Codex Windows 26.623.70822 consumes CPU continuously while idle in system tray and appears to trigger Defender activity

Codex Windows 26.623.70822 consumes CPU continuously while idle in system tray and appears to trigger Defender activity

Hello OpenAI / Codex team,

I am reporting a performance issue with the Codex Windows desktop application. Codex appears to consume CPU continuously while idle, including when minimized to the Windows system tray and no task is running. Microsoft Defender also appears to become more active while Codex is open, which amplifies the total CPU load and causes sustained fan noise.

Summary

Codex for Windows consumes around 1-3% total CPU continuously while idle, even immediately after startup, with:

• no user-initiated task running;
• no active prompt;
• no visible agent/tool activity;
• the application minimized to the Windows system tray.

This causes a practical usability issue on my laptop: fans ramp up and remain noisy even though Codex is only open in the background.

Why this may be distinct from related reports

I found related high-CPU / idle reports, but this case may add useful signal because the issue:

• reproduces immediately after launching Codex, before any task is started;
• persists even when Codex is minimized to the Windows system tray;
• still reproduces after temporarily disabling Microsoft Defender real-time protection;
• appears to correlate with increased Defender CPU activity when real-time protection is enabled.

Related issues that look adjacent:

• <https://github.com/openai/codex/issues/29281> - Windows 11 Codex idle fan noise / GPU/CPU activity.
• <https://github.com/openai/codex/issues/30021> - Windows desktop burns a CPU core while visible and idle.
• <https://github.com/openai/codex/issues/30527> - Windows / Defender activity while Codex is open.
• <https://github.com/openai/codex/issues/29499> - WMI Provider Host CPU activity after launching Codex.
• <https://github.com/openai/codex/issues/20567> - repeated background Git process spawning.

Codex version

Visible Codex app version:

• Codex 26.623.70822
• Released: June 29, 2026

Process observed consuming CPU:

C:\Program Files\WindowsApps\OpenAI.Codex_26.623.9142.0_x64__2p2nqsd0c76g0\app\Codex.exe

Another Codex-related process observed in Microsoft Defender performance data:

C:\Program Files\WindowsApps\OpenAI.Codex_26.623.9142.0_x64__2p2nqsd0c76g0\app\resources\codex.exe

Reproduction steps

1. Start the Codex Windows desktop application.
2. Do not start any Codex task.
3. Do not submit a prompt.
4. Do not interact with the application.
5. Minimize Codex to the Windows system tray.
6. Monitor CPU usage.

The CPU usage starts immediately after launching Codex and continues while the app is idle in the system tray.

Expected behavior

When Codex is open but idle, with no running task and no user interaction, CPU usage should be close to zero except for occasional short spikes.

Minimizing the app to the Windows system tray should make the app effectively idle and should not cause sustained fan noise.

Actual behavior

Codex continuously consumes CPU while idle.

Measured with the app open, minimized to the system tray, just after startup, with no user activity and no task requested:

• Measurement duration: 132.5 seconds
• Average Codex CPU usage: 1.45% total CPU
• Minimum instantaneous Codex CPU usage: 0.78% total CPU
• Maximum instantaneous Codex CPU usage: 2.14% total CPU
• Average number of Codex-related processes: 12

This behavior persists even when Codex is minimized to the system tray.

I also tested temporarily disabling Microsoft Defender real-time protection. Codex still continued to consume around 1-3% CPU while idle, which suggests that Codex itself has sustained background CPU activity.

Microsoft Defender interaction

When Codex is open, Microsoft Defender's MsMpEng.exe also appears to consume significantly more CPU, typically around 5-9% according to Windows Task Manager estimates.

When Codex is closed, MsMpEng.exe quickly returns to much lower CPU usage.

I was not able to obtain a reliable average CPU measurement for MsMpEng.exe, as PowerShell-based process CPU measurements did not work correctly for this protected Windows process. However, the behavior is clearly visible in Windows Task Manager.

A Microsoft Defender Performance Report showed Defender activity related to several Codex files and components, including:

• Codex.exe
• resources\codex.exe
• local Codex Node runtime:
• %LOCALAPPDATA%\OpenAI\Codex\runtimes\cua_node\...\bin\node_repl.exe
• Codex session/cache files:
• %USERPROFILE%\.codex\session_index.jsonl
• %USERPROFILE%\.codex\models_cache.json
• %USERPROFILE%\.codex\cache\...
• Codex WebView / local cache files:
• %LOCALAPPDATA%\Packages\OpenAI.Codex_2p2nqsd0c76g0\LocalCache\Roaming\Codex\...
• temporary JavaScript and CSS files under %LOCALAPPDATA%\Temp

I also tested adding a targeted Microsoft Defender exclusion for:

%LOCALAPPDATA%\OpenAI\Codex\runtimes

The exclusion was correctly applied, but it did not reduce either Codex CPU usage or Microsoft Defender CPU usage. I then removed the exclusion.

This makes me think the root cause is not simply Defender scanning one specific runtime file. It looks more like Codex has continuous idle background activity, and Defender reacts to that activity.

User impact

The issue is very noticeable in day-to-day use:

• the laptop fans ramp up and remain noisy;
• the machine becomes unpleasant to use while Codex is merely open;
• this happens even when Codex is minimized to the system tray;
• this happens immediately after launching Codex, before any task is started;
• the issue makes it impractical to keep Codex open in the background.

System information

Relevant PC information:

• Device type: laptop / Windows PC
• CPU: 11th Gen Intel(R) Core(TM) i5-1145G7 @ 2.60GHz
• RAM: 16 GB
• GPU: Intel(R) Iris(R) Xe Graphics
• System type: 64-bit operating system, x64-based processor
• OS edition: Windows 11 Professional
• Windows version: 25H2
• OS build: 26200.8655
• Windows Feature Experience Pack: 1000.26100.315.0
• Storage usage: 232 GB used out of 238 GB

Additional diagnostic notes

The issue appears immediately after starting Codex and does not require opening a project or launching a task.

The main problem seems to be sustained idle CPU usage from Codex itself. Microsoft Defender appears to amplify the overall CPU load, but Codex still consumes CPU even when Defender real-time protection is temporarily disabled.

Potential areas to investigate:

• idle-loop or polling behavior in the Windows desktop app;
• WebView / renderer activity while idle or minimized to tray;
• background filesystem or cache writes that may trigger Defender scanning;
• telemetry or session-index updates while idle;
• local runtime or app-server processes that remain active without a task;
• repeated project/workspace discovery, Git checks, or process enumeration.

Could you please investigate whether Codex for Windows has an idle-loop, polling, WebView, telemetry, runtime, cache, or background-service issue that prevents the app from becoming truly idle when no task is running?

Thank you.

%LOCALAPPDATA%\Packages\OpenAI.Codex_2p2nqsd0c76g0\
LocalCache\Roaming\Codex\web\Codex\sentry\scope_v3.json

ScanType:  RealTimeScan
Reason:    OnClose
SkipReason: Not skipped