The Capture / Integrate agent as defined with the agent / agentplugin action is running as an integral part of the replication stream. It is part of the replication job (hence the term plug in), HVR is capturing its output & status and acts upon it.
When a running replication job is suspended, HVR will clean up all parts of this job including a running agent.
This clean up is done gracefully, by sending a termination signal to the agent process . The agent can therefore be programmed to catch the termination signal and perform a proper rollback when needed.