Grok 4.20 vs Muse Spark Open
Muse Spark Open leads Grok 4.20 on coding, 47.4 to 33.3 on the Vibe Coding Index, and Grok 4.20 costs 1.7x less per output token ($2.50 vs $4.25 per million). Updated October 21, 2026; 12 benchmarks have a result for both.
Grok 4.20 or Muse Spark Open: which to pick
Pick Muse Spark Open for coding: it scores 47.4 on the Vibe Coding Index against 33.3 for Grok 4.20.
Pick Grok 4.20 for output tokens 1.7x cheaper ($2.50 vs $4.25 per million) and a larger context window (2M against 1.05M tokens).
- Shared results
- 12
- Grok 4.20 only
- 43
- Muse Spark Open only
- 16
- 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
Muse Spark Open
Muse Spark Open scores 47.4 against 33.3.
2 and 4 benchmarks behind the scores
Intelligence
AA Intelligence Index
No call
Only Grok 4.20 has a AA Intelligence Index result, 25.7.
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
Muse Spark Open
Muse Spark Open leads, 1317 against 1229.
Same board, both measured
General
Vals Index
No call
Only Muse Spark Open has a Vals Index result, 48.6%.
Directional only
Long documents
Listed context window
Grok 4.20
Grok 4.20 takes 2M tokens against 1.05M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Grok 4.20
Grok 4.20 $0.0025, Muse Spark Open $0.0034 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
- Grok 4.20 33.3 from 2 benchmarks, Muse Spark Open 47.4 from 4 benchmarks.
- Widest category
- Coding, 46.5 points apart on average over 2 shared benchmarks.
- Widest single gap
- Vibe Code Bench (Vals AI): Grok 4.20 4.1% against Muse Spark Open 76.2%, 72.1 points apart on a 0 to 100 scale.
- Output price
- Grok 4.20 $2.50 against Muse Spark Open $4.25 per million output tokens, 1.7x apart.
- Context window
- Grok 4.20 takes 2M tokens, Muse Spark Open 1.05M.
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 | Grok 4.20 | Bars | Muse Spark Open | Ties |
|---|---|---|---|---|
| Coding | 0 | 2 | ||
| Intelligence | 0 | 1 | ||
| Agentic work | 0 | 4 | ||
| Reasoning | 1 | 1 | ||
| Web design | 0 | 2 | ||
| General | 0 | 1 | ||
| All shared boards | 1 | 11 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index02
| Benchmark | Grok 4.20 | Muse Spark Open | Leader |
|---|---|---|---|
| LiveBench coding | Not measured | 73.6% | Only Muse Spark Open measured |
| LMArena WebDev | Not measured | 1528 | Only Muse Spark Open measured |
| LiveCodeBench (Vals AI) | 84.3% | Not measured | Only Grok 4.20 measured |
| SWE-bench Verified (Vals AI) | 72.2% | Not measured | Only Grok 4.20 measured |
| Terminal-Bench 4 (Vals AI) | Not measured | 6.6% | Only Muse Spark Open measured |
| Vibe Code Bench (Vals AI) | 4.1% | 76.2% | Muse Spark Open |
| Code migration (Vals AI) | 0.3% | 21.2% | Muse Spark Open |
| Terminal-Bench 2.1 (Vals AI) | 44.2% | Not measured | Only Grok 4.20 measured |
| SciCode | Not measured | 58.4% | Only Muse Spark Open measured |
| Terminal-Bench Hard (Artificial Analysis run) | 37.9% | Not measured | Only Grok 4.20 measured |
| Terminal-Bench | 57.3% | Not measured | Only Grok 4.20 measured |
| WeirdML | 52.3% | Not measured | Only Grok 4.20 measured |
| ALE-Bench | Not measured | 1590.1 | Only Muse Spark Open measured |
| LMArena WebDev: React | Not measured | 1529 | Only Muse Spark Open measured |
| LMArena WebDev: HTML | Not measured | 1495 | Only Muse Spark Open measured |
| Neither model has a result on the other 24 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | Grok 4.20 | Muse Spark Open | Leader |
|---|---|---|---|
| AA Intelligence Index | 25.7 | Not measured | Only Grok 4.20 measured |
| Epoch Capabilities Index | 152.1 | 155.1 | Muse Spark Open |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index04
| Benchmark | Grok 4.20 | Muse Spark Open | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1144 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building full-stack apps | 1054 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building mobile apps | 1090 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building Android apps | 1052 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building Godot games | 1089 | Not measured | Only Grok 4.20 measured |
| Design Arena: HTML slides | 1180 | Not measured | Only Grok 4.20 measured |
| LiveBench research | Not measured | 80.3% | Only Muse Spark Open measured |
| LiveBench browser | Not measured | 36.0% | Only Muse Spark Open measured |
| LiveBench long agentic | Not measured | 18.9% | Only Muse Spark Open measured |
| Finance Agent (Vals AI) | 28.5% | 61.3% | Muse Spark Open |
| Tax Agent Bench (Vals AI) | 7.0% | 26.3% | Muse Spark Open |
| Legal Research Bench (Vals AI) | 13.9% | 38.5% | Muse Spark Open |
| Harvey's Legal Agent Benchmark (Vals AI) | Not measured | 25.0% | Only Muse Spark Open measured |
| Excel Modeling Benchmark (Vals AI) | 11.7% | 53.7% | Muse Spark Open |
| τ²-Bench Telecom | 93.0% | Not measured | Only Grok 4.20 measured |
