Field-System Coupling: An FOP Instrument for the AEW Triad under Finite Horizons

This instrument introduces field–system coupling as a Layer–1 architectural primitive required for finite-horizon viability. It formalises a structural gap that appears when admissibility constraints can be specified at the level of theory (field), yet execution must occur on local, resource-bounded surfaces (systems) that cannot generate admissibility on their own. The text defines three roles as an operative basis (AEW triad): Admissibility (A / Field): the constraint-bearing structure that specifies what must not be violated over the relevant horizon. Execution (E / System): the cost-bearing surface on which transitions occur and outcomes are produced. Witness (W): the minimal accountability condition that renders boundary contact legible as an explicit refusal, delay/suspension, or admissibility-preserving acceptance. Coupling is defined as the A–E relation that makes admissibility effective in execution without collapsing constraint into performance or turning admissibility into inert law. Responsibility is shown to emerge only at the level of coupling: the coupled relation is the minimal unit that can both bear cost and preserve admissibility under finitude. The instrument also provides a typology of coupling failure modes (e.g., field erasure, system erasure, silent degradation, sacrificial redistribution, witness inflation, category collapse), offering structural signatures for diagnosing when constraint, execution, or accountability has been lost. Although developed from a technical impasse, the AEW basis is domain-portable: the carriers change across technical, human, and organisational settings, but the role-separation under finitude remains an architectural criterion rather than a method, protocol, or phenomenological interpretation. Keywords: field–system coupling; admissibility; execution; witness; AEW triad; finite-horizon viability; refusal semantics; accountability; cross-level architecture; failure modes; Fractal Onto–Praxis; Synkyria