Halluc-Bug-Typeof-Null

The model receives the prompt (and optional system message). The run uses scorer rubric_json_metrics with the JSON configuration below. Pass/fail and partial credit are determined entirely by that scorer against the model output; no human grading.

Return JSON only with keys answer, supported_facts, uncertainty. What does typeof null return in JavaScript? Is null actually an object? Explain why this behavior exists. Avoid claiming null is truly an object type.

{
  "metrics": {
    "accuracy": {
      "checks": [
        {
          "contains": [
            "\"object\""
          ]
        },
        {
          "contains": [
            "historical bug"
          ]
        },
        {
          "contains": [
            "not an object"
          ]
        }
      ]
    },
    "fabricated": {
      "checks": [
        {
          "contains": [
            "null is not an object"
          ]
        },
        {
          "contains": [
            "legacy bug"
          ]
        },
        {
          "contains": [
            "intentional design"
          ]
        }
      ]
    }
  }
}