diff --git a/lib/model/autocomplete.dart b/lib/model/autocomplete.dart
index 9222a817a5..6007dd6730 100644
--- a/lib/model/autocomplete.dart
+++ b/lib/model/autocomplete.dart
@@ -1,3 +1,5 @@
+import 'dart:math';
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 
@@ -5,11 +7,12 @@ import '../api/model/events.dart';
 import '../api/model/model.dart';
 import '../api/route/channels.dart';
 import '../widgets/compose_box.dart';
+import 'emoji.dart';
 import 'narrow.dart';
 import 'store.dart';
 
 extension ComposeContentAutocomplete on ComposeContentController {
-  AutocompleteIntent<MentionAutocompleteQuery>? autocompleteIntent() {
+  AutocompleteIntent<ComposeAutocompleteQuery>? autocompleteIntent() {
     if (!selection.isValid || !selection.isNormalized) {
       // We don't require [isCollapsed] to be true because we've seen that
       // autocorrect and even backspace involve programmatically expanding the
@@ -18,28 +21,52 @@ extension ComposeContentAutocomplete on ComposeContentController {
       // see below.
       return null;
     }
+
+    // To avoid spending a lot of time searching for autocomplete intents
+    // in long messages, we bound how far back we look for the intent's start.
+    final earliest = max(0, selection.end - 30);
+
+    if (selection.start < earliest) {
+      // The selection extends to before any position we'd consider
+      // for the start of the intent.  So there can't be a match.
+      return null;
+    }
+
     final textUntilCursor = text.substring(0, selection.end);
-    for (
-      int position = selection.end - 1;
-      position >= 0 && (selection.end - position <= 30);
-      position--
-    ) {
-      if (textUntilCursor[position] != '@') {
+    int pos;
+    for (pos = selection.end - 1; pos > selection.start; pos--) {
+      final charAtPos = textUntilCursor[pos];
+      if (charAtPos == '@') {
+        final match = _mentionIntentRegex.matchAsPrefix(textUntilCursor, pos);
+        if (match == null) continue;
+      } else if (charAtPos == ':') {
+        final match = _emojiIntentRegex.matchAsPrefix(textUntilCursor, pos);
+        if (match == null) continue;
+      } else {
         continue;
       }
-      final match = mentionAutocompleteMarkerRegex.matchAsPrefix(textUntilCursor, position);
-      if (match == null) {
+      // See comment about [TextSelection.isCollapsed] above.
+      return null;
+    }
+
+    for (; pos >= earliest; pos--) {
+      final charAtPos = textUntilCursor[pos];
+      final ComposeAutocompleteQuery query;
+      if (charAtPos == '@') {
+        final match = _mentionIntentRegex.matchAsPrefix(textUntilCursor, pos);
+        if (match == null) continue;
+        query = MentionAutocompleteQuery(match[2]!, silent: match[1]! == '_');
+      } else if (charAtPos == ':') {
+        final match = _emojiIntentRegex.matchAsPrefix(textUntilCursor, pos);
+        if (match == null) continue;
+        query = EmojiAutocompleteQuery(match[1]!);
+      } else {
         continue;
       }
-      if (selection.start < position) {
-        // See comment about [TextSelection.isCollapsed] above.
-        return null;
-      }
-      return AutocompleteIntent(
-        syntaxStart: position,
-        query: MentionAutocompleteQuery(match[2]!, silent: match[1]! == '_'),
-        textEditingValue: value);
+      return AutocompleteIntent(syntaxStart: pos, textEditingValue: value,
+        query: query);
     }
+
     return null;
   }
 }
@@ -53,7 +80,7 @@ extension ComposeTopicAutocomplete on ComposeTopicController {
   }
 }
 
-final RegExp mentionAutocompleteMarkerRegex = (() {
+final RegExp _mentionIntentRegex = (() {
   // What's likely to come before an @-mention: the start of the string,
   // whitespace, or punctuation. Letters are unlikely; in that case an email
   // might be intended. (By punctuation, we mean *some* punctuation, like "(".
@@ -78,6 +105,60 @@ final RegExp mentionAutocompleteMarkerRegex = (() {
     unicode: true);
 })();
 
+final RegExp _emojiIntentRegex = (() {
+  // Similar reasoning as in _mentionIntentRegex.
+  // Specifically forbid a preceding ":", though, to make "::" not a query.
+  const before = r'(?<=^|\s|\p{Punctuation})(?<!:)';
+  // TODO(dart-future): Regexps in ES 2024 have a /v aka unicodeSets flag;
+  //   if Dart matches that, we could combine into one character class
+  //   meaning "whitespace and punctuation, except not `:`":
+  //     r'(?<=^|[[\s\p{Punctuation}]--[:]])'
+
+  // What possible emoji queries do we want to anticipate?
+  //
+  // First, look only for queries aimed at emoji names (and aliases);
+  // there's little point in searching by literal emoji here, because once the
+  // user has entered a literal emoji they can simply leave it in.
+  // (Searching by literal emoji is useful, by contrast, for adding a reaction.)
+  //
+  // Then, what are the possible names (including aliases)?
+  // For custom emoji, the names the server allows are r'^[0-9a-z_-]*[0-9a-z]$';
+  // see check_valid_emoji_name in zerver/lib/emoji.py.
+  // So only ASCII lowercase alnum, underscore, and dash.
+  // A few Unicode emoji have more general names in the server's list:
+  // Latin letters with diacritics, a few kana and kanji, and the name "+1".
+  // (And the only "Zulip extra emoji" has one name, "zulip".)
+  // Details: https://github.com/zulip/zulip-flutter/pull/1069#discussion_r1855964953
+  //
+  // We generalize [0-9a-z] to "any letter or number".
+  // That handles the existing names except "+1", plus a potential future
+  // loosening of the constraints on custom emoji's names.
+  //
+  // Then "+1" we take as a special case, without generalizing,
+  // in order to recognize that name without adding false positives.
+  //
+  // Even though there could be a custom emoji whose name begins with "-",
+  // we reject queries that begin that way: ":-" is much more likely to be
+  // the start of an emoticon.
+
+  /// Characters that might be meant as part of (a query for) an emoji's name
+  /// at any point in the query.
+  const nameCharacters = r'_\p{Letter}\p{Number}';
+
+  return RegExp(unicode: true,
+    before
+    + r':'
+    + r'(|'
+      // Recognize '+' only as part of '+1', the only emoji name that has it.
+      + r'\+1?|'
+      // Reject on whitespace right after ':'; interpret that
+      // as the user choosing to get out of the emoji autocomplete.
+      // Similarly reject starting with ':-', which is common for emoticons.
+      + r'['    + nameCharacters + r']'
+      + r'[-\s' + nameCharacters + r']*'
+    + r')$');
+})();
+
 /// The text controller's recognition that the user might want autocomplete UI.
 class AutocompleteIntent<QueryT extends AutocompleteQuery> {
   AutocompleteIntent({
@@ -123,6 +204,7 @@ class AutocompleteIntent<QueryT extends AutocompleteQuery> {
 class AutocompleteViewManager {
   final Set<MentionAutocompleteView> _mentionAutocompleteViews = {};
   final Set<TopicAutocompleteView> _topicAutocompleteViews = {};
+  final Set<EmojiAutocompleteView> _emojiAutocompleteViews = {};
 
   AutocompleteDataCache autocompleteDataCache = AutocompleteDataCache();
 
@@ -146,6 +228,16 @@ class AutocompleteViewManager {
     assert(removed);
   }
 
+  void registerEmojiAutocomplete(EmojiAutocompleteView view) {
+    final added = _emojiAutocompleteViews.add(view);
+    assert(added);
+  }
+
+  void unregisterEmojiAutocomplete(EmojiAutocompleteView view) {
+    final removed = _emojiAutocompleteViews.remove(view);
+    assert(removed);
+  }
+
   void handleRealmUserRemoveEvent(RealmUserRemoveEvent event) {
     autocompleteDataCache.invalidateUser(event.userId);
   }
@@ -177,39 +269,71 @@ class AutocompleteViewManager {
 
 /// A view-model for an autocomplete interaction.
 ///
+/// Subclasses correspond to subclasses of [AutocompleteQuery],
+/// i.e. different types of autocomplete interaction initiated by the user.
+/// Each subclass specifies the corresponding [AutocompleteQuery] subclass
+/// as `QueryT`,
+/// and the [AutocompleteResult] subclass in `ResultT` describes the
+/// possible results that the user might choose in the autocomplete interaction.
+///
+/// When an [AutocompleteView] is created, its constructor begins the search
+/// for results corresponding to the initial [query].
+/// The query may later be updated, causing a new search.
+///
 /// The owner of one of these objects must call [dispose] when the object
 /// will no longer be used, in order to free resources on the [PerAccountStore].
 ///
 /// Lifecycle:
-///  * Create an instance of a concrete subtype.
+///  * Create an instance of a concrete subtype, beginning a search
 ///  * Add listeners with [addListener].
-///  * Use the [query] setter to start a search for a query.
+///  * When the user edits the query, use the [query] setter to update the search.
 ///  * On reassemble, call [reassemble].
 ///  * When the object will no longer be used, call [dispose] to free
 ///    resources on the [PerAccountStore].
 abstract class AutocompleteView<QueryT extends AutocompleteQuery, ResultT extends AutocompleteResult> extends ChangeNotifier {
-  AutocompleteView({required this.store});
+  /// Construct a view-model for an autocomplete interaction,
+  /// and begin the search for the initial query.
+  AutocompleteView({required this.store, required QueryT query})
+      : _query = query {
+    _startSearch();
+  }
 
   final PerAccountStore store;
 
-  QueryT? get query => _query;
-  QueryT? _query;
-  set query(QueryT? query) {
+  /// True just if this [AutocompleteView] is of the appropriate type
+  /// to handle the given query.
+  bool acceptsQuery(AutocompleteQuery query) => query is QueryT;
+
+  /// The last query this [AutocompleteView] was asked to perform for the user.
+  ///
+  /// If this view-model is currently performing a search,
+  /// the search is for this query.
+  /// If not, then [results] reflect this query.
+  ///
+  /// When set, the existing query is aborted if still in progress,
+  /// and a search for the new query is begun.
+  /// Any existing value in [results] remains until the new query finishes.
+  QueryT get query => _query;
+  QueryT _query;
+  set query(QueryT query) {
     _query = query;
-    if (query != null) {
-      _startSearch();
-    }
+    _startSearch();
   }
 
   /// Called when the app is reassembled during debugging, e.g. for hot reload.
   ///
   /// This will redo the search from scratch for the current query, if any.
   void reassemble() {
-    if (_query != null) {
-      _startSearch();
-    }
+    _startSearch();
   }
 
+  /// The latest set of results available for any value of [query].
+  ///
+  /// When this changes, listeners will be notified with [notifyListeners].
+  ///
+  /// These results might not correspond to the current value of [query],
+  /// if a search is still in progress.
+  /// Before any search completes, [results] will be empty.
   Iterable<ResultT> get results => _results;
   List<ResultT> _results = [];
 
@@ -264,8 +388,7 @@ abstract class AutocompleteView<QueryT extends AutocompleteQuery, ResultT extend
     required Iterable<T> candidates,
     required List<ResultT> results,
   }) async {
-    assert(_query != null);
-    final query = _query!;
+    final query = _query;
 
     final iterator = candidates.iterator;
     outer: while (true) {
@@ -284,9 +407,16 @@ abstract class AutocompleteView<QueryT extends AutocompleteQuery, ResultT extend
   }
 }
 
