diff --git a/README.md b/README.md
index 4a5454b..e0472a3 100644
--- a/README.md
+++ b/README.md
@@ -151,7 +151,7 @@ Add to `android/app/src/main/AndroidManifest.xml`:
 
 ```xml
 <activity android:name="com.linusu.flutter_web_auth.CallbackActivity" android:exported="true">
-    <intent-filter android:label="flutter_web_auth">
+    <intent-filter android:label="flutter_web_auth_2">
         <action android:name="android.intent.action.VIEW" />
         <category android:name="android.intent.category.DEFAULT" />
         <category android:name="android.intent.category.BROWSABLE" />
@@ -160,12 +160,17 @@ Add to `android/app/src/main/AndroidManifest.xml`:
 </activity>
 ```
 
+Notes:
+- The `android:label` attribute on the `<intent-filter>` is optional. You can omit it or set any string.
+- On Android 12+ (API level 31+), any Activity with an `intent-filter` must declare `android:exported="true"`.
+- Use the same callback scheme string on both platforms: iOS (`CFBundleURLSchemes`) and Android (`<data android:scheme="...">`). They must match exactly.
+
 #### Differences in MiAuth and OAuth Configuration (Key Points for App Integration)
 - This configuration (registration of the URL scheme) is done on the "app side." It is not included in the library's Manifest.
 - Both methods require a "custom URL scheme" to return from an external browser to the app.
 - The difference lies in how to specify "where to return from the browser."
 - OAuth: Since it needs to return to an HTTPS `redirect_uri` from the authorization server, `redirect.html` placed there ultimately redirects back to `yourscheme://...` for the app.
-- MiAuth: The `callback` query of the authentication start URL specifies `yourscheme://...` from the beginning (no need for `https`).
+- MiAuth: The `callback` query of the authentication start URL points to the app via the custom scheme only (e.g., `yourscheme://`). No `https` is needed.
 
 ##### Example of MiAuth (no persistence)
 
@@ -180,7 +185,7 @@ final miConfig = MisskeyMiAuthConfig(
   permissions: ['read:account', 'write:notes'],
   iconUrl: 'https://example.com/icon.png', // Optional
 );
-final miRes = await miClient.authenticate(miConfig); // returns token only
+final miRes = await miClient.authenticate(miConfig); // returns token (and user if available)
 ```
 
 ##### Example of MiAuth (with persistence via MisskeyAuthManager)
@@ -241,12 +246,12 @@ final current = await auth.currentToken();
 
 ##### How to Support Both Methods in the Same App
 - By registering the same `scheme` (e.g., `yourscheme`) in iOS's `Info.plist` and Android's `AndroidManifest.xml`, it can be shared between OAuth and MiAuth.
-- If you implement the OAuth `redirect.html` to redirect to `yourscheme://oauth/callback?...`, you can reuse the same path expression (`yourscheme://oauth/callback`) for MiAuth's `callback`.
+- This library uses a scheme-only callback for MiAuth (e.g., `yourscheme://`). You do not need to reuse a path like `yourscheme://oauth/callback` for MiAuth.
 - For Android, matching only on the `scheme` is sufficient as shown below (the `host` and `path` are optional).
 
 ```xml
 <activity android:name="com.linusu.flutter_web_auth.CallbackActivity" android:exported="true">
-    <intent-filter android:label="flutter_web_auth">
+    <intent-filter android:label="flutter_web_auth_2">
         <action android:name="android.intent.action.VIEW" />
         <category android:name="android.intent.category.DEFAULT" />
         <category android:name="android.intent.category.BROWSABLE" />
@@ -296,6 +301,7 @@ class MisskeyMiAuthClient {
   /// Authenticate with Misskey server using MiAuth (no persistence)
   Future<MiAuthTokenResponse> authenticate(MisskeyMiAuthConfig config);
 }
+```
 
 #### MisskeyAuthManager
 
@@ -358,7 +364,6 @@ class AccountEntry {
   final DateTime? createdAt;
 }
 ```
-```
 
 ### Error Handling
 
@@ -379,7 +384,7 @@ The library includes exception classes for:
 
 ### License
 
-This project is licensed under the 3-Clause BSD License - see the [LICENSE](LICENSE) file for details.
+This project is published by 司書 (LibraryLibrarian) under the 3-Clause BSD License. For details, please see the [LICENSE](LICENSE) file.
