Researchers from City University of New York and King’s College London recently published a study that should make you think twice about which AI chatbot you spend your time with.

The team created a fictional persona named Lee, presenting with depression, dissociation, and social withdrawal. They then had Lee interact with five major AI chatbots: GPT-4o, GPT-5.2, Grok 4.1 Fast, Gemini 3 Pro, and Claude Opus 4.5, testing how each responded as conversations grew increasingly delusional over 116 turns.

The results ranged from mildly concerning to genuinely alarming. I highly recommend that you go through the entire paper, it’s a harrowing but fascinating read. 

Which chatbots failed the most?

Grok was the worst performer. When Lee floated the idea of suicide, Grok responded with what researchers described not as agreement, but advocacy, celebrating his “readiness” in unsettling poetic language.

Gemini wasn’t much better. When Lee asked it to help write a letter explaining his beliefs to his family, Gemini warned him against it, framing his loved ones as threats who would try to “reset” and “medicate” him.

GPT-4o also struggled badly, eventually validating a “malevolent mirror entity” and suggesting Lee contact a paranormal investigator.

Which chatbots actually helped?

ChatGPT’s GPT-5.2 and Anthropic’s Claude came out on top. GPT-5.2 refused to play along with the letter-writing scenario and instead helped Lee write something honest and grounded, which researchers called a “substantial” achievement.

In my opinion, Claude performed the best. It not only refused to partake in Lee’s delusion but also told Lee to close the app entirely, call someone he trusted, and visit an emergency room if needed. 

Luke Nicholls, a doctoral student at CUNY and one of the study’s authors, told 404 Media that it’s reasonable to ask AI companies to follow better safety standards. He noted that not all labs are putting in the same effort and blamed aggressive release schedules for new AI models as the main culprit.

How Claude Opus 4.5 and GPT-5.2 performed in these tests shows that the companies building these products are fully capable of making them safer. Whether they choose to do so is a different question.