diff --git a/composer/Plugin/ProjectMessage/Message.php b/composer/Plugin/ProjectMessage/Message.php
index b0cea11b929..34bfd12e5e3 100644
--- a/composer/Plugin/ProjectMessage/Message.php
+++ b/composer/Plugin/ProjectMessage/Message.php
@@ -6,6 +6,8 @@ use Composer\Package\RootPackageInterface;
 
 /**
  * Determine configuration.
+ *
+ * @internal
  */
 class Message {
 
diff --git a/composer/Plugin/ProjectMessage/MessagePlugin.php b/composer/Plugin/ProjectMessage/MessagePlugin.php
index 5e4f6614a52..8a5333d8f1c 100644
--- a/composer/Plugin/ProjectMessage/MessagePlugin.php
+++ b/composer/Plugin/ProjectMessage/MessagePlugin.php
@@ -11,6 +11,8 @@ use Composer\Script\ScriptEvents;
 
 /**
  * A Composer plugin to display a message after creating a project.
+ *
+ * @internal
  */
 class MessagePlugin implements PluginInterface, EventSubscriberInterface {
 
diff --git a/composer/Plugin/Scaffold/AllowedPackages.php b/composer/Plugin/Scaffold/AllowedPackages.php
index ca46d62dd17..9b28368bbd4 100644
--- a/composer/Plugin/Scaffold/AllowedPackages.php
+++ b/composer/Plugin/Scaffold/AllowedPackages.php
@@ -12,6 +12,8 @@ use Composer\Package\PackageInterface;
  *
  * If the root-level composer.json allows drupal/core, and drupal/core allows
  * drupal/assets, then the later package will also implicitly be allowed.
+ *
+ * @internal
  */
 class AllowedPackages implements PostPackageEventListenerInterface {
 
diff --git a/composer/Plugin/Scaffold/CommandProvider.php b/composer/Plugin/Scaffold/CommandProvider.php
index b13a48c5ed7..6597039399b 100644
--- a/composer/Plugin/Scaffold/CommandProvider.php
+++ b/composer/Plugin/Scaffold/CommandProvider.php
@@ -6,6 +6,8 @@ use Composer\Plugin\Capability\CommandProvider as CommandProviderCapability;
 
 /**
  * List of all commands provided by this package.
+ *
+ * @internal
  */
 class CommandProvider implements CommandProviderCapability {
 
diff --git a/composer/Plugin/Scaffold/ComposerScaffoldCommand.php b/composer/Plugin/Scaffold/ComposerScaffoldCommand.php
index fd8becb3d07..6de8aa4bf8f 100644
--- a/composer/Plugin/Scaffold/ComposerScaffoldCommand.php
+++ b/composer/Plugin/Scaffold/ComposerScaffoldCommand.php
@@ -11,6 +11,8 @@ use Symfony\Component\Console\Output\OutputInterface;
  *
  * Manually run the scaffold operation that normally happens after
  * 'composer install'.
+ *
+ * @internal
  */
 class ComposerScaffoldCommand extends BaseCommand {
 
diff --git a/composer/Plugin/Scaffold/GenerateAutoloadReferenceFile.php b/composer/Plugin/Scaffold/GenerateAutoloadReferenceFile.php
index cfbd6c1523b..ba27bef99cf 100644
--- a/composer/Plugin/Scaffold/GenerateAutoloadReferenceFile.php
+++ b/composer/Plugin/Scaffold/GenerateAutoloadReferenceFile.php
@@ -8,6 +8,8 @@ use Drupal\Composer\Plugin\Scaffold\Operations\ScaffoldResult;
 
 /**
  * Generates an 'autoload.php' that includes the autoloader created by Composer.
+ *
+ * @internal
  */
 final class GenerateAutoloadReferenceFile {
 
diff --git a/composer/Plugin/Scaffold/Git.php b/composer/Plugin/Scaffold/Git.php
index 779b8f034b2..015e472eb24 100644
--- a/composer/Plugin/Scaffold/Git.php
+++ b/composer/Plugin/Scaffold/Git.php
@@ -7,6 +7,8 @@ use Composer\Util\ProcessExecutor;
 
 /**
  * Provide some Git utility operations
+ *
+ * @internal
  */
 class Git {
 
diff --git a/composer/Plugin/Scaffold/Handler.php b/composer/Plugin/Scaffold/Handler.php
index 68410a68149..0e1b75665d4 100644
--- a/composer/Plugin/Scaffold/Handler.php
+++ b/composer/Plugin/Scaffold/Handler.php
@@ -17,6 +17,8 @@ use Drupal\Composer\Plugin\Scaffold\Operations\ScaffoldFileCollection;
  *
  * Contains the primary logic which determines the files to be fetched and
  * processed.
+ *
+ * @internal
  */
 class Handler {
 
diff --git a/composer/Plugin/Scaffold/Interpolator.php b/composer/Plugin/Scaffold/Interpolator.php
index 3c8cad839b7..c9f6a4fedb5 100644
--- a/composer/Plugin/Scaffold/Interpolator.php
+++ b/composer/Plugin/Scaffold/Interpolator.php
@@ -4,6 +4,8 @@ namespace Drupal\Composer\Plugin\Scaffold;
 
