[BUG] Illegal instruction (SIGILL/AVX) on Intel Core i7 MacBookPro9,1 - crashes on startup

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 on startup with "Illegal instruction: 4". The binary requires AVX CPU instructions that this Intel Core i7 (MacBookPro9,1, 2012) does not support.

What Should Happen?

Claude Code should start normally, or provide a fallback binary for older Intel CPUs without AVX support.

Error Messages/Logs

Illegal instruction: 4
Exception Type: EXC_BAD_INSTRUCTION (SIGILL)
Termination Reason: Code 4 Illegal instruction
Instruction stream contains AVX opcode: [c4]e2 f9 f7 d1

Steps to Reproduce

1. Install via: npm install -g @anthropic-ai/claude-code
2. Run: claude
3. Immediate crash with "Illegal instruction: 4"

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

Unknown - binary crashes before running (Illegal instruction: 4)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Machine: MacBook Pro (MacBookPro9,1, Mid 2012)
CPU: 2.3 GHz Quad-Core Intel Core i7 (no AVX support)
OS: macOS Monterey 12.7.5
Node.js: v20.20.2
The native installer produces the same error.