tl;dr: Anthropic apologized for shipping Claude Fable 5 with invisible guardrails that silently degraded responses suspected of being distillation attempts, without notifying users. Going forward, flagged queries will be rerouted to the older Claude Opus 4.8 model with visible notification, matching how Fable handles other high-risk areas like bio, chem, and cybersecurity. The company conceded that invisible safeguards were the "wrong tradeoff," though it noted some visible safeguards (notably biology) are calibrated so broadly that Fable is nearly unusable for basic queries.