How do stop AI coding tools from rewriting your entire codebase when just asked for a tiny fix?

Every time I ask for a simple bug patch the agent feels the need to reorganize half the directory and refactor utilities that weren't even broken.

It’s like giving an over-enthusiastic intern a screwdriver and coming back to find they took apart the engine.

For those using Cursor or local agents daily, what’s your go-to way to lock down scope and keep them strictly on task?