Overview
StepFun’s next flagship preview for agents and professional work, using sparse MoE with 600B total parameters, 27B active, and 1M context.
Step 5 Preview
StepFun’s next flagship preview for agents and professional work, using sparse MoE with 600B total parameters, 27B active, and 1M context.
The official page currently says Step 5 Preview is available through products and the API; open weights are planned for 2026-10-15, so it remains Preview and is not open-weight yet.
MODEL NUMBER341
- First public date
- 2026-09-20
- Organization
- StepFun
- Family
- Step
01
Specifications
Only published specifications are shown.
02
Overview
Why it mattered
Step 5 Preview advances StepFun’s model line to larger-scale long-horizon agents and professional knowledge work, while its open weights are not yet available.
PreviousStep 3.7 Flash198B · 256K ctx
CurrentStep 5 Preview600B · 1M ctx
04
Architecture & capabilities
Model capabilities
ReasoningCodingTool useLong contextVision
Connected tools
Computer use
05
Release history
Step 5 Preview entered product and API preview on StepFun; open weights are not yet released.
View source06
Related models
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07
Sources
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