StepFun launches Step 5 Preview: 600B MoE, 27B active, 1M context at 65% lower cost
realmrfakename · x · 2026-09-21
China's StepFun has launched Step 5 Preview, a 600B-parameter MoE model with just 27B active parameters and a 1M-token context window.
- Scores 44 on Artificial Analysis, matching Kimi K3 (max) while costing roughly 65% less per task, putting it on the cost/intelligence Pareto frontier
- Available via API now, with open weights promised for October 15
Related event: StepFun Launches Step 5 Preview: 600B MoE Flagship, Open-Weights on Oct 15(17 posts)→
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