Methods, systems and computer program products for architecting fault tolerant applications. Embodiments of the invention include a method for executing an application in a computer system, the method including monitoring a behavior of the computer system, the computer system having a subsystem in an operating system of the computer system, in response to encountering a problem in the computer system, performing switching the application from a normal mode of operation to a critical mode of operation, executing the application in the critical mode of operation, determining if the computer system has returned to the normal mode of operation, in response to the computer system returning to the normal mode of operation switching the application to execute in the normal mode and executing the application in the normal mode of operation.