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Last Reviewed: December 13, 2022

Troubleshoot Integrated Composer

Learn how to troubleshoot Integrated Composer issues.

This section provides information on troubleshooting common Integrated Composer errors and issues.

Troubleshooting Code Syncs, Upstream Updates, and Redirect Errors

Site-local Drush Is Required for Drupal Sites

Do not remove drush/drush from composer.json. If it's removed, terminus drush commands will fail with errors related to Twig.

Build Step Affected Files That Are Not Ignored by Git

This error occurs when your composer install or composer update files are tracked in your Git repository and are modified unexpectedly. This causes the build process to stop because Integrated Composer should not overwrite custom code.

The solution is to ensure that Composer does not modify these files, and that the files are removed from being tracked in the Git repository.

  1. Remove the files from the Git repository.

  2. Commit the removal.

  3. Add the file paths to the .gitignore file so that the files are not tracked again.

View the Output of the Commit Log First

If you encounter an error during a code sync or if the site is missing files that should be added by Integrated Composer, the Build Log may contain information that can help you troubleshoot:

  1. Navigate to Code in the Dev tab of your Site Dashboard.

  2. Navigate to the Commit Log section, find the most recent commit, and click View Log to view the Composer command that was run and the output that was given by that command.

Dashboard Workflow Shows an Error During Sync Code or Deploying to a New Environment

If there is an error in the output, it may be due to an error in the site's composer.json or composer.lock file, or there may be an issue with a Composer library the site uses.

To resolve this issue, examine the error in the log. It may be a syntax or parse error of the JSON files, or some sort of error loading a library via Composer. You can also try running the same command on your local Git checkout of the site's code and see if you can update the composer.json and composer.lock files to run the command successfully.

Creating a New Multidev or Deploying to an Environment Results in an Empty Site

You must manually allow any plugin that acts on the code base of your site in your composer.json file. This is a Composer 2.2 requirement introduced on July 1, 2022 that provides an additional layer of security. Sites that were working previously will have builds that fail because of this new requirement. Failed builds can arise as a broken environment or as unreflected code changes after a commit.

Read more about this security requirement in Composer's Documentation.

You might see one of the following issues:

  • Fatal error: Cannot redeclare format_size() (previously declared in /code/web/core/includes/ in /code/vendor/drupal/core/includes/ on line 137

  • Pantheon error page with “No code” or “No site detected” on newly initialized environments

  • Fatal error: Cannot redeclare drupal_get_filename() (previously declared in /code/vendor/drupal/core/includes/ in /code/web/core/includes/ on line 164

Follow the steps below to resolve the issue:

  1. Clone the site to your local computer and ensure that Composer 2.2 or later is installed locally.

  2. Run composer install and complete the interactive prompts to allow plugins.

    • The prompts will look like this:

      composer install
      composer/installers contains a Composer plugin which is currently not in your allow-plugins config. See
      Do you trust "composer/installers" to execute code and wish to enable it now? (writes "allow-plugins" to composer.json) [y,n,d,?] y
      cweagans/composer-patches contains a Composer plugin which is currently not in your allow-plugins config. See
      Do you trust "cweagans/composer-patches" to execute code and wish to enable it now? (writes "allow-plugins" to composer.json) [y,n,d,?]
  3. Commit and push the code up to your site.

Upstream Updates Cannot Be Applied

When you click Apply Updates, the process completes with the error, Something went wrong when applying updates. View log. Click View log to view the output of the log:

We were not able to perform the merge safely. See the Applying Upstream Updates doc ( for further debugging tips. Conflicts: [
  "CONFLICT (content): Merge conflict in composer.json"

Issue 1: The site might use a Custom Upstream.

Solution 1: Copy the Upstream URL and then follow Solution 2:

  1. Go to the Site Dashboard, and click the Dev tab.

  2. Click Settings, then click About site.

  3. Copy the Upstream URL and use it instead of the Pantheon Upstream URL in Solution 2.

Issue 2: The upstream updates and your Composer changes to the site are in a conflict that cannot be automatically merged by Git.

  • We do not recommend using Auto-resolve updates in this case since it will cause your changes to the site's composer.json file to be lost.

