postmortem

A retrospective analysis tool for testing a specific explanation of an outcome against evidence that has already been validated. It separates what happened from possible causes, alternatives, and unknowns.

In plain words
What is it for?
Use it to investigate a causal question after an outcome, compare possible explanations, and return evidence for the person responsible for delivery decisions.
Why use it?
It helps teams examine why something happened without confusing a sequence of events with proof of cause. It also avoids inventing a confident lesson when the evidence is inconclusive.

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/boshu2/agentops/postmortem
Any agent
npx skills add boshu2/agentops --skill postmortem
Clone the repo
git clone --depth 1 https://github.com/boshu2/agentops

Made for: Claude Code, Codex.

Per session 35 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 957 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 $0.00035 $0.00957
Opus 5 $0.00017 $0.00478
Sonnet 5 $0.00007 $0.00191
Haiku 4.5 $0.00003 $0.00096

Measured 2d ago against content hash e46937a20b5d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

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.

images/gemini/skills/postmortem/SKILL.md · 107 lines

How it starts

The opening of the file, as written. The whole thing — 107 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Postmortem

Purpose: Answer an explicit retrospective causal question using the already-validated outcome and evidence.

Critical Constraints

  • Because proof and causal inference are different judgments, Postmortem is retrospective causal analysis, not the general learning umbrella and not a completion gate.
  • It consumes immutable Validate verdict evidence and does not re-run acceptance validation because Validate already owns that proof.
  • Treat causal statements as hypotheses because causal confidence must survive alternatives. Separate observed sequence, contributing conditions, counterfactuals, and unknowns.
  • A correlation is not promoted to cause without evidence that discriminates plausible alternatives.
  • Because the caller owns delivery decisions, do not rewrite proof, operate tracker state, change the remaining plan, or promote a rule. Return evidence to the caller.
  • Empty or inconclusive analysis is valid; manufacture neither certainty nor a lesson to make the retrospective feel useful.

Workflow

  1. Pin the verdict, subject evidence, and explicit causal question.
  2. Reconstruct the evidence-backed timeline without importing hidden author reasoning as fact.
  3. List candidate contributing conditions and at least one plausible alternative explanation.
  4. Test each claim against cited evidence and a counterfactual: what should differ if the claim were false?
  5. Optionally use independent judges to challenge contested causal claims.
  6. Emit a report containing supported claims, rejected claims, unknowns, evidence references, and suggested experiments. Stop.

Correlation-to-cause discrimination

A fix is proven when the mechanism is demonstrated, not when symptoms stop. Promoting a claim from correlation to cause requires all three:

  • a stated mechanism — the specific path by which the condition produced the outcome, in terms a reader could check against the subject;
  • discriminating evidence — an observation that the mechanism predicts and at least one plausible alternative does not;
  • a counterfactual test — what should have differed if the claim were false, with the cited evidence showing it did differ.

Read the full file on GitHub · 107 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. 2d ago First seen · 107 lines · 35 tokens per session scan A e46937a20b5d

Subscribe to this mod's changes

postmortem is a skill published in the GitHub repository boshu2/agentops (431 stars, last pushed 4d ago), licensed Apache-2.0. It adds 35 tokens to every session and 957 once invoked, about $0.0002 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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