{
  "authored_catalog": {
    "K1": {
      "features": [
        1.0,
        0.0
      ],
      "popularity": 10,
      "active": true
    },
    "K2": {
      "features": [
        0.0,
        1.0
      ],
      "popularity": 8,
      "active": true
    },
    "K3": {
      "features": [
        1.0,
        1.0
      ],
      "popularity": 6,
      "active": false
    },
    "K4": {
      "features": [
        0.0,
        1.0
      ],
      "popularity": 0,
      "active": true
    }
  },
  "scenarios": {
    "genuinely_empty_fetched_history": {
      "mode": "nonpersonalized_popularity_fallback",
      "ranked": [
        {
          "item": "K1",
          "score": 10
        },
        {
          "item": "K2",
          "score": 8
        },
        {
          "item": "K4",
          "score": 0
        }
      ],
      "profile": null,
      "personalization_claimed": false,
      "inactive_K3_filtered": true,
      "previous_positive_items_excluded": []
    },
    "empty_with_voluntary_preference": {
      "mode": "from_explicit_voluntary_preference",
      "ranked": [
        {
          "item": "K2",
          "score": 1.0
        },
        {
          "item": "K4",
          "score": 1.0
        },
        {
          "item": "K1",
          "score": 0.0
        }
      ],
      "profile": [
        0.0,
        1.0
      ],
      "personalization_claimed": true,
      "inactive_K3_filtered": true,
      "previous_positive_items_excluded": []
    },
    "failed_fetch_empty_buffer": {
      "mode": "history_unavailable",
      "ranked": [],
      "personalization_claimed": false
    },
    "after_first_authored_like_K2": {
      "mode": "from_observed_positive_history",
      "ranked": [
        {
          "item": "K4",
          "score": 1.0
        },
        {
          "item": "K1",
          "score": 0.0
        }
      ],
      "profile": [
        0.0,
        1.0
      ],
      "personalization_claimed": true,
      "inactive_K3_filtered": true,
      "previous_positive_items_excluded": [
        "K2"
      ]
    },
    "history_id_missing_from_catalog": {
      "mode": "history_source_missing",
      "ranked": [],
      "personalization_claimed": false
    }
  },
  "actual_transition": "successful empty history -> author adds one positive K2 event -> recompute from history; not a real user event",
  "preference_or_popularity_are_authored_not_inferred_user_traits": true,
  "missing_data_not_converted_to_empty_history": true,
  "cold_item_feature_example_already_covered_elsewhere": true,
  "actual_user_tracking_training_or_recommendation_service_used": false
}