diff --git a/domains/games/apis/one_d4/src/main/java/com/muchq/games/one_d4/worker/IndexWorker.java b/domains/games/apis/one_d4/src/main/java/com/muchq/games/one_d4/worker/IndexWorker.java
index 991c1cb0..a1698b19 100644
--- a/domains/games/apis/one_d4/src/main/java/com/muchq/games/one_d4/worker/IndexWorker.java
+++ b/domains/games/apis/one_d4/src/main/java/com/muchq/games/one_d4/worker/IndexWorker.java
@@ -214,6 +214,7 @@ private void flushBatch(
       Map<String, Map<Motif, List<GameFeatures.MotifOccurrence>>> occurrencesBatch) {
     if (featureBatch.isEmpty()) return;
     gameFeatureStore.insertBatch(featureBatch);
+    gameFeatureStore.deleteOccurrencesByGameUrls(new ArrayList<>(occurrencesBatch.keySet()));
     gameFeatureStore.insertOccurrencesBatch(occurrencesBatch);
     featureBatch.clear();
     occurrencesBatch.clear();
diff --git a/domains/games/apis/one_d4/src/test/java/com/muchq/games/one_d4/db/GameFeatureDaoTest.java b/domains/games/apis/one_d4/src/test/java/com/muchq/games/one_d4/db/GameFeatureDaoTest.java
index e88f3c6e..0815625b 100644
--- a/domains/games/apis/one_d4/src/test/java/com/muchq/games/one_d4/db/GameFeatureDaoTest.java
+++ b/domains/games/apis/one_d4/src/test/java/com/muchq/games/one_d4/db/GameFeatureDaoTest.java
@@ -572,6 +572,29 @@ public void query_paginatesStablyWhenPlayedAtIsEqual() {
     assertThat(page2.get(0).gameUrl()).isEqualTo("https://chess.com/game/zzz-last");
   }
 
+  @Test
+  public void deleteOccurrencesByGameUrls_thenReinsert_doesNotDuplicate() {
+    // Regression test: re-indexing a partial month must not accumulate duplicate occurrences.
+    // The fix is in IndexWorker.flushBatch: delete occurrences for each game_url before inserting.
+    String gameUrl = "https://chess.com/game/reindex-dedup";
+    dao.insertBatch(List.of(createGame(gameUrl)));
+
+    GameFeatures.MotifOccurrence pin =
+        new GameFeatures.MotifOccurrence(
+            5, 3, "white", "Pin on c6", null, "Bb5", "nc6", false, false, "ABSOLUTE");
+    Map<String, Map<Motif, List<GameFeatures.MotifOccurrence>>> occurrences =
+        Map.of(gameUrl, Map.of(Motif.PIN, List.of(pin)));
+
+    // First index run
+    dao.insertOccurrencesBatch(occurrences);
+    // Simulate re-index: delete then re-insert (what flushBatch now does)
+    dao.deleteOccurrencesByGameUrls(List.of(gameUrl));
+    dao.insertOccurrencesBatch(occurrences);
+
+    Map<String, Map<String, List<OccurrenceRow>>> result = dao.queryOccurrences(List.of(gameUrl));
+    assertThat(result.get(gameUrl).get("pin")).hasSize(1);
+  }
+
   private GameFeature createGame(String url) {
     return new GameFeature(
         null,