+/// An [AutocompleteView] for an autocomplete interaction
+/// in the compose box's content input.
+typedef ComposeAutocompleteView = AutocompleteView<ComposeAutocompleteQuery, ComposeAutocompleteResult>;
+
+/// An [AutocompleteView] for an @-mention autocomplete interaction,
+/// an example of a [ComposeAutocompleteView].
 class MentionAutocompleteView extends AutocompleteView<MentionAutocompleteQuery, MentionAutocompleteResult> {
   MentionAutocompleteView._({
     required super.store,
+    required super.query,
     required this.narrow,
     required this.sortedUsers,
   });
@@ -294,9 +424,11 @@ class MentionAutocompleteView extends AutocompleteView<MentionAutocompleteQuery,
   factory MentionAutocompleteView.init({
     required PerAccountStore store,
     required Narrow narrow,
+    required MentionAutocompleteQuery query,
   }) {
     final view = MentionAutocompleteView._(
       store: store,
+      query: query,
       narrow: narrow,
       sortedUsers: _usersByRelevance(store: store, narrow: narrow),
     );
@@ -493,11 +625,29 @@ class MentionAutocompleteView extends AutocompleteView<MentionAutocompleteQuery,
   }
 }
 
+/// A query the user has entered into some form of autocomplete.
+///
+/// Subclasses correspond to different types of autocomplete interaction
+/// initiated by the user:
+/// for example typing `@` into a compose box's content input
+/// to autocomplete an @-mention ([MentionAutocompleteQuery]),
+/// or typing into a topic input
+/// to autocomplete a topic name ([TopicAutocompleteQuery]).
+/// Each subclass has a corresponding subclass of [AutocompleteView].
+///
+/// An [AutocompleteQuery] object stores the user's actual query string
+/// as [raw].
+/// It may also store processed forms of the query
+/// (for example, converted to lowercase or split on whitespace)
+/// to prepare for whatever particular form of searching will be done
+/// for the given type of autocomplete interaction.
 abstract class AutocompleteQuery {
   AutocompleteQuery(this.raw)
     : _lowercaseWords = raw.toLowerCase().split(' ');
 
+  /// The actual string the user entered.
   final String raw;
+
   final List<String> _lowercaseWords;
 
   /// Whether all of this query's words have matches in [words] that appear in order.
@@ -523,12 +673,27 @@ abstract class AutocompleteQuery {
   }
 }
 
-class MentionAutocompleteQuery extends AutocompleteQuery {
+/// Any autocomplete query in the compose box's content input.
+abstract class ComposeAutocompleteQuery extends AutocompleteQuery {
+  ComposeAutocompleteQuery(super.raw);
+
+  /// Construct an [AutocompleteView] initialized with this query
+  /// and ready to handle queries of the same type.
+  ComposeAutocompleteView initViewModel(PerAccountStore store, Narrow narrow);
+}
+
+/// A @-mention autocomplete query, used by [MentionAutocompleteView].
+class MentionAutocompleteQuery extends ComposeAutocompleteQuery {
   MentionAutocompleteQuery(super.raw, {this.silent = false});
 
   /// Whether the user wants a silent mention (@_query, vs. @query).
   final bool silent;
 
+  @override
+  MentionAutocompleteView initViewModel(PerAccountStore store, Narrow narrow) {
+    return MentionAutocompleteView.init(store: store, narrow: narrow, query: this);
+  }
+
   bool testUser(User user, AutocompleteDataCache cache) {
     // TODO(#236) test email too, not just name
 
@@ -555,6 +720,10 @@ class MentionAutocompleteQuery extends AutocompleteQuery {
   int get hashCode => Object.hash('MentionAutocompleteQuery', raw, silent);
 }
 
+/// Cached data that is used for autocomplete
+/// but kept around in between autocomplete interactions.
+///
+/// An instance of this class is managed by [AutocompleteViewManager].
 class AutocompleteDataCache {
   final Map<int, String> _normalizedNamesByUser = {};
 
@@ -575,10 +744,34 @@ class AutocompleteDataCache {
   }
 }
 
+/// A result the user chose, or might choose, from an autocomplete interaction.
+///
+/// Different subclasses of [AutocompleteView],
+/// representing different types of autocomplete interaction,
+/// have corresponding subclasses of [AutocompleteResult] they might produce.
 class AutocompleteResult {}
 
-sealed class MentionAutocompleteResult extends AutocompleteResult {}
+/// A result from some autocomplete interaction in
+/// the compose box's content input, initiated by a [ComposeAutocompleteQuery]
+/// and managed by some [ComposeAutocompleteView].
+sealed class ComposeAutocompleteResult extends AutocompleteResult {}
+
+/// An emoji chosen in an autocomplete interaction, via [EmojiAutocompleteView].
+class EmojiAutocompleteResult extends ComposeAutocompleteResult {
+  EmojiAutocompleteResult(this.candidate);
+
+  final EmojiCandidate candidate;
+}
+
+/// A result from an @-mention autocomplete interaction,
+/// managed by a [MentionAutocompleteView].
+///
+/// This is abstract because there are several kinds of result
+/// that can all be offered in the same @-mention autocomplete interaction:
+/// a user, a wildcard, or a user group.
+sealed class MentionAutocompleteResult extends ComposeAutocompleteResult {}
 
+/// An autocomplete result for an @-mention of an individual user.
 class UserMentionAutocompleteResult extends MentionAutocompleteResult {
   UserMentionAutocompleteResult({required this.userId});
 
@@ -589,17 +782,29 @@ class UserMentionAutocompleteResult extends MentionAutocompleteResult {
 
 // TODO(#234): // class WildcardMentionAutocompleteResult extends MentionAutocompleteResult {
 
+/// An autocomplete interaction for choosing a topic for a message.
 class TopicAutocompleteView extends AutocompleteView<TopicAutocompleteQuery, TopicAutocompleteResult> {
-  TopicAutocompleteView._({required super.store, required this.streamId});
+  TopicAutocompleteView._({
+    required super.store,
+    required super.query,
+    required this.streamId,
+  });
 
-  factory TopicAutocompleteView.init({required PerAccountStore store, required int streamId}) {
-    final view = TopicAutocompleteView._(store: store, streamId: streamId);
+  factory TopicAutocompleteView.init({
+    required PerAccountStore store,
+    required int streamId,
+    required TopicAutocompleteQuery query,
+  }) {
+    final view = TopicAutocompleteView._(
+      store: store, streamId: streamId, query: query);
     store.autocompleteViewManager.registerTopicAutocomplete(view);
     view._fetch();
     return view;
   }
 
+  /// The channel/stream the eventual message will be sent to.
   final int streamId;
+
   Iterable<String> _topics = [];
   bool _isFetching = false;
 
@@ -615,7 +820,7 @@ class TopicAutocompleteView extends AutocompleteView<TopicAutocompleteQuery, Top
     final result = await getStreamTopics(store.connection, streamId: streamId);
     _topics = result.topics.map((e) => e.name);
     _isFetching = false;
-    if (_query != null) return _startSearch();
+    return _startSearch();
   }
 
   @override
@@ -642,6 +847,8 @@ class TopicAutocompleteView extends AutocompleteView<TopicAutocompleteQuery, Top
   }
 }
 
+/// A query for autocompleting a topic to send to,
+/// used by [TopicAutocompleteView].
 class TopicAutocompleteQuery extends AutocompleteQuery {
   TopicAutocompleteQuery(super.raw);
 
@@ -664,6 +871,7 @@ class TopicAutocompleteQuery extends AutocompleteQuery {
   int get hashCode => Object.hash('TopicAutocompleteQuery', raw);
 }
 
+/// A topic chosen in an autocomplete interaction, via a [TopicAutocompleteView].
 class TopicAutocompleteResult extends AutocompleteResult {
   final String topic;
 
diff --git a/lib/model/emoji.dart b/lib/model/emoji.dart
index 2eea7fcde2..d3fcaad67f 100644
--- a/lib/model/emoji.dart
+++ b/lib/model/emoji.dart
@@ -1,7 +1,13 @@
+import 'package:collection/collection.dart';
+import 'package:flutter/foundation.dart';
+
 import '../api/model/events.dart';
 import '../api/model/initial_snapshot.dart';
 import '../api/model/model.dart';
 import '../api/route/realm.dart';
+import 'autocomplete.dart';
+import 'narrow.dart';
+import 'store.dart';
 
 /// An emoji, described by how to display it in the UI.
 sealed class EmojiDisplay {
@@ -51,6 +57,37 @@ class TextEmojiDisplay extends EmojiDisplay {
   TextEmojiDisplay({required super.emojiName});
 }
 
+/// An emoji that might be offered in an emoji picker UI.
+final class EmojiCandidate {
+  /// The Zulip "emoji type" for this emoji.
+  final ReactionType emojiType;
+
+  /// The Zulip "emoji code" for this emoji.
+  ///
+  /// This is the value that would appear in [Reaction.emojiCode].
+  final String emojiCode;
+
+  /// The Zulip "emoji name" to use for this emoji.
+  ///
+  /// This might not be the only name this emoji has; see [aliases].
+  final String emojiName;
+
+  /// Additional Zulip "emoji name" values for this emoji,
+  /// to show in the emoji picker UI.
+  Iterable<String> get aliases => _aliases ?? const [];
+  final List<String>? _aliases;
+
+  final EmojiDisplay emojiDisplay;
+
+  EmojiCandidate({
+    required this.emojiType,
+    required this.emojiCode,
+    required this.emojiName,
+    required List<String>? aliases,
+    required this.emojiDisplay,
+  }) : _aliases = aliases;
+}
+
 /// The portion of [PerAccountStore] describing what emoji exist.
 mixin EmojiStore {
   /// The realm's custom emoji (for [ReactionType.realmEmoji],
@@ -63,6 +100,8 @@ mixin EmojiStore {
     required String emojiName,
   });
 
+  Iterable<EmojiCandidate> allEmojiCandidates();
+
   // TODO cut debugServerEmojiData once we can query for lists of emoji;
   //   have tests make those queries end-to-end
   Map<String, List<String>>? get debugServerEmojiData;
@@ -148,12 +187,168 @@ class EmojiStoreImpl with EmojiStore {
   /// retrieving the data.
   Map<String, List<String>>? _serverEmojiData;
 
+  List<EmojiCandidate>? _allEmojiCandidates;
+
+  EmojiCandidate _emojiCandidateFor({
+    required ReactionType emojiType,
+    required String emojiCode,
+    required String emojiName,
+    required List<String>? aliases,
+  }) {
+    return EmojiCandidate(
+      emojiType: emojiType, emojiCode: emojiCode, emojiName: emojiName,
+      aliases: aliases,
+      emojiDisplay: emojiDisplayFor(
+        emojiType: emojiType, emojiCode: emojiCode, emojiName: emojiName));
+  }
+
+  List<EmojiCandidate> _generateAllCandidates() {
+    final results = <EmojiCandidate>[];
+
+    final namesOverridden = {
+      for (final emoji in realmEmoji.values) emoji.name,
+      'zulip',
+    };
+    // TODO(log) if _serverEmojiData missing
+    for (final entry in (_serverEmojiData ?? {}).entries) {
+      final allNames = entry.value;
+      final String emojiName;
+      final List<String>? aliases;
+      if (allNames.any(namesOverridden.contains)) {
+        final names = allNames.whereNot(namesOverridden.contains).toList();
+        if (names.isEmpty) continue;
+        emojiName = names.removeAt(0);
+        aliases = names;
+      } else {
+        // Most emoji aren't overridden, so avoid copying the list.
+        emojiName = allNames.first;
+        aliases = allNames.length > 1 ? allNames.sublist(1) : null;
+      }
+      results.add(_emojiCandidateFor(
+        emojiType: ReactionType.unicodeEmoji,
+        emojiCode: entry.key, emojiName: emojiName,
+        aliases: aliases));
+    }
+
+    for (final entry in realmEmoji.entries) {
+      final emojiName = entry.value.name;
+      if (emojiName == 'zulip') {
+        // TODO does 'zulip' really override realm emoji?
+        //   (This is copied from zulip-mobile's behavior.)
+        continue;
+      }
+      results.add(_emojiCandidateFor(
+        emojiType: ReactionType.realmEmoji,
+        emojiCode: entry.key, emojiName: emojiName,
+        aliases: null));
+    }
+
+    results.add(_emojiCandidateFor(
+      emojiType: ReactionType.zulipExtraEmoji,
+      emojiCode: 'zulip', emojiName: 'zulip',
+      aliases: null));
+
+    return results;
+  }
+
+  @override
+  Iterable<EmojiCandidate> allEmojiCandidates() {
+    return _allEmojiCandidates ??= _generateAllCandidates();
+  }
+
   @override
   void setServerEmojiData(ServerEmojiData data) {
     _serverEmojiData = data.codeToNames;
+    _allEmojiCandidates = null;
   }
 
