diff --git a/lib/api/model/events.dart b/lib/api/model/events.dart
index 9faa3d367e..ae997adc57 100644
--- a/lib/api/model/events.dart
+++ b/lib/api/model/events.dart
@@ -708,13 +708,13 @@ class UpdateMessageEvent extends Event {
   @JsonKey(includeToJson: true)
   String get type => 'update_message';
 
-  final int? userId; // TODO(server-5)
-  final bool? renderingOnly; // TODO(server-5)
+  final int userId;
+  final bool renderingOnly;
   final int messageId;
   final List<int> messageIds;
 
   final List<MessageFlag> flags;
-  final int? editTimestamp; // TODO(server-5)
+  final int editTimestamp;
 
   // final String? streamName; // ignore
 
diff --git a/lib/api/model/events.g.dart b/lib/api/model/events.g.dart
index 5d47444ecd..dc56b1d157 100644
--- a/lib/api/model/events.g.dart
+++ b/lib/api/model/events.g.dart
@@ -416,8 +416,8 @@ const _$UserTopicVisibilityPolicyEnumMap = {
 UpdateMessageEvent _$UpdateMessageEventFromJson(Map<String, dynamic> json) =>
     UpdateMessageEvent(
       id: (json['id'] as num).toInt(),
-      userId: (json['user_id'] as num?)?.toInt(),
-      renderingOnly: json['rendering_only'] as bool?,
+      userId: (json['user_id'] as num).toInt(),
+      renderingOnly: json['rendering_only'] as bool,
       messageId: (json['message_id'] as num).toInt(),
       messageIds: (json['message_ids'] as List<dynamic>)
           .map((e) => (e as num).toInt())
@@ -425,7 +425,7 @@ UpdateMessageEvent _$UpdateMessageEventFromJson(Map<String, dynamic> json) =>
       flags: (json['flags'] as List<dynamic>)
           .map((e) => $enumDecode(_$MessageFlagEnumMap, e))
           .toList(),
-      editTimestamp: (json['edit_timestamp'] as num?)?.toInt(),
+      editTimestamp: (json['edit_timestamp'] as num).toInt(),
       origStreamId: (json['stream_id'] as num?)?.toInt(),
       newStreamId: (json['new_stream_id'] as num?)?.toInt(),
       propagateMode:
diff --git a/lib/api/model/initial_snapshot.dart b/lib/api/model/initial_snapshot.dart
index 1adc44196f..fcccf0dcf3 100644
--- a/lib/api/model/initial_snapshot.dart
+++ b/lib/api/model/initial_snapshot.dart
@@ -18,7 +18,7 @@ class InitialSnapshot {
   final int lastEventId;
   final int zulipFeatureLevel;
   final String zulipVersion;
-  final String? zulipMergeBase; // TODO(server-5)
+  final String zulipMergeBase;
 
   final List<String> alertWords;
 
@@ -54,13 +54,7 @@ class InitialSnapshot {
 
   final List<ZulipStream> streams;
 
-  // Servers pre-5.0 don't have `user_settings`, and instead provide whatever
-  // user settings they support at toplevel in the initial snapshot. Since we're
-  // likely to desupport pre-5.0 servers before wide release, we prefer to
-  // ignore the toplevel fields and use `user_settings` where present instead,
-  // even at the expense of functionality with pre-5.0 servers.
-  // TODO(server-5) remove pre-5.0 comment
-  final UserSettings? userSettings; // TODO(server-5)
+  final UserSettings userSettings;
 
   final List<UserTopicItem>? userTopics; // TODO(server-6)
 
@@ -312,15 +306,9 @@ class UnreadMessagesSnapshot {
 /// An item in [UnreadMessagesSnapshot.dms].
 @JsonSerializable(fieldRename: FieldRename.snake)
 class UnreadDmSnapshot {
-  @JsonKey(readValue: _readOtherUserId)
   final int otherUserId;
   final List<int> unreadMessageIds;
 
