[BUG] Can't switch reasoning effort to Xhigh in Codex app

What version of Codex is running?

Codex app 26.406.31014

What subscription do you have?

Not specified

Which model were you using?

GPT-5.4

What platform is your computer?

macOS Tahoe v26.4

What issue are you seeing?

In the Codex desktop app, I can't switch the reasoning effort from High to Xhigh. When I use the reasoning effort dropdown and try to select Xhigh, the setting stays on High.

What steps can reproduce the bug?

1. Open the Codex desktop app.
2. Select the GPT-5.4 model.
3. Open the reasoning effort dropdown.
4. Try to change the reasoning effort from High to Xhigh.
5. Notice that the selection remains on High instead of switching to Xhigh.

What is the expected behavior?

Selecting Xhigh in the reasoning effort dropdown should update the setting to Xhigh and use that reasoning effort for subsequent prompts.

Additional information

This seems to happen specifically when using the dropdown to toggle between reasoning efforts. The desktop app build is 26.406.31014, and the bundled CLI reports codex-cli 0.118.0.