Safe Refactoring with Claude Code: Diagnose First, Change Minimum, Verify Always

Saying "refactor this" to Claude Code without constraints is asking for trouble. It might rename things, change APIs, add abstractions you didn't ask for, or "improve" code that wasn't part of the problem. These patterns keep refactoring safe and focused. 1. Diagnose Before Fixing Before asking for any changes, ask Claude Code to audit the code: Analyze this file for refactoring opportunities. List specific issues and what could be improved. Do NOT make any changes yet. [paste the code] The "do NOT make changes yet" is critical. Once you have the list, you decide what to address and in what order. 2. Constrain the Scope Explicitly Never refactor an entire file at once. Specify exactly what to touch: Refactor ONLY the processPayment() function in this file. The function currently has 3 responsibilities mixed together. Split them into separate functions. Do not change any other functions or the public API signature. [paste the file] CLAUDE.md can reinforce this automatically: ## Refactor