America's strongest open source model just dropped. Meta released Muse Spark Open: 816B total parameters, 42B active, 1M context. It runs away with the agentic tool-calling leaderboard (89.2 on MCP-Atlas, clear margin), but loses on Terminal-Bench, GPQA and SWE-bench style tasks to Kimi K3 and GLM 5.3. Meta also demoed a fully local end-to-end agentic workflow: two M5 Ultra Mac St Studios running the whole model on MLX. The license has a catch though. Once your model API business clears $20M in revenue, you owe Meta a separate deal, and your interface has to carry a "Built with Muse Spark Open" badge.
America's strongest open source model just dropped.