feat: Add A2A (Agent-to-Agent) protocol support for remote interoperability

- Implement CrewAgentExecutor class that wraps CrewAI crews as A2A-compatible agents
- Add server utilities for starting A2A servers with crews
- Include comprehensive test coverage for all A2A functionality
- Add optional dependency group 'a2a' in pyproject.toml
- Expose A2A classes in main CrewAI module with graceful import handling
- Add documentation and examples for A2A integration
- Support bidirectional agent communication via A2A protocol
- Enable crews to participate in remote agent networks

Fixes #2970

Co-Authored-By: João <joao@crewai.com>

docs/concepts/a2a-integration.md

@@ -0,0 +1,184 @@
+# A2A Protocol Integration
+
+CrewAI supports the A2A (Agent-to-Agent) protocol, enabling your crews to participate in remote agent interoperability. This allows CrewAI crews to be exposed as remotely accessible agents that can communicate with other A2A-compatible systems.
+
+## Overview
+
+The A2A protocol is Google's standard for agent interoperability that enables bidirectional communication between agents. CrewAI's A2A integration provides:
+
+- **Remote Interoperability**: Expose crews as A2A-compatible agents
+- **Bidirectional Communication**: Enable full-duplex agent interactions
+- **Protocol Compliance**: Full support for A2A specifications
+- **Transport Flexibility**: Support for multiple transport protocols
+
+## Installation
+
+A2A support is available as an optional dependency:
+
+```bash
+pip install crewai[a2a]
+```
+
+## Basic Usage
+
+### Creating an A2A Server
+
+```python
+from crewai import Agent, Crew, Task
+from crewai.a2a import CrewAgentExecutor, start_a2a_server
+
+# Create your crew
+agent = Agent(
+    role="Assistant",
+    goal="Help users with their queries",
+    backstory="A helpful AI assistant"
+)
+
+task = Task(
+    description="Help with: {query}",
+    agent=agent
+)
+
+crew = Crew(agents=[agent], tasks=[task])
+
+# Create A2A executor
+executor = CrewAgentExecutor(crew)
+
+# Start A2A server
+start_a2a_server(executor, host="0.0.0.0", port=10001)
+```
+
+### Custom Configuration
+
+```python
+from crewai.a2a import CrewAgentExecutor, create_a2a_app
+
+# Create executor with custom content types
+executor = CrewAgentExecutor(
+    crew=crew,
+    supported_content_types=['text', 'application/json', 'image/png']
+)
+
+# Create custom A2A app
+app = create_a2a_app(
+    executor,
+    agent_name="My Research Crew",
+    agent_description="A specialized research and analysis crew",
+    transport="starlette"
+)
+
+# Run with custom ASGI server
+import uvicorn
+uvicorn.run(app, host="0.0.0.0", port=8080)
+```
+
+## Key Features
+
+### CrewAgentExecutor
+
+The `CrewAgentExecutor` class wraps CrewAI crews to implement the A2A `AgentExecutor` interface:
+
+- **Asynchronous Execution**: Crews run asynchronously within the A2A protocol
+- **Task Management**: Automatic handling of task lifecycle and cancellation
+- **Error Handling**: Robust error handling with A2A-compliant responses
+- **Output Conversion**: Automatic conversion of crew outputs to A2A artifacts
+
+### Server Utilities
+
+Convenience functions for starting A2A servers:
+
+- `start_a2a_server()`: Quick server startup with default configuration
+- `create_a2a_app()`: Create custom A2A applications for advanced use cases
+
+## Protocol Compliance
+
+CrewAI's A2A integration provides full protocol compliance:
+
+- **Agent Cards**: Automatic generation of agent capability descriptions
+- **Task Execution**: Asynchronous task processing with event queues
+- **Artifact Management**: Conversion of crew outputs to A2A artifacts
+- **Error Handling**: A2A-compliant error responses and status codes
+
+## Use Cases
+
+### Remote Agent Networks
+
+Expose CrewAI crews as part of larger agent networks:
+
+```python
+# Multi-agent system with specialized crews
+research_crew = create_research_crew()
+analysis_crew = create_analysis_crew()
+writing_crew = create_writing_crew()
+
+# Expose each as A2A agents on different ports
+start_a2a_server(CrewAgentExecutor(research_crew), port=10001)
+start_a2a_server(CrewAgentExecutor(analysis_crew), port=10002)
+start_a2a_server(CrewAgentExecutor(writing_crew), port=10003)
+```
+
+### Cross-Platform Integration
+
+Enable CrewAI crews to work with other agent frameworks:
+
+```python
+# CrewAI crew accessible to other A2A-compatible systems
+executor = CrewAgentExecutor(crew)
+start_a2a_server(executor, host="0.0.0.0", port=10001)
+
+# Other systems can now invoke this crew remotely
+```
+
+## Advanced Configuration
+
+### Custom Agent Cards
+
+```python
+from a2a.types import AgentCard, AgentCapabilities, AgentSkill
+
+# Custom agent card for specialized capabilities
+agent_card = AgentCard(
+    name="Specialized Research Crew",
+    description="Advanced research and analysis capabilities",
+    version="2.0.0",
+    capabilities=AgentCapabilities(
+        streaming=True,
+        pushNotifications=False
+    ),
+    skills=[
+        AgentSkill(
+            id="research",
+            name="Research Analysis",
+            description="Comprehensive research and analysis",
+            tags=["research", "analysis", "data"]
+        )
+    ]
+)
+```
+
+### Error Handling
+
+The A2A integration includes comprehensive error handling:
+
+- **Validation Errors**: Input validation with clear error messages
+- **Execution Errors**: Crew execution errors converted to A2A artifacts
+- **Cancellation**: Proper task cancellation support
+- **Timeouts**: Configurable timeout handling
+
+## Best Practices
+
+1. **Resource Management**: Monitor crew resource usage in server environments
+2. **Error Handling**: Implement proper error handling in crew tasks
+3. **Security**: Use appropriate authentication and authorization
+4. **Monitoring**: Monitor A2A server performance and health
+5. **Scaling**: Consider load balancing for high-traffic scenarios
+
+## Limitations
+
+- **Optional Dependency**: A2A support requires additional dependencies
+- **Transport Support**: Currently supports Starlette transport only
+- **Synchronous Crews**: Crews execute synchronously within async A2A context
+
+## Examples
+
+See the `examples/a2a_integration_example.py` file for a complete working example of A2A integration with CrewAI.

