fix(android): fix application connection

2026-07-16 18:50:21 +02:00
parent 34e9d3f9ef
commit 161f09d88c
28 changed files with 559 additions and 241 deletions
@@ -82,6 +82,33 @@ The format is based on Keep a Changelog and this project follows Semantic Versio

 ### Fixed

+- Fixed Android box registration discovery by scanning nearby BLE
+  advertisements before applying the OpenParcelBox name/service filter in the
+  application, waiting for the actual scan timeout, and refreshing registration
+  results as advertisements arrive.
+- Replaced the per-device registration icon with radio-button box selection and
+  an explicit add button, with inline errors and terminal diagnostics for
+  provisioning failures.
+- Kept a completed administrator registration when the following clock
+  synchronization fails instead of reporting the whole addition as failed.
+- Serialized Android BLE connection, secure bonding, MTU negotiation, and GATT
+  discovery before the first encrypted state read.
+- Added one-time stale-bond recovery when Android disconnects during the first
+  encrypted provisioning read.
+- Requested BLE security immediately on firmware connection and restarted
+  connectable advertising after every recycled connection, including failed
+  initial pairing attempts.
+- Replaced Zephyr Secure Connections Only Mode, which implicitly required
+  unavailable level-4 passkey/OOB authentication, with Secure Connections
+  pairing-only mode and encrypted level-2 bonding for the headless XIAO.
+- Added a Material surface behind registration radio rows so Android ink and
+  selection rendering no longer emits an invisible-background warning.
+- Increased the firmware ATT MTU to 247 bytes with matching ACL buffers so the
+  120-byte administrator provisioning JSON fits in one acknowledged GATT write
+  instead of exceeding the previous 62-byte payload limit.
+- Fixed the Android startup logo safe area so the complete logo remains
+  centered instead of being cropped by the system splash icon mask, while
+  restoring `background.jpg` and increasing the visible logo size.
 - Removed oversized Settings callback allocations that exceeded the 1024-byte
  main stack once opening-history or application-identity records existed.
 - Moved Settings/NVS loading to a dedicated 4096-byte services thread and
@@ -19,9 +19,13 @@ at the newest persisted opening timestamp after a reboot.

 ## Security

-Pairing is restricted to BLE LE Secure Connections. BLE AES-CCM link encryption
-protects every GATT command, state read, and notification, and Zephyr persists
-bonding keys.
+Pairing is restricted to BLE LE Secure Connections with legacy pairing
+disabled. The headless XIAO uses encrypted Security Mode 1 Level 2 pairing;
+Security Mode 1 Level 4 is not requested because it requires a passkey display,
+input, or out-of-band confirmation that the box does not provide. BLE AES-CCM
+link encryption protects every GATT command, state read, and notification, and
+Zephyr persists bonding keys. The separate random application identity remains
+mandatory for command authorization.

 At startup, the controller is enabled first, the Zephyr `bt/*` settings subtree
 is then restored, and advertising starts only after the Bluetooth identity has
@@ -32,6 +36,23 @@ This complete sequence runs in a dedicated thread after local keypad
 initialization. Bluetooth failure or slow bond restoration therefore cannot
 prevent offline keypad access or lock operation.

+On each connection, the peripheral immediately requests encrypted Bluetooth
+security before the application reads or writes an administration
+characteristic. Android completes bonding before MTU negotiation and GATT
+service discovery. This ordering avoids a disconnect caused by overlapping the
+first encrypted read, pairing, and MTU negotiation.
+
+The firmware supports an ATT MTU of 247 bytes with matching 251-byte ACL
+buffers. This provides a 244-byte GATT payload, allowing provisioning and other
+JSON commands to remain atomic writes with responses. The default Zephyr MTU of
+65 bytes only provides a 62-byte payload and cannot carry the administrator
+provisioning document.
+
+Connectable advertising stops when Zephyr allocates the only connection object.
+The firmware restarts advertising from the connection `recycled` callback after
+every disconnect, including failed initial pairing, so the box remains
+discoverable for another attempt.
+
 Each phone also owns a random 128-bit identity key stored in its secure
 keystore. The first phone can send `provision_admin` only while no administrator
 exists. Afterwards every command requires a valid administrator or guest
@@ -25,7 +25,10 @@ CONFIG_BT_MAX_CONN=1
 CONFIG_BT_SMP=y
 CONFIG_BT_BONDABLE=y
 CONFIG_BT_SETTINGS=y
-CONFIG_BT_SMP_SC_ONLY=y
+CONFIG_BT_SMP_SC_PAIR_ONLY=y
 CONFIG_BT_PRIVACY=y
 CONFIG_BT_RX_STACK_SIZE=2048
+CONFIG_BT_BUF_ACL_RX_SIZE=251
+CONFIG_BT_BUF_ACL_TX_SIZE=251
+CONFIG_BT_L2CAP_TX_MTU=247
 CONFIG_ENTROPY_GENERATOR=y
@@ -69,6 +69,7 @@ static ssize_t command_write(struct bt_conn *conn,
                             const struct bt_gatt_attr *attr, const void *buf,
                             uint16_t len, uint16_t offset, uint8_t flags);
 static void state_ccc_changed(const struct bt_gatt_attr *attr, uint16_t value);
+static void restart_advertising(void);

 static void factory_reset_work_handler(struct k_work *work) {
  ARG_UNUSED(work);
@@ -76,8 +77,23 @@ static void factory_reset_work_handler(struct k_work *work) {
  printf("BLE bonds cleared after factory reset\n");
 }

