Debug Pattern — Failures

Pattern: Debug
Component: failures.md
Version: 1.1 | Updated: 2026-07-16

---

Failure 1: Symptom → fix

Symptom: Catch-all handler returns 200; underlying race remains.
Cause: No hypothesis testing.
Recovery: Revert masking change; restart debug workflow; fix cause.

Failure 2: Multi-variable thrash

Symptom: “It works” after changing code, config, and infra together.
Cause: Experiments not isolated.
Recovery: Bisect; re-confirm with one variable; discard unrelated changes.

Failure 3: No regression test

Symptom: Bug returns after a refactor.
Cause: Fix merged without failing-first test.
Recovery: Add test; keep it in CI; treat absence as process defect.

Failure 4: Cannot reproduce → guess

Symptom: Patch based on intuition; prod still broken.
Cause: Skipped repro locking.
Recovery: Capture more telemetry; improve repro; avoid prod speculation patches.

Failure 5: Fix everywhere silently

Symptom: Huge PR “while debugging” touches unrelated modules.
Cause: Similarity scan turned into drive-by rewrite.
Recovery: Split follow-ups; merge only causal fix + test.