A Claude Code skill that runs a premortem on any plan, launch, product, hire, strategy, or decision. Imagines the plan failed 6 months from now, works backward to find every reason why, then produces a revised plan with the blind spots exposed.

A premortem is the opposite of a postmortem. Instead of figuring out what went wrong after a failure, you imagine the failure has already happened and explain how, before you start.

• Method: Gary Klein, Harvard Business Review, 2007.
• Daniel Kahneman called it his single most valuable decision-making technique.
• Used by Google, Goldman Sachs, P&G.

The mechanism: "what could go wrong?" produces hedged, polite answers. "This already failed, explain why" puts the brain into narrative mode and generates specific, honest causes. Wharton and Cornell call this prospective hindsight.

This matters for AI assistance. Claude defaults to agreeable. Asking "is this a good plan?" gets reasons it's good. The premortem reframe forces honest failure analysis instead of polite risk assessment.

Six steps. Linear flow. Parallel sub-agents do the heavy lifting in step 4.

flowchart TD
    A[Plan / launch / decision in] --> B[Step 1: gather minimum context]
    B --> B1{Three things known?<br/>What is it?<br/>Who is it for?<br/>What does success look like?}
    B1 -->|No| B2[Ask one question]
    B2 --> B1
    B1 -->|Yes| C[Step 2: set the premortem frame<br/>It is 6 months from now. The plan failed.]
    C --> D[Step 3: generate failure reasons<br/>comprehensive raw list]
    D --> E[Step 4: spawn parallel sub-agents<br/>one per failure reason]
    E --> E1[Agent 1: failure A]
    E --> E2[Agent 2: failure B]
    E --> E3[Agent 3: failure C]
    E --> E4[Agent N: ...]
    E1 --> F[Step 5: synthesise]
    E2 --> F
    E3 --> F
    E4 --> F
    F --> F1[Most likely failure]
    F --> F2[Most dangerous failure]
    F --> F3[Hidden assumption]
    F --> F4[Revised plan]
    F --> F5[Pre-launch checklist]
    F1 --> G[Step 6: HTML report + 3-sentence chat summary]
    F2 --> G
    F3 --> G
    F4 --> G
    F5 --> G

Each sub-agent in step 4 takes one failure reason and writes the story of how it played out. Three things come back per agent: the failure narrative, the underlying assumption that made it possible, and 1–2 early warning signs the user can watch for.

Failure classes that polite risk assessment routinely misses:

• Audience mismatch. The plan targets people who don't actually buy, or don't self-identify the way the plan assumes.
• Hidden friction. Approval cycles, integration costs, prep time the user didn't budget.
• Wrong-buyer drift. Early customers or testimonials that pull the plan away from the intended target, compounding over time.
• Tooling gaps. Demo environments, infrastructure, content prep that takes longer than estimated.
• Revenue / cost mismatch. Max upside doesn't justify the prep effort against alternative uses of the time.
• Foundational assumption. The single thing the user takes for granted that the whole plan rests on. Often the real value of the premortem.

• Vague ideas with no concrete plan yet. Help plan first, then premortem.
• Questions with one right answer. Just answer.
• Creative feedback on a draft. That's editing.
• Decisions already made and irreversible. A premortem only helps when course correction is possible.
• Multi-perspective decision support. Use a council or devil's-advocate flow instead. Different mechanism, different output.
• Simple feedback or factual questions.

A single self-contained HTML report saved to the workspace. Synthesis at the top, one card per failure reason below showing the story, the assumption, and the warning signs.

In the chat: a 3-sentence summary covering the most likely failure, the hidden assumption, and the single most important revision. The HTML has the full detail.

git clone https://github.com/b1rdmania/claude-premortem-skill.git ~/.claude/skills/premortem

(Adjust the URL if the repo name differs.)

premortem this, premortem my, what could kill this, stress test this plan, find the blind spots, poke holes in this, where will this break, am I missing anything, what could go wrong, future-proof this, devil's advocate this.

• Gary Klein, "Performing a Project Premortem," Harvard Business Review (2007).
• Daniel Kahneman, Thinking, Fast and Slow (2011) — chapter on prospective hindsight.
• Mitchell, Russo, Pennington, "Back to the future: temporal perspective in the explanation of events," Journal of Behavioral Decision Making (1989). The academic origin.

MIT