Windows: codex-code-mode-host opens a visible Windows Terminal window

What version of Codex CLI is running?

@openai/codex 0.147.0 (current npm latest at the time of filing).

Also observed while Codex Desktop 26.803.5235.0 was installed, but the visible window captured in this report identified the global npm package path, not the protected WindowsApps package path.

Subscription and model

This appears independent of subscription and model. It occurs when a local Code Mode tool call causes the standalone host process to be spawned.

Platform

• Windows 11 x64
• Version 10.0.26200, build 26200
• Windows Terminal configured as the default terminal application

What issue are you seeing?

When the standalone Code Mode host is started from the Windows npm package, Windows Terminal opens a visible window whose command is the packaged console executable:

%APPDATA%\npm\node_modules\@openai\codex\node_modules\@openai\codex-win32-x64\vendor\x86_64-pc-windows-msvc\bin\codex-code-mode-host.exe

The window can remain open and requires manual closing. A live process/window capture correlated the following components in the same creation-time cluster:

codex.exe
  -> codex-code-mode-host.exe
     -> conhost.exe

OpenConsole.exe / WindowsTerminal.exe -> visible terminal window

The packaged codex-code-mode-host.exe is PE subsystem 3 (IMAGE_SUBSYSTEM_WINDOWS_CUI).

The current source starts the host in codex-rs/code-mode/src/remote_session/connection.rs, Connection::spawn():

https://github.com/openai/codex/blob/3aae5d885bac39c1262491aa3fd100dfd8b3919f/codex-rs/code-mode/src/remote_session/connection.rs#L213-L224

The command configures Unix process groups, stdio pipes, and kill_on_drop, but has no Windows creation flag before .spawn():

let mut command = Command::new(host_program);
#[cfg(unix)]
command.process_group(0);
let mut child = command
    .stdin(Stdio::piped())
    .stdout(Stdio::piped())
    .stderr(Stdio::piped())
    .kill_on_drop(true)
    .spawn()?;

Because the parent is a GUI/headless process and the child is a Windows console-subsystem executable, Windows can allocate the configured default terminal for it.

Steps to reproduce

1. Install @openai/codex@0.147.0 globally on Windows.
2. Configure Windows Terminal as the default terminal application.
3. Start a Codex session that uses local Code Mode.
4. Invoke a local Code Mode tool so the standalone host is created.
5. Observe a visible Windows Terminal window whose command is codex-code-mode-host.exe.

This may be easier to reproduce after terminating an existing long-lived host so the next tool call must create a fresh one.

Expected behavior

codex-code-mode-host.exe should run as an internal background helper without creating a visible terminal window or stealing focus. Its stdin/stdout/stderr protocol and exit behavior must remain unchanged.

Root-cause hypothesis and validated mitigation

A local proof of concept placed a Windows GUI-subsystem shim at the expected host path and retained the signed vendor binary as codex-code-mode-host.real.exe. The shim:

• forwards all arguments;
• inherits stdin, stdout, and stderr;
• starts the real host with CREATE_NO_WINDOW;
• waits for it and returns the same exit code.

Validation results:

shim -> codex-code-mode-host.real.exe: confirmed
stdin/stdout round trip: passed
exit-code propagation: passed
real host startup and EOF shutdown: passed
visible host Terminal windows: 0

Before the mitigation, the visible Terminal window identified codex-code-mode-host.exe. After forcing a fresh host start through the shim, no matching visible window was created.

The binary-replacement shim is only a diagnostic mitigation and is not proposed as the product fix. It is update-fragile and changes the packaged executable identity.

Suggested product fix

In Connection::spawn(), apply CREATE_NO_WINDOW (or the equivalent supported Tokio/Windows process option) to the host command on Windows before .spawn(), while preserving the existing pipe and lifecycle behavior.

Conceptually:

let mut command = Command::new(host_program);

#[cfg(unix)]
command.process_group(0);

#[cfg(windows)]
command.creation_flags(CREATE_NO_WINDOW);

A Windows regression test should verify both protocol behavior and absence of an allocated visible console for a freshly spawned host.

Related but not duplicate

• #18984 tracks the command-safety PowerShell parser console flash.
• #20510 tracks the long-lived PowerShell helper spawned by background codex exec.
• #33254 tracks the Computer Use turn-ended notifier console window.

Those issues involve different child executables. This report is specifically about the standalone codex-code-mode-host.exe spawn boundary.