feat(llc, ui): Add handling of the CreateMention permission

packages/stream_chat/CHANGELOG.md

@@ -6,6 +6,7 @@
 - Added user-group APIs on `StreamChatClient`: `listUserGroups`, `searchUserGroups`, `getUserGroup`, `createUserGroup`, `updateUserGroup`, `deleteUserGroup`, `addUserGroupMembers`, `removeUserGroupMembers`.
 - Added enhanced-mention fields on `Message`: `mentionedChannel`, `mentionedHere`, `mentionedRoles`, `mentionedGroupIds`, and `mentionedGroups`.
 - Added `ChannelCapability.notifyChannel`, `notifyHere`, `notifyRole`, and `notifyGroup` capabilities, with matching `Channel.canNotifyChannel` / `canNotifyHere` / `canNotifyRole` / `canNotifyGroup` getters.
+- Added `ChannelCapability.createMention` capability with a matching `Channel.canCreateMention` getter.
 - Added `ChannelConfig.pushLevel`, `pushNotifications`, and `chatPreferences` for per-channel-type push configuration.
 - Added `PushLevel` and `ChatPreferenceLevel` extension types and the `ChatPreferences` model — granular per-category push preferences (direct, channel, here, role, group mentions, thread replies, default).
 - Added `chatPreferences` field to `PushPreferenceInput`, `PushPreference`, and `ChannelPushPreference`.

packages/stream_chat/lib/src/client/channel.dart

@@ -4589,4 +4589,9 @@ extension ChannelCapabilityCheck on Channel {
   bool get canNotifyGroup {
     return ownCapabilities.contains(ChannelCapability.notifyGroup);
   }
+
+  /// True, if the current user can mention a user in a message.
+  bool get canCreateMention {
+    return ownCapabilities.contains(ChannelCapability.createMention);
+  }
 }

packages/stream_chat/lib/src/core/models/channel_model.dart

@@ -407,4 +407,7 @@ extension type const ChannelCapability(String capability) implements String {
 
   /// Ability to mention one or more user groups in a message.
   static const notifyGroup = ChannelCapability('notify-group');
+
+  /// Ability to mention a user in a message.
+  static const createMention = ChannelCapability('create-mention');
 }

packages/stream_chat/test/src/client/channel_test.dart

@@ -8529,6 +8529,12 @@ void main() {
       (channel) => channel.canNotifyGroup,
     );
 
+    testCapability(
+      'CreateMentions',
+      ChannelCapability.createMention,
+      (channel) => channel.canCreateMention,
+    );
+
     test('returns correct values with multiple capabilities', () {
       final channelState = _generateChannelState(
         channelId,

packages/stream_chat_flutter/CHANGELOG.md

@@ -7,6 +7,7 @@
 ✅ Added
 
 - Added support for `@channel`, `@here`, role, and user-group mentions — parsed on incoming messages, rendered as styled tappable spans in message text, and selectable from the composer's `@` autocomplete.
+- `StreamMentionAutocompleteOptions` now hides user suggestions when the channel lacks the `create-mention` capability, skipping the `queryMembers` / `queryUsers` calls.
 - Added a single `mentionItemBuilder` on `StreamMessageComposer` and `StreamMentionAutocompleteOptions` that receives `StreamMentionItemProps` and covers every mention kind. Customise globally via `streamChatComponentBuilders(mentionItem: ...)` or per-instance via the new constructor parameter. Defaults are rendered by `DefaultStreamMentionItem`. Also added `onMention*Tap` callbacks on `StreamMentionAutocompleteOptions`.
 - Added `StreamMessageListView.onMentionTap` and `StreamMessageItem.onMentionTap` — receives a typed `StreamMention` (`StreamUserMention`, `StreamChannelMention`, `StreamHereMention`, `StreamRoleMention`, or `StreamGroupMention`).
 - `StreamMessageComposer` now surfaces the hold-to-record hint through `StreamSnackbar` anchored above the composer, and `StreamChat` provides an app-wide `StreamSnackbarScope` fallback.

packages/stream_chat_flutter/lib/src/autocomplete/stream_mention_autocomplete_options.dart

@@ -242,6 +242,7 @@ class _StreamMentionAutocompleteOptionsState extends State<StreamMentionAutocomp
   }
 
   Future<List<User>> _fetchUsers(String query) async {
+    if (!widget.channel.canCreateMention) return const [];
     try {
       if (widget.mentionAllAppUsers) {
         return await _queryUsers(query);

packages/stream_chat_flutter/test/src/autocomplete/stream_mention_autocomplete_options_test.dart

