feat(api): Synchronize history and summary from DB in chat stream

backend/src/ea_chatbot/api/routers/agent.py

@@ -7,10 +7,12 @@ from ea_chatbot.api.utils import convert_to_json_compatible
 from ea_chatbot.graph.workflow import app
 from ea_chatbot.graph.checkpoint import get_checkpointer
 from ea_chatbot.history.models import User as UserDB, Conversation
+from ea_chatbot.history.utils import map_db_messages_to_langchain
 from ea_chatbot.api.schemas import ChatRequest
 import io
 import base64
 from langchain_core.runnables.config import RunnableConfig
+from langchain_core.messages import BaseMessage
 
 router = APIRouter(prefix="/chat", tags=["agent"])
 
@@ -18,14 +20,15 @@ async def stream_agent_events(
     message: str, 
     thread_id: str, 
     user_id: str,
-    summary: str
+    summary: str,
+    messages: List[BaseMessage] = []
 ) -> AsyncGenerator[str, None]:
     """
     Generator that invokes the LangGraph agent and yields SSE formatted events.
     Persists assistant responses and plots to the database.
     """
     initial_state = {
-        "messages": [], 
+        "messages": messages, 
         "question": message,
         "summary": summary,
         "analysis": None,
@@ -150,7 +153,15 @@ async def chat_stream(
         if conv.user_id != current_user.id:
             raise HTTPException(status_code=403, detail="Not authorized to access this conversation")
         
-    # Save user message immediately
+        # Load existing summary from DB if not provided in request
+        db_summary = conv.summary or ""
+
+    # Load last 10 messages for context (BEFORE saving the current user message)
+    # This ensures we don't include the current message twice if the graph reduces it.
+    db_messages = history_manager.get_messages_by_window(request.thread_id, window_size=10)
+    lc_messages = map_db_messages_to_langchain(db_messages)
+
+    # Save user message immediately to DB
     history_manager.add_message(request.thread_id, "user", request.message)
 
     return StreamingResponse(
@@ -158,7 +169,8 @@ async def chat_stream(
             request.message, 
             request.thread_id, 
             current_user.id,
-            request.summary or ""
+            db_summary,
+            lc_messages
         ),
         media_type="text/event-stream"
     )

backend/tests/api/test_history_sync.py

@@ -0,0 +1,79 @@
+import pytest
+from fastapi.testclient import TestClient
+from unittest.mock import MagicMock, patch
+from ea_chatbot.api.main import app
+from ea_chatbot.history.models import User, Conversation, Message
+from langchain_core.messages import HumanMessage, AIMessage
+
+@pytest.fixture
+def client():
+    return TestClient(app)
+
+@pytest.fixture
+def mock_user():
+    return User(id="user-123", username="test@test.com")
+
+def test_chat_stream_loads_history(client, mock_user):
+    """
+    Test that the /chat/stream endpoint loads history from the DB
+    and passes it to stream_agent_events.
+    """
+    # 1. Setup mocks
+    from ea_chatbot.api.dependencies import get_current_user
+    app.dependency_overrides[get_current_user] = lambda: mock_user
+    
+    try:
+        with patch("ea_chatbot.api.routers.agent.history_manager") as mock_hm, \
+             patch("ea_chatbot.api.routers.agent.stream_agent_events") as mock_stream:
+            
+            # Mock conversation exists and belongs to user
+            mock_conv = Conversation(id="conv-123", user_id=mock_user.id, summary="Old summary")
+            
+            mock_session = MagicMock()
+            mock_session.get.return_value = mock_conv
+            mock_hm.get_session.return_value.__enter__.return_value = mock_session
+            
+            # Mock history window returns some messages
+            mock_db_messages = [
+                Message(role="user", content="Question 1"),
+                Message(role="assistant", content="Answer 1")
+            ]
+            mock_hm.get_messages_by_window.return_value = mock_db_messages
+            
+            # Mock stream_agent_events to return an empty generator
+            async def empty_gen(*args, **kwargs):
+                yield 'data: {"type": "done"}\n\n'
+            
+            mock_stream.side_effect = empty_gen
+            
+            # 2. Execute request
+            response = client.post(
+                "/api/v1/chat/stream",
+                json={"message": "New question", "thread_id": "conv-123"}
+            )
+            
+            # 3. Assertions
+            assert response.status_code == 200
+            
+            # Verify history_manager was called to get history
+            mock_hm.get_messages_by_window.assert_called_once_with("conv-123", window_size=10)
+            
+            # Verify stream_agent_events was called with loaded history and summary
+            args, kwargs = mock_stream.call_args
+            # args: message, thread_id, user_id, summary, messages
+            assert args[0] == "New question"
+            assert args[1] == "conv-123"
+            assert args[2] == mock_user.id
+            assert args[3] == "Old summary"
+            
+            passed_messages = args[4]
+            assert len(passed_messages) == 2
+            assert isinstance(passed_messages[0], HumanMessage)
+            assert passed_messages[0].content == "Question 1"
+            assert isinstance(passed_messages[1], AIMessage)
+            assert passed_messages[1].content == "Answer 1"
+            
+            # Verify current message was saved AFTER loading history (based on code logic)
+            mock_hm.add_message.assert_called_with("conv-123", "user", "New question")
+    finally:
+        app.dependency_overrides.clear()