Which suffix should not be added to classes within customer package spaces?

The suffix that should not be added to classes within customer package spaces is _Ext. This is because the _Ext suffix typically denotes an extension of a class from the Guidewire libraries. When working within customer package spaces, it's important to maintain a clear separation between customizations and the core Guidewire classes. Using the _Ext suffix could lead to confusion about the nature of the class and its relationship with core classes, making it harder to manage and understand the customization.

On the other hand, other suffixes like _Custom, _Pkg, and _Base have specific roles in identifying custom classes, package classes, or base classes, respectively. These suffixes are appropriate as they help developers easily recognize the purpose of the class and its origin within the architecture of the application. Adopting naming conventions that include designated suffixes helps enhance maintainability and clarity, which are essential goals when developing in Guidewire.