Step 5 Preview
Step 5 Preview is StepFun's flagship model for agentic work, built on a sparse Mixture-of-Experts architecture (27B active / 600B total parameters).
Specifications
| Lab | StepFun |
|---|---|
| Context window | 1M tokens |
| Input price | $1.00/1M |
| Output price | $2.70/1M |
| Release | Sep 2026 |
Strengths
- Frontier-class agentic coding at open-tier pricing ($1.00 in / $2.70 out per 1M tokens)
- 1M-token context window with text, image, and video input
- Standout finance-domain results (FrontierFinance 66.4%, ahead of open peers)
- Fast inference for a reasoning model with adjustable reasoning effort (low/medium/high)
- Native tool calling, structured output, and prompt caching for agent workflows
Weaknesses
- All launch benchmarks are vendor-reported with no technical report published yet
- Verbose output inflates output-token costs on high-effort runs
- Trails closed-frontier models on the hardest long-horizon coding tasks
Best for
- Agentic coding workflows and long-horizon software engineering tasks
- Financial analysis and research over large document sets
- Cost-sensitive long-context applications with repeated prompts
In Depth: Step 5 Preview
Summary
Step 5 Preview is an AI model from StepFun.
Released in Sep 2026. It takes text, image, and video input and produces text output, with a context window of 1M tokens. Input pricing is $1.00 per 1M tokens and output is $2.70 per 1M tokens on OpenRouter.