Best AI tool to fix and clean up code you (or an AI) already wrote
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Every vibe-coded project hits the wall: it worked yesterday, now one fix breaks two other things, and the files are 900 lines long. Time for a cleanup.
The short pick
Claude Code — it reads the whole repo, runs your tests and commands, and makes changes across many files. Included with Claude Pro $20/mo ($17/mo annual); heavy users go to Max at $100 or $200/mo ✅.
Alternatives
| Tool | Good for | Price (checked Oct 16, 2026) |
|---|---|---|
| Cursor | Reviewing each diff visually before accepting | Free; Plus $8/mo (Cursor/Grok models only); Premium $30/mo adds third-party models at API price ✅ |
| OpenAI Codex | If you already have ChatGPT Plus | Included with Plus $20/mo ✅ |
| GitHub Copilot | Cloud agent + code review on GitHub PRs | Free; Pro $10/mo; Pro+ $39/mo ✅ |
How to start
- Commit everything first. You want an undo button:
git add . && git commit -m "before cleanup". - Ask the agent to look, not touch: "Read this project and list the 5 biggest problems, ranked by risk. Don't change any code."
- Ask it to add a few tests (or a manual test checklist) for what currently works.
- Fix one problem per session. After each: run the app, run tests, commit.
- If a fix goes sideways,
git restore .and try a smaller prompt. Don't argue with the AI for an hour.
Skip the blank page
👉 Codebase Fixer Agent — $8
A drop-in AGENTS.md/CLAUDE.md rules file plus a 4-phase prompt sequence (audit → safety net → fix → verify) that stops the agent from "fixing" things you didn't ask about.