Proxy authentication conflict between GitHub Copilot and GitHub CLI

[rchard]

Describe the bug

Describe the bug:
There is a conflict in how the http_proxy environment variable is interpreted by GitHub Copilot and GitHub CLI during authentication.

GitHub Copilot requires the proxy to be set as:
http_proxy=http://myproxy.me.com:911
GitHub CLI requires the proxy to be set without the scheme:
http_proxy=myproxy.me.com:911
However, setting the variable in either form causes one of the tools to fail. This makes it impossible to use GitHub Copilot and GitHub CLI with proxy authentication at the same time.

To reproduce:

Set up http_proxy environment variable for your proxy.
Try to authenticate using GitHub CLI and Copilot.
Observe that one fails depending on the format.
Expected behavior:
Both GitHub Copilot and GitHub CLI should support a compatible proxy environment variable format, or handle both formats gracefully.

System information:

Proxy: myproxy.me.com:911
OS: Windows 11
GitHub CLI version: 2.83.1 (2025-11-13)
Copilot version: 0.0.365 (76d0881)
Additional context:
A unified or flexible parsing for proxy environment variables is needed to avoid setup conflicts for users.

Affected version

0.0.365 Commit: 76d0881

Steps to reproduce the behavior

No response

Expected behavior

No response

Additional context

No response