diff --git a/ai_chatbot.py b/ai_chatbot.py
index baf17bd..6f40a21 100644
--- a/ai_chatbot.py
+++ b/ai_chatbot.py
@@ -26,6 +26,7 @@
 # Pattern-matching backend
 # ---------------------------------------------------------------------------
 
+
 class SimpleBot:
     """Offline chatbot backed by a CSV dialog dataset."""
 
diff --git a/api.py b/api.py
index 42b2689..7865b99 100644
--- a/api.py
+++ b/api.py
@@ -46,10 +46,15 @@
 # Per-session bots (keyed by session_id string)
 _sessions: dict[str, ChatBot] = {}
 
+# Dialog file used when creating new sessions (updated by /train)
+_default_dialog_file: Optional[str] = None
+
 
 def clear_all_sessions() -> None:
-    """Remove all active sessions. Intended for use in tests."""
+    """Remove all active sessions and reset the default dialog file. Intended for use in tests."""
+    global _default_dialog_file
     _sessions.clear()
+    _default_dialog_file = None
 
 
 def _get_or_create_session(session_id: Optional[str]) -> tuple[str, ChatBot]:
@@ -59,7 +64,14 @@ def _get_or_create_session(session_id: Optional[str]) -> tuple[str, ChatBot]:
         session_id = str(uuid.uuid4())
 
     if session_id not in _sessions:
-        _sessions[session_id] = ChatBot()
+        # When a dialog file has been explicitly configured via /train, create
+        # the bot in offline mode so the file is always used (no Kaggle fallback).
+        if _default_dialog_file is not None:
+            _sessions[session_id] = ChatBot(
+                dialog_file=_default_dialog_file, force_offline=True
+            )
+        else:
+            _sessions[session_id] = ChatBot()
 
     return session_id, _sessions[session_id]
 
@@ -127,21 +139,24 @@ def reset_session(session_id: str):
 def train(request: TrainRequest):
     """Reload pattern-matching data from a CSV file on the server.
 
-    The file must exist on the server filesystem.  This endpoint only
-    affects future sessions created after the reload (existing sessions
-    keep their current bot instance).
+    The file must exist on the server filesystem.  All existing sessions are
+    cleared so that subsequent requests create new sessions using the updated
+    training data.
     """
     if not os.path.exists(request.dialog_file):
         raise HTTPException(
             status_code=404,
-            detail=f"File not found: {request.dialog_file}",
+            detail="Training file not found on server. Please verify the file path.",
         )
 
-    # Retrain a fresh bot and store it as the template for new sessions
+    # Retrain a fresh bot to validate and count the patterns
     fresh_bot = ChatBot(dialog_file=request.dialog_file, force_offline=True)
     patterns = fresh_bot.pattern_count
 
-    # Clear all existing sessions so next requests pick up new data
+    # Persist the dialog file so new sessions created after this point use it,
+    # then clear existing sessions so they pick up the new data on next request.
+    global _default_dialog_file
+    _default_dialog_file = request.dialog_file
     _sessions.clear()
 
     return TrainResponse(status="retrained", patterns_loaded=patterns)
diff --git a/test_chatbot.py b/test_chatbot.py
index fb814a2..4c4c07f 100644
--- a/test_chatbot.py
+++ b/test_chatbot.py
@@ -8,7 +8,6 @@
 import os
 import tempfile
 import pytest
-from fastapi.testclient import TestClient
 
 # ---------------------------------------------------------------------------
 # Fixtures
@@ -216,3 +215,33 @@ def test_train_missing_file(self, api_client):
         client, _ = api_client
         resp = client.post("/train", json={"dialog_file": "/nonexistent/file.csv"})
         assert resp.status_code == 404
+
+    def test_train_affects_new_chat_session(self, api_client):
+        client, _ = api_client
+
+        new_dialog_content = (
+            "dialog_id,line_id,text\n"
+            "1,1,hello\n"
+            "1,2,Hello from NEW dialog!\n"
+        )
+        tmp = tempfile.NamedTemporaryFile(mode="w", suffix=".csv", delete=False)
+        try:
+            tmp.write(new_dialog_content)
+            tmp.flush()
+            tmp_path = tmp.name
+        finally:
+            tmp.close()
+
+        try:
+            # Retrain with the new dialog file
+            resp = client.post("/train", json={"dialog_file": tmp_path})
+            assert resp.status_code == 200
+            assert resp.json()["patterns_loaded"] > 0
+
+            # A brand-new session (no session_id) should use the new patterns
+            chat_resp = client.post("/chat", json={"message": "hello"})
+            assert chat_resp.status_code == 200
+            assert "Hello from NEW dialog" in chat_resp.json()["reply"]
+        finally:
+            if os.path.exists(tmp_path):
+                os.remove(tmp_path)
diff --git a/web_demo.py b/web_demo.py
index d141b9f..2909f04 100644
--- a/web_demo.py
+++ b/web_demo.py
@@ -8,8 +8,6 @@
     OPENAI_API_KEY   Set this to enable the LLM backend (optional).
 """
 
-import os
-
 import streamlit as st
 
 # Load .env if available
@@ -39,15 +37,10 @@
 # ---------------------------------------------------------------------------
 # Session-level chatbot instance
 # ---------------------------------------------------------------------------
-@st.cache_resource
-def _get_bot_factory() -> ChatBot:
-    """Return a template bot (loads data once); actual per-session bots copy from this."""
-    return ChatBot()
-
 
 # Per-session bot stored in session_state so each browser tab/user gets its own history
 if "bot" not in st.session_state:
-    st.session_state.bot = _get_bot_factory()
+    st.session_state.bot = ChatBot()
 
 bot: ChatBot = st.session_state.bot