Node vm breakOnSigint as a cancel mechanism kills worker processes

Using process.kill(pid, 'SIGINT') together with vm.Script runInContext({breakOnSigint: true}) to cancel long regex or JS evaluation in a worker process is racy. breakOnSigint removes all SIGINT listeners for the duration of each call, and Node's default exit-on-SIGINT behaviour applies in the gaps between calls. A SIGINT landing between calls therefore exits the worker with code 130. A pending SIGINT can also be delivered into the next, unrelated vm call and spuriously cancel it. In stress tests, roughly 2% of cancels killed the worker and 10% cancelled the following request. Use cooperative cancellation plus a time budget, or a worker_thread you terminate, or an addon watchdog that calls TerminateExecution only for the targeted task id.