Root Cause Analysis

Delegated investigation: symptom → hypothesis → elimination → root cause → prevention.

Steps

1. Load the outfitter:debugging skill for systematic investigation
2. Apply elimination techniques from this skill's references
3. Document investigation trail using RCA templates
4. Deliver root cause report with prevention recommendations

<when_to_use>

• Diagnosing system failures or unexpected behavior
• Investigating incidents or outages
• Finding the actual cause vs surface symptoms
• Preventing recurrence through understanding
• Post-incident reviews requiring formal documentation

NOT for: known issues with documented fixes, simple configuration errors, routine debugging (use debugging skill directly)

</when_to_use>

<rca_focus>

This skill extends debugging with formal RCA practices:

Aspect	Debugging	Root Cause Analysis
Scope	Fix the immediate issue	Understand why it happened
Output	Working code	RCA report + prevention
Documentation	Investigation notes	Formal templates
Goal	Resolution	Prevention of recurrence

Use debugging for day-to-day bug fixes. Use find-root-causes for incidents requiring formal investigation and documentation.

</rca_focus>

<elimination_techniques>

Three core techniques for narrowing to root cause:

Technique	When to Use	Method
Binary Search	Large problem space, ordered changes	Bisect the change range
Variable Isolation	Multiple variables, need causation	Control all but one
Process of Elimination	Finite set of possible causes	Rule out systematically

See elimination-techniques.md for detailed methods and examples.

</elimination_techniques>

Investigation Trail

Log every step for handoff and pattern recognition:

[TIME] STAGE: Action → Result
[10:15] DISCOVERY: Gathered error logs → Found NullPointerException
[10:22] HYPOTHESIS: User object not initialized
[10:28] TEST: Added null check logging → Confirmed user is null

RCA Report Structure

1. Summary — one-sentence root cause
2. Timeline — events leading to incident
3. Impact — what was affected, duration
4. Root Cause — why it happened (not just what)
5. Contributing Factors — conditions that enabled it
6. Prevention — changes to prevent recurrence
7. Detection — how to catch it earlier next time

See documentation-templates.md for full templates.

<common_pitfalls>

Trap	Counter
"I already looked at that"	Re-examine with fresh evidence
"That can't be the issue"	Test anyway, let evidence decide
"We need to fix this quickly"	Methodical investigation is faster
Confirmation bias	Actively seek disconfirming evidence
Correlation = causation	Test direct causal mechanism

See pitfalls.md for detailed resistance patterns and recovery.

</common_pitfalls>

ALWAYS:

• Load debugging skill for systematic investigation methodology
• Use elimination techniques to narrow root cause
• Document investigation trail as you go
• Produce formal RCA report for incidents
• Include prevention recommendations
• Identify contributing factors, not just root cause

NEVER:

• Skip formal documentation for incidents
• Stop at "what happened" without "why"
• Propose fixes without understanding root cause
• Omit prevention recommendations
• Blame individuals (focus on systems)

• elimination-techniques.md — binary search, variable isolation, process of elimination
• pitfalls.md — cognitive biases and resistance patterns
• documentation-templates.md — investigation logs and RCA reports