   void handleRealmEmojiUpdateEvent(RealmEmojiUpdateEvent event) {
     realmEmoji = event.realmEmoji;
+    _allEmojiCandidates = null;
   }
 }
+
+class EmojiAutocompleteView extends AutocompleteView<EmojiAutocompleteQuery, EmojiAutocompleteResult> {
+  EmojiAutocompleteView._({required super.store, required super.query});
+
+  factory EmojiAutocompleteView.init({
+    required PerAccountStore store,
+    required EmojiAutocompleteQuery query,
+  }) {
+    final view = EmojiAutocompleteView._(store: store, query: query);
+    store.autocompleteViewManager.registerEmojiAutocomplete(view);
+    return view;
+  }
+
+  @override
+  Future<List<EmojiAutocompleteResult>?> computeResults() async {
+    // TODO(#1068): rank emoji results (popular, realm, other; exact match, prefix, other)
+    final results = <EmojiAutocompleteResult>[];
+    if (await filterCandidates(filter: _testCandidate,
+          candidates: store.allEmojiCandidates(), results: results)) {
+      return null;
+    }
+    return results;
+  }
+
+  EmojiAutocompleteResult? _testCandidate(EmojiAutocompleteQuery query, EmojiCandidate candidate) {
+    return query.matches(candidate) ? EmojiAutocompleteResult(candidate) : null;
+  }
+}
+
+class EmojiAutocompleteQuery extends ComposeAutocompleteQuery {
+  EmojiAutocompleteQuery(super.raw)
+    : _adjusted = _adjustQuery(raw);
+
+  final String _adjusted;
+
+  static String _adjustQuery(String raw) {
+    return raw.toLowerCase().replaceAll(' ', '_'); // TODO(#1067) remove diacritics too
+  }
+
+  @override
+  EmojiAutocompleteView initViewModel(PerAccountStore store, Narrow narrow) {
+    return EmojiAutocompleteView.init(store: store, query: this);
+  }
+
+  // Compare get_emoji_matcher in Zulip web:shared/src/typeahead.ts .
+  bool matches(EmojiCandidate candidate) {
+    if (candidate.emojiDisplay case UnicodeEmojiDisplay(:var emojiUnicode)) {
+      if (_adjusted == emojiUnicode) return true;
+    }
+    return _nameMatches(candidate.emojiName)
+      || candidate.aliases.any((alias) => _nameMatches(alias));
+  }
+
+  // Compare query_matches_string_in_order in Zulip web:shared/src/typeahead.ts .
+  bool _nameMatches(String emojiName) {
+    // TODO(#1067) this assumes emojiName is already lower-case (and no diacritics)
+    const String separator = '_';
+
+    if (!_adjusted.contains(separator)) {
+      // If the query is a single token (doesn't contain a separator),
+      // the match can be anywhere in the string.
+      return emojiName.contains(_adjusted);
+    }
+
+    // If there is a separator in the query, then we
+    // require the match to start at the start of a token.
+    // (E.g. for 'ab_cd_ef', query could be 'ab_c' or 'cd_ef',
+    // but not 'b_cd_ef'.)
+    return emojiName.startsWith(_adjusted)
+      || emojiName.contains(separator + _adjusted);
+  }
+
+  @override
+  String toString() {
+    return '${objectRuntimeType(this, 'EmojiAutocompleteQuery')}($raw)';
+  }
+
+  @override
+  bool operator ==(Object other) {
+    return other is EmojiAutocompleteQuery && other.raw == raw;
+  }
+
+  @override
+  int get hashCode => Object.hash('EmojiAutocompleteQuery', raw);
+}
diff --git a/lib/model/store.dart b/lib/model/store.dart
index 7e230a6fa9..05178142e3 100644
--- a/lib/model/store.dart
+++ b/lib/model/store.dart
@@ -408,6 +408,9 @@ class PerAccountStore extends ChangeNotifier with EmojiStore, ChannelStore, Mess
     notifyListeners();
   }
 
+  @override
+  Iterable<EmojiCandidate> allEmojiCandidates() => _emoji.allEmojiCandidates();
+
   EmojiStoreImpl _emoji;
 
   ////////////////////////////////
diff --git a/lib/widgets/autocomplete.dart b/lib/widgets/autocomplete.dart
index 277048f6a9..ba0d003a8f 100644
--- a/lib/widgets/autocomplete.dart
+++ b/lib/widgets/autocomplete.dart
@@ -1,6 +1,8 @@
 import 'package:flutter/material.dart';
 
+import '../model/emoji.dart';
 import 'content.dart';
+import 'emoji.dart';
 import 'store.dart';
 import '../model/autocomplete.dart';
 import '../model/compose.dart';
@@ -23,7 +25,7 @@ abstract class AutocompleteField<QueryT extends AutocompleteQuery, ResultT exten
 
   Widget buildItem(BuildContext context, int index, ResultT option);
 
-  AutocompleteView<QueryT, ResultT> initViewModel(BuildContext context);
+  AutocompleteView<QueryT, ResultT> initViewModel(BuildContext context, QueryT query);
 
   @override
   State<AutocompleteField<QueryT, ResultT>> createState() => _AutocompleteFieldState<QueryT, ResultT>();
@@ -32,23 +34,30 @@ abstract class AutocompleteField<QueryT extends AutocompleteQuery, ResultT exten
 class _AutocompleteFieldState<QueryT extends AutocompleteQuery, ResultT extends AutocompleteResult> extends State<AutocompleteField<QueryT, ResultT>> with PerAccountStoreAwareStateMixin<AutocompleteField<QueryT, ResultT>> {
   AutocompleteView<QueryT, ResultT>? _viewModel;
 
-  void _initViewModel() {
-    _viewModel = widget.initViewModel(context)
+  void _initViewModel(QueryT query) {
+    _viewModel = widget.initViewModel(context, query)
       ..addListener(_viewModelChanged);
   }
 
   void _handleControllerChange() {
-    final newAutocompleteIntent = widget.autocompleteIntent();
-    if (newAutocompleteIntent != null) {
+    final newQuery = widget.autocompleteIntent()?.query;
+    // First, tear down the old view-model if necessary.
+    if (_viewModel != null
+        && (newQuery == null
+            || !_viewModel!.acceptsQuery(newQuery))) {
+      // The autocomplete interaction has ended, or has switched to a
+      // different kind of autocomplete (e.g. @-mention vs. emoji).
+      _viewModel!.dispose(); // removes our listener
+      _viewModel = null;
+      _resultsToDisplay = [];
+    }
+    // Then, update the view-model or build a new one.
+    if (newQuery != null) {
       if (_viewModel == null) {
-        _initViewModel();
-      }
-      _viewModel!.query = newAutocompleteIntent.query;
-    } else {
-      if (_viewModel != null) {
-        _viewModel!.dispose(); // removes our listener
-        _viewModel = null;
-        _resultsToDisplay = [];
+        _initViewModel(newQuery);
+      } else {
+        assert(_viewModel!.acceptsQuery(newQuery));
+        _viewModel!.query = newQuery;
       }
     }
   }
@@ -64,7 +73,7 @@ class _AutocompleteFieldState<QueryT extends AutocompleteQuery, ResultT extends
     if (_viewModel != null) {
       final query = _viewModel!.query;
       _viewModel!.dispose();
-      _initViewModel();
+      _initViewModel(query);
       _viewModel!.query = query;
     }
   }
@@ -144,7 +153,7 @@ class _AutocompleteFieldState<QueryT extends AutocompleteQuery, ResultT extends
   }
 }
 
-class ComposeAutocomplete extends AutocompleteField<MentionAutocompleteQuery, MentionAutocompleteResult> {
+class ComposeAutocomplete extends AutocompleteField<ComposeAutocompleteQuery, ComposeAutocompleteResult> {
   const ComposeAutocomplete({
     super.key,
     required this.narrow,
@@ -159,15 +168,15 @@ class ComposeAutocomplete extends AutocompleteField<MentionAutocompleteQuery, Me
   ComposeContentController get controller => super.controller as ComposeContentController;
 
   @override
-  AutocompleteIntent<MentionAutocompleteQuery>? autocompleteIntent() => controller.autocompleteIntent();
+  AutocompleteIntent<ComposeAutocompleteQuery>? autocompleteIntent() => controller.autocompleteIntent();
 
   @override
-  MentionAutocompleteView initViewModel(BuildContext context) {
+  ComposeAutocompleteView initViewModel(BuildContext context, ComposeAutocompleteQuery query) {
     final store = PerAccountStoreWidget.of(context);
-    return MentionAutocompleteView.init(store: store, narrow: narrow);
+    return query.initViewModel(store, narrow);
   }
 
-  void _onTapOption(BuildContext context, MentionAutocompleteResult option) {
+  void _onTapOption(BuildContext context, ComposeAutocompleteResult option) {
     // Probably the same intent that brought up the option that was tapped.
     // If not, it still shouldn't be off by more than the time it takes
     // to compute the autocomplete results, which we do asynchronously.
@@ -175,14 +184,20 @@ class ComposeAutocomplete extends AutocompleteField<MentionAutocompleteQuery, Me
     if (intent == null) {
       return; // Shrug.
     }
+    final query = intent.query;
 
     final store = PerAccountStoreWidget.of(context);
     final String replacementString;
     switch (option) {
+      case EmojiAutocompleteResult(:var candidate):
+        replacementString = ':${candidate.emojiName}:';
       case UserMentionAutocompleteResult(:var userId):
+        if (query is! MentionAutocompleteQuery) {
+          return; // Shrug; similar to `intent == null` case above.
+        }
         // TODO(i18n) language-appropriate space character; check active keyboard?
         //   (maybe handle centrally in `controller`)
-        replacementString = '${mention(store.users[userId]!, silent: intent.query.silent, users: store.users)} ';
+        replacementString = '${mention(store.users[userId]!, silent: query.silent, users: store.users)} ';
     }
 
     controller.value = intent.textEditingValue.replaced(
@@ -194,7 +209,26 @@ class ComposeAutocomplete extends AutocompleteField<MentionAutocompleteQuery, Me
   }
 
   @override
-  Widget buildItem(BuildContext context, int index, MentionAutocompleteResult option) {
+  Widget buildItem(BuildContext context, int index, ComposeAutocompleteResult option) {
+    final child = switch (option) {
+      MentionAutocompleteResult() => _MentionAutocompleteItem(option: option),
+      EmojiAutocompleteResult() => _EmojiAutocompleteItem(option: option),
+    };
+    return InkWell(
+      onTap: () {
+        _onTapOption(context, option);
+      },
+      child: child);
+  }
+}
+
+class _MentionAutocompleteItem extends StatelessWidget {
+  const _MentionAutocompleteItem({required this.option});
+
+  final MentionAutocompleteResult option;
+
+  @override
+  Widget build(BuildContext context) {
     Widget avatar;
     String label;
     switch (option) {
@@ -202,18 +236,58 @@ class ComposeAutocomplete extends AutocompleteField<MentionAutocompleteQuery, Me
         avatar = Avatar(userId: userId, size: 32, borderRadius: 3);
         label = PerAccountStoreWidget.of(context).users[userId]!.fullName;
     }
-    return InkWell(
-      onTap: () {
-        _onTapOption(context, option);
-      },
-      child: Padding(
-        padding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
-        child: Row(
-          children: [
-            avatar,
-            const SizedBox(width: 8),
-            Text(label),
-          ])));
+
+    return Padding(
+      padding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
+      child: Row(children: [
+        avatar,
+        const SizedBox(width: 8),
+        Text(label),
+      ]));
+  }
+}
+
+class _EmojiAutocompleteItem extends StatelessWidget {
+  const _EmojiAutocompleteItem({required this.option});
+
+  final EmojiAutocompleteResult option;
+
+  static const _size = 32.0;
+  static const _notoColorEmojiTextSize = 25.7;
+
+  @override
+  Widget build(BuildContext context) {
+    final store = PerAccountStoreWidget.of(context);
+    final candidate = option.candidate;
+
+    final emojiDisplay = candidate.emojiDisplay.resolve(store.userSettings);
+    final Widget? glyph = switch (emojiDisplay) {
+      ImageEmojiDisplay() =>
+        ImageEmojiWidget(size: _size, emojiDisplay: emojiDisplay),
+      UnicodeEmojiDisplay() =>
+        UnicodeEmojiWidget(
+          size: _size, notoColorEmojiTextSize: _notoColorEmojiTextSize,
+          emojiDisplay: emojiDisplay),
+      TextEmojiDisplay() => null, // The text is already shown separately.
+    };
+
+    final label = candidate.aliases.isEmpty
+      ? candidate.emojiName
+      : [candidate.emojiName, ...candidate.aliases].join(", "); // TODO(#1080)
+
+    return Padding(
+      padding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
+      child: Row(children: [
+        if (glyph != null) ...[
+          glyph,
+          const SizedBox(width: 8),
+        ],
+        Expanded(
+          child: Text(
+            maxLines: 2,
+            overflow: TextOverflow.ellipsis,
+            label)),
+      ]));
   }
 }
 
