Meta has released Muse Spark Open, billed as the most capable US open-weight model to date. This powerful new model was developed in collaboration with Apple, enabling it to efficiently run on Mac desktop setups. Specifically, two Mac Studios equipped with Apple's M5 Ultra chips and the MLX framework can host the model. Muse Spark Open boasts 816 billion total parameters and a substantial 1 million-token context window. Its primary applications are in coding and agentic tasks, excelling in extended operations and complex reasoning. The model is optimized to leverage the unified memory architecture of the M5 Ultra, allowing a combined terabyte of memory across two Mac Studios. While Apple has not yet released the 512GB Mac Studio, it is expected soon. Muse Spark Open is accessible through various API platforms and its model weights are downloadable from major cloud providers and Hugging Face. The model is free to download and permits limited commercial use. This partnership between Meta and Apple marks a significant, albeit surprising, collaboration between the two tech giants.