By No Code MBA · Facts checked
- Provider
- StepFun
- Announcement date
- Status at last check
- Generally available
- Model family
- Step 5
- Capabilities
- Text, Image, Coding
What changed
Step 5 Preview is StepFun's flagship agentic model, a sparse mixture-of-experts with 600B total and 27B active parameters and a context of up to 1M tokens shared between input and output. The model card lists text and image input with text output and claims frontier-level results in software engineering and professional knowledge work, especially finance, on GDPval-AA v2.1 and DeepSWE v1.1, though the scores appear only in a chart.
Access and availability
Open weights are on Hugging Face (stepfun-ai/Step-5-Preview-BF16, plus an FP8 checkpoint) under the StepFun Model License 1.0, an Apache-2.0-style license with attribution and commercial-license conditions. It is also offered through the StepFun API Platform, and self-hosting is documented with vLLM, SGLang or Transformers.
Official access documentationWhat you can build
Evaluate it for long-horizon coding and agentic workflows through the StepFun API. The 1M context window makes it suited for tasks that require sustained context across many turns.
Limitations
Still labeled a preview. Self-hosting needs at least 4 B300 or 8 H200 GPUs for FP8, StepFun says 1M-token requests are not guaranteed on listed configurations, and the two-node BF16 Transformers path is not validated end to end.