chore: refactors hello world example

[msampathkumar]

Description

This pull request refactors the Hello World agent sample and test client to align with the latest A2A Python SDK v1.0 patterns, improving modularity for documentation rendering, runtime clarity, and overall code maintainability.

• AgentExecutor: used TaskUpdater class to simply updates to EventQueue
• Client: re-arrange imports to user visibility

• Follow the CONTRIBUTING Guide.

[msampathkumar]

Sharing test-logs

$ date
Fri May 15 00:31:24 CEST 2026
$ python test_client.py 
Initializes the A2ACardResolver instance with an HTTP client

Successfully fetched the public agent card:
====================================================
                     AgentCard                      
====================================================
--- General ---
Name        : Hello World Agent
Description : Just a hello world agent
Version     : 0.0.1

--- Interfaces ---
  [0] http://127.0.0.1:9999  (JSONRPC)

--- Capabilities ---
Streaming           : True
Push notifications  : False
Extended agent card : True

--- I/O Modes ---
Input  : text/plain
Output : text/plain

--- Skills ---
----------------------------------------------------
  ID          : hello_world
  Name        : Returns hello world
  Description : just returns hello world
  Tags        : hello world
  Example     : hi
  Example     : hello world
====================================================

--- Public Agent Card - Non-Streaming Call ---

Initializing a non-streaming client.
Response:
task {
  id: "993c64d2-223b-409b-86d4-20f60d057508"
  context_id: "ac0809eb-15c2-4dc0-8f0a-ede60043deeb"
  status {
    state: TASK_STATE_COMPLETED
    message {
      message_id: "0abb39b3-9f5b-4a7c-916d-6e15d533836e"
      role: ROLE_AGENT
      parts {
        text: "Request is completed!"
      }
    }
    timestamp {
      seconds: 1778797889
      nanos: 129454000
    }
  }
  artifacts {
    artifact_id: "e277355b-7f92-43de-81e1-e4d5feb826de"
    parts {
      text: "Hello, World! I have received your request (Say hello.)"
      media_type: "text/plain"
    }
  }
  history {
    message_id: "1fc12616-a1aa-4354-8325-9c7311456130"
    context_id: "ac0809eb-15c2-4dc0-8f0a-ede60043deeb"
    task_id: "993c64d2-223b-409b-86d4-20f60d057508"
    role: ROLE_USER
    parts {
      text: "Say hello."
    }
  }
  history {
    message_id: "51bf8d48-ea16-41bf-9152-4a9965a5f13c"
    role: ROLE_AGENT
    parts {
      text: "Processing request..."
    }
  }
}


--- Public Agent Card - Streaming Call ---

Initializing a streaming client.
Response:
task {
  id: "2ba4d092-e7db-46d5-b24d-69d97afd046e"
  context_id: "587f906a-7158-48db-9721-cdf592083a90"
  status {
    state: TASK_STATE_SUBMITTED
  }
  history {
    message_id: "1fc12616-a1aa-4354-8325-9c7311456130"
    context_id: "587f906a-7158-48db-9721-cdf592083a90"
    task_id: "2ba4d092-e7db-46d5-b24d-69d97afd046e"
    role: ROLE_USER
    parts {
      text: "Say hello."
    }
  }
}

status_update {
  task_id: "2ba4d092-e7db-46d5-b24d-69d97afd046e"
  context_id: "587f906a-7158-48db-9721-cdf592083a90"
  status {
    state: TASK_STATE_WORKING
    message {
      message_id: "434e2050-96b0-4891-b845-2ca925aa40b6"
      role: ROLE_AGENT
      parts {
        text: "Processing request..."
      }
    }
    timestamp {
      seconds: 1778797889
      nanos: 141284000
    }
  }
}

artifact_update {
  task_id: "2ba4d092-e7db-46d5-b24d-69d97afd046e"
  context_id: "587f906a-7158-48db-9721-cdf592083a90"
  artifact {
    artifact_id: "ba71abee-0cb5-4d9e-85e2-e927e7fbb150"
    parts {
      text: "Hello, World! I have received your request (Say hello.)"
      media_type: "text/plain"
    }
  }
}

status_update {
  task_id: "2ba4d092-e7db-46d5-b24d-69d97afd046e"
  context_id: "587f906a-7158-48db-9721-cdf592083a90"
  status {
    state: TASK_STATE_COMPLETED
    message {
      message_id: "41bc3c20-ba83-4c3b-a286-ba2685607c34"
      role: ROLE_AGENT
      parts {
        text: "Request is completed!"
      }
    }
    timestamp {
      seconds: 1778797889
      nanos: 141317000
    }
  }
}


--- Extended Agent Card - Non-Streaming Call ---

Successfully fetched the authenticated extended agent card:
====================================================
                     AgentCard                      
====================================================
--- General ---
Name        : Hello World Agent - Extended Edition
Description : The full-featured hello world agent for authenticated users.
Version     : 0.0.2

--- Interfaces ---
  [0] http://127.0.0.1:9999  (JSONRPC)

--- Capabilities ---
Streaming           : True
Push notifications  : False
Extended agent card : True

--- I/O Modes ---
Input  : text/plain
Output : text/plain

--- Skills ---
----------------------------------------------------
  ID          : hello_world
  Name        : Returns hello world
  Description : just returns hello world
  Tags        : hello world
  Example     : hi
  Example     : hello world
----------------------------------------------------
  ID          : super_hello_world
  Name        : Returns a SUPER Hello World
  Description : A more enthusiastic greeting, only for authenticated users.
  Tags        : hello world, super, extended
  Example     : super hi
  Example     : give me a super hello
====================================================

[gemini-code-assist]

Code Review

This pull request refactors the HelloWorldAgent and its executor to utilize the TaskUpdater utility for managing task statuses and artifacts. It also updates test_client.py by moving imports into the main function and enhancing console output. The review feedback suggests using str.join() for more idiomatic string concatenation and replacing the generic Exception with NotImplementedError in the cancel method.

[sokoliva]

lets utilize get_text_parts helper

[sokoliva]

The reason we put print('Response chunk:') inside the response iteration from send_message was to display the difference between streaming and non-streaming. Can we somehow make the difference between streaming and non-streaming obvious in the stdout?

[msampathkumar]

In the tutorial, we have both streaming and non-stream snippets, one after the other.

To make it easy to identify the differences in ClientConfig, I am keep this pattern.

[sokoliva]

In non-streaming response comes as a one chunk, in streaming we get multiple chunks. With this setup this is not visible. Can we somehow make that obvious?

[msampathkumar]

Suggested change

	streaming_config = ClientConfig(streaming=True)
	streaming_config = ClientConfig(streaming=True) # Enable streaming