Copilot CLI exits immediately with no visible error when HTTP_PROXY/HTTPS_PROXY point to an invalid local proxy

[Gumbraise]

Describe the bug

When launching copilot interactively on Windows, the UI opens briefly, clears/returns to the top of the terminal, and exits without showing any error message.

The root trigger appears to be invalid proxy environment variables. In my case, HTTP_PROXY, HTTPS_PROXY, and ALL_PROXY were set to http://127.0.0.1:9. Instead of displaying a clear network/proxy error, the CLI silently exits.

Affected version

GitHub Copilot CLI 1.0.10

Steps to reproduce the behavior

1. On Windows, set invalid proxy variables in the shell:
   $env:HTTP_PROXY='http://127.0.0.1:9'
   $env:HTTPS_PROXY='http://127.0.0.1:9'
   $env:ALL_PROXY='http://127.0.0.1:9'
   $env:NO_PROXY='localhost,127.0.0.1,::1'

2. Launch Copilot CLI interactively:
   copilot

3. Observe that the terminal switches briefly, then returns to the top and exits with no visible error.

4. copilot --help and copilot --version still work:
   copilot --version
   Output:
   GitHub Copilot CLI 1.0.10.
   Run 'copilot update' to check for updates.

5. Check the Copilot log file. It shows a proxy-related fetch failure:
   [INFO] Proxy configuration: HTTP_PROXY=http://127.0.0.1:9, HTTPS_PROXY=http://127.0.0.1:9, NO_PROXY=localhost,127.0.0.1,::1
   [ERROR] Error fetching copilot user: TypeError: fetch failed
   [ERROR] Unhandled Rejection: fetch failed

6. If I clear the proxy variables first, the silent-exit behavior no longer occurs:
   Remove-Item Env:HTTP_PROXY,Env:HTTPS_PROXY,Env:ALL_PROXY,Env:NO_PROXY,Env:GIT_HTTP_PROXY,Env:GIT_HTTPS_PROXY,Env:http_proxy,Env:https_proxy,Env:all_proxy,Env:no_proxy -ErrorAction SilentlyContinuecopilot --no-alt-screen

Expected behavior

If Copilot CLI cannot reach GitHub because of invalid proxy settings, it should show a clear and actionable error message in the terminal, such as a proxy/network configuration failure.

It should not silently exit after briefly taking over the terminal screen.

Additional context

Environment:

• Windows
• Installed with winget
• Command resolves to the WinGet link under %LOCALAPPDATA%\Microsoft\WinGet\Links\copilot.exe

Notes:

• help and --version work normally
• The failure happens during startup/auth/user fetch
• This looks like an error-handling issue in interactive mode rather than an installation issue
• A more user-friendly error would make this much easier to diagnose

[Gumbraise]

I was able to get it working again by re-authenticating with:

copilot login

After logging in again, copilot started working normally.

It would be helpful if the CLI surfaced an explicit authentication error and suggested running copilot login instead of silently exiting.