diff --git a/lib/notifications/display.dart b/lib/notifications/display.dart
index c782ad1a66..0787a61bee 100644
--- a/lib/notifications/display.dart
+++ b/lib/notifications/display.dart
@@ -1,4 +1,5 @@
 import 'dart:convert';
+import 'dart:io';
 
 import 'package:http/http.dart' as http;
 import 'package:collection/collection.dart';
@@ -279,10 +280,12 @@ class NotificationDisplayManager {
     try {
       // TODO timeout to prevent waiting indefinitely
       final resp = await http.get(url);
-      return resp.bodyBytes;
+      if (resp.statusCode == HttpStatus.ok) {
+        return resp.bodyBytes;
+      }
     } catch (e) {
       // TODO(log)
-      return null;
     }
+    return null;
   }
 }
diff --git a/test/notifications/display_test.dart b/test/notifications/display_test.dart
index aadd1eb504..d65eb2b558 100644
--- a/test/notifications/display_test.dart
+++ b/test/notifications/display_test.dart
@@ -1,4 +1,5 @@
 import 'dart:convert';
+import 'dart:io';
 import 'dart:typed_data';
 
 import 'package:checks/checks.dart';
@@ -8,6 +9,8 @@ import 'package:firebase_messaging/firebase_messaging.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_local_notifications/flutter_local_notifications.dart' hide Message, Person;
 import 'package:flutter_test/flutter_test.dart';
+import 'package:http/http.dart' as http;
+import 'package:http/testing.dart' as http_testing;
 import 'package:zulip/api/model/model.dart';
 import 'package:zulip/api/notifications.dart';
 import 'package:zulip/host/android_notifications.dart';
@@ -25,6 +28,7 @@ import 'package:zulip/widgets/theme.dart';
 import '../fake_async.dart';
 import '../model/binding.dart';
 import '../example_data.dart' as eg;
+import '../test_images.dart';
 import '../test_navigation.dart';
 import '../widgets/message_list_checks.dart';
 import '../widgets/page_checks.dart';
@@ -74,6 +78,24 @@ void main() {
   TestZulipBinding.ensureInitialized();
   final zulipLocalizations = GlobalLocalizations.zulipLocalizations;
 
+  http.Client makeFakeHttpClient({http.Response? response, Exception? exception}) {
+    return http_testing.MockClient((request) async {
+      assert((response != null) ^ (exception != null));
+      if (exception != null) throw exception;
+      return response!; // TODO return 404 on non avatar urls
+    });
+  }
+
+  final fakeHttpClientGivingSuccess = makeFakeHttpClient(
+    response: http.Response.bytes(kSolidBlueAvatar, HttpStatus.ok));
+
+  T runWithHttpClient<T>(
+    T Function() callback, {
+    http.Client Function()? httpClientFactory,
+  }) {
+    return http.runWithClient(callback, httpClientFactory ?? () => fakeHttpClientGivingSuccess);
+  }
+
   Future<void> init() async {
     addTearDown(testBinding.reset);
     testBinding.firebaseMessagingInitialToken = '012abc';
@@ -102,7 +124,11 @@ void main() {
       required String expectedTitle,
       required String expectedTagComponent,
       required bool expectedIsGroupConversation,
+      List<int>? expectedIconBitmap = kSolidBlueAvatar,
     }) {
+      assert(messageStyleMessages.every((e) => e.userId == data.userId));
+      assert(messageStyleMessages.every((e) => e.realmUri == data.realmUri));
+
       final expectedTag = '${data.realmUri}|${data.userId}|$expectedTagComponent';
       final expectedGroupKey = '${data.realmUri}|${data.userId}';
       final expectedId =
@@ -113,9 +139,6 @@ void main() {
 
       final messageStyleMessagesChecks =
         messageStyleMessages.mapIndexed((i, messageData) {
-          assert(messageData.realmUri == data.realmUri);
-          assert(messageData.userId == data.userId);
-
           final expectedSenderKey =
             '${messageData.realmUri}|${messageData.senderId}';
           final isLast = i == (messageStyleMessages.length - 1);
@@ -123,7 +146,8 @@ void main() {
             ..text.equals(messageData.content)
             ..timestampMs.equals(messageData.time * 1000)
             ..person.which((it) => it.isNotNull()
-              ..iconBitmap.which((it) => isLast ? it.isNotNull() : it.isNull())
+              ..iconBitmap.which((it) => (isLast && expectedIconBitmap != null)
+                ? it.isNotNull().deepEquals(expectedIconBitmap) : it.isNull())
               ..key.equals(expectedSenderKey)
               ..name.equals(messageData.senderFullName));
         });
@@ -209,7 +233,7 @@ void main() {
       async.flushMicrotasks();
     }
 
