The report examines the challenges of developing software systems (SS) under conditions of technical, technological, cognitive, and mental uncertainty: gaps between software lifecycle (SLC) stages, team misalignment, and complexities in designing interactions. The goal is to develop methodological principles for interface planning (IP) to coordinate SLC processes with system functionality. The IP methodology integrates conceptual design, human resources, functional solutions, and user interface elements. The outcome is a software solution enabling incremental functional expansion while maintaining the system's adaptability to change.