+static void connected(struct bt_conn *conn, uint8_t err) {
+  int ret;
+
+  if (err != 0U) {
+    printf("BLE connection failed: %u\n", err);
+    return;
+  }
+
+  printf("BLE connected\n");
+  ret = bt_conn_set_security(conn, BT_SECURITY_L2);
+  if (ret < 0) {
+    printf("BLE security request failed: %d\n", ret);
+  }
+}
+
 static void disconnected(struct bt_conn *conn, uint8_t reason) {
-  ARG_UNUSED(reason);
+  printf("BLE disconnected: %u\n", reason);
  if (conn == authenticated_conn) {
    authenticated_conn = NULL;
    memset(&authenticated_identity, 0, sizeof(authenticated_identity));
@@ -85,8 +101,27 @@ static void disconnected(struct bt_conn *conn, uint8_t reason) {
  }
 }

+static void security_changed(struct bt_conn *conn, bt_security_t level,
+                             enum bt_security_err err) {
+  ARG_UNUSED(conn);
+
+  if (err == BT_SECURITY_ERR_SUCCESS) {
+    printf("BLE security established: level %u\n", level);
+    return;
+  }
+
+  printf("BLE security failed: level %u error %d\n", level, err);
+  if (!app_identities_has_admin()) {
+    (void)bt_unpair(BT_ID_DEFAULT, NULL);
+    printf("BLE bonds cleared after failed initial pairing\n");
+  }
+}
+
 BT_CONN_CB_DEFINE(opb_conn_callbacks) = {
+    .connected = connected,
    .disconnected = disconnected,
+    .recycled = restart_advertising,
+    .security_changed = security_changed,
 };

 BT_GATT_SERVICE_DEFINE(
@@ -111,6 +146,19 @@ static const struct bt_data scan_response_data[] = {
            sizeof(CONFIG_BT_DEVICE_NAME) - 1),
 };

+static void restart_advertising(void) {
+  int ret = bt_le_adv_start(BT_LE_ADV_CONN_FAST_1, advertising_data,
+                            ARRAY_SIZE(advertising_data), scan_response_data,
+                            ARRAY_SIZE(scan_response_data));
+
+  if (ret < 0 && ret != -EALREADY) {
+    printf("BLE advertising restart failed: %d\n", ret);
+    return;
+  }
+
+  printf("BLE advertising: OpenParcelBox\n");
+}
+
 static const char *json_skip_ws(const char *cursor) {
  while (*cursor != '\0' && isspace((unsigned char)*cursor)) {
    cursor++;
@@ -7,7 +7,11 @@ Flutter application for local OpenParcelBox setup and administration.
 - Dark solid background `#333333`, button surfaces `#292929`, modal surfaces
  `#303030`, accent `#c19d60`, and text `#c6c6c6`.
 - Project logo used for the Android launcher icon and centered native splash.
- Native splash uses the project `background.jpg`.
+  The splash variant includes transparent safe-area padding so Android displays
+  the complete logo instead of cropping it through the system icon mask.
+- Native splash uses the project `background.jpg`. Android 12 only permits a
+  solid color behind its system splash icon, so the first Flutter frame keeps
+  the same centered logo over `background.jpg` for a consistent startup screen.
 - Automatic French or English selection from the phone, with a manual override.
 - Empty state restricted to box registration and encrypted-backup restoration.
 - Shortcut bar for opening and history, plus modal cards for codes, NFC tags,
@@ -20,9 +24,11 @@ Flutter application for local OpenParcelBox setup and administration.
 The first phone connecting to an unprovisioned box:

 1. chooses the box identifier;
-2. generates a random 128-bit administrator identity;
-3. sends both values over the encrypted BLE link;
-4. stores the remote BLE identifier, box name, role, and identity in the phone
+2. selects one detected box with a radio button and confirms with the explicit
+   add button;
+3. generates a random 128-bit administrator identity;
+4. sends both values over the encrypted BLE link;
+5. stores the remote BLE identifier, box name, role, and identity in the phone
   secure keystore.

 An administrator creates named guest identities and displays an invitation QR
@@ -53,6 +59,16 @@ Bluetooth uses AES-CCM link encryption. Every application command is also
 authorized with the random administrator or guest identity stored in the phone
 keystore.

+On Android, connection setup is serialized as connection, secure bonding, MTU
+negotiation, and GATT service discovery. The application does not perform the
+first encrypted state read until bonding has completed. If the initial
+provisioning connection is dropped because Android retained an obsolete bond,
+the application removes that bond and retries the setup once.
+
+The firmware negotiates an ATT MTU of 247 bytes, leaving 244 bytes for a single
+GATT write. This keeps the administrator provisioning JSON in one acknowledged
+write instead of relying on prepared long-write support.
+
 Service UUID:

 ```text
@@ -87,6 +103,11 @@ The app uses:
 `flutter_blue_plus` 2.3.10 requires a license mode when connecting. The app uses
 `License.nonprofit` for this open-source project.

+The discovery scan is intentionally unfiltered at the Android API level, then
+restricted in the application to advertisements carrying the OpenParcelBox
+name or service UUID. The registration modal listens to scan results in real
+time and the scan action remains active until the plugin's timeout completes.
+
 ## Development

 ```powershell
@@ -7,151 +7,131 @@ class AppStrings {

  bool get isFrench => locale.languageCode == 'fr';

