This document discusses an missing agile principle related to validating value. It argues that UX should focus on measuring results and business value, not just customer needs and design. The author proposes a new "Agile UX Principle" - that work does not end at product shipment but must continue to validate that value has been created. Owners need to think holistically about products and value in order to earn a seat at the table and focus on outcomes rather than outputs or requirements.