sencha architect/sencha touch , to prevent breakpoint lost when you debug

add this to your loader config:

Ext.Loader.setConfig({
    disableCaching: false
});

or :

click 'application' on sencha architect , find out 'loader config' config, click the plus icon on the right, click right icon on the right,

find out 'disableCaching' config,  click the checkbox and make sure it as checked.