diff --git a/server/im_http.go b/server/im_http.go
index 85f8adf..b8894a6 100644
--- a/server/im_http.go
+++ b/server/im_http.go
@@ -407,8 +407,8 @@ type imMessageRevisionRequest struct {
 
 type imFavoritesBatchCreateRequest struct {
 	Messages []struct {
-		Topic string `json:"topic"`
-		Seq   int64  `json:"seq,string"`
+		Topic string       `json:"topic"`
+		Seq   imForwardSeq `json:"seq"`
 	} `json:"messages"`
 }
 
@@ -3557,27 +3557,28 @@ func serveIMFavoriteBatchCreate(wrt http.ResponseWriter, req *http.Request) {
 	failed := make([]map[string]any, 0)
 	for _, src := range body.Messages {
 		sourceTopic, sourceOK := normalizeIMFavoriteSourceTopic(principal.Uid, src.Topic)
-		if !sourceOK || src.Seq <= 0 {
-			failed = append(failed, map[string]any{"topic": src.Topic, "seq": src.Seq, "reason": imReasonMalformedRequest})
+		seq := int64(src.Seq)
+		if !sourceOK || seq <= 0 {
+			failed = append(failed, map[string]any{"topic": src.Topic, "seq": seq, "reason": imReasonMalformedRequest})
 			continue
 		}
 		if err := requireTopicReader(principal, sourceTopic); err != nil {
-			failed = append(failed, map[string]any{"topic": sourceTopic, "seq": src.Seq, "reason": relationErrorReason(err)})
+			failed = append(failed, map[string]any{"topic": sourceTopic, "seq": seq, "reason": relationErrorReason(err)})
 			continue
 		}
-		msg, err := store.Messages.GetOne(principal.TenantID, sourceTopic, src.Seq)
+		msg, err := store.Messages.GetOne(principal.TenantID, sourceTopic, seq)
 		if err != nil {
-			failed = append(failed, map[string]any{"topic": sourceTopic, "seq": src.Seq, "reason": relationErrorReason(err)})
+			failed = append(failed, map[string]any{"topic": sourceTopic, "seq": seq, "reason": relationErrorReason(err)})
 			continue
 		}
-		idempotencyKey := favoriteItemIdempotencyKey(req.Header.Get("Idempotency-Key"), sourceTopic, src.Seq)
+		idempotencyKey := favoriteItemIdempotencyKey(req.Header.Get("Idempotency-Key"), sourceTopic, seq)
 		fav := &types.FavoriteItem{
 			TenantID:       principal.TenantID,
 			FavoriteID:     "fav_" + store.Store.GetUidString(),
 			UserID:         principal.Uid,
 			ItemType:       imMessageType(msg),
 			SourceTopic:    sourceTopic,
-			SourceSeq:      src.Seq,
+			SourceSeq:      seq,
 			Snapshot:       favoriteSnapshot(msg),
 			AttachmentRefs: favoriteAttachmentRefs(msg),
 			Availability:   messageAvailability(*msg),
@@ -3588,7 +3589,7 @@ func serveIMFavoriteBatchCreate(wrt http.ResponseWriter, req *http.Request) {
 		}
 		item, err := store.Favorites.Create(principal.TenantID, fav)
 		if err != nil {
-			failed = append(failed, map[string]any{"topic": src.Topic, "seq": src.Seq, "reason": relationErrorReason(err)})
+			failed = append(failed, map[string]any{"topic": src.Topic, "seq": seq, "reason": relationErrorReason(err)})
 			continue
 		}
 		if item.FavoriteID == fav.FavoriteID {
diff --git a/server/im_http_test.go b/server/im_http_test.go
index 14c6955..8dde05f 100644
--- a/server/im_http_test.go
+++ b/server/im_http_test.go
@@ -4929,6 +4929,63 @@ func TestServeIMFavoriteBatchCreateCountsExisting(t *testing.T) {
 	}
 }
 
+func TestServeIMFavoriteBatchCreateAcceptsNumericSeq(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+	mockStore := expectIMBearer(t, ctrl, "token-1", 7, 42)
+	mockStore.EXPECT().GetUidString().Return("new-fav")
+
+	oldFavorites := store.Favorites
+	oldSubs := store.Subs
+	oldMessages := store.Messages
+	now := time.Date(2026, 8, 13, 9, 0, 0, 0, time.UTC)
+	favorites := &testFavoritesStore{}
+	subs := mock_store.NewMockSubsPersistenceInterface(ctrl)
+	messages := mock_store.NewMockMessagesPersistenceInterface(ctrl)
+	store.Favorites = favorites
+	store.Subs = subs
+	store.Messages = messages
+	t.Cleanup(func() {
+		store.Favorites = oldFavorites
+		store.Subs = oldSubs
+		store.Messages = oldMessages
+	})
+
+	subs.EXPECT().Get(types.TenantID(7), "grpAlpha", types.Uid(42), false).Return(&types.Subscription{
+		TenantID:  7,
+		User:      types.Uid(42).String(),
+		Topic:     "grpAlpha",
+		ModeWant:  types.ModeCPublic,
+		ModeGiven: types.ModeCPublic,
+	}, nil)
+	messages.EXPECT().GetOne(types.TenantID(7), "grpAlpha", int64(3)).Return(&types.Message{
+		TenantID: 7,
+		Topic:    "grpAlpha",
+		SeqId:    3,
+		From:     types.Uid(42).String(),
+		Head:     types.KVMap{"type": "text"},
+		Content:  map[string]any{"text": "hello"},
+		ObjHeader: types.ObjHeader{
+			CreatedAt: now,
+		},
+	}, nil)
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/im/favorites/batch", bytes.NewBufferString(`{"messages":[{"topic":"grpAlpha","seq":3}]}`))
+	req.Header.Set("Authorization", "Bearer token-1")
+	rec := httptest.NewRecorder()
+	serveIMFavoriteResource(rec, req)
+	if rec.Code != http.StatusOK {
+		t.Fatalf("create status: got %d body=%s", rec.Code, rec.Body.String())
+	}
+	data := decodeIMHTTPResponse(t, rec).Data.(map[string]any)
+	if data["created_count"].(float64) != 1 || data["existing_count"].(float64) != 0 {
+		t.Fatalf("unexpected favorite counts: %#v", data)
+	}
+	if favorites.created == nil || favorites.created.SourceSeq != 3 {
+		t.Fatalf("favorite source seq was not saved: %#v", favorites.created)
+	}
+}
+
 func TestFavoriteItemIdempotencyKeyIncludesMessageIdentity(t *testing.T) {
 	first := favoriteItemIdempotencyKey("same-key", "grpAlpha", 1)
 	second := favoriteItemIdempotencyKey("same-key", "grpAlpha", 2)