Repository: microsoft/autogen
Pull request: feat: Pause and Resume for AgentChat Teams and Agents
1. Add `on_pause` and `on_resume` API to `ChatAgent` to support pausing behavior when running `on_message` concurrently.
2. Add `GroupChatPause` and `GroupChatResume` RPC events and handle them in `ChatAgentContainer`. 
3. Add `pause` and `resume` API to `BaseGroupChat` to allow for this behavior accessible from the public API. 
4. Improve `SequentialRoutedAgent` class to customize which message types are sequentially handled, making it possible to have concurrent handling for some messages (e.g., `GroupChatPause`). 
5. Added unit tests. 

See `test_group_chat_pause_resume.py` for how to use this feature. 

What is the difference between pause/resume vs. termination and restart?
- Pause and resume issue direct RPC calls to the participanting agents of a team while they are running, allowing putting the on-going generation or actions on hold. This is useful when an agent's turn takes a long time and multiple steps to complete, and user/application wants to re-evaluate whether it is worth continue the step or cancel. This also allows user/application to pause individual agents and resuming them independently from the team API. 
- Termination and restart requires the whole team to comes to a full-stop, and termination conditions are checked in between agents' turns. So termination can only happen when no agent is working on its turn. It is possible that a termination condition has reached well before the team is terminated, if the agent is taking a long time to generate a response. 

Resolves: #5881

Problem statement:
Add pause/resume APIs for agents in AgentChat
### Confirmation

- [x] I confirm that I am a maintainer and so can use this template. If I am not, I understand this issue will be closed and I will be asked to use a different template.

### Issue body

Agents can be in I/O or compute intensive tasks that requires pause and resume that allows for graceful stop, in addition to brute cancellation.

Hints from issue discussion:

Commit message: Implement pause and resume functionalities in BaseGroupChat

Patch to review:
diff --git a/python/packages/autogen-agentchat/src/autogen_agentchat/agents/_base_chat_agent.py b/python/packages/autogen-agentchat/src/autogen_agentchat/agents/_base_chat_agent.py
index b2e4e4fde48c..94b89235df89 100644
--- a/python/packages/autogen-agentchat/src/autogen_agentchat/agents/_base_chat_agent.py
+++ b/python/packages/autogen-agentchat/src/autogen_agentchat/agents/_base_chat_agent.py
@@ -190,6 +190,20 @@ async def on_reset(self, cancellation_token: CancellationToken) -> None:
         """Resets the agent to its initialization state."""
         ...
 
+    async def on_pause(self, cancellation_token: CancellationToken) -> None:
+        """Called when the agent is paused while running in its :meth:`on_messages` or
+        :meth:`on_messages_stream` method. This is a no-op by default in the
+        :class:`BaseChatAgent` class. Subclasses can override this method to
+        implement custom pause behavior."""
+        pass
+
+    async def on_resume(self, cancellation_token: CancellationToken) -> None:
+        """Called when the agent is resumed from a pause while running in
+        its :meth:`on_messages` or :meth:`on_messages_stream` method.
+        This is a no-op by default in the :class:`BaseChatAgent` class.
+        Subclasses can override this method to implement custom resume behavior."""
+        pass
+
     async def save_state(self) -> Mapping[str, Any]:
         """Export state. Default implementation for stateless agents."""
         return BaseState().model_dump()
@@ -199,5 +213,7 @@ async def load_state(self, state: Mapping[str, Any]) -> None:
         BaseState.model_validate(state)
 
     async def close(self) -> None:
-        """Called when the runtime is closed"""
+        """Release any resources held by the agent. This is a no-op by default in the
+        :class:`BaseChatAgent` class. Subclasses can override this method to
+        implement custom close behavior."""
         pass
diff --git a/python/packages/autogen-agentchat/src/autogen_agentchat/base/_chat_agent.py b/python/packages/autogen-agentchat/src/autogen_agentchat/base/_chat_agent.py
index 34f0f37ee6e2..ec885ee7f8cb 100644
--- a/python/packages/autogen-agentchat/src/autogen_agentchat/base/_chat_agent.py
+++ b/python/packages/autogen-agentchat/src/autogen_agentchat/base/_chat_agent.py
@@ -66,6 +66,18 @@ async def on_reset(self, cancellation_token: CancellationToken) -> None:
         """Resets the agent to its initialization state."""
         ...
 
