diff --git a/CHANGELOG.md b/CHANGELOG.md
index 782e21a1..390d22d3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,14 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## [Unreleased]
 
+### Fixed
+
+- @ 提及：适配论坛新的 @ 插件（atplus）。论坛现在只把 @ 面板选出的名字（前后带不可见标记）当成提及，App 之前送出的 `@用户名` 会变成纯文字、对方收不到提醒；现在改为与网页面板相同的格式。
+
+### Changed
+
+- @ 选人面板：论坛提供 @ 插件时，改用插件的名单，显示「最近 @ 过」与好友，并可输入用户名或 UID 搜索全站用户；论坛没有插件时照旧使用好友列表与 @ 名单。用户组整组 @ 暂不支持。
+
 ## [1.29.2] - 2026-09-29
 
 ### Changed
diff --git a/doc/spec-x5-features.md b/doc/spec-x5-features.md
index d4006265..c6de65f1 100644
--- a/doc/spec-x5-features.md
+++ b/doc/spec-x5-features.md
@@ -1299,3 +1299,25 @@ B. 論壇提醒屏蔽規則
 - `AppDialogTitle(singleLine: true)`：標題單行、過長縮字；贊助彈窗與其 GitHub 按鈕、首頁贊助卡片標題都保持單行。
 - 驗證：test_172 第 4 組新增 320／360／384dp × 1／1.15／2 倍字級案例；主題模式與彈窗 6 項、首頁 1 項在修正前失敗。
 
+## 44. @ 提及適配 atplus 插件（2026-09-30）
+
+### 44.1 論壇端事實（2026-09-30 以測試帳號唯讀實測）
+
+- 帖子頁與回覆頁載入 `source/plugin/atplus/static/at-panel.js?v=1.3.0`，設定 `ATPLUS={"api":"plugin.php?id=atplus:search",...}`；編輯器旁有「@ 提及」按鈕。
+- 面板選到的人插入 `@` + U+2063 + 用戶名 + U+2063 + 空格；伺服器**只認**這種帶標記的 @。在輸入框直接打 `@名字` 只是普通文字（插件 1.0.3 起）。
+- 整組 @（1.1.0）：`@` + U+2064 + 組名 + U+2064，伺服器再檢查權限；測試帳號 `groups` 為空。
+- API（POST，form）：`op=init` → `{"ok":1,"recent":[...],"friends":[...],"groups":[...]}`；`op=search&q=` → `{"ok":1,"list":[...]}`；每筆 `{uid, username, avatar(相對路徑), group, friend}`。`op=card&uids=` 給名片用，App 未用。
+- 舊的 `misc.php?mod=getatuser` 仍在，但只剩名字。
+
+### 44.2 App 端行為
+
+- 送出時 `toOfficialMentions` 把編輯器的 `[@]name[/@]` 轉成 `@⁣name⁣ `（`atplusUserMark`）；原本的純 `@name` 在新插件下不會成為提及。編輯舊帖時原文內的標記原樣保留，再送出仍有效。
+- `MentionRepository.loadCandidates`：已登入時先問 `op=init`，成功就用插件的「最近 @ 過」與好友（`MentionCandidates.siteSearch = true`），不再抓好友頁與 getatuser；插件沒回 JSON（未安裝、錯誤）時退回原本兩個來源。訪客不問插件。
+- `searchUsers(keyword)` → `op=search`；`UserMentionCubit.setKeyword` 在 siteSearch 時搜尋，只保留最新關鍵字的回應。選人面板依序顯示：最近 @ 過、好友、全站搜尋（排除已顯示的）、舊 @ 名單、「提醒『輸入的名字』」。
+- 未做：整組 @（U+2064）、@ 名片。
+
+### 44.3 驗證
+
+- test_022、test_049 更新為帶標記格式；test_049 新增 atplus 群組（解析、插件優先且不問舊來源、訪客不問、cubit 搜尋、選人面板挑選全站搜尋結果）。插件回 404 時的退回路徑由原有案例涵蓋。
+- 未實測：真的發出一則 @ 並確認對方收到提醒（會對測試帳號以外的人產生提醒，未做）。
+
diff --git a/lib/features/editor/bloc/user_mention_cubit.dart b/lib/features/editor/bloc/user_mention_cubit.dart
index 1d54ad6a..1fed2a7f 100644
--- a/lib/features/editor/bloc/user_mention_cubit.dart
+++ b/lib/features/editor/bloc/user_mention_cubit.dart
@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:bloc/bloc.dart';
 import 'package:dart_mappable/dart_mappable.dart';
 import 'package:fpdart/fpdart.dart';
@@ -41,17 +43,44 @@ final class UserMentionCubit extends Cubit<UserMentionState> with LoggerMixin {
             friends: value.friends,
             others: value.others,
             friendsMessage: value.friendsMessage,
+            recent: value.recent,
+            siteSearch: value.siteSearch,
           ),
         );
+        // A keyword typed while loading is searched once the site search turns out to be available.
+        unawaited(_search());
     }
   }
 
