Fix runtime error: prevent multiple demo initializations on Spaces

- Add guard flag to prevent multiple calls to _create_demo()
- Add check to only create demo if it doesn't exist or is invalid
- Explicitly set demo in module namespace for Spaces compatibility
- Fixes issue where demo was being created twice causing runtime errors

app.py

@@ -819,11 +819,18 @@ IS_SPACES = (
     os.getenv("HF_SPACE_ID") is not None
 )
 
-# Initialize demo variable
+# Initialize demo variable and creation flag
 demo = None
+_demo_created = False
 
 def _create_demo():
     """Create the demo - separated into function for better error handling"""
+    global _demo_created, demo
+    if _demo_created and demo is not None and isinstance(demo, (gr.Blocks, gr.Interface)):
+        logger.warning("Demo already created, skipping...")
+        return demo
+    
+    _demo_created = True
     try:
         logger.info("=" * 80)
         logger.info("Starting demo creation...")
@@ -862,9 +869,9 @@ def _create_demo():
             logger.warning("Vector database is empty. The chatbot may not find relevant documents.")
         
         logger.info("Creating interface...")
-        demo = create_interface(bot)
-        logger.info(f"Demo created successfully: {type(demo)}")
-        return demo
+        created_demo = create_interface(bot)
+        logger.info(f"Demo created successfully: {type(created_demo)}")
+        return created_demo
         
     except Exception as bot_error:
         logger.error(f"Error initializing: {bot_error}", exc_info=True)
@@ -893,40 +900,44 @@ def _create_demo():
         logger.info(f"Error demo created: {type(error_demo)}")
         return error_demo
 
-# Create demo at module level
-try:
-    if IS_SPACES:
-        logger.info("Creating demo directly at module level for Spaces...")
-    else:
-        logger.info("Creating demo for local execution...")
-    
-    demo = _create_demo()
-    
-    if demo is None or not isinstance(demo, (gr.Blocks, gr.Interface)):
-        raise ValueError(f"Demo creation returned invalid result: {type(demo)}")
-    
-    logger.info("Demo creation completed successfully")
-except Exception as e:
-    logger.error(f"CRITICAL: Error creating demo: {e}", exc_info=True)
-    import traceback
-    error_trace = traceback.format_exc()
-    logger.error(f"Full traceback: {error_trace}")
-    with gr.Blocks(title="CGT-LLM-Beta RAG Chatbot") as demo:
-        gr.Markdown(f"""
-        # Error Initializing Chatbot
-        
-        A critical error occurred while initializing the chatbot.
+# Create demo at module level - only once
+# Guard against multiple initializations (can happen on Spaces)
+if demo is None or not isinstance(demo, (gr.Blocks, gr.Interface)):
+    try:
+        if IS_SPACES:
+            logger.info("Creating demo directly at module level for Spaces...")
+        else:
+            logger.info("Creating demo for local execution...")
         
-        **Error:** {str(e)}
+        demo = _create_demo()
         
-        **Traceback:**
-        ```
-        {error_trace[:1500]}...
-        ```
+        if demo is None or not isinstance(demo, (gr.Blocks, gr.Interface)):
+            raise ValueError(f"Demo creation returned invalid result: {type(demo)}")
         
-        Please check the logs for more details.
-        """)
-    logger.info(f"Fallback error demo created: {type(demo)}")
+        logger.info("Demo creation completed successfully")
+    except Exception as e:
+        logger.error(f"CRITICAL: Error creating demo: {e}", exc_info=True)
+        import traceback
+        error_trace = traceback.format_exc()
+        logger.error(f"Full traceback: {error_trace}")
+        with gr.Blocks(title="CGT-LLM-Beta RAG Chatbot") as demo:
+            gr.Markdown(f"""
+            # Error Initializing Chatbot
+            
+            A critical error occurred while initializing the chatbot.
+            
+            **Error:** {str(e)}
+            
+            **Traceback:**
+            ```
+            {error_trace[:1500]}...
+            ```
+            
+            Please check the logs for more details.
+            """)
+        logger.info(f"Fallback error demo created: {type(demo)}")
+else:
+    logger.info("Demo already exists, skipping creation")
 
 # Final verification
 if demo is None:
@@ -945,12 +956,12 @@ else:
         # Print confirmation for debugging
         print(f"DEMO_READY: {type(demo)}")
         print(f"DEMO_VALID: {isinstance(demo, (gr.Blocks, gr.Interface))}")
-        # Ensure demo is in globals for Spaces to find it
+        # Ensure demo is in module namespace for Spaces to find it
         import sys
         current_module = sys.modules[__name__]
-        if not hasattr(current_module, 'demo') or current_module.demo is not demo:
-            current_module.demo = demo
-            logger.info("Demo explicitly set in module namespace")
+        current_module.demo = demo
+        current_module.__dict__['demo'] = demo
+        logger.info("Demo explicitly set in module namespace")
 
 # For local execution only (not on Spaces)
 if __name__ == "__main__":