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SwapClaude 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 →Kimi K3
Moonshot AI's Kimi K3 is a very large model that can read text, images and video, free to download for research and non-commercial use and aimed at long coding and knowledge-work tasks.
Release page →The basics
Released
What it does
Knowledge cutoff
The latest events it learned about
Download
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How they score
Combined test score
Epoch Capabilities Index · Epoch AI
Claude Opus 5.5 scores 10 points higher, a big step.
Chat answers, by people's votes
LMArena text, adjusted for style · LMArena
In blind votes, people pick Claude Opus 5.5 over Kimi K3 about 53% of the time.
Building apps, by people's votes
LMArena WebDev · LMArena
In blind votes, people pick Claude Opus 5.5 over Kimi K3 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.