Meta has launched Muse Spark Open, a significant 816-billion-parameter open-weight model. This model is specifically optimized to operate locally on Apple's M5 Ultra Mac Studios. It leverages Apple's MLX framework for efficient execution. Meta claims it is the most capable U.S. open-weight model available. Muse Spark Open boasts 816 billion total parameters with 42 billion active parameters and a massive 1 million-token context window. It is designed for coding and agentic tasks, performing particularly well in extended operations and multi-step reasoning. The model was tuned to run optimally on Mac Studio hardware. Meta suggests this Mac Studio setup is the premier method for desktop deployment of powerful models. Apple's unified memory architecture on the M5 Ultra allows for substantial memory capacity and bandwidth. This setup enables two Mac Studios to function as a single terabyte-scale supercomputer for the model. While the 512GB Mac Studio is not yet released, it is expected soon and will be a high-cost investment.