StepFunText Generation/v1/ai/chat

Step 5 Preview API

Access Step 5 Preview through one API key. StepFun StepFun Flagship Agent Model.

Step 5 Preview is StepFun's flagship model for agentic work, a sparse Mixture-of-Experts model with 27B active and 600B total parameters. It suits software engineering and professional tasks run by agents, at a mid-range price.

Full Docs Get API Key — Free $5 Credit

No credit card required. Takes 30 seconds.

Step 5 Preview API pricing

Pay per request from your YepAPI balance — no subscription, no monthly minimum. Prices updated October 23, 2026.

Token type	Price
Input	$1.48 / 1M tokens
Output	$3.99 / 1M tokens
Context window	1.0M tokens

What it costs	Per job	Per 1,000
Chat reply1K input + 500 output tokens	$0.0035	$3.47
RAG answer8K input + 800 output tokens	$0.015	$15.03
Agent step with tools30K input + 2K output tokens	$0.052	$52.38
Long document summary100K input + 2K output tokens	$0.156	$155.98

2,400+

Developers

1.2M+

API calls served

100+

Endpoints

$0.01

Per call

Yep, that's it.

Try it live

Send a message and see Step 5 Preview respond in real time.

POST/v1/ai/chatstepfun/step-5-preview

Message *

Max Tokens

Maximum tokens in the response.

Stream

Real-time tokens

Hit "Send Request" to see the response

Step 5 Preview specs

Provider	StepFun
Model ID	stepfun/step-5-preview
Endpoint	/v1/ai/chat
Type	Text Generation
Context window	1.05M tokens
Max output	64K tokens
Reasoning	No
OpenAI-compatible	Yes — /v1/ai/chat/completions

How to get a Step 5 Preview API key

1
Create a free account
Sign up at yepapi.com with Google or email. It takes about 30 seconds and needs no card.
2
Create an API key
Open the dashboard, go to API Keys and create a key. Copy it — it starts with yep_sk_.
3
Call Step 5 Preview
Send a request to /v1/ai/chat with the x-api-key header and model "stepfun/step-5-preview".
4
Pay as you go
Usage is billed per request from your balance. Top up any amount; there is no subscription.

Strengths

✓

StepFun's flagship

The most capable StepFun model, for agents and software engineering.

✓

Efficient MoE

27B active parameters out of 600B keeps responses fast for its size.

✓

1M token context

Up to 1,048,576 input tokens per call.

✓

Multimodal input

Accepts text, images and video.

Quick start

Copy this snippet and start making calls with Step 5 Preview.

const res = await fetch('https://api.yepapi.com/v1/ai/chat', {
  method: 'POST',
  headers: {
    'x-api-key': 'YOUR_API_KEY',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    "model": "stepfun/step-5-preview",
    "messages": [
      {
        "role": "user",
        "content": "Explain API gateways in 2 sentences."
      }
    ],
    "maxTokens": 256
  }),
});
const { data } = await res.json();
console.log(data.message.content);

Step 5 Preview vs similar models

Every model below runs on the same API key — switch by changing the model ID.

Model	Provider	Price	Context
Step 5 Preview	StepFun	$1.48 in / $3.99 out per 1M	1.0M
Step 3.5 Flash	StepFun	$0.15 in / $0.44 out per 1M	262K
Nemotron 3 Super	NVIDIA	$0 in / $0 out per 1M	262K
Qwen3.7 Flash	Qwen	$0.04 in / $0.19 out per 1M	1M
Solar Mini 4	Upstage	$0.07 in / $0.30 out per 1M	524K
Nemotron 3.5 Lightning	NVIDIA	$0.10 in / $0.30 out per 1M	262K
DeepSeek V4 Flash	DeepSeek	$0.13 in / $0.27 out per 1M	1.0M
Qwen 3.5 Flash	Qwen	$0.10 in / $0.38 out per 1M	1M

Why use Step 5 Preview through YepAPI?

✓One API key for all models — no separate accounts

✓OpenAI SDK compatible — just change the base URL

✓No monthly minimums — pay per token

✓Switch models with one line of code

✓Full provider passthrough — citations, search results, and all extras included

✓Streaming and non-streaming support on every model

✓Works with Cursor, Claude, LangChain, and any LLM tool

✓Unified billing across all providers

Step 5 Preview API — pricing, context window & access

Step 5 Preview is StepFun's flagship model for agentic work, a sparse Mixture-of-Experts model with 27B active and 600B total parameters. It pairs a 1,048,576-token context window with up to 64,000 output tokens per response, at $1.48 per 1M input and $3.99 per 1M output tokens through YepAPI.

Through YepAPI you call Step 5 Preview on an OpenAI-compatible endpoint with a single key — the same key that reaches GPT-6, Claude, Gemini, Grok and the SEO, SERP and scraping APIs. Input: text, images, video.

What is Step 5 Preview?

Step 5 Preview is StepFun's flagship model for agentic work, a sparse Mixture-of-Experts model with 27B active and 600B total parameters. It is a preview release of StepFun's next generation, well above Step 3.5 Flash in capability. It accepts text, images, video as input, handles up to 1,048,576 tokens of context and returns up to 64,000 output tokens per call.

Build with Step 5 Preview via YepAPI

YepAPI serves Step 5 Preview on the OpenAI-compatible /v1/ai/chat endpoint. Point your base URL at YepAPI, add your key, and set the model string to step-5-preview (or the full stepfun/step-5-preview). Function calling, structured outputs and reasoning settings pass straight through, and switching to any other model on the platform is a one-string change per request.

Step 5 Preview API pricing — $1.48 / 1M input, $3.99 / 1M output

Step 5 Preview costs $1.48 per 1M input tokens and $3.99 per 1M output tokens through YepAPI, pay per token with no minimums. Failed calls are never charged, and every request is itemised in your dashboard API Logs.

Step 5 Preview use cases

It suits software engineering and professional tasks run by agents, at a mid-range price.

Try Step 5 Preview free

Every new YepAPI account includes $5 in free credit with no card required — enough to test Step 5 Preview on your own prompts before committing to paid usage. Create an account, copy your key, and call step-5-preview right away.

Start generating in 30 seconds

$5 free credit on signup. No credit card required. Pay per call.

Get API Key

What developers say

“Switched from SerpAPI and cut our SERP costs by 80%. Same data quality, way simpler billing.”
Marcus T.
SEO Platform Founder

“One API key for AI models, SERP data, and web scraping. Saved us from managing 4 separate providers.”
Priya S.
Full-Stack Developer

“The $5 free credit let us prototype our entire rank tracking feature before committing. No other API does that.”
Jake R.
Indie Hacker

Frequently asked questions

Step 5 Preview costs $1.48 per 1M input tokens and $3.99 per 1M output tokens through YepAPI, billed per request with no monthly fee. For example, a chat reply (1K input + 500 output tokens) costs about $0.0035.

Sign up at yepapi.com (Google or email, about 30 seconds), open the dashboard and create an API key. The same key works for Step 5 Preview and every other model — no separate StepFun account or waitlist.

New YepAPI accounts in most countries get free signup credit, enough to test Step 5 Preview without a card. After that you pay per request at the rates above — there is no subscription.

Use "stepfun/step-5-preview" as the model on /v1/ai/chat. The short alias "step-5-preview" also works.

Yes. Point the OpenAI SDK at https://api.yepapi.com/v1/ai with your YepAPI key and set model to "stepfun/step-5-preview". Streaming works the same way, so existing OpenAI code only needs the base URL and key changed.

Step 5 Preview supports a 1.0M token context window with up to 64K output tokens per request.