Meta releases Muse Spark Open, saying it is the most capable US open-weight model, with 816B total and 42B active parameters and a 1M-token context window

Muse Spark Open is available today and brings leading agentic capabilities to your desktop for the first time on Apple M5 Ultra Mac Studios.

Meta AI Research 2026-10-15

Context & Ripple Effects

Muse Spark began as the model behind Meta AI queries and its shopping mode, alongside an announced plan to release an open version. Meta then released Muse Glimmer as an open-weight model in August and said an open-weight version of its more advanced Spark line would follow.

The release turns that roadmap into a desktop-focused distribution move on Apple M5 Ultra Mac Studios. It also extends a model family already used in Meta's consumer AI products into an ecosystem where developers can inspect and adapt the weights.

First-order effects

Developers with Apple M5 Ultra Mac Studios can obtain Muse Spark Open's weights for local desktop use, rather than accessing the Spark family only through Meta's products and services.
Meta converts its earlier plan to open-source a Muse Spark version into an open-weight offering while retaining Spark's role in Meta AI.

Second-order effects

Apple gains a high-profile local AI workload for M5 Ultra Mac Studios, making desktop hardware a more direct part of model deployment decisions.
Enterprise developers and inference providers must weigh the model's claimed capabilities against its license terms; public discussion flagged those terms as a meaningful constraint on commercial use.

Third-order effects

If developers fine-tune and deploy the model broadly, open weights can expand the surrounding tooling and hosting market while Meta keeps the consumer distribution layer through Meta AI.
The move reinforces a split model strategy: foundation-model weights circulate outside the company, while product integration and user reach remain concentrated with the platform owner.

The trend: Frontier-model developers are using open weights to widen adoption and complementary infrastructure while preserving proprietary consumer services as the primary control point.

