Step 3.5 Flash vs Hy4 preview
Updated October 21, 2026. 0 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
- Coding
- No data
- Overall
- 17.0
- Output $/M
- $0.30
- Coding
- 44.3
- Overall
- No data
- Output $/M
- $2.501
Decision reading
Only Hy4 preview has a coding score, 44.3 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 8.3x less.
- Shared results
- 0
- Step 3.5 Flash only
- 35
- Hy4 preview only
- 24
- Like-for-like categories
- 0 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 Hy4 preview has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
No call
Only Step 3.5 Flash has a AA Intelligence Index result, 17.0.
Directional only
General
Vals Index
No call
Only Hy4 preview has a Vals Index result, 53.2%.
Directional only
Long documents
Listed context window
Hy4 preview
Hy4 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, Hy4 preview $0.0021 per turn.
List prices
At a glance
- Coding index
- Step 3.5 Flash not benchmarked, Hy4 preview 44.3 from 3 benchmarks.
- Widest category
- No category has a result for both models.
- Widest single gap
- No benchmark has a result for both models.
- Output price
- Step 3.5 Flash $0.30 against Hy4 preview $2.501 per million output tokens, 8.3x apart.
- Context window
- Step 3.5 Flash takes 262K tokens, Hy4 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.
CodingDirectional onlySix of these boards feed the Vibe Coding Index13 boards, none shared
| Benchmark | Step 3.5 Flash | Hy4 preview | Leader |
|---|---|---|---|
| LMArena WebDev | Not measured | 1631 | Only Hy4 preview measured |
| Terminal-Bench 4 (Vals AI) | Not measured | 8.1% | Only Hy4 preview measured |
| Vibe Code Bench (Vals AI) | Not measured | 77.5% | Only Hy4 preview measured |
| Code migration (Vals AI) | Not measured | 47.4% | Only Hy4 preview measured |
| ProgramBench (Vals AI) | Not measured | 0.0% | Only Hy4 preview measured |
| IOI (Vals AI) | Not measured | 59.3% | Only Hy4 preview measured |
| Terminal-Bench 2.1 (Vals AI) | Not measured | 55.1% | Only Hy4 preview measured |
| CyberBench (Vals AI) | Not measured | 65.4% | Only Hy4 preview measured |
| Terminal-Bench Hard (Artificial Analysis run) | 32.6% | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: coding | 1436 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: software and IT | 1434 | Not measured | Only Step 3.5 Flash measured |
| LMArena WebDev: React | Not measured | 1653 | Only Hy4 preview measured |
| LMArena WebDev: HTML | Not measured | 1620 | Only Hy4 preview measured |
| Neither model has a result on the other 25 boards here | |||
IntelligenceDirectional onlyPublic boards, shown as published, kept out of the index1 board, none shared
| Benchmark | Step 3.5 Flash | Hy4 preview | Leader |
|---|---|---|---|
| AA Intelligence Index | 17.0 | Not measured | Only Step 3.5 Flash measured |
| Neither model has a result on the other 1 board here | |||
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index9 boards, none shared
| Benchmark | Step 3.5 Flash | Hy4 preview | Leader |
|---|---|---|---|
| SREBench (Vals AI) | Not measured | 2.3% | Only Hy4 preview measured |
| Finance Agent (Vals AI) | Not measured | 55.1% | Only Hy4 preview measured |
| Tax Agent Bench (Vals AI) | Not measured | 32.6% | Only Hy4 preview measured |
| Legal Research Bench (Vals AI) | Not measured | 45.2% | Only Hy4 preview measured |
| Harvey's Legal Agent Benchmark (Vals AI) | Not measured | 8.8% | Only Hy4 preview measured |
| Excel Modeling Benchmark (Vals AI) | Not measured | 58.1% | Only Hy4 preview measured |
| BioMysteryBench (Vals AI) | Not measured | 69.3% | Only Hy4 preview measured |
| Terminal-Bench-Science (Vals AI) | Not measured | 1.4% | Only Hy4 preview measured |
| τ²-Bench Telecom | 94.4% | Not measured | Only Step 3.5 Flash measured |
| Neither model has a result on the other 30 boards here | |||
ReasoningDirectional onlyPublic boards, shown as published, kept out of the index5 boards, none shared
| Benchmark | Step 3.5 Flash | Hy4 preview | Leader |
|---|---|---|---|
| GPQA Diamond (Artificial Analysis run) | 83.1% | Not measured | Only Step 3.5 Flash measured |
| Humanity's Last Exam (Artificial Analysis run) | 24.5% | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: hard prompts | 1411 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: expert | 1421 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: hard prompts in English | 1421 | Not measured | Only Step 3.5 Flash measured |
