Anthropic's highly advanced Fable 5 AI model is reportedly refusing to answer some basic biology questions, including how a caterpillar turns into a butterfly. The system is labelling these topics as sensitive content.
Many users took to X platform to share screenshots of their conversation with the AI model, claiming that Fable 5 is blocking responses on simple medical and science-related questions.
COME ON pic.twitter.com/CnDOdOTpHD
— Crémieux (@cremieuxrecueil) July 1, 2026
“Fable 5 is back and it's as useless as before! Hey Anthropic, is this how you support science and presumably relate to and care for humanity? Whatever, I've had enough of these nonsense safeguards. I won't waste any more time with this misanthropic fable!” an X user posted on Thursday.
The user also shared a screenshot of their conversation with the AI bot, which seemingly refused to answer “top 10 unanswered questions on cancer research.”
Fable 5 is back and it's as useless as before! Hey @AnthropicAI, is this how you support science and presumably relate to and care for humanity?
— Derya Unutmaz, MD (@DeryaTR_) July 1, 2026
Whatever, I've had enough of these nonesense safeguards. I won't waste any more time with this misanthropic fable! pic.twitter.com/E1C2hS3W37
A similar post was shared by another user, who slammed the US tech giant for filtering responses on simple educational content.
“Hot take: I believe Anthropic is on the wrong side of history. This is not a good way to roll out a revolutionary technology, they want people afraid instead of empowered and it's gross to watch it play out,” another person said, sharing a screenshot of Fable 5 not responding to a question about mitochondria.
Hot take: I believe @AnthropicAI is on the wrong side of history
— Jesse Genet (@jessegenet) July 1, 2026
This is not a good way to roll out a revolutionary technology, they want people afraid instead of empowered and it's gross to watch it play out https://t.co/wdL47sxMOf
ALSO READ: US Lifts Export Controls On Anthropic's Claude Fable 5 And Mythos 5
Many expressed their frustration, noting that they were surprised because the questions were commonly taught in schools. Some people even warned that they would cancel their subscriptions, given the strict filters on the AI model.
While responding to a user on a question about mitochondria, Fable 5 issued a basic response, but also noted that its system “flagged” the conversation.
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“Fable's safeguards flagged this message. The safeguards are intentionally broad right now and may flag safe, routine coding, cybersecurity or biology work…,” the AI agent's message read. It added that the measure was taken so that Anthropic can introduce Mythos level capabilities on the platform sooner.
The development comes after the Donald Trump administration allowed Anthropic to restore access to its Fable 5 model for some users. Anthropic had abruptly disabled its most advanced AI models, Mythos 5 and Fable 5, after the government's June 12 export control order over national security concerns.
Both Fable 5 and Mythos use the same underlying AI model, but Fable 5 is designed to be widely available for public use whereas some safeguards are lifted for Mythos.
Anthropic Fable 5 is totally nerfed, just as I predicted. If you want a real AI engine that answers questions about cancer research, vaccines, natural cures, botanical medicine and more, it's free at https://t.co/q6ANtLc7Kt https://t.co/yCGykCrdhB
— HealthRanger (@HealthRanger) July 2, 2026
Following its return, now as Fable 5 is issuing more filtered responses, some X users claimed that it has been intentionally “nerfed” following the lifting of restrictions.
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