-  // TODO(server-5): Simplify away.
-  static dynamic _readOtherUserId(Map<dynamic, dynamic> json, String key) {
-    return json[key] ?? json['sender_id'];
-  }
-
   UnreadDmSnapshot({
     required this.otherUserId,
     required this.unreadMessageIds,
diff --git a/lib/api/model/initial_snapshot.g.dart b/lib/api/model/initial_snapshot.g.dart
index a69b6ebafe..59ffc0b6aa 100644
--- a/lib/api/model/initial_snapshot.g.dart
+++ b/lib/api/model/initial_snapshot.g.dart
@@ -14,7 +14,7 @@ InitialSnapshot _$InitialSnapshotFromJson(Map<String, dynamic> json) =>
       lastEventId: (json['last_event_id'] as num).toInt(),
       zulipFeatureLevel: (json['zulip_feature_level'] as num).toInt(),
       zulipVersion: json['zulip_version'] as String,
-      zulipMergeBase: json['zulip_merge_base'] as String?,
+      zulipMergeBase: json['zulip_merge_base'] as String,
       alertWords: (json['alert_words'] as List<dynamic>)
           .map((e) => e as String)
           .toList(),
@@ -51,10 +51,8 @@ InitialSnapshot _$InitialSnapshotFromJson(Map<String, dynamic> json) =>
       streams: (json['streams'] as List<dynamic>)
           .map((e) => ZulipStream.fromJson(e as Map<String, dynamic>))
           .toList(),
-      userSettings: json['user_settings'] == null
-          ? null
-          : UserSettings.fromJson(
-              json['user_settings'] as Map<String, dynamic>),
+      userSettings:
+          UserSettings.fromJson(json['user_settings'] as Map<String, dynamic>),
       userTopics: (json['user_topics'] as List<dynamic>?)
           ?.map((e) => UserTopicItem.fromJson(e as Map<String, dynamic>))
           .toList(),
@@ -258,9 +256,7 @@ Map<String, dynamic> _$UnreadMessagesSnapshotToJson(
 
 UnreadDmSnapshot _$UnreadDmSnapshotFromJson(Map<String, dynamic> json) =>
     UnreadDmSnapshot(
-      otherUserId:
-          (UnreadDmSnapshot._readOtherUserId(json, 'other_user_id') as num)
-              .toInt(),
+      otherUserId: (json['other_user_id'] as num).toInt(),
       unreadMessageIds: (json['unread_message_ids'] as List<dynamic>)
           .map((e) => (e as num).toInt())
           .toList(),
diff --git a/lib/api/model/model.dart b/lib/api/model/model.dart
index fad8ddc5bc..c8011598a4 100644
--- a/lib/api/model/model.dart
+++ b/lib/api/model/model.dart
@@ -205,7 +205,7 @@ class User {
   // bool isOwner; // obsoleted by [role]; ignore
   // bool isAdmin; // obsoleted by [role]; ignore
   // bool isGuest; // obsoleted by [role]; ignore
-  bool? isBillingAdmin; // TODO(server-5)
+  bool isBillingAdmin;
   final bool isBot;
   final int? botType; // TODO enum
   int? botOwnerId;
@@ -221,7 +221,9 @@ class User {
   @JsonKey(readValue: _readProfileData)
   Map<int, ProfileFieldUserData>? profileData;
 
-  @JsonKey(readValue: _readIsSystemBot)
+  // This field is absent in `realm_users` and `realm_non_active_users`,
+  // which contain no system bots; it's present in `cross_realm_bots`.
+  @JsonKey(defaultValue: false)
   final bool isSystemBot;
 
   static Map<String, dynamic>? _readProfileData(Map<dynamic, dynamic> json, String key) {
@@ -233,14 +235,6 @@ class User {
     return (value != null && value.isNotEmpty) ? value : null;
   }
 
-  static bool _readIsSystemBot(Map<dynamic, dynamic> json, String key) {
-    // This field is absent in `realm_users` and `realm_non_active_users`,
-    // which contain no system bots; it's present in `cross_realm_bots`.
-    return (json[key] as bool?)
-        ?? (json['is_cross_realm_bot'] as bool?) // TODO(server-5): renamed to `is_system_bot`
-        ?? false;
-  }
-
   User({
     required this.userId,
     required this.deliveryEmail,
@@ -924,18 +918,15 @@ enum MessageEditState {
         continue;
       }
 
-      // TODO(server-5) prev_subject was the old name of prev_topic on pre-5.0 servers
-      final prevTopicStr = (entry['prev_topic'] ?? entry['prev_subject']) as String?;
+      final prevTopicStr = entry['prev_topic'] as String?;
       final prevTopic = prevTopicStr == null ? null : TopicName.fromJson(prevTopicStr);
       final topicStr = entry['topic'] as String?;
       final topic = topicStr == null ? null : TopicName.fromJson(topicStr);
-      if (prevTopic != null) {
-        // TODO(server-5) pre-5.0 servers do not have the 'topic' field
-        if (topic == null) {
-          hasMoved = true;
-        } else {
-          hasMoved |= !topicMoveWasResolveOrUnresolve(topic, prevTopic);
-        }
+      if (topic != null || prevTopic != null) {
+        // Crunchy-shell validation: Both are present if the topic was edited
+        topic as TopicName;
+        prevTopic as TopicName;
+        hasMoved |= !topicMoveWasResolveOrUnresolve(topic, prevTopic);
       }
     }
 
