Tighten parsing, error handling, and Keychain hygiene

ios/Runner/AppDelegate.swift

@@ -55,10 +55,12 @@ import UIKit
   }
 
   private func keychainQuery(service: String, account: String) -> [String: Any] {
+    // Pin synchronizable=false so credentials never sync to iCloud Keychain.
     return [
       kSecClass as String: kSecClassGenericPassword,
       kSecAttrService as String: service,
-      kSecAttrAccount as String: account
+      kSecAttrAccount as String: account,
+      kSecAttrSynchronizable as String: false
     ]
   }
 

lib/src/backup_models.dart

@@ -380,12 +380,18 @@ class BackupRunManifest {
         .whereType<Map<String, Object?>>()
         .map(BackupNotebookOutcome.fromJson)
         .toList();
+    final createdAtRaw = json['createdAt'];
+    if (createdAtRaw is! String) {
+      throw const FormatException(
+        'Backup run manifest is missing required date "createdAt".',
+      );
+    }
+    final createdAt = DateTime.parse(createdAtRaw);
     return BackupRunManifest(
       id: json['id'] as String? ?? '',
-      createdAt: DateTime.parse(json['createdAt'] as String),
+      createdAt: createdAt,
       completedAt:
-          DateTime.tryParse(json['completedAt'] as String? ?? '') ??
-          DateTime.parse(json['createdAt'] as String),
+          DateTime.tryParse(json['completedAt'] as String? ?? '') ?? createdAt,
       totalNotebookCount:
           json['totalNotebookCount'] as int? ??
           json['notebookCount'] as int? ??
@@ -724,7 +730,7 @@ class RenderNotebook {
     final rawNodes = json['nodes'] as List<Object?>? ?? const [];
     return RenderNotebook(
       name: json['name'] as String? ?? 'Untitled notebook',
-      createdAt: DateTime.parse(json['createdAt'] as String),
+      createdAt: _requiredCreatedAt(json),
       archivePath: json['archivePath'] as String? ?? '',
       sourceLayout: json['sourceLayout'] as String? ?? 'json',
       nodes: rawNodes
@@ -734,6 +740,16 @@ class RenderNotebook {
     );
   }
 
+  static DateTime _requiredCreatedAt(Map<String, Object?> json) {
+    final value = json['createdAt'];
+    if (value is String) {
+      return DateTime.parse(value);
+    }
+    throw const FormatException(
+      'Render notebook is missing required date "createdAt".',
+    );
+  }
+
   String toPrettyJson() => const JsonEncoder.withIndent('  ').convert(toJson());
 }
 
@@ -766,7 +782,7 @@ class RenderNode {
   static RenderNode fromJson(Map<String, Object?> json) {
     final rawParts = json['parts'] as List<Object?>? ?? const [];
     return RenderNode(
-      id: json['id'] as int,
+      id: _requiredId(json),
       parentId: json['parentId'] as int? ?? 0,
       title: json['title'] as String? ?? 'Untitled',
       isPage: json['isPage'] as bool? ?? false,
@@ -777,6 +793,16 @@ class RenderNode {
           .toList(),
     );
   }
+
+  static int _requiredId(Map<String, Object?> json) {
+    final value = json['id'];
+    if (value is int) {
+      return value;
+    }
+    throw const FormatException(
+      'Render node is missing required integer "id".',
+    );
+  }
 }
 
 class RenderPart {
@@ -848,7 +874,7 @@ class RenderPart {
 
   static RenderPart fromJson(Map<String, Object?> json) {
     return RenderPart(
-      id: json['id'] as int,
+      id: _requiredId(json),
       kindCode: json['kindCode'] as int? ?? -1,
       kindLabel: json['kindLabel'] as String? ?? 'Entry part',
       renderText: json['renderText'] as String? ?? '',
@@ -866,6 +892,16 @@ class RenderPart {
       attachmentOriginalVersion: json['attachmentOriginalVersion'] as int?,
     );
   }
+
+  static int _requiredId(Map<String, Object?> json) {
+    final value = json['id'];
+    if (value is int) {
+      return value;
+    }
+    throw const FormatException(
+      'Render part is missing required integer "id".',
+    );
+  }
 }
 
