Premortem

premortem

Forward-looking imagined-failure analysis. Sibling of blameless-post-mortem (which analyses what actually went wrong after the fact) and risk-officer (which scores pre-commit risks per likelihood × impact). This skill adds the prospective frame: "Assume total failure at horizon H — reconstruct why."

When to use

Before committing to a plan that is:

• Heavy to execute (multi-sprint, multi-team, or high coordination cost), or
• Irreversible or costly to reverse (schema migration, public API change, infrastructure restructure, major dependency swap, architecture decision).

Trigger phrasing: "premortem this", "what if this fails?", "imagine it's 6 months later and this shipped badly", "help me stress-test this plan".

Do NOT use when:

• The failure is already evidenced — root cause is known → use systematic-debugging.
• Analysing something that already failed in the past → use blameless-post-mortem.
• The plan is trivial or fully reversible — overhead exceeds value.

Procedure

1. State the plan and set the horizon

Summarise the plan in one sentence: "We are doing X for outcome Y, touching Z." Set the prospective-failure frame explicitly: "Assume total failure at horizon H (e.g. 6 months post-launch). What went wrong?"

If the plan cannot be summarised in one sentence, it is not reviewable — stop and ask for scope clarification.

2. Enumerate failure stories

Generate failure scenarios across multiple angles (people, process, technical, external, timing). Each scenario is a short narrative in past tense: "We shipped, but adoption collapsed because …"

For each scenario:

• Invoke adversarial-review to attack the plan's assumptions and surface hidden coupling or over-engineering.
• Invoke risk-officer to assign L × I (likelihood × impact) scores to each failure mode.

Do NOT re-implement L × I scoring inline — delegate to risk-officer.

3. Derive early-warning signals and preventive guardrails

For each top failure mode (sorted by L × I from risk-officer):

1. Early-warning signal — what would you observe first if this failure mode were activating? Name a concrete, observable indicator (metric, alert, user behaviour, team signal). This is the load-bearing output.
2. Preventive guardrail — one specific change to the plan, process, or rollout strategy that reduces the likelihood of this failure mode. Keep it executable; flag as accept if no practical guardrail exists.

3b. Compress into the four-part failure register

When the pre-mortem accompanies a plan artefact (a roadmap, an ADR, a design doc), compress the analysis into the four-part failure register — the fixed, comparable shape the roadmap template's optional ## Pre-mortem section consumes:

1. Three most probable causes of death, ranked — one paragraph each, naming the concrete mechanism by which the plan most plausibly dies. Mechanisms, not topics: "the gate's two inputs are unmeasurable from this corpus" is a cause; "measurement risk" is not.
2. One untested hidden dependency — the assumption the plan relies on but never tests.
3. One modification that makes failure survivable — a concrete plan change that converts a fatal outcome into a recoverable one.
4. One tripwire metric with a horizon — a measurable signal plus a threshold and deadline that says early that cause #1 is materializing.

The register was validated blind against this repo's own closed nulls (3 of 4 registers named the actual failure cause at rank 1 — agents/evidence/analysis/premortem-blind-retro-validation.md). The hits were all failures of measurability; the miss was a mechanism that worked but added nothing — weight the register toward "can this experiment answer its question" and state redundancy risks explicitly.

4. Optional memory write-back

If the analysis surfaces a pattern worth preserving for future decisions:

1. Run a dedup pre-check: call retrieve() over the same key-space (plan type, affected paths, decision area). If a match is found, propose a frequency/supersedes update to the existing entry rather than a new one.
2. Draft a historical-patterns candidate and send it to /memory propose per docs/contracts/analysis-memory-loop.md.
3. Never auto-promote. Human action drives /memory promote.

Output format

1. Ranked prospective failure modes — L × I ordered list (from risk-officer)
2. Early-warning signal per failure mode — concrete, observable indicator
3. Preventive guardrails — one per failure mode (or accept with rationale)
4. Four-part failure register (when accompanying a plan artefact) — three ranked causes of death · one untested hidden dependency · one survivable-failure modification · one tripwire metric with a horizon (step 3b; feeds the roadmap template's optional ## Pre-mortem section)
5. Optional memory candidate — drafted to /memory propose if the pattern clears the admission gate (≥ 2 distinct file paths OR ≥ 3 future decisions)

Do NOT

• Do NOT invent strawman failure modes — each must be grounded in the actual plan's structure, assumptions, or dependencies.
• Do NOT re-implement L × I scoring — invoke risk-officer; don't duplicate its five-lens framework inline.
• Do NOT present speculation as evidence — premortem is imaginative framing, not a prediction; label scenarios as prospective.
• Do NOT auto-promote memory candidates — /memory propose is the intake; /memory promote requires explicit human action and passes check_memory_proposal.ts.

Gotchas

• Premortem is forward-looking — it imagines a future failure to improve the present plan. blameless-post-mortem is backward-looking — it analyses a past failure. Do not conflate them.
• The early-warning signal is the load-bearing output, not the doom list. A failure mode without a detectable signal cannot be caught in time — flag it explicitly.
• Failure stories in past tense ("we shipped, and then X happened") are more generative than abstract risk statements. Force the past-tense narrative.

See also

• risk-officer — L × I scoring; invoked in Step 2. Not duplicated here.
• adversarial-review — assumption attack; invoked in Step 2. Not duplicated here.
• blameless-post-mortem — post-hoc analysis of an actual failure; backward-looking counterpart to this skill.
• Invocation surfaces: /analyze premortem, feature:plan, roadmap-create (surface the premortem step as optional before committing to a plan).