a2a.server.request_handlers.request_handler module

class a2a.server.request_handlers.request_handler.RequestHandler

Bases: ABC

A2A request handler interface.

This interface defines the methods that an A2A server implementation must provide to handle incoming JSON-RPC requests.

abstractmethod async on_cancel_task(params: TaskIdParams, context: ServerCallContext | None = None) → Task | None

Handles the ‘tasks/cancel’ method.

Requests the agent to cancel an ongoing task.

Parameters:

  • params – Parameters specifying the task ID.

  • context – Context provided by the server.

Returns:

The Task object with its status updated to canceled, or None if the task was not found.

abstractmethod async on_delete_task_push_notification_config(params: DeleteTaskPushNotificationConfigParams, context: ServerCallContext | None = None) → None

Handles the ‘tasks/pushNotificationConfig/delete’ method.

Deletes a push notification configuration associated with a task.

Parameters:

  • params – Parameters including the task ID.

  • context – Context provided by the server.

Returns:

None

abstractmethod async on_get_task(params: TaskQueryParams, context: ServerCallContext | None = None) → Task | None

Handles the ‘tasks/get’ method.

Retrieves the state and history of a specific task.

Parameters:

  • params – Parameters specifying the task ID and optionally history length.

  • context – Context provided by the server.

Returns:

The Task object if found, otherwise None.

abstractmethod async on_get_task_push_notification_config(params: TaskIdParams | GetTaskPushNotificationConfigParams, context: ServerCallContext | None = None) → TaskPushNotificationConfig

Handles the ‘tasks/pushNotificationConfig/get’ method.

Retrieves the current push notification configuration for a task.

Parameters:

  • params – Parameters including the task ID.

  • context – Context provided by the server.

Returns:

The TaskPushNotificationConfig for the task.

abstractmethod async on_list_task_push_notification_config(params: ListTaskPushNotificationConfigParams, context: ServerCallContext | None = None) → list[TaskPushNotificationConfig]

Handles the ‘tasks/pushNotificationConfig/list’ method.

Retrieves the current push notification configurations for a task.

Parameters:

  • params – Parameters including the task ID.

  • context – Context provided by the server.

Returns:

The list[TaskPushNotificationConfig] for the task.

abstractmethod async on_message_send(params: MessageSendParams, context: ServerCallContext | None = None) → Task | Message

Handles the ‘message/send’ method (non-streaming).

Sends a message to the agent to create, continue, or restart a task, and waits for the final result (Task or Message).

Parameters:

  • params – Parameters including the message and configuration.

  • context – Context provided by the server.

Returns:

The final Task object or a final Message object.

abstractmethod async on_message_send_stream(params: MessageSendParams, context: ServerCallContext | None = None) → AsyncGenerator[Message | Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent]

Handles the ‘message/stream’ method (streaming).

Sends a message to the agent and yields stream events as they are produced (Task updates, Message chunks, Artifact updates).

Parameters:

  • params – Parameters including the message and configuration.

  • context – Context provided by the server.

Yields:

Event objects from the agent’s execution.

Raises:

ServerError(UnsupportedOperationError) – By default, if not implemented.

abstractmethod async on_resubscribe_to_task(params: TaskIdParams, context: ServerCallContext | None = None) → AsyncGenerator[Message | Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent]

Handles the ‘tasks/resubscribe’ method.

Allows a client to re-subscribe to a running streaming task’s event stream.

Parameters:

  • params – Parameters including the task ID.

  • context – Context provided by the server.

Yields:

Event objects from the agent’s ongoing execution for the specified task.

Raises:

ServerError(UnsupportedOperationError) – By default, if not implemented.

abstractmethod async on_set_task_push_notification_config(params: TaskPushNotificationConfig, context: ServerCallContext | None = None) → TaskPushNotificationConfig

Handles the ‘tasks/pushNotificationConfig/set’ method.

Sets or updates the push notification configuration for a task.

Parameters:

  • params – Parameters including the task ID and push notification configuration.

  • context – Context provided by the server.

Returns:

The provided TaskPushNotificationConfig upon success.