Claude Fable 5.1 vs Grok 4.20
Claude Fable 5.1 
Grok 4.20 Verdict
- Claude Fable 5.1 (high) leads on quality: 72.0 vs 59.9.
- Claude Fable 5.1 (high) is stronger in agents & tools, coding, composite, knowledge, long context, reasoning.
- Grok 4.20 (thinking) is stronger in human preference, instruction following, maths, multimodal.
- Grok 4.20 (thinking) is 13× cheaper ($1.56 vs $20.00 per 1M blended).
- Grok 4.20 (thinking) streams 1.8× faster (101 vs 55 tokens per second).
| Metric | Claude Fable 5.1 (high) | Grok 4.20 (thinking) |
|---|---|---|
| BenchLeader Index | 72.0 | 59.9 |
| Agents & tools score | 66.6 | 51.7 |
| Coding score | 74.1 | 54.7 |
| Composite score | 94.0 | 61.5 |
| Knowledge score | 83.7 | 56.8 |
| Long context score | 68.4 | 60.7 |
| Reasoning score | 81.0 | 60.7 |
| Human preference score | – | 67.1 |
| Instruction following score | – | 79.9 |
| Maths score | – | 55.6 |
| Multimodal score | – | 59.9 |
| Blended price $/M | $20.00 | $1.56 |
| Output speed | 55 tok/s | 101 tok/s |
| Time to first answer | 14.7 s | 21.4 s |
| Context window | 1M | 1M |
| GPQA Diamond | – | 89.3% |
| FrontierMath Tiers 1–3 | – | 44.9% |
| FrontierMath Tier 4 | – | 17.1% |
| OTIS Mock AIME | – | 92.2% |
| SimpleQA Verified | – | 30.2% |
| Terminal-Bench | 54.5% | – |
| SciCode | 57.6% | – |
| WeirdML | 92.3% | – |
| APEX-Agents | 44.4% | – |
| ProofBench | – | 14.0% |
| LMArena Text | – | 1472 |
| LMArena Hard Prompts | – | 1488 |
| LMArena Coding | – | 1510 |
| LMArena WebDev | – | 1374 |
| LMArena Vision | – | 1263 |
| AA Intelligence Index | 51.2 | 25.7 |
| IFBench | – | 82.9% |
| AA-LCR | 83.7% | 69.0% |
| MMMU-Pro | – | 74.6% |
| AA-Omniscience | 40.8 | 14.8 |
| Terminal-Bench Hard | – | 40.9% |
| GPQA Diamond (AA) | 90.6% | 91.1% |
| Humanity's Last Exam (AA) | 55.9% | 34.5% |
| SciCode (AA) | 58.7% | – |
| τ²-Bench Telecom (AA) | – | 96.5% |
| AIME (Vals) | – | 96.5% |
| LiveCodeBench | – | 84.3% |
| MMLU-Pro | – | 86.3% |
| LegalBench | – | 77.7% |
| CorpFin | – | 63.7% |
| TaxEval | – | 74.1% |
| MedQA | – | 94.5% |
| Terminal-Bench 2.1 (Vals) | – | 44.2% |
| SWE-bench (Vals) | – | 72.2% |
| GPQA Diamond (Vals) | – | 88.6% |
| Vals Index | – | 17.6 |
| Kagi LLM Benchmark | – | 75.0% |
| ARC-AGI-1 | 96.0% | 89.5% |
| ARC-AGI-2 | 88.8% | 65.1% |
| ARC-AGI-3 | – | 0.1% |
| CritPt | 30.3% | 6.6% |
| GDPval (AA) | 57.5% | – |
| τ²-Bench Banking (AA) | 43.1% | – |
| APEX-Agents (AA) | – | 14.2% |
| CaseLaw v2 | – | 54.5% |
| Code Migration | – | 0.3% |
| Excel Modeling Benchmark | – | 11.7% |
| Finance Agent v2 | – | 28.5% |
| Harvey's Legal Agent Benchmark | – | 0.0% |
| Legal Research Bench | – | 13.9% |
| MedCode | – | 32.2% |
| MedScribe | – | 63.4% |
| MMMU-Pro (Vals) | – | 83.5% |
| MortgageTax | – | 45.4% |
| SAGE | – | 38.2% |
| Terminal-Bench 2.0 (Vals) | – | 40.5% |
| Vals Multimodal Index | – | 39.1% |
| Vibe Code Bench v1.1 | – | 4.1% |
| LMArena Maths | – | 1467 |
| LMArena Creative Writing | – | 1446 |
| LMArena Instruction Following | – | 1445 |
| LMArena Multi-turn | – | 1480 |
| LMArena Longer Queries | – | 1465 |
| LMArena Document | – | 1439 |
| Chess Puzzles | – | 24.0% |
| MirrorCode | 73.3% | – |
| ForecastBench | – | 60.7% |
| CursorBench | 69.4% | – |
| ALE-Bench | 2143.2 | – |
Data as of 2026-09-19. Best configuration of each model; every score links to its source on the model pages.
Claude Fable 5.1 vs Grok 4.20: questions
- Is Claude Fable 5.1 better than Grok 4.20?
- Claude Fable 5.1 (high) leads on quality: 72.0 vs 59.9. The BenchLeader Index combines every independent quality benchmark; Claude Fable 5.1 (high) is ahead overall as of 2026-09-19, but check the category scores for your use.
- Is Claude Fable 5.1 better than Grok 4.20 for coding?
- Claude Fable 5.1 scores higher in coding (74 vs 55 on the category index, where 50 is average).
- Is Claude Fable 5.1 better than Grok 4.20 for agentic tasks?
- Claude Fable 5.1 scores higher in agentic tasks (67 vs 52 on the category index, where 50 is average).
- Which is cheaper, Claude Fable 5.1 or Grok 4.20?
- Grok 4.20 is cheaper: $1.56 against $20.00 per million tokens, blended at three input tokens per output token.
- Which is faster, Claude Fable 5.1 or Grok 4.20?
- Grok 4.20 streams faster: 101 against 55 output tokens per second.
- Which has the larger context window?
- Both accept 1M tokens of context.