Claude Sonnet 5.5 vs Muse Spark Open
Updated October 21, 2026. 25 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
Decision reading
Pick Claude Sonnet 5.5 for coding: it scores 88.9 on the Vibe Coding Index against 62.1 for Muse Spark Open.
Pick Muse Spark Open when output tokens cost 2.4x less, or when the context window is larger, 1.05M against 1M tokens.
- Shared results
- 25
- Claude Sonnet 5.5 only
- 70
- Muse Spark Open only
- 1
- Like-for-like categories
- 6 of 9
Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.
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, four public coding benchmarks
Claude Sonnet 5.5
Claude Sonnet 5.5 scores 88.9 against 62.1.
2 benchmarks behind each score
Intelligence
AA Intelligence Index
No call
Only Claude Sonnet 5.5 has a AA Intelligence Index result, 56.0.
Directional only
Web design
Design Arena: websites
Claude Sonnet 5.5
Claude Sonnet 5.5 leads, 1326 against 1311.
Same board, both measured
General
Vals Index
No call
Only Claude Sonnet 5.5 has a Vals Index result, 70.8%.
Directional only
Long documents
Listed context window
Muse Spark Open
Muse Spark Open takes 1.05M tokens against 1M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Muse Spark Open
Claude Sonnet 5.5 $0.0070, Muse Spark Open $0.0034 per turn.
List prices
At a glance
- Coding index
- Claude Sonnet 5.5 88.9 from 2 benchmarks, Muse Spark Open 62.1 from 2 benchmarks.
- Widest category
- Agentic work, 25.5 points apart on average over 8 shared benchmarks.
- Widest single gap
- LiveBench long agentic: Claude Sonnet 5.5 78.8% against Muse Spark Open 18.9%, 59.9 points apart on a 0 to 100 scale.
- Output price
- Claude Sonnet 5.5 $10.00 against Muse Spark Open $4.25 per million output tokens, 2.4x apart.
- Context window
- Claude Sonnet 5.5 takes 1M 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 | Claude Sonnet 5.5 | Bars | Muse Spark Open | Ties |
|---|---|---|---|---|
| Coding | 9 | 0 | ||
| Intelligence | 1 | 0 | ||
| Agentic work | 7 | 1 | ||
| Reasoning | 2 | 0 | ||
| Web design | 3 | 0 | ||
| General | 1 | 1 | ||
| All shared boards | 23 | 2 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index90
| Benchmark | Claude Sonnet 5.5 | Muse Spark Open | Leader |
|---|---|---|---|
| LiveBench coding | 94.7% | 73.6% | Claude Sonnet 5.5 |
| LMArena WebDev | 1768 | 1528 | Claude Sonnet 5.5 |
| Terminal-Bench 4 (Vals AI) | 64.1% | 6.6% | Claude Sonnet 5.5 |
| Vibe Code Bench (Vals AI) | 92.4% | 76.2% | Claude Sonnet 5.5 |
| Code migration (Vals AI) | 69.8% | 21.2% | Claude Sonnet 5.5 |
| ProgramBench (Vals AI) | 6.5% | Not measured | Only Claude Sonnet 5.5 measured |
| IOI (Vals AI) | 83.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Terminal-Bench 2.1 (Vals AI) | 83.2% | Not measured | Only Claude Sonnet 5.5 measured |
| SWE-bench Multimodal (Vals AI) | 58.3% | Not measured | Only Claude Sonnet 5.5 measured |
| CyberBench (Vals AI) | 59.6% | Not measured | Only Claude Sonnet 5.5 measured |
| SciCode | 61.0% | 58.4% | Claude Sonnet 5.5 |
| FrontierCode | 52.1% | Not measured | Only Claude Sonnet 5.5 measured |
| FrontierSWE | 61.9% | Not measured | Only Claude Sonnet 5.5 measured |
| ALE-Bench | 1819.1 | 1590.1 | Claude Sonnet 5.5 |
| LMArena Text: coding | 1513 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: software and IT | 1504 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena WebDev: React | 1817 | 1529 | Claude Sonnet 5.5 |
| LMArena WebDev: HTML | 1741 | 1495 | Claude Sonnet 5.5 |
| LMArena WebDev: from an image | 1737 | Not measured | Only Claude Sonnet 5.5 measured |
| Neither model has a result on the other 19 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Claude Sonnet 5.5 | Muse Spark Open | Leader |
|---|---|---|---|
| AA Intelligence Index | 56.0 | Not measured | Only Claude Sonnet 5.5 measured |
| Epoch Capabilities Index | 166.2 | 155.1 | Claude Sonnet 5.5 |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index71
| Benchmark | Claude Sonnet 5.5 | Muse Spark Open | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1303 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: agents building mobile apps | 1265 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: spreadsheets | 1245 | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench research | 83.6% | 80.3% | Claude Sonnet 5.5 |
