Meta releases weights for Muse Spark Open

Meta has released the weights for its Muse Spark Open model, describing it as the “most capable US open-weight model to date.”

Natively multimodal, Muse Spark Open comes with 816 billion total parameters (42B active) and a 1M-token context window.

Meta noted that the model’s strengths include coding and agentic work, long-horizon tasks, complex software engineering, and multi-step reasoning.

The social media giant announced that Muse Spark Open was available through API platforms at Baseten, Fireworks AI, Groq, Modal, Nebius, OpenRouter and Together AI. The model weights can be downloaded via Amazon SageMaker AI, Google Cloud Model Garden, Hugging Face, and Microsoft Foundry Models.

Meta said it was releasing the weights under the Muse Model License with limited commercial terms; in other words, many developers can use the model for free, per the company.

“We believe the future is for everyone, and that includes the freedom to run advanced models wherever, including at home. Muse Spark Open is the first model in its class to run on your desktop using two Apple M5 Ultra Mac Studios with the latest MLX framework,” said Meta in a blog post.

As Chinese AI labs release powerful open weight and open-source models, American tech companies such as Meta and Nvidia have also raced to compete in this area, in order to encourage the wider adoption of American AI.