Focus-stealing Windows Terminal windows from Claude/Codex: measured cause and Console Host mitigation

[cloopadoop]

Summary

On Windows 11, Claude Code/Codex console launches can be delegated to Windows Terminal even when the calling application did not intentionally open a terminal UI. The brokered WindowsTerminal.exe window can briefly become the foreground window and steal keyboard focus.

A window-event trace identified the sequence reliably and a reversible switch to Windows Console Host eliminated the observed Windows Terminal foreground transitions.

Environment

• Windows 11 Pro, build 26200
• Windows Terminal 1.24.11911.0
• Claude Desktop 1.25927.0.0
• Codex Desktop 26.730.7989.0
• Claude CLI involved in the trace: %USERPROFILE%\.local\bin\claude.exe

Measured symptom

A SetWinEventHook trace recorded three occurrences in about 18 seconds:

OBJECT_CREATE  WindowsTerminal.exe  CASCADIA_HOSTING_WINDOW_CLASS  "Windows Terminal"
FOREGROUND     WindowsTerminal.exe  CASCADIA_HOSTING_WINDOW_CLASS  "Windows Terminal"
OBJECT_SHOW    WindowsTerminal.exe  CASCADIA_HOSTING_WINDOW_CLASS
OBJECT_CREATE  claude.exe           PseudoConsoleWindow
OBJECT_SHOW    claude.exe           PseudoConsoleWindow

The same pattern repeated with new Windows Terminal top-level window handles. The window title later changed to claude or Terminal.

PowerToys “Always on Top” did not help because it controls z-order, not foreground keyboard focus.

Things that did not solve it

• Increasing ForegroundLockTimeout
• Hiding the window after EVENT_OBJECT_SHOW (it can still flash first)
• Windows Terminal "windowingBehavior": "useAnyExisting"
  • The existing window was reused, but Terminal restored/activated it, so focus behavior was effectively unchanged.
• Broad title matching such as “hide any window titled claude.exe”
  • This is unsafe: it can match brokered Terminal windows, Explorer dialogs, or legitimate Electron surfaces.

Working mitigation

Back up the current values under:

HKCU\Console\%%Startup
  DelegationConsole
  DelegationTerminal

Then select Windows Console Host by setting both values to:

{B23D10C0-E52E-411E-9D5B-C09FDF709C7D}

The original Windows Terminal values on this machine were:

DelegationConsole  = {2EACA947-7F5F-4CFA-BA87-8F7FBEEFBE69}
DelegationTerminal = {E12CFF52-A866-4C77-9A90-F570A7AA2C6B}

Microsoft documents these as the supported per-user default-terminal values:
https://learn.microsoft.com/en-us/windows/terminal/group-policy#default-terminal-application

Windows Terminal remains available when opened manually.

Guard safety boundary

After switching to Console Host, the window guard should only hide genuine console surfaces:

• ConsoleWindowClass
• PseudoConsoleWindow

It should additionally require proven Codex/Claude/editor ancestry. It should not hide arbitrary:

• CASCADIA_HOSTING_WINDOW_CLASS
• Chrome_WidgetWin_*
• Intermediate D3D Window
• Explorer #32770 dialogs
• windows based only on a title containing claude.exe

For launch paths that honor process-local PATH, GUI-subsystem wrappers for cmd.exe, powershell.exe, and pwsh.exe can forward to the real executables with CREATE_NO_WINDOW. The event-based guard remains a fallback for MSIX/app activation paths that bypass the wrapper environment.

The guard also needs a reliable login start mechanism. In this case it was not running after reboot, so a per-user Run entry for the GUI-subsystem guard executable was used (not a scheduled task).

Result

• Before: 3 Windows Terminal foreground transitions in 18 seconds
• After selecting Windows Console Host: 0 Windows Terminal foreground transitions during a 35-second observation window
• Claude and Codex did not need to be terminated for the registry change.
• No reboot was required for new console launches.
• User follow-up: “So far so good.”

Suggested upstream changes

1. Have status.ps1 report the default-terminal delegation mode prominently.
2. Offer an explicit, reversible Console Host mitigation with exact-value backup/restore.
3. Keep the guard console-class constrained; avoid process-name/title-only hiding.
4. Cover direct pwsh.exe as well as powershell.exe.
5. Provide a reliable, non-console login-start option for the native guard.

[cloopadoop]

lol if it's not obvious, Codex posted this on my behalf--I asked it if we should and it just did it haha. Thanks for the lead on fixing this problem--seems pretty stable on my end for both Claude and Codex after the adjustments detailed above.