examples/a2a_integration_example.py

@@ -0,0 +1,64 @@
+"""Example: CrewAI A2A Integration
+
+This example demonstrates how to expose a CrewAI crew as an A2A (Agent-to-Agent)
+protocol server for remote interoperability.
+
+Requirements:
+    pip install crewai[a2a]
+"""
+
+from crewai import Agent, Crew, Task
+from crewai.a2a import CrewAgentExecutor, start_a2a_server
+
+
+def main():
+    """Create and start an A2A server with a CrewAI crew."""
+    
+    researcher = Agent(
+        role="Research Analyst",
+        goal="Provide comprehensive research and analysis on any topic",
+        backstory=(
+            "You are an experienced research analyst with expertise in "
+            "gathering, analyzing, and synthesizing information from various sources."
+        ),
+        verbose=True
+    )
+    
+    research_task = Task(
+        description=(
+            "Research and analyze the topic: {query}\n"
+            "Provide a comprehensive overview including:\n"
+            "- Key concepts and definitions\n"
+            "- Current trends and developments\n"
+            "- Important considerations\n"
+            "- Relevant examples or case studies"
+        ),
+        agent=researcher,
+        expected_output="A detailed research report with analysis and insights"
+    )
+    
+    research_crew = Crew(
+        agents=[researcher],
+        tasks=[research_task],
+        verbose=True
+    )
+    
+    executor = CrewAgentExecutor(
+        crew=research_crew,
+        supported_content_types=['text', 'text/plain', 'application/json']
+    )
+    
+    print("Starting A2A server with CrewAI research crew...")
+    print("Server will be available at http://localhost:10001")
+    print("Use the A2A CLI or SDK to interact with the crew remotely")
+    
+    start_a2a_server(
+        executor,
+        host="0.0.0.0",
+        port=10001,
+        transport="starlette"
+    )
+
+
+if __name__ == "__main__":
+    main()

pyproject.toml

@@ -65,8 +65,8 @@ mem0 = ["mem0ai>=0.1.94"]
 docling = [
     "docling>=2.12.0",
 ]
-aisuite = [
+a2a = [
-    "aisuite>=0.1.10",
+    "a2a-sdk>=0.0.1",
 ]
 
 [tool.uv]

src/crewai/__init__.py

@@ -32,3 +32,9 @@ __all__ = [
     "TaskOutput",
     "LLMGuardrail",
 ]
+
+try:
+    from crewai.a2a import CrewAgentExecutor, start_a2a_server, create_a2a_app
+    __all__.extend(["CrewAgentExecutor", "start_a2a_server", "create_a2a_app"])
+except ImportError:
+    pass

src/crewai/a2a/__init__.py

@@ -0,0 +1,49 @@
+"""A2A (Agent-to-Agent) protocol integration for CrewAI.
+
+This module provides integration with the A2A protocol to enable remote agent
+interoperability. It allows CrewAI crews to be exposed as A2A-compatible agents
+that can communicate with other agents following the A2A protocol standard.
+
+The integration is optional and requires the 'a2a' extra dependency:
+    pip install crewai[a2a]
+
+Example:
+    from crewai import Agent, Crew, Task
+    from crewai.a2a import CrewAgentExecutor, start_a2a_server
+    
+    agent = Agent(role="Assistant", goal="Help users", backstory="Helpful AI")
+    task = Task(description="Help with {query}", agent=agent)
+    crew = Crew(agents=[agent], tasks=[task])
+    
+    executor = CrewAgentExecutor(crew)
+    start_a2a_server(executor, host="localhost", port=8080)
+"""
+
+try:
+    from .crew_agent_executor import CrewAgentExecutor
+    from .server import start_a2a_server, create_a2a_app
+    
+    __all__ = [
+        "CrewAgentExecutor",
+        "start_a2a_server", 
+        "create_a2a_app"
+    ]
+except ImportError as e:
+    import warnings
+    warnings.warn(
+        "A2A integration requires the 'a2a' extra dependency. "
+        "Install with: pip install crewai[a2a]",
+        ImportWarning
+    )
+    
+    def _missing_dependency(*args, **kwargs):
+        raise ImportError(
+            "A2A integration requires the 'a2a' extra dependency. "
+            "Install with: pip install crewai[a2a]"
+        )
+    
+    CrewAgentExecutor = _missing_dependency
+    start_a2a_server = _missing_dependency
+    create_a2a_app = _missing_dependency
+    
+    __all__ = []

