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
Context262,144
Tagsreasoning, tool-use, implicit-caching, vision
Overall
Rank #190 across 600
26.0
Coding
No rank
n/a
Blended Price
Rank #43 across 379
$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
Max Output65,536
Streaming speed is not measured for this model yet.
Pricing
Blended$0.150/M
Input$0.100/M
Output$0.300/M
Catalog$0.090/M in / $0.300/M out
Metadata
Modalities
All Benchmarks
| Metric | Domain | Value | Rank |
|---|---|---|---|
| Artificial Analysis Intelligence Index | overall | 26.0 | #190 |
| GPQA | reasoning | 82.6% | #134 |
| Humanity's Last Exam | reasoning | 22.6% | #103 |
| SciCode | coding, reasoning | 38.5% | #185 |
| Blended Price |