diff --git a/api/oss/src/core/evaluations/service.py b/api/oss/src/core/evaluations/service.py
index 4aa211180..9e24f3208 100644
--- a/api/oss/src/core/evaluations/service.py
+++ b/api/oss/src/core/evaluations/service.py
@@ -1338,6 +1338,12 @@ async def create(
             log.info("[EVAL] [failure] missing simple evaluation data")
             return None
 
+        if evaluation.flags.is_live and not evaluation.data.query_steps:
+            log.info(
+                "[EVAL] [failure] missing query for live evaluation (query_steps required)"
+            )
+            return None
+
         # ----------------------------------------------------------------------
         log.info("[EVAL] [create]")
         log.info("[EVAL] [scope]       ", project_id=project_id, user_id=user_id)
diff --git a/web/oss/src/components/pages/evaluations/onlineEvaluation/OnlineEvaluationDrawer.tsx b/web/oss/src/components/pages/evaluations/onlineEvaluation/OnlineEvaluationDrawer.tsx
index 4bbb698d4..258391228 100644
--- a/web/oss/src/components/pages/evaluations/onlineEvaluation/OnlineEvaluationDrawer.tsx
+++ b/web/oss/src/components/pages/evaluations/onlineEvaluation/OnlineEvaluationDrawer.tsx
@@ -289,7 +289,10 @@ const OnlineEvaluationDrawer = ({open, onClose, onCreate}: OnlineEvaluationDrawe
             const queryResponse = await createSimpleQuery({query: queryPayload})
             const queryId = queryResponse.query?.id
             if (!queryId) {
-                throw new Error("Unable to create query for online evaluation.")
+                message.error(
+                    "Unable to create the query required for live evaluation. Please add at least one query filter and try again.",
+                )
+                return
             }
 
             const revisionResponse = await retrieveQueryRevision({
@@ -297,7 +300,10 @@ const OnlineEvaluationDrawer = ({open, onClose, onCreate}: OnlineEvaluationDrawe
             })
             const queryRevisionId = revisionResponse.query_revision?.id
             if (!queryRevisionId) {
-                throw new Error("Unable to resolve query revision for online evaluation.")
+                message.error(
+                    "Unable to resolve the query revision required for live evaluation. Please try again.",
+                )
+                return
             }
 
             // Prefer preview evaluator artifact id; fall back to selected config id if preview not available