Debug

Systematically find and fix the root cause of a bug.

Steps

1. Reproduce — Get the exact error message, stack trace, or steps to reproduce. Understand what happens vs. what should happen.
2. Locate — Narrow down where the problem is:
   • Read the error message and stack trace — they usually point to the exact location.
   • Search for relevant keywords (error strings, function names).
   • Trace the data flow from input to the failure point.
3. Understand — Before fixing, understand why it fails:
   • What assumption is violated?
   • When was it introduced? (git log, git blame)
   • Logic error? Data problem? Race condition? Missing edge case?
4. Fix — Make the smallest change that correctly addresses the root cause.
5. Verify — Write or update a test that catches this bug. Run the full test suite for regressions.
6. Explain — Briefly describe what caused it and why the fix is correct.