Meta Releases Muse Spark Open, an 816B Open-Weight Model That Runs on Two Mac Studios

Meta released the weights for Muse Spark Open on October 15, 2026, calling it “the most capable US open-weight model to date.”

What it is

According to Meta, Muse Spark Open is a natively multimodal model with 816 billion total parameters (42 billion active) and a 1 million-token context window. Meta says it is built for coding and agentic work, including long-horizon tasks, complex software engineering and multi-step reasoning.

Built to run on Macs

Meta says it is the first model in its class to run on a desktop, using two Apple M5 Ultra Mac Studios with Apple’s latest MLX framework. Each M5 Ultra Mac Studio’s integrated GPU can use up to 512 GB of unified memory, so two machines together hold the whole model in about a terabyte of memory. CNBC reports that customers will be able to pair between two and four Mac Studios, and that the collaboration followed months of work between the two longtime rivals.

Meta says it tested agentic workflows running entirely on-device with Muse Code, its coding tool, including shipping real iOS changes to Ice Cubes, an open-source Mastodon client (bug fixes, new features and a full build), and driving DaVinci Resolve end to end, with the model reviewing footage frame by frame and cropping the best moments vertically.

Where to get it

The model is available through API platforms including Baseten, Fireworks AI, Groq, Modal, Nebius, OpenRouter and Together AI, and the weights can be downloaded from Hugging Face, Amazon SageMaker AI, Google Cloud Model Garden and Microsoft Foundry Models. Meta is releasing it under the Muse Model License with limited commercial terms, which it says allow many developers to use the model for free.

Not Meta’s top model

Muse Spark Open is a step below Meta’s proprietary Muse Wonder models, which launched earlier this week. “These aren’t the most capable models that we’ve developed or released,” Meta AI chief Alexandr Wang told CNBC. “But we think that there will be a lot of companies and developers who sort of use this model and tinker with it at small scale and then seek to ramp up and scale up their usage.”

Meta says the model received additional safety post-training because its weights are open, and that it met the release thresholds in its Meta Superintelligence Scaling Framework.