# Claude Fable 5.1 decoded a centuries-old royalist message hidden in plain sight since 1653 > Source: > Published: 2026-09-03 14:15:28+00:00 # Claude Fable 5.1 decoded a centuries-old royalist message hidden in plain sight since 1653 **Anthropic's Claude Fable 5.1 appears to have cracked a centuries-old number puzzle that researchers considered unsolved.** The "Cyphral Distich" by Sir Thomas Urquhart, published in 1653, consists of two lines of 32 numbers each. [According to Vals AI](https://www.vals.ai/blogs/fable-solves-cyphral-distich), Fable 5.1 solved it in 44 minutes with no human help. The author had spent months testing other frontier models on unsolved puzzles. None produced a verifiable solution. Fable 5.1 was tasked with finding a solvable puzzle on its own. It sifted through various problems and flagged the Cyphral Distich as promising. The key was hiding in the book itself. Each number points to a word in one of the 32 sections of Urquhart's publication. The first letters of those words spell out: "O God uphold King Charls the Second and make him the supreme ruler of this land." In hindsight, the solution is simple, and humans could have solved it too. [Fable 5.1 succeeded](https://the-decoder.com/anthropics-claude-fable-5-1-promises-better-coding-and-research-at-up-to-45-percent-less/) not through better cryptanalysis but through systematic trial and error and sheer persistence, according to Vals AI. ``` AI News Without the Hype – Curated by Humans Subscribe to THE DECODER for ad-free reading, a weekly AI newsletter, our exclusive "AI Radar" frontier report six times a year, full archive access, and access to our comment section. Subscribe now ``` [Vals AI / Cyphral Distich](https://www.vals.ai/blogs/fable-solves-cyphral-distich)