Muse Spark Open is Meta's open-weight model for coding and agent work, released on 15 October 2026, so developers can download it and run it on their own hardware.
In plain words
It is a mixture-of-experts model: of its 816 billion parameters, about 42 billion work on each token. It takes in text, images, audio and video, writes text, and can hold up to 1 million tokens. It shares its base model with Muse Spark 1.3 but got extra safety training, because open weights can run without Meta's own guardrails. Meta says two Mac Studios with M5 Ultra chips can run it. Its licence lets many developers use it for free, with limited commercial terms.
A quick example
Imagine a developer who cannot send company code to an outside service. They could run a model like this on their own machines as the brain of a coding agent that fixes bugs across many files.
Where you'll meet it
- Coding agents that read a codebase, write and debug code, and call tools.
- Apps that call it through API platforms such as Groq, OpenRouter and Together AI.
Related
Sources
- DocsIntroducing Muse Spark Open, The Most Capable US Open-Weight Model to Date, Meta AI Research · read 15 Oct 2026
- DocsMuse Spark Is Now an Open-Weights Model, PyTorch · read 15 Oct 2026
- DocsWelcome Muse Spark Open, Hugging Face · read 15 Oct 2026
Checked by WhatIsAI against the sources above · 15 Oct 2026. A full five-minute explainer with a diagram may follow. Spotted an error? Report it.