A SISTRIX analysis of 3.8 million German-language ChatGPT responses found that citation patterns changed after ChatGPT began implementing GPT-5.5. The analysis , published by SISTRIX founder Johannes Beus, tracked 38 daily samples of 100,000 ChatGPT responses. SISTRIX compared citations in the four days before the change with the four days after it. The company describes the event as a “ChatGPT Core Update,” comparing it to the way Google Core Updates change search rankings. SISTRIX also notes that the data shows correlation, not proof that the model change caused the citation movement. For transparency, SISTRIX sells Prompt Tracking, the product used to gather the data for the analysis. What The Data Shows On a typical day during the tracking period, citation patterns varied by 1-2%. During the May 22-23 model-identifier change, that number jumped to 47%. The average number of cited sources per response also dropped, from 30.9 before the change to 28.4 after.…