[human in loop]how to interrupt the agent flow and give a confirm/new information to the agent to continue the flow when coding by fastapi?

The current agent flow is coding by fastapi，the agent is a plan agent.

we have two situations:

1.when the agent give a plan, how can I interrupt the agent and make the agent wait the confirm message to continue in the current flow?

2.how to interrupt the current agent flow and add the new message to the agent to continue in the current flow not a new agent? may a new agent with the memory history by the old agent is a another solution?

Thanks for suggestions!