Illegal hardware instruction on macOS Intel Ivy Bridge (SIGILL on BMI2/shlxq) #26877

Description

opencode crashes immediately on this machine with:
zsh: illegal hardware instruction opencode

I did some local debugging and the failure appears to be a CPU instruction-set incompatibility in the shipped macOS x64 binary.

Details:

• Machine: Mac Pro 6,1 (Late 2013)
• CPU: Intel Xeon E5-1680 v2 (Ivy Bridge)
• OS: macOS 12.7.6
• Binary path: ~/.opencode/bin/opencode
• file ~/.opencode/bin/opencode reports a Mach-O x86_64 executable
• opencode --version crashes with Illegal instruction: 4
• macOS crash report shows SIGILL / EXC_BAD_INSTRUCTION
• lldb stops on shlxq %rax, %rcx, %rdx, which is a BMI2 instruction
• sysctl machdep.cpu.features machdep.cpu.leaf7_features shows AVX1.0, but no AVX2/BMI2 support on this CPU

This suggests the current macOS x64 build requires Haswell-era instructions (BMI2 and possibly AVX2), so it is not compatible with Ivy Bridge Xeons.

Possibly related to #8345, but I am filing this with the concrete low-level crash details from this machine.

Plugins

none

OpenCode version

Unable to retrieve, because the binary crashes before opencode --version can print anything.

The embedded Bun runtime strings in the binary include v1.3.13.

Steps to reproduce

1. Use a Mac Pro 6,1 or another Intel Mac with an Ivy Bridge CPU lacking AVX2/BMI2.
2. Install the latest OpenCode CLI so that the binary is placed at ~/.opencode/bin/opencode.
3. Run opencode or opencode --version.
4. Observe the immediate crash: zsh: illegal hardware instruction opencode.
5. If launched under lldb, the process stops on shlxq %rax, %rcx, %rdx before startup completes.

Screenshot and/or share link

No response

Operating System

macOS 12.7.6 on Mac Pro 6,1 (Late 2013), Intel Xeon E5-1680 v2 / Ivy Bridge

Terminal

Terminal.app