diagnoselisted

## Overview Systematic debugging that produces evidence at every step — not guesswork, not shotgun fixes. ## Process Do NOT guess. Follow the loop. Every step produces evidence. ## The Loop ``` 1. REPRODUCE — make it fail on demand. If you can't reproduce, you can't fix. 2. MINIMISE — strip everything until only the bug remains. Smallest failing case. 3. HYPOTHESISE — ONE theory. Not three. One. State it clearly. 4. INSTRUMENT — add the ONE measurement that proves/disproves your hypothesis. 5. EVALUATE — run it. Was hypothesis correct? YES → go to step 6 NO → back to step 3 with new information 6. FIX — minimal change that addresses root cause (not symptoms) 7. REGRESSION TEST — write a test that would have caught this. Run it red then green. ``` ## Rules - Never skip REPRODUCE. "I think it fails when..." is not reproducing. - Never fix without a hypothesis. Shotgun debugging = wasted time. - One hypothesis at a time. Changing two things = you learn nothing. - The fix must address ROOT CAUSE. If you're fixing symptoms, you're not done. - The regression test must FAIL without the fix applied. ## Anti-Patterns (stop yourself) - "Let me try adding a null check here" → NO. Where's your hypothesis? What evidence? - "It's probably a timing issue" → Probably? REPRODUCE it. PROVE it's timing. - "I'll add some console.logs" → WHICH log proves WHICH hypothesis? Be specific. - "Fixed! (without running the test)" → NO. Prove it. Run it. Evidence. ## Common Mistakes - Ch