Step 3.5 Flash vs Step 5 Preview
Updated October 21, 2026. 28 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
Decision reading
Only Step 5 Preview has a coding score, 61.1 on the Vibe Coding Index; Step 3.5 Flash has none, so the two cannot be ranked on coding.
Step 3.5 Flash has the edge where output tokens cost 9.0x less.
- Shared results
- 28
- Step 3.5 Flash only
- 7
- Step 5 Preview only
- 33
- 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, six public coding benchmarks
No call
Only Step 5 Preview has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
Step 5 Preview
Step 5 Preview leads, 43.7 against 17.0.
Same board, both measured
Long documents
Listed context window
Step 5 Preview
Step 5 Preview takes 1.05M tokens against 262K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Step 3.5 Flash
Step 3.5 Flash $0.0003, Step 5 Preview $0.0024 per turn.
List prices
At a glance
- Coding index
- Step 3.5 Flash not benchmarked, Step 5 Preview 61.1 from 4 benchmarks.
- Widest category
- Intelligence, 26.7 points apart on average over 1 shared benchmark.
- Widest single gap
- AA Intelligence Index: Step 3.5 Flash 17.0 against Step 5 Preview 43.7, 26.7 points apart on a 0 to 100 scale.
- Output price
- Step 3.5 Flash $0.30 against Step 5 Preview $2.70 per million output tokens, 9.0x apart.
- Context window
- Step 3.5 Flash takes 262K tokens, Step 5 Preview 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 | Step 3.5 Flash | Bars | Step 5 Preview | Ties |
|---|---|---|---|---|
| Coding | 0 | 2 | ||
| Intelligence | 0 | 1 | ||
| Reasoning | 0 | 4 | ||
| Math | 0 | 2 | ||
| Knowledge | 0 | 4 | ||
| General | 0 | 15 | ||
| All shared boards | 0 | 28 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index02
| Benchmark | Step 3.5 Flash | Step 5 Preview | Leader |
|---|---|---|---|
| LiveBench coding | Not measured | 85.6% | Only Step 5 Preview measured |
| LMArena WebDev | Not measured | 1567 | Only Step 5 Preview measured |
| Terminal-Bench 4 (Vals AI) | Not measured | 31.8% | Only Step 5 Preview measured |
| Vibe Code Bench (Vals AI) | Not measured | 70.4% | Only Step 5 Preview measured |
| Code migration (Vals AI) | Not measured | 39.0% | Only Step 5 Preview measured |
| IOI (Vals AI) | Not measured | 38.1% | Only Step 5 Preview measured |
| SWE-bench Multimodal (Vals AI) | Not measured | 40.8% | Only Step 5 Preview measured |
| SciCode | Not measured | 58.9% | Only Step 5 Preview measured |
| Terminal-Bench Hard (Artificial Analysis run) | 32.6% | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: coding | 1436 | 1485 | Step 5 Preview |
| LMArena Text: software and IT | 1434 | 1473 | Step 5 Preview |
| LMArena WebDev: React | Not measured | 1583 | Only Step 5 Preview measured |
| LMArena WebDev: HTML | Not measured | 1556 | Only Step 5 Preview measured |
| LMArena WebDev: from an image | Not measured | 1550 | Only Step 5 Preview 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 | Step 3.5 Flash | Step 5 Preview | Leader |
|---|---|---|---|
| AA Intelligence Index | 17.0 | 43.7 | Step 5 Preview |
| Neither model has a result on the other 1 board here | |||
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index12 boards, none shared
| Benchmark | Step 3.5 Flash | Step 5 Preview | Leader |
|---|---|---|---|
| LiveBench research | Not measured | 72.8% | Only Step 5 Preview measured |
| LiveBench browser | Not measured | 24.0% | Only Step 5 Preview measured |
| LiveBench long agentic | Not measured | 27.5% | Only Step 5 Preview measured |
| SREBench (Vals AI) | Not measured | 0.4% | Only Step 5 Preview measured |
| Finance Agent (Vals AI) | Not measured | 50.7% | Only Step 5 Preview measured |
| Tax Agent Bench (Vals AI) | Not measured | 27.3% | Only Step 5 Preview measured |
| Legal Research Bench (Vals AI) | Not measured | 40.4% | Only Step 5 Preview measured |
| Excel Modeling Benchmark (Vals AI) | Not measured | 57.1% | Only Step 5 Preview measured |
| BioMysteryBench (Vals AI) | Not measured | 67.4% | Only Step 5 Preview measured |
| Terminal-Bench-Science (Vals AI) | Not measured | 2.9% | Only Step 5 Preview measured |
| Vals Science Index | Not measured | 29.6% | Only Step 5 Preview measured |
| τ²-Bench Telecom | 94.4% | Not measured | Only Step 3.5 Flash measured |
| Neither model has a result on the other 27 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index04
| Benchmark | Step 3.5 Flash | Step 5 Preview | Leader |
|---|---|---|---|
| LiveBench reasoning | Not measured | 83.8% | Only Step 5 Preview measured |
| MysteryMechanism (Vals AI) | Not measured | 18.5% | Only Step 5 Preview measured |
| GPQA Diamond (Artificial Analysis run) | 83.1% | Not measured | Only Step 3.5 Flash measured |
| Humanity's Last Exam (Artificial Analysis run) | 24.5% | 46.5% | Step 5 Preview |
