GPT-6 Astra has successfully decoded a previously unsolved World War I German radio cipher from the ADFGVX family. The message, originally transmitted on November 27, 1918, appears on Scienceblogs.de's list of 50 unsolved ciphers. Using the encryption key "TRUPPENVERSCHIEBUNG" documented in J. Rives Childs's "The History and Principles of German Military Ciphers, 1914–1918" (pages 214-215), the model reconstructed the transposition table and decrypted the 170-character ciphertext.

The decoded German text reads: "EIN ENGLISCHER KREUZER EINLIEG X SEWASTOPOL X S4STEN X EIN GESCHWADER DER X ALLIIERTEN FOLGT 26STEN X" which translates to "AN ENGLISH CRUISER ARRIVED AT SEVASTOPOL ON THE ?4TH AN ALLIED SQUADRON FOLLOWS ON THE 26TH." Codebreaking expert George Lasry had previously decoded hundreds of similar messages, but over a dozen remained unsolved.

Astra identified a historical discrepancy: the key "TRUPPENVERSCHIEBUNG" was reportedly implemented starting December 9, 1918, yet this message predates that by 12 days. Cross-referencing naval logs confirmed HMS Canterbury arrived in Sevastopol on November 24, 1918, with an allied squadron following on November 26, validating the decryption's historical accuracy.