Meta Opens the Weights of Muse Spark, Its Largest Model Yet
Meta has released Muse Spark Open, a natively multimodal model with 816 billion total parameters and 42 billion active, calling it the most capable US open-weight model to date. The weights come under the Muse Model License, which allows free use for many developers but keeps limited commercial terms.
The headline numbers from Meta’s own scorecard: MCP-Atlas 89.2, JobBench 61.8, DeepSWE 1.1 60, and HLE-Diamond 26.1 with no tools. The model trails Kimi K3 (85.0) and GLM 5.3 (83.9) on Terminal-Bench 2.1, where it scores 76.4, and its DeepSWE row is marked as a self reported harness, so the comparison against separately measured rivals is not like for like.
The 1M-token context model is the first in its class that Meta says can run on a desktop: two Apple M5 Ultra Mac Studios with MLX hold the full weights. It is available on Hugging Face, Amazon SageMaker AI, Google Cloud Model Garden, and Microsoft Foundry Models, plus hosting through Baseten, Fireworks AI, Groq, Modal, Nebius, OpenRouter, and Together AI.
Related: Meta Releases Muse Wonder Models for Agentic Tasks, Muse Glimmer: Open-Weight 30B Model for Local Agent Workflows