Code Review: electron: more robust sidecar kill handling

⚠️ CRITICAL ISSUES

1. Race Condition in Signal Handlers

The app.exit(0) call immediately terminates the process without waiting for killSidecar() to complete. Since sidecar killing might be asynchronous (tree-kill), this creates a race condition where the main process exits before the sidecar is properly terminated.

Fix: Remove app.exit(0) or make the handler async and await cleanup.

2. Process Group Kill Without Validation

Sending signals to process groups (-pid) can kill unintended processes if the PID was reused. The silent catch masks potential issues.

Fix: Add PID validation and better error handling:

if (pid && process.platform !== "win32" && pid === sidecar?.pid) {
  try {
    process.kill(-pid, "SIGTERM")
  } catch (error) {
    console.warn(`Failed to kill process group ${pid}:`, error)
  }
}

🔶 SUGGESTIONS

Multiple Signal Handler Registration

If this code runs multiple times, it will register duplicate handlers. Consider using process.once() instead of process.on().

Enhanced killSidecar

Consider adding a small delay before the process group kill to let tree-kill complete:

// Give tree-kill time to work, then fallback
await new Promise(resolve => setTimeout(resolve, 100))

The approach is solid overall, but the race condition with app.exit(0) should be addressed.