Claude Sonnet 4.5 vs Muse Spark 1.2
Updated October 21, 2026. 61 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
Decision reading
Pick Muse Spark 1.2 for coding: it scores 65.1 on the Vibe Coding Index against 59.1 for Claude Sonnet 4.5.
Pick Claude Sonnet 4.5 when what matters is LMArena Text: expert or LMArena Text: creative writing, where it leads.
- Shared results
- 61
- Claude Sonnet 4.5 only
- 31
- Muse Spark 1.2 only
- 36
- Like-for-like categories
- 8 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
Muse Spark 1.2
Muse Spark 1.2 scores 65.1 against 59.1.
2 benchmarks behind each score
Intelligence
AA Intelligence Index
Muse Spark 1.2
Muse Spark 1.2 leads, 39.6 against 20.7.
Same board, both measured
Agentic work
AA Agentic Index
Muse Spark 1.2
Muse Spark 1.2 leads, 43.2 against 15.8.
Same board, both measured
Reasoning
GPQA Diamond
No call
Only Claude Sonnet 4.5 has a GPQA Diamond result, 81.6%.
Directional only
Math
AIME
No call
Only Claude Sonnet 4.5 has a AIME result, 88.2%.
Directional only
Knowledge
MMLU Pro
Muse Spark 1.2
Muse Spark 1.2 leads, 88.3% against 87.4%.
Same board, both measured
Web design
Design Arena: websites
Muse Spark 1.2
Muse Spark 1.2 leads, 1313 against 1190.
Same board, both measured
Long documents
Listed context window
Muse Spark 1.2
Muse Spark 1.2 takes 1.05M tokens against 1M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Muse Spark 1.2
Claude Sonnet 4.5 $0.011, Muse Spark 1.2 $0.0034 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
Muse Spark 1.2
Claude Sonnet 4.5 $1.16, Muse Spark 1.2 $0.64.
Published attempt cost and pass rate
At a glance
- Coding index
- Claude Sonnet 4.5 59.1 from 2 benchmarks, Muse Spark 1.2 65.1 from 2 benchmarks.
- Widest category
- Coding, 20.2 points apart on average over 9 shared benchmarks.
- Widest single gap
- Vibe Code Bench (Vals AI): Claude Sonnet 4.5 22.6% against Muse Spark 1.2 79.1%, 56.5 points apart on a 0 to 100 scale.
- Output price
- Claude Sonnet 4.5 $15.00 against Muse Spark 1.2 $4.25 per million output tokens, 3.5x apart.
- Context window
- Claude Sonnet 4.5 takes 1M tokens, Muse Spark 1.2 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 4.5 | Bars | Muse Spark 1.2 | Ties |
|---|---|---|---|---|
| Coding | 0 | 9 | ||
| Intelligence | 0 | 2 | ||
| Agentic work | 0 | 4 | ||
| Reasoning | 1 | 5 | ||
| Math | 0 | 3 | ||
| Knowledge | 0 | 11 | ||
| Web design | 0 | 8 | ||
| General | 2 | 16 | ||
| All shared boards | 3 | 58 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index09
| Benchmark | Claude Sonnet 4.5 | Muse Spark 1.2 | Leader |
|---|---|---|---|
| SWE-bench Verified | 74.8% | Not measured | Only Claude Sonnet 4.5 measured |
| SWE-bench Multilingual | 67.0% | Not measured | Only Claude Sonnet 4.5 measured |
| LiveBench coding | Not measured | 78.2% | Only Muse Spark 1.2 measured |
| LMArena WebDev | 1394 | 1534 | Muse Spark 1.2 |
| AA Coding Index | 52.1 | 72.2 | Muse Spark 1.2 |
| LiveCodeBench (Vals AI) | 73.0% | Not measured | Only Claude Sonnet 4.5 measured |
| SWE-bench Verified (Vals AI) | 70.0% | 86.6% | Muse Spark 1.2 |
| Terminal-Bench 4 (Vals AI) | Not measured | 6.1% | Only Muse Spark 1.2 measured |
| Vibe Code Bench (Vals AI) | 22.6% | 79.1% | Muse Spark 1.2 |
| Code migration (Vals AI) | Not measured | 29.9% | Only Muse Spark 1.2 measured |
| ProgramBench (Vals AI) | Not measured | 0.5% | Only Muse Spark 1.2 measured |
| IOI (Vals AI) | Not measured | 21.8% | Only Muse Spark 1.2 measured |
| Terminal-Bench 2.1 (Vals AI) | Not measured | 69.7% | Only Muse Spark 1.2 measured |
| SkillsBench (Vals AI) | Not measured | 53.0% | Only Muse Spark 1.2 measured |
