diff --git a/apps/web/src/app/(portal)/admin/modules/grants/grants-matrix.test.tsx b/apps/web/src/app/(portal)/admin/modules/grants/grants-matrix.test.tsx
index 83a96bd..d19ead5 100644
--- a/apps/web/src/app/(portal)/admin/modules/grants/grants-matrix.test.tsx
+++ b/apps/web/src/app/(portal)/admin/modules/grants/grants-matrix.test.tsx
@@ -18,6 +18,7 @@ const messages: Record<string, Record<string, unknown>> = {
     adminNote:
       'ADMIN und SUPER_ADMIN haben immer Zugriff auf alle aktiven Module — diese Matrix betrifft nur die Rolle USER.',
     saveError: 'Freigabe konnte nicht gespeichert werden. Bitte erneut versuchen.',
+    noSearchResults: 'Kein Treffer für "{search}" — weder bei den Modulen noch bei den Gruppen.',
   },
   'admin.groups.grants': {
     matrixCheckboxLabel: '{module} für Gruppe {group} {granted, select, true {freigeben} other {entziehen}}',
@@ -93,6 +94,7 @@ const mockMatrix = {
   groups: [
     { id: 'g1', name: 'Alle Benutzer' },
     { id: 'g2', name: 'Buchhaltung' },
+    { id: 'g3', name: 'Claude_VT', internalName: 'Vertrieb' },
   ],
   grants: [{ moduleId: 'm1', groupId: 'g1' }],
 };
@@ -203,6 +205,102 @@ describe('AdminModuleGrantsPage (Permission-Matrix)', () => {
     expect(screen.getByText('DKV Flotte')).toBeInTheDocument();
   });
 
+  it('a module-name search leaves all group columns standing (WINDOWS #14)', async () => {
+    vi.stubGlobal(
+      'fetch',
+      vi.fn(() => Promise.resolve({ ok: true, json: () => Promise.resolve(mockMatrix) })),
+    );
+
+    render(<AdminModuleGrantsPage />);
+
+    await waitFor(() => {
+      expect(screen.getByText('DKV Flotte')).toBeInTheDocument();
+    });
+
+    const searchInput = screen.getByPlaceholderText('Module oder Gruppen durchsuchen...');
+    await userEvent.type(searchInput, 'Buchhaltung');
+
+    await waitFor(() => {
+      expect(screen.getByText('Ausschreibungs-Radar')).toBeInTheDocument();
+    });
+    expect(screen.getByText('DKV Flotte')).toBeInTheDocument();
+    expect(screen.queryByText('Alle Benutzer')).not.toBeInTheDocument();
+    expect(screen.getAllByRole('checkbox').length).toBeGreaterThan(0);
+  });
+
+  it('a group-name search leaves all module rows standing (WINDOWS #14)', async () => {
+    vi.stubGlobal(
+      'fetch',
+      vi.fn(() => Promise.resolve({ ok: true, json: () => Promise.resolve(mockMatrix) })),
+    );
+
+    render(<AdminModuleGrantsPage />);
+
+    await waitFor(() => {
+      expect(screen.getByText('DKV Flotte')).toBeInTheDocument();
+    });
+
+    const searchInput = screen.getByPlaceholderText('Module oder Gruppen durchsuchen...');
+    await userEvent.type(searchInput, 'Flotte');
+
+    await waitFor(() => {
+      expect(screen.getByText('Alle Benutzer')).toBeInTheDocument();
+    });
+    expect(screen.getByText('Buchhaltung')).toBeInTheDocument();
+    expect(screen.queryByText('Ausschreibungs-Radar')).not.toBeInTheDocument();
+  });
+
+  it('finds an imported group by both internal and AD name (WINDOWS #6c regression)', async () => {
+    vi.stubGlobal(
+      'fetch',
+      vi.fn(() => Promise.resolve({ ok: true, json: () => Promise.resolve(mockMatrix) })),
+    );
+
+    render(<AdminModuleGrantsPage />);
+
+    await waitFor(() => {
+      expect(screen.getByText('DKV Flotte')).toBeInTheDocument();
+    });
+
+    const searchInput = screen.getByPlaceholderText('Module oder Gruppen durchsuchen...');
+
+    await userEvent.type(searchInput, 'Vertrieb');
+    await waitFor(() => {
+      expect(screen.getByText('Vertrieb')).toBeInTheDocument();
+    });
+    expect(screen.getByText('Ausschreibungs-Radar')).toBeInTheDocument();
+    expect(screen.getByText('DKV Flotte')).toBeInTheDocument();
+
+    await userEvent.clear(searchInput);
+    await userEvent.type(searchInput, 'Claude_VT');
+    await waitFor(() => {
+      expect(screen.getByText('Vertrieb')).toBeInTheDocument();
+    });
+    expect(screen.getByText('Ausschreibungs-Radar')).toBeInTheDocument();
+    expect(screen.getByText('DKV Flotte')).toBeInTheDocument();
+  });
+
+  it('shows a visible message when the search term matches neither modules nor groups', async () => {
+    vi.stubGlobal(
+      'fetch',
+      vi.fn(() => Promise.resolve({ ok: true, json: () => Promise.resolve(mockMatrix) })),
+    );
+
+    render(<AdminModuleGrantsPage />);
+
+    await waitFor(() => {
+      expect(screen.getByText('DKV Flotte')).toBeInTheDocument();
+    });
+
+    const searchInput = screen.getByPlaceholderText('Module oder Gruppen durchsuchen...');
+    await userEvent.type(searchInput, 'zzz');
+
+    await waitFor(() => {
+      expect(screen.getByText(/Kein Treffer für "zzz"/)).toBeInTheDocument();
+    });
+    expect(screen.queryAllByRole('checkbox')).toHaveLength(0);
+  });
+
   it('gives every matrix checkbox an aria-label', async () => {
     vi.stubGlobal(
       'fetch',
diff --git a/apps/web/src/app/(portal)/admin/modules/grants/page.tsx b/apps/web/src/app/(portal)/admin/modules/grants/page.tsx
index a271cb9..0891d57 100644
--- a/apps/web/src/app/(portal)/admin/modules/grants/page.tsx
+++ b/apps/web/src/app/(portal)/admin/modules/grants/page.tsx
@@ -133,19 +133,33 @@ export default function AdminModuleGrantsPage() {
   const searchLower = search.trim().toLowerCase();
   const matches = (text: string) => searchLower === '' || text.toLowerCase().includes(searchLower);
 
