Ask HN: How do I make sure ChatGPT/Claude/Gemini forget all prior conversations?

I am referring to the regular chat, not the API. I want to make sure that every time I start a new chat, it is a completely clean slate with no recall from other chats. I have tried turning off memory, I have also tried prompting it to forget everything, which it claims it has done but hasn't.

Later in the conversation I will see something like, "Given your expertise in..." or "This ties in nicely with your ...", things that it would only know from prior chats.