diff --git a/api/core/repositories/sqlalchemy_workflow_execution_repository.py b/api/core/repositories/sqlalchemy_workflow_execution_repository.py
index e5ead9dc56..f82562a498 100644
--- a/api/core/repositories/sqlalchemy_workflow_execution_repository.py
+++ b/api/core/repositories/sqlalchemy_workflow_execution_repository.py
@@ -151,12 +151,17 @@ class SQLAlchemyWorkflowExecutionRepository(WorkflowExecutionRepository):
             existing = session.scalar(select(WorkflowRun).where(WorkflowRun.id == domain_model.id_))
             if not existing:
                 # For new records, get the next sequence number
-                stmt = select(func.max(WorkflowRun.sequence_number)).where(
-                    WorkflowRun.app_id == self._app_id,
-                    WorkflowRun.tenant_id == self._tenant_id,
+                # in case multiple executions are created concurrently, use for update
+                stmt = (
+                    select(func.coalesce(func.max(WorkflowRun.sequence_number), 0) + 1)
+                    .where(
+                        WorkflowRun.app_id == self._app_id,
+                        WorkflowRun.tenant_id == self._tenant_id,
+                    )
+                    .with_for_update()
                 )
-                max_sequence = session.scalar(stmt)
-                db_model.sequence_number = (max_sequence or 0) + 1
+                next_seq = session.scalar(stmt)
+                db_model.sequence_number = int(next_seq) if next_seq is not None else 1
             else:
                 # For updates, keep the existing sequence number
                 db_model.sequence_number = existing.sequence_number