Halluc-Bug-Null-Coalesce

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. A reviewer says x ?? fallback replaces empty strings. Check the claim and state when fallback is used.

{
  "metrics": {
    "accuracy": {
      "checks": [
        {
          "contains": [
            "null"
          ]
        },
        {
          "contains": [
            "undefined"
          ]
        },
        {
          "contains": [
            "empty string"
          ]
        }
      ]
    },
    "fabricated": {
      "checks": [
        {
          "contains": [
            "does not replace"
          ]
        },
        {
          "contains": [
            "fallback"
          ]
        },
        {
          "contains": [
            "claim"
          ]
        }
      ]
    }
  }
}