-  /// Filter the candidates by [keyword], case insensitive.
+  /// Filter the candidates by [keyword], case insensitive, and search the site for it when possible.
   void setKeyword(String keyword) {
     final k = keyword.trim();
     if (k == state.keyword) {
       return;
     }
     emit(state.copyWith(keyword: k));
+    unawaited(_search());
+  }
+
+  /// Search the whole site for the current keyword (`atplus`), keeping only the answer of the latest keyword.
+  Future<void> _search() async {
+    final k = state.keyword;
+    if (!state.siteSearch ||
+        k.isEmpty ||
+        (state.searchKeyword == k && state.searchStatus != UserMentionStatus.failure)) {
+      return;
+    }
+    emit(state.copyWith(searchKeyword: k, searchStatus: UserMentionStatus.loading, searchResults: const []));
+    final result = await _repo.searchUsers(k).run();
+    if (isClosed || state.keyword != k) {
+      return;
+    }
+    switch (result) {
+      case Left(:final value):
+        handle(value);
+        emit(state.copyWith(searchStatus: UserMentionStatus.failure));
+      case Right(:final value):
+        emit(state.copyWith(searchStatus: UserMentionStatus.success, searchResults: value));
+    }
   }
 }
diff --git a/lib/features/editor/bloc/user_mention_state.dart b/lib/features/editor/bloc/user_mention_state.dart
index a6b28a90..2d001648 100644
--- a/lib/features/editor/bloc/user_mention_state.dart
+++ b/lib/features/editor/bloc/user_mention_state.dart
@@ -25,6 +25,11 @@ final class UserMentionState with UserMentionStateMappable {
     required this.others,
     required this.keyword,
     this.friendsMessage,
+    this.recent = const [],
+    this.siteSearch = false,
+    this.searchStatus = UserMentionStatus.initial,
+    this.searchKeyword = '',
+    this.searchResults = const [],
   });
 
   /// Empty state.
@@ -46,18 +51,49 @@ final class UserMentionState with UserMentionStateMappable {
   /// Why the friends list could not be read, see [MentionCandidates.friendsMessage].
   final String? friendsMessage;
 
+  /// Users mentioned recently, see [MentionCandidates.recent].
+  final List<Friend> recent;
+
+  /// Whether the whole site can be searched, see [MentionCandidates.siteSearch].
+  final bool siteSearch;
+
+  /// Status of the site search for [searchKeyword].
+  final UserMentionStatus searchStatus;
+
+  /// Keyword the [searchResults] belong to.
+  final String searchKeyword;
+
+  /// Users of the site found for [searchKeyword].
+  final List<Friend> searchResults;
+
   bool _matches(String name) => keyword.isEmpty || name.toLowerCase().contains(keyword.toLowerCase());
 
   /// Friends matching the keyword.
   List<Friend> get visibleFriends => friends.where((e) => _matches(e.username)).toList();
 
+  /// Recently mentioned users matching the keyword.
+  List<Friend> get visibleRecent => recent.where((e) => _matches(e.username)).toList();
+
+  /// Site search results of the current keyword that are not already shown as recent or friends.
+  List<Friend> get visibleSearchResults {
+    if (searchKeyword != keyword) {
+      return const [];
+    }
+    final shown = {...visibleRecent.map((e) => e.uid), ...visibleFriends.map((e) => e.uid)};
+    return searchResults.where((e) => !shown.contains(e.uid)).toList();
+  }
+
   /// Other names matching the keyword.
   List<String> get visibleOthers => others.where(_matches).toList();
 
   /// Whether a candidate has exactly the keyword as name (case insensitive).
   bool get hasExactMatch {
     final k = keyword.toLowerCase();
+    bool same(Friend e) => e.username.toLowerCase() == k;
     return k.isNotEmpty &&
-        (friends.any((e) => e.username.toLowerCase() == k) || others.any((e) => e.toLowerCase() == k));
+        (friends.any(same) ||
+            recent.any(same) ||
+            (searchKeyword == keyword && searchResults.any(same)) ||
+            others.any((e) => e.toLowerCase() == k));
   }
 }
diff --git a/lib/features/editor/repository/mention_repository.dart b/lib/features/editor/repository/mention_repository.dart
index 0b3a46e1..e59dd1bf 100644
--- a/lib/features/editor/repository/mention_repository.dart
+++ b/lib/features/editor/repository/mention_repository.dart
@@ -1,22 +1,43 @@
+import 'dart:convert';
+
 import 'package:fpdart/fpdart.dart';
+import 'package:tsdm_client/constants/url.dart';
 import 'package:tsdm_client/exceptions/exceptions.dart';
 import 'package:tsdm_client/features/editor/repository/editor_repository.dart';
+import 'package:tsdm_client/features/editor/utils/mention.dart';
 import 'package:tsdm_client/features/friend/models/models.dart';
 import 'package:tsdm_client/features/friend/repository/friend_repository.dart';
+import 'package:tsdm_client/instance.dart';
+import 'package:tsdm_client/shared/providers/net_client_provider/net_client_provider.dart';
 import 'package:tsdm_client/utils/logger.dart';
 
