StepFun launches Step 5 Preview API and Studio for 600B-parameter MoE model with claimed 1M-token context
Summary
StepFun launches its Step 5 Preview API and Studio for a 600B-parameter sparse MoE model claiming a 1M-token context window, though public BF16 weights are not scheduled until October 15, 2026.
Key Points
- StepFun launches the Step 5 Preview API and Studio for its 600B-parameter sparse MoE flagship, with 27B active parameters per token and a claimed 1M-token context window.
- The Hugging Face repository contains only a .gitattributes file, with no weights, license, model card or configuration; StepFun schedules open BF16 weights for October 15, 2026.
- Artificial Analysis scores Step 5 Preview 44 on its Intelligence Index, ranking it 24th of 200 models, while pricing is $1.00 per million input tokens and $2.70 per million output tokens.