[BUG] Illegal instruction: 4 on Intel Ivy Bridge CPUs (no AVX2 support)

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?

Environment

• OS: macOS 12.6.7 (Monterey)
• CPU: Intel Xeon E5-1650 v2 (Ivy Bridge, 2013) — no AVX2 support
• Node.js: v22.15.0 (x64, universal binary)
• npm: latest

Problem

Installing @anthropic-ai/claude-code fails with:

What Should Happen?

bash: line 151: 1304 Illegal instruction: 4 "$binary_path" install

The binary never lands — claude is not found after install.

Root Cause

The Claude Code binary uses AVX2 CPU instructions. Intel Ivy Bridge CPUs
(E5-1650 v2 and similar, ~2013) support AVX but not AVX2, causing an
illegal instruction crash at postinstall time.

Expected Behavior

Either:

1. A clear error message explaining the CPU is unsupported, or
2. A fallback binary compiled without AVX2 for older Intel CPUs

Workaround

None available on the client side — this is a hardware limitation.

Error Messages/Logs

Steps to Reproduce

Steps to Reproduce

1. Use a Mac with an Intel Ivy Bridge CPU (e.g. Xeon E5-1650 v2, 2013 Mac Pro)
2. Install Node.js v18+ (tested with v22.15.0 universal binary)
3. Run: npm install -g @anthropic-ai/claude-code
4. Observe: install appears to run but crashes with "Illegal instruction: 4"
5. Run: which claude
6. Observe: "claude not found" — binary never installed

Claude Model

Other

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

I cant install claude code

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_