-  String text(String key) => (_values[key] ?? const <String, String>{})[
-          isFrench ? 'fr' : 'en'] ??
-      key;
+  String text(String key) =>
+      (_values[key] ?? const <String, String>{})[isFrench ? 'fr' : 'en'] ?? key;

-  static const Map<String, Map<String, String>> _values =
-      <String, Map<String, String>>{
-        'add_box': {
-          'fr': 'Ajouter une nouvelle OpenParcelBox',
-          'en': 'Add a new OpenParcelBox',
-        },
-        'restore_backup': {
-          'fr': 'Restaurer une sauvegarde',
-          'en': 'Restore a backup',
-        },
-        'open': {'fr': 'Ouvrir', 'en': 'Open'},
-        'history': {'fr': 'Historique', 'en': 'History'},
-        'permanent_codes': {
-          'fr': 'Codes permanents',
-          'en': 'Permanent codes',
-        },
-        'temporary_codes': {
-          'fr': 'Codes temporaires',
-          'en': 'Temporary codes',
-        },
-        'nfc_tags': {'fr': 'Tags NFC', 'en': 'NFC tags'},
-        'guests': {'fr': 'Invités', 'en': 'Guests'},
-        'settings': {'fr': 'Paramètres', 'en': 'Settings'},
-        'close': {'fr': 'Fermer', 'en': 'Close'},
-        'add': {'fr': 'Ajouter', 'en': 'Add'},
-        'delete': {'fr': 'Supprimer', 'en': 'Delete'},
-        'edit': {'fr': 'Modifier', 'en': 'Edit'},
-        'cancel': {'fr': 'Annuler', 'en': 'Cancel'},
-        'save': {'fr': 'Enregistrer', 'en': 'Save'},
-        'scan': {'fr': 'Scanner', 'en': 'Scan'},
-        'scan_qr': {
-          'fr': 'Scanner un QR code invité',
-          'en': 'Scan a guest QR code',
-        },
-        'box_name': {
-          'fr': 'Identifiant de la box',
-          'en': 'Box identifier',
-        },
-        'nearby_boxes': {
-          'fr': 'OpenParcelBox détectées',
-          'en': 'Detected OpenParcelBox devices',
-        },
-        'search': {'fr': 'Rechercher', 'en': 'Search'},
-        'no_results': {
-          'fr': 'Aucune OpenParcelBox détectée.',
-          'en': 'No OpenParcelBox detected.',
-        },
-        'connected': {'fr': 'Connectée', 'en': 'Connected'},
-        'disconnected': {'fr': 'Déconnectée', 'en': 'Disconnected'},
-        'connecting': {'fr': 'Connexion…', 'en': 'Connecting…'},
-        'no_code': {'fr': 'Aucun code.', 'en': 'No code.'},
-        'new_code': {'fr': 'Générer un code', 'en': 'Generate a code'},
-        'code_limit': {
-          'fr': 'La limite de codes est atteinte.',
-          'en': 'The code limit has been reached.',
-        },
-        'no_history': {
-          'fr': 'Aucune ouverture enregistrée.',
-          'en': 'No opening has been recorded.',
-        },
-        'opened_by_permanent': {
-          'fr': 'Code permanent',
-          'en': 'Permanent code',
-        },
-        'opened_by_temporary': {
-          'fr': 'Code temporaire',
-          'en': 'Temporary code',
-        },
-        'opened_by_nfc': {'fr': 'Tag NFC', 'en': 'NFC tag'},
-        'opened_by_app': {'fr': 'Application', 'en': 'Application'},
-        'tag_name': {'fr': 'Nom du tag', 'en': 'Tag name'},
-        'tag_uid': {'fr': 'UID du tag', 'en': 'Tag UID'},
-        'scan_phone_nfc': {
-          'fr': 'Scanner avec le téléphone',
-          'en': 'Scan with phone',
-        },
-        'pair_on_box': {
-          'fr': 'Appairer sur la box',
-          'en': 'Pair on the box',
-        },
-        'manual_uid': {'fr': 'Ajouter un UID', 'en': 'Add a UID'},
-        'nfc_unavailable': {
-          'fr': 'Le NFC est indisponible sur ce téléphone.',
-          'en': 'NFC is unavailable on this phone.',
-        },
-        'hold_tag': {
-          'fr': 'Approchez un tag NFC du téléphone…',
-          'en': 'Hold an NFC tag near the phone…',
-        },
-        'guest_name': {'fr': "Nom de l'invité", 'en': 'Guest name'},
-        'show_qr': {'fr': 'Voir le QR code', 'en': 'Show QR code'},
-        'no_guest': {'fr': 'Aucun invité.', 'en': 'No guest.'},
-        'language': {'fr': 'Langue', 'en': 'Language'},
-        'automatic': {'fr': 'Automatique', 'en': 'Automatic'},
-        'french': {'fr': 'Français', 'en': 'French'},
-        'english': {'fr': 'Anglais', 'en': 'English'},
-        'backup': {
-          'fr': "Sauvegarder les paramètres de l'app",
-          'en': 'Back up app settings',
-        },
-        'backup_location': {
-          'fr': "Choisir l'emplacement de sauvegarde",
-          'en': 'Choose backup location',
-        },
-        'restore': {
-          'fr': 'Restaurer une sauvegarde',
-          'en': 'Restore a backup',
-        },
-        'password': {'fr': 'Mot de passe', 'en': 'Password'},
-        'firmware_update': {
-          'fr': 'Mise à jour du firmware (à venir)',
-          'en': 'Firmware update (coming later)',
-        },
-        'factory_reset': {
-          'fr': "Réinitialiser la box",
-          'en': 'Factory-reset the box',
-        },
-        'forget_box': {'fr': 'Supprimer la box', 'en': 'Forget the box'},
-        'danger': {'fr': 'Danger', 'en': 'Danger'},
-        'factory_warning': {
-          'fr':
-              "Cette action supprime tous les paramètres de la box et autorise l'appairage d'un nouvel administrateur.",
-          'en':
-              'This deletes every setting on the box and allows a new administrator to pair.',
-        },
-        'forget_warning': {
-          'fr':
-              "Seules les informations de l'application seront supprimées. Les paramètres de la box restent inchangés et un administrateur peut perdre définitivement l'accès.",
-          'en':
-              'Only app information will be deleted. Box settings remain unchanged and an administrator may permanently lose access.',
-        },
-        'confirm': {'fr': 'Confirmer', 'en': 'Confirm'},
-        'administrator': {'fr': 'Administrateur', 'en': 'Administrator'},
-        'guest': {'fr': 'Invité', 'en': 'Guest'},
-        'backup_done': {
-          'fr': 'Sauvegarde chiffrée créée.',
-          'en': 'Encrypted backup created.',
-        },
-        'restore_done': {
-          'fr': 'Sauvegarde restaurée.',
-          'en': 'Backup restored.',
-        },
-      };
+  static const Map<String, Map<String, String>>
+  _values = <String, Map<String, String>>{
+    'add_box': {
+      'fr': 'Ajouter une nouvelle OpenParcelBox',
+      'en': 'Add a new OpenParcelBox',
+    },
+    'restore_backup': {
+      'fr': 'Restaurer une sauvegarde',
+      'en': 'Restore a backup',
+    },
+    'open': {'fr': 'Ouvrir', 'en': 'Open'},
+    'history': {'fr': 'Historique', 'en': 'History'},
+    'permanent_codes': {'fr': 'Codes permanents', 'en': 'Permanent codes'},
