Meta Platforms has released Muse Spark Open, an 816-billion-parameter open-weight artificial intelligence model, making it available for developers to download and modify while keeping its most advanced proprietary models closed as the company seeks to convert its AI investments into revenue. The model features 42 billion active parameters, a one-million-token context window, and is designed for coding and agentic work, with Meta saying it excels at extended tasks, multi-step reasoning, and software engineering.

Meta described Muse Spark Open as the first model in its class capable of running on a desktop, specifically on two Apple M5 Ultra Mac Studios using Apple's MLX framework. A compressed 4-bit version of the model occupies roughly 493GB, making it too large to fit on a single 512GB Mac Studio. Apple published benchmarks measuring the 4-bit model at 24.99 tokens per second on two M5 Ultra Mac Studios using tensor parallelism, rising to 36.73 tokens per second across four machines. Apple's technical documentation describes the use of RDMA — remote direct memory access — over Thunderbolt 5 cables to transfer data between units with low latency.

Meta chief executive Mark Zuckerberg thanked Apple's John Ternus for the collaboration on the release. Alexandr Wang, Meta's chief of AI, said on X that Muse Spark Open 'is the most capable US open-weight model to date' [Source: The Guardian]. Wang also told Axios: 'We're excited for mommy and daddy to be playing nice again,' in reference to the Apple-Meta partnership [Source: MacRumors].

The open-weight release ships with custom Helion GPU kernels in SGLang that Meta says deliver 1.03 to 3.95 times kernel-level speedups on Nvidia and AMD GPUs, and a 3% end-to-end speedup on AMD MI350. Model weights are available for download on Amazon SageMaker AI, Google Cloud Model Garden, Hugging Face, and Microsoft Foundry Models, and the model can be accessed via API platforms including Baseten, Fireworks AI, Groq, Modal, Nebius, OpenRouter, and Together AI. The weights are released under the Muse Model License with limited commercial terms, which Meta says allow many developers to use the model for free. Meta also said it evaluated the model under its Meta Superintelligence Scaling Framework covering its most severe risk categories before release.

Muse Spark Open follows the earlier 2026 launch of Muse Spark, the closed proprietary flagship model that powers the Meta AI assistant and was the first product released by Meta Superintelligence Labs. The open-weight release is positioned against Chinese competitors including Alibaba's Qwen and Moonshot AI's Kimi, which have been dominant in the open-weight model market.

Sources: Bloomberg, The Verge, The Guardian, Meta AI Research blog, MacRumors, iClarified, OfficeChai