@@ -0,0 +1,15 @@
+---
+'@object-ui/app-shell': patch
+---
+
+Studio's *Explain access* panel picks the object and the operation with the shared `Select`, the control Studio's validation rule editor already picks with (objectui#11865, the *Explain access* part of that card).
+
+The two pickers were browser-native selects, so they looked and behaved differently from Studio's other dropdowns. They now use the shared Radix `Select`: the same trigger, dropdown and keyboard behaviour. In the object list, typing an object's leading letters jumps to it.
+
+What they set is unchanged. Each option makes Explain send the same request as before: an object sends its name, an operation sends its name, and "Select an object…" leaves Explain disabled until an object is picked. Re-picking the current option changes nothing. Each picker keeps the accessible name its label gave the native select.
+
+One display change: when the object the panel holds is not one of the package's objects, the object picker now shows that object. The native select showed "Select an object…" instead, while Explain still asked about the held object.
+
+Unchanged: without a package's object list the object is still a free-text input, and the user picker, the record selector and the explain request itself are untouched.
+
+**Clause-②: no.** No published face moves: `AccessExplainPanel` takes the same props, the package entry exports the same names, and no i18n key is added. What moves is the panel's own markup, described above.
@@ -0,0 +1,213 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * *Explain access* picks its object and its operation with the shared `Select`
+ * (objectui#11865).
+ *
+ * The request form picked the object (a package's objects, plus "select an
+ * object") and the operation with browser-native selects, beside the shared
+ * Radix `Select` the rest of Studio picks with. The card asks for one control
+ * for one kind of choice, surface by surface; this suite covers this panel's
+ * two pickers.
+ *
+ * What is pinned:
+ *   - each picker IS the primitive (a Radix combobox trigger), keeps the name
+ *     its `<label htmlFor>` gave the native control, and no native select is
+ *     left;
+ *   - every option of both pickers sets what the native control set, read
+ *     back as the explain request the panel then sends: the JSON body, or a
+ *     disabled Explain button for "select an object" (the object is `''`);
+ *   - re-picking the current option sets nothing;
+ *   - an object the package does not list is what the object trigger shows;
+ *   - the keyboard alone opens a picker and selects.
+ *
+ * Not pinned, because the panel has none: a disabled or read-only state. The
+ * panel asks a question and writes no metadata, so a read-only package
+ * renders the same form (objectui#11781 has no reach here).
+ *
+ * DIRECTION, observed against the native controls: every pin here is red
+ * there, because each one opens the primitive's listbox or reads its trigger.
+ * What makes the request pins guards of "the conversion changed nothing the
+ * form sends" is the literal each compares against: a `change` event on the
+ * pre-conversion panel's native control, followed by Explain, sent that same
+ * body, read once on that component.
+ */
+
+import '@testing-library/jest-dom/vitest';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { cleanup, fireEvent, render, screen, waitFor, within } from '@testing-library/react';
+
+const fetchSpy = vi.fn();
+// The package's objects, as the metadata client lists them; unsorted, as a
+// server may send them. A `mock` prefix so the hoisted factory may close over it.
+const mockObjectList = [
+  { item: { name: 'showcase_task' } },
+  { item: { name: 'showcase_account', label: 'Account' } },
+  { item: { name: 'showcase_project', label: 'showcase_project' } },
+];
+// One client for every render, so the panel's list effect runs once per open.
+const mockClient = { list: async () => mockObjectList };
+
+vi.mock('@object-ui/auth', async (importOriginal) => ({
+  ...(await importOriginal<Record<string, unknown>>()),
+  createAuthenticatedFetch: () => fetchSpy,
+}));
+vi.mock('@object-ui/react', async (importOriginal) => ({
+  ...(await importOriginal<Record<string, unknown>>()),
+  useAdapter: () => ({ find: vi.fn(async () => []) }),
+}));
+vi.mock('./useMetadata', () => ({
+  useMetadataClient: () => mockClient,
+}));
+// The record and user pickers have their own coverage.
+vi.mock('@object-ui/fields', async (importOriginal) => ({
+  ...(await importOriginal<typeof import('@object-ui/fields')>()),
+  RecordPickerDialog: () => null,
+}));
+
+import { AccessExplainPanel } from './AccessExplainPanel';
+
+afterEach(() => {
+  cleanup();
+  fetchSpy.mockReset();
+});
+
+const DECISION = {
+  allowed: true,
+  object: 'showcase_task',
+  operation: 'read',
+  principal: { userId: 'u_1', positions: [], permissionSets: [] },
+  layers: [{ layer: 'object_crud', verdict: 'grants', detail: 'granted', contributors: [] }],
+};
+
+/**
+ * Mount the panel scoped to a package, starting on `defaultObject` (`null`: on
+ * no object), and wait for the object picker to replace the free-text input.
