Persistent goals, not one-shot prompts
An agent holds a stateful objective ("answer this complaint," "prepare for the deposition on the 18th," "reconcile the new production against the outstanding discovery requests") and returns to it across days and turns. That is the single feature that separates an agent from a chat box: the work does not restart every time the tab closes. For a solo running twenty active matters, this is the difference between a tool that saves five minutes per prompt and a tool that saves five hours per matter.