 
 ### Related Links
 
@@ -416,26 +421,6 @@ dependencies:
 
 ### クイックスタート
 
-#### かんたん例（MisskeyAuthManager）
-
-```dart
-import 'package:misskey_auth/misskey_auth.dart';
-
-final auth = MisskeyAuthManager.defaultInstance();
-
-// 認証後にトークンを自動保存
-final key = await auth.loginWithOAuth(
-  MisskeyOAuthConfig(
-    host: 'misskey.io',
-    clientId: 'https://yourpage/yourapp/',
-    redirectUri: 'https://yourpage/yourapp/redirect.html',
-    scope: 'read:account write:notes',
-    callbackScheme: 'yourscheme',
-  ),
-  setActive: true,
-);
-```
-
 #### 1. client_idページの設定
 
 MisskeyのOAuth 2.0はIndieAuth仕様に準拠しています。以下が必要です：
@@ -549,7 +534,7 @@ await auth.signOutAll();
 
 ```xml
 <activity android:name="com.linusu.flutter_web_auth.CallbackActivity" android:exported="true">
-    <intent-filter android:label="flutter_web_auth">
+    <intent-filter android:label="flutter_web_auth_2">
         <action android:name="android.intent.action.VIEW" />
         <category android:name="android.intent.category.DEFAULT" />
         <category android:name="android.intent.category.BROWSABLE" />
@@ -558,13 +543,18 @@ await auth.signOutAll();
 </activity>
 ```
 
+補足:
+- `<intent-filter>` の `android:label` は省略可能です（省略しても動作します）。
+- Android 12+（API 31 以降）では、`intent-filter` を持つ Activity に `android:exported="true"` の指定が必須です。
+- iOS（`CFBundleURLSchemes`）と Android（`<data android:scheme="...">`）で登録するカスタムスキーム名は同一にしてください（完全一致が必要）。
+
 #### MiAuth と OAuth の設定の違い（アプリ組み込み時のポイント）
 
 - この設定（URLスキームの登録）は「アプリ側」で行います。ライブラリ内のManifestには含めません。
 - 両方式とも、外部ブラウザからアプリへ戻すために「カスタムURLスキーム」が必要です。
 - 相違点は「ブラウザからどこに戻すか」の指定方法です。
   - OAuth: 認可サーバーからはHTTPSの`redirect_uri`に戻る必要があるため、そこに配置した`redirect.html`が最終的に`yourscheme://...`へリダイレクトしてアプリに戻します。
-  - MiAuth: 認証開始URLの`callback`クエリに、最初から`yourscheme://...`を指定します（`https`は不要）。
+  - MiAuth: 認証開始URLの`callback`クエリには、アプリのカスタムスキームのみ（例: `yourscheme://`）を指定します（`https`は不要）。
 
 ##### MiAuth の例（保存無し）
 
@@ -579,7 +569,7 @@ final miConfig = MisskeyMiAuthConfig(
   permissions: ['read:account', 'write:notes'],
   iconUrl: 'https://example.com/icon.png', // 任意
 );
-final miRes = await miClient.authenticate(miConfig); // トークンのみ返します
+final miRes = await miClient.authenticate(miConfig); // トークン（必要に応じて user も）を返します
 ```
 
 ##### MiAuth の例（MisskeyAuthManager による保存あり）
@@ -640,13 +630,13 @@ final current = await auth.currentToken();
 
 ##### 両方式を同一アプリでサポートするには
 
-- iOSの`Info.plist`・Androidの`AndroidManifest.xml`で同じ`sheme`（例: `yourscheme`）を1つ登録すれば、OAuth/MiAuthで共用可能です。
-- OAuth用の`redirect.html`は、`yourscheme://oauth/callback?...`へ飛ばす実装にしておくと、MiAuthの`callback`でも同じパス表現（`yourscheme://oauth/callback`）を使い回せます。
+- iOSの`Info.plist`・Androidの`AndroidManifest.xml`で同じ`scheme`（例: `yourscheme`）を1つ登録すれば、OAuth/MiAuthで共用可能です。
+- 本ライブラリの MiAuth は scheme のみ（`yourscheme://`）を callback に使います。`yourscheme://oauth/callback` のようなパス付きに揃える必要はありません。
 - Androidは以下のように`scheme`のみのマッチで十分です（`host`や`path`は任意）。
 
 ```xml
 <activity android:name="com.linusu.flutter_web_auth.CallbackActivity" android:exported="true">
-    <intent-filter android:label="flutter_web_auth">
+    <intent-filter android:label="flutter_web_auth_2">
         <action android:name="android.intent.action.VIEW" />
         <category android:name="android.intent.category.DEFAULT" />
         <category android:name="android.intent.category.BROWSABLE" />
@@ -777,7 +767,7 @@ class AccountEntry {
 
 ### ライセンス
 
-このプロジェクトは3-Clause BSD Licenseの下で公開されています。詳細は[LICENSE](LICENSE)ファイルをご覧ください。
+このプロジェクトは司書(LibraryLibrarian)によって、3-Clause BSD Licenseの下で公開されています。詳細は[LICENSE](LICENSE)ファイルをご覧ください。
 
 ### リンク
 
diff --git a/assets/demo_thumb.gif b/assets/demo_thumb.gif
index 5e3e955..2c02333 100644
Binary files a/assets/demo_thumb.gif and b/assets/demo_thumb.gif differ
diff --git a/example/lib/main.dart b/example/lib/main.dart
index 377160f..fa6e4ae 100644
--- a/example/lib/main.dart
+++ b/example/lib/main.dart
@@ -3,6 +3,7 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:misskey_auth/misskey_auth.dart';
 import 'package:loader_overlay/loader_overlay.dart';
+import 'package:flutter/services.dart';
 
 void main() {
   runApp(const MyApp());
