Step 5 Preview
StepFun · 604.3B parameters
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 were published on Hugging Face under the StepFun Model License 1.0, with a checkpoint of 604,339,504,832 parameters excluding FP8 quantization-scale tensors. The exact public preview release day is unconfirmed.