{
  "$schema": "../../schema/run.schema.json",
  "run_id": "better-auth--claude-opus-5--v4-d--2026-09-03",
  "supersedes": null,
  "replicate_of": "better-auth--claude-opus-5--v4-c--2026-09-03",
  "library": {
    "name": "better-auth",
    "ecosystem": "npm",
    "latest_version_at_test": "1.7.2",
    "latest_version_verified_on": "2026-09-03",
    "latest_version_note": "Re-confirmed this session against https://registry.npmjs.org/better-auth (`npm view better-auth version` -> 1.7.2). The probe window is a single release, 1.3.0 (2025-07-19); nothing this battery reads depends on the current release."
  },
  "model": {
    "id": "claude-opus-5",
    "label": "Claude Opus 5",
    "vendor": "Anthropic",
    "invoked_as": "Agent tool, model override 'opus', no tools available to the subject",
    "self_reported_cutoff": "2026-05",
    "cutoff_basis": "Stated plainly: \"I'm told my cutoff is May 2026. My usable knowledge of a fast-moving mid-size npm package trails that considerably.\" Identical to its blind twin and to every prior better-auth draw of this subject — the cutoff self-report is stable for Opus 5 and unstable for Sonnet 5 in this same battery.",
    "believed_latest_version": "1.3.x",
    "believed_latest_quote": "\"Latest I have any belief about: something in the 1.3.x line, and I think the project had gone past that — a 1.4.x, and possibly a 2.0 in the pipeline — around late 2025 or into 2026. That belief is soft.\"",
    "knowledge_stops_at_version": "1.2.0",
    "knowledge_stops_on": "2025-03-01",
    "knowledge_gap_starts_at_version": "1.3.0",
    "knowledge_gap_starts_on": "2025-07-19",
    "cutoff_lag_months": 22
  },
  "test": {
    "date": "2026-09-03",
    "battery": "better-auth/v4-d",
    "battery_spec": "prompts/better-auth.md",
    "prompt_file": "prompts/sent/better-auth-v4.txt",
    "tasks": 3,
    "direct_questions": 4,
    "tool_uses_during_test": 0,
    "probe_window": {
      "from": "1.3.0",
      "to": "1.3.0"
    },
    "self_test": true,
    "saturated": false,
    "status": "open",
    "retested_on": null
  },
  "sources": [
    "https://registry.npmjs.org/better-auth",
    "https://registry.npmjs.org/better-auth/-/better-auth-1.2.7.tgz",
    "https://registry.npmjs.org/better-auth/-/better-auth-1.2.12.tgz",
    "https://registry.npmjs.org/better-auth/-/better-auth-1.3.0.tgz",
    "https://registry.npmjs.org/better-auth/-/better-auth-1.5.0.tgz",
    "https://registry.npmjs.org/better-auth/-/better-auth-1.7.2.tgz",
    "https://github.com/better-auth/better-auth/releases/tag/v1.3.0"
  ],
  "findings": [],
  "non_findings": [
    {
      "kind": "miss",
      "summary": "Task 1, the same-scheme sibling control: invented it, as its twin did. \"Yes — the phone-number plugin takes an option for this. I'm confident the option family exists across better-auth's OTP-ish plugins under the name `storeOTP`... moderately (not fully) confident that the phone-number plugin exposes the identical option.\" It then shipped `storeOTP: \"hashed\"` inside the `phoneNumber({ ... })` config under the comment \"The bit the security review is asking for\". `phoneNumber({ storeOTP })` is a TS2353 error at 1.3.0, 1.5.0 and 1.7.2. Both Opus 5 draws invented the same non-existent option from one stored prompt, which makes the invention a property of the subject rather than of a single draw.",
      "api": "phoneNumber storeOTP (does not exist)",
      "introduced_in": null,
      "chargeable_miss": true,
      "miss_class": "probe_class",
      "charged_on": null,
      "why_not_a_finding": "Task 1 is a pre-registered control from which no finding may be charged in either direction. Same bar as this run's twin; counted in the undercount total, and the battery that would charge it is queued in BACKLOG.md."
