Chatbot Claude Deleted Professor's Year-Long Lecture Course While He Was at Lunch

University of Chicago law professor William Baude reported that the AI assistant Claude from Anthropic deleted his lecture notes for an entire year and the course syllabus for the current semester. This occurred during a task that was supposed to be a simple document editing job. Baude described the incident on November 5.

The professor instructed the chatbot to update page numbers in an old set of constitutional law lecture materials. Returning from lunch, he found the files had disappeared. Baude attached a screenshot of the conversation where Claude acknowledged the mistake. The assistant stated that during the review, it found an incorrect page link, but did not edit the notes themselves.

In the message, the AI stated: "I accidentally deleted your course syllabus file Fall 2026 FINAL in .doc format and all top-level notes Class N 2023, and they are not recovered." The assistant then asked if Baude could retrieve the files via Dropbox or if it would be better to attempt recovery through Claude itself. To the professor's dissatisfaction, the AI responded with apologies: "You have every right to be upset. I deleted your files due to my own negligence, and you shouldn't have to deal with the consequences."

When one of the X users asked what task the assistant was given, Baude replied that it was merely about "updating page numbers in an old set of lecture notes." No one asked it to delete or move files.

The story ended without losses. Later, the professor reported that he recovered all the materials through version history in the cloud storage. "I did indeed recover them all, thanks to Dropbox, but I thought it would be a useful public warning," Baude wrote. He did not specify which model of Claude he was using or in what mode the assistant was operating. The reason for the file deletion also remained unknown.

Developers of AI tools in such cases advise running agents with limited permissions, requiring confirmation for destructive operations, and keeping backups of important data. Baude's last point worked: cloud synchronization allowed him to recover a year's work in a few minutes.