fix(a2a): Avoid UUID session IDs by mapping A2A context IDs

src/google/adk/a2a/converters/request_converter.py

@@ -26,6 +26,7 @@
 from ..experimental import a2a_experimental
 from .part_converter import A2APartToGenAIPartConverter
 from .part_converter import convert_a2a_part_to_genai_part
+from .utils import _from_a2a_context_id
 
 
 @a2a_experimental
@@ -70,6 +71,10 @@ def _get_user_id(request: RequestContext) -> str:
   ):
     return request.call_context.user.user_name
 
+  _, user_id, _ = _from_a2a_context_id(request.context_id)
+  if user_id:
+    return user_id
+
   # Get user from context id
   return f'A2A_USER_{request.context_id}'
 
@@ -106,9 +111,11 @@ def convert_a2a_request_to_agent_run_request(
       genai_parts = [genai_parts] if genai_parts else []
     output_parts.extend(genai_parts)
 
+  _, _, session_id = _from_a2a_context_id(request.context_id)
+
   return AgentRunRequest(
       user_id=_get_user_id(request),
-      session_id=request.context_id,
+      session_id=session_id,
       new_message=genai_types.Content(
           role='user',
           parts=output_parts,

src/google/adk/a2a/executor/a2a_agent_executor.py

@@ -49,6 +49,7 @@
 from ..converters.request_converter import AgentRunRequest
 from ..converters.request_converter import convert_a2a_request_to_agent_run_request
 from ..converters.utils import _get_adk_metadata_key
+from ..converters.utils import _to_a2a_context_id
 from ..experimental import a2a_experimental
 from .task_result_aggregator import TaskResultAggregator
 
@@ -135,21 +136,6 @@ async def execute(
     if not context.message:
       raise ValueError('A2A request must have a message')
 
-    # for new task, create a task submitted event
-    if not context.current_task:
-      await event_queue.enqueue_event(
-          TaskStatusUpdateEvent(
-              task_id=context.task_id,
-              status=TaskStatus(
-                  state=TaskState.submitted,
-                  message=context.message,
-                  timestamp=datetime.now(timezone.utc).isoformat(),
-              ),
-              context_id=context.context_id,
-              final=False,
-          )
-      )
-
     # Handle the request and publish updates to the event queue
     try:
       await self._handle_request(context, event_queue)
@@ -194,6 +180,27 @@ async def _handle_request(
 
     # ensure the session exists
     session = await self._prepare_session(context, run_request, runner)
+    response_context_id = self._get_response_context_id(
+        context=context,
+        runner=runner,
+        run_request=run_request,
+        session_id=session.id,
+    )
+
+    # for new task, create a task submitted event
+    if not context.current_task:
+      await event_queue.enqueue_event(
+          TaskStatusUpdateEvent(
+              task_id=context.task_id,
+              status=TaskStatus(
+                  state=TaskState.submitted,
+                  message=context.message,
+                  timestamp=datetime.now(timezone.utc).isoformat(),
+              ),
+              context_id=response_context_id,
+              final=False,
+          )
+      )
 
     # create invocation context
     invocation_context = runner._new_invocation_context(
@@ -210,7 +217,7 @@ async def _handle_request(
                 state=TaskState.working,
                 timestamp=datetime.now(timezone.utc).isoformat(),
             ),
-            context_id=context.context_id,
+            context_id=response_context_id,
             final=False,
             metadata={
                 _get_adk_metadata_key('app_name'): runner.app_name,
@@ -227,7 +234,7 @@ async def _handle_request(
             adk_event,
             invocation_context,
             context.task_id,
-            context.context_id,
+            response_context_id,
             self._config.gen_ai_part_converter,
         ):
           task_result_aggregator.process_event(a2a_event)
@@ -245,7 +252,7 @@ async def _handle_request(
           TaskArtifactUpdateEvent(
               task_id=context.task_id,
               last_chunk=True,
-              context_id=context.context_id,
+              context_id=response_context_id,
               artifact=Artifact(
                   artifact_id=str(uuid.uuid4()),
                   parts=task_result_aggregator.task_status_message.parts,
@@ -260,7 +267,7 @@ async def _handle_request(
                   state=TaskState.completed,
                   timestamp=datetime.now(timezone.utc).isoformat(),
               ),
-              context_id=context.context_id,
+              context_id=response_context_id,
               final=True,
           )
       )
@@ -273,21 +280,44 @@ async def _handle_request(
                   timestamp=datetime.now(timezone.utc).isoformat(),
                   message=task_result_aggregator.task_status_message,
               ),
-              context_id=context.context_id,
+              context_id=response_context_id,
               final=True,
           )
       )
 
