Meta Releases Muse Spark Open: 816B Open-Weight Model Tops US Open Models

Key Info

Meta released Muse Spark Open, an 816B total / 42B active parameter open-weight model with a 1M token context window, built for coding and agentic work. It scores 39 on the Artificial Analysis Intelligence Index, making it the #1 US open-weights model.

Highlights

• 816B total / 42B active parameters, 1M token context window
• Scores 39 on the Artificial Analysis Intelligence Index, 22 points above Meta's Muse Glimmer (17)
• Ahead of NVIDIA's Nemotron 3.5 Super VL (26), the next highest US open-weights model
• Built for long-horizon tasks, complex software engineering, and multi-step reasoning
• In an independent game-building test, it produced the most playable game of four models at $0.59 and 19m 58s