Pre-Mortem

Overview

Identify failure modes before they occur. Based on Gary Klein's technique.

"Imagine it's 3 months from now and this project has failed spectacularly. Why did it fail?"

When to Use

•Decision-level (during brainstorming): Before committing to any individual design choice. Quick checklist. Propose options → premortem each → choose deliberately.
•Plan-level (before implementation): After the full plan is written, before writing code. Deep checklist. Stress-test the integrated design.

A decision without a premortem is a guess, not a design choice.

Risk Categories (Shreyas Doshi Framework)

Category	Symbol	Meaning
Tiger	`[TIGER]`	Clear threat that will hurt us if not addressed
Paper Tiger	`[PAPER]`	Looks threatening but probably fine
Elephant	`[ELEPHANT]`	Thing nobody wants to talk about

Two-Pass Verification

CRITICAL: Do NOT flag risks based on pattern-matching alone.

Pass 1 — Gather potential risks (hypotheses only)

Pass 2 — Verify each one:

•Read ±20 lines around the finding
•Check for fallback/error handling
•Confirm it's in scope (not test/dev-only code)
•Look for existing mitigations

If ANY verification check fails, it's not a tiger.

Every tiger MUST include evidence:

yaml

tiger:
  risk: "<description>"
  location: "file.go:42"
  severity: high|medium
  mitigation_checked: "No fallback found, no error handling, no retry"

Quick Checklist (Plans, PRs)

•What's the single biggest thing that could go wrong?
•Any external dependencies that could fail?
•Is rollback possible if this breaks?
•Edge cases not covered in tests?
•Unclear requirements that could cause rework?

Deep Checklist (Before Implementation)

Technical: Scalability, dependencies + fallbacks, data consistency, latency, security, error handling

Integration: Breaking changes, migration path, rollback strategy, feature flags

Process: Requirements clarity, stakeholder input, tech debt tracking, maintenance burden

Testing: Coverage gaps, integration tests, load testing, manual test plan

Output Format

yaml

premortem:
  mode: quick|deep
  context: "<what was analyzed>"

  tigers:
    - risk: "<description>"
      severity: high|medium
      mitigation_checked: "<what was NOT found>"

  elephants:
    - risk: "<unspoken concern>"

  paper_tigers:
    - risk: "<looks scary>"
      reason: "<why it's fine — cite the mitigation>"

Severity Thresholds

Severity	Blocking?	Action
HIGH	Yes	Must address or explicitly accept
MEDIUM	No	Recommend addressing
LOW	No	Note for awareness

After Analysis

Present findings to the user with options:

•Accept risks and proceed — acknowledged, not blocking
•Add mitigations to plan — update plan before building
•Research mitigation options — investigate solutions
•Discuss specific risks — talk through concerns

Red Flags

•Flagging risks without reading surrounding code
•Trusting grep results as evidence of missing handling
•Marking dev-only or test code as production risks
•Skipping Pass 2 verification