diff --git a/src/api/friends/MessengerThread.test.ts b/src/api/friends/MessengerThread.test.ts
new file mode 100644
index 0000000..1045c50
--- /dev/null
+++ b/src/api/friends/MessengerThread.test.ts
@@ -0,0 +1,26 @@
+import { describe, expect, it } from 'vitest';
+import { MessengerFriend } from './MessengerFriend';
+import { MessengerThread } from './MessengerThread';
+import { MessengerThreadChat } from './MessengerThreadChat';
+
+const makeThread = (participantId: number): MessengerThread =>
+{
+    const friend = new MessengerFriend();
+    friend.id = participantId;
+    return new MessengerThread(friend);
+};
+
+describe('MessengerThread.setMessagesReadFromUser', () =>
+{
+    it('marks only the given user\'s messages as READ', () =>
+    {
+        const thread = makeThread(7);
+        const mine = thread.addMessage(100, 'a', 0, null, MessengerThreadChat.CHAT);
+        const theirs = thread.addMessage(7, 'b', 0, null, MessengerThreadChat.CHAT);
+
+        thread.setMessagesReadFromUser(100);
+
+        expect(mine.status).toBe(MessengerThreadChat.READ);
+        expect(theirs.status).toBe(MessengerThreadChat.SENT);
+    });
+});
diff --git a/src/api/friends/MessengerThread.ts b/src/api/friends/MessengerThread.ts
index a8cdb3c..d64ecdb 100644
--- a/src/api/friends/MessengerThread.ts
+++ b/src/api/friends/MessengerThread.ts
@@ -99,6 +99,16 @@ export class MessengerThread
         this._unreadCount = 0;
     }
 
+    public setMessagesReadFromUser(userId: number): void
+    {
+        for(const group of this._groups)
+        {
+            if(group.userId !== userId) continue;
+
+            for(const chat of group.chats) chat.setStatus(MessengerThreadChat.READ);
+        }
+    }
+
     public get threadId(): number
     {
         return this._threadId;
diff --git a/src/api/friends/MessengerThreadChat.test.ts b/src/api/friends/MessengerThreadChat.test.ts
index 53320c4..1a31e0d 100644
--- a/src/api/friends/MessengerThreadChat.test.ts
+++ b/src/api/friends/MessengerThreadChat.test.ts
@@ -27,3 +27,19 @@ describe('MessengerThreadChat.offlineDelivered', () =>
         expect(chat.offlineDelivered).toBe(false);
     });
 });
+
+describe('MessengerThreadChat status', () =>
+{
+    it('defaults to SENT', () =>
+    {
+        const chat = new MessengerThreadChat(5, 'hi', 0, null, MessengerThreadChat.CHAT);
+        expect(chat.status).toBe(MessengerThreadChat.SENT);
+    });
+
+    it('can be set to READ', () =>
+    {
+        const chat = new MessengerThreadChat(5, 'hi', 0, null, MessengerThreadChat.CHAT);
+        chat.setStatus(MessengerThreadChat.READ);
+        expect(chat.status).toBe(MessengerThreadChat.READ);
+    });
+});
diff --git a/src/api/friends/MessengerThreadChat.ts b/src/api/friends/MessengerThreadChat.ts
index c58b366..cbf5c9a 100644
--- a/src/api/friends/MessengerThreadChat.ts
+++ b/src/api/friends/MessengerThreadChat.ts
@@ -4,10 +4,13 @@ export class MessengerThreadChat
     public static ROOM_INVITE: number = 1;
     public static STATUS_NOTIFICATION: number = 2;
     public static SECURITY_NOTIFICATION: number = 3;
+    public static SENT: number = 0;
+    public static READ: number = 1;
     private static CHAT_ID: number = 0;
 
     private _id: number;
     private _type: number;
+    private _status: number = MessengerThreadChat.SENT;
     private _senderId: number;
     private _message: string;
     private _secondsSinceSent: number;
@@ -79,6 +82,16 @@ export class MessengerThreadChat
         return (this._type === MessengerThreadChat.CHAT) && (this._extraData === 'offline');
     }
 
+    public get status(): number
+    {
+        return this._status;
+    }
+
+    public setStatus(status: number): void
+    {
+        this._status = status;
+    }
+
     public get date(): Date
     {
         return this._date;