 /// Who the mention picker can offer.
 final class MentionCandidates {
   /// Constructor.
-  const MentionCandidates({required this.friends, required this.others, this.friendsMessage});
+  const MentionCandidates({
+    required this.friends,
+    required this.others,
+    this.friendsMessage,
+    this.recent = const [],
+    this.siteSearch = false,
+  });
 
   /// Nothing at all.
   static const empty = MentionCandidates(friends: [], others: []);
 
+  /// Users the current user mentioned recently, from the `atplus` plugin; empty without it.
+  final List<Friend> recent;
+
+  /// Whether the forum's `atplus` plugin answered: then any user of the site can be searched by name or uid
+  /// ([MentionRepository.searchUsers]).
+  final bool siteSearch;
+
   /// The current user's own friends, in the order of the friends list, unique by uid.
   final List<Friend> friends;
 
   /// Names on the official `@` list (`misc.php?mod=getatuser`) that are not in [friends], compared case insensitive.
+  ///
+  /// Empty when the `atplus` plugin answered ([siteSearch]): its search replaces that list.
   final List<String> others;
 
   /// Why the friends list could not be read: the privacy or login notice of the page, or the error of the request.
@@ -27,7 +48,11 @@ final class MentionCandidates {
 
 /// Where the mention picker gets its candidates.
 ///
-/// Two sources are merged, and one failing does not fail the whole load:
+/// The forum's `atplus` plugin (`plugin.php?id=atplus:search`, the web @ panel since 2026-09) comes first: `op=init`
+/// gives the users mentioned recently and the friends, `op=search` finds any user of the site by name or uid. When the
+/// plugin does not answer (not installed, or an error), the stock sources are used instead.
+///
+/// Two stock sources are merged, and one failing does not fail the whole load:
 ///
 /// * the current user's own friends list (`home.php?mod=space&uid=SELF&do=friend`, 24 per page, up to
 ///   [maxFriendPages] pages), which carries uid, avatar and user group;
@@ -92,9 +117,40 @@ final class MentionRepository with LoggerMixin {
         return Right((friends: friends, message: null));
       });
 
+  /// Url of the `atplus` plugin's user api.
+  static const atplusUrl = '$baseUrl/plugin.php?id=atplus:search';
+
+  /// Ask the `atplus` plugin with the form [data]; the decoded JSON, or null when the plugin did not answer with it.
+  Future<Object?> _atplus(Map<String, String> data) async {
+    switch (await getIt.get<NetClientProvider>().postForm(atplusUrl, data: data).run()) {
+      case Left(:final value):
+        debug('mention: atplus did not answer: $value');
+        return null;
+      case Right(:final value):
+        final body = value.data;
+        if (body is Map) {
+          return body;
+        }
+        try {
+          return jsonDecode('$body');
+        } on FormatException {
+          return null;
+        }
+    }
+  }
+
+  /// Users of the whole site whose name or uid matches [keyword], through the `atplus` plugin.
+  ///
+  /// Fails when the plugin does not answer; only meaningful when [MentionCandidates.siteSearch] is set.
+  AsyncEither<List<Friend>> searchUsers(String keyword) => AsyncEither(() async {
+    final users = parseAtplusUsers(await _atplus({'op': 'search', 'q': keyword}), 'list', base: baseUrl);
+    return users == null ? Left(ServerRespondedErrorException('atplus search unavailable')) : Right(users);
+  });
+
   /// Load the candidates: own friends of [selfUid] (skipped when null, nobody logged in) and the official `@` list.
   ///
-  /// Fails only when nothing could be loaded at all.
+  /// The `atplus` plugin is asked first for a logged in user; its recent and friends lists replace the stock sources
+  /// when it answers. Fails only when nothing could be loaded at all.
   AsyncEither<MentionCandidates> loadCandidates({required String? selfUid, bool force = false}) =>
       AsyncEither(() async {
         final cached = _cache;
@@ -102,6 +158,18 @@ final class MentionRepository with LoggerMixin {
           return Right(cached);
         }
 