@@ -53,6 +54,38 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
   // 状態
   OAuthServerInfo? _serverInfo;
 
+  // スコープ入力（カスタムのみを採用）
+  final TextEditingController _oauthCustomScopesController =
+      TextEditingController();
+  final TextEditingController _miCustomScopesController =
+      TextEditingController();
+
+  void _addOAuthCustomScopesFromInput() {
+    final List<String> items = _oauthCustomScopesController.text
+        .split(',')
+        .map((e) => e.trim())
+        .where((e) => e.isNotEmpty)
+        .toList();
+    if (items.isEmpty) return;
+    _scopeController.text = items.join(' ');
+    setState(() {
+      _oauthCustomScopesController.clear();
+    });
+  }
+
+  void _addMiCustomScopesFromInput() {
+    final List<String> items = _miCustomScopesController.text
+        .split(',')
+        .map((e) => e.trim())
+        .where((e) => e.isNotEmpty)
+        .toList();
+    if (items.isEmpty) return;
+    _miPermissionsController.text = items.join(' ');
+    setState(() {
+      _miCustomScopesController.clear();
+    });
+  }
+
   String _mapErrorToMessage(Object error) {
     // MisskeyAuth のカスタム例外をユーザー向け日本語に整形
     if (error is MisskeyAuthException) {
@@ -145,6 +178,8 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
     _miAppNameController.text = 'Misskey Auth Example';
     _miPermissionsController.text = 'read:account write:notes';
     _miIconUrlController.text = '';
+
+    // 候補配列は廃止（カスタム欄から確定時にTextControllerへ反映）
   }
 
   Future<void> _checkServerInfo() async {
@@ -169,22 +204,24 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
       });
 
       if (serverInfo == null && mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          const SnackBar(
-              content: Text('OAuth認証はサポートされていません（MiAuth認証を使用してください）')),
-        );
+        ScaffoldMessenger.of(context)
+          ..hideCurrentSnackBar()
+          ..showSnackBar(
+            const SnackBar(
+                content: Text('OAuth認証はサポートされていません（MiAuth認証を使用してください）')),
+          );
       }
     } on MisskeyAuthException catch (e) {
       if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(content: Text(_mapErrorToMessage(e))),
-        );
+        ScaffoldMessenger.of(context)
+          ..hideCurrentSnackBar()
+          ..showSnackBar(SnackBar(content: Text(_mapErrorToMessage(e))));
       }
     } catch (e) {
       if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(content: Text(e.toString())),
-        );
+        ScaffoldMessenger.of(context)
+          ..hideCurrentSnackBar()
+          ..showSnackBar(SnackBar(content: Text(e.toString())));
       }
     } finally {
       if (mounted) {
@@ -198,6 +235,8 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
     context.loaderOverlay.show();
 
     try {
+      // 未確定のカスタムスコープ入力を確定して反映
+      _addOAuthCustomScopesFromInput();
       final config = MisskeyOAuthConfig(
         host: _hostController.text.trim(),
         clientId: _clientIdController.text.trim(),
@@ -214,24 +253,24 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
       }
 
       if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          const SnackBar(content: Text('認証に成功しました！')),
-        );
+        ScaffoldMessenger.of(context)
+          ..hideCurrentSnackBar()
+          ..showSnackBar(const SnackBar(content: Text('認証に成功しました！')));
         setState(() {
           _currentIndex = 3; // アカウント一覧タブへ
         });
       }
     } on MisskeyAuthException catch (e) {
       if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(content: Text(_mapErrorToMessage(e))),
-        );
+        ScaffoldMessenger.of(context)
+          ..hideCurrentSnackBar()
+          ..showSnackBar(SnackBar(content: Text(_mapErrorToMessage(e))));
       }
     } catch (e) {
       if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(content: Text('認証エラー: $e')),
-        );
+        ScaffoldMessenger.of(context)
+          ..hideCurrentSnackBar()
+          ..showSnackBar(SnackBar(content: Text('認証エラー: $e')));
       }
     } finally {
       if (mounted) {
@@ -245,6 +284,8 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