+    'temporary_codes': {'fr': 'Codes temporaires', 'en': 'Temporary codes'},
+    'nfc_tags': {'fr': 'Tags NFC', 'en': 'NFC tags'},
+    'guests': {'fr': 'Invités', 'en': 'Guests'},
+    'settings': {'fr': 'Paramètres', 'en': 'Settings'},
+    'close': {'fr': 'Fermer', 'en': 'Close'},
+    'add': {'fr': 'Ajouter', 'en': 'Add'},
+    'delete': {'fr': 'Supprimer', 'en': 'Delete'},
+    'edit': {'fr': 'Modifier', 'en': 'Edit'},
+    'cancel': {'fr': 'Annuler', 'en': 'Cancel'},
+    'save': {'fr': 'Enregistrer', 'en': 'Save'},
+    'scan': {'fr': 'Scanner', 'en': 'Scan'},
+    'scan_qr': {
+      'fr': 'Scanner un QR code invité',
+      'en': 'Scan a guest QR code',
+    },
+    'box_name': {'fr': 'Identifiant de la box', 'en': 'Box identifier'},
+    'nearby_boxes': {
+      'fr': 'OpenParcelBox détectées',
+      'en': 'Detected OpenParcelBox devices',
+    },
+    'search': {'fr': 'Rechercher', 'en': 'Search'},
+    'register_box': {'fr': 'Ajouter cette box', 'en': 'Add this box'},
+    'select_box': {
+      'fr': 'Sélectionnez une OpenParcelBox dans la liste.',
+      'en': 'Select an OpenParcelBox from the list.',
+    },
+    'no_results': {
+      'fr': 'Aucune OpenParcelBox détectée.',
+      'en': 'No OpenParcelBox detected.',
+    },
+    'connected': {'fr': 'Connectée', 'en': 'Connected'},
+    'disconnected': {'fr': 'Déconnectée', 'en': 'Disconnected'},
+    'connecting': {'fr': 'Connexion…', 'en': 'Connecting…'},
+    'no_code': {'fr': 'Aucun code.', 'en': 'No code.'},
+    'new_code': {'fr': 'Générer un code', 'en': 'Generate a code'},
+    'code_limit': {
+      'fr': 'La limite de codes est atteinte.',
+      'en': 'The code limit has been reached.',
+    },
+    'no_history': {
+      'fr': 'Aucune ouverture enregistrée.',
+      'en': 'No opening has been recorded.',
+    },
+    'opened_by_permanent': {'fr': 'Code permanent', 'en': 'Permanent code'},
+    'opened_by_temporary': {'fr': 'Code temporaire', 'en': 'Temporary code'},
+    'opened_by_nfc': {'fr': 'Tag NFC', 'en': 'NFC tag'},
+    'opened_by_app': {'fr': 'Application', 'en': 'Application'},
+    'tag_name': {'fr': 'Nom du tag', 'en': 'Tag name'},
+    'tag_uid': {'fr': 'UID du tag', 'en': 'Tag UID'},
+    'scan_phone_nfc': {
+      'fr': 'Scanner avec le téléphone',
+      'en': 'Scan with phone',
+    },
+    'pair_on_box': {'fr': 'Appairer sur la box', 'en': 'Pair on the box'},
+    'manual_uid': {'fr': 'Ajouter un UID', 'en': 'Add a UID'},
+    'nfc_unavailable': {
+      'fr': 'Le NFC est indisponible sur ce téléphone.',
+      'en': 'NFC is unavailable on this phone.',
+    },
+    'hold_tag': {
+      'fr': 'Approchez un tag NFC du téléphone…',
+      'en': 'Hold an NFC tag near the phone…',
+    },
+    'guest_name': {'fr': "Nom de l'invité", 'en': 'Guest name'},
+    'show_qr': {'fr': 'Voir le QR code', 'en': 'Show QR code'},
+    'no_guest': {'fr': 'Aucun invité.', 'en': 'No guest.'},
+    'language': {'fr': 'Langue', 'en': 'Language'},
+    'automatic': {'fr': 'Automatique', 'en': 'Automatic'},
+    'french': {'fr': 'Français', 'en': 'French'},
+    'english': {'fr': 'Anglais', 'en': 'English'},
+    'backup': {
+      'fr': "Sauvegarder les paramètres de l'app",
+      'en': 'Back up app settings',
+    },
+    'backup_location': {
+      'fr': "Choisir l'emplacement de sauvegarde",
+      'en': 'Choose backup location',
+    },
+    'restore': {'fr': 'Restaurer une sauvegarde', 'en': 'Restore a backup'},
+    'password': {'fr': 'Mot de passe', 'en': 'Password'},
+    'firmware_update': {
+      'fr': 'Mise à jour du firmware (à venir)',
+      'en': 'Firmware update (coming later)',
+    },
+    'factory_reset': {
+      'fr': "Réinitialiser la box",
+      'en': 'Factory-reset the box',
+    },
+    'forget_box': {'fr': 'Supprimer la box', 'en': 'Forget the box'},
+    'danger': {'fr': 'Danger', 'en': 'Danger'},
+    'factory_warning': {
+      'fr':
+          "Cette action supprime tous les paramètres de la box et autorise l'appairage d'un nouvel administrateur.",
+      'en':
+          'This deletes every setting on the box and allows a new administrator to pair.',
+    },
+    'forget_warning': {
+      'fr':
+          "Seules les informations de l'application seront supprimées. Les paramètres de la box restent inchangés et un administrateur peut perdre définitivement l'accès.",
+      'en':
+          'Only app information will be deleted. Box settings remain unchanged and an administrator may permanently lose access.',
+    },
+    'confirm': {'fr': 'Confirmer', 'en': 'Confirm'},
+    'administrator': {'fr': 'Administrateur', 'en': 'Administrator'},
+    'guest': {'fr': 'Invité', 'en': 'Guest'},
+    'backup_done': {
+      'fr': 'Sauvegarde chiffrée créée.',
+      'en': 'Encrypted backup created.',
+    },
+    'restore_done': {'fr': 'Sauvegarde restaurée.', 'en': 'Backup restored.'},
+  };
 }
@@ -97,10 +97,8 @@ class OpenParcelBoxBleController extends ChangeNotifier {
          .timeout(const Duration(seconds: 8));
      isScanning = true;
      notifyListeners();
-      await FlutterBluePlus.startScan(
-        withServices: <Guid>[Guid(_serviceUuid)],
-        timeout: const Duration(seconds: 8),
-      );
+      await FlutterBluePlus.startScan(timeout: const Duration(seconds: 8));
+      await FlutterBluePlus.isScanning.where((scanning) => !scanning).first;
    } catch (error) {
      errorMessage = '$error';
    } finally {
@@ -117,8 +115,8 @@ class OpenParcelBoxBleController extends ChangeNotifier {
    }
    _setBusy(true);
    try {
-      await _connectDevice(result.device);
-      final publicState = await _readState(updateCollections: false);
+      errorMessage = null;
+      final publicState = await _connectForRegistration(result.device);
      if (publicState?['admin_exists'] == true) {
        throw StateError('This box already has an administrator.');
      }
@@ -140,12 +138,72 @@ class OpenParcelBoxBleController extends ChangeNotifier {
      await _upsertSavedBox(saved);
      currentBox = saved;
      isAuthenticated = true;
-      await syncClock();
+      try {
+        await syncClock();
+      } catch (error, stackTrace) {
+        debugPrint(
+          'OpenParcelBox clock synchronization after registration failed: '
+          '$error\n$stackTrace',
+        );
+        errorMessage = null;
+      }
+      notifyListeners();
+    } catch (error, stackTrace) {
+      errorMessage = '$error';
+      debugPrint(
+        'OpenParcelBox administrator registration failed: '
+        '$error\n$stackTrace',
+      );
+      notifyListeners();
+      rethrow;
    } finally {
      _setBusy(false);
    }
  }

