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/samples/02-agents/middleware/agent_and_run_level_middleware.py

@@ -54,7 +54,7 @@ Agent Middleware Execution Order:
 """
 
 
-# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_threads.py.
+# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_sessions.py.
 @tool(approval_mode="never_require")
 def get_weather(
     location: Annotated[str, Field(description="The location to get the weather for.")],

python/samples/02-agents/middleware/chat_middleware.py

@@ -37,7 +37,7 @@ The example covers:
 """
 
 
-# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_threads.py.
+# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_sessions.py.
 @tool(approval_mode="never_require")
 def get_weather(
     location: Annotated[str, Field(description="The location to get the weather for.")],

python/samples/02-agents/middleware/class_based_middleware.py

@@ -34,7 +34,7 @@ from object-oriented design patterns.
 """
 
 
-# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_threads.py.
+# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_sessions.py.
 @tool(approval_mode="never_require")
 def get_weather(
     location: Annotated[str, Field(description="The location to get the weather for.")],

python/samples/02-agents/middleware/decorator_middleware.py

@@ -42,7 +42,7 @@ Key benefits of decorator approach:
 """
 
 
-# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_threads.py.
+# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_sessions.py.
 @tool(approval_mode="never_require")
 def get_current_time() -> str:
     """Get the current time."""

python/samples/02-agents/middleware/exception_handling_with_middleware.py

@@ -24,7 +24,7 @@ a helpful message for the user, preventing raw exceptions from reaching the end
 """
 
 
-# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_threads.py.
+# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_sessions.py.
 @tool(approval_mode="never_require")
 def unstable_data_service(
     query: Annotated[str, Field(description="The data query to execute.")],

python/samples/02-agents/middleware/function_based_middleware.py

@@ -31,7 +31,7 @@ can be implemented as async functions that accept context and call_next paramete
 """
 
 
-# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_threads.py.
+# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_sessions.py.
 @tool(approval_mode="never_require")
 def get_weather(
     location: Annotated[str, Field(description="The location to get the weather for.")],

python/samples/02-agents/middleware/middleware_termination.py

@@ -30,7 +30,7 @@ This is useful for implementing security checks, rate limiting, or early exit co
 """
 
 
-# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_threads.py.
+# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_sessions.py.
 @tool(approval_mode="never_require")
 def get_weather(
     location: Annotated[str, Field(description="The location to get the weather for.")],

python/samples/02-agents/middleware/override_result_with_middleware.py

@@ -39,7 +39,7 @@ it creates a custom async generator that yields the override message in chunks.
 """
 
 
-# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_threads.py.
+# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_sessions.py.
 @tool(approval_mode="never_require")
 def get_weather(
     location: Annotated[str, Field(description="The location to get the weather for.")],

python/samples/02-agents/middleware/runtime_context_delegation.py

@@ -81,7 +81,7 @@ class SessionContextContainer:
 runtime_context = SessionContextContainer()
 
 
-# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_threads.py.
+# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_sessions.py.
 @tool(approval_mode="never_require")
 async def send_email(
     to: Annotated[str, Field(description="Recipient email address")],

python/samples/02-agents/middleware/session_behavior_middleware.py

@@ -6,7 +6,6 @@ from typing import Annotated
 
 from agent_framework import (
     AgentContext,
-    ChatMessageStore,
     tool,
 )
 from agent_framework.azure import AzureOpenAIChatClient
@@ -16,23 +15,23 @@ from pydantic import Field
 """
 Thread Behavior MiddlewareTypes Example
 
-This sample demonstrates how middleware can access and track thread state across multiple agent runs.
+This sample demonstrates how middleware can access and track session state across multiple agent runs.
 The example shows:
 
-- How AgentContext.thread property behaves across multiple runs
-- How middleware can access conversation history through the thread
-- The timing of when thread messages are populated (before vs after call_next() call)
-- How to track thread state changes across runs
+- How AgentContext.session property behaves across multiple runs
+- How middleware can access conversation history through the session
+- The timing of when session messages are populated (before vs after call_next() call)
+- How to track session state changes across runs
 
