diff --git a/backend/internal/service/openai_gateway_response_handling.go b/backend/internal/service/openai_gateway_response_handling.go
index 95e5db3193..d4c8f723b6 100644
--- a/backend/internal/service/openai_gateway_response_handling.go
+++ b/backend/internal/service/openai_gateway_response_handling.go
@@ -687,8 +687,12 @@ func (s *OpenAIGatewayService) handleStreamingResponseWithReasoning(ctx context.
 			// OpenAI Responses streams that terminate with an empty
 			// response.completed (no output, no usage, no error, nothing sent
 			// to the client) are silent upstream refusals: fail over instead of
-			// recording a successful 0/0 usage turn (issue #5009).
-			if account != nil && account.Platform == PlatformOpenAI &&
+			// recording a successful 0/0 usage turn (issue #5009). Grok
+			// subscriptions behind vendor gateways show the same silent-refusal
+			// shape on /v1/responses (forwardGrokResponses reaches this same
+			// handler), so cover PlatformGrok too — the passthrough-path guard
+			// is already unconditional.
+			if account != nil && (account.Platform == PlatformOpenAI || account.Platform == PlatformGrok) &&
 				(eventType == "response.completed" || eventType == "response.done") &&
 				!sawFailedEvent && !responsesSemanticOutputSeen && !clientOutputStarted &&
 				openAIResponsesCompletedEventIsEmpty(dataBytes, usage) {