diff --git a/backend/internal/service/gateway_anthropic_apikey_passthrough_test.go b/backend/internal/service/gateway_anthropic_apikey_passthrough_test.go
index 428231ee..87cfc4f8 100644
--- a/backend/internal/service/gateway_anthropic_apikey_passthrough_test.go
+++ b/backend/internal/service/gateway_anthropic_apikey_passthrough_test.go
@@ -1138,6 +1138,99 @@ func TestGatewayService_AnthropicAPIKeyPassthrough_StreamingDataIntervalTimeout(
 	require.False(t, result.clientDisconnect)
 }
 
+func TestGatewayService_AnthropicAPIKeyPassthrough_StreamingSendsKeepaliveDuringIdle(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/messages", nil)
+
+	svc := &GatewayService{
+		cfg: &config.Config{
+			Gateway: config.GatewayConfig{
+				StreamKeepaliveInterval: 1,
+				MaxLineSize:             defaultMaxLineSize,
+			},
+		},
+		rateLimitService: &RateLimitService{},
+	}
+
+	pr, pw := io.Pipe()
+	resp := &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}},
+		Body:       pr,
+	}
+
+	done := make(chan struct{})
+	go func() {
+		defer close(done)
+		time.Sleep(1200 * time.Millisecond)
+		_, _ = pw.Write([]byte(strings.Join([]string{
+			`data: {"type":"message_start","message":{"usage":{"input_tokens":3}}}`,
+			"",
+			`data: {"type":"message_delta","usage":{"output_tokens":2}}`,
+			"",
+			"data: [DONE]",
+			"",
+		}, "\n")))
+		_ = pw.Close()
+	}()
+
+	result, err := svc.handleStreamingResponseAnthropicAPIKeyPassthrough(context.Background(), resp, c, &Account{ID: 8}, time.Now(), "claude-3-7-sonnet-20250219")
+	_ = pr.Close()
+	<-done
+
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Contains(t, rec.Body.String(), "event: ping\ndata: {\"type\": \"ping\"}\n\n")
+	require.Contains(t, rec.Body.String(), "data: [DONE]")
+}
+
+func TestGatewayService_AnthropicAPIKeyPassthrough_StreamingKeepaliveDoesNotInterleavePartialEvent(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/messages", nil)
+
+	svc := &GatewayService{
+		cfg: &config.Config{
+			Gateway: config.GatewayConfig{
+				StreamKeepaliveInterval: 1,
+				MaxLineSize:             defaultMaxLineSize,
+			},
+		},
+		rateLimitService: &RateLimitService{},
+	}
+
+	pr, pw := io.Pipe()
+	resp := &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}},
+		Body:       pr,
+	}
+
+	done := make(chan struct{})
+	go func() {
+		defer close(done)
+		_, _ = pw.Write([]byte(`data: {"type":"message_start","message":{"usage":{"input_tokens":4}}}` + "\n"))
+		time.Sleep(1200 * time.Millisecond)
+		_, _ = pw.Write([]byte("\n"))
+		_, _ = pw.Write([]byte("data: [DONE]\n\n"))
+		_ = pw.Close()
+	}()
+
+	result, err := svc.handleStreamingResponseAnthropicAPIKeyPassthrough(context.Background(), resp, c, &Account{ID: 9}, time.Now(), "claude-3-7-sonnet-20250219")
+	_ = pr.Close()
+	<-done
+
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	body := rec.Body.String()
+	require.NotContains(t, body, `data: {"type":"message_start","message":{"usage":{"input_tokens":4}}}`+"\n"+"event: ping")
+	require.NotContains(t, body, "event: ping")
+	require.Contains(t, body, "data: [DONE]")
+}
+
 func TestGatewayService_AnthropicAPIKeyPassthrough_StreamingReadError(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 	rec := httptest.NewRecorder()
diff --git a/backend/internal/service/gateway_service.go b/backend/internal/service/gateway_service.go
index 6151d78e..b8cbf715 100644
--- a/backend/internal/service/gateway_service.go
+++ b/backend/internal/service/gateway_service.go
@@ -5357,6 +5357,22 @@ func (s *GatewayService) handleStreamingResponseAnthropicAPIKeyPassthrough(
 		intervalCh = intervalTicker.C
 	}
 
+	keepaliveInterval := time.Duration(0)
+	if s.cfg != nil && s.cfg.Gateway.StreamKeepaliveInterval > 0 {
+		keepaliveInterval = time.Duration(s.cfg.Gateway.StreamKeepaliveInterval) * time.Second
+	}
+	var keepaliveTicker *time.Ticker
+	if keepaliveInterval > 0 {
+		keepaliveTicker = time.NewTicker(keepaliveInterval)
+		defer keepaliveTicker.Stop()
+	}
+	var keepaliveCh <-chan time.Time
+	if keepaliveTicker != nil {
+		keepaliveCh = keepaliveTicker.C
+	}
+	lastDataAt := time.Now()
+	inPartialEvent := false
+
 	for {
 		select {
 		case ev, ok := <-events:
@@ -5422,6 +5438,10 @@ func (s *GatewayService) handleStreamingResponseAnthropicAPIKeyPassthrough(
 				} else if line == "" {
 					// 按 SSE 事件边界刷出，减少每行 flush 带来的 syscall 开销。
 					flusher.Flush()
+					lastDataAt = time.Now()
+					inPartialEvent = false
+				} else {
+					inPartialEvent = true
 				}
 			}
 
@@ -5438,6 +5458,21 @@ func (s *GatewayService) handleStreamingResponseAnthropicAPIKeyPassthrough(
 				s.rateLimitService.HandleStreamTimeout(ctx, account, model)
 			}
 			return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, fmt.Errorf("stream data interval timeout")
+
+		case <-keepaliveCh:
+			if clientDisconnected || inPartialEvent {
+				continue
+			}
+			if time.Since(lastDataAt) < keepaliveInterval {
+				continue
+			}
+			if _, err := fmt.Fprint(w, "event: ping\ndata: {\"type\": \"ping\"}\n\n"); err != nil {
+				clientDisconnected = true
+				logger.LegacyPrintf("service.gateway", "[Anthropic passthrough] Client disconnected during keepalive ping, continue draining upstream for usage: account=%d", account.ID)
+				continue
+			}
+			flusher.Flush()
+			lastDataAt = time.Now()
 		}
 	}
 }