zulip · sm-sayedi · Aug 7, 2025
diff --git a/lib/api/model/narrow.dart b/lib/api/model/narrow.dart
@@ -14,24 +14,29 @@ typedef ApiNarrow = List<ApiNarrowElement>;
 /// reasonably be omitted will be omitted.
 ApiNarrow resolveApiNarrowForServer(ApiNarrow narrow, int zulipFeatureLevel) {
   final supportsOperatorDm = zulipFeatureLevel >= 177; // TODO(server-7)
+  final supportsOperatorChannel = zulipFeatureLevel >= 250; // TODO(server-9)
   final supportsOperatorWith = zulipFeatureLevel >= 271; // TODO(server-9)
 
   bool hasDmElement = false;
+  bool hasChannelElement = false;
   bool hasWithElement = false;
   for (final element in narrow) {
     switch (element) {
-      case ApiNarrowDm():   hasDmElement = true;
-      case ApiNarrowWith(): hasWithElement = true;
+      case ApiNarrowChannel(): hasChannelElement = true;
+      case ApiNarrowDm():      hasDmElement = true;
+      case ApiNarrowWith():    hasWithElement = true;
       default:
     }
   }
-  if (!(hasDmElement || (hasWithElement && !supportsOperatorWith))) {
+  if (!(hasChannelElement || hasDmElement || (hasWithElement && !supportsOperatorWith))) {
     return narrow;
   }
 
   final result = <ApiNarrowElement>[];
   for (final element in narrow) {
     switch (element) {
+      case ApiNarrowChannel():
+        result.add(element.resolve(legacy: !supportsOperatorChannel));
       case ApiNarrowDm():
         result.add(element.resolve(legacy: !supportsOperatorDm));
       case ApiNarrowWith() when !supportsOperatorWith:
@@ -93,17 +98,51 @@ sealed class ApiNarrowElement {
   };
 }
 
-class ApiNarrowStream extends ApiNarrowElement {
-  @override String get operator => 'stream';
+class ApiNarrowChannel extends ApiNarrowElement {
+  @override String get operator {
+    assert(false,
+      "The [operator] getter was called on a plain [ApiNarrowChannel].  "
+      "Before passing to [jsonEncode] or otherwise getting [operator], "
+      "the [ApiNarrowChannel] must be replaced by the result of [ApiNarrowChannel.resolve]."
+    );
+    return "channel";
+  }
 
   @override final int operand;
 
-  ApiNarrowStream(this.operand, {super.negated});
+  ApiNarrowChannel(this.operand, {super.negated});
 
-  factory ApiNarrowStream.fromJson(Map<String, dynamic> json) => ApiNarrowStream(
-    json['operand'] as int,
-    negated: json['negated'] as bool? ?? false,
-  );
+  factory ApiNarrowChannel.fromJson(Map<String, dynamic> json) {
+    var operand = (json['operand'] as int);
+    var negated = json['negated'] as bool? ?? false;
+    return json['operator'] == 'stream'
+      ? ApiNarrowStream._(operand, negated: negated)
+      : ApiNarrowChannelModern._(operand, negated: negated);
+  }
+
+  /// This element resolved, as either an [ApiNarrowChannelModern] or an [ApiNarrowStream].
+  ApiNarrowChannel resolve({required bool legacy}) {
+    return legacy ? ApiNarrowStream._(operand, negated: negated)
+                  : ApiNarrowChannelModern._(operand, negated: negated);
+  }
+}
+
+/// An [ApiNarrowElement] with the 'channel' operator (and not the legacy 'stream').
+///
+/// To construct one of these, use [ApiNarrowChannel.resolve].
+class ApiNarrowChannelModern extends ApiNarrowChannel {
+  @override String get operator => 'channel';
+
+  ApiNarrowChannelModern._(super.operand, {super.negated});
+}
+
+/// An [ApiNarrowElement] with the legacy 'stream' operator.
+///
+/// To construct one of these, use [ApiNarrowChannel.resolve].
+class ApiNarrowStream extends ApiNarrowChannel {
+  @override String get operator => 'stream';
+
+  ApiNarrowStream._(super.operand, {super.negated});
 }
 
 class ApiNarrowTopic extends ApiNarrowElement {

diff --git a/lib/model/internal_link.dart b/lib/model/internal_link.dart
@@ -71,11 +71,14 @@ Uri narrowLink(PerAccountStore store, Narrow narrow, {int? nearMessageId}) {
     fragment.write('${element.operator}/');
 