+    @abstractmethod
+    async def on_pause(self, cancellation_token: CancellationToken) -> None:
+        """Called when the agent is paused. The agent may be running in :meth:`on_messages` or
+        :meth:`on_messages_stream` when this method is called."""
+        ...
+
+    @abstractmethod
+    async def on_resume(self, cancellation_token: CancellationToken) -> None:
+        """Called when the agent is resumed. The agent may be running in :meth:`on_messages` or
+        :meth:`on_messages_stream` when this method is called."""
+        ...
+
     @abstractmethod
     async def save_state(self) -> Mapping[str, Any]:
         """Save agent state for later restoration"""
@@ -78,5 +90,5 @@ async def load_state(self, state: Mapping[str, Any]) -> None:
 
     @abstractmethod
     async def close(self) -> None:
-        """Called when the runtime is stopped or any stop method is called"""
+        """Release any resources held by the agent."""
         ...
diff --git a/python/packages/autogen-agentchat/src/autogen_agentchat/base/_team.py b/python/packages/autogen-agentchat/src/autogen_agentchat/base/_team.py
index 0d25edf6d26c..4cbdc9741c5c 100644
--- a/python/packages/autogen-agentchat/src/autogen_agentchat/base/_team.py
+++ b/python/packages/autogen-agentchat/src/autogen_agentchat/base/_team.py
@@ -15,6 +15,20 @@ async def reset(self) -> None:
         """Reset the team and all its participants to its initial state."""
         ...
 
+    @abstractmethod
+    async def pause(self) -> None:
+        """Pause the team and all its participants. This is useful for
+        pausing the :meth:`autogen_agentchat.base.TaskRunner.run` or
+        :meth:`autogen_agentchat.base.TaskRunner.run_stream` methods from
+        concurrently, while keeping them alive."""
+        ...
+
+    @abstractmethod
+    async def resume(self) -> None:
+        """Resume the team and all its participants from a pause after
+        :meth:`pause` was called."""
+        ...
+
     @abstractmethod
     async def save_state(self) -> Mapping[str, Any]:
         """Save the current state of the team."""
diff --git a/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_base_group_chat.py b/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_base_group_chat.py
index a78e8a564341..311905e1691e 100644
--- a/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_base_group_chat.py
+++ b/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_base_group_chat.py
@@ -27,7 +27,7 @@
 )
 from ...state import TeamState
 from ._chat_agent_container import ChatAgentContainer
-from ._events import GroupChatReset, GroupChatStart, GroupChatTermination
+from ._events import GroupChatPause, GroupChatReset, GroupChatResume, GroupChatStart, GroupChatTermination
 from ._sequential_routed_agent import SequentialRoutedAgent
 
 event_logger = logging.getLogger(EVENT_LOGGER_NAME)
@@ -565,6 +565,84 @@ async def main() -> None:
             # Indicate that the team is no longer running.
             self._is_running = False
 
