diff --git a/agent/forward.go b/agent/forward.go
index f399b1e..d1fcd43 100644
--- a/agent/forward.go
+++ b/agent/forward.go
@@ -3,6 +3,7 @@ package agent
 import (
 	"io"
 	"net"
+	"time"
 )
 
 // handleData 处理节点主动打开的数据流：
@@ -35,6 +36,12 @@ func (a *Agent) handleData(stream net.Conn) {
 		return
 	}
 	defer conn.Close()
+	// agent↔目标段 TCP 保活: 目标假死(进程在但不响应/不发 FIN)时是
+	// 全链路唯一没有存活检测的段, 不开 keepalive 观看端会无限挂死画面
+	if tc, ok := conn.(*net.TCPConn); ok {
+		tc.SetKeepAlive(true)
+		tc.SetKeepAlivePeriod(5 * time.Second)
+	}
 
 	rf := NewFrame(FrameVersion, CmdTarget, f.StreamID())
 	_ = rf.Marshal(Ret{Code: 0, Msg: "ok"})
diff --git a/e2e/handshake_test.go b/e2e/handshake_test.go
index 9d4625a..8f19788 100644
--- a/e2e/handshake_test.go
+++ b/e2e/handshake_test.go
@@ -8,6 +8,7 @@ package e2e
 import (
 	"errors"
 	"fmt"
+	"io"
 	"net"
 	"strconv"
 	"testing"
@@ -134,3 +135,63 @@ func TestAgentDialTimeoutCutsViewer(t *testing.T) {
 
 	assertViewerCutBy(t, port, 3*time.Second)
 }
+
+// startCloseAfterEchoServer 回显一段即关闭的目标：模拟 tvnserver 进程退出。
+func startCloseAfterEchoServer(t *testing.T) string {
+	t.Helper()
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { l.Close() })
+	go func() {
+		for {
+			c, err := l.Accept()
+			if err != nil {
+				return
+			}
+			go func(c net.Conn) {
+				defer c.Close()
+				buf := make([]byte, 512)
+				n, _ := c.Read(buf)
+				if n > 0 {
+					c.Write(buf[:n]) // 回显一次随即断开
+				}
+			}(c)
+		}
+	}()
+	return l.Addr().String()
+}
+
+// TestTargetCloseCutsViewer 目标端→观看端断开同步：目标(如 tvnserver)关闭后,
+// 观看端必须在时限内被同步断开, 不允许残留悬挂连接。
+func TestTargetCloseCutsViewer(t *testing.T) {
+	n, a := startEnv(t)
+	target := startCloseAfterEchoServer(t)
+	_, port := mustRegister(t, n, a, target)
+
+	viewer, err := net.DialTimeout("tcp", net.JoinHostPort("127.0.0.1", strconv.Itoa(port)), 2*time.Second)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer viewer.Close()
+	_ = viewer.SetDeadline(time.Now().Add(3 * time.Second))
+	payload := []byte("probe")
+	if _, err := viewer.Write(payload); err != nil {
+		t.Fatal(err)
+	}
+	got := make([]byte, len(payload))
+	if _, err := io.ReadFull(viewer, got); err != nil {
+		t.Fatal(err)
+	}
+	// 回显已到, 目标随即关闭 → 观看端应读到 EOF/重置(而非超时)
+	buf := make([]byte, 16)
+	_, err = viewer.Read(buf)
+	if err == nil {
+		t.Fatal("目标已关闭, 观看端却读到数据")
+	}
+	var netErr net.Error
+	if errors.As(err, &netErr) && netErr.Timeout() {
+		t.Fatal("目标关闭 3s 内未同步断开观看端")
+	}
+}