 /**
  * Injects config values from an associative array into a string.
+ *
+ * @internal
  */
 class Interpolator {
 
diff --git a/composer/Plugin/Scaffold/ManageGitIgnore.php b/composer/Plugin/Scaffold/ManageGitIgnore.php
index 5f1bb9dc957..dcb03fafcb8 100644
--- a/composer/Plugin/Scaffold/ManageGitIgnore.php
+++ b/composer/Plugin/Scaffold/ManageGitIgnore.php
@@ -6,6 +6,8 @@ use Composer\IO\IOInterface;
 
 /**
  * Manage the .gitignore file.
+ *
+ * @internal
  */
 class ManageGitIgnore {
 
diff --git a/composer/Plugin/Scaffold/ManageOptions.php b/composer/Plugin/Scaffold/ManageOptions.php
index d54cf017bfc..56cb1a0a1a4 100644
--- a/composer/Plugin/Scaffold/ManageOptions.php
+++ b/composer/Plugin/Scaffold/ManageOptions.php
@@ -12,6 +12,8 @@ use Composer\Util\Filesystem;
  * Projects that describe scaffold files do so via their scaffold options.
  * This data is pulled from the 'drupal-scaffold' portion of the extras
  * section of the project data.
+ *
+ * @internal
  */
 class ManageOptions {
 
diff --git a/composer/Plugin/Scaffold/Operations/AbstractOperation.php b/composer/Plugin/Scaffold/Operations/AbstractOperation.php
index 5f7261fd262..96bd5904d00 100644
--- a/composer/Plugin/Scaffold/Operations/AbstractOperation.php
+++ b/composer/Plugin/Scaffold/Operations/AbstractOperation.php
@@ -6,6 +6,8 @@ use Drupal\Composer\Plugin\Scaffold\ScaffoldFilePath;
 
 /**
  * Provides default behaviors for operations.
+ *
+ * @internal
  */
 abstract class AbstractOperation implements OperationInterface {
 
diff --git a/composer/Plugin/Scaffold/Operations/AppendOp.php b/composer/Plugin/Scaffold/Operations/AppendOp.php
index 7f5c7e8b0db..802b474bb6d 100644
--- a/composer/Plugin/Scaffold/Operations/AppendOp.php
+++ b/composer/Plugin/Scaffold/Operations/AppendOp.php
@@ -8,6 +8,8 @@ use Drupal\Composer\Plugin\Scaffold\ScaffoldOptions;
 
 /**
  * Scaffold operation to add to the beginning and/or end of a scaffold file.
+ *
+ * @internal
  */
 class AppendOp extends AbstractOperation {
 
diff --git a/composer/Plugin/Scaffold/Operations/ConjunctionOp.php b/composer/Plugin/Scaffold/Operations/ConjunctionOp.php
index 83b2441271c..fbbb176b8ae 100644
--- a/composer/Plugin/Scaffold/Operations/ConjunctionOp.php
+++ b/composer/Plugin/Scaffold/Operations/ConjunctionOp.php
@@ -8,6 +8,8 @@ use Drupal\Composer\Plugin\Scaffold\ScaffoldOptions;
 
 /**
  * Joins two operations on the same file into a single operation.
+ *
+ * @internal
  */
 class ConjunctionOp extends AbstractOperation {
 
diff --git a/composer/Plugin/Scaffold/Operations/OperationData.php b/composer/Plugin/Scaffold/Operations/OperationData.php
index 66b85229aed..9aa73611c06 100644
--- a/composer/Plugin/Scaffold/Operations/OperationData.php
+++ b/composer/Plugin/Scaffold/Operations/OperationData.php
@@ -4,6 +4,8 @@ namespace Drupal\Composer\Plugin\Scaffold\Operations;
 
 /**
  * Holds parameter data for operation objects during operation creation only.
+ *
+ * @internal
  */
 class OperationData {
 
diff --git a/composer/Plugin/Scaffold/Operations/OperationFactory.php b/composer/Plugin/Scaffold/Operations/OperationFactory.php
index 7742e4bb9d7..b256e0e15fb 100644
--- a/composer/Plugin/Scaffold/Operations/OperationFactory.php
+++ b/composer/Plugin/Scaffold/Operations/OperationFactory.php
@@ -8,6 +8,8 @@ use Drupal\Composer\Plugin\Scaffold\ScaffoldFilePath;
 
 /**
  * Create Scaffold operation objects based on provided metadata.
+ *
+ * @internal
  */
 class OperationFactory {
 
diff --git a/composer/Plugin/Scaffold/Operations/OperationInterface.php b/composer/Plugin/Scaffold/Operations/OperationInterface.php
index 409b4761a2a..4b57c743536 100644
--- a/composer/Plugin/Scaffold/Operations/OperationInterface.php
+++ b/composer/Plugin/Scaffold/Operations/OperationInterface.php
@@ -8,6 +8,8 @@ use Drupal\Composer\Plugin\Scaffold\ScaffoldOptions;
 