Discussion

@finkd Mark Zuckerberg on x
Muse Spark Open — weights releasing today — runs great on new Mac Studios thanks to work with @johnternus and Apple.
@ccatalini Christian Catalini on x
Unlike the labs, Meta doesn't need to sell intelligence to win. It just needs to make it useful to a few billion people. https://x.com/...
@skasriel Stephane Kasriel on x
This is a big deal. Can't wait to see how the community uses this model and fine tunes it with their own data to build next generation AI applications.
@natolambert Nathan Lambert on x
The Meta Muse Open License is trash. Thankfully no one really cares about licenses, expect the inference providers who will happily comply.
@natolambert Nathan Lambert on x
If it performs roughly what like the scores indicate, adoption of this model is going to go gangbusters. First open-weigh model in the US with near frontier agentic capabilities (GLM 5.2 + Kimi K3 was that step change from China). US models get crazy adoption.
@levie Aaron Levie on x
They did it. They made a Muse open weights model, which is a huge step forward for OSS in the US. This is going to further accelerate AI diffusion because enterprises will be able to mix and match frontier performance for orchestration and high end tasks, while being able to have…
@clementdelangue Clem on x
Meta is back! https://huggingface.co/...
@kimmonismus @kimmonismus on x
Meta is so back! They are finally releasing Meta Muse Spark open weight. Best US open weight model 816B total / 42B active parameters 1M token context window Natively multimodal across text, image, video, audio Love to see!
@armandjoulin Armand Joulin on x
congratulations @AIatMeta this is amazing to see you back in open model space with such an amazing model!
@pratanchandani Prashant Ratanchandani on x
Every time I meet people to talk about the Muse family of models, one of the questions has been when we will release weights. The wait is over. Muse Spark Open is now available. The most capable US open weights model.
@iam_rajuptvs Raju Penmatsa on x
huge! congrats on the launch! I think this is a great move, and hope more follow.. releasing older model weights after launch of newer model. Hope this trend continues.
@beffjezos @beffjezos on x
Meta just keeps winning. Ended up teaming up with Apple too!!! Beginning of the Golden Age of Local Superintelligence
@natolambert Nathan Lambert on x
Okay now I really gotta blog 🎉
@bubbleboi Bubble Boi on x
Let's gooo
@mehulmpt Mehul Mohan on x
question is who's gonna host it cheaper than deepseek
@eliebakouch Elie on x
another major american lab doing hybrid sliding window attention :)
@alexfinn Alex Finn on x
America is SO back Zuck just announced Muse Spark Open is dropping later today, built with Mac Studios in mind This is bigger than you think The Meta Muse model was trained specifically for agent tasks. Now we can run it locally, plugged into agents like Hermes This is the future…
@digitalix Alex Ziskind on x
What's this? New model gonna need these bad boys. Meta's 816B param Muse Spark is open wieghts 🤯 1M-token context window. And MoE, so likely relatively fast. Now I'm really curious what my cluster can do!
@tokengremlin @tokengremlin on x
This is a brilliant release for those of us who love open source. The more, the better. But it also shows just how far ahead Chinese AI labs have gotten compared to the US, and I'm excited to see what they can pull off by distilling Opus 5.5 and GPT-6 Astra.
@ollama @ollama on x
Amazing to see @AIatMeta launch the best US open-weight model so far! The model will be available on Ollama shortly. 🫡
@alexandr_wang Alexandr Wang on x
muse spark open. why 2026 won't be like 1984 
@mattdeitke Matt Deitke on x
We're open-sourcing Muse Spark Open! This is an important release which is the most capable US open-weight model yet. 🇺🇸 - 816B parameters (42B active) - 1M token context window - Built for coding and long-horizon agents - Runs locally on two Apple M5 Ultra Mac Studios More here:…
@aiatmeta @aiatmeta on x
To help make advanced models more accessible, Muse Spark Open is optimized to run on two Apple M5 Ultra Mac Studios with the latest MLX framework. It also runs on leading inference engines like SGLang, vLLM, TensorRT-LLM, Hugging Face Transformers, llama.cpp, and Unsloth with opt…
@aiatmeta @aiatmeta on x
Today we're releasing Muse Spark Open, the most capable US open-weight model to date. Built for coding and agentic work, it excels at long-horizon tasks, complex software engineering, and multi-step reasoning. Key Model Specs: → 816B total / 42B active parameters → 1M token conte…
@alexandr_wang Alexandr Wang on x
3/ muse spark open is available today through API platforms at Baseten, Fireworks AI, Groq, Modal, Nebius, OpenRouter and Together AI. model weights are available for download on Amazon SageMaker AI, Google Cloud Model Garden, Hugging Face, and Microsoft Foundry Model Catalog. it…
Allen Bolourchi, PhD, MBA Allen Bolourchi, PhD, MBA on linkedin
Excited to share the release of Muse Spark Open, our best open-weight model at Meta and the most capable US open-weight model! …
Annie Hu Annie Hu on linkedin
Try Muse Spark Open!! It's been a Wonder(full) week! :)
@aaronp613 Aaron on x
So weird to see John Ternus and Zuck interacting on X
@viticci Federico Viticci on x
yeah, safe to say we're entering a new Apple era indeed
@johnternus John Ternus on x
@finkd Congrats to the team! Amazing to run a model of Muse Spark Open's caliber and scale this efficiently, right from your desk. Mac Studio keeps pushing the boundaries of on-device AI!
@bubbleboi Bubble Boi on x
Meta released a model that runs better on apple silicon than apple. [embedded post]
@bzamayo Benjamin Mayo on x
Nvidia, Netflix, now Meta ... Apple really is putting old feuds to rest https://x.com/...
@mweinbach Max Weinbach on x
Meta worked with Apple on optimizing MLX for this, including native multimodal support in mlx-lm and optimizations to MoEs and thunderbolt clustering It should get roughly 20 tokens per second on 2 M5 Ultra but I'm sure that could get way better
@mehulmpt Mehul Mohan on x
M5 Ultra (and beyond) might be the future of local AI
@chancehmiller Chance Miller on x
Zuckerberg having to use X to thank Ternus because Apple doesn't use Threads is fascinating.
@artisny @artisny on bluesky
(*Just* when you think this company could not *possibly* do or say anything that would be even *more* weird or disturbing...) — Lol—Wut ??!! Have they still not read the memo: “Be Normal.” ? — 😱😂 [embedded post]
Chenyang Zhao Chenyang Zhao on linkedin
Meta? Finally back with a new open-weight model, Muse Spark OSSed. — 816B total parameters, 42B active, 1M context, native multimodal capabilities …
@mattdeitke Matt Deitke on x