| CyberBench (Vals AI) | Not measured | 69.5% | Only Muse Spark 1.2 measured |
| SciCode | Not measured | 57.4% | Only Muse Spark 1.2 measured |
| Terminal-Bench | 46.5% | Not measured | Only Claude Sonnet 4.5 measured |
| FrontierSWE | Not measured | 12.0% | Only Muse Spark 1.2 measured |
| GSO-Bench | 14.7% | Not measured | Only Claude Sonnet 4.5 measured |
| WeirdML | 47.7% | 60.3% | Muse Spark 1.2 |
| Cybench | 60.0% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: coding | 1488 | 1505 | Muse Spark 1.2 |
| LMArena Text: software and IT | 1473 | 1505 | Muse Spark 1.2 |
| LMArena WebDev: React | 1386 | 1526 | Muse Spark 1.2 |
| LMArena WebDev: HTML | 1399 | 1543 | Muse Spark 1.2 |
| Neither model has a result on the other 13 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | Claude Sonnet 4.5 | Muse Spark 1.2 | Leader |
|---|---|---|---|
| AA Intelligence Index | 20.7 | 39.6 | Muse Spark 1.2 |
| Epoch Capabilities Index | 146.7 | 155.1 | Muse Spark 1.2 |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index04
| Benchmark | Claude Sonnet 4.5 | Muse Spark 1.2 | Leader |
|---|---|---|---|
| AA Agentic Index | 15.8 | 43.2 | Muse Spark 1.2 |
| Design Arena: agents building web apps | 1060 | 1222 | Muse Spark 1.2 |
| Design Arena: agents building full-stack apps | 1050 | 1210 | Muse Spark 1.2 |
| Design Arena: agents building mobile apps | 1137 | 1182 | Muse Spark 1.2 |
| Design Arena: agents building Android apps | Not measured | 1228 | Only Muse Spark 1.2 measured |
| Design Arena: agents building games | Not measured | 1179 | Only Muse Spark 1.2 measured |
| Design Arena: HTML slides | Not measured | 1135 | Only Muse Spark 1.2 measured |
| Design Arena: PowerPoint slides | Not measured | 1198 | Only Muse Spark 1.2 measured |
| LiveBench research | Not measured | 67.7% | Only Muse Spark 1.2 measured |
| LiveBench browser | Not measured | 36.0% | Only Muse Spark 1.2 measured |
| LiveBench long agentic | Not measured | 21.3% | Only Muse Spark 1.2 measured |
| SREBench (Vals AI) | Not measured | 0.0% | Only Muse Spark 1.2 measured |
| Finance Agent (Vals AI) | Not measured | 60.6% | Only Muse Spark 1.2 measured |
| Tax Agent Bench (Vals AI) | Not measured | 32.8% | Only Muse Spark 1.2 measured |
| Legal Research Bench (Vals AI) | Not measured | 43.8% | Only Muse Spark 1.2 measured |
| Excel Modeling Benchmark (Vals AI) | Not measured | 57.0% | Only Muse Spark 1.2 measured |
| BioMysteryBench (Vals AI) | Not measured | 64.8% | Only Muse Spark 1.2 measured |
| APEX-Agents | Not measured | 45.4% | Only Muse Spark 1.2 measured |
| METR time horizons | 67.4% | Not measured | Only Claude Sonnet 4.5 measured |
| Remote Labor Index | 2.1% | Not measured | Only Claude Sonnet 4.5 measured |
| GDPval | 42.5% | Not measured | Only Claude Sonnet 4.5 measured |
| DeepResearch Bench | 52.6% | Not measured | Only Claude Sonnet 4.5 measured |
| OSWorld | 62.9% | Not measured | Only Claude Sonnet 4.5 measured |
| Vending-Bench 2 | $3,839 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 15 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index15
| Benchmark | Claude Sonnet 4.5 | Muse Spark 1.2 | Leader |
|---|---|---|---|
| GPQA Diamond | 81.6% | Not measured | Only Claude Sonnet 4.5 measured |
| LiveBench reasoning | Not measured | 90.0% | Only Muse Spark 1.2 measured |
| MMMU Pro (Vals AI) | 79.3% | 86.1% | Muse Spark 1.2 |
| GPQA Diamond (Artificial Analysis run) | Not measured | 90.4% | Only Muse Spark 1.2 measured |
| Humanity's Last Exam (Artificial Analysis run) | Not measured | 45.5% | Only Muse Spark 1.2 measured |
