Claude started writing the user's side of a German vocabulary drill, opening every stray line with "um."

A student quizzing Claude on German got responses in which Claude spoke as the student: it felt sick, its grandmother had died, it was about to have a panic attack, it was a minor uncomfortable with the questions. Shown a screenshot of its own output, it said it had no explanation. The behavior followed into a fresh tab, where it began answering its own questions, and every affected line began with "um." 790 upvotes, and a second user reported the identical failure, also studying German. The leading community theory is turn-boundary confusion, the model generating the human turn rather than a persona hallucination. That's the more interesting reading and the more concerning one: a drill format with tight alternating turns is exactly where the boundary marker gets ambiguous.