diff --git a/backend/internal/service/openai_ws_forwarder_success_test.go b/backend/internal/service/openai_ws_forwarder_success_test.go
index e775104fa2..6923352d7d 100644
--- a/backend/internal/service/openai_ws_forwarder_success_test.go
+++ b/backend/internal/service/openai_ws_forwarder_success_test.go
@@ -804,6 +804,73 @@ func TestOpenAIGatewayService_Forward_WSv2_OAuthStoreFalseByDefault(t *testing.T
 	require.Equal(t, isolateOpenAIUpstreamSessionID(0, account, "conv-oauth-1"), captureDialer.lastHeaders.Get("conversation_id"))
 }
 
+func TestOpenAIGatewayService_Forward_WSv2_OAuthSanitizesInvalidNativeToolItemID(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/openai/v1/responses", nil)
+	c.Request.Header.Set("User-Agent", "codex_cli_rs/0.144.1")
+	groupID := int64(5662)
+	c.Set("api_key", &APIKey{GroupID: &groupID})
+
+	cfg := newOpenAIWSV2TestConfig()
+	cfg.Security.URLAllowlist.Enabled = false
+	cfg.Security.URLAllowlist.AllowInsecureHTTP = true
+	cfg.Gateway.OpenAIWS.MaxConnsPerAccount = 1
+	cfg.Gateway.OpenAIWS.MinIdlePerAccount = 0
+	cfg.Gateway.OpenAIWS.MaxIdlePerAccount = 1
+	cfg.Gateway.OpenAIWS.QueueLimitPerConn = 8
+	cfg.Gateway.OpenAIWS.DialTimeoutSeconds = 3
+	cfg.Gateway.OpenAIWS.ReadTimeoutSeconds = 3
+	cfg.Gateway.OpenAIWS.WriteTimeoutSeconds = 3
+
+	captureConn := &openAIWSCaptureConn{events: [][]byte{
+		[]byte(`{"type":"response.completed","response":{"id":"resp_oauth_tool_history","model":"gpt-5.6-sol","usage":{"input_tokens":1,"output_tokens":1}}}`),
+	}}
+	captureDialer := &openAIWSCaptureDialer{conn: captureConn}
+	pool := newOpenAIWSConnPool(cfg)
+	pool.setClientDialerForTest(captureDialer)
+
+	svc := &OpenAIGatewayService{
+		cfg:              cfg,
+		httpUpstream:     &httpUpstreamRecorder{},
+		cache:            &stubGatewayCache{},
+		openaiWSResolver: NewOpenAIWSProtocolResolver(cfg),
+		toolCorrector:    NewCodexToolCorrector(),
+		openaiWSPool:     pool,
+	}
+
+	account := &Account{
+		ID:          5662,
+		Name:        "openai-oauth-ws-tool-history",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeOAuth,
+		Status:      StatusActive,
+		Schedulable: true,
+		Concurrency: 1,
+		Credentials: map[string]any{"access_token": "test-oauth-token"},
+		Extra: map[string]any{
+			"responses_websockets_v2_enabled": true,
+		},
+	}
+
+	body := []byte(`{"model":"gpt-5.6-sol","stream":false,"instructions":"Continue the task.","input":[{"type":"custom_tool_call","id":"fc_hotfix_probe","call_id":"fc_hotfix","name":"exec","input":"pwd","status":"completed"},{"type":"custom_tool_call_output","call_id":"fc_hotfix","output":"done"}]}`)
+	result, err := svc.Forward(context.Background(), c, account, body)
+	require.NoError(t, err)
+	require.NotNil(t, result)
+
+	captureConn.mu.Lock()
+	requestPayload := cloneMapStringAny(captureConn.lastWrite)
+	captureConn.mu.Unlock()
+	requestJSON := requestToJSONString(requestPayload)
+	require.Equal(t, "response.create", gjson.Get(requestJSON, "type").String())
+	require.False(t, gjson.Get(requestJSON, "input.0.id").Exists(), "stale fc_* ID must not be replayed as a native custom_tool_call ID")
+	require.Equal(t, "ctc_hotfix", gjson.Get(requestJSON, "input.0.call_id").String())
+	require.Equal(t, "custom_tool_call_output", gjson.Get(requestJSON, "input.1.type").String())
+	require.Equal(t, "ctc_hotfix", gjson.Get(requestJSON, "input.1.call_id").String())
+}
+
 func TestOpenAIGatewayService_Forward_WSv2_OAuthOriginatorCompatibility(t *testing.T) {
 	gin.SetMode(gin.TestMode)