Claude Fable 5 is our first generally available Mythos-class model. It ships with new safety classifiers that may flag certain prompts in dual-use domains like cyber and bio. We've added fallbacks: a refused request retries on Claude Opus 4.8 instead of dead-ending.
Claude Fable 5 is Our First Mythos-Class Model
Claude Fable 5 is our first generally available Mythos-class model with new safety classifiers.