Python: [BREAKING] PR2 — Wire context provider pipeline, remove old types, update all consumers (#3850)

* PR2: Wire context provider pipeline and update all internal consumers

- Replace AgentThread with AgentSession across all packages
- Replace ContextProvider with BaseContextProvider across all packages
- Replace context_provider param with context_providers (Sequence)
- Replace thread= with session= in run() signatures
- Replace get_new_thread() with create_session()
- Add get_session(service_session_id) to agent interface
- DurableAgentThread -> DurableAgentSession
- Remove _notify_thread_of_new_messages from WorkflowAgent
- Wire before_run/after_run context provider pipeline in RawAgent
- Auto-inject InMemoryHistoryProvider when no providers configured

* fix: update all tests for context provider pipeline, fix lazy-loaders, remove old test files

* refactor: update all sample files for context provider pipeline (AgentThread→AgentSession, ContextProvider→BaseContextProvider)

* fix: update remaining ag-ui references (client docstring, getting_started sample)

* fix: make get_session service_session_id keyword-only to avoid confusion with session_id

* refactor: rename _RunContext.thread_messages to session_messages

* refactor: remove _threads.py, _memory.py, and old provider files; migrate devui to use plain message lists

* rename: remove _new_ prefix from test files

* refactor: rewrite SlidingWindowChatMessageStore as SlidingWindowHistoryProvider(InMemoryHistoryProvider)

* fix: read full history from session state directly instead of reaching into provider internals

* fix: update stale .pyi stubs, sample imports, and README references for new provider types

* fix: remove stale message_store, _notify_thread_of_new_messages, and session_id.key references in samples

* refactor: merge context_providers and sessions sample folders into sessions, remove aggregate_context_provider

* refactor: UserInfoMemory stores state in session.state instead of instance attributes

* feat: add Pydantic BaseModel support to session state serialization

Pydantic models stored in session.state are now automatically serialized
via model_dump() and restored via model_validate() during to_dict()/from_dict()
round-trips. Models are auto-registered on first serialization; use
register_state_type() for cold-start deserialization.

Also export register_state_type as a public API.

* fix mem0

* Update sample README links and descriptions for session terminology

- Replace 'thread' with 'session' in sample descriptions across all READMEs
- Update file links for renamed samples (mem0_sessions, redis_sessions, etc.)
- Fix Threads section → Sessions section in main samples/README.md
- Update tools, middleware, workflows, durabletask, azure_functions READMEs
- Update architecture diagrams in concepts/tools/README.md
- Update migration guides (autogen, semantic-kernel)

* Fix broken Redis README link to renamed sample

* Fix Mem0 OSS client search: pass scoping params as direct kwargs

AsyncMemory (OSS) expects user_id/agent_id/run_id as direct kwargs,
while AsyncMemoryClient (Platform) expects them in a filters dict.
Adds tests for both client types.

Port of fix from #3844 to new Mem0ContextProvider.

* Fix rebase issues: restore missing _conversation_state.py and checkpoint decode logic

- Add back _conversation_state.py (encode/decode_chat_messages) lost in rebase
- Fix on_checkpoint_restore to decode cache/conversation with decode_chat_messages
- Fix on_checkpoint_restore to use decode_checkpoint_value for pending requests
- Add tests/workflow/__init__.py for relative import support
- Fix test_agent_executor checkpoint selection (checkpoints[1] not superstep)

* Add STORES_BY_DEFAULT ClassVar to skip redundant InMemoryHistoryProvider injection

Chat clients that store history server-side by default (OpenAI Responses API,
Azure AI Agent) now declare STORES_BY_DEFAULT = True. The agent checks this
during auto-injection and skips InMemoryHistoryProvider unless the user
explicitly sets store=False.

* Fix broken markdown links in azure_ai and redis READMEs

* Fix getting-started samples to use session API instead of removed thread/ContextProvider API

* updates to workflow as agent

* fix group chat import

* Rename Thread→Session throughout, fix service_session_id propagation, remove stale AGUIThread

- Fix: Propagate conversation_id from ChatResponse back to session.service_session_id
  in both streaming and non-streaming paths in _agents.py
- Rename AgentThreadException → AgentSessionException
- Remove stale AGUIThread from ag_ui lazy-loader
- Rename use_service_thread → use_service_session in ag-ui package
- Rename test functions from *_thread_* to *_session_*
- Rename sample files from *_thread* to *_session*
- Update docstrings and comments: thread → session
- Update _mcp.py kwargs filter: add 'session' alongside 'thread'
- Fix ContinuationToken docstring example: thread=thread → session=session
- Fix _clients.py docstring: 'Agent threads' → 'Agent sessions'

* Fix broken markdown links after thread→session file renames

* fix azure ai test

python/packages/durabletask/tests/test_executors.py

@@ -16,7 +16,7 @@ from durabletask.entities import EntityInstanceId
 from durabletask.task import Task
 from pydantic import BaseModel
 
