Meta releases Muse Spark Open, an open-weight model for coding and agentic work

Meta releases Muse Spark Open, an open-weight model that it describes as the most capable US open-weight model to date.

Meta says the model is built for coding and agentic work, including long-horizon tasks, complex software engineering and multi-step reasoning. Its specifications are 816B total parameters with 42B active, and a 1M token context window.

The only other item in the record is a post by Nathan Lambert on X saying he is going to blog, which does not add a claim about the model. The capability claims are Meta's own and have not been independently evaluated in the reports.