Meta built a huge open-weight AI model for Macs, but you'll need 1TB of RAM to run it

Muse Spark Open is "the most capable US open-weight model to date," the company says.

Apple

In case there was still any doubt about Meta's commitment to open models, the company is open-sourcing Muse Spark with a new open-weight model called Muse Spark Open. The 800-billion parameter model was optimized for Apple Silicon, but you'll need a staggering 1TB of RAM to run it locally.

Meta, which has said it believes the US should not allow Chinese labs to lead on open-source AI, calls Muse Spark Open "the most capable US open-weight model to date." Benchmarks released by the company suggest Meta's model outperforms two leading Chinese models, GLM 5.3 and Kimi K3, on agentic tasks and visual reasoning.

It's also the first model optimized to run locally on Apple's M5 Ultra-equipped Mac Studio machines. "Apple's unified memory architecture lets the M5 Ultra's integrated GPU use up to 512 GB per Mac Studio, so two machines can hold an entire model," Meta explains. "The result is two Mac Studios behave like one supercomputer with a terabyte of unified memory."

Muse Spark Open — weights releasing today — runs great on new Mac Studios thanks to work with @johnternus and Apple. pic.twitter.com/U2wJNrKBOg

— Mark Zuckerberg (@finkd) October 15, 2026

Apple still hasn't announced specific pricing or a ship date for the 512GB Mac Studio — just that it will be available in "late October" — any setup that can run Muse Spark Open will require a hefty investment. Muse Spark Open can also run on four 256GB M5 Ultra Mac Studios, which will cost roughly $38,000. That amount of compute is pretty squarely out of reach for the typical vibe coder. But if you're a larger organization that's been burning through your token budget, investing in a few Mac Studios might seem like a pretty good deal, provided Meta's model performs as well as the company suggests.

Muse Spark Open is available to download now from Hugging Face.