SIGILL crash on Intel Westmere (Xeon X5675) — native binary requires AVX2SIGILL crash on Intel Westmere (Xeon X5675) — native binary requires AVX2

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?

The bundled native binary in the VSCode extension (v2.1.68) crashes immediately with SIGILL on an Intel Xeon X5675 (Westmere, no AVX/AVX2):

zsh: illegal hardware instruction   claude --version

VSCode extension log:

Error: Claude Code process terminated by signal SIGILL

The binary is correctly typed as x86_64 (Mach-O 64-bit executable x86_64), but strings on the binary reveals AVX2 codepaths (SlimAVX2, FatAVX2). The Xeon X5675 supports up to SSE4.2 but has no AVX or AVX2.

The npm-installed version (npm install -g @anthropic-ai/claude-code) works fine because it uses Node.js rather than a native binary. However, the VSCode extension always uses the bundled native binary and offers no setting to override the path (see also #8510).

What Should Happen?

An x86_64 binary should run on all x86_64 processors without requiring AVX2. Either the binary should be compiled with a lower baseline (SSE4.2 minimum), or the minimum CPU requirements should be clearly documented. Alternatively, the VSCode extension should support configuring a custom path to the claude binary (see #8510) so users can fall back to the npm version.

Error Messages/Logs

$ file ~/.vscode/extensions/anthropic.claude-code-2.1.68-darwin-x64/resources/native-binary/claude
/Users/arno/.vscode/extensions/anthropic.claude-code-2.1.68-darwin-x64/resources/native-binary/claude: Mach-O 64-bit executable x86_64

$ ~/.vscode/extensions/anthropic.claude-code-2.1.68-darwin-x64/resources/native-binary/claude --version
zsh: illegal hardware instruction

$ sysctl -n machdep.cpu.brand_string
Intel(R) Xeon(R) CPU           X5675  @ 3.07GHz

$ sysctl -a | grep machdep.cpu.features
machdep.cpu.features: FPU VME DE PSE TSC MSR PAE MCE CX8 APIC SEP MTRR PGE MCA CMOV PAT PSE36 CLFSH DS ACPI MMX FXSR SSE SSE2 SS HTT TM PBE SSE3 PCLMULQDQ DTES64 MON DSCPL VMX SMX EST TM2 SSSE3 CX16 TPR PDCM SSE4.1 SSE4.2 POPCNT AES PCID

$ strings .../native-binary/claude | grep AVX
SlimAVX2
FatAVX2
AVX2

VSCode extension log:
2026-03-04 16:12:26.432 [error] Error from Claude (on channel zrv0iya9urj): Error: Claude Code process terminated by signal SIGILL

Steps to Reproduce

1. Install Claude Code VSCode extension v2.1.68 on a Mac with Intel Xeon X5675 (Westmere, macOS 13.7.4)
2. Open VSCode — extension fails to start
3. Run the bundled binary directly: ~/.vscode/extensions/anthropic.claude-code-2.1.68-darwin-x64/resources/native-binary/claude --version
4. Observe: zsh: illegal hardware instruction

Claude Model

Sonnet (default)

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.73

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Claude generated issue...