     switch (element) {
+      case ApiNarrowChannelModern():
       case ApiNarrowStream():
         final streamId = element.operand;
         final name = store.streams[streamId]?.name ?? 'unknown';
         final slugifiedName = _encodeHashComponent(name.replaceAll(' ', '-'));
         fragment.write('$streamId-$slugifiedName');
+      case ApiNarrowChannel():
+        assert(false, 'ApiNarrowChannel should have been resolved');
       case ApiNarrowTopic():
         fragment.write(_encodeHashComponent(element.operand.apiName));
       case ApiNarrowDmModern():
@@ -182,7 +185,7 @@ NarrowLink? _interpretNarrowSegments(List<String> segments, PerAccountStore stor
   assert(segments.isNotEmpty);
   assert(segments.length.isEven);
 
-  ApiNarrowStream? streamElement;
+  ApiNarrowChannel? channelElement;
   ApiNarrowTopic? topicElement;
   ApiNarrowDm? dmElement;
   ApiNarrowWith? withElement;
@@ -196,10 +199,10 @@ NarrowLink? _interpretNarrowSegments(List<String> segments, PerAccountStore stor
     switch (operator) {
       case _NarrowOperator.stream:
       case _NarrowOperator.channel:
-        if (streamElement != null) return null;
+        if (channelElement != null) return null;
         final streamId = _parseStreamOperand(operand, store);
         if (streamId == null) return null;
-        streamElement = ApiNarrowStream(streamId, negated: negated);
+        channelElement = ApiNarrowChannel(streamId, negated: negated);
 
       case _NarrowOperator.topic:
       case _NarrowOperator.subject:
@@ -238,7 +241,7 @@ NarrowLink? _interpretNarrowSegments(List<String> segments, PerAccountStore stor
 
   final Narrow? narrow;
   if (isElementOperands.isNotEmpty) {
-    if (streamElement != null || topicElement != null || dmElement != null || withElement != null) {
+    if (channelElement != null || topicElement != null || dmElement != null || withElement != null) {
       return null;
     }
     if (isElementOperands.length > 1) return null;
@@ -257,10 +260,10 @@ NarrowLink? _interpretNarrowSegments(List<String> segments, PerAccountStore stor
         return null;
     }
   } else if (dmElement != null) {
-    if (streamElement != null || topicElement != null || withElement != null) return null;
+    if (channelElement != null || topicElement != null || withElement != null) return null;
     narrow = DmNarrow.withUsers(dmElement.operand, selfUserId: store.selfUserId);
-  } else if (streamElement != null) {
-    final streamId = streamElement.operand;
+  } else if (channelElement != null) {
+    final streamId = channelElement.operand;
     if (topicElement != null) {
       narrow = TopicNarrow(streamId, topicElement.operand, with_: withElement?.operand);
     } else {

diff --git a/lib/model/narrow.dart b/lib/model/narrow.dart
@@ -80,7 +80,7 @@ class ChannelNarrow extends Narrow {
   }
 
   @override
-  ApiNarrow apiEncode() => [ApiNarrowStream(streamId)];
+  ApiNarrow apiEncode() => [ApiNarrowChannel(streamId)];
 
   @override
   String toString() => 'ChannelNarrow($streamId)';
@@ -117,7 +117,7 @@ class TopicNarrow extends Narrow implements SendableNarrow {
 
   @override
   ApiNarrow apiEncode() => [
-    ApiNarrowStream(streamId),
+    ApiNarrowChannel(streamId),
     ApiNarrowTopic(topic),
     if (with_ != null) ApiNarrowWith(with_!),
   ];

diff --git a/test/api/route/messages_test.dart b/test/api/route/messages_test.dart
@@ -214,14 +214,14 @@ void main() {
 
