@@ -0,0 +1,17 @@
+---
+'@object-ui/app-shell': patch
+---
+
+feat(app-shell): Studio customizes an installed package's page into the base's customization package (#30063)
+
+Clause-②: no
+Metadata-protocol: none
+
+On a read-only (installed or code-shipped) package, a page opened in the Interfaces pillar now offers Customize, the same button a dashboard, report or view shows. Before, Studio showed the page as read-only with no way to change it, although the server already serves a page override from the paired customization package (`<base>.custom`).
+
+- Customize unlocks the page designer. Nothing is written until an edit is saved. The first saved edit copies the whole page into the pair, declaring `overrides: { package: <base>, basedOn: <base manifest version> }`. Later edits update that copy. The base package is never written.
+- The edit is a draft in the pair's pending changes; once published, the running app serves the customized page at its usual address.
+- The page's header carries the override mark, whose popover offers "Restore package original": it deletes the pair's draft and copy of the page after a confirmation, and the shipped page reads back.
+- The Interfaces rail marks a customized page, "only customizations" counts and lists it, and the All metadata directory's page tile counts it.
+
+A customized page is a whole copy: a change the vendor ships to that page in a later version does not appear until the customization is restored and redone. A writable package's page editing is unchanged. No spec, server or metadata-type change.
@@ -18,7 +18,8 @@
  *  - the directory's object tile counts the extension, and the header the base's total;
  *  - a failed read draws no mark, no filter and no number, with the server's sentence;
  *  - a base without a pair is unchanged, and Setup (no area) never reads;
- *  - in the cross-package leg an item of a pair is labelled with its base.
+ *  - in the cross-package leg an item of a pair is labelled with its base;
+ *  - objectstack#30063 — the page tile counts a page's override.
  */
 
 import '@testing-library/jest-dom/vitest';
@@ -69,6 +70,7 @@ const ENTRIES = [
   entry('translation', 'ui'),
   entry('email_template', 'system'),
   entry('permission', 'security'),
+  entry('page', 'ui'),
 ];
 
 vi.mock('./useMetadata', async (importOriginal) => ({
@@ -81,7 +83,7 @@ vi.mock('./useMetadata', async (importOriginal) => ({
     summary: { entries: [], total: 0, scannedTypes: 0, scannedItems: 0 },
     byType: {},
     warnByType: {},
-    countsByType: { object: 3, translation: 2, email_template: 1 },
+    countsByType: { object: 3, translation: 2, email_template: 1, page: 1 },
     lockedByType: {},
     packagesByType: Object.fromEntries(ENTRIES.map((e) => [e.type, [BASE, PLAIN]])),
     allPackages: [BASE, PLAIN],
@@ -119,6 +121,13 @@ const HOTCRM_READ = {
 const EMPTY_READ = { packageId: PLAIN, overrides: [], extensions: [], switchedOff: [], contributions: [], counts: { overrides: 0, extensions: 0, switchedOff: 0, contributions: 0 } };
 
 let customizationsFail = false;
+/** objectstack#30063 — the read also lists a page's override. */
+let readListsPage = false;
+const withPage = (read: typeof HOTCRM_READ) => ({
+  ...read,
+  overrides: [...read.overrides, { type: 'page', name: 'crm_welcome', basedOn: '2.1.0' }],
+  counts: { ...read.counts, overrides: read.counts.overrides + 1 },
+});
 const fetchMock = vi.fn(async (url: string) => {
   const json = (status: number, body: unknown) =>
     new Response(JSON.stringify(body), { status, headers: { 'Content-Type': 'application/json' } });
@@ -131,7 +140,8 @@ const fetchMock = vi.fn(async (url: string) => {
     if (customizationsFail) {
       return json(503, { success: false, error: { code: 'SERVICE_UNAVAILABLE', message: 'The customization ledger is unavailable.' } });
     }
-    return json(200, { success: true, data: decodeURIComponent(m[1]) === BASE ? HOTCRM_READ : EMPTY_READ });
+    const hotcrm = readListsPage ? withPage(HOTCRM_READ) : HOTCRM_READ;
+    return json(200, { success: true, data: decodeURIComponent(m[1]) === BASE ? hotcrm : EMPTY_READ });
   }
   if (u.startsWith('/api/v1/data/sys_metadata_activation')) {
     return json(200, { object: 'sys_metadata_activation', records: [], hasMore: false });
@@ -141,6 +151,7 @@ const fetchMock = vi.fn(async (url: string) => {
 
