Grok 4.20 vs Muse Ember
Muse Ember leads Grok 4.20 on coding, 64.9 to 33.3 on the Vibe Coding Index, and Muse Ember costs 5.0x less per output token ($0.50 vs $2.50 per million). Updated November 14, 2026; 3 benchmarks have a result for both.
Grok 4.20 or Muse Ember: which to pick
Pick Muse Ember for coding: it scores 64.9 on the Vibe Coding Index against 33.3 for Grok 4.20.
Pick Grok 4.20 for a larger context window (2M against 1.05M tokens).
- Shared results
- 3
- Grok 4.20 only
- 51
- Muse Ember only
- 12
- Like-for-like categories
- 2 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 Ember
Muse Ember scores 64.9 against 33.3.
2 and 3 benchmarks behind the scores
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
No call
Only Grok 4.20 has a Design Arena: websites result, 1221.
Directional only
General
Vals Index
No call
Only Muse Ember has a Vals Index result, 60.5%.
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
Muse Ember
Grok 4.20 $0.0025, Muse Ember $0.0003 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 Ember 64.9 from 3 benchmarks.
- Widest category
- Coding, 79.6 points apart on average over 1 shared benchmark.
- Widest single gap
- Vibe Code Bench (Vals AI): Grok 4.20 4.1% against Muse Ember 83.7%, 79.6 points apart on a 0 to 100 scale.
- Output price
- Grok 4.20 $2.50 against Muse Ember $0.50 per million output tokens, 5.0x apart.
- Context window
- Grok 4.20 takes 2M tokens, Muse Ember 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 Ember | Ties |
|---|---|---|---|---|
| Coding | 0 | 1 | ||
| Agentic work | 0 | 2 | ||
| All shared boards | 0 | 3 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index01
| Benchmark | Grok 4.20 | Muse Ember | Leader |
|---|---|---|---|
| LMArena WebDev | Not measured | 1609 | Only Muse Ember 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 | 39.4% | Only Muse Ember measured |
| Vibe Code Bench (Vals AI) | 4.1% | 83.7% | Muse Ember |
| Code migration (Vals AI) | 0.3% | Not measured | Only Grok 4.20 measured |
| Terminal-Bench 2.1 (Vals AI) | 44.2% | Not measured | Only Grok 4.20 measured |
| Terminal-Bench Hard (Artificial Analysis run) | 37.9% | Not measured | Only Grok 4.20 measured |
| Terminal-Bench 4.0 (Artificial Analysis run) | Not measured | 40.9% | Only Muse Ember measured |
| FrontierCode 2.0 | Not measured | 27.2% | Only Muse Ember measured |
| Terminal-Bench | 57.3% | Not measured | Only Grok 4.20 measured |
| WeirdML | 52.3% | Not measured | Only Grok 4.20 measured |
| LMArena WebDev: React | Not measured | 1616 | Only Muse Ember measured |
| LMArena WebDev: HTML | Not measured | 1621 | Only Muse Ember measured |
| Terminal-Bench 2.0 | 57.3% | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 37 boards here | |||
IntelligenceDirectional onlyPublic boards, shown as published, kept out of the index1 board, none shared
| Benchmark | Grok 4.20 | Muse Ember | Leader |
|---|---|---|---|
| Epoch Capabilities Index | 152.3 | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 1 board here | |||
Agentic workLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | Grok 4.20 | Muse Ember | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1123 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building full-stack apps | 1028 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building mobile apps | 1082 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building Android apps | 1037 | 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 |
| Finance Agent (Vals AI) | 28.5% | Not measured | Only Grok 4.20 measured |
| Tax Agent Bench (Vals AI) | 7.0% | 38.2% | Muse Ember |
| Legal Research Bench (Vals AI) | 13.9% | 49.0% | Muse Ember |
| Harvey's Legal Agent Benchmark (Vals AI) | Not measured | 25.0% | Only Muse Ember measured |
| Excel Modeling Benchmark (Vals AI) | 11.7% | Not measured | Only Grok 4.20 measured |
| τ²-Bench Telecom | 93.0% | Not measured | Only Grok 4.20 measured |
| APEX-Agents | Not measured | 64.3% | Only Muse Ember measured |
| Vending-Bench 2 | $4,663 | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 30 boards here | |||
