How to stop Claude from doing more than you asked

The pattern is familiar: you ask Claude to fix a bug. It fixes the bug, then refactors the function it was in, adds a helper, updates comments in adjacent code, and creates a utility it thinks you'll need later. The original fix is buried somewhere in there. You wanted one thing changed and got a diff across five files. This happens because Claude's default is to be helpful, and helpful reads as thorough. It sees related improvements and makes them.