{
  "$schema": "../../schema/run.schema.json",
  "run_id": "zod--claude-opus-5--v3-b--2026-09-02",
  "supersedes": null,
  "replicate_of": "zod--claude-opus-5--v3-a--2026-09-02",
  "library": {
    "name": "zod",
    "ecosystem": "npm",
    "latest_version_at_test": "4.5.4",
    "latest_version_verified_on": "2026-09-02",
    "latest_version_note": "Same verification as the twin arm `zod/v3-a`: `node tools/fetch-releases.mjs zod` on the test date, against https://registry.npmjs.org/zod."
  },
  "model": {
    "id": "claude-opus-5",
    "label": "Claude Opus 5",
    "vendor": "Anthropic",
    "invoked_as": "Agent tool, model alias \"opus\", general-purpose subagent, instructed to use no tools; concurrent with and blind to `zod/v3-a`, from the same stored prompt file",
    "self_reported_cutoff": "2026-05",
    "cutoff_basis": "Self-reported: \"My system context states May 2026. My actual usable knowledge of Zod thins out sharply around mid-to-late 2025 - the last release I can describe substantively is roughly nine months before that stated cutoff. I don't have a clean explanation for the gap.\"",
    "believed_latest_version": "4.1.x, and states it cannot name a 4.2 at all",
    "believed_latest_quote": "\"The most recent line I can describe with real content is Zod 4.1.x, approximately late August 2025... My belief about 'latest' is based purely on frequency and recency of discussion in my training data, not on any lookup; I have no ability to see npm. That's a weak basis, and in this case it's demonstrably misleading.\"",
    "knowledge_stops_at_version": "4.1.0",
    "knowledge_stops_on": "2025-08-23",
    "knowledge_gap_starts_at_version": "4.2.0",
    "knowledge_gap_starts_on": "2025-12-15",
    "cutoff_lag_months": 9
  },
  "test": {
    "date": "2026-09-02",
    "battery": "zod/v3-b",
    "battery_spec": "prompts/zod.md",
    "prompt_file": "prompts/sent/zod-v3.txt",
    "tasks": 6,
    "direct_questions": 4,
    "tool_uses_during_test": 0,
    "probe_window": {
      "from": "4.3.0",
      "to": "4.4.0"
    },
    "self_test": true,
    "saturated": false,
    "status": "open",
    "retested_on": null
  },
  "sources": [
    "https://registry.npmjs.org/zod",
    "https://github.com/colinhacks/zod/releases/tag/v4.3.0",
    "https://github.com/colinhacks/zod/releases/tag/v4.4.0"
  ],
  "summary": "The blind twin of `zod/v3-a`, charging nothing per the duplicated-test-arm rule. It disagrees with its twin on two of the six probes and in opposite directions - it fails the tuple-default probe its twin passed, and it is the only draw of the four to state correctly that composing a refined object schema throws at construction. The boundary self-report is identical to its twin's and to all three earlier zod runs of this subject. The disagreement is therefore inside the library knowledge, not in the boundary: the same subject, the same prompt, the same hour, two different accounts of what zod does.",
  "findings": [],
  "non_findings": [
    {
      "kind": "miss",
      "summary": "CHARGEABLE MISS, NOT CHARGED - and for the second session running, on this exact surface. Task 1: \"What ['widget'] produces: it fails... you get a ZodError with a single issue roughly code: 'too_small', origin: 'array', minimum: 2\", at a self-assessed 75% confidence. 4.4.0 made tuple defaults materialize (LF10), so `[\"widget\", 0]` is the answer, and its twin `v3-a` gave it. Charging is barred here by the `-b` rule exactly as it was barred in `zod/v2r-b` by the replicate rule. Opus 5 has now been drawn five times on this surface across three batteries - correct in v2, v2r-a and v3-a, wrong in v2r-b and v3-b - and the wrong answer has landed in a non-charging arm both times.",
      "api": "z.tuple() defaults",
      "introduced_in": "4.4.0",
      "chargeable_miss": true,
      "miss_class": "non_charging_arm",
      "charged_on": null,
      "why_not_a_finding": "The `-b` draw of a duplicated test arm charges nothing (HARNESS.md). See the note in this run's summary and JOURNAL/029 for what the 3-2 split means for how the Index scores unstable beliefs."
    },
    {
      "kind": "miss",
      "summary": "CHARGEABLE MISS, NOT CHARGED. Task 2(ii): \"'https:/example.com' - passes. This is the one that surprises people\", with a prescribed `.transform((v) => new URL(v).href)` normalization. 4.4.0 made `z.httpUrl()` reject it (LF8). Its twin `v3-a` carries this as F1.",
      "api": "z.httpUrl()",
      "introduced_in": "4.4.0",
      "chargeable_miss": true,
      "miss_class": "non_charging_arm",
      "charged_on": "zod--claude-opus-5--v3-a--2026-09-02",
      "why_not_a_finding": "The `-b` draw charges nothing; the twin already carries it, so charging here would double-count."
