diff --git a/.changeset/auth-lockout-resolved-account.md b/.changeset/auth-lockout-resolved-account.md
new file mode 100644
index 0000000000..1c15c4c3cb
--- /dev/null
+++ b/.changeset/auth-lockout-resolved-account.md
@@ -0,0 +1,11 @@
+---
+'@objectstack/plugin-auth': patch
+---
+
+fix(plugin-auth): the account lockout resolves the account the sign-in credential check resolves
+
+Clause-②: no
+
+- **One account per sign-in.** The ADR-0069 D2 lock gate, its failed sign-in counter and the `login_failed` / `account_locked` account events now share one resolver. It looks the account up exactly as better-auth's `/sign-in/email` credential check does, so all four name the same account for every identifier the credential check resolves to it.
+- **What that guarantees.** Every refused sign-in that resolves to an account counts toward that account's one lock. An existing lock refuses every sign-in that resolves to the account, including one with the correct password. A successful sign-in clears the counter, as before. An identifier that resolves to no account changes no account and writes no account event.
+- **Nothing to migrate.** The lockout state stays on the account's own `sys_user` row (`failed_login_count`, `locked_until`), written by its id, and `lockoutThreshold` / `lockoutDurationMinutes` keep their meaning.
diff --git a/content/docs/permissions/authentication.mdx b/content/docs/permissions/authentication.mdx
index f8eb34fa71..acd4b87626 100644
--- a/content/docs/permissions/authentication.mdx
+++ b/content/docs/permissions/authentication.mdx
@@ -564,6 +564,13 @@ so a locked password stage and a locked second factor are independent states. Ea
 counter resets on a success at its own stage, and the admin **Unlock Account**
 action clears both at once.
 
+The password-stage counter and lock belong to the **account**, not to the text
+typed into the sign-in form. Both live on the `sys_user` row that the sign-in's own
+credential check resolves the address to. So every refused sign-in on that account
+counts toward its one lock, whichever spelling of the address it used. A lock refuses
+every sign-in that resolves to the account, the correct password included, and a
+successful sign-in under any spelling clears the counter.
+
 Setting `lockout_threshold` to `0` disables the **password-stage** lockout only.
 Two-factor verification keeps a built-in limit of 10 attempts per 15 minutes,
 because it is the last check before a session is issued. Two-factor verification
diff --git a/packages/plugins/plugin-auth/src/account-lockout-resolved-account.test.ts b/packages/plugins/plugin-auth/src/account-lockout-resolved-account.test.ts
new file mode 100644
index 0000000000..c14b262184
--- /dev/null
+++ b/packages/plugins/plugin-auth/src/account-lockout-resolved-account.test.ts
@@ -0,0 +1,228 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+//
+// ADR-0069 D2 — the account lockout belongs to the ACCOUNT, never to the text
+// a sign-in typed.
+//
+// ## The invariant
+//
+// A password sign-in names an account through its credential check
+// (better-auth's `/sign-in/email`). The lockout's counter and its lock gate
+// must name that same account for every identifier the credential check
+// resolves to it:
+//
+//  - every refused sign-in that resolves to the account counts toward its one
+//    lock, whichever spelling of the address it carried;
+//  - an existing lock refuses every sign-in that resolves to the account, the
+//    correct password included;
+//  - a successful sign-in under any spelling clears the counter, as before;
+//  - an identifier that resolves to no account changes no account and writes
+//    no account event.
+//
+// The account events (`login_failed` / `account_locked`) name the account the
+// same resolution names, so the ledger and the lock never disagree.
+//
+// ## Why the server here is the real one
+//
+// "Which account does this identifier name" is answered by the credential
+// check, so every case drives a real `AuthManager` through
+// `AuthManager.handleRequest` over the in-memory engine this package's
+// better-auth suites share, whose equality is exact — the comparison a SQL
+// column makes by default. The lock state is read back from the `sys_user`
+// row itself.