+  Future<Map<String, dynamic>?> _connectForRegistration(
+    BluetoothDevice device,
+  ) async {
+    try {
+      await _connectDevice(device);
+      return await _readState(updateCollections: false);
+    } catch (error, stackTrace) {
+      final canRecover =
+          !kIsWeb &&
+          defaultTargetPlatform == TargetPlatform.android &&
+          error is FlutterBluePlusException &&
+          error.code == FbpErrorCode.deviceIsDisconnected.index;
+      if (!canRecover) {
+        rethrow;
+      }
+
+      debugPrint(
+        'OpenParcelBox initial pairing disconnected; resetting the Android '
+        'bond and retrying once.\n$error\n$stackTrace',
+      );
+      await _resetAndroidBond(device);
+      await Future<void>.delayed(const Duration(milliseconds: 750));
+      await _connectDevice(device);
+      return _readState(updateCollections: false);
+    }
+  }
+
+  Future<void> _resetAndroidBond(BluetoothDevice device) async {
+    connectedDevice = null;
+    _commandCharacteristic = null;
+    _stateCharacteristic = null;
+    isAuthenticated = false;
+
+    if (device.isConnected) {
+      await device.disconnect();
+    }
+    try {
+      await device.removeBond();
+    } catch (error) {
+      debugPrint('OpenParcelBox Android bond removal reported: $error');
+    }
+  }
+
  Future<void> importGuestInvitation(String rawPayload) async {
    final decoded = jsonDecode(rawPayload);
    if (decoded is! Map<String, dynamic> ||
@@ -193,6 +251,7 @@ class OpenParcelBoxBleController extends ChangeNotifier {
    await device.connect(
      license: License.nonprofit,
      timeout: const Duration(seconds: 12),
+      mtu: null,
    );
    _connectionSubscription?.cancel();
    _connectionSubscription = device.connectionState.listen((state) {
@@ -205,6 +264,10 @@ class OpenParcelBoxBleController extends ChangeNotifier {
        notifyListeners();
      }
    });
+    await _ensureAndroidBond(device);
+    if (!kIsWeb && defaultTargetPlatform == TargetPlatform.android) {
+      await device.requestMtu(512);
+    }
    final services = await device.discoverServices();
    _commandCharacteristic = _findCharacteristic(services, _commandUuid);
    _stateCharacteristic = _findCharacteristic(services, _stateUuid);
@@ -215,6 +278,26 @@ class OpenParcelBoxBleController extends ChangeNotifier {
    status = 'connected';
  }

