Climate change is expected to intensify water stress even in historically overall water-abundant countries like Germany, where expanding irrigation depicts an effective adaptation strategy. Such path-dependent irrigation growth—here referred to as an irrigation trap—can lock farmers into high and potentially unsustainable water use, heightening trade-offs between food, water, and energy (FWE) sector policy objectives. However, no comprehensive assessment of future policy impacts and cross-sector trade-offs within the FWE nexus exists for Germany. This study evaluates the impacts of six sectoral policies on the future irrigation demand of eight major field crops and related FWE indicators, using a hybrid modeling framework that links hydrological and machine learning models with a hydro-economic multi-agent system. The results show divergent effects of sectoral policies on the FWE nexus. Water sector policies—such as abstraction limits and pricing—substantially curb future irrigation expansion under climatic and socioeconomic change, with only marginal profit losses if implemented early. In contrast, bioenergy policies further raise irrigation demand, reaching up to 13.7-fold the historic levels by the far future (2069–2098). Drought compensation schemes weaken incentives for farmers to adapt to climate change, and irrigation efficiency subsidies do not deliver net water savings. By using a hybrid modeling framework capturing irrigation expansion and adaptive farmer behavior, our ex ante policy assessment shows that unregulated irrigation expansion triggers increasingly steep trade-offs between FWE objectives. Avoiding this irrigation trap requires timely and coordinated cross-sector policies to balance competing demands under growing climatic and socioeconomic pressure.