Claude Fable 5.2 vs Grok 4.20
Claude Fable 5.2 leads Grok 4.20 on coding, 87.8 to 33.3 on the Vibe Coding Index, and Grok 4.20 costs 16.0x less per output token ($2.50 vs $40.00 per million). Updated November 14, 2026; 17 benchmarks have a result for both.
Claude Fable 5.2 or Grok 4.20: which to pick
Pick Claude Fable 5.2 for coding: it scores 87.8 on the Vibe Coding Index against 33.3 for Grok 4.20.
Pick Grok 4.20 for output tokens 16.0x cheaper ($2.50 vs $40.00 per million) and a larger context window (2M against 1M tokens).
- Shared results
- 17
- Claude Fable 5.2 only
- 51
- Grok 4.20 only
- 37
- Like-for-like categories
- 6 of 9
Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.
Which one for your work
Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.
Coding
Vibe Coding Index, six public coding benchmarks
Claude Fable 5.2
Claude Fable 5.2 scores 87.8 against 33.3.
4 and 2 benchmarks behind the scores
Intelligence
AA Intelligence Index
No call
Only Claude Fable 5.2 has a AA Intelligence Index result, 64.6.
Directional only
Reasoning
GPQA Diamond
No call
Only Grok 4.20 has a GPQA Diamond result, 88.6%.
Directional only
Math
AIME
No call
Only Grok 4.20 has a AIME result, 96.5%.
Directional only
Knowledge
MMLU Pro
No call
Only Grok 4.20 has a MMLU Pro result, 86.3%.
Directional only
Web design
Design Arena: websites
Claude Fable 5.2
Claude Fable 5.2 leads, 1351 against 1221.
Same board, both measured
General
Vals Index
No call
Only Claude Fable 5.2 has a Vals Index result, 71.3%.
Directional only
Long documents
Listed context window
Grok 4.20
Grok 4.20 takes 2M tokens against 1M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Grok 4.20
Claude Fable 5.2 $0.028, Grok 4.20 $0.0025 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Grok 4.20 has the number, $0.72.
Directional only
At a glance
- Coding index
- Claude Fable 5.2 87.8 from 4 benchmarks, Grok 4.20 33.3 from 2 benchmarks.
- Widest category
- Coding, 89.7 points apart on average over 1 shared benchmark.
- Widest single gap
- Vibe Code Bench (Vals AI): Claude Fable 5.2 93.8% against Grok 4.20 4.1%, 89.7 points apart on a 0 to 100 scale.
- Output price
- Claude Fable 5.2 $40.00 against Grok 4.20 $2.50 per million output tokens, 16.0x apart.
- Context window
- Claude Fable 5.2 takes 1M tokens, Grok 4.20 2M.
Benchmark by benchmark
First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.
| Category | Claude Fable 5.2 | Bars | Grok 4.20 | Ties |
|---|---|---|---|---|
| Coding | 1 | 0 | ||
| Intelligence | 1 | 0 | ||
| Agentic work | 4 | 0 | ||
| Reasoning | 3 | 0 | ||
| Web design | 5 | 0 | ||
| General | 3 | 0 | ||
| All shared boards | 17 | 0 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index10
| Benchmark | Claude Fable 5.2 | Grok 4.20 | Leader |
|---|---|---|---|
| LiveBench coding | 79.2% | Not measured | Only Claude Fable 5.2 measured |
| LMArena WebDev | 1838 | Not measured | Only Claude Fable 5.2 measured |
| LiveCodeBench (Vals AI) | Not measured | 84.3% | Only Grok 4.20 measured |
| SWE-bench Verified (Vals AI) | Not measured | 72.2% | Only Grok 4.20 measured |
| Terminal-Bench 4 (Vals AI) | 65.2% | Not measured | Only Claude Fable 5.2 measured |
| Vibe Code Bench (Vals AI) | 93.8% | 4.1% | Claude Fable 5.2 |
| Code migration (Vals AI) | Not measured | 0.3% | Only Grok 4.20 measured |
| ProgramBench (Vals AI) | 19.0% | Not measured | Only Claude Fable 5.2 measured |
| Terminal-Bench 2.1 (Vals AI) | Not measured | 44.2% | Only Grok 4.20 measured |