+  Future<void> _ensureAndroidBond(BluetoothDevice device) async {
+    if (kIsWeb || defaultTargetPlatform != TargetPlatform.android) {
+      return;
+    }
+
+    var bondState = await device.bondState.first;
+    if (bondState == BluetoothBondState.bonded) {
+      return;
+    }
+
+    await device.createBond(timeout: 30);
+    bondState = await device.bondState
+        .where((state) => state != BluetoothBondState.bonding)
+        .first
+        .timeout(const Duration(seconds: 30));
+    if (bondState != BluetoothBondState.bonded) {
+      throw StateError('Secure Bluetooth pairing did not complete.');
+    }
+  }
+
  BluetoothCharacteristic? _findCharacteristic(
    List<BluetoothService> services,
    String uuid,
@@ -236,8 +319,9 @@ class OpenParcelBoxBleController extends ChangeNotifier {
    final name = result.advertisementData.advName.isNotEmpty
        ? result.advertisementData.advName
        : result.device.platformName;
-    return name.toUpperCase().startsWith('OPB-') ||
-        name.toLowerCase().contains('openparcelbox') ||
+    final normalizedName = name.trim().toLowerCase();
+    return normalizedName.startsWith('opb-') ||
+        normalizedName.contains('openparcelbox') ||
        result.advertisementData.serviceUuids.any(
          (uuid) => uuid.str.toLowerCase() == _serviceUuid,
        );
@@ -17,6 +17,7 @@ import 'models.dart';
 import 'secure_box_store.dart';

 const _logoAsset = 'images/openparcelbox-logo-256.png';
+const _backgroundAsset = 'images/background.jpg';
 const _background = Color(0xFF333333);
 const _surface = Color(0xFF292929);
 const _modalSurface = Color(0xFF303030);
@@ -29,10 +30,16 @@ void main() {
 }

 class MyApp extends StatefulWidget {
-  const MyApp({this.store, this.backupService, super.key});
+  const MyApp({
+    this.store,
+    this.backupService,
+    this.splashDuration = const Duration(milliseconds: 900),
+    super.key,
+  });

  final SecureBoxStore? store;
  final BackupService? backupService;
+  final Duration splashDuration;

  @override
  State<MyApp> createState() => _MyAppState();
@@ -50,12 +57,14 @@ class _MyAppState extends State<MyApp> {
  }

  Future<void> _loadLanguage() async {
+    final minimumSplashTime = Future<void>.delayed(widget.splashDuration);
    try {
      final language = await _store.loadLanguage();
      _locale = language == null ? null : Locale(language);
    } catch (_) {
      _locale = null;
    }
+    await minimumSplashTime;
    if (mounted) {
      setState(() => _languageLoaded = true);
    }
@@ -122,11 +131,35 @@ class _MyAppState extends State<MyApp> {
              selectedLanguage: _locale?.languageCode,
              onLanguageChanged: _changeLanguage,
            )
-          : const ColoredBox(color: _background),
+          : const _StartupSplash(),
    );
  }
 }

+class _StartupSplash extends StatelessWidget {
+  const _StartupSplash();
+
+  @override
+  Widget build(BuildContext context) => ColoredBox(
+    color: _background,
+    child: Stack(
+      fit: StackFit.expand,
+      children: <Widget>[
+        Image.asset(_backgroundAsset, fit: BoxFit.cover),
+        Center(
+          child: LayoutBuilder(
+            builder: (context, constraints) => Image.asset(
+              _logoAsset,
+              width: (constraints.maxWidth * 0.62).clamp(220.0, 300.0),
+              fit: BoxFit.contain,
+            ),
+          ),
+        ),
+      ],
+    ),
+  );
+}
+
 class OpenParcelBoxHome extends StatefulWidget {
  const OpenParcelBoxHome({
    required this.store,
@@ -216,94 +249,157 @@ class _OpenParcelBoxHomeState extends State<OpenParcelBoxHome> {

