Codex Desktop high CPU/GPU usage causes severe macOS slowdown on Intel MacBook Pro

Summary

Codex Desktop is causing severe sustained system slowdown on an Intel MacBook Pro 16". The slowdown is especially noticeable while using the Codex app UI. During the issue, Codex helper processes and WindowServer consume significant CPU/GPU, and macOS drops CPU_Speed_Limit heavily, making the whole system feel extremely laggy.

This looks related to existing reports such as #21326, #18567, #20435, and #18467.

Environment

• Codex Desktop: 26.519.41501 (CFBundleVersion 3044)
• Electron: 42.1.0 observed in Codex process/crashpad annotations
• macOS: 26.5 build 25F71
• Machine: MacBookPro16,1 Intel, 12 logical CPUs, 32 GB RAM
• Displays: built-in Retina display + 2 external Dell U2721DE displays, one rotated portrait
• Power: Apple 140 W USB-C power adapter, negotiated by macOS as 94 W
• Low Power Mode: off

Symptoms

• Codex Desktop UI becomes extremely slow.
• The entire macOS UI becomes sluggish, not only Codex.
• Fans run high and the machine feels very hot.
• WindowServer usage rises substantially.
• Codex keeps several processes active with sustained CPU/GPU use:
• Codex Helper --type=gpu-process
• Codex Helper (Renderer)
• codex app-server --analytics-default-enabled
• Minimizing/restarting the app reduces symptoms temporarily, but the issue returns.

Observed diagnostics

After a reboot, with memory pressure normal and no swap, Codex still becomes a major load contributor:

Codex app: 26.519.41501
macOS: 26.5 (25F71)
Machine: MacBookPro16,1
Power adapter: 94 W negotiated
Memory: no swap, no compression after reboot

Representative process sample:

WindowServer                         ~67% CPU
Codex Helper --type=gpu-process      ~32-60% CPU
codex app-server                     ~40-80% CPU
Codex Helper (Renderer)              ~40-64% CPU

Thermal/power sample during the issue:

CPU_Scheduler_Limit = 94
CPU_Available_CPUs  = 12
CPU_Speed_Limit     = 22

Earlier, before reboot, the system reached an even worse state:

load averages: 493 -> 553
~249 processes/threads in running state
CPU_Speed_Limit = 22
System Average frequency ~= 1000 MHz
Fan ~= 5325 rpm

powermetrics also showed the CPU frequency pinned very low while the GPU/display path was active:

System Average frequency as fraction of nominal: 38.46% (1000 MHz)
Cores Active: ~99%
GPU Active: ~70%
CPU Plimit: 35
GPU Plimit (Int): 15

Local Codex logs

Local Codex logs show repeated feature synchronization errors and renderer-loop warnings around startup/resume. Sanitized examples:

unsupported feature enablement `auth_elicitation`
Failed to sync experimental feature enablement
ResizeObserver loop completed with undelivered notifications.

There are also repeated app-server/config/thread hydration calls during startup/resume. I can provide fuller logs privately if helpful.

Notes

This does not appear to be caused by insufficient power. The adapter is correctly negotiated at 94 W. It also does not appear to be memory pressure immediately after reboot: swap and compressor are both zero after restart.

External displays likely amplify the problem because they keep the discrete GPU and WindowServer active, but the process samples point to Codex Desktop renderer/GPU/app-server activity as a key contributor.

Expected behavior

Codex Desktop should not keep sustained renderer/GPU/app-server CPU usage high enough to make macOS globally sluggish or trigger heavy CPU speed limiting during normal interactive use.

Current workaround

• Use Codex CLI from terminal for long sessions.
• Minimize or restart Codex Desktop when it starts consuming CPU/GPU.
• Disconnect external displays or close other GPU-heavy apps to reduce the amplification, but this is not a practical fix.