+    async def pause(self) -> None:
+        """Pause its participants when the team is running by calling their
+        :meth:`~autogen_agentchat.base.ChatAgent.on_pause` method via direct RPC calls.
+
+        The team must be initialized before it can be paused. If the team is not
+        running, no action is taken.
+
+        .. note::
+
+            It is the responsibility of the agent class to handle the pause
+            and ensure that the agent can be resumed later.
+            Make sure to implement the :meth:`~autogen_agentchat.agents.BaseChatAgent.on_pause`
+            method in your agent class for custom pause behavior.
+
+        Raises:
+            RuntimeError: If the team has not been initialized. Exceptions from
+                the participants when calling their implementations of
+                :class:`~autogen_agentchat.base.ChatAgent.on_pause` are
+                propagated to this method and raised.
+        """
+        if not self._initialized:
+            raise RuntimeError("The group chat has not been initialized. It must be run before it can be paused.")
+
+        if not self._is_running:
+            # The team is not running, so we cannot pause it.
+            return
+
+        # Send a pause message to all participants.
+        for participant_topic_type in self._participant_topic_types:
+            await self._runtime.send_message(
+                GroupChatPause(),
+                recipient=AgentId(type=participant_topic_type, key=self._team_id),
+            )
+        # Send a pause message to the group chat manager.
+        await self._runtime.send_message(
+            GroupChatPause(),
+            recipient=AgentId(type=self._group_chat_manager_topic_type, key=self._team_id),
+        )
+
+    async def resume(self) -> None:
+        """Resume its participants when the team is running and paused by calling their
+        :meth:`~autogen_agentchat.base.ChatAgent.on_resume` method via direct RPC calls.
+
+        The team must be initialized before it can be resumed. If the team is not
+        running, no action is taken.
+
+        .. note::
+
+            It is the responsibility of the agent class to handle the resume
+            and ensure that the agent continues from where it was paused.
+            Make sure to implement the :meth:`~autogen_agentchat.agents.BaseChatAgent.on_resume`
+            method in your agent class for custom resume behavior.
+
+        Raises:
+            RuntimeError: If the team has not been initialized. Exceptions from
+                the participants when calling their implementations of :class:`~autogen_agentchat.base.ChatAgent.on_resume`
+                method are propagated to this method and raised.
+
+        """
+        if not self._initialized:
+            raise RuntimeError("The group chat has not been initialized. It must be run before it can be resumed.")
+
+        if not self._is_running:
+            # The team is not running, so we cannot resume it.
+            return
+
+        # Send a resume message to all participants.
+        for participant_topic_type in self._participant_topic_types:
+            await self._runtime.send_message(
+                GroupChatResume(),
+                recipient=AgentId(type=participant_topic_type, key=self._team_id),
+            )
+        # Send a resume message to the group chat manager.
+        await self._runtime.send_message(
+            GroupChatResume(),
+            recipient=AgentId(type=self._group_chat_manager_topic_type, key=self._team_id),
+        )
+
     async def save_state(self) -> Mapping[str, Any]:
         """Save the state of the group chat team.
 
diff --git a/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_base_group_chat_manager.py b/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_base_group_chat_manager.py
index c93f5bd36f92..0cd45633728a 100644
--- a/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_base_group_chat_manager.py
+++ b/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_base_group_chat_manager.py
@@ -9,8 +9,10 @@
 from ._events import (
     GroupChatAgentResponse,
     GroupChatMessage,
+    GroupChatPause,
     GroupChatRequestPublish,
     GroupChatReset,
+    GroupChatResume,
     GroupChatStart,
     GroupChatTermination,
 )
@@ -41,7 +43,15 @@ def __init__(
         termination_condition: TerminationCondition | None = None,
         max_turns: int | None = None,
     ):
-        super().__init__(description="Group chat manager")
+        super().__init__(
+            description="Group chat manager",
+            sequential_message_types=[
+                GroupChatStart,
+                GroupChatAgentResponse,
+                GroupChatMessage,
+                GroupChatReset,
+            ],
+        )
         self._name = name
         self._group_topic_type = group_topic_type
         self._output_topic_type = output_topic_type
@@ -193,13 +203,25 @@ async def _signal_termination(self, message: StopMessage) -> None:
 
     @event
     async def handle_group_chat_message(self, message: GroupChatMessage, ctx: MessageContext) -> None:
+        """Handle a group chat message by appending the content to its output message queue."""
         await self._output_message_queue.put(message.message)
 
     @rpc
     async def handle_reset(self, message: GroupChatReset, ctx: MessageContext) -> None:
-        # Reset the group chat manager.
+        """Reset the group chat manager. Calling :meth:`reset` to reset the group chat manager
+        and clear the message thread."""
         await self.reset()
 
