A prompt to map a legacy codebase before vibe coding
A prompt for agents like Opus 5.5 and GPT-6 Astra that asks them to trace dependencies, dead code and guesses in a legacy repo and wait for manual approval before editing.
If you're vibe coding on old code with Opus 5.5, GPT-6 Astra, or Grok Bot, steal this prompt. Paste it before your agent touches a single line of your legacy repo: "Before we change anything, map this entire codebase. Trace every piece of code this task and session will touch, what depends on it, and what breaks if it changes. Flag any dead code, hidden side effects, and literally anything you're guessing about that's not proven by code reads and specific lines. No code edits until I approve the map manually." Agents love to skim through old repos, and that's where the guesses hide. Save this prompt. It's how I make mine actually read code.