@@ -0,0 +1,19 @@
+---
+'@objectstack/plugin-auth': patch
+---
+
+fix(plugin-auth)!: a user preference's owner is fixed when the preference is saved
+
+Clause-②: no (narrowing) — a non-system update of a `sys_user_preference` row that sends a `user_id` other than the stored one is refused `403 PERMISSION_DENIED`, which some callers' writes were admitted before. Nothing is widened.
+Metadata-protocol: none
+
+<!-- adr-0087: not-required (no-migration-prescription) No key of any schema is added, removed, renamed or re-shaped, and no export or type changes: a save rule on one platform object refuses a change of the row's owner. The refusal is a 403 a caller cannot work around by rewriting metadata, so there is nothing for a migration to rewrite and no tombstone. -->
+
+**BREAKING** accept-set narrowing at the generic data door for `sys_user_preference` (`@objectstack/plugin-auth`).
+
+- **Now.** A preference belongs to the user it was saved for. An update that sends a different `user_id` is refused `403 PERMISSION_DENIED`, for every caller but the system: a member, an organization administrator and a platform administrator alike. The refusal names the row and the `user_id` column. The row is unchanged.
+- **Unchanged.** An update that echoes the stored `user_id`, or does not send it, saves as before. The console's preference writer updates `value` only and creates rows in the caller's own name, so it is not affected. A system write (the platform's own writers) is not judged.
+- **Shared rule.** `sys_personal_view` and `sys_user_preference` now hold this with one check, `owner-fixed-rule.ts`. The personal view's behaviour and message are unchanged.
+- **Who sees it.** A client that changes the `user_id` of a saved preference.
+
+**The remedy.** Save a new preference in the other user's name, as that user, instead of moving one.
@@ -143,7 +143,7 @@ bugs — it is the protection or the side effect that silently does not happen.
 | 25 | Engine-owned / append-only write guard bypassed | plugin-security | Get: generic writes to `managedBy` engine-owned objects | `packages/plugins/plugin-security/src/system-write-guard.ts#isUserContextWrite`, `packages/plugins/plugin-security/src/system-write-guard.ts#assertEngineOwnedWriteAllowed` |
 | 26 | Identity write guard bypassed (ADR-0092) | plugin-auth | Get: direct writes to identity tables through the generic data path | `packages/plugins/plugin-auth/src/identity-write-guard.ts#isUserContextWrite` |
 | 26b | API key restore guard does not refuse | plugin-auth | Get: a write setting `revoked: false` on a `sys_api_key` row an administrator's forced password reset revoked is admitted without the platform-administrator check a user-context restore must pass; the reason is still cleared. Lose: nothing a caller reaches: no system writer restores a key, and the mint, the last-used stamp and the forced reset itself never set `revoked: false` | `packages/plugins/plugin-auth/src/api-key-restore-guard.ts#isUserContextWrite` |
-| 26c | **Personal-view owner rule does not refuse** — a `sys_personal_view` update that changes `user_id` is admitted | plugin-auth | Get: a system writer can move a personal view to another owner (no shipped system writer does). Lose: nothing a caller reaches. A non-system update whose `user_id` differs from the stored owner is refused `403 PERMISSION_DENIED`, for every caller, a platform administrator included; an echo of the stored owner is no change. The rule exists because, for an organization member, `member_default`'s `'*'` update floor (`created_by == current_user.id`) applies to an update in place of the object's own row scope | `packages/plugins/plugin-auth/src/personal-view-hooks.ts#registerPersonalViewHooks` |
+| 26c | **Per-user owner rule does not refuse** — a `sys_personal_view` or `sys_user_preference` update that changes `user_id` is admitted | plugin-auth | Get: a system writer can move a personal view or a preference to another owner (no shipped system writer does). Lose: nothing a caller reaches. A non-system update whose `user_id` differs from the stored owner is refused `403 PERMISSION_DENIED`, for every caller, a platform administrator included; an echo of the stored owner is no change. One shared check holds it for both objects. The rule exists because, for an organization member, `member_default`'s `'*'` update floor (`created_by == current_user.id`) applies to an update beside the object's own row scope | `packages/plugins/plugin-auth/src/owner-fixed-rule.ts#isOwnerChange` |
 | 27 | Search-companion column **kept** in a read's rows when it was explicitly requested | objectql | Get: the internal companion column is readable. Lose: nothing for app code — this is the engine reading its own index | `stripSearchCompanionFromRead` |
 | 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `dependentCountIsDisclosable` |
 | 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `recordReferenceCheckElevation` |
@@ -575,7 +575,7 @@ and CI refuses one that differs from what the tree produces.
 | `packages/plugins/plugin-auth/src/api-key-restore-guard.ts#isUserContextWrite` | 1 | 26b |
 | `packages/plugins/plugin-auth/src/auth-plugin.ts#start` | 1 | 12 |
 | `packages/plugins/plugin-auth/src/identity-write-guard.ts#isUserContextWrite` | 1 | 26 |
-| `packages/plugins/plugin-auth/src/personal-view-hooks.ts#registerPersonalViewHooks` | 1 | 26c |
+| `packages/plugins/plugin-auth/src/owner-fixed-rule.ts#isOwnerChange` | 1 | 26c |
 | `packages/plugins/plugin-auth/src/principal-session-mint.ts#refuseUpFront` | 1 | 61b |
 | `packages/plugins/plugin-email/src/email-template-door.ts#isOrganizationWrite` | 1 | 59 |
 | `packages/plugins/plugin-security/src/flow-system-identity-write-refusal.ts#elevationSource` | 1 | 1b |
 