diff --git a/lib/api/model/model.g.dart b/lib/api/model/model.g.dart
index cfa38aec5f..ee76a4ae72 100644
--- a/lib/api/model/model.g.dart
+++ b/lib/api/model/model.g.dart
@@ -97,7 +97,7 @@ User _$UserFromJson(Map<String, dynamic> json) => User(
       fullName: json['full_name'] as String,
       dateJoined: json['date_joined'] as String,
       isActive: json['is_active'] as bool,
-      isBillingAdmin: json['is_billing_admin'] as bool?,
+      isBillingAdmin: json['is_billing_admin'] as bool,
       isBot: json['is_bot'] as bool,
       botType: (json['bot_type'] as num?)?.toInt(),
       botOwnerId: (json['bot_owner_id'] as num?)?.toInt(),
@@ -112,7 +112,7 @@ User _$UserFromJson(Map<String, dynamic> json) => User(
         (k, e) => MapEntry(int.parse(k),
             ProfileFieldUserData.fromJson(e as Map<String, dynamic>)),
       ),
-      isSystemBot: User._readIsSystemBot(json, 'is_system_bot') as bool,
+      isSystemBot: json['is_system_bot'] as bool? ?? false,
     );
 
 Map<String, dynamic> _$UserToJson(User instance) => <String, dynamic>{
diff --git a/lib/api/model/web_auth.dart b/lib/api/model/web_auth.dart
index 490c4b79db..5029a8e39f 100644
--- a/lib/api/model/web_auth.dart
+++ b/lib/api/model/web_auth.dart
@@ -7,7 +7,7 @@ import 'package:flutter/foundation.dart';
 class WebAuthPayload {
   final Uri realm;
   final String email;
-  final int? userId; // TODO(server-5) new in FL 108
+  final int userId;
   final String otpEncryptedApiKey;
 
   WebAuthPayload._({
@@ -25,7 +25,7 @@ class WebAuthPayload {
         queryParameters: {
           'realm': String realmStr,
           'email': String email,
-          // 'user_id' handled below
+          'user_id': String userIdStr,
           'otp_encrypted_api_key': String otpEncryptedApiKey,
         },
       )
@@ -33,13 +33,8 @@ class WebAuthPayload {
       final Uri? realm = Uri.tryParse(realmStr);
       if (realm == null) throw const FormatException();
 
-      // TODO(server-5) require in queryParameters (new in FL 108)
-      final userIdStr = url.queryParameters['user_id'];
-      int? userId;
-      if (userIdStr != null) {
-        userId = int.tryParse(userIdStr, radix: 10);
-        if (userId == null) throw const FormatException();
-      }
+      final userId = int.tryParse(userIdStr, radix: 10);
+      if (userId == null) throw const FormatException();
 
       if (!RegExp(r'^[0-9a-fA-F]{64}$').hasMatch(otpEncryptedApiKey)) {
         throw const FormatException();
diff --git a/lib/api/notifications.dart b/lib/api/notifications.dart
index 6d028aa267..9c5df3c749 100644
--- a/lib/api/notifications.dart
+++ b/lib/api/notifications.dart
@@ -177,13 +177,9 @@ sealed class FcmMessageRecipient {
 @JsonSerializable(fieldRename: FieldRename.snake, createToJson: false)
 @_IntConverter()
 class FcmMessageChannelRecipient extends FcmMessageRecipient {
-  // Sending the stream ID in notifications is new in Zulip Server 5.
-  // But handling the lack of it would add complication, and we don't strictly
-  // need to -- we intend (#268) to cut pre-server-5 support before beta release.
-  // TODO(server-5): cut comment
   final int streamId;
 
-  // Current servers (as of 2023) always send the stream name.  But
+  // Current servers (as of 2025) always send the stream name.  But
   // future servers might not, once clients get the name from local data.
   // So might as well be ready.
   @JsonKey(name: 'stream')
diff --git a/lib/api/route/messages.dart b/lib/api/route/messages.dart
index 5af312ce45..a735523abd 100644
--- a/lib/api/route/messages.dart
+++ b/lib/api/route/messages.dart
@@ -1,64 +1,16 @@
 import 'package:json_annotation/json_annotation.dart';
 
 import '../core.dart';
-import '../exception.dart';
 import '../model/model.dart';
 import '../model/narrow.dart';
 
 part 'messages.g.dart';
 
