fix: preserve API prefix in session Location header (fixes #247)

chatbot-core/api/routes/chatbot.py

@@ -20,6 +20,7 @@
 from fastapi import (
     APIRouter,
     HTTPException,
+    Request,
     Response,
     WebSocket,
     WebSocketDisconnect,
@@ -155,17 +156,17 @@ async def chatbot_stream(websocket: WebSocket, session_id: str):
     response_model=SessionResponse,
     status_code=status.HTTP_201_CREATED,
 )
-def start_chat(response: Response):
+def start_chat(request: Request, response: Response):
     """
     Create a new chat session.
 
     Returns a unique session ID that can be used for subsequent
     chatbot interactions.
     """
     session_id = init_session()
-    response.headers["Location"] = (
-        f"/sessions/{session_id}/message"
-    )
+    response.headers["Location"] = request.url_for(
+        "chatbot_reply", session_id=session_id
+    ).path
     return SessionResponse(session_id=session_id)
 
 @router.delete(

chatbot-core/tests/unit/routes/test_chatbot.py

@@ -1,5 +1,11 @@
 """Unit Tests for FastAPI routes."""
 
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+
+from api.routes.chatbot import router
+
+
 def test_start_chat(client, mock_init_session):
     """Testing that creating a session returns session ID and location."""
     mock_init_session.return_value = "test-session-id"
@@ -11,6 +17,20 @@ def test_start_chat(client, mock_init_session):
     assert response.headers["location"] == "/sessions/test-session-id/message"
 
 
+def test_start_chat_location_includes_router_prefix(mock_init_session):
+    """Location header should include API prefix when router is mounted with one."""
+    mock_init_session.return_value = "test-session-id"
+
+    app = FastAPI()
+    app.include_router(router, prefix="/api/chatbot")
+    prefixed_client = TestClient(app)
+
+    response = prefixed_client.post("/api/chatbot/sessions")
+
+    assert response.status_code == 201
+    assert response.headers["location"] == "/api/chatbot/sessions/test-session-id/message"
+
+
 def test_chatbot_reply_success(client, mock_session_exists, mock_get_chatbot_reply):
     """Testing that sending a valid message in a valid session returns a response."""
     mock_session_exists.return_value = True