Surgical Changes: edit only what the request requires

When you ask an LLM to fix a bug, you expect a focused diff. What you often get instead is a sweeping “improvement” that touches comments, reformats whitespace, adds type hints, upgrades validation logic, and restructures boolean returns — none of which you asked for. Surgical Changes enforces a simple discipline: every changed line must trace directly to the user’s request, nothing more.

Two rules

Don’t touch what you shouldn’t

When editing existing code:

Don’t “improve” adjacent code, comments, or formatting
Don’t refactor things that aren’t broken
Match existing style, even if you’d do it differently
If you notice unrelated dead code, mention it — don’t delete it

Clean up your own orphans

When your changes create unused artifacts:

Remove imports, variables, and functions that your changes made unused
Don’t remove pre-existing dead code unless explicitly asked

The test

Every changed line should trace directly to the user’s request. If you can’t answer “why did this line change?” with a direct reference to the task, the change shouldn’t be there.

Drive-by refactoring example

Request: “Fix the bug where empty emails crash the validator”

What LLMs do wrong — “fixing” adjacent username logic, adding a docstring, improving email validation beyond the bug

  def validate_user(user_data):
-     # Check email format
-     if not user_data.get('email'):
+     """Validate user data."""
+     email = user_data.get('email', '').strip()
+
+     # Validate email
+     if not email:
          raise ValueError("Email required")
-
-     # Basic email validation
-     if '@' not in user_data['email']:
+     if '@' not in email or '.' not in email.split('@')[1]:
          raise ValueError("Invalid email")

-     # Check username
-     if not user_data.get('username'):
+     # Validate username
+     username = user_data.get('username', '').strip()
+     if not username:
          raise ValueError("Username required")
+     if len(username) < 3:
+         raise ValueError("Username too short")
+     if not username.isalnum():
+         raise ValueError("Username must be alphanumeric")

      return True

Unasked-for changes: improved email validation, added username length and alphanumeric checks, changed comments, added a docstring.

The correct approach — only the lines that fix the empty email crash

  def validate_user(user_data):
      # Check email format
-     if not user_data.get('email'):
+     email = user_data.get('email', '')
+     if not email or not email.strip():
          raise ValueError("Email required")

      # Basic email validation
-     if '@' not in user_data['email']:
+     if '@' not in email:
          raise ValueError("Invalid email")

      # Check username
      if not user_data.get('username'):
          raise ValueError("Username required")

      return True

Only changed: the specific lines that fix empty email handling.

Style drift example

Request: “Add logging to the upload function”

What LLMs do wrong — changing quote style, adding type hints, adding a docstring, reformatting whitespace

- def upload_file(file_path, destination):
+ def upload_file(file_path: str, destination: str) -> bool:
+     """Upload file to destination with logging."""
+     logger.info(f"Uploading {file_path} to {destination}")
+
      try:
-         with open(file_path, 'rb') as f:
-             data = f.read()
-
-         response = requests.post(destination, files={'file': data})
-
-         if response.status_code == 200:
-             return True
-         else:
-             return False
+         with open(file_path, "rb") as f:
+             data = f.read()
+         response = requests.post(destination, files={"file": data})
+         success = response.status_code == 200
+
+         if success:
+             logger.info(f"Upload successful: {file_path}")
+         else:
+             logger.error(f"Upload failed: {file_path}, status={response.status_code}")
+
+         return success
      except Exception as e:
-         print(f"Error: {e}")
+         logger.exception(f"Upload error for {file_path}: {e}")
          return False

Unasked-for changes: type hints, docstring, quote style changed from ' to ", whitespace reformatted, boolean return logic restructured.

The correct approach — match existing style, add only the logging lines

+ import logging
+
+ logger = logging.getLogger(__name__)
+
  def upload_file(file_path, destination):
+     logger.info(f'Starting upload: {file_path}')
      try:
          with open(file_path, 'rb') as f:
              data = f.read()

          response = requests.post(destination, files={'file': data})

          if response.status_code == 200:
+             logger.info(f'Upload successful: {file_path}')
              return True
          else:
+             logger.error(f'Upload failed: {file_path}, status={response.status_code}')
              return False
      except Exception as e:
-         print(f"Error: {e}")
+         logger.exception(f'Upload error: {file_path}')
          return False

Matched: single quotes, no type hints, existing boolean pattern, original spacing style.

When this principle is working

Diffs are small and focused — only requested changes appear
PRs are clean with no drive-by refactoring or “improvements”
Code style is consistent within each file, even across contributors
Every line in the diff has an obvious reason for changing

Get Started

The Four Principles

Guides

Surgical Changes: edit only what the request requires

Two rules

Don’t touch what you shouldn’t

Clean up your own orphans

The test

Drive-by refactoring example

Style drift example

When this principle is working

​Two rules

​Don’t touch what you shouldn’t

​Clean up your own orphans

​The test

​Drive-by refactoring example

​Style drift example

​When this principle is working

Two rules

Don’t touch what you shouldn’t

Clean up your own orphans

The test

Drive-by refactoring example

Style drift example

When this principle is working