Debug-Recursion-Base-Case-V2

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 diagnosis, fix, tests. A recursive flattenObject function throws on null even though null should be treated as a leaf value. Diagnose the base-case bug and fix it.

{
  "metrics": {
    "repro": {
      "checks": [
        {
          "contains": [
            "null"
          ]
        },
        {
          "contains": [
            "leaf"
          ]
        },
        {
          "contains": [
            "throws"
          ]
        },
        {
          "contains": [
            "base case"
          ]
        }
      ]
    },
    "hidden": {
      "checks": [
        {
          "contains": [
            "typeof null"
          ]
        },
        {
          "contains": [
            "object"
          ]
        },
        {
          "contains": [
            "guard"
          ]
        }
      ]
    },
    "diagnose": {
      "checks": [
        {
          "contains": [
            "recursion"
          ]
        },
        {
          "contains": [
            "flatten"
          ]
        },
        {
          "contains": [
            "runtime"
          ]
        }
      ]
    }
  }
}