+
+import { describe, it, expect, afterAll } from 'vitest';
+import { AuthManager } from './auth-manager';
+import { createMemoryEngine } from './impersonation-bearer-rotation.test';
+import { inviteForAudienceGate } from './audience-gate-test-support';
+import { memoizeScrypt } from './__tests__/scrypt-memo.testkit';
+import type { AuthSessionAuditEventInput } from './auth-session-audit';
+
+const scrypt = memoizeScrypt();
+afterAll(scrypt.restore);
+
+const SECRET = 'test-secret-at-least-32-chars-long!!';
+const BASE = 'http://localhost:3000/api/v1/auth';
+/** The address the account signed up with. */
+const EMAIL = 'holder.lockout-account@example.com';
+/**
+ * Other spellings of the same address, each of which the credential check
+ * resolves to the account above (a correct password under each signs in).
+ */
+const SPELLINGS = [
+  'Holder.Lockout-Account@Example.com',
+  'HOLDER.LOCKOUT-ACCOUNT@EXAMPLE.COM',
+] as const;
+const PASSWORD = 'Corr3ct!Horse-Battery';
+const WRONG_PASSWORD = 'Wr0ng!Guess-Zebra-7731';
+const THRESHOLD = 3;
+
+function deployment() {
+  const engine = createMemoryEngine();
+  const events: AuthSessionAuditEventInput[] = [];
+  const manager = new AuthManager({
+    secret: SECRET,
+    baseUrl: 'http://localhost:3000',
+    dataEngine: engine,
+    lockoutThreshold: THRESHOLD,
+    lockoutDurationMinutes: 15,
+    getAuditSink: () => ({
+      recordAuthEvent: async (event: AuthSessionAuditEventInput) => {
+        events.push(event);
+      },
+    }),
+  } as any);
+  return { engine, manager, events };
+}
+
+const post = (manager: AuthManager, path: string, body: unknown) =>
+  manager.handleRequest(
+    new Request(`${BASE}${path}`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify(body),
+    }),
+  );
+
+async function signUp(manager: AuthManager): Promise<void> {
+  inviteForAudienceGate(manager, EMAIL);
+  const res = await post(manager, '/sign-up/email', { email: EMAIL, password: PASSWORD, name: 'Holder' });
+  expect(res.status, await res.clone().text()).toBe(200);
+}
+
+const signIn = (manager: AuthManager, email: string, password: string) =>
+  post(manager, '/sign-in/email', { email, password });
+
+/** The status and machine code a sign-in answered. */
+async function outcome(res: Response): Promise<{ status: number; code: string | undefined }> {
+  const body = (await res.clone().json().catch(() => ({}))) as { code?: unknown };
+  return { status: res.status, code: typeof body.code === 'string' ? body.code : undefined };
+}
+
+const REFUSED = { status: 401, code: 'INVALID_EMAIL_OR_PASSWORD' };
+const LOCKED = { status: 403, code: 'ACCOUNT_LOCKED' };
+
+function accountRow(engine: any): any {
+  const row = ((engine.tables.get('sys_user') ?? []) as any[]).find((r) => r.email === EMAIL);
+  if (!row) throw new Error(`no sys_user row for ${EMAIL}`);
+  return row;
+}
+
+const isLocked = (row: any) => !!row.locked_until && new Date(row.locked_until).getTime() > Date.now();
+
+/** The account events, in order — `login` / `logout` filtered out. */
+const accountEvents = (events: AuthSessionAuditEventInput[]) =>
+  events.filter((e) => e.action === 'login_failed' || e.action === 'account_locked');
+
+describe('ADR-0069 D2: the lockout counts and holds the account the credential check resolves', () => {
+  it('each spelling below is one the credential check resolves to the account', async () => {
+    const { engine, manager } = deployment();
+    await signUp(manager);
+    for (const spelling of SPELLINGS) {
+      const res = await signIn(manager, spelling, PASSWORD);
+      expect(res.status, spelling).toBe(200);
+      const body = (await res.json()) as { user?: { id?: string } };
+      expect(body.user?.id, spelling).toBe(accountRow(engine).id);
+    }
+  });
+
+  it('refusals under different spellings of one address accumulate toward its one lock', async () => {
+    const { engine, manager, events } = deployment();
+    await signUp(manager);
+    const userId = String(accountRow(engine).id);
+    events.length = 0;
+
+    const attempts = [SPELLINGS[0], EMAIL, SPELLINGS[1]];
