diff --git a/frontend/src/lib/generated/api.ts b/frontend/src/lib/generated/api.ts
index 9c901d56..36c2996c 100644
--- a/frontend/src/lib/generated/api.ts
+++ b/frontend/src/lib/generated/api.ts
@@ -2471,6 +2471,8 @@ export interface components {
             pageSize: number;
             /** Format: int32 */
             totalPages: number;
+            /** Format: int64 */
+            undatedCount: number;
         };
         MatchOffset: {
             /** Format: int32 */
diff --git a/frontend/src/routes/SearchFilterBar.svelte b/frontend/src/routes/SearchFilterBar.svelte
index 344d6f26..5bec7245 100644
--- a/frontend/src/routes/SearchFilterBar.svelte
+++ b/frontend/src/routes/SearchFilterBar.svelte
@@ -16,6 +16,7 @@ let {
 	tagQ = $bindable(''),
 	tagOperator = $bindable<'AND' | 'OR'>('AND'),
 	undated = $bindable(false),
+	undatedCount = 0,
 	sort = $bindable('DATE'),
 	dir = $bindable('desc'),
 	showAdvanced = $bindable(false),
@@ -37,6 +38,7 @@ let {
 	tagQ?: string;
 	tagOperator?: 'AND' | 'OR';
 	undated?: boolean;
+	undatedCount?: number;
 	sort?: string;
 	dir?: string;
 	showAdvanced?: boolean;
@@ -275,6 +277,18 @@ $effect(() => {
 						{#if undated}✓{/if}
 					</span>
 					{m.docs_filter_undated_only()}
+					<!-- Global count of undated docs matching the current filter across ALL
+					     pages (not the page slice). Stays visible regardless of the toggle
+					     state so it advertises the triage backlog size (issue #668). -->
+					{#if undatedCount > 0}
+						<span
+							data-testid="undated-count"
+							class="inline-flex min-w-[1.5rem] items-center justify-center rounded-full px-1.5 py-0.5 text-[0.65rem] leading-none tabular-nums {undated
+								? 'bg-primary-fg/20 text-primary-fg'
+								: 'bg-line text-ink-2'}"
+							>{undatedCount}</span
+						>
+					{/if}
 				</button>
 			</div>
 		</div>
diff --git a/frontend/src/routes/SearchFilterBar.svelte.spec.ts b/frontend/src/routes/SearchFilterBar.svelte.spec.ts
index 11f4c32d..446cd046 100644
--- a/frontend/src/routes/SearchFilterBar.svelte.spec.ts
+++ b/frontend/src/routes/SearchFilterBar.svelte.spec.ts
@@ -162,6 +162,20 @@ describe('SearchFilterBar – undated-only toggle (#668)', () => {
 		await page.getByTestId('undated-only-toggle').click();
 		await expect.poll(() => onSearchImmediate.mock.calls.length).toBeGreaterThan(0);
 	});
+
+	it('shows the global undated count chip when undatedCount > 0', async () => {
+		// The count is the backend's global filtered total (#668), passed straight
+		// through — the chip must render it verbatim, not a page-derived number.
+		render(SearchFilterBar, { ...defaultProps, sort: 'DATE', dir: 'desc', undatedCount: 42 });
+		await openAdvanced();
+		await expect.element(page.getByTestId('undated-count')).toHaveTextContent('42');
+	});
+
+	it('hides the undated count chip when undatedCount is 0', async () => {
+		render(SearchFilterBar, { ...defaultProps, sort: 'DATE', dir: 'desc', undatedCount: 0 });
+		await openAdvanced();
+		await expect.element(page.getByTestId('undated-count')).not.toBeInTheDocument();
+	});
 });
 
 describe('SearchFilterBar – tagQ live filter', () => {
diff --git a/frontend/src/routes/documents/+page.server.ts b/frontend/src/routes/documents/+page.server.ts
index acd8f666..a4e2242b 100644
--- a/frontend/src/routes/documents/+page.server.ts
+++ b/frontend/src/routes/documents/+page.server.ts
@@ -85,6 +85,7 @@ export async function load({ url, fetch }) {
 			pageNumber: 0,
 			pageSize: PAGE_SIZE,
 			totalPages: 0,
+			undatedCount: 0,
 			q,
 			from,
 			to,
@@ -116,6 +117,8 @@ export async function load({ url, fetch }) {
 		pageNumber: result.data?.pageNumber ?? page,
 		pageSize: result.data?.pageSize ?? PAGE_SIZE,
 		totalPages: result.data?.totalPages ?? 0,
+		// Global undated count for the active filter, across all pages (issue #668).
+		undatedCount: result.data?.undatedCount ?? 0,
 		q,
 		from,
 		to,
diff --git a/frontend/src/routes/documents/+page.svelte b/frontend/src/routes/documents/+page.svelte
index eabfea8c..5006d9eb 100644
--- a/frontend/src/routes/documents/+page.svelte
+++ b/frontend/src/routes/documents/+page.svelte
@@ -268,6 +268,7 @@ $effect(() => {
 		bind:tagQ={tagQ}
 		bind:tagOperator={tagOperator}
 		bind:undated={undated}
+		undatedCount={data.undatedCount ?? 0}
 		initialSenderName={initialSenderName}
 		initialReceiverName={initialReceiverName}
 		navKey={navKey}
diff --git a/frontend/src/routes/documents/page.server.spec.ts b/frontend/src/routes/documents/page.server.spec.ts
index 69726562..c51eb3f0 100644
--- a/frontend/src/routes/documents/page.server.spec.ts
+++ b/frontend/src/routes/documents/page.server.spec.ts
@@ -225,6 +225,51 @@ describe('documents page load — search params', () => {
 		expect(result.totalElements).toBe(42);
 	});
 
+	it('forwards the global undatedCount from the search result (#668)', async () => {
+		// The backend returns the global undated total for the active filter across
+		// ALL pages; the loader must pass it straight through, not recompute it locally.
+		const mockGet = vi.fn().mockResolvedValue({
+			response: { ok: true, status: 200 },
+			data: {
+				items: [],
+				totalElements: 200,
+				pageNumber: 0,
+				pageSize: 50,
+				totalPages: 4,
+				undatedCount: 73
+			}
+		});
+		vi.mocked(createApiClient).mockReturnValue({ GET: mockGet } as ReturnType<
+			typeof createApiClient
+		>);
+
+		const result = await load({
+			url: makeUrl({ q: 'test' }),
+			request: new Request('http://localhost/documents'),
+			fetch: vi.fn() as unknown as typeof fetch
+		});
+
+		expect(result.undatedCount).toBe(73);
+	});
+
+	it('defaults undatedCount to 0 when the search result omits it', async () => {
+		const mockGet = vi.fn().mockResolvedValue({
+			response: { ok: true, status: 200 },
+			data: { items: [], totalElements: 0, pageNumber: 0, pageSize: 50, totalPages: 0 }
+		});
+		vi.mocked(createApiClient).mockReturnValue({ GET: mockGet } as ReturnType<
+			typeof createApiClient
+		>);
+
+		const result = await load({
+			url: makeUrl(),
+			request: new Request('http://localhost/documents'),
+			fetch: vi.fn() as unknown as typeof fetch
+		});
+
+		expect(result.undatedCount).toBe(0);
+	});
+
 	it('returns filter values in the result for pre-filling the UI', async () => {
 		const mockGet = vi.fn().mockResolvedValue({
 			response: { ok: true, status: 200 },