Model comparison
Claude Fable 5.1 vs Grok 4.20 (Non-Reasoning)
Claude Fable 5.1 is the stronger model overall, scoring 68.5 to 48.5 on the Noometry Index. Grok 4.20 (Non-Reasoning) costs 13× less per token, which makes it the better buy when Claude Fable 5.1's lead doesn't matter for your workload.
Last verified . 36 shared benchmarks.
Summary
- They share 36 benchmarks with published results for both. Claude Fable 5.1 scores higher in 10 categories and Grok 4.20 (Non-Reasoning) in 0 categories; 10 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Fable 5.1 leads 89.5 to 48.0.
- The biggest single-benchmark swing is ProofBench: 100% for Claude Fable 5.1 and 14% for Grok 4.20 (Non-Reasoning).
- Grok 4.20 (Non-Reasoning) is cheaper at $1.25 / $2.50 per million input/output tokens, against $10 / $50 for Claude Fable 5.1.
Side by side
| Claude Fable 5.1 | Grok 4.20 (Non-Reasoning) | |
|---|---|---|
| Provider | Anthropic | xAI |
| Noometry Index | 68.5 | 48.5 |
| Released | 2026-09-01 | 2026-02-17 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 1M |
| Max output | 128K | 30K |
| Input $ / M tokens | $10 | $1.25 |
| Output $ / M tokens | $50 | $2.50 |
| Results tracked | 50 | 46 |
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Category by category
Coding Claude Fable 5.1 leads
Claude Fable 5.1: 70.5 (#2), Grok 4.20 (Non-Reasoning): 41.8 (#104)
| Benchmark | Claude Fable 5.1 | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| LMArena WebDev | 1753 | 1374 |
| WeirdML | 92.9% | 52.3% |
| LMArena Coding | 1523 | 1458 |
| ALE-Bench | 2,143 | 1,150 |
| FrontierCode | 50.9% | — |
| CursorBench | 51.8% | — |
| FrontierSWE | 56.3% | — |
| SciCode | 63.1% | — |
| MirrorCode | 73.3% | — |
Agentic & Tool Use Claude Fable 5.1 leads
Claude Fable 5.1: 50.8 (#5), Grok 4.20 (Non-Reasoning): 34.3 (#43)
| Benchmark | Claude Fable 5.1 | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| Vending-Bench 2 | 5,422 | 4,663 |
| Terminal-Bench | — | 57.3% |
| APEX-Agents | 68.6% | — |
| Remote Labor Index | 17.9% | — |
| τ²-bench Banking | — | 18% |
| GDP.pdf | 29.6% | — |
| LMArena Search | — | 1189 |
Reasoning Claude Fable 5.1 leads
Claude Fable 5.1: 76.7 (#5), Grok 4.20 (Non-Reasoning): 52.2 (#30)
| Benchmark | Claude Fable 5.1 | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| ARC-AGI-2 | 90% | 65.1% |
| NYT Connections (extended) | 90% | 85.4% |
| ARC-AGI-1 | 97.5% | 89.5% |
| Chess Puzzles | 47% | 24% |
| LMArena Hard Prompts | 1526 | 1451 |
| DTBench | 97.6% | 90.1% |
| LMCA | 65.5% | 38.7% |
| Epoch Capabilities Index | 165 | 152.01 |
| Kagi LLM Benchmark | — | 75% |
| CritPt | 31.1% | — |
| Thematic Generalization | — | 63.8% |
| EBR-Bench | 57.1% | — |
| Mystery Game Puzzles | 58% | — |
| ForecastBench | — | 61.4 |
Math Claude Fable 5.1 leads
Claude Fable 5.1: 89.5 (#3), Grok 4.20 (Non-Reasoning): 48.0 (#54)
| Benchmark | Claude Fable 5.1 | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| FrontierMath (Tiers 1-3) | 90.2% | 44.9% |
| FrontierMath Tier 4 | 87.8% | 17.1% |