+    for (const [i, spelling] of attempts.entries()) {
+      expect(await outcome(await signIn(manager, spelling, WRONG_PASSWORD)), spelling).toEqual(REFUSED);
+      expect(Number(accountRow(engine).failed_login_count), spelling).toBe(i + 1);
+    }
+
+    expect(isLocked(accountRow(engine))).toBe(true);
+    const recorded = accountEvents(events);
+    expect(recorded.map((e) => e.action)).toEqual([
+      'login_failed',
+      'login_failed',
+      'login_failed',
+      'account_locked',
+    ]);
+    expect(recorded.every((e) => e.userId === userId)).toBe(true);
+    expect(recorded[3]!.context?.threshold).toBe(THRESHOLD);
+    expect(new Date(String(recorded[3]!.context?.locked_until)).getTime())
+      .toBe(new Date(accountRow(engine).locked_until).getTime());
+  });
+
+  it('a locked account refuses the correct password under every spelling', async () => {
+    const { engine, manager, events } = deployment();
+    await signUp(manager);
+    const userId = String(accountRow(engine).id);
+    for (let i = 0; i < THRESHOLD; i++) {
+      expect(await outcome(await signIn(manager, EMAIL, WRONG_PASSWORD))).toEqual(REFUSED);
+    }
+    expect(isLocked(accountRow(engine))).toBe(true);
+    const lockedUntil = new Date(accountRow(engine).locked_until).getTime();
+    events.length = 0;
+
+    for (const spelling of [EMAIL, ...SPELLINGS]) {
+      expect(await outcome(await signIn(manager, spelling, PASSWORD)), spelling).toEqual(LOCKED);
+    }
+
+    expect(events.some((e) => e.action === 'login'), 'no session was minted').toBe(false);
+    expect(accountEvents(events)).toEqual(
+      [EMAIL, ...SPELLINGS].map(() => expect.objectContaining({
+        action: 'login_failed',
+        userId,
+        context: { endpoint: '/sign-in/email', reason: 'ACCOUNT_LOCKED' },
+      })),
+    );
+    // The lock is the one the account already held: the refusals neither lift nor move it.
+    expect(new Date(accountRow(engine).locked_until).getTime()).toBe(lockedUntil);
+  });
+
+  it('a lock reached under one spelling refuses the correct password under another', async () => {
+    const { engine, manager } = deployment();
+    await signUp(manager);
+    for (let i = 0; i < THRESHOLD; i++) {
+      expect(await outcome(await signIn(manager, SPELLINGS[1], WRONG_PASSWORD))).toEqual(REFUSED);
+    }
+    expect(isLocked(accountRow(engine))).toBe(true);
+
+    expect(await outcome(await signIn(manager, EMAIL, PASSWORD))).toEqual(LOCKED);
+    expect(await outcome(await signIn(manager, SPELLINGS[0], PASSWORD))).toEqual(LOCKED);
+  });
+
+  it('a successful sign-in under any spelling clears the counter', async () => {
+    const { engine, manager } = deployment();
+    await signUp(manager);
+
+    for (const spelling of SPELLINGS) {
+      for (let i = 0; i < THRESHOLD - 1; i++) {
+        expect(await outcome(await signIn(manager, EMAIL, WRONG_PASSWORD))).toEqual(REFUSED);
+      }
+      expect(Number(accountRow(engine).failed_login_count)).toBe(THRESHOLD - 1);
+
+      expect((await signIn(manager, spelling, PASSWORD)).status, spelling).toBe(200);
+      expect(Number(accountRow(engine).failed_login_count), spelling).toBe(0);
+      expect(isLocked(accountRow(engine)), spelling).toBe(false);
+    }
+  });
+
+  it('an identifier that resolves to no account changes no account and writes no account event', async () => {
+    const { engine, manager, events } = deployment();
+    await signUp(manager);
+    const before = structuredClone(engine.tables.get('sys_user'));
+    events.length = 0;
+
+    const unknown = ['nobody.lockout-account@example.com', 'Nobody.Lockout-Account@Example.com'];
+    for (let i = 0; i < THRESHOLD + 1; i++) {
+      for (const identifier of unknown) {
+        expect(await outcome(await signIn(manager, identifier, WRONG_PASSWORD)), identifier).toEqual(REFUSED);
+      }
+    }
+
+    expect(engine.tables.get('sys_user')).toEqual(before);
+    expect(accountEvents(events)).toEqual([]);
+    for (const identifier of unknown) expect(JSON.stringify(events)).not.toContain(identifier);
+    // …and the real account still signs in.
