One agent session
1M input tokens and 100K output tokens, no caching.
- Input1M x $0.10 = $0.10
- Output0.1M x $0.30 = $0.03
$0.13per session
StepFun - Open weights
Step 3.5 Flash pricing and specs
Step 3.5 Flash is an open-weights model from StepFun that costs $0.10 per 1M input tokens and $0.30 per 1M output tokens on the first-party API, with a 256K-token context window.
Last verified from platform.stepfun.ai. All sources
- Input / 1M
- $0.10
- Output / 1M
- $0.30
- Context
- 256K tokens
- Weights
- Open
Pricing per 1M tokens
| Item | Price / 1M tokens |
|---|---|
| Input | $0.10 |
| Output | $0.30 |
| Cache read | $0.02 |
Note: StepFun international platform, priced in USD. Text-only reasoning model, 196B total / 11B active sparse MoE. Context listed as 256K tokens (recorded as 256,000). max output is not stated because no primary page states a fixed output cap (max_tokens defaults to no limit, bounded by context length). The release date is left blank: the launch post shows only a '2026-02-12 updated' stamp, not an original release date. Not listed in the Vercel AI Gateway model list on 2026-10-17.
Specs
- Context window
- 256,000 tokens
- Provider
- StepFun
- API model id
step-3.5-flash- Weights
- Open weights
- License
- Apache-2.0
- Weights download
- huggingface.co
What Step 3.5 Flash costs in practice
Worked from the standard list rates above, with the math shown so you can swap in your own token counts.
A chat app
10,000 requests a day at 2K input and 500 output tokens each.
- Input20M x $0.10 = $2.00
- Output5M x $0.30 = $1.50
$3.50per day
$105.00 per 30-day month
The same session at a 90% cache hit
90% of the input is read from the prompt cache. The one-time cache write premium is not included.
- Cached input0.9M x $0.02 = $0.018
- Uncached input0.1M x $0.10 = $0.01
- Output0.1M x $0.30 = $0.03
$0.058per session
Compare with
| Model | Input / 1M | Output / 1M |
|---|---|---|
| Step 3.5 Flash (this page) | $0.10 | $0.30 |
| Step 3.5 Flash 2603StepFun | $0.10 | $0.30 |
| Hy-MT2-PlusTencent | $0.074 | $0.295 |
| Hy-MT2-ProTencent | $0.074 | $0.295 |
| MiMo-V2.6-FlashXiaomi MiMo | $0.14 | $0.28 |
| Step 3.7 FlashStepFun | $0.20 | $1.15 |
| Step-1o Turbo VisionStepFun | $0.36 | $1.15 |
| Step 5 PreviewStepFun | $1 | $2.70 |
Related reading
- Step 5 Preview: Pricing, Benchmarks and the October 15 Open WeightsStep 5 Preview is StepFun's 600B MoE with 27B active and a 1M window. What it scores, what a session costs, and what to check before the October 15 weights.
- Build Your First Agent with Vercel eve: A Step-by-Step TutorialBuild your first AI agent with Vercel eve: scaffold a project, add a typed tool with defineTool, run it locally, call the session API and deploy to Vercel.
- Agent Architecture: Building Multi-Step AI Workflows That Survive ProductionAgent architecture for multi-step Claude workflows: loop patterns, state management, error recovery, and the production gotchas that break agents at scale.
- The Agent Reliability Cliff: Why Your 10-Step Chain Only Succeeds 20% of the TimeThe agent reliability cliff: 85% per-step success compounds to about 20% over 10 steps. Why long chains collapse, and six patterns that fight the decay.
FAQ
How much does Step 3.5 Flash cost per million tokens?
Step 3.5 Flash costs $0.10 per 1M input tokens and $0.30 per 1M output tokens on StepFun's first-party API, per platform.stepfun.ai on October 17, 2026. Per 1M tokens, cache reads cost $0.02.
What is Step 3.5 Flash's context window?
Step 3.5 Flash has a 256,000-token context window.
Are Step 3.5 Flash's weights open?
Yes. Step 3.5 Flash's weights are published at https://huggingface.co/stepfun-ai/Step-3.5-Flash under the Apache-2.0.
Sources
Last verified from platform.stepfun.ai.
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