       checkNarrow(const CombinedFeedNarrow().apiEncode(), jsonEncode([]));
       checkNarrow(const ChannelNarrow(12).apiEncode(), jsonEncode([
-        {'operator': 'stream', 'operand': 12},
+        {'operator': 'channel', 'operand': 12},
       ]));
       checkNarrow(eg.topicNarrow(12, 'stuff').apiEncode(), jsonEncode([
-        {'operator': 'stream', 'operand': 12},
+        {'operator': 'channel', 'operand': 12},
         {'operator': 'topic', 'operand': 'stuff'},
       ]));
       checkNarrow(eg.topicNarrow(12, 'stuff', with_: 1).apiEncode(), jsonEncode([
-        {'operator': 'stream', 'operand': 12},
+        {'operator': 'channel', 'operand': 12},
         {'operator': 'topic', 'operand': 'stuff'},
         {'operator': 'with', 'operand': 1},
       ]));
@@ -235,7 +235,7 @@ void main() {
 
       connection.zulipFeatureLevel = 270;
       checkNarrow(eg.topicNarrow(12, 'stuff', with_: 1).apiEncode(), jsonEncode([
-        {'operator': 'stream', 'operand': 12},
+        {'operator': 'channel', 'operand': 12},
         {'operator': 'topic', 'operand': 'stuff'},
       ]));
       checkNarrow([ApiNarrowDm([123, 234])], jsonEncode([
@@ -245,6 +245,19 @@ void main() {
         {'operator': 'dm', 'operand': [123, 234]},
       ]));
 
+      connection.zulipFeatureLevel = 249;
+      checkNarrow(const ChannelNarrow(12).apiEncode(), jsonEncode([
+        {'operator': 'stream', 'operand': 12},
+      ]));
+      checkNarrow(eg.topicNarrow(12, 'stuff').apiEncode(), jsonEncode([
+        {'operator': 'stream', 'operand': 12},
+        {'operator': 'topic', 'operand': 'stuff'},
+      ]));
+      checkNarrow(eg.topicNarrow(12, 'stuff', with_: 1).apiEncode(), jsonEncode([
+        {'operator': 'stream', 'operand': 12},
+        {'operator': 'topic', 'operand': 'stuff'},
+      ]));
+
       connection.zulipFeatureLevel = 176;
       checkNarrow(eg.topicNarrow(12, 'stuff', with_: 1).apiEncode(), jsonEncode([
         {'operator': 'stream', 'operand': 12},

diff --git a/test/model/compose_test.dart b/test/model/compose_test.dart
@@ -351,11 +351,11 @@ hello
 
     check(quoteAndReplyPlaceholder(
       GlobalLocalizations.zulipLocalizations, store, message: message)).equals('''
-@_**Full Name|123** [said](${eg.selfAccount.realmUrl}#narrow/stream/1-test-here/topic/some.20topic/near/${message.id}): *(loading message ${message.id})*
+@_**Full Name|123** [said](${eg.selfAccount.realmUrl}#narrow/channel/1-test-here/topic/some.20topic/near/${message.id}): *(loading message ${message.id})*
 ''');
 
     check(quoteAndReply(store, message: message, rawContent: 'Hello world!')).equals('''
-@_**Full Name|123** [said](${eg.selfAccount.realmUrl}#narrow/stream/1-test-here/topic/some.20topic/near/${message.id}):
+@_**Full Name|123** [said](${eg.selfAccount.realmUrl}#narrow/channel/1-test-here/topic/some.20topic/near/${message.id}):
 ```quote
 Hello world!
 ```

diff --git a/test/model/internal_link_test.dart b/test/model/internal_link_test.dart
@@ -60,15 +60,16 @@ void main() {
         .equals(store.realmUrl.resolve('#narrow/is/starred/near/1'));
     });
 
-    test('ChannelNarrow / TopicNarrow', () {
+    group('ChannelNarrow / TopicNarrow', () {
       void checkNarrow(String expectedFragment, {
         required int streamId,
         required String name,
         String? topic,
         int? nearMessageId,
+        int? zulipFeatureLevel = eg.futureZulipFeatureLevel,
       }) async {
         assert(expectedFragment.startsWith('#'), 'wrong-looking expectedFragment');
-        final store = eg.store();
+        final store = eg.store()..connection.zulipFeatureLevel = zulipFeatureLevel;
         await store.addStream(eg.stream(streamId: streamId, name: name));
         final narrow = topic == null
           ? ChannelNarrow(streamId)
@@ -77,22 +78,54 @@ void main() {
           .equals(store.realmUrl.resolve(expectedFragment));
       }
 