-/// Convenience function to get a single message from any server.
-///
-/// This encapsulates a server-feature check.
-///
-/// Gives null if the server reports that the message doesn't exist.
-// TODO(server-5) Simplify this away; just use getMessage.
-Future<Message?> getMessageCompat(ApiConnection connection, {
-  required int messageId,
-  bool? applyMarkdown,
-}) async {
-  final useLegacyApi = connection.zulipFeatureLevel! < 120;
-  if (useLegacyApi) {
-    final response = await getMessages(connection,
-      narrow: [ApiNarrowMessageId(messageId)],
-      anchor: NumericAnchor(messageId),
-      numBefore: 0,
-      numAfter: 0,
-      applyMarkdown: applyMarkdown,
-
-      // Hard-code this param to `true`, as the new single-message API
-      // effectively does:
-      //   https://chat.zulip.org/#narrow/stream/378-api-design/topic/.60client_gravatar.60.20in.20.60messages.2F.7Bmessage_id.7D.60/near/1418337
-      clientGravatar: true,
-    );
-    return response.messages.firstOrNull;
-  } else {
-    try {
-      final response = await getMessage(connection,
-        messageId: messageId,
-        applyMarkdown: applyMarkdown,
-      );
-      return response.message;
-    } on ZulipApiException catch (e) {
-      if (e.code == 'BAD_REQUEST') {
-        // Servers use this code when the message doesn't exist, according to
-        // the example in the doc.
-        return null;
-      }
-      rethrow;
-    }
-  }
-}
-
 /// https://zulip.com/api/get-message
-///
-/// This binding only supports feature levels 120+.
-// TODO(server-5) remove FL 120+ mention in doc, and the related `assert`
 Future<GetMessageResult> getMessage(ApiConnection connection, {
   required int messageId,
   bool? applyMarkdown,
 }) {
-  assert(connection.zulipFeatureLevel! >= 120);
   return connection.get('getMessage', GetMessageResult.fromJson, 'messages/$messageId', {
     if (applyMarkdown != null) 'apply_markdown': applyMarkdown,
   });
diff --git a/lib/api/route/realm.dart b/lib/api/route/realm.dart
index a43c2e9921..d80fc69286 100644
--- a/lib/api/route/realm.dart
+++ b/lib/api/route/realm.dart
@@ -36,7 +36,8 @@ class GetServerSettingsResult {
 
   final int zulipFeatureLevel;
   final String zulipVersion;
-  final String? zulipMergeBase; // TODO(server-5)
+  // TODO(server-5): Modernize this once we get to #267.
+  final String? zulipMergeBase;
 
   final bool pushNotificationsEnabled;
   final bool isIncompatible;
@@ -50,7 +51,7 @@ class GetServerSettingsResult {
   final String realmName;
   final String realmIcon;
   final String realmDescription;
-  final bool? realmWebPublicAccessEnabled; // TODO(server-5)
+  final bool realmWebPublicAccessEnabled;
 
   GetServerSettingsResult({
     required this.authenticationMethods,
diff --git a/lib/api/route/realm.g.dart b/lib/api/route/realm.g.dart
index e34fbc9d0c..77362eb60d 100644
--- a/lib/api/route/realm.g.dart
+++ b/lib/api/route/realm.g.dart
@@ -31,7 +31,7 @@ GetServerSettingsResult _$GetServerSettingsResultFromJson(
       realmIcon: json['realm_icon'] as String,
       realmDescription: json['realm_description'] as String,
       realmWebPublicAccessEnabled:
-          json['realm_web_public_access_enabled'] as bool?,
+          json['realm_web_public_access_enabled'] as bool,
     );
 
 Map<String, dynamic> _$GetServerSettingsResultToJson(
diff --git a/lib/model/emoji.dart b/lib/model/emoji.dart
index b0ec5f7324..6ac675986a 100644
--- a/lib/model/emoji.dart
+++ b/lib/model/emoji.dart
@@ -18,9 +18,9 @@ sealed class EmojiDisplay {
 
   EmojiDisplay({required this.emojiName});
 
-  EmojiDisplay resolve(UserSettings? userSettings) { // TODO(server-5)
+  EmojiDisplay resolve(UserSettings userSettings) {
     if (this is TextEmojiDisplay) return this;
-    if (userSettings?.emojiset == Emojiset.text) {
+    if (userSettings.emojiset == Emojiset.text) {
       return TextEmojiDisplay(emojiName: emojiName);
     }
     return this;
diff --git a/lib/model/message.dart b/lib/model/message.dart
index 84f3bbc3e5..30645b7a7f 100644
--- a/lib/model/message.dart
+++ b/lib/model/message.dart
@@ -128,9 +128,7 @@ class MessageStoreImpl with MessageStore {
   }
 
   void _handleUpdateMessageEventTimestamp(UpdateMessageEvent event) {
-    // TODO(server-5): Cut this fallback; rely on renderingOnly from FL 114
-    final isRenderingOnly = event.renderingOnly ?? (event.userId == null);
-    if (event.editTimestamp == null || isRenderingOnly) {
+    if (event.renderingOnly) {
       // A rendering-only update gets omitted from the message edit history,
       // and [Message.lastEditTimestamp] is the last timestamp of that history.
       // So on a rendering-only update, the timestamp doesn't get updated.
diff --git a/lib/model/store.dart b/lib/model/store.dart
index 94f6c56084..9483c699d2 100644
--- a/lib/model/store.dart
+++ b/lib/model/store.dart
@@ -456,7 +456,7 @@ class PerAccountStore extends ChangeNotifier with EmojiStore, UserStore, Channel
   /// Will throw if called after [dispose] has been called.
   Account get account => _globalStore.getAccount(accountId)!;
 
