Meta releases Muse Spark Open, an open-weight model for agentic coding

Meta has released Muse Spark Open, an open-weight model built for agentic coding, and Hugging Face has published a guide to running it. It is a mixture-of-experts model with about 816B total parameters, of which about 42B are active per token, and it takes text, images, audio and video as input, with a context window of up to 1M tokens. Hugging Face calls it the most capable US open-weights model to date. It is big: the BF16 checkpoint is about 1.5 TB and runs across 4 nodes of 8 H200 GPUs, while a 4-bit NVFP4 version runs on a single B200 node. It already works with Transformers, llama.cpp, vLLM, SGLang and MLX, and can be fine-tuned with TRL. Sorted take: few small teams can host this themselves, so for most people it will matter through hosted providers and as a strong open option to compare against closed coding models.