Meta Muse Spark Open

Muse Spark Open 816B A42B is a natively multimodal Mixture-of-Experts model for coding agents, tool use, and reasoning over images, audio, and video. It features 816B total parameters with 42B active, using a 62-layer architecture with 8,192 hidden size, 128 attention heads, and 16 KV heads. Every layer routes tokens to 8 of 256 experts, while the attention stack interleaves 46 sliding-window layers with 16 full-attention layers. Supporting a 1M-token context, it adds a 1.8B-parameter Perception Encoder and an audio encoder, with adjustable reasoning effort for agentic workloads.