Meta releases Muse Spark Open, an 816B open-weight model tuned for Apple M5 Ultra Mac Studios

Muse Spark Open is a natively multimodal model with 816B total parameters, 42B active per token, and a 1M-token context window. Meta positions it for coding and long-horizon agent work. Its own benchmarks, as reported by Engadget, put it ahead of China's GLM 5.3 and Kimi K3 on agentic tasks and visual reasoning. Those numbers are Meta's, and a full evaluation report is still to come. Hosted access is live at Baseten, Fireworks, Groq, Modal, Nebius, OpenRouter and Together AI. Weights can be downloaded from Hugging Face, Amazon SageMaker, Google Cloud Model Garden and Microsoft Foundry. The Muse Model License carries limited commercial terms. Local use is the catch: it takes two M5 Ultra Mac Studios with 512 GB each, about 1 TB of memory, and Apple has only said the 512 GB machine arrives in late October. On Monday Meta shipped Muse Wonder with only the smaller model on its API. This time the weights are out. Builders get a self-hostable alternative to Chinese open models with day-one hosting, subject to the license.