+ */
+async function mount(defaultObject: string | null = 'showcase_task'): Promise<void> {
+  render(
+    <AccessExplainPanel
+      open
+      onOpenChange={() => {}}
+      packageId="com.example.showcase"
+      defaultObject={defaultObject ?? undefined}
+    />,
+  );
+  await waitFor(() => expect(screen.getByLabelText('Object')).toHaveAttribute('role', 'combobox'));
+}
+
+const trigger = (name: 'Object' | 'Operation') => screen.getByRole('combobox', { name });
+
+/** Open a picker from the keyboard and return the options it lists, in order. */
+async function openPicker(name: 'Object' | 'Operation'): Promise<HTMLElement[]> {
+  fireEvent.keyDown(trigger(name), { key: 'ArrowDown' });
+  const listbox = await screen.findByRole('listbox');
+  return within(listbox).getAllByRole('option');
+}
+
+async function pick(name: 'Object' | 'Operation', label: string): Promise<void> {
+  const options = await openPicker(name);
+  const option = options.find((o) => o.textContent === label);
+  if (!option) throw new Error(`${name} lists no "${label}": ${options.map((o) => o.textContent).join(' | ')}`);
+  fireEvent.click(option);
+  await waitFor(() => expect(screen.queryByRole('listbox')).toBeNull());
+}
+
+/** What Explain sends now: the request body, or `DISABLED` when the button cannot be pressed. */
+async function explainBody(): Promise<string> {
+  const button = screen.getByRole('button', { name: /explain$/i });
+  if ((button as HTMLButtonElement).disabled) return 'DISABLED';
+  fetchSpy.mockResolvedValue({ ok: true, status: 200, statusText: '', json: async () => DECISION });
+  fireEvent.click(button);
+  await screen.findByTestId('explain-verdict');
+  expect(fetchSpy).toHaveBeenCalledTimes(1);
+  return String(fetchSpy.mock.calls[0][1].body);
+}
+
+describe('Explain access pickers are the shared Select (objectui#11865)', () => {
+  it('renders each picker as the Radix combobox trigger, named by its label, with no native select left', async () => {
+    await mount();
+    expect(document.querySelector('select')).toBeNull();
+
+    for (const [name, id, shown] of [
+      ['Object', 'explain-object', 'showcase_task'],
+      ['Operation', 'explain-operation', 'Read'],
+    ] as const) {
+      const el = trigger(name);
+      expect(el.tagName).toBe('BUTTON');
+      expect(el).toHaveAttribute('id', id);
+      expect(el).toHaveTextContent(shown);
+    }
+  });
+
+  it('opens on "select an object" when nothing is chosen, and Explain waits for an object', async () => {
+    await mount(null);
+    expect(trigger('Object')).toHaveTextContent('Select an object…');
+    expect(await explainBody()).toBe('DISABLED');
+  });
+});
+
+/**
+ * [picker, option label, what Explain sends after the pick]. The panel starts
+ * on `showcase_task` / `Read`, so the `showcase_task` and `Read` rows re-pick
+ * the current option, and set nothing.
+ */
+const PICKS: ReadonlyArray<readonly ['Object' | 'Operation', string, string]> = [
+  ['Object', 'Select an object…', 'DISABLED'],
+  ['Object', 'Account (showcase_account)', '{"object":"showcase_account","operation":"read"}'],
+  ['Object', 'showcase_project', '{"object":"showcase_project","operation":"read"}'],
+  ['Object', 'showcase_task', '{"object":"showcase_task","operation":"read"}'],
+  ['Operation', 'Read', '{"object":"showcase_task","operation":"read"}'],
+  ['Operation', 'Create', '{"object":"showcase_task","operation":"create"}'],
+  ['Operation', 'Update', '{"object":"showcase_task","operation":"update"}'],
+  ['Operation', 'Delete', '{"object":"showcase_task","operation":"delete"}'],
+  ['Operation', 'Transfer', '{"object":"showcase_task","operation":"transfer"}'],
+  ['Operation', 'Restore', '{"object":"showcase_task","operation":"restore"}'],
+  ['Operation', 'Purge', '{"object":"showcase_task","operation":"purge"}'],
+];
+
+describe('every option sets what the native control set', () => {
+  it('the table covers every option of both pickers, in the order each lists them', async () => {
+    for (const name of ['Object', 'Operation'] as const) {
+      await mount();
+      const listed = (await openPicker(name)).map((o) => o.textContent);
+      expect(listed, name).toEqual(PICKS.filter(([p]) => p === name).map(([, label]) => label));
+      cleanup();
+    }
+  });
+
+  it.each(PICKS.map((row) => [`${row[0]} → ${row[1]}`, ...row] as const))('%s', async (_name, name, label, sent) => {
+    await mount();
+    await pick(name, label);
+    expect(trigger(name)).toHaveTextContent(label);
+    expect(await explainBody()).toBe(sent);
+  });
+});
+
+describe('an object the package does not list is what the trigger shows', () => {
+  it('shown, listed first, and re-picking it sets nothing', async () => {
+    await mount('crm_lead');
+    // The native control showed "Select an object…" here, while Explain asked about crm_lead.
