claude.exe APPCRASH on Intel Xeon X5460 (no AVX) — regression in v2.1.119/120 on Windows 10

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?

claude.exe crashes with APPCRASH / ntdll.dll access violation (0xc0000005) on Windows 10 Pro with older Intel Xeon X5460 CPU. Was working fine until approximately April 20, 2026. Versions 2.1.119 and 2.1.120 both crash before fully initializing. Rolled back to an earlier version as a workaround.

What Should Happen?

Claude Code should launch and run normally without crashing on Windows 10 Pro 64-bit with older CPUs that lack modern instruction sets such as AVX.

Error Messages/Logs

Windows Event Log APPCRASH:

Faulting module: ntdll.dll
Fault module version: 10.0.19041.7058
Exception code: 0xc0000005 (Access Violation)
Fault offset: 0x0000000000064a16
Crash occurs before claude.exe fully initializes — only 14 DLLs load before crash

Steps to Reproduce

Install Claude Code on Windows 10 Pro Build 19045 with Intel Xeon X5460 CPU
Run any claude command in terminal
Wait 1-2 minutes — Windows error dialog appears saying "Claude Code has stopped working"

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.100 (or earlier — still identifying exact last working version)

Claude Code Version

2.1.120 (also tested 2.1.119, both crash)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

CPU: Intel Xeon X5460 (2007, dual socket) — does not support AVX/modern instruction sets
RAM: 8GB
Installation method: npm
WSL2 workaround not possible — CPU too old to support hardware virtualization
node.exe works fine independently
api.anthropic.com reachable via curl
SFC /scannow shows no corruption
claude.exe digital signature verified as valid