-    test('stream message', () => awaitFakeAsync((async) async {
+    test('stream message', () => runWithHttpClient(() => awaitFakeAsync((async) async {
       await init();
       final stream = eg.stream();
       final message = eg.streamMessage(stream: stream);
@@ -217,9 +241,9 @@ void main() {
         expectedIsGroupConversation: true,
         expectedTitle: '#${stream.name} > ${message.topic}',
         expectedTagComponent: 'stream:${message.streamId}:${message.topic}');
-    }));
+    })));
 
-    test('stream message: multiple messages, same topic', () => awaitFakeAsync((async) async {
+    test('stream message: multiple messages, same topic', () => runWithHttpClient(() => awaitFakeAsync((async) async {
       await init();
       final stream = eg.stream();
       const topic = 'topic 1';
@@ -253,9 +277,69 @@ void main() {
         expectedIsGroupConversation: true,
         expectedTitle: expectedTitle,
         expectedTagComponent: expectedTagComponent);
-    }));
+    })));
+
+    test('stream message: multiple messages, different topics', () => runWithHttpClient(() => awaitFakeAsync((async) async {
+      await init();
+      final stream = eg.stream();
+      const topicA = 'topic A';
+      const topicB = 'topic B';
+      final message1 = eg.streamMessage(topic: topicA, stream: stream);
+      final data1 = messageFcmMessage(message1, streamName: stream.name);
+      final message2 = eg.streamMessage(topic: topicB, stream: stream);
+      final data2 = messageFcmMessage(message2, streamName: stream.name);
+      final message3 = eg.streamMessage(topic: topicA, stream: stream);
+      final data3 = messageFcmMessage(message3, streamName: stream.name);
+
+      await receiveFcmMessage(async, data1);
+      checkNotification(data1,
+        messageStyleMessages: [data1],
+        expectedIsGroupConversation: true,
+        expectedTitle: '#${stream.name} > $topicA',
+        expectedTagComponent: 'stream:${stream.streamId}:$topicA');
+
+      await receiveFcmMessage(async, data2);
+      checkNotification(data2,
+        messageStyleMessages: [data2],
+        expectedIsGroupConversation: true,
+        expectedTitle: '#${stream.name} > $topicB',
+        expectedTagComponent: 'stream:${stream.streamId}:$topicB');
 
-    test('stream message: stream name omitted', () => awaitFakeAsync((async) async {
+      await receiveFcmMessage(async, data3);
+      checkNotification(data3,
+        messageStyleMessages: [data1, data3],
+        expectedIsGroupConversation: true,
+        expectedTitle: '#${stream.name} > $topicA',
+        expectedTagComponent: 'stream:${stream.streamId}:$topicA');
+    })));
+
+    test('stream message: conversation stays same when stream is renamed', () => runWithHttpClient(() => awaitFakeAsync((async) async {
+      await init();
+      var stream = eg.stream(streamId: 1, name: 'Before');
+      const topic = 'topic';
+      final message1 = eg.streamMessage(topic: topic, stream: stream);
+      final data1 = messageFcmMessage(message1, streamName: stream.name);
+
+      await receiveFcmMessage(async, data1);
+      checkNotification(data1,
+        messageStyleMessages: [data1],
+        expectedIsGroupConversation: true,
+        expectedTitle: '#Before > $topic',
+        expectedTagComponent: 'stream:${stream.streamId}:$topic');
+
+      stream = eg.stream(streamId: 1, name: 'After');
+      final message2 = eg.streamMessage(topic: topic, stream: stream);
+      final data2 = messageFcmMessage(message2, streamName: stream.name);
+
+      await receiveFcmMessage(async, data2);
+      checkNotification(data2,
+        messageStyleMessages: [data1, data2],
+        expectedIsGroupConversation: true,
+        expectedTitle: '#After > $topic',
+        expectedTagComponent: 'stream:${stream.streamId}:$topic');
+    })));
+
+    test('stream message: stream name omitted', () => runWithHttpClient(() => awaitFakeAsync((async) async {
       await init();
       final stream = eg.stream();
       final message = eg.streamMessage(stream: stream);
@@ -263,18 +347,18 @@ void main() {
         expectedIsGroupConversation: true,
         expectedTitle: '#(unknown channel) > ${message.topic}',
         expectedTagComponent: 'stream:${message.streamId}:${message.topic}');
-    }));
+    })));
 