 class RenderComment {

lib/src/backup_service.dart

@@ -2281,7 +2281,11 @@ class BackupService {
       return await action();
     } finally {
       if (locked) {
-        await lock.unlock();
+        try {
+          await lock.unlock();
+        } catch (_) {
+          // Still close the file handle below even if unlock fails.
+        }
       }
       await lock.close();
     }
@@ -2517,7 +2521,9 @@ class BackupService {
     if (lower.contains('authorization failed') ||
         lower.contains('missing local credentials') ||
         lower.contains('missing labarchives uid') ||
-        lower.contains('auth')) {
+        lower.contains('authoriz') ||
+        lower.contains('auth_code') ||
+        lower.contains('auth code')) {
       return _BackupFailure(
         category: BackupFailureCategory.authorization,
         message: _oneLine(message),

lib/src/help_search_service.dart

@@ -312,7 +312,11 @@ class HelpSearchService {
       final response = await request.close().timeout(
         const Duration(seconds: 90),
       );
-      final responseBody = await utf8.decoder.bind(response).join();
+      // Timeout the body read independently; response.close() only covers headers.
+      final responseBody = await utf8.decoder
+          .bind(response)
+          .join()
+          .timeout(const Duration(seconds: 120));
       if (response.statusCode < 200 || response.statusCode >= 300) {
         throw AiApiHttpException(response.statusCode, responseBody);
       }

lib/src/labarchives_client.dart

@@ -182,8 +182,12 @@ class LabArchivesClient {
       } catch (_) {
         // Best-effort cleanup after an interrupted response.
       }
-      if (await partial.exists()) {
-        await partial.delete();
+      try {
+        if (await partial.exists()) {
+          await partial.delete();
+        }
+      } catch (_) {
+        // Don't let cleanup mask the original download failure.
       }
       rethrow;
     }

test/backup_models_test.dart

@@ -73,4 +73,58 @@ void main() {
     expect(records, hasLength(1));
     expect(records.single.id, 'run_001_demo_lab');
   });
+
+  test('render notebooks reject missing or invalid createdAt', () {
+    final valid = <String, Object?>{
+      'name': 'Demo Lab Notebook',
+      'createdAt': '2026-05-14T12:00:00.000Z',
+      'archivePath': 'notebooks/demo_lab/2026/05/14/run_001/notebook.7z',
+      'nodes': const <Object?>[],
+    };
+
+    final missingCreatedAt = Map<String, Object?>.of(valid)
+      ..remove('createdAt');
+    final invalidCreatedAt = Map<String, Object?>.of(valid)
+      ..['createdAt'] = 'not-a-date';
+
+    expect(
+      () => RenderNotebook.fromJson(missingCreatedAt),
+      throwsA(isA<FormatException>()),
+    );
+    expect(
+      () => RenderNotebook.fromJson(invalidCreatedAt),
+      throwsA(isA<FormatException>()),
+    );
+  });
+
+  test('render nodes and parts reject missing structural IDs', () {
+    final validNode = <String, Object?>{
+      'id': 42,
+      'parentId': 0,
+      'title': 'Zebrafish hypoxia assay',
+      'isPage': true,
+      'position': 1,
+      'parts': const <Object?>[],
+    };
+    final validPart = <String, Object?>{
+      'id': 7,
+      'kindCode': 2,
+      'kindLabel': 'Attachment',
+      'renderText': 'Raw imaging export',
+      'position': 1,
+      'comments': const <Object?>[],
+    };
+
+    final missingNodeId = Map<String, Object?>.of(validNode)..remove('id');
+    final missingPartId = Map<String, Object?>.of(validPart)..remove('id');
+
+    expect(
+      () => RenderNode.fromJson(missingNodeId),
+      throwsA(isA<FormatException>()),
+    );
+    expect(
+      () => RenderPart.fromJson(missingPartId),
+      throwsA(isA<FormatException>()),
+    );
+  });
 }