Advance care planning (ACP) is a process rooted in the bioethical principles of autonomy (patient self-determination), beneficence (acting in the patient's best interest), non-maleficence (avoiding harm), and justice (equitable resource allocation). The ethical framework for goals-of-care conversations is built on the concept of informed consent, which requires that a patient with decision-making capacity receives adequate information about their diagnosis, prognosis, treatment options (including the option of no treatment), and the benefits, risks, and burdens of each option. Decision-making capacity is distinct from legal competence and is assessed along four dimensions: the ability to understand relevant information, appreciate how it applies to one's own situation, reason about the options using consistent values, and communicate a choice. Capacity is decision-specific (a patient may have capacity for simple decisions but not complex ones) and may fluctuate with delirium, medication effects, or disease progression. When a patient lacks capacity, the substitute decision-maker (SDM) must apply substituted judgment — making the decision the patient would have made based on previously expressed wishes, values, and beliefs — rather than the SDM's own preferences. The principle of...