StepFun: Step 3.5 Flash
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
262K tokens
Context Window
Proprietary
License
Jan 29, 2026
Released
💰 Pricing
Input
$0.10
per 1M tokens
Output
$0.30
per 1M tokens
API Available
This model is accessible via API for integration into your applications.
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