Composer "Allowed memory size exhausted" - Fix OOM in CI

The PHP process running Composer hit PHP’s memory_limit and was killed mid-resolution. Dependency solving on a large composer.json can be memory-hungry, and CLI PHP often has a low limit.

What this error means

composer update (resolution is the heaviest step) dies with "Allowed memory size of N bytes exhausted". The same command may pass locally where PHP’s CLI memory_limit is higher or unlimited.

PHP Fatal error:  Allowed memory size of 1610612736 bytes exhausted (tried to
allocate 20480 bytes) in phar:///usr/bin/composer/src/Composer/DependencyResolver/...
on line 215

Common causes

PHP memory_limit too low for resolution

The dependency solver builds a large in-memory graph. A CLI memory_limit of 128M–1.5G can be exceeded on big projects.

Running update instead of install in CI

composer update re-resolves everything (memory-heavy); composer install replays the lockfile and uses far less.

How to fix it

Remove the limit for Composer

Composer respects COMPOSER_MEMORY_LIMIT; setting it to -1 disables PHP’s limit for that process only.

COMPOSER_MEMORY_LIMIT=-1 composer update --no-interaction

Raise PHP’s CLI memory_limit

Alternatively pass a higher limit to the PHP that runs Composer.

php -d memory_limit=-1 /usr/bin/composer update --no-interaction

Install from the lockfile instead of updating

CI should replay the lock, which needs much less memory than re-resolving.

composer install --no-interaction --prefer-dist

How to prevent it

• Set COMPOSER_MEMORY_LIMIT=-1 in CI for any composer update step.
• Run composer install (lockfile replay) in CI rather than update.
• Give CI runners enough RAM for large dependency graphs.

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