How do you stop AI coding agents from rewriting entire files when you only need 3 lines changed?

I’ve been using VS Code with ChatGPT Codex for development, but I keep running into a frustrating workflow bottleneck: when I ask the agent to edit or fix a tiny section of a file, it often insists on rewriting the entire codebase or file from scratch.

This burns context windows, introduces random side-effect bugs, and wastes a ton of time reviewing diffs.

For those using AI coding assistants in VS Code, how are you isolating issues so the agent strictly operates on the target lines? Are there specific extensions, prompt patterns, or scoping tools you rely on to keep the edits surgical?