Introducing Solar Pro 2

Upstage today officially released Solar Pro 2, its next-generation large language model (LLM) designed to perform complex reasoning and tool-integrated task execution—all with just 31 billion parameters.

Solar Pro 2 builds on the foundation of its predecessor with a significant performance upgrade, increasing its parameter size from 22B to 31B while remaining in the small language model (sLLM) category. The model introduces a hybrid architecture with two user-selectable modes: “Chat Mode” for fast responses and “Reasoning Mode” for structured, multi-step logical thinking. Its Chain-of-Thought (CoT) reasoning approach significantly improves performance in advanced tasks like math, coding, and logic-heavy workflows.

“Solar Pro 2 represents a new generation of AI agents that don’t just talk but think, reason, and act,” said Sung Kim, CEO and co-founder of Upstage. “Our mission is to fundamentally reshape how work gets done with AI, and Solar Pro 2 marks a key milestone in advancing that future of work.”

In benchmark tests such as MMLU-Pro, Math500, AIME, and SWE-Bench, Solar Pro 2 delivered results comparable to leading frontier-scale models including OpenAI’s GPT-4o, DeepSeek’s R1, Mistral’s Small 3.2, and Alibaba’s Qwen 3—despite being less than half their size. This performance validates the AI startup's ability to develop globally competitive LLMs based entirely on homegrown technology.

Solar Pro 2 also showcases remarkable strength in Korean language understanding. Across key benchmarks like Arena-Hard-Auto, Hae-Rae, and Ko-MMLU, the model matched or outperformed language models by tech giants. It demonstrates deep capabilities in vocabulary, context comprehension, and cultural nuance, while also excelling in high-stakes domains such as finance, medicine, and law.

In addition to its reasoning capabilities, Solar Pro 2 has evolved into a fully agentic LLM, capable of executing multi-step tasks by interacting with external tools. Given a prompt like “Research recent product launches and marketing activities by competitor over the past three months and draft a presentation with news links,” the model autonomously searches the web, analyzes results, and generates a structured PowerPoint file—handling the full workflow from planning to output with minimal user intervention.

Solar Pro 2 is now available via API through the Upstage Console.