[BUG] - .NET SDK doesn't catch error "session was not created with authentication info or custom provider"

[dstamand-msft]

In the .NET SDK, when enabling the logs in the Copilot CLI, the logs show

2026-02-16T10:41:19.068Z [ERROR] Error during session send 06fe7049-10b3-4fdc-a92c-7c4c453067c1: Error: Session was not created with authentication info or custom provider

That error is not being resurfaced into the SDK which cannot be handled gracefully. The session thus hangs forever.
Granted, one could add mechanism to check for long-running requests and stop, but this error should be resurfaced for users to take action.

SDK Version: 0.1.23

[github-actions]

Thanks for reporting this issue, @dstamand-msft!

I've labeled this as a bug affecting the sdk/dotnet. You're correct that this error should be surfaced to the SDK rather than leaving the session hanging. The authentication error from the CLI needs proper error handling and propagation to allow applications to handle it gracefully.

This will be reviewed by the team.

AI generated by Issue Triage Agent

[SteveSandersonMS]

Thanks for the details! A couple of questions to help narrow this down:

1. Are you using the CliUrl option to connect to a separately-running CLI server, or letting the SDK spawn the CLI process itself (the default)? If you're connecting to an external CLI server, the GithubToken option won't work - the token needs to be provided when starting the CLI server itself.
2. Check the environment variable name: You mentioned GITHUB_COPILOT_TOKEN, but the supported variable is actually COPILOT_GITHUB_TOKEN (words reversed).

Could you try with the correct env var name and let me know if that helps?