wshobson/postmortem-writing
Write effective blameless postmortems with root cause analysis, timelines, and action items. Use when conducting incident reviews, writing postmortem documents, or improving incident response processes.
npx skills add https://github.com/wshobson/agents --skill postmortem-writingComprehensive guide to writing effective, blameless postmortems that drive organizational learning and prevent incident recurrence.
| Blame-Focused | Blameless |
| ------------------------ | --------------------------------- |
| "Who caused this?" | "What conditions allowed this?" |
| "Someone made a mistake" | "The system allowed this mistake" |
| Punish individuals | Improve systems |
| Hide information | Share learnings |
| Fear of speaking up | Psychological safety |
Day 0: Incident occurs
Day 1-2: Draft postmortem document
Day 3-5: Postmortem meeting
Day 5-7: Finalize document, create tickets
Week 2+: Action item completion
Quarterly: Review patterns across incidents
Full template library and detailed worked examples live in references/details.md. Read that file when you need the concrete templates.
### Template 2: 5 Whys Analysis
Payment service experienced 47-minute outage due to database connection exhaustion.
Answer: Database connections were exhausted, causing all new requests to fail.
Evidence: Metrics showed connection count at 100/100 (max), with 500+ pending requests.
Answer: Each incoming request opened a new database connection instead of using the connection pool.
Evidence: Code diff shows direct DriverManager.getConnection() instead of pooled DataSource.
Answer: A developer refactored the repository class and inadvertently changed the connection acquisition method.
Evidence: PR #1234 shows the change, made while fixing a different bug.
Answer: The reviewer focused on the functional change (the bug fix) and didn't notice the infrastructure change.
Evidence: Review comments only discuss business logic.
Answer: We lack automated tests that verify connection pool behavior and lack documentation about our connection patterns.
Evidence: Test suite has no tests for connection handling; wiki has no article on database connections.
| Root Cause | Improvement | Type |
| ------------- | --------------------------------- | ---------- |
| Missing tests | Add infrastructure behavior tests | Prevention |
| Missing docs | Document connection patterns | Prevention |
| Review gaps | Update review checklist | Detection |
| No canary | Implement canary deployments | Mitigation |
### Template 3: Quick Postmortem (Minor Incidents)
Date: 2024-01-15 | Duration: 12 min | Severity: SEV3
API latency spiked to 5s due to cache miss storm after cache flush.
Full cache flush for minor config update caused thundering herd.
Don't full-flush cache in production; use targeted invalidation.
## Facilitation Guide
### Running a Postmortem Meeting
## Anti-Patterns to Avoid
| Anti-Pattern | Problem | Better Approach |
| ----------------------- | -------------------------- | ------------------------------- |
| **Blame game** | Shuts down learning | Focus on systems |
| **Shallow analysis** | Doesn't prevent recurrence | Ask "why" 5 times |
| **No action items** | Waste of time | Always have concrete next steps |
| **Unrealistic actions** | Never completed | Scope to achievable tasks |
| **No follow-up** | Actions forgotten | Track in ticketing system |
## Best Practices
### Do's
- **Start immediately** - Memory fades fast
- **Be specific** - Exact times, exact errors
- **Include graphs** - Visual evidence
- **Assign owners** - No orphan action items
- **Share widely** - Organizational learning
### Don'ts
- **Don't name and shame** - Ever
- **Don't skip small incidents** - They reveal patterns
- **Don't make it a blame doc** - That kills learning
- **Don't create busywork** - Actions should be meaningful
- **Don't skip follow-up** - Verify actions completed
Take wshobson/postmortem-writing from the repository into ~/.claude/skills for personal
use, or into .claude/skills inside a project.
The agent identifies a skill by the name field in its header. Two skills with the
same name cannot sit side by side — one of them will be ignored.