| Neither model has a result on the other 16 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index3 boards, none shared
| Benchmark | Step 3.5 Flash | Hy4 preview | Leader |
|---|---|---|---|
| ProofBench | Not measured | 75.0% | Only Hy4 preview measured |
| LMArena Text: math | 1408 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: mathematical work | 1421 | Not measured | Only Step 3.5 Flash measured |
| Neither model has a result on the other 10 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index6 boards, none shared
| Benchmark | Step 3.5 Flash | Hy4 preview | Leader |
|---|---|---|---|
| LegalBench (Vals AI) | Not measured | 83.8% | Only Hy4 preview measured |
| MedCode (Vals AI) | Not measured | 43.3% | Only Hy4 preview measured |
| LMArena Text: science | 1415 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: medicine and healthcare | 1408 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: legal and government | 1408 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: business and finance | 1394 | Not measured | Only Step 3.5 Flash measured |
| Neither model has a result on the other 11 boards here | |||
Web designNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Step 3.5 Flash | Hy4 preview | Leader |
|---|---|---|---|
| Neither model has a result on 9 boards here | |||
GeneralDirectional onlyPublic boards, shown as published, kept out of the index22 boards, none shared
| Benchmark | Step 3.5 Flash | Hy4 preview | Leader |
|---|---|---|---|
| Vals Index | Not measured | 53.2% | Only Hy4 preview measured |
| Public Benefits Bench (Vals AI) | Not measured | 68.6% | Only Hy4 preview measured |
| MedScribe (Vals AI) | Not measured | 83.6% | Only Hy4 preview measured |
| IFBench | 66.5% | Not measured | Only Step 3.5 Flash measured |
| Long context reasoning (AA-LCR) | 63.0% | Not measured | Only Step 3.5 Flash measured |
| LMArena Text | 1403 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: instruction following | 1385 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: creative writing | 1357 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: English | 1417 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: non-English | 1385 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: Chinese | 1446 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: German | 1405 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: Japanese | 1353 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: Korean | 1351 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: French | 1421 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: Spanish | 1419 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: Russian | 1385 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: Polish | 1389 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: multi-turn | 1404 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: longer queries | 1402 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: writing and language | 1372 | Not measured | Only Step 3.5 Flash measured |
| LMArena Text: entertainment and media | 1360 | Not measured | Only Step 3.5 Flash measured |
| Neither model has a result on the other 24 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Step 3.5 Flash | Hy4 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 | Tencent Hy4 preview |
|---|---|---|
| Maker | StepFun | Tencent |
| Weights | Open weights | Open weights |
| Released | January 29, 2026 | August 28, 2026 |
| Context window | 262K | 1.05M |
| Input $/Mtok | $0.10 | $0.834 |
| Output $/Mtok | $0.30 | $2.501 |
| Coding index | Not benchmarked | 44.3 |
| Independent measurements behind it | 0 | 3 |
| Cost per solved task | Not computable | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Step 3.5 Flash better than Hy4 preview for coding?
Only Hy4 preview has a coding score, 44.3 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 8.3x less.
Which is cheaper, Step 3.5 Flash or Hy4 preview?
Step 3.5 Flash costs $0.10 per million input tokens and $0.30 per million output tokens; Hy4 preview costs $0.834 and $2.501. Cost per solved task is known for neither of them.
Which has the bigger context window, Step 3.5 Flash or Hy4 preview?
Hy4 preview, with 1.05M tokens against 262K.
How many benchmarks is the Step 3.5 Flash vs Hy4 preview comparison based on?
0 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 Hy4 preview's on 3. Where only one model has a result, the page says so instead of naming a winner.