[BUG] AVX-512 bug report

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?

No, not using Claude Code, because it does not work, and this report is what is needed to fix it.

What Should Happen?

Here's the relevant portion of the conversation, ready to paste:

Bug Report: Claude Code / Node.js compiled with AVX-512 — fails on CPUs without AVX-512 support
Summary:
Claude's container environment includes binaries compiled with AVX-512 instructions, causing hard crashes on CPUs that don't support AVX-512. This includes a large amount of perfectly capable server and desktop hardware.
Findings from objdump analysis of container binaries:

Node.js — 25,012 AVX, 32,796 AVX2, 84,336 AVX-512 instructions (zmm registers)
Pandoc — 199 AVX, 209 AVX2, 39,164 AVX-512 instructions
ffmpeg, python3, wkhtmltopdf, tesseract — clean, no AVX issues

Impact:

Claude Code is a Node.js application and will fail to launch entirely on any CPU without AVX-512 support
Affected hardware includes: older Xeon generations, most EPYC generations, most consumer CPUs before ~2021, and many current server CPUs — hardware that is otherwise fully capable and commonly used
The failure is a hard illegal instruction crash with no workaround on the user side

Root cause:
The Node.js binary appears to have been compiled with -march=native or an equivalent AVX-512 targeting flag on a machine that supports AVX-512, baking that assumption into the binary. Plain x86-64 baseline does not include AVX-512.
Fix:
Recompile Node.js (and Pandoc) with -march=x86-64 or at most -march=x86-64-v2 as the target architecture. This is a single build flag change. There is no meaningful performance loss for tool/CLI workloads — AVX-512 only benefits highly specific vectorized math operations.
Verification command:
bashobjdump -d $(which node) | grep -c "zmm"
Any result above 0 confirms AVX-512 instructions are present.
Note: Python3, ffmpeg, and other tools in the same environment were built correctly against the baseline target and work fine. This is not a systemic issue — just these specific binaries need a clean rebuild.

That should give them everything they need to find it, understand it, and fix it in one sitting.

Error Messages/Logs

See previous paste.

Steps to Reproduce

See previous paste.
Claude Code does NOT work at all.

Need to un-check AVX at compile time. Even the AI can confirm it's not needed, and was probably missed because it's a default setting.
It is 100% unnecessary, and not needed, but does crash server CPUs that don't have AVX.
It does NOT slow anything down for AVX machines, again, 100% unnecessary.

Claude Model

Other

Is this a regression?

Yes, this worked in a previous version

Last Working Version

1.1

Claude Code Version

1.1

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Not OS specific, will fail on MacOS, Linux, or Windows. This is a hardware issue in the CPU.

I am primarily on MacOS, but also on Ubuntu a lot.