@@ -238,9 +312,9 @@ class TopicAutocomplete extends AutocompleteField<TopicAutocompleteQuery, TopicA
   AutocompleteIntent<TopicAutocompleteQuery>? autocompleteIntent() => controller.autocompleteIntent();
 
   @override
-  TopicAutocompleteView initViewModel(BuildContext context) {
+  TopicAutocompleteView initViewModel(BuildContext context, TopicAutocompleteQuery query) {
     final store = PerAccountStoreWidget.of(context);
-    return TopicAutocompleteView.init(store: store, streamId: streamId);
+    return TopicAutocompleteView.init(store: store, streamId: streamId, query: query);
   }
 
   void _onTapOption(BuildContext context, TopicAutocompleteResult option) {
diff --git a/lib/widgets/emoji.dart b/lib/widgets/emoji.dart
new file mode 100644
index 0000000000..d8af9827d7
--- /dev/null
+++ b/lib/widgets/emoji.dart
@@ -0,0 +1,131 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter/widgets.dart';
+
+import '../model/emoji.dart';
+import 'content.dart';
+
+class UnicodeEmojiWidget extends StatelessWidget {
+  const UnicodeEmojiWidget({
+    super.key,
+    required this.emojiDisplay,
+    required this.size,
+    required this.notoColorEmojiTextSize,
+    this.textScaler = TextScaler.noScaling,
+  });
+
+  final UnicodeEmojiDisplay emojiDisplay;
+
+  /// The base width and height to use for the emoji.
+  ///
+  /// This will be scaled by [textScaler].
+  final double size;
+
+  /// A font size that, with Noto Color Emoji and our line-height config,
+  /// causes a Unicode emoji to occupy a square of size [size] in the layout.
+  ///
+  /// This has to be determined experimentally, as far as we know.
+  final double notoColorEmojiTextSize;
+
+  /// The text scaler to apply to [size].
+  ///
+  /// Defaults to [TextScaler.noScaling].
+  final TextScaler textScaler;
+
+  @override
+  Widget build(BuildContext context) {
+    switch (defaultTargetPlatform) {
+      case TargetPlatform.android:
+      case TargetPlatform.fuchsia:
+      case TargetPlatform.linux:
+      case TargetPlatform.windows:
+        return Text(
+          textScaler: textScaler,
+          style: TextStyle(
+            fontFamily: 'Noto Color Emoji',
+            fontSize: notoColorEmojiTextSize,
+          ),
+          strutStyle: StrutStyle(
+            fontSize: notoColorEmojiTextSize, forceStrutHeight: true),
+          emojiDisplay.emojiUnicode);
+
+      case TargetPlatform.iOS:
+      case TargetPlatform.macOS:
+        // We expect the font "Apple Color Emoji" to be used. There are some
+        // surprises in how Flutter ends up rendering emojis in this font:
+        // - With a font size of 17px, the emoji visually seems to be about 17px
+        //   square. (Unlike on Android, with Noto Color Emoji, where a 14.5px font
+        //   size gives an emoji that looks 17px square.) See:
+        //     <https://github.com/flutter/flutter/issues/28894>
+        // - The emoji doesn't fill the space taken by the [Text] in the layout.
+        //   There's whitespace above, below, and on the right. See:
+        //     <https://github.com/flutter/flutter/issues/119623>
+        //
+        // That extra space would be problematic, except we've used a [Stack] to
+        // make the [Text] "positioned" so the space doesn't add margins around the
+        // visible part. Key points that enable the [Stack] workaround:
+        // - The emoji seems approximately vertically centered (this is
+        //   accomplished with help from a [StrutStyle]; see below).
+        // - There seems to be approximately no space on its left.
+        final boxSize = textScaler.scale(size);
+        return Stack(alignment: Alignment.centerLeft, clipBehavior: Clip.none, children: [
+          SizedBox(height: boxSize, width: boxSize),
+          PositionedDirectional(start: 0, child: Text(
+            textScaler: textScaler,
+            style: TextStyle(fontSize: size),
+            strutStyle: StrutStyle(fontSize: size, forceStrutHeight: true),
+            emojiDisplay.emojiUnicode)),
+        ]);
+    }
+  }
+}
+
+
+class ImageEmojiWidget extends StatelessWidget {
+  const ImageEmojiWidget({
+    super.key,
+    required this.emojiDisplay,
+    required this.size,
+    this.textScaler = TextScaler.noScaling,
+    this.errorBuilder,
+  });
+
+  final ImageEmojiDisplay emojiDisplay;
+
+  /// The base width and height to use for the emoji.
+  ///
+  /// This will be scaled by [textScaler].
+  final double size;
+
+  /// The text scaler to apply to [size].
+  ///
+  /// Defaults to [TextScaler.noScaling].
+  final TextScaler textScaler;
+
+  final ImageErrorWidgetBuilder? errorBuilder;
+
+  @override
+  Widget build(BuildContext context) {
+    // Some people really dislike animated emoji.
+    final doNotAnimate =
+      // From reading code, this doesn't actually get set on iOS:
+      //   https://github.com/zulip/zulip-flutter/pull/410#discussion_r1408522293
+      MediaQuery.disableAnimationsOf(context)
+      || (defaultTargetPlatform == TargetPlatform.iOS
+        // TODO(upstream) On iOS 17+ (new in 2023), there's a more closely
+        //   relevant setting than "reduce motion". It's called "auto-play
+        //   animated images", and we should file an issue to expose it.
+        //   See GitHub comment linked above.
+        && WidgetsBinding.instance.platformDispatcher.accessibilityFeatures.reduceMotion);
+
+    final size = textScaler.scale(this.size);
+
+    final resolvedUrl = doNotAnimate
+      ? (emojiDisplay.resolvedStillUrl ?? emojiDisplay.resolvedUrl)
+      : emojiDisplay.resolvedUrl;
+
+    return RealmContentNetworkImage(
+      width: size, height: size,
+      errorBuilder: errorBuilder,
+      resolvedUrl);
+  }
+}
diff --git a/lib/widgets/emoji_reaction.dart b/lib/widgets/emoji_reaction.dart
index d92a050b05..39264eb3b6 100644
--- a/lib/widgets/emoji_reaction.dart
+++ b/lib/widgets/emoji_reaction.dart
@@ -1,11 +1,10 @@
-import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 
 import '../api/model/model.dart';
 import '../api/route/messages.dart';
 import '../model/emoji.dart';
 import 'color.dart';
-import 'content.dart';
+import 'emoji.dart';
 import 'store.dart';
 import 'text.dart';
 
@@ -183,7 +182,7 @@ class ReactionChip extends StatelessWidget {
 
     final emoji = switch (emojiDisplay) {
       UnicodeEmojiDisplay() => _UnicodeEmoji(
-        emojiDisplay: emojiDisplay, selected: selfVoted),
+        emojiDisplay: emojiDisplay),
       ImageEmojiDisplay() => _ImageEmoji(
         emojiDisplay: emojiDisplay, emojiName: emojiName, selected: selfVoted),
       TextEmojiDisplay() => _TextEmoji(
@@ -294,57 +293,17 @@ TextScaler _labelTextScalerClamped(BuildContext context) =>
   MediaQuery.textScalerOf(context).clamp(maxScaleFactor: 2);
 
 class _UnicodeEmoji extends StatelessWidget {
-  const _UnicodeEmoji({
-    required this.emojiDisplay,
-    required this.selected,
-  });
+  const _UnicodeEmoji({required this.emojiDisplay});
 
   final UnicodeEmojiDisplay emojiDisplay;
-  final bool selected;
 
   @override
   Widget build(BuildContext context) {
-    switch (defaultTargetPlatform) {
-      case TargetPlatform.android:
-      case TargetPlatform.fuchsia:
-      case TargetPlatform.linux:
-      case TargetPlatform.windows:
-        return Text(
-          textScaler: _squareEmojiScalerClamped(context),
-          style: const TextStyle(
-            fontFamily: 'Noto Color Emoji',
-            fontSize: _notoColorEmojiTextSize,
-          ),
-          strutStyle: const StrutStyle(fontSize: _notoColorEmojiTextSize, forceStrutHeight: true),
-          emojiDisplay.emojiUnicode);
-      case TargetPlatform.iOS:
-      case TargetPlatform.macOS:
-        // We expect the font "Apple Color Emoji" to be used. There are some
-        // surprises in how Flutter ends up rendering emojis in this font:
-        // - With a font size of 17px, the emoji visually seems to be about 17px
-        //   square. (Unlike on Android, with Noto Color Emoji, where a 14.5px font
-        //   size gives an emoji that looks 17px square.) See:
-        //     <https://github.com/flutter/flutter/issues/28894>
-        // - The emoji doesn't fill the space taken by the [Text] in the layout.
-        //   There's whitespace above, below, and on the right. See:
-        //     <https://github.com/flutter/flutter/issues/119623>
-        //
-        // That extra space would be problematic, except we've used a [Stack] to
-        // make the [Text] "positioned" so the space doesn't add margins around the
-        // visible part. Key points that enable the [Stack] workaround:
-        // - The emoji seems approximately vertically centered (this is
-        //   accomplished with help from a [StrutStyle]; see below).
-        // - There seems to be approximately no space on its left.
-        final boxSize = _squareEmojiScalerClamped(context).scale(_squareEmojiSize);
-        return Stack(alignment: Alignment.centerLeft, clipBehavior: Clip.none, children: [
-          SizedBox(height: boxSize, width: boxSize),
-          PositionedDirectional(start: 0, child: Text(
-            textScaler: _squareEmojiScalerClamped(context),
-            style: const TextStyle(fontSize: _squareEmojiSize),
-            strutStyle: const StrutStyle(fontSize: _squareEmojiSize, forceStrutHeight: true),
-            emojiDisplay.emojiUnicode)),
-        ]);
-    }
+    return UnicodeEmojiWidget(
+      size: _squareEmojiSize,
+      notoColorEmojiTextSize: _notoColorEmojiTextSize,
+      textScaler: _squareEmojiScalerClamped(context),
+      emojiDisplay: emojiDisplay);
   }
 }
 
