Cache Magento Action

A Github Action that creates a composer cache for a Magento extension or store.

Inputs

See the action.yml

Input	Description	Required	Default
`composer_cache_key`	A key to version the composer cache. Can be incremented if you need to bust the cache.	false	`__mageos`
`working-directory`	The directory where Magento is installed (location of `vendor/` and `composer.lock`).	false	`.`
`stamp`	Cache the `vendor/` directory in addition to the Composer download cache.	false	`false`

Cache keys

The download cache key has the format:

composer | v5.8 | <os> | <composer_cache_key> | <composer-version> | <php-version>

When stamp: true, the vendor/ cache key has the format:

composer | stamp | v5.8 | <os> | <composer_cache_key> | <composer-version> | <php-version> | <composer.lock-hash>

The composer.lock hash is derived from working-directory/composer.lock using hashFiles. The download key also gains the hash suffix when a Magento product package is detected at working-directory.

Usage

Extension (download cache only)

- uses: graycoreio/github-actions-magento2/cache-magento@v8.5.0 # x-release-please-version
  with:
    composer_cache_key: ${{ inputs.composer_cache_key }}

Extension or store (download + vendor stamp cache)

- uses: graycoreio/github-actions-magento2/setup-magento@v8.5.0 # x-release-please-version
  id: setup-magento
  with:
    mode: extension # or store
    # ...

- uses: graycoreio/github-actions-magento2/cache-magento@v8.5.0 # x-release-please-version
  with:
    composer_cache_key: ${{ inputs.composer_cache_key }}
    working-directory: ${{ steps.setup-magento.outputs.path }}
    stamp: true

- run: composer install
  working-directory: ${{ steps.setup-magento.outputs.path }}

Stamp Mode

On a warm cache hit, composer install completes in ~0s because vendor/ is already present — Composer sees everything installed and exits immediately. For a full Magento install this saves 2–5 minutes of package extraction per job.

The trade-off is size. The vendor/ directory for a Magento project runs 300–600 MB, so a frequent cache miss means you are consistently paying the upload cost without recouping it on the next run.

As such, use stamp: true when composer.lock is stable across most runs — a store on a release branch, or extension CI against a pinned Magento version. Skip it when the lock changes often or when runner storage is constrained.

Warning

Dependabot / Renovate: Each time a Dependabot or Renovate PR is merged, the remaining open PRs rebase and each produces a new composer.lock. This cascades into a large number of unique cache entries, inflating storage costs without delivering proportional compute savings — because automated PRs are not waiting on fast feedback. The fix is to disable stamp caching for automated dependency PRs entirely:
- uses: graycoreio/github-actions-magento2/cache-magento@v8.5.0 # x-release-please-version
  with:
    stamp: ${{ github.actor != 'dependabot[bot]' }}
If you use Renovate, check its bot account name and adjust the condition accordingly. Dependabot PRs will pay full composer install time on every run, which is acceptable — nobody is waiting on them.

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