fix(mobile): preserve exact mention recipients in saved drafts

mobile/lib/features/activity/compose_drafts_provider.dart

@@ -4,6 +4,7 @@ import 'package:flutter/foundation.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 
 import '../../shared/relay/relay.dart';
+import '../../shared/mentions/draft_mention.dart';
 import '../../shared/theme/theme_provider.dart';
 
 const _draftsPrefsKey = 'compose_drafts_v1';
@@ -22,13 +23,15 @@ class ComposeDraft {
   final String channelId;
   final String? threadHeadId;
   final String text;
+  final Map<String, DraftMention> mentions;
   final int updatedAt; // unix seconds
 
   const ComposeDraft({
     required this.key,
     required this.channelId,
     required this.threadHeadId,
     required this.text,
+    this.mentions = const {},
     required this.updatedAt,
   });
 
@@ -37,6 +40,8 @@ class ComposeDraft {
     'channel_id': channelId,
     if (threadHeadId != null) 'thread_head_id': threadHeadId,
     'text': text,
+    if (mentions.isNotEmpty)
+      'mentions': {for (final e in mentions.entries) e.key: e.value.toJson()},
     'updated_at': updatedAt,
   };
 
@@ -53,6 +58,7 @@ class ComposeDraft {
       channelId: channelId,
       threadHeadId: raw['thread_head_id'] as String?,
       text: text,
+      mentions: DraftMention.decode(raw['mentions']),
       updatedAt: updatedAt is int ? updatedAt : 0,
     );
   }
@@ -108,18 +114,24 @@ class ComposeDraftsNotifier extends Notifier<List<ComposeDraft>> {
     required String channelId,
     String? threadHeadId,
     required String text,
+    Map<String, DraftMention> mentions = const {},
   }) {
     if (text.trim().isEmpty) {
       remove(key);
       return;
     }
     final existing = state.where((d) => d.key == key).firstOrNull;
-    if (existing?.text == text) return;
+    if (existing?.text == text &&
+        jsonEncode(existing?.mentions.map((k, v) => MapEntry(k, v.toJson()))) ==
+            jsonEncode(mentions.map((k, v) => MapEntry(k, v.toJson())))) {
+      return;
+    }
     final draft = ComposeDraft(
       key: key,
       channelId: channelId,
       threadHeadId: threadHeadId,
       text: text,
+      mentions: Map.unmodifiable(mentions),
       updatedAt: DateTime.now().millisecondsSinceEpoch ~/ 1000,
     );
     final next = [draft, ...state.where((d) => d.key != key)];
@@ -131,6 +143,9 @@ class ComposeDraftsNotifier extends Notifier<List<ComposeDraft>> {
     _persist([...state.where((d) => d.key != key)]);
   }
 
+  ComposeDraft? draftFor(String key) =>
+      state.where((d) => d.key == key).firstOrNull;
+
   String? textFor(String key) =>
       state.where((d) => d.key == key).firstOrNull?.text;
 

mobile/lib/features/channels/compose_bar.dart

@@ -19,6 +19,7 @@ import 'package:nostr/nostr.dart' as nostr;
 
 import '../../shared/mentions/agent_identity_provider.dart';
 import '../../shared/mentions/mention_bindings.dart';
+import '../../shared/mentions/draft_mention.dart';
 import '../../shared/huddle/huddle_session.dart';
 import '../../shared/relay/relay.dart';
 import '../../shared/theme/theme.dart';

mobile/lib/features/channels/compose_bar/compose_bar_widget.dart

@@ -40,6 +40,7 @@ class ComposeBar extends HookConsumerWidget {
     useEffect(() => controller.dispose, [controller]);
     final draftKey = composeDraftKey(channelId, threadHeadId: threadHeadId);
     final draftRevision = useRef(0);
+    final mentionMap = useRef(<String, MentionCandidate>{});
     final draftIdentity = _composerDraftIdentity(ref);
     final isComposerExpanded = useState(false);
     final androidImeTransitionStarted = useState(
@@ -94,6 +95,7 @@ class ComposeBar extends HookConsumerWidget {
       threadHeadId: threadHeadId,
       draftIdentity: draftIdentity,
       draftRevision: draftRevision,
+      mentionMap: mentionMap,
       attachments: attachments,
       uploadGeneration: uploadGeneration,
       activeUploadCancellation: activeUploadCancellation,
@@ -219,11 +221,6 @@ class ComposeBar extends HookConsumerWidget {
     // Map of displayName → selected mention candidate built as the user selects
     // mentions. Used to pass resolved pubkeys directly to onSend and to attach
     // selected non-member agents before the message is published.
-    final mentionMap = useRef(<String, MentionCandidate>{});
-    useEffect(() {
-      mentionMap.value.clear();
-      return null;
-    }, [draftIdentity, draftKey]);
 
