Composer "Allowed memory size of X bytes exhausted" in CI

Composer's dependency solver is memory-hungry on large graphs. When it exceeds PHP's memory_limit, the CLI dies with a fatal memory error. Composer is meant to run without a memory cap, set via COMPOSER_MEMORY_LIMIT.

What this error means

composer update or install aborts with "PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate ...)" inside a Composer source file.

composer

PHP Fatal error:  Allowed memory size of 134217728 bytes exhausted
(tried to allocate 20480 bytes) in
phar:///usr/local/bin/composer/src/Composer/DependencyResolver/...

Common causes

A restrictive php.ini memory_limit

The runner PHP caps memory_limit (often 128M) and the solver needs more for a large dependency graph.

A heavy update over many packages

A full composer update builds a large solve state; on a big project it can outgrow the default cap.

How to fix it

Remove the limit for the Composer process

Set COMPOSER_MEMORY_LIMIT to -1 so Composer runs without a PHP memory cap.

.github/workflows/ci.yml

env:
  COMPOSER_MEMORY_LIMIT: '-1'

Or raise it inline for one command

Override memory_limit just for the Composer call without changing global php.ini.

Terminal

php -d memory_limit=-1 /usr/local/bin/composer update

How to prevent it

Set COMPOSER_MEMORY_LIMIT=-1 in CI for install and update steps.
Prefer composer install from a lock so the solver does little work.
Scope composer update <pkg> to specific packages instead of the whole graph.