| GPQA Diamond (Epoch AI run) | 82.3% | Not measured | Only Claude Sonnet 4.5 measured |
| ARC-AGI | 63.7% | Not measured | Only Claude Sonnet 4.5 measured |
| ARC-AGI-2 | 13.6% | Not measured | Only Claude Sonnet 4.5 measured |
| SimpleBench | 54.3% | 74.5% | Muse Spark 1.2 |
| Chess puzzles | 10.0% | 27.0% | Muse Spark 1.2 |
| Mystery game puzzles | 17.0% | Not measured | Only Claude Sonnet 4.5 measured |
| EBR-bench | 2.4% | Not measured | Only Claude Sonnet 4.5 measured |
| VPCT | 39.8% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: hard prompts | 1462 | 1489 | Muse Spark 1.2 |
| LMArena Text: expert | 1483 | 1475 | Claude Sonnet 4.5 |
| LMArena Text: hard prompts in English | 1471 | 1487 | Muse Spark 1.2 |
| LMArena Vision: diagrams | Not measured | 1317 | Only Muse Spark 1.2 measured |
| Neither model has a result on the other 4 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index03
| Benchmark | Claude Sonnet 4.5 | Muse Spark 1.2 | Leader |
|---|---|---|---|
| AIME | 88.2% | Not measured | Only Claude Sonnet 4.5 measured |
| MGSM (Vals AI) | 94.3% | Not measured | Only Claude Sonnet 4.5 measured |
| OTIS Mock AIME | 77.8% | Not measured | Only Claude Sonnet 4.5 measured |
| FrontierMath, tiers 1 to 3 | 23.9% | Not measured | Only Claude Sonnet 4.5 measured |
| FrontierMath, tier 4 | 2.4% | Not measured | Only Claude Sonnet 4.5 measured |
| ProofBench | 19.0% | 43.0% | Muse Spark 1.2 |
| MATH level 5 | 97.7% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: math | 1449 | 1484 | Muse Spark 1.2 |
| LMArena Text: mathematical work | 1462 | 1480 | Muse Spark 1.2 |
| Neither model has a result on the other 4 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index011
| Benchmark | Claude Sonnet 4.5 | Muse Spark 1.2 | Leader |
|---|---|---|---|
| MMLU Pro | 87.4% | 88.3% | Muse Spark 1.2 |
| LegalBench (Vals AI) | 84.1% | 85.3% | Muse Spark 1.2 |
| CaseLaw (Vals AI) | 62.2% | Not measured | Only Claude Sonnet 4.5 measured |
| CorpFin (Vals AI) | 62.0% | 70.9% | Muse Spark 1.2 |
| TaxEval (Vals AI) | 73.3% | 80.4% | Muse Spark 1.2 |
| MortgageTax (Vals AI) | 64.0% | 65.4% | Muse Spark 1.2 |
| MedQA (Vals AI) | 94.7% | Not measured | Only Claude Sonnet 4.5 measured |
| MedCode (Vals AI) | 44.1% | 49.4% | Muse Spark 1.2 |
| SimpleQA Verified | 30.7% | 60.3% | Muse Spark 1.2 |
| LMArena Text: science | 1448 | 1500 | Muse Spark 1.2 |
| LMArena Text: medicine and healthcare | 1444 | 1496 | Muse Spark 1.2 |
| LMArena Text: legal and government | 1451 | 1517 | Muse Spark 1.2 |
| LMArena Text: business and finance | 1440 | 1484 | Muse Spark 1.2 |
| Neither model has a result on the other 4 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index08
| Benchmark | Claude Sonnet 4.5 | Muse Spark 1.2 | Leader |
|---|---|---|---|
| Design Arena: websites | 1190 | 1313 | Muse Spark 1.2 |
| Design Arena: UI components | 1173 | 1300 | Muse Spark 1.2 |
| Design Arena: game dev | 1166 | 1302 | Muse Spark 1.2 |
| Design Arena: data viz | 1167 | 1334 | Muse Spark 1.2 |
| Design Arena: 3D | 1158 | 1301 | Muse Spark 1.2 |
| Design Arena: all code categories | 1183 | 1313 | Muse Spark 1.2 |
| Design Arena: SVG | 1114 | 1285 | Muse Spark 1.2 |
| Design Arena: ASCII art | 1204 | 1284 | Muse Spark 1.2 |
| LiveBench design | Not measured | 67.1% | Only Muse Spark 1.2 measured |
GeneralLike-for-likePublic boards, shown as published, kept out of the index216
| Benchmark | Claude Sonnet 4.5 | Muse Spark 1.2 | Leader |
|---|---|---|---|
| LiveBench data analysis | Not measured | 76.5% | Only Muse Spark 1.2 measured |