     // Channel autocomplete state ----------------------------------------------
     final channelQuery = useState<String?>(null);
@@ -413,6 +410,14 @@ class ComposeBar extends HookConsumerWidget {
       } finally {
         isModifyingText.value = false;
       }
+      _persistComposeDraft(
+        ref,
+        controller,
+        mentionMap.value,
+        draftKey,
+        channelId,
+        threadHeadId,
+      );
       mentionQuery.value = null;
     }
 
@@ -455,9 +460,9 @@ class ComposeBar extends HookConsumerWidget {
 
     void clearComposer() {
       draftRevision.value += 1;
+      mentionMap.value.clear();
       controller.clear();
       attachments.value = [];
-      mentionMap.value.clear();
       mentionQuery.value = null;
       channelQuery.value = null;
       attachmentSurface.value = _AttachmentSurface.closed;
@@ -620,12 +625,12 @@ class ComposeBar extends HookConsumerWidget {
             if (context.mounted &&
                 queueGeneration == uploadGeneration.value &&
                 draftRevision.value == clearedDraftRevision) {
-              controller.value = draftText;
-              attachments.value = draftAttachments;
-              retainedForRetry = true;
               mentionMap.value
                 ..clear()
                 ..addAll(draftMentions);
+              controller.value = draftText;
+              attachments.value = draftAttachments;
+              retainedForRetry = true;
               focusNode.requestFocus();
             }
           } finally {

mobile/lib/features/channels/compose_bar/draft_lifecycle.dart

@@ -26,10 +26,10 @@ Future<void> _sendTextOnlyDraft({
         draftRevision.value != clearedDraftRevision) {
       return;
     }
-    controller.value = clearedDraftText;
     mentionMap.value
       ..clear()
       ..addAll(clearedDraftMentions);
+    controller.value = clearedDraftText;
     focusNode.requestFocus();
   }
 
@@ -70,6 +70,7 @@ void _useComposeDraftLifecycle({
   required String? threadHeadId,
   required String draftIdentity,
   required ObjectRef<int> draftRevision,
+  required ObjectRef<Map<String, MentionCandidate>> mentionMap,
   required ValueNotifier<List<_PendingAttachment>> attachments,
   required ObjectRef<int> uploadGeneration,
   required ObjectRef<UploadCancellationToken?> activeUploadCancellation,
@@ -80,13 +81,34 @@ void _useComposeDraftLifecycle({
   required _IOSAttachmentPopoverController iosAttachmentPopover,
   required VoidCallback onDraftIdentityChanged,
 }) {
+  // Retire the old listener before restoring another scope's text: replacement
+  // effects can run before the previous effect's cleanup.
+  final owner = useMemoized(Object.new, [draftKey, draftIdentity]);
+  final currentOwner = useRef(owner)..value = owner;
   final lastDraftIdentity = useRef<String?>(null);
+  final lastDraftKey = useRef<String?>(null);
   useEffect(() {
     final identityChanged =
         lastDraftIdentity.value != null &&
-        lastDraftIdentity.value != draftIdentity;
+        (lastDraftIdentity.value != draftIdentity ||
+            lastDraftKey.value != draftKey);
     lastDraftIdentity.value = draftIdentity;
-    final saved = ref.read(composeDraftsProvider.notifier).textFor(draftKey);
+    lastDraftKey.value = draftKey;
+    final saved = ref.read(composeDraftsProvider.notifier).draftFor(draftKey);
+    void restoreBindings() {
+      mentionMap.value
+        ..clear()
+        ..addAll({
+          for (final e
+              in (saved?.mentions ?? const <String, DraftMention>{}).entries)
+            e.key: MentionCandidate(
+              pubkey: e.value.pubkey,
+              displayName: e.key,
+              isAgent: e.value.isAgent,
+            ),
+        });
+    }
+
     if (identityChanged) {
       draftRevision.value += 1;
       onDraftIdentityChanged();
@@ -101,28 +123,60 @@ void _useComposeDraftLifecycle({
       final staleAttachments = attachments.value;
       attachments.value = const [];
       unawaited(_deleteOwnedAttachments(staleAttachments));
-      controller.text = saved ?? '';
+      restoreBindings();
+      controller.text = saved?.text ?? '';
     } else if (saved != null && controller.text.isEmpty) {
-      controller.text = saved;
+      restoreBindings();
+      controller.text = saved.text;
     }
 
     var lastPersistedText = controller.text;
     void persistDraft() {
+      if (!identical(currentOwner.value, owner)) return;
       final text = controller.text;
       if (text == lastPersistedText) return;
       lastPersistedText = text;
       draftRevision.value += 1;
-      ref
-          .read(composeDraftsProvider.notifier)
-          .save(
-            key: draftKey,
-            channelId: channelId,
-            threadHeadId: threadHeadId,
-            text: text,
-          );
+      _persistComposeDraft(
+        ref,
+        controller,
+        mentionMap.value,
+        draftKey,
+        channelId,
+        threadHeadId,
+      );
     }
 
