fix: eliminate pull-to-refresh flicker by holding stale data during re-fetch

lib/app.dart

@@ -236,13 +236,13 @@ class _ShellState extends ConsumerState<_Shell> with WidgetsBindingObserver {
   /// Refresh every major data provider. Safe to call speculatively —
   /// providers that aren't currently watched are already disposed.
   void _refreshAll() {
-    ref.invalidate(conversationsProvider);
-    ref.invalidate(calendarProvider);
-    ref.invalidate(newsProvider);
-    // Notifier (not AsyncNotifier) — needs explicit refresh call.
+    ref.read(conversationsProvider.notifier).refresh();
+    ref.read(calendarProvider.notifier).refresh();
+    ref.read(newsProvider.notifier).refresh();
     ref.read(knowledgeProvider.notifier).refresh();
-    // briefingProvider is an AsyncNotifier family; invalidating the family
-    // is safe even if no conversation is open.
+    // briefingProvider is an AsyncNotifier family; invalidating is safe
+    // even if no conversation is open — it doesn't cause flicker since
+    // the briefing screen isn't a list view.
     ref.invalidate(briefingProvider);
   }
 
@@ -254,7 +254,7 @@ class _ShellState extends ConsumerState<_Shell> with WidgetsBindingObserver {
       case 1:
         ref.read(knowledgeProvider.notifier).refresh();
       case 2:
-        ref.invalidate(conversationsProvider);
+        ref.read(conversationsProvider.notifier).refresh();
     }
   }
 

lib/providers/calendar_provider.dart

@@ -56,6 +56,17 @@ class CalendarNotifier extends AsyncNotifier<CalendarState> {
     );
   }
 
+  /// Re-fetch events for the current range without clearing state (no flicker).
+  Future<void> refresh() async {
+    final current = state.value;
+    if (current == null) return;
+    final events = await ref.read(eventsApiProvider).getEvents(
+      current.loadedRange.start,
+      current.loadedRange.end,
+    );
+    state = AsyncData(current.copyWith(eventsByDay: _groupByDay(events)));
+  }
+
   /// Synchronously updates selectedDay and focusedMonth. No API call.
   void selectDay(DateTime day) {
     final current = state.value;

lib/providers/chat_provider.dart

@@ -58,6 +58,12 @@ class ConversationsNotifier extends AsyncNotifier<List<Conversation>> {
     ]);
   }
 
+  /// Re-fetch conversations without clearing the current list (no flicker).
+  Future<void> refresh() async {
+    final fresh = await ref.read(chatRepositoryProvider).getConversations();
+    state = AsyncData(fresh);
+  }
+
   // Called after a message is sent to patch the server-generated title
   // in-place without triggering a full reload or loading state.
   void patchConversation(Conversation updated) {
@@ -86,6 +92,13 @@ class MessagesNotifier extends AsyncNotifier<List<Message>> {
     return messages;
   }
 
+  /// Re-fetch messages without clearing the current list (no flicker).
+  Future<void> refresh() async {
+    final (_, messages) =
+        await ref.read(chatRepositoryProvider).getMessages(_convId);
+    state = AsyncData(messages);
+  }
+
   Future<void> sendMessage(String content) async {
     final convId = _convId;
     final repo = ref.read(chatRepositoryProvider);

lib/providers/news_provider.dart

@@ -71,6 +71,25 @@ class NewsNotifier extends AsyncNotifier<NewsState> {
     );
   }
 
+  /// Re-fetch the first page without clearing state (no flicker).
+  Future<void> refresh() async {
+    final current = state.value;
+    final items = await ref.read(newsApiProvider).getNewsItems(
+          days: 90,
+          limit: _limit,
+          offset: 0,
+          feedId: current?.selectedFeedId,
+        );
+    state = AsyncData(NewsState(
+      items: items,
+      offset: items.length,
+      hasMore: items.length == _limit,
+      loadingMore: false,
+      selectedFeedId: current?.selectedFeedId,
+      reactions: {for (final item in items) item.id: item.reaction},
+    ));
+  }
+
   Future<void> loadMore() async {
     final current = state.value;
     if (current == null || current.loadingMore || !current.hasMore) return;

lib/providers/projects_provider.dart

@@ -15,6 +15,12 @@ class ProjectsNotifier extends AsyncNotifier<List<Project>> {
         .getAll(sort: 'updated_at', order: 'desc');
   }
 
