Meta has published the weights for Muse Spark Open, a coding and agent model it says is less advanced than the Muse Wonder frontier model it launched on Monday. Chief AI officer Alexandr Wang said Meta will generally not open-source its most powerful models, which is the split the EU AI Act’s open-source exemption is built around.
Meta has published the weights for a model it says is deliberately not its best, and put the policy on the record. In Europe, that split is the one the AI Act’s open-source exemption is built around.
Bloomberg reported the release on Thursday. Muse Spark Open is built for coding and agents, and Meta says it is less capable than Muse Wonder, which launched on Monday.
“Because of both safety and capabilities, we will generally not open-source our most powerful models,” Alexandr Wang said. He said Meta intends to keep releasing good open models.
The weights sit on Hugging Face, Amazon SageMaker AI and Google Cloud Model Garden. One platform serving it is Nebius, the Dutch firm Meta has committed up to $27B to.
Meta said on Monday that Muse Wonder had reached the frontier, and published no benchmarks. That model stays closed.
This is the second open release from the Muse line. Meta published Glimmer in August, a 30-billion-parameter model distilled from Muse Spark, under Apache 2.0. It also worked with Apple so the new model runs on two M5 Ultra Mac Studios.
In September the company had not decided whether to publish the weights for Muse Spark 1.3. It has answered with a different model instead.
Article 53 of the AI Act exempts a genuinely free and open model from the documentation owed to the AI Office. The exemption stops at systemic risk, where every obligation applies whatever the licence.
Meta’s founder said close to the opposite five weeks ago. Zuckerberg told the Sources podcast that rivals training more advanced models and then not releasing them was quite dangerous. He named no company.
The Commission can fine 3% of global turnover and demand evaluations before release. Meta declined to sign the code of practice written to operationalise those duties, and Joel Kaplan said last year that Europe was on the wrong path.
Wang said most of the world’s AI will run on open models, and that they should be American. Eight days earlier, Alibaba chairman Joe Tsai told a Turin conference that open source was Europe’s only way to independence.
Wang expects Chinese developers to build on Muse Spark Open, and said it might even be good if they adopted its principles.
Europe’s own answer is already in the market. Mistral launched Large 4, a trillion-parameter open-weight model, to take on China’s lead in this category.