Welcome Muse Spark Open: open-weight frontier multimodal mixture-of-experts model from Meta

Meta has open-sourced Muse Spark Open, a large-scale multimodal mixture-of-experts AI model with approximately 816 billion parameters designed for agentic coding and multimodal inputs including text, images, audio, and video. It features a context window of up to 1 million tokens and supports complex developer workflows such as multi-file refactors, long debugging sessions, and web browsing with images.

This Wire brief sits within Fusion42's coverage of AI & ML, and 21 sources have reported it between 5 Sep 2026 and 15 Oct 2026.