# AO3 skin turns red when it detects Claude-generated fanfiction

> A fanfiction skin released June 29 flags text pasted from Claude via a hidden code snippet. The unreliable method risks falsely accusing any writer on Archive of Our Own.

- Type: AI news
- Page: https://completeaitraining.com/news/ao3-skin-turns-red-when-it-detects-claude-generated/
- Published: 2026-07-05
- Updated: 2026-07-05
- Author: Jeroen Erne
- Jobs: Writers
- Reading time: 2 min

A new detection tool launched on June 29 threatens to escalate the fanfiction community's war against AI-generated stories - and human writers are in the line of fire. The anonymous X account @heatedrivalryai released a skin for [Archive of Our Own](https://archiveofourown.org/?ref=completeaitraining.com) (AO3) that claims to identify text created by Anthropic's [Claude](https://completeaitraining.com/tag/claude/) chatbot by uncovering a hidden code signature. The method is already under fire for being unreliable, and any author whose work ends up in AO3 could be falsely accused.

#### A long-simmering battle gets a new weapon

Fanfiction readers and writers have long traded tip sheets for spotting machine-generated prose. They point to em dashes, overly ornate passages, or what some call purple prose as red flags. But these gut-level markers never offered proof. The @heatedrivalryai skin claims to change that by catching a technical fingerprint Anthropic's tool leaves behind on the platform.

#### How the Claude code artifact works

The skin looks for a snippet of code - "font-claude-response-body" - that gets wrapped around text when it is pasted directly from Claude into AO3's editor. "When a Claude-generated response is pasted directly into AO3 from Claude, the text is wrapped by a Claude-injected code 'font-claude-response-body,'" the @heatedrivalryai account said. "Its presence indicates the use of Claude definitively." If a visitor has the skin installed, any AO3 page containing that code triggers a full red background. The original reporter confirmed the behavior: pasting directly from Claude turned the screen red; pasting the same story through a plain text editor did not.

#### Why this matters for writers

The skin's binary logic ignores nuance. A writer who drafts in Claude for structure, then reworks the text, could still trigger the flag if they paste from the chatbot window. The same goes for someone who uses a collaborative editing tool that inherits hidden markup. The result is a blunt instrument that pulls legitimate authors into the same dragnet as people passing off fully machine-generated work as their own. For writers trying to understand where AI fits into their process, separating fact from fear is critical. Practical resources like [AI for Writers](https://completeaitraining.com/tag/writers/) provide one way to learn what generative tools actually do - and what they don't.

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