No ActivityHandler events raised for new messages in group chats with bot installed

Version

4.14.1

Describe the bug

I created a group chat and installed my bot into it. I can post proactively using a connectorclient, and I get events for participants being added and removed, but there are no activities raised for new messages in the chat thread.

To Reproduce

Using graph, create a group chat and add a bot like this:

                Chat c = new Chat
                {
                    ChatType = ChatType.Group,
                    Topic = "Group chat:" + Guid.NewGuid(),
                    Members = new ChatMembersCollectionPage()
                    {
                        new AadUserConversationMember
                        {
                            Roles = new List<String>()
                            {
                                "owner"
                            },
                            AdditionalData = new Dictionary<string, object>()
                            {
                                {"[e-mail]", "https://graph.microsoft.com/v1.0/users/"+ userID}
                            }
                        },
                        new AadUserConversationMember
                        {
                            Roles = new List<String>()
                            {
                                "owner"
                            },
                            AdditionalData = new Dictionary<string, object>()
                            {
                                {"[e-mail]", $"https://graph.microsoft.com/v1.0/users/" + AppId}
                            }
                        }
                    }
                };
                //requires TeamsAppInstallation.ReadWriteForChat
                Chat resp = await m_graphClientUser.Chats.Request().AddAsync(c);
                m_chatID = resp.Id;
                var teamsAppInstallation = new TeamsAppInstallation
                {
                    AdditionalData = new Dictionary<string, object>()
                {
                    {"[e-mail]", "https://graph.microsoft.com/v1.0/appCatalogs/teamsApps/" + catalogAppID}
                }
                };
                await m_graphClientUser.Chats[resp.Id].InstalledApps.Request().AddAsync(teamsAppInstallation);

Then, override OnTurnAsync in a bot that derives from ActivityHandler (I just left the default and set a breakpoint to inspect activities:

    public class ACSBot : ActivityHandler
    {
        public override Task OnTurnAsync(ITurnContext turnContext, CancellationToken cancellationToken = default)
        {
            return base.OnTurnAsync(turnContext, cancellationToken);
        }

Note if you add/remove participants from the chat in Teams, OnTurnAsync (and the appropriate other events) will fire. Reactions to bot messages also fire events. If another user sends a message to the chat thread though, nothing is fired on the bot, so the bot can’t react to the new messages like it would in a 1:1 chat.

Expected behavior

I’d expect to get message activity for any other user message in the chat.

[chrisbardon]

@stevkan - it seems like this is by design, so at this point the only other assistance would be to amend that design so that bots installed to a group chat with chat.readwrite should get notified of all messages in the chat as they happen. It’s possible to do this with a change notification subscription, but it’s harder than it should be (I actually put together a blog post describing how to do this here)

[compulim]

Copying from https://docs.microsoft.com/en-us/learn/modules/msteams-conversation-bots/2-conversation-bots:

Group chats are non-threaded conversations between three or more people. They tend to have fewer members than a channel and are more transient. Similar to a channel, your bot will only have access to messages where it’s @mentioned directly.

Scenarios that work well in a channel will usually work as well in a group chat.

I think this is by-design and is a feature request: Bot on Teams should react/receive messages without explicit at-mentions.