1) Recreate the agent upon a change in the settings.

2) When mid-session, disable the widgets triggering the change in the settings.

llama_stack/distribution/ui/page/playground/rag.py

@@ -16,6 +16,13 @@ from llama_stack.distribution.ui.modules.utils import data_url_from_file
 def rag_chat_page():
     st.title("🦙 RAG")
 
+    def reset_agent_and_chat():
+        st.session_state.clear()
+        st.cache_resource.clear()
+
+    def should_disable_input():
+        return "messages" in st.session_state and len(st.session_state.messages) > 0
+
     with st.sidebar:
         # File/Directory Upload Section
         st.subheader("Upload Documents")
@@ -69,21 +76,27 @@ def rag_chat_page():
         vector_dbs = llama_stack_api.client.vector_dbs.list()
         vector_dbs = [vector_db.identifier for vector_db in vector_dbs]
         selected_vector_dbs = st.multiselect(
-            "Select Vector Databases",
+            label="Select Vector Databases",
-            vector_dbs,
+            options=vector_dbs,
+            on_change=reset_agent_and_chat,
+            disabled=should_disable_input(),
         )
 
         available_models = llama_stack_api.client.models.list()
         available_models = [model.identifier for model in available_models if model.model_type == "llm"]
         selected_model = st.selectbox(
-            "Choose a model",
+            label="Choose a model",
-            available_models,
+            options=available_models,
             index=0,
+            on_change=reset_agent_and_chat,
+            disabled=should_disable_input(),
         )
         system_prompt = st.text_area(
             "System Prompt",
             value="You are a helpful assistant. ",
             help="Initial instructions given to the AI to set its behavior and context",
+            on_change=reset_agent_and_chat,
+            disabled=should_disable_input(),
         )
         temperature = st.slider(
             "Temperature",
@@ -92,6 +105,8 @@ def rag_chat_page():
             value=0.0,
             step=0.1,
             help="Controls the randomness of the response. Higher values make the output more creative and unexpected, lower values make it more conservative and predictable",
+            on_change=reset_agent_and_chat,
+            disabled=should_disable_input(),
         )
 
         top_p = st.slider(
@@ -100,12 +115,14 @@ def rag_chat_page():
             max_value=1.0,
             value=0.95,
             step=0.1,
+            on_change=reset_agent_and_chat,
+            disabled=should_disable_input(),
         )
 
         # Add clear chat button to sidebar
         if st.button("Clear Chat", use_container_width=True):
-            st.session_state.clear()
+            reset_agent_and_chat()
-            st.cache_resource.clear()
+            st.rerun()
 
     # Chat Interface
     if "messages" not in st.session_state:
@@ -151,15 +168,8 @@ def rag_chat_page():
 
     session_id = st.session_state["agent_session_id"]
 
-    # Chat input
+    def process_prompt(prompt):
-    if prompt := st.chat_input("Ask a question about your documents"):
+        # Send the prompt to the agent
-        # Add user message to chat history
-        st.session_state.messages.append({"role": "user", "content": prompt})
-
-        # Display user message
-        with st.chat_message("user"):
-            st.markdown(prompt)
-
         response = agent.create_turn(
             messages=[
                 {
@@ -188,5 +198,24 @@ def rag_chat_page():
 
             st.session_state.messages.append({"role": "assistant", "content": full_response})
 
+    # Chat input
+    if prompt := st.chat_input("Ask a question about your documents"):
+        # Add user message to chat history
+        st.session_state.messages.append({"role": "user", "content": prompt})
+
+        # Display user message
+        with st.chat_message("user"):
+            st.markdown(prompt)
+
+        # store the prompt to process it after page refresh
+        st.session_state.prompt = prompt
+
+        # force page refresh to disable the settings widgets
+        st.rerun()
+
+    if "prompt" in st.session_state and st.session_state.prompt is not None:
+        process_prompt(st.session_state.prompt)
+        st.session_state.prompt = None
+
 
 rag_chat_page()