 /**
  * Interface for scaffold operation objects.
+ *
+ * @internal
  */
 interface OperationInterface {
 
diff --git a/composer/Plugin/Scaffold/Operations/ReplaceOp.php b/composer/Plugin/Scaffold/Operations/ReplaceOp.php
index 5b4c4b9b1d8..9f3eba09634 100644
--- a/composer/Plugin/Scaffold/Operations/ReplaceOp.php
+++ b/composer/Plugin/Scaffold/Operations/ReplaceOp.php
@@ -9,6 +9,8 @@ use Drupal\Composer\Plugin\Scaffold\ScaffoldOptions;
 
 /**
  * Scaffold operation to copy or symlink from source to destination.
+ *
+ * @internal
  */
 class ReplaceOp extends AbstractOperation {
 
diff --git a/composer/Plugin/Scaffold/Operations/ScaffoldFileCollection.php b/composer/Plugin/Scaffold/Operations/ScaffoldFileCollection.php
index c000e64a478..59cc93c3612 100644
--- a/composer/Plugin/Scaffold/Operations/ScaffoldFileCollection.php
+++ b/composer/Plugin/Scaffold/Operations/ScaffoldFileCollection.php
@@ -10,6 +10,8 @@ use Drupal\Composer\Plugin\Scaffold\ScaffoldOptions;
 
 /**
  * Collection of scaffold files.
+ *
+ * @internal
  */
 class ScaffoldFileCollection implements \IteratorAggregate {
 
diff --git a/composer/Plugin/Scaffold/Operations/ScaffoldResult.php b/composer/Plugin/Scaffold/Operations/ScaffoldResult.php
index 3fc1699777a..3445b5307ff 100644
--- a/composer/Plugin/Scaffold/Operations/ScaffoldResult.php
+++ b/composer/Plugin/Scaffold/Operations/ScaffoldResult.php
@@ -6,6 +6,8 @@ use Drupal\Composer\Plugin\Scaffold\ScaffoldFilePath;
 
 /**
  * Record the result of a scaffold operation.
+ *
+ * @internal
  */
 class ScaffoldResult {
 
diff --git a/composer/Plugin/Scaffold/Operations/SkipOp.php b/composer/Plugin/Scaffold/Operations/SkipOp.php
index 3e6c111bdfc..b9f81085c7d 100644
--- a/composer/Plugin/Scaffold/Operations/SkipOp.php
+++ b/composer/Plugin/Scaffold/Operations/SkipOp.php
@@ -8,6 +8,8 @@ use Drupal\Composer\Plugin\Scaffold\ScaffoldOptions;
 
 /**
  * Scaffold operation to skip a scaffold file (do nothing).
+ *
+ * @internal
  */
 class SkipOp extends AbstractOperation {
 
diff --git a/composer/Plugin/Scaffold/Plugin.php b/composer/Plugin/Scaffold/Plugin.php
index e440c5dcc61..a1252cfac14 100644
--- a/composer/Plugin/Scaffold/Plugin.php
+++ b/composer/Plugin/Scaffold/Plugin.php
@@ -18,6 +18,8 @@ use Drupal\Composer\Plugin\Scaffold\CommandProvider as ScaffoldCommandProvider;
 
 /**
  * Composer plugin for handling drupal scaffold.
+ *
+ * @internal
  */
 class Plugin implements PluginInterface, EventSubscriberInterface, Capable {
 
diff --git a/composer/Plugin/Scaffold/PostPackageEventListenerInterface.php b/composer/Plugin/Scaffold/PostPackageEventListenerInterface.php
index 702ab0f54ba..61356b145cf 100644
--- a/composer/Plugin/Scaffold/PostPackageEventListenerInterface.php
+++ b/composer/Plugin/Scaffold/PostPackageEventListenerInterface.php
@@ -8,6 +8,8 @@ use Composer\Installer\PackageEvent;
  * Interface for post package event listeners.
  *
  * @see \Drupal\Composer\Plugin\Scaffold\Handler::onPostPackageEvent
+ *
+ * @internal
  */
 interface PostPackageEventListenerInterface {
 
diff --git a/composer/Plugin/Scaffold/ScaffoldFileInfo.php b/composer/Plugin/Scaffold/ScaffoldFileInfo.php
index 95cba8ba2d8..94e35e5bc2c 100644
--- a/composer/Plugin/Scaffold/ScaffoldFileInfo.php
+++ b/composer/Plugin/Scaffold/ScaffoldFileInfo.php
@@ -12,6 +12,8 @@ use Drupal\Composer\Plugin\Scaffold\Operations\OperationInterface;
  * scaffold file also has an 'operation' object that controls how the scaffold
  * file will be placed (e.g. via copy or symlink, or maybe by appending multiple
  * files together). The operation may have one or more source files.
+ *
+ * @internal
  */
 class ScaffoldFileInfo {
 
diff --git a/composer/Plugin/Scaffold/ScaffoldFilePath.php b/composer/Plugin/Scaffold/ScaffoldFilePath.php
index f225a226282..5fb5af41d0a 100644
--- a/composer/Plugin/Scaffold/ScaffoldFilePath.php
