StepFun Launches Step 5 Preview: A 600B-Total, 27B-Active MoE Model With 1M Context for Long-Horizon Agentic Work
StepFun has released Step 5 Preview, its new flagship model for agentic work. The target workloads are software engineering, professional knowledge work, and finance. The main pitch is cost. StepFun team states the model delivers comparable intelligence at a substantially lower task cost. That is the ‘Pareto frontier’ framing in the launch title. Is it deployable? Yes, as a hosted API and on the StepFun platform. Self-hosting waits for open weights. StepFun says open weights land
StepFun released Step 5 Preview, a new artificial intelligence model designed for tasks like software engineering, knowledge work, and finance. The model contains 600 billion total parameters but only activates 27 billion per token, making it sparse and potentially cost-efficient compared to rival models. It supports a 1 million token context window, accepts text, images, and video as input, and is available through an API at $1.00 per million input tokens and $2.70 per million output tokens. Open source weights are scheduled for release on October 15, 2026, allowing others to download and self-host the model on multi-GPU servers.
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