GitHub Copilot CLI error with Codex 5.3

[tuukkatoivonen-nestai]

Describe the bug

I'm getting server error when using Codex 5.3, tested with GitHub Copilot CLI v0.0.420. Other models do work.

Affected version

GitHub Copilot CLI 0.0.420.

Steps to reproduce the behavior

1. Start GitHub Copilot CLI
2. Select model Codex 5.3
3. Enter a prompt (any prompt)

Expected behavior

The LLM/AI should write a response. Instead of it, I get "server error".

Additional context

Linux x86

[christiansparre]

We are also seeing this on our GitHub Enterprise accounts. Both in the CLI, Visual Studio and on web.

On my personal account gpt-5.3-codex works fine