Streaming

Streaming is available through client APIs and server stream sessions.

Client APIs

• A2AClient::SendStreamingMessage(request, observer, options)
• A2AClient::SubscribeTask(request, observer, options)

Implement a2a::client::StreamObserver:

• OnEvent(const StreamResponse&) for each event.
• OnError(const core::Error&) for transport or protocol failures.
• OnCompleted() when the stream finishes normally.

Both calls return a StreamHandle. Call Cancel() to request cancellation and IsActive() to check handle state.

Threading contract

Observer callbacks run on transport-managed background threads. Keep observers alive until stream completion, cancellation, or handle destruction. Callback code should be thread-safe, fast, and non-blocking.

Server side

Executors return std::unique_ptr<ServerStreamSession> from SendStreamingMessage and, optionally, SubscribeTask. A stream session publishes StreamResponse values until it returns an empty optional or an error.

Examples

• examples/apps/streaming_client/main.cpp
• examples/apps/streaming_server/main.cpp