Teams Client Hangs with SPFX based solution built with 365 Agents SDK

[SimonDoy]

Describe the bug
When our SPFX based Teams app is opened up in a meeting app, the Teams client hangs and becomes completely unresponsive to mouse events. It is as if there is a hidden dialog waiting for an event. The issue occurs during load up (possible SSO?).

Looking at the logs there is no report of an issue, or try/catch log does not get called.

The issue does not seem to effect Teams running in the web browser.

To Reproduce
Steps to reproduce the behavior:

1. Create Meeting based Teams App with SPFX.
2. Open app in meeting tab.
3. Teams client hangs.

Expected behavior
I expect the app to continue loading and the Teams client not to hang. The resolution is to restart Teams from the System Tray Icon.

Screenshots

VS Code Extension Information (please complete the following information):

• OS:
  WindowsProductName WindowsVersion OsBuildNumber

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Windows 10 Pro 2009 26100

• Version Microsoft 365 Agents Toolkit VS Code Extension - 6.0.2

CLI Information (please complete the following information):

• OS: Windows 11
• Version teams cli ^3.0.4

Additional context
The application is used inside Microsoft Teams meetings it is available on the meeting stage.

[m365-agent-toolkit-assistant]

👋 Hi @SimonDoy,

Thank you for reporting this issue! We want to let you know that:

⏱️ Our team will personally review your issue
🎯 You can expect a response within 2 business days

✨ This is an AI-generated initial response
🤖 AI-Generated Preliminary Analysis:

There are known issues where SPFx-based Teams apps, especially those involving SSO or Graph, hang or cause the Teams desktop client to become unresponsive—often during the authentication/token retrieval process. Common causes include:

• Mismatched manifest validDomains or app origin for SSO (see related issue).
• Issues in the desktop Teams client with auth popups or hidden dialogs (e.g., the TeamsFx SDK or microsoftTeams.authentication.getAuthToken() sometimes hangs or fails to callback—reference).
• Manifest, token, or permission problems in SPFx solutions (see Stack Overflow for advanced troubleshooting).

Recommended steps:

1. Double-check your app manifest: Ensure validDomains includes your hosting domain and manifest fields match your app's deployment.
2. Try removing breakpoints or debug hooks in code where SSO is invoked, as these can halt auth popups.
3. Test the app in the latest Teams client and on web—if the issue persists only on desktop, it’s likely a client bug related to auth or context management.
4. If using custom SSO or SPFx context, ensure all Microsoft 365 Agent dependencies are up to date.
5. If the issue persists, please provide:
   • A snippet around SSO/token acquisition in your app
   • Your Teams app manifest validDomains
   • Confirmation whether your Teams client is the latest version

Let me know if you need targeted troubleshooting for your SSO code or manifest configuration!

✨We'd love your feedback! Please take a moment to fill out our survey.

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Note: This is an automated first response generated by AI. A human team member will review your issue and provide a more detailed response soon. We appreciate your patience!

[HuihuiWu-Microsoft]

Hi @SimonDoy I'd like to confirm with you on some items:
1> How did you create your solution? Did you scaffold with Microsoft 365 Agents Toolkit VSC extension or CLI?
2> Our template doesn't support meetings type yet, did you add it by yourself? Could you provide a sample source?
3> When did this start to happen? Have this app worked fine before in Teams client?

[SimonDoy]

@HuihuiWu-Microsoft
Thanks for coming back to us.
1> How did you create your solution? Did you scaffold with Microsoft 365 Agents Toolkit VSC extension or CLI?
This was with the Teams Toolkit VSC extension.
2> Our template doesn't support meetings type yet, did you add it by yourself? Could you provide a sample source?
Yes we created it ourselves. I will have a think about how we do this, it has our IP in it.
3> When did this start to happen? Have this app worked fine before in Teams client?
Yes it has been working fine for a number of months.

We have some additional information the issue seems to be occur when getting meeting transcriptions from Microsoft Teams Channels based meetings.

[HuihuiWu-Microsoft]

@SimonDoy This looks like a issue that's related to specific scenario. More info on how the app is working is needed to troubleshoot this problem. And actually SPFx project in meetings is out of our scope. You could raise feature request to support this.
Loop @summzhan for awareness