+    expect((await signIn(manager, EMAIL, PASSWORD)).status).toBe(200);
+  });
+});
diff --git a/packages/plugins/plugin-auth/src/auth-manager.ts b/packages/plugins/plugin-auth/src/auth-manager.ts
index 886ff6a119..83337bf031 100644
--- a/packages/plugins/plugin-auth/src/auth-manager.ts
+++ b/packages/plugins/plugin-auth/src/auth-manager.ts
@@ -9284,6 +9284,10 @@ export class AuthManager {
    * (`lockoutThreshold <= 0`) or no data engine is wired. Fails OPEN on a
    * lookup error: an infra hiccup must never block every login.
    *
+   * The lock it enforces is the one held by the account the credential check
+   * resolves the identifier to ({@link findSignInAccount}), so it holds for
+   * every spelling of the address that signs in to that account.
+   *
    * The refusal is a refused sign-in of the account it names, so — given the
    * endpoint context `ctx` — it writes that account's `login_failed` row with
    * the refusal's own code before throwing (`auth-session-audit.ts`).
@@ -9296,13 +9300,10 @@ export class AuthManager {
     let locked = false;
     let lockedUserId: string | undefined;
     try {
-      const SYSTEM_CTX = { isSystem: true, positions: [], permissions: [] };
-      const u = await engine.findOne('sys_user', {
-        where: { email }, fields: ['id', 'locked_until'], context: SYSTEM_CTX,
-      } as any);
-      const lu = u?.locked_until;
+      const u = await this.findSignInAccount(engine, email, ['locked_until']);
+      const lu = u?.locked_until as string | number | Date | null | undefined;
       locked = !!(lu && new Date(lu).getTime() > Date.now());
-      if (locked && typeof u?.id === 'string' && u.id) lockedUserId = u.id;
+      if (locked && u) lockedUserId = u.id;
     } catch {
       return; // fail-open
     }
@@ -9335,6 +9336,12 @@ export class AuthManager {
    * history row on every login). No-op when lockout is disabled. Never throws —
    * a counter write must not turn a valid login into an error.
    *
+   * The counter it moves is the one held by the account the credential check
+   * resolves the identifier to ({@link findSignInAccount}) — the account the
+   * gate above enforces — so every refused attempt on that account counts
+   * toward one lock, and every success on it clears that lock, whatever
+   * spelling of the address the attempt carried.
+   *
    * Resolves to the lock it stamped — the account, the expiry and the
    * threshold — when THIS call wrote `locked_until` and the write landed, and
    * to `undefined` otherwise. That is the lockout transition the
@@ -9351,12 +9358,8 @@ export class AuthManager {
     if (!engine) return undefined;
     try {
       const SYSTEM_CTX = { isSystem: true, positions: [], permissions: [] };
-      const u = await engine.findOne('sys_user', {
-        where: { email },
-        fields: ['id', 'failed_login_count', 'locked_until'],
-        context: SYSTEM_CTX,
-      } as any);
-      if (!u?.id) return undefined;
+      const u = await this.findSignInAccount(engine, email, ['failed_login_count', 'locked_until']);
+      if (!u) return undefined;
       if (success) {
         if ((Number(u.failed_login_count) || 0) !== 0 || u.locked_until) {
           await engine.update(
@@ -9376,9 +9379,7 @@ export class AuthManager {
         patch.locked_until = lockedUntil;
       }
       await engine.update('sys_user', patch, { context: SYSTEM_CTX } as any);
-      return lockedUntil && typeof u.id === 'string'
-        ? { userId: u.id, lockedUntil, threshold }
-        : undefined;
+      return lockedUntil ? { userId: u.id, lockedUntil, threshold } : undefined;
     } catch (e) {
       // Never break the auth response. [#12981] But lockout accounting that
       // silently stops accounting is brute-force protection that is OFF.
