Fix @mcp_enabled decorator not working if defined after the app constructor

Author: KoolADE85

dash/mcp/_server.py

@@ -50,9 +50,6 @@
 def enable_mcp_server(app: Dash, mcp_path: str) -> None:
     """Add MCP routes to a Dash app."""
 
-    app.mcp_decorated_functions = dict(MCP_DECORATED_FUNCTIONS)
-    MCP_DECORATED_FUNCTIONS.clear()
-
     def _get_or_create_session_id() -> str:
         """
         Creates a shared session ID shared across all clients. The session is
@@ -247,6 +244,7 @@ def _process_mcp_message(data: dict[str, Any]) -> dict[str, Any] | None:
     app = get_app()
     if app.mcp_callback_map is None:
         app.mcp_callback_map = CallbackAdapterCollection(app)
+        app.mcp_decorated_functions = dict(MCP_DECORATED_FUNCTIONS)
 
     mcp_methods = {
         "initialize": _handle_initialize,