fix(app): stop probing the control plane while disconnected

VpnConnection._init() started a 30 s /health poll from the constructor
with no lifecycle gating, so it ran for the life of the app process -
backgrounded, and whether or not the user ever connected. The app is
excluded from its own tunnel, so those requests left in the clear. A
periodic request that fires while the user is deliberately not connected
is an avoidable fingerprint, and rule 60 already ruled probes out:
reachability is meant to be passive.

All it bought was the status dot before the first connect, and it got
that wrong in both directions - "Offline" on a transient resolver
failure against a server that was fine.

Reachability now comes from a session sync that succeeded. serverHealthy
is isConnected && hasSyncedOnce, so a green dot means a working session
rather than a check made beforehand; while disconnected the bar reads
"Ready" and claims nothing either way.

checkHealth() goes with it. Nothing calls it, and leaving a probe helper
in place invites its reuse.

Pinned in test/session_lifecycle_regression_test.dart so it cannot come
back as a tidy-up. flutter analyze clean, 10/10 tests pass.

Co-Authored-By: Claude Opus 5 <[email protected]>

CHANGELOG.md

@@ -5,6 +5,19 @@ Versions follow [semver](https://semver.org/): MAJOR.MINOR.PATCH
 
 ---
 
+## [Unreleased]
+
+### Removed
+- **The background server check while disconnected.** The app no longer contacts
+  the server every 30 seconds while you are not connected to it. Nothing about
+  the connected session changes.
+
+### Changed
+- **The status bar no longer guesses whether the server is up.** It reads
+  "Ready" while disconnected and shows "Online" once a session has synced, so a
+  green dot now means a session that is actually working rather than a
+  reachability check made beforehand.
+
 ## [3.3.8] — 2026-10-17
 
 ### Changed

lib/components/status_bar.dart

@@ -49,15 +49,14 @@ class StatusBar extends StatelessWidget {
       builder: (context, vpn, timer, _) {
         final isConnected = vpn.status == VpnStatus.connected;
         final isConnecting = vpn.status == VpnStatus.connecting;
-        final serverHealthy =
-            vpn.serverReachable || (isConnected && timer.hasSyncedOnce);
-        final sessionOrTunnelHealthy = timer.hasSyncedOnce || vpn.serverReachable;
+        // Rule 60: reachability is known only from a session sync that
+        // succeeded, never from a probe. While disconnected the app knows
+        // nothing about the server, so it claims nothing either way.
+        final serverHealthy = isConnected && timer.hasSyncedOnce;
 
         final statusLabel = isConnected
-            ? (sessionOrTunnelHealthy ? 'Online' : 'Syncing…')
-            : (isConnecting
-                ? 'Connecting…'
-                : (vpn.serverReachable ? 'Ready' : 'Offline'));
+            ? (timer.hasSyncedOnce ? 'Online' : 'Syncing…')
+            : (isConnecting ? 'Connecting…' : 'Ready');
 
         final detail = _detail(vpn, timer);
 

lib/logic/hivemind_service.dart

@@ -197,18 +197,6 @@ class HivemindService {
     throw Exception('Session not activated. Server callback may have timed out.');
   }
 
-  static Future<bool> checkHealth() async {
-    try {
-      final response = await controlGet(
-        _publicUrl('/health'),
-        timeout: const Duration(seconds: 3),
-      );
-      return response.statusCode == 200;
-    } catch (_) {
-      return false;
-    }
-  }
-
   static String newNonce() {
     final random = Random.secure();
     final high = random.nextInt(0x7FFFFFFF);

lib/logic/vpn_connection.dart

@@ -38,9 +38,6 @@ class VpnConnection extends ChangeNotifier {
   bool _adoptedRunningRuntime = false;
   bool get adoptedRunningRuntime => _adoptedRunningRuntime;
 
-  bool _serverReachable = false;
-  bool get serverReachable => _serverReachable;
-
   ConnectionMode _activeMode = ConnectionMode.tun;
   ConnectionMode get activeMode => _activeMode;
 
@@ -73,7 +70,6 @@ class VpnConnection extends ChangeNotifier {
     );
   }
 
-  Timer? _healthTimer;
   StreamSubscription<NetworkSnapshot>? _networkSubscription;
 
   SecureSocksSession? _lastSecureSocks;
@@ -142,11 +138,6 @@ class VpnConnection extends ChangeNotifier {
       },
     );
 
-    unawaited(_checkHealth());
-    _healthTimer = Timer.periodic(const Duration(seconds: 30), (_) {
-      unawaited(_checkHealth());
-    });
-
     try {
       final coreVersion = await _vless.getCoreVersion();
       if (!_disposed) {
@@ -472,14 +463,6 @@ class VpnConnection extends ChangeNotifier {
     notifyListeners();
   }
 
-  Future<void> _checkHealth() async {
-    if (_disposed || _status == VpnStatus.connected) return;
-    final reachable = await HivemindService.checkHealth();
-    if (_disposed || _status == VpnStatus.connected) return;
-    _serverReachable = reachable;
-    notifyListeners();
-  }
-
   @override
   void dispose() {
     _disposed = true;
@@ -487,7 +470,6 @@ class VpnConnection extends ChangeNotifier {
     _suppressNativeConnect = true;
     _userDisconnecting = true;
     HivemindService.cancel();
-    _healthTimer?.cancel();
     _networkSubscription?.cancel();
     // Provider/UI disposal is not a user disconnect command. Keeping teardown
     // in disconnect() prevents lifecycle churn from silently dropping the VPN.

test/session_lifecycle_regression_test.dart

@@ -164,4 +164,24 @@ void main() {
       reason: 'the nonce check must not be skippable',
     );
   });
+
+  test('nothing probes the control plane while disconnected - rule 60', () {
+    final vpn = File('lib/logic/vpn_connection.dart').readAsStringSync();
+    final hivemind = File('lib/logic/hivemind_service.dart').readAsStringSync();
+    final bar = File('lib/components/status_bar.dart').readAsStringSync();
+
+    // The runtime excludes the app from its own tunnel
+    // (XrayVPNService.kt addDisallowedApplication), so a periodic /health probe
+    // was a cleartext-SNI metronome to the API host - which resolves to the
+    // tunnel IP. It fed step 1 of the kill chain in KNOWN_SECURITY_ISSUES #3,
+    // in exchange for a green dot before the user had connected to anything.
+    expect(vpn, isNot(contains('_healthTimer')));
+    expect(vpn, isNot(contains('_checkHealth')));
+    expect(hivemind, isNot(contains('checkHealth')));
+    expect(hivemind, isNot(contains("'/health'")));
+
+    // Reachability is passive now: a session sync that succeeded, nothing else.
+    expect(bar, isNot(contains('serverReachable')));
+    expect(bar, contains('isConnected && timer.hasSyncedOnce'));
+  });
 }