Postmortem

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. Neighbours: how a plan not yet run could fail is Premortem; whether a finished change meets acceptance is Validate.

First check: correlation or cause?

Treat every causal statement as a hypothesis, including the one the caller arrives with. 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 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 the recovery and the change may share an unobserved cause. Keep such claims as correlations, name the alternatives still standing, and suggest the discriminating experiment. A recommendation built on an unproven cause is framed as that experiment, not as a supported change. Every supported causal claim needs all three elements with citations; anything less stays a correlation or an unknown.

Prompt

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Postmortem last Thursday's release: the deploy needed four attempts and two
rollbacks before it stuck. Using the deploy log, the CI runs and the incident
channel notes, which failures were avoidable and what caused each one?
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, so 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, and keep the overall request incomplete until the 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 question, accepted intent, subject identity, actual outcome and available judgment with exact ids (commits, checks, messages, an existing verdict); keep missing evidence explicit.
2. Rebuild only the timeline the claims depend on, keeping delivered behavior, failed or stopped work and process output distinct. For a correction or stop, locate the first observable departure from the accepted behavior and the instruction, tool result or missing input immediately before it. Compare a successful case under similar conditions when available; otherwise name that missing comparison. A pause required by the caller is expected behavior. Hidden author reasoning is not fact; missing judgment is not a PASS or a FAIL.
3. Put each causal claim through the first check above. Distinguish necessary validation and compatibility work from avoidable rework; repeated review alone proves no waste. If the inputs include an earlier postmortem of the same subject, account for its recommendations before issuing new ones: applied, partly applied, not applied, or unknown, with evidence from the supplied work since then. Preserve whether a change was authorized, held or never approved; missing evidence of application is not failed adoption. Report recurrence of the targeted failure only when observed. For repeated unapplied advice, name known obstacles or an unresolved question instead of simply repeating it. Nonapplication alone proves neither cause, blame nor that the advice helps.
4. For time or token claims, state source, interval, units, included and 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 the output below and stop; suggestions do not authorize implementation.

Output Specification

• Default to concise inline Markdown, no mandatory report or worksheet:

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  Question: <the causal question>
  Inputs: <intent, outcome and evidence, with exact ids>; missing: <gaps>
  Timeline: <only the events the claims depend on>
  Claims:
  - <claim>: supported | correlation | rejected | unknown
    mechanism / discriminating evidence / counterfactual: <each, cited, or "none">
    alternatives still standing: <rivals the evidence cannot rule out>
  Unknowns: <what would settle them>
  Changes (at most three, or "no change"): <change> - <its limit, or the experiment that tests it>
  

• Aim each change at what the next run will meet, usually the instruction, tool result or missing input found in step 2, not at re-fixing code that is already repaired. The kind of avoidable miss picks the lever:

  • Mechanical slip (wrong path, skipped command, forbidden call): a lint rule, test or hook. Read the repository's check commands, hooks and CI first; an existing check that did not run or could not fail is the change, not a duplicate. When no seam in the code can hold such a check, name Architecture as the follow-up, with that defect as its named pain.
  • Judgment miss: one proposed standard or instruction line; writing it is separately authorized Memory work.
  • Fact found slowly: one pointer where the search began. Fact out of reach: a way to expose it next time, such as a captured log; changing access needs caller authority.

• 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.

• The caller owns bookkeeping, planning and delivery. Optional Memory 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.
• At most three changes, each aimed at what the next run meets, bounded or framed as an experiment.
• The report stops short of proof, planning, tracker, and delivery authority.

Behavior examples are in postmortem.feature.