  Future<void> _showAddBox() async {
    var boxName = '';
+    ScanResult? selectedResult;
    await showOpbModal(
      context,
      title: strings.text('add_box'),
      child: StatefulBuilder(
-        builder: (context, setModalState) => Column(
-          crossAxisAlignment: CrossAxisAlignment.stretch,
-          children: <Widget>[
-            TextFormField(
-              maxLength: 31,
-              onChanged: (value) => boxName = value,
-              decoration: InputDecoration(labelText: strings.text('box_name')),
-            ),
-            const SizedBox(height: 8),
-            FilledButton.icon(
-              onPressed: () async {
-                final payload = await _scanQrCode();
-                if (payload == null) {
-                  return;
-                }
-                try {
-                  await _controller.importGuestInvitation(payload);
-                  if (context.mounted) {
-                    Navigator.of(context).pop();
+        builder: (context, setModalState) => ListenableBuilder(
+          listenable: _controller,
+          builder: (context, child) => Column(
+            crossAxisAlignment: CrossAxisAlignment.stretch,
+            children: <Widget>[
+              TextFormField(
+                maxLength: 31,
+                textInputAction: TextInputAction.done,
+                onChanged: (value) {
+                  boxName = value;
+                  setModalState(() {});
+                },
+                onFieldSubmitted: (_) => FocusScope.of(context).unfocus(),
+                decoration: InputDecoration(
+                  labelText: strings.text('box_name'),
+                ),
+              ),
+              const SizedBox(height: 8),
+              FilledButton.icon(
+                onPressed: () async {
+                  final payload = await _scanQrCode();
+                  if (payload == null) {
+                    return;
                  }
-                } catch (error) {
-                  if (context.mounted) {
-                    _showMessage('$error');
+                  try {
+                    await _controller.importGuestInvitation(payload);
+                    if (context.mounted) {
+                      Navigator.of(context).pop();
+                    }
+                  } catch (error) {
+                    if (context.mounted) {
+                      _showMessage('$error');
+                    }
                  }
-                }
-              },
-              icon: const Icon(Icons.qr_code_scanner),
-              label: Text(strings.text('scan_qr')),
-            ),
-            const SizedBox(height: 16),
-            Row(
-              children: <Widget>[
-                Expanded(
-                  child: Text(
-                    strings.text('nearby_boxes'),
-                    style: Theme.of(context).textTheme.titleMedium?.copyWith(
-                      color: _accent,
-                      fontWeight: FontWeight.w700,
+                },
+                icon: const Icon(Icons.qr_code_scanner),
+                label: Text(strings.text('scan_qr')),
+              ),
+              const SizedBox(height: 16),
+              Row(
+                children: <Widget>[
+                  Expanded(
+                    child: Text(
+                      strings.text('nearby_boxes'),
+                      style: Theme.of(context).textTheme.titleMedium?.copyWith(
+                        color: _accent,
+                        fontWeight: FontWeight.w700,
+                      ),
                    ),
                  ),
+                  IconButton.filledTonal(
+                    onPressed: _controller.isScanning
+                        ? null
+                        : _controller.startScan,
+                    icon: const Icon(Icons.radar),
+                    tooltip: strings.text('search'),
+                  ),
+                ],
+              ),
+              const SizedBox(height: 8),
+              if (_controller.errorMessage != null) ...<Widget>[
+                Text(
+                  _controller.errorMessage!,
+                  style: TextStyle(color: Theme.of(context).colorScheme.error),
                ),
-                IconButton.filledTonal(
-                  onPressed: _controller.isScanning
-                      ? null
-                      : () async {
-                          await _controller.startScan();
-                          setModalState(() {});
-                        },
-                  icon: const Icon(Icons.radar),
-                  tooltip: strings.text('search'),
+                const SizedBox(height: 8),
+              ],
+              if (_controller.scanResults.isEmpty)
+                _EmptyRow(text: strings.text('no_results'))
+              else
+                RadioGroup<ScanResult>(
+                  groupValue: selectedResult,
+                  onChanged: (result) =>
+                      setModalState(() => selectedResult = result),
+                  child: Column(
+                    children: _controller.scanResults
+                        .map(
+                          (result) => Padding(
+                            padding: const EdgeInsets.only(bottom: 8),
+                            child: Material(
+                              color: _surface,
+                              shape: RoundedRectangleBorder(
+                                borderRadius: BorderRadius.circular(10),
+                                side: BorderSide(
+                                  color: selectedResult == result
+                                      ? _accent
+                                      : Colors.white10,
+                                ),
+                              ),
+                              clipBehavior: Clip.antiAlias,
+                              child: RadioListTile<ScanResult>(
+                                value: result,
+                                activeColor: _accent,
+                                selected: selectedResult == result,
+                                secondary: const Icon(
+                                  Icons.inventory_2_outlined,
+                                  color: _accent,
+                                ),
+                                title: Text(_deviceName(result)),
+                                subtitle: Text(result.device.remoteId.str),
+                                contentPadding: const EdgeInsets.symmetric(
+                                  horizontal: 8,
+                                ),
+                              ),
+                            ),
+                          ),
+                        )
+                        .toList(),
+                  ),
+                ),
+              if (selectedResult == null &&
+                  _controller.scanResults.isNotEmpty) ...<Widget>[
+                const SizedBox(height: 4),
+                Text(
+                  strings.text('select_box'),
+                  textAlign: TextAlign.center,
+                  style: Theme.of(context).textTheme.bodySmall,
                ),
              ],
-            ),
-            const SizedBox(height: 8),
-            if (_controller.scanResults.isEmpty)
-              _EmptyRow(text: strings.text('no_results'))
-            else
-              ..._controller.scanResults.map(
-                (result) => _DataRowCard(
-                  icon: Icons.inventory_2_outlined,
-                  title: _deviceName(result),
-                  subtitle: result.device.remoteId.str,
-                  actions: <Widget>[
-                    IconButton(
-                      onPressed: () async {
+              const SizedBox(height: 16),
+              FilledButton.icon(
+                onPressed:
+                    selectedResult == null ||
+                        boxName.trim().isEmpty ||
+                        _controller.isBusy
+                    ? null
+                    : () async {
+                        FocusScope.of(context).unfocus();
                        try {
                          await _controller.registerAdministrator(
-                            result,
+                            selectedResult!,
                            boxName,
                          );
                          if (context.mounted) {
                            Navigator.of(context).pop();
                          }
-                        } catch (error) {
-                          _showMessage('$error');
+                        } catch (_) {
+                          // The controller logs the detailed failure and exposes
+                          // it inline in this modal.
                        }
                      },
-                      icon: const Icon(Icons.link),
-                      color: _accent,
-                    ),
-                  ],
-                ),
+                icon: const Icon(Icons.add_link),
+                label: Text(strings.text('register_box')),
              ),
-          ],
+            ],
+          ),
        ),
      ),
    );
@@ -69,6 +69,7 @@ flutter:
  assets:
    - images/background.jpg
    - images/openparcelbox-logo-256.png
+    - images/openparcelbox-splash.png

