High-Level Synthesis (HLS) code is often developed using a subset of C/C++, along with specialized libraries. This allows HLS engineers to make use of standard software engineering tools and techniques during the development and debug phase of their project. This paper introduces the topic of time-travel debugging, whereby the state of a design can be examined by going backwards and forwards in time. This approach saves huge amounts of effort, allowing the root cause of bugs, including challenging concurrency bugs, to be found with ease and a new codebase to be understood rapidly. Furthermore, it is possible to extract “waveforms” from a time-travel recording and thus allow HLS implementations to be analyzed in a style more familiar to many hardware engineers. We explain the application of time-travel debugging to HLS designs and the advantages, availability and limitations of this approach.