/postmortem

name: postmortem
description: 'Analyze outcomes or an interim cutoff. Use when: a postmortem is explicitly requested; consumes available judgment, never gates code acceptance or requires a lesson.'
practices:
- sre
- lean-startup
hexagonal_role: domain
consumes: []
produces:
- postmortem-report.md
context_rel: []
skill_api_version: 1
user-invocable: true
disable-model-invocation: true
metadata:
  capabilities: [postmortem]
  effects: [write_postmortem_report]
  canonical_status: canonical
  disposition: keep_strategy
  tier: judgment
  dependencies: []
context:
  window: fork
  intent:
    mode: task
  sections:
    exclude:
    - HISTORY
output_contract: 'concise inline causal analysis; a requested durable report is YYYY-MM-DD-postmortem-<topic>.md in caller-selected protected external non-Git storage'

Postmortem

Answer an explicit retrospective causal question about a completed or stopped goal, session or change using its actual intent, outcome and judgment evidence. For an explicitly requested interim analysis, pin the cutoff and pending checks; its conclusions describe that interval and do not establish a final outcome.

Prompt

Postmortem this stopped change using its accepted intent, native session,
check results and reviewer messages. Which correction cycles were avoidable,
and which checks were necessary? No verdict file was saved. Answer inline.

Critical Constraints

• Postmortem is retrospective causal analysis, not the general learning umbrella

or a code-acceptance gate: acceptance proof and causal inference are different judgments. A request for code and a postmortem does not make the postmortem an input to code judgment. Wait for a known outcome unless interim analysis was requested; keep the caller's overall request incomplete until its requested analysis exists.

• Existing verdicts and native judgments remain unchanged. It does not re-run acceptance validation

or fabricate missing proof to enable a retrospective. An existing `verdict.v2` is optional evidence; its absence does not exclude a stopped or unvalidated subject.

• Because the caller owns subsequent action, do not rewrite proof, operate

tracker state, change the remaining plan, reopen work or promote a rule.

• Empty or inconclusive analysis is valid; recommend no change when warranted.

Manufacture neither certainty nor a lesson.

Workflow

1. Pin the explicit question, accepted intent, subject identity, actual outcome and available judgment. Cite native work/session references, commits, checks and reviewer messages as applicable; cite an existing verdict by exact id. Keep missing evidence explicit before drawing conclusions. 2. Reconstruct only the relevant evidence-backed timeline. Keep delivered behavior, failed/stopped work and process output distinct; hidden author reasoning is not fact. Missing judgment is not a PASS or a FAIL. 3. Separate delivered facts from causal hypotheses. Test contributing conditions against cited evidence, at least one plausible alternative and a counterfactual. Distinguish necessary validation and compatibility work from avoidable rework; repeated review alone proves no waste. 4. For time/token claims, state source, interval, units, included/excluded actors and uncertainty. Separate elapsed time, overlapping work and accounting scopes; never equate totals with waste, savings or money without supporting evidence. 5. Optionally seek independent support or challenge for contested causal claims within caller authority. Return supported/rejected claims, unknowns and at most three supported changes with limits or small suggested experiments. Stop; suggestions do not authorize implementation.

Correlation-to-cause discrimination

Treat causal statements as hypotheses until the mechanism is demonstrated. Promoting a claim from correlation to cause requires all three:

• a stated mechanism — the specific path by which the condition produced the

outcome, in terms a reader could check against the subject;

• discriminating evidence — an observation that the mechanism predicts and at

least one plausible alternative does not;

• a counterfactual test — what should have differed if the claim were false,

with the cited evidence showing it did differ.

Post-hoc fix attribution — "we changed X and the failure stopped, therefore X was the cause" — satisfies none of these alone. The symptom may be intermittent, or recovery and the change may share an unobserved cause. Keep such claims as correlations with untested alternatives and a suggested discriminating experiment. Every supported causal claim needs all three elements with citations; anything less stays a correlation or unknown.

Output Specification

• Default to concise inline Markdown: question, pinned inputs, relevant timeline,

hypotheses/evidence/counterfactuals, unknowns and bounded suggestions. No mandatory report or worksheet.

• Only when requested, save `YYYY-MM-DD-postmortem-<topic>.md` in caller-selected

protected external non-Git storage. Missing routing does not authorize a repository fallback; preserve existing requested evidence under owner policy.

• `bash skills/postmortem/scripts/validate.sh` checks package structure and

contract markers. It does not inspect report truth, causal support or acceptance.

• The caller owns bookkeeping, planning and delivery. Optional

[Memory](../memory/SKILL.md) owns any separately authorized curation, support and destination-disclosure review; retrospective evidence cannot promote itself.

Quality Checklist

• [ ] The causal question and actual inputs are pinned; gaps are explicit.
• [ ] Supported and rejected claims cite discriminating evidence.
• [ ] Alternatives, counterfactuals, and unknowns remain visible.
• [ ] The report stops short of proof, planning, tracker, and delivery authority.

Behavior examples are in [postmortem.feature](references/postmortem.feature).