Ask HN: How to stop OS X resizing a window dragged to the menubar?

As Ezhik mentions, this doesn't happen for me either so you might have installed a third party software that does this.

OS X doesn't seem to do this for me. Did you install something simulating Windows' Aero Snap?

Change BetterSnapTool behavior

I can confirm betterSnapTool does that. When you install certain utilities (like Ubar dock replacement), it even tells you to disable window snapping.

Do you have the Window Tidy utility installed? Could be that.

Thanks, it was HyperDock!