Task state

A task state is the TaskState enum value in a task’s status.state field that tells a client where the task is in its lifecycle. A2A v1.0 defines eight lifecycle values, plus TASK_STATE_UNSPECIFIED for an unknown or indeterminate state (a2a.proto).

v1.0 value	v0.3 string	Kind
TASK_STATE_SUBMITTED	submitted	In progress: submitted and acknowledged
TASK_STATE_WORKING	working	In progress: being processed
TASK_STATE_INPUT_REQUIRED	input-required	Interrupted: needs input from the client
TASK_STATE_AUTH_REQUIRED	auth-required	Interrupted: needs authorization
TASK_STATE_COMPLETED	completed	Terminal: finished successfully
TASK_STATE_FAILED	failed	Terminal: finished with an error
TASK_STATE_CANCELED	canceled	Terminal: canceled before completion
TASK_STATE_REJECTED	rejected	Terminal: the agent decided not to perform it

In v0.3, the string unknown played the role of TASK_STATE_UNSPECIFIED.

Encoding. v1.0 JSON follows ProtoJSON, so the state is the enum name as a string (section 5.5). It sits in a TaskStatus object next to an optional status message and a timestamp:

{"state": "TASK_STATE_WORKING", "timestamp": "2026-09-25T14:03:11.482Z"}

Why the groups matter. A blocking Send Message call returns once the task reaches a terminal or an interrupted state (section 3.2.2). A streaming response for a task closes when it reaches a terminal state. Interrupted tasks still accept messages on the same task; terminal tasks do not, and follow-up work needs a new task. Clients can filter List Tasks by state, for example to find every task still in TASK_STATE_WORKING.

Extending states. The A2A extensions guide says extensions should not add values to enums such as this one. An extension that needs a finer-grained status should keep the standard state and put the extra meaning in metadata.