The .mdc rules I use to stop Cursor from expanding my PRs

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DEV Community · Hideaki Kubo · 2026-06-27 개발(SW)

Cursor is fast. But left unchecked, it expands PRs.

Here are the three .mdc rules I use to keep that from happening.
Free on GitHub.

The problem in one sentence

You ask for one fix. Cursor touches five files.

Each change might look reasonable. But the PR becomes harder to review,
harder to revert, and harder to explain.

Rule 1: no-unrequested-changes.mdc

This rule tells Cursor not to modify anything outside the scope of
the original request.

- Do not edit unrelated files that are outside the current task scope
- Do not refactor working code as part of an unrelated task
- Do not add new utilities, helpers, or abstractions unless asked

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Rule 2: one-pr-one-topic.mdc

This rule tells Cursor that a PR should answer one question:
what decision is this asking the human reviewer to make?

- Do not combine unrelated changes in a single PR
- Do not mix implementation and refactoring in the same PR
- If the user adds a new request that introduces a separate concern,
  ask whether it should be handled as a separate PR.

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Rule 3: classify-before-merging.mdc

Before merging, this rule prompts a classification step.
The human decides. Not the AI.

- Do not merge without identifying which changes are accepted as-is
- Do not carry over follow-up work silently — make it explicit before merge
- If any item requires a human decision before merge, do not proceed.

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