GoKawiilOver the past week, a new fanworks movement has kicked off, with the aim to root out authors using generative AI. But the detection methods being implemented are questionable, and any fanfic writer could be caught in the crossfire.
Broad distaste around the use of Claude, ChatGPT, and other AI tools has long been a thing in creative communities, including the world of fanfiction. Readers and writers have passed around tips for spotting supposedly AI-generated works, citing anything from em dashes to the broad concept of purple prose. But on June 29th, an anonymous X account called @heatedrivalryai promised a seemingly more reliable solution. It posted a skin — similar to an extension — for the popular fanfic repository Archive of Our Own (AO3) that would purportedly identify coding artifacts left behind by Anthropic’s Claude bot.
“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,’” said the @heatedrivalryai account. “Its presence indicates the use of Claude definitively.” When a user visits a page (like a work of fanfic) with this code, the skin turns the entire background red.
Several test posts have been published to AO3 that allow users to check if it works. The screen immediately turned red when I tested the skin against these examples myself, and I published a Claude-generated short story to run my own experiment just in case. The red screen appeared when I directly pasted from the chatbot into the editor and vanished if I pasted text (including the exact same generated story) that didn’t come straight from Claude.
As far as “red flags” go, this is pretty hard to miss. Image: AO3 via The Verge
The Claude detector post was accompanied by examples of fanfic where the artifacts were spotted, which the anonymous creator said was meant to demonstrate the system works, not “create an environment of mistrust or accuse particular users.” But fanfic communities have quickly mobilized to publicly name and shame writers whose published works were flagged by the tool, and its creator certainly doesn’t consider AI a positive thing. “Fandom is a uniquely connective, collaborative space. It thrives on the human element and the creative spark which drives it and feeds off it,” they said. “If we unknowingly allow AI to corrupt these spaces, what will be left of them?”
Anthropic did not respond to my request to verify if the fan-made Claude detector works as described. The methodology here does look sound, however, and our own testing backs it up. There’s no apparent reason for the Claude code to be present in a story if the bot wasn’t used somehow. But there’s a clear risk of both false negatives and overgeneralizations.
The code wrapping is only preserved if text is copied directly from Claude into AO3’s editor, so it won’t catch anything edited in Google Docs or Microsoft Word and then moved to AO3 — and as someone who writes for a living, I can testify to how risky writing straight into a CMS is. Some writers who have been flagged have already updated their works to remove the artifacts, and future works can easily evade the tool.
Conversely, the tag doesn’t reveal how heavily Claude was used in a given work. That flashbanged scarlet screen could mean the entire story was fully AI-generated, or that an author pasted a few human-written sentences into Claude for spell-checking or translation, then moved them back into AO3.
That hasn’t mattered to some fandom members, who view any use of generative AI as an inexcusable betrayal to the wider creative community. Many people cite concerns over the environmental impact of the technology and how it’s trained by scraping the open web, which likely includes fanworks uploaded to platforms like AO3.
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