Step 3.5 Flash
Step 3.5 Flash is StepFun’s sparse language model optimized for reasoning, coding, and tool-driven agents. A 3:1 sliding-window/full-attention pattern reduces long-context inference cost while multi-token prediction increases throughput. The model activates 11B of 196B parameters and supports 256K context. Public access predates the February 12 technical-blog update; repositories and contemporaneous API catalogs establish the early-February release. The full weight footprint, context length, and selected reasoning mode affect deployment cost and latency.
2026-02-02
196B total, 11B active
Hybrid-attention Mixture of Experts
Apache-2.0
Specifications
- Parameters
- 196B total, 11B active
- Architecture
- Hybrid-attention Mixture of Experts
- License
- Apache-2.0
- Context Window
- 262,144 tokens
- Type
- text
- Modalities
- text
Benchmark Scores
Advanced Specifications
- Model Family
- Step
- API Access
- Not Available
- Chat Interface
- Not Available
Capabilities & Limitations
- Capabilities
- reasoningcodingtool use
- Known Limitations
- Sparse models still require storage for all weightsParallel reasoning consumes additional inference computeEvaluation settings strongly affect reported scores
- Notable Use Cases
- private assistantscoding or document researchmultimodal experimentation
