You can now spin up a brand, shiny, new Drupal 9 site on Pantheon using Integrated Composer and manage the site using Localdev 1.0!
You can learn how using the freshly updated Integrated Composer documentation.
However, this only works for new Drupal 9 sites. If you have an existing Drupal 8 site that you’re considering upgrading, check out how to test your site for D9 compatibility.
What’s the timeline for enabling D9.1 support and integrated composer on existing sites?
Hi @aaronbauman - thanks for reaching out. I assume you’re referring to working with existing Drupal 8 sites.
We don’t have a fixed release date for this feature yet, but it’s coming soon. Pantheon development teams are actively developing the feature set that enables moving Drupal 8.9 sites to Drupal 9.1 + Integrated Composer.
Until then, site owners can focus on upgrading to Drupal 8.9, if you haven’t yet. After that, go through the compatibility steps listed in the Drupal 9 doc. Check your contributed modules and custom code to ensure they’re Drupal 9 compatible.