Step 3.5 Flash
API model name: step-3.5-flash
Step 3.5 Flash is StepFun's chat model, served on the Api.Airforce unified API. It has a 128K-token context window. It is priced at $0.11 per million input tokens and $0.32 per million output tokens. That is below the provider's $0.10 official input rate. Knowledge cutoff: 2025-05. Access it through the OpenAI-compatible API with one key, alongside 100+ other models on Api.Airforce.
Pricing
Api.Airforce price vs. the provider's official rate.
Specifications
- Provider
- StepFun
- Type
- chat model
- Context window
- 128K tokens
- Max output
- 8K tokens
- Knowledge cutoff
- 2025-05
- Input
- text
- Output
- text
Capabilities
Benchmarks
Independent evaluations and measured speed from Artificial Analysis.
Step 3.5 Flash 2603
Source: Benchmark data by Artificial Analysis (artificialanalysis.ai)
What is Step 3.5 Flash used for?
- Chatbots & assistants — conversational AI, drafting, summarizing and Q&A.
- Real-time experiences — stream tokens for responsive chat and apps.
Step 3.5 Flash vs. similar models
| Model | Intelligence | Context | Input / 1M | Output / 1M |
|---|---|---|---|---|
| Step 3.5 Flash | 26.5 | 128K | $0.11 | $0.32 |
| Step 3.7 Flash | 30.9 | — | $15.60 | $15.60 |
| Claude Opus 4.6 | 44.9 | — | $2.50 | $12.50 |
| Claude Opus 4.7 | 55.0 | 1M | $2.50 | $12.50 |
Prices are Api.Airforce pay-as-you-go rates per 1M tokens. Context is the maximum input length.
Related models
Step 3.5 Flash — frequently asked questions
- How much does Step 3.5 Flash cost?
- Step 3.5 Flash is billed pay-as-you-go at $0.11 per 1M input tokens and $0.32 per 1M output tokens. There is no subscription — you only pay for what you use.
- What is the context window of Step 3.5 Flash?
- Step 3.5 Flash supports a context window of up to 128K tokens. It can return up to 8K tokens in a single response.
- What can Step 3.5 Flash do?
- Step 3.5 Flash is StepFun's chat model, accessible through the Api.Airforce API.
- Is Step 3.5 Flash free to use?
- Step 3.5 Flash is a paid, pay-as-you-go model — no subscription, you are only charged for usage.
- How do I use Step 3.5 Flash via the API?
- Step 3.5 Flash is OpenAI-compatible. Point any OpenAI SDK at https://api.airforce/v1 and pass the model ID step-3.5-flash with your Api.Airforce API key.
- Who makes Step 3.5 Flash?
- Step 3.5 Flash is StepFun's chat model, served through the unified Api.Airforce gateway alongside 100+ other models.
Use Step 3.5 Flash via the API
OpenAI-compatible — point any OpenAI SDK at https://api.airforce/v1 and pass step-3.5-flash as the model.
curl https://api.airforce/v1/chat/completions \
-H "Authorization: Bearer $AIRFORCE_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "step-3.5-flash",
"messages": [{ "role": "user", "content": "Hello!" }]
}'from openai import OpenAI
client = OpenAI(base_url="https://api.airforce/v1", api_key="$AIRFORCE_API_KEY")
r = client.chat.completions.create(
model="step-3.5-flash",
messages=[{"role": "user", "content": "Hello!"}],
)
print(r.choices[0].message.content)import OpenAI from "openai";
const client = new OpenAI({ baseURL: "https://api.airforce/v1", apiKey: process.env.AIRFORCE_API_KEY });
const r = await client.chat.completions.create({
model: "step-3.5-flash",
messages: [{ role: "user", content: "Hello!" }],
});
console.log(r.choices[0].message.content);