[BUG] Windows Security Update KB5074109 was causing the Claude Code VS Code extension's native binary to crash with error 0xC0000005

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Investigation Summary:
The report documents a thorough debugging process that systematically ruled out:

Configuration file corruption
MCP server issues
AteraAgent RMM interference
Windows Defender blocking
Extension version problems
Workspace-specific settings
The breakthrough came from correlating the timing - the extension "worked for weeks" but broke "this morning" - with the Windows Update history showing KB5074109 was installed on January 14, 2026.

Root Cause:
The security update likely introduced stricter memory protection policies or code signing requirements that the native claude.exe binary couldn't satisfy, triggering the access violation approximately 10 seconds after successful initialization.

What Should Happen?

claude session should run

Error Messages/Logs

error 0xC0000005 (Access Violation)

Steps to Reproduce

launch a new claude session

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.7

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

See above for resolution