Agent2Agent (A2A)
Returning a checkpoint as an artifact
Section titled “Returning a checkpoint as an artifact”An A2A agent that hands work to another agent, or pauses a task, can return the checkpoint as an
Artifact with a data part containing the document, and the part’s media type set to
application/vnd.opencheckpoint+json. The receiving agent treats it as untrusted input and
follows the restoration procedure.
Referencing A2A records
Section titled “Referencing A2A records”"session_refs": [ { "protocol": "a2a", "id": "ctx-holiday-2026", "event": "task-holiday-hours-07" }]Use the contextId as id and the task id as event. A consumer with access to the originating
agent may retrieve history; one without it relies on the checkpoint alone.
Mapping
Section titled “Mapping”| A2A | OpenCheckpoint |
|---|---|
TaskState.INPUT_REQUIRED |
task.status: awaiting_input, and an operation of kind input |
TaskState.AUTH_REQUIRED |
an operation of kind approval, or a requirement of kind access |
Artifact (deliverable) |
a resource of kind artifact |
Part with url |
a resource with uri and media_type |
contextId, referenceTaskIds |
source.session_refs |
A checkpoint sits alongside A2A task history and holds the distilled state a different agent needs to continue without that history.