Solar Pro

Solar Mini 4

Upstage

Solar Mini 4 is Upstage’s compact agent model for high-volume retrieval, structured generation, and tool-driven workflows. Its mixture-of-experts architecture has 35B total parameters and 3B active per token, with a 512K context and up to 128K output tokens. It supports parallel function calling and is offered through Upstage’s hosted API, with on-premises deployment options. The model emphasizes compute efficiency for repetitive work while retaining long-context reasoning. On-premises availability does not imply publicly downloadable weights; memory requirements still reflect the full 35B parameters.

Solar Pro 4

Upstage

Solar Pro 4 is Upstage’s hosted commercial flagship for long-running enterprise agents. It focuses on terminal tasks, multi-turn tool use, document-grounded reasoning, and producing deliverables across multiple files. It supports English, Korean, and Japanese, adjustable reasoning effort, a 512K context, and up to 128K output tokens. The model is offered through Upstage Console and partner APIs rather than open weights. Its August 11 launch blog precedes the August 20 press release. Benchmarks depend on agent environments and do not guarantee task completion in a particular production workflow.

Solar Open 2

Upstage

Solar Open 2 is Upstage’s 250B-parameter open-weight model for document-heavy agents, office productivity, and coding. It activates 15B parameters per token and interleaves linear attention with standard attention to improve long-context inference efficiency. A 1M-token context supports large document collections and extended tool histories. Its release includes weights and a technical report describing training and evaluation. The custom Solar Open license governs redistribution and commercial use. Sparse activation lowers computation relative to a dense model of the same total size but does not eliminate the storage and memory requirements of the full weights.