Old code paydown guide
Give it a large old codebase. Get a safe plan to make it legible, bounded and resilient, step by step.
Old code paydown guide is a free AI skill for the job "Test and fix code". Give the instructions to an AI assistant that supports the required files and tools, then review its output.
Free · No account · MIT licence · Made by Wondel.ai · Level: advanced · Thinking: high
Made by Wondel.ai. See the original on GitHub; we copied it as it is, with its licence.
What it does
A safe plan for fixing an old codebase that everyone is afraid to touch, without a rewrite. The old system keeps shipping while you improve it in place. The plan runs through eight phases, each with a question and a document it leaves behind. First you make the code safe to change by adding tests around what you touch. Then you reshape its structure, make it readable, hide complexity inside simple modules, and separate business rules from frameworks. Later phases build habits that stop debt coming back, test how it behaves under real production stress, and split a large monolith into clear areas. It keeps a tracker, so you can stop and resume.
You give it
- Access to the codebase or a description of it
- The areas that hurt most
- Your team size and release schedule
- Existing tests or docs (optional)
You get
- A phased cleanup plan
- A debt and testing log
- A tracker you can resume
- Architecture notes with suggested boundaries
Use it when
- You inherited a large app with no tests and every change feels risky.
- Your team wants to rewrite and you need a safer alternative.
- You must split a monolith but do not know where to cut.
- You want one plan and tracker for a long cleanup spread over months.
How to use it
- Add it to your AI once: download it and add the folder to Claude, ChatGPT or Codex as a skill.
- Ask for the job in your own words. Your AI opens the skill when it fits.