diff --git a/mnemo_cards_backend/lib/api/v2/auth_api_v2.dart b/mnemo_cards_backend/lib/api/v2/auth_api_v2.dart
index 1568a76..5f876a0 100644
--- a/mnemo_cards_backend/lib/api/v2/auth_api_v2.dart
+++ b/mnemo_cards_backend/lib/api/v2/auth_api_v2.dart
@@ -238,17 +238,26 @@ class AuthApiV2 {
   Future<Response> authenticateTelegramWebApp(Request request) async {
     try {
       final body = await request.readAsString();
-      log('Telegram Web App auth request body: ${body.length} chars', name: 'AuthApiV2');
+      log('Telegram Web App auth request body length: ${body.length} chars', name: 'AuthApiV2');
+      log('Telegram Web App auth request body (first 200 chars): ${body.length > 200 ? body.substring(0, 200) : body}', name: 'AuthApiV2');
+      
+      Map<String, dynamic> json;
+      try {
+        json = jsonDecode(body) as Map<String, dynamic>;
+      } catch (e, s) {
+        log('Telegram Web App auth: Failed to parse JSON body: $e', error: e, stackTrace: s, name: 'AuthApiV2');
+        return _badRequest('Invalid JSON in request body: $e');
+      }
       
-      final json = jsonDecode(body) as Map<String, dynamic>;
       final initData = json['initData'] as String?;
 
       if (initData == null || initData.isEmpty) {
-        log('Telegram Web App auth: initData is null or empty', name: 'AuthApiV2');
+        log('Telegram Web App auth: initData is null or empty. JSON keys: ${json.keys.toList()}', name: 'AuthApiV2');
         return _badRequest('Telegram Web App init data is required');
       }
 
       log('Telegram Web App auth: initData received, length: ${initData.length}', name: 'AuthApiV2');
+      log('Telegram Web App auth: initData preview (first 100 chars): ${initData.length > 100 ? initData.substring(0, 100) : initData}', name: 'AuthApiV2');
 
       // Use the existing telegram utils to get user ID
       final telegramUtils = TelegramUtils();
diff --git a/mnemo_cards_web_v2/lib/domain/services/http_repository_v2.dart b/mnemo_cards_web_v2/lib/domain/services/http_repository_v2.dart
index 4283f3f..97a5b7d 100644
--- a/mnemo_cards_web_v2/lib/domain/services/http_repository_v2.dart
+++ b/mnemo_cards_web_v2/lib/domain/services/http_repository_v2.dart
@@ -430,6 +430,11 @@ class HttpRepositoryV2 {
 
       return null;
     } on DioException catch (e) {
+      log(
+        'Telegram Web App auth DioException: ${e.response?.statusCode}, '
+        'message: ${e.message}, data: ${e.response?.data}',
+        name: 'HttpRepositoryV2',
+      );
       if (e.error is ApiException) {
         rethrow;
       }