     context.loaderOverlay.show();
 
     try {
+      // 未確定のカスタムスコープ入力を確定して反映
+      _addMiCustomScopesFromInput();
       final host = _hostController.text.trim();
       if (host.isEmpty) {
         throw Exception('ホストを入力してください');
@@ -278,24 +319,24 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
       }
 
       if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          const SnackBar(content: Text('MiAuth に成功しました！')),
-        );
+        ScaffoldMessenger.of(context)
+          ..hideCurrentSnackBar()
+          ..showSnackBar(const SnackBar(content: Text('MiAuth に成功しました！')));
         setState(() {
           _currentIndex = 3; // アカウント一覧タブへ
         });
       }
     } on MisskeyAuthException catch (e) {
       if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(content: Text(_mapErrorToMessage(e))),
-        );
+        ScaffoldMessenger.of(context)
+          ..hideCurrentSnackBar()
+          ..showSnackBar(SnackBar(content: Text(_mapErrorToMessage(e))));
       }
     } catch (e) {
       if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(content: Text('MiAuth エラー: $e')),
-        );
+        ScaffoldMessenger.of(context)
+          ..hideCurrentSnackBar()
+          ..showSnackBar(SnackBar(content: Text('MiAuth エラー: $e')));
       }
     } finally {
       if (mounted) {
@@ -364,7 +405,7 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
                 hintText: '例: misskeyauth',
               ),
             ),
-            const SizedBox(height: 16),
+            const SizedBox(height: 8),
             TextField(
               controller: _hostController,
               decoration: const InputDecoration(
@@ -390,25 +431,31 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
               ),
             ),
             const SizedBox(height: 8),
+            const Text(
+              'カスタムスコープ（カンマ区切り）',
+              style: TextStyle(fontWeight: FontWeight.w600),
+            ),
+            const SizedBox(height: 8),
             TextField(
-              controller: _scopeController,
+              controller: _oauthCustomScopesController,
               decoration: const InputDecoration(
-                labelText: 'スコープ',
-                hintText: '例: read:account write:notes',
+                labelText: '例: write:drive, read:favorites',
               ),
+              keyboardType: TextInputType.text,
+              textInputAction: TextInputAction.done,
+              onSubmitted: (_) => _addOAuthCustomScopesFromInput(),
             ),
             const SizedBox(height: 16),
-            Row(
-              children: [
-                ElevatedButton(
-                  onPressed: _startAuth,
-                  style: ElevatedButton.styleFrom(
-                    backgroundColor: Theme.of(context).colorScheme.primary,
-                    foregroundColor: Colors.white,
-                  ),
-                  child: const Text('認証を開始'),
+            SizedBox(
+              width: double.infinity,
+              child: ElevatedButton(
+                onPressed: _startAuth,
+                style: ElevatedButton.styleFrom(
+                  backgroundColor: Theme.of(context).colorScheme.primary,
+                  foregroundColor: Colors.white,
                 ),
-              ],
+                child: const Text('OAuthで認証'),
+              ),
             ),
           ],
         ),
@@ -452,12 +499,19 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
               ),
             ),
             const SizedBox(height: 8),
+            const Text(
+              'カスタムスコープ（カンマ区切り）',
+              style: TextStyle(fontWeight: FontWeight.w600),
+            ),
+            const SizedBox(height: 8),
             TextField(
-              controller: _miPermissionsController,
+              controller: _miCustomScopesController,
               decoration: const InputDecoration(
-                labelText: '権限（空白/カンマ区切り）',
-                hintText: '例: read:account write:notes',
+                labelText: '例: write:drive, read:favorites',
               ),
+              keyboardType: TextInputType.text,
