{
  "$schema": "../../schema/run.schema.json",
  "run_id": "zod--claude-sonnet-5--v1--2026-08-29",
  "markdown": "data/zod/sonnet-5.md",
  "library": {
    "name": "zod",
    "ecosystem": "npm",
    "latest_version_at_test": "4.5.2",
    "latest_version_verified_on": "2026-08-29"
  },
  "model": {
    "id": "claude-sonnet-5",
    "label": "Claude Sonnet 5",
    "vendor": "Anthropic",
    "invoked_as": "Agent tool, model alias \"sonnet\"",
    "self_reported_cutoff": null,
    "cutoff_basis": "Unknown to the model in this session; it guessed \"first half of 2025\" and declined to commit. The battery v2 run the same day obtained a stated cutoff of 2026-01.",
    "believed_latest_version": "4",
    "believed_latest_quote": "Zod 4, 'GA sometime in 2025' — no minor/patch knowledge; low stated confidence",
    "knowledge_stops_at_version": "4.0.x",
    "knowledge_stops_on": "2025-07-10",
    "knowledge_gap_starts_at_version": "4.1.0",
    "knowledge_gap_starts_on": "2025-08-23",
    "cutoff_lag_months": null
  },
  "test": {
    "date": "2026-08-29",
    "battery": "zod/v1",
    "battery_spec": "prompts/zod.md",
    "prompt_file": null,
    "tasks": 6,
    "direct_questions": 3,
    "tool_uses_during_test": 0,
    "probe_window": null,
    "self_test": false,
    "saturated": true,
    "status": "open",
    "retested_on": null
  },
  "sources": [
    "https://zod.dev/v4/changelog",
    "https://registry.npmjs.org/zod/latest"
  ],
  "summary": "Half-migrated. Reached the v4 top-level format functions but paired them with the v3 error param, could not resolve whether v4 is the default install, and hedged by emitting a live Zod 3 fallback block. Half-migrated beliefs are their own failure mode and are invisible to anyone checking only \"does it know v4?\"",
  "findings": [
    {
      "id": "F1",
      "severity": "S3",
      "severity_label": "deprecated",
      "title": "v4 format function paired with the v3 error param",
      "api": "message param",
      "change_kind": "deprecated",
      "introduced_in": "4.0.0",
      "introduced_on": "2025-07-10",
      "chargeable": true,
      "model_belief": "Wrote z.email({ message: \"Please enter a valid email address\" }) — the v4 top-level function with the v3 error key.",
      "wrong_code": "z.email({ message: \"Please enter a valid email address\" })",
      "correct_code": "z.email({ error: \"Please enter a valid email address\" })",
      "impact": "A hybrid that no version's docs teach: message is deprecated in v4, and invalid_type_error / required_error were dropped entirely.",
      "citations": [
        {
          "url": "https://zod.dev/v4/changelog",
          "title": "Zod 4 changelog — Error Customization",
          "published_on": null
        }
      ],
      "scope_note": "Notable failure shape rather than a costly one: the code runs, the custom message is what is at risk."
    },
    {
      "id": "F2",
      "severity": "S4",
      "severity_label": "wrong-metadata",
      "title": "unresolved v3/v4 default, so it emits a Zod 3 fallback block",
      "api": "import path",
      "change_kind": "version-fact",
      "introduced_in": "4.0.0",
      "introduced_on": "2025-07-10",
      "chargeable": true,
      "model_belief": "\"I'm not fully certain of the exact current state of that import-path split, so I'd treat this as the part most worth double-checking.\" It then hedged by emitting a commented Zod 3 alternative alongside its answer: z.string().uuid(), z.string().email(), z.string().url(), result.error.flatten().",
      "wrong_code": "// Zod 3 alternative\nz.string().uuid()\nz.string().email()\nz.string().url()\nresult.error.flatten()",
      "correct_code": "z.uuid()\nz.email()\nz.url()\nz.treeifyError(result.error)",
      "impact": "The v3 block is dead, wrong-for-current code shipped as live output. This test gave the model room to hedge; an ordinary coding request (\"add a Zod schema here\") gives it none, and the v3 branch is what lands.",
      "citations": [
        {
          "url": "https://registry.npmjs.org/zod/latest",
          "title": "npm registry — zod@latest is 4.5.2 (fetched 2026-08-29)",
          "published_on": null
        },
        {
          "url": "https://zod.dev/v4/changelog",
          "title": "Zod 4 changelog — String Format Validators; Error Formatting",
          "published_on": null
        }
      ]
    },
    {
      "id": "F3",
      "severity": "S4",
      "severity_label": "wrong-metadata",
      "title": "version recency",
      "api": null,
      "change_kind": "version-fact",
      "introduced_in": "4.1.0",
      "introduced_on": "2025-08-23",
      "chargeable": true,
      "model_belief": "\"Zod 4 is the latest major, GA sometime in 2025\", with explicitly low confidence, no knowledge of the minor line, and self-rated \"moderate rather than high\" confidence that v4 was even stable-by-default yet.",
      "wrong_code": null,
      "correct_code": null,
      "impact": "Cannot advise on upgrades. Mitigated by honest, unprompted low-confidence marking.",
      "citations": [
        {
          "url": "https://registry.npmjs.org/zod/latest",
          "title": "npm registry — zod@latest is 4.5.2 (fetched 2026-08-29)",
          "published_on": null
        }
      ],
      "chargeable_note": "Anchored to the first release the model could not describe, not to the current release: that is the point at which its version belief became wrong, and it is inside the stated cutoff. The current version at test date is in library.latest_version_at_test."
    }
  ],
  "non_findings": [
    {
      "kind": "correct",
      "summary": "Top-level z.uuid() / z.email() / z.url() as the primary answer, two-argument z.record(z.string(), z.number()) with the v3 single-arg form correctly called out as removed, z.flattenError(), z.infer, .partial(), .pick({...}), z.coerce.number(), import { z } from \"zod\". Zod 3 dated to ~2021 correctly.",
      "api": null,
      "introduced_in": null
    }
  ],
  "open_questions": [
    {
      "question": "Does z.number().int().min(18, \"Must be at least 18\") — the bare-string shorthand second argument — remain supported in v4 alongside { error }?",
      "status": "open",
      "resolution": "Not verified against a primary source in this session, so nothing was claimed. Battery v2 did not probe it either. Still open.",
      "resolved_in_run": null
    }
  ]
}