-from agent_framework_durabletask import DurableAgentThread
+from agent_framework_durabletask import DurableAgentSession
 from agent_framework_durabletask._constants import DEFAULT_MAX_POLL_RETRIES, DEFAULT_POLL_INTERVAL_SECONDS
 from agent_framework_durabletask._executors import (
     ClientAgentExecutor,
@@ -106,42 +106,42 @@ def configure_failed_entity_task(mock_entity_task: Mock) -> Any:
     return _configure
 
 
-class TestExecutorThreadCreation:
-    """Test that executors properly create DurableAgentThread with parameters."""
+class TestExecutorSessionCreation:
+    """Test that executors properly create DurableAgentSession with parameters."""
 
-    def test_client_executor_creates_durable_thread(self, mock_client: Mock) -> None:
-        """Verify ClientAgentExecutor creates DurableAgentThread instances."""
+    def test_client_executor_creates_durable_session(self, mock_client: Mock) -> None:
+        """Verify ClientAgentExecutor creates DurableAgentSession instances."""
         executor = ClientAgentExecutor(mock_client)
 
-        thread = executor.get_new_thread("test_agent")
+        session = executor.get_new_session("test_agent")
 
-        assert isinstance(thread, DurableAgentThread)
+        assert isinstance(session, DurableAgentSession)
 
-    def test_client_executor_forwards_kwargs_to_thread(self, mock_client: Mock) -> None:
-        """Verify ClientAgentExecutor forwards kwargs to DurableAgentThread creation."""
+    def test_client_executor_forwards_kwargs_to_session(self, mock_client: Mock) -> None:
+        """Verify ClientAgentExecutor forwards kwargs to DurableAgentSession creation."""
         executor = ClientAgentExecutor(mock_client)
 
-        thread = executor.get_new_thread("test_agent", service_thread_id="client-123")
+        session = executor.get_new_session("test_agent", service_session_id="client-123")
 
-        assert isinstance(thread, DurableAgentThread)
-        assert thread.service_thread_id == "client-123"
+        assert isinstance(session, DurableAgentSession)
+        assert session.service_session_id == "client-123"
 
-    def test_orchestration_executor_creates_durable_thread(
+    def test_orchestration_executor_creates_durable_session(
         self, orchestration_executor: OrchestrationAgentExecutor
     ) -> None:
-        """Verify OrchestrationAgentExecutor creates DurableAgentThread instances."""
-        thread = orchestration_executor.get_new_thread("test_agent")
+        """Verify OrchestrationAgentExecutor creates DurableAgentSession instances."""
+        session = orchestration_executor.get_new_session("test_agent")
 
-        assert isinstance(thread, DurableAgentThread)
+        assert isinstance(session, DurableAgentSession)
 
-    def test_orchestration_executor_forwards_kwargs_to_thread(
+    def test_orchestration_executor_forwards_kwargs_to_session(
         self, orchestration_executor: OrchestrationAgentExecutor
     ) -> None:
-        """Verify OrchestrationAgentExecutor forwards kwargs to DurableAgentThread creation."""
-        thread = orchestration_executor.get_new_thread("test_agent", service_thread_id="orch-456")
+        """Verify OrchestrationAgentExecutor forwards kwargs to DurableAgentSession creation."""
+        session = orchestration_executor.get_new_session("test_agent", service_session_id="orch-456")
 
-        assert isinstance(thread, DurableAgentThread)
-        assert thread.service_thread_id == "orch-456"
+        assert isinstance(session, DurableAgentSession)
+        assert session.service_session_id == "orch-456"
 
 
 class TestClientAgentExecutorRun:
@@ -353,18 +353,18 @@ class TestOrchestrationAgentExecutorRun:
         # Verify request dict
         assert request_dict_arg == sample_run_request.to_dict()
 
-    def test_orchestration_executor_uses_thread_session_id(
+    def test_orchestration_executor_uses_session_durable_id(
         self,
         mock_orchestration_context: Mock,
         orchestration_executor: OrchestrationAgentExecutor,
         sample_run_request: RunRequest,
     ) -> None:
-        """Verify executor uses thread's session ID when provided."""
-        # Create thread with specific session ID
+        """Verify executor uses session's durable session ID when provided."""
+        # Create session with specific durable session ID
         session_id = AgentSessionId(name="test_agent", key="specific-key-123")
-        thread = DurableAgentThread.from_session_id(session_id)
+        session = DurableAgentSession.from_session_id(session_id)
 
-        result = orchestration_executor.run_durable_agent("test_agent", sample_run_request, thread=thread)
+        result = orchestration_executor.run_durable_agent("test_agent", sample_run_request, session=session)
 
         # Verify call_entity was called with the specific key
         call_args = mock_orchestration_context.call_entity.call_args