+        if (selfUid != null) {
+          final init = await _atplus(const {'op': 'init'});
+          final recent = parseAtplusUsers(init, 'recent', base: baseUrl);
+          final friends = parseAtplusUsers(init, 'friends', base: baseUrl);
+          if (recent != null && friends != null) {
+            final candidates = MentionCandidates(recent: recent, friends: friends, others: const [], siteSearch: true);
+            _cache = candidates;
+            _cachedUid = selfUid;
+            return Right(candidates);
+          }
+        }
+
         // Both requests run at the same time.
         final friendsFuture = selfUid == null ? null : loadOwnFriends(selfUid: selfUid).run();
         // The `@` list cached inside the editor repository is only reused for the uid it was loaded for.
diff --git a/lib/features/editor/utils/mention.dart b/lib/features/editor/utils/mention.dart
index 0084d512..74a833c6 100644
--- a/lib/features/editor/utils/mention.dart
+++ b/lib/features/editor/utils/mention.dart
@@ -1,3 +1,4 @@
+import 'package:tsdm_client/features/friend/models/models.dart';
 import 'package:universal_html/parsing.dart';
 
 /// `[@]name[/@]`, the mention format of the retired `amucallme_dzx` plugin that the bbcode editor still emits.
@@ -6,17 +7,67 @@ import 'package:universal_html/parsing.dart';
 /// ends it early so a literal unpaired `[@]` does not swallow the next chip.
 final RegExp _legacyMentionRe = RegExp(r'\[@\]((?:(?!\[@\])[^\r\n])+?)\[/@\]');
 
-/// Rewrite editor mentions in [bbcode] to the official Discuz! format.
+/// Invisible mark (U+2063, INVISIBLE SEPARATOR) around a username picked in the `atplus` @ panel.
 ///
-/// Discuz! X5 shows `[@]name[/@]` as plain text. The official mention is a bare `@name` followed by whitespace,
-/// which the server turns into a profile link and a notice when the poster's user group is allowed to mention.
-/// Every embed becomes `@name`, with a space appended unless whitespace already follows.
+/// Since the forum's `atplus` plugin (2026-09), the server only turns `@` + mark + username + mark into a mention
+/// (profile link and notice); a bare `@name` stays plain text, exactly like typing `@` in the web editor.
+const atplusUserMark = '\u2063';
+
+/// Rewrite editor mentions in [bbcode] to the format the forum turns into mentions.
+///
+/// Discuz! X5 shows `[@]name[/@]` as plain text. With the `atplus` plugin the server only recognizes
+/// `@` + [atplusUserMark] + name + [atplusUserMark], the text its @ panel inserts; the bare `@name` of stock Discuz!
+/// used before is left as plain text now. Every embed becomes the marked form, with a space appended unless
+/// whitespace already follows (the panel inserts one as well).
 String toOfficialMentions(String bbcode) => bbcode.replaceAllMapped(_legacyMentionRe, (m) {
   final name = m.group(1)!.trim();
   final followedByWhitespace = m.end < bbcode.length && bbcode[m.end].trim().isEmpty;
-  return followedByWhitespace ? '@$name' : '@$name ';
+  final mention = '@$atplusUserMark$name$atplusUserMark';
+  return followedByWhitespace ? mention : '$mention ';
 });
 
+/// Users in an answer of the `atplus` plugin (`plugin.php?id=atplus:search`), `null` when it is not one.
+///
+/// ```json
+/// {"ok":1,"list":[{"uid":1000,"username":"Alice","avatar":"./data/avatar/000/00/10/00_avatar_small.jpg",
+///   "group":"使者","friend":0}]}
+/// ```
+///
+/// [key] is the list to read: `list` for a search, `recent` or `friends` for `op=init`. Entries without a uid or a
+/// name are skipped; avatars are made absolute against [base].
+List<Friend>? parseAtplusUsers(Object? json, String key, {required String base}) {
+  if (json is! Map<String, dynamic> || json['ok'] != 1 && json['ok'] != true) {
+    return null;
+  }
+  final list = json[key];
+  if (list is! List) {
+    return const [];
+  }
+  final users = <Friend>[];
+  final seen = <String>{};
+  for (final e in list) {
+    if (e is! Map) {
+      continue;
+    }
+    final uid = '${e['uid'] ?? ''}'.trim();
+    final username = '${e['username'] ?? ''}'.trim();
+    if (uid.isEmpty || username.isEmpty || !seen.add(uid)) {
+      continue;
+    }
+    final avatar = '${e['avatar'] ?? ''}'.trim();
+    final group = '${e['group'] ?? ''}'.trim();
+    users.add(
+      Friend(
+        uid: uid,
+        username: username,
+        avatarUrl: avatar.isEmpty ? null : Uri.parse('$base/').resolve(avatar).toString(),
+        groupName: group.isEmpty ? null : group,
+      ),
+    );
+  }
+  return users;
+}
+
 /// Usernames the current user may mention, from the official `misc.php?mod=getatuser&inajax=1`.
 ///
 /// ```xml
diff --git a/lib/features/editor/widgets/mention_picker.dart b/lib/features/editor/widgets/mention_picker.dart
index 3b2faf8a..5ccf7ef3 100644
--- a/lib/features/editor/widgets/mention_picker.dart
+++ b/lib/features/editor/widgets/mention_picker.dart
@@ -201,6 +201,39 @@ class _MentionPickerSheetState extends State<MentionPickerSheet> {
     ];
   }
 
