Correct, this indicates that recompilation occurred. The first time Graal compiled some of the UI machinery, which is all written in Smalltalk, no input events were triggered in the IDE. Consequently, the partial evaluator removed those code paths from compiled code. When we move the mouse over the window or start to click on UI elements, we cause recompilation, now with event handling compiled in. That's why these performance cliffs go away over time.