diff --git a/cmd/worker/workers/notice.go b/cmd/worker/workers/notice.go
index c8e6c32..dc069a9 100644
--- a/cmd/worker/workers/notice.go
+++ b/cmd/worker/workers/notice.go
@@ -575,10 +575,16 @@ func (w *NoticeWorker) ToTender(n *notice.Notice) (*tender.Tender, error) {
 	return t, nil
 }
 
-// resolveExistingTender finds the tender that this notice should update, preferring the procedure-level
-// ContractFolderID (so follow-up notices like a Result for an earlier Competition notice merge into the
-// same tender), then UBL ProcurementProject/ID (merges per-lot CAN/CN notices), then NoticePublicationID.
+// resolveExistingTender finds the tender that this notice should update. TED ContractNoticeID uniquely
+// identifies the notice document; try it first so we never open a second tender row for the same notice.
+// Then procedure-level ContractFolderID (follow-up notices merge), UBL ProcurementProject/ID (per-lot),
+// then NoticePublicationID.
 func (w *NoticeWorker) resolveExistingTender(ctx context.Context, n *notice.Notice) *tender.Tender {
+	if strings.TrimSpace(n.ContractNoticeID) != "" {
+		if t, err := w.TenderRepo.GetByContractNoticeID(ctx, n.ContractNoticeID); err == nil && t != nil {
+			return t
+		}
+	}
 	if strings.TrimSpace(n.ContractFolderID) != "" {
 		if t, err := w.TenderRepo.GetByContractFolderID(ctx, n.ContractFolderID); err == nil && t != nil {
 			return t
@@ -998,7 +1004,7 @@ func (w *NoticeWorker) persistTender(ctx context.Context, t *tender.Tender, n *n
 		lastErr = err
 
 		// Another goroutine inserted the same procedure/publication first: merge into the winner row.
-		if isDuplicateKeyError(err) && (isDuplicateTenderBusinessKeyError(err) || isDuplicateContractFolderIDKeyError(err) || isDuplicateProcurementProjectIDKeyError(err)) {
+		if isDuplicateKeyError(err) && (isDuplicateTenderBusinessKeyError(err) || isDuplicateContractNoticeIDKeyError(err) || isDuplicateContractFolderIDKeyError(err) || isDuplicateProcurementProjectIDKeyError(err)) {
 			tMerged, convErr := w.ToTender(n)
 			if convErr != nil {
 				return convErr
@@ -1062,6 +1068,13 @@ func isDuplicateTenderBusinessKeyError(err error) bool {
 	return strings.Contains(msg, "notice_publication_id")
 }
 
+func isDuplicateContractNoticeIDKeyError(err error) bool {
+	if err == nil {
+		return false
+	}
+	return strings.Contains(err.Error(), "contract_notice_id")
+}
+
 func isDuplicateContractFolderIDKeyError(err error) bool {
 	if err == nil {
 		return false
diff --git a/internal/tender/repository.go b/internal/tender/repository.go
index 41e940e..474f8d9 100644
--- a/internal/tender/repository.go
+++ b/internal/tender/repository.go
@@ -54,6 +54,9 @@ func NewRepository(mongoManager *orm.ConnectionManager, logger logger.Logger) Te
 		*orm.CreateUniqueIndex("tender_id_idx", bson.D{{Key: "tender_id", Value: 1}}),
 		*orm.NewIndex("project_name_idx", bson.D{{Key: "project_name", Value: 1}}),
 		*orm.NewIndex("contract_notice_id_idx", bson.D{{Key: "contract_notice_id", Value: 1}}),
+		// One tender row per TED ContractNoticeID when present (parallel ingest / lookup gaps).
+		*orm.CreateUniqueIndex("contract_notice_id_unique", bson.D{{Key: "contract_notice_id", Value: 1}}).
+			WithPartialFilterExpression(bson.M{"contract_notice_id": bson.M{"$type": "string", "$ne": ""}}),
 		*orm.NewIndex("contract_folder_id_idx", bson.D{{Key: "contract_folder_id", Value: 1}}),
 		// One tender row per TED publication / procedure when ids are present (prevents parallel worker races).
 		*orm.CreateUniqueIndex("notice_publication_id_unique", bson.D{{Key: "notice_publication_id", Value: 1}}).