Muse Spark Open

Muse Spark Open is the open-weights version of Meta's Muse Spark model, released by Meta Superintelligence Labs on 15 October 2026. Meta calls it the most capable US open-weight model to date and aims it at coding and agentic work: long-horizon tasks, complex software engineering and multi-step reasoning. It is a mixture-of-experts model with 816 billion parameters, of which 42 billion are active for each token, and it holds a context of up to one million tokens.

What it does

The model reads text, images, video and audio and returns text; it does not generate images, sound or video. Meta ships the weights in BF16 and in an NVFP4 build that quantises only the experts. The model card asks for at least 700 GB of accelerator memory for NVFP4 and 2 TB for BF16. Meta's headline deployment is a desktop one: two Apple Mac Studios with the M5 Ultra chip, each with up to 512 GB of unified memory, run the model through Apple's MLX framework, and Meta describes on-device tests in which its Muse Code agent made changes to an open-source iOS app and edited video in DaVinci Resolve. In the data centre it runs on SGLang, vLLM, TensorRT-LLM, Hugging Face Transformers, llama.cpp and Unsloth, with optimisations for AMD, Apple, Intel and NVIDIA hardware.

Who it is for

Meta says hosted access is available on day one through Baseten, Fireworks AI, Groq, Modal, Nebius, OpenRouter and Together AI, and the weights can be downloaded from Amazon SageMaker AI, Google Cloud Model Garden, Hugging Face and Microsoft Foundry Models. The Muse Model License allows use, fine-tuning, distillation and redistribution, with two conditions a business should read: products built on it must display "Built with Muse Spark Open", and a company offering models as a service with more than $20 million of revenue in any twelve months needs a separate written agreement with Meta. Internal use and features inside a company's own product are outside that clause. VentureBeat, reporting the release on 16 October, notes that Meta's own table puts the model ahead on some tool-use tests and behind leading Chinese open models on others; those are Meta's figures and no score is stored here.

Key facts

Maker: Meta Platforms (Meta Superintelligence Labs) Released: 15 October 2026 Size: 816B total parameters, 42B active Context: up to 1M tokens Inputs: text, image, video, audio; output text Licence: Muse Model License (separate agreement for model-as-a-service providers above $20M revenue) Weights: BF16 and NVFP4 on Hugging Face, gated access