Step 5 Preview is StepFun's flagship model for agentic work, built on a sparse Mixture-of-Experts architecture (27B active / 600B total parameters). It performs strongly in software engineering and professional knowledge work, with particular strength in finance.
It is designed for extended tasks that span large codebases and documents, using tools and refining results over multiple steps.
This model is hosted by one provider. OpenRouter forwards every request to it directly — no routing decisions to make.
Pricing
The average price customers actually pay for this model, next to the prices providers post. Caching and discounts mean the price actually paid is often well below the listed one.
Performance
Throughput is how fast the model writes (tokens per second — higher is better). Latency is total round-trip time (lower is better). TTFT is time-to-first-token — how long before you see anything appear (lower is better).
Uptime
Uptime is the percentage of the past 3 days that at least one provider was responding to requests. Availability is the percentage of time that inference was successfully served. OpenRouter continuously monitors and uses the next-best provider when one returns an error.
Apps
Public apps that send the most traffic to this model. Good signal for what real production workloads look like — and a hint at which use cases this model is best suited for. Activity
Token volume and request traffic to this model over time.
API
Drop-in code to call this model. OpenRouter's API is OpenAI-compatible — most SDKs work by just swapping the base URL. The only thing that changes between models is the model slug below.
Uptime (3d)The model was reachable. Request routed to a provider.
99.94%
Availability (3d)The model returned inference from any provider. Errors and empty responses count against it.
99.43%
Availability over the last 3 days
Last 72 hours
Availability 99.43%
3 Days Ago2 Days AgoYesterdayNow
Availability over the last 24 hours
OpenRouter Availability
99.75%
When an error occurs in an upstream provider, we can recover by routing to another healthy provider, if your request filters allow it. You can access per-provider uptime data programmatically through the Endpoints API. Learn more about our load balancing and customization options.
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Frequently asked questions
What is 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). It performs strongly in software engineering and professional knowledge work, with particular strength in finance. It is designed for extended tasks that span large codebases and documents, using tools and refining results over multiple steps.
How much does Step 5 Preview cost?
Step 5 Preview costs $1.00/M input tokens and $2.70/M output tokens, with separate rates for Cache Read at $0.05/M tokens.
What is the context length of Step 5 Preview?
Step 5 Preview has a 1,000,000 token context window. It supports up to 64,000 completion tokens.
Does Step 5 Preview support tool calling and structured outputs?
Yes. Step 5 Preview accepts tools for function calling. It also supports structured outputs via a JSON schema in response_format.
What inputs and outputs does Step 5 Preview support?
Step 5 Preview accepts text, images, and video as input and returns text.