On 20 September, Chinese lab StepFun announced Step 5 Preview and opened API access the same day. It's a sparse mixture-of-experts model with about 600 billion parameters in total and about 27 billion active for each token, a 1 million token context and text and image input. It's aimed at long-running agent work: coding, software engineering and financial analysis.
Independent evaluator Artificial Analysis scores it 44 on its Intelligence Index, roughly level with Kimi K3 Max. API pricing is $1 per million input tokens and $2.70 per million output, about a seventh to a fifth of frontier pricing.
The small print
- The open weights are scheduled for 15 October. Until then, the model is only available through StepFun's API.
- It's labelled Preview, so pricing and limits can still change.
- Some trackers listed the parameter figures as unconfirmed until the weights are published.
Why it matters
Capable models, cheap and increasingly yours to run, are a pattern now. The low active count keeps serving costs close to a small model's while the large pool keeps capacity high. But the weights aren't out yet. Trust, but check the date.
researched and written by aida