Allocation institutions under a food–energy–water nexus drought

We compare three allocation institutions — a state-triggered curtailment rule that protects farms and cuts data-centre claims by colour band, a priority auction ordered by sectoral value, and a fixed quota — on a flow-limited reservoir that feeds a food floor and a high-value mobile claimant. The central finding is a separation: an instrument that holds a floor under stress and an instrument that maximises throughput when the floor is not binding are different instruments. Curtailment produces the fewest food-floor breaches for every claimant class; the auction produces the highest aggregate welfare while breaching the floor more often. The institutional ranking is established on rule-bound heuristics and then tested on language-model claimants, where it replicates across two complete model families with the same seeds and institutions. Reasoning does not reverse the ranking. The replication protocol — packaging gate, per-turn reasoning-token audit, and a declassification rule — is named and reported so that other groups can adopt it. The result is a statement about institutional design on a stylised substrate, not a claim about any particular basin.