Claude Opus 5.5: The System Card

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. That means it’s time for a good old system card reading. 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 w...