Certificate used to sign teams app https connection is invalid

[kale1d0code]

Describe the bug
teams refuses to load teams app because the certificate vscode generates for the teams app is not trusted by Microsoft teams
currently if someone wants to test a Microsoft teams app they would need to do so within a webbrowser that skips SSL verification.

To Reproduce
Steps to reproduce the behaviour:

1. Create teams app
2. attempt to test in Microsoft teams

Expected behaviour
to be able to test the app within Microsoft teams without skipping SSL verification

Screenshots
If applicable, add screenshots to help explain your problem.

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

• OS: Ubuntu 24.04.2 LTS
• Version 6.4.2

CLI Information (please complete the following information):

• OS: Ubuntu 24.04.2 LTS
• Version ???

Additional context
Add any other context about the problem here.

[m365-agent-toolkit-assistant]

👋 Hi @kale1d0code,

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:

This is a common issue in local development—Teams refuses connections due to an untrusted/self-signed HTTPS certificate generated by the VS Code extension.

Actionable Workarounds:

1. Bypass certificate warning:
   Open the Teams app URL directly in your browser (e.g., https://localhost:port), accept the certificate warning ("Proceed anyway"). This trusts the certificate and allows Teams to load your app.

2. Trust certificates:
   On Ubuntu, run:

   dotnet dev-certs https --trust

   If using Node.js, manually add the .fx/certificate/localhost.crt file to your OS's trusted certificates.

3. VS Code settings:
   Go to Settings → Application → Proxy, and uncheck "Http: System Certificates" and "Proxy Strict SSL". Reload VS Code.

4. Debug browser:
   Try running/debugging in a different browser (Edge, Chrome) from the "Run and Debug" panel.

References:

• Teams Toolkit SSL Certificate Issues
• Linux Certificate Troubleshooting

If you still face issues, provide error logs and exact reproduction steps.

✨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!

[qinzhouxu]

Hi @kale1d0code, please refer to the answer in #14857 and have a try.
Feel free to let us know if the solution works.

[wh-alice]

Close the issue. Let us know if workaround mentioned by Qinzhou