@@ -361,29 +320,11 @@ class _ImageEmoji extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    // Some people really dislike animated emoji.
-    final doNotAnimate =
-      // From reading code, this doesn't actually get set on iOS:
-      //   https://github.com/zulip/zulip-flutter/pull/410#discussion_r1408522293
-      MediaQuery.disableAnimationsOf(context)
-      || (defaultTargetPlatform == TargetPlatform.iOS
-        // TODO(upstream) On iOS 17+ (new in 2023), there's a more closely
-        //   relevant setting than "reduce motion". It's called "auto-play
-        //   animated images", and we should file an issue to expose it.
-        //   See GitHub comment linked above.
-        && WidgetsBinding.instance.platformDispatcher.accessibilityFeatures.reduceMotion);
-
-    final resolvedUrl = doNotAnimate
-      ? (emojiDisplay.resolvedStillUrl ?? emojiDisplay.resolvedUrl)
-      : emojiDisplay.resolvedUrl;
-
-    // Unicode and text emoji get scaled; it would look weird if image emoji didn't.
-    final size = _squareEmojiScalerClamped(context).scale(_squareEmojiSize);
-
-    return RealmContentNetworkImage(
-      resolvedUrl,
-      width: size,
-      height: size,
+    return ImageEmojiWidget(
+      size: _squareEmojiSize,
+      // Unicode and text emoji get scaled; it would look weird if image emoji didn't.
+      textScaler: _squareEmojiScalerClamped(context),
+      emojiDisplay: emojiDisplay,
       errorBuilder: (context, _, __) => _TextEmoji(
         emojiDisplay: TextEmojiDisplay(emojiName: emojiName), selected: selected),
     );
diff --git a/test/model/autocomplete_checks.dart b/test/model/autocomplete_checks.dart
index 93c4dbe196..cb94735894 100644
--- a/test/model/autocomplete_checks.dart
+++ b/test/model/autocomplete_checks.dart
@@ -3,7 +3,7 @@ import 'package:zulip/model/autocomplete.dart';
 import 'package:zulip/widgets/compose_box.dart';
 
 extension ComposeContentControllerChecks on Subject<ComposeContentController> {
-  Subject<AutocompleteIntent<MentionAutocompleteQuery>?> get autocompleteIntent => has((c) => c.autocompleteIntent(), 'autocompleteIntent');
+  Subject<AutocompleteIntent<ComposeAutocompleteQuery>?> get autocompleteIntent => has((c) => c.autocompleteIntent(), 'autocompleteIntent');
 }
 
 extension ComposeTopicControllerChecks on Subject<ComposeTopicController> {
diff --git a/test/model/autocomplete_test.dart b/test/model/autocomplete_test.dart
index 9830b2a734..9d6667ca3f 100644
--- a/test/model/autocomplete_test.dart
+++ b/test/model/autocomplete_test.dart
@@ -2,19 +2,20 @@ import 'dart:async';
 import 'dart:convert';
 
 import 'package:checks/checks.dart';
-import 'package:fake_async/fake_async.dart';
 import 'package:flutter/widgets.dart';
 import 'package:test/scaffolding.dart';
 import 'package:zulip/api/model/initial_snapshot.dart';
 import 'package:zulip/api/model/model.dart';
 import 'package:zulip/api/route/channels.dart';
 import 'package:zulip/model/autocomplete.dart';
+import 'package:zulip/model/emoji.dart';
 import 'package:zulip/model/narrow.dart';
 import 'package:zulip/model/store.dart';
 import 'package:zulip/widgets/compose_box.dart';
 
 import '../api/fake_api.dart';
 import '../example_data.dart' as eg;
+import '../fake_async.dart';
 import 'test_store.dart';
 import 'autocomplete_checks.dart';
 
@@ -68,7 +69,7 @@ void main() {
     ///
     /// For example, "~@chris^" means the text is "@chris", the selection is
     /// collapsed at index 6, and we expect the syntax to start at index 0.
-    void doTest(String markedText, MentionAutocompleteQuery? expectedQuery) {
+    void doTest(String markedText, ComposeAutocompleteQuery? expectedQuery) {
       final description = expectedQuery != null
         ? 'in ${jsonEncode(markedText)}, query ${jsonEncode(expectedQuery.raw)}'
         : 'no query in ${jsonEncode(markedText)}';
@@ -87,14 +88,17 @@ void main() {
       });
     }
 
-    MentionAutocompleteQuery queryOf(String raw) => MentionAutocompleteQuery(raw, silent: false);
-    MentionAutocompleteQuery silentQueryOf(String raw) => MentionAutocompleteQuery(raw, silent: true);
+    MentionAutocompleteQuery mention(String raw) => MentionAutocompleteQuery(raw, silent: false);
+    MentionAutocompleteQuery silentMention(String raw) => MentionAutocompleteQuery(raw, silent: true);
+    EmojiAutocompleteQuery emoji(String raw) => EmojiAutocompleteQuery(raw);
 
     doTest('', null);
     doTest('^', null);
 
     doTest('!@#\$%&*()_+', null);
 
+    // @-mentions.
+
     doTest('^@', null);                doTest('^@_', null);
     doTest('^@abc', null);             doTest('^@_abc', null);
     doTest('@abc', null);              doTest('@_abc', null); // (no cursor)
@@ -125,61 +129,139 @@ void main() {
 
     doTest('`@chris^', null); doTest('`@_chris^', null);
 
-    doTest('~@^_', queryOf('')); // Odd/unlikely, but should not crash
+    doTest('~@^_', mention('')); // Odd/unlikely, but should not crash
 
-    doTest('~@__^', silentQueryOf('_'));
+    doTest('~@__^', silentMention('_'));
 
-    doTest('~@^abc^', queryOf('abc')); doTest('~@_^abc^', silentQueryOf('abc'));
-    doTest('~@a^bc^', queryOf('abc')); doTest('~@_a^bc^', silentQueryOf('abc'));
-    doTest('~@ab^c^', queryOf('abc')); doTest('~@_ab^c^', silentQueryOf('abc'));
-    doTest('~^@^', queryOf(''));       doTest('~^@_^', silentQueryOf(''));
+    doTest('~@^abc^', mention('abc')); doTest('~@_^abc^', silentMention('abc'));
+    doTest('~@a^bc^', mention('abc')); doTest('~@_a^bc^', silentMention('abc'));
+    doTest('~@ab^c^', mention('abc')); doTest('~@_ab^c^', silentMention('abc'));
+    doTest('~^@^', mention(''));       doTest('~^@_^', silentMention(''));
     // but:
     doTest('^hello @chris^', null);    doTest('^hello @_chris^', null);
 
-    doTest('~@me@zulip.com^', queryOf('me@zulip.com'));  doTest('~@_me@zulip.com^', silentQueryOf('me@zulip.com'));
-    doTest('~@me@^zulip.com^', queryOf('me@zulip.com')); doTest('~@_me@^zulip.com^', silentQueryOf('me@zulip.com'));
-    doTest('~@me^@zulip.com^', queryOf('me@zulip.com')); doTest('~@_me^@zulip.com^', silentQueryOf('me@zulip.com'));
-    doTest('~@^me@zulip.com^', queryOf('me@zulip.com')); doTest('~@_^me@zulip.com^', silentQueryOf('me@zulip.com'));
-
-    doTest('~@abc^', queryOf('abc'));   doTest('~@_abc^', silentQueryOf('abc'));
-    doTest(' ~@abc^', queryOf('abc'));  doTest(' ~@_abc^', silentQueryOf('abc'));
-    doTest('(~@abc^', queryOf('abc'));  doTest('(~@_abc^', silentQueryOf('abc'));
-    doTest('—~@abc^', queryOf('abc'));  doTest('—~@_abc^', silentQueryOf('abc'));
-    doTest('"~@abc^', queryOf('abc'));  doTest('"~@_abc^', silentQueryOf('abc'));
-    doTest('“~@abc^', queryOf('abc'));  doTest('“~@_abc^', silentQueryOf('abc'));
-    doTest('。~@abc^', queryOf('abc')); doTest('。~@_abc^', silentQueryOf('abc'));
-    doTest('«~@abc^', queryOf('abc'));  doTest('«~@_abc^', silentQueryOf('abc'));
-
-    doTest('~@ab^c', queryOf('ab')); doTest('~@_ab^c', silentQueryOf('ab'));
-    doTest('~@a^bc', queryOf('a'));  doTest('~@_a^bc', silentQueryOf('a'));
-    doTest('~@^abc', queryOf(''));   doTest('~@_^abc', silentQueryOf(''));
-    doTest('~@^', queryOf(''));      doTest('~@_^', silentQueryOf(''));
-
-    doTest('~@abc ^', queryOf('abc '));  doTest('~@_abc ^', silentQueryOf('abc '));
-    doTest('~@abc^ ^', queryOf('abc ')); doTest('~@_abc^ ^', silentQueryOf('abc '));
-    doTest('~@ab^c ^', queryOf('abc ')); doTest('~@_ab^c ^', silentQueryOf('abc '));
-    doTest('~@^abc ^', queryOf('abc ')); doTest('~@_^abc ^', silentQueryOf('abc '));
-
-    doTest('Please ask ~@chris^', queryOf('chris'));             doTest('Please ask ~@_chris^', silentQueryOf('chris'));
-    doTest('Please ask ~@chris bobbe^', queryOf('chris bobbe')); doTest('Please ask ~@_chris bobbe^', silentQueryOf('chris bobbe'));
-
-    doTest('~@Rodion Romanovich Raskolnikov^', queryOf('Rodion Romanovich Raskolnikov'));
-    doTest('~@_Rodion Romanovich Raskolniko^', silentQueryOf('Rodion Romanovich Raskolniko'));
-    doTest('~@Родион Романович Раскольников^', queryOf('Родион Романович Раскольников'));
-    doTest('~@_Родион Романович Раскольнико^', silentQueryOf('Родион Романович Раскольнико'));
+    doTest('~@me@zulip.com^', mention('me@zulip.com'));  doTest('~@_me@zulip.com^', silentMention('me@zulip.com'));
+    doTest('~@me@^zulip.com^', mention('me@zulip.com')); doTest('~@_me@^zulip.com^', silentMention('me@zulip.com'));
+    doTest('~@me^@zulip.com^', mention('me@zulip.com')); doTest('~@_me^@zulip.com^', silentMention('me@zulip.com'));
+    doTest('~@^me@zulip.com^', mention('me@zulip.com')); doTest('~@_^me@zulip.com^', silentMention('me@zulip.com'));
+
+    doTest('~@abc^', mention('abc'));   doTest('~@_abc^', silentMention('abc'));
+    doTest(' ~@abc^', mention('abc'));  doTest(' ~@_abc^', silentMention('abc'));
+    doTest('(~@abc^', mention('abc'));  doTest('(~@_abc^', silentMention('abc'));
+    doTest('—~@abc^', mention('abc'));  doTest('—~@_abc^', silentMention('abc'));
+    doTest('"~@abc^', mention('abc'));  doTest('"~@_abc^', silentMention('abc'));
+    doTest('“~@abc^', mention('abc'));  doTest('“~@_abc^', silentMention('abc'));
+    doTest('。~@abc^', mention('abc')); doTest('。~@_abc^', silentMention('abc'));
+    doTest('«~@abc^', mention('abc'));  doTest('«~@_abc^', silentMention('abc'));
+
+    doTest('~@ab^c', mention('ab')); doTest('~@_ab^c', silentMention('ab'));
+    doTest('~@a^bc', mention('a'));  doTest('~@_a^bc', silentMention('a'));
+    doTest('~@^abc', mention(''));   doTest('~@_^abc', silentMention(''));
+    doTest('~@^', mention(''));      doTest('~@_^', silentMention(''));
+
+    doTest('~@abc ^', mention('abc '));  doTest('~@_abc ^', silentMention('abc '));
+    doTest('~@abc^ ^', mention('abc ')); doTest('~@_abc^ ^', silentMention('abc '));
+    doTest('~@ab^c ^', mention('abc ')); doTest('~@_ab^c ^', silentMention('abc '));
+    doTest('~@^abc ^', mention('abc ')); doTest('~@_^abc ^', silentMention('abc '));
+
+    doTest('Please ask ~@chris^', mention('chris'));             doTest('Please ask ~@_chris^', silentMention('chris'));
+    doTest('Please ask ~@chris bobbe^', mention('chris bobbe')); doTest('Please ask ~@_chris bobbe^', silentMention('chris bobbe'));
+
+    doTest('~@Rodion Romanovich Raskolnikov^', mention('Rodion Romanovich Raskolnikov'));
+    doTest('~@_Rodion Romanovich Raskolniko^', silentMention('Rodion Romanovich Raskolniko'));
+    doTest('~@Родион Романович Раскольников^', mention('Родион Романович Раскольников'));
+    doTest('~@_Родион Романович Раскольнико^', silentMention('Родион Романович Раскольнико'));
     doTest('If @chris is around, please ask him.^', null); // @ sign is too far away from cursor
     doTest('If @_chris is around, please ask him.^', null); // @ sign is too far away from cursor
+
+    // Emoji (":smile:").
+
+    // Basic positive examples, to contrast with all the negative examples below.
+    doTest('~:^', emoji(''));
+    doTest('~:a^', emoji('a'));
+    doTest('~:a ^', emoji('a '));
+    doTest('~:a_^', emoji('a_'));
+    doTest('~:a b^', emoji('a b'));
+    doTest('ok ~:s^', emoji('s'));
+    doTest('this: ~:s^', emoji('s'));
+
+    doTest('^:', null);
+    doTest('^:abc', null);
+    doTest(':abc', null); // (no cursor)
+
+    // Avoid interpreting colons in normal prose as queries.
+    doTest(': ^', null);
+    doTest(':\n^', null);
+    doTest('this:^', null);
+    doTest('this: ^', null);
+    doTest('là ~:^', emoji('')); // ambiguous in French prose, tant pis
+    doTest('là : ^', null);
+    doTest('8:30^', null);
+
+    // Avoid interpreting already-entered `:foo:` syntax as queries.
+    doTest(':smile:^', null);
+
+    // Avoid interpreting emoticons as queries.
+    doTest(':-^', null);
+    doTest(':)^', null); doTest(':-)^', null);
+    doTest(':(^', null); doTest(':-(^', null);
+    doTest(':/^', null); doTest(':-/^', null);
+    doTest('~:p^', emoji('p')); // ambiguously an emoticon
+    doTest(':-p^', null);
+
+    // Avoid interpreting as queries some ways colons appear in source code.
+    doTest('::^', null);
+    doTest(':<^', null);
+    doTest(':=^', null);
+
+    // Emoji names may have letters and numbers in various scripts.
+    // (A few appear in the server's list of Unicode emoji;
+    // many more might be in a given realm's custom emoji.)
+    doTest('~:コ^', emoji('コ'));
+    doTest('~:空^', emoji('空'));
+    doTest('~:φ^', emoji('φ'));
+    doTest('~:100^', emoji('100'));
+    doTest('~:１^', emoji('１')); // U+FF11 FULLWIDTH DIGIT ONE
+    doTest('~:٢^', emoji('٢')); // U+0662 ARABIC-INDIC DIGIT TWO
+
+    // Emoji names may have dashes '-'.
+    doTest('~:e-m^', emoji('e-m'));
+    doTest('~:jack-o-l^', emoji('jack-o-l'));
+
+    // Just one emoji has a '+' in its name, namely ':+1:'.
+    doTest('~:+^', emoji('+'));
+    doTest('~:+1^', emoji('+1'));
+    doTest(':+2^', null);
+    doTest(':+100^', null);
+    doTest(':+1 ^', null);
+    doTest(':1+1^', null);
+
+    // Accept punctuation before the emoji: opening…
+    doTest('(~:^', emoji('')); doTest('(~:a^', emoji('a'));
+    doTest('[~:^', emoji('')); doTest('[~:a^', emoji('a'));
+    doTest('«~:^', emoji('')); doTest('«~:a^', emoji('a'));
+    doTest('（~:^', emoji('')); doTest('（~:a^', emoji('a'));
+    // … closing…
+    doTest(')~:^', emoji('')); doTest(')~:a^', emoji('a'));
+    doTest(']~:^', emoji('')); doTest(']~:a^', emoji('a'));
+    doTest('»~:^', emoji('')); doTest('»~:a^', emoji('a'));
+    doTest('）~:^', emoji('')); doTest('）~:a^', emoji('a'));
+    // … and other.
+    doTest('.~:^', emoji('')); doTest('.~:a^', emoji('a'));
+    doTest(',~:^', emoji('')); doTest(',~:a^', emoji('a'));
+    doTest('，~:^', emoji('')); doTest('，~:a^', emoji('a'));
+    doTest('。~:^', emoji('')); doTest('。~:a^', emoji('a'));
   });
 
