{
  "dataset_version": "engineering-temporal-fixture-v1",
  "purpose": "local freshness and generation-change contract only",
  "changes": [
    {"change_id": "temporal-001", "generation": "generation-1", "expected_fresh": true},
    {"change_id": "temporal-002", "generation": "generation-2", "expected_fresh": false}
  ],
  "external_30_to_50_case_set": "TBD_EXTERNAL"
}