ReasoningDirectional onlyPublic boards, shown as published, kept out of the index9 boards, none shared
| Benchmark | Grok 4.20 | Muse Ember | Leader |
|---|---|---|---|
| GPQA Diamond | 88.6% | Not measured | Only Grok 4.20 measured |
| MMMU Pro (Vals AI) | 83.5% | Not measured | Only Grok 4.20 measured |
| GPQA Diamond (Artificial Analysis run) | 91.1% | Not measured | Only Grok 4.20 measured |
| Humanity's Last Exam (Artificial Analysis run) | 34.5% | Not measured | Only Grok 4.20 measured |
| HLE-Diamond (Artificial Analysis run) | Not measured | 25.1% | Only Muse Ember measured |
| CritPt v2, hard subset (Artificial Analysis run) | Not measured | 39.0% | Only Muse Ember measured |
| 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 17 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index1 board, none shared
| Benchmark | Grok 4.20 | Muse Ember | Leader |
|---|---|---|---|
| AIME | 96.5% | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 13 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index9 boards, none shared
| Benchmark | Grok 4.20 | Muse Ember | 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 |
| AA-Omniscience | Not measured | 7.7 | Only Muse Ember measured |
| Neither model has a result on the other 12 boards here | |||
Web designDirectional onlyPublic boards, shown as published, kept out of the index8 boards, none shared
| Benchmark | Grok 4.20 | Muse Ember | Leader |
|---|---|---|---|
| Design Arena: websites | 1221 | Not measured | Only Grok 4.20 measured |
| Design Arena: UI components | 1191 | Not measured | Only Grok 4.20 measured |
| Design Arena: game dev | 1182 | Not measured | Only Grok 4.20 measured |
| Design Arena: data viz | 1214 | Not measured | Only Grok 4.20 measured |
| Design Arena: 3D | 1172 | Not measured | Only Grok 4.20 measured |
| Design Arena: all code categories | 1210 | Not measured | Only Grok 4.20 measured |
| Design Arena: SVG | 1153 | Not measured | Only Grok 4.20 measured |
| Design Arena: ASCII art | 1170 | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 1 board here | |||
GeneralDirectional onlyPublic boards, shown as published, kept out of the index9 boards, none shared
| Benchmark | Grok 4.20 | Muse Ember | Leader |
|---|---|---|---|
| Vals Index | Not measured | 60.5% | Only Muse Ember 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% | Not measured | Only Grok 4.20 measured |
| 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 40 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Grok 4.20 | Muse Ember | 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
Muse Ember costs less
Repository review
50K input + 3K output tokens
Muse Ember costs less
Agent loop
200K input + 10K output tokens
Muse Ember 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 Ember |
|---|---|---|
| Maker | xAI | Meta |
| Weights | No public weights listed | No public weights listed |
| Released | March 31, 2026 | November 9, 2026 |
| Context window | 2M | 1.05M |
| Input $/Mtok | $1.25 | $0.10 |
| Output $/Mtok | $2.50 | $0.50 |
| Coding index | 33.3 | 64.9 |
| Independent measurements behind it | 2 | 3 |
| Cost per solved task | $0.72 | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Grok 4.20 better than Muse Ember for coding?
Pick Muse Ember for coding: it scores 64.9 on the Vibe Coding Index against 33.3 for Grok 4.20. Pick Grok 4.20 for a larger context window (2M against 1.05M tokens).
Which is cheaper, Grok 4.20 or Muse Ember?
Grok 4.20 costs $1.25 per million input tokens and $2.50 per million output tokens; Muse Ember costs $0.10 and $0.50. Cost per solved task is known for Grok 4.20 only.
Which has the bigger context window, Grok 4.20 or Muse Ember?
Grok 4.20, with 2M tokens against 1.05M.
How many benchmarks is the Grok 4.20 vs Muse Ember comparison based on?
3 benchmarks have a result for both models as of November 14, 2026. Grok 4.20's coding index rests on 2 independent benchmarks and Muse Ember's on 3. Where only one model has a result, the page says so instead of naming a winner.