this issue is caused by GPUI not being able to render some texts (chat messages). I suspect it may be caused by URLs or specific characters. I will do something about this issue, worst case, I'll just render message as plain text. there are a lot of parts of GPUI that I don't understand yet. anyway, I've created another github account: https://github.com/reyakov/coop. If you find other issues, you can create a PR here.