| SWE-bench Multimodal (Vals AI) | 62.3% | Not measured | Only Claude Fable 5.2 measured |
| SciCode | 67.7% | Not measured | Only Claude Fable 5.2 measured |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 37.9% | Only Grok 4.20 measured |
| Terminal-Bench 4.0 (Artificial Analysis run) | 61.6% | Not measured | Only Claude Fable 5.2 measured |
| FrontierCode 2.0 | 49.1% | Not measured | Only Claude Fable 5.2 measured |
| Terminal-Bench | Not measured | 57.3% | Only Grok 4.20 measured |
| FrontierSWE | 69.9% | Not measured | Only Claude Fable 5.2 measured |
| WeirdML | Not measured | 52.3% | Only Grok 4.20 measured |
| ALE-Bench | 2509.8 | Not measured | Only Claude Fable 5.2 measured |
| LMArena WebDev: React | 1915 | Not measured | Only Claude Fable 5.2 measured |
| LMArena WebDev: HTML | 1738 | Not measured | Only Claude Fable 5.2 measured |
| GameBench 2 | 99.1 | Not measured | Only Claude Fable 5.2 measured |
| Terminal-Bench 2.0 | Not measured | 57.3% | Only Grok 4.20 measured |
| CursorBench 4.0 | 60.0% | Not measured | Only Claude Fable 5.2 measured |
| Neither model has a result on the other 29 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Claude Fable 5.2 | Grok 4.20 | Leader |
|---|---|---|---|
| AA Intelligence Index | 64.6 | Not measured | Only Claude Fable 5.2 measured |
| Epoch Capabilities Index | 173.4 | 152.3 | Claude Fable 5.2 |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index40
| Benchmark | Claude Fable 5.2 | Grok 4.20 | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | Not measured | 1123 | Only Grok 4.20 measured |
| Design Arena: agents building full-stack apps | 1402 | 1028 | Claude Fable 5.2 |
| Design Arena: agents building mobile apps | 1325 | 1082 | Claude Fable 5.2 |
| Design Arena: agents building Android apps | Not measured | 1037 | Only Grok 4.20 measured |
| Design Arena: agents building Godot games | Not measured | 1089 | Only Grok 4.20 measured |
| Design Arena: HTML slides | Not measured | 1180 | Only Grok 4.20 measured |
| Design Arena: spreadsheets | 1434 | Not measured | Only Claude Fable 5.2 measured |
| LiveBench research | 94.5% | Not measured | Only Claude Fable 5.2 measured |
| LiveBench browser | 86.9% | Not measured | Only Claude Fable 5.2 measured |
| LiveBench long agentic | 82.9% | Not measured | Only Claude Fable 5.2 measured |
| Finance Agent (Vals AI) | Not measured | 28.5% | Only Grok 4.20 measured |
| Tax Agent Bench (Vals AI) | 32.1% | 7.0% | Claude Fable 5.2 |
| Legal Research Bench (Vals AI) | 46.1% | 13.9% | Claude Fable 5.2 |
| Harvey's Legal Agent Benchmark (Vals AI) | 5.0% | Not measured | Only Claude Fable 5.2 measured |
| Excel Modeling Benchmark (Vals AI) | Not measured | 11.7% | Only Grok 4.20 measured |
| BioMysteryBench (Vals AI) | 83.7% | Not measured | Only Claude Fable 5.2 measured |
| Terminal-Bench-Science (Vals AI) | 55.7% | Not measured | Only Claude Fable 5.2 measured |
| Vals Science Index | 63.7% | Not measured | Only Claude Fable 5.2 measured |
| τ²-Bench Telecom | Not measured | 93.0% | Only Grok 4.20 measured |
| APEX-Agents | 80.1% | Not measured | Only Claude Fable 5.2 measured |
| Remote Labor Index | 41.3% | Not measured | Only Claude Fable 5.2 measured |
| SpireClimb | 15.5% | Not measured | Only Claude Fable 5.2 measured |
| Vending-Bench 2 | Not measured | $4,663 | Only Grok 4.20 measured |
| Neither model has a result on the other 21 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index30
