[BUG] Unable to disable fast mode in desktop app after activating it

What version of Codex is running?

codex-cli 0.106.0

What subscription do you have?

Pro

Which model were you using?

gpt-5.4

What platform is your computer?

macOS Tahoe v26.3.1

What issue are you seeing?

After activating fast mode in the Codex desktop app on macOS, there is no way to disable it. The toggle appears to be one-directional — once fast mode is turned on, it stays on for the session with no option to revert back to standard mode.

What steps can reproduce the bug?

1. Open the Codex desktop app on macOS
2. Start a session with gpt-5.4
3. Activate fast mode (e.g., via /fast)
4. Attempt to disable fast mode — no option available to do so

What is the expected behavior?

Fast mode should be togglable — running /fast again (or an equivalent command) should disable fast mode and return to standard reasoning.

Additional information

_No response_