Pantheon release notes

The final set of sites previously excluded from the PHP Runtime Generation 2 rollout are now being migrated. These sites were excluded because they were using Solr 3 with Drupal 9+. With Solr 3 support for Drupal 9+ ending in December 2025, these sites are no longer excluded from the Generation 2 rollout.

Rollout Timeline

Opting Out

Sites may continue to opt out of PHP Runtime Generation 2 until the Gen 1 removal takes place starting April 6, 2026.

Editorial note: These updates were completed and deployed to the platform on December 23rd 2025.

PHP versions 8.1.34, 8.2.30, 8.3.29, and 8.4.16 are now available on the platform. These updates include important security fixes, along with bug fixes and enhancements that improve performance and stability. Updates will be applied automatically over the next few days, so no manual action is required.

PHP 8.4 is only available with the new PHP Runtime Generation 2.

The PHP 8.4 upgrade process automatically includes an upgrade to PHP Runtime Generation 2 if your site hasn't been upgraded already.

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.

The phpredis extension has been updated to the latest version, 6.3.0, for environments using PHP 7.4+ on PHP Runtime Generation 2.

To view the latest improvements and fixes, view the changelog on GitHub.

Following the successful rollout of PHP Runtime Generation 2 for all environments that have not opted-out, we are now preparing to remove PHP Runtime Generation 1 from the platform starting April 6, 2026.

What's changing when?

Between April 6 and April 17, 2026, all environments that have not been upgraded will be auto-upgraded to Generation 2. Opting out will no longer be available.

Action Required

Please view the Known Changes and Requirements list if you are still in the process of upgrading your site. We recommend all site owners proactively test and upgrade to Generation 2 rather than waiting for this auto-upgrade.

PHP versions 8.3.28 and 8.4.15, are now available on the platform. These updates bring the latest bug fixes, improving performance and security for your sites. The latest versions have already rolled out to all sites.

PHP 8.3.28 is available on both PHP Runtime Generation 1 and PHP Runtime Generation 2.

PHP 8.4 is only available with the new PHP Runtime Generation 2.

We are removing ionCube support from the platform on March 8, 2026. This PHP extension was prevously only available for PHP 8.1 on PHP Runtime Generation 1.

Pantheon continually reviews our PHP runtime and explores opportunities to optimize performance and build times.

If your application uses ionCube, please contact support or your Customer Success Manager to explore options for your use case.

Pantheon is updating its platform to align with current IANA standards by removing support for deprecated MIME types that use the x- prefix. This change will be introduced on November 17, 2025.

The following deprecated types have been updated to their modern, IANA-standard equivalents. No action is required for these files unless you have custom code explicitly referencing the old format.

• application/mathml+xml mml
• application/javascript js mjs
• image/vnd.microsoft.icon ico
• image/bmp bmp
• application/vnd.rar rar
• audio/mp4 m4a
• video/mp4 m4v
• font/ttf ttf
• text/vcard vcf
• application/vnd.amazon.mobi8-ebook mobi

The following deprecated x- prefixed MIME types will be removed entirely from platform support:

• text/x-component htc
• image/x-jng jng
• application/x-7z-compressed 7z
• application/x-cocoa cco
• application/x-javascript
• application/x-java-archive-diff jardiff
• application/x-java-jnlp-file jnlp
• application/x-makeself run
• application/x-perl pl pm
• application/x-pilot prc pdb
• application/x-redhat-package-manager rpm
• application/x-sea sea
• application/x-shockwave-flash swf
• application/x-stuffit sit
• application/x-tcl tcl tk
• audio/x-realaudio ra
• video/x-flv flv
• video/x-mng mng
• video/x-ms-asf asx asf
• video/x-ms-wmv wmv
• video/x-msvideo avi
• application/x-plist plist

Action Required

Review any custom code or configurations that utilize the removed MIME types and update them to use their respective IANA-standard equivalents.

If you encounter a file type that IANA does not yet handle, or if you require an alternative configuration, please follow the instructions in our documentation.

PHP versions 8.3.27 and 8.4.14, are now available on the platform. These updates bring the latest bug fixes, improving performance and security for your sites. The latest versions have already rolled out to all sites.

PHP 8.4 is only available with the new PHP Runtime Generation 2.

The PHP 8.4 upgrade process automatically includes an upgrade to PHP Runtime Generation 2 if your site hasn't been upgraded already.

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.