Meta Open-Sources Muse Spark Open, an 816B-Parameter MoE Model

On October 16, Meta officially released and open-sourced Muse Spark Open, calling it the most capable American open-weights model to date. The model uses a MoE architecture with 816B total parameters and 42B active parameters, a 1M-token context window, and an official collection on Hugging Face. Community users widely shared and discussed deployment details and benchmarks.

Confirmed

• Official specs: 816B total parameters / 42B active (MoE), 1M-token context window
• Natively multimodal, supporting text, image, video, and audio input
• Positioned for coding and agentic use cases; Meta says it excels at long-horizon tasks, complex software engineering, and multi-step reasoning
• The model underwent additional safety post-training and is open-sourced under the corresponding Meta license
• Available on Hugging Face (official collection confirmed by @victormustar)
• Meta claims the model can run on just two Macs
• Meta posted detailed notes on deployment, fine-tuning, and benchmarks in r/LocalLlama

Why it matters

• One of Meta's largest open-weights releases ever: 816B total but only 42B active parameters significantly cuts inference costs and makes local deployment more feasible
• 1M context plus native multimodality make it competitive for long-horizon agentic tasks and complex software engineering, directly benchmarking against today's top open models
• If the "runs on two Macs" claim holds, it dramatically lowers the barrier to using ultra-large models, with clear impact on the open-source and local deployment ecosystem

2026-10-16 ~ 2026-10-16 · 44 related posts

• [source] Meta's Muse Spark Open: full specs, Helion kernel speedups and benchmark tables — AIatMeta · 2026-10-16
• Meta's Muse Spark Open: 816B/A42B, 1M context, top US open-weight model — alexandr_wang · 2026-10-16
• Zuckerberg: Meta's Muse Spark Open weights out today, runs on Mac Studios — AIatMeta · 2026-10-16
• Meta's Muse Spark Open (816B/A42B) weights land on Hugging Face — Bob_SUS · 2026-10-16
• Unsloth Hosts Meta's Muse-Spark-Open-816B-A42B on Hugging Face — Bob_SUS · 2026-10-16
• [source] Meta releases Muse Spark Open: 816B/42B active, 1M context, most capable US open-weight model — AIatMeta · 2026-10-16
• Meta quietly open-sources Muse Spark, an 816B-parameter MoE model with 42B active params — victormustar · 2026-10-16
• Alexandr Wang announces muse spark open weights, "best US open-source model," runs on Mac Studio — LukeZettlemoyer · 2026-10-16
• Meta open-sources Muse Spark Open: 816B MoE with 42B active, 1M context, strong benchmarks — testingcatalog · 2026-10-16
• Meta open-sources Muse Spark, first base model from its new MSL org — RylanSchaeffer · 2026-10-16
• Meta releases 816B-A42B open-weight Muse Spark Open; Apple MLX optimized for it — BenBajarin · 2026-10-16
• [source] Muse Spark Open: Meta's 816B multimodal MoE built for agentic coding hits Hugging Face — mervenoyann · 2026-10-16
• Meta open-sources Muse Spark Open: 816B MoE that runs on two Mac Studios — op7418 · 2026-10-16
• Meta open-sources Muse Spark, topping Kimi and GLM on most agentic and multimodal benchmarks — bindureddy · 2026-10-16
• Meta researcher hails Muse Spark Open as the most capable open-weight US model yet — ThomasScialom · 2026-10-16
• Zuck announces Meta Muse Spark Open weights: 816B-param image-text model tuned for Mac Studio — bansalg_ · 2026-10-16
• Scale's Muse Spark Open claims strongest US open-weight model: 816B params, 1M context — bansalg_ · 2026-10-16
• Meta's 816B Muse Spark Open lands with Unsloth quants from 176GB and KLD benchmarks — danielhanchen · 2026-10-16
• Meta releases Muse Spark Open: 816B params, 1M context, top US open-weight model — Polymarket · 2026-10-16
• Meta open-weights Muse Spark Open: 816B total/42B active, 1M context, coding-focused — PyTorch · 2026-10-16
• Meta publishes Muse Spark Open collection on Hugging Face: 816B total, 42B active — sn2006gy · 2026-10-16
• Meta's 816B Muse Spark Open runs locally on two Mac Studios via llama.cpp — mervenoyann · 2026-10-16
• Meta releases Muse Spark Open 816B-A42B weights on Hugging Face — mishig25 · 2026-10-16
• Meta open-weights Muse Spark Open: 816B-A42B MoE with 1M context, day-0 on vLLM — vllm_project · 2026-10-16
• Muse Spark Open architecture: latent MoE with 256 experts per layer, 46 SWA + 16 full layers — vllm_project · 2026-10-16
• Meta open-sources Muse Spark Open: 816B/42B MoE reasoning model with 1M context, vLLM Day-0 support — vllm_project · 2026-10-16
• Meta releases open-weight Muse Spark Open: 816B MoE, 42B active, 1M context — QGallouedec · 2026-10-16
• Open-weight Muse Spark posts eye-catching benchmark sweep, topping Kimi K3 and GLM 5.3 on several evals — Xianbao_QIAN · 2026-10-16
• Muse Spark Open launches: 816B-param MoE billed as the most capable US open-weight model — altryne · 2026-10-16
• Meta open-weights Muse Spark: 816B-parameter multimodal model with 42B active — qinzytech · 2026-10-16
• Muse Spark weights land on Hugging Face in BF16 and NVFP4 variants — Dimillian · 2026-10-16

13 near-duplicate retellings: AIatMeta · AIatMeta · MaziyarPanahi · airesearch12 · victormustar · op7418 · gabriberton · TorturedPoet30 · parth007_96 · BanghuaZ · jiayi_pirate · awnihannun · qinzytech