-  final UserSettings? userSettings; // TODO(server-5)
+  final UserSettings userSettings;
 
   final TypingNotifier typingNotifier;
 
@@ -626,11 +626,11 @@ class PerAccountStore extends ChangeNotifier with EmojiStore, UserStore, Channel
         }
         switch (event.property!) {
           case UserSettingName.twentyFourHourTime:
-            userSettings?.twentyFourHourTime        = event.value as bool;
+            userSettings.twentyFourHourTime        = event.value as bool;
           case UserSettingName.displayEmojiReactionUsers:
-            userSettings?.displayEmojiReactionUsers = event.value as bool;
+            userSettings.displayEmojiReactionUsers = event.value as bool;
           case UserSettingName.emojiset:
-            userSettings?.emojiset                  = event.value as Emojiset;
+            userSettings.emojiset                  = event.value as Emojiset;
         }
         notifyListeners();
 
diff --git a/lib/widgets/action_sheet.dart b/lib/widgets/action_sheet.dart
index aa81461421..5ebe6c7032 100644
--- a/lib/widgets/action_sheet.dart
+++ b/lib/widgets/action_sheet.dart
@@ -693,17 +693,20 @@ Future<String?> fetchRawContentWithFeedback({
     //   On final failure or success, auto-dismiss the snackbar.
     final zulipLocalizations = ZulipLocalizations.of(context);
     try {
-      fetchedMessage = await getMessageCompat(PerAccountStoreWidget.of(context).connection,
+      fetchedMessage = (await getMessage(PerAccountStoreWidget.of(context).connection,
         messageId: messageId,
         applyMarkdown: false,
-      );
-      if (fetchedMessage == null) {
-        errorMessage = zulipLocalizations.errorMessageDoesNotSeemToExist;
-      }
+      )).message;
     } catch (e) {
       switch (e) {
         case ZulipApiException():
-          errorMessage = e.message;
+          if (e.code == 'BAD_REQUEST') {
+            // Servers use this code when the message doesn't exist, according
+            // to the example in the doc.
+            errorMessage = zulipLocalizations.errorMessageDoesNotSeemToExist;
+          } else {
+            errorMessage = e.message;
+          }
         // TODO specific messages for common errors, like network errors
         //   (support with reusable code)
         default:
diff --git a/lib/widgets/emoji_reaction.dart b/lib/widgets/emoji_reaction.dart
index c418337e62..c3a5035aba 100644
--- a/lib/widgets/emoji_reaction.dart
+++ b/lib/widgets/emoji_reaction.dart
@@ -121,7 +121,7 @@ class ReactionChipsList extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final store = PerAccountStoreWidget.of(context);
-    final displayEmojiReactionUsers = store.userSettings?.displayEmojiReactionUsers ?? false;
+    final displayEmojiReactionUsers = store.userSettings.displayEmojiReactionUsers ?? false;
     final showNames = displayEmojiReactionUsers && reactions.total <= 3;
 
     return Wrap(spacing: 4, runSpacing: 4, crossAxisAlignment: WrapCrossAlignment.center,
diff --git a/lib/widgets/login.dart b/lib/widgets/login.dart
index 504289adc1..31848d953f 100644
--- a/lib/widgets/login.dart
+++ b/lib/widgets/login.dart
@@ -309,8 +309,7 @@ class _LoginPageState extends State<LoginPage> {
       if (payload.realm.origin != widget.serverSettings.realmUrl.origin) throw Error();
       final apiKey = payload.decodeApiKey(_otp!);
       await _tryInsertAccountAndNavigate(
-        // TODO(server-5): Rely on userId from payload.
-        userId: payload.userId ?? await _getUserId(payload.email, apiKey),
+        userId: payload.userId,
         email: payload.email,
         apiKey: apiKey,
       );
diff --git a/test/api/model/events_checks.dart b/test/api/model/events_checks.dart
index c1fa0a117f..01f5243568 100644
--- a/test/api/model/events_checks.dart
+++ b/test/api/model/events_checks.dart
@@ -42,12 +42,12 @@ extension MessageEventChecks on Subject<MessageEvent> {
 }
 
