Running: swaymsg for_window "[app_id=mpv] opacity 0.5"

Works as expected on my end, are you missing just executing for_window?

Note, you can also add multiple rules in the same execution, e.g.

for_window {
    [app_id=mpv] opacity 0.85
    [app_id=LibreWolf] opacity 0.85
}

Also, note that app_id of LibreWolf is capitalized in that manner. You can get that information [app_id, shell etc] by running swaymsg -t get_tree

Feel like most people still do the scripting in Bash for portability reasons, and then just run Fish as the interactive shell

Archlinux’s XZ was compromised as well.

News post

Git change for not using tarballs from source