GPT-6 Astra autonomously decrypted an unbroken Enigma message (Nr. 172, MVUEH) by analyzing historical ciphertexts, identifying a repeated place name crib (ROSENOW), and developing custom Enigma simulator and Bombe software. Carter Leffer prompted the AI to attempt the task, but the system independently selected the target and executed the cryptanalysis.
On September 15, 2026, Carter Leffer validated OpenAI's GPT-6 Astra breaking a German Army Enigma message (MVUEH) from July 10, 1941, that had resisted solution since 2005. GPT-6 Astra autonomously analyzed unbroken messages, identified MVUEH as promising, and developed Enigma simulator software to execute a successful break using the crib ROSENOW, discovering the correct key and plaintext.