postmortem-writing

postmortem-writing is a skill for Claude Code from tranhieutt/software_development_department. It costs 51 tokens per session (1,181 once invoked), scanned A, original, MIT.

A template and process for writing a blameless postmortem, a review of a production incident focused on causes and system conditions rather than individuals.

In plain words
What is it for?
Use it to record an incident timeline, explain root and contributing causes, and assign corrective actions.
Why use it?
It turns outages, data loss, and security incidents into documented lessons and concrete follow-up work.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Good fit Use it to record an incident timeline, explain root and contributing causes, and assign corrective actions.

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Install with agentmods
npx agentmods add skills/tranhieutt/software_development_department/postmortem-writing
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add tranhieutt/software_development_department --skill postmortem-writing
Clone the repo
git clone --depth 1 https://github.com/tranhieutt/software_development_department

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for postmortem-writing

README.md
[![agentmods](https://agentmods.dev/badge/skills/tranhieutt/software_development_department/postmortem-writing/github.svg)](https://agentmods.dev/skills/tranhieutt/software_development_department/postmortem-writing)
Your own site
<a href="https://agentmods.dev/skills/tranhieutt/software_development_department/postmortem-writing"><img src="https://agentmods.dev/badge/skills/tranhieutt/software_development_department/postmortem-writing/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for postmortem-writing

Your own site · 80×15
<a href="https://agentmods.dev/skills/tranhieutt/software_development_department/postmortem-writing"><img src="https://agentmods.dev/badge/skills/tranhieutt/software_development_department/postmortem-writing.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 51 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,181 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00051 $0.01181
Opus 5 $0.00026 $0.00590
Sonnet 5 $0.00010 $0.00236
Haiku 4.5 $0.00005 $0.00118

Measured 8d ago against content hash a5d5c807bec5, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

postmortem-writing scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/postmortem-writing/SKILL.md · 134 lines

How it starts

The opening of the file, as written. The whole thing — 134 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Postmortem Writing

Blameless mindset: the non-obvious part

"Blame-focused: Who caused this? → Blameless: What conditions allowed this?"

Engineers don't fail — systems create conditions where failures become inevitable. The goal is improving systems, not punishing people.

Triggers (when to write one)

  • SEV1/SEV2 incidents
  • Customer-facing outage > 15 minutes
  • Data loss or security incident
  • Novel failure modes worth sharing

Timeline: Day 0 → Day 7

Day 0:   Incident occurs
Day 1-2: Draft postmortem (memory is freshest)
Day 3-5: Postmortem meeting
Day 5-7: Finalize + create tickets
Week 2+: Action item completion

Standard template

# Postmortem: [Title]

**Date**: YYYY-MM-DD | **Severity**: SEV2 | **Duration**: 47 min
**Authors**: @alice, @bob | **Status**: Draft

## Executive Summary
[2-3 sentences: what broke, impact, how resolved]

**Impact**: [N customers, N minutes, revenue loss, no data loss]

## Timeline (UTC)

| Time  | Event |
|-------|-------|
| 14:23 | v2.3.4 deployed to production |
| 14:31 | Alert: payment_error_rate > 5% |
| 14:33 | On-call @alice acknowledges |
| 14:45 | Root cause identified: DB connections |
| 14:52 | Decision to rollback |
| 15:10 | Rollback complete, error rate normalizing |
| 15:18 | Service recovered |

## Root Cause Analysis

### What happened
[Technical description of failure]

### 5 Whys
- Why did service fail? → DB connections exhausted
- Why exhausted? → Each request opened new connection
- Why new connections? → Code bypassed connection pool
- Why bypassed? → Developer unfamiliar with DB patterns
- Why unfamiliar? → No documentation on connection management

### Contributing factors
- Code review missed the infrastructure change
- No integration tests for connection pool behavior
- Staging traffic too low to expose the issue
- Alert threshold too high (90%, should be 70%)

## What worked / what didn't

| Worked | Didn't work |
|---|---|
| Alert fired within 8 min | Took 10 min to correlate with deployment |
| Clear Grafana dashboard | No deployment-correlated alerting |
| Fast rollback decision | No canary deployment |

## Action items

| Priority | Action | Owner | Due | Ticket |
|---|---|---|---|---|
| P0 | Integration test for connection pool | @alice | 2024-01-22 | ENG-1234 |
| P0 | Lower DB alert threshold to 70% | @bob | 2024-01-17 | OPS-567 |
| P1 | Document connection management patterns | @alice | 2024-01-29 | DOC-89 |
| P2 | Evaluate canary deployment | @charlie | 2024-02-15 | ENG-1235 |

Read the full file on GitHub · 134 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 8d ago First seen · 134 lines · 51 tokens per session scan A a5d5c807bec5

Subscribe to this mod's changes

postmortem-writing is a skill published in the GitHub repository tranhieutt/software_development_department (72 stars, last pushed 4mo ago), licensed MIT. It adds 51 tokens to every session and 1,181 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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