Muse Spark 1.3 vs Step 3.5 Flash
Muse Spark 1.3 leads Step 3.5 Flash on the Artificial Analysis Intelligence Index, 48.1 to 17.0, and Step 3.5 Flash costs 14.2x less per output token ($0.30 vs $4.25 per million). Updated October 21, 2026; 32 benchmarks have a result for both.
Muse Spark 1.3 or Step 3.5 Flash: which to pick
Only Muse Spark 1.3 has a coding score, 57.4 on the Vibe Coding Index; Step 3.5 Flash has none, so the two cannot be ranked on coding.
Pick Step 3.5 Flash for output tokens 14.2x cheaper ($0.30 vs $4.25 per million).
- Shared results
- 32
- Muse Spark 1.3 only
- 60
- Step 3.5 Flash only
- 3
- 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
No call
Only Muse Spark 1.3 has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
Muse Spark 1.3
Muse Spark 1.3 leads, 48.1 against 17.0.
Same board, both measured
Agentic work
AA Agentic Index
No call
Only Muse Spark 1.3 has a AA Agentic Index result, 55.5.
Directional only
Web design
Design Arena: websites
No call
Only Muse Spark 1.3 has a Design Arena: websites result, 1356.
Directional only
Long documents
Listed context window
Muse Spark 1.3
Muse Spark 1.3 takes 1.05M tokens against 262K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Step 3.5 Flash
Muse Spark 1.3 $0.0034, Step 3.5 Flash $0.0003 per turn.
List prices
At a glance
- Coding index
- Muse Spark 1.3 57.4 from 4 benchmarks, Step 3.5 Flash not benchmarked.
- Widest category
- Intelligence, 31.1 points apart on average over 1 shared benchmark.
- Widest single gap
- AA Intelligence Index: Muse Spark 1.3 48.1 against Step 3.5 Flash 17.0, 31.1 points apart on a 0 to 100 scale.
- Output price
- Muse Spark 1.3 $4.25 against Step 3.5 Flash $0.30 per million output tokens, 14.2x apart.
- Context window
- Muse Spark 1.3 takes 1.05M tokens, Step 3.5 Flash 262K.
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 | Muse Spark 1.3 | Bars | Step 3.5 Flash | Ties |
|---|---|---|---|---|
| Coding | 2 | 0 | ||
| Intelligence | 1 | 0 | ||
| Reasoning | 5 | 0 | ||
| Math | 2 | 0 | ||
| Knowledge | 4 | 0 | ||
| General | 18 | 0 | ||
| All shared boards | 32 | 0 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index20
| Benchmark | Muse Spark 1.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| LiveBench coding | 90.2% | Not measured | Only Muse Spark 1.3 measured |
| LMArena WebDev | 1659 | Not measured | Only Muse Spark 1.3 measured |
| AA Coding Index | 75.8 | Not measured | Only Muse Spark 1.3 measured |
| Terminal-Bench 4 (Vals AI) | 10.6% | Not measured | Only Muse Spark 1.3 measured |
| Vibe Code Bench (Vals AI) | 82.9% | Not measured | Only Muse Spark 1.3 measured |
| Code migration (Vals AI) | 27.6% | Not measured | Only Muse Spark 1.3 measured |
| ProgramBench (Vals AI) | 0.5% | Not measured | Only Muse Spark 1.3 measured |
| IOI (Vals AI) | 43.9% | Not measured | Only Muse Spark 1.3 measured |
| Terminal-Bench 2.1 (Vals AI) | 72.3% | Not measured | Only Muse Spark 1.3 measured |
| CyberBench (Vals AI) | 69.4% | Not measured | Only Muse Spark 1.3 measured |
| SciCode | 59.7% | Not measured | Only Muse Spark 1.3 measured |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 32.6% | Only Step 3.5 Flash measured |
| FrontierSWE | 25.8% | Not measured | Only Muse Spark 1.3 measured |
| ALE-Bench | 1688.3 | Not measured | Only Muse Spark 1.3 measured |
| LMArena Text: coding | 1510 | 1436 | Muse Spark 1.3 |
| LMArena Text: software and IT | 1511 | 1434 | Muse Spark 1.3 |
| LMArena WebDev: React | 1672 | Not measured | Only Muse Spark 1.3 measured |
| LMArena WebDev: HTML | 1653 | Not measured | Only Muse Spark 1.3 measured |
| LMArena WebDev: from an image | 1640 | Not measured | Only Muse Spark 1.3 measured |
| Neither model has a result on the other 20 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Muse Spark 1.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| AA Intelligence Index | 48.1 | 17.0 | Muse Spark 1.3 |
| Epoch Capabilities Index | 157.2 | Not measured | Only Muse Spark 1.3 measured |
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index17 boards, none shared
