Conversation: make state.events.append a default callback; remove manual appends in CodeActAgent (#57)

Co-authored-by: openhands <[email protected]>

Author: xingyaoww

openhands/core/agent/codeact_agent/codeact_agent.py

@@ -52,8 +52,6 @@ def init_state(
         if len(messages) == 0:
             # Prepare system message
             event = SystemPromptEvent(source="agent", system_prompt=self.system_message, tools=[t.to_openai_tool() for t in self.tools.values()])
-            # TODO: maybe we should combine this into on_event?
-            state.events.append(event)
             on_event(event)
 
     def step(
@@ -99,15 +97,13 @@ def step(
                 if action_event is None:
                     continue
                 action_events.append(action_event)
-                state.events.append(action_event)
 
             for action_event in action_events:
                 self._execute_action_events(state, action_event, on_event=on_event)
         else:
             logger.info("LLM produced a message response - awaits user input")
             state.agent_finished = True
             msg_event = MessageEvent(source="agent", llm_message=message)
-            state.events.append(msg_event)
             on_event(msg_event)
 
     def _get_action_events(
@@ -131,7 +127,6 @@ def _get_action_events(
             err = f"Tool '{tool_name}' not found. Available: {list(self.tools.keys())}"
             logger.error(err)
             event = AgentErrorEvent(error=err)
-            state.events.append(event)
             on_event(event)
             state.agent_finished = True
             return
@@ -142,7 +137,6 @@ def _get_action_events(
         except (json.JSONDecodeError, ValidationError) as e:
             err = f"Error validating args {tool_call.function.arguments} for tool '{tool.name}': {e}"
             event = AgentErrorEvent(error=err)
-            state.events.append(event)
             on_event(event)
             return
 
@@ -172,5 +166,4 @@ def _execute_action_events(self, state: ConversationState, action_event: ActionE
         # Set conversation state
         if tool.name == FinishTool.name:
             state.agent_finished = True
-        state.events.append(obs_event)
         return obs_event

openhands/core/conversation/conversation.py

@@ -30,12 +30,19 @@ class Conversation:
     def __init__(self, agent: "AgentBase", callbacks: list[ConversationCallbackType] | None = None, max_iteration_per_run: int = 500, env_context: EnvContext | None = None):
         """Initialize the conversation."""
         self._visualizer = ConversationVisualizer()
-        # Compose multiple callbacks if a list is provided
-        self._on_event = compose_callbacks([self._visualizer.on_event] + (callbacks if callbacks else []))
-        self.max_iteration_per_run = max_iteration_per_run
-
         self.agent = agent
         self.state = ConversationState()
+
+        # Default callback: persist every event to state
+        def _append_event(e):
+            self.state.events.append(e)
+
+        # Compose callbacks; default appender runs last to keep agent-emitted event order (on_event then persist)
+        composed_list = [self._visualizer.on_event] + (callbacks if callbacks else []) + [_append_event]
+        self._on_event = compose_callbacks(composed_list)
+
+        self.max_iteration_per_run = max_iteration_per_run
+
         with self.state:
             self.agent.init_state(self.state, on_event=self._on_event)
 
@@ -65,7 +72,6 @@ def send_message(self, message: Message) -> None:
                 pass
 
             user_msg_event = MessageEvent(source="user", llm_message=message, activated_microagents=activated_microagents)
-            self.state.events.append(user_msg_event)
             self._on_event(user_msg_event)
 
     def run(self) -> None:

openhands/core/tests/conversation/test_conversation_default_callback.py

@@ -0,0 +1,57 @@
+
+from typing import List
+from unittest.mock import MagicMock
+
+from openhands.core.agent.base import AgentBase
+from openhands.core.conversation import Conversation
+from openhands.core.conversation.state import ConversationState
+from openhands.core.conversation.types import ConversationCallbackType
+from openhands.core.event.llm_convertible import MessageEvent, SystemPromptEvent
+from openhands.core.llm import Message, TextContent
+
+
+class DummyAgent(AgentBase):
+    def __init__(self):
+        super().__init__(llm=MagicMock(name="LLM"), tools=[])
+        self.prompt_manager = MagicMock()
+
+    def init_state(self, state: ConversationState, on_event: ConversationCallbackType) -> None:
+        event = SystemPromptEvent(source="agent", system_prompt=TextContent(text="dummy"), tools=[])
+        on_event(event)
+
+    def step(self, state: ConversationState, on_event: ConversationCallbackType) -> None:
+        on_event(MessageEvent(source="agent", llm_message=Message(role="assistant", content=[TextContent(text="ok")])) )
+
+
+def test_default_callback_appends_on_init():
+    agent = DummyAgent()
+    events_seen: List[str] = []
+
+    convo = Conversation(agent=agent, callbacks=[lambda e: events_seen.append(e.id)])
+
+    assert len(convo.state.events) == 1
+    assert isinstance(convo.state.events[0], SystemPromptEvent)
+    assert convo.state.events[0].id in events_seen
+
+
+def test_send_message_appends_once():
+    agent = DummyAgent()
+    seen_ids: List[str] = []
+
+    def user_cb(event):
+        seen_ids.append(event.id)
+
+    convo = Conversation(agent=agent, callbacks=[user_cb])
+
+    convo.send_message(Message(role="user", content=[TextContent(text="hi")]))
+
+    # Now we should have two events: initial system prompt and the user message
+    assert len(convo.state.events) == 2
+    assert isinstance(convo.state.events[-1], MessageEvent)
+
+    # Ensure the user message event is appended exactly once in state
+    last_id = convo.state.events[-1].id
+    assert sum(1 for e in convo.state.events if e.id == last_id) == 1
+
+    # Ensure callback saw both events
+    assert set(seen_ids) == {e.id for e in convo.state.events}