example-debuglisted

# Debug, root cause first > **Announce on activation:** "Using example-debug — I'll find the root cause before fixing." The expensive mistake in debugging is fixing a *symptom*. This skill forces the order: understand, then change. ## Process 1. **Reproduce.** Get a reliable, minimal way to trigger the bug. If you can't reproduce it, you can't know you fixed it. Capture the exact input, environment, and the actual vs expected behaviour. 2. **Locate.** Read the code on the path from trigger to symptom. Add a probe (log/print/test) that confirms *where* reality diverges from expectation — don't guess. 3. **HARD GATE: root cause identified.** State the cause in one sentence ("X is null because Y never sets it when Z"). Do **not** write a fix until you can. A fix without a named cause is a guess. 4. **Fix the cause, not the symptom.** Make the smallest change that addresses the root cause. Note if you find sibling bugs — don't silently expand scope. 5. **Prove it.** Add a test that **fails before** the fix and **passes after**. Re-run the reproduction. A bug fix without a regression test invites the bug back. ## Anti-rationalization | You'll think | Reality | |---|---| | "I'm pretty sure it's this line" | "Pretty sure" is a hypothesis. Confirm it with a probe before changing code. | | "I'll add a null-check and move on" | A null-check on a value that should never be null hides the real cause. Ask why it's null. | | "It's fixed, it works now" | Works *on