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name: legacy-refactor description: Specifically designed to guide agents through the process of modernizing old codebases without breaking existing dependencies.

Legacy Refactor Protocol

This skill guides the safe refactoring of "legacy" code (code without tests or difficult to understand code).

The Algorithm

1. Identify Seams: A place where you can alter behavior without editing the place in question (e.g., via subclassing, interface extraction).
2. Characterization Tests: Before changing ANY code, write tests that capture the current behavior (bugs and all).
   • Goal: Ensure you don't change behavior unintentionally.
3. Break Dependencies: Use dependency injection to isolate the code module.
4. Refactor: Make your changes (clean code, upgrade lib, etc.).
5. Verify: Run characterization tests.

Strategies

• Sprout Method: Write new logic in a new method and call it from the old one.
• Wrap Method: Rename the old method, create a new method with the old name that calls the new logic + the old method.