ALBANY — Judges from New York’s highest court heard final arguments Thursday in the long-running case regarding the controversial plan to switch the city’s 250,000 retirees to Medicare Advantage, a move tied to hundreds of millions in potential annual savings on health costs.

At the heart of the case before the Court of Appeals is whether the proposed switch breaches the city’s promise that all retired city workers are entitled to city-funded healthcare, which traditionally combines Medicare with supplemental insurance.

In the summer of 2023, a Manhattan Supreme Court judge ruled in favor of a group representing city retirees, blocking the city from implementing the plan, which had been negotiated with the city’s labor unions during then-Mayor Bill de Blasio’s administration. Prior to this ruling, the plan was slated to take effect that September, with the goal of saving the city more than $600 million annually for its stabilization fund, which helps cover premiums for active city workers. Despite multiple appeals from the Adams administration, appellate judges have consistently sided with the retirees. The Court of Appeals is expected to render its decision in the coming months.

During the 30-minute hearing, the court’s seven judges pressed attorneys for both the city and the plaintiffs, the NYC Organization of Public Service Retirees, on whether the city had ever explicitly promised retirees traditional Medicare. Several justices questioned the city’s stance, pointing to assertions from retirees’ lawyers and an affidavit from a former deputy mayor, which argued that healthcare benefits had long served as a “vital recruitment and retention tool” for city employees.