One-tap GitHub connect via a baked-in OAuth App client id

Previously "Connect GitHub" (OAuth device flow) still required entering an
OAuth App client id and owner/repo — friction that returned on every
reinstall once shared_prefs were wiped.

- Bake the app's own device-flow OAuth App client id in as
  SyncSettings.defaultClientId and default to it in load() (alongside the
  existing kuhyx/todo-sync repo default). A device-flow client id is a
  public identifier, not a secret, so it is safe to commit.
- Settings now leads with a single "Connect GitHub" button; the manual
  client-id / token fields and Test connection move under an "Advanced"
  expander. Result: fresh install (or post-reinstall) is one tap →
  authorize the code in the browser → synced. No tokens, no setup.

Note: an OAuth App authorizes with the classic `repo` scope (all repos),
broader than the prior fine-grained PAT — the trade-off for one-tap
device-flow convenience. 151 tests, 100% line coverage.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/sync/sync_settings.dart

@@ -19,10 +19,15 @@ class SyncSettings {
   final String token;
 
   /// GitHub OAuth App client id used by the device-flow "Connect" button.
-  /// Not a secret (device flow needs no client secret), so it is safe to
-  /// store here and could later be shipped as a compile-time default.
+  /// Not a secret (device flow needs no client secret), so it is safe to ship
+  /// as a compile-time default and commit to source — see [defaultClientId].
   final String clientId;
 
+  /// The app's own GitHub OAuth App (device-flow enabled) client id, baked in
+  /// so "Connect GitHub" works with zero setup — even after a reinstall. A
+  /// device-flow client id is a public identifier, not a secret.
+  static const defaultClientId = 'Ov23li9tF2R46PqzJgch';
+
   /// True when enough is set to attempt a sync.
   bool get isConfigured =>
       owner.isNotEmpty && repo.isNotEmpty && token.isNotEmpty;
@@ -35,15 +40,16 @@ class SyncSettings {
   static const _kToken = 'sync.token';
   static const _kClientId = 'sync.clientId';
 
-  /// Loads settings, defaulting the repo to `kuhyx/todo-sync` so the user
-  /// only has to authorize on first run.
+  /// Loads settings, defaulting the repo to `kuhyx/todo-sync` and the client id
+  /// to the baked-in [defaultClientId] so first run (and any reinstall) needs
+  /// nothing but a single "Connect GitHub" tap.
   static Future<SyncSettings> load() async {
     final prefs = await SharedPreferences.getInstance();
     return SyncSettings(
       owner: prefs.getString(_kOwner) ?? 'kuhyx',
       repo: prefs.getString(_kRepo) ?? 'todo-sync',
       token: prefs.getString(_kToken) ?? '',
-      clientId: prefs.getString(_kClientId) ?? '',
+      clientId: prefs.getString(_kClientId) ?? defaultClientId,
     );
   }
 

