A project nearing the end of execution is told by a senior stakeholder that a critical requirement was omitted from scope and without it the project delivers no value. What is the first thing the project manager should do?

The first step when a new requirement is introduced, especially late in a project, is to evaluate its impact. This involves assessing how the change affects scope, schedule, cost, quality, resources, and risks. This evaluation provides the necessary information to make an informed decision. Informing the stakeholder that it's impossible to add requirements is incorrect; changes can be managed. Including the requirement immediately without assessment is premature and risky, as it bypasses proper change control. While informing the sponsor is important, it should happen after an initial impact assessment, so you can present them with data and options rather than just a problem.