April 2021 Changelog
Convert your Pantheon-hosted Drupal 8 sites to Drupal 9 with Integrated Composer, using the Drupal 8 to 9 Conversion Guide. Integrated Composer helps keep your Drupal 9 repository lean, avoid build artifacts on the main branch, and keep the one-click updates for both upstream commits & Composer dependencies that you have come to know and love with Pantheon.
WordPress 5.7 is now available on the Pantheon platform. Detailed information on applying and debugging core updates can be found in the Core Updates documentation. For more information, see the WordPress 5.7 release notes.
Drupal 9 Migration Guide - Guided and manual migration steps to upgrade and migrate existing Drupal sites to Drupal 9 with Integrated Composer.