Only do the automatic-rename dance if the pane has changed (seen output,

or new active pane).

input.c

@@ -844,6 +844,8 @@ input_parse(struct window_pane *wp)
 	if (EVBUFFER_LENGTH(evb) == 0)
 		return;
 
+	wp->flags |= PANE_CHANGED;
+
 	wp->window->flags |= WINDOW_ACTIVITY;
 	wp->window->flags &= ~WINDOW_SILENCE;
 

names.c

@@ -50,6 +50,10 @@ window_name_callback(unused int fd, unused short events, void *data)
 	if (w->active == NULL)
 		return;
 
+	if (~w->active->flags & PANE_CHANGED)
+		return;
+	w->active->flags &= ~PANE_CHANGED;
+
 	if (!options_get_number(&w->options, "automatic-rename")) {
 		if (event_initialized(&w->name_timer))
 			event_del(&w->name_timer);

tmux.h

@@ -826,6 +826,7 @@ struct window_pane {
 #define PANE_RESIZE 0x8
 #define PANE_FOCUSPUSH 0x10
 #define PANE_INPUTOFF 0x20
+#define PANE_CHANGED 0x40
 
 	int		 argc;
 	char	       **argv;

window.c

@@ -412,6 +412,7 @@ window_set_active_pane(struct window *w, struct window_pane *wp)
 			return (1);
 	}
 	w->active->active_point = next_active_point++;
+	w->active->flags |= PANE_CHANGED;
 	return (1);
 }