Windows App causes elevated Desktop Window Manager (dwm.exe) GPU usage when visible on multi-monitor high-refresh setup

[meAloex]

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

26.305.950.0

What subscription do you have?

Pro

What platform is your computer?

Microsoft Windows NT 10.0.26200.0 x64

What issue are you seeing?

When the Codex desktop app window is visible on screen, Desktop Window Manager (dwm.exe) GPU usage rises significantly on Windows.

On my system:

• if Codex is visible, dwm.exe rises to roughly ~8-10% GPU (sometimes higher in Task Manager snapshots), and the Codex app also uses GPU

• if I minimize Codex (without closing it), both Codex GPU usage and dwm.exe GPU usage drop sharply, close to zero

This strongly suggests the problem is related to visible window rendering / composition rather than background work, network activity, or the process merely being open. All displays are now connected to the NVIDIA GPU, and this Codex-visible-window behavior still reproduces.

20260306-1455-14.8181842.mp4

Sorry the clip is only ~5 seconds because of the 10 MB upload limit, but I hope it is enough to show how sharply GPU/DWM usage drops when Codex is minimized

What steps can reproduce the bug?

1. Launch the Codex desktop app on Windows
2. Keep Task Manager visible and sort by GPU usage
3. Leave Codex open and visible on screen
4. Observe that both Codex and Desktop Window Manager use noticeable GPU
5. Minimize Codex without closing it
6. Observe that GPU usage for both Codex and 'dwm.exe' drops sharply, close to zero

This appears to depend on the Codex window being visible rather than the app simply running in the background

What is the expected behavior?

No response

Additional information

System:

• Laptop: Lenovo model 83F5 (Legion-class system)
• Codex package: OpenAI.Codex_26.305.950.0_x64__2p2nqsd0c76g0
• Windows: 25H2, build 26200.7840
• NVIDIA GPU: GeForce RTX 5080 Laptop GPU
  • Driver: 32.0.15.9571
  • Driver date: 2026-02-27
• Intel GPU: Intel(R) Graphics
  • Driver: 32.0.101.8243
  • Driver date: 2026-01-26

Display / graphics configuration:

• All three displays are now connected to NVIDIA according to Windows Advanced Display
• Internal panel: ATNA60HU01-0, 2560x1600 @ 240 Hz
• External displays: 2560x1600 @ 144 Hz + 2560x1600 @ 144 Hz
• Lenovo graphics mode: Discrete
• Optimizations for windowed games: On
• Variable refresh rate: On
• Hardware-accelerated GPU scheduling: Off
• MPO workaround had already been applied on this machine (OverlayTestMode=5)

[novovictus]

I built a small Windows/NVIDIA telemetry tool called WTG for this kind of debugging: figuring out whether a workload is really using the NVIDIA GPU, or whether Windows Task Manager is just not showing the relevant activity clearly.

Project page:
https://ninja-neer.net/

GitHub:
https://github.com/novovictus/WTG

Basic test:

.\wtg.exe --watch 250

Run that side-by-side with the workload and compare Task Manager, VRAM movement, GPU utilization, and power draw.

If Task Manager is flat but WTG shows VRAM/power/utilization movement, the GPU may be active and Task Manager may be misleading. If WTG is also flat, the workload probably is not reaching the NVIDIA GPU.

Happy to help interpret output if anyone posts a sample or emails wtg@ninja-neer.net.

[0x000005]

好像还会导致拖动所有窗口的时候有延迟