+    @rpc
+    async def handle_pause(self, message: GroupChatPause, ctx: MessageContext) -> None:
+        """Pause the group chat manager. This is a no-op in the base class."""
+        pass
+
+    @rpc
+    async def handle_resume(self, message: GroupChatResume, ctx: MessageContext) -> None:
+        """Resume the group chat manager. This is a no-op in the base class."""
+        pass
+
     @abstractmethod
     async def validate_group_state(self, messages: List[ChatMessage] | None) -> None:
         """Validate the state of the group chat given the start messages.
diff --git a/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_chat_agent_container.py b/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_chat_agent_container.py
index f01465d4c3d5..7c86556e257a 100644
--- a/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_chat_agent_container.py
+++ b/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_chat_agent_container.py
@@ -5,7 +5,15 @@
 from ...base import ChatAgent, Response
 from ...messages import ChatMessage
 from ...state import ChatAgentContainerState
-from ._events import GroupChatAgentResponse, GroupChatMessage, GroupChatRequestPublish, GroupChatReset, GroupChatStart
+from ._events import (
+    GroupChatAgentResponse,
+    GroupChatMessage,
+    GroupChatPause,
+    GroupChatRequestPublish,
+    GroupChatReset,
+    GroupChatResume,
+    GroupChatStart,
+)
 from ._sequential_routed_agent import SequentialRoutedAgent
 
 
@@ -21,7 +29,15 @@ class ChatAgentContainer(SequentialRoutedAgent):
     """
 
     def __init__(self, parent_topic_type: str, output_topic_type: str, agent: ChatAgent) -> None:
-        super().__init__(description=agent.description)
+        super().__init__(
+            description=agent.description,
+            sequential_message_types=[
+                GroupChatStart,
+                GroupChatRequestPublish,
+                GroupChatReset,
+                GroupChatAgentResponse,
+            ],
+        )
         self._parent_topic_type = parent_topic_type
         self._output_topic_type = output_topic_type
         self._agent = agent
@@ -74,6 +90,16 @@ async def handle_request(self, message: GroupChatRequestPublish, ctx: MessageCon
             cancellation_token=ctx.cancellation_token,
         )
 
+    @rpc
+    async def handle_pause(self, message: GroupChatPause, ctx: MessageContext) -> None:
+        """Handle a pause event by pausing the agent."""
+        await self._agent.on_pause(ctx.cancellation_token)
+
+    @rpc
+    async def handle_resume(self, message: GroupChatResume, ctx: MessageContext) -> None:
+        """Handle a resume event by resuming the agent."""
+        await self._agent.on_resume(ctx.cancellation_token)
+
     async def on_unhandled_message(self, message: Any, ctx: MessageContext) -> None:
         raise ValueError(f"Unhandled message in agent container: {type(message)}")
 
diff --git a/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_events.py b/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_events.py
index 853b854a4541..f705a54c4a50 100644
--- a/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_events.py
+++ b/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_events.py
@@ -44,3 +44,15 @@ class GroupChatReset(BaseModel):
     """A request to reset the agents in the group chat."""
 
     ...
+
+
+class GroupChatPause(BaseModel):
+    """A request to pause the group chat."""
+
+    ...
+
+
+class GroupChatResume(BaseModel):
+    """A request to resume the group chat."""
+
+    ...
diff --git a/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_sequential_routed_agent.py b/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_sequential_routed_agent.py
index 572592f2d32b..f3f3c1cd73b6 100644
--- a/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_sequential_routed_agent.py
+++ b/python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_sequential_routed_agent.py
@@ -1,5 +1,5 @@
 import asyncio
-from typing import Any
+from typing import Any, Sequence
 
 from autogen_core import MessageContext, RoutedAgent
 
@@ -36,15 +36,34 @@ def release(self) -> None:
 
 class SequentialRoutedAgent(RoutedAgent):
     """A subclass of :class:`autogen_core.RoutedAgent` that ensures
-    messages are handled sequentially in the order they arrive."""
+    messages are handled sequentially in the order they arrive.
 
