Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

root cause

The first exception in a chain: the last Caused by section of a stack trace.

Debugging starts from the root cause and the first frame of your own code under it; the exceptions above it are wrappers added on the way up.