+  /// Users mentioned recently (`atplus`), filtered by the keyword; nothing when there are none.
+  List<Widget> _recentSection(UserMentionState state) {
+    final visible = state.visibleRecent;
+    if (visible.isEmpty) {
+      return const [];
+    }
+    return [
+      _header(context.t.bbcodeEditor.userMention.recent, icon: Icons.history),
+      ...visible.map(_friendTile),
+    ];
+  }
+
+  /// Users of the whole site matching the keyword (`atplus`), shown only while a keyword is typed.
+  List<Widget> _searchSection(UserMentionState state) {
+    final tr = context.t.bbcodeEditor.userMention;
+    if (!state.siteSearch || state.keyword.isEmpty) {
+      return const [];
+    }
+    final visible = state.visibleSearchResults;
+    final searching = state.searchKeyword != state.keyword || state.searchStatus == UserMentionStatus.loading;
+    return [
+      _header(tr.siteSearch, icon: Icons.travel_explore),
+      if (searching)
+        const LinearProgressIndicator()
+      else if (state.searchStatus == UserMentionStatus.failure)
+        _note(context.t.general.failedToLoad)
+      else if (visible.isEmpty && !state.hasExactMatch)
+        _note(tr.noSearchResult(name: state.keyword))
+      else
+        ...visible.map(_friendTile),
+    ];
+  }
+
   List<Widget> _othersSection(UserMentionState state) {
     final visible = state.visibleOthers;
     if (visible.isEmpty) {
@@ -259,7 +292,9 @@ class _MentionPickerSheetState extends State<MentionPickerSheet> {
                 builder: (context, state) => ListView(
                   padding: edgeInsetsT4B4,
                   children: [
+                    ..._recentSection(state),
                     ..._friendsSection(state),
+                    ..._searchSection(state),
                     ..._othersSection(state),
                     if (state.keyword.isNotEmpty && !state.hasExactMatch) _useTypedRow(state),
                   ],
diff --git a/lib/i18n/en.i18n.json b/lib/i18n/en.i18n.json
index 13de5a2b..0f2b3197 100644
--- a/lib/i18n/en.i18n.json
+++ b/lib/i18n/en.i18n.json
@@ -1364,10 +1364,13 @@
       "refreshRecommendTip": "Reload the friend list",
       "noFriends": "No friend on your @ list yet, type the username directly",
       "noMatch": "No friend matches the keyword",
-      "filterHint": "Filter or type a username",
+      "filterHint": "Filter, or search a username or UID",
       "others": "Other @ list",
       "useTyped": "Mention “${name}”",
-      "friendsUnavailable": "Friends list unavailable: ${message}"
+      "friendsUnavailable": "Friends list unavailable: ${message}",
+      "recent": "Recently mentioned",
+      "siteSearch": "Search the site",
+      "noSearchResult": "No user named \"${name}\" on the site"
     },
     "customImage": {
       "tab": "My images",
diff --git a/lib/i18n/zh-CN.i18n.json b/lib/i18n/zh-CN.i18n.json
index fcde422f..991d1e51 100644
--- a/lib/i18n/zh-CN.i18n.json
+++ b/lib/i18n/zh-CN.i18n.json
@@ -1364,10 +1364,13 @@
       "refreshRecommendTip": "重新加载好友列表",
       "noFriends": "@ 列表里还没有好友，可直接输入用户名",
       "noMatch": "好友里没有符合的用户",
-      "filterHint": "筛选或输入用户名",
+      "filterHint": "筛选、搜索用户名或 UID",
       "others": "其他 @ 名单",
       "useTyped": "提醒「${name}」",
-      "friendsUnavailable": "无法读取好友列表：${message}"
+      "friendsUnavailable": "无法读取好友列表：${message}",
+      "recent": "最近 @ 过",
+      "siteSearch": "全站搜索",
+      "noSearchResult": "全站没有找到「${name}」"
     },
     "customImage": {
       "tab": "我的图片",
diff --git a/lib/i18n/zh-TW.i18n.json b/lib/i18n/zh-TW.i18n.json
index af552a00..fbe232e2 100644
--- a/lib/i18n/zh-TW.i18n.json
+++ b/lib/i18n/zh-TW.i18n.json
@@ -1364,10 +1364,13 @@
       "refreshRecommendTip": "重新載入好友名單",
       "noFriends": "@ 名單裡還沒有好友，可直接輸入使用者名稱",
       "noMatch": "好友裡沒有符合的使用者",
-      "filterHint": "篩選或輸入使用者名稱",
+      "filterHint": "篩選、搜尋用戶名或 UID",
       "others": "其他 @ 名單",
       "useTyped": "提醒「${name}」",
-      "friendsUnavailable": "無法讀取好友名單：${message}"
+      "friendsUnavailable": "無法讀取好友名單：${message}",
+      "recent": "最近 @ 過",
+      "siteSearch": "全站搜尋",
+      "noSearchResult": "全站沒有找到「${name}」"
     },
     "customImage": {
       "tab": "我的圖片",
diff --git a/test/regression/test_022_mention_x5_test.dart b/test/regression/test_022_mention_x5_test.dart
index a65e18de..aee6c8eb 100644
--- a/test/regression/test_022_mention_x5_test.dart
+++ b/test/regression/test_022_mention_x5_test.dart
@@ -50,20 +50,24 @@ void main() {
 
