Upstage AI API
Access Upstage AI instantly with Puter.js, and add AI to any app in a few lines of code without backend or API keys.
// npm install @heyputer/puter.js
import { puter } from '@heyputer/puter.js';
puter.ai.chat("Explain AI like I'm five!", {
model: "upstage/solar-pro-4"
}).then(response => {
console.log(response);
});
<html>
<body>
<script src="https://js.puter.com/v2/"></script>
<script>
puter.ai.chat("Explain AI like I'm five!", {
model: "upstage/solar-pro-4"
}).then(response => {
console.log(response);
});
</script>
</body>
</html>
List of Upstage AI Models
Solar Mini 4
upstage/solar-mini4
Solar Mini 4 is Upstage's compact, cost-efficient large language model, released September 23, 2026 as a smaller sibling to Solar Pro 4. It uses a 35-billion-parameter Mixture-of-Experts architecture with 3 billion active parameters, and shares its larger sibling's 524,288-token context window. Upstage built it for agentic use cases where response speed and cost matter more than peak capability, with fluent Korean alongside strong English and Japanese support. Pricing is $0.05 per million input tokens and $0.20 per million output tokens. Upstage has not published a benchmark table for Solar Mini 4, and no independent evaluation exists yet, so its accuracy relative to Solar Pro 4 or other models is unverified. It suits developers building high-volume, latency-sensitive agents or long-context workflows in Korean, English, or Japanese who don't need Solar Pro 4's full capability.
ChatSolar Pro 4
upstage/solar-pro-4
Solar Pro 4 is an agentic large language model from Upstage, built for multi-step work that spans documents, terminals, and tool calls, with a 524K token context window. Compared to Solar Pro 3, it shows large gains on agent-focused evaluations. Terminal-Bench v2.1 rose from 43.2 to 57, and AA-LCR long-document reasoning rose from 62.7 to 71. It scores 89.0 on GPQA Diamond and 81.9 on Arena-Hard v2 for Japanese. The model supports English, Korean, and Japanese, with adjustable reasoning effort for either deep analysis or faster responses. It is designed to flag when information can't be verified rather than fabricate an answer. Solar Pro 4 targets contract review, multi-document reconciliation, terminal-based automation, and document-heavy workflows like generating Excel, Word, and PowerPoint outputs.
ChatSolar Pro 3
upstage/solar-pro-3
Solar Pro 3 is a Mixture-of-Experts large language model from Upstage, featuring 102B total parameters with only 12B active per forward pass and a 128K token context window. The model is built for agentic workflows and complex reasoning, trained using Upstage's proprietary SnapPO reinforcement learning framework. It scores 72.3 on Tau2-all (the comprehensive agentic evaluation), roughly doubling its predecessor's 36.0. It also claims 100% schema compliance for structured output generation. Solar Pro 3 is particularly strong in Korean, with robust English and Japanese support — making it a standout choice for multilingual teams operating in East Asian markets. It targets enterprise use cases in domains like finance, healthcare, and legal, where reliable instruction following and structured outputs matter most.
Frequently Asked Questions
The Upstage AI API gives you access to models for AI chat. Through Puter.js, you can start using Upstage AI models instantly with zero setup or configuration.
Puter.js supports a variety of Upstage AI models, including Solar Mini 4, Solar Pro 4, and Solar Pro 3. Find all AI models supported by Puter.js in the AI model list.
With the User-Pays model, users cover their own AI costs through their Puter account. This means you can build apps without worrying about infrastructure expenses.
Puter.js is a JavaScript library that provides access to AI, storage, and other cloud services directly from a single API. It handles authentication, infrastructure, and scaling so you can focus on building your app.
Yes — the Upstage AI API through Puter.js works with any JavaScript framework, Node.js, or plain HTML. Just include the library and start building. See the documentation for more details.