| LMArena Text: hard prompts | 1411 | 1461 | Step 5 Preview |
| LMArena Text: expert | 1421 | 1485 | Step 5 Preview |
| LMArena Text: hard prompts in English | 1421 | 1454 | Step 5 Preview |
| LMArena Vision: diagrams | Not measured | 1308 | Only Step 5 Preview measured |
| LMArena Vision: homework | Not measured | 1265 | Only Step 5 Preview measured |
| Neither model has a result on the other 12 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | Step 3.5 Flash | Step 5 Preview | Leader |
|---|---|---|---|
| ProofBench | Not measured | 42.0% | Only Step 5 Preview measured |
| LMArena Text: math | 1408 | 1458 | Step 5 Preview |
| LMArena Text: mathematical work | 1421 | 1460 | Step 5 Preview |
| Neither model has a result on the other 10 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index04
| Benchmark | Step 3.5 Flash | Step 5 Preview | Leader |
|---|---|---|---|
| LMArena Text: science | 1415 | 1454 | Step 5 Preview |
| LMArena Text: medicine and healthcare | 1408 | 1439 | Step 5 Preview |
| LMArena Text: legal and government | 1408 | 1437 | Step 5 Preview |
| LMArena Text: business and finance | 1394 | 1435 | Step 5 Preview |
| Neither model has a result on the other 13 boards here | |||
Web designDirectional onlyPublic boards, shown as published, kept out of the index1 board, none shared
| Benchmark | Step 3.5 Flash | Step 5 Preview | Leader |
|---|---|---|---|
| LiveBench design | Not measured | 76.9% | Only Step 5 Preview measured |
| Neither model has a result on the other 8 boards here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index015
| Benchmark | Step 3.5 Flash | Step 5 Preview | Leader |
|---|---|---|---|
| LiveBench data analysis | Not measured | 63.5% | Only Step 5 Preview measured |
| Public Benefits Bench (Vals AI) | Not measured | 58.1% | Only Step 5 Preview measured |
| IFBench | 66.5% | Not measured | Only Step 3.5 Flash measured |
| Long context reasoning (AA-LCR) | 63.0% | 88.3% | Step 5 Preview |
| LMArena Text | 1403 | 1440 | Step 5 Preview |
| LMArena Text: instruction following | 1385 | 1438 | Step 5 Preview |
| LMArena Text: creative writing | 1357 | 1409 | Step 5 Preview |
| LMArena Vision | Not measured | 1265 | Only Step 5 Preview measured |
| LMArena Text: English | 1417 | 1447 | Step 5 Preview |
| LMArena Text: non-English | 1385 | 1428 | Step 5 Preview |
| LMArena Text: Chinese | 1446 | 1500 | Step 5 Preview |
| LMArena Text: German | 1405 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: Japanese | 1353 | 1383 | Step 5 Preview |
| LMArena Text: Korean | 1351 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: French | 1421 | 1438 | Step 5 Preview |
| LMArena Text: Spanish | 1419 | 1441 | Step 5 Preview |
| LMArena Text: Russian | 1385 | 1433 | Step 5 Preview |
| LMArena Text: Polish | 1389 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: multi-turn | 1404 | 1437 | Step 5 Preview |
| LMArena Text: longer queries | 1402 | 1449 | Step 5 Preview |
| LMArena Text: writing and language | 1372 | 1425 | Step 5 Preview |
| LMArena Text: entertainment and media | 1360 | 1412 | Step 5 Preview |
| LMArena Vision: English | Not measured | 1290 | Only Step 5 Preview measured |
| LMArena Vision: reading text | Not measured | 1282 | Only Step 5 Preview measured |
| Neither model has a result on the other 22 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Step 3.5 Flash | Step 5 Preview | 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 | StepFun Step 3.5 Flash | StepFun Step 5 Preview |
|---|---|---|
| Maker | StepFun | StepFun |
| Weights | Open weights | Open weights |
| Released | January 29, 2026 | October 8, 2026 |
| Context window | 262K | 1.05M |
| Input $/Mtok | $0.10 | $1.00 |
| Output $/Mtok | $0.30 | $2.70 |
| Coding index | Not benchmarked | 61.1 |
| Independent measurements behind it | 0 | 4 |
| Cost per solved task | Not computable | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Step 3.5 Flash better than Step 5 Preview for coding?
Only Step 5 Preview has a coding score, 61.1 on the Vibe Coding Index; Step 3.5 Flash has none, so the two cannot be ranked on coding. Step 3.5 Flash has the edge where output tokens cost 9.0x less.
Which is cheaper, Step 3.5 Flash or Step 5 Preview?
Step 3.5 Flash costs $0.10 per million input tokens and $0.30 per million output tokens; Step 5 Preview costs $1.00 and $2.70. Cost per solved task is known for neither of them.
Which has the bigger context window, Step 3.5 Flash or Step 5 Preview?
Step 5 Preview, with 1.05M tokens against 262K.
How many benchmarks is the Step 3.5 Flash vs Step 5 Preview comparison based on?
28 benchmarks have a result for both models as of October 21, 2026. Step 3.5 Flash's coding index rests on 0 independent benchmarks and Step 5 Preview's on 4. Where only one model has a result, the page says so instead of naming a winner.