ChatGPT/Codex desktop app crashes with SIGILL (illegal instruction) in renderer on AMD EPYC 7551 (Zen 1: AVX2 present, no AVX-512)

Description
The official ChatGPT desktop app with Codex for Linux crash-loops on startup/use on a Zen 1 CPU. Every crash is SIGILL (si_code: ILL_ILLOPN) in the Electron renderer process, suggesting a code path (or bundled runtime) compiled for, or JIT-emitting, instructions newer than this CPU supports. The CPU supports SSE4.2, AVX, and AVX2, but not AVX-512.

Each crash also produces a very large core dump (up to ~4.5 GB), so the crash loop fills disk quickly.

Environment

• App: openai-codex-desktop 26.901.20858-1 (Arch Linux package; executable /usr/lib/chatgpt/ChatGPT)
• OS: Omarchy (Arch Linux), kernel 7.1.9-arch1-2, Wayland (Hyprland), --ozone-platform=wayland
• CPU: AMD EPYC 7551 32-Core (Zen 1 / Naples) — has AVX/AVX2/FMA/SSE4.2; no AVX-512
• Running in a KVM/QEMU VM (Proxmox) with cpu: host passthrough — guest sees the full, real EPYC 7551 flag set

Crash evidence (systemd-coredump)

Signal: 4 (ILL) si_code: ILL_ILLOPN
Executable: /usr/lib/chatgpt/ChatGPT
Command Line: /usr/lib/chatgpt/ChatGPT --type=renderer ... --ozone-platform=wayland ...

Two identical SIGILL crashes captured on 2026-09-04 (plus earlier ones); reproducible on two separate VMs on the same host.

Expected behavior
Either run on x86-64-v3 class CPUs (AVX2 baseline, no AVX-512), or detect missing CPU features at startup and fail with a clear message instead of SIGILL, or provide a fallback build.

Steps to reproduce

1. Install the app on a machine with a Zen 1 (or any AVX2-but-no-AVX-512) CPU.
2. Launch it and sign in / open a chat.
3. Renderer process dies with SIGILL; app crash-loops.

Happy to provide the core dump backtrace or run a debug build if useful.

Start by reproducing the crash on a Zen 1 or AVX2-but-no-AVX-512 system and inspect /usr/lib/chatgpt/ChatGPT with the systemd-coredump evidence. The issue mentions a core dump backtrace and a debug build as useful next steps. Done means the app avoids SIGILL, detects unsupported CPU features with a clear message, or provides a compatible fallback.