 flutter_launcher_icons:
  android: true
@@ -78,14 +79,14 @@ flutter_launcher_icons:
  adaptive_icon_foreground: images/openparcelbox-logo-256.png

 flutter_native_splash:
-  color: "#333333"
  background_image: images/background.jpg
-  image: images/openparcelbox-logo-256.png
+  image: images/openparcelbox-splash.png
+  android_gravity: center
  android: true
  ios: false
  android_12:
    color: "#333333"
-    image: images/openparcelbox-logo-256.png
+    image: images/openparcelbox-splash.png

  # An image asset can refer to one or more resolution-specific "variants", see
  # https://flutter.dev/to/resolution-aware-images
@@ -38,10 +38,29 @@ class _FakeBackupService extends BackupService {
 }

 void main() {
-  testWidgets('empty home only exposes registration and restore actions', (
+  testWidgets('startup splash shows the background and centered logo', (
    WidgetTester tester,
  ) async {
    await tester.pumpWidget(MyApp(store: _MemoryStore()));
+
+    expect(
+      find.image(const AssetImage('images/background.jpg')),
+      findsOneWidget,
+    );
+    expect(
+      find.image(const AssetImage('images/openparcelbox-logo-256.png')),
+      findsOneWidget,
+    );
+
+    await tester.pump(const Duration(milliseconds: 900));
+  });
+
+  testWidgets('empty home only exposes registration and restore actions', (
+    WidgetTester tester,
+  ) async {
+    await tester.pumpWidget(
+      MyApp(store: _MemoryStore(), splashDuration: Duration.zero),
+    );
    await tester.pumpAndSettle();

    expect(find.text('Add a new OpenParcelBox'), findsOneWidget);
@@ -53,7 +72,9 @@ void main() {
  testWidgets('registration opens the styled setup modal', (
    WidgetTester tester,
  ) async {
-    await tester.pumpWidget(MyApp(store: _MemoryStore()));
+    await tester.pumpWidget(
+      MyApp(store: _MemoryStore(), splashDuration: Duration.zero),
+    );
    await tester.pumpAndSettle();

    await tester.tap(find.text('Add a new OpenParcelBox'));
@@ -62,13 +83,23 @@ void main() {
    expect(find.text('Box identifier'), findsOneWidget);
    expect(find.text('Scan a guest QR code'), findsOneWidget);
    expect(find.text('Detected OpenParcelBox devices'), findsOneWidget);
+    expect(find.text('Add this box'), findsOneWidget);
+    final addButton = tester.widget<FilledButton>(
+      find.widgetWithText(FilledButton, 'Add this box'),
+    );
+    expect(addButton.onPressed, isNull);
    expect(find.byIcon(Icons.close), findsOneWidget);
  });

  testWidgets('registration text field works with the French locale', (
    WidgetTester tester,
  ) async {
-    await tester.pumpWidget(MyApp(store: _MemoryStore(language: 'fr')));
+    await tester.pumpWidget(
+      MyApp(
+        store: _MemoryStore(language: 'fr'),
+        splashDuration: Duration.zero,
+      ),
+    );
    await tester.pumpAndSettle();

    await tester.tap(find.text('Ajouter une nouvelle OpenParcelBox'));
@@ -81,7 +112,9 @@ void main() {
  testWidgets(
    'closing registration after editing does not dispose input early',
    (WidgetTester tester) async {
-      await tester.pumpWidget(MyApp(store: _MemoryStore()));
+      await tester.pumpWidget(
+        MyApp(store: _MemoryStore(), splashDuration: Duration.zero),
+      );
      await tester.pumpAndSettle();

      await tester.tap(find.text('Add a new OpenParcelBox'));
@@ -100,7 +133,11 @@ void main() {
  ) async {
    final backupService = _FakeBackupService();
    await tester.pumpWidget(
-      MyApp(store: _MemoryStore(), backupService: backupService),
+      MyApp(
+        store: _MemoryStore(),
+        backupService: backupService,
+        splashDuration: Duration.zero,
+      ),
    );
    await tester.pumpAndSettle();