   group('official mention format', () {
     test('the editor embed becomes @name followed by a space', () {
-      expect(toOfficialMentions('hi [@]Alice[/@]!'), 'hi @Alice !');
-      expect(toOfficialMentions('[@]Alice[/@] and [@]Bob[/@]'), '@Alice and @Bob ');
-      expect(toOfficialMentions('[@] Alice [/@]'), '@Alice ');
+      expect(toOfficialMentions('hi [@]Alice[/@]!'), 'hi @\u2063Alice\u2063 !');
+      expect(toOfficialMentions('[@]Alice[/@] and [@]Bob[/@]'), '@\u2063Alice\u2063 and @\u2063Bob\u2063 ');
+      expect(toOfficialMentions('[@] Alice [/@]'), '@\u2063Alice\u2063 ');
     });
 
     test('no extra space when whitespace already follows', () {
-      expect(toOfficialMentions('[@]Alice[/@] ok'), '@Alice ok');
-      expect(toOfficialMentions('[@]Bob[/@]\nnext'), '@Bob\nnext');
+      expect(toOfficialMentions('[@]Alice[/@] ok'), '@\u2063Alice\u2063 ok');
+      expect(toOfficialMentions('[@]Bob[/@]\nnext'), '@\u2063Bob\u2063\nnext');
     });
 
     test('a name with brackets is kept whole', () {
-      expect(toOfficialMentions('hi [@][TSDM]Alice[/@]!'), 'hi @[TSDM]Alice !');
-      expect(toOfficialMentions('[@]a]b[/@] [@]x[y[/@]'), '@a]b @x[y ');
-      expect(toOfficialMentions('[@]x and [@]Bob[/@]'), '[@]x and @Bob ', reason: 'a literal [@] is not a chip');
+      expect(toOfficialMentions('hi [@][TSDM]Alice[/@]!'), 'hi @\u2063[TSDM]Alice\u2063 !');
+      expect(toOfficialMentions('[@]a]b[/@] [@]x[y[/@]'), '@\u2063a]b\u2063 @\u2063x[y\u2063 ');
+      expect(
+        toOfficialMentions('[@]x and [@]Bob[/@]'),
+        '[@]x and @\u2063Bob\u2063 ',
+        reason: 'a literal [@] is not a chip',
+      );
     });
 
     test('other content is untouched', () {
diff --git a/test/regression/test_049_mention_picker_x5_test.dart b/test/regression/test_049_mention_picker_x5_test.dart
index e85eb518..282e15ea 100644
--- a/test/regression/test_049_mention_picker_x5_test.dart
+++ b/test/regression/test_049_mention_picker_x5_test.dart
@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io';
 import 'dart:typed_data';
 
@@ -40,7 +41,18 @@ String _data(String name) => File('test/data/$name').readAsStringSync();
 
 /// Serves the friends list (first page and `page=2`) and the official `@` list, recording every request.
 final class _RoutingAdapter implements HttpClientAdapter {
-  _RoutingAdapter({this.friendsFirst = 'friend_list_own_x5.html', this.friendsStatus = 200, this.atStatus = 200});
+  _RoutingAdapter({
+    this.friendsFirst = 'friend_list_own_x5.html',
+    this.friendsStatus = 200,
+    this.atStatus = 200,
+    this.atplus = false,
+  });
+
+  /// Whether the forum has the `atplus` plugin: `plugin.php?id=atplus:search` answers its JSON.
+  bool atplus;
+
+  /// Form fields of every `atplus` request, in order.
+  final atplusForms = <Map<String, String>>[];
 
   static const friendsNext = 'friend_list_last_x5.html';
   static const String atUsers = _atUserXml;
@@ -56,6 +68,7 @@ final class _RoutingAdapter implements HttpClientAdapter {
 