@@ -69,6 +69,7 @@ import {
 import { registerLastAdminGuard } from './last-admin-guard.js';
 import { registerApiKeyRestoreGuard } from './api-key-restore-guard.js';
 import { registerPersonalViewHooks } from './personal-view-hooks.js';
+import { registerUserPreferenceHooks } from './user-preference-hooks.js';
 import { personalViewCallerResolver, registerPersonalViewRoutes, PERSONAL_VIEW_REMOVE_ROUTE, type PersonalViewEngine } from './personal-view-routes.js';
 import { registerMembershipEndedSessionTrigger } from './membership-ended-session.js';
 import { registerMemberRoleCanonicalization } from './member-role-canonical.js';
@@ -1872,6 +1873,12 @@ export class AuthPlugin implements Plugin {
           packageId: 'com.objectstack.plugin-auth.personal-view',
           logger: ctx.logger,
         });
+        // A user's own preferences: the owner (user_id) is fixed when the row
+        // is saved, for every caller but the system. See user-preference-hooks.ts.
+        registerUserPreferenceHooks(engine, {
+          packageId: 'com.objectstack.plugin-auth.user-preference',
+          logger: ctx.logger,
+        });
         // [cloud ADR-0024 D5.2] Break-glass — the same identity write
         // chokepoints, guarding a different question: not "may this caller
         // write identity tables" (above, and system writes bypass it by
 
@@ -64,6 +64,7 @@ import { resolveTenancyPosture } from '@objectstack/types';
 import { ensureDefaultOrganizationExists } from './default-organization-invariant.js';
 import { authIdentityManifest } from './manifest.js';
 import { registerPersonalViewHooks } from './personal-view-hooks.js';
+import { registerUserPreferenceHooks } from './user-preference-hooks.js';
 
