StepFun: Step 3.5 Flash
Stepfunllm
Published January 29, 2026
About
Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parameters per token. It is a reasoning model that is incredibly speed efficient even at long contexts.
Try StepFun: Step 3.5 Flash
Test this model in the Sandbase Playground with your own prompts.
Open in Playground