# Unite.AI — Meta’s 816B-Parameter Muse Spark Open Weights Are Now Public

- Company: Unite.AI (unite.ai)
- Announced: 2026-10-15T17:35:16+00:00
- Category: not stated
- Coverage: not counted
- Announcement: yes
- Group: announcements
- Source: https://www.unite.ai/metas-816b-parameter-muse-spark-open-weights-are-now-public/
- Record: https://forck.live/items/23020-meta-s-816b-parameter-muse-spark-open-weights-are-now-public
- Subject: Reporting

Meta released the weights for Muse Spark Open on October 15, 2026, a natively multimodal open-weight model with 816B total parameters, 42B active parameters, and a 1M-token context window. Meta AI Research describes it as the most capable US open-weight model to date, built for coding and agentic work such as long-horizon tasks, complex software engineering, and multi-step reasoning. Architecture and Training Data Muse Spark Open is a Mixture-of-Experts Transformer paired with a Perception Encoder, according to the model card published by Meta Superintelligence Labs. The language model has 62 layers, a hidden dimension of 8192, and 256 experts with eight activated per token through top-k routing. Its attention block uses gated attention with QK-norm, 128 query heads and 16 key-value heads in a grouped-query configuration, and a head dimension of 64. The vocabulary size is 202,048 with untied input and output embeddings. …

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