Meta releases Muse Spark Open, an 816B parameter open-weight model for coding and agentic tasks

Meta introduced Muse Spark Open, which it claims is the most capable US open-weight model, featuring 816 billion parameters (42 billion active), up to one million tokens of context, and support for text, image, video, and audio. Meta states that Muse Spark Open scores ahead of Qwen 3.8, GLM 5.3, and Kimi K3 on benchmarks like JobBench, MCP-Atlas, HLE-Diamond, and ZeroBench in Agentic, Knowledge & Reasoning, and Multimodal categories, though it falls short of paid Muse Wonder Full models and some competitors on coding benchmarks. The model is optimized for Apple's M5 Ultra and weights are available on Hugging Face under a free license, but providers earning over $20 million annually from API services require a separate agreement with Meta.