GoKawiilAI model Claude Fable 5.1 cracks Thomas Urquhart's 370-year-old Cyphral Distich cipher
Anthropic tasked its Claude Fable 5.1 model with solving Sir Thomas Urquhart's unsolved 17th-century cryptogram, the Cyphral Distich, and the AI produced a solution within about a day after roughly 44 minutes of reasoning. The cipher, two lines of 32 numbers each, had resisted human cryptographers for centuries and was even featured on Klaus Schmeh's list of top unsolved historical ciphers. Fable 5.1 succeeded by noticing that the number 32 and surrounding textual clues in Urquhart's book pointed to the decoding method that human researchers had overlooked.