Windows Terminal: Japanese IME becomes stuck in alphanumeric mode in Codex CLI; opening another tab restores it

What version of Codex CLI is running?

codex-cli 0.145.0

What subscription do you have?

ChatGPT subscription via ChatGPT sign-in (the exact tier is not exposed by the CLI).

Which model were you using?

gpt-5.6-sol

What platform is your computer?

Microsoft Windows NT 10.0.26200.0 x64 (Windows 11, Japanese locale)

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

• Windows Terminal 1.24.11911.0
• PowerShell 7.6.3
• Native Windows / ConPTY
• No terminal multiplexer

Codex doctor report

Sanitized relevant fields:

{
  "overallStatus": "ok",
  "codexVersion": "0.145.0",
  "runtime": "windows-x86_64",
  "os": "Windows 10.0.26200 (Windows 11 Professional) [64-bit]",
  "osLanguage": "ja-JP",
  "consoleInputCodePage": 932,
  "consoleOutputCodePage": 65001,
  "installation": "ok",
  "configLoad": "ok",
  "stateDbIntegrity": "ok"
}

What issue are you seeing?

Intermittently, the Codex CLI tab becomes unable to switch the Microsoft Japanese IME from alphanumeric mode (A) to Hiragana mode (あ).

The CLI otherwise remains responsive and half-width alphanumeric text can still be typed. The failure is limited to Japanese IME activation/composition in the Codex tab.

At the same time:

• Japanese input continues to work normally in Notepad.
• ctfmon.exe and TextInputHost.exe remain running.
• No system-wide IME failure is observed.

Opening a new Windows Terminal tab and immediately returning to the original Codex tab restores Japanese input. Codex does not need to be restarted and the thread does not need to be resumed.

This suggests that the Codex TUI tab's IME/TSF focus or ConPTY input context becomes desynchronized and is refreshed by the terminal tab-focus cycle.

What steps can reproduce the bug?

The exact trigger is intermittent, but the observed sequence is:

1. On Japanese Windows 11, open Windows Terminal with PowerShell.
2. Start Codex CLI and use it normally.
3. After some time, attempt to switch Microsoft Japanese IME from A to あ in the Codex composer.
4. Observe that it remains in A mode. Half-width alphanumeric input still works.
5. Switch to Notepad and verify that あ mode and Japanese composition work normally there.
6. Return to Windows Terminal. Create another terminal tab.
7. Immediately return to the original Codex tab.
8. Observe that A to あ switching and Japanese input work again without restarting Codex.

What is the expected behavior?

The Codex CLI composer should continue to accept Microsoft Japanese IME mode switches and composition events for the lifetime of the terminal tab. Switching terminal tabs should not be required to restore Japanese input.

Additional information

The CLI is otherwise stable; this appears specific to Japanese IME activation rather than general keyboard input, process responsiveness, authentication, networking, or state integrity.

Possibly related: #35438 reports Codex CLI 0.145.0 on Windows build 26200 losing IME-produced characters and exposing cursor/redraw issues during active turns. This report differs because the Japanese IME becomes stuck in alphanumeric mode only in the Codex tab, while another Windows Terminal tab refreshes the input state and restores it.