Meta released Muse Spark Open, an open-weight model with a one-million-token context window, on 15 October 2026; hosted services above a revenue threshold need a separate agreement.
- Meta says Muse Spark Open has 816 billion parameters, activates 42 billion per token and has a context window of one million tokens.
- Under the Muse Model License, Model as a Service providers above 20 million US dollars in gross revenue over any consecutive 12 months must sign a separate agreement.
- Meta's own table scores it 39 on the Artificial Analysis Intelligence Index, below GLM 5.3 (45) and Kimi K3 (44), and 89.2 on MCP-Atlas, above both (84.2, 82.3).
The benchmark figures come from Meta's own model card table, so treat the comparison as a vendor claim until an independent evaluation repeats it. On that table the model trails GLM 5.3 and Kimi K3 on the Intelligence Index and Terminal-Bench 2.1 and leads on MCP-Atlas, which points to testing the measure closest to your workload. The licence matters as much as the weights. Internal use and research sit outside the Model as a Service condition, but a team that offers access through an API should read the revenue threshold and the display requirement before building on it. Ask your legal team whether your planned use counts as Model as a Service, and run your own test set before any switch. Read on →