 extension UpdateMessageEventChecks on Subject<UpdateMessageEvent> {
-  Subject<int?> get userId => has((e) => e.userId, 'userId');
-  Subject<bool?> get renderingOnly => has((e) => e.renderingOnly, 'renderingOnly');
+  Subject<int> get userId => has((e) => e.userId, 'userId');
+  Subject<bool> get renderingOnly => has((e) => e.renderingOnly, 'renderingOnly');
   Subject<int> get messageId => has((e) => e.messageId, 'messageId');
   Subject<List<int>> get messageIds => has((e) => e.messageIds, 'messageIds');
   Subject<List<MessageFlag>> get flags => has((e) => e.flags, 'flags');
-  Subject<int?> get editTimestamp => has((e) => e.editTimestamp, 'editTimestamp');
+  Subject<int> get editTimestamp => has((e) => e.editTimestamp, 'editTimestamp');
   Subject<int?> get origStreamId => has((e) => e.origStreamId, 'origStreamId');
   Subject<int?> get newStreamId => has((e) => e.newStreamId, 'newStreamId');
   Subject<PropagateMode?> get propagateMode => has((e) => e.propagateMode, 'propagateMode');
diff --git a/test/api/model/model_checks.dart b/test/api/model/model_checks.dart
index 8b39b1ad57..469078ccca 100644
--- a/test/api/model/model_checks.dart
+++ b/test/api/model/model_checks.dart
@@ -9,7 +9,7 @@ extension UserChecks on Subject<User> {
   Subject<String> get fullName => has((x) => x.fullName, 'fullName');
   Subject<String> get dateJoined => has((x) => x.dateJoined, 'dateJoined');
   Subject<bool> get isActive => has((x) => x.isActive, 'isActive');
-  Subject<bool?> get isBillingAdmin => has((x) => x.isBillingAdmin, 'isBillingAdmin');
+  Subject<bool> get isBillingAdmin => has((x) => x.isBillingAdmin, 'isBillingAdmin');
   Subject<bool> get isBot => has((x) => x.isBot, 'isBot');
   Subject<int?> get botType => has((x) => x.botType, 'botType');
   Subject<int?> get botOwnerId => has((x) => x.botOwnerId, 'botOwnerId');
diff --git a/test/api/model/model_test.dart b/test/api/model/model_test.dart
index 95737c173f..d512c60c80 100644
--- a/test/api/model/model_test.dart
+++ b/test/api/model/model_test.dart
@@ -62,7 +62,6 @@ void main() {
 
     test('is_system_bot', () {
       check(mkUser({}).isSystemBot).isFalse();
-      check(mkUser({'is_cross_realm_bot': true}).isSystemBot).isTrue();
       check(mkUser({'is_system_bot': true}).isSystemBot).isTrue();
     });
   });
@@ -286,16 +285,6 @@ void main() {
         checkEditState(MessageEditState.edited,
           [{'prev_content': 'old_content'}]);
       });
-
-      test("'prev_topic' present without the 'topic' field -> moved", () {
-        checkEditState(MessageEditState.moved,
-          [{'prev_topic': 'old_topic'}]);
-      });
-
-      test("'prev_subject' present from a pre-5.0 server -> moved", () {
-        checkEditState(MessageEditState.moved,
-          [{'prev_subject': 'old_topic'}]);
-      });
     });
 
     group('topic resolved in edit history', () {
diff --git a/test/api/model/web_auth_test.dart b/test/api/model/web_auth_test.dart
index 01a670103f..7f8c326ed6 100644
--- a/test/api/model/web_auth_test.dart
+++ b/test/api/model/web_auth_test.dart
@@ -23,19 +23,6 @@ void main() {
       check(payload.decodeApiKey(otp)).equals(eg.selfAccount.apiKey);
     });
 
-    // TODO(server-5) remove
-    test('legacy: no userId', () {
-      final queryParams = {...wellFormed.queryParameters}..remove('user_id');
-      final payload = WebAuthPayload.parse(
-        wellFormed.replace(queryParameters: queryParams));
-      check(payload)
-        ..otpEncryptedApiKey.equals(encryptedApiKey)
-        ..email.equals('self@example')
-        ..userId.isNull()
-        ..realm.equals(Uri.parse('https://chat.example/'));
-      check(payload.decodeApiKey(otp)).equals(eg.selfAccount.apiKey);
-    });
-
     test('parse fails when an expected field is missing', () {
       final queryParams = {...wellFormed.queryParameters}..remove('email');
       final input = wellFormed.replace(queryParameters: queryParams);
@@ -93,6 +80,6 @@ void main() {
 extension WebAuthPayloadChecks on Subject<WebAuthPayload> {
   Subject<String> get otpEncryptedApiKey => has((x) => x.otpEncryptedApiKey, 'otpEncryptedApiKey');
   Subject<String> get email => has((x) => x.email, 'email');
-  Subject<int?> get userId => has((x) => x.userId, 'userId');
+  Subject<int> get userId => has((x) => x.userId, 'userId');
   Subject<Uri> get realm => has((x) => x.realm, 'realm');
 }
diff --git a/test/api/route/messages_test.dart b/test/api/route/messages_test.dart
index a29a87e24b..3c4ce7b028 100644
--- a/test/api/route/messages_test.dart
+++ b/test/api/route/messages_test.dart
@@ -15,110 +15,6 @@ import '../fake_api.dart';
 import 'route_checks.dart';
 
