fix: add thinking when agent is not responding

Gradio_UI.py

@@ -192,12 +192,36 @@ class GradioUI:
     def interact_with_agent(self, prompt, messages):
         import gradio as gr
 
+        # Add user message
         messages.append(gr.ChatMessage(role="user", content=prompt))
+        # Add a temporary assistant placeholder to indicate the model is working
+        thinking_msg = gr.ChatMessage(role="assistant", content="⏳ Thinking…")
+        messages.append(thinking_msg)
         yield messages
-        for msg in stream_to_gradio(self.agent, task=prompt, reset_agent_memory=True):
-            messages.append(msg)
+
+        placeholder_active = True
+        try:
+            for msg in stream_to_gradio(self.agent, task=prompt, reset_agent_memory=True):
+                if placeholder_active:
+                    # Replace the placeholder with the first real assistant event
+                    messages[-1] = msg
+                    placeholder_active = False
+                else:
+                    messages.append(msg)
+                yield messages
+        except Exception as e:
+            # Replace the placeholder with an error message if something goes wrong
+            error_msg = gr.ChatMessage(role="assistant", content=f"💥 Error: {e}")
+            if placeholder_active:
+                messages[-1] = error_msg
+            else:
+                messages.append(error_msg)
+            yield messages
+        finally:
+            # Ensure no dangling placeholder remains
+            if placeholder_active and messages and messages[-1] is thinking_msg:
+                messages.pop()
             yield messages
-        yield messages
 
     def upload_file(
         self,
@@ -337,7 +361,7 @@ class GradioUI:
                 <p class=\"support\"><strong>Supported by:</strong> This work is supported by the <a href=\"https://pink-project.eu/\" target=\"_blank\">PINK Project</a> - a Horizon Europe initiative for Safe-and-Sustainable-by-Design computational approaches for chemicals and materials.</p>
             </div>
             """)
-            
+
             stored_messages = gr.State([])
             file_uploads_log = gr.State([])
             chatbot = gr.Chatbot(