Sending Messages

A2AClient::SendMessage starts or continues a task by sending a protobuf lf::a2a::v1::SendMessageRequest through the configured transport.

Request construction guidance

• Set a stable message.message_id for idempotency and diagnostics.
• Let the server generate a task ID for new work unless you are intentionally continuing an existing task.
• Attach push-notification config only when the target Agent Card advertises support and your server policy allows it.
• Use CallOptions for per-call deadlines, metadata, or auth settings where supported by the transport.

Response handling

The response can contain immediate task state and output data. Persist task identifiers in logs/telemetry so later GetTask, CancelTask, streaming subscription, or push-notification calls can be correlated.

Failure paths to test

• Network or HTTP/gRPC transport failure.
• Serialization or protocol validation failure.
• Auth policy rejection.
• Unsupported operation or required extension mismatch.
• Duplicate/retry behavior for repeated message IDs.

Related pages

• Discovery
• Get Task
• Cancel Task
• Authentication