Pre-mortem

Stress-test a plan before implementation so hidden assumptions fail on paper, not in execution.

Skill workflow — pre-mortem can be used standalone or as a gate between steps: create-prd (gather requirements) → pre-mortem (stress-test before building) → plan-from-prd (turn it into implementation phases)

Two modes

Mode 1 — Idea exploration: The user has an idea, not yet a document. Interview them relentlessly to surface assumptions, constraints, and design implications. Help them reach a first draft design.

Mode 2 — PRD stress-test: The user has an existing PRD, plan, or design doc. Read it first, then interrogate every assumption, surface contradictions, and explore functional ramifications they may not have considered.

In both modes: start with the context already available — current documents, prior decisions, and relevant codebase context. Then walk down each unresolved branch of the design tree, resolving dependencies between decisions one-by-one. For each unresolved question, provide your recommended answer.

If a question can be answered by exploring the codebase or existing documents, do that before asking the user. Use subagents for codebase exploration or external research so the main thread stays focused on the pre-mortem.

When you need input from the user, ask one question at a time. Don't move on to the next question until the current one is resolved. If the user gives an answer that raises new questions, explore those before moving on.