-      checkNarrow(streamId: 1,   name: 'announce',       '#narrow/stream/1-announce');
-      checkNarrow(streamId: 378, name: 'api design',     '#narrow/stream/378-api-design');
-      checkNarrow(streamId: 391, name: 'Outreachy',      '#narrow/stream/391-Outreachy');
-      checkNarrow(streamId: 415, name: 'chat.zulip.org', '#narrow/stream/415-chat.2Ezulip.2Eorg');
-      checkNarrow(streamId: 419, name: 'français',       '#narrow/stream/419-fran.C3.A7ais');
-      checkNarrow(streamId: 403, name: 'Hshs[™~}(.',     '#narrow/stream/403-Hshs.5B.E2.84.A2~.7D.28.2E');
-      checkNarrow(streamId: 60,  name: 'twitter', nearMessageId: 1570686, '#narrow/stream/60-twitter/near/1570686');
-
-      checkNarrow(streamId: 48,  name: 'mobile', topic: 'Welcome screen UI',
-                  '#narrow/stream/48-mobile/topic/Welcome.20screen.20UI');
-      checkNarrow(streamId: 243, name: 'mobile-team', topic: 'Podfile.lock clash #F92',
-                  '#narrow/stream/243-mobile-team/topic/Podfile.2Elock.20clash.20.23F92');
-      checkNarrow(streamId: 377, name: 'translation/zh_tw', topic: '翻譯 "stream"',
-                  '#narrow/stream/377-translation.2Fzh_tw/topic/.E7.BF.BB.E8.AD.AF.20.22stream.22');
-      checkNarrow(streamId: 42,  name: 'Outreachy 2016-2017', topic: '2017-18 Stream?', nearMessageId: 302690,
-                  '#narrow/stream/42-Outreachy-2016-2017/topic/2017-18.20Stream.3F/near/302690');
+      test('modern including "channel" operator', () {
+        checkNarrow(streamId: 1,   name: 'announce',       '#narrow/channel/1-announce');
+        checkNarrow(streamId: 378, name: 'api design',     '#narrow/channel/378-api-design');
+        checkNarrow(streamId: 391, name: 'Outreachy',      '#narrow/channel/391-Outreachy');
+        checkNarrow(streamId: 415, name: 'chat.zulip.org', '#narrow/channel/415-chat.2Ezulip.2Eorg');
+        checkNarrow(streamId: 419, name: 'français',       '#narrow/channel/419-fran.C3.A7ais');
+        checkNarrow(streamId: 403, name: 'Hshs[™~}(.',     '#narrow/channel/403-Hshs.5B.E2.84.A2~.7D.28.2E');
+        checkNarrow(streamId: 60,  name: 'twitter', nearMessageId: 1570686, '#narrow/channel/60-twitter/near/1570686');
+
+        checkNarrow(streamId: 48,  name: 'mobile', topic: 'Welcome screen UI',
+                    '#narrow/channel/48-mobile/topic/Welcome.20screen.20UI');
+        checkNarrow(streamId: 243, name: 'mobile-team', topic: 'Podfile.lock clash #F92',
+                    '#narrow/channel/243-mobile-team/topic/Podfile.2Elock.20clash.20.23F92');
+        checkNarrow(streamId: 377, name: 'translation/zh_tw', topic: '翻譯 "stream"',
+                    '#narrow/channel/377-translation.2Fzh_tw/topic/.E7.BF.BB.E8.AD.AF.20.22stream.22');
+        checkNarrow(streamId: 42,  name: 'Outreachy 2016-2017', topic: '2017-18 Stream?', nearMessageId: 302690,
+                    '#narrow/channel/42-Outreachy-2016-2017/topic/2017-18.20Stream.3F/near/302690');
+      });
+
+      test('legacy including "stream" operator', () {
+        checkNarrow(streamId: 1,   name: 'announce',       zulipFeatureLevel: 249,
+                    '#narrow/stream/1-announce');
+        checkNarrow(streamId: 378, name: 'api design',     zulipFeatureLevel: 249,
+                    '#narrow/stream/378-api-design');
+        checkNarrow(streamId: 391, name: 'Outreachy',      zulipFeatureLevel: 249,
+                    '#narrow/stream/391-Outreachy');
+        checkNarrow(streamId: 415, name: 'chat.zulip.org', zulipFeatureLevel: 249,
+                    '#narrow/stream/415-chat.2Ezulip.2Eorg');
+        checkNarrow(streamId: 419, name: 'français',       zulipFeatureLevel: 249,
+                    '#narrow/stream/419-fran.C3.A7ais');
+        checkNarrow(streamId: 403, name: 'Hshs[™~}(.',     zulipFeatureLevel: 249,
+                    '#narrow/stream/403-Hshs.5B.E2.84.A2~.7D.28.2E');
+        checkNarrow(streamId: 60,  name: 'twitter', nearMessageId: 1570686, zulipFeatureLevel: 249,
+                    '#narrow/stream/60-twitter/near/1570686');
+
+        checkNarrow(streamId: 48,  name: 'mobile', topic: 'Welcome screen UI',
+                    zulipFeatureLevel: 249,
+                    '#narrow/stream/48-mobile/topic/Welcome.20screen.20UI');
+        checkNarrow(streamId: 243, name: 'mobile-team', topic: 'Podfile.lock clash #F92',
+                    zulipFeatureLevel: 249,
+                    '#narrow/stream/243-mobile-team/topic/Podfile.2Elock.20clash.20.23F92');
+        checkNarrow(streamId: 377, name: 'translation/zh_tw', topic: '翻譯 "stream"',
+                    zulipFeatureLevel: 249,
+                    '#narrow/stream/377-translation.2Fzh_tw/topic/.E7.BF.BB.E8.AD.AF.20.22stream.22');
+        checkNarrow(streamId: 42,  name: 'Outreachy 2016-2017', topic: '2017-18 Stream?', nearMessageId: 302690,
+                    zulipFeatureLevel: 249,
+                    '#narrow/stream/42-Outreachy-2016-2017/topic/2017-18.20Stream.3F/near/302690');
+      });
     });
 
