Debug-Graph-Cycle-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 directed graph cycle detector reports false positives after visiting nodes from a previous DFS branch. Explain the bug and the minimal fix.

{
  "metrics": {
    "repro": {
      "checks": [
        {
          "contains": [
            "DAG"
          ]
        },
        {
          "contains": [
            "false positive"
          ]
        },
        {
          "contains": [
            "visited"
          ]
        },
        {
          "contains": [
            "branch"
          ]
        }
      ]
    },
    "hidden": {
      "checks": [
        {
          "contains": [
            "recursion stack"
          ]
        },
        {
          "contains": [
            "remove on unwind"
          ]
        },
        {
          "contains": [
            "visiting"
          ]
        }
      ]
    },
    "diagnose": {
      "checks": [
        {
          "contains": [
            "cycle"
          ]
        },
        {
          "contains": [
            "DFS"
          ]
        },
        {
          "contains": [
            "visited set"
          ]
        }
      ]
    }
  }
}