     controller.addListener(persistDraft);
     return () => controller.removeListener(persistDraft);
   }, [controller, draftKey, draftIdentity, onDraftIdentityChanged]);
 }
+
+void _persistComposeDraft(
+  WidgetRef ref,
+  TextEditingController controller,
+  Map<String, MentionCandidate> mentions,
+  String key,
+  String channelId,
+  String? threadHeadId,
+) {
+  final text = controller.text;
+  ref
+      .read(composeDraftsProvider.notifier)
+      .save(
+        key: key,
+        channelId: channelId,
+        threadHeadId: threadHeadId,
+        text: text,
+        mentions: {
+          for (final range in mentionOccurrences(
+            text.replaceAll('`', ' '),
+            mentions.keys,
+          ))
+            range.label: DraftMention(
+              pubkey: mentions[range.label]!.pubkey,
+              isAgent: mentions[range.label]!.isAgent,
+            ),
+        },
+      );
+}

mobile/lib/shared/mentions/draft_mention.dart

@@ -0,0 +1,29 @@
+/// A device-local exact selection. Display classification is not authorization;
+/// membership and owner policy must still be checked when sending.
+class DraftMention {
+  final String pubkey;
+  final bool isAgent;
+  const DraftMention({required this.pubkey, this.isAgent = false});
+  Map<String, Object> toJson() => {'pubkey': pubkey, 'is_agent': isAgent};
+
+  /// Ignore malformed legacy entries rather than guessing an identity.
+  static Map<String, DraftMention> decode(Object? raw) {
+    if (raw is! Map) return const {};
+    final result = <String, DraftMention>{};
+    for (final entry in raw.entries) {
+      if (entry.key is! String || entry.value is! Map) continue;
+      final label = entry.key as String;
+      final key = entry.value['pubkey'];
+      if (label.isEmpty ||
+          key is! String ||
+          !RegExp(r'^[0-9a-fA-F]{64}$').hasMatch(key)) {
+        continue;
+      }
+      result[label] = DraftMention(
+        pubkey: key.toLowerCase(),
+        isAgent: entry.value['is_agent'] == true,
+      );
+    }
+    return result;
+  }
+}

mobile/test/features/activity/compose_drafts_provider_test.dart

@@ -1,4 +1,5 @@
 import 'package:buzz/features/activity/compose_drafts_provider.dart';
+import 'package:buzz/shared/mentions/draft_mention.dart';
 import 'package:buzz/shared/relay/relay.dart';
 import 'package:buzz/shared/theme/theme_provider.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -81,6 +82,57 @@ void main() {
     expect(notifier.textFor('ch1'), 'hello there');
   });
 
+  test(
+    'exact bindings persist atomically with text and binding-only replacements',
+    () async {
+      SharedPreferences.setMockInitialValues({});
+      final container = await containerWithPrefs();
+      final notifier = container.read(composeDraftsProvider.notifier);
+      final first = 'a' * 64;
+      final second = 'b' * 64;
+      notifier.save(
+        key: 'ch1',
+        channelId: 'ch1',
+        text: '@Scout',
+        mentions: {'Scout': DraftMention(pubkey: first)},
+      );
+      notifier.save(
+        key: 'ch1',
+        channelId: 'ch1',
+        text: '@Scout',
+        mentions: {'Scout': DraftMention(pubkey: second, isAgent: true)},
+      );
+      final restarted = await containerWithPrefs();
+      final draft = restarted.read(composeDraftsProvider).single;
+      expect(draft.text, '@Scout');
+      expect(draft.mentions['Scout']!.pubkey, second);
+      expect(draft.mentions['Scout']!.isAgent, isTrue);
+      final other = await containerWithPrefs(pubkey: 'different');
+      expect(other.read(composeDraftsProvider), isEmpty);
+    },
+  );
+
+  test('malformed binding data never guesses keys or discards legacy text', () {
+    final draft = ComposeDraft.fromJson({
+      'key': 'c',
+      'channel_id': 'c',
+      'text': '@Scout',
+      'mentions': {
+        'Scout': {'pubkey': 'not-a-key'},
+      },
+    });
+    expect(draft!.text, '@Scout');
+    expect(draft.mentions, isEmpty);
+    expect(
+      ComposeDraft.fromJson({
+        'key': 'c',
+        'channel_id': 'c',
+        'text': '@Scout',
+      })!.mentions,
+      isEmpty,
+    );
+  });
+
   test('empty text removes the draft', () async {
     SharedPreferences.setMockInitialValues({});
     final container = await containerWithPrefs();