StepFun Launches Step 5 Preview: A 600B-Total, 27B-Active MoE Model With 1M Context for Long-Horizon Agentic Work
600B parameters, 27B active, 1M context. StepFun's Step 5 Preview targets long-horizon agentic work at $1/1M input tokens.
Why it matters
StepFun enters the sparse MoE race with a large-context model positioned for agent and knowledge-work use cases. The pricing and multimodal capabilities signal competitive pressure in the frontier lab space, and the October open-weight timeline affects the open-model landscape.
The key facts
7 to know600B total parameters, 27B active per token (sparse MoE architecture)
1M token context window
Multimodal: text, image, video input
API pricing: $1.00 per 1M input tokens, $2.70 per 1M output tokens
Open weights scheduled October 15, 2026
Target use cases: software engineering, professional knowledge work, finance, long-horizon agentic work
API access live now (as of Sep 2026)
Go to the source
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Publisher excerpt: StepFun has released Step 5 Preview, a sparse Mixture-of-Experts model with 600B total parameters and 27B active per token. It supports a 1M-token context window and accepts text, image, and video input. The model targets long-horizon agentic work in software engineering, professional knowledge…