Muse Spark Open (Xhigh)

Muse Spark Open is an open-weight mixture-of-experts language and multimodal model developed by Meta. Released on October 15, 2026, the model features 816 billion total parameters with roughly 42 billion active parameters per token, offering a balance between massive capacity and operational efficiency. It includes a native 1 million-token context window designed for long-horizon agentic workflows, complex software engineering, and multi-step reasoning.

The architecture incorporates a deep transformer backbone utilizing grouped-query attention, alongside a dedicated perception encoder that processes text, images, video, and audio inputs. Its design heavily emphasizes native multimodal perception and tool-equipped agent tasks, enabling it to operate across diverse environments and reason through multi-step challenges. The model supports configurable reasoning tiers, with default configurations tailored toward thorough problem-solving and code generation.

The model is distributed under the Muse Model License, making its weights available for developer research and specific commercial applications. It stands as a significant addition to Meta's open-weight lineup, offering robust capabilities for autonomous coding agents and deep analytical tasks.