After many policy discussions it has been decided that Seven and Bartik will be marked @internal. This means they can change over time and no one should depend on their markup and CSS staying exactly the same.
See:
#2544740: [policy] Consider not supporting core module markup and CSS between minor releases →
🌱
[meta] Document @internal APIs both explicitly in phpdoc and implicitly in d.o documentation
Active
The recommendation for themers and site builders/owners is that if you wish to make modifications to Seven or Bartik, you should copy, not subtheme, them. If you still choose to subtheme, be aware that it can change with an update to Drupal so be prepared to chase the current release.
In this issue, we need a patch to add a warning message to Seven's and Bartik's info file with the recommendation to copy instead of subtheming.
Fixed
8.0 ⚰️
Last updated
It would make a good project for someone who is new to the Drupal contribution process. It's preferred over Newbie.
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