Make restart reconnect persistent

tests/integration_smoke.rs

@@ -2338,6 +2338,72 @@ fn session_survives_server_restart_same_shell_and_screen() {
     );
 }
 
+#[test]
+fn implicit_session_survives_server_restart_for_same_ticket_holder() {
+    let dir = tempfile::tempdir().unwrap();
+    let sessions_dir = dir.path().join("sessions");
+    let port = free_udp_port();
+    let config = write_persistent_server_config(&dir, port);
+    let session = protocol::generate_implicit_session_name();
+
+    let mut server = start_server(&dir, &config);
+    let (socket, bootstrap, ok) = direct_attach_session(&config, port, "read-write", &session);
+    let key = bootstrap.session_key;
+    type_line(
+        &socket,
+        port,
+        &ok,
+        &key,
+        2,
+        "export IMPLICIT_MARK=implicit_restart_42\n",
+    );
+    let _ = collect_frame_text(&socket, &key, 1000);
+    thread::sleep(Duration::from_secs(3));
+
+    let shell_pid_before = holder_shell_pid(&sessions_dir, &session);
+    assert!(
+        shell_pid_before.is_some(),
+        "implicit sessions should get a persistent holder when persistence is enabled"
+    );
+
+    let _ = server.kill();
+    let _ = server.wait();
+    thread::sleep(Duration::from_millis(300));
+
+    let pid = shell_pid_before.unwrap();
+    assert!(
+        unsafe { libc::kill(pid, 0) } == 0,
+        "implicit session shell pid {pid} must survive server restart"
+    );
+
+    let mut server = start_server(&dir, &config);
+    let (socket2, bootstrap2, ok2) = direct_attach_session(&config, port, "read-write", &session);
+    let key2 = bootstrap2.session_key;
+    type_line(
+        &socket2,
+        port,
+        &ok2,
+        &key2,
+        2,
+        "printf 'IMPLICIT_MARK=%s\\n' \"$IMPLICIT_MARK\"\n",
+    );
+    let post = collect_frame_text(&socket2, &key2, 2000);
+    let shell_pid_after = holder_shell_pid(&sessions_dir, &session);
+
+    let _ = server.kill();
+    let _ = server.wait();
+    kill_holder(&sessions_dir, &session);
+
+    assert_eq!(
+        shell_pid_after, shell_pid_before,
+        "implicit session should re-adopt the same shell pid"
+    );
+    assert!(
+        post.contains("IMPLICIT_MARK=implicit_restart_42"),
+        "implicit session state must survive restart, got {post:?}"
+    );
+}
+
 #[test]
 fn multiple_persistent_named_sessions_survive_restart_independently() {
     let dir = tempfile::tempdir().unwrap();