 beforeEach(() => {
   customizationsFail = false;
+  readListsPage = false;
   fetchMock.mockClear();
   vi.stubGlobal('fetch', fetchMock);
 });
@@ -265,6 +276,18 @@ describe('the All metadata directory counts a base\'s customizations (objectstac
     expect(screen.queryByTestId('directory-tile-customized-permission')).toBeNull();
   });
 
+  it('objectstack#30063 — the page tile counts a page\'s override, and the header the total with it', async () => {
+    readListsPage = true;
+    mountDirectory(area(BASE));
+    const total = await screen.findByTestId('directory-customizations-total');
+    expect(total).toHaveTextContent(
+      tFormat('engine.directory.customizations.total', 'en-US', { customized: 4, baseName: 'HotCRM' }),
+    );
+    expect(screen.getByTestId('directory-tile-customized-page')).toHaveTextContent(
+      tFormat('engine.directory.customizations.tile', 'en-US', { customized: 1 }),
+    );
+  });
+
   it('a failed read draws no number, never "0", and says the server\'s sentence', async () => {
     customizationsFail = true;
     mountDirectory(area(BASE));
 
@@ -30,6 +30,11 @@
  * editor: the first saved edit copies the whole app into the pair, declaring
  * the override; the pickers offer the pair's items; the rail marks the
  * override and counts it under "only customizations"; Restore deletes it.
+ *
+ * objectstack#30063 — and a page, through its designer as a dashboard is:
+ * the first saved edit copies the whole page into the pair, declaring the
+ * override; Restore deletes it; the rail marks the page and counts it under
+ * "only customizations"; on a writable package the page saves in place.
  */
 
 import '@testing-library/jest-dom/vitest';
@@ -67,6 +72,15 @@ const BASE_ROWS: Record<string, Record<string, unknown>> = {
   'app/crm_app': { ...APP, _packageId: BASE },
   'dashboard/pipeline': { name: 'pipeline', label: 'Pipeline', widgets: [], _packageId: BASE },
   'dashboard/forecast': { name: 'forecast', label: 'Forecast', widgets: [], _packageId: BASE },
+  // objectstack#30063 — a page no navigation entry opens: the rail lists it under its type.
+  'page/crm_welcome': {
+    name: 'crm_welcome',
+    label: 'Welcome',
+    type: 'home',
+    kind: 'full',
+    regions: [{ name: 'main', components: [{ type: 'element:text', properties: { content: 'Shipped text' } }] }],
+    _packageId: BASE,
+  },
   'view/opportunity.default': {
     name: 'opportunity.default',
     object: 'opportunity',
@@ -104,6 +118,7 @@ const mockClient = vi.hoisted(() => ({
     if (opts.packageId === PAIR) return clone(srv.pairListed.get(type) ?? []);
     if (type === 'app') return [{ name: 'crm_app', label: 'CRM' }];
     if (type === 'object') return [{ name: 'opportunity', label: 'Opportunity' }];
+    if (type === 'page') return [{ name: 'crm_welcome', label: 'Welcome', _packageId: BASE }];
     return [];
   }),
   listDrafts: vi.fn(async () => []),
@@ -188,6 +203,27 @@ function BoardCanvas({ draft, onPatch }: { draft: Record<string, unknown>; onPat
   );
 }
 
+/** objectstack#30063 — the page designer, reduced to its first text block and one in-place edit of it. */
+function PageCanvas({ draft, onPatch }: { draft: Record<string, unknown>; onPatch?: (patch: Record<string, unknown>) => void }) {
+  const regions = (draft?.regions ?? []) as Array<{ name: string; components: Array<{ type: string; properties: { content: string } }> }>;
+  const content = regions[0]?.components[0]?.properties.content ?? '';
+  return (
+    <div>
+      <p data-testid="page-text">{content}</p>
+      <button
+        type="button"
+        onClick={() =>
+          onPatch?.({
+            regions: [{ ...regions[0], components: [{ type: 'element:text', properties: { content: `${content} (ours)` } }] }],
+          })
+        }
+      >
+        patch the page
+      </button>
+    </div>
+  );
+}
+
 /** Stands in for `plugin-view`'s `object-view`, recording the schema the canvas hands it. */
 function ObjectViewRecorder({ schema }: { schema: Record<string, unknown> }) {
   return <pre data-testid="object-view-schema">{JSON.stringify(schema)}</pre>;
@@ -214,6 +250,7 @@ function json(body: unknown, status = 200): Response {
 
