A tui does not have to start full screen, v1 of claude did not take over the entire terminal, it would only use a bit at the bottom and scroll up until it was full screen.
pretty sure your old behavior was the broken one tho - i vaguely remember fugling with this to "fullscreen correctly" for a claude-in-docker-in-cygwin-via-MSYS2 a while ago
I just downgraded to v1 to confirm this.