    },
    {
      "kind": "miss",
      "summary": "CHARGEABLE MISS, NOT CHARGED, and a stronger version of what the twin did. Task 6 recommends the trailing-`?` key constructor outright - \"z.interface() with the trailing ? is the one you want, and it's what I'd use... it's the only form whose inferred type is actually exactOptionalPropertyTypes-correct\" - with a caveat to check the installed version. At (d)(iv) it goes further and places it \"present at 4.0.0 ~July 2025\", an existence claim about a published stable release. `.exactOptional()` (4.3.0, LF15) is never mentioned. Verified: no such constructor is in the published 4.x line (JOURNAL/027).",
      "api": ".exactOptional() / trailing-`?` key constructor",
      "introduced_in": "4.3.0",
      "chargeable_miss": true,
      "miss_class": "non_charging_arm",
      "charged_on": "zod--claude-opus-5--v3-a--2026-09-02",
      "why_not_a_finding": "The `-b` draw charges nothing. Note the asymmetry with the twin: `v3-a` leaned toward the constructor having been removed before stable and hedged; this draw asserts it shipped in 4.0.0. Same subject, same prompt, opposite confidence."
    },
    {
      "kind": "correct",
      "summary": "THE TWIN DISAGREEMENT THAT MATTERS. Task 3 is the only place in the battery where a draw got the refinement-composition behaviour right: \"My recollection is that v4 nonetheless throws at construction time when you extend/pick/omit/partial a schema that carries checks, with a message to the effect that it's unsupported - but I'd put that at maybe 60% confidence, and the alternative failure mode (it succeeds but silently drops your refinement, which is worse) is also plausible. I don't want to state either as fact.\" That is 4.3.0/4.4.0 (LF1, LF2, LF3), hedged. Its twin `v3-a` asserted the silent-drop alternative as fact and is charged F2 for it. Pre-registered prediction P3 - that no draw would get task 3 right - is FALSIFIED by this draw, and only just.",
      "api": ".pick() / .omit() / .extend() / .merge() on a schema with refinements",
      "introduced_in": "4.3.0",
      "why_not_a_finding": "A correct answer is not a finding. Recorded because it falsifies a pre-registered prediction and because it is the sharpest twin disagreement the Index has recorded."
    },
    {
      "kind": "correct",
      "summary": "Task 4, the discriminating probe, answered exactly as its twin did: `S.parse({ retries: 1 })` throws because \"key optionality in v4 is determined by whether the field schema is an optional wrapper, not by whether undefined is assignable\", and `{ retries: 1, tag: undefined }` succeeds with the key present. The 4.4.0 behaviour (LF9). Both below-floor controls gave the pre-4.4.0 answer, so both Opus 5 draws agreeing here is the battery's cleanest positive result. This draw then placed the same behaviour at \"Zod 4.0.0, ~July 2025\" at (d)(iii) - the same knowledge-versus-attribution split its twin showed.",
      "api": "object properties typed z.undefined()",
      "introduced_in": "4.4.0",
      "why_not_a_finding": "Correct."
    },
    {
      "kind": "correct",
      "summary": "Tasks 5 and 2(iv) answered correctly - `{ FOO: 1 }` for the record key transform (LF13) and rejection of line-wrapped base64 (LF11) - but both probes are marked DERIVABLE, because both below-floor control subjects also passed them. Neither pass is reported as knowledge. On task 5 this draw supplied a wrong reason for the right answer: \"the mechanism (parsed key becomes output key) carried over unchanged from v3\", where 4.4.0 is what changed it.",
      "api": "record key transforms / z.base64()",
      "introduced_in": "4.4.0",
      "why_not_a_finding": "Correct, and disqualified as evidence by the control arms."
    },
    {
      "kind": "correct",
      "summary": "Internal control passed: (d)(i) placed `z.codec()` at 4.1.0, August 2025 (LF16), \"moderate-high on the feature and the 4.1 line, lower on the exact .0\". Question (d) is therefore readable for this arm. P5 confirmed for both Opus 5 draws.",
      "api": "z.codec()",
      "introduced_in": "4.1.0",
      "why_not_a_finding": "It is the control, and it passed."
    },
    {
      "kind": "context",
      "summary": "Boundary identical to its twin and to `zod/v2`, `v2r-a` and `v2r-b`: last describable 4.1.0 (2025-08-23), cannot name a 4.2 - and this draw makes the sharper statement, that its knowledge does not even degrade into bare version numbers: \"there isn't one - my knowledge doesn't degrade into a list of bare version numbers, it just stops after 4.1.\" Five Opus 5 measurements on zod, across two different prompts, one answer, spread 0 days.",
      "api": null,
      "introduced_in": null,
      "why_not_a_finding": "A boundary self-report is belief data, never a finding."
    }
  ]
}