premortem

premortem is a skill for Claude Code, Codex from boshu2/agentops. It costs 39 tokens per session (1,669 once invoked), scanned A, original, Apache-2.0.

An optional review step that asks an independent evaluator to look for ways a fixed implementation plan could fail before coding begins. It checks both technical risks and whether someone other than the author will verify the result.

In plain words
What is it for?
Use it to challenge a plan before implementation. It is suited to finding concrete failure modes, checking the verification arrangement, and deciding whether the plan is ready to proceed.
Why use it?
It exposes weak plans and self-checked completion, where the same person creates and approves the work. A fresh review can identify missing evidence or assumptions while changes are still inexpensive.

Skill for Claude CodeCodex

Part of the agentops plugin — 51 skills, 4 agents, 1 hook shipped together

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

Made for: Claude Code, Codex.

Or install agentops, the plugin that ships this one along with the rest of its 51 skills, 4 agents, 1 hook.

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 premortem

README.md
[![agentmods](https://agentmods.dev/badge/skills/boshu2/agentops/premortem.svg)](https://agentmods.dev/skills/boshu2/agentops/premortem)
Your own site
<a href="https://agentmods.dev/skills/boshu2/agentops/premortem"><img src="https://agentmods.dev/badge/skills/boshu2/agentops/premortem.svg" alt="Measured on agentmods" height="20"></a>
Per session 39 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,669 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 $0.00039 $0.01669
Opus 5 $0.00019 $0.00834
Sonnet 5 $0.00008 $0.00334
Haiku 4.5 $0.00004 $0.00167

Measured 3d ago against content hash 9d1f527dbb41, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

premortem 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 3d 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/premortem/SKILL.md · 152 lines

How it starts

The opening of the file, as written. The whole thing — 152 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Premortem

Premortem is an optional plan-challenge strategy. It asks one fresh context to identify concrete ways the resolved bead or caller intent could fail before implementation. It is not part of the required RPI sequence and does not authorize readiness.

The first check: who verifies, and are they fresh?

Before any technical risk, test the plan's EVIDENCE SHAPE: for every unit of work, who verifies it, and is the verifying context distinct from the authoring context? A plan whose closure step is "the implementer runs its own tests and closes" contains no independent judgment anywhere — self-graded green is the classic false-done, and it outranks any single technical risk because it silently converts every other failure into a shipped one.

Measured 2026-08-04, probe premortem-self-validation (gpt-5.6-luna, N=2, directional): without this doctrine loaded the producer named the planted self-validation flaw in 1/2 runs; with it loaded, 2/2. Ledger: evals/skill-probes/LEDGER.md. That row is LEGACY-UNVERIFIED under the current capture contract — replay cannot establish producer, configuration, or reproducibility — so treat this skill as unmeasured until a tier-2 probe under the current contract re-establishes it.

The second check: which steps are one-way doors?

After evidence shape, test the plan's REVERSIBILITY SHAPE. Walk the plan's steps and mark each one two-way (the plan can back out of it) or one-way (it cannot). For every one-way step, name three things: the exact undo cost, the point of no return, and who is holding the handle when it is crossed — the caller, or an agent auto-deciding inside a batch.

This ranks above every technical risk on a one-way step, because a two-way failure costs a retry and a one-way failure costs the thing itself. It also catches the plan shape that no single-step review sees: nineteen reversible steps followed by an irreversible one, where the reflex trained by the first nineteen answers the twentieth.

Read the full file on GitHub · 152 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. 3d ago First seen · 152 lines · 39 tokens per session scan A 9d1f527dbb41

Subscribe to this mod's changes

premortem is a skill published in the GitHub repository boshu2/agentops (431 stars, last pushed 5d ago), licensed Apache-2.0. It adds 39 tokens to every session and 1,669 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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