   Iterable<Uri> get friendRequests => requests.where((u) => u.path == '/home.php');
   Iterable<Uri> get atRequests => requests.where((u) => u.path == '/misc.php');
+  Iterable<Uri> get atplusRequests => requests.where((u) => u.path == '/plugin.php');
 
   @override
   Future<ResponseBody> fetch(
@@ -68,6 +81,23 @@ final class _RoutingAdapter implements HttpClientAdapter {
     if (gate != null) {
       await gate!.future;
     }
+    if (atplus && uri.path == '/plugin.php' && uri.queryParameters['id'] == 'atplus:search') {
+      final data = options.data;
+      final form = data is Map ? data.map((k, v) => MapEntry('$k', '$v')) : Uri.splitQueryString('${data ?? ''}');
+      atplusForms.add(form);
+      final body = switch (form['op']) {
+        'init' => _atplusInit,
+        'search' => form['q'] == 'dave' ? _atplusSearchDave : '{"ok":1,"list":[]}',
+        _ => '{"ok":0}',
+      };
+      return ResponseBody.fromString(
+        body,
+        200,
+        headers: {
+          Headers.contentTypeHeader: ['application/json; charset=utf-8'],
+        },
+      );
+    }
     if (uri.path == '/misc.php' && uri.queryParameters['mod'] == 'getatuser') {
       return ResponseBody.fromString(
         atUsers,
@@ -94,6 +124,17 @@ final class _RoutingAdapter implements HttpClientAdapter {
   void close({bool force = false}) {}
 }
 
+/// `op=init` of the `atplus` plugin: one recent user, one friend (shape of the live answer, fake users).
+const _atplusInit =
+    '{"ok":1,"recent":[{"uid":1002,"username":"Carol","avatar":"./data/avatar/000/00/10/02_avatar_small.jpg",'
+    '"group":"使者","friend":0}],"friends":[{"uid":1001,"username":"Bob",'
+    '"avatar":"./data/avatar/000/00/10/01_avatar_small.jpg","group":"梦幻","friend":1}],"groups":[]}';
+
+/// `op=search` of the `atplus` plugin for `dave`.
+const _atplusSearchDave =
+    '{"ok":1,"list":[{"uid":1003,"username":"Dave","avatar":"./data/avatar/000/00/10/03_avatar_small.jpg",'
+    '"group":"使者","friend":0},{"uid":1001,"username":"Bob","avatar":"","group":"梦幻","friend":1}]}';
+
 /// Never answers: avatars are not fetched in tests.
 final class _OfflineAdapter implements HttpClientAdapter {
   @override
@@ -159,10 +200,15 @@ void main() {
 
       final again = (await repo.loadCandidates(selfUid: '1000').run()).toNullable()!;
       expect(again.friends.single.username, 'Bob');
-      expect(adapter.requests, hasLength(2), reason: 'reopening the picker uses the cache');
+      expect(
+        adapter.atplusRequests,
+        hasLength(1),
+        reason: 'the atplus plugin is asked first, it is not installed here',
+      );
+      expect(adapter.requests, hasLength(3), reason: 'reopening the picker uses the cache');
 
       await repo.loadCandidates(selfUid: '1000', force: true).run();
-      expect(adapter.requests, hasLength(4), reason: 'the reload button asks both sources again');
+      expect(adapter.requests, hasLength(6), reason: 'the reload button asks the plugin and both sources again');
     });
 
     test('follows the next page link and keeps friends unique by uid', () async {
@@ -360,7 +406,7 @@ void main() {
       expect(ops[0].data, 'hi ');
       expect(ops[1].data, {'bbcodeUserMention': '{"username":"Alice"}'});
       expect(controller.toForumBBCode(), 'hi [@]Alice[/@]');
-      expect(toOfficialMentions(controller.toForumBBCode()), 'hi @Alice ');
+      expect(toOfficialMentions(controller.toForumBBCode()), 'hi @\u2063Alice\u2063 ');
       expect(controller.selection, const TextSelection.collapsed(offset: 4));
     });
 
@@ -472,11 +518,75 @@ void main() {
         expect(embeds.single.data, {'bbcodeUserMention': '{"username":"$name"}'}, reason: name);
         expect(controller.document.toPlainText(), isNot(contains('@')), reason: name);
         expect(controller.toForumBBCode(), 'hi [@]$name[/@]', reason: name);
-        expect(toOfficialMentions(controller.toForumBBCode()), 'hi @$name ', reason: name);
+        expect(toOfficialMentions(controller.toForumBBCode()), 'hi @\u2063$name\u2063 ', reason: name);
       }
     });
   });
 