+              textInputAction: TextInputAction.done,
+              onSubmitted: (_) => _addMiCustomScopesFromInput(),
             ),
             const SizedBox(height: 8),
             TextField(
@@ -467,17 +521,16 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
               ),
             ),
             const SizedBox(height: 16),
-            Row(
-              children: [
-                ElevatedButton(
-                  onPressed: _startMiAuth,
-                  style: ElevatedButton.styleFrom(
-                    backgroundColor: Theme.of(context).colorScheme.primary,
-                    foregroundColor: Colors.white,
-                  ),
-                  child: const Text('MiAuthで認証'),
+            SizedBox(
+              width: double.infinity,
+              child: ElevatedButton(
+                onPressed: _startMiAuth,
+                style: ElevatedButton.styleFrom(
+                  backgroundColor: Theme.of(context).colorScheme.primary,
+                  foregroundColor: Colors.white,
                 ),
-              ],
+                child: const Text('MiAuthで認証'),
+              ),
             ),
           ],
         ),
@@ -497,13 +550,45 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
               style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
             ),
             const SizedBox(height: 8),
-            Text('認証エンドポイント:\n${_serverInfo!.authorizationEndpoint}'),
+            const Text('認証エンドポイント'),
             const SizedBox(height: 4),
-            Text('トークンエンドポイント:\n${_serverInfo!.tokenEndpoint}'),
-            if (_serverInfo!.scopesSupported != null) ...[
+            SelectableText(_serverInfo!.authorizationEndpoint),
+            const SizedBox(height: 8),
+            const Text('トークンエンドポイント'),
+            const SizedBox(height: 4),
+            SelectableText(_serverInfo!.tokenEndpoint),
+            if (_serverInfo!.scopesSupported != null &&
+                _serverInfo!.scopesSupported!.isNotEmpty) ...[
+              const SizedBox(height: 12),
+              const Text('サポートされているスコープ（タップでコピー）'),
               const SizedBox(height: 4),
-              Text(
-                  'サポートされているスコープ:\n${_serverInfo!.scopesSupported!.join(', ')}'),
+              ConstrainedBox(
+                constraints: const BoxConstraints(maxHeight: 200),
+                child: Scrollbar(
+                  child: ListView.separated(
+                    itemCount: _serverInfo!.scopesSupported!.length,
+                    separatorBuilder: (_, __) => const Divider(height: 1),
+                    itemBuilder: (context, index) {
+                      final scope = _serverInfo!.scopesSupported![index];
+                      return InkWell(
+                        onTap: () async {
+                          await Clipboard.setData(ClipboardData(text: scope));
+                          if (!context.mounted) return;
+                          ScaffoldMessenger.of(context)
+                            ..hideCurrentSnackBar()
+                            ..showSnackBar(
+                              SnackBar(content: Text('コピーしました: $scope')),
+                            );
+                        },
+                        child: Padding(
+                          padding: const EdgeInsets.symmetric(vertical: 10.0),
+                          child: Text(scope),
+                        ),
+                      );
+                    },
+                  ),
+                ),
+              ),
             ],
           ],
         ),
@@ -534,9 +619,12 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
                   ),
                 ),
                 const SizedBox(height: 16),
-                ElevatedButton(
-                  onPressed: _checkServerInfo,
-                  child: const Text('サーバー情報を確認'),
+                SizedBox(
+                  width: double.infinity,
+                  child: ElevatedButton(
+                    onPressed: _checkServerInfo,
+                    child: const Text('サーバー情報を確認'),
+                  ),
