diff --git a/api/schedule/clean_workflow_runs_task.py b/api/schedule/clean_workflow_runs_task.py
index b59dc7f823..0f34c534ab 100644
--- a/api/schedule/clean_workflow_runs_task.py
+++ b/api/schedule/clean_workflow_runs_task.py
@@ -4,10 +4,8 @@ import app
 from configs import dify_config
 from services.clear_free_plan_expired_workflow_run_logs import WorkflowRunCleanup
 
-CLEANUP_QUEUE = "retention"
 
-
-@app.celery.task(queue=CLEANUP_QUEUE)
+@app.celery.task(queue="retention")
 def clean_workflow_runs_task() -> None:
     """
     Scheduled cleanup for workflow runs and related records (sandbox tenants only).
diff --git a/api/services/clear_free_plan_expired_workflow_run_logs.py b/api/services/clear_free_plan_expired_workflow_run_logs.py
index c3fbd6600a..0589bb4868 100644
--- a/api/services/clear_free_plan_expired_workflow_run_logs.py
+++ b/api/services/clear_free_plan_expired_workflow_run_logs.py
@@ -39,6 +39,9 @@ class WorkflowRunCleanup:
         if self.window_start and self.window_end <= self.window_start:
             raise ValueError("end_before must be greater than start_after.")
 
+        if batch_size <= 0:
+            raise ValueError("batch_size must be greater than 0.")
+
         self.batch_size = batch_size
         self.billing_cache: dict[str, TenantPlanInfo | None] = {}
         self.dry_run = dry_run