Meta released the weights of Muse Spark Open on 15 October, calling it the most capable US open-weight model so far. It has 816 billion parameters, 42 billion active at a time, a one-million-token context window and native multimodal input, and is aimed at coding, agent work and long multi-step reasoning. Meta worked with Apple on a version tuned for the Mac Studio with M5 Ultra, using the latest release of Apple's MLX framework.
“We're excited for mommy and daddy to be playing nice again”
Alexandr Wang, Meta AI chief, to Axios, to Axios · macrumors.com ↗
The pairing rests on memory. An M5 Ultra can address up to 512GB in one Mac Studio at 1.2 TB/s of bandwidth, so two machines hold the whole model. Demos ran Muse Code on-device to ship iOS changes to the Ice Cubes Mastodon client and edit video in DaVinci Resolve. The 512GB Mac Studio is expected later in October, and the 256GB model already costs over $10,000.
Benchmark evaluation table for Muse Spark Open from Meta's announcement
Meta · Image: 9to5Mac
The weights are free to download from Hugging Face and the big cloud catalogues, with a licence that allows limited commercial use. Hosted access is offered through providers such as Groq, OpenRouter and Together AI.
About Muse Spark
Muse Spark is a large language model developed by Meta through its Meta Superintelligence Labs. The open-weight Muse Spark Open, released on 15 October 2026, is a mixture-of-experts model with 816 billion total parameters, 42 billion of them active.
The model family was introduced in April 2026 and launched as Muse Spark 1.1 on 9 July 2026. On 5 August 2026 Meta released Muse Spark 1.2 together with Muse Code, a terminal-based coding agent that writes and debugs code and runs several sub-agents at once, and made the model available through the Meta Model API and OpenRouter. On 10 August 2026 it released a smaller open-weight model, Muse Glimmer.
Apr 2026
Released
The tie-up surprised observers, given the rivalry. Meta AI chief Alexandr Wang says they have worked together for several months, crediting Daniel Gross, once at Apple, for bringing them together. Apple CEO John Ternus congratulated the team on X.
Sources · 3