StepFun's 600B-parameter open-weights MoE model built for long-running AI agents, coding, and finance research.
Step 5 Preview announcement
1 / 2Overview
What is Step 5 Preview?
600B open weights, trained for long-running agents
Step 5 Preview is StepFun's open-weights Mixture-of-Experts model: 600B total parameters with 27B active per token and 1M-token context, released as open weights. It is designed for long-running agent tasks such as 24-hour GPU kernel optimization, full software-engineering workflows (StepCodeBench), and finance research (FrontierFinance, FinStepBench). Available via Hugging Face and GitHub for self-hosting with vLLM, SGLang, or Transformers, plus StepFun's OpenAPI and AI Studio. Access is via paid Step Plan subscriptions (from $6.99/month) or pay-as-you-go OpenAPI; new free trials are currently closed.
Platforms and languages
Step 5 Preview Availability
Platforms
Languages
Capabilities
Step 5 Preview Key Features
600B open-weights MoE
600B total parameters, 27B active per token, 1M-token context; weights published for self-hosting.
Built for long-horizon agents
Trained for extended agent runs such as day-long GPU kernel optimization and long game rollouts.
Full-stack code ability
Covers the software engineering lifecycle, evaluated on StepCodeBench across 553 repos and 29 languages.
Finance specialization
Strong on finance research via FrontierFinance external evals and FinStepBench (LiveSearch, CorporateValuation, DeepResearch).
Flexible deployment
Self-host with vLLM, SGLang, or Transformers, or use StepFun OpenAPI and AI Studio.
Best for
Who uses Step 5 Preview?
Developers and enterprises building AI agents
Run long-horizon agent tasks, code workflows, and finance research on an open-weights model
Plans and access
Step 5 Preview Pricing
Paid
Step Plan from $6.99/mo; OpenAPI pay-as-you-go. Free trial currently closed.
Common questions
Step 5 Preview FAQs
What is Step 5 Preview?
StepFun's open-weights MoE flagship model for agentic work: 600B parameters, 27B active per token, 1M context.
How can I access the weights?
The open weights were published for download via Hugging Face and GitHub, deployable with vLLM, SGLang, or Transformers.
How is it priced?
Via Step Plan subscriptions (Mini $6.99, Plus $9.99, Pro $29 per month) or pay-as-you-go OpenAPI.
Is there a free trial?
New free trial signups are currently closed due to capacity, per StepFun's service update.
What is it best at?
Long-running agent tasks, software engineering workflows, and finance research.
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