When a Fan Detector Turned AO3 Red: What Happened in the Heated Rivalry Fandom

An anonymous X account called @heatedrivalryai posted a document on June 29, 2026 that showed hidden Claude HTML artifacts in stories on Archive of Our Own (AO3). The document listed 38 works and provided a browser skin that highlights pages containing the artifact by turning the background red. The artifacts appear when text is copied directly from the Anthropic model Claude into AO3’s editor, and they can be removed by moving text through a word processor first. Although the skin flags a clear pattern, it does not prove how much AI helped write a story; authors can also use AI for small edits.

The community response has been intense. Some readers felt betrayed and stopped reading works they had loved, while others warned that accusations can harm real people. Several authors temporarily made works private or closed comments. AO3’s site policy continues to preserve fanworks broadly and does not ban AI-assisted writing, so moderation teams must balance evidence, context, and abuse reports. Public debate continues.