lib/ui/settings_screen.dart

@@ -215,6 +215,23 @@ class _SettingsScreenState extends State<SettingsScreen> {
       body: ListView(
         padding: const EdgeInsets.all(16),
         children: [
+          Text(
+            'Connect to GitHub',
+            style: Theme.of(context).textTheme.titleMedium,
+          ),
+          const SizedBox(height: 4),
+          Text(
+            'Authorize in your browser — no token to paste. Syncs to '
+            'kuhyx/todo-sync by default.',
+            style: Theme.of(context).textTheme.bodySmall,
+          ),
+          const SizedBox(height: 12),
+          FilledButton.icon(
+            onPressed: _connectGitHub,
+            icon: const Icon(Icons.login),
+            label: const Text('Connect GitHub'),
+          ),
+          const SizedBox(height: 16),
           TextField(
             controller: _owner,
             decoration: const InputDecoration(
@@ -230,47 +247,36 @@ class _SettingsScreenState extends State<SettingsScreen> {
               border: OutlineInputBorder(),
             ),
           ),
-          const SizedBox(height: 24),
-          Text(
-            'Connect with GitHub',
-            style: Theme.of(context).textTheme.titleMedium,
-          ),
           const SizedBox(height: 8),
+          // Manual escape hatches — most users never open this.
+          ExpansionTile(
+            title: const Text('Advanced'),
+            tilePadding: EdgeInsets.zero,
+            childrenPadding: const EdgeInsets.only(bottom: 8),
+            children: [
               TextField(
                 controller: _clientId,
                 decoration: const InputDecoration(
                   labelText: 'OAuth App client id',
-              helperText: 'From your GitHub OAuth App (device flow enabled)',
+                  helperText:
+                      'Leave as the baked-in default unless self-hosting',
                   border: OutlineInputBorder(),
                 ),
               ),
               const SizedBox(height: 12),
-          FilledButton.icon(
-            onPressed: _connectGitHub,
-            icon: const Icon(Icons.login),
-            label: const Text('Connect GitHub'),
-          ),
-          const SizedBox(height: 24),
-          const Divider(),
-          const SizedBox(height: 8),
-          Text(
-            'Or paste a token (fallback)',
-            style: Theme.of(context).textTheme.titleMedium,
-          ),
-          const SizedBox(height: 8),
               TextField(
                 controller: _token,
                 obscureText: true,
                 decoration: const InputDecoration(
-              labelText: 'Access token (fine-grained PAT)',
+                  labelText: 'Access token (fallback)',
                   helperText: 'Contents: read/write on the sync repo only',
                   border: OutlineInputBorder(),
                 ),
               ),
-          const SizedBox(height: 16),
-          Row(
-            children: [
-              OutlinedButton.icon(
+              const SizedBox(height: 12),
+              Align(
+                alignment: Alignment.centerLeft,
+                child: OutlinedButton.icon(
                   onPressed: _testing ? null : _test,
                   icon: _testing
                       ? const SizedBox(
@@ -281,13 +287,17 @@ class _SettingsScreenState extends State<SettingsScreen> {
                       : const Icon(Icons.wifi_tethering),
                   label: const Text('Test connection'),
                 ),
-              const Spacer(),
-              FilledButton.icon(
+              ),
+            ],
+          ),
+          const SizedBox(height: 8),
+          Align(
+            alignment: Alignment.centerRight,
+            child: FilledButton.icon(
               onPressed: _save,
               icon: const Icon(Icons.save),
               label: const Text('Save'),
             ),
-            ],
           ),
           const SizedBox(height: 24),
           const Divider(),

test/settings_screen_test.dart

@@ -130,6 +130,8 @@ void main() {
     final mock = MockClient((_) async => http.Response('{}', 200));
     await pumpSettings(tester, httpClient: mock);
 
+    await tester.tap(find.text('Advanced')); // Test connection lives here now
+    await tester.pumpAndSettle();
     await tester.tap(find.text('Test connection'));
     await tester.pump(); // start
     await tester.pump(); // resolve future + rebuild
@@ -141,6 +143,8 @@ void main() {
     final mock = MockClient((_) async => http.Response('', 404));
     await pumpSettings(tester, httpClient: mock);
 
+    await tester.tap(find.text('Advanced'));
+    await tester.pumpAndSettle();
     await tester.tap(find.text('Test connection'));
     await tester.pump();
     await tester.pump();
@@ -152,6 +156,8 @@ void main() {
     final mock = MockClient((_) async => throw Exception('offline'));
     await pumpSettings(tester, httpClient: mock);
 
+    await tester.tap(find.text('Advanced'));
+    await tester.pumpAndSettle();
     await tester.tap(find.text('Test connection'));
     await tester.pump();
     await tester.pump();

test/sync_settings_test.dart

@@ -11,7 +11,8 @@ void main() {
       expect(s.owner, 'kuhyx');
       expect(s.repo, 'todo-sync');
       expect(s.token, '');
-      expect(s.clientId, '');
+      // Client id defaults to the baked-in OAuth App id (one-tap connect).
+      expect(s.clientId, SyncSettings.defaultClientId);
     },
   );