StepFun Provider

Step 5 Preview is StepFun's next-generation flagship foundation model for real-world tasks, with a focus on coding and professional knowledge work. It natively supports text, image, and video input, offers a 1M-token context window, and is well suited for workflows that require processing large amounts of information, using tools, and driving tasks through to deliverable results.

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.

Step 3.7 Flash is StepFun's latest high-efficiency multimodal Mixture-of-Experts model. It pairs a 196B-parameter language backbone with a vision encoder for native image and video understanding, activating roughly 11B parameters per token. The model supports a 256K context window and exposes selectable reasoning levels (high/medium/low), letting callers trade off speed, cost, and depth of reasoning.

Designed for coding, agentic workflows, structured outputs, and long-context productivity tasks.