GPT-6 Astra recovers wheel order 253 and full key for MVUEH Enigma message of 10 July 1941

Carter Leffer directed GPT-6 Astra to attempt any unbroken Enigma messages on the Crypto Cellar site. The model identified MVUEH (Nr. 172) as highest priority, noted its similarity to the already-broken SIPVX (Nr. 173), and isolated the repeated crib ROSENOW ROSENOW. It generated Python and C++ code for an Enigma simulator and Bombe, executed the search, and recovered a key set distinct from the daily key 512 used on the same date.

The recovered plaintext is 82 letters long and matches SIPVX except for an enciphering error on 'Bitte' and the repeated signature 'Waschbusch'. The break also revealed a left-wheel turnover at position 72 and multiple transcription errors in the published ciphertext. These factors explain why manual and conventional attacks since 2005 had failed.

The Bundesarchiv note on Nachschubführer message copies, published July 2026, supplied context the model exploited. Prior breaks on 10 July traffic used wheel order 512 with different rings and stecker; MVUEH required an entirely separate daily key. This demonstrates an LLM chain that combined historical document search, crib selection, code synthesis, and exhaustive search without human intervention after the initial prompt.

Further log analysis will quantify the exact search tree and turnover handling. The result supplies a verifiable benchmark for LLM performance on historical cryptanalysis tasks that resisted human solution for 21 years.