Meta opened up Muse Spark, and it takes two Mac Studios to run it at home

Meta released Muse Spark Open on October 15, a model with 816 billion parameters, 42 billion of them active. MacRumors reports it’s free to download under a license that allows limited commercial use. Meta calls it the most capable U.S. open-weight model to date, and says you can run it on your desktop using two Apple M5 Ultra Mac Studios.

MacObserver reported Apple and Meta teamed up to run it on the Mac Studio, and Apple’s machine learning research team published the numbers. Meta says two are enough because each M5 Ultra Mac Studio’s GPU can use up to 512 GB, and in a 4-bit format the model takes about 493GB, Apple wrote. The Macs talk over a low-latency driver on Thunderbolt 5, and Apple’s speed figure, over 36 tokens per second, comes from four of them. That’s Apple’s test, so I’d wait for someone else to time it.

The Decoder reported the license requires a “Built with Muse Spark Open” label. Digital Applied reported that model-as-a-service providers above $20 million in revenue must notify Meta and sign a separate agreement, while Trending Topics reported that threshold doesn’t apply to internal use, research or building the model into your own products. Even the download is gated: the Hugging Face page asks you to log in and review the conditions first.

It isn’t Meta’s best model, either. The Hugging Face model card lists a score of 39 on the Artificial Analysis Intelligence Index, and The Decoder says it still falls well short of Meta’s paid Muse Wonder Full models.

If you’re curious, I wouldn’t buy two Mac Studios for this. Meta says it’s already available through Baseten, Fireworks AI and Groq, so I’d try it there first, read the license before building anything a customer pays for, and watch for smaller versions that fit one machine. If you already own two M5 Ultra Mac Studios, you’re the audience Apple had in mind.

Open weights are the headline. Two Mac Studios are the fine print.