| APEX-Agents | Not measured | 33.4% | Only Muse Spark Open measured |
| Vending-Bench 2 | $4,663 | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 24 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index11
| Benchmark | Grok 4.20 | Muse Spark Open | Leader |
|---|---|---|---|
| GPQA Diamond | 88.6% | Not measured | Only Grok 4.20 measured |
| LiveBench reasoning | Not measured | 73.7% | Only Muse Spark Open measured |
| MMMU Pro (Vals AI) | 83.5% | Not measured | Only Grok 4.20 measured |
| GPQA Diamond (Artificial Analysis run) | 91.1% | 89.0% | Grok 4.20 |
| Humanity's Last Exam (Artificial Analysis run) | 34.5% | 43.9% | Muse Spark Open |
| ARC-AGI | 89.5% | Not measured | Only Grok 4.20 measured |
| ARC-AGI-2 | 65.1% | Not measured | Only Grok 4.20 measured |
| Kagi LLM Benchmark | 75.0% | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 14 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index1 board, none shared
| Benchmark | Grok 4.20 | Muse Spark Open | Leader |
|---|---|---|---|
| AIME | 96.5% | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 12 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index8 boards, none shared
| Benchmark | Grok 4.20 | Muse Spark Open | Leader |
|---|---|---|---|
| MMLU Pro | 86.3% | Not measured | Only Grok 4.20 measured |
| LegalBench (Vals AI) | 77.7% | Not measured | Only Grok 4.20 measured |
| CaseLaw (Vals AI) | 54.4% | Not measured | Only Grok 4.20 measured |
| CorpFin (Vals AI) | 63.7% | Not measured | Only Grok 4.20 measured |
| TaxEval (Vals AI) | 74.1% | Not measured | Only Grok 4.20 measured |
| MortgageTax (Vals AI) | 45.4% | Not measured | Only Grok 4.20 measured |
| MedQA (Vals AI) | 94.5% | Not measured | Only Grok 4.20 measured |
| MedCode (Vals AI) | 32.2% | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 10 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | Grok 4.20 | Muse Spark Open | Leader |
|---|---|---|---|
| Design Arena: websites | 1229 | 1317 | Muse Spark Open |
| Design Arena: UI components | 1199 | Not measured | Only Grok 4.20 measured |
| Design Arena: game dev | 1192 | 1294 | Muse Spark Open |
| Design Arena: data viz | 1217 | Not measured | Only Grok 4.20 measured |
| Design Arena: 3D | 1193 | Not measured | Only Grok 4.20 measured |
| Design Arena: all code categories | 1221 | Not measured | Only Grok 4.20 measured |
| Design Arena: SVG | 1164 | Not measured | Only Grok 4.20 measured |
| Design Arena: ASCII art | 1174 | Not measured | Only Grok 4.20 measured |
| LiveBench design | Not measured | 60.3% | Only Muse Spark Open measured |
GeneralLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | Grok 4.20 | Muse Spark Open | Leader |
|---|---|---|---|
| Vals Index | Not measured | 48.6% | Only Muse Spark Open measured |
| LiveBench data analysis | Not measured | 60.2% | Only Muse Spark Open measured |
| SAGE (Vals AI) | 38.2% | Not measured | Only Grok 4.20 measured |
| MedScribe (Vals AI) | 63.4% | Not measured | Only Grok 4.20 measured |
| Vals Multimodal Index | 39.1% | Not measured | Only Grok 4.20 measured |
| IFBench | 81.2% | Not measured | Only Grok 4.20 measured |
| Long context reasoning (AA-LCR) | 69.0% | 78.3% | Muse Spark Open |
| DTBench | 90.1% | Not measured | Only Grok 4.20 measured |
| LMCA | 38.7% | Not measured | Only Grok 4.20 measured |
| CL-bench | 22.2% | Not measured | Only Grok 4.20 measured |
| CL-bench Life | 11.9% | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 35 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Grok 4.20 | Muse Spark Open | 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 | SpaceXAI Grok 4.20 | Meta Muse Spark Open |
|---|---|---|
| Maker | xAI | Meta |
| Weights | No public weights listed | Open weights |
| Released | March 31, 2026 | October 15, 2026 |
| Context window | 2M | 1.05M |
| Input $/Mtok | $1.25 | $1.25 |
| Output $/Mtok | $2.50 | $4.25 |
| Coding index | 33.3 | 47.4 |
| Independent measurements behind it | 2 | 4 |
| Cost per solved task | $0.72 | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Grok 4.20 better than Muse Spark Open for coding?
Pick Muse Spark Open for coding: it scores 47.4 on the Vibe Coding Index against 33.3 for Grok 4.20. Pick Grok 4.20 for output tokens 1.7x cheaper ($2.50 vs $4.25 per million) and a larger context window (2M against 1.05M tokens).
Which is cheaper, Grok 4.20 or Muse Spark Open?
Grok 4.20 costs $1.25 per million input tokens and $2.50 per million output tokens; Muse Spark Open costs $1.25 and $4.25. Cost per solved task is known for Grok 4.20 only.
Which has the bigger context window, Grok 4.20 or Muse Spark Open?
Grok 4.20, with 2M tokens against 1.05M.
How many benchmarks is the Grok 4.20 vs Muse Spark Open comparison based on?
12 benchmarks have a result for both models as of October 21, 2026. Grok 4.20's coding index rests on 2 independent benchmarks and Muse Spark Open's on 4. Where only one model has a result, the page says so instead of naming a winner.