GPT-6 Astra successfully decoded a previously unsolved German WWI radio message encrypted with the ADFGVX cipher method, revealing information about an English cruiser arriving at Sevastopol on November 24, 1918, and an allied squadron following on November 26. The decryption used the key "TRUPPENVERSCHIEBUNG," which historical records suggest was not officially adopted until December 9, 1918, explaining why the message had remained unsolved.