Lock user ID to HF username for security - prevent accessing other users' memories

app.py

@@ -353,27 +353,28 @@ with st.sidebar:
     provider = MODEL_TO_PROVIDER[model_id]
     set_model(model_id)
 
-    st.markdown("#### Choose user persona")
+    st.markdown("#### User Identity")
     
     # Get Hugging Face user ID if available (in HF Spaces)
     hf_user_id = os.getenv("SPACE_USER") or os.getenv("HF_USERNAME")
     
     if hf_user_id:
-        # Use HF user ID as default, but allow override
+        # Lock to HF user ID - no override allowed for security
         st.info(f"👤 Signed in as: **{hf_user_id}**")
-        default_persona = hf_user_id
+        persona_name = hf_user_id
+        # Hide persona selection when HF user ID is available
+        st.caption("Your memories are personalized to your account.")
     else:
-        default_persona = "Charlie"
-    
-    selected_persona = st.selectbox(
-        "Choose user persona",
-        ["Charlie", "Jing", "Charles", "Control"],
-        label_visibility="collapsed",
-    )
-    custom_persona = st.text_input("Or enter your name", default_persona if hf_user_id else "")
-    persona_name = (
-        custom_persona.strip() if custom_persona.strip() else (hf_user_id if hf_user_id else selected_persona)
-    )
+        # Local/testing mode - allow persona selection
+        selected_persona = st.selectbox(
+            "Choose user persona",
+            ["Charlie", "Jing", "Charles", "Control"],
+            label_visibility="collapsed",
+        )
+        custom_persona = st.text_input("Or enter your name", "")
+        persona_name = (
+            custom_persona.strip() if custom_persona.strip() else selected_persona
+        )
 
     compare_personas = st.checkbox("Compare with Control persona")
     show_rationale = st.checkbox("Show Persona Rationale")