diff --git a/.changeset/adr-0069-hibp-breached-password.md b/.changeset/adr-0069-hibp-breached-password.md
new file mode 100644
index 0000000000..79d5389e1b
--- /dev/null
+++ b/.changeset/adr-0069-hibp-breached-password.md
@@ -0,0 +1,17 @@
+---
+'@objectstack/spec': minor
+'@objectstack/service-settings': minor
+'@objectstack/plugin-auth': minor
+'@objectstack/cli': minor
+---
+
+Auth: reject breached passwords via Have I Been Pwned (ADR-0069 D1, P1)
+
+First slice of ADR-0069 (enterprise authentication hardening) and the enforcement-wired pattern template the rest of the ADR follows. Adds a `password_reject_breached` auth setting (default **off**) bound end-to-end to better-auth's native `haveibeenpwned` plugin — a k-anonymity range check on sign-up / change-password / reset-password (the plaintext password never leaves the process).
+
+- **spec**: new `passwordRejectBreached` flag on `AuthPluginConfigSchema`.
+- **service-settings**: new "Reject breached passwords" toggle in the `auth` manifest's password-policy group (`global` scope, `manage_platform_settings`).
+- **plugin-auth**: `bindAuthSettings` maps the setting into the plugin config; `buildPluginList` gates and mounts the `haveIBeenPwned` plugin (env `OS_AUTH_PASSWORD_REJECT_BREACHED` wins over config, mirroring `OS_AUTH_TWO_FACTOR`).
+- **cli**: surface the knob in the `serve` boot config alongside `twoFactor`.
+
+Default-off and additive — no behavior change on upgrade. Per ADR-0049 the toggle ships with its enforcement (no false surface). No new identity fields (the `[custom]` D1 items — complexity / expiry / history — land in follow-up PRs).
diff --git a/packages/cli/src/commands/serve.ts b/packages/cli/src/commands/serve.ts
index db7889a463..4ec132454a 100644
--- a/packages/cli/src/commands/serve.ts
+++ b/packages/cli/src/commands/serve.ts
@@ -1243,6 +1243,12 @@ export default class Serve extends Command {
               plugins: {
                 admin: String(process.env.OS_AUTH_ADMIN ?? 'true').toLowerCase() !== 'false',
                 twoFactor: String(process.env.OS_AUTH_TWO_FACTOR ?? 'false').toLowerCase() === 'true',
+                // ADR-0069 D1: reject breached passwords (Have I Been Pwned).
+                // Opt-in; the auth Settings toggle (password_reject_breached) is
+                // the primary control, OS_AUTH_PASSWORD_REJECT_BREACHED the
+                // operator override (env wins in buildPluginList()).
+                passwordRejectBreached:
+                  String(process.env.OS_AUTH_PASSWORD_REJECT_BREACHED ?? 'false').toLowerCase() === 'true',
               },
               advanced: process.env.OS_COOKIE_DOMAIN
                 ? ({
diff --git a/packages/plugins/plugin-auth/src/auth-manager.test.ts b/packages/plugins/plugin-auth/src/auth-manager.test.ts
index 51dec9d1f3..cfd14c985a 100644
--- a/packages/plugins/plugin-auth/src/auth-manager.test.ts
+++ b/packages/plugins/plugin-auth/src/auth-manager.test.ts
@@ -29,6 +29,10 @@ vi.mock('better-auth/plugins/custom-session', () => ({
   customSession: vi.fn((fn: any) => ({ id: 'custom-session', _fn: fn })),
 }));
 
+vi.mock('better-auth/plugins/haveibeenpwned', () => ({
+  haveIBeenPwned: vi.fn((opts: any) => ({ id: 'have-i-been-pwned', _opts: opts })),
+}));
+
 import { betterAuth } from 'better-auth';
 