-  const filteredModules = useMemo(
-    () => modules.filter((m) => matches(m.name)),
-    // eslint-disable-next-line react-hooks/exhaustive-deps
-    [modules, searchLower],
-  );
-  const filteredGroups = useMemo(
+  // Both axes are searched independently, then combined with the following
+  // semantics (WINDOWS #14): a term that hits only one axis must not empty
+  // the other axis, or no clickable cell ever remains. See <behavior> in
+  // 260909-ab3-PLAN.md for the full truth table.
+  const { filteredModules, filteredGroups, noMatch } = useMemo(() => {
+    if (searchLower === '') {
+      return { filteredModules: modules, filteredGroups: groups, noMatch: false };
+    }
+
+    const moduleHits = modules.filter((m) => matches(m.name));
     // Matches both the display name (internalName ?? name) and the stored
     // AD name — a search for either the internal or the AD-original name
     // must find the group (D-04).
-    () => groups.filter((g) => matches(g.internalName ?? g.name) || matches(g.name)),
+    const groupHits = groups.filter((g) => matches(g.internalName ?? g.name) || matches(g.name));
+
+    if (moduleHits.length === 0 && groupHits.length === 0) {
+      return { filteredModules: [], filteredGroups: [], noMatch: true };
+    }
+    if (moduleHits.length > 0 && groupHits.length === 0) {
+      return { filteredModules: moduleHits, filteredGroups: groups, noMatch: false };
+    }
+    if (groupHits.length > 0 && moduleHits.length === 0) {
+      return { filteredModules: modules, filteredGroups: groupHits, noMatch: false };
+    }
+    return { filteredModules: moduleHits, filteredGroups: groupHits, noMatch: false };
     // eslint-disable-next-line react-hooks/exhaustive-deps
-    [groups, searchLower],
-  );
+  }, [modules, groups, searchLower]);
 
   const groupedModules = useMemo(() => {
     const result: { category: string; mods: Module[] }[] = [];
@@ -202,6 +216,11 @@ export default function AdminModuleGrantsPage() {
             className="flex h-9 w-full max-w-sm rounded-md border border-input bg-background px-3 py-1 text-sm"
           />
 
+          {noMatch ? (
+            <div className="rounded-md border border-border bg-card p-6 text-center">
+              <p className="text-sm text-muted-foreground">{t('noSearchResults', { search })}</p>
+            </div>
+          ) : (
           <div className="overflow-x-auto overflow-y-auto max-h-[70vh] rounded-md border border-border">
             <table className="w-full text-sm border-collapse">
               <thead>
@@ -274,6 +293,7 @@ export default function AdminModuleGrantsPage() {
               </tbody>
             </table>
           </div>
+          )}
 
           <p className="text-xs text-muted-foreground">{t('adminNote')}</p>
         </>
diff --git a/apps/web/src/messages/de.json b/apps/web/src/messages/de.json
index 06a41b4..a7b5f97 100644
--- a/apps/web/src/messages/de.json
+++ b/apps/web/src/messages/de.json
@@ -457,7 +457,8 @@
       "emptyModules": "Es sind noch keine Module für diesen Mandanten aktiviert. Aktiviere zuerst ein Modul unter Module.",
       "emptyModulesLink": "Zu Module",
       "adminNote": "ADMIN und SUPER_ADMIN haben immer Zugriff auf alle aktiven Module — diese Matrix betrifft nur die Rolle USER.",
-      "saveError": "Freigabe konnte nicht gespeichert werden. Bitte erneut versuchen."
+      "saveError": "Freigabe konnte nicht gespeichert werden. Bitte erneut versuchen.",
+      "noSearchResults": "Kein Treffer für „{search}\" — weder bei den Modulen noch bei den Gruppen."
     },
     "activationDialog": {
       "title": "Modul aktivieren: {module}",
diff --git a/apps/web/src/messages/en.json b/apps/web/src/messages/en.json
index 536f921..a4529a4 100644
--- a/apps/web/src/messages/en.json
+++ b/apps/web/src/messages/en.json
@@ -457,7 +457,8 @@
       "emptyModules": "No modules are activated for this tenant yet. Activate a module under Modules first.",
       "emptyModulesLink": "Go to Modules",
       "adminNote": "ADMIN and SUPER_ADMIN always have access to all active modules — this matrix only applies to the USER role.",
-      "saveError": "Could not save grant. Please try again."
+      "saveError": "Could not save grant. Please try again.",
+      "noSearchResults": "No match for \"{search}\" — neither in the modules nor in the groups."
     },
     "activationDialog": {
       "title": "Activate Module: {module}",