After its Llama series, Meta is returning to open-weight territory with Muse Spark Open. Meta calls it the most capable US open-weight model, built for coding and agentic tasks, with 816 billion parameters (42 billion active), up to one million tokens of context, and support for text, image, video, and audio. On benchmarks like JobBench, MCP-Atlas, HLE-Diamond, and ZeroBench, Meta says it scores well ahead of Qwen 3.8, GLM 5.3, and Kimi K3 in several categories but still falls well short of Meta's paid Muse Wonder Full models.
The model is optimized for Apple's M5 Ultra and runs locally on two Mac Studios with 512 GB of unified memory each, according to Meta. Weights are on Hugging Face. The license is free to use but requires the label "Built with Muse Spark Open." Providers pulling in more than $20 million a year who want to offer the model as an API service need a separate agreement with Meta. More details are in the research blog.
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