How does the client record the task IDs that have been sent

There is a scenario where the client initiates event subscription to the server and maintains a long connection through SSE. When the SSE is disconnected due to network fluctuations, the client needs to re-subscribe.

But at this point, how can the client know the task ID of the subscription?

Can it only be achieved by persisting the context ID or the task ID?

What should the best practices be like?