 beforeAll(() => {
   registerMetadataPreview('dashboard', BoardCanvas as never);
+  registerMetadataPreview('page', PageCanvas as never);
   ComponentRegistry.register('object-view', ObjectViewRecorder as never, { namespace: 'plugin-view' });
 });
 
@@ -849,3 +886,145 @@ describe('Customize a read-only base’s navigation into its pair (objectstack#3
     expect(within(rail()).queryByTestId('if-nav-saved-to')).toBeNull();
   });
 });
+
+/* ───────────── objectstack#30063 — a page ───────────── */
+
+const SHIPPED_REGIONS = BASE_ROWS['page/crm_welcome']!.regions;
+const OURS_REGIONS = [{ name: 'main', components: [{ type: 'element:text', properties: { content: 'Shipped text (ours)' } }] }];
+/** The served page override: the pair's whole copy, its text changed. */
+const PAGE_OVERRIDE = {
+  name: 'crm_welcome',
+  label: 'Welcome',
+  type: 'home',
+  kind: 'full',
+  regions: OURS_REGIONS,
+  overrides: { package: BASE, basedOn: '4.0.0' },
+};
+const patchPage = () => fireEvent.click(screen.getByRole('button', { name: 'patch the page' }));
+
+/** The Welcome page open from its rail row, past the first leaf the pillar opens. */
+async function openWelcome(text: RegExp = /^Shipped text$/): Promise<void> {
+  await openPipeline();
+  fireEvent.click(await within(rail()).findByRole('button', { name: /Welcome/ }, { timeout: 8000 }));
+  await waitFor(() => expect(screen.getByTestId('page-text')).toHaveTextContent(text), { timeout: 8000 });
+}
+
+/** The base's customization read listing the page's override. */
+function marksListingThePage(): PackageCustomizationsState {
+  const read = {
+    packageId: BASE,
+    overrides: [{ type: 'page', name: 'crm_welcome', basedOn: '4.0.0' }],
+    extensions: [],
+    switchedOff: [],
+    contributions: [],
+    counts: { overrides: 1, extensions: 0, switchedOff: 0 },
+  } as never;
+  return { status: 'read', read, index: indexCustomizations(BASE, read)!, baseName: 'HotCRM', contributorNames: new Map() };
+}
+
+describe('Customize a read-only base’s page into its pair (objectstack#30063)', () => {
+  it('Customize is offered and writes nothing; the first designer edit copies the whole page into the pair, declaring the override; the base is untouched', async () => {
+    mount();
+    await openWelcome();
+    expect(within(header()).getByTestId('studio-customize')).toBeEnabled();
+    // Until it is pressed the designer edits nothing.
+    patchPage();
+    expect(screen.getByTestId('page-text')).toHaveTextContent(/^Shipped text$/);
+
+    await customize();
+    await sleep(1500);
+    expect(srv.ensure).toEqual([]);
+    expect(srv.saves).toEqual([]);
+
+    patchPage();
+    await waitFor(() => expect(srv.saves).toHaveLength(1), { timeout: 8000 });
+    expect(srv.ensure).toEqual([201]);
+    const [saved] = srv.saves;
+    // Read at the base before the pair was there: pinned to "no draft in the pair".
+    expect(saved).toMatchObject({ type: 'page', name: 'crm_welcome', opts: { mode: 'draft', packageId: PAIR, ifNoneMatch: '*' } });
+    // The whole page, without the base's `_` keys, declaring the override at the base's version.
+    expect(saved!.body).toStrictEqual({
+      name: 'crm_welcome',
+      label: 'Welcome',
+      type: 'home',
+      kind: 'full',
+      regions: OURS_REGIONS,
+      overrides: { package: BASE, basedOn: '4.0.0' },
+    });
+    expect(srv.base.get('page/crm_welcome')).toStrictEqual(BASE_ROWS['page/crm_welcome']);
+    await within(header()).findByTestId('studio-override-chip', undefined, { timeout: 8000 });
+
+    // The next designer edit saves into the pair's copy, at the version it was answered.
+    patchPage();
+    await waitFor(() => expect(srv.saves).toHaveLength(2), { timeout: 8000 });
+    expect(srv.ensure).toEqual([201]);
+    expect(srv.saves[1]!.opts).toMatchObject({ packageId: PAIR, ifMatch: 'v1' });
+    expect(srv.saves[1]!.body.overrides).toEqual({ package: BASE, basedOn: '4.0.0' });
