Opening helix or neovim in `boo ui` freezes boo

[ldb]

boo freezes when running helix or neovim in a fresh session within boo ui.

Steps to reproduce:

1. Start boo ui
2. <Ctrl-a c> to create a new session
3. Start hx or nvim

Result: boo freezes.

Interestingly, this does not happen when I launch a boo new session and run helix or nvim there.
I can then use boo ui to take over this existing session without issues. However, launching a new session with helix or nvim will again freeze boo.