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Step 3.5 Flash

StepFunOpen-weight

262K context · — params · —

stepfun/step-3-5-flash

Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parameters per token....

Cheapest blended: ¥0.15 / 1M tokens on StepFunGet custom quote

Reachability & verification

Live reachability

Probing…

Target (StepFun): https://api.stepfun.com/v1

Live reachability probe

Measured in real time from the ModelHub gateway egress to this model's API endpoint. Green means reachable right now. Overseas reference latencies are estimates; the live probe is the proof of current reachability.

Pricing across providers

1

Prices are shown in each provider's billing currency — ¥ (CNY) for Chinese providers, $ (USD) for overseas gateways.

ProviderInput /1MOutput /1MBlendedCtxp50 latencyAPIVerified
StepFunstep-3.5-flash¥0.1¥0.3¥0.15262K OAI119d ago

Works with

CursorClineAiderContinueOpenCodeOpen WebUI

Any OpenAI-compatible client works — point the base URL at the provider endpoint.

Capabilities

chatreasoningcode

Languages: zh, en

Code samples

Python
from openai import OpenAI

client = OpenAI(
    base_url="https://api.stepfun.com/v1",
    api_key="YOUR_API_KEY",
)

resp = client.chat.completions.create(
    model="step-3.5-flash",
    messages=[{"role": "user", "content": "Hello!"}],
)
print(resp.choices[0].message.content)
cURL
curl https://api.stepfun.com/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "step-3.5-flash",
    "messages": [{"role": "user", "content": "Hello!"}]
  }'
Node.js
import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "https://api.stepfun.com/v1",
  apiKey: "YOUR_API_KEY",
});

const resp = await client.chat.completions.create({
  model: "step-3.5-flash",
  messages: [{ role: "user", content: "Hello!" }],
});
console.log(resp.choices[0].message.content);

Technical specs

Context

262K

Max output

66K

Parameters

Release

Training cutoff

License

Similar models

Frequently asked questions

How much does Step 3.5 Flash cost?

The cheapest tracked blended price is ¥0.15 per 1M tokens on StepFun. See the pricing matrix above for input/output splits per provider.

Can I use Step 3.5 Flash from outside China?

Availability depends on the hosting provider. Use our Path Planner on the StepFun page to map a verified official-vs-brokered access path, including payment and KYC constraints.

Is Step 3.5 Flash open source?

Yes — Step 3.5 Flash is open-weight under the — license. You can self-host it or use any listed inference provider.

Is Step 3.5 Flash OpenAI-compatible?

Yes — at least one tracked provider exposes an OpenAI-compatible endpoint, so Cursor, Cline, Aider and similar clients work with just a base-URL change.

What is the maximum context window?

Step 3.5 Flash supports up to 262K tokens of context with a maximum output of 66K tokens.

Need verified access to Step 3.5 Flash?

We broker vetted intros to StepFun — payment, KYC and endpoint verification handled.

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