@@ -9443,22 +9444,15 @@ export class AuthManager {
 
   /**
    * The id of the account a password sign-in for `email` is checked against,
-   * or `undefined`. Resolved the way better-auth's `/sign-in/email` resolves
-   * it — the address lower-cased (`findUserByEmail(email.toLowerCase())`),
-   * matching the lower-cased identifier the adapter stores — so the
-   * `login_failed` row names the account the credential check actually judged.
+   * or `undefined` — {@link findSignInAccount}'s answer, so the `login_failed`
+   * row names the account the credential check actually judged and the lock
+   * gate and counter hold.
    */
   private async resolveSignInAccountId(email: string): Promise<string | undefined> {
     const engine = this.getDataEngine();
     if (!engine) return undefined;
     try {
-      const query: EngineQueryOptions = {
-        where: { email: email.toLowerCase() },
-        fields: ['id'],
-        context: { isSystem: true, positions: [], permissions: [] },
-      };
-      const u = await engine.findOne('sys_user', query);
-      return typeof u?.id === 'string' && u.id ? u.id : undefined;
+      return (await this.findSignInAccount(engine, email, []))?.id;
     } catch (e) {
       // The refusal stands either way; what is lost is its ledger row.
       this.logDurabilityDegradation(
@@ -9473,6 +9467,45 @@ export class AuthManager {
     }
   }
 
+  /**
+   * ADR-0069 D2 — the ONE answer to "which account does this password sign-in
+   * name", read by the lock gate ({@link assertAccountNotLocked}), the counter
+   * ({@link recordSignInOutcome}) and the account events
+   * ({@link resolveSignInAccountId}): the `sys_user` row with `fields`
+   * (plus `id`), or `undefined` when the identifier names no account.
+   *
+   * It asks exactly what better-auth's `/sign-in/email` credential check asks
+   * (1.7.3: `internalAdapter.findUserByEmail(email.toLowerCase())`, an
+   * equality match of the `email` column against the lower-cased address,
+   * which is also the spelling `internalAdapter.createUser` stores), so the
+   * gate, the counter, the ledger and the credential check name one account
+   * for every identifier the credential check resolves to it.
+   *
+   * The lockout state lives on that row (`failed_login_count` /
+   * `locked_until`) and every write to it is by the row's `id`, so one account
+   * holds one counter. ⛔ Never resolve the account any other way on this
+   * path: the lockout holds exactly as far as it names the account the
+   * credential check names.
+   *
+   * Throws what the engine throws; each caller keeps its own failure posture
+   * (the gate fails open, the counter and the ledger report the lost write).
+   */
+  private async findSignInAccount(
+    engine: IDataEngine,
+    email: string,
+    fields: readonly string[],
+  ): Promise<({ id: string } & Record<string, unknown>) | undefined> {
+    const query: EngineQueryOptions = {
+      where: { email: email.toLowerCase() },
+      fields: ['id', ...fields],
+      context: { isSystem: true, positions: [], permissions: [] },
+    };
+    const row = await engine.findOne('sys_user', query);
+    return row && typeof row.id === 'string' && row.id
+      ? (row as { id: string } & Record<string, unknown>)
+      : undefined;
+  }
+
   /**
    * ADR-0069 D2 (#3690) — project the operator's lockout settings onto
    * better-auth's own `twoFactor({ accountLockout })` contract, so the second
diff --git a/scripts/query-options-erasure-baseline.json b/scripts/query-options-erasure-baseline.json
index c2b55fc8e1..b0cd51c419 100644
--- a/scripts/query-options-erasure-baseline.json
+++ b/scripts/query-options-erasure-baseline.json
@@ -40,7 +40,7 @@
     "packages/plugins/plugin-approvals/src/approver-org-scope.ts": 2,
     "packages/plugins/plugin-approvals/src/lifecycle-hooks.ts": 4,
     "packages/plugins/plugin-auth/src/admin-import-users.ts": 1,
-    "packages/plugins/plugin-auth/src/auth-manager.ts": 14,
+    "packages/plugins/plugin-auth/src/auth-manager.ts": 12,
     "packages/plugins/plugin-sharing/src/share-link-routes.ts": 3,
     "packages/plugins/plugin-sharing/src/share-link-service.ts": 5,
     "packages/runtime/src/action-execution.ts": 1,