-    test('group DM: 3 users', () => awaitFakeAsync((async) async {
+    test('group DM: 3 users', () => runWithHttpClient(() => awaitFakeAsync((async) async {
       await init();
       final message = eg.dmMessage(from: eg.thirdUser, to: [eg.otherUser, eg.selfUser]);
       await checkNotifications(async, messageFcmMessage(message),
         expectedIsGroupConversation: true,
         expectedTitle: "${eg.thirdUser.fullName} to you and 1 other",
         expectedTagComponent: 'dm:${message.allRecipientIds.join(",")}');
-    }));
+    })));
 
-    test('group DM: more than 3 users', () => awaitFakeAsync((async) async {
+    test('group DM: more than 3 users', () => runWithHttpClient(() => awaitFakeAsync((async) async {
       await init();
       final message = eg.dmMessage(from: eg.thirdUser,
         to: [eg.otherUser, eg.selfUser, eg.fourthUser]);
@@ -282,25 +366,135 @@ void main() {
         expectedIsGroupConversation: true,
         expectedTitle: "${eg.thirdUser.fullName} to you and 2 others",
         expectedTagComponent: 'dm:${message.allRecipientIds.join(",")}');
-    }));
+    })));
 
-    test('1:1 DM', () => awaitFakeAsync((async) async {
+    test('group DM: title updates with latest sender', () => runWithHttpClient(() => awaitFakeAsync((async) async {
+      await init();
+      final message1 = eg.dmMessage(from: eg.otherUser, to: [eg.selfUser, eg.thirdUser]);
+      final data1 = messageFcmMessage(message1);
+      final message2 = eg.dmMessage(from: eg.thirdUser, to: [eg.selfUser, eg.otherUser]);
+      final data2 = messageFcmMessage(message2);
+
+      final expectedTagComponent = 'dm:${message1.allRecipientIds.join(",")}';
+
+      await receiveFcmMessage(async, data1);
+      checkNotification(data1,
+        messageStyleMessages: [data1],
+        expectedIsGroupConversation: true,
+        expectedTitle: "${eg.otherUser.fullName} to you and 1 other",
+        expectedTagComponent: expectedTagComponent);
+
+      await receiveFcmMessage(async, data2);
+      checkNotification(data2,
+        messageStyleMessages: [data1, data2],
+        expectedIsGroupConversation: true,
+        expectedTitle: "${eg.thirdUser.fullName} to you and 1 other",
+        expectedTagComponent: expectedTagComponent);
+    })));
+
+    test('1:1 DM', () => runWithHttpClient(() => awaitFakeAsync((async) async {
       await init();
       final message = eg.dmMessage(from: eg.otherUser, to: [eg.selfUser]);
       await checkNotifications(async, messageFcmMessage(message),
         expectedIsGroupConversation: false,
         expectedTitle: eg.otherUser.fullName,
         expectedTagComponent: 'dm:${message.allRecipientIds.join(",")}');
-    }));
+    })));
+
+    test('1:1 DM: title updates when sender name changes', () => runWithHttpClient(() => awaitFakeAsync((async) async {
+      await init();
+      final otherUser = eg.user(fullName: 'Before');
+      final message1 = eg.dmMessage(from: otherUser, to: [eg.selfUser]);
+      final data1 = messageFcmMessage(message1);
+
+      final expectedTagComponent = 'dm:${message1.allRecipientIds.join(",")}';
+
+      await receiveFcmMessage(async, data1);
+      checkNotification(data1,
+        messageStyleMessages: [data1],
+        expectedIsGroupConversation: false,
+        expectedTitle: 'Before',
+        expectedTagComponent: expectedTagComponent);
 
