cyclefocus.key needs to have the modifier option if not using Mod1

[c-meier]

First at line 1071 you have :

    args.modifier = args.modifier or mods[0]

In lua the index of an array start by default at 1, so it should be :

    args.modifier = args.modifier or mods[1]

But that break the release as modifiers are like Mod1 or Mod4 or Shift and the key event that you listen to correspond to Super_L or Alt_L. So if you don't use Mod1 (and get the default value of Alt_L as the modifier keysym) as your modifier, you need to specify the keysym of your modifier in your options.

cyclefocus.key({ "Mod4", }, "Tab", {
   modifier = "Super_L",
   -- cycle_filters from the default filters:
   cycle_filters = { cyclefocus.filters.same_screen, cyclefocus.filters.common_tag }
 })

[blueyed]

Thanks for the report - #30 should fix/handle this.