Hi, I instrumented WorkingSession with a log collection that holds timing info for each #startUp: executed. In a clean Pharo 6 image, 62 were run. Most of them resulted in a 0ms execution time (#millisecondsToRun: i.e. they were faster than 1ms). Here is the list of the non zero ones: 1ms startup:true a ClassSessionHandler(ProcessorScheduler) 1ms startup:true a ClassSessionHandler(OSPlatform) 6ms startup:true a ClassSessionHandler(ExternalObject) 1ms startup:true a ClassSessionHandler(DiskStore) 5ms startup:true a ClassSessionHandler(SmalltalkImage) 9ms startup:true a ClassSessionHandler(DisplayScreen) 1ms startup:true a ClassSessionHandler(Cursor) 41ms startup:true a ClassSessionHandler(FT2Handle) 238ms startup:true a ClassSessionHandler(FreeTypeSettings) 1ms startup:true a ClassSessionHandler(WorldMorph) 14ms startup:true a ClassSessionHandler(OmSessionStore) For a total of 318ms I think being able to inspect the WorkingSession and see this list (ordered, with timing info) would be generally useful (and low cost). Even headless, we could access the list using eval. Sven PS: The code of SessionManager/WorkingSession was very readable, well done Christophe !