Compare Step 3.5 Flash from StepFun and Step 5 Preview from StepFun on key metrics including benchmarks, price, context length, and other model features. Access both models and hundreds of others through the AIHubMix API.
Step 3.5 FlashStep 5 Previewstep-3.5-flash is stepfun's flagship inference model, designed for high-complexity tasks that require deep reasoning and fast execution. It excels at decomposing multi-step problems, performing tool calls, and maintaining consistency across massive datasets. It is the preferred choice for complex workloads such as long-context agents, advanced software engineering, and end-to-end research automation.
Step 5 Preview is StepFun's next-generation flagship base model designed for real-world tasks, with a focus on programming and professional expertise.
Prices are per million tokens. Time to First Token and throughput are rolling averages measured on AIHubMix.
Promotional prices show the discounted rate; see each model page for promotion windows.
Daily traffic served through AIHubMix — how demand for each model is trending.
Measured on real AIHubMix traffic, hourly buckets. Gaps mean no traffic in that hour.
Estimate your monthly bill for the same workload on each model.
Monthly = daily × 30. Discounted rates applied where a promotion is active.
Step 3.5 Flash: $0.33/M output tokens; Step 5 Preview: $3.0888/M. Use the cost calculator above to estimate your own workload.
Step 3.5 Flash: 1.4s time to first token measured on AIHubMix; see the live performance charts above for how each model behaves across the day.
Step 3.5 Flash accepts 256,000 and Step 5 Preview accepts 1,000,000 input tokens.
Step 3.5 Flash at 36.6 tok/s and Step 5 Preview at 31.3 tok/s, measured as output throughput on AIHubMix — a separate metric from time to first token.
Step 3.5 Flash accepts text input; Step 5 Preview accepts text, image and video input.
Yes. AIHubMix serves every model on this page behind one OpenAI-compatible endpoint, so switching between them is a one-line change to the model field — no second account, key or SDK.
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