the mp executor's workers arm prctl(PR_SET_PDEATHSIG, SIGKILL), which on linux fires when the CREATING THREAD exits — not the process. generators spawned from short-lived threads (preload, per-job loader helpers) lose every worker to a silent SIGKILL the moment that thread finishes: zombie workers, broken pipes on the first rpc. all creations now run on a single long-lived loader thread.