NeuralStackMeta has released Muse Spark Open as an open-weight artificial intelligence model, giving developers access to the trained files so they can download, adapt and run the system on their own hardware. The company said it worked with Apple to make the model run on two to four linked Mac Studios using Apple’s M5 Ultra chip.
Meta CEO Mark Zuckerberg publicly thanked Apple CEO John Ternus for the collaboration, writing that Muse Spark Open “runs great on new Mac Studios” because of work with Ternus and Apple. Ternus replied that the model demonstrated how efficiently large AI systems could run from a desktop.
The release is notable because it represents the first public partnership between Meta and Apple since around 2017. The companies have spent years at odds, including after Apple’s privacy changes in 2021 reduced the data available for Meta’s advertising business.
Muse Spark Open uses a sparse mixture-of-experts design with 816 billion total parameters, while activating roughly 42 billion parameters for each token. That architecture allows only part of the model to work on an individual word, helping it fit across desktop hardware rather than requiring the entire system to run at once.
Apple is tuning the model through MLX, its framework for running AI on Apple silicon. The collaboration supports Apple’s push for on-device AI, although the hardware required is aimed primarily at developers and professionals rather than ordinary consumers.
Apple prices a Mac Studio with M5 Ultra and 256GB of memory from $10,799, and multi-machine configurations cost more. The model can also run on other hardware, and neither company disclosed exclusivity, financial terms or how long the collaboration will last.
Why this matters
Meta’s open-weight strategy lets developers build around its models without Meta paying the computing costs of every deployment. Local execution can also keep sensitive data on a user’s machine and reduce reliance on rented cloud infrastructure, though a shift of some agent workloads to desktops would likely affect cloud demand only at the margin.
The release also highlights a divide in Meta’s AI strategy: the company is willing to distribute model weights while keeping its most capable technology closed. Meta’s chief AI officer said Muse Spark Open is not the company’s most capable model, limiting what the Apple partnership reveals about Meta’s frontier systems.
The next test will be whether the relationship expands beyond this launch. Months of joint work and the involvement of former Apple executive Daniel Gross suggest a functioning technical partnership, but there is no indication yet that it will extend to Siri, advertising or Meta’s glasses.