 void main() {
-  group('getMessageCompat', () {
-    Future<Message?> checkGetMessageCompat(FakeApiConnection connection, {
-      required bool expectLegacy,
-      required int messageId,
-      bool? applyMarkdown,
-    }) async {
-      final result = await getMessageCompat(connection,
-        messageId: messageId,
-        applyMarkdown: applyMarkdown,
-      );
-      if (expectLegacy) {
-        check(connection.lastRequest).isA<http.Request>()
-          ..method.equals('GET')
-          ..url.path.equals('/api/v1/messages')
-          ..url.queryParameters.deepEquals({
-            'narrow': jsonEncode([ApiNarrowMessageId(messageId)]),
-            'anchor': messageId.toString(),
-            'num_before': '0',
-            'num_after': '0',
-            if (applyMarkdown != null) 'apply_markdown': applyMarkdown.toString(),
-            'client_gravatar': 'true',
-          });
-      } else {
-        check(connection.lastRequest).isA<http.Request>()
-          ..method.equals('GET')
-          ..url.path.equals('/api/v1/messages/$messageId')
-          ..url.queryParameters.deepEquals({
-            if (applyMarkdown != null) 'apply_markdown': applyMarkdown.toString(),
-          });
-      }
-      return result;
-    }
-
-    test('modern; message found', () {
-      return FakeApiConnection.with_((connection) async {
-        final message = eg.streamMessage();
-        final fakeResult = GetMessageResult(message: message);
-        connection.prepare(json: fakeResult.toJson());
-        final result = await checkGetMessageCompat(connection,
-          expectLegacy: false,
-          messageId: message.id,
-          applyMarkdown: true,
-        );
-        check(result).isNotNull().jsonEquals(message);
-      });
-    });
-
-    test('modern; message not found', () {
-      return FakeApiConnection.with_((connection) async {
-        final message = eg.streamMessage();
-        connection.prepare(
-          apiException: eg.apiBadRequest(message: 'Invalid message(s)'));
-        final result = await checkGetMessageCompat(connection,
-          expectLegacy: false,
-          messageId: message.id,
-          applyMarkdown: true,
-        );
-        check(result).isNull();
-      });
-    });
-
-    test('legacy; message found', () {
-      return FakeApiConnection.with_(zulipFeatureLevel: 119, (connection) async {
-        final message = eg.streamMessage();
-        final fakeResult = GetMessagesResult(
-          anchor: message.id,
-          foundNewest: false,
-          foundOldest: false,
-          foundAnchor: true,
-          historyLimited: false,
-          messages: [message],
-        );
-        connection.prepare(json: fakeResult.toJson());
-        final result = await checkGetMessageCompat(connection,
-          expectLegacy: true,
-          messageId: message.id,
-          applyMarkdown: true,
-        );
-        check(result).isNotNull().jsonEquals(message);
-      });
-    });
-
-    test('legacy; message not found', () {
-      return FakeApiConnection.with_(zulipFeatureLevel: 119, (connection) async {
-        final message = eg.streamMessage();
-        final fakeResult = GetMessagesResult(
-          anchor: message.id,
-          foundNewest: false,
-          foundOldest: false,
-          foundAnchor: false,
-          historyLimited: false,
-          messages: [],
-        );
-        connection.prepare(json: fakeResult.toJson());
-        final result = await checkGetMessageCompat(connection,
-          expectLegacy: true,
-          messageId: message.id,
-          applyMarkdown: true,
-        );
-        check(result).isNull();
-      });
-    });
-  });
-
   group('getMessage', () {
     Future<GetMessageResult> checkGetMessage(
       FakeApiConnection connection, {
@@ -158,15 +54,6 @@ void main() {
           expected: {'apply_markdown': 'false'});
       });
     });
-
-    test('Throws assertion error when FL <120', () {
-      return FakeApiConnection.with_(zulipFeatureLevel: 119, (connection) async {
-        connection.prepare(json: fakeResult.toJson());
-        check(() => getMessage(connection,
-          messageId: 1,
-        )).throws<AssertionError>();
-      });
-    });
   });
 
   test('ApiNarrow.toJson', () {
diff --git a/test/example_data.dart b/test/example_data.dart
index 04d6723b7a..a275e47705 100644
--- a/test/example_data.dart
+++ b/test/example_data.dart
@@ -635,8 +635,8 @@ DeleteMessageEvent deleteMessageEvent(List<StreamMessage> messages) {
 
