What should happen when a user changes the task while an agent job is still running?

Consider a scheduling agent: a user asks it to find Friday slots, the lookup starts, then they say 'Actually, Monday, and don't book anything yet.' The Friday result comes back after that correction. Showing stale options is annoying. Using them to book something is a different problem. Canceling the worker may not help if a tool call is already in flight. My instinct is to give each task revision an ID, attach it to background work, and check it again before any action that changes something. Old results could still be kept as context, but couldn't silently become the current plan. If an earlier action has already happened, the agent should report that explicitly. Where would you draw the boundary between amending the existing task and starting a new one? And how do you handle a correction arriving at almost the same moment as the external action? Curious about concrete cases where a simple cancel-and-restart approach wasn't enough.