Don't really know what thread to catalog this under so I'm putting it here. (I'm inclined to go with triumph of the day but that seems a little callous.)
My sibling and I had a falling out years ago and didn't speak afterwards. The specifics of it aren't terribly relevant--and I wouldn't share them here even if they were--so use your imagination if you want to know why.
Somewhat recently
we started speaking again. I laid out some opt-in boundaries that were mutually agreed to when this started, one of which was that we weren't going to relitigate the past. (I did however acknowledge the feelings that may have made them want to do so.) I did that because I knew that there was a 0% chance of having a durable relationship without a reboot, and also because talking about the past with a person whose schizophrenia is not treated properly is ill-advised.
Over the ensuing months I would give respectful yet laconic replies to absolute garrulity and that seemed to work fine for both of us. Whenever things got personal I was happy to let them talk about themselves but evasive about myself because my schtick of mocking people who have interpersonal trust isn't the slightest bit cynical when it comes to my sibling.
About a week ago something happened with them and they became very hostile. (For example, instead of a tome about something I didn't agree with I'd get 6 insulting emails in a row over the course of 10 minutes.) These emails eventually drifted into relitigating the past so I replied and said, "6 months ago I wrote this, seems applicable now:" and then quoted the boundary from my first email in January. My sibling responded with 5 or 6 emails that were, even in the context of the past few days, pretty extreme (while rejecting the boundary).
A couple of hours later they sent an email that said (paraphrasing) "I think I shouldn't talk to you for awhile . . . I'd like to avoid further insensitivity because it just makes things worse." That's the kind of garbo thing our more abusive parent would do growing up instead of apologizing and if there was one person on the entire planet who should know better it's them so I wrote back, "I think it's better if you don't ever talk to me again unless there's an emergency."