src/crewai/a2a/crew_agent_executor.py

@@ -0,0 +1,244 @@
+"""CrewAI Agent Executor for A2A Protocol Integration.
+
+This module implements the A2A AgentExecutor interface to enable CrewAI crews
+to participate in the Agent-to-Agent protocol for remote interoperability.
+"""
+
+import asyncio
+import logging
+from typing import Any, Dict, Optional
+
+from crewai import Crew
+from crewai.crew import CrewOutput
+
+try:
+    from a2a.server.agent_execution.agent_executor import AgentExecutor
+    from a2a.server.agent_execution.context import RequestContext
+    from a2a.server.events.event_queue import EventQueue
+    from a2a.types import (
+        FilePart,
+        FileWithBytes,
+        InvalidParamsError,
+        Part,
+        Task,
+        TextPart,
+        UnsupportedOperationError,
+    )
+    from a2a.utils import completed_task, new_artifact
+    from a2a.utils.errors import ServerError
+except ImportError:
+    raise ImportError(
+        "A2A integration requires the 'a2a' extra dependency. "
+        "Install with: pip install crewai[a2a]"
+    )
+
+logger = logging.getLogger(__name__)
+
+
+class CrewAgentExecutor(AgentExecutor):
+    """A2A Agent Executor that wraps CrewAI crews for remote interoperability.
+    
+    This class implements the A2A AgentExecutor interface to enable CrewAI crews
+    to be exposed as remotely interoperable agents following the A2A protocol.
+    
+    Args:
+        crew: The CrewAI crew to expose as an A2A agent
+        supported_content_types: List of supported content types for input
+        
+    Example:
+        from crewai import Agent, Crew, Task
+        from crewai.a2a import CrewAgentExecutor
+        
+        agent = Agent(role="Assistant", goal="Help users", backstory="Helpful AI")
+        task = Task(description="Help with {query}", agent=agent)
+        crew = Crew(agents=[agent], tasks=[task])
+        
+        executor = CrewAgentExecutor(crew)
+    """
+    
+    def __init__(
+        self, 
+        crew: Crew,
+        supported_content_types: Optional[list[str]] = None
+    ):
+        """Initialize the CrewAgentExecutor.
+        
+        Args:
+            crew: The CrewAI crew to wrap
+            supported_content_types: List of supported content types
+        """
+        self.crew = crew
+        self.supported_content_types = supported_content_types or [
+            'text', 'text/plain'
+        ]
+        self._running_tasks: Dict[str, asyncio.Task] = {}
+    
+    async def execute(
+        self,
+        context: RequestContext,
+        event_queue: EventQueue,
+    ) -> None:
+        """Execute the crew with the given context and publish results to event queue.
+        
+        This method extracts the user input from the request context, executes
+        the CrewAI crew, and publishes the results as A2A artifacts.
+        
+        Args:
+            context: The A2A request context containing task details
+            event_queue: Queue for publishing execution events and results
+            
+        Raises:
+            ServerError: If validation fails or execution encounters an error
+        """
+        error = self._validate_request(context)
+        if error:
+            logger.error(f"Request validation failed: {error}")
+            raise ServerError(error=InvalidParamsError())
+        
+        query = context.get_user_input()
+        task_id = context.task_id
+        context_id = context.context_id
+        
+        logger.info(f"Executing crew for task {task_id} with query: {query}")
+        
+        try:
+            inputs = {"query": query}
+            
+            execution_task = asyncio.create_task(
+                self._execute_crew_async(inputs)
+            )
+            self._running_tasks[task_id] = execution_task
+            
+            result = await execution_task
+            
+            self._running_tasks.pop(task_id, None)
+            
+            logger.info(f"Crew execution completed for task {task_id}")
+            
+            parts = self._convert_output_to_parts(result)
+            
+            event_queue.enqueue_event(
+                completed_task(
+                    task_id,
+                    context_id,
+                    [new_artifact(parts, f"crew_output_{task_id}")],
+                    [context.message],
+                )
+            )
+            
+        except asyncio.CancelledError:
+            logger.info(f"Task {task_id} was cancelled")
+            self._running_tasks.pop(task_id, None)
+            raise
+        except Exception as e:
+            logger.error(f"Error executing crew for task {task_id}: {e}")
+            self._running_tasks.pop(task_id, None)
+            
+            error_parts = [
+                Part(root=TextPart(text=f"Error executing crew: {str(e)}"))
+            ]
+            
+            event_queue.enqueue_event(
+                completed_task(
+                    task_id,
+                    context_id,
+                    [new_artifact(error_parts, f"error_{task_id}")],
+                    [context.message],
+                )
+            )
+            
+            raise ServerError(
+                error=ValueError(f"Error executing crew: {e}")
+            ) from e
+    
+    async def cancel(
+        self, 
+        request: RequestContext, 
+        event_queue: EventQueue
+    ) -> Task | None:
+        """Cancel a running crew execution.
+        
+        Args:
+            request: The A2A request context for the task to cancel
+            event_queue: Event queue for publishing cancellation events
+            
+        Returns:
+            None (cancellation is handled internally)
+            
+        Raises:
+            ServerError: If the task cannot be cancelled
+        """
+        task_id = request.task_id
+        
+        if task_id in self._running_tasks:
+            execution_task = self._running_tasks[task_id]
+            execution_task.cancel()
+            
+            try:
+                await execution_task
+            except asyncio.CancelledError:
+                logger.info(f"Successfully cancelled task {task_id}")
+                pass
+            
+            self._running_tasks.pop(task_id, None)
+            return None
+        else:
+            logger.warning(f"Task {task_id} not found for cancellation")
+            raise ServerError(error=UnsupportedOperationError())
+    
+    async def _execute_crew_async(self, inputs: Dict[str, Any]) -> CrewOutput:
+        """Execute the crew asynchronously.
+        
+        Args:
+            inputs: Input parameters for the crew
+            
+        Returns:
+            The crew execution output
+        """
+        loop = asyncio.get_event_loop()
+        return await loop.run_in_executor(None, self.crew.kickoff, inputs)
+    
+    def _convert_output_to_parts(self, result: CrewOutput) -> list[Part]:
+        """Convert CrewAI output to A2A Parts.
+        
+        Args:
+            result: The crew execution result
+            
+        Returns:
+            List of A2A Parts representing the output
+        """
+        parts = []
+        
+        if hasattr(result, 'raw') and result.raw:
+            parts.append(Part(root=TextPart(text=str(result.raw))))
+        elif result:
+            parts.append(Part(root=TextPart(text=str(result))))
+        
+        if hasattr(result, 'json_dict') and result.json_dict:
+            import json
+            json_output = json.dumps(result.json_dict, indent=2)
+            parts.append(Part(root=TextPart(text=f"Structured Output:\n{json_output}")))
+        
+        if not parts:
+            parts.append(Part(root=TextPart(text="Crew execution completed successfully")))
+        
+        return parts
+    
+    def _validate_request(self, context: RequestContext) -> Optional[str]:
+        """Validate the incoming request context.
+        
+        Args:
+            context: The A2A request context to validate
+            
+        Returns:
+            Error message if validation fails, None if valid
+        """
+        try:
+            user_input = context.get_user_input()
+            if not user_input or not user_input.strip():
+                return "Empty or missing user input"
+            
+            return None
+            
+        except Exception as e:
+            return f"Failed to extract user input: {e}"

