One more thought - Lead with the limit before any small talk: “Hi which, yeah... i’ve got 90 seconds as I head to a call,” keep moving then close with a cheerful “that’s my minute - see you!” If they keep going, use the same line again word-for-word (the broken-record technique) while taking a step away and waving. You can also set a clear signal for longer chats, like “If I stop and take off my earbuds, I’m free,” so quick hellos don’t turn into 20 minutes.
