The growth in System-on-Chip complexity puts pressure on system verification. Due to limitations in the pre-silicon verification process, errors in hardware and software slip through to the stage when silicon and the complete software stack are first brought together. Finding the remaining errors at this stage is becoming increasing difficult. We propose that debugging should be communication-centric at first and based on transactions. We combine run-time, on-chip abstraction of system data to the transaction level, with system-level debug control over the communication infrastructure. We prove our concepts and architecture with a gate-level implementation that includes a Network-on- Chip, breakpoint monitors, clock and reset control (all programmable through an IEEE 1149.1 TAP), and give a quantification of the associated hardware cost.