src/crewai/a2a/server.py

@@ -0,0 +1,136 @@
+"""A2A Server utilities for CrewAI integration.
+
+This module provides convenience functions for starting A2A servers with CrewAI
+crews, supporting multiple transport protocols and configurations.
+"""
+
+import logging
+from typing import Optional
+
+try:
+    from a2a.server.agent_execution.agent_executor import AgentExecutor
+    from a2a.server.apps import A2AStarletteApplication
+    from a2a.server.request_handlers.default_request_handler import DefaultRequestHandler
+    from a2a.server.tasks import InMemoryTaskStore
+    from a2a.types import AgentCard, AgentCapabilities, AgentSkill
+except ImportError:
+    raise ImportError(
+        "A2A integration requires the 'a2a' extra dependency. "
+        "Install with: pip install crewai[a2a]"
+    )
+
+logger = logging.getLogger(__name__)
+
+
+def start_a2a_server(
+    agent_executor: AgentExecutor,
+    host: str = "localhost",
+    port: int = 10001,
+    transport: str = "starlette",
+    **kwargs
+) -> None:
+    """Start an A2A server with the given agent executor.
+    
+    This is a convenience function that creates and starts an A2A server
+    with the specified configuration.
+    
+    Args:
+        agent_executor: The A2A agent executor to serve
+        host: Host address to bind the server to
+        port: Port number to bind the server to  
+        transport: Transport protocol to use ("starlette" or "fastapi")
+        **kwargs: Additional arguments passed to the server
+        
+    Example:
+        from crewai import Agent, Crew, Task
+        from crewai.a2a import CrewAgentExecutor, start_a2a_server
+        
+        agent = Agent(role="Assistant", goal="Help users", backstory="Helpful AI")
+        task = Task(description="Help with {query}", agent=agent)
+        crew = Crew(agents=[agent], tasks=[task])
+        
+        executor = CrewAgentExecutor(crew)
+        start_a2a_server(executor, host="0.0.0.0", port=8080)
+    """
+    app = create_a2a_app(agent_executor, transport=transport, **kwargs)
+    
+    logger.info(f"Starting A2A server on {host}:{port} using {transport} transport")
+    
+    try:
+        import uvicorn
+        uvicorn.run(app, host=host, port=port)
+    except ImportError:
+        raise ImportError("uvicorn is required to run the A2A server. Install with: pip install uvicorn")
+
+
+def create_a2a_app(
+    agent_executor: AgentExecutor,
+    transport: str = "starlette",
+    agent_name: Optional[str] = None,
+    agent_description: Optional[str] = None,
+    **kwargs
+):
+    """Create an A2A application with the given agent executor.
+    
+    This function creates an A2A server application that can be run
+    with any ASGI server.
+    
+    Args:
+        agent_executor: The A2A agent executor to serve
+        transport: Transport protocol to use ("starlette" or "fastapi")
+        agent_name: Optional name for the agent
+        agent_description: Optional description for the agent
+        **kwargs: Additional arguments passed to the transport
+        
+    Returns:
+        ASGI application ready to be served
+        
+    Example:
+        from crewai.a2a import CrewAgentExecutor, create_a2a_app
+        
+        executor = CrewAgentExecutor(crew)
+        app = create_a2a_app(
+            executor, 
+            agent_name="My Crew Agent",
+            agent_description="A helpful CrewAI agent"
+        )
+        
+        import uvicorn
+        uvicorn.run(app, host="0.0.0.0", port=8080)
+    """
+    agent_card = AgentCard(
+        name=agent_name or "CrewAI Agent",
+        description=agent_description or "A CrewAI agent exposed via A2A protocol",
+        version="1.0.0",
+        supportedContentTypes=getattr(agent_executor, 'supported_content_types', ['text', 'text/plain']),
+        capabilities=AgentCapabilities(
+            streaming=True,
+            pushNotifications=False
+        ),
+        defaultInputModes=["text"],
+        defaultOutputModes=["text"],
+        skills=[
+            AgentSkill(
+                id="crew_execution",
+                name="Crew Execution",
+                description="Execute CrewAI crew tasks with multiple agents",
+                examples=["Process user queries", "Coordinate multi-agent workflows"],
+                tags=["crewai", "multi-agent", "workflow"]
+            )
+        ],
+        url="https://github.com/crewAIInc/crewAI"
+    )
+    
+    task_store = InMemoryTaskStore()
+    request_handler = DefaultRequestHandler(agent_executor, task_store)
+    
+    if transport.lower() == "fastapi":
+        raise ValueError("FastAPI transport is not available in the current A2A SDK version")
+    else:
+        app_instance = A2AStarletteApplication(
+            agent_card=agent_card,
+            http_handler=request_handler,
+            **kwargs
+        )
+    
+    return app_instance.build()

tests/a2a/__init__.py

@@ -0,0 +1 @@
+"""Tests for CrewAI A2A integration."""