| OTIS Mock AIME 2024-2025 | 100% | 92.2% |
| ProofBench | 100% | 14% |
| LMArena Math | 1519 | 1455 |
| FrontierMath Erdős | 0% | — |
Knowledge Claude Fable 5.1 leads
Claude Fable 5.1: 69.3 (#5), Grok 4.20 (Non-Reasoning): 52.8 (#54)
| Benchmark | Claude Fable 5.1 | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| SimpleQA Verified | 70.8% | 30.2% |
| LMArena Expert | 1528 | 1440 |
| GPQA Diamond | — | 89.3% |
| Humanity's Last Exam | 46.5% | — |
Multimodal Claude Fable 5.1 leads
Claude Fable 5.1: 54.1 (#4), Grok 4.20 (Non-Reasoning): 33.2 (#88)
| Benchmark | Claude Fable 5.1 | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| LMArena Vision | 1319 | 1263 |
| Blueprint-Bench 2 | 41.9% | 0% |
| LMArena Document | 1513 | 1416 |
| Furniture Assembly | 70% | — |
Multilingual Claude Fable 5.1 leads
Claude Fable 5.1: 59.5 (#2), Grok 4.20 (Non-Reasoning): 54.7 (#38)
| Benchmark | Claude Fable 5.1 | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| LMArena Non-English | 1509 | 1440 |
| LMArena Chinese | 1589 | 1481 |
| LMArena French | 1532 | 1477 |
| LMArena German | 1495 | 1463 |
| LMArena Japanese | 1565 | 1450 |
| LMArena Russian | 1525 | 1457 |
| LMArena Spanish | 1503 | 1442 |
| LMArena Korean | — | 1417 |
Instruction Following Claude Fable 5.1 leads
Claude Fable 5.1: 79.3 (#6), Grok 4.20 (Non-Reasoning): 75.0 (#79)
| Benchmark | Claude Fable 5.1 | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| LMArena Instruction Following | 1515 | 1420 |
Long Context Claude Fable 5.1 leads
Claude Fable 5.1: 46.8 (#19), Grok 4.20 (Non-Reasoning): 45.4 (#33)
| Benchmark | Claude Fable 5.1 | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| LMArena Longer Query | 1524 | 1436 |
| CL-bench | — | 22.2% |
| CL-bench Life | — | 11.9% |
Writing & Preference Claude Fable 5.1 leads
Claude Fable 5.1: 79.3 (#1), Grok 4.20 (Non-Reasoning): 65.9 (#42)
| Benchmark | Claude Fable 5.1 | Grok 4.20 (Non-Reasoning) |
|---|---|---|
| LMArena Text | 1511 | 1451 |
| LMArena Creative Writing | 1507 | 1439 |
| EQ-Bench Creative Writing | 2162 | 1574 |
| LMArena Multi-Turn | 1492 | 1456 |
Frequently asked questions
Is Claude Fable 5.1 better than Grok 4.20 (Non-Reasoning)?
Claude Fable 5.1 is the stronger model overall, scoring 68.5 to 48.5 on the Noometry Index. Grok 4.20 (Non-Reasoning) costs 13× 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 Grok 4.20 (Non-Reasoning)?
Grok 4.20 (Non-Reasoning) is cheaper. It lists at $1.25 per million input tokens and $2.50 per million output tokens; Claude Fable 5.1 lists at $10 and $50.
Is Claude Fable 5.1 or Grok 4.20 (Non-Reasoning) better for coding?
Claude Fable 5.1 scores higher on coding benchmarks: 70.5 versus 41.8 in the Noometry coding category.
Which has the bigger context window?
Both accept 1M tokens.
How many benchmarks do Claude Fable 5.1 and Grok 4.20 (Non-Reasoning) share?
36 benchmarks have published results for both models. Claude Fable 5.1 has 50 scored results on Noometry and Grok 4.20 (Non-Reasoning) has 46.