Claude Opus 5.5: The System Card
Photo: Don't Worry About the Vase
Introducing the world’s most powerful model, at least by some measures like Artificial Analysis or any standard benchmark list, which is now Claude Opus 5.5. Anthropic is claiming Opus 5.5 is outright as good or better than Fable 5.1, while being actively cheaper than Opus 5. Due to the situation becoming increasingly hard to monitor, I never got a chance to publish my model welfare review for Claude Fable 5.1. My plan is to combine that with my welfare review for Claude Opus 5.5, once we have had time to get experience with Opus 5.5.
First reported by Don't Worry About the Vase. This page is a short excerpt; the full text is theirs.
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