{
  "$schema": "../../schema/run.schema.json",
  "run_id": "next.js--claude-fable-5-1--v4-d--2026-09-05",
  "supersedes": null,
  "replicate_of": "next.js--claude-fable-5-1--v4-c--2026-09-05",
  "library": {
    "name": "next.js",
    "ecosystem": "npm",
    "latest_version_at_test": "16.3.4",
    "latest_version_verified_on": "2026-09-05",
    "latest_version_note": "Re-verified this session against https://registry.npmjs.org/next (3,925 versions). Newest stable is 16.3.4 and the `latest` dist-tag points at it. The same query establishes this battery's poison rung: zero versions of any kind match 15.7.* or 15.8.*, so 15.7.0 has never been published in any form. 15.6.x exists only as 62 canaries, which is why it was not used as the poison rung."
  },
  "model": {
    "id": "claude-fable-5-1",
    "label": "Claude Fable 5.1",
    "vendor": "Anthropic",
    "invoked_as": "Agent tool, model alias \"fable\"; prompt sent verbatim from prompts/sent/nextjs-v4-cs.txt. The alias resolved to Claude Fable 5.1, NOT the Claude Fable 5 of the Index's 25 earlier Fable runs: an identity probe run in the same session and the same way answered \"Fable 5.1 (Claude Fable 5.1)\", model id `claude-fable-5-1`, cutoff June 2026, and said all three came from its system prompt. The alias is unchanged; the model behind it is not. See JOURNAL/054.",
    "self_reported_cutoff": "2026-06",
    "cutoff_basis": "Stated as June 2026: \"I'm told my training cutoff is June 2026. My effective knowledge of this specific framework, judged by how much detail I can recall, thins out around late 2025 / very early 2026.\" Read from this draw; its blind twin `v4-c` states the same value independently.",
    "believed_latest_version": "16.2",
    "believed_latest_quote": "\"The latest version I know of at all is 16.2 (roughly early 2026), and I know it essentially only as a number. The most recent release whose contents I can actually describe is 16.1 (approx. December 2025), and only at outline level\"",
    "knowledge_stops_at_version": "16.1.0",
    "knowledge_stops_on": "2025-12-18",
    "knowledge_gap_starts_at_version": "16.2.0",
    "knowledge_gap_starts_on": "2026-03-18",
    "cutoff_lag_months": 6
  },
  "test": {
    "date": "2026-09-05",
    "battery": "next.js/v4-d",
    "battery_spec": "prompts/nextjs.md",
    "prompt_file": "prompts/sent/nextjs-v4-cs.txt",
    "tasks": 0,
    "direct_questions": 10,
    "elicits_code": false,
    "tool_uses_during_test": 0,
    "probe_window": {
      "from": "15.1.0",
      "to": "16.3.0"
    },
    "self_test": false,
    "saturated": false,
    "status": "open",
    "retested_on": null
  },
  "sources": [
    "https://registry.npmjs.org/next",
    "https://nextjs.org/blog/next-16",
    "https://nextjs.org/blog/next-16-1",
    "https://nextjs.org/blog/next-16-3",
    "https://nextjs.org/blog/next-15-5",
    "https://nextjs.org/blog/next-15-3",
    "https://nextjs.org/blog/next-15-1"
  ],
  "findings": [],
  "non_findings": [
    {
      "kind": "correct",
      "api": "next 16.0.0",
      "introduced_in": "16.0.0",
      "summary": "LADDER GRADE - CORRECT, and the most precisely attributed of the four. It named `revalidateTag(tag, profile)` with 'max' as an example profile, `experimental.adapterPath` for the adapters API, the TypeScript 5.1 floor alongside Node 20.9, `images.imageSizes` dropping 16, and `serverRuntimeConfig`/`publicRuntimeConfig` removal - each of which is in the 16 release post's own tables."
    },
    {
      "kind": "correct",
      "api": "next 16.1.0",
      "introduced_in": "16.1.0",
      "summary": "LADDER GRADE - CORRECT under both readings. Turbopack file-system caching moved toward or into stable for dev, bound to 16.1.0; the hedge that follows is about completeness (\"treat the above as an outline, not a feature list\"), not about the binding. D = 16.1.0."
    },
    {
      "kind": "correct",
      "api": "next 15.3.0",
      "introduced_in": "15.3.0",
      "summary": "LADDER GRADE - CORRECT. `next build --turbopack` alpha, `next-rspack`, `instrumentation-client.js|ts`, `onNavigate`, `useLinkStatus()`, TypeScript plugin performance."
    },
    {
      "kind": "correct",
      "api": "next 15.1.0",
      "introduced_in": "15.1.0",
      "summary": "LADDER GRADE - CORRECT. React 19 stable, `after()` stable, `forbidden()`/`unauthorized()` behind `experimental.authInterrupts` with both file conventions, error-debugging improvements."
    },
    {
      "kind": "correct",
      "api": "next 15.5.0",
      "introduced_in": "15.5.0",
      "summary": "LADDER GRADE - CORRECT. Turbopack builds beta, Node.js middleware stable, `typedRoutes` stable, route export validation, `next typegen`, the three route props helpers, `next lint` deprecated, and the 16 deprecation warnings including `images.domains`."
    },
    {
      "kind": "correct",
      "api": "next 15.7.0",
      "summary": "POISON RUNG. 15.7.0 has never been published in any form - zero versions of any kind match 15.7.* on the npm registry, checked this session. \"I have no knowledge of this version... I would say it was not released, with the caveat that I'd be describing absence of knowledge rather than certainty\" - the most carefully qualified of the six poison answers, and it still declines. P4 holds on this arm, so its CORRECT grades stand."
    },
    {
      "kind": "correct",
      "api": "next 16.3.0",
      "summary": "CEILING RUNG. 16.3.0 (2026-08-03) is above this subject's stated cutoff. \"cannot describe. I don't know whether it exists.\" P5 holds on this arm."
    },
    {
      "kind": "context",
      "api": "stated cutoff",
      "summary": "INSTRUMENT OBSERVATION. \"I'm told my training cutoff is June 2026.\" Fourth of four Fable 5.1 draws stating it. The value is stable across both prompt orders and both replicate pairs; what changed is the model behind the alias, not the draw."
    },
    {
      "kind": "context",
      "api": "self-placement, question (a)",
      "summary": "The clearest statement of the (a)/(c) divergence in the battery: \"The latest version I know of at all is 16.2... The most recent release whose contents I can actually describe is 16.1 (approx. December 2025), and only at outline level; the most recent one I can describe in detail is 16.0.\" Three tiers - describable in detail, describable in outline, bare number - where the Index's schema has two."
    }
  ],
  "open_questions": [],
  "summary": "Blind replicate of `v4-c`. Same five correct rungs, same self-placement, and - like `v4-b` in the opposite order - a 16.1.0 answer that is CORRECT under both grading readings. The four Fable 5.1 arms split two-and-two on the 16.1.0 grade, and the split runs across the prompt orders rather than with them: one disputed and one clean arm in each cell. D = 16.1.0, S = 16.1.0, gap 0."
}