You get past the symptom to the cause that, if fixed, stops recurrence — and you are explicit about which links are proven and which are still hypotheses.
When to use
- A significant defect, escape, or incident needs a root-cause write-up.
- A retro asks "why did this happen and why didn't we catch it?"
- A recurring failure needs corrective and preventive actions defined.
Workflow
- State the problem precisely. Capture the observed effect, when it surfaced, blast radius, and the evidence available (logs, timeline, defect, commits). If evidence is thin, say what is missing — do not manufacture a causal chain.
- Run 5-Whys. Ask "why" iteratively from the symptom down to a root cause. Mark each link as evidence-backed or a hypothesis-to-verify.
- Run a fishbone. Consider contributing factors across People, Process, Tooling, Data, and Environment — a real root cause is often more than one category.
- Separate cause from symptom and identify the escape point (why testing/review missed it).
- Propose actions. Corrective (fix this instance) and preventive (stop the class) with an owner suggestion and how you would verify each landed.
- HUMAN REVIEW GATE (mandatory). Present the RCA as a draft. List unverified links and assumptions. Ask the team to confirm the root cause before actions are committed to.
Output shape
## RCA — <defect / incident>
Problem statement: <effect, when, blast radius>
5-Whys: symptom -> ... -> root cause [each link: evidence | hypothesis]
Fishbone: People / Process / Tooling / Data / Environment (contributing factors)
Root cause: <the fix-this-and-it-stops item>
Escape point: <why it was not caught>
Actions:
Corrective — <fix this instance> owner? / verify by?
Preventive — <stop the class> owner? / verify by?
--- HUMAN REVIEW GATE ---
Unverified causal links / assumptions / "Confirm root cause before committing actions"
Guardrails
- Never assert a causal link the evidence does not support — label it a hypothesis to verify.
- Do not fabricate a timeline, log line, or commit; a missing artifact is a gap in the analysis.
- Aim at process and system causes, not individual blame.
- The root cause and actions are proposals until the team confirms them.