Solar Mini 4

Solar Mini 4 is Upstage's small, fast agentic model released 2026-09-23, a distinct product from Solar Pro 4 (not a refresh of Solar Mini 3). Mixture-of-Experts with 35B total / 3B active parameters. Text input and output with reasoning, structured outputs, and tool calling. 524,288-token context window and up to 128,000 max output tokens — a ~16x larger context than Solar Mini 3, which it also adds reasoning to. Proprietary (no open-weights release planned). Multilingual with particular optimization for Korean alongside strong English and Japanese, aimed at agentic use where latency and cost matter. List pricing $0.10 / 1M input ($0.01 cached), $0.40 / 1M output; a 50% launch discount runs through 2026-10-23 UTC ($0.05 / $0.20).