Codex App visible window causes sustained high GPU/WindowServer CPU and MacBook Air extreme heat

What version of the Codex App are you using (From “About Codex” dialog)?

26.623.42026

What subscription do you have?

Pro

What platform is your computer?

Darwin 25.5.0 arm64 arm

What issue are you seeing?

The Codex macOS app makes my MacBook Air become very hot during normal use. I investigated this from within an active Codex session and found that the load is tied to the visible Codex desktop window, not to the CLI/app-server doing work.

Observed on macOS 26.5.1, Apple M4 MacBook Air, Codex App 26.623.42026.

While the Codex window was visible, process snapshots repeatedly showed high CPU in the Codex GPU/renderer path and WindowServer, for example:

• WindowServer: ~39-54% CPU
• Codex GPU process (Codex (Service) --type=gpu-process): ~35-42% CPU
• Codex renderer: ~11-31% CPU
• Codex app-server: usually low when not actively handling tool work

Sampling the hot processes showed the app-server mostly idle in Tokio/kevent/condition waits, while the hot GPU/renderer samples were in Chromium/Electron display/compositor paths and macOS graphics plumbing: CoreAnimation, IOSurface, ColorSync, Metal, AGX GPU driver calls, and compositor threads.

A hide/show test was especially clear:

• Before hiding Codex: WindowServer ~45%, Codex GPU ~42%, Codex renderer ~31%
• After hiding Codex with Cmd-H / setting the app invisible: WindowServer ~3.5%, Codex renderer ~0.6%, Codex GPU dropped out of the hot list
• After restoring Codex: WindowServer ~39%, Codex GPU ~38%, renderer ~13%

So the issue appears to be a visible-window repaint/compositing loop in the Codex desktop app. The background agent/session can continue without the heat spike when the Codex window is hidden.

I initially suspected my external display because I sometimes use a 3840x1620 @ 180 Hz external monitor, but I can reproduce the same heating on the MacBook Air by itself with no external display connected.

What steps can reproduce the bug?

1. Open Codex App on macOS.
2. Start or resume a normal Codex chat/session.
3. Leave the Codex window visible while the session is active.
4. Watch Activity Monitor or run ps -axo pid,ppid,%cpu,%mem,rss,etime,command | sort -k3 -nr.
5. Observe sustained high CPU in WindowServer plus Codex GPU/renderer processes.
6. Hide the Codex app window.
7. Observe CPU drop sharply.
8. Restore/show the Codex app window.
9. Observe CPU rise again.

In my case, hiding the window reduced WindowServer from ~45% to ~3.5% and the Codex renderer from ~31% to ~0.6%. Restoring the window brought the load back immediately.

Profiling performed with sample showed the app-server was not the main source of work; the hot path was the visible UI/compositor/graphics path.

What is the expected behavior?

The Codex App window should not cause sustained high WindowServer/GPU/renderer CPU usage while visible during normal chat/session use. CPU/GPU activity should drop when the UI is idle, similar to what happens when the app is hidden.

Additional information

I checked for the syspolicyd pattern locally and did not see syspolicyd/trustd as the source of the load. I also checked thermal status with pmset -g therm; macOS had not recorded a thermal or performance warning at the time of testing, but the machine physically becomes hot during Codex use.

There were some stale/old Codex helper processes from previous sessions, but they were mostly idle and did not explain the high heat. The decisive signal was that hiding the visible Codex window immediately reduced WindowServer/Codex renderer/GPU load, and showing it brought the load back.