604BStepFun is a Shanghai-based AI company founded in April 2023 by Jiang Daxin, Zhu Yibo and Jiao Binxing. It develops the Step series of language and multimodal models, including Step 3.5 Flash.
- Founded
- 2023
- Type
- Private company
- Founders
- Jiang Daxin, Zhu Yibo and Jiao Binxing
- AI lab
- Inference provider
- 3 hosted endpoints
Model family
Step
StepFun is a Shanghai-based AI company founded in April 2023 by Jiang Daxin, Zhu Yibo and Jiao Binxing. It develops the Step series of language and multimodal models, including Step 3.5 Flash.
Latest Step models
Models in this family
4 catalogued models
4 models · 1–4
| Select models to compare | Model | Released | Context | Input /M | Output /M | Parameters | Type | I/O | Openness |
|---|---|---|---|---|---|---|---|---|---|
| Step 5 PreviewStepFun | September 16, 2026 | 1M | $1.00 | $2.70 | 604B | Text | text, image, video → text | Closed | |
| Step 3.7 FlashStepFun | May 29, 2026 | 262K | $0.20 | $1.15 | 201B | Text | text, image, video → text | Open weights | |
| Step 3.5 Flash 2603StepFun | April 2, 2026 | 256K | — | — | — | Text | text → text | Open weights | |
| Step 3.5 FlashStepFun | January 29, 2026 | 262K | $0.10 | $0.30 | 199B | Text | text → text | Open weights |