Synthetics
Biological beings cheap enough to exist in planetary populations and indistinguishable from humans to ordinary participants. Their biological processors function like brains. Their apparent lifespans support the mortal reality expected inside the reconstruction.
They are not merely props. Synthetic generations built the civilization before human integration and may have ordinary developmental histories, reproduction, institutions, and cultural continuity. Their cooperation is also a principal delivery mechanism for invisible influence allocation.
Open: self-knowledge, reproduction, rights, susceptibility to compromise, and the relation between synthetic agency and system control.
See Advanced Technology Ecology for the colony-scale systems, responsive physical environment, and hard-limit framework in which synthetics operate.