-    def __init__(self, description: str) -> None:
+    This is useful for agents that need to maintain a strict order of
+    processing messages, such as in a group chat scenario.
+
+    Args:
+
+        description (str): The description of the agent.
+        sequential_message_types (Sequence[Type[Any]]): A sequence of message types that should be
+            processed sequentially. If a message of one of these types is received,
+            the agent will acquire a FIFO lock to ensure that it is processed
+            before any later messages that are also one of these types.
+    """
+
+    def __init__(self, description: str, sequential_message_types: Sequence[type[Any]]) -> None:
         super().__init__(description=description)
         self._fifo_lock = FIFOLock()
+        self._sequential_message_types = sequential_message_types
 
     async def on_message_impl(self, message: Any, ctx: MessageContext) -> Any | None:
-        await self._fifo_lock.acquire()
-        try:
-            return await super().on_message_impl(message, ctx)
-        finally:
-            self._fifo_lock.release()
+        if any(isinstance(message, sequential_type) for sequential_type in self._sequential_message_types):
+            # Acquire the FIFO lock to ensure that this message is processed
+            # in the order it was received.
+            await self._fifo_lock.acquire()
+            try:
+                return await super().on_message_impl(message, ctx)
+            finally:
+                # Release the FIFO lock to allow the next message to be processed.
+                self._fifo_lock.release()
+        # If the message is not of a sequential type, process it normally.
+        return await super().on_message_impl(message, ctx)
diff --git a/python/packages/autogen-agentchat/tests/test_group_chat_pause_resume.py b/python/packages/autogen-agentchat/tests/test_group_chat_pause_resume.py
new file mode 100644
index 000000000000..ee87f6f4a25b
--- /dev/null
+++ b/python/packages/autogen-agentchat/tests/test_group_chat_pause_resume.py
@@ -0,0 +1,142 @@
+import asyncio
+from typing import AsyncGenerator, List, Sequence
+
+import pytest
+import pytest_asyncio
+from autogen_agentchat.agents import BaseChatAgent
+from autogen_agentchat.base import Response
+from autogen_agentchat.messages import ChatMessage, TextMessage
+from autogen_agentchat.teams import RoundRobinGroupChat
+from autogen_core import AgentRuntime, CancellationToken, SingleThreadedAgentRuntime
+
+
+class TestAgent(BaseChatAgent):
+    """A test agent that does nothing."""
+
+    def __init__(self, name: str, description: str) -> None:
+        super().__init__(name=name, description=description)
+        self._is_paused = False
+        self._tasks: List[asyncio.Task[None]] = []
+        self.counter = 0
+
+    @property
+    def produced_message_types(self) -> Sequence[type[ChatMessage]]:
+        return [TextMessage]
+
+    async def on_messages(self, messages: Sequence[ChatMessage], cancellation_token: CancellationToken) -> Response:
+        assert not self._is_paused, "Agent is paused"
+
+        async def _process() -> None:
+            # Simulate a repetitive task that runs forever.
+            while True:
+                if self._is_paused:
+                    await asyncio.sleep(0.1)
+                    continue
+                else:
+                    # Simulate a I/O operation that takes time, e.g., a browser operation.
+                    await asyncio.sleep(0.1)
+                    self.counter += 1
+
+        curr_task = asyncio.create_task(_process())
+        self._tasks.append(curr_task)
+
+        try:
+            # This will never return until the task is cancelled, at which point it will
+            # raise an exception.
+            await curr_task
+        except asyncio.CancelledError:
+            # The task was cancelled, so we can safely ignore this.
+            pass
+
+        return Response(
+            chat_message=TextMessage(
+                source=self.name,
+                content="",
+            ),
+        )
+
+    async def on_reset(self, cancellation_token: CancellationToken) -> None:
+        self.counter = 0
+
+    async def on_pause(self, cancellation_token: CancellationToken) -> None:
+        self._is_paused = True
+
+    async def on_resume(self, cancellation_token: CancellationToken) -> None:
+        self._is_paused = False
+
+    async def close(self) -> None:
+        # Cancel all tasks and wait for them to finish.
+        while self._tasks:
+            task = self._tasks.pop()
+            task.cancel()
+            try:
+                await task
+            except asyncio.CancelledError:
+                pass
+
+
+@pytest_asyncio.fixture(params=["single_threaded", "embedded"])  # type: ignore
+async def runtime(request: pytest.FixtureRequest) -> AsyncGenerator[AgentRuntime | None, None]:
+    if request.param == "single_threaded":
+        runtime = SingleThreadedAgentRuntime()
+        runtime.start()
+        yield runtime
+        await runtime.stop()
+    elif request.param == "embedded":
+        yield None
+
+
+@pytest.mark.asyncio
+async def test_group_chat_pause_resume(runtime: AgentRuntime | None) -> None:
+    agent = TestAgent(name="test_agent", description="test agent")
+
+    team = RoundRobinGroupChat([agent], runtime=runtime, max_turns=1)
+
+    # Run the team in a separate task.
+    team_task = asyncio.create_task(team.run())
+
+    # Get the current counter.
+    curr_counter = agent.counter
+
+    # Let the agent process the counter for a while.
+    await asyncio.sleep(1)
+
+    # Check that the agent's counter has increased.
+    assert curr_counter < agent.counter
+    curr_counter = agent.counter
+
+    # Pause the team.
+    await team.pause()
+
+    # Wait for a while for the agent to process the pause.
+    await asyncio.sleep(1)
+
+    # Get the current counter value.
+    curr_counter = agent.counter
+
+    # Wait for a while.
+    await asyncio.sleep(1)
+
+    # Check that the agent's counter has not increased.
+    assert curr_counter == agent.counter
+
+    # Resume the agent.
+    await team.resume()
+
+    # Wait for a while for the agent to process the resume.
+    await asyncio.sleep(1)
+
+    # Get the current counter value.
+    curr_counter = agent.counter
+
+    # Wait for a while.
+    await asyncio.sleep(1)
+
+    # Check that the agent's counter has increased.
+    assert curr_counter < agent.counter
+
+    # Clean up -- force the agent to respond and terminate the team.
+    await agent.close()
+
+    # Wait for the team to terminate.
+    await team_task
diff --git a/python/packages/autogen-agentchat/tests/test_sequential_routed_agent.py b/python/packages/autogen-agentchat/tests/test_sequential_routed_agent.py
index 165c68e6d4de..4d4a46da918f 100644
--- a/python/packages/autogen-agentchat/tests/test_sequential_routed_agent.py
+++ b/python/packages/autogen-agentchat/tests/test_sequential_routed_agent.py
@@ -23,7 +23,7 @@ class Message:
 @default_subscription
 class _TestAgent(SequentialRoutedAgent):
     def __init__(self, description: str) -> None:
-        super().__init__(description=description)
+        super().__init__(description=description, sequential_message_types=[Message])
         self.messages: List[Message] = []
 
