Client Overview

Use a2a::client::A2AClient with a concrete ClientTransport to call A2A servers.

Client capabilities

• SendMessage
• GetTask
• ListTasks
• CancelTask
• SendStreamingMessage
• SubscribeTask
• CreateTaskPushNotificationConfig
• GetTaskPushNotificationConfig
• ListTaskPushNotificationConfigs
• DeleteTaskPushNotificationConfig
• Client interceptors via ClientInterceptor
• Per-call settings through CallOptions

Typical flow

1. Fetch an Agent Card with DiscoveryClient.
2. Select an endpoint with AgentCardResolver::SelectPreferredInterface.
3. Construct HttpJsonTransport, JsonRpcTransport, or GrpcTransport.
4. Create A2AClient with the transport.
5. Invoke task, streaming, or push-notification APIs.
6. Call Destroy() during shutdown when you need transport cleanup.

Default outbound HTTP

When libcurl is available and A2A_ENABLE_LIBCURL=ON, default constructors/factories can perform buffered outbound REST, JSON-RPC, and discovery calls. For tests, custom TLS policy, mTLS, retries, or embedded runtimes, inject your own requester/fetcher callbacks.

Runnable examples

• examples/apps/hello_agent/main.cpp
• examples/apps/simple_client/main.cpp
• examples/apps/streaming_client/main.cpp
• examples/apps/push_notifications/main.cpp