 Key behaviors demonstrated:
-1. First run: context.messages is populated, context.thread is initially empty (before call_next())
-2. After call_next(): thread contains input message + response from agent
-3. Second run: context.messages contains only current input, thread contains previous history
-4. After call_next(): thread contains full conversation history (all previous + current messages)
+1. First run: context.messages is populated, context.session is initially empty (before call_next())
+2. After call_next(): session contains input message + response from agent
+3. Second run: context.messages contains only current input, session contains previous history
+4. After call_next(): session contains full conversation history (all previous + current messages)
 """
 
 
-# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_threads.py.
+# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_sessions.py.
 @tool(approval_mode="never_require")
 def get_weather(
     location: Annotated[str, Field(description="The location to get the weather for.")],
@@ -48,28 +47,30 @@ async def thread_tracking_middleware(
     context: AgentContext,
     call_next: Callable[[], Awaitable[None]],
 ) -> None:
-    """MiddlewareTypes that tracks and logs thread behavior across runs."""
-    thread_messages = []
-    if context.thread and context.thread.message_store:
-        thread_messages = await context.thread.message_store.list_messages()
+    """MiddlewareTypes that tracks and logs session behavior across runs."""
+    session_message_count = 0
+    if context.session:
+        memory_state = context.session.state.get("memory", {})
+        session_message_count = len(memory_state.get("messages", []))
 
     print(f"[MiddlewareTypes pre-execution] Current input messages: {len(context.messages)}")
-    print(f"[MiddlewareTypes pre-execution] Thread history messages: {len(thread_messages)}")
+    print(f"[MiddlewareTypes pre-execution] Session history messages: {session_message_count}")
 
     # Call call_next to execute the agent
     await call_next()
 
-    # Check thread state after agent execution
-    updated_thread_messages = []
-    if context.thread and context.thread.message_store:
-        updated_thread_messages = await context.thread.message_store.list_messages()
+    # Check session state after agent execution
+    updated_session_message_count = 0
+    if context.session:
+        memory_state = context.session.state.get("memory", {})
+        updated_session_message_count = len(memory_state.get("messages", []))
 
-    print(f"[MiddlewareTypes post-execution] Updated thread messages: {len(updated_thread_messages)}")
+    print(f"[MiddlewareTypes post-execution] Updated session messages: {updated_session_message_count}")
 
 
 async def main() -> None:
-    """Example demonstrating thread behavior in middleware across multiple runs."""
-    print("=== Thread Behavior MiddlewareTypes Example ===")
+    """Example demonstrating session behavior in middleware across multiple runs."""
+    print("=== Session Behavior MiddlewareTypes Example ===")
 
     # For authentication, run `az login` command in terminal or replace AzureCliCredential with preferred
     # authentication option.
@@ -78,23 +79,21 @@ async def main() -> None:
         instructions="You are a helpful weather assistant.",
         tools=get_weather,
         middleware=[thread_tracking_middleware],
-        # Configure agent with message store factory to persist conversation history
-        chat_message_store_factory=ChatMessageStore,
     )
 
-    # Create a thread that will persist messages between runs
-    thread = agent.get_new_thread()
+    # Create a session that will persist messages between runs
+    session = agent.create_session()
 
     print("\nFirst Run:")
     query1 = "What's the weather like in Tokyo?"
     print(f"User: {query1}")
-    result1 = await agent.run(query1, thread=thread)
+    result1 = await agent.run(query1, session=session)
     print(f"Agent: {result1.text}")
 
     print("\nSecond Run:")
     query2 = "How about in London?"
     print(f"User: {query2}")
-    result2 = await agent.run(query2, thread=thread)
+    result2 = await agent.run(query2, session=session)
     print(f"Agent: {result2.text}")
 
 

python/samples/02-agents/middleware/shared_state_middleware.py

@@ -27,7 +27,7 @@ This approach shows how middleware can work together by sharing state within the
 """
 
 
-# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_threads.py.
+# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production; see samples/02-agents/tools/function_tool_with_approval.py and samples/02-agents/tools/function_tool_with_approval_and_sessions.py.
 @tool(approval_mode="never_require")
 def get_weather(
     location: Annotated[str, Field(description="The location to get the weather for.")],