Pantheon release notes

Editorial note: The date has been moved from October 21 to December 2.

As part of our ongoing platform maintenance and security improvements, sites on the platform running Drupal 8.0-9.3 will no longer be able to access Pantheon Search services (Apache Solr-based search) starting December 2, 2025.

After this date, affected sites will not be able to fetch Solr search results or index new content. Views or blocks that rely on Solr-powered Search API indexes may fail to load, return no results, or throw errors.

Drupal 8 reached end-of-life (EOL) in November 2021 and Drupal 9 in November 2023. EOL software does not receive security or feature updates, and could expose sites to attack if any vulnerabilities or exploits are discovered.

To find out which version of Drupal your site is running, go to your site in the Pantheon Dashboard > Status then look for the Drupal value in the Status block, or use the Terminus CLI command terminus drush <site>.<env> status.

Action Required

Affected Drupal 8.0-9.3 sites will need to be upgraded to Drupal 9.4+, Solr 8, and search_api_pantheon 8.2+. Drupal core and Solr upgrade guides are available in our documentation.

Alternatively, Pantheon Search can be disabled and site owners may choose to implement Drupal’s built-in database search or another alternative such as a third-party search service provider.

We have released version 3.0.0 of the Pantheon WP Coding Standards. This is a major release over the previous 2.x versions which adds new sniffs for use of the PHP rename() function, which is not supported on Pantheon, and commenting. Upgrading to this version may cause some existing code to fail the new sniffs, so we recommend reviewing the release notes.

The Pantheon WP Coding Standards are a set of custom rules for PHP_CodeSniffer that help developers write maintainable code that is compatible with Pantheon’s platform. They are not used by default in Pantheon’s WordPress sites, but can be installed and configured to run in your local development environment or CI/CD pipelines and are actively used by the WordPress plugins that Pantheon maintains.

For a full list of changes in this release, please refer to the 3.0.0 release notes. Learn more about our Pantheon WP Coding Standard in our video on YouTube.

The latest version of WordPress, 6.8.2, is available on Pantheon as of July 15, 2025.

Action required

Upgrade to WordPress 6.8.2 right from your Pantheon dashboard or Terminus to access the latest features, fixes, and security enhancements. See related documentation for how to apply core updates.

Highlights

• 35 bugs throughout Core and the Block Editor.

• The release announcement mentions that security updates will no longer be provided for WordPress 4.1-4.6.

For full details about WordPress 6.8.2, see the official release announcement.

We have released version 0.7.0 of the 'Push to Pantheon' GitHub Action. This version adds a new input to skip the Terminus install if your workflow is already installing Terminus. Documentation in the readme.md has been updated to include definitions for both the skip_terminus_install and relative_site_root (which was previously undocumented) inputs. Additionally, documentation guidance has been added for using the action with robots (like Dependabot) to ensure robot-created workflows don't fail due to lack of permissions.

For more details and a full list of changes in this release, please refer to the 0.7.0 release notes. To update to the latest version, modify your workflow file to use 0.7.0:

Support for PHP 8.4 is now available on the platform with the new PHP Runtime Generation 2. PHP 8.4 is the latest version of the server-side language powering Drupal and WordPress.

CMS support

PHP 8.4 is recommended for sites running Drupal 10.4+ or 11.1+. See the Drupal PHP requirements documentation for more details.

WordPress 6.7+ only has "beta support" for PHP 8.4, therefore Pantheon does not recommend using WordPress in a production environment with this PHP version yet.

Pantheon currently recommends at least PHP 8.2 for all production sites.

New features

PHP 8.4 is not expected to bring new performance gains for sites. But for developers looking to take advantage of the latest PHP functionalities, a few new updates are notable:

• Property Hooks: Introduces support for computed properties, allowing for pre/post-processing of values.
• Asymmetric Visibility: Provides independent control over property read/write scope.
• Enhanced DOM API: Adds new classes for HTML5 parsing.
• New Array Functions: Introduces array_find(), array_find_key(), array_any(), and array_all().
• PDO Driver Subclasses: PDO now includes driver-specific subclasses.
• Updated JIT: Includes a new implementation of the Just-In-Time compiler.
• Expanded String Functions: New mb_trim(), mb_ltrim(), mb_rtrim(), mb_ucfirst(), and mb_lcfirst() functions.

See the PHP 8.4 release announcement from php.net for full details.

How to upgrade

To upgrade your site, set the following in your pantheon.yml file:

Note: PHP 8.4 is only available with the new PHP Runtime Generation 2. Upgrading to PHP 8.4 will automatically upgrade the environment to the second generation PHP Runtime.

The latest update to the Pantheon Advanced Page Cache Drupal module focuses on improving the functionality of the surrogate key header limit in your local development environment.

Key Update

Surrogate Key Header Limit Adjustment: To prevent oversized response headers and enhance the ease of work in your local environment, developers now have the ability to override the surrogate key header limit.

By default, the limit is set to 25,000 bytes. It can be adjusted by adding the following line to your site's settings.php file:

Please note that the maximum value for this setting is capped at 25,000 bytes. Adjust the value as needed to suit your local development requirements.

Editorial notes:

• The start date of the PHP Runtime Generation 2 rollout has been moved from August 15 to September 24, 2025.

Starting September 17, 2025, Pantheon will begin rolling out PHP Runtime Generation 2 to all sites on the platform. The new PHP Runtime enforces the use of TLS 1.2 or 1.3 for external connections. This change is part of our ongoing efforts to enhance security and comply with modern best practices.

What is TLS?

Transport Layer Security (TLS) is the cryptographic protocol that secures connections between systems — for example, when your website connects to a third-party API. TLS 1.0 and 1.1 were introduced in 1999 and 2006, respectively, and are now considered deprecated due to known vulnerabilities and lack of support for modern encryption standards.

TLS 1.2 was released in 2008 and remains the industry standard, with widespread adoption across browsers and APIs. TLS 1.3, released in 2018, offers additional performance and security benefits.

Action Required

Sites using external services that still rely on TLS 1.0 or 1.1 will experience failed connections once PHP Runtime Generation 2 is enabled. We strongly recommend auditing your site’s outgoing connections to ensure compatibility with TLS 1.2 or higher.

Follow our guide for testing TLS compatibility to check whether your site is making external requests using outdated TLS versions. Our DevRel team has created a WordPress plugin and Drupal module that can help expedite your testing.

Need More Time?

If you discover that your site relies on services that do not yet support TLS 1.2 or higher and need more time to upgrade, you can opt out of Generation 2 temporarily while you update those dependencies. Opting out will be available until early 2026.

PHP versions 8.1.33, 8.2.29, and 8.3.23 are now available on the platform. These updates brings the latest bug fixes and enhancements, improving performance and security for your sites. Updates will be applied automatically over the next few days, so no manual action is required.

Important PHP version information

• PHP 8.1 and 8.2 are currently receiving security-only updates.
• For more details, see the full list of PHP supported versions.

For the best performance and security, Pantheon recommends running PHP 8.2 and above.