| LiveBench browser | 84.0% | 36.0% | Claude Sonnet 5.5 |
| LiveBench long agentic | 78.8% | 18.9% | Claude Sonnet 5.5 |
| SREBench (Vals AI) | 30.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Finance Agent (Vals AI) | 58.1% | 61.3% | Muse Spark Open |
| Tax Agent Bench (Vals AI) | 42.0% | 26.3% | Claude Sonnet 5.5 |
| Legal Research Bench (Vals AI) | 48.1% | 38.5% | Claude Sonnet 5.5 |
| Harvey's Legal Agent Benchmark (Vals AI) | 10.4% | Not measured | Only Claude Sonnet 5.5 measured |
| Excel Modeling Benchmark (Vals AI) | 75.7% | 53.7% | Claude Sonnet 5.5 |
| BioMysteryBench (Vals AI) | 81.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Terminal-Bench-Science (Vals AI) | 47.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Vals Science Index | 59.1% | Not measured | Only Claude Sonnet 5.5 measured |
| APEX-Agents | 75.5% | 33.4% | Claude Sonnet 5.5 |
| SpireClimb | 1.3% | Not measured | Only Claude Sonnet 5.5 measured |
| Vending-Bench 2 | $11,165 | Not measured | Only Claude Sonnet 5.5 measured |
| Neither model has a result on the other 21 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Sonnet 5.5 | Muse Spark Open | Leader |
|---|---|---|---|
| LiveBench reasoning | 91.6% | 73.7% | Claude Sonnet 5.5 |
| MysteryMechanism (Vals AI) | 49.1% | Not measured | Only Claude Sonnet 5.5 measured |
| GPQA Diamond (Artificial Analysis run) | Not measured | 89.0% | Only Muse Spark Open measured |
| Humanity's Last Exam (Artificial Analysis run) | 55.0% | 43.9% | Claude Sonnet 5.5 |
| GPQA Diamond (Epoch AI run) | 95.6% | Not measured | Only Claude Sonnet 5.5 measured |
| Chess puzzles | 59.0% | Not measured | Only Claude Sonnet 5.5 measured |
| Mystery game puzzles | 65.0% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: hard prompts | 1494 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: expert | 1531 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: hard prompts in English | 1502 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Vision: diagrams | 1329 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Vision: homework | 1331 | Not measured | Only Claude Sonnet 5.5 measured |
| Neither model has a result on the other 9 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index6 boards, none shared
| Benchmark | Claude Sonnet 5.5 | Muse Spark Open | Leader |
|---|---|---|---|
| OTIS Mock AIME | 100.0% | Not measured | Only Claude Sonnet 5.5 measured |
| FrontierMath, tiers 1 to 3 | 88.8% | Not measured | Only Claude Sonnet 5.5 measured |
| FrontierMath, tier 4 | 80.5% | Not measured | Only Claude Sonnet 5.5 measured |
| ProofBench | 100.0% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: math | 1497 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: mathematical work | 1510 | Not measured | Only Claude Sonnet 5.5 measured |
| Neither model has a result on the other 7 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index6 boards, none shared
| Benchmark | Claude Sonnet 5.5 | Muse Spark Open | Leader |
|---|---|---|---|
| MedCode (Vals AI) | 52.9% | Not measured | Only Claude Sonnet 5.5 measured |
| SimpleQA Verified | 46.5% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: science | 1483 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: medicine and healthcare | 1464 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: legal and government | 1483 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: business and finance | 1468 | Not measured | Only Claude Sonnet 5.5 measured |
| Neither model has a result on the other 11 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index30
| Benchmark | Claude Sonnet 5.5 | Muse Spark Open | Leader |
|---|---|---|---|
| Design Arena: websites | 1326 | 1311 | Claude Sonnet 5.5 |
| Design Arena: UI components | 1367 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: game dev | 1469 | 1290 | Claude Sonnet 5.5 |
