Step 3.5 Flash
Open Source
About
Step 3.5 Flash is StepFun's most capable open-source foundation model. Its sparse Mixture of Experts architecture activates only 11B of 196B total parameters per token, making it highly efficient at long contexts. Achieves 60.47% on SWE-Bench Verified and 56.2% on SWE-Pro, competing with frontier closed models on agentic coding benchmarks. Supports 256K token context.
Capabilities
VisionMultimodalReasoningFunction CallingTool UseStructured OutputsCode Execution
Providers(1)
| Provider | Input (per 1M) | Output (per 1M) | Type | |
|---|---|---|---|---|
| OpenRouter | $0.10 | $0.30 | Serverless |
Specifications
FamilyStep
Released2026-01-29
Parameters196B (11B active)
Context256K
ArchitectureMixture of Experts
Specializationgeneral
Trainingpretraining