Linux Claude Code binary executes unsupported POPCNT on Core 2 Duo T8100 #109184

Summary

Claude Code crashes immediately with SIGILL on an Intel Core 2 Duo T8100 (ThinkPad X61). GDB identifies the unsupported instruction as POPCNT inside the installed Linux binary.

This is related to prior reports #50384 and #37065, which are closed and locked. This report adds the exact failing instruction and CPU model for a Linux Core 2 system.

Environment

• OS: Arch Linux x86_64
• CPU: Intel Core 2 Duo T8100 @ 2.10 GHz (ThinkPad X61)
• CPU flags include sse4_1, but do not include popcnt, sse4_2, or AVX
• /usr/bin/claude is a wrapper that execs /opt/claude-code/bin/claude
• The target is a 64-bit ELF binary

Reproduction

Run:

claude --version

It exits with status 132 and no output. GDB catches:

Program received signal SIGILL, Illegal instruction.
=> popcnt %rbx,%r12

Expected behavior

Claude Code should either run on baseline x86_64 CPUs such as Core 2, or report a clear minimum CPU requirement before crashing.

Could Anthropic provide a baseline x86_64 build or runtime CPU feature detection/fallback that avoids executing POPCNT on CPUs that do not advertise support?