If a message that is longer than the screen is tall is being updated it causes the screen to be repainted and scroll every time an update is made. This must be affecting literally many thousands of users if not more that use cli tools.

I did not find this, but I am reporting it. I saw someone discussing it in this thread:

https://www.reddit.com/r/ClaudeAI/comments/1m1xdqh/anyone_else_seeing_screen_flashes_when_using/

worth checking more deeply