From 7511e4de59aee7e2bd6f912b138c263de01e05e2 Mon Sep 17 00:00:00 2001
From: MHJoy99 <75517252+MHJoy99@users.noreply.github.com>
Date: Sun, 13 Sep 2026 12:09:28 +0600
Subject: [PATCH] fix(streaming): drop Anthropic ping keepalives before OpenAI
 conversion

Upstream Anthropic keepalive frames (event: ping) leaked into OpenAI
Chat Completions SSE streams, crashing strict clients (Cursor, Hermes,
OpenAI SDKs) on unexpected event types. Error events still forward.

Fixes #5203
---
 .../service/gateway_forward_as_chat_completions.go       | 9 +++++++++
 1 file changed, 9 insertions(+)

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())