@@ -511,11 +511,39 @@ void main() {
       user: User(id: id, name: name),
     );
 
+    testWidgets('query does not call queryUser or queryMembers when createMention capability is missing', (
+      tester,
+    ) async {
+      final mocks = _setupMocks(ownCapabilities: const []);
+
+      await _pumpMentionOptions(
+        tester,
+        client: mocks.client,
+        channel: mocks.channel,
+        query: 'ali',
+      );
+
+      verifyNever(
+        () => mocks.channel.queryMembers(
+          filter: any(named: 'filter'),
+          pagination: any(named: 'pagination'),
+        ),
+      );
+      verifyNever(
+        () => mocks.client.queryUsers(
+          presence: any(named: 'presence'),
+          filter: any(named: 'filter'),
+          sort: any(named: 'sort'),
+          pagination: any(named: 'pagination'),
+        ),
+      );
+    });
+
     testWidgets(
       'all members cached use in-memory search and skip queryMembers API call',
       (tester) async {
         final mocks = _setupMocks(
-          ownCapabilities: const [],
+          ownCapabilities: const [ChannelCapability.createMention],
           members: [
             buildMember('alice-id', 'Alice'),
             buildMember('bob-id', 'Bob'),
@@ -546,7 +574,7 @@ void main() {
       'partial cache (memberCount > cached members) triggers queryMembers API call',
       (tester) async {
         final mocks = _setupMocks(
-          ownCapabilities: const [],
+          ownCapabilities: const [ChannelCapability.createMention],
           members: [
             buildMember('user-1', 'User 1'),
             buildMember('user-2', 'User 2'),
@@ -583,7 +611,7 @@ void main() {
       'null memberCount falls back to remote queryMembers',
       (tester) async {
         final mocks = _setupMocks(
-          ownCapabilities: const [],
+          ownCapabilities: const [ChannelCapability.createMention],
           members: [buildMember('cached-id', 'Cached')],
           memberCount: null,
         );
@@ -618,7 +646,7 @@ void main() {
       'local search includes watchers',
       (tester) async {
         final mocks = _setupMocks(
-          ownCapabilities: const [],
+          ownCapabilities: const [ChannelCapability.createMention],
           members: [buildMember('alice-id', 'Alice')],
           watchers: [User(id: 'wally-id', name: 'Wally')],
         );
@@ -638,7 +666,7 @@ void main() {
       'local results render alphabetically by name',
       (tester) async {
         final mocks = _setupMocks(
-          ownCapabilities: const [],
+          ownCapabilities: const [ChannelCapability.createMention],
           members: [
             buildMember('c-id', 'Charlie'),
             buildMember('a-id', 'Alice'),
@@ -665,7 +693,7 @@ void main() {
       'remote queryMembers results render in server order',
       (tester) async {
         final mocks = _setupMocks(
-          ownCapabilities: const [],
+          ownCapabilities: const [ChannelCapability.createMention],
           members: [buildMember('cached-id', 'Cached')],
           memberCount: 50,
         );
@@ -701,7 +729,7 @@ void main() {
     testWidgets(
       'mentionAllAppUsers calls client.queryUsers instead of channel.queryMembers',
       (tester) async {
-        final mocks = _setupMocks(ownCapabilities: const []);
+        final mocks = _setupMocks(ownCapabilities: const [ChannelCapability.createMention]);
         when(
           () => mocks.client.queryUsers(
             presence: any(named: 'presence'),
@@ -743,7 +771,10 @@ void main() {
       'queryMembers error is swallowed and does not blank the list',
       (tester) async {
         final mocks = _setupMocks(
-          ownCapabilities: const [ChannelCapability.notifyHere],
+          ownCapabilities: const [
+            ChannelCapability.notifyHere,
+            ChannelCapability.createMention,
+          ],
           members: [buildMember('cached-id', 'Cached')],
           memberCount: 50,
         );
@@ -775,6 +806,7 @@ void main() {
           ChannelCapability.notifyHere,
           ChannelCapability.notifyRole,
           ChannelCapability.notifyGroup,
+          ChannelCapability.createMention,
         ],
         members: [
           Member(
@@ -858,6 +890,7 @@ void main() {
             ChannelCapability.notifyHere,
             ChannelCapability.notifyRole,
             ChannelCapability.notifyGroup,
+            ChannelCapability.createMention,
           ],
           members: [
             Member(