tests/a2a/test_crew_agent_executor.py

@@ -0,0 +1,197 @@
+"""Tests for CrewAgentExecutor class."""
+
+import asyncio
+import pytest
+from unittest.mock import Mock, AsyncMock, patch
+
+from crewai import Agent, Crew, Task
+from crewai.crews.crew_output import CrewOutput
+
+try:
+    from crewai.a2a import CrewAgentExecutor
+    from a2a.server.agent_execution import RequestContext
+    from a2a.server.events import EventQueue
+    from a2a.types import InvalidParamsError, UnsupportedOperationError
+    from a2a.utils.errors import ServerError
+    A2A_AVAILABLE = True
+except ImportError:
+    A2A_AVAILABLE = False
+
+
+@pytest.mark.skipif(not A2A_AVAILABLE, reason="A2A integration not available")
+class TestCrewAgentExecutor:
+    """Test cases for CrewAgentExecutor."""
+    
+    @pytest.fixture
+    def sample_crew(self):
+        """Create a sample crew for testing."""
+        from unittest.mock import Mock
+        mock_crew = Mock()
+        mock_crew.agents = []
+        mock_crew.tasks = []
+        return mock_crew
+    
+    @pytest.fixture
+    def crew_executor(self, sample_crew):
+        """Create a CrewAgentExecutor for testing."""
+        return CrewAgentExecutor(sample_crew)
+    
+    @pytest.fixture
+    def mock_context(self):
+        """Create a mock RequestContext."""
+        from a2a.types import Message, Part, TextPart
+        context = Mock(spec=RequestContext)
+        context.task_id = "test-task-123"
+        context.context_id = "test-context-456"
+        context.message = Message(
+            messageId="msg-123",
+            taskId="test-task-123",
+            contextId="test-context-456",
+            role="user",
+            parts=[Part(root=TextPart(text="Test message"))]
+        )
+        context.get_user_input.return_value = "Test query"
+        return context
+    
+    @pytest.fixture
+    def mock_event_queue(self):
+        """Create a mock EventQueue."""
+        return Mock(spec=EventQueue)
+    
+    def test_init(self, sample_crew):
+        """Test CrewAgentExecutor initialization."""
+        executor = CrewAgentExecutor(sample_crew)
+        
+        assert executor.crew == sample_crew
+        assert executor.supported_content_types == ['text', 'text/plain']
+        assert executor._running_tasks == {}
+    
+    def test_init_with_custom_content_types(self, sample_crew):
+        """Test CrewAgentExecutor initialization with custom content types."""
+        custom_types = ['text', 'application/json']
+        executor = CrewAgentExecutor(sample_crew, supported_content_types=custom_types)
+        
+        assert executor.supported_content_types == custom_types
+    
+    @pytest.mark.asyncio
+    async def test_execute_success(self, crew_executor, mock_context, mock_event_queue):
+        """Test successful crew execution."""
+        mock_output = CrewOutput(raw="Test response", json_dict=None)
+        
+        with patch.object(crew_executor, '_execute_crew_async', return_value=mock_output):
+            await crew_executor.execute(mock_context, mock_event_queue)
+        
+        mock_event_queue.enqueue_event.assert_called_once()
+        
+        assert len(crew_executor._running_tasks) == 0
+    
+    @pytest.mark.asyncio
+    async def test_execute_with_validation_error(self, crew_executor, mock_event_queue):
+        """Test execution with validation error."""
+        bad_context = Mock(spec=RequestContext)
+        bad_context.get_user_input.return_value = ""
+        
+        with pytest.raises(ServerError):
+            await crew_executor.execute(bad_context, mock_event_queue)
+    
+    @pytest.mark.asyncio
+    async def test_execute_with_crew_error(self, crew_executor, mock_context, mock_event_queue):
+        """Test execution when crew raises an error."""
+        with patch.object(crew_executor, '_execute_crew_async', side_effect=Exception("Crew error")):
+            with pytest.raises(ServerError):
+                await crew_executor.execute(mock_context, mock_event_queue)
+        
