[BUG] Illegal instruction: 4 (SIGILL/BMI2) on 2013 Mac Pro (Xeon E5 v2 / Ivy Bridge) — regression after 2.1.30

[kokokino]

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?

What's Wrong?

Claude Code crashes immediately on startup with Illegal instruction: 4 on a 2013 Mac Pro. The bundled binary uses CPU instructions (BMI2 / AVX2, Haswell-era) that this machine's Intel Xeon E5 v2 (Ivy Bridge) does not support. Ivy Bridge supports AVX1 but not BMI2/AVX2, so the process is killed with SIGILL before the CLI starts.

This previously worked via npm. Rolling back fixes it (see below), so this is a packaging/build regression, not a config issue.

Last Working Version

2.1.30 runs perfectly. Reinstalling with npm install -g @anthropic-ai/claude-code@2.1.30 resolved the crash completely. The current latest build crashes. So the regression landed somewhere after 2.1.30.

Is this a regression?

Yes. 2.1.30 works; a current build does not.

Additional Information

• Machine: Mac Pro (Late 2013, "trash can")
• CPU: Intel Xeon E5 v2 (Ivy Bridge) — supports AVX1, no AVX2/BMI2
• OS: macOS 12.7.6
• Node.js: v24.12.0

What Should Happen?

A fallback binary (or x86-64-v2 baseline build) for older Intel Macs without AVX2/BMI2, or at minimum documenting the minimum CPU requirement so users know to pin an older version. Related: #19931, #50904.

Error Messages/Logs

Illegal instruction: 4
Exception Type:        EXC_BAD_INSTRUCTION (SIGILL)
Termination Reason:    Code 4 Illegal instruction

The crashing opcode reported in related issues (`c4 e2 f9 f7 d1`) is a VEX-encoded BMI2 instruction, which Ivy Bridge lacks.

Steps to Reproduce

1. On a 2013 Mac Pro (Xeon E5 v2 / Ivy Bridge), install the latest: npm install -g @anthropic-ai/claude-code
2. Run: claude
3. Immediate crash: Illegal instruction: 4
4. Workaround: npm install -g @anthropic-ai/claude-code@2.1.30 — works.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.30

Claude Code Version

Illegal instruction: 4

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

No response

[github-actions]

Found 3 possible duplicate issues:

1. [BUG] 2.1.113 crashes with SIGILL "illegal hardware instruction" on Ivy Bridge (AVX2-less) Intel Macs — regression from 2.1.112 #50466
2. Native claude binary SIGILLs at startup on non-AVX2 x86_64 CPUs (Ivy Bridge / pre-Haswell) #51433
3. [BUG] Illegal instruction (SIGILL/AVX) on Intel Core i7 MacBookPro9,1 - crashes on startup #50904

This issue will be automatically closed as a duplicate in 3 days.

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[github-actions]

This issue has been automatically closed as a duplicate of #50466.

If this is incorrect, please re-open this issue or create a new one.

🤖 Generated with Claude Code