Pantheon release notes

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.

A refreshed, modernized site migration experience is now available in the Pantheon Dashboard for all users.

Share questions and feedback in the Pantheon Community Slack.

Key Changes

• Design improvements to align with the latest usability standards for increased consistency.
• The previous Drupal migration process (which leveraged drush ard) led to failures for most users. The Drupal migration process has now been streamlined so that, when the site deployment is complete, users are instead prompted to migrate manually with crosslinks to respective docs for each step.

The latest version of WordPress, 6.9, is available on Pantheon as of December 02, 2025.

Action required

Upgrade to WordPress 6.9 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.

For full details about WordPress 6.9, see the release notes

Today, Pantheon's new solution for Next.js enters Private Beta. To request an invite, submit this form.

Front-End Sites, our previous offering for Next.js, will be discontinued. We encourage users to migrate to the updated architecture.

For more information, see this related blog post.

What's new?

Some key changes for Next.js on Pantheon include:

• Improved runtime architecture, including support for Pantheon's Global CDN.
• Site creation via the command line or the dashboard.
• Sites listed in your workspace alongside WordPress and Drupal, instead of a separate tab.
• Unified site dashboard design that's consistent with WordPress and Drupal user interfaces:

For more detailed information on the differences from Front-End Sites, see our migration guide.

Documentation

For usage instructions and guidance, see the following new docs:

• Next.js Overview
• Runtime Architecture
• Limitations and considerations
• Hello World Tutorial
• Content Publisher Tutorial
• Migrating from Front-End Sites
• Managing environment variables

Starting today, the new Site Dashboard enters General Availability for Professional Workspaces. Specifically, this release changes the following for Professional Workspaces:

• The new experience is now the default, previously it could be enabled and disabled.
• The option to disable the new experience has been removed.

Personal Workspaces are not impacted, and still require opting in to enable the new experience.

• Same functionality, familiar workflows – No need to relearn anything. Your day-to-day tasks remain unchanged.
• Modern, accessible design – We’ve made significant improvements to align with the latest usability design standards, enhancing readability, contrast, and navigation.
• Performance improvements under the hood – While this may feel mostly visual, we’ve reworked key infrastructure for long-term speed and reliability.
• Small but powerful UX upgrades – New conveniences like one-click to copy the commit SHA, along with other thoughtful touches for enhanced usability.

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.

The Pantheon Content Publisher plugin is now officially available in the WordPress Plugin Repository. You can now install or update it directly from your WordPress dashboard.

Action required

We recommend that all customers switch their sites to the WordPress.org–hosted version to take advantage of seamless updates and improved long-term support. By switching, you’ll:

• Receive automatic update notifications and one-click upgrades within the WordPress admin panel
• Stay up to date with the latest security, stability, and compatibility improvements
• Benefit from WordPress’s official distribution system, including built-in changelogs, and version tracking

Switching to the repository version helps ensure your site runs the most stable and officially supported release of the plugin.