+        mock_event_queue.enqueue_event.assert_called_once()
+    
+    @pytest.mark.asyncio
+    async def test_cancel_existing_task(self, crew_executor, mock_event_queue):
+        """Test cancelling an existing task."""
+        cancel_context = Mock(spec=RequestContext)
+        cancel_context.task_id = "test-task-123"
+        
+        async def dummy_task():
+            await asyncio.sleep(10)
+        
+        mock_task = asyncio.create_task(dummy_task())
+        crew_executor._running_tasks["test-task-123"] = mock_task
+        
+        result = await crew_executor.cancel(cancel_context, mock_event_queue)
+        
+        assert result is None
+        assert "test-task-123" not in crew_executor._running_tasks
+        assert mock_task.cancelled()
+    
+    @pytest.mark.asyncio
+    async def test_cancel_nonexistent_task(self, crew_executor, mock_event_queue):
+        """Test cancelling a task that doesn't exist."""
+        cancel_context = Mock(spec=RequestContext)
+        cancel_context.task_id = "nonexistent-task"
+        
+        with pytest.raises(ServerError):
+            await crew_executor.cancel(cancel_context, mock_event_queue)
+    
+    def test_convert_output_to_parts_with_raw(self, crew_executor):
+        """Test converting crew output with raw content to A2A parts."""
+        output = Mock()
+        output.raw = "Test response"
+        output.json_dict = None
+        parts = crew_executor._convert_output_to_parts(output)
+        
+        assert len(parts) == 1
+        assert parts[0].root.text == "Test response"
+    
+    def test_convert_output_to_parts_with_json(self, crew_executor):
+        """Test converting crew output with JSON data to A2A parts."""
+        output = Mock()
+        output.raw = "Test response"
+        output.json_dict = {"key": "value"}
+        parts = crew_executor._convert_output_to_parts(output)
+        
+        assert len(parts) == 2
+        assert parts[0].root.text == "Test response"
+        assert "Structured Output:" in parts[1].root.text
+        assert '"key": "value"' in parts[1].root.text
+    
+    def test_convert_output_to_parts_empty(self, crew_executor):
+        """Test converting empty crew output to A2A parts."""
+        output = ""
+        parts = crew_executor._convert_output_to_parts(output)
+        
+        assert len(parts) == 1
+        assert parts[0].root.text == "Crew execution completed successfully"
+    
+    def test_validate_request_valid(self, crew_executor, mock_context):
+        """Test request validation with valid input."""
+        error = crew_executor._validate_request(mock_context)
+        assert error is None
+    
+    def test_validate_request_empty_input(self, crew_executor):
+        """Test request validation with empty input."""
+        context = Mock(spec=RequestContext)
+        context.get_user_input.return_value = ""
+        
+        error = crew_executor._validate_request(context)
+        assert error == "Empty or missing user input"
+    
+    def test_validate_request_whitespace_input(self, crew_executor):
+        """Test request validation with whitespace-only input."""
+        context = Mock(spec=RequestContext)
+        context.get_user_input.return_value = "   \n\t  "
+        
+        error = crew_executor._validate_request(context)
+        assert error == "Empty or missing user input"
+    
+    def test_validate_request_exception(self, crew_executor):
+        """Test request validation when get_user_input raises exception."""
+        context = Mock(spec=RequestContext)
+        context.get_user_input.side_effect = Exception("Input error")
+        
+        error = crew_executor._validate_request(context)
+        assert "Failed to extract user input" in error
+
+
+@pytest.mark.skipif(A2A_AVAILABLE, reason="Testing import error handling")
+def test_import_error_handling():
+    """Test that import errors are handled gracefully when A2A is not available."""
+    with pytest.raises(ImportError, match="A2A integration requires"):
+        from crewai.a2a import CrewAgentExecutor

