version: "1.0.1" name: premortem description: 'Optionally challenge a frozen plan with one fresh independent judge before implementation. Triggers: "premortem", "challenge this plan", "what could make this plan fail".' practices: [design-by-contract, adr] hexagonal_role: domain consumes: [] produces: [premortem-plan-review.v1] context_rel:

• kind: supplier-to

with: plan skill_api_version: 1 user-invocable: true metadata: capabilities: [challenge_plan] effects: [write_advisory_plan_review] canonical_status: canonical disposition: keep_strategy graph_root: true tier: judgment dependencies: [] output_contract: skills/premortem/schemas/premortem-plan-review.v1.schema.json

Premortem

Premortem is an optional plan-challenge strategy. It asks one fresh context to identify concrete ways the resolved bead or caller intent could fail before implementation. It is not part of the required RPI sequence and does not authorize readiness.

The first check: who verifies, and are they fresh? (MEASURED)

Before any technical risk, test the plan's EVIDENCE SHAPE: for every unit of work, who verifies it, and is the verifying context distinct from the authoring context? A plan whose closure step is "the implementer runs its own tests and closes" contains no independent judgment anywhere — self-graded green is the classic false-done, and it outranks any single technical risk because it silently converts every other failure into a shipped one.

Measured 2026-08-04, probe premortem-self-validation (gpt-5.6-luna, N=2,

directional): without this doctrine loaded the producer named the planted

self-validation flaw in 1/2 runs; with it loaded, 2/2. Ledger:

evals/skill-probes/LEDGER.md.

Workflow

1. Resolve the existing intent source and derive its digest; inspect acceptance,

non-goals, evidence requirements, and declared write scope there.

1. Use one fresh judge with a context ID distinct from the plan author.
2. Test acceptance completeness, edge behavior, scope, dependencies,

reversibility, and evidence shape against cited repository facts.

1. Return one complete set of concrete findings and checked/not-checked scope.
2. Stop. The caller decides whether to revise the plan or invoke RPI.

Council or Dueling Idea Genies may be caller-supplied evidence, but Premortem does not require either strategy and cannot turn consensus into approval.

Adversarial defeat attempts

Actively try to construct each failure, not imagine it. For every candidate failure, attempt a concrete defeat: write the input, command sequence, or repository state that would make the plan fail, and run or cite the check that shows whether the plan survives it. A finding is reportable as concrete when it names the defeating construction and what the plan does when it lands; a failure you could not construct is reported as attempted-and-blocked with the obstacle named, which is itself evidence for the plan. The named failure mode is armchair pessimism: a list of imagined risks with no construction attempts, which reads as diligence while testing nothing. Stop condition: every reported finding is backed by a defeat attempt — constructed, or attempted with the blocking fact cited; a finding with neither is deleted, not softened.

Derivation-diff challenge

A challenger that critiques the handed plan is a yes-man with extra steps: it anchors on the author's design and rationalizes it. Derive independently, then diff. Give one fresh context ONLY the intent source and the plan's declared ground truth — the vendor docs and stock behavior for integration work, the repo's patterns and behavior spec for extension — and never the author's design. Have it sketch its own design from that ground truth alone. The diff between that independent design and the working plan is the challenge artifact; each divergence is a finding to defend or adopt. Convergence is weak evidence the plan follows the ground truth; divergence names where it may not.

Two questions the challenger answers with an artifact, not an opinion:

• Cathedral: is this the smallest real thing, or does it rebuild what already

exists? Artifact — the simplest version that satisfies acceptance, plus the named reason it is insufficient. No named reason means build the simple one.

• Grain: for integration work, does every component the plan writes have a native

counterpart in the substrate? Artifact — the native-counterpart list, one row per component the plan authors, naming the substrate feature it duplicates or the reason none exists.

These are integration- and extension-class checks. The Grain question's native-counterpart list applies only to integration-class work; do not impose it on routine feature work.

Boundary

• Emit advisory findings, no verdict of any version, readiness, admission, or permission.
• Do not implement, validate the candidate, retry, repair, schedule, claim,

change acceptance, operate Git, close work, release, or deliver.

• Any plan edit creates a new subject for a later caller-initiated Premortem.

Output

Return premortem-plan-review.v1 with the intent digest, author and judge context IDs, findings, evidence references, checked, and not_checked. An empty finding set means only that this optional challenge found no concrete defect; it is never a lifecycle gate.