Meta Releases Muse Spark Open, an Open-Weight Model That Runs on Mac Studio

Meta has publicly released the weights of Muse Spark Open, which it calls the most capable US open-weight model to date. It is the open version of Muse Spark and is built for coding, agentic work and multi-step reasoning. The model uses a Mixture of Experts architecture with 816 billion total parameters, of which only about 42 billion are active per token. It offers a one-million-token context window and accepts text, image, audio and video input. The most notable part of the launch is the collaboration with Apple. According to Meta, it is the first model in its class to run on a desktop setup of two M5 Ultra Mac Studios with 512 GB of unified memory each, using the latest version of Apple's MLX framework. Apple says a cluster of four Mac Studios generates more than 36 tokens per second. The weights are available on Hugging Face and in the model catalogs of Amazon, Google Cloud and Microsoft, while providers such as Groq, Together AI and OpenRouter offer hosted API access. The release is widely seen as a US push to compete with Chinese open-weight models, which have led the field in recent months.