| Benchmark | Muse Spark 1.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| AA Agentic Index | 55.5 | Not measured | Only Muse Spark 1.3 measured |
| Design Arena: agents building web apps | 1297 | Not measured | Only Muse Spark 1.3 measured |
| Design Arena: agents building full-stack apps | 1295 | Not measured | Only Muse Spark 1.3 measured |
| Design Arena: agents building mobile apps | 1217 | Not measured | Only Muse Spark 1.3 measured |
| Design Arena: agents building Godot games | 1241 | Not measured | Only Muse Spark 1.3 measured |
| Design Arena: PowerPoint slides | 1243 | Not measured | Only Muse Spark 1.3 measured |
| Design Arena: spreadsheets | 1043 | Not measured | Only Muse Spark 1.3 measured |
| LiveBench research | 68.6% | Not measured | Only Muse Spark 1.3 measured |
| LiveBench browser | 80.0% | Not measured | Only Muse Spark 1.3 measured |
| LiveBench long agentic | 40.4% | Not measured | Only Muse Spark 1.3 measured |
| Finance Agent (Vals AI) | 58.9% | Not measured | Only Muse Spark 1.3 measured |
| Tax Agent Bench (Vals AI) | 36.0% | Not measured | Only Muse Spark 1.3 measured |
| Legal Research Bench (Vals AI) | 40.9% | Not measured | Only Muse Spark 1.3 measured |
| Excel Modeling Benchmark (Vals AI) | 62.7% | Not measured | Only Muse Spark 1.3 measured |
| Terminal-Bench-Science (Vals AI) | 4.3% | Not measured | Only Muse Spark 1.3 measured |
| τ²-Bench Telecom | Not measured | 94.4% | Only Step 3.5 Flash measured |
| APEX-Agents | 58.6% | Not measured | Only Muse Spark 1.3 measured |
| Neither model has a result on the other 24 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index50
| Benchmark | Muse Spark 1.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| LiveBench reasoning | 89.7% | Not measured | Only Muse Spark 1.3 measured |
| GPQA Diamond (Artificial Analysis run) | 94.1% | 83.1% | Muse Spark 1.3 |
| Humanity's Last Exam (Artificial Analysis run) | 48.7% | 24.5% | Muse Spark 1.3 |
| Chess puzzles | 37.0% | Not measured | Only Muse Spark 1.3 measured |
| Mystery game puzzles | 25.0% | Not measured | Only Muse Spark 1.3 measured |
| LMArena Text: hard prompts | 1503 | 1411 | Muse Spark 1.3 |
| LMArena Text: expert | 1519 | 1421 | Muse Spark 1.3 |
| LMArena Text: hard prompts in English | 1500 | 1421 | Muse Spark 1.3 |
| LMArena Vision: diagrams | 1330 | Not measured | Only Muse Spark 1.3 measured |
| LMArena Vision: homework | 1296 | Not measured | Only Muse Spark 1.3 measured |
| Neither model has a result on the other 12 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Muse Spark 1.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| OTIS Mock AIME | 99.2% | Not measured | Only Muse Spark 1.3 measured |
| FrontierMath, tiers 1 to 3 | 74.4% | Not measured | Only Muse Spark 1.3 measured |
| FrontierMath, tier 4 | 46.3% | Not measured | Only Muse Spark 1.3 measured |
| ProofBench | 58.0% | Not measured | Only Muse Spark 1.3 measured |
| LMArena Text: math | 1497 | 1408 | Muse Spark 1.3 |
| LMArena Text: mathematical work | 1491 | 1421 | Muse Spark 1.3 |
| Neither model has a result on the other 7 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index40
| Benchmark | Muse Spark 1.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| LMArena Text: science | 1507 | 1415 | Muse Spark 1.3 |
| LMArena Text: medicine and healthcare | 1493 | 1408 | Muse Spark 1.3 |
| LMArena Text: legal and government | 1499 | 1408 | Muse Spark 1.3 |
| LMArena Text: business and finance | 1490 | 1394 | Muse Spark 1.3 |
| Neither model has a result on the other 14 boards here | |||
Web designDirectional onlyPublic boards, shown as published, kept out of the index9 boards, none shared
| Benchmark | Muse Spark 1.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| Design Arena: websites | 1356 | Not measured | Only Muse Spark 1.3 measured |
| Design Arena: UI components | 1351 | Not measured | Only Muse Spark 1.3 measured |
| Design Arena: game dev | 1329 | Not measured | Only Muse Spark 1.3 measured |
| Design Arena: data viz | 1343 | Not measured | Only Muse Spark 1.3 measured |
| Design Arena: 3D | 1359 | Not measured | Only Muse Spark 1.3 measured |
