Upstage model releases

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).

The flagship of South Korean lab Upstage's in-house Solar family, surfaced on developer platforms around Aug 10 2026 and formally unveiled Aug 14 2026. An agent-first reasoning model pitched as a reliable workhorse — 'save frontier models for frontier problems' — with strong office-productivity, document-intensive, and coding performance rather than raw frontier scores. Carries a 524K-token context and up to 131K output tokens. Upstage reports large gains over Solar Pro 3: ~71 on the AA-LCR long-document benchmark (about 2.3x its predecessor) and 23 on Tau3-Banking tool-use (a 2.6x jump); Artificial Analysis scores it 42 on its Intelligence Index. API pricing is $0.30 / $1.20 per 1M input/output tokens, with a launch promo cutting that 90% to $0.03 / $0.12. Upstage is the first Korean company registered as an official model provider alongside OpenAI, Anthropic, Google, and NVIDIA. Served via Upstage's API and OpenRouter; weights were not published at launch, so treated as proprietary.