diff --git a/backend/internal/service/gateway_service.go b/backend/internal/service/gateway_service.go
index b9bd992e..3a003bd2 100644
--- a/backend/internal/service/gateway_service.go
+++ b/backend/internal/service/gateway_service.go
@@ -5343,6 +5343,12 @@ func (s *GatewayService) handleStreamingResponseAnthropicAPIKeyPassthrough(
 					flusher.Flush()
 				}
 				if !sawTerminalEvent {
+					if clientDisconnected && streamInterval > 0 {
+						lastRead := time.Unix(0, atomic.LoadInt64(&lastReadAt))
+						if time.Since(lastRead) >= streamInterval {
+							return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: true}, fmt.Errorf("stream usage incomplete after timeout")
+						}
+					}
 					return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: clientDisconnected}, fmt.Errorf("stream usage incomplete: missing terminal event")
 				}
 				return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: clientDisconnected}, nil