 UpdateMessageEvent updateMessageEditEvent(
   Message origMessage, {
-  int? userId = -1, // null means null; default is [selfUser.userId]
-  bool? renderingOnly = false,
+  int? userId,
+  bool renderingOnly = false,
   int? messageId,
   List<MessageFlag>? flags,
   int? editTimestamp,
@@ -647,7 +647,7 @@ UpdateMessageEvent updateMessageEditEvent(
   messageId ??= origMessage.id;
   return UpdateMessageEvent(
     id: 0,
-    userId: userId == -1 ? selfUser.userId : userId,
+    userId: userId ?? selfUser.userId,
     renderingOnly: renderingOnly,
     messageId: messageId,
     messageIds: [messageId],
diff --git a/test/model/message_test.dart b/test/model/message_test.dart
index 9c9a940d42..3b2f678412 100644
--- a/test/model/message_test.dart
+++ b/test/model/message_test.dart
@@ -246,16 +246,14 @@ void main() {
         ..content.not((it) => it.equals(updateEvent.renderedContent!));
     });
 
-    // TODO(server-5): Cut legacy case for rendering-only message update
-    Future<void> checkRenderingOnly({required bool legacy}) async {
+    test('rendering-only update does not change timestamp', () async {
       final originalMessage = eg.streamMessage(
         lastEditTimestamp: 78492,
         content: "<p>Hello, world</p>");
       final updateEvent = eg.updateMessageEditEvent(originalMessage,
         renderedContent: "<p>Hello, world</p> <div>Some link preview</div>",
         editTimestamp: 99999,
-        renderingOnly: legacy ? null : true,
-        userId: null,
+        renderingOnly: true,
       );
       await prepare();
       await prepareMessages([originalMessage]);
@@ -270,14 +268,6 @@ void main() {
         // ... edit timestamp is not.
         ..lastEditTimestamp.equals(originalMessage.lastEditTimestamp)
         ..lastEditTimestamp.not((it) => it.equals(updateEvent.editTimestamp));
-    }
-
-    test('rendering-only update does not change timestamp', () async {
-      await checkRenderingOnly(legacy: false);
-    });
-
-    test('rendering-only update does not change timestamp (for old server versions)', () async {
-      await checkRenderingOnly(legacy: true);
     });
 
     group('Handle message edit state update', () {
diff --git a/test/model/store_checks.dart b/test/model/store_checks.dart
index 00ada1eea5..1d9d16dca5 100644
--- a/test/model/store_checks.dart
+++ b/test/model/store_checks.dart
@@ -38,7 +38,7 @@ extension PerAccountStoreChecks on Subject<PerAccountStore> {
   Subject<int> get accountId => has((x) => x.accountId, 'accountId');
   Subject<Account> get account => has((x) => x.account, 'account');
   Subject<int> get selfUserId => has((x) => x.selfUserId, 'selfUserId');
-  Subject<UserSettings?> get userSettings => has((x) => x.userSettings, 'userSettings');
+  Subject<UserSettings> get userSettings => has((x) => x.userSettings, 'userSettings');
   Subject<Map<int, ZulipStream>> get streams => has((x) => x.streams, 'streams');
   Subject<Map<String, ZulipStream>> get streamsByName => has((x) => x.streamsByName, 'streamsByName');
   Subject<Map<int, Subscription>> get subscriptions => has((x) => x.subscriptions, 'subscriptions');
diff --git a/test/model/store_test.dart b/test/model/store_test.dart
index eb6444309d..44519ab1a2 100644
--- a/test/model/store_test.dart
+++ b/test/model/store_test.dart
@@ -623,14 +623,14 @@ void main() {
       await preparePoll();
 
       // Pick some arbitrary event and check it gets processed on the store.
-      check(store.userSettings!.twentyFourHourTime).isFalse();
+      check(store.userSettings.twentyFourHourTime).isFalse();
       connection.prepare(json: GetEventsResult(events: [
         UserSettingsUpdateEvent(id: 2,
           property: UserSettingName.twentyFourHourTime, value: true),
       ], queueId: null).toJson());
       updateMachine.debugAdvanceLoop();
       async.elapse(Duration.zero);
-      check(store.userSettings!.twentyFourHourTime).isTrue();
+      check(store.userSettings.twentyFourHourTime).isTrue();
     }));
 
     void checkReload(FutureOr<void> Function() prepareError, {
@@ -660,14 +660,14 @@ void main() {
         // The new UpdateMachine updates the new store.
         updateMachine.debugPauseLoop();
         updateMachine.poll();
-        check(store.userSettings!.twentyFourHourTime).isFalse();
+        check(store.userSettings.twentyFourHourTime).isFalse();
         connection.prepare(json: GetEventsResult(events: [
           UserSettingsUpdateEvent(id: 2,
             property: UserSettingName.twentyFourHourTime, value: true),
         ], queueId: null).toJson());
         updateMachine.debugAdvanceLoop();
         async.elapse(Duration.zero);
-        check(store.userSettings!.twentyFourHourTime).isTrue();
+        check(store.userSettings.twentyFourHourTime).isTrue();
       });
     }