StepFun
Step 3.5 Flash 2603
Step 3.5 Flash is an open-source reasoning model by StepFun with 196B total parameters (11B active) using Mixture of Experts. It features a 256K context window, deep reasoning, tool calling, and agentic capabilities, achieving 97.3 on AIME 2025 and 74.4% on SWE-bench Verified.
StepFun researchModel Snapshot
TypeLanguage
ReleaseJan 29, 2026
Context262,114
Tagsreasoning, tool-use, implicit-caching
Overall
Rank #88 across 526
38.5
Coding
Rank #99 across 436
34.6
Blended Price
Rank #52 across 357
$0.150/M
Strength Profile
Percentile score by analysis domain.
* Cost is inverted: lower input, output, and blended prices rank higher.
Benchmark Percentiles
Higher bars mean stronger relative placement.
Model Details
Runtime
Output Speed231 tok/s
First Token0.82s
Max Output262,114
Pricing
Blended$0.150/M
Input$0.100/M
All Benchmarks
| Metric | Domain | Value | Rank |
|---|---|---|---|
| Artificial Analysis Intelligence Index | overall | 38.5 | #88 |
| Artificial Analysis Coding Index | coding | 34.6 | #99 |
| GPQA | reasoning | 82.6% | #95 |
| Humanity's Last Exam | reasoning | 22.6% | #66 |
| SciCode |