 describe('AuthManager', () => {
@@ -1524,4 +1528,70 @@ describe('AuthManager', () => {
       expect(result.user.roles).toBeUndefined();
     });
   });
+
+  // ADR-0069 D1: breached-password rejection enables better-auth's native
+  // `haveibeenpwned` plugin. Default OFF (no false surface, ADR-0049); the
+  // settings toggle (`password_reject_breached`) and the
+  // `OS_AUTH_PASSWORD_REJECT_BREACHED` env override both gate it, with env
+  // winning over config — mirroring the twoFactor / scim gating pattern.
+  describe('haveibeenpwned plugin (ADR-0069 breached-password rejection)', () => {
+    const captureConfig = () => {
+      let capturedConfig: any;
+      (betterAuth as any).mockImplementation((config: any) => {
+        capturedConfig = config;
+        return { handler: vi.fn(), api: {} };
+      });
+      return () => capturedConfig;
+    };
+
+    it('does NOT register the plugin by default (off by default)', async () => {
+      const get = captureConfig();
+      const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+      const manager = new AuthManager({
+        secret: 'test-secret-at-least-32-chars-long',
+        baseUrl: 'http://localhost:3000',
+      });
+      await manager.getAuthInstance();
+      warnSpy.mockRestore();
+
+      expect(get().plugins.map((p: any) => p.id)).not.toContain('have-i-been-pwned');
+    });
+
+    it('registers the plugin when plugins.passwordRejectBreached is true', async () => {
+      const get = captureConfig();
+      const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+      const manager = new AuthManager({
+        secret: 'test-secret-at-least-32-chars-long',
+        baseUrl: 'http://localhost:3000',
+        plugins: { passwordRejectBreached: true } as any,
+      });
+      await manager.getAuthInstance();
+      warnSpy.mockRestore();
+
+      const hibp = get().plugins.find((p: any) => p.id === 'have-i-been-pwned');
+      expect(hibp).toBeDefined();
+      // A custom user-facing message is passed (the default error is generic).
+      expect(typeof hibp._opts.customPasswordCompromisedMessage).toBe('string');
+    });
+
+    it('lets OS_AUTH_PASSWORD_REJECT_BREACHED env override the config (env wins)', async () => {
+      const get = captureConfig();
+      const prev = process.env.OS_AUTH_PASSWORD_REJECT_BREACHED;
+      process.env.OS_AUTH_PASSWORD_REJECT_BREACHED = 'true';
+      const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+      try {
+        const manager = new AuthManager({
+          secret: 'test-secret-at-least-32-chars-long',
+          baseUrl: 'http://localhost:3000',
+          plugins: { passwordRejectBreached: false } as any,
+        });
+        await manager.getAuthInstance();
+        expect(get().plugins.map((p: any) => p.id)).toContain('have-i-been-pwned');
+      } finally {
+        if (prev === undefined) delete process.env.OS_AUTH_PASSWORD_REJECT_BREACHED;
+        else process.env.OS_AUTH_PASSWORD_REJECT_BREACHED = prev;
+        warnSpy.mockRestore();
+      }
+    });
+  });
 });
diff --git a/packages/plugins/plugin-auth/src/auth-manager.ts b/packages/plugins/plugin-auth/src/auth-manager.ts
index 2c8b35855e..e8c653dbb8 100644
--- a/packages/plugins/plugin-auth/src/auth-manager.ts
+++ b/packages/plugins/plugin-auth/src/auth-manager.ts
@@ -829,9 +829,11 @@ export class AuthManager {
     // forces `admin` on (organization already defaults on). See ADR-0071.
     const scimEffective = scimFromEnv ?? (pluginConfig as any).scim ?? false;
     const twoFactorFromEnv = readBooleanEnv('OS_AUTH_TWO_FACTOR');
+    const hibpFromEnv = readBooleanEnv('OS_AUTH_PASSWORD_REJECT_BREACHED');
     const enabled = {
       organization: pluginConfig.organization ?? true,
       twoFactor: twoFactorFromEnv ?? pluginConfig.twoFactor ?? false,
+      passwordRejectBreached: hibpFromEnv ?? pluginConfig.passwordRejectBreached ?? false,
       passkeys: pluginConfig.passkeys ?? false,
       magicLink: pluginConfig.magicLink ?? false,
       oidcProvider: oidcFromEnv ?? pluginConfig.oidcProvider ?? false,
@@ -1077,6 +1079,19 @@ export class AuthManager {
       }));
     }
 
+    // Breached-password rejection (ADR-0069 D1). Native, stateless: a
+    // k-anonymity range check against Have I Been Pwned on better-auth's
+    // password-mutating endpoints (sign-up / change / reset — the plugin's
+    // defaults). The plaintext password is never sent; only the first 5 SHA-1
+    // hex chars leave the process. Rejects with PASSWORD_COMPROMISED.
+    if (enabled.passwordRejectBreached) {
+      const { haveIBeenPwned } = await import('better-auth/plugins/haveibeenpwned');
+      plugins.push(haveIBeenPwned({
+        customPasswordCompromisedMessage:
+          'This password has appeared in a known data breach. Please choose a different one.',
+      }));
+    }
+
     if (enabled.admin) {
       const { admin } = await import('better-auth/plugins/admin');
       // Platform admin: ban/unban, set-password, impersonate, set-role.
diff --git a/packages/plugins/plugin-auth/src/auth-plugin.test.ts b/packages/plugins/plugin-auth/src/auth-plugin.test.ts
index 7d35b6366e..8cdb3fa9a0 100644
--- a/packages/plugins/plugin-auth/src/auth-plugin.test.ts
+++ b/packages/plugins/plugin-auth/src/auth-plugin.test.ts
@@ -634,6 +634,20 @@ describe('AuthPlugin', () => {
       expect(cfg.session?.updateAge).toBeUndefined();
     });
 
