Fix mobile DM recipient routing

mobile/lib/features/channels/channel_detail_page.dart

@@ -326,6 +326,9 @@ class ChannelDetailPage extends HookConsumerWidget {
                         channelId: channel.id,
                         content: content,
                         mentionPubkeys: mentionPubkeys,
+                        recipientPubkeys: resolvedChannel.isDm
+                            ? resolvedChannel.participantPubkeys
+                            : const [],
                         mediaTags: mediaTags,
                       ),
             )

mobile/lib/features/channels/send_message_provider.dart

@@ -27,13 +27,16 @@ class SendMessage {
   /// If [rootEventId] is null it defaults to [parentEventId] (direct reply to
   /// thread head). Tags are built to match the desktop's `buildReplyTags`
   /// convention with `root` / `reply` markers. Pass [mediaTags] to append
-  /// relay-validated `imeta` tags and NIP-30 `emoji` tags.
+  /// relay-validated `imeta` tags and NIP-30 `emoji` tags. Direct-message
+  /// callers must pass [recipientPubkeys] so the other participant receives a
+  /// `p` tag even when the message body contains no explicit @mention.
   Future<void> call({
     required String channelId,
     required String content,
     String? parentEventId,
     String? rootEventId,
     List<String>? mentionPubkeys,
+    List<String> recipientPubkeys = const [],
     List<List<String>> mediaTags = const [],
   }) async {
     // Use explicitly passed pubkeys, or resolve @mentions against
@@ -42,19 +45,22 @@ class SendMessage {
         mentionPubkeys ?? await _resolveMentions(content, channelId);
     final authorPubkey = _signedEventRelay.pubkey;
 
-    // Normalize mentions: lowercase, deduplicate, exclude self (matching
+    // Normalize recipients: lowercase, deduplicate, exclude self (matching
     // the desktop's normalizeMentionPubkeys).
     final selfLower = authorPubkey?.toLowerCase();
-    final seenMentions = <String>{?selfLower};
-    final normalizedMentions = <String>[
-      for (final pk in resolvedMentions)
-        if (seenMentions.add(pk.toLowerCase())) pk,
-    ];
+    final seenRecipients = <String>{?selfLower};
+    final normalizedRecipients = <String>[];
+    for (final pubkey in [...recipientPubkeys, ...resolvedMentions]) {
+      final lower = pubkey.toLowerCase();
+      if (lower.isNotEmpty && seenRecipients.add(lower)) {
+        normalizedRecipients.add(lower);
+      }
+    }
 
     final tags = <List<String>>[
       ['h', channelId],
       if (parentEventId != null) ..._buildReplyTags(parentEventId, rootEventId),
-      for (final pk in normalizedMentions) ['p', pk],
+      for (final pk in normalizedRecipients) ['p', pk],
       ...mediaTags,
     ];
 

mobile/lib/features/channels/thread_detail_page.dart

@@ -139,9 +139,13 @@ class ThreadDetailPage extends HookConsumerWidget {
     // Channel names for message content rendering.
     final channelsAsync = ref.watch(channelsProvider);
     final channelNamesMap = <String, String>{};
+    var recipientPubkeys = const <String>[];
     channelsAsync.whenData((channels) {
       for (final ch in channels) {
         channelNamesMap[ch.name.toLowerCase()] = ch.id;
+        if (ch.id == channelId && ch.isDm) {
+          recipientPubkeys = ch.participantPubkeys;
+        }
       }
     });
 
@@ -275,6 +279,7 @@ class ThreadDetailPage extends HookConsumerWidget {
                         channelId: channelId,
                         content: content,
                         mentionPubkeys: mentionPubkeys,
+                        recipientPubkeys: recipientPubkeys,
                         parentEventId: threadHead.id,
                         rootEventId: effectiveRootId,
                         mediaTags: mediaTags,

mobile/test/features/channels/send_message_provider_test.dart

@@ -0,0 +1,95 @@
+import 'package:buzz/features/channels/channel_management_provider.dart';
+import 'package:buzz/features/channels/send_message_provider.dart';
+import 'package:buzz/features/profile/user_profile.dart';
+import 'package:buzz/shared/relay/relay.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  test('adds DM recipients without requiring an explicit mention', () async {
+    final relay = _RecordingSignedEventRelay(pubkey: 'self');
+    final sendMessage = SendMessage(
+      signedEventRelay: relay,
+      fetchMembers: (_) async => const <ChannelMember>[],
+      readUserCache: () => const <String, UserProfile>{},
+    );
+
+    await sendMessage.call(
+      channelId: 'dm-channel',
+      content: 'hello from mobile',
+      recipientPubkeys: const ['SELF', 'AGENT', 'agent', ''],
+    );
+
+    expect(relay.tags, [
+      ['h', 'dm-channel'],
+      ['p', 'agent'],
+    ]);
+  });
+
+  test('keeps non-DM messages mention-only', () async {
+    final relay = _RecordingSignedEventRelay(pubkey: 'self');
+    final sendMessage = SendMessage(
+      signedEventRelay: relay,
+      fetchMembers: (_) async => const <ChannelMember>[],
+      readUserCache: () => const <String, UserProfile>{},
+    );
+
+    await sendMessage.call(
+      channelId: 'shared-channel',
+      content: 'ordinary channel message',
+    );
+
+    expect(relay.tags, [
+      ['h', 'shared-channel'],
+    ]);
+  });
+
+  test('deduplicates DM recipients and explicit mentions', () async {
+    final relay = _RecordingSignedEventRelay(pubkey: 'self');
+    final sendMessage = SendMessage(
+      signedEventRelay: relay,
+      fetchMembers: (_) async => const <ChannelMember>[],
+      readUserCache: () => const <String, UserProfile>{},
+    );
+
+    await sendMessage.call(
+      channelId: 'dm-channel',
+      content: '@agent please check this',
+      recipientPubkeys: const ['agent'],
+      mentionPubkeys: const ['agent', 'reviewer'],
+    );
+
+    expect(relay.tags, [
+      ['h', 'dm-channel'],
+      ['p', 'agent'],
+      ['p', 'reviewer'],
+    ]);
+  });
+}
+
+class _RecordingSignedEventRelay implements SignedEventRelay {
+  _RecordingSignedEventRelay({required this.pubkey});
+
+  @override
+  final String? pubkey;
+
+  List<List<String>>? tags;
+
+  @override
+  Future<NostrEvent> submit({
+    required int kind,
+    required String content,
+    required List<List<String>> tags,
+    int? createdAt,
+  }) async {
+    this.tags = tags;
+    return const NostrEvent(
+      id: 'stub',
+      pubkey: '',
+      createdAt: 0,
+      kind: 0,
+      tags: [],
+      content: '',
+      sig: '',
+    );
+  }
+}