UpstageText Generation/v1/ai/chat

Solar Pro 4 API

Access Solar Pro 4 through one API key. Upstage Cost-Efficient Long-Horizon LLM.

Solar Pro 4 is Upstage's cost-efficient large language model with a 524,288-token context window, built for long-horizon tasks and agentic workflows with strong capabilities in office productivity and document-intensive work. Solar Pro 4 suits document pipelines and back-office agents — contracts, reports, spreadsheets — that need a long context at a very low price.

Full Docs Get API Key

Takes 30 seconds.

Solar Pro 4 API pricing

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

Token type	Price
Input	$0.22 / 1M tokens
Output	$0.89 / 1M tokens
Context window	524K tokens

What it costs	Per job	Per 1,000
Chat reply1K input + 500 output tokens	$0.0007	$0.665
RAG answer8K input + 800 output tokens	$0.0025	$2.47
Agent step with tools30K input + 2K output tokens	$0.0084	$8.38
Long document summary100K input + 2K output tokens	$0.024	$23.78

4,900+

Developers

2.3M+

API calls served

184

Endpoints

$0.01

Per call

Yep, that's it.

Try it live

Send a message and see Solar Pro 4 respond in real time.

POST/v1/ai/chatupstage/solar-pro4

Message *

Max Tokens

Maximum tokens in the response.

Stream

Real-time tokens

Hit "Send Request" to see the response

Solar Pro 4 specs

Provider	Upstage
Model ID	upstage/solar-pro4
Endpoint	/v1/ai/chat
Type	Text Generation
Context window	524K tokens
Max output	131K tokens
Reasoning	No
OpenAI-compatible	Yes — /v1/ai/chat/completions

How to get a Solar Pro 4 API key

1
Create an account
Sign up at yepapi.com with Google or email. It takes about 30 seconds.
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 Solar Pro 4
Send a request to /v1/ai/chat with the x-api-key header and model "upstage/solar-pro4".
4
Pay as you go
Usage is billed per request from your balance. Top up any amount; there is no subscription.

Strengths

✓

Document and office work

Tuned for productivity and document-intensive tasks.

✓

524K context

Handles up to 524,288 input tokens and returns up to 131,072 output tokens per call.

✓

Very low cost

$0.22 per 1M input and $0.89 per 1M output tokens.

✓

Tools and structured output

Function calling and JSON schema outputs.

Quick start

Copy this snippet and start making calls with Solar Pro 4.

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": "upstage/solar-pro4",
    "messages": [
      {
        "role": "user",
        "content": "Explain API gateways in 2 sentences."
      }
    ],
    "maxTokens": 256
  }),
});
const { data } = await res.json();
console.log(data.message.content);

Solar Pro 4 vs similar models

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

Model	Provider	Price	Context
Solar Pro 4	Upstage	$0.22 in / $0.89 out per 1M	524K
Solar Mini 4	Upstage	$0.07 in / $0.30 out per 1M	524K
Nemotron 3 Super	NVIDIA	$0 in / $0 out per 1M	262K
Qwen3.7 Flash	Qwen	$0.04 in / $0.19 out per 1M	1M
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
Seed 1.6 Flash	ByteDance	$0.11 in / $0.44 out per 1M	262K

Why use Solar Pro 4 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

Solar Pro 4 API — pricing, context window & access

Solar Pro 4 is Upstage's cost-efficient large language model with a 524,288-token context window, built for long-horizon tasks and agentic workflows with strong capabilities in office productivity and document-intensive work. It pairs a 524,288-token context window with up to 131,072 output tokens per response, at $0.22 per 1M input and $0.89 per 1M output tokens through YepAPI.

Through YepAPI you call Solar Pro 4 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.

What is Solar Pro 4?

Solar Pro 4 is Upstage's cost-efficient large language model with a 524,288-token context window, built for long-horizon tasks and agentic workflows with strong capabilities in office productivity and document-intensive work. It returns up to 131,072 output tokens and is priced at $0.22 / $0.89 per 1M tokens. It accepts text as input, handles up to 524,288 tokens of context and returns up to 131,072 output tokens per call.

Build with Solar Pro 4 via YepAPI

YepAPI serves Solar Pro 4 on the OpenAI-compatible /v1/ai/chat endpoint. Point your base URL at YepAPI, add your key, and set the model string to solar-pro4 (or the full upstage/solar-pro4). 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.

Solar Pro 4 API pricing — $0.22 / 1M input, $0.89 / 1M output

Solar Pro 4 costs $0.22 per 1M input tokens and $0.89 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 so you can see exactly what a 131,072-token response cost.

Solar Pro 4 use cases

Solar Pro 4 suits document pipelines and back-office agents — contracts, reports, spreadsheets — that need a long context at a very low price.

Start generating in 30 seconds

Pay per call, no subscriptions.

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

Solar Pro 4 costs $0.22 per 1M input tokens and $0.89 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 $0.0007.

Sign up at yepapi.com (Google or email, about 30 seconds), open the dashboard and create an API key. The same key works for Solar Pro 4 and every other model — no separate Upstage account or waitlist.

Use "upstage/solar-pro4" as the model on /v1/ai/chat. The short alias "solar-pro4" also works.

Yes. Point the OpenAI SDK at https://api.yepapi.com/v1/ai with your YepAPI key and set model to "upstage/solar-pro4". Streaming works the same way, so existing OpenAI code only needs the base URL and key changed.

Solar Pro 4 supports a 524K token context window with up to 131K output tokens per request.