Meta open-sources Muse Spark Open, its strongest open-weight model

Meta released and open-weighted Muse Spark Open on October 16, with the company and Chief AI Officer Alexandr Wang calling it "the most capable American open-weights model to date." The model targets coding and agentic use cases, excelling at long-horizon tasks, complex software engineering, and multi-step reasoning. Weights are available on Hugging Face under the Muse Model License.

Confirmed

• Core specs: 816B total parameters, 42B activated (MoE architecture), 1M token context window, natively multimodal (text/image/video/audio)
• Muse-Spark-Open-816B-A42B under the meta-models org on Hugging Face ships in BF16 and NVFP4; unsloth also has it available
• Day-0 support in transformers and llama.cpp; the community already has an MLX 3bit quantized version; config files reveal low/medium/high/xhigh reasoning effort tiers
• Zuckerberg announced the open release and thanked Apple for the collaboration, saying it runs well on the new Mac Studio; Hugging Face CEO Clement Delangue reshared a demo running GGUF Q2K quantization across two Mac Studios with a single llama serve command
• Alexandr Wang said the model is available immediately via seven API platforms—Baseten, Fireworks AI, Groq, Modal, Nebius, OpenRouter, and Together AI—with support for mainstream inference engines like vLLM/SGLang
• Official benchmark tables show the model surpassing GLM and Kimi on multiple leaderboards; it has undergone additional safety post-training

Unconfirmed

• @op7418's post claims 1T token context, contradicting the 1M token figure from official sources and multiple others; the official 1M stands

Why it matters

This is another major move in Meta's open-source strategy and a direct declaration of "America's strongest open-weights model." The combination of multimodality, ultra-long context, and agentic capability—plus full-stack deployment support from local Macs to cloud APIs—makes it appealing to both developers and the local-deployment community, and @bindureddy sees it as a key step for Meta to catch up with other AI labs.

2026-10-16 ~ 2026-10-16 · 57 related posts

Full story(2 episodes)→

• Episode 1: Meta open-sources Muse Spark Open, its strongest open-weight model(2026-10-16, 57 posts)
• Episode 2: Meta Open-Sources 816B MoE Model Muse Spark Open; Baseten Offers Day 0 API(2026-10-16, 2 posts)

• 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
• Scale AI's open muse spark model hits seven API platforms, runs on vLLM, SGLang, MLX — alexandr_wang · 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
• 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
• Muse Spark Open lands on MLX just 30 minutes after release — pcuenq · 2026-10-16
• Muse Spark Open hits MLX 30 minutes after release, but even 3-bit quant needs 256GB+ RAM — pcuenq · 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
• Muse-Spark open-weights drop: 816B-A42B MoE model gets 359GB MLX 3-bit build — ns123abc · 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
• Meta's Muse-Spark-Open-816B-A42B, an 816B MoE vision-language model, trends on Hugging Face — meta-models · 2026-10-16

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