StepFun: Step 3.5 Flash (free)
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.
Undisclosed
Parameters
256K tokens
Context Window
Proprietary
License
Jan 29, 2026
Released
API Available
This model is accessible via API for integration into your applications.
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