61 I T M O D E R N I Z AT ION CA SE AI agents streamlined code migration and shifted human roles to orchestration A regional lender used AI agents to modernize its banking application for small and medium-size enterprises. The aim was to update various program ming languages to speed up internal development. The project would previously have required months of work, large budgets, and extensive engineering capacity for manual documentation, code refactoring, and testing of millions of lines of code. To accelerate the process, the bank launched a pilot using AI agents for multiple modernization tasks (Exhibit 4). An assessment agent scans legacy code bases and identifies dependencies, while a function ality agent generates the target-state architecture. A coding agent migrates code to new frameworks and performs automated tests. Developers collaborated with 15 to 20 agents each, verifying and refining out puts to ensure architectural integrity, compliance, and functional accuracy. The modernization also shifted applications from desktop to mobile, on premises to cloud, and monolithic to microservice architectures. As AI agents took on most of the repetitive exe cution, the focus of human work shifted toward planning, orchestration, and testing. Early results show up to 70 percent code accuracy. Following the pilot module, the bank now plans to extend the use of agents to the entire modern ization effort. It estimates that this could reduce required human hours by up to 50 percent. A mod ernization planning agent could coordinate the process, supported by quality assurance agents and testing agents . Anu Madgavkar is a partner at the McKinsey Global Institute (MGI) and is based in McKinsey’s New Jersey office; Sven Smit is a senior partner emeritus and senior adviser in the Amsterdam office; Alexis Krivkovich is a senior partner in the Bay Area office, where Michael Chui is an MGI senior fellow and María Jesús Ramírez is an associate partner; and Diego Castresana is a consultant in the New York office. - - - - - - » Courageous Leadership: New Workflow