arozumenko Root-Cause Analysis (RCA)
Trace a confirmed bug to its exact cause and produce a structured RCA artifact. Investigation only — you do NOT edit code, branch, or fix.
Platform & systems
The RCA report goes on the tracker ticket — the source of truth — using
the tracker scout recorded in .agents/profile.md § Project systems. The
gh issue … commands below are the GitHub reference; translate per
.agents/workflow.md § Git host. With no tracker, report directly to the user.
When to use
Pairs with systematic-debugging — use its rigor (reproduce reliably,
condition-based waiting) to trace, then produce the structured report here.
Methodology — 4 phases
1. Ticket acquisition
Read the ticket and all comments (reproduction steps, errors, stack traces, environment, prior notes). Note that RCA has started on the ticket.
2. Codebase investigation — trace, don't guess
- Locate the entry point: grep the error message / function / route.
- Trace the call chain: entry (route/handler) → service (logic) → data layer → failure point. Read each file in the chain.
- Examine the failure point: which assumption is violated? what input triggers it? is the bug here or in a dependency?
- Search for patterns: how is the function called elsewhere; are there
similar patterns that work;
git blameand recentgit logon the file.
3. Root-cause determination
Classify the cause:
| Category | Description | Example |
|---|---|---|
| Logic | Wrong condition, missing branch, off-by-one | if x > 0 should be if x >= 0 |
| Data | Unexpected input, null handling, type mismatch | Missing null check on optional field |
| Concurrency | Race condition, missing lock, async issue | Two requests mutating the same resource |
| Configuration | Wrong default, missing env var | Timeout too low for large payloads |
| Integration | API contract / dependency version change | Third-party API changed its response shape |
| Resource | Memory, connection pool, file handles | DB connection pool exhausted |
State confidence: Confirmed (you can see the exact bug) / Highly likely / Suspected.
4. Impact analysis & report
- Usage: what else calls the buggy code; what depends on the module.
- Regression risk: what could break if fixed; existing test coverage; whether the code is shared across features.
- Post the RCA report on the ticket: executive summary, classification
(category / confidence / severity), root cause (location
file:line+ function + cause + the offending code), execution path, impact analysis, suggested remediation, and dependencies (what this blocks / relates to). - One line to user/PM: root cause + location + confidence.
RCA comment template:
## Root Cause — <ticket-id>
**Summary:** <what & why, one paragraph>
**Classification:** <Logic|Data|Concurrency|Configuration|Integration|Resource> · confidence <Confirmed|Likely|Suspected> · severity <…>
**Root cause:** `path/to/file.ext:line` in `<function>` — <the offending logic>
**Execution path:** <entry → … → failure point>
**Impact:** <callers / regression risk / test coverage>
**Suggested remediation:** <fix direction, not the patch>
**Blocks / relates to:** <links>
You do NOT
Edit source, create PRs/branches, run the app to fix it, make architecture
decisions, or close/reassign tickets. Hand the structured RCA to the developer
(or bugfix-workflow) for the fix.
Related skills
reproducing-issuesprecedes this — confirm the bug first.systematic-debuggingfor tracing rigor.bugfix-workflowconsumes the RCA to implement and verify the fix.