StepFun Launches Step 5 Preview: A 600B-Total, 27B-Active MoE Model With 1M Context for Long-Horizon Agentic Work

StepFun unveiled Step 5 Preview, a sparse MoE AI model with 600 billion parameters total and 27 billion active per token, featuring a 1 million token context window for complex tasks in software, knowledge work, and finance. API access is available now, with open weights planned for October 15, 2026.