StepFun: step-3.5-flash

About step-3.5-flash

StepFun step-3.5-flash — text-only reasoning model with 256K context for logic, mathematics, software engineering, and deep research. Reasoning depth is selectable per request (low, medium, high), with tool calling, JSON Schema structured output, streaming, and prompt caching.

Quickstart

Copy-paste API request.

curl -X POST https://api.chinaapi.ai/v1/chat/completions \
  -H "Authorization: Bearer $CHINAAPI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "step-3.5-flash",
    "messages": [
      {"role": "user", "content": "Summarize the main tradeoffs for this API workload."}
    ]
  }'

import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["CHINAAPI_API_KEY"],
    base_url="https://api.chinaapi.ai/v1",
)

response = client.chat.completions.create(
    model="step-3.5-flash",
    messages=[
        {"role": "user", "content": "Summarize the main tradeoffs for this API workload."}
    ],
)
print(response.choices[0].message.content)