Feature of the Sourced runtime: as each handler produces events from a command, the runtime tags the pair so every downstream command/event in the chain is correlated back to the original trigger. The request ID from a load balancer can be used as the first command's ID, giving end-to-end workflow traces even across servers and async workers. Enables UIs that list exactly what happened in a workflow (UI command → event → reaction → new command → …) and time-travel UIs that load historical state from events.