unable to create/modify stimulus controllers

Hi,

Bit embarrassed, but I am not sure what I'm doing wrong.  I was fiddling with the stimulusJS controllers, and for some reason I can't modify them.  That is, I would successfully create a tooltip div, like

<div data-controller="tooltip" data-tippy-content="Hello world">test</div>

And then I would delete the tooltip_controller.js.  And yet, after restarting the server, reloading the page, the tooltip still works.  Similarly, if I add new methods to the controllers, they're not picked up.

I'm guessing there's some sort of cache or something that I'm not reloading correctly, but I'm not sure what to do next.  Has anyone encountered this before?

thanks!