+    expect(trigger('Object')).toHaveTextContent('crm_lead');
+    const listed = (await openPicker('Object')).map((o) => o.textContent);
+    expect(listed).toEqual(['crm_lead', 'Select an object…', 'Account (showcase_account)', 'showcase_project', 'showcase_task']);
+    fireEvent.click(screen.getAllByRole('option')[0]);
+    await waitFor(() => expect(screen.queryByRole('listbox')).toBeNull());
+    expect(await explainBody()).toBe('{"object":"crm_lead","operation":"read"}');
+  });
+});
+
+describe('the keyboard alone picks', () => {
+  it.each([
+    ['Object', 'showcase_project', '{"object":"showcase_project","operation":"read"}'],
+    ['Operation', 'Delete', '{"object":"showcase_task","operation":"delete"}'],
+  ] as const)('%s: Enter opens it and Enter on an option selects it', async (name, label, sent) => {
+    await mount();
+    fireEvent.keyDown(trigger(name), { key: 'Enter' });
+    const listbox = await screen.findByRole('listbox');
+    fireEvent.keyDown(within(listbox).getByRole('option', { name: label }), { key: 'Enter' });
+    await waitFor(() => expect(screen.queryByRole('listbox')).toBeNull());
+    expect(trigger(name)).toHaveTextContent(label);
+    expect(await explainBody()).toBe(sent);
+  });
+});
@@ -201,17 +201,21 @@ describe('AccessExplainPanel (ADR-0090 D6)', () => {
     ];
     render(<AccessExplainPanel open onOpenChange={() => {}} packageId="com.example.showcase" />);
 
-    // The object field swaps from a free-text input to a <select> once loaded.
-    await waitFor(() => expect(screen.getByLabelText('Object').tagName).toBe('SELECT'));
+    // The object field swaps from a free-text input to the shared Select's
+    // trigger once loaded (objectui#11865).
+    await waitFor(() => expect(screen.getByLabelText('Object')).toHaveAttribute('role', 'combobox'));
     const objectField = screen.getByLabelText('Object');
-    expect(within(objectField).getByRole('option', { name: 'Account (showcase_account)' })).toBeInTheDocument();
-    expect(within(objectField).getByRole('option', { name: 'showcase_task' })).toBeInTheDocument();
+    fireEvent.keyDown(objectField, { key: 'ArrowDown' });
+    const listbox = await screen.findByRole('listbox');
+    expect(within(listbox).getByRole('option', { name: 'Account (showcase_account)' })).toBeInTheDocument();
+    expect(within(listbox).getByRole('option', { name: 'showcase_task' })).toBeInTheDocument();
     // The misleading free-text placeholder example is gone.
     expect(screen.queryByPlaceholderText(/crm_lead/)).toBeNull();
 
     // Selecting an object and explaining posts that object.
     fetchSpy.mockResolvedValue(jsonResponse(200, DECISION));
-    fireEvent.change(objectField, { target: { value: 'showcase_account' } });
+    fireEvent.click(within(listbox).getByRole('option', { name: 'Account (showcase_account)' }));
+    await waitFor(() => expect(screen.queryByRole('listbox')).toBeNull());
     fireEvent.click(screen.getByRole('button', { name: /explain$/i }));
     await waitFor(() => expect(fetchSpy).toHaveBeenCalled());
     const body = JSON.parse(String((fetchSpy.mock.calls[0]?.[1] as any)?.body ?? '{}'));