diff --git a/lib/shared/messages/join-thread-message-spec.js b/lib/shared/messages/join-thread-message-spec.js
--- a/lib/shared/messages/join-thread-message-spec.js
+++ b/lib/shared/messages/join-thread-message-spec.js
@@ -15,6 +15,7 @@
 import type { NotifTexts } from '../../types/notif-types';
 import type { ThreadInfo } from '../../types/thread-types';
 import type { RelativeUserInfo } from '../../types/user-types';
+import { ET, type EntityText } from '../../utils/entity-text';
 import { values } from '../../utils/objects';
 import { pluralize } from '../../utils/text-utils';
 import {
@@ -27,7 +28,6 @@
   MessageSpec,
   MessageTitleParam,
   NotificationTextsParams,
-  RobotextParams,
 } from './message-spec';
 import { joinResult } from './utils';
 
@@ -94,15 +94,12 @@
     return { ...messageData, id };
   },
 
-  robotext(
-    messageInfo: JoinThreadMessageInfo,
-    creator: string,
-    params: RobotextParams,
-  ): string {
-    return (
-      `${creator} joined ` +
-      params.encodedThreadEntity(messageInfo.threadID, 'this chat')
-    );
+  robotext(messageInfo: JoinThreadMessageInfo): EntityText {
+    const creator = ET.user({ userInfo: messageInfo.creator });
+    return ET`${creator} joined ${ET.thread({
+      display: 'alwaysDisplayShortName',
+      threadID: messageInfo.threadID,
+    })}`;
   },
 
   notificationTexts(
diff --git a/lib/shared/messages/leave-thread-message-spec.js b/lib/shared/messages/leave-thread-message-spec.js
--- a/lib/shared/messages/leave-thread-message-spec.js
+++ b/lib/shared/messages/leave-thread-message-spec.js
@@ -15,6 +15,7 @@
 import type { NotifTexts } from '../../types/notif-types';
 import type { ThreadInfo } from '../../types/thread-types';
 import type { RelativeUserInfo } from '../../types/user-types';
+import { ET, type EntityText } from '../../utils/entity-text';
 import { values } from '../../utils/objects';
 import { pluralize } from '../../utils/text-utils';
 import {
@@ -27,7 +28,6 @@
   MessageSpec,
   MessageTitleParam,
   NotificationTextsParams,
-  RobotextParams,
 } from './message-spec';
 import { joinResult } from './utils';
 
@@ -94,15 +94,12 @@
     return { ...messageData, id };
   },
 
-  robotext(
-    messageInfo: LeaveThreadMessageInfo,
-    creator: string,
-    params: RobotextParams,
-  ): string {
-    return (
-      `${creator} left ` +
-      params.encodedThreadEntity(messageInfo.threadID, 'this chat')
-    );
+  robotext(messageInfo: LeaveThreadMessageInfo): EntityText {
+    const creator = ET.user({ userInfo: messageInfo.creator });
+    return ET`${creator} left ${ET.thread({
+      display: 'alwaysDisplayShortName',
+      threadID: messageInfo.threadID,
+    })}`;
   },
 
   notificationTexts(