Interface contract: Routing architecture

The implementation model permits:

1. exact carriage of a finite register along a prescribed future causal curve;

2. local unitary gates and complete instruments on registers meeting at the same station;

3. local preparation of a specified input-independent ancilla;

4. local storage, resets, and discards;

5. classical records carried along the same kind of causal communication routes.

Gate durations are positive and explicitly assigned. These are ideal model primitives, not claims of laboratory realization or a quantum-field description of a point register.