4.3 Upgrade Prompt Exit Injects Characters #12232

Version: fish, version 4.3.1
OS: Darwin (MacOS 15.7.2)

When upgrading fish 4.2.1 -> 4.3.1 I noticed a new issue occur where it seems to inject a capital 'I' after running certain commands. I mainly see it outside of Tmux. I've removed my custom plugins (fisher) and the issue still persists.

Outside of Tmux:

❯ lazygit
Not in a git repository. Create a new git repository? (y/N): ^[[I^[[I

Inside of Tmux:

❯ lazygit
Not in a git repository. Create a new git repository? (y/N):

I'll also see it after interactive prompts. For example I have a script which lists Tmux sessions I can attach to. As you can see, it injects the 'I':

My hunch is it has something to do with vi mode because of the 'I' is inserting to the beginning of the line. Could it also be related to this part of the release notes?

Focus reporting is enabled unconditionally, not just inside tmux. To use it, define functions that handle the fish_focus_in or fish_focus_out [events](file:///opt/homebrew/Cellar/fish/4.3.1/share/doc/fish/language.html#event).