diff --git a/.github/oxid-esales/defaults/defaults_light.yaml b/.github/oxid-esales/defaults/defaults_light.yaml
index 277f069e..73b1d9fb 100644
--- a/.github/oxid-esales/defaults/defaults_light.yaml
+++ b/.github/oxid-esales/defaults/defaults_light.yaml
@@ -123,6 +123,9 @@ global:
     # Options for composer update
     update_options: '--no-interaction'
 
+    # Composer version (e.g., 2.8.12). Empty = use docker image default
+    version: ''
+
   # This grep pattern is applied to the generated phpunit, Codeception, and runtest log file. If we have
   # a hit matching the pattern below, the step will fail.
   failure_pattern: |
diff --git a/.github/workflows/universal_workflow_light.yaml b/.github/workflows/universal_workflow_light.yaml
index 12f1b322..2669a2d8 100644
--- a/.github/workflows/universal_workflow_light.yaml
+++ b/.github/workflows/universal_workflow_light.yaml
@@ -324,6 +324,7 @@ jobs:
           composer_update: ${{ steps.iltp.outputs.install_composer_update}}
           composer_update_options: ${{ steps.iltp.outputs.install_composer_update_options}}
           composer_dev_ref: ${{ steps.iltp.outputs.install_composer_dev_ref}}
+          composer_version: ${{ steps.iltp.outputs.install_composer_version }}
           enterprise_github_token: ${{ secrets.enterprise_github_token || github.token }}
           copy_script_targets: ${{ steps.iltp.outputs.install_copy_script_targets }}
           debug: ${{ needs.init.outputs.debug }}
diff --git a/docs/actions/prepare_shop.md b/docs/actions/prepare_shop.md
index 082da6a7..1b26364c 100644
--- a/docs/actions/prepare_shop.md
+++ b/docs/actions/prepare_shop.md
@@ -91,6 +91,11 @@ Options to pass along to composer during installation.
 **composer_dev_ref:** *not required*, *default:* 'dev-b-8.0.x'  
 Development package reference.
 
+**composer_version:** *not required*, *default:* `''`  
+Composer version (e.g., '2.8.12'). When specified, runs `composer self-update`
+to set the desired version before any composer commands. Leave empty to use the
+default version from the Docker image.
+
 **enterprise_github_token:** *not required*, *default:* `''`  
 OAuth token to access enterprise repos. This should be populated with
 \${{ secrets.enterprise_github_token }} and will be hidden by GitHub.
diff --git a/prepare_shop/action.yaml b/prepare_shop/action.yaml
index 0e7e5cf9..ca09a237 100644
--- a/prepare_shop/action.yaml
+++ b/prepare_shop/action.yaml
@@ -138,6 +138,11 @@ inputs:
     required: false
     description: 'OAuth token to access enterprise repos'
     default: ''
+  composer_version:
+    type: string
+    required: false
+    description: 'Composer version (e.g., 2.8.12). Empty = use docker image default'
+    default: ''
   docker_login:
     type: boolean
     required: false
@@ -310,6 +315,19 @@ runs:
           ${{ inputs.container_name}} \
           composer config -g github-oauth.github.com "${{ inputs.enterprise_github_token }}"
 
+    - name: 'Set Composer version'
+      if: ${{ inputs.composer_version != '' }}
+      shell: bash
+      run: |
+        # prepare_shop: Set Composer version
+        ${{ inputs.debug }}
+        echo -e "\033[0;35mSetting Composer to version ${{ inputs.composer_version }}\033[0m"
+        docker compose ${{ inputs.container_method }} -T \
+          -u root \
+          ${{ inputs.container_options }} \
+          ${{ inputs.container_name }} \
+          composer self-update ${{ inputs.composer_version }}
+
     - name: 'Modify composer.json'
       if: ${{ inputs.composer_transform != '' }}
       uses: 'OXID-eSales/github-actions/composer_merge@v5'