Field-Defined Infrastructure: From Structure-Centric Grids to Adaptive Spatial-Mode Networks

This preprint formulates Field-Defined Infrastructure (FDI): electromagnetic energy and information infrastructure is redefined as a stoppable, falsifiable spatial-mode maintenance map rather than a passive conductor-laying problem. It contributes a Level 0–5 stoppable maturity matrix, interprets grid-forming inverters as dynamic boundary nodes, and identifies near-term insertion points in enclosed structural surface-wave channels and chip-scale SSPP/CPO pathways. Six falsifiable protocols (C1–C6) define scientific off-ramps. This record is a conceptual and theoretical preprint. No original experimental dataset is reported. Unshielded megawatt-scale free-space transmission is explicitly excluded from near-term recommendation. It is Paper 3 of the SBE/DSR programme.