A fresh push has emerged in fanworks circles over the last week, focused on identifying writers who may be relying on generative AI. Yet the tools being used to make those calls are far from foolproof, raising concerns that ordinary fanfiction authors could end up wrongly targeted.
Creative communities, including fanfiction fandoms, have been wary of Claude, ChatGPT, and similar AI systems for some time. Readers and writers have circulated informal advice on how to recognize work they suspect was machine-generated, pointing to signs as broad as frequent em dashes or overly ornate prose. Then, on June 29th, an anonymous X account using the handle @heatedrivalryai claimed to offer a more concrete method: a skin — functioning much like an extension — for Archive of Our Own (AO3) that was said to detect code traces left by Anthropic’s Claude chatbot.
According to @heatedrivalryai, when text produced by Claude is copied directly from Claude into AO3, it may carry a Claude-added code marker called “font-claude-response-body.” The account argued that finding that marker is definitive evidence Claude was used. Once the skin encounters a page containing the code — such as a fanfic work — it changes the page’s background to bright red.
AO3 now includes several test works designed to let users see whether the skin functions as advertised. In my own trial using those examples, the page turned red right away. I also uploaded a short story generated by Claude to test it independently. The warning appeared when I copied the chatbot’s output straight into AO3’s editor, but it disappeared when I pasted text — even the identical AI-generated story — that had not come directly from Claude.
The post introducing the Claude detector also included examples of fanfiction where the code artifacts had allegedly been found. Its anonymous creator said the goal was to show the tool in action, not to “create an environment of mistrust or accuse particular users.” Even so, fanfic communities have rapidly begun organizing around the tool, publicly identifying and criticizing writers whose works trigger it. The creator has also made clear they view AI as a threat to fandom, saying the space depends on connection, collaboration, human creativity, and the spark that sustains it. “If we unknowingly allow AI to corrupt these spaces, what will be left of them?” they said.
Anthropic did not respond to a request for confirmation on whether the fan-built Claude detector operates as claimed. On its face, the approach appears plausible, and our testing supported the account’s description. There does not seem to be an obvious reason for Claude-specific code to appear in a story unless the chatbot had been involved in some way. Still, the method leaves room for both missed detections and sweeping conclusions that may not be justified.
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.
This particular tool’s applicability is limited — AO3 isn’t the only platform for publishing fanworks, and Claude is just one of many AI models. At least one person claims they’ve written separate code that can detect “Claude, Deepseek, and some ChatGPT” usage, but they haven’t released that solution to the public or explained how it works. I asked Google and OpenAI if their models leave any traceable artifacts in text generation that could be detected by similar means, but they haven’t responded.
In fact, it’d be highly surprising if a universally reliable system existed. I’ve been reporting on the issues surrounding AI detection for a few years now, and to my knowledge, there isn’t currently a reliable technological solution for distinguishing generated text from that typed out by human hands. Systems like C2PA Content Credentials and Google’s SynthID are making some progress toward identifying generative AI in images, videos, and even audio, but these rely on invisible watermarks and metadata that don’t carry over for copy-pasted text.
AI companies have every incentive to at least solve the problem internally
That could change in the future, and AI companies have every incentive to at least solve the problem internally. Early models were trained on text indiscriminately scraped from the internet, and as human writing is crowded out by its synthetic counterpart, they could risk a “model collapse” scenario that would degrade the accuracy of outputs.
For now, though, fandom communities are still mostly relying on vibes. Most fanfics aren’t judged by a tool like the AO3 skin, but by “tells” that could include anything from specific sentence structures — like the notorious “it’s not X, it’s Y” — to overuse of flowery metaphors. (At least nobody in fandom, so far, has benches becoming men.) But we have to remember that AI often Writes Like That because it was trained on stuff that real people have written. It’s trying to replicate us. I’m not bold enough to share my own AO3 bookmarks, but I’ve definitely read some overly grandiloquent fanfics in the pre-ChatGPT internet days that wouldn’t pass this dubious sniff test.
The best solution for distinguishing AI works on AO3 is already available: the site’s robust tagging system. A “Created Using Generative AI” tag exists, and many authors do include it to disclose the use of tools like Claude. That requires honest transparency, though, and there’s little incentive for honesty given the backlash. It’s also worth remembering that fanfiction is supposed to be a hobby, not a regulated industry.
With these efforts to prevent AI from taking eyeballs away from genuine human-driven creativity, authors who don’t conform to what’s deemed to be an acceptable quality of writing may become innocent victims of the ongoing witch hunt. At least one writer has already been caught up in this because another person they trusted to edit their fic did so using Claude. So if the next fanfic you read feels a little robotic, just bear in mind that it might not actually be the product of a robot.
