JumboTrace is a tool that can track and record what happens when a Java program runs, including the values of variables and which lines of code get executed. It modifies the program's code to add logging, and the logs get stored in a file for later viewing. This can help understand how a program works and find bugs.

JumboTrace is an experimental tracer for Java programs that records the evolution of program state during execution to build a trace (sequence of events and executed lines). It works by injecting logging calls into the program using a compiler plugin for javac. The logged events are written to a binary file using serialization, and a minimal frontend can display the traces in the console.