+  Future<void> refresh() async {
+    final fresh = await ref.read(projectsRepositoryProvider)
+        .getAll(sort: 'updated_at', order: 'desc');
+    state = AsyncData(fresh);
+  }
+
   Future<Project> create({
     required String title,
     String? description,

lib/providers/tasks_provider.dart

@@ -17,6 +17,11 @@ class TasksNotifier extends AsyncNotifier<List<Task>> {
     return ref.watch(tasksRepositoryProvider).getAll();
   }
 
+  Future<void> refresh() async {
+    final fresh = await ref.read(tasksRepositoryProvider).getAll();
+    state = AsyncData(fresh);
+  }
+
   Future<Task> create({
     required String title,
     String? description,

lib/screens/calendar/calendar_screen.dart

@@ -68,7 +68,7 @@ class CalendarScreen extends ConsumerWidget {
             const Divider(height: 1),
             Expanded(
               child: RefreshIndicator(
-                onRefresh: () async => ref.invalidate(calendarProvider),
+                onRefresh: () => ref.read(calendarProvider.notifier).refresh(),
                 child: _AgendaList(
                   events:
                       cal.eventsByDay[dateOnly(cal.selectedDay)] ?? [],

lib/screens/chat/chat_screen.dart

@@ -30,7 +30,7 @@ class _ChatScreenState extends ConsumerState<ChatScreen>
   @override
   void didChangeAppLifecycleState(AppLifecycleState state) {
     if (state == AppLifecycleState.resumed) {
-      ref.invalidate(messagesProvider(widget.conversationId));
+      ref.read(messagesProvider(widget.conversationId).notifier).refresh();
     }
   }
 

lib/screens/chat/conversations_tab_screen.dart

@@ -64,7 +64,7 @@ class ConversationsTabScreen extends ConsumerWidget {
             );
           }
           return RefreshIndicator(
-            onRefresh: () async => ref.invalidate(conversationsProvider),
+            onRefresh: () => ref.read(conversationsProvider.notifier).refresh(),
             child: ListView.builder(
               itemCount: convs.length,
               itemBuilder: (ctx, i) {

lib/screens/library/project_tasks_screen.dart

@@ -151,8 +151,10 @@ class _ProjectTasksScreenState extends ConsumerState<ProjectTasksScreen> {
     return RefreshIndicator(
       onRefresh: () async {
         setState(() => _pendingStatus.clear());
-        ref.invalidate(projectTasksProvider(widget.projectId));
-        ref.invalidate(projectMilestonesProvider(widget.projectId));
+        await Future.wait([
+          ref.refresh(projectTasksProvider(widget.projectId).future),
+          ref.refresh(projectMilestonesProvider(widget.projectId).future),
+        ]);
       },
       child: CustomScrollView(
         slivers: [

lib/screens/news/news_screen.dart

@@ -97,7 +97,7 @@ class _NewsScreenState extends ConsumerState<NewsScreen> {
             const Divider(height: 1),
             Expanded(
               child: RefreshIndicator(
-                onRefresh: () async => ref.invalidate(newsProvider),
+                onRefresh: () => ref.read(newsProvider.notifier).refresh(),
                 child: ListView.builder(
                 padding:
                     const EdgeInsets.symmetric(horizontal: 8, vertical: 8),

lib/screens/projects/projects_screen.dart

@@ -19,7 +19,7 @@ class ProjectsScreen extends ConsumerWidget {
         data: (projects) => projects.isEmpty
             ? const Center(child: Text('No projects yet.'))
             : RefreshIndicator(
-                onRefresh: () async => ref.invalidate(projectsProvider),
+                onRefresh: () => ref.read(projectsProvider.notifier).refresh(),
                 child: ListView.separated(
                   itemCount: projects.length,
                   separatorBuilder: (_, _) => const Divider(height: 1),