| Benchmark | Claude Fable 5.2 | Grok 4.20 | Leader |
|---|---|---|---|
| GPQA Diamond | Not measured | 88.6% | Only Grok 4.20 measured |
| LiveBench reasoning | 88.8% | Not measured | Only Claude Fable 5.2 measured |
| MysteryMechanism (Vals AI) | 51.8% | Not measured | Only Claude Fable 5.2 measured |
| MMMU Pro (Vals AI) | Not measured | 83.5% | Only Grok 4.20 measured |
| GPQA Diamond (Artificial Analysis run) | Not measured | 91.1% | Only Grok 4.20 measured |
| Humanity's Last Exam (Artificial Analysis run) | 74.3% | 34.5% | Claude Fable 5.2 |
| HLE-Diamond (Artificial Analysis run) | 80.2% | Not measured | Only Claude Fable 5.2 measured |
| CritPt v2, hard subset (Artificial Analysis run) | 76.5% | Not measured | Only Claude Fable 5.2 measured |
| GPQA Diamond (Epoch AI run) | 93.9% | Not measured | Only Claude Fable 5.2 measured |
| ARC-AGI | 98.5% | 89.5% | Claude Fable 5.2 |
| ARC-AGI-2 | 93.8% | 65.1% | Claude Fable 5.2 |
| SimpleBench | 94.9% | Not measured | Only Claude Fable 5.2 measured |
| Chess puzzles | 79.0% | Not measured | Only Claude Fable 5.2 measured |
| Mystery game puzzles | 90.0% | Not measured | Only Claude Fable 5.2 measured |
| EBR-bench | 90.5% | Not measured | Only Claude Fable 5.2 measured |
| Kagi LLM Benchmark | Not measured | 75.0% | Only Grok 4.20 measured |
| Humanity's Last Exam (Scale run) | 72.4% | Not measured | Only Claude Fable 5.2 measured |
| GoBench | 2566 | Not measured | Only Claude Fable 5.2 measured |
| Neither model has a result on the other 8 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index6 boards, none shared
| Benchmark | Claude Fable 5.2 | Grok 4.20 | Leader |
|---|---|---|---|
| AIME | Not measured | 96.5% | Only Grok 4.20 measured |
| OTIS Mock AIME | 99.7% | Not measured | Only Claude Fable 5.2 measured |
| FrontierMath, tiers 1 to 3 | 95.1% | Not measured | Only Claude Fable 5.2 measured |
| FrontierMath, tier 4 | 100.0% | Not measured | Only Claude Fable 5.2 measured |
| ProofBench | 100.0% | Not measured | Only Claude Fable 5.2 measured |
| MathArena | 82.8% | Not measured | Only Claude Fable 5.2 measured |
| Neither model has a result on the other 8 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index12 boards, none shared
| Benchmark | Claude Fable 5.2 | Grok 4.20 | Leader |
|---|---|---|---|
| MMLU Pro | Not measured | 86.3% | Only Grok 4.20 measured |
| LegalBench (Vals AI) | Not measured | 77.7% | Only Grok 4.20 measured |
| CaseLaw (Vals AI) | Not measured | 54.4% | Only Grok 4.20 measured |
| CorpFin (Vals AI) | Not measured | 63.7% | Only Grok 4.20 measured |
| TaxEval (Vals AI) | Not measured | 74.1% | Only Grok 4.20 measured |
| MortgageTax (Vals AI) | Not measured | 45.4% | Only Grok 4.20 measured |
| MedQA (Vals AI) | Not measured | 94.5% | Only Grok 4.20 measured |
| MedCode (Vals AI) | Not measured | 32.2% | Only Grok 4.20 measured |
| AA-Omniscience | 66.8 | Not measured | Only Claude Fable 5.2 measured |
| SimpleQA Verified | 94.0% | Not measured | Only Claude Fable 5.2 measured |
| PRBench Finance | 47.1% | Not measured | Only Claude Fable 5.2 measured |
| PRBench Legal | 49.0% | Not measured | Only Claude Fable 5.2 measured |
| Neither model has a result on the other 9 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index50
| Benchmark | Claude Fable 5.2 | Grok 4.20 | Leader |
|---|---|---|---|
| Design Arena: websites | 1351 | 1221 | Claude Fable 5.2 |
| Design Arena: UI components | 1371 | 1191 | Claude Fable 5.2 |