| Design Arena: all code categories | 1353 | Not measured | Only Muse Spark 1.3 measured |
| Design Arena: SVG | 1301 | Not measured | Only Muse Spark 1.3 measured |
| Design Arena: ASCII art | 1280 | Not measured | Only Muse Spark 1.3 measured |
| LiveBench design | 74.8% | Not measured | Only Muse Spark 1.3 measured |
GeneralLike-for-likePublic boards, shown as published, kept out of the index180
| Benchmark | Muse Spark 1.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| LiveBench data analysis | 79.6% | Not measured | Only Muse Spark 1.3 measured |
| IFBench | Not measured | 66.5% | Only Step 3.5 Flash measured |
| Long context reasoning (AA-LCR) | 83.0% | 63.0% | Muse Spark 1.3 |
| DTBench | 96.5% | Not measured | Only Muse Spark 1.3 measured |
| LMCA | 53.9% | Not measured | Only Muse Spark 1.3 measured |
| LMArena Text | 1490 | 1403 | Muse Spark 1.3 |
| LMArena Text: instruction following | 1479 | 1385 | Muse Spark 1.3 |
| LMArena Text: creative writing | 1462 | 1357 | Muse Spark 1.3 |
| LMArena Vision | 1308 | Not measured | Only Muse Spark 1.3 measured |
| LMArena Text: English | 1495 | 1417 | Muse Spark 1.3 |
| LMArena Text: non-English | 1481 | 1385 | Muse Spark 1.3 |
| LMArena Text: Chinese | 1532 | 1446 | Muse Spark 1.3 |
| LMArena Text: German | 1513 | 1405 | Muse Spark 1.3 |
| LMArena Text: Japanese | 1470 | 1353 | Muse Spark 1.3 |
| LMArena Text: Korean | 1490 | 1351 | Muse Spark 1.3 |
| LMArena Text: French | 1511 | 1421 | Muse Spark 1.3 |
| LMArena Text: Spanish | 1496 | 1419 | Muse Spark 1.3 |
| LMArena Text: Russian | 1491 | 1385 | Muse Spark 1.3 |
| LMArena Text: Polish | 1490 | 1389 | Muse Spark 1.3 |
| LMArena Text: multi-turn | 1487 | 1404 | Muse Spark 1.3 |
| LMArena Text: longer queries | 1488 | 1402 | Muse Spark 1.3 |
| LMArena Text: writing and language | 1470 | 1372 | Muse Spark 1.3 |
| LMArena Text: entertainment and media | 1457 | 1360 | Muse Spark 1.3 |
| LMArena Vision: English | 1298 | Not measured | Only Muse Spark 1.3 measured |
| LMArena Vision: Chinese | 1384 | Not measured | Only Muse Spark 1.3 measured |
| LMArena Vision: reading text | 1319 | Not measured | Only Muse Spark 1.3 measured |
| LMArena Vision: humor | 1293 | Not measured | Only Muse Spark 1.3 measured |
| LMArena Vision: creative writing | 1296 | Not measured | Only Muse Spark 1.3 measured |
| Neither model has a result on the other 18 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Muse Spark 1.3 | Step 3.5 Flash | 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
Step 3.5 Flash costs less
Repository review
50K input + 3K output tokens
Step 3.5 Flash costs less
Agent loop
200K input + 10K output tokens
Step 3.5 Flash 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 | Meta Muse Spark 1.3 | StepFun Step 3.5 Flash |
|---|---|---|
| Maker | Meta | StepFun |
| Weights | No public weights listed | Open weights |
| Released | September 2, 2026 | January 29, 2026 |
| Context window | 1.05M | 262K |
| Input $/Mtok | $1.25 | $0.10 |
| Output $/Mtok | $4.25 | $0.30 |
| Coding index | 57.4 | Not benchmarked |
| Independent measurements behind it | 4 | 0 |
| Cost per solved task | Not computable | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Muse Spark 1.3 better than Step 3.5 Flash for coding?
Only Muse Spark 1.3 has a coding score, 57.4 on the Vibe Coding Index; Step 3.5 Flash has none, so the two cannot be ranked on coding. Pick Step 3.5 Flash for output tokens 14.2x cheaper ($0.30 vs $4.25 per million).
Which is cheaper, Muse Spark 1.3 or Step 3.5 Flash?
Muse Spark 1.3 costs $1.25 per million input tokens and $4.25 per million output tokens; Step 3.5 Flash costs $0.10 and $0.30. Cost per solved task is known for neither of them.
Which has the bigger context window, Muse Spark 1.3 or Step 3.5 Flash?
Muse Spark 1.3, with 1.05M tokens against 262K.
How many benchmarks is the Muse Spark 1.3 vs Step 3.5 Flash comparison based on?
32 benchmarks have a result for both models as of October 21, 2026. Muse Spark 1.3's coding index rests on 4 independent benchmarks and Step 3.5 Flash's on 0. Where only one model has a result, the page says so instead of naming a winner.