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/purview/agent_framework_purview/_middleware.py

@@ -48,12 +48,12 @@ class PurviewPolicyMiddleware(AgentMiddleware):
         """Resolve a session/conversation id from the agent run context.
 
         Resolution order:
-          1. thread.service_thread_id
+          1. session.service_session_id
           2. First message whose additional_properties contains 'conversation_id'
           3. None: the downstream processor will generate a new UUID
         """
-        if context.thread and context.thread.service_thread_id:
-            return context.thread.service_thread_id
+        if context.session and context.session.service_session_id:
+            return context.session.service_session_id
 
         for message in context.messages:
             conversation_id = message.additional_properties.get("conversation_id")

python/packages/purview/tests/purview/test_middleware.py

@@ -5,7 +5,7 @@
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
-from agent_framework import AgentContext, AgentResponse, AgentThread, Message, MiddlewareTermination
+from agent_framework import AgentContext, AgentResponse, AgentSession, Message, MiddlewareTermination
 from azure.core.credentials import AccessToken
 
 from agent_framework_purview import PurviewPolicyMiddleware, PurviewSettings
@@ -337,12 +337,12 @@ class TestPurviewPolicyMiddleware:
             with pytest.raises(ValueError, match="Test error"):
                 await middleware.process(context, mock_next)
 
-    async def test_middleware_uses_thread_service_thread_id_as_session_id(
+    async def test_middleware_uses_session_service_session_id_as_session_id(
         self, middleware: PurviewPolicyMiddleware, mock_agent: MagicMock
     ) -> None:
-        """Test that session_id is extracted from thread.service_thread_id."""
-        thread = AgentThread(service_thread_id="thread-123")
-        context = AgentContext(agent=mock_agent, messages=[Message(role="user", text="Hello")], thread=thread)
+        """Test that session_id is extracted from session.service_session_id."""
+        session = AgentSession(service_session_id="thread-123")
+        context = AgentContext(agent=mock_agent, messages=[Message(role="user", text="Hello")], session=session)
 
         with patch.object(middleware._processor, "process_messages", return_value=(False, "user-123")) as mock_proc:
 
@@ -373,13 +373,13 @@ class TestPurviewPolicyMiddleware:
             assert mock_proc.call_count == 2
             mock_proc.assert_any_call(messages, Activity.UPLOAD_TEXT, session_id="conv-456")
 
-    async def test_middleware_thread_id_takes_precedence_over_message_conversation_id(
+    async def test_middleware_session_id_takes_precedence_over_message_conversation_id(
         self, middleware: PurviewPolicyMiddleware, mock_agent: MagicMock
     ) -> None:
-        """Test that thread.service_thread_id takes precedence over message conversation_id."""
-        thread = AgentThread(service_thread_id="thread-789")
+        """Test that session.service_session_id takes precedence over message conversation_id."""
+        session = AgentSession(service_session_id="thread-789")
         messages = [Message(role="user", text="Hello", additional_properties={"conversation_id": "conv-456"})]
-        context = AgentContext(agent=mock_agent, messages=messages, thread=thread)
+        context = AgentContext(agent=mock_agent, messages=messages, session=session)
 
         with patch.object(middleware._processor, "process_messages", return_value=(False, "user-123")) as mock_proc:
 
@@ -388,13 +388,13 @@ class TestPurviewPolicyMiddleware:
 
             await middleware.process(context, mock_next)
 
-            # Verify thread ID is used, not message conversation_id
+            # Verify session ID is used, not message conversation_id
             mock_proc.assert_any_call(messages, Activity.UPLOAD_TEXT, session_id="thread-789")
 
     async def test_middleware_passes_none_session_id_when_not_available(
         self, middleware: PurviewPolicyMiddleware, mock_agent: MagicMock
     ) -> None:
-        """Test that session_id is None when no thread or conversation_id is available."""
+        """Test that session_id is None when no session or conversation_id is available."""
         context = AgentContext(agent=mock_agent, messages=[Message(role="user", text="Hello")])
 
         with patch.object(middleware._processor, "process_messages", return_value=(False, "user-123")) as mock_proc:
@@ -411,8 +411,8 @@ class TestPurviewPolicyMiddleware:
         self, middleware: PurviewPolicyMiddleware, mock_agent: MagicMock
     ) -> None:
         """Test that session_id is passed to post-check process_messages call."""
-        thread = AgentThread(service_thread_id="thread-999")
-        context = AgentContext(agent=mock_agent, messages=[Message(role="user", text="Hello")], thread=thread)
+        session = AgentSession(service_session_id="thread-999")
+        context = AgentContext(agent=mock_agent, messages=[Message(role="user", text="Hello")], session=session)
 
         with patch.object(middleware._processor, "process_messages", return_value=(False, "user-123")) as mock_proc: