TYPO3 error with symfony/dependency-injection 7.3.4 under PHP < 8.3

Since September 27, 2025, the freshly released version 7.3.4 of symfony/dependency-injection has been causing problems in TYPO3 13 environments running PHP 8.2.

The background: In TYPO3 13, the system extension form uses a class "ConfigurationManager" marked as readonly. Symfony tries to generate a lazy proxy from this, but this is only supported as of PHP 8.3. Under PHP 8.2 this leads to an abort with the following error message:

Symfony\Component\VarExporter\Exception\LogicException: Cannot generate lazy proxy with PHP < 8.3: class "TYPO3\CMS\Form\Mvc\Configuration\ConfigurationManager" is readonly.

This error only occurs in Composer-based installations where a "composer update" has been performed within the last few days or where TYPO3 has been freshly installed in the last few days. Classic installations with zip or tar.gz are not affected.

Although this error occurs due to a third-party package, TYPO3 has already reacted with a patch: https://review.typo3.org/c/Packages/TYPO3.CMS/+/90833 With the next TYPO3 release, symfony/dependency-injection in version 7.3.4 and following can be used again.

Workarounds

Composer blocking

Projects can block the problematic version:

composer req symfony/dependency-injection "^7.3 !=7.3.4"

If symfony/dependency-injection 7.3.5 is released BEFORE the new TYPO3 release, 7.3.5 must also be specified here as an exclusion.

Composer patches

Another recommendation from the TYPO3 Core Slack Channel is the use of https://github.com/cweagans/composer-patches This allows you to apply the core patch https://review.typo3.org/c/Packages/TYPO3.CMS/+/90833/3/typo3/sysext/form/Classes/EventListener/DataStructureIdentifierListener.php directly in the TYPO3 project.