@@ -0,0 +1,89 @@
+/**
+ * ObjectUI
+ * Copyright (c) 2024-present ObjectStack Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * objectstack#27241 — the host slot at the end of `page:header`'s action row.
+ * The console's record view hands in the reader's panel switches through
+ * `PageHeaderTrailingContext`; the row draws them as its LAST segment, after
+ * the `⋯` menu, behind a vertical hairline, and wraps inside the header
+ * (`max-w-full`) rather than running past a narrow page. No slot, no change:
+ * the row is what it was.
+ */
+
+import { describe, it, expect, afterEach } from 'vitest';
+import { render, cleanup } from '@testing-library/react';
+import { ComponentRegistry } from '@object-ui/core';
+import { ActionProvider, RecordContextProvider } from '@object-ui/react';
+import { PageHeaderActions, PageHeaderTrailingContext } from '../index';
+
+const RECORD = { id: 'lead-1', name: 'Ada' };
+const SYSTEM = [
+  { name: 'sys_edit', label: 'Edit', type: 'script', locations: ['record_header'], order: 100, onClick: () => {} },
+  { name: 'sys_delete', label: 'Delete', type: 'script', locations: ['record_header'], order: 120, component: 'action:menu', onClick: () => {} },
+];
+
+function inRecord(node: React.ReactNode, headerSystemActions: unknown[] = SYSTEM) {
+  return (
+    <ActionProvider>
+      <RecordContextProvider
+        objectName="lead"
+        recordId={RECORD.id}
+        data={RECORD}
+        objectSchema={{ name: 'lead', label: 'Lead' }}
+        headerSystemActions={headerSystemActions as never}
+      >
+        {node}
+      </RecordContextProvider>
+    </ActionProvider>
+  );
+}
+
+const SWITCHES = <div data-testid="switches">switches</div>;
+
+afterEach(() => cleanup());
+
+describe('page:header — the trailing host slot (objectstack#27241)', () => {
+  it('draws the slot as the toolbar’s last segment, after ⋯, behind a vertical hairline', () => {
+    const PageHeader = ComponentRegistry.get('page:header')!;
+    const { container, getByTestId } = render(
+      inRecord(
+        <PageHeaderTrailingContext.Provider value={SWITCHES}>
+          <PageHeader schema={{ type: 'page:header' }} />
+        </PageHeaderTrailingContext.Provider>,
+      ),
+    );
+    const toolbar = container.querySelector('[role="toolbar"]')!;
+    const trailing = toolbar.lastElementChild!;
+    expect(trailing.hasAttribute('data-page-header-trailing')).toBe(true);
+    expect(trailing.contains(getByTestId('switches'))).toBe(true);
+    const rule = trailing.querySelector('[role="separator"]')!;
+    expect(rule.getAttribute('aria-orientation')).toBe('vertical');
+    // The ⋯ trigger comes before the segment.
+    const more = toolbar.querySelector('[aria-label="More actions"]')!;
+    expect(more.compareDocumentPosition(trailing) & Node.DOCUMENT_POSITION_FOLLOWING).toBeTruthy();
+    // The row wraps inside the header instead of overflowing it.
+    expect(toolbar.className.split(/\s+/)).toEqual(expect.arrayContaining(['flex-wrap', 'shrink-0', 'max-w-full']));
+  });
+
+  it('with no action the row is the slot alone, with no hairline', () => {
+    const { container, getByTestId } = render(inRecord(<PageHeaderActions trailing={SWITCHES} />, []));
+    const toolbar = container.querySelector('[role="toolbar"]')!;
+    expect(toolbar.contains(getByTestId('switches'))).toBe(true);
+    expect(toolbar.querySelector('[role="separator"]')).toBeNull();
+  });
+
+  it('no slot: no trailing segment, and the empty slot still stands in for an empty row', () => {
+    const PageHeader = ComponentRegistry.get('page:header')!;
+    const withActions = render(inRecord(<PageHeader schema={{ type: 'page:header' }} />));
+    expect(withActions.container.querySelector('[data-page-header-trailing]')).toBeNull();
+    cleanup();
+    const empty = render(inRecord(<PageHeaderActions emptySlot={<span data-testid="empty" />} />, []));
+    expect(empty.container.querySelector('[role="toolbar"]')).toBeNull();
+    expect(empty.getByTestId('empty')).toBeTruthy();
+  });
+});