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SwapMuse Spark 1.3
Meta's Muse Spark 1.3 is a major chatbot model for writing and answering questions, offered to developers online.
Release page →Claude Opus 5.5
Anthropic's new Claude Opus 5.5 writes text and answers questions, offered to developers and paying users, not free to download.
Release page →The basics
Released
What it does
Knowledge cutoff
The latest events it learned about
Download
Where to use it
Price and limits, for developers
Input
Per million tokens
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How much it takes in at once
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How they score
Combined test score
Epoch Capabilities Index · Epoch AI
Claude Opus 5.5 scores 11 points higher, a big step.
Chat answers, by people's votes
LMArena text, adjusted for style · LMArena
Neck and neck: in blind votes, people pick each about as often as the other.
Building apps, by people's votes
LMArena WebDev · LMArena
In blind votes, people pick Claude Opus 5.5 over Muse Spark 1.3 about 72% of the time.
Green marks the better of the two on each row, red the other. Rows where one side isn't listed, or where the gap is too close to call, stay plain.
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Rankings from LMArena and Epoch AI, both CC BY 4.0, updated . Developer prices, context windows and knowledge cutoffs from the labs' own listings on models.dev and from OpenRouter. The app links go to each maker's own app when no source says exactly where the model is available.