+  });
+
+  it('a served override opens in the designer as the pair’s copy, editable, with no Customize to press', async () => {
+    srv.pairExists = true;
+    srv.pairActive.set('page/crm_welcome', clone(PAGE_OVERRIDE));
+    mount({ listedPair: PAIR });
+    await openWelcome(/^Shipped text \(ours\)$/);
+    await within(header()).findByTestId('studio-override-chip', undefined, { timeout: 8000 });
+    expect(within(header()).queryByTestId('studio-customize')).toBeNull();
+
+    patchPage();
+    await waitFor(() => expect(srv.saves).toHaveLength(1), { timeout: 8000 });
+    expect(srv.saves[0]).toMatchObject({ type: 'page', name: 'crm_welcome', opts: { packageId: PAIR } });
+    expect(srv.saves[0]!.body.overrides).toEqual({ package: BASE, basedOn: '4.0.0' });
+  });
+
+  it('Restore deletes the pair’s draft and row of the page, and the shipped page reads back', async () => {
+    srv.pairExists = true;
+    srv.pairActive.set('page/crm_welcome', clone(PAGE_OVERRIDE));
+    mount({ listedPair: PAIR });
+    await openWelcome(/^Shipped text \(ours\)$/);
+    await restore();
+    await waitFor(() => expect(srv.resets).toHaveLength(2), { timeout: 8000 });
+    expect(srv.resets).toEqual([
+      { type: 'page', name: 'crm_welcome', opts: { state: 'draft', packageId: PAIR } },
+      { type: 'page', name: 'crm_welcome', opts: { packageId: PAIR } },
+    ]);
+    await waitFor(() => expect(screen.getByTestId('page-text')).toHaveTextContent(/^Shipped text$/), { timeout: 8000 });
+    await waitFor(() => expect(within(header()).queryByTestId('studio-override-chip')).toBeNull());
+    expect(within(header()).getByTestId('studio-customize')).toBeInTheDocument();
+    expect(srv.base.get('page/crm_welcome')!.regions).toStrictEqual(SHIPPED_REGIONS);
+    expect(srv.saves).toEqual([]);
+  });
+
+  it('the rail marks a customized page and counts it under "only customizations", which lists it', async () => {
+    srv.pairExists = true;
+    srv.pairActive.set('page/crm_welcome', clone(PAGE_OVERRIDE));
+    mount({ listedPair: PAIR, marks: marksListingThePage() });
+    await openPipeline();
+    const row = await within(rail()).findByRole('button', { name: /Welcome/ }, { timeout: 8000 });
+    await waitFor(() => expect(within(row).getByTestId('customization-mark')).toHaveAttribute('data-kind', 'customized'), {
+      timeout: 8000,
+    });
+    const only = await within(rail()).findByTestId('studio-rail-customizations-only', undefined, { timeout: 8000 });
+    expect(only).toHaveTextContent(tFormat('engine.list.customizations.only', 'en', { marked: 1 }));
+
+    fireEvent.click(only);
+    expect(only).toHaveAttribute('aria-pressed', 'true');
+    expect(within(rail()).getByRole('button', { name: /Welcome/ })).toBeInTheDocument();
+    expect(within(rail()).queryByRole('button', { name: /Forecast/ })).toBeNull();
+  });
+
+  it('CONTROL: on a writable package a page edit saves at the package, with no door and no declaration', async () => {
+    mockClient.save.mockImplementationOnce(async (type: string, name: string, item: unknown, opts: Record<string, unknown> = {}) => {
+      srv.saves.push({ type, name, body: clone(item) as Record<string, unknown>, opts: clone(opts) });
+      return { success: true, version: 'v1', state: 'draft' };
+    });
+    mount({ readOnly: false });
+    await openWelcome();
+    expect(within(header()).queryByTestId('studio-customize')).toBeNull();
+    patchPage();
+    await waitFor(() => expect(srv.saves).toHaveLength(1), { timeout: 8000 });
+    expect(srv.saves[0]).toMatchObject({ type: 'page', name: 'crm_welcome', opts: { packageId: BASE } });
+    expect(srv.saves[0]!.body).not.toHaveProperty('overrides');
+    expect(srv.saves[0]!.body.regions).toStrictEqual(OURS_REGIONS);
+    expect(srv.ensure).toEqual([]);
+  });
+});
@@ -50,11 +50,12 @@ afterEach(() => {
 
