My Emacs configuration https://git.cjennings.net/dotemacs/atom?h=main 2026-05-26T19:21:20+00:00 2026-05-26T19:21:20+00:00 Craig Jennings c@cjennings.net 2026-05-26T19:21:20+00:00 urn:sha1:6c7f9ae225b91dee81a04d2271a6648924c0f3cf slack-buffer-function defaulted to switch-to-buffer-other-window, which gives no real guarantee about placement: with three or more panes it picks a least-recently-used window, and it offers nothing that keeps Slack out of the window point is in. So opening a room in a split could land it wherever, including over the buffer I was working in. I set slack-buffer-function to cj/slack--display-buffer, a pop-to-buffer call with inhibit-same-window and a reuse / use-some-window / pop-up-window action list. In a split it reuses one of the other windows and leaves the selected window alone; with a lone window it splits. Tests cover both the split-placement case and the selected-window-preserved invariant.