Model comparison
Claude Fable 5.1 vs Grok 4 Fast
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 39.4 on the Noometry Index.
Last verified . 23 shared benchmarks.
Summary
- They share 23 benchmarks with published results for both. Claude Fable 5.1 scores higher in 8 categories and Grok 4 Fast in 1 category; 9 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Claude Fable 5.1 leads 76.7 to 22.2.
- The biggest single-benchmark swing is ARC-AGI-2: 90% for Claude Fable 5.1 and 5.3% for Grok 4 Fast.
Side by side
| Claude Fable 5.1 | Grok 4 Fast | |
|---|---|---|
| Provider | Anthropic | xAI |
| Noometry Index | 69.0 | 39.4 |
| Released | 2026-09-01 | 2025-09-19 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | — |
| Max output | 128K | — |
| Input $ / M tokens | $10 | — |
| Output $ / M tokens | $50 | — |
| Results tracked | 52 | 30 |
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Category by category
Coding Claude Fable 5.1 leads
Claude Fable 5.1: 74.7 (#1), Grok 4 Fast: 32.5 (#271)
| Benchmark | Claude Fable 5.1 | Grok 4 Fast |
|---|---|---|
| LMArena WebDev | 1744 | 1159 |
| WeirdML | 92.9% | 42.9% |
| LMArena Coding | 1528 | 1429 |
| FrontierCode | 50.9% | — |
| CursorBench | 51.8% | — |
| FrontierSWE | 56.3% | — |
| SciCode | 63.1% | — |
| GSO | 88.2% | — |
| MirrorCode | 73.3% | — |
| ALE-Bench | 2,143 | — |
Agentic & Tool Use Claude Fable 5.1 leads
Claude Fable 5.1: 50.7 (#5), Grok 4 Fast: 29.5 (#86)
| Benchmark | Claude Fable 5.1 | Grok 4 Fast |
|---|---|---|
| APEX-Agents | 68.6% | — |
| Remote Labor Index | 17.9% | — |
| τ²-bench Banking | — | 15.7% |
| Cybench | — | 30% |
| GDP.pdf | 29.6% | — |
| LMArena Search | — | 1171 |
| Vending-Bench 2 | 5,422 | — |
Reasoning Claude Fable 5.1 leads
Claude Fable 5.1: 76.7 (#7), Grok 4 Fast: 22.2 (#201)
| Benchmark | Claude Fable 5.1 | Grok 4 Fast |
|---|---|---|
| ARC-AGI-2 | 90% | 5.3% |
| ARC-AGI-1 | 97.5% | 48.5% |
| LMArena Hard Prompts | 1526 | 1412 |
| DTBench | 97.6% | 82.7% |
| Epoch Capabilities Index | 164.7 | 144.2 |
| Kagi LLM Benchmark | — | 66.1% |
| NYT Connections (extended) | 90% | — |
| CritPt | 31.1% | — |
| Chess Puzzles | 47% | — |
| EBR-Bench | 57.1% | — |
| Mystery Game Puzzles | 58% | — |
| LMCA | 65.5% | — |
| ForecastBench | — | 60.5 |
Math Claude Fable 5.1 leads
Claude Fable 5.1: 89.6 (#4), Grok 4 Fast: 38.9 (#123)
| Benchmark | Claude Fable 5.1 | Grok 4 Fast |
|---|---|---|
| LMArena Math | 1525 | 1419 |
| FrontierMath (Tiers 1-3) | 90.2% | — |
| FrontierMath Tier 4 | 87.8% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| ProofBench | 100% | — |
| FrontierMath Erdős | 0% | — |
Knowledge Claude Fable 5.1 leads
Claude Fable 5.1: 69.6 (#6), Grok 4 Fast: 32.0 (#214)
| Benchmark | Claude Fable 5.1 | Grok 4 Fast |
|---|---|---|
| LMArena Expert | 1535 | 1411 |
| Humanity's Last Exam | 46.5% | — |
| SimpleQA Verified | 70.8% | — |
| Vectara Hallucination Rate | — | 19.7% |
Multimodal Not comparable
Claude Fable 5.1: 53.9 (#4), Grok 4 Fast: —
| Benchmark | Claude Fable 5.1 | Grok 4 Fast |
|---|---|---|
| LMArena Vision | 1318 | — |
| Blueprint-Bench 2 | 41.9% | — |
| Furniture Assembly | 70% | — |
| LMArena Document | 1513 | — |
Multilingual Claude Fable 5.1 leads
Claude Fable 5.1: 59.1 (#3), Grok 4 Fast: 51.3 (#111)
| Benchmark | Claude Fable 5.1 | Grok 4 Fast |
|---|---|---|
| LMArena Non-English | 1507 | 1396 |
| LMArena Chinese | 1586 | 1457 |
| LMArena French | 1525 | 1431 |
| LMArena German | 1500 | 1383 |
| LMArena Japanese | 1543 | 1352 |
| LMArena Korean | 1534 | 1357 |
| LMArena Russian | 1521 | 1389 |
| LMArena Spanish | 1516 | 1415 |
Instruction Following Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#6), Grok 4 Fast: 73.2 (#121)
| Benchmark | Claude Fable 5.1 | Grok 4 Fast |
|---|---|---|
| LMArena Instruction Following | 1517 | 1387 |
Long Context Grok 4 Fast leads
Claude Fable 5.1: 46.7 (#20), Grok 4 Fast: 63.2 (#3)
| Benchmark | Claude Fable 5.1 | Grok 4 Fast |
|---|---|---|
| LMArena Longer Query | 1522 | 1415 |
| Fiction.LiveBench | — | 94.4% |
Writing & Preference Claude Fable 5.1 leads
Claude Fable 5.1: 79.2 (#2), Grok 4 Fast: 60.0 (#102)
| Benchmark | Claude Fable 5.1 | Grok 4 Fast |
|---|---|---|
| LMArena Text | 1510 | 1407 |
| LMArena Creative Writing | 1507 | 1387 |
| LMArena Multi-Turn | 1492 | 1414 |
| EQ-Bench Creative Writing | 2162 | — |
Frequently asked questions
Is Claude Fable 5.1 better than Grok 4 Fast?
Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 39.4 on the Noometry Index.
Is Claude Fable 5.1 or Grok 4 Fast better for coding?
Claude Fable 5.1 scores higher on coding benchmarks: 74.7 versus 32.5 in the Noometry coding category.
How many benchmarks do Claude Fable 5.1 and Grok 4 Fast share?
23 benchmarks have published results for both models. Claude Fable 5.1 has 52 scored results on Noometry and Grok 4 Fast has 30.