     test('DmNarrow', () {

diff --git a/test/model/message_list_test.dart b/test/model/message_list_test.dart
@@ -156,7 +156,7 @@ void main() {
       ..method.equals('GET')
       ..url.path.equals('/api/v1/messages')
       ..url.queryParameters.deepEquals({
-        'narrow': jsonEncode(narrow),
+        'narrow': jsonEncode(resolveApiNarrowForServer(narrow, connection.zulipFeatureLevel!)),
         'anchor': anchor,
         if (includeAnchor != null) 'include_anchor': includeAnchor.toString(),
         'num_before': numBefore.toString(),

diff --git a/test/widgets/action_sheet_test.dart b/test/widgets/action_sheet_test.dart
@@ -347,7 +347,7 @@ void main() {
             'num_before': '0',
             'num_after': '1000',
             'narrow': jsonEncode([
-              {'operator': 'stream', 'operand': channelId},
+              {'operator': 'channel', 'operand': channelId},
               {'operator': 'is', 'operand': 'unread'},
             ]),
             'op': 'add',
@@ -1011,7 +1011,9 @@ void main() {
         check(connection.lastRequest).isA<http.Request>()
           ..url.path.equals('/api/v1/messages/flags/narrow')
           ..bodyFields['narrow'].equals(jsonEncode([
-              ...eg.topicNarrow(someChannel.streamId, someTopic).apiEncode(),
+              ...resolveApiNarrowForServer(
+                eg.topicNarrow(someChannel.streamId, someTopic).apiEncode(),
+                connection.zulipFeatureLevel!),
               ApiNarrowIs(IsOperand.unread),
             ]))
           ..bodyFields['op'].equals('add')
@@ -1607,7 +1609,9 @@ void main() {
                 'include_anchor': 'true',
                 'num_before': '0',
                 'num_after': '1000',
-                'narrow': jsonEncode(TopicNarrow.ofMessage(message).apiEncode()),
+                'narrow': jsonEncode(resolveApiNarrowForServer(
+                  TopicNarrow.ofMessage(message).apiEncode(),
+                  connection.zulipFeatureLevel!)),
                 'op': 'remove',
                 'flag': 'read',
               });
@@ -1652,7 +1656,9 @@ void main() {
             ..method.equals('POST')
             ..url.path.equals('/api/v1/messages/flags/narrow')
             ..bodyFields['narrow'].equals(
-                jsonEncode(eg.topicNarrow(newStream.streamId, newTopic).apiEncode()));
+                jsonEncode(resolveApiNarrowForServer(
+                  eg.topicNarrow(newStream.streamId, newTopic).apiEncode(),
+                  connection.zulipFeatureLevel!)));
         });
 
         testWidgets('shows error when fails', (tester) async {