The theory of graceful extensibility defines the basic rules governing adaptive systems, including the socio-technical systems involved in building and operating software. A key concept in this theory is the competence envelope — the boundary within which a system can function robustly in the face of failure. When a system is pushed beyond its competence envelope, it becomes brittle and is more likely to fail. This model provides a valuable lens for understanding system failure, as seen in the complex failures that led to the 2024 Canva outage. Residuality theory, a recent development in software architecture thinking, offers a way to test a system’s competence envelope by deliberately introducing stressors and analyzing how the system has adapted to historical stressors over time. The approaches align with concepts of anti-fragility, resilience and robustness in socio-technical systems, and we’re eager to see practical applications of these ideas emerge in the field.
