codexkit-incident-postmortem

A post-incident writing guide based on Google SRE practices, where SRE means operating software reliably through engineering methods.

In plain words
What is it for?
Use it to reconstruct a timeline, assess user impact, analyse causes with the Five Whys, classify severity, and assign follow-up actions.
Why use it?
It turns an outage, production bug, or near-miss into a factual record focused on causes and prevention rather than blame.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/hoavdc/codexkit/codexkit-incident-postmortem
Any agent
npx skills add hoavdc/CodexKit --skill codexkit-incident-postmortem
Clone the repo
git clone --depth 1 https://github.com/hoavdc/CodexKit

Made for: Claude Code, Codex.

Per session 58 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,362 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00058 $0.01362
Opus 5 $0.00029 $0.00681
Sonnet 5 $0.00012 $0.00272
Haiku 4.5 $0.00006 $0.00136

Measured 2d ago against content hash 27d5968df7cf, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

codexkit-incident-postmortem 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 2d 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.

skills/codexkit-incident-postmortem/SKILL.md · 159 lines

How it starts

The opening of the file, as written. The whole thing — 159 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Incident Postmortem

When to Use

  • After any production incident that affected users
  • After near-misses that revealed systemic weaknesses
  • When establishing a blameless postmortem culture
  • When leadership requests incident RCA (Root Cause Analysis)

Procedure

Step 1 — Incident Summary

Write a 2–3 sentence summary:

  • What happened, when, and how long
  • Impact in business terms (users affected, revenue lost, SLA breach)
  • Current status (resolved, monitoring, partially mitigated)

Severity classification:

Severity Criteria
SEV-1 Complete outage or data loss affecting all users
SEV-2 Major feature unavailable or significant degradation
SEV-3 Minor feature impact, workaround available
SEV-4 Cosmetic or non-user-facing issue

Step 2 — Timeline

Build a minute-by-minute timeline:

Time (UTC) Event Source
14:02 Deploy v2.3.1 to production CI/CD
14:05 Error rate spikes to 15% Datadog
14:08 PagerDuty alerts on-call engineer PagerDuty
14:12 On-call begins investigation Slack thread
14:25 Root cause identified: DB migration timeout Logs
14:30 Rollback initiated CI/CD
14:35 Service fully recovered Monitoring

Time to Detect (TTD): 3 min | Time to Resolve (TTR): 33 min

Step 3 — Root Cause Analysis (5 Whys)

  1. Why did the service fail? → Database queries timed out
  2. Why did queries time out? → Migration locked a critical table for 8 minutes
  3. Why was the table locked? → ALTER TABLE ran without CONCURRENTLY flag
  4. Why wasn't it concurrent? → Migration script didn't follow the safe-migration checklist
  5. Why wasn't the checklist followed? → No automated check in CI pipeline

Root cause: Missing CI check for safe migration patterns.

Step 4 — Impact Assessment

Metric Value
Duration 33 minutes
Users affected ~12,000 (8% of DAU)
Requests failed ~45,000 (500 errors)
Revenue impact ~$2,400 estimated
SLA impact 99.92% (target: 99.95%) — SLA breached

Read the full file on GitHub · 159 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 2d ago First seen · 159 lines · 58 tokens per session scan A 27d5968df7cf

Subscribe to this mod's changes

codexkit-incident-postmortem is a skill published in the GitHub repository hoavdc/CodexKit (21 stars, last pushed 3mo ago), licensed MIT. It adds 58 tokens to every session and 1,362 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 2026-08-30.

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