OpenAI's GPT-6 Astra reconstructed 20 missing characters in a 1918 German transmission to decode its contents for the first time. The communication, identified as RICHI-240, used an ADFGVX cipher and had resisted human cryptanalysis because it contained only 220 of its intended 240 characters. Astra identified the missing block between the 4th and 5th lines of text by scoring hypothetical gaps against common patterns in the German language.

The decoded text informed the German Supreme Army Command that Serbian forces occupied the city of Vršac on Nov 11, 1918. To resolve numerical gaps in the cipher, Astra cross-referenced French intelligence telegrams and military records of the 217th to 219th infantry divisions. This reconstruction was possible because the characters were omitted as a single block, avoiding a vast search space that had deterred human reviewers since the war.