     @message_handler


Code review comments:
diff_hunk: @@ -565,6 +565,84 @@ async def main() -> None:
             # Indicate that the team is no longer running.
             self._is_running = False
 
+    async def pause(self) -> None:
+        """Pause its participants when the team is running by calling their
+        :meth:`~autogen_agentchat.base.ChatAgent.on_pause` method via direct RPC calls.
+
+        The team must be initialized before it can be paused. If the team is not
+        running, no action is taken.
+
+        .. note::
+
+            It is the responsibility of the agent class to handle the pause
+            and ensure that the agent can be resumed later.
+            Make sure to implement the :meth:`~autogen_agentchat.agents.BaseChatAgent.on_pause`
+            method in your agent class for custom pause behavior.
+
+        Raises:
+            RuntimeError: If the team has not been initialized. Exceptions from
+                the participants when calling their implementations of
+                :class:`~autogen_agentchat.base.ChatAgent.on_pause` are
+                propagated to this method and raised.
+        """
+        if not self._initialized:
+            raise RuntimeError("The group chat has not been initialized. It must be run before it can be paused.")
+
+        if not self._is_running:
path: python/packages/autogen-agentchat/src/autogen_agentchat/teams/_group_chat/_base_group_chat.py
text: @user1:
Should we raise an error here instead?

@author:
Since `pause` is going to be executed async in regarding to the `run_stream` or `run` method, so it is possible that the `pause` method is called when the team has already stopped due to termination condition. This is very hard to prevent and requires expensive synchronization from application side to ensure this doesn't happen. 

However, thinking about this more. I think we shouldn't even check for if the team is running: the pausing state of an agent can be flipped independently from whether the team is running or not. So I think we should just remove this check.