How much does Step 3.5 Flash cost?

Step 3.5 Flash is billed pay-as-you-go at $0.12 per 1M input tokens and $0.34 per 1M output tokens. There is no subscription — you only pay for what you use.

What can Step 3.5 Flash do?

Step 3.5 Flash supports Tool calling.

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.

StepFunPaidOperational

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. Capabilities include Tool calling. It is priced at $0.12 per million input tokens and $0.34 per million output tokens. That is below the provider's $0.10 official input rate. Access it through the OpenAI-compatible API with one key, alongside 100+ other models on Api.Airforce.

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Pricing

Input / 1M tokens

$0.12

Output / 1M tokens

$0.34

Cache read / 1M tokens

$0.01

Official input rate

$0.10

Official output rate

$0.30

Api.Airforce price vs. the provider's official rate.

Specifications

Provider: StepFun
Type: chat model

Capabilities

Tool calling

Benchmarks

Independent evaluations and measured speed from Artificial Analysis.

Intelligence Index

17.0/100

GPQA Diamond83%

Humanity's Last Exam25%

τ²-bench87%

Terminal-Bench Hard33%

LCR63%

IFBench67%

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.
Agents & automation — function calling and tool use for multi-step workflows.

Step 3.5 Flash vs. similar models

Model	Intelligence	Context	Input / 1M	Output / 1M
Step 3.5 Flash	17.0	—	$0.12	$0.34
Step 3.7 Flash	19.5	—	$15.60	$15.60
Step 5 Preview	43.7	—	$1.10	$2.97
Voxtral Small Latest	—	—	Free	Free

Prices are Api.Airforce pay-as-you-go rates per 1M tokens. Context is the maximum input length.

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 $0.12 per 1M input tokens and $0.34 per 1M output tokens. There is no subscription — you only pay for what you use.
What can Step 3.5 Flash do?: Step 3.5 Flash supports Tool calling.
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.

All models·Quickstart·Chat API reference

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

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!" }]
  }'

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