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Sunday, October 18, 2026

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Models · Sunday, October 18, 2026

Meta releases weights for Muse Spark Open

Thursday, Oct. 15

The File desk · Oct 18, 2026, 11:30 AM UTC

Status

Confirmed that Meta published the weights and the license on Thursday, Oct. 15. The ranking, the size, and the claim that two Macs can run it are company claims.
  • Confirmed
    Meta posted Muse Spark Open weights on Oct. 15, 2026, under the Muse Model License.
  • Partially confirmed
    Meta says it is the most capable U.S. open-weight model, with 816 billion parameters and 42 billion active. That is the company's claim.
  • Confirmed
    The license requires a separate deal if a large company offers the model as a service and yearly revenue tops $20 million.
Meta published the weights for Muse Spark Open on Thursday. Anyone can download them under the company's license. Meta calls it the most capable open-weight model from a U.S. lab. That ranking is Meta's claim.1
Meta says the model handles text, pictures, video, and sound. It says the model has 816 billion parameters, with 42 billion of them active, and can take a million tokens of context. It says the model is built for coding and for long jobs.2
The weights are on Hugging Face and on catalogs from Amazon, Google, and Microsoft. Several companies are hosting it as a service.3
The license has a term for big sellers. If a company and its affiliates offer models as a service and take in more than $20 million in any 12 months, they must tell Meta and sign a separate agreement first.4
Meta also asks anyone who ships it to show the words “Built with Muse Spark Open.”
Why it matters (Estimate). People can download the weights. A large company that sells access to them may have to make a separate deal with Meta first.
Meta says two Apple computers, each an M5 Ultra Mac Studio, can run it.

Notes

  1. 1.Meta AI Research, “Introducing Muse Spark Open,” Oct. 15, 2026. “Today, we’re releasing the weights for Muse Spark Open, the most capable US open-weight model to date.” https://research.meta.ai/blog/muse-spark-open
  2. 2.Same post. “Muse Spark Open is a natively multimodal model with 816B total parameters (42B active) and a 1M-token context window. Built for coding and agentic work, it excels at long-horizon tasks, complex software engineering, and multi-step reasoning.” Those figures and the ranking are company claims.
  3. 3.Same post. Available through API platforms at Baseten, Fireworks AI, Groq, Modal, Nebius, OpenRouter, and Together AI. Weights on Amazon SageMaker AI, Google Cloud Model Garden, Hugging Face, and Microsoft Foundry Models. Hugging Face model card: https://huggingface.co/meta-models/Muse-Spark-Open-816B-A42B
  4. 4.Muse Model License on that Hugging Face page, section 3. If the licensee or its affiliates provide others with access to AI models as a product or service and aggregate gross revenue exceeds twenty (20) million U.S. dollars during any consecutive 12-month period, the licensee must notify Meta and enter a separate written agreement before offering the software or derivatives as part of that business. The section does not apply to internal use, research, commercial activity that is not model-as-a-service, or using the model as a component of the licensee's own product that is not model-as-a-service. Section 2 requires prominently displaying “Built with Muse Spark Open.” The model card says the release date is October 2026 and the license is the Muse Model License. Meta's blog says the model met the thresholds of the Meta Superintelligence Scaling Framework and that a full evaluation report is available soon. That safety language is the company's.

What is still unknown or disputed

Primary sources

Every claim in this story is drawn from the documents below. If a fetch failed, that is recorded on the card.

  1. Source 1

    Introducing Muse Spark Open

    Meta AI Research · October 15, 2026

    Today, we’re releasing the weights for Muse Spark Open, the most capable US open-weight model to date. Muse Spark Open is a natively multimodal model with 816B total parameters (42B active) and a 1M-token context window.

    https://research.meta.ai/blog/muse-spark-open

  2. Source 2

    Muse Spark Open model card and Muse Model License

    Hugging Face · October 15, 2026

    If aggregate gross revenue exceeds twenty (20) million US dollars during any consecutive twelve (12) month period, the Licensee must notify Meta and enter into a separate written agreement before offering the Software as part of that Model as a Service business. Licensee shall prominently display “Built with Muse Spark Open.”

    https://huggingface.co/meta-models/Muse-Spark-Open-816B-A42B