An engineering record of a bug that has already been fixed and tested. It explains the root cause, how the bug worked, how it was fixed, and how it escaped earlier checks.

Documenting validated bug fixes, writing root-cause analyses, and recording what should be tested or changed to prevent a similar bug.

It preserves the reasoning behind a fix so other engineers can understand the issue later instead of repeating the investigation.

How hashangit/openfusion configures Claude Code and Codex

Reuse

Borrowing it

Nothing to install: this file belongs to hashangit/openfusion. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/hashangit/openfusion/main/.agents/skills/post-mortem/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/hashangit/openfusion

Made for: Claude Code, Codex.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/hashangit/openfusion/post-mortem/github.svg)](https://agentmods.dev/skills/hashangit/openfusion/post-mortem)

Your own site

<a href="https://agentmods.dev/skills/hashangit/openfusion/post-mortem"><img src="https://agentmods.dev/badge/skills/hashangit/openfusion/post-mortem/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/hashangit/openfusion/post-mortem"><img src="https://agentmods.dev/badge/skills/hashangit/openfusion/post-mortem.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 120 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 3,157 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.

Model	Per session	Once invoked
Fable 5.1	$0.00120	$0.03157
Opus 5.5	$0.00048	$0.01263
Sonnet 5.5	$0.00024	$0.00631
Haiku 4.5	$0.00012	$0.00316

Measured 2mo ago against content hash 847aba4e28b7, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

post-mortem 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 2mo 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.

.agents/skills/post-mortem/SKILL.md · 156 lines

How it starts

The opening of the file, as written. The whole thing — 156 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Post-mortem

The canonical engineering record of a bug fix. Written after debugging lands a real fix, for other engineers (and future-you, who will have forgotten everything in 6 months). Code identifiers are welcome here — this is the artifact that lets the next person recover the mental model fast.

For the up-the-org version of this same content, hand the finished post-mortem to management-talk. They compose: post-mortem owns the engineering truth, management-talk reframes it for leadership.

When to invoke

"/post-mortem"
"write the post-mortem / postmortem / RCA / root-cause analysis"
"document this fix" / "write up the root cause" / "close out this bug with a writeup"
After a debug session has clearly landed a fix, proactively offer to draft one.

When NOT to use

Bug not fixed yet, or fix not validated. A post-mortem of a hypothesis is misleading. Refuse and tell the user what's missing.
Customer-visible outage / incident. Those need a separate incident report (timeline, blast radius, paging history, comms). This skill is bug-fix scope. Flag and confirm before producing one.
Trivial fix (typo, obvious one-liner). The PR description is the record. Don't manufacture ceremony.

Required inputs — refuse to draft without these

Before writing a single line, confirm all four. If any are missing, list what's missing and stop:

Reliable repro exists (not "happens sometimes" — a deterministic or high-rate-flake repro the next person can run).
Root cause is known (the mechanism is identified, not a hypothesis).
Fix is identified (PR / commit / branch pointer).
Fix is validated (the original repro now passes; the customer workload / failing test now succeeds).

These map directly to debug-mantra steps 1–4. If you came in via debug-mantra, the breadcrumb ledger from step 4 is your raw material — pull from it.

Structure

Use these blocks in this order. Summary, Root cause, Fix, and Validation are mandatory. The rest are conditional but usually present.

Read the full file on GitHub · 156 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.

2mo ago First seen · 156 lines · 120 tokens per session scan A 847aba4e28b7

Subscribe to this mod's changes

post-mortem is a skill published in the GitHub repository hashangit/openfusion (35 stars, last pushed 3d ago), licensed MIT. It adds 120 tokens to every session and 3,157 once invoked, about $0.0005 per session on Opus 5.5. 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.

Debugging Writing and docs

post-mortem next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
post-mortemhashangit/openfusion	Skill	35	3d ago	MIT	A	120	Claude Code, Codex
systematic-debuggingopen-metadata/OpenMetadata	Skill	16k	yesterday	Apache-2.0	A	37	Claude Code
log-error-digestzebbern/claude-code-guide	Skill	4.7k	3d ago	MIT	A	71	Claude Code, Codex
cwv-optimizeradobe/skills	Skill	319	yesterday	Apache-2.0	A	112	Claude Code
ci-fixersipyourdrink-ltd/bernstein	Skill	1.2k	yesterday	Apache-2.0	A	15	Claude Code, Codex
incident-response-incident-responsermyndharis/antigravity-skills	Skill	1.9k	23d ago	MIT	A	36	Claude Code
triaging-web-analytics-supportPostHog/posthog	Skill	41k	yesterday	none	A	151	Claude Code, Codex

openfusion: Skill for Claude Code