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Playful Programming profile image Emanuele Bartolesi
Emanuele Bartolesi for Playful Programming

Posted on AI-assisted

My Windows 11 Laptop Was Struggling with Claude and Codex. Defender Exclusions Helped.

#ai #githubcopilot #claude

My Windows 11 laptop sometimes struggled while I was working with Claude and Codex or GitHub Copilot. CPU usage was high, and the fans were running like crazy.
It means also that my battery runs out in 1 hour and 30 minutes 😀

When I checked Task Manager, Antimalware Service Executable stood out. Disk usage was around 90%, with heavy CPU activity as well, while the two tools were running.

That process belongs to Microsoft Defender Antivirus. You can find it as Antimalware Service Executable in Task Manager's Processes tab, or MsMpEng.exe in the Details tab. Microsoft documents both names here.

I suspected Defender's scanning of the tools' local folders was contributing to the slowdown. Adding folder exclusions solved the problem I was seeing on my laptop. This is my experience with one machine, rather than proof that Claude or Codex always causes this behavior.

The folders I excluded

These are the four entries in my Windows Security exclusion list:

C:\Users\barto\.claude
C:\Users\barto\.codex
C:\Users\barto\.copilot
C:\Users\barto\.github-copilot-cli
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Windows Security exclusion list showing the .claude, .codex, .copilot, and .github-copilot-cli folders under my Windows user profile.

The last two entries are for my Copilot tooling. Their presence in this list does not establish that they contributed to the Claude and Codex slowdown.

There is a security tradeoff: a folder exclusion removes Defender antivirus scanning coverage for that folder and its contents. Files placed there later are also covered by the exclusion. Trusting the tool does not guarantee that every file it writes or downloads is safe. Microsoft explains the exclusion options and risks.

Treat this list as a record of my setup. For your machine, identify the affected folder first and keep any exclusion as narrow as possible.

How to add a folder exclusion in Windows 11

  1. Open Start, search for Windows Security, and open it.
  2. Select Virus & threat protection.
  3. Under Virus & threat protection settings, select Manage settings.
  4. Scroll to Exclusions and select Add or remove exclusions. Approve the administrator prompt if it appears.
  5. Select Add an exclusion, then Folder.
  6. Browse to the folder you want to exclude, for example C:\Users\YOUR_USERNAME\.claude, and select Select Folder. Replace YOUR_USERNAME with your Windows user folder name.
  7. Confirm that the folder appears in the exclusion list. Repeat for other folders only where needed.

These steps follow Microsoft's Windows Security guidance. On a company-managed laptop, your IT team may control these settings.

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