+    it('binds password_reject_breached into plugins.passwordRejectBreached (ADR-0069 D1)', async () => {
+      const { manager } = await bootWithAuthSettings({
+        password_reject_breached: { value: true, source: 'global' },
+      });
+      expect((manager as any).config.plugins?.passwordRejectBreached).toBe(true);
+    });
+
+    it('does not set passwordRejectBreached when the setting is default-source (off by default)', async () => {
+      const { manager } = await bootWithAuthSettings({
+        password_reject_breached: { value: false, source: 'default' }, // not explicit → no patch
+      });
+      expect((manager as any).config.plugins?.passwordRejectBreached).toBeUndefined();
+    });
+
     it('enables Google from env credentials when google_enabled is explicit true', async () => {
       process.env.GOOGLE_CLIENT_ID = 'google-env-client-id';
       process.env.GOOGLE_CLIENT_SECRET = 'google-env-client-secret';
diff --git a/packages/plugins/plugin-auth/src/auth-plugin.ts b/packages/plugins/plugin-auth/src/auth-plugin.ts
index a8638279af..8790a3bd55 100644
--- a/packages/plugins/plugin-auth/src/auth-plugin.ts
+++ b/packages/plugins/plugin-auth/src/auth-plugin.ts
@@ -486,6 +486,17 @@ export class AuthPlugin implements Plugin {
           patch.emailAndPassword = emailAndPassword as AuthManagerOptions['emailAndPassword'];
         }
 
+        // Breached-password rejection (ADR-0069 D1) — enables better-auth's
+        // native `haveibeenpwned` plugin via the plugin-config gate. Default
+        // off; only an explicit toggle applies (manifest defaults must not
+        // mask the deployment env var). See buildPluginList() for the seam.
+        if (isExplicit('password_reject_breached')) {
+          patch.plugins = {
+            ...(patch.plugins ?? {}),
+            passwordRejectBreached: asBoolean(values.password_reject_breached, false),
+          } as AuthManagerOptions['plugins'];
+        }
+
         // Session lifetime — days → seconds for better-auth's `session`
         // (`expiresIn` = absolute lifetime; `updateAge` = refresh threshold).
         const session: { expiresIn?: number; updateAge?: number } = {};
diff --git a/packages/services/service-settings/src/manifests/auth.manifest.test.ts b/packages/services/service-settings/src/manifests/auth.manifest.test.ts
index e1564dc47c..2f76f41c67 100644
--- a/packages/services/service-settings/src/manifests/auth.manifest.test.ts
+++ b/packages/services/service-settings/src/manifests/auth.manifest.test.ts
@@ -25,6 +25,7 @@ describe('authSettingsManifest', () => {
     expect(keys).toEqual([
       'email_password_enabled',
       'google_enabled',
+      'password_reject_breached',
       'require_email_verification',
       'signup_enabled',
     ]);
diff --git a/packages/services/service-settings/src/manifests/auth.manifest.ts b/packages/services/service-settings/src/manifests/auth.manifest.ts
index c7d1733677..f181422706 100644
--- a/packages/services/service-settings/src/manifests/auth.manifest.ts
+++ b/packages/services/service-settings/src/manifests/auth.manifest.ts
@@ -75,6 +75,16 @@ const manifest = {
       description: 'Upper bound guards against denial-of-service via very long password hashing.',
       visible: "${data.email_password_enabled !== false}",
     },
+    {
+      type: 'toggle',
+      key: 'password_reject_breached',
+      label: 'Reject breached passwords',
+      required: false,
+      default: false,
+      description:
+        'Block passwords found in public breach corpora via Have I Been Pwned (k-anonymity range check; the password is never sent in full).',
+      visible: "${data.email_password_enabled !== false}",
+    },
 
     {
       type: 'group',
diff --git a/packages/spec/src/system/auth-config.zod.ts b/packages/spec/src/system/auth-config.zod.ts
index dce08b9870..ae11eaf323 100644
--- a/packages/spec/src/system/auth-config.zod.ts
+++ b/packages/spec/src/system/auth-config.zod.ts
@@ -21,6 +21,9 @@ export const AuthPluginConfigSchema = lazySchema(() => z.object({
   organization: z.boolean().default(true).describe('Enable Organization/Teams support (frontend AuthProvider expects this enabled)'),
   twoFactor: z.boolean().default(false).describe('Enable 2FA'),
   passkeys: z.boolean().default(false).describe('Enable Passkey support'),
+  passwordRejectBreached: z.boolean().default(false).describe(
+    "Reject passwords found in the Have I Been Pwned breach corpus (enables better-auth's haveibeenpwned plugin)",
+  ),
   magicLink: z.boolean().default(false).describe('Enable Magic Link login'),
   /**
    * Enable better-auth's `oidc-provider` plugin so that ObjectStack itself