Importing using the following:

from textual.widgets import CollapsibleTitle or from textual.widgets import *

results in:

ModuleNotFoundError: No module named 'textual.widgets._collapsible_title'

I traced this down to textual.widgets.__init__.py; when the widget modules are being importing the class name is being converted to a module name using textual.case.camel_to_snake which is converting CollapsibleTitle to _collapsible_title. However, CollapsibleTitle is stored in the _collapsible module; there is no _collapsible_title module.

Textual: 6.7.1
Python: 3.14.0