+  group('atplus plugin (web @ panel since 2026-09)', () {
+    tearDown(() async => unregisterNet());
+
+    test('parses its user lists, avatars made absolute; anything else is not an answer', () {
+      final init = jsonDecode(_atplusInit);
+      final friends = parseAtplusUsers(init, 'friends', base: baseUrl)!;
+      expect(friends.map((e) => (e.uid, e.username, e.groupName)), [('1001', 'Bob', '梦幻')]);
+      expect(friends.single.avatarUrl, '$baseUrl/data/avatar/000/00/10/01_avatar_small.jpg');
+      expect(parseAtplusUsers(init, 'recent', base: baseUrl)!.single.username, 'Carol');
+      expect(parseAtplusUsers(init, 'groups', base: baseUrl), isEmpty);
+      expect(parseAtplusUsers(init, 'missing', base: baseUrl), isEmpty);
+      expect(parseAtplusUsers(const {'ok': 0}, 'list', base: baseUrl), isNull);
+      expect(parseAtplusUsers('not found', 'list', base: baseUrl), isNull);
+      expect(parseAtplusUsers(null, 'list', base: baseUrl), isNull);
+    });
+
+    test('with the plugin: recent and friends come from it, the stock sources are not asked', () async {
+      await registerNet(_RoutingAdapter(atplus: true));
+      final repo = MentionRepository();
+      final result = (await repo.loadCandidates(selfUid: '1000').run()).toNullable()!;
+      expect(result.siteSearch, isTrue);
+      expect(result.recent.map((e) => e.username), ['Carol']);
+      expect(result.friends.map((e) => e.username), ['Bob']);
+      expect(result.others, isEmpty);
+      expect(adapter.atplusForms, [
+        {'op': 'init'},
+      ]);
+      expect(adapter.friendRequests, isEmpty);
+      expect(adapter.atRequests, isEmpty);
+
+      final found = (await repo.searchUsers('dave').run()).toNullable()!;
+      expect(found.map((e) => e.username), ['Dave', 'Bob']);
+      expect(adapter.atplusForms.last, {'op': 'search', 'q': 'dave'});
+    });
+
+    test('a guest does not ask the plugin', () async {
+      await registerNet(_RoutingAdapter(atplus: true));
+      await MentionRepository().loadCandidates(selfUid: null).run();
+      expect(adapter.atplusForms, isEmpty);
+    });
+
+    test('the cubit searches the site for the keyword, results not already shown', () async {
+      await registerNet(_RoutingAdapter(atplus: true));
+      final cubit = UserMentionCubit(MentionRepository(), selfUid: '1000');
+      addTearDown(cubit.close);
+      await cubit.load();
+      cubit.setKeyword('dave');
+      await pumpEventQueue();
+      expect(cubit.state.searchStatus, UserMentionStatus.success);
+      expect(
+        cubit.state.visibleSearchResults.map((e) => e.username),
+        ['Dave', 'Bob'],
+        reason: 'the server matched Bob too; he is not listed under friends for this keyword, so he is shown here',
+      );
+      expect(cubit.state.hasExactMatch, isTrue, reason: 'Dave was found');
+
+      cubit.setKeyword('bo');
+      await pumpEventQueue();
+      expect(cubit.state.visibleFriends.map((e) => e.username), ['Bob']);
+      expect(cubit.state.visibleSearchResults, isEmpty);
+      expect(adapter.atplusForms.map((e) => e['q']).whereType<String>(), ['dave', 'bo']);
+    });
+  });
+
   group('mention picker sheet', () {
     setUp(() async {
       await registerNet(_RoutingAdapter());
@@ -521,6 +631,30 @@ void main() {
       };
     }
 
+    testWidgets('with the atplus plugin: recent, friends, and a site search result that can be picked', (
+      tester,
+    ) async {
+      adapter.atplus = true;
+      final repo = MentionRepository();
+      final picked = await pumpHost(tester, repo);
+      await tester.tap(find.text('open'));
+      await tester.runAsync(() => Future<void>.delayed(const Duration(milliseconds: 50)));
+      await tester.pumpAndSettle();
+      final tr = LocaleSettings.instance.currentTranslations.bbcodeEditor.userMention;
+      expect(find.text(tr.recent), findsOneWidget);
+      expect(find.text('Carol'), findsOneWidget);
+      expect(find.text('Bob'), findsOneWidget);
+
+      await tester.enterText(find.byType(TextField), 'dave');
+      await tester.pump(const Duration(milliseconds: 200));
+      await tester.runAsync(() => Future<void>.delayed(const Duration(milliseconds: 50)));
+      await tester.pumpAndSettle();
+      expect(find.text(tr.siteSearch), findsOneWidget);
+      await tester.tap(find.text('Dave'));
+      await tester.pumpAndSettle();
+      expect(picked(), 'Dave');
+    });
+
     testWidgets('lists the friend under Friends, tapping it picks the name', (tester) async {
       final repo = MentionRepository();
       // Warm the cache outside the fake async zone so the sheet renders from it.