v1.5.2: Replace localStorage with server-side file persistence - bulletproof on HF Spaces

app.py

@@ -4,7 +4,6 @@ An AI-powered chatbot for designing R/R TCL clinical trials.
 """
 
 import streamlit as st
-from streamlit_javascript import st_javascript
 import anthropic
 import os
 import time
@@ -185,19 +184,13 @@ def get_theme_css(dark_mode: bool = True) -> str:
     """
 
 
-SESSIONS_LS_KEY = "clinical_trial_sessions"
-CURRENT_SESSION_LS_KEY = "clinical_trial_current_session"
+SESSIONS_FILE = os.path.join(os.environ.get("HOME", "/tmp"), ".clinical_trial_sessions.json")
 
 
 def _new_session_id() -> str:
     return datetime.now().strftime("%Y%m%d_%H%M%S_%f")
 
 
-def _js_key(base: str) -> str:
-    """Generate a unique key for each st_javascript call to avoid duplicate element ID errors."""
-    return f"{base}_{time.time_ns()}"
-
-
 def _session_title(messages: list) -> str:
     """Auto-generate a session title from the first user message."""
     for m in messages:
@@ -207,53 +200,65 @@ def _session_title(messages: list) -> str:
     return "New conversation"
 
 
+def _read_sessions_file() -> dict:
+    """Read sessions from the JSON file on disk. Returns empty dict on any error."""
+    try:
+        if os.path.exists(SESSIONS_FILE):
+            with open(SESSIONS_FILE, "r", encoding="utf-8") as f:
+                data = json.load(f)
+            if isinstance(data, dict) and "sessions" in data:
+                return data
+    except Exception:
+        pass
+    return {}
+
+
+def _write_sessions_file(sessions: dict, current_sid: str) -> None:
+    """Write sessions and current session ID to the JSON file on disk."""
+    try:
+        data = {"sessions": sessions, "current_session_id": current_sid}
+        with open(SESSIONS_FILE, "w", encoding="utf-8") as f:
+            json.dump(data, f, ensure_ascii=False, indent=2)
+    except Exception:
+        pass  # Non-critical — session state in memory still works
+
+
 def save_all_sessions() -> None:
-    """Persist all sessions + current session ID to localStorage."""
-    # Sync current messages into sessions dict before saving
+    """Sync current messages into sessions dict and persist to disk."""
     sid = st.session_state.current_session_id
     if sid in st.session_state.sessions:
-        st.session_state.sessions[sid]["messages"] = st.session_state.messages
+        st.session_state.sessions[sid]["messages"] = list(st.session_state.messages)
         st.session_state.sessions[sid]["title"] = _session_title(st.session_state.messages)
-
-    sessions_json = json.dumps(st.session_state.sessions, ensure_ascii=False)
-    encoded = sessions_json.replace('\\', '\\\\').replace('`', '\\`')
-    # Unique keys prevent StreamlitDuplicateElementId when called multiple times per render
-    st_javascript(f"localStorage.setItem('{SESSIONS_LS_KEY}', `{encoded}`); 1;", key=_js_key("save_sess"))
-    st_javascript(f"localStorage.setItem('{CURRENT_SESSION_LS_KEY}', '{sid}'); 1;", key=_js_key("save_cur"))
+    _write_sessions_file(st.session_state.sessions, sid)
 
 
 def load_all_sessions() -> None:
-    """
-    Restore all sessions from localStorage on first page load.
-    st_javascript returns JS values directly to Python — no URL tricks.
-    """
+    """Restore sessions from disk into session state. Runs once per page load."""
     if st.session_state.get("_sessions_restored"):
         return
     st.session_state._sessions_restored = True
 
-    raw_sessions = st_javascript(f"localStorage.getItem('{SESSIONS_LS_KEY}');", key="load_sessions_once")
-    raw_current = st_javascript(f"localStorage.getItem('{CURRENT_SESSION_LS_KEY}');", key="load_current_once")
+    data = _read_sessions_file()
+    if not data:
+        return
 
-    if raw_sessions and raw_sessions not in ("null", "undefined", "", None):
-        try:
-            sessions = json.loads(raw_sessions)
-            if isinstance(sessions, dict) and sessions:
-                st.session_state.sessions = sessions
-                # Restore last active session
-                if raw_current and raw_current in sessions:
-                    st.session_state.current_session_id = raw_current
-                else:
-                    # Fall back to most recent
-                    st.session_state.current_session_id = sorted(sessions.keys())[-1]
-                st.session_state.messages = sessions[
-                    st.session_state.current_session_id
-                ]["messages"]
-        except Exception:
-            pass  # Corrupted — start fresh
+    sessions = data.get("sessions", {})
+    current_sid = data.get("current_session_id", "")
+
+    if sessions:
+        st.session_state.sessions = sessions
+        if current_sid and current_sid in sessions:
+            st.session_state.current_session_id = current_sid
+        else:
+            st.session_state.current_session_id = sorted(sessions.keys())[-1]
+        st.session_state.messages = list(
+            st.session_state.sessions[st.session_state.current_session_id]["messages"]
+        )
 
 
 def create_new_session() -> None:
     """Create a brand-new empty session and switch to it."""
+    save_all_sessions()  # Save the current session first
     sid = _new_session_id()
     st.session_state.sessions[sid] = {
         "title": "New conversation",
@@ -268,10 +273,10 @@ def create_new_session() -> None:
 
 def switch_session(sid: str) -> None:
     """Switch to an existing session."""
-    # Save current session first
-    save_all_sessions()
+    save_all_sessions()  # Save current session first
     st.session_state.current_session_id = sid
-    st.session_state.messages = st.session_state.sessions[sid]["messages"]
+    st.session_state.messages = list(st.session_state.sessions[sid]["messages"])
+    save_all_sessions()
     st.rerun()
 
 
@@ -280,11 +285,10 @@ def delete_session(sid: str) -> None:
     st.session_state.sessions.pop(sid, None)
     if st.session_state.sessions:
         st.session_state.current_session_id = sorted(st.session_state.sessions.keys())[-1]
-        st.session_state.messages = st.session_state.sessions[
-            st.session_state.current_session_id
-        ]["messages"]
+        st.session_state.messages = list(
+            st.session_state.sessions[st.session_state.current_session_id]["messages"]
+        )
     else:
-        # No sessions left — create fresh one
         new_sid = _new_session_id()
         st.session_state.sessions[new_sid] = {
             "title": "New conversation",
@@ -321,11 +325,11 @@ def initialize_session_state() -> None:
         st.session_state.current_session_id = first_sid
 
     if "messages" not in st.session_state:
-        st.session_state.messages = st.session_state.sessions[
-            st.session_state.current_session_id
-        ]["messages"]
+        st.session_state.messages = list(
+            st.session_state.sessions[st.session_state.current_session_id]["messages"]
+        )
 
-    # Restore persisted sessions from localStorage (once per page load)
+    # Restore persisted sessions from disk (once per page load)
     load_all_sessions()
 
 

requirements.txt

@@ -1,4 +1,3 @@
 # Core dependencies
 streamlit>=1.28.0
 anthropic>=0.45.0
-streamlit-javascript>=0.1.5