Trevor Arjeski <tmarjeski@gmail.com> writes:

> Using a few new emacs 31 window configurations, upon creating a new erc
> query buffer with `/query yournick`, hitting RET or sending a message
> makes the window the sole window in the frame as if C-x 1 was entered.
>
> Minimal reproduction:
>
> (use-package window
>   :custom
>   (kill-buffer-quit-windows t)
>   (quit-restore-window-no-switch 'skip-first))
>
> 1. Start erc
> 2. Open a query from the server buffer with `/query trev`
> 3. Hit enter
> 4. Notice that the query buffer that was created as a split becomes the
> only window in the frame.
>
> This seems to trigger in `erc--split-line` in erc-backend.el, where a
> temp buffer is created and then subsequently killed.

Thanks for investigating. Does the attached patch improve the situation?