Muse Spark Open

Muse Spark Open is an open-weights language model from Meta. The weights are published on Hugging Face under the name Muse-Spark-Open-816B-A42B; the license is dated 2026-10-15. By its name and the repository data, the model has about 816 billion parameters, of which about 42 billion work on each step, and it accepts images together with text. The chat template shows that the model has an adjustable depth of reasoning (four levels from low to extra high) and supports tool calls.

The weights are gated: to download them you log in to Hugging Face and fill in a form with your name, date of birth, country, organization and job role, and accept the license. The model card itself is also visible only after this step, so we could not read the authors' own description, hardware requirements or test results. Figures such as the size of the context window and the quality of answers are therefore not confirmed here.

The license is Meta's own Muse Model License. It lets you use, change, fine-tune, copy and sell the model for free, and create other models based on it, with these conditions: keep the license notice and the usage policy; show the line "Built with Muse Spark Open" in each product or service that uses the model or models made from it; and if you sell access to the model through an API and your company's yearly revenue is above 20 million US dollars, sign a separate agreement with Meta first. Because of these conditions we mark commercial use as limited. Meta claims no ownership of the answers the model produces. The usage policy forbids, among other things, military and weapons use, deception, spam and use by people under 18. We found no territorial restrictions in the license text; read the license before use.

Date of check: 2026-10-21.