Streaming Demo

examples/02_streaming demonstrates tasks/sendSubscribe and Server-Sent Events (SSE). The server streams an article word by word, and the client prints chunks as they arrive.

Files

File	Purpose
examples/02_streaming/server.rb	Defines StreamingExecutor, advertises streaming support, and emits status and artifact events
examples/02_streaming/client.rb	Uses A2A.sse_client and send_subscribe to consume streamed events

Run it

From the repository root:

bundle exec ruby examples/run 02_streaming

Manual run:

bundle exec ruby examples/02_streaming/server.rb
bundle exec ruby examples/02_streaming/client.rb

Server behavior

The streaming executor starts the task, emits a working status, sends artifact chunks, completes the task, and emits a final status.

def call(ctx)
  ctx.task.start!
  ctx.emit_status

  WORDS.each_with_index do |word, i|
    text = i.zero? ? word : " #{word}"

    artifact = A2A::Models::Artifact.new(
      parts: [A2A::Models::Part.text(text)]
    )

    ctx.emit_artifact(artifact, append: i > 0, last_chunk: i == WORDS.length - 1)
  end

  ctx.task.complete!
  ctx.emit_status(final: true)
end

The agent card declares streaming support:

A2A::Models::AgentCapabilities.new(streaming: true)

Client behavior

The client uses A2A.sse_client instead of A2A.client:

client = A2A.sse_client(url: "http://localhost:9292")

client.send_subscribe(message: A2A::Models::Message.user("stream")) do |event|
  case event
  when A2A::Models::TaskStatusUpdateEvent
    # task state changed
  when A2A::Models::TaskArtifactUpdateEvent
    print event.artifact.parts.map(&:text).join
  end
end

It also tracks event count, word count, elapsed time, and effective words per minute, which makes it useful for checking end-to-end streaming behavior.

Relationship to the guide

The Streaming Responses guide explains the API in isolation. This demo shows the same flow as a runnable pair of scripts.