503 Service Unavailable: no healthy upstream when running codex CLI

What version of Codex CLI is running?

codex-cli 0.107.0

What subscription do you have?

ChatGPT Plus

Which model were you using?

gpt-5.3-codex

What platform is your computer?

Linux 6.17.0-14-generic x86_64 x86_64

What terminal emulator and version are you using (if applicable)?

Warp Terminal v0.2026.02.18.08.22.stable_02

What issue are you seeing?

Error output:
Unexpected status 503 Service Unavailable: no healthy upstream
url: https://chatgpt.com/backend-api/codex/responses**

The error appears immediately when the CLI sends the request.
Retrying later does not work.

What steps can reproduce the bug?

1. Open terminal
2. Run codex
3. CLI attempts to call the backend API
4. Request fails with HTTP 503

What is the expected behavior?

_No response_

Additional information

_No response_