Postmortem Writing

When to use this skill

Use Postmortem Writing when an AI agent needs a reusable SKILL.md workflow for this job: 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.

When not to use it

Skip Postmortem Writing when the task is outside the coding category, or when a more specific skill in this directory already covers the same workflow with clearer triggers.

How to install

1. Personal install: create ~/.claude/skills/postmortem-writing/SKILL.md (and any bundled scripts) so Claude Code, Claude Desktop, and compatible agents can load it in every project.
2. Project install: commit the same folder at .claude/skills/postmortem-writing/ so teammates get the skill with the repo.
3. Restart the agent session after copying files so it re-scans the skills directory, then ask for the task in words that match the skill description.

Full install guide for Claude, Cursor, and Codex

What this skill does

# Postmortem Writing

Comprehensive guide to writing effective, blameless postmortems that drive organizational learning and prevent incident recurrence.

## When to Use This Skill

- Conducting post-incident reviews - Writing postmortem documents - Facilitating blameless postmortem meetings - Identifying root causes and contributing factors - Creating actionable follow-up items - Building organizational learning culture

## Core Concepts

### 1. Blameless Culture

| 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 |

### 2. Postmortem Triggers

- SEV1 or SEV2 incidents - Customer-facing outages > 15 minutes - Data loss or security incidents - Near-misses that could have been severe - Novel failure modes - Incidents requiring unusual intervention

## Quick Start

### Postmortem Timeline

``` 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 ```

## Templates and detailed worked examples

Full template library and detailed worked examples live in `references/details.md`. Read that file when you need the concrete templates.

## References - [Connection Pool Best Practices](internal-wiki/connection-pools) - [Deployment Runbook](internal-wiki/deployment-runbook) ```

### Template 2: 5 Whys Analysis

```markdown # 5 Whys Analysis: [Incident]

## Problem Statement

Payment service experienced 47-minute outage due to database connection exhaustion.

## Analysis

### Why #1: Why did the service fail?

**Answer**: Database connections were exhausted, causing all new requests to fail.

**Evidence**: Metrics showed connection count at 100/100 (max), with 500+ pending requests.

---

### Why #2: Why were database connections exhausted?

**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`.

---

### Why #3: Why did the code bypass the connection pool?

**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.

---

### Why #4: Why wasn't this caught in code review?

**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.

---

### Why #5: Why isn't there a safety net for this type of change?

**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 Causes Identified

1. **Primary**: Missing automated tests for infrastructure behavior 2. **Secondary**: Insufficient documentation of architectural patterns 3. **Tertiary**: Code review checklist doesn't include infrastructure considerations

## Systemic Improvements

| 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)

```markdown # Quick Postmortem: [Brief Title]

**Date**: 2024-01-15 | **Duration**: 12 min | **Severity**: SEV3

## What Happened

API latency spiked to 5s due to cache miss storm after cache flush.

## Timeline

- 10:00 - Cache flush initiated for config update - 10:02 - Latency alerts fire - 10:05 - Identified as cache miss storm - 10:08 - Enabled cache warming - 10:12 - Latency normalized

## Root Cause

Full cache flush for minor config update caused thundering herd.

## Fix

- Immediate: Enabled cache warming - Long-term: Implement partial cache invalidation (ENG-999)

## Lessons

Don't full-flush cache in production; use targeted invalidation. ```

## Facilitation Guide

### Running a Postmortem Meeting

```markdown ## Meeting Structure (60 minutes)

### 1. Opening (5 min)

- Remind everyone of blameless culture - "We're here to learn, not to blame" - Review meeting norms

### 2. Timeline Review (15 min)

- Walk through events chronologically - Ask clarifying questions - Identify gaps in timeline

### 3. Analysis Discussion (20 min)

- What failed? - Why did it fail? - What conditions allowed this? - What would have prevented it?

### 4. Action Items (15 min)

- Brainstorm improvements - Prioritize by impact and effort - Assign owners and due dates

### 5. Closing (5 min)

- Summarize key learnings - Confirm action item owners - Schedule follow-up if needed

## Facilitation Tips

- Keep discussion on track - Redirect blame to systems - Encourage quiet participants - Document dissenting views - Time-box tangents ```

## 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

Intended uses

• Conducting post-incident reviews
• Writing postmortem documents
• Facilitating blameless postmortem meetings
• Identifying root causes and contributing factors
• Creating actionable follow-up items
• Building organizational learning culture