Forum Discussion

Chiyo's avatar
Chiyo
Copper Contributor
Jul 15, 2026

SystemError in Teams Group Chat for Copilot Studio Agent

Hi,

 

I'm seeing what appears to be a Teams group chat issue with a Copilot Studio agent created using the new Copilot Studio UI.

 

Scenario:

- Agent is published and available in Teams.

- Other users can chat with the agent successfully in 1:1 conversations.

- The agent does not use SharePoint knowledge, authenticated knowledge sources, or external actions/connectors.

- The agent works correctly for me in a Teams group chat.

- However, when other participants in the same group chat mention or interact with the agent, they receive:

 

"Sorry, an unexpected error occurred.

Reference code: MCS-4041

Error code: SystemError"

 

Additional details:

- The agent was created recently using the new Copilot Studio experience, so this does not appear to be related to an older migrated bot.

 

Has anyone experienced the same MCS-4041 / SystemError behavior in Teams group chats? Is this a known issue, limitation, or registration/caching bug between Copilot Studio and Teams?

 

Thanks!

copilot studio
microsoft 365 copilot

2 Replies

  • AurelienAtibard's avatar
    AurelienAtibard
    MCT
    Jul 17, 2026

    The error code MCS-4041 with SystemError means the failure is happening inside the Copilot Studio service itself, not in your agent logic. Microsoft has not published that specific code publicly, which basically confirms it is a server side issue that their engineers need to trace on their end.

    As for why it works for you in the group chat but not for the others, the most likely explanation is that when the new Copilot Studio UI publishes your agent to Teams, it generates an app manifest that does not always include the right permissions for other participants in a group chat to interact with it. You are fine because as the creator you have implicit access, but everyone else hits a wall when they try to send a message.

    A quick thing to try first: go into your agent's Teams channel settings in Copilot Studio, toggle off "Use this for group and meeting chat", save, toggle it back on, and republish. This forces a fresh manifest to be generated. You can also ask the affected users to type /debug clearstate in the chat, which clears any stuck conversation state on their end.

    If that does not fix it, the best move is to raise a support ticket through the Microsoft 365 admin center. Make sure to include the reference code MCS-4041, the conversation IDs from the affected users, and the exact times the errors happened. That reference code is what lets Microsoft support pull the right server side trace and actually get to the bottom of it rather than giving you the standard checklist.

  • SunitaTrivedi's avatar
    SunitaTrivedi
    MCT
    Jul 15, 2026

    Hi Chiyo​ 

    Thanks for sharing. It's interesting scenario.

    since the agent works in 1:1 chats for all user and also works in the group chat for you, this doesn't immediately point to a problem with the agent configuration itself. It may be worth checking whether the issue is related to how the agent is being resolved or authorized for other users within that specific Teams group chat.

    I would first check whether the behavior is reproducible in a new Teams group chat and whether it affects all users or only specific users. If the problem only occurs for other users in Teams group chats while 1:1 conversation continues to work, I would recommend opening a support ticket and including the MCS-4041 reference code.