diff --git a/stores/__tests__/email-store-refresh-category-tab.test.ts b/stores/__tests__/email-store-refresh-category-tab.test.ts
new file mode 100644
index 000000000..5dc7b467d
--- /dev/null
+++ b/stores/__tests__/email-store-refresh-category-tab.test.ts
@@ -0,0 +1,81 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { useEmailStore } from '../email-store';
+import { useSettingsStore } from '../settings-store';
+import { useAuthStore } from '../auth-store';
+import { useMessageListTabsStore } from '../message-list-tabs-store';
+import type { Email, Mailbox } from '@/lib/jmap/types';
+import type { IJMAPClient } from '@/lib/jmap/client-interface';
+
+// #1264: refreshing the open folder re-queries it with the active category
+// tab's filter, as the first load and pagination do. Without it the refresh
+// merged other tabs' mail into the list and took it for new mail.
+
+const inbox = { id: 'inbox', role: 'inbox', isShared: false } as Mailbox;
+const RECEIPTS = { subject: 'receipt' };
+
+function email(id: string, receivedAt: string): Email {
+  return {
+    id, threadId: `thread-${id}`, mailboxIds: { inbox: true }, keywords: {},
+    subject: id, receivedAt, from: [{ email: 'sender@example.com' }], to: [],
+    preview: '', size: 1, hasAttachment: false,
+  } as Email;
+}
+
+function client(rows: Email[]) {
+  return {
+    getEmails: vi.fn(async () => ({ emails: rows, total: rows.length, hasMore: false, state: 's' })),
+    getThreads: vi.fn(async () => []),
+    getAccountId: () => 'me',
+  } as unknown as IJMAPClient;
+}
+
+describe('refreshing a folder with a category tab open (#1264)', () => {
+  beforeEach(() => {
+    useAuthStore.setState(useAuthStore.getInitialState());
+    useMessageListTabsStore.setState(useMessageListTabsStore.getInitialState());
+    useSettingsStore.setState({
+      emailsPerPage: 25, messageListOrder: [], messageListOrderScope: 'inbox',
+      notificationMutes: { accounts: [], mailboxes: {} },
+    });
+    useEmailStore.setState({
+      ...useEmailStore.getInitialState(),
+      selectedMailbox: 'inbox', mailboxes: [inbox],
+    });
+    useMessageListTabsStore.getState().registerTabs('receipts-plugin', {
+      tabs: [
+        { id: 'other', label: 'Inbox', order: 1 },
+        { id: 'receipts', label: 'Receipts', order: 2, query: RECEIPTS },
+      ],
+    });
+  });
+
+  it('queries the folder with the active tab filter', async () => {
+    useMessageListTabsStore.getState().setActiveTab('receipts', 'inbox');
+    const c = client([]);
+    await useEmailStore.getState().refreshCurrentMailbox(c);
+    expect(vi.mocked(c.getEmails).mock.calls[0][6]).toEqual(RECEIPTS);
+  });
+
+  it('queries the default tab as everything the other tabs leave out', async () => {
+    const c = client([]);
+    await useEmailStore.getState().refreshCurrentMailbox(c);
+    expect(vi.mocked(c.getEmails).mock.calls[0][6]).toEqual({ operator: 'NOT', conditions: [RECEIPTS] });
+  });
+
+  it('does not take mail from another tab for new mail', async () => {
+    useMessageListTabsStore.getState().setActiveTab('receipts', 'inbox');
+    const receipt = email('receipt', '2026-10-01T00:00:00Z');
+    useEmailStore.setState({ emails: [receipt], totalEmails: 1 });
+    // A server that honours the filter answers with the tab's own mail only.
+    const c = {
+      ...client([]),
+      getEmails: vi.fn(async (...args: unknown[]) => {
+        const rows = args[6] ? [receipt] : [email('newsletter', '2026-10-15T00:00:00Z'), receipt];
+        return { emails: rows, total: rows.length, hasMore: false, state: 's' };
+      }),
+    } as unknown as IJMAPClient;
+    await useEmailStore.getState().refreshCurrentMailbox(c);
+    expect(useEmailStore.getState().emails.map((e) => e.id)).toEqual(['receipt']);
+    expect(useEmailStore.getState().newEmailNotification).toBeNull();
+  });
+});
diff --git a/stores/email-store.ts b/stores/email-store.ts
index aecbea409..05df7885a 100644
--- a/stores/email-store.ts
+++ b/stores/email-store.ts
@@ -5189,7 +5189,10 @@ export const useEmailStore = create<EmailStore>((set, get) => ({
             windowSize = Math.min(Math.max(emailsPerPage, inOrder), effectiveClient.getMaxObjectsInGet());
             keepOpenThread = true;
           }
-          result = await effectiveClient.getEmails(jmapMailboxId, accountId, windowSize, 0, undefined, true, undefined, order);
+          // The open category tab filters the refresh like the first load and
+          // pagination, or other tabs' mail would merge into the list (#1264).
+          const categoryFilter = useMessageListTabsStore.getState().getCategoryFilter(mailbox?.role);
+          result = await effectiveClient.getEmails(jmapMailboxId, accountId, windowSize, 0, undefined, true, categoryFilter ?? undefined, order);
           // This page is the new delta-sync baseline for the folder; the
           // search / unified paths above cannot be delta-synced.
           syncAfterRefresh = result.state