Label: Reference execution
Generated by: scripts/generate_paa_walkthrough_captures.py
Read first: docs/assets/paa-walkthrough/README.md

# Failure path: approval fails closed on tampered evidence

A second motion proposes the declared demotion, binding the redacted gate-block artifact as its evidence. The generator then appends one byte to the stored evidence file, standing in for any modification after proposal. Approval re-hashes the bytes, finds the mismatch, and writes nothing: the motion stays proposed and the position stays hotl. The operator then rejects the stale motion; rejection is terminal.

$ scout paa propose inbound_reply_surfacing --to hitl --evidence evidence/paa/reference/bundle/gate-block.json --actor operator-a --reason "reference execution: blocking evaluator fired"
{
  "approved_at": null,
  "approved_by": null,
  "approved_reason": null,
  "declaration_version": 1,
  "evidence_ref": "evidence/paa/16a9c77147cc8b8336c830f99af2ef4e214e1fcef6bc8f35c3e724980253ba8f/evidence.json",
  "evidence_sha256": "16a9c77147cc8b8336c830f99af2ef4e214e1fcef6bc8f35c3e724980253ba8f",
  "executed_at": null,
  "from_position": "hotl",
  "motion_id": "00000000-0000-4000-8000-000000000002",
  "proposed_at": "2026-01-01T00:00:04.000000Z",
  "proposed_by": "operator-a",
  "proposed_reason": "reference execution: blocking evaluator fired",
  "rejected_at": null,
  "rejected_by": null,
  "rejected_reason": null,
  "scope": null,
  "status": "proposed",
  "task": "inbound_reply_surfacing",
  "to_position": "hitl"
}

The stored evidence file is modified here, outside the CLI.

$ scout paa approve 00000000-0000-4000-8000-000000000002 --actor operator-b --reason "reference execution: attempted approval"
paa approve error: evidence at <evidence-root>/evidence/paa/16a9c77147cc8b8336c830f99af2ef4e214e1fcef6bc8f35c3e724980253ba8f/evidence.json has been tampered with: bytes hash to e45423b5672ac4ddff066e24d7cfe9bcd3ab34daf50ea935fc4e96602fddfa8c, expected 16a9c77147cc8b8336c830f99af2ef4e214e1fcef6bc8f35c3e724980253ba8f
[exit status 1]

$ scout paa show inbound_reply_surfacing
{
  "current_position": "hotl",
  "declaration_version": 1,
  "deployment": "shadow",
  "initial_position": "hitl",
  "latest_position_event": {
    "actor": "operator-b",
    "created_at": "2026-01-01T00:00:03.000000Z",
    "declaration_version": 1,
    "event": "position_changed",
    "event_schema": "paa-autonomy-event/0.1.0-draft",
    "evidence_ref": "evidence/paa/b38c40982b34b130d1f790146b432467a8e9819a671f10b723fcb1ccafc20701/evidence.json",
    "evidence_sha256": "b38c40982b34b130d1f790146b432467a8e9819a671f10b723fcb1ccafc20701",
    "from_position": "hitl",
    "id": "00000000-0000-4000-8000-0000ffff0003",
    "motion_id": "00000000-0000-4000-8000-000000000001",
    "reason": "reference execution: second operator approved",
    "scope": null,
    "task": "inbound_reply_surfacing",
    "to_position": "hotl"
  },
  "scope": null,
  "task": "inbound_reply_surfacing"
}

$ scout paa reject 00000000-0000-4000-8000-000000000002 --actor operator-b --reason "reference execution: evidence no longer matches its recorded hash"
{
  "approved_at": null,
  "approved_by": null,
  "approved_reason": null,
  "declaration_version": 1,
  "evidence_ref": "evidence/paa/16a9c77147cc8b8336c830f99af2ef4e214e1fcef6bc8f35c3e724980253ba8f/evidence.json",
  "evidence_sha256": "16a9c77147cc8b8336c830f99af2ef4e214e1fcef6bc8f35c3e724980253ba8f",
  "executed_at": null,
  "from_position": "hotl",
  "motion_id": "00000000-0000-4000-8000-000000000002",
  "proposed_at": "2026-01-01T00:00:04.000000Z",
  "proposed_by": "operator-a",
  "proposed_reason": "reference execution: blocking evaluator fired",
  "rejected_at": "2026-01-01T00:00:05.000000Z",
  "rejected_by": "operator-b",
  "rejected_reason": "reference execution: evidence no longer matches its recorded hash",
  "scope": null,
  "status": "rejected",
  "task": "inbound_reply_surfacing",
  "to_position": "hitl"
}