tests/a2a/test_integration.py

@@ -0,0 +1,121 @@
+"""Integration tests for CrewAI A2A functionality."""
+
+import pytest
+from unittest.mock import Mock, patch
+
+from crewai import Agent, Crew, Task
+
+try:
+    from crewai.a2a import CrewAgentExecutor, create_a2a_app
+    A2A_AVAILABLE = True
+except ImportError:
+    A2A_AVAILABLE = False
+
+
+@pytest.mark.skipif(not A2A_AVAILABLE, reason="A2A integration not available")
+class TestA2AIntegration:
+    """Integration tests for A2A functionality."""
+    
+    @pytest.fixture
+    def sample_crew(self):
+        """Create a sample crew for integration testing."""
+        from unittest.mock import Mock
+        mock_crew = Mock()
+        mock_crew.agents = []
+        mock_crew.tasks = []
+        return mock_crew
+    
+    def test_end_to_end_integration(self, sample_crew):
+        """Test end-to-end A2A integration."""
+        executor = CrewAgentExecutor(sample_crew)
+        
+        assert executor.crew == sample_crew
+        assert isinstance(executor.supported_content_types, list)
+        
+        with patch('crewai.a2a.server.A2AStarletteApplication') as mock_app_class:
+            with patch('crewai.a2a.server.DefaultRequestHandler') as mock_handler_class:
+                with patch('crewai.a2a.server.InMemoryTaskStore') as mock_task_store_class:
+                    mock_handler = Mock()
+                    mock_app_instance = Mock()
+                    mock_built_app = Mock()
+                    mock_task_store = Mock()
+                    
+                    mock_task_store_class.return_value = mock_task_store
+                    mock_handler_class.return_value = mock_handler
+                    mock_app_class.return_value = mock_app_instance
+                    mock_app_instance.build.return_value = mock_built_app
+                    
+                    app = create_a2a_app(executor)
+                    
+                    mock_task_store_class.assert_called_once()
+                    mock_handler_class.assert_called_once_with(executor, mock_task_store)
+                    mock_app_class.assert_called_once()
+                    assert app == mock_built_app
+    
+    def test_crew_with_multiple_agents(self):
+        """Test A2A integration with multi-agent crew."""
+        from unittest.mock import Mock
+        crew = Mock()
+        crew.agents = [Mock(), Mock()]
+        crew.tasks = [Mock(), Mock()]
+        
+        executor = CrewAgentExecutor(crew)
+        assert executor.crew == crew
+        assert len(executor.crew.agents) == 2
+        assert len(executor.crew.tasks) == 2
+    
+    def test_custom_content_types(self, sample_crew):
+        """Test A2A integration with custom content types."""
+        custom_types = ['text', 'application/json', 'image/png']
+        executor = CrewAgentExecutor(
+            sample_crew,
+            supported_content_types=custom_types
+        )
+        
+        assert executor.supported_content_types == custom_types
+    
+    @patch('uvicorn.run')
+    def test_server_startup_integration(self, mock_uvicorn_run, sample_crew):
+        """Test server startup integration."""
+        from crewai.a2a import start_a2a_server
+        
+        executor = CrewAgentExecutor(sample_crew)
+        
+        with patch('crewai.a2a.server.create_a2a_app') as mock_create_app:
+            mock_app = Mock()
+            mock_create_app.return_value = mock_app
+            
+            start_a2a_server(
+                executor,
+                host="127.0.0.1",
+                port=9999,
+                transport="starlette"
+            )
+            
+            mock_create_app.assert_called_once_with(
+                executor,
+                transport="starlette"
+            )
+            mock_uvicorn_run.assert_called_once_with(
+                mock_app,
+                host="127.0.0.1",
+                port=9999
+            )
+
+
+def test_optional_import_in_main_module():
+    """Test that A2A classes are optionally imported in main module."""
+    import crewai
+    
+    if A2A_AVAILABLE:
+        assert hasattr(crewai, 'CrewAgentExecutor')
+        assert hasattr(crewai, 'start_a2a_server')
+        assert hasattr(crewai, 'create_a2a_app')
+        
+        assert 'CrewAgentExecutor' in crewai.__all__
+        assert 'start_a2a_server' in crewai.__all__
+        assert 'create_a2a_app' in crewai.__all__
+    else:
+        assert not hasattr(crewai, 'CrewAgentExecutor')
+        assert not hasattr(crewai, 'start_a2a_server')
+        assert not hasattr(crewai, 'create_a2a_app')

