1. A computer-implemented method for optimizing inventory of a supply chain, comprising: generating, by a computer comprising one or more processing units and one or more memory units, an inventory plan for a supply chain, the supply chain comprising a plurality of buffers, the inventory plan describing an amount of inventory for each buffer of the plurality of buffers; generating, by the computer, a supply chain plan in accordance with the inventory plan; initiating, by the computer, execution of the supply chain plan at the supply chain; monitoring, by the computer, the supply chain to generate supply chain data, the supply chain data comprising a plurality of metric values describing the supply chain; detecting, by the computer, a watchpoint triggered by a metric value of the plurality of metric values; identifying, by the computer, one or more causes of the triggered watchpoint using a causal tree, the causal tree identifying at least one possible cause of unanticipated variability in the metric value; adjusting, by the computer, the inventory plan in response to the detected triggered watchpoint and in accordance with the one or more identified causes; adjusting, by the computer, the supply chain plan in accordance with the adjusted inventory plan; initiating, by the computer, execution of the adjusted supply chain plan; measuring, by the computer, the plurality of metric values in response to the execution of the adjusted supply chain plan; and updating, by the computer, the causal tree in response to the measured plurality of metric values.