Add support for Drupal 11

Rajan Kumar@2026 → made their first commit to this issue’s fork.

Hi @opdavies

I’ve added Drupal 11 support and created a MR. See the screenshot for reference. Thanks You!

@Rajan Kumar@2026 your MR will not work, as it stipulates that stable is the base theme, but that is not available in Drupal 11.

You will need to update the core_version_requirement and also change stable to stable9.

I'd also suggest, the core_version_requirement removes support for 8 and 9, but that is up to the maintainer to decide.

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Thanks to The Confident for sponsoring my time to work on this.

@markconroy I think you will find the contrib version of stable is named stable and not stable9. I've added a composer.json file that requires that dependency, and the theme now installs with composer and can be enabled in D11. Please confirm.

Why are you requiring the contrib version of the Stable theme rather than core's version?

@markconroy because after repeated searching I cannot find any evidence that stable9 has a future -- all the docs I can find specify Drupal 9 or 10 and do not mention 11+. The only link to documentation in the README file for stable9 actually specifies Drupal 8 in its URL rather than the current link supplied with Olivero. Can you please point me to some evidence that stable9 is not deprecated? Thank you!

Stable9 is a core theme, so that should be decent evidence for it having a future. It's the core base theme that other themes (in general) are encouraged to use as their base. It was introduced in Drupal 9, then we deprecated stable in 9.5 and moved stable to contrib (I doubt many are using it from contrib) in favour of using Stable9.

Stable9 is the default core theme for Drupal 9 + Drupal 10 + Drupal 11. You can see it's code is here in Drupal 11 - https://git.drupalcode.org/project/drupal/-/tree/11.x/core/themes/stable... - with the note:

Warning: Themes that decide to not use Stable 9 as a base theme will need
continuous maintenance as core changes, so only opt out if you are prepared to
keep track of those changes and how they affect your theme.

Here's the change record from Drupal 9.5 saying to use Stable9 instead of Stable if possible - https://www.drupal.org/node/3309392 →

Here's the Drupal (sub) theming guide - https://www.drupal.org/docs/develop/theming-drupal/sub-theming-using-sta... →

OK, thanks for the additional info. The theme should now be installable in D11 without the contrib stable theme. Please confirm.

I think that MR looks good now, but maybe we should drop support for Drupal 8 + 9 since they are no longer supported.

Also, have you tested that this theme actually works in Drupal 11?

@markconroy I have, yes, but the status is Needs Review because someone besides me needs to review it. :)

This works for me on my local site, so I'll go ahead and merge it.