Claude Fable won’t answer basic biology questions

Anthropic just released Claude Fable 5, calling it the most powerful AI model it has ever made widely available and praising its skills in biology, among others. But the model won't answer basic biology questions - the kind you'd expect a high schooler to handle.

Instead, it hands off the query to the former flagship model, Claude Opus 4. 8. It isn't because Fable doesn't know the answers. It's because Anthropic won't let it, by design.