% |
| Epoch Capabilities Index | — | 164.7 |
Math Not comparable
Aion 3.5: —, Claude Fable 5.1: 89.6 (#4)
| Benchmark | Aion 3.5 | Claude Fable 5.1 |
|---|---|---|
| FrontierMath (Tiers 1-3) | — | 90.2% |
| FrontierMath Tier 4 | — | 87.8% |
| OTIS Mock AIME 2024-2025 | — | 100% |
| ProofBench | — | 100% |
| LMArena Math | — | 1525 |
| FrontierMath Erdős | — | 0% |
Knowledge Not comparable
Aion 3.5: —, Claude Fable 5.1: 69.6 (#6)
| Benchmark | Aion 3.5 | Claude Fable 5.1 |
|---|---|---|
| Humanity's Last Exam | — | 46.5% |
| SimpleQA Verified | — | 70.8% |
| LMArena Expert | — | 1535 |
Multimodal Not comparable
Aion 3.5: —, Claude Fable 5.1: 53.9 (#4)
| Benchmark | Aion 3.5 | Claude Fable 5.1 |
|---|---|---|
| LMArena Vision | — | 1318 |
| Blueprint-Bench 2 | — | 41.9% |
| Furniture Assembly | — | 70% |
| LMArena Document | — | 1513 |
Multilingual Not comparable
Aion 3.5: —, Claude Fable 5.1: 59.1 (#3)
| Benchmark | Aion 3.5 | Claude Fable 5.1 |
|---|---|---|
| LMArena Non-English | — | 1507 |
| LMArena Chinese | — | 1586 |
| LMArena French | — | 1525 |
| LMArena German | — | 1500 |
| LMArena Japanese | — | 1543 |
| LMArena Korean | — | 1534 |
| LMArena Russian | — | 1521 |
| LMArena Spanish | — | 1516 |
Instruction Following Not comparable
Aion 3.5: —, Claude Fable 5.1: 79.2 (#6)
| Benchmark | Aion 3.5 | Claude Fable 5.1 |
|---|---|---|
| LMArena Instruction Following | — | 1517 |
Long Context Not comparable
Aion 3.5: —, Claude Fable 5.1: 46.7 (#20)
| Benchmark | Aion 3.5 | Claude Fable 5.1 |
|---|---|---|
| LMArena Longer Query | — | 1522 |
Writing & Preference Claude Fable 5.1 leads
Aion 3.5: 74.9, Claude Fable 5.1: 79.2 (#2)
| Benchmark | Aion 3.5 | Claude Fable 5.1 |
|---|---|---|
| EQ-Bench Creative Writing | 1929 | 2162 |
| LMArena Text | — | 1510 |
| LMArena Creative Writing | — | 1507 |
| LMArena Multi-Turn | — | 1492 |
Frequently asked questions
Is Aion 3.5 better than Claude Fable 5.1?
Claude Fable 5.1 has enough public results to be ranked (#2); Aion 3.5 does not yet, so treat this comparison as directional.
Which is cheaper, Aion 3.5 or Claude Fable 5.1?
Aion 3.5 is cheaper. It lists at $3 per million input tokens and $6 per million output tokens; Claude Fable 5.1 lists at $10 and $50.
Which has the bigger context window?
Claude Fable 5.1 does, with 1M tokens against 262K.
How many benchmarks do Aion 3.5 and Claude Fable 5.1 share?
1 benchmark has published results for both models. Aion 3.5 has 1 scored results on Noometry and Claude Fable 5.1 has 52.