Step 3.5 Flash
StepFun · 2026-02-02 · 199.4B parameters
Step 3.5 Flash is StepFun's open-weight language reasoning model released in February 2026. It is marketed as a 196.81B sparse Mixture-of-Experts model with about 11B parameters active per token; the complete released checkpoint contains 199,384,301,376 parameters. It supports a 256K-token context window and targets mathematical reasoning, software engineering, deep research, and agentic tool use.