SIGILL (EXC_BAD_INSTRUCTION) crash when TUI starts over Termius/Android SSH on macOS 12 Intel

Summary

Running opencode (v1.18.16) crashes immediately with SIGILL (EXC_BAD_INSTRUCTION) when the interactive TUI starts over an SSH connection from the Termius app on Android. It works fine:

• locally in Terminal.app,
• over a plain ssh localhost TTY,
• at any terminal size.

The crash is reproducible in both a plain SSH shell and inside tmux over the same Termius connection. It is a startup crash — the process dies before any log lines are written.

Environment

• opencode 1.18.16 (Bun single binary, /Users/USER/.opencode/bin/opencode, 148 MB, x86_64)
• macOS 12.7.6 (21H1320) on an Intel MacBookPro11,4 (i7-4770HQ)
• Client: Termius on Android, SSH over Tailscale, TERM=xterm-256color, ~58x22 terminal
• No tmux/opencode config involved; fresh session also crashes

Steps to reproduce

1. From Termius on Android, SSH into the Mac (TERM=xterm-256color).
2. Run opencode (also reproduced inside tmux).
3. The process dies immediately with zsh: illegal hardware instruction.

Expected

The TUI starts and renders (as it does locally and over plain ssh).

Crash report

macOS crash reports (~/Library/Logs/DiagnosticReports/opencode-2026-08-10-13*.ips) all show the same signature:

exception: EXC_BAD_INSTRUCTION  signal: SIGILL
termination: Illegal instruction: 4
faultingThread: 0

crashed stack (main thread):
  opencode  (no symbol)   +57846957
  opencode  (no symbol)   +57809547
  opencode  (no symbol)   +17528424
  libsystem_platform.dylib  _sigtramp  +15869
  opencode  (no symbol)   +58597659
  ...

main image: x86_64, uuid 18601ead-261d-3873-a0a1-c9b95e96d94e

This looks like a JavaScriptCore (Bun) JIT code-generation crash on an old Intel macOS build, triggered only by a code path reached during TUI startup through the Termius terminal interaction. Happy to attach the full .ips files if useful.

Workarounds found

• opencode serve / opencode web (headless, no TUI) works.
• Plain ssh from another client (tested via ssh localhost) does not crash, so it appears specific to Termius's terminal capability responses.