Muse Spark Open, released Thursday, has 816 billion parameters in total, 42 billion active per token and a one-million-token context window. Meta’s desktop recipe uses two M5 Ultra Mac Studios with 512 GB each, linked directly over Thunderbolt 5 with RDMA. The NVFP4 checkpoint is about 530 GB; the full BF16 weights are about 1.6 TB. Those numbers make “runs locally” a much more specific proposition. Release · Deployment guide
The weights use the Muse Model License with limited commercial terms, rather than a permissive open-source license. Meta’s on-device demonstrations and benchmark claims are vendor evidence, not a reproduced evaluation here. Model collection and card