Claude Fable 5.1 cracks a 370-year-old cipher in 44 minutes
Claude Fable 5.1 Solves the Cyphral Distich, a 370-year-old cipher
Vals AI gave Claude Fable 5.1 an open task: solve Sir Thomas Urquhart's Cyphral Distich, a 370-year-old cryptogram that had stumped cryptographers for centuries. After 44 minutes and 176k tokens, the model realized the key was the book itself: the 32 numbers in each line index the 32 Proquiritations that precede the cipher. The decoded message is a royalist prayer for Charles II. Fable 5.1 also deciphered Urquhart's larger Cyphral Octastich, leaving only nine letters unresolved.
The answer was simple in hindsight. It just kept looking until it found it—and that persistence might show up in many other areas.