# premortem
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.
## The method
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.
- Kahneman endorsed it in *Thinking, Fast and Slow* as a counter to overconfidence.
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.
## How it works
Six steps. Linear flow. Parallel sub-agents do the heavy lifting in step 4.
```mermaid
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: write context file, spawn parallel sonnet sub-agents<br/>one per failure reason + one assumption excavator]
E --> E1[Agent 1: failure A]
E --> E2[Agent 2: failure B]
E --> E3[Agent N: ...]
E --> E4[Excavator: unstated assumptions]
E1 --> F[Step 5: synthesise + gate]
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. Four things come back per agent: the failure narrative, the underlying assumption that made it possible, 1–2 early warning signs the user can watch for, and a probability/impact rating. A separate excavator agent returns the unstated assumptions the plan rests on, rated load-bearing and testable.
Cost discipline, learned from running this shape inside a larger research pipeline: the plan context is written to a file once rather than pasted into every prompt, every sub-agent runs on `sonnet` with the model set explicitly, and each returns under 300 words with no preamble. Synthesis stays with the parent model. Before the report is written, a gate checks that every failure maps to a revision and every checklist item names the failure it guards against.
## What it catches
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.
## When NOT to apply
- 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.
## Output
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.
## Install
```
git clone https://github.com/b1rdmania/claude-premortem-skill.git ~/.claude/skills/premortem
```
## Trigger phrases
*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.*
## Sources
- 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.
## License
MIT