Preflight Checklist

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

What's Wrong?

Starting from version 2.1.113, the CLI crashes immediately with "Illegal instruction".

Version 2.1.112 works correctly in the same environment.

This regression appears to coincide with the change to spawning a native binary instead of running bundled JavaScript.

The issue is likely caused by the native binary requiring CPU instructions (e.g. AVX/AVX2) that are not available on older CPUs.

What Should Happen?

The CLI should start normally.

If the system CPU does not support required instructions, the CLI should:

• either provide a compatible baseline binary (no AVX requirement), or
• gracefully fall back to a compatible implementation instead of crashing.

Error Messages/Logs

Illegal instruction

Steps to Reproduce

1. Install latest version:
   npm install -g @anthropic-ai/claude-code@2.1.113

2. Run:
   claude --version

3. Observe crash:
   Illegal instruction

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.112

Claude Code Version

2.1.113

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

VS Code integrated terminal

Additional Information

CPU:
AMD A4-3310MX APU (older CPU without AVX/AVX2 support)

Relevant CPU flags:
sse, sse2, sse4a (NO avx / avx2)

Environment:

• Running inside Docker container
• Node.js v24.13.0
• npm 11.6.2

Key observation:
Version 2.1.112 works correctly, but 2.1.113+ crashes immediately.

This strongly suggests the newly introduced native binary is compiled with CPU instructions not supported on older hardware.

Suggested fix:

• Provide a baseline x86_64 build without AVX requirements, or
• Detect CPU capabilities at runtime and provide a fallback