January 2021 Changelog
You can now create and launch Drupal 9 sites on Pantheon with Integrated Composer, now in Limited Availability. Composer is completely integrated, so you can keep your sites up-to-date with one click. For more information, see the Drupal 9 documentation.
Drupal 8.9.11 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 Drupal 8.9.11 release notes.
New: Debug Caching Issues - New troubleshooting guide to assist in resolving cache conflicts.