Meta releases open-weight Muse Spark Open, an 816B-parameter model for coding and agent work

Meta has released open weights for Muse Spark Open, an 816 billion-parameter model built for coding and long-running agent work, with 42 billion parameters active per token.

The model supports up to 1 million tokens of context and mixed text, image, audio and video prompts. In Meta's benchmarks it scored 89.2 on MCP-Atlas, ahead of the rivals it listed, but trailed Chinese open models on the Terminal-Bench 2.1 coding test.