Model comparison
Claude Fable 5.1 vs o3-pro
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 42.9 on the Noometry Index.
Last verified . 6 shared benchmarks.
Summary
- They share 6 benchmarks with published results for both. Claude Fable 5.1 scores higher in 4 categories and o3-pro in 1 category; 5 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Claude Fable 5.1 leads 76.7 to 23.8.
- The biggest single-benchmark swing is ARC-AGI-2: 90% for Claude Fable 5.1 and 4.9% for o3-pro.
- Claude Fable 5.1 is cheaper at $10 / $50 per million input/output tokens, against $20 / $80 for o3-pro.
- Claude Fable 5.1 accepts more context: 1M tokens versus 200K.
Side by side
| Claude Fable 5.1 | o3-pro | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Noometry Index | 69.0 | 42.9 |
| Released | 2026-09-01 | 2025-06-10 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 200K |
| Max output | 128K | 100K |
| Input $ / M tokens | $10 | $20 |
| Output $ / M tokens | $50 | $80 |
| Results tracked | 52 | 12 |
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Category by category
Coding Claude Fable 5.1 leads
Claude Fable 5.1: 74.7 (#1), o3-pro: 55.5 (#24)
| Benchmark | Claude Fable 5.1 | o3-pro |
|---|---|---|
| WeirdML | 92.9% | 58.2% |
| FrontierCode | 50.9% | — |
| Aider Polyglot | — | 84.9% |
| CursorBench | 51.8% | — |
| LMArena WebDev | 1744 | — |
| FrontierSWE | 56.3% | — |
| SciCode | 63.1% | — |
| GSO | 88.2% | — |
| LMArena Coding | 1528 | — |
| MirrorCode | 73.3% | — |
| ALE-Bench | 2,143 | — |
Agentic & Tool Use Not comparable
Claude Fable 5.1: 50.7 (#5), o3-pro: —
| Benchmark | Claude Fable 5.1 | o3-pro |
|---|---|---|
| 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), o3-pro: 23.8 (#171)
| Benchmark | Claude Fable 5.1 | o3-pro |
|---|---|---|
| ARC-AGI-2 | 90% | 4.9% |
| ARC-AGI-1 | 97.5% | 59.3% |
| DTBench | 97.6% | 86.9% |
| LMCA | 65.5% | 38.5% |
| Epoch Capabilities Index | 164.7 | 147.42 |
| Kagi LLM Benchmark | — | 72.1% |
| NYT Connections (extended) | 90% | — |
| CritPt | 31.1% | — |
| Chess Puzzles | 47% | — |
| EBR-Bench | 57.1% | — |
| LMArena Hard Prompts | 1526 | — |
| Mystery Game Puzzles | 58% | — |
Math Not comparable
Claude Fable 5.1: 89.6 (#4), o3-pro: —
| Benchmark | Claude Fable 5.1 | o3-pro |
|---|---|---|
| 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 Claude Fable 5.1 leads
Claude Fable 5.1: 69.6 (#6), o3-pro: 29.5 (#238)
| Benchmark | Claude Fable 5.1 | o3-pro |
|---|---|---|
| Humanity's Last Exam | 46.5% | — |
| SimpleQA Verified | 70.8% | — |
| Confabulations | — | 14.2% |
| Vectara Hallucination Rate | — | 23.3% |
| LMArena Expert | 1535 | — |
Multimodal Not comparable
Claude Fable 5.1: 53.9 (#4), o3-pro: —
| Benchmark | Claude Fable 5.1 | o3-pro |
|---|---|---|
| LMArena Vision | 1318 | — |
| Blueprint-Bench 2 | 41.9% | — |
| Furniture Assembly | 70% | — |
| LMArena Document | 1513 | — |
Multilingual Not comparable
Claude Fable 5.1: 59.1 (#3), o3-pro: —
| Benchmark | Claude Fable 5.1 | o3-pro |
|---|---|---|
| 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
Claude Fable 5.1: 79.2 (#6), o3-pro: —
| Benchmark | Claude Fable 5.1 | o3-pro |
|---|---|---|
| LMArena Instruction Following | 1517 | — |
Long Context o3-pro leads
Claude Fable 5.1: 46.7 (#20), o3-pro: 72.2 (#1)
| Benchmark | Claude Fable 5.1 | o3-pro |
|---|---|---|
| Fiction.LiveBench | — | 97.2% |
| LMArena Longer Query | 1522 | — |
Writing & Preference Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#2), o3-pro: 57.1 (#133)
| Benchmark | Claude Fable 5.1 | o3-pro |
|---|---|---|
| LMArena Text | 1510 | — |
| LMArena Creative Writing | 1507 | — |
| Short-Story Creative Writing | — | 84.4% |
| EQ-Bench Creative Writing | 2162 | — |
| LMArena Multi-Turn | 1492 | — |
Frequently asked questions
Is Claude Fable 5.1 better than o3-pro?
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 42.9 on the Noometry Index.
Which is cheaper, Claude Fable 5.1 or o3-pro?
Claude Fable 5.1 is cheaper. It lists at $10 per million input tokens and $50 per million output tokens; o3-pro lists at $20 and $80.
Is Claude Fable 5.1 or o3-pro 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?
Claude Fable 5.1 does, with 1M tokens against 200K.
How many benchmarks do Claude Fable 5.1 and o3-pro share?
6 benchmarks have published results for both models. Claude Fable 5.1 has 52 scored results on Noometry and o3-pro has 12.