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/providers/github_copilot/README.md

@@ -29,7 +29,7 @@ The following environment variables can be configured:
 | File | Description |
 |------|-------------|
 | [`github_copilot_basic.py`](github_copilot_basic.py) | The simplest way to create an agent using `GitHubCopilotAgent`. Demonstrates both streaming and non-streaming responses with function tools. |
-| [`github_copilot_with_session.py`](github_copilot_with_session.py) | Shows session management with automatic creation, persistence via thread objects, and resuming sessions by ID. |
+| [`github_copilot_with_session.py`](github_copilot_with_session.py) | Shows session management with automatic creation, persistence via session objects, and resuming sessions by ID. |
 | [`github_copilot_with_shell.py`](github_copilot_with_shell.py) | Shows how to enable shell command execution permissions. Demonstrates running system commands like listing files and getting system information. |
 | [`github_copilot_with_file_operations.py`](github_copilot_with_file_operations.py) | Shows how to enable file read and write permissions. Demonstrates reading file contents and creating new files. |
 | [`github_copilot_with_url.py`](github_copilot_with_url.py) | Shows how to enable URL fetching permissions. Demonstrates fetching and processing web content. |

python/samples/02-agents/providers/github_copilot/github_copilot_basic.py

@@ -22,7 +22,7 @@ from agent_framework.github import GitHubCopilotAgent
 from pydantic import Field
 
 
-# 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/providers/github_copilot/github_copilot_with_session.py

@@ -17,7 +17,7 @@ from agent_framework.github import GitHubCopilotAgent
 from pydantic import Field
 
 
-# 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.")],
@@ -61,31 +61,31 @@ async def example_with_session_persistence() -> None:
     )
 
     async with agent:
-        # Create a thread to maintain conversation context
-        thread = agent.get_new_thread()
+        # Create a session to maintain conversation context
+        session = agent.create_session()
 
         # First query
         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}")
 
         # Second query - using same thread maintains context
         query2 = "How about London?"
         print(f"\nUser: {query2}")
-        result2 = await agent.run(query2, thread=thread)
+        result2 = await agent.run(query2, session=session)
         print(f"Agent: {result2}")
 
         # Third query - agent should remember both previous cities
         query3 = "Which of the cities I asked about has better weather?"
         print(f"\nUser: {query3}")
-        result3 = await agent.run(query3, thread=thread)
+        result3 = await agent.run(query3, session=session)
         print(f"Agent: {result3}")
         print("Note: The agent remembers context from previous messages in the same session.\n")
 
 
 async def example_with_existing_session_id() -> None:
-    """Resume session in new agent instance using service_thread_id."""
+    """Resume session in new agent instance using service_session_id."""
     print("=== Existing Session ID Example ===")
 
     existing_session_id = None
@@ -97,15 +97,15 @@ async def example_with_existing_session_id() -> None:
     )
 
     async with agent1:
-        thread = agent1.get_new_thread()
+        session = agent1.create_session()
 
         query1 = "What's the weather in Paris?"
         print(f"User: {query1}")
-        result1 = await agent1.run(query1, thread=thread)
+        result1 = await agent1.run(query1, session=session)
         print(f"Agent: {result1}")
 
         # Capture the session ID for later use
-        existing_session_id = thread.service_thread_id
+        existing_session_id = session.service_session_id
         print(f"Session ID: {existing_session_id}")
 
     if existing_session_id:
@@ -118,12 +118,12 @@ async def example_with_existing_session_id() -> None:
         )
 
         async with agent2:
-            # Create thread with existing session ID
-            thread = agent2.get_new_thread(service_thread_id=existing_session_id)
+            # Create session with existing session ID
+            session = agent2.create_session(service_session_id=existing_session_id)
 
             query2 = "What was the last city I asked about?"
             print(f"User: {query2}")
-            result2 = await agent2.run(query2, thread=thread)
+            result2 = await agent2.run(query2, session=session)
             print(f"Agent: {result2}")
             print("Note: The agent continues the conversation using the session ID.\n")