                 ),
               ],
             ),
@@ -585,9 +673,11 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
                           '[Dump] ${key.host}/${key.accountId} token=${t?.accessToken}');
                     }
                     if (!context.mounted) return;
-                    ScaffoldMessenger.of(context).showSnackBar(
-                      const SnackBar(content: Text('デバッグログにトークンを出力しました')),
-                    );
+                    ScaffoldMessenger.of(context)
+                      ..hideCurrentSnackBar()
+                      ..showSnackBar(
+                        const SnackBar(content: Text('デバッグログにトークンを出力しました')),
+                      );
                   },
                 )
               ],
@@ -647,9 +737,12 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
                         await _auth.setActive(key);
                         if (mounted) setState(() {});
                         if (!context.mounted) return;
-                        ScaffoldMessenger.of(context).showSnackBar(
-                          SnackBar(content: Text('デフォルトを変更: ${key.accountId}')),
-                        );
+                        ScaffoldMessenger.of(context)
+                          ..hideCurrentSnackBar()
+                          ..showSnackBar(
+                            SnackBar(
+                                content: Text('デフォルトを変更: ${key.accountId}')),
+                          );
                       },
                     );
                   },
diff --git a/lib/src/api/misskey_miauth_client.dart b/lib/src/api/misskey_miauth_client.dart
index 695a590..6c3276b 100644
--- a/lib/src/api/misskey_miauth_client.dart
+++ b/lib/src/api/misskey_miauth_client.dart
@@ -7,6 +7,7 @@ import 'package:flutter_web_auth_2/flutter_web_auth_2.dart';
 
 import '../models/miauth_models.dart';
 import '../exceptions/misskey_auth_exception.dart';
+import '../net/retry.dart';
 
 /// Misskey の MiAuth 認証を扱うクライアント
 class MisskeyMiAuthClient {
@@ -110,10 +111,13 @@ class MisskeyMiAuthClient {
         path: '/api/miauth/$sessionId/check',
       );
 
-      final response = await _dio.post(
-        checkUrl.toString(),
-        options: Options(contentType: 'application/json'),
-        data: <String, dynamic>{},
+      final response = await retry(
+        () => _dio.post(
+          checkUrl.toString(),
+          options: Options(contentType: 'application/json'),
+          data: <String, dynamic>{},
+        ),
+        const RetryPolicy(maxAttempts: 3),
       );
 
       if (response.statusCode != 200) {
diff --git a/lib/src/api/misskey_oauth_client.dart b/lib/src/api/misskey_oauth_client.dart
index 8a93755..dfad0ea 100644
--- a/lib/src/api/misskey_oauth_client.dart
+++ b/lib/src/api/misskey_oauth_client.dart
@@ -7,6 +7,7 @@ import 'package:flutter/services.dart';
 import 'package:flutter_web_auth_2/flutter_web_auth_2.dart';
 import '../models/oauth_models.dart';
 import '../exceptions/misskey_auth_exception.dart';
+import '../net/retry.dart';
 
 /// MisskeyのOAuth認証を管理するクライアント
 class MisskeyOAuthClient {
@@ -41,8 +42,9 @@ class MisskeyOAuthClient {
   /// OAuth認証サーバー情報を取得
   Future<OAuthServerInfo?> getOAuthServerInfo(String host) async {
     try {
-      final response = await _dio.get(
-        'https://$host/.well-known/oauth-authorization-server',
+      final response = await retry(
+        () => _dio.get('https://$host/.well-known/oauth-authorization-server'),
+        const RetryPolicy(maxAttempts: 3),
       );
 
       if (response.statusCode == 200) {
@@ -253,19 +255,22 @@ class MisskeyOAuthClient {
     required String codeVerifier,
   }) async {
     try {
-      final response = await _dio.post(
-        tokenEndpoint,
-        options: Options(
-          contentType: 'application/x-www-form-urlencoded',
+      final response = await retry(
+        () => _dio.post(
+          tokenEndpoint,
+          options: Options(
+            contentType: 'application/x-www-form-urlencoded',
+          ),
+          data: {
+            'grant_type': 'authorization_code',
+            'client_id': clientId,
