diff --git a/internal/proxy/impl.go b/internal/proxy/impl.go
index 2d138ce2ce..087d126b63 100644
--- a/internal/proxy/impl.go
+++ b/internal/proxy/impl.go
@@ -3431,6 +3431,16 @@ func (node *Proxy) handleIfSearchByPK(ctx context.Context, request *milvuspb.Sea
 		return nil // Not search by PK, do nothing
 	}
 
+	// Check for duplicate IDs (fail fast before query)
+	inputIDsCount := typeutil.GetSizeOfIDs(ids)
+	checker, err := typeutil.NewIDsChecker(ids)
+	if err != nil {
+		return err
+	}
+	if checker.Size() != inputIDsCount {
+		return merr.WrapErrParameterInvalidMsg("duplicate IDs found in search request")
+	}
+
 	// Get collection schema for validation and plan building
 	collectionInfo, err := globalMetaCache.GetCollectionInfo(ctx,
 		request.GetDbName(), request.GetCollectionName(), 0)
@@ -3438,11 +3448,19 @@ func (node *Proxy) handleIfSearchByPK(ctx context.Context, request *milvuspb.Sea
 		return err
 	}
 
-	// Validate that anns_field is provided
+	// Get anns_field from search params, or infer from schema if only one vector field exists
 	annsFieldName, err := funcutil.GetAttrByKeyFromRepeatedKV(AnnsFieldKey, request.SearchParams)
 	if err != nil || annsFieldName == "" {
-		return merr.WrapErrParameterInvalid("valid anns_field in search_params", "missing",
-			"anns_field is required for search by IDs")
+		vecFields := typeutil.GetVectorFieldSchemas(collectionInfo.schema.CollectionSchema)
+		if len(vecFields) == 0 {
+			return merr.WrapErrParameterInvalid("valid anns_field in search_params", "missing",
+				"no vector field found in schema")
+		}
+		if enableMultipleVectorFields && len(vecFields) > 1 {
+			return merr.WrapErrParameterInvalid("valid anns_field in search_params", "missing",
+				"multiple vector fields exist, please specify anns_field in search_params")
+		}
+		annsFieldName = vecFields[0].Name
 	}
 
 	annField := typeutil.GetFieldByName(collectionInfo.schema.CollectionSchema, annsFieldName)
@@ -3527,7 +3545,6 @@ func (node *Proxy) handleIfSearchByPK(ctx context.Context, request *milvuspb.Sea
 	}
 
 	// Check if the returned pk count matches the input IDs count
-	inputIDsCount := typeutil.GetSizeOfIDs(ids)
 	returnedPKCount := typeutil.GetPKSize(pkFieldData)
 	if returnedPKCount != inputIDsCount {
 		// Find which IDs are missing