 /** The kernel plugin name of {@link IdentityObjectsPlugin}. */
 export const IDENTITY_OBJECTS_PLUGIN_NAME = 'com.objectstack.auth.identity-objects';
@@ -123,11 +124,12 @@ export class IdentityObjectsPlugin implements Plugin {
    * plugin keeps it. A failure throws and fails the boot, never warn-only.
    */
   async start(ctx: PluginContext): Promise<void> {
-    // The manifest above registers `sys_personal_view`; its two write rules
-    // travel with it, exactly as `AuthPlugin` registers them.
+    // The manifest above registers `sys_personal_view` and `sys_user_preference`;
+    // their write rules travel with them, exactly as `AuthPlugin` registers them.
     const engine = ctx.getService<{ registerHook?: unknown }>('objectql');
     if (engine && typeof engine.registerHook === 'function') {
       registerPersonalViewHooks(engine, { packageId: `${IDENTITY_OBJECTS_PLUGIN_NAME}.personal-view` });
+      registerUserPreferenceHooks(engine, { packageId: `${IDENTITY_OBJECTS_PLUGIN_NAME}.user-preference` });
     }
     if (postureInForce(ctx) !== 'single') return;
     const invariant = await ensureDefaultOrganizationExists(ctx.getService<IDataEngine>('objectql'), {
 
@@ -0,0 +1,71 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * **The owner of a per-user row is fixed when the row is saved.** The one
+ * spelling of that rule, shared by `sys_personal_view`
+ * (`personal-view-hooks.ts`) and `sys_user_preference`
+ * (`user-preference-hooks.ts`), whose owner column is `user_id`.
+ *
+ * An update that sends an owner other than the stored one is refused
+ * `403 PERMISSION_DENIED`, for every caller but the system: a member, an
+ * organization administrator and a platform administrator alike. An echo of
+ * the stored owner is no change, and saves.
+ *
+ * A save rule is the one place that judges the CHANGE of owner; why the row
+ * scope alone does not is row 26c of `content/docs/permissions/system-context.mdx`.
+ *
+ * The refusal names the row and the owner column, and never the id the write
+ * sent.
+ */
+
+/** The string form two stored ids are compared by (an echo of the stored owner is no change). */
+function sameId(a: unknown, b: unknown): boolean {
+  const norm = (v: unknown) => (v === undefined || v === null || v === '' ? null : String(v));
+  return norm(a) === norm(b);
+}
+
+const sets = (data: unknown, key: string): boolean =>
+  !!data && typeof data === 'object' && Object.prototype.hasOwnProperty.call(data, key);
+
+/**
+ * Whether a `beforeUpdate` hook context is a non-system write handing a row to
+ * another owner: it sends `ownerField` with a value other than the stored one
+ * (`ctx.previous`, present on the by-id path and per row on a multi-row
+ * update). A system write is never one: the platform's own writers are
+ * trusted to mean it.
+ */
+export function isOwnerChange(ctx: any, ownerField = 'user_id'): boolean {
+  if (ctx?.session?.isSystem === true) return false;
+  const data = ctx?.input?.data;
+  const previous = ctx?.previous;
+  if (!sets(data, ownerField) || !previous || typeof previous !== 'object') return false;
+  return !sameId((data as Record<string, unknown>)[ownerField], (previous as Record<string, unknown>)[ownerField]);
+}
+
+/** How a refusal names the row it guards. */
+export interface OwnerFixedSubject {
+  /** The row's kind as a sentence starts it: `Personal view`, `User preference`. */
+  label: string;
+  /** The row's kind inside a sentence: `view`, `preference`. */
+  noun: string;
+}
+
+/** The refusal for an update that would hand a row to another user: `PERMISSION_DENIED` / `403`. */
+export function ownerFixedError(subject: OwnerFixedSubject, id: unknown, ownerField = 'user_id'): Error {
+  const { label, noun } = subject;
+  const err = new Error(
+    `${label} ${String(id ?? '')} was not changed: a ${noun}'s owner (${ownerField}) is fixed when the ${noun} is saved, `
+      + `and nobody can hand a ${noun} to another user. Save a new ${noun} in that user's name instead. `
+      + `The ${noun} is unchanged.`,
+  ) as Error & { code?: string; status?: number };
+  err.code = 'PERMISSION_DENIED';
+  err.status = 403;
+  return err;
+}
+
+/** Throw {@link ownerFixedError} when {@link isOwnerChange} holds for `ctx`. */
+export function assertOwnerUnchanged(ctx: any, subject: OwnerFixedSubject, ownerField = 'user_id'): void {
+  if (isOwnerChange(ctx, ownerField)) {
+    throw ownerFixedError(subject, ctx?.previous?.id ?? ctx?.input?.id, ownerField);
+  }
+}
@@ -20,11 +20,8 @@
  *
  * **The owner is fixed when the view is saved.** An update that sends a
  * `user_id` other than the stored one is refused `403 PERMISSION_DENIED`, for
- * every caller but the system. The row scope alone does not hold this: for an
- * organization member, `member_default`'s `'*'` update floor
- * (`created_by == current_user.id`) is a held update policy, so the object's
- * declared default does not apply to an update, and the post-image of a
- * re-parent still carries the member's own `created_by`.
+ * every caller but the system. The rule, and why the row scope alone does not
+ * hold it, is `owner-fixed-rule.ts`'s, shared with `sys_user_preference`.
  *
  * Which view opens by default is not this object's: the reader's existing
  * per-object pin holds a view id (seat ruling 6587007982 on #29443).
@@ -37,6 +34,7 @@
 import { ListViewSchema } from '@objectstack/spec/ui';
 import { zodIssuesToFields } from '@objectstack/spec/api';
 import { validationFailure } from '@objectstack/types';
+import { assertOwnerUnchanged } from './owner-fixed-rule.js';
 
