Replying “haha” to things that actually hurt teaches people it’s fine to keep saying them.

A laugh is read as permission. When something lands badly and you send the easy reaction anyway, the other person receives clear feedback that this is fine with you, and they keep going, often with no idea. The gap between what you felt and what you sent is a gap they cannot see across.

You do not need a confrontation to close it. A short flat sentence works: that one actually stung, or I would rather you did not. Said once, without heat, it usually ends the pattern immediately.