   test('MentionAutocompleteView misc', () async {
     const narrow = ChannelNarrow(1);
     final store = eg.store();
     await store.addUsers([eg.selfUser, eg.otherUser, eg.thirdUser]);
-    final view = MentionAutocompleteView.init(store: store, narrow: narrow);
 
+    final view = MentionAutocompleteView.init(store: store, narrow: narrow,
+      query: MentionAutocompleteQuery('Third'));
     bool done = false;
     view.addListener(() { done = true; });
-    view.query = MentionAutocompleteQuery('Third');
     await Future(() {});
     await Future(() {});
     check(done).isTrue();
@@ -189,16 +271,12 @@ void main() {
   });
 
   test('MentionAutocompleteView not starve timers', () {
-    fakeAsync((binding) async {
+    return awaitFakeAsync((binding) async {
       const narrow = ChannelNarrow(1);
       final store = eg.store();
       await store.addUsers([eg.selfUser, eg.otherUser, eg.thirdUser]);
-      final view = MentionAutocompleteView.init(store: store, narrow: narrow);
 
       bool searchDone = false;
-      view.addListener(() {
-        searchDone = true;
-      });
 
       // Schedule a timer event with zero delay.
       // This stands in for a user interaction, or frame rendering timer,
@@ -210,9 +288,11 @@ void main() {
         check(searchDone).isFalse();
       });
 
-      view.query = MentionAutocompleteQuery('Third');
-      check(timerDone).isFalse();
-      check(searchDone).isFalse();
+      final view = MentionAutocompleteView.init(store: store, narrow: narrow,
+        query: MentionAutocompleteQuery('Third'));
+      view.addListener(() {
+        searchDone = true;
+      });
 
       binding.elapse(const Duration(seconds: 1));
 
@@ -230,11 +310,11 @@ void main() {
     for (int i = 1; i <= 2500; i++) {
       await store.addUser(eg.user(userId: i, email: 'user$i@example.com', fullName: 'User $i'));
     }
-    final view = MentionAutocompleteView.init(store: store, narrow: narrow);
 
     bool done = false;
+    final view = MentionAutocompleteView.init(store: store, narrow: narrow,
+      query: MentionAutocompleteQuery('User 2222'));
     view.addListener(() { done = true; });
-    view.query = MentionAutocompleteQuery('User 2222');
 
     await Future(() {});
     check(done).isFalse();
@@ -253,11 +333,11 @@ void main() {
     for (int i = 1; i <= 1500; i++) {
       await store.addUser(eg.user(userId: i, email: 'user$i@example.com', fullName: 'User $i'));
     }
-    final view = MentionAutocompleteView.init(store: store, narrow: narrow);
 
     bool done = false;
+    final view = MentionAutocompleteView.init(store: store, narrow: narrow,
+      query: MentionAutocompleteQuery('User 1111'));
     view.addListener(() { done = true; });
-    view.query = MentionAutocompleteQuery('User 1111');
 
     await Future(() {});
     check(done).isFalse();
@@ -288,11 +368,11 @@ void main() {
     for (int i = 1; i <= 2500; i++) {
       await store.addUser(eg.user(userId: i, email: 'user$i@example.com', fullName: 'User $i'));
     }
-    final view = MentionAutocompleteView.init(store: store, narrow: narrow);
 
     bool done = false;
+    final view = MentionAutocompleteView.init(store: store, narrow: narrow,
+      query: MentionAutocompleteQuery('User 110'));
     view.addListener(() { done = true; });
-    view.query = MentionAutocompleteQuery('User 110');
 
     await Future(() {});
     check(done).isFalse();
@@ -544,7 +624,8 @@ void main() {
 
     group('ranking across signals', () {
       void checkPrecedes(Narrow narrow, User userA, Iterable<User> usersB) {
-        final view = MentionAutocompleteView.init(store: store, narrow: narrow);
+        final view = MentionAutocompleteView.init(store: store, narrow: narrow,
+          query: MentionAutocompleteQuery(''));
         for (final userB in usersB) {
           check(view.debugCompareUsers(userA, userB)).isLessThan(0);
           check(view.debugCompareUsers(userB, userA)).isGreaterThan(0);
@@ -552,7 +633,8 @@ void main() {
       }
 
       void checkRankEqual(Narrow narrow, List<User> users) {
-        final view = MentionAutocompleteView.init(store: store, narrow: narrow);
+        final view = MentionAutocompleteView.init(store: store, narrow: narrow,
+          query: MentionAutocompleteQuery(''));
         for (int i = 0; i < users.length; i++) {
           for (int j = i + 1; j < users.length; j++) {
             check(view.debugCompareUsers(users[i], users[j])).equals(0);
@@ -669,21 +751,24 @@ void main() {
       test('CombinedFeedNarrow gives error', () async {
         await prepare(users: [eg.user(), eg.user()], messages: []);
         const narrow = CombinedFeedNarrow();
-        check(() => MentionAutocompleteView.init(store: store, narrow: narrow))
+        check(() => MentionAutocompleteView.init(store: store, narrow: narrow,
+                      query: MentionAutocompleteQuery('')))
           .throws<AssertionError>();
       });
 
       test('MentionsNarrow gives error', () async {
         await prepare(users: [eg.user(), eg.user()], messages: []);
         const narrow = MentionsNarrow();
-        check(() => MentionAutocompleteView.init(store: store, narrow: narrow))
+        check(() => MentionAutocompleteView.init(store: store, narrow: narrow,
+                      query: MentionAutocompleteQuery('')))
           .throws<AssertionError>();
       });
 
       test('StarredMessagesNarrow gives error', () async {
         await prepare(users: [eg.user(), eg.user()], messages: []);
         const narrow = StarredMessagesNarrow();
-        check(() => MentionAutocompleteView.init(store: store, narrow: narrow))
+        check(() => MentionAutocompleteView.init(store: store, narrow: narrow,
+                      query: MentionAutocompleteQuery('')))
           .throws<AssertionError>();
       });
     });
@@ -692,9 +777,9 @@ void main() {
       Future<Iterable<int>> getResults(
           Narrow narrow, MentionAutocompleteQuery query) async {
         bool done = false;
-        final view = MentionAutocompleteView.init(store: store, narrow: narrow);
+        final view = MentionAutocompleteView.init(store: store, narrow: narrow,
+          query: query);
         view.addListener(() { done = true; });
-        view.query = query;
         await Future(() {});
         check(done).isTrue();
         final results = view.results
@@ -777,13 +862,14 @@ void main() {
     final third = eg.getStreamTopicsEntry(maxId: 3, name: 'Third Topic');
     connection.prepare(json: GetStreamTopicsResult(
       topics: [first, second, third]).toJson());
+
     final view = TopicAutocompleteView.init(
       store: store,
-      streamId: eg.stream().streamId);
-
+      streamId: eg.stream().streamId,
+      query: TopicAutocompleteQuery('Third'));
     bool done = false;
     view.addListener(() { done = true; });
-    view.query = TopicAutocompleteQuery('Third');
+
     // those are here to wait for topics to be loaded
     await Future(() {});
     await Future(() {});
@@ -802,11 +888,10 @@ void main() {
 
     final view = TopicAutocompleteView.init(
       store: store,
-      streamId: eg.stream().streamId);
-
+      streamId: eg.stream().streamId,
+      query: TopicAutocompleteQuery('te'));
     bool done = false;
     view.addListener(() { done = true; });
-    view.query = TopicAutocompleteQuery('te');
 
     check(done).isFalse();
     await Future(() {});
diff --git a/test/model/emoji_test.dart b/test/model/emoji_test.dart
index f3fdbf3b0a..3a0ddc5e95 100644
--- a/test/model/emoji_test.dart
+++ b/test/model/emoji_test.dart
@@ -1,7 +1,11 @@
 import 'package:checks/checks.dart';
 import 'package:test/scaffolding.dart';
+import 'package:zulip/api/model/events.dart';
 import 'package:zulip/api/model/model.dart';
+import 'package:zulip/api/route/realm.dart';
+import 'package:zulip/model/autocomplete.dart';
 import 'package:zulip/model/emoji.dart';
+import 'package:zulip/model/store.dart';
 
 import '../example_data.dart' as eg;
 
