[Windows] Owner-only ChatGPT Sites auth dead-ends in Codex in-app browser because WebAuthn is unavailable

Summary

Opening an owner-only ChatGPT Sites deployment from the Codex desktop in-app browser redirects to the OpenAI passkey challenge, but the in-app browser does not expose WebAuthn. The user is left unable to authenticate to their own Site.

Environment

• OS: Windows
• Codex desktop package: OpenAI.Codex_26.803.10989.0_x64
• Embedded Chromium/File version observed: 151.0.7922.76
• Observed: 2026-08-11
• Site access mode: owner-only (not workspace-only)
• Workspace SSO: not applicable/unknown for this owner-only flow
• In-app browser developer mode: not checked
• Chrome/Edge comparison: not tested in this report

Steps to reproduce

1. Publish a ChatGPT Site with access set to owner-only.
2. Open the Site from the Codex desktop in-app browser.
3. The flow redirects to https://auth.openai.com/auth_challenge/passkey.
4. Select Continue with passkey.
5. No cross-device QR code or usable passkey chooser appears.
6. Select Try another way.
7. The only alternatives shown are Passkey or security key and Recovery key; no email-verification fallback is available.

Technical observation

On the passkey challenge page inside the Codex in-app browser:

window.isSecureContext === true
typeof PublicKeyCredential === "undefined"

Consequently, WebAuthn capability checks such as PublicKeyCredential.getClientCapabilities and PublicKeyCredential.isConditionalMediationAvailable are unavailable.

Actual behavior

A user without a recovery key reaches an authentication dead end and cannot access their own owner-only ChatGPT Site from the Codex in-app browser.

Expected behavior

When WebAuthn is unavailable, one of the following should occur:

• the in-app browser supports WebAuthn, including the cross-device passkey QR flow;
• authentication opens in a passkey-capable system browser; or
• the challenge provides a supported fallback such as email verification.

Workaround

Changing the Site from owner-only to public removes the authentication requirement. Completing authentication in a passkey-capable external browser may also work, but that external-browser path was not tested as part of this report.

Impact

This can lock an owner out of an owner-only ChatGPT Sites deployment when entering through the Codex in-app browser. No credentials, recovery keys, or private authentication data are included in this issue.

Start by reproducing the owner-only flow in the Codex desktop in-app browser and inspect the auth_challenge/passkey page, including window.isSecureContext, PublicKeyCredential, and the available authentication alternatives. Compare the embedded browser behavior with the expected passkey-capable external-browser path. Done means the flow supports WebAuthn, opens in a capable system browser, or offers a supported fallback when WebAuthn is unavailable.