Brittle threshold: When adaptive success is the warning sign

What happens when a system keeps working-not because it is well designed but because people keep absorbing the strain? That question stayed with me after studying a community-led vaccination clinic during the COVID-19 pandemic. It delivered hundreds of vaccinations a day, with no formal chain of command or protocols. By any measure, it was a success. What it cost to sustain that success was never examined. Across my empirical work, I kept encountering the same pattern: systems functioning because people stretched roles, coordinated through workarounds and relied on relationships that were not designed to carry the full load. These adaptations were effective. Yet they were also hiding strain.

In this paper, I introduce Brittle Threshold as a concept for attending to this condition. Rather than treating adaptive action as evidence of success, Brittle Threshold frames adaptive action as diagnostic information: evidence of how a system is coping and how close it may be operating to its limits. Drawing on resilience engineering and on empirical patterns from studies of team adaptation and community crisis response, I argue that adaptive success and vulnerability regularly coexist. The more smoothly work appears to run, the more it may depend on fragile support.

Brittle Threshold offers three contributions. It translates what adaptive success conceals in health professions education, it shifts what counts as evidence of system strain and it unsettles the moralisation of endurance as professional virtue. The question it opens is not why systems fail, but when is endurance no longer enough?