@@ -73,6 +77,345 @@ void main() {
         ..resolvedStillUrl.isNull();
     });
   });
+
+  Condition<Object?> isUnicodeCandidate(String? emojiCode, List<String>? names) {
+    return (it_) {
+      final it = it_.isA<EmojiCandidate>();
+      it.emojiType.equals(ReactionType.unicodeEmoji);
+      if (emojiCode != null) it.emojiCode.equals(emojiCode);
+      if (names != null) {
+        it.emojiName.equals(names.first);
+        it.aliases.deepEquals(names.sublist(1));
+      }
+    };
+  }
+
+  Condition<Object?> isRealmCandidate({String? emojiCode, String? emojiName}) {
+    return (it_) {
+      final it = it_.isA<EmojiCandidate>();
+      it.emojiType.equals(ReactionType.realmEmoji);
+      if (emojiCode != null) it.emojiCode.equals(emojiCode);
+      if (emojiName != null) it.emojiName.equals(emojiName);
+      it.aliases.isEmpty();
+    };
+  }
+
+  Condition<Object?> isZulipCandidate() {
+    return (it) => it.isA<EmojiCandidate>()
+      ..emojiType.equals(ReactionType.zulipExtraEmoji)
+      ..emojiCode.equals('zulip')
+      ..emojiName.equals('zulip')
+      ..aliases.isEmpty();
+  }
+
+  group('allEmojiCandidates', () {
+    // TODO test emojiDisplay of candidates matches emojiDisplayFor
+
+    PerAccountStore prepare({
+      Map<String, RealmEmojiItem> realmEmoji = const {},
+      Map<String, List<String>>? unicodeEmoji,
+    }) {
+      final store = eg.store(
+        initialSnapshot: eg.initialSnapshot(realmEmoji: realmEmoji));
+      if (unicodeEmoji != null) {
+        store.setServerEmojiData(ServerEmojiData(codeToNames: unicodeEmoji));
+      }
+      return store;
+    }
+
+    test('realm emoji overrides Unicode emoji', () {
+      final store = prepare(realmEmoji: {
+        '1': eg.realmEmojiItem(emojiCode: '1', emojiName: 'smiley'),
+      }, unicodeEmoji: {
+        '1f642': ['smile'],
+        '1f603': ['smiley'],
+      });
+      check(store.allEmojiCandidates()).deepEquals([
+        isUnicodeCandidate('1f642', ['smile']),
+        isRealmCandidate(emojiCode: '1', emojiName: 'smiley'),
+        isZulipCandidate(),
+      ]);
+    });
+
+    test('Unicode emoji with overridden aliases survives with remaining names', () {
+      final store = prepare(realmEmoji: {
+        '1': eg.realmEmojiItem(emojiCode: '1', emojiName: 'tangerine'),
+      }, unicodeEmoji: {
+        '1f34a': ['orange', 'tangerine', 'mandarin'],
+      });
+      check(store.allEmojiCandidates()).deepEquals([
+        isUnicodeCandidate('1f34a', ['orange', 'mandarin']),
+        isRealmCandidate(emojiCode: '1', emojiName: 'tangerine'),
+        isZulipCandidate(),
+      ]);
+    });
+
+    test('Unicode emoji with overridden primary name survives with remaining names', () {
+      final store = prepare(realmEmoji: {
+        '1': eg.realmEmojiItem(emojiCode: '1', emojiName: 'orange'),
+      }, unicodeEmoji: {
+        '1f34a': ['orange', 'tangerine', 'mandarin'],
+      });
+      check(store.allEmojiCandidates()).deepEquals([
+        isUnicodeCandidate('1f34a', ['tangerine', 'mandarin']),
+        isRealmCandidate(emojiCode: '1', emojiName: 'orange'),
+        isZulipCandidate(),
+      ]);
+    });
+
+    test('updates on setServerEmojiData', () {
+      final store = prepare();
+      check(store.allEmojiCandidates()).deepEquals([
+        isZulipCandidate(),
+      ]);
+
+      store.setServerEmojiData(ServerEmojiData(codeToNames: {
+        '1f642': ['smile'],
+      }));
+      check(store.allEmojiCandidates()).deepEquals([
+        isUnicodeCandidate('1f642', ['smile']),
+        isZulipCandidate(),
+      ]);
+    });
+
+    test('updates on RealmEmojiUpdateEvent', () {
+      final store = prepare();
+      check(store.allEmojiCandidates()).deepEquals([
+        isZulipCandidate(),
+      ]);
+
+      store.handleEvent(RealmEmojiUpdateEvent(id: 1, realmEmoji: {
+        '1': eg.realmEmojiItem(emojiCode: '1', emojiName: 'happy'),
+      }));
+      check(store.allEmojiCandidates()).deepEquals([
+        isRealmCandidate(emojiCode: '1', emojiName: 'happy'),
+        isZulipCandidate(),
+      ]);
+    });
+
+    test('memoizes result', () {
+      final store = prepare(realmEmoji: {
+        '1': eg.realmEmojiItem(emojiCode: '1', emojiName: 'happy'),
+      }, unicodeEmoji: {
+        '1f642': ['smile'],
+      });
+      final candidates = store.allEmojiCandidates();
+      check(store.allEmojiCandidates()).identicalTo(candidates);
+    });
+  });
+
+  group('EmojiAutocompleteView', () {
+    Condition<Object?> isUnicodeResult({String? emojiCode, List<String>? names}) {
+      return (it) => it.isA<EmojiAutocompleteResult>().candidate.which(
+        isUnicodeCandidate(emojiCode, names));
+    }
+
+    Condition<Object?> isRealmResult({String? emojiCode, String? emojiName}) {
+      return (it) => it.isA<EmojiAutocompleteResult>().candidate.which(
+        isRealmCandidate(emojiCode: emojiCode, emojiName: emojiName));
+    }
+
+    Condition<Object?> isZulipResult() {
+      return (it) => it.isA<EmojiAutocompleteResult>().candidate.which(
+        isZulipCandidate());
+    }
+
+    PerAccountStore prepare({
+      Map<String, String> realmEmoji = const {},
+      Map<String, List<String>>? unicodeEmoji,
+    }) {
+      final store = eg.store(
+        initialSnapshot: eg.initialSnapshot(realmEmoji: {
+          for (final MapEntry(:key, :value) in realmEmoji.entries)
+            key: eg.realmEmojiItem(emojiCode: key, emojiName: value),
+        }));
+      if (unicodeEmoji != null) {
+        store.setServerEmojiData(ServerEmojiData(codeToNames: unicodeEmoji));
+      }
+      return store;
+    }
+
+    test('results can include all three emoji types', () async {
+      final store = prepare(
+        realmEmoji: {'1': 'happy'}, unicodeEmoji: {'1f642': ['smile']});
+      final view = EmojiAutocompleteView.init(store: store,
+        query: EmojiAutocompleteQuery(''));
+      bool done = false;
+      view.addListener(() { done = true; });
+      await Future(() {});
+      check(done).isTrue();
+      check(view.results).deepEquals([
+        isUnicodeResult(names: ['smile']),
+        isRealmResult(emojiName: 'happy'),
+        isZulipResult(),
+      ]);
+    });
+
+    test('results update after query change', () async {
+      final store = prepare(
+        realmEmoji: {'1': 'happy'}, unicodeEmoji: {'1f642': ['smile']});
+      final view = EmojiAutocompleteView.init(store: store,
+        query: EmojiAutocompleteQuery('h'));
+      bool done = false;
+      view.addListener(() { done = true; });
+      await Future(() {});
+      check(done).isTrue();
+      check(view.results).single.which(
+        isRealmResult(emojiName: 'happy'));
+
+      done = false;
+      view.query = EmojiAutocompleteQuery('s');
+      await Future(() {});
+      check(done).isTrue();
+      check(view.results).single.which(
+        isUnicodeResult(names: ['smile']));
+    });
+  });
+
+  group('EmojiAutocompleteQuery.matches', () {
+    EmojiCandidate unicode(List<String> names, {String? emojiCode}) {
+      emojiCode ??= '10ffff';
+      return EmojiCandidate(emojiType: ReactionType.unicodeEmoji,
+        emojiCode: emojiCode,
+        emojiName: names.first, aliases: names.sublist(1),
+        emojiDisplay: UnicodeEmojiDisplay(
+          emojiName: names.first,
+          emojiUnicode: tryParseEmojiCodeToUnicode(emojiCode)!));
+    }
+
+    bool matchesName(String query, String emojiName) {
+      return EmojiAutocompleteQuery(query).matches(unicode([emojiName]));
+    }
+
+    test('one-word query matches anywhere in name', () {
+      check(matchesName('', 'smile')).isTrue();
+      check(matchesName('s', 'smile')).isTrue();
+      check(matchesName('sm', 'smile')).isTrue();
+      check(matchesName('smile', 'smile')).isTrue();
+      check(matchesName('m', 'smile')).isTrue();
+      check(matchesName('mile', 'smile')).isTrue();
+      check(matchesName('e', 'smile')).isTrue();
+
+      check(matchesName('smiley', 'smile')).isFalse();
+      check(matchesName('a', 'smile')).isFalse();
+
+      check(matchesName('o', 'open_book')).isTrue();
+      check(matchesName('open', 'open_book')).isTrue();
+      check(matchesName('pe', 'open_book')).isTrue();
+      check(matchesName('boo', 'open_book')).isTrue();
+      check(matchesName('ok', 'open_book')).isTrue();
+    });
+
+    test('multi-word query matches from start of a word', () {
+      check(matchesName('open_', 'open_book')).isTrue();
+      check(matchesName('open_b', 'open_book')).isTrue();
+      check(matchesName('open_book', 'open_book')).isTrue();
+
+      check(matchesName('pen_', 'open_book')).isFalse();
+      check(matchesName('n_b', 'open_book')).isFalse();
+
+      check(matchesName('blue_dia', 'large_blue_diamond')).isTrue();
+    });
+
+    test('spaces in query behave as underscores', () {
+      check(matchesName('open ', 'open_book')).isTrue();
+      check(matchesName('open b', 'open_book')).isTrue();
+      check(matchesName('open book', 'open_book')).isTrue();
+
+      check(matchesName('pen ', 'open_book')).isFalse();
+      check(matchesName('n b', 'open_book')).isFalse();
+
+      check(matchesName('blue dia', 'large_blue_diamond')).isTrue();
+    });
+
+    test('query is lower-cased', () {
+      check(matchesName('Smi', 'smile')).isTrue();
+    });
+
+    test('query matches aliases same way as primary name', () {
+      bool matchesNames(String query, List<String> names) {
+        return EmojiAutocompleteQuery(query).matches(unicode(names));
+      }
+
+      check(matchesNames('a', ['a', 'b'])).isTrue();
+      check(matchesNames('b', ['a', 'b'])).isTrue();
+      check(matchesNames('c', ['a', 'b'])).isFalse();
+
+      check(matchesNames('pe', ['x', 'open_book'])).isTrue();
+      check(matchesNames('ok', ['x', 'open_book'])).isTrue();
+
+      check(matchesNames('open_', ['x', 'open_book'])).isTrue();
+      check(matchesNames('open b', ['x', 'open_book'])).isTrue();
+      check(matchesNames('pen_', ['x', 'open_book'])).isFalse();
+
+      check(matchesNames('Smi', ['x', 'smile'])).isTrue();
+    });
+
+    test('query matches literal Unicode value', () {
+      bool matchesLiteral(String query, String emojiCode, {required String aka}) {
+        assert(aka == query);
+        return EmojiAutocompleteQuery(query)
+          .matches(unicode(['asdf'], emojiCode: emojiCode));
+      }
+
+      // Matching the code, in hex, doesn't count.
+      check(matchesLiteral('1f642', aka: '1f642', '1f642')).isFalse();
+
+      // Matching the Unicode value the code describes does count…
+      check(matchesLiteral('🙂', aka: '\u{1f642}', '1f642')).isTrue();
+      // … and failing to match it doesn't make a match.
+      check(matchesLiteral('🙁', aka: '\u{1f641}', '1f642')).isFalse();
+
+      // Multi-code-point emoji work fine.
+      check(matchesLiteral('🏳‍🌈', aka: '\u{1f3f3}\u{200d}\u{1f308}',
+        '1f3f3-200d-1f308')).isTrue();
+      // Only exact matches count; no partial matches.
+      check(matchesLiteral('🏳', aka: '\u{1f3f3}',
+        '1f3f3-200d-1f308')).isFalse();
+      check(matchesLiteral('‍🌈', aka: '\u{200d}\u{1f308}',
+        '1f3f3-200d-1f308')).isFalse();
+      check(matchesLiteral('🏳‍🌈', aka: '\u{1f3f3}\u{200d}\u{1f308}',
+        '1f3f3')).isFalse();
+    });
+
+    test('can match realm emoji', () {
+      EmojiCandidate realmCandidate(String emojiName) {
+        return EmojiCandidate(
+          emojiType: ReactionType.realmEmoji,
+          emojiCode: '1', emojiName: emojiName, aliases: null,
+          emojiDisplay: ImageEmojiDisplay(
+            emojiName: emojiName,
+            resolvedUrl: eg.realmUrl.resolve('/emoji/1.png'),
+            resolvedStillUrl: eg.realmUrl.resolve('/emoji/1-still.png')));
+      }
+
+      check(EmojiAutocompleteQuery('eqeq')
+        .matches(realmCandidate('eqeq'))).isTrue();
+      check(EmojiAutocompleteQuery('open_')
+        .matches(realmCandidate('open_book'))).isTrue();
+      check(EmojiAutocompleteQuery('n_b')
+        .matches(realmCandidate('open_book'))).isFalse();
+      check(EmojiAutocompleteQuery('blue dia')
+        .matches(realmCandidate('large_blue_diamond'))).isTrue();
+      check(EmojiAutocompleteQuery('Smi')
+        .matches(realmCandidate('smile'))).isTrue();
+    });
+
+    test('can match Zulip extra emoji', () {
+      final store = eg.store();
+      final zulipCandidate = EmojiCandidate(
+        emojiType: ReactionType.zulipExtraEmoji,
+        emojiCode: 'zulip', emojiName: 'zulip', aliases: null,
+        emojiDisplay: store.emojiDisplayFor(
+          emojiType: ReactionType.zulipExtraEmoji,
+          emojiCode: 'zulip', emojiName: 'zulip'));
+
+      check(EmojiAutocompleteQuery('z').matches(zulipCandidate)).isTrue();
+      check(EmojiAutocompleteQuery('Zulip').matches(zulipCandidate)).isTrue();
+      check(EmojiAutocompleteQuery('p').matches(zulipCandidate)).isTrue();
+      check(EmojiAutocompleteQuery('x').matches(zulipCandidate)).isFalse();
+    });
+  });
 }
 
