Reports: Fable 5 won’t answer even simple questions on its restricted topics

As more people are testing out Anthropic’s new, Mythos-class Fable 5, many are finding it so restrictive it wont even answer the most basic questions, TechCrunch writes.

The Verge tested it on the fundamentals of biology and found it wouldn’t even answer «easy» questions, about cell membranes or on how mRNA vaccines work.

TechCrunch is reporting on several developers who are complaining that just including the word «cyber» in a query is enough to trip it up, while others say it even refuses to write «secure» code, thinking it might be cybersecurity related.

In order to release the Mythos-based model, Anthropic made a tradeoff on very strict limits for it, and the fallback option is the still very capable Claude Opus 4.8, released in late May.

These tight restrictions aren’t by mistake, Anthropic says;

— To deploy Fable 5 safely, we believe it was necessary to be overly conservative with our safeguards so they block most queries tied to biology work, Anthropic spokesperson Paruul Maheshwary told The Verge.

Read more: TechCrunch and The Verge.