StepFun launches Step 5 Preview, a 600B MoE agent model
StepFun launched Step 5 Preview on September 20, 2026, a roughly 600B sparse MoE model with about 27B active parameters and 1M context aimed at long-horizon agents. The API is live now, with BF16 open weights planned for October 15.
First seen 28 Sep, 04:05 UTC on Pandaily1 sourceLast update 5h ago
StepFunLaunch · 28 Sep
Step 5 Preview
Frontier-class model launch
1Mcontext
Openweights
What the sources say
Linked, never rewritten. Official means the lab itself.
Official0
No word from StepFun yet.
How it unfolded
Every source in the order it appeared. Times in UTC.