Unable to authenticate with MCP server when running in remote environment

What version of Codex is running?

0.79.0

What subscription do you have?

Own API key

Which model were you using?

gpt-5.1

What platform is your computer?

Linux 5.15.0-305.176.4.el8uek.x86_64 x86_64 x86_64

What issue are you seeing?

We are running the codex CLI tool in a remote codeserver/WebIDE environment. It is impossible to access OAuth protected MCP servers in this environment due to Codex using localhost as callback URI: the localhost will point to the machine that the user is on, not the machine that codex is running on.

What steps can reproduce the bug?

1. Setup a codeserver/WebIDE environment.
2. Define config for an OAuth protected MCP server in config.toml
3. try to authenticate with codex mcp login [NAME]
4. new tab opens in browser window
5. but OH NO: "This site can’t be reached"

What is the expected behavior?

New tab in browser should indicate successful authentication and when going back to codeserver tab, the MCP server authentication process in the terminal should be completed.

Additional information

_No response_