Step 5 Preview
StepFun released Step 5 Preview, its flagship agentic model built on a sparse MoE architecture with 600B total parameters (27B active) and a 1M token context window. It targets software engineering, professional knowledge work, and finance, and is available via the StepFun API. Open weights are expected by October 15, 2026.
For buildersEvaluate it for long-horizon coding and agentic workflows through the StepFun API. The 1M context window makes it suited for tasks that require sustained context across many turns.