Solar Mini 4

Solar Mini 4 is Upstage's compact language model, built for agentic workloads where speed and cost matter most. It uses a mixture-of-experts architecture. The model is large overall, but it draws only on the parts it needs for each response, which keeps quality high while cutting serving costs substantially. It can take in long documents in a single pass and produce lengthy outputs. It also supports a step-by-step reasoning mode, tool calling, and structured outputs that follow a defined schema. It is fluent in Korean and strong in English and Japanese as well.

On paper, it closely resembles its larger sibling, Solar Pro 4, with the same document length limits, the same languages, and the same training cutoff. The two differ in how demanding a task they can handle. Pro 4 is the one to reach for when an agent has to plan on its own, juggle tools, and recover from its own mistakes across many steps. Mini 4 costs far less, which makes it the efficient choice for high-volume, repetitive work such as extraction and classification. Send everyday bulk processing to Mini 4 and save the demanding agentic tasks for Pro 4 to get the best of both cost and performance.