Step 5 Preview
- Price
- Freemium
- API
- Yes
- Weights
- Yes
WHAT IT DOES
Step 5 Preview is StepFun's flagship model, published as downloadable weights on October 15, 2026 after an earlier hosted release. It is a sparse mixture-of-experts model with about 600 billion total parameters and 27 billion active per token, takes text and images as input, returns text, and supports up to one million tokens of context, aimed at coding and long professional work. Weights ship in BF16 and FP8 under the StepFun Model License 1.0, which StepFun describes as Apache-2.0-style with additional attribution and commercial-licence conditions. The model card gives example deployments of four B300 or eight H200 GPUs for FP8, and twice that for BF16, with vLLM, SGLang or Transformers.
WHY WE PICKED IT
It is one of the largest open-weight models you can actually download, and it is built for the long agent runs that most open models still struggle with. The licence is not plain Apache 2.0 and the hardware bill is serious, so it is listed for teams that can run it, not as a default.
QUICK FACTS
STRENGTHS
- ✓About 600B parameters with only 27B active per token
- ✓1M-token context
- ✓Text and image input
- ✓BF16 and FP8 checkpoints with vLLM, SGLang and Transformers recipes
- ✓Hosted API alongside the downloadable weights
LIMITATIONS
- ⚠StepFun Model License 1.0 adds attribution and commercial-licence conditions
- ⚠Needs multiple high-memory GPUs even in FP8
- ⚠A preview release; the model card gives benchmark results only as a chart
- ⚠No third-party inference provider serves it yet
GETTING STARTED
Try it first through the StepFun API platform. To self-host, start from the FP8 checkpoint on four B300 or eight H200 GPUs with vLLM or SGLang, following the deployment notes on the model card. Read LICENSE.txt before commercial use, because the licence adds conditions on top of its Apache-style base.
OFFICIAL LINKS
SIMILAR TOOLS
PRICING
Free tier includes limited features. Paid plans unlock full access, higher usage limits, and commercial usage rights.
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EXPLORE ALTERNATIVES
Compare Step 5 Preview with 5+ similar llms AI tools.
FREQUENTLY ASKED QUESTIONS
Is Step 5 Preview free?
Step 5 Preview offers a free tier with optional paid upgrades.
Does Step 5 Preview have an API?
Yes, Step 5 Preview offers an API for programmatic integration.
What is Step 5 Preview best for?
Step 5 Preview is best for Best Large Open Agent Model. Step 5 Preview is StepFun's flagship model, published as downloadable weights on October 15, 2026 after an earlier hosted release. It is one of the largest open-weight models you can actually download, and it is built for the long agent runs that most open models still struggle with. The licence is not plain Apache 2.0 and the hardware bill is serious, so it is listed for teams that can run it, not as a default.
What platforms does Step 5 Preview support?
Step 5 Preview supports api, local.
Is Step 5 Preview open source?
Yes, Step 5 Preview is open source. You can access the source code, contribute, and deploy it on your own infrastructure.
How do I get started with Step 5 Preview?
Try it first through the StepFun API platform. To self-host, start from the FP8 checkpoint on four B300 or eight H200 GPUs with vLLM or SGLang, following the deployment notes on the model card. Read LICENSE.txt before commercial use, because the licence adds conditions on top of its Apache-style bas...
How do I use Step 5 Preview?
Step 5 Preview is a large language model for text generation, analysis, and conversation. Use the API for programmatic access. Enter prompts or questions to get responses. It excels at about 600b parameters with only 27b active per token.
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