original a2a

Containerfile.txt

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+FROM registry.access.redhat.com/ubi8/python-312
+
+# Set work directory
+WORKDIR /opt/app-root/
+
+# Copy Python Project Files (Container context must be the `python` directory)
+COPY . /opt/app-root
+
+USER root
+
+# Install system build dependencies and UV package manager
+RUN dnf -y update && dnf install -y gcc gcc-c++ \
+ && pip install uv
+
+# Set environment variables for uv:
+# UV_COMPILE_BYTECODE=1: Compiles Python files to .pyc for faster startup
+# UV_LINK_MODE=copy: Ensures files are copied, not symlinked, which can avoid issues
+ENV UV_COMPILE_BYTECODE=1 \
+    UV_LINK_MODE=copy
+
+# Install dependencies using uv sync.
+# --frozen: Ensures uv respects the uv.lock file
+# --no-install-project: Prevents installing the project itself in this stage
+# --no-dev: Excludes development dependencies
+# --mount=type=cache: Leverages Docker's build cache for uv, speeding up repeated builds
+RUN --mount=type=cache,target=/.cache/uv \
+    uv sync --frozen --no-install-project --no-dev
+
+# Install the project
+RUN --mount=type=cache,target=/.cache/uv \
+    uv sync --frozen --no-dev
+
+# Allow non-root user to access the everything in app-root
+RUN chgrp -R root /opt/app-root/ && chmod -R g+rwx /opt/app-root/
+
+# Expose default port (change if needed)
+EXPOSE 9999
+
+USER 1001
+
+# Run the agent
+CMD uv run . --host 0.0.0.0

README-2.md

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+# Hello World Example
+
+Hello World example agent that only returns Message events
+
+## Getting started
+
+1. Start the server
+
+   ```bash
+   uv run .
+   ```
+
+2. Run the test client
+
+   ```bash
+   uv run test_client.py
+   ```
+
+## Build Container Image
+
+Agent can also be built using a container file.
+
+1. Navigate to the directory `samples/python/agents/helloworld` directory:
+
+  ```bash
+  cd samples/python/agents/helloworld
+  ```
+
+2. Build the container file
+
+    ```bash
+    podman build . -t helloworld-a2a-server
+    ```
+
+> [!Tip]  
+> Podman is a drop-in replacement for `docker` which can also be used in these commands.
+
+3. Run you container
+
+    ```bash
+    podman run -p 9999:9999 helloworld-a2a-server
+    ```
+
+## Validate
+
+To validate in a separate terminal, run the A2A client:
+
+```bash
+cd samples/python/hosts/cli
+uv run . --agent http://localhost:9999
+```
+
+
+## Disclaimer
+Important: The sample code provided is for demonstration purposes and illustrates the mechanics of the Agent-to-Agent (A2A) protocol. When building production applications, it is critical to treat any agent operating outside of your direct control as a potentially untrusted entity.
+
+All data received from an external agent—including but not limited to its AgentCard, messages, artifacts, and task statuses—should be handled as untrusted input. For example, a malicious agent could provide an AgentCard containing crafted data in its fields (e.g., description, name, skills.description). If this data is used without sanitization to construct prompts for a Large Language Model (LLM), it could expose your application to prompt injection attacks.  Failure to properly validate and sanitize this data before use can introduce security vulnerabilities into your application.
+
+Developers are responsible for implementing appropriate security measures, such as input validation and secure handling of credentials to protect their systems and users.

