something like this: 1770 [AWT-EventQueue-0] INFO Contributors - kotlin: loaded 40 repos 2025 [AWT-EventQueue-0] INFO Contributors - kotlin-examples: loaded 23 contributors 2229 [AWT-EventQueue-0] INFO Contributors the one called loadContributorsBlocking() is from, which is the main UI thread (in Swing, it's an AWT event dispatching thread). This main thread becomes blocked, and that's why the UI is frozen: 885 you ensure that the updateResults() call, which updates the results, happens on the main UI thread (AWT event dispatching thread). However, if you try to load the contributors via the BACKGROUND option