 extension EmojiDisplayChecks on Subject<EmojiDisplay> {
@@ -87,3 +430,15 @@ extension ImageEmojiDisplayChecks on Subject<ImageEmojiDisplay> {
   Subject<Uri> get resolvedUrl => has((x) => x.resolvedUrl, 'resolvedUrl');
   Subject<Uri?> get resolvedStillUrl => has((x) => x.resolvedStillUrl, 'resolvedStillUrl');
 }
+
+extension EmojiCandidateChecks on Subject<EmojiCandidate> {
+  Subject<ReactionType> get emojiType => has((x) => x.emojiType, 'emojiType');
+  Subject<String> get emojiCode => has((x) => x.emojiCode, 'emojiCode');
+  Subject<String> get emojiName => has((x) => x.emojiName, 'emojiName');
+  Subject<Iterable<String>> get aliases => has((x) => x.aliases, 'aliases');
+  Subject<EmojiDisplay> get emojiDisplay => has((x) => x.emojiDisplay, 'emojiDisplay');
+}
+
+extension EmojiAutocompleteResultChecks on Subject<EmojiAutocompleteResult> {
+  Subject<EmojiCandidate> get candidate => has((x) => x.candidate, 'candidate');
+}
diff --git a/test/widgets/autocomplete_test.dart b/test/widgets/autocomplete_test.dart
index 34d0885967..24ae2dba83 100644
--- a/test/widgets/autocomplete_test.dart
+++ b/test/widgets/autocomplete_test.dart
@@ -1,10 +1,14 @@
 import 'package:checks/checks.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter_checks/flutter_checks.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:zulip/api/model/events.dart';
 import 'package:zulip/api/model/model.dart';
 import 'package:zulip/api/route/messages.dart';
 import 'package:zulip/api/route/channels.dart';
+import 'package:zulip/api/route/realm.dart';
 import 'package:zulip/model/compose.dart';
+import 'package:zulip/model/emoji.dart';
 import 'package:zulip/model/localizations.dart';
 import 'package:zulip/model/narrow.dart';
 import 'package:zulip/model/store.dart';
@@ -28,8 +32,11 @@ import 'test_app.dart';
 /// The caller must set [debugNetworkImageHttpClientProvider] back to null
 /// before the end of the test.
 Future<Finder> setupToComposeInput(WidgetTester tester, {
-  required List<User> users,
+  List<User> users = const [],
 }) async {
+  TypingNotifier.debugEnable = false;
+  addTearDown(TypingNotifier.debugReset);
+
   addTearDown(testBinding.reset);
   await testBinding.globalStore.add(eg.selfAccount, eg.initialSnapshot());
   final store = await testBinding.globalStore.perAccount(eg.selfAccount.id);
@@ -105,19 +112,20 @@ Future<Finder> setupToTopicInput(WidgetTester tester, {
   return finder;
 }
 
-void main() {
-  TestZulipBinding.ensureInitialized();
+Finder findNetworkImage(String url) {
+  return find.byWidgetPredicate((widget) => switch(widget) {
+    Image(image: NetworkImage(url: var imageUrl)) when imageUrl == url
+      => true,
+    _ => false,
+  });
+}
 
-  group('ComposeAutocomplete', () {
+typedef ExpectedEmoji = (String label, EmojiDisplay display);
 
-    Finder findNetworkImage(String url) {
-      return find.byWidgetPredicate((widget) => switch(widget) {
-        Image(image: NetworkImage(url: var imageUrl)) when imageUrl == url
-          => true,
-        _ => false,
-      });
-    }
+void main() {
+  TestZulipBinding.ensureInitialized();
 
+  group('@-mentions', () {
     void checkUserShown(User user, PerAccountStore store, {required bool expected}) {
       check(find.text(user.fullName).evaluate().length).equals(expected ? 1 : 0);
       final avatarFinder =
@@ -132,9 +140,6 @@ void main() {
       final composeInputFinder = await setupToComposeInput(tester, users: [user1, user2, user3]);
       final store = await testBinding.globalStore.perAccount(eg.selfAccount.id);
 
-      TypingNotifier.debugEnable = false;
-      addTearDown(TypingNotifier.debugReset);
-
       // Options are filtered correctly for query
       // TODO(#226): Remove this extra edit when this bug is fixed.
       await tester.enterText(composeInputFinder, 'hello @user ');
@@ -174,6 +179,98 @@ void main() {
     });
   });
 
+  group('emoji', () {
+    void checkEmojiShown(ExpectedEmoji option, {required bool expected}) {
+      final (label, display) = option;
+      final labelSubject = check(find.text(label));
+      expected ? labelSubject.findsOne() : labelSubject.findsNothing();
+
+      final Subject<Finder> displaySubject;
+      switch (display) {
+        case UnicodeEmojiDisplay():
+          displaySubject = check(find.text(display.emojiUnicode));
+        case ImageEmojiDisplay():
+          displaySubject = check(findNetworkImage(display.resolvedUrl.toString()));
+        case TextEmojiDisplay():
+          // We test this case in the "text emoji" test below,
+          // but that doesn't use this helper method.
+          throw UnimplementedError();
+      }
+      expected ? displaySubject.findsOne(): displaySubject.findsNothing();
+    }
+
+    testWidgets('show, update, choose', (tester) async {
+      final composeInputFinder = await setupToComposeInput(tester);
+      final store = await testBinding.globalStore.perAccount(eg.selfAccount.id);
+      store.setServerEmojiData(ServerEmojiData(codeToNames: {
+        '1f4a4': ['zzz', 'sleepy'], // (just 'zzz' in real data)
+      }));
+      await store.handleEvent(RealmEmojiUpdateEvent(id: 1, realmEmoji: {
+        '1': eg.realmEmojiItem(emojiCode: '1', emojiName: 'buzzing'),
+      }));
+
+      final zulipOption = ('zulip', store.emojiDisplayFor(
+        emojiType: ReactionType.zulipExtraEmoji,
+        emojiCode: 'zulip', emojiName: 'zulip'));
+      final buzzingOption = ('buzzing', store.emojiDisplayFor(
+        emojiType: ReactionType.realmEmoji,
+        emojiCode: '1', emojiName: 'buzzing'));
+      final zzzOption = ('zzz, sleepy', store.emojiDisplayFor(
+        emojiType: ReactionType.unicodeEmoji,
+        emojiCode: '1f4a4', emojiName: 'zzz'));
+
+      // Enter a query; options appear, of all three emoji types.
+      // TODO(#226): Remove this extra edit when this bug is fixed.
+      await tester.enterText(composeInputFinder, 'hi :');
+      await tester.enterText(composeInputFinder, 'hi :z');
+      await tester.pump();
+      checkEmojiShown(expected: true, zzzOption);
+      checkEmojiShown(expected: true, buzzingOption);
+      checkEmojiShown(expected: true, zulipOption);
+
+      // Edit query; options change.
+      await tester.enterText(composeInputFinder, 'hi :zz');
+      await tester.pump();
+      checkEmojiShown(expected: true, zzzOption);
+      checkEmojiShown(expected: true, buzzingOption);
+      checkEmojiShown(expected: false, zulipOption);
+
+      // Choosing an option enters result and closes autocomplete.
+      await tester.tap(find.text('buzzing'));
+      await tester.pump();
+      check(tester.widget<TextField>(composeInputFinder).controller!.text)
+        .equals('hi :buzzing:');
+      checkEmojiShown(expected: false, zzzOption);
+      checkEmojiShown(expected: false, buzzingOption);
+      checkEmojiShown(expected: false, zulipOption);
+
+      debugNetworkImageHttpClientProvider = null;
+    });
+
+    testWidgets('text emoji means just show text', (tester) async {
+      final composeInputFinder = await setupToComposeInput(tester);
+      final store = await testBinding.globalStore.perAccount(eg.selfAccount.id);
+      await store.handleEvent(UserSettingsUpdateEvent(id: 1,
+        property: UserSettingName.emojiset, value: Emojiset.text));
+
+      // TODO(#226): Remove this extra edit when this bug is fixed.
+      await tester.enterText(composeInputFinder, 'hi :');
+      await tester.enterText(composeInputFinder, 'hi :z');
+      await tester.pump();
+
+      // The emoji's name appears.  (And only once.)
+      check(find.text('zulip')).findsOne();
+
+      // But no emoji image appears.
+      check(find.byWidgetPredicate((widget) => switch(widget) {
+        Image(image: NetworkImage()) => true,
+        _ => false,
+      })).findsNothing();
+
+      debugNetworkImageHttpClientProvider = null;
+    });
+  });
+
   group('TopicAutocomplete', () {
     void checkTopicShown(GetStreamTopicsEntry topic, PerAccountStore store, {required bool expected}) {
       check(find.text(topic.name).evaluate().length).equals(expected ? 1 : 0);
@@ -186,9 +283,6 @@ void main() {
       final topicInputFinder = await setupToTopicInput(tester, topics: [topic1, topic2, topic3]);
       final store = await testBinding.globalStore.perAccount(eg.selfAccount.id);
 
-      TypingNotifier.debugEnable = false;
-      addTearDown(TypingNotifier.debugReset);
-
       // Options are filtered correctly for query
       // TODO(#226): Remove this extra edit when this bug is fixed.
       await tester.enterText(topicInputFinder, 'Topic');