Meta's Muse Spark Open model
- Meta released Muse Spark Open on October 15, an 816 billion parameter open-weight model on HuggingFace, calling it 'the most capable US open-weight model to date' and reversing a closed-weight strategy announced in April.
- It shares its base with the proprietary Muse Spark 1.3; the license allows free commercial use with attribution, though API resellers over $20 million in annual revenue must negotiate separately.
- Artificial Analysis placed it third on HLE reasoning at 39.9%, behind Gemini 3.1 Pro Preview and GPT-5.4, and said agentic performance 'does not stand out,' scoring 1427 on GDPval-AA against GPT-5.4 at 1676 and Claude Sonnet 4.6 at 1648.
Releasing an 816 billion parameter open-weight model shifts what developers and organizations can run and modify locally without API dependencies. The reversal from a closed-weight strategy means weights that Meta had previously withheld are now publicly available under a commercial license.