Meta and Apple launch Muse Spark Open, an 816B open-weight model that runs on Mac Studios

Meta positions Muse Spark Open as a coding and agentic-work model. It has 816B total parameters, 42B of which are active per token, and a 1M-token context window. It is built for long-running, multi-step agents that call tools. Meta describes it as the most capable US open-weight model, released under a license that allows limited commercial use. Zuckerberg posted that it 'runs great on new Mac Studios thanks to work with @johnternus and Apple.' Ternus replied with congratulations.

CNBC frames the Apple partnership as a thaw after years of hostility between the two companies. That relationship bottomed out with Apple's 2021 privacy changes, which Meta estimated would cost it $10B in revenue. Customers pair two to four Mac Studios to run the model locally. Apple and Meta pitch this as both a security win and a cost saving compared with cloud inference. NVIDIA, meanwhile, published guidance on scaling agentic coding with the model on GB300 NVL72 racks. Hugging Face hosts the Muse-Spark-Open-816B-A42B repository.

Competitively, this is Meta's answer to the Chinese open-weight lead. A popular r/LocalLLaMA thread this week claimed Chinese open models trail US closed models by only about seven months. The release lands the same week as NVIDIA's Nemotron 3.5, Mistral's preview of Large 4 and StepFun's Step 5, which makes open weights the clearest theme of the week. It also sits alongside Meta's closed Muse Wonder, so Meta is splitting its line between open and proprietary models.

The skeptics have a point on the Mac claim. A 256GB Mac Studio starts at $10,799 and the model needs several of them, so 'runs on a Mac' really means a five-figure cluster. Watch for independent benchmarks, quantized community builds, and whether Apple and Meta go further than this single model, which both companies declined to address.