StepFun releases Step 5 Preview, an open-weight agent model with a 1M context

StepFun has published Step 5 Preview on Hugging Face, a mixture-of-experts model with 600B total and 27B active parameters, a context window of up to 1 million tokens, and text and image input. StepFun says it is built for agentic work such as coding and long tool-using tasks, with particular strength in finance; the benchmark results are its own. The weights use the StepFun Model License 1.0, which is free to use and modify but requires a "Powered by StepFun AI" notice for products above 100 million monthly active users or $20 million in monthly revenue, and a separate commercial licence for device makers and for model-as-a-service businesses with more than $20 million a year in revenue. Running it needs a server with at least four B300 or eight H200 GPUs.