Solution 2:

Merge the changes manually:

  1. Create a local Git clone of the Pantheon site repository.

  2. Merge in the upstream changes:

    git remote add upstream <upstream_url> && git fetch upstream
    git merge upstream/master
    • You will get a message that there are conflicts in composer.json that cannot be merged automatically:

      Auto-merging composer.json
      CONFLICT (content): Merge conflict in composer.json
      Automatic merge failed; fix conflicts and then commit the result.
  3. Resolve the conflict and follow the instructions to commit the merged changes.

  4. Run composer install on your local branch to verify that the composer.json parses correctly, and that the correct libraries are installed or updated. If the command fails, then the merge was not made correctly and the error message may point to how composer.json needs to change.

  5. Push the changes to Pantheon. Integrated Composer will run again with the updated composer.json.

Changes Lost During Direct Upload or Commit

Do not commit module/plugin or theme files directly to your site when in Git mode. You also should not upload module/plugin or theme files directly to your site when in SFTP mode. Direct commits and uploads will be lost because the .gitignore file in your upstream repository has several defined paths, which causes files in those directories to be ignored. These directories are:

└─ core/
└─ drush/Commands/contrib/
└─ libraries/
└─ modules/contrib/
└─ private/scripts/quicksilver
└─ profiles/contrib/
└─ sites/*/files/
└─ sites/*/private/
└─ themes/contrib/

See the .gitignore file for Drupal here.

The contrib folders are where community contributed modules, profiles, and themes reside. The custom folders, which are not ignored, are where modules, profiles, and themes created by you reside.

Refer to Add a Dependency to an Individual Site to add a module/plugin or theme as a dependency to your site.

Changes Lost During Upstream Updates

When Auto-Resolve Updates is selected and the composer.json contents are changed in the upstream, all changes the site's developers made to composer.json will be removed if Git cannot automatically merge the changes.

There are two potential solutions to resolve this issue:

Issues using wikimedia/composer-merge-plugin

Use of the wikimedia/composer-merge-plugin is deprecated within Drupal.

When using Pantheon's Integrated Composer, this plugin often tries to run a composer update during the composer install, which is not allowed and will cause errors. We recommend removing composer-merge-plugin from your Composer toolchain.

Patches containing binary diffs fail in Pantheon

If your site contains a binary patch, such as, the Composer build step will fail. This is because cweagans/composer-patches use the patch utility to apply patches. The most recent version of this utility does not support binary patches and fails when deployed.

A workaround for this issue is to reconfigure the patch to exclude the binary contents in it.

Potential WordPress Multisite with Composer Subdirectory Solution

We support WordPress Multisites with subdirectories. However, if you are working with a Composer-based Multisite ​setup, your sub sites might produce redirect errors. Your reference URLs might be incorrect if your WordPress core file path looks like this: /code/web/wp.


While the solution outlined below has worked for select customers, it might not work for your specific configuration / environment.

Move your WordPress core files from /code/web/wp to the /code/web root by using the example WordPress Composer script.

Note that this script is only intended as an example to help you get started. You will most likely need to make changes to match your current configuration.

GrumPHP breaks Integrated Composer when using Lando or other local development commands

GrumPHP is a code quality tool that installs into Git hooks via a Composer plugin. The hook runs whatever tasks you specify in your grumphp.yml file, including unit tests, code sniffing, etc., and allows or prevents a commit as needed.

You can use both GrumPHP and a containerized local dev environment (such as Lando or Docksal). However, if you choose to run GrumPHP within that environment by changing the command triggered by GrumPHP on commit in your grumphp.yml file shown in the example below, you may encounter a build fail.

    EXEC_GRUMPHP_COMMAND: 'lando php'

The build fails because GrumPHP runs in Integrated Composer. Composer installs GrumPHP, then Integrated Composer tries to make a commit, GrumPHP tries to run Lando (or another containerized local dev environment) PHP and then fails because Lando doesn't exist in Pantheon's build environment.


The solution is to set EXEC_GRUMPHP_COMMAND to run a script that tests for the needed dependencies and only runs the GrumPHP tasks if all dependencies are found. For example:


Lando script example:

if command -v lando; then
  lando php "$@"

The test in the script can be whatever is needed in your particular case. The example below tests for the existence of the PANTHEON_ENVIRONMENT env var:

if [ -z "$PANTHEON_ENVIRONMENT" ]; then
  lando php "$@"

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