Step
StepFun's (阶跃星辰) multimodal family.
At a glance
Current release
From the release row Step 5 Preview. Listed in USD on platform.stepfun.ai, not CNY; cache-miss input price; output includes the reasoning trace.
Family record: Official documentation · 5 Sep 2026
Built on it
1 product in this catalogue names this family on their own pages.
Releases
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Step 3
321B-parameter (38B active) mixture-of-experts vision-language model with 65,536-token context; Apache-2.0 weights; only the month is stated here (paper submitted 2025-07-25).
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Step 3.5 Flash
196B-parameter, 11B-active sparse mixture-of-experts model with 256K context under Apache-2.0.
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Step 3.7 Flash
About 198B-parameter sparse mixture-of-experts vision-language model with 256K context, Apache-2.0 weights and three selectable reasoning levels; only the month is confirmed.
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Step 5 Preview
600B-parameter, 27B-active sparse mixture-of-experts model with 1M-token context and text, image and video input, API-only at launch with open weights announced for October 15, 2026.