Windows Codex login redirects to add-phone and rejects existing phone number

Description

I cannot log in to Codex for Windows.

After signing in with my existing ChatGPT account, I am redirected to:

https://auth.openai.com/add-phone

When I enter my existing phone number, I get this error:

"이미 사용 중인 전화번호입니다. 다른 전화번호를 사용하세요."

The same issue occurs with both the Codex Windows app and Codex CLI.

Environment

• Windows 11 Professional
• Codex Windows app: 26.908.9136.0
• Codex CLI: 0.154.0

Reproduction

1. Open Codex for Windows.
2. Click "Continue with login".
3. Sign in with my existing ChatGPT account.
4. The browser redirects to the add-phone page.
5. Enter my existing phone number.
6. The phone number is rejected as already being in use.

I also tested InPrivate browsing, using only one Google account, reinstalling Codex, codex login, and codex login --device-auth. The same issue occurs every time.

Login log

The login log only contains:

2026-09-15T07:48:43.318669Z INFO codex_cli::login: starting browser login flow
2026-09-15T07:51:33.626087Z INFO codex_cli::login: starting device code login flow

Please investigate why my account is being redirected to the add-phone flow and why my existing phone number is rejected.

codex-login.log

codex-login.log

codex-login.log

codex-login.log

Start with the reported Codex CLI login entry point, codex_cli::login, and reproduce both browser and device-auth flows on Windows 11 using the listed versions. Review the attached codex-login.log files and trace where authentication hands off to the add-phone page; done means identifying whether the redirect and existing-number rejection are caused by Codex or the external authentication service, with a confirmed resolution or clear escalation.