debugging-before-fixeslisted

# Debugging before fixes No fix without a root cause first. Patching symptoms burns review iterations and often adds a second bug. Guess-and-check thrashing is how tasks end blocked or review-exhausted under [[blocked-state]]. ## Step 1: build the feedback loop Before investigating or fixing, stand up a fast, deterministic, agent-runnable loop that reproduces the failure on demand. Reach for the highest item on this list that actually reproduces the failure: 1. A failing unit, integration, or browser test. 2. The targeted command from the task record's Required Checks. 3. A `curl` or API smoke call against the dev stack. 4. A small CLI or script run against a checked-in fixture. 5. Replaying a captured payload, request, or log line through the failing code. 6. A throwaway harness in `.agenticloop/tmp/` that calls the failing unit directly. 7. A fuzz or property loop when the triggering input is unknown. 8. `git bisect` or a differential loop when a previously passing behavior regressed. Prefer the cheapest deterministic loop that still fails for the real reason. Capture the exact command: it becomes RED proof for [[tdd-implementation]] and evidence for [[verification-evidence]]. ## Phase 2: investigate - Read the entire error message and stack trace. - Run the Step 1 loop and watch the real failure. - Diff what changed. - Trace the bad value or state back to where it originates. ## Phase 3: compare Find code in this repo that does the same kind of thing and works. Re