Claude Code vs Codex in the kind of refactor that can actually break an old repo

📰 Dev.to · Saqueib Ansari

Learn how Claude Code and Codex handle test-first refactoring in aging codebases, and why caution is key to avoiding breakage

intermediate Published 1 May 2026

Action Steps

Run a test suite on an old repo to identify areas for refactoring
Configure Claude Code or Codex to assist with test-first refactoring
Apply cautious refactoring techniques to avoid breaking the repo
Test and verify changes after refactoring
Compare the results of refactoring with Claude Code and Codex

Who Needs to Know This

Developers and maintainers of legacy codebases will benefit from understanding the refactoring capabilities of Claude Code and Codex, and how to apply them safely

Key Insight

💡 Test-first refactoring with Claude Code and Codex requires caution and respect for change boundaries to avoid breaking aging codebases