[BUG] "illegal hardware instruction" on CPU without AVX2 (Xeon E5 v2)

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 Code crashes immediately with "zsh: illegal hardware instruction" on macOS 12 with Intel Xeon E5-2697 v2 CPU.

This CPU (Ivy Bridge, 2013) does not support AVX2 instructions:

• sysctl -a | grep avx2 returns hw.optional.avx2_0: 0

Claude Code worked fine until recently. After updating, all versions from 1.0.x fail with this error.

Older versions (0.2.40) launch but cannot connect because server requires 1.0.88+.

Environment:

• macOS 12 Monterey
• CPU: Intel Xeon E5-2697 v2 (no AVX2)
• Node: v18.x (via nvm)

Request: Please provide builds without AVX2 requirement, or document minimum CPU requirements.

What Should Happen?

Claude Code should launch and run normally on CPUs without AVX2 support.

Error Messages/Logs

$ claude
zsh: illegal hardware instruction  claude

$ sysctl -n machdep.cpu.brand_string
Intel(R) Xeon(R) CPU E5-2697 v2 @ 2.70GHz

$ sysctl -a | grep avx2
hw.optional.avx2_0: 0

Steps to Reproduce

Steps to Reproduce:

1. Have a Mac with CPU without AVX2 support (e.g., Intel Xeon E5-2697 v2)
2. Install Claude Code: npm install -g @anthropic-ai/claude-code
3. Run: claude
4. Error appears: "zsh: illegal hardware instruction claude"

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Cannot run claude --version (crashes with illegal hardware instruction). Installed version: 1.0.88 (latest via npm)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_