| Design Arena: game dev | 1396 | 1182 | Claude Fable 5.2 |
| Design Arena: data viz | Not measured | 1214 | Only Grok 4.20 measured |
| Design Arena: 3D | 1517 | 1172 | Claude Fable 5.2 |
| Design Arena: all code categories | 1373 | 1210 | Claude Fable 5.2 |
| Design Arena: SVG | Not measured | 1153 | Only Grok 4.20 measured |
| Design Arena: ASCII art | Not measured | 1170 | Only Grok 4.20 measured |
| LiveBench design | 85.1% | Not measured | Only Claude Fable 5.2 measured |
GeneralLike-for-likePublic boards, shown as published, kept out of the index30
| Benchmark | Claude Fable 5.2 | Grok 4.20 | Leader |
|---|---|---|---|
| Vals Index | 71.3% | Not measured | Only Claude Fable 5.2 measured |
| LiveBench data analysis | 81.5% | Not measured | Only Claude Fable 5.2 measured |
| MedScribe (Vals AI) | Not measured | 63.4% | Only Grok 4.20 measured |
| Vals Multimodal Index | Not measured | 39.1% | Only Grok 4.20 measured |
| IFBench | Not measured | 81.2% | Only Grok 4.20 measured |
| Long context reasoning (AA-LCR) | 83.3% | 69.0% | Claude Fable 5.2 |
| GDPval-AA | 1831 | Not measured | Only Claude Fable 5.2 measured |
| DTBench | 99.2% | 90.1% | Claude Fable 5.2 |
| LMCA | 70.6% | 38.7% | Claude Fable 5.2 |
| CL-bench | Not measured | 22.2% | Only Grok 4.20 measured |
| Furniture assembly | 90.0% | Not measured | Only Claude Fable 5.2 measured |
| CL-bench Life | Not measured | 11.9% | Only Grok 4.20 measured |
| Neither model has a result on the other 37 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Fable 5.2 | Grok 4.20 | Leader |
|---|---|---|---|
| Neither model has a result on 5 boards here | |||
What each workload costs
Three fixed token mixes at each model's listed price, so per-token rates become a bill.
Chat turn
1K input + 500 output tokens
Grok 4.20 costs less
Repository review
50K input + 3K output tokens
Grok 4.20 costs less
Agent loop
200K input + 10K output tokens
Grok 4.20 costs less
Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.
Specification differences
The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.
| Specification | Anthropic Claude Fable 5.2 | SpaceXAI Grok 4.20 |
|---|---|---|
| Maker | Anthropic | xAI |
| Weights | No public weights listed | No public weights listed |
| Released | November 9, 2026 | March 31, 2026 |
| Context window | 1M | 2M |
| Input $/Mtok | $8.00 | $1.25 |
| Output $/Mtok | $40.00 | $2.50 |
| Coding index | 87.8 | 33.3 |
| Independent measurements behind it | 4 | 2 |
| Cost per solved task | Not computable | $0.72 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Fable 5.2 better than Grok 4.20 for coding?
Pick Claude Fable 5.2 for coding: it scores 87.8 on the Vibe Coding Index against 33.3 for Grok 4.20. Pick Grok 4.20 for output tokens 16.0x cheaper ($2.50 vs $40.00 per million) and a larger context window (2M against 1M tokens).
Which is cheaper, Claude Fable 5.2 or Grok 4.20?
Claude Fable 5.2 costs $8.00 per million input tokens and $40.00 per million output tokens; Grok 4.20 costs $1.25 and $2.50. Cost per solved task is known for Grok 4.20 only.
Which has the bigger context window, Claude Fable 5.2 or Grok 4.20?
Grok 4.20, with 2M tokens against 1M.
How many benchmarks is the Claude Fable 5.2 vs Grok 4.20 comparison based on?
17 benchmarks have a result for both models as of November 14, 2026. Claude Fable 5.2's coding index rests on 4 independent benchmarks and Grok 4.20's on 2. Where only one model has a result, the page says so instead of naming a winner.