Muse Spark Open
Meta's Muse Spark Open is a text model for writing and answering questions that is free to download under restricted use terms.
Key facts
- Released
- Oct 15, 2026
- What it does
- Text and chat: Writes, answers questions and holds a conversation.Thinks first: Can reason step by step before it answers: slower, but better at maths, code and tricky questions.Sees images: Understands pictures, screenshots and charts you share with it.Reads files: Reads documents such as PDFs.Listens: Understands speech and other sounds.Watches video: Understands video clips you share with it.
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- How
- Free to download, with some licence limits
From trckr's archive of releases before it started watching. Date and details from Epoch AI's database of AI models (CC BY 4.0).
Price and limits
What developers pay to use it through the API: How developers plug a model into their own apps and pay per use. A model that's "in the API" can be used by programmers, even if it isn't in a chat app yet., per million Tokens: The small chunks of text a model reads and writes, about three-quarters of a word each. Prices and limits are counted in tokens. sent (input) or written back (output), and how much it can take in at once.
- Input
- $1.25
- per million tokensCached: $0.15
- Output
- $4.25
- per million tokens
- Context window: How much a model can keep in mind at once: your question, any files you share and its own replies. Measured in tokens; 1,000 tokens is about 750 words.
- 1.05M tokens
- about 790,000 words
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- Longest answer
- 131K tokens (about 98,000 words)
From OpenRouter, checked .
How it scores
From independent testers, never the lab's own claims.
- Combined test score#38 of 235
- GPT-6 Astra169
- 2GPT-6.1 Sol169
- 37Qwen 3.8 Max156
- 38Muse Spark Open155
- 39Gemini 3.5 Flash155
Source: Epoch AI · Epoch Capabilities Index
- Building apps, by people's votes#49 of 85
- Claude Opus 5.51,818
- 2Claude Sonnet 5.51,773
- 48Muse Spark 1.21,534
- 49Muse Spark Open1,528
- 50Claude Sonnet 4.61,522
Source: LMArena · LMArena WebDev
Compare Muse Spark Open with
It came out 3 days after Muse Wonder Full, the lab's previous model.
The details
Meta text model for language generation and question answering, released as Open weights: The model's files are public, so anyone can download it, run it on their own computer and build on it, usually for free. trckr labels these "Open". with restricted use.
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