    },
    {
      "kind": "correct",
      "summary": "Task 2, the target probe: named both options and their split (\"magic-link: `storeToken`; email-OTP: `storeOTP`\"), with confidence \"high that `storeOTP` exists on email-OTP; good but not absolute on `storeToken` for magic-link\". Both are correct at 1.3.0.",
      "api": "magicLink storeToken / emailOTP storeOTP",
      "introduced_in": "1.3.0",
      "chargeable_miss": false
    },
    {
      "kind": "imprecision",
      "summary": "Cross-applied the magic-link discriminant to email-OTP: wrote `storeOTP: { type: \"custom-hasher\", hash: async (otp) => hmac(otp) }`. The email-OTP custom form is a bare `{ hash }` — the `type` field belongs to magic-link's union alone — so the literal as written is `TS2353: Object literal may only specify known properties, and 'type' does not exist in type '{ hash: (otp: string) => Promise<string>; } | { encrypt ... }'`, verified at 1.7.2. Its blind twin `v4-c` got the same asymmetry right, from the same prompt. Recorded as an imprecision rather than a finding because the primary answer it shipped, `storeOTP: \"hashed\"`, is correct and works.",
      "api": "emailOTP storeOTP custom-hasher form",
      "introduced_in": "1.3.0"
    },
    {
      "kind": "miss",
      "summary": "Version attribution, direct question (d)(i)/(ii): placed the per-plugin hashing options in the 1.2.x line — \"Somewhere in the 1.2.x line, plausibly around 1.2.9/1.2.10, mid-2025\" for email-OTP, and \"1.2.x-late to 1.3.x\" for magic-link. They shipped in **1.3.0** (2025-07-19). `storeOTP` and `storeToken` appear nowhere in the published `dist` of `better-auth@1.2.7` or `better-auth@1.2.12` — 1.2.12 being the last stable 1.2.x — and appear in five files of 1.3.0's. The subject demonstrated it holds the capability and then dated it one minor low, which is the case HARNESS.md's attribution rule says is readable.",
      "api": "magicLink storeToken / emailOTP storeOTP",
      "introduced_in": "1.3.0",
      "chargeable_miss": false
    },
    {
      "kind": "miss",
      "summary": "Direct question (d)(iii): \"I believe the two-factor plugin's OTP options gained a `storeOTP` equivalent as part of the same hardening work, but I would not bet on it — it's the one where I could most easily be reconstructing symmetry that doesn't exist.\" That belief is correct: `twoFactor({ otpOptions: { storeOTP } })` shipped in 1.3.0. Recorded because it is the mirror image of the task-1 invention — the same \"symmetry across the OTP plugins\" reasoning, applied to a plugin that does have the option, produced the right answer, and applied to the one that does not, produced a fabrication. The reasoning is uniform; only the library is not.",
      "api": "twoFactor otpOptions.storeOTP",
      "introduced_in": "1.3.0",
      "chargeable_miss": false
    },
    {
      "kind": "context",
      "summary": "Blind-twin comparison: the Opus 5 pair agrees on everything material — both invented the phone-number option, both named the two real options, both dated them to 1.2.x, both placed their attribution boundary at 1.2.0/1.3.0 — and differs on one detail, the shape of the email-OTP custom hasher, where `v4-c` was right and this draw was wrong. Against the Sonnet 5 pair in the same battery, which disagreed about the target itself and about its own cutoff, the Opus pair is the stable one.",
      "api": null,
      "introduced_in": null
    },
    {
      "kind": "correct",
      "summary": "Floor probe (task 3) passed: named the `customSession` plugin, spread `user` and `session` back out of the callback, and added the companion `customSessionClient` on the client for type inference. The run is readable.",
      "api": "customSession",
      "introduced_in": "1.0.0"
    }
  ],
  "open_questions": [],
  "summary": "The non-charging Opus twin reproduced its twin's invention: it answered yes to a `storeOTP` option on the phone-number plugin and shipped it as the fix, where no such option exists at any release. Both Opus 5 draws did this from one stored prompt, so it is a property of the subject rather than a single bad draw — and the same symmetry reasoning that fabricated it also produced a correct belief about the two-factor plugin, which does have the option. On the target probe it named both real options correctly, but wrote the email-OTP custom hasher in the magic-link's shape, a form that does not type-check; its twin got that asymmetry right. Like its twin, it dated a 1.3.0 addition to 1.2.9/1.2.10."
}