 describe('the types Studio customizes (objectstack#28562)', () => {
   // objectstack#30059 — the app, whose navigation the Interfaces rail customizes.
-  it.each(['view', 'dashboard', 'report', 'app'])('%s is customized', (type) => {
+  // objectstack#30063 — the page, edited in its designer as a dashboard is.
+  it.each(['view', 'dashboard', 'report', 'page', 'app'])('%s is customized', (type) => {
     expect(isStudioCustomizeType(type)).toBe(true);
   });
 
-  it.each(['page', 'object', 'flow', 'translation', '', undefined, null])(
+  it.each(['object', 'flow', 'translation', '', undefined, null])(
     '%s is not: no pillar here customizes it, or it is not overridable',
     (type) => {
       expect(isStudioCustomizeType(type as string | undefined)).toBe(false);
 
@@ -2,14 +2,14 @@
 
 /**
  * objectstack#28562 (ADR-0146 D2, D3) — Customize in Studio: a read-only
- * base's view, dashboard or report becomes an item of the base's paired
+ * base's view, dashboard, report or page becomes an item of the base's paired
  * customization package `<base>.custom`, declared as an override of the
  * base's item, and "Restore package original" brings the base's item back.
  *
  * What this module holds, and what it reads:
  *
  *  - which types Studio customizes ({@link STUDIO_CUSTOMIZE_TYPES}): the
- *    Interfaces pillar's three and the app its rail navigates, each an
+ *    Interfaces pillar's four and the app its rail navigates, each an
  *    `overridable` type of the spec's closed classification
  *    (`isOverridableMetadataType`);
  *  - the body the pair's draft is written with ({@link overrideDraftBody}):
@@ -66,16 +66,18 @@ import { readFields, writeFields, type FieldEntry } from '../metadata-admin/prev
 
 /**
  * The types Studio's Customize door covers: the Interfaces pillar's view,
- * dashboard and report (an `object` leaf's list view is a `view`), and the
- * app whose navigation that pillar's rail edits (objectstack#30059: the whole
- * app is copied into the pair on the first saved navigation edit). Each is an
+ * dashboard, report and page (an `object` leaf's list view is a `view`;
+ * objectstack#30063: a page, block or source, is edited in its designer as
+ * a dashboard is), and the app whose navigation that pillar's rail edits
+ * (objectstack#30059: the whole app is copied into the pair on the first
+ * saved navigation edit). Each is an
  * `overridable` type of the spec's classification. Translations and email
  * templates are too: no pillar designs them, and the All metadata area's form
  * editor customizes them (`StudioBundleItemEditor`, objectstack#28569). So is
  * a read-only package's dataset, in that editor with its own designer
  * (objectstack#30064, `metadataArea.ts#AREA_CUSTOMIZE_EDITOR_TYPES`).
  */
-export const STUDIO_CUSTOMIZE_TYPES: readonly string[] = ['view', 'dashboard', 'report', 'app'];
+export const STUDIO_CUSTOMIZE_TYPES: readonly string[] = ['view', 'dashboard', 'report', 'page', 'app'];
 
 /** Whether Studio customizes an item of `type` into a read-only base's pair. */
 export function isStudioCustomizeType(type: string | undefined | null): boolean {