| Design Arena: data viz | 1389 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: 3D | 1458 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: all code categories | 1364 | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench design | 85.0% | 60.3% | Claude Sonnet 5.5 |
| Neither model has a result on the other 2 boards here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index11
| Benchmark | Claude Sonnet 5.5 | Muse Spark Open | Leader |
|---|---|---|---|
| Vals Index | 70.8% | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench data analysis | 59.5% | 60.2% | Muse Spark Open |
| Public Benefits Bench (Vals AI) | 67.2% | Not measured | Only Claude Sonnet 5.5 measured |
| SAGE (Vals AI) | 51.8% | Not measured | Only Claude Sonnet 5.5 measured |
| MedScribe (Vals AI) | 91.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Long context reasoning (AA-LCR) | 82.7% | 78.3% | Claude Sonnet 5.5 |
| DTBench | 97.3% | Not measured | Only Claude Sonnet 5.5 measured |
| LMCA | 68.3% | Not measured | Only Claude Sonnet 5.5 measured |
| Furniture assembly | 75.0% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text | 1473 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: instruction following | 1492 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: creative writing | 1467 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Vision | 1287 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: English | 1484 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: non-English | 1456 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: Chinese | 1535 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: French | 1499 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: Spanish | 1451 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: Russian | 1454 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: multi-turn | 1465 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: longer queries | 1495 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: writing and language | 1474 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: entertainment and media | 1461 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Vision: English | 1289 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Vision: reading text | 1297 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Vision: creative writing | 1242 | Not measured | Only Claude Sonnet 5.5 measured |
| Neither model has a result on the other 20 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Sonnet 5.5 | 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
Muse Spark Open costs less
Repository review
50K input + 3K output tokens
Muse Spark Open costs less
Agent loop
200K input + 10K output tokens
Muse Spark Open 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 Sonnet 5.5 | Meta Muse Spark Open |
|---|---|---|
| Maker | Anthropic | Meta |
| Weights | No public weights listed | Open weights |
| Released | September 28, 2026 | October 15, 2026 |
| Context window | 1M | 1.05M |
| Input $/Mtok | $2.00 | $1.25 |
| Output $/Mtok | $10.00 | $4.25 |
| Coding index | 88.9 | 62.1 |
| Independent measurements behind it | 2 | 2 |
| Cost per solved task | Not computable | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Sonnet 5.5 better than Muse Spark Open for coding?
Pick Claude Sonnet 5.5 for coding: it scores 88.9 on the Vibe Coding Index against 62.1 for Muse Spark Open. Pick Muse Spark Open when output tokens cost 2.4x less, or when the context window is larger, 1.05M against 1M tokens.
Which is cheaper, Claude Sonnet 5.5 or Muse Spark Open?
Claude Sonnet 5.5 costs $2.00 per million input tokens and $10.00 per million output tokens; Muse Spark Open costs $1.25 and $4.25. Cost per solved task is known for neither of them.
Which has the bigger context window, Claude Sonnet 5.5 or Muse Spark Open?
Muse Spark Open, with 1.05M tokens against 1M.
How many benchmarks is the Claude Sonnet 5.5 vs Muse Spark Open comparison based on?
25 benchmarks have a result for both models as of October 21, 2026. Claude Sonnet 5.5's coding index rests on 2 independent benchmarks and Muse Spark Open's on 2. Where only one model has a result, the page says so instead of naming a winner.