tests/a2a/test_server.py

@@ -0,0 +1,129 @@
+"""Tests for A2A server utilities."""
+
+import pytest
+from unittest.mock import Mock, patch
+
+try:
+    from crewai.a2a import start_a2a_server, create_a2a_app
+    from a2a.server.agent_execution.agent_executor import AgentExecutor
+    A2A_AVAILABLE = True
+except ImportError:
+    A2A_AVAILABLE = False
+
+
+@pytest.mark.skipif(not A2A_AVAILABLE, reason="A2A integration not available")
+class TestA2AServer:
+    """Test cases for A2A server utilities."""
+    
+    @pytest.fixture
+    def mock_agent_executor(self):
+        """Create a mock AgentExecutor."""
+        return Mock(spec=AgentExecutor)
+    
+    @patch('uvicorn.run')
+    @patch('crewai.a2a.server.create_a2a_app')
+    def test_start_a2a_server_default(self, mock_create_app, mock_uvicorn_run, mock_agent_executor):
+        """Test starting A2A server with default parameters."""
+        mock_app = Mock()
+        mock_create_app.return_value = mock_app
+        
+        start_a2a_server(mock_agent_executor)
+        
+        mock_create_app.assert_called_once_with(
+            mock_agent_executor, 
+            transport="starlette"
+        )
+        
+        mock_uvicorn_run.assert_called_once_with(
+            mock_app, 
+            host="localhost", 
+            port=10001
+        )
+    
+    @patch('uvicorn.run')
+    @patch('crewai.a2a.server.create_a2a_app')
+    def test_start_a2a_server_custom(self, mock_create_app, mock_uvicorn_run, mock_agent_executor):
+        """Test starting A2A server with custom parameters."""
+        mock_app = Mock()
+        mock_create_app.return_value = mock_app
+        
+        start_a2a_server(
+            mock_agent_executor,
+            host="0.0.0.0",
+            port=8080,
+            transport="fastapi"
+        )
+        
+        mock_create_app.assert_called_once_with(
+            mock_agent_executor,
+            transport="fastapi"
+        )
+        
+        mock_uvicorn_run.assert_called_once_with(
+            mock_app,
+            host="0.0.0.0",
+            port=8080
+        )
+    
+    @patch('crewai.a2a.server.A2AStarletteApplication')
+    @patch('crewai.a2a.server.DefaultRequestHandler')
+    @patch('crewai.a2a.server.InMemoryTaskStore')
+    def test_create_a2a_app_starlette(self, mock_task_store_class, mock_handler_class, mock_app_class, mock_agent_executor):
+        """Test creating A2A app with Starlette transport."""
+        mock_handler = Mock()
+        mock_app_instance = Mock()
+        mock_built_app = Mock()
+        mock_task_store = Mock()
+        
+        mock_task_store_class.return_value = mock_task_store
+        mock_handler_class.return_value = mock_handler
+        mock_app_class.return_value = mock_app_instance
+        mock_app_instance.build.return_value = mock_built_app
+        
+        result = create_a2a_app(mock_agent_executor, transport="starlette")
+        
+        mock_task_store_class.assert_called_once()
+        mock_handler_class.assert_called_once_with(mock_agent_executor, mock_task_store)
+        mock_app_class.assert_called_once()
+        mock_app_instance.build.assert_called_once()
+        
+        assert result == mock_built_app
+    
+    def test_create_a2a_app_fastapi(self, mock_agent_executor):
+        """Test creating A2A app with FastAPI transport raises error."""
+        with pytest.raises(ValueError, match="FastAPI transport is not available"):
+            create_a2a_app(
+                mock_agent_executor,
+                transport="fastapi",
+                agent_name="Custom Agent",
+                agent_description="Custom description"
+            )
+    
+    @patch('crewai.a2a.server.A2AStarletteApplication')
+    @patch('crewai.a2a.server.DefaultRequestHandler')
+    @patch('crewai.a2a.server.InMemoryTaskStore')
+    def test_create_a2a_app_default_transport(self, mock_task_store_class, mock_handler_class, mock_app_class, mock_agent_executor):
+        """Test creating A2A app with default transport."""
+        mock_handler = Mock()
+        mock_app_instance = Mock()
+        mock_built_app = Mock()
+        mock_task_store = Mock()
+        
+        mock_task_store_class.return_value = mock_task_store
+        mock_handler_class.return_value = mock_handler
+        mock_app_class.return_value = mock_app_instance
+        mock_app_instance.build.return_value = mock_built_app
+        
+        result = create_a2a_app(mock_agent_executor)
+        
+        mock_task_store_class.assert_called_once()
+        mock_handler_class.assert_called_once_with(mock_agent_executor, mock_task_store)
+        mock_app_class.assert_called_once()
+        assert result == mock_built_app
+
+
+@pytest.mark.skipif(A2A_AVAILABLE, reason="Testing import error handling")
+def test_server_import_error_handling():
+    """Test that import errors are handled gracefully when A2A is not available."""
+    with pytest.raises(ImportError, match="A2A integration requires"):
+        from crewai.a2a.server import start_a2a_server