Muse Spark Open is live on @huggingface! 🤗 - Strong agentic model (especially for personal agents) - Multimodal from the ground up - 816B parameter model - 42B Active parameters Models link: https://huggingface.co/... [image]
@anantn Anant Narayanan on x
Muse Spark Open weights available today! (And 👌 use of the Muse mac app) https://huggingface.co/... [embedded post]
r/apple r on reddit
Apple and Meta team up to make Muse AI model run on Mac computers
@meghanbobrowsky Meghan Bobrowsky on x
Meta today released a new open-weight AI model that can run locally on Apple's high-end Mac computers. It's a big deal that the two companies are collabing after their long feud, during which Mark Zuckerberg in 2018 said he wanted to “inflict pain” on Apple. (1/2)
@meghanbobrowsky Meghan Bobrowsky on x
It's also a mutually beneficial deal. Meta gets more researchers and developers to use its AI model and Apple gets to sell more Macs. Read more here in my story with @RolfeWinkler: https://www.wsj.com/... (2/2)
Jonathan Vanian Jonathan Vanian on linkedin
Apple and Meta team up to make Muse AI open-weight model run on Mac computers - with Kif Leswing — The iPhone maker and social media giant …
@teortaxestex @teortaxestex on x
Muse Spark Open is substantially weaker than Spark 1.3 What gives? Is Spark 1.3 a much bigger model, or just non-nerfed?
Ash Jhaveri Ash Jhaveri on linkedin
Today we released Muse Spark Open with a large and diverse set of ecosystem partners to ensure developers can access the best western open model on their platform of choice, including running locally. …
Saurabh Baji Saurabh Baji on linkedin
Muse Spark Open is here - the most capable US open-weights model! — Strong agentic performance — 816B total / 42B active params — 1M context …
Sidhartha Reddy Potu Sidhartha Reddy Potu on linkedin
Muse Spark Open is out today: the most capable US open-weight model to date, from Meta Superintelligence Labs. …
Tatyana P. Tatyana P. on linkedin
Muse Spark Open! Many people were eagerly awaiting this release! It is the most capable U.S. open weight model to date built for coding, agentic, and natively multimodal. https://lnkd.in/gB8SS9t3 …
Tatyana P. Tatyana P. on linkedin
Muse Spark Open! Many people were eagerly awaiting this release! It is the most capable U.S. open weight model to date built for coding, agentic, and natively multimodal. https://lnkd.in/... …
@eriskii.net Eris on bluesky
Muse spark is out now and it mogs every other open weight model — research.meta.ai/blog/muse-sp... [image]
@sungkim Sung Kim on bluesky
Meta released the open weight of Muse Spark Open — Muse Spark Open is an 816B total/42B active parameter open weights model with a context window of 1M tokens. — Blog: research.meta.ai/blog/muse-sp...
@andymstone Andy Stone on x
Meta + Apple + the most capable US open-weight model to date
@alexandr_wang Alexandr Wang on x
great doing business with you john apple 🍎🤝
@garrytan Garry Tan on x
Open weight models rising
@davis7 Ben Davis on x
I'm starting to really, really like Meta
@michaeldell Michael Dell on x
Customers love choice! @AIatMeta Muse Spark Open and @nvidia Nemotron 3.5 Super VL are now available on the Dell Enterprise Hub with @huggingface 🤗 https://dell.huggingface.co/ ...
@badlogicgames Mario Zechner on x
meta going scorched earth in this economy https://research.meta.ai/...
@xlr8harder @xlr8harder on x
@natolambert hey they managed to get themselves to drop the absurd derivative model naming requirement from llama era. some serious progress here!
@natolambert Nathan Lambert on x
@xlr8harder Its got all the restrictions across all license eras 1. Built with muse branding nonsense that no one followed 2. Revenue gate like kimi/glm (reasonable) 3. Restricted domains / authorized use policy 4. All of the above applies to models trained on ai outputs (maybe)
@xlr8harder @xlr8harder on x
wow he's not kidding. they managed to make the llama 3.1 license worse complete trash zuck will not save you, open source users.
@elder_plinius @elder_plinius on x
WTF IS THIS 🤬
@groqllc @groqllc on x
Muse Spark Open from @AIatMeta is now in limited preview on GroqCloud, running at 350+ tokens/sec per user. Meta trained it for agentic coding. It has 816B parameters (42B active). On GroqCloud, it supports 131,072 tokens of context and text and image input, with text output. Rea…
@almmaasoglu Alim on x
Meta is so unbelievably back and they made me eat my own words. I didn't expect them back so fast
Hyung Won Chung Hyung Won Chung on linkedin
We have one more launch this week: Muse Spark Open! — Open weights, 816B total parameters, 42B active. This is a good model. …
Mahesh Pasupuleti Mahesh Pasupuleti on linkedin
Another Muse release this week and this time its a open weight model - 816B parameters (42B active), 1M-token context window, natively multimodal across text, image, video and audio. …
@shshnkp Shashank Prasanna on x
Today we also published benchmarks and a deep dive into LLM inference on M5 Ultra Mac Studio, covering MLX, GPU Neural Accelerators, tensor and pipeline parallelism, and Thunderbolt 5 RDMA. https://machinelearning.apple.com/ ... [embedded post]
@beffjezos @beffjezos on x
John Ternus making moves. Very smart play here to compete with Nvidia / Nemotron
@avichal Avichal Garg on x
The CEOs of @Apple and @Meta are tweeting about how efficient it is to run inference on Mac Silicon Someone should really build a distributed inference network that runs on top of Mac Silicon. It's probably a $10b company or protocol. 🙃
@trebolloc Ronan Collobert on x
So proud of the MLX team! Muse Spark Open, on your desk: 816B params at 36+ tokens/sec on 4 Mac Studio computers. We've been hard at work on better M5 GPU Neural Accelerator support, a smoother Thunderbolt experience (including multi-cable meshes), and kernel optimizations for Mo…
@stammy @stammy on x
meta is just teasing us that they have prerelease M5 Ultra 512GB unified memory Mac Studios https://research.meta.ai/...
Lomit Patel Lomit Patel on linkedin
Apple and Meta putting years of rivalry aside to bring powerful AI models to Mac hardware says something important about where this market is heading. …
@clementdelangue Clem on x
llama serve -hf ggml-org/Muse-Spark-Open-816B-A42B- GGUF:Q2_K (on two mac studios). Well done @finkd & @johnternus!
@asherdipps Asher on x
@johnternus @finkd This looks like 2 AIs talking to each other lmfao
@scaleailabs @scaleailabs on x
Congratulations to @AIatMeta on releasing Muse Spark Open. An incredible achievement and an exciting step toward a future with more choice in AI. The @Muse family has been especially strong on multi-step coding workflows, and open weights make it much easier to tune those capab…

Chronicles