 /** The object these hooks guard. */
 export const PERSONAL_VIEW_OBJECT = 'sys_personal_view';
@@ -95,22 +93,8 @@ export function assertPersonalViewConfig(config: unknown, objectName?: unknown):
   );
 }
 
-/** The string form two stored ids are compared by (an echo of the stored owner is no change). */
-function sameId(a: unknown, b: unknown): boolean {
-  const norm = (v: unknown) => (v === undefined || v === null || v === '' ? null : String(v));
-  return norm(a) === norm(b);
-}
-
-/** The refusal for an update that would hand a view to another user: `PERMISSION_DENIED` / `403`. */
-export function ownerChangeError(id: unknown): Error {
-  const err = new Error(
-    `Personal view ${String(id ?? '')} was not changed: a view's owner (user_id) is fixed when the view is saved, `
-      + 'and nobody can hand a view to another user. Save a new view in that user\'s name instead. The view is unchanged.',
-  ) as Error & { code?: string; status?: number };
-  err.code = 'PERMISSION_DENIED';
-  err.status = 403;
-  return err;
-}
+/** How the shared owner rule names this object's rows. */
+const PERSONAL_VIEW_SUBJECT = { label: 'Personal view', noun: 'view' } as const;
 
 const sets = (data: Record<string, unknown> | null | undefined, key: string): boolean =>
   !!data && typeof data === 'object' && Object.prototype.hasOwnProperty.call(data, key);
@@ -133,14 +117,7 @@ export function registerPersonalViewHooks(engine: any, opts: PersonalViewHooksOp
     // The row as it will be: what the write sends, over what is stored
     // (`ctx.previous`, present on the by-id path and per row on a multi-row update).
     const previous = (ctx.previous ?? undefined) as Record<string, unknown> | undefined;
-    if (
-      ctx?.session?.isSystem !== true
-      && sets(data, 'user_id')
-      && previous
-      && !sameId(data!.user_id, previous.user_id)
-    ) {
-      throw ownerChangeError(previous.id ?? ctx.input?.id);
-    }
+    assertOwnerUnchanged(ctx, PERSONAL_VIEW_SUBJECT);
     const sendsConfig = sets(data, CONFIG_FIELD);
     if (!sendsConfig && !sets(data, 'object_name')) return;
     const config = sendsConfig ? data![CONFIG_FIELD] : previous?.[CONFIG_FIELD];