-    test('self-DM', () => awaitFakeAsync((async) async {
+      otherUser.fullName = 'After';
+      final message2 = eg.dmMessage(from: otherUser, to: [eg.selfUser]);
+      final data2 = messageFcmMessage(message2);
+
+      await receiveFcmMessage(async, data2);
+      checkNotification(data2,
+        messageStyleMessages: [data1, data2],
+        expectedIsGroupConversation: false,
+        expectedTitle: 'After',
+        expectedTagComponent: expectedTagComponent);
+    })));
+
+    test('1:1 DM: conversation stays same when sender email changes', () => runWithHttpClient(() => awaitFakeAsync((async) async {
+      await init();
+      final otherUser = eg.user(email: 'before@example.com');
+      final message1 = eg.dmMessage(from: otherUser, to: [eg.selfUser]);
+      final data1 = messageFcmMessage(message1);
+
+      final expectedTagComponent = 'dm:${message1.allRecipientIds.join(",")}';
+
+      await receiveFcmMessage(async, data1);
+      checkNotification(data1,
+        messageStyleMessages: [data1],
+        expectedIsGroupConversation: false,
+        expectedTitle: otherUser.fullName,
+        expectedTagComponent: expectedTagComponent);
+
+      otherUser.email = 'after@example.com';
+      final message2 = eg.dmMessage(from: otherUser, to: [eg.selfUser]);
+      final data2 = messageFcmMessage(message2);
+
+      await receiveFcmMessage(async, data2);
+      checkNotification(data2,
+        messageStyleMessages: [data1, data2],
+        expectedIsGroupConversation: false,
+        expectedTitle: otherUser.fullName,
+        expectedTagComponent: expectedTagComponent);
+    })));
+
+    test('1:1 DM: sender avatar loading fails, remote error', () => runWithHttpClient(
+      () => awaitFakeAsync((async) async {
+        await init();
+        final message = eg.dmMessage(from: eg.otherUser, to: [eg.selfUser]);
+        final data = messageFcmMessage(message);
+        await receiveFcmMessage(async, data);
+        checkNotification(data,
+          messageStyleMessages: [data],
+          expectedIsGroupConversation: false,
+          expectedTitle: eg.otherUser.fullName,
+          expectedTagComponent: 'dm:${message.allRecipientIds.join(",")}',
+          expectedIconBitmap: null); // Failed to fetch avatar photo
+      }),
+      httpClientFactory: () => makeFakeHttpClient(
+        response: http.Response.bytes([], HttpStatus.internalServerError))));
+
+    test('1:1 DM: sender avatar loading fails, local error', () => runWithHttpClient(
+      () => awaitFakeAsync((async) async {
+        await init();
+        final message = eg.dmMessage(from: eg.otherUser, to: [eg.selfUser]);
+        final data = messageFcmMessage(message);
+        await receiveFcmMessage(async, data);
+        checkNotification(data,
+          messageStyleMessages: [data],
+          expectedIsGroupConversation: false,
+          expectedTitle: eg.otherUser.fullName,
+          expectedTagComponent: 'dm:${message.allRecipientIds.join(",")}',
+          expectedIconBitmap: null); // Failed to fetch avatar photo
+      }),
+      httpClientFactory: () => makeFakeHttpClient(
+        exception: http.ClientException('Network failure'))));
+
+    test('self-DM', () => runWithHttpClient(() => awaitFakeAsync((async) async {
       await init();
       final message = eg.dmMessage(from: eg.selfUser, to: []);
       await checkNotifications(async, messageFcmMessage(message),
         expectedIsGroupConversation: false,
         expectedTitle: eg.selfUser.fullName,
         expectedTagComponent: 'dm:${message.allRecipientIds.join(",")}');
-    }));
+    })));
   });
 
   group('NotificationDisplayManager open', () {