StepfunFree

Step 3.5 Flash

API model name: step-3.5-flash:free

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 available on the free tier at no per-token cost. Knowledge cutoff: 2025-05. Access it through the OpenAI-compatible API with one key, alongside 65+ other models on Api.Airforce.

Get an API key View pricing

Pricing

Input / 1M tokens

Free

Output / 1M tokens

Free

Specifications

Provider: Stepfun
Type: chat model
Context window: 128K tokens
Max output: 8K tokens
Knowledge cutoff: 2025-05
Input: text
Output: text

Capabilities

Streaming

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:free as the model.

cURL

curl https://api.airforce/v1/chat/completions \
  -H "Authorization: Bearer $AIRFORCE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "step-3.5-flash:free",
    "messages": [{ "role": "user", "content": "Hello!" }]
  }'

Python

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:free",
    messages=[{"role": "user", "content": "Hello!"}],
)
print(r.choices[0].message.content)

JavaScript

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:free",
  messages: [{ role: "user", content: "Hello!" }],
});
console.log(r.choices[0].message.content);

Live performance

Real throughput and latency across the suppliers serving this model.

Loading live metrics…

All models·Quickstart·Chat API reference