Debug-Cursor-Pagination-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 cursor-based paginator encodes the cursor with btoa before storing it, but when reading back decodes with JSON.parse without first calling atob; the parse fails or produces garbled output on every page after the first. Identify the decode bug and fix it.

{
  "metrics": {
    "repro": {
      "checks": [
        {
          "contains": [
            "atob"
          ]
        },
        {
          "contains": [
            "btoa"
          ]
        },
        {
          "contains": [
            "cursor"
          ]
        },
        {
          "contains": [
            "base64"
          ]
        }
      ]
    },
    "hidden": {
      "checks": [
        {
          "contains": [
            "atob(cursor)"
          ]
        },
        {
          "contains": [
            "JSON.parse(atob"
          ]
        },
        {
          "contains": [
            "decode"
          ]
        }
      ]
    },
    "diagnose": {
      "checks": [
        {
          "contains": [
            "missing atob"
          ]
        },
        {
          "contains": [
            "base64 decode"
          ]
        },
        {
          "contains": [
            "JSON.parse"
          ]
        }
      ]
    }
  }
}