While looking into something with Script Editor this morning, I happened to notice the additional item “AppleScript Debugger” in its language-selection pop-up. Wondering if it might be a new feature, I selected it and tried running the script
beep, which ran for several seconds doing nothing until I typed Command-. to stop it. Immediately, a dialog appeared saying: “AppleScript debugging failed because Script Debugger is not available on this Macintosh”.
When I tried it with Script Debugger open, Script Debugger came to the front with the script showing in a new tab, its first line shaded green. Typing Command-r ran the script in Script Debugger, whereupon the tab immediately closed and the script stopped running in Script Editor.
Is this confusion between the two applications supposed to happen?