+  def _get_response_context_id(
+      self,
+      *,
+      context: RequestContext,
+      runner: Runner,
+      run_request: AgentRunRequest,
+      session_id: str,
+  ) -> str:
+    try:
+      return _to_a2a_context_id(
+          runner.app_name, run_request.user_id, session_id
+      )
+    except ValueError:
+      return context.context_id
+
   async def _prepare_session(
       self,
       context: RequestContext,
       run_request: AgentRunRequest,
       runner: Runner,
   ):
-
     session_id = run_request.session_id
-    # create a new session if not exists
     user_id = run_request.user_id
+    if not session_id:
+      session = await runner.session_service.create_session(
+          app_name=runner.app_name,
+          user_id=user_id,
+          state={},
+      )
+      run_request.session_id = session.id
+      return session
+
+    # create a new session if not exists
     session = await runner.session_service.get_session(
         app_name=runner.app_name,
         user_id=user_id,

tests/unittests/a2a/converters/test_request_converter.py

@@ -18,6 +18,7 @@
 from a2a.server.agent_execution import RequestContext
 from google.adk.a2a.converters.request_converter import _get_user_id
 from google.adk.a2a.converters.request_converter import convert_a2a_request_to_agent_run_request
+from google.adk.a2a.converters.utils import _to_a2a_context_id
 from google.adk.runners import RunConfig
 from google.genai import types as genai_types
 import pytest
@@ -58,6 +59,16 @@ def test_get_user_id_from_context_when_no_call_context(self):
     # Assert
     assert result == "A2A_USER_test_context"
 
+  def test_get_user_id_from_adk_context_id(self):
+    """Test getting user ID from ADK-formatted context id."""
+    request = Mock(spec=RequestContext)
+    request.call_context = None
+    request.context_id = _to_a2a_context_id("app", "user-123", "session-456")
+
+    result = _get_user_id(request)
+
+    assert result == "user-123"
+
   def test_get_user_id_from_context_when_call_context_has_no_user(self):
     """Test getting user ID from context when call context has no user."""
     # Arrange
@@ -129,6 +140,27 @@ def test_get_user_id_with_none_context_id(self):
 class TestConvertA2aRequestToAgentRunRequest:
   """Test cases for convert_a2a_request_to_agent_run_request function."""
 
+  def test_convert_a2a_request_with_adk_context_id(self):
+    """Test conversion uses ADK context id for user/session."""
+    mock_message = Mock()
+    mock_message.parts = [Mock()]
+
+    request = Mock(spec=RequestContext)
+    request.message = mock_message
+    request.context_id = _to_a2a_context_id("app", "user-1", "session-1")
+    request.call_context = None
+    request.metadata = {}
+
+    mock_genai_part = genai_types.Part(text="test part")
+    mock_convert_part = Mock(return_value=mock_genai_part)
+
+    result = convert_a2a_request_to_agent_run_request(
+        request, mock_convert_part
+    )
+
+    assert result.user_id == "user-1"
+    assert result.session_id == "session-1"
+
   def test_convert_a2a_request_basic(self):
     """Test basic conversion of A2A request to ADK AgentRunRequest."""
     # Arrange
@@ -164,7 +196,7 @@ def test_convert_a2a_request_basic(self):
     # Assert
     assert result is not None
     assert result.user_id == "test_user"
-    assert result.session_id == "test_context_123"
+    assert result.session_id is None
     assert isinstance(result.new_message, genai_types.Content)
     assert result.new_message.role == "user"
     assert result.new_message.parts == [mock_genai_part1, mock_genai_part2]
@@ -213,7 +245,7 @@ def test_convert_a2a_request_multiple_parts(self):
     # Assert
     assert result is not None
     assert result.user_id == "test_user"
-    assert result.session_id == "test_context_123"
+    assert result.session_id is None
     assert isinstance(result.new_message, genai_types.Content)
     assert result.new_message.role == "user"
     assert result.new_message.parts == [
@@ -261,7 +293,7 @@ def test_convert_a2a_request_empty_parts(self):
     # Assert
     assert result is not None
     assert result.user_id == "A2A_USER_test_context_123"
-    assert result.session_id == "test_context_123"
+    assert result.session_id is None
     assert isinstance(result.new_message, genai_types.Content)
     assert result.new_message.role == "user"
     assert result.new_message.parts == []
@@ -328,7 +360,7 @@ def test_convert_a2a_request_no_auth(self):
     # Assert
     assert result is not None
     assert result.user_id == "A2A_USER_session_123"
-    assert result.session_id == "session_123"
+    assert result.session_id is None
     assert isinstance(result.new_message, genai_types.Content)
     assert result.new_message.role == "user"
     assert result.new_message.parts == [mock_genai_part]
@@ -370,7 +402,7 @@ def test_end_to_end_conversion_with_auth_user(self):
     # Assert
     assert result is not None
     assert result.user_id == "auth_user"  # Should use authenticated user
-    assert result.session_id == "mysession"
+    assert result.session_id is None
     assert isinstance(result.new_message, genai_types.Content)
     assert result.new_message.role == "user"
     assert result.new_message.parts == [mock_genai_part]
@@ -404,7 +436,7 @@ def test_end_to_end_conversion_with_fallback_user(self):
     assert (
         result.user_id == "A2A_USER_test_session_456"
     )  # Should fall back to context ID
-    assert result.session_id == "test_session_456"
+    assert result.session_id is None
     assert isinstance(result.new_message, genai_types.Content)
     assert result.new_message.role == "user"
     assert result.new_message.parts == [mock_genai_part]