diff --git a/backend/internal/service/gateway_forward_as_chat_completions.go b/backend/internal/service/gateway_forward_as_chat_completions.go
index 32d38cf40d..0f6611c142 100644
--- a/backend/internal/service/gateway_forward_as_chat_completions.go
+++ b/backend/internal/service/gateway_forward_as_chat_completions.go
@@ -418,6 +418,15 @@ func (s *GatewayService) handleCCStreamingFromAnthropic(
 	}
 
 	processAnthropicEvent := func(event *apicompat.AnthropicStreamEvent) bool {
+		if event == nil {
+			return false
+		}
+		// Drop Anthropic keepalive pings before OpenAI conversion:
+		// leaking `event: ping` frames crashes OpenAI-stream clients.
+		// Error events must still forward — they carry upstream failures.
+		if event.Type == "ping" {
+			return false
+		}
 		if firstChunk {
 			firstChunk = false
 			ms := int(time.Since(startTime).Milliseconds())