diff --git a/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java b/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java
index b4762502..d25cf03c 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java
@@ -839,11 +839,12 @@ public class DocumentService {
             // Undated documents (null documentDate) must order last regardless of
             // direction — Postgres puts NULLs FIRST on ASC by default, which would
             // surface the undated pile at the top with no explanation (issue #668).
-            // The createdAt tiebreaker gives a stable total order when every row is
+            // The title tiebreaker gives a stable total order when every row is
             // null-dated (the "Nur undatierte" filter), so pagination is deterministic.
+            // title is @Column(nullable=false), so it is always present.
             return Sort.by(
                     new Sort.Order(direction, "documentDate").nullsLast(),
-                    Sort.Order.asc("createdAt"));
+                    Sort.Order.asc("title"));
         }
         // SENDER and RECEIVER are sorted in-memory before this method is called
         return switch (sort) {
diff --git a/backend/src/test/java/org/raddatz/familienarchiv/document/DocumentServiceTest.java b/backend/src/test/java/org/raddatz/familienarchiv/document/DocumentServiceTest.java
index b0f16574..04b84fba 100644
--- a/backend/src/test/java/org/raddatz/familienarchiv/document/DocumentServiceTest.java
+++ b/backend/src/test/java/org/raddatz/familienarchiv/document/DocumentServiceTest.java
@@ -1463,6 +1463,11 @@ class DocumentServiceTest {
         assertThat(dateOrder).isNotNull();
         assertThat(dateOrder.getDirection()).isEqualTo(Sort.Direction.DESC);
         assertThat(dateOrder.getNullHandling()).isEqualTo(Sort.NullHandling.NULLS_LAST);
+        // Owner-decided tiebreaker (#668): title ASC, not createdAt.
+        Sort.Order tiebreak = captor.getValue().getSort().getOrderFor("title");
+        assertThat(tiebreak).isNotNull();
+        assertThat(tiebreak.getDirection()).isEqualTo(Sort.Direction.ASC);
+        assertThat(captor.getValue().getSort().getOrderFor("createdAt")).isNull();
     }
 
     @Test
@@ -1481,6 +1486,11 @@ class DocumentServiceTest {
         assertThat(dateOrder).isNotNull();
         assertThat(dateOrder.getDirection()).isEqualTo(Sort.Direction.ASC);
         assertThat(dateOrder.getNullHandling()).isEqualTo(Sort.NullHandling.NULLS_LAST);
+        // Owner-decided tiebreaker (#668): title ASC, not createdAt.
+        Sort.Order tiebreak = captor.getValue().getSort().getOrderFor("title");
+        assertThat(tiebreak).isNotNull();
+        assertThat(tiebreak.getDirection()).isEqualTo(Sort.Direction.ASC);
+        assertThat(captor.getValue().getSort().getOrderFor("createdAt")).isNull();
     }
 
     @Test
diff --git a/backend/src/test/java/org/raddatz/familienarchiv/document/UndatedDocumentOrderingIntegrationTest.java b/backend/src/test/java/org/raddatz/familienarchiv/document/UndatedDocumentOrderingIntegrationTest.java
index e7e50d74..e1eeddc7 100644
--- a/backend/src/test/java/org/raddatz/familienarchiv/document/UndatedDocumentOrderingIntegrationTest.java
+++ b/backend/src/test/java/org/raddatz/familienarchiv/document/UndatedDocumentOrderingIntegrationTest.java
@@ -63,6 +63,51 @@ class UndatedDocumentOrderingIntegrationTest {
         assertThat(result.get(3).getDocumentDate()).isNull();
     }
 
+    @Test
+    void sameDate_tiebreaksByTitleAsc_notCreatedAt_forBothDirections() throws Exception {
+        // Owner decision (#668): equal-date rows tie-break by title ASC, NOT
+        // createdAt. Insert two same-date docs so that createdAt order (insertion
+        // order) is the OPPOSITE of title order: the first-saved doc gets the later
+        // title ("zzz-first"), the second-saved doc gets the earlier title
+        // ("aaa-second"). If the tiebreaker were still createdAt-asc the first-saved
+        // row would lead; because it is title-asc the "aaa-second" row must lead —
+        // and it must lead in BOTH ASC and DESC date directions, since the date is
+        // equal so only the title tiebreaker decides.
+        //
+        // The Sort under test is built by the PRODUCTION resolveSort(DATE, dir) (via
+        // reflection — it is private), not hand-rolled here, so this test proves the
+        // real Postgres ordering that production emits, on real same-date rows.
+        documentRepository.deleteAll();
+        LocalDate sameDate = LocalDate.of(1920, 3, 3);
+        save("zzz-first", sameDate);   // saved first  → earlier createdAt
+        save("aaa-second", sameDate);  // saved second → later createdAt
+
+        List<Document> asc = documentRepository.findAll(resolveProductionSort("ASC"));
+        assertThat(asc).extracting(Document::getTitle)
+                .containsExactly("aaa-second", "zzz-first");
+
+        List<Document> desc = documentRepository.findAll(resolveProductionSort("DESC"));
+        assertThat(desc).extracting(Document::getTitle)
+                .containsExactly("aaa-second", "zzz-first");
+    }
+
+    /**
+     * Invokes the production {@link DocumentService#resolveSort(DocumentSort, String)}
+     * for the DATE sort so the integration assertions exercise the real tiebreaker
+     * choice rather than a sort hand-built in the test.
+     */
+    private Sort resolveProductionSort(String dir) throws Exception {
+        // resolveSort is a pure function of its arguments (uses no instance state), so a
+        // bean instance with null collaborators is sufficient to exercise it.
+        var ctor = DocumentService.class.getDeclaredConstructors()[0];
+        ctor.setAccessible(true);
+        Object[] args = new Object[ctor.getParameterCount()];
+        DocumentService service = (DocumentService) ctor.newInstance(args);
+        var m = DocumentService.class.getDeclaredMethod("resolveSort", DocumentSort.class, String.class);
+        m.setAccessible(true);
+        return (Sort) m.invoke(service, DocumentSort.DATE, dir);
+    }
+
     @Test
     void undatedOnly_returnsExactlyTheNullDatedRows() {
         List<Document> result = documentRepository.findAll(undatedOnly(true));