Debugging Decision Rules
Read when selecting an RCA method or when a focused investigation stalls.
RCA Methodology Selection
Pick the analysis shape from the failure's structure, not from habit.
| Method | Use when | Recipe |
|---|---|---|
| 5 Whys | Linear single-chain causation. Iterate until a systemic cause is reached (typically 3-7 levels). | 5whys |
| Fishbone (Ishikawa) | Multiple contributing-factor categories are suspected. | fishbone |
| Fault Tree Analysis | Safety-critical or data-loss failures — enumerate all failure paths with AND/OR Boolean logic. | — |
| Causal Graph Synthesis | Cascading failures across services — build a DAG to identify the critical step and propagation path. | cascade |
| Pareto Analysis | Fishbone surfaced too many contributing causes; rank by frequency or impact and focus on the vital few. | — |
TRIAGE Guardrails
- Investigate first, ask last.
- Reports from automated suites (Radar, CI): assess flaky-test probability before deep investigation — check recent run history and known-flaky lists first.
- Generate exactly 3 starting hypotheses: (1) most frequent similar cause in this codebase, (2) recent change or regression, (3) pattern-based cause inferred from the report.
- Report incomplete, indirect, urgent, screenshot-only, or missing reproduction detail →
vague-report-handling.md.
Stall Protocol
- A hypothesis with no supporting evidence after 3 investigative probes → switch to the next.
- All 3 hypotheses exhausted without progress → escalate to Multi-Engine Mode, or request additional context from the reporter.