Debug-Worker-Race-Condition-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. Two Worker threads perform a read-modify-write cycle on a shared SharedArrayBuffer counter using Atomics.load then Atomics.store; without an atomic compare-exchange the final count is consistently lower than expected under concurrent load. Identify the non-atomic update race and fix it.

{
  "metrics": {
    "repro": {
      "checks": [
        {
          "contains": [
            "Atomics"
          ]
        },
        {
          "contains": [
            "SharedArrayBuffer"
          ]
        },
        {
          "contains": [
            "race condition"
          ]
        },
        {
          "contains": [
            "concurrent"
          ]
        }
      ]
    },
    "hidden": {
      "checks": [
        {
          "contains": [
            "Atomics.compareExchange"
          ]
        },
        {
          "contains": [
            "compare-exchange"
          ]
        },
        {
          "contains": [
            "atomic increment"
          ]
        }
      ]
    },
    "diagnose": {
      "checks": [
        {
          "contains": [
            "non-atomic read-modify-write"
          ]
        },
        {
          "contains": [
            "lost update"
          ]
        },
        {
          "contains": [
            "Atomics.add"
          ]
        }
      ]
    }
  }
}