Muse Spark Open
Key facts · verified Oct 18, 2026
Muse Spark Open is a Meta model released on 15 Oct 2026. Pricing: Free - open weights, self-hosted (no first-party API price). Its context window is 1,048,576 tokens. It is not yet ranked on LMArena's text leaderboard. Source: dev.meta.ai.
Muse Spark Open is the open-weight release of Muse Spark, Meta's agentic and coding model. It is a sparse mixture-of-experts transformer with 816 billion parameters in total and 42 billion active per token, with built-in perception encoders: it takes text, image, audio and video input and returns text, with a 1,048,576-token context window. Meta publishes it in two checkpoints - BF16 (about 1.65 TB of weights, served on eight GPUs such as 8 x B300) and NVFP4 (about 537 GB, served on one 4-GPU Blackwell node) - under the Muse Model License. It can be self-hosted with runtimes such as SGLang and vLLM, or called through hosted providers.
Free - open weights, self-hosted (no first-party API price)
1,048,576 tokens
Not rated
Not ranked
Full Specifications
Free - open weights, self-hosted (no first-party API price) | |
|---|---|
| Identity | |
| Developer | Meta |
| Released | Oct 2026 |
| Status | GA |
| Licence | Muse Model License, plus Meta's Acceptable Use Policy |
| Self-hostable | Yes - BF16 (~1.65 TB, 8 x B300) or NVFP4 (~537 GB, 4 x B300); weights on Hugging Face (meta-models/Muse-Spark-Open-816B-A42B), gated |
| Cost | |
| Input price | Self-hosted - no first-party API price |
| Output price | Self-hosted - no first-party API price |
| Free tier | Yes - weights are free to download and run |
| Capacity | |
| Context window | 1,048,576 tokens |
| Capability | |
| Vision in | Yes - image and video |
| Audio in | Yes |
| Function calling | Yes - tool calling (per Meta's prompting guide) |
| Extended reasoning | Yes |
| Access | |
| API | Not offered first-party (hosted providers and OpenRouter) |
| Chat app | No |
| Cloud marketplaces | Amazon SageMaker AI, Google Cloud Model Garden, Microsoft Foundry Model Catalog |
| Fine-tuning | Yes - open weights; Meta publishes a post-training guide |