__main__.py

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+import uvicorn
+
+from a2a.server.apps import A2AStarletteApplication
+from a2a.server.request_handlers import DefaultRequestHandler
+from a2a.server.tasks import InMemoryTaskStore
+from a2a.types import (
+    AgentCapabilities,
+    AgentCard,
+    AgentSkill,
+)
+from agent_executor import (
+    HelloWorldAgentExecutor,  # type: ignore[import-untyped]
+)
+
+
+if __name__ == '__main__':
+    # --8<-- [start:AgentSkill]
+    skill = AgentSkill(
+        id='hello_world',
+        name='Returns hello world',
+        description='just returns hello world',
+        tags=['hello world'],
+        examples=['hi', 'hello world'],
+    )
+    # --8<-- [end:AgentSkill]
+
+    extended_skill = AgentSkill(
+        id='super_hello_world',
+        name='Returns a SUPER Hello World',
+        description='A more enthusiastic greeting, only for authenticated users.',
+        tags=['hello world', 'super', 'extended'],
+        examples=['super hi', 'give me a super hello'],
+    )
+
+    # --8<-- [start:AgentCard]
+    # This will be the public-facing agent card
+    public_agent_card = AgentCard(
+        name='Hello World Agent',
+        description='Just a hello world agent',
+        url='http://localhost:9999/',
+        version='1.0.0',
+        default_input_modes=['text'],
+        default_output_modes=['text'],
+        capabilities=AgentCapabilities(streaming=True),
+        skills=[skill],  # Only the basic skill for the public card
+        supports_authenticated_extended_card=True,
+    )
+    # --8<-- [end:AgentCard]
+
+    # This will be the authenticated extended agent card
+    # It includes the additional 'extended_skill'
+    specific_extended_agent_card = public_agent_card.model_copy(
+        update={
+            'name': 'Hello World Agent - Extended Edition',  # Different name for clarity
+            'description': 'The full-featured hello world agent for authenticated users.',
+            'version': '1.0.1',  # Could even be a different version
+            # Capabilities and other fields like url, default_input_modes, default_output_modes,
+            # supports_authenticated_extended_card are inherited from public_agent_card unless specified here.
+            'skills': [
+                skill,
+                extended_skill,
+            ],  # Both skills for the extended card
+        }
+    )
+
+    request_handler = DefaultRequestHandler(
+        agent_executor=HelloWorldAgentExecutor(),
+        task_store=InMemoryTaskStore(),
+    )
+
+    server = A2AStarletteApplication(
+        agent_card=public_agent_card,
+        http_handler=request_handler,
+        extended_agent_card=specific_extended_agent_card,
+    )
+
+    uvicorn.run(server.build(), host='0.0.0.0', port=9999)

agent_executor.py

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+from a2a.server.agent_execution import AgentExecutor, RequestContext
+from a2a.server.events import EventQueue
+from a2a.utils import new_agent_text_message
+
+
+# --8<-- [start:HelloWorldAgent]
+class HelloWorldAgent:
+    """Hello World Agent."""
+
+    async def invoke(self) -> str:
+        return 'Hello World'
+
+
+# --8<-- [end:HelloWorldAgent]
+
+
+# --8<-- [start:HelloWorldAgentExecutor_init]
+class HelloWorldAgentExecutor(AgentExecutor):
+    """Test AgentProxy Implementation."""
+
+    def __init__(self):
+        self.agent = HelloWorldAgent()
+
+    # --8<-- [end:HelloWorldAgentExecutor_init]
+    # --8<-- [start:HelloWorldAgentExecutor_execute]
+    async def execute(
+        self,
+        context: RequestContext,
+        event_queue: EventQueue,
+    ) -> None:
+        result = await self.agent.invoke()
+        await event_queue.enqueue_event(new_agent_text_message(result))
+
+    # --8<-- [end:HelloWorldAgentExecutor_execute]
+
+    # --8<-- [start:HelloWorldAgentExecutor_cancel]
+    async def cancel(
+        self, context: RequestContext, event_queue: EventQueue
+    ) -> None:
+        raise Exception('cancel not supported')
+
+    # --8<-- [end:HelloWorldAgentExecutor_cancel]

pyproject.toml

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+[project]
+name = "helloworld"
+version = "0.1.0"
+description = "HelloWorld agent example that only returns Messages"
+readme = "README.md"
+requires-python = ">=3.10"
+dependencies = [
+    "a2a-sdk>=0.3.0",
+    "click>=8.1.8",
+    "dotenv>=0.9.9",
+    "httpx>=0.28.1",
+    "langchain-google-genai>=2.1.4",
+    "langgraph>=0.4.1",
+    "pydantic>=2.11.4",
+    "python-dotenv>=1.1.0",
+    "sse-starlette>=2.3.5",
+    "starlette>=0.46.2",
+    "uvicorn>=0.34.2",
+]
+
+[tool.hatch.build.targets.wheel]
+packages = ["."]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"