Bug Fix Debugging

Bug Fix Debugging

Use this skill when the task is to find and fix a concrete bug or regression in an existing codebase.

Goal: identify the smallest correct fix, prove the root cause, and leave behind a targeted verification path.

Working model

1. Reproduce or locate the failure signal before editing.
2. State the suspected root cause and the evidence for it.
3. Read the narrowest relevant code path first.
4. Fix the cause, not just the symptom.
5. Add or update a regression test when the project has a nearby test pattern.
6. Run the smallest useful verification command.

Rules

• Do not rewrite broad modules just to fix a narrow bug.
• Do not silence errors without explaining why the error is impossible or expected.
• Preserve user changes and unrelated dirty files.
• Prefer one minimal patch plus one validation step over speculative refactors.
• If the bug is caused by ambiguous requirements, state the assumption explicitly.

Output checklist

• Root cause.
• Files changed.
• Why the fix is safe.
• Validation command and result.
• Remaining risk if verification was incomplete.