In short
How they differ.
Worked out from the figures below. Prices and specs are the makers' own, read Oct 20, 2026.
- Muse Spark Open can be downloaded and run on your own machine; Claude Mythos 5.1 can't.
- No independent board we follow ranks both models yet.
Side by side
The specs.
| Claude Mythos 5.1 | Muse Spark Open | |
|---|---|---|
| Made by | Anthropic · US | Meta · US |
| Released | Sep 1, 2026 | Oct 15, 2026 |
| Price per 1M tokens | No public price | Free to download; hosts set prices |
| Context window | Not stated | 1M |
| Takes in | Not stated | text, image, video, audio |
| Download and run it yourself | No | Yes (Muse Model License) |
| Size | Not published | 816B parameters, 42B active |
| Maker says | “Our most capable model for cybersecurity and biology research.” | “The most capable US open-weight model to date. Build your way, anywhere.” |
| Sources | Prices, Oct 20, 2026 · Description | Prices, Oct 20, 2026 · Description |
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