diff --git a/web/scripts/test-menu-switch.mjs b/web/scripts/test-menu-switch.mjs
new file mode 100644
index 0000000..886a475
--- /dev/null
+++ b/web/scripts/test-menu-switch.mjs
@@ -0,0 +1,92 @@
+// Regression for cross-menu data leaks. All catalog responses are fictional;
+// no network calls or patient data are used.
+import assert from 'node:assert/strict';
+import { parseHTML } from 'linkedom';
+import { createServer } from 'vite';
+
+const { window } = parseHTML('<html><body><div id="root"></div></body></html>');
+Object.assign(globalThis, { window, document: window.document, HTMLElement: window.HTMLElement, IS_REACT_ACT_ENVIRONMENT: true });
+window.location = new URL('https://menu-test.invalid/');
+document.oninput = null;
+const { default: React, act } = await import('react');
+const { createRoot } = await import('react-dom/client');
+const { Simulate } = await import('react-dom/test-utils');
+const { MemoryRouter } = await import('react-router-dom');
+const vite = await createServer({ server: { middlewareMode: true, hmr: false }, appType: 'custom' });
+const { default: Header } = await vite.ssrLoadModule('/src/components/Header.jsx');
+const { api } = await vite.ssrLoadModule('/src/api.js');
+const { ApiDataProvider } = await vite.ssrLoadModule('/src/context/ApiData.jsx');
+const pending = [];
+for (const [method, kind] of [['services', 'services'], ['specialties', 'doctors'], ['priceSections', 'prices']]) {
+  api[method] = ({ signal }) => new Promise((resolve, reject) => pending.push({ kind, signal, resolve, reject }));
+}
+const container = document.getElementById('root');
+const root = createRoot(container);
+const prices = [{ id: 1, name: 'Тестовая консультация', slug: 'test-price', count: 411 }];
+const specialties = [{ id: 2, name: 'Тестовые педиатры', slug: 'test-kids', count: 3 }];
+const services = [{ id: 3, name: 'Тестовая услуга', path: 'test-service', children: [] }];
+const panel = () => container.querySelector('.mega');
+const panelText = () => panel()?.textContent || '';
+const links = () => [...(panel()?.querySelectorAll('.mega__item') || [])].map((link) => link.getAttribute('href'));
+const trigger = (title) => [...container.querySelectorAll('.nav__item')].find((node) => node.textContent === title);
+async function open(title, focus = false) {
+  await act(async () => Simulate[focus ? 'focus' : 'mouseEnter'](trigger(title)));
+  return pending.at(-1);
+}
+async function reply(request, data) { await act(async () => request.resolve({ data })); }
+async function render(initial = {}) {
+  await act(async () => root.render(React.createElement(MemoryRouter, {},
+    React.createElement(ApiDataProvider, { value: initial }, React.createElement(Header)))));
+}
+
+try {
+  await render();
+  const priceRequest = await open('Цены');
+  await reply(priceRequest, prices);
+  assert.match(panelText(), /411 услуг/);
+  const doctorRequest = await open('Врачи');
+  assert.equal(panel().getAttribute('aria-label'), 'Меню «Врачи»');
+  assert.deepEqual(links(), [], 'Price sections must disappear immediately when switching to doctors');
+  assert.match(panelText(), /Загружаем/);
+  assert.equal(priceRequest.signal.aborted, true, 'Previous menu request is cancelled on switch');
+  await reply(doctorRequest, specialties);
+  assert.match(panelText(), /3 врача/);
+  assert.deepEqual(links(), ['/company/staff/test-kids/']);
+  assert.doesNotMatch(panelText(), /411|Тестовая консультация/);
+
+  const delayedPrice = await open('Цены');
+  assert.deepEqual(links(), [], 'Doctor specialties must not leak into the price menu');
+  const delayedServices = await open('Услуги');
+  const latestDoctor = await open('Врачи', true);
+  assert.equal(delayedPrice.signal.aborted, true);
+  assert.equal(delayedServices.signal.aborted, true);
+  await reply(latestDoctor, specialties);
+  // Deliberately resolve cancelled requests: even a transport ignoring AbortSignal
+  // must not overwrite a newly opened menu.
+  await reply(delayedPrice, prices);
+  await reply(delayedServices, services);
+  assert.deepEqual(links(), ['/company/staff/test-kids/']);
+  assert.match(panelText(), /3 врача/);
+  assert.doesNotMatch(panelText(), /411|Тестовая консультация|Тестовая услуга/);
+
+  const serviceRequest = await open('Услуги');
+  await reply(serviceRequest, services);
+  assert.deepEqual(links(), ['/services/test-service/']);
+  const failedPrice = await open('Цены');
+  await act(async () => failedPrice.reject(new Error('Fictional failure')));
+  assert.match(panelText(), /Не удалось загрузить список/);
+  assert.deepEqual(links(), [], 'An error must not leave links from another menu');
+
+  await act(async () => root.render(null));
+  await render({ specialties: { data: specialties, meta: {} } });
+  const initialPrices = await open('Цены');
+  await reply(initialPrices, prices);
+  const initialDoctors = await open('Врачи', true);
+  assert.deepEqual(links(), ['/company/staff/test-kids/'], 'SSR data belongs only to its own catalog');
+  assert.match(panelText(), /3 врача/);
+  await reply(initialDoctors, specialties);
+  console.log('PASS: hover/focus menu switching, delayed replies, cancellation, errors, and SSR data isolation');
+} finally {
+  await act(async () => root.unmount());
+  await vite.close();
+}
diff --git a/web/src/components/Header.jsx b/web/src/components/Header.jsx
index aa2c9b7..e3f5256 100644
--- a/web/src/components/Header.jsx
+++ b/web/src/components/Header.jsx
@@ -115,7 +115,9 @@ export default function Header() {
 
         {openMenu && (
           <div className="header__mega">
-            <MegaMenu menu={openMenu} onNavigate={() => setOpenMenu(null)} />
+            {/* Каталоги имеют разную структуру: при смене меню сбрасываем
+                данные и отменяем запрос предыдущего, не меняя лишь заголовок. */}
+            <MegaMenu key={openMenu} menu={openMenu} onNavigate={() => setOpenMenu(null)} />
           </div>
         )}
       </div>