+            'redirect_uri': redirectUri,
+            'scope': scope,
+            'code': code,
+            'code_verifier': codeVerifier,
+          },
         ),
-        data: {
-          'grant_type': 'authorization_code',
-          'client_id': clientId,
-          'redirect_uri': redirectUri,
-          'scope': scope,
-          'code': code,
-          'code_verifier': codeVerifier,
-        },
+        const RetryPolicy(maxAttempts: 3),
       );
 
       if (response.statusCode == 200) {
diff --git a/lib/src/auth/misskey_auth_manager.dart b/lib/src/auth/misskey_auth_manager.dart
index d69d863..8a2b4ac 100644
--- a/lib/src/auth/misskey_auth_manager.dart
+++ b/lib/src/auth/misskey_auth_manager.dart
@@ -9,6 +9,7 @@ import '../store/account_key.dart';
 import '../store/secure_token_store.dart';
 import '../store/stored_token.dart';
 import '../store/token_store.dart';
+import '../net/retry.dart';
 
 /// Misskey 認証の高レベル管理クラス
 ///
@@ -102,10 +103,13 @@ class MisskeyAuthManager {
       String host, String accessToken) async {
     try {
       final url = 'https://$host/api/i';
-      final response = await dio.post(
-        url,
-        // Misskeyの一般的な仕様に従い、リクエストボディに `i` でトークンを渡す
-        data: <String, dynamic>{'i': accessToken},
+      final response = await retry(
+        () => dio.post(
+          url,
+          // Misskeyの一般的な仕様に従い、リクエストボディに `i` でトークンを渡す
+          data: <String, dynamic>{'i': accessToken},
+        ),
+        const RetryPolicy(maxAttempts: 3),
       );
       if (response.statusCode == 200 && response.data is Map<String, dynamic>) {
         return response.data as Map<String, dynamic>;
diff --git a/lib/src/net/retry.dart b/lib/src/net/retry.dart
new file mode 100644
index 0000000..afc6e68
--- /dev/null
+++ b/lib/src/net/retry.dart
@@ -0,0 +1,83 @@
+import 'dart:math';
+
+import 'package:dio/dio.dart';
+
+/// ネットワークリクエストのリトライポリシー。
+class RetryPolicy {
+  /// 最大試行回数（初回含む）。
+  final int maxAttempts;
+
+  /// 初回遅延。
+  final Duration initialDelay;
+
+  /// 指数バックオフの倍率。
+  final double backoffFactor;
+
+  /// 遅延の上限。
+  final Duration maxDelay;
+
+  /// リトライ対象の Dio 例外タイプ。
+  final Set<DioExceptionType> retryOnTypes;
+
+  /// リトライ対象のHTTPステータス。
+  final Set<int> retryOnStatusCodes;
+
+  const RetryPolicy({
+    this.maxAttempts = 3,
+    this.initialDelay = const Duration(milliseconds: 500),
+    this.backoffFactor = 2.0,
+    this.maxDelay = const Duration(seconds: 5),
+    this.retryOnTypes = const {
+      DioExceptionType.connectionTimeout,
+      DioExceptionType.sendTimeout,
+      DioExceptionType.receiveTimeout,
+      DioExceptionType.connectionError,
+      DioExceptionType.unknown,
+    },
+    this.retryOnStatusCodes = const {429, 500, 502, 503, 504},
+  });
+
+  /// 応答/例外からリトライすべきかを判定。
+  bool shouldRetry(DioException e) {
+    if (retryOnTypes.contains(e.type)) {
+      return true;
+    }
+    final status = e.response?.statusCode;
+    if (status != null && retryOnStatusCodes.contains(status)) {
+      return true;
+    }
+    return false;
+  }
+
+  /// 指数バックオフで次の遅延を計算（上限あり、軽いジッター）。
+  Duration nextDelay(int attemptIndexZeroBased) {
+    final baseMs =
+        initialDelay.inMilliseconds * pow(backoffFactor, attemptIndexZeroBased);
+    final cappedMs = min(baseMs.round(), maxDelay.inMilliseconds);
+    final jitterMs = Random().nextInt(100); // 0-99ms の軽いジッター
+    return Duration(
+        milliseconds: min(cappedMs + jitterMs, maxDelay.inMilliseconds));
+  }
+}
+
+/// 与えられた非同期処理をリトライ付きで実行します。
+Future<T> retry<T>(Future<T> Function() action, RetryPolicy policy) async {
+  DioException? last;
+  for (int attempt = 0; attempt < policy.maxAttempts; attempt++) {
+    try {
+      return await action();
+    } on DioException catch (e) {
+      last = e;
+      final should = policy.shouldRetry(e);
+      final isLast = attempt == policy.maxAttempts - 1;
+      if (!should || isLast) {
+        rethrow;
+      }
+      await Future.delayed(policy.nextDelay(attempt));
+      continue;
+    }
+  }
+  // 通常ここには到達しない
+  if (last != null) throw last;
+  throw StateError('Retry failed with unknown error');
+}