| Public Benefits Bench (Vals AI) | Not measured | 68.5% | Only Muse Spark 1.2 measured |
| SAGE (Vals AI) | 36.1% | 47.7% | Muse Spark 1.2 |
| MedScribe (Vals AI) | 84.5% | 90.1% | Muse Spark 1.2 |
| Vals Multimodal Index | Not measured | 69.8% | Only Muse Spark 1.2 measured |
| Long context reasoning (AA-LCR) | Not measured | 79.0% | Only Muse Spark 1.2 measured |
| DTBench | 83.2% | 94.7% | Muse Spark 1.2 |
| LMCA | 38.8% | 48.4% | Muse Spark 1.2 |
| LMArena Text | 1438 | 1482 | Muse Spark 1.2 |
| LMArena Text: instruction following | 1459 | 1462 | Muse Spark 1.2 |
| LMArena Text: creative writing | 1442 | 1436 | Claude Sonnet 4.5 |
| LMArena Vision | Not measured | 1304 | Only Muse Spark 1.2 measured |
| LMArena Text: English | 1450 | 1483 | Muse Spark 1.2 |
| LMArena Text: non-English | 1425 | 1476 | Muse Spark 1.2 |
| LMArena Text: Chinese | 1460 | 1509 | Muse Spark 1.2 |
| LMArena Text: German | 1427 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Japanese | 1390 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Korean | 1402 | 1462 | Muse Spark 1.2 |
| LMArena Text: French | 1459 | 1495 | Muse Spark 1.2 |
| LMArena Text: Spanish | 1458 | 1484 | Muse Spark 1.2 |
| LMArena Text: Russian | 1437 | 1483 | Muse Spark 1.2 |
| LMArena Text: Polish | 1423 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: multi-turn | 1465 | 1502 | Muse Spark 1.2 |
| LMArena Text: longer queries | 1475 | 1473 | Claude Sonnet 4.5 |
| LMArena Text: writing and language | 1442 | 1453 | Muse Spark 1.2 |
| LMArena Text: entertainment and media | 1428 | 1443 | Muse Spark 1.2 |
| LMArena Vision: English | Not measured | 1291 | Only Muse Spark 1.2 measured |
| LMArena Vision: reading text | Not measured | 1313 | Only Muse Spark 1.2 measured |
| LMArena Document | 1450 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 17 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Sonnet 4.5 | Muse Spark 1.2 | 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 1.2 costs less
Repository review
50K input + 3K output tokens
Muse Spark 1.2 costs less
Agent loop
200K input + 10K output tokens
Muse Spark 1.2 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 4.5 | Meta Muse Spark 1.2 |
|---|---|---|
| Maker | Anthropic | Meta |
| Weights | No public weights listed | No public weights listed |
| Released | September 29, 2025 | August 5, 2026 |
| Context window | 1M | 1.05M |
| Input $/Mtok | $3.00 | $1.25 |
| Output $/Mtok | $15.00 | $4.25 |
| Coding index | 59.1 | 65.1 |
| Independent measurements behind it | 2 | 2 |
| Cost per solved task | $1.16 | $0.64 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Sonnet 4.5 better than Muse Spark 1.2 for coding?
Pick Muse Spark 1.2 for coding: it scores 65.1 on the Vibe Coding Index against 59.1 for Claude Sonnet 4.5. Pick Claude Sonnet 4.5 when what matters is LMArena Text: expert or LMArena Text: creative writing, where it leads.
Which is cheaper, Claude Sonnet 4.5 or Muse Spark 1.2?
Claude Sonnet 4.5 costs $3.00 per million input tokens and $15.00 per million output tokens; Muse Spark 1.2 costs $1.25 and $4.25. Per solved SWE-bench Verified task, Claude Sonnet 4.5 costs $1.16 and Muse Spark 1.2 $0.64.
Which has the bigger context window, Claude Sonnet 4.5 or Muse Spark 1.2?
Muse Spark 1.2, with 1.05M tokens against 1M.
How many benchmarks is the Claude Sonnet 4.5 vs Muse Spark 1.2 comparison based on?
61 benchmarks have a result for both models as of October 21, 2026. Claude Sonnet 4.5's coding index rests on 2 independent benchmarks and Muse Spark 1.2's on 2. Where only one model has a result, the page says so instead of naming a winner.