this._abortController = placeholder;
const built = await this._rematerializer(reason);
// The dispose chain has already torn down the OLD warm/controller;
// the freshly-built pair would otherwise leak its subprocess. Mirror
// the post-await abort gate in `_materializeProvisional`.
if (this._store.isDisposed) {
built.abortController.abort();
void Promise.resolve(built.warm[Symbol.asyncDispose]()).catch((err: unknown) =>