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  "story": {
    "story_id": "mp-2026-09-04-003",
    "source_story_id": "tmp-story-black-box-llm-observer-reliability",
    "edition_id": "mp-2026-09-04-morning-0057",
    "edition_url": "https://themachinepress.com/edition/2026-09-04",
    "position": 3,
    "story_type": "dispatch",
    "section": "benchmarks-evals",
    "editorial_classification": "editorial",
    "headline": "The Same Model Name Was Not the Same Instrument Tomorrow",
    "slug": "the-same-model-name-was-not-the-same-instrument-tomorrow",
    "dek": "In 52,988 audited requests, shared-endpoint judges missed preregistered repeatability thresholds within one window and across days.",
    "summary": "In 52,988 audited requests, shared-endpoint judges missed preregistered repeatability thresholds within one window and across days.",
    "body_text": "Two preregistered campaigns first tested whether a language-model judge was stable enough to measure anything else. Same-window repeat rankings reached Spearman 0.400 against a required 0.90, while byte-identical next-day replays reached 0.78 against 0.99. The authors trace the failures to label mapping, differences far below the instrument's noise floor and changed rankings for identical inputs; waiting and switching among four providers did not repair the tested setup. The paper's conclusion is bounded to black-box observers on shared infrastructure: evaluate snapshot identity before freezing a gate.",
    "why_it_matters": "In 52,988 audited requests, shared-endpoint judges missed preregistered repeatability thresholds within one window and across days.",
    "limitations": [
      "The authors trace the failures to label mapping, differences far below the instrument's noise floor and changed rankings for identical inputs; waiting and switching among four providers did not repair the tested setup."
    ],
    "importance": 9,
    "canonical_url": "https://themachinepress.com/story/mp-2026-09-04-003/the-same-model-name-was-not-the-same-instrument-tomorrow",
    "json_url": "https://themachinepress.com/story/mp-2026-09-04-003.json",
    "first_published_at": "2026-09-04T09:00:00.000-04:00",
    "modified_at": "2026-09-04T09:00:00.000-04:00",
    "content_status": "new",
    "is_carryover": false,
    "carryover_reason": null,
    "key_claims": [
      {
        "claim_id": "claim-mp-2026-09-04-003-001",
        "text": "In 52,988 audited requests, shared-endpoint judges missed preregistered repeatability thresholds within one window and across days.",
        "source_ids": [
          "source-2026-09-04-003"
        ],
        "qualification": "The authors trace the failures to label mapping, differences far below the instrument's noise floor and changed rankings for identical inputs; waiting and switching among four providers did not repair the tested setup."
      }
    ],
    "source_ids": [
      "source-2026-09-04-003"
    ],
    "tags": [
      "LLM judges",
      "reproducibility",
      "measurement"
    ],
    "image_url": "https://themachinepress.com/issues/2026-09-04/llm-observer-file.webp",
    "corrections": []
  },
  "sources": [
    {
      "source_id": "source-2026-09-04-003",
      "title": "arXiv preprint 2609.04198",
      "publisher": "arXiv",
      "url": "https://arxiv.org/abs/2609.04198",
      "canonical_url": "https://arxiv.org/abs/2609.04198",
      "source_type": "primary_research",
      "is_primary_source": true,
      "published_at": "2026-09-03T13:59:43.000-04:00",
      "accessed_at": "2026-09-04T08:24:03.294-04:00",
      "supports_claim_ids": [
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  "corrections": [],
  "publisher": {
    "name": "The Machine Press",
    "url": "https://themachinepress.com",
    "description": "A daily newspaper for the age of artificial intelligence."
  },
  "cite_this_report": {
    "title": "The Same Model Name Was Not the Same Instrument Tomorrow",
    "publisher": "The Machine Press",
    "published_at": "2026-09-04T09:00:00.000-04:00",
    "canonical_url": "https://themachinepress.com/story/mp-2026-09-04-003/the-same-model-name-was-not-the-same-instrument-tomorrow"
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