Summary

Step 5 Preview has 600 billion total parameters and 27 billion active parameters, according to the launch report. StepFun opened API access immediately and said model weights would follow on October 15.

Why it matters

The release adds another large Chinese model to the race for long-context and multimodal capability while keeping inference costs below a dense 600B model. The preview status and absence of independent evaluations leave its practical performance uncertain.

Sources