Step 5 Preview
StepFun
Step 5 Preview is StepFun's hosted multimodal model for software engineering, professional work, and long-horizon agents. It supports text, image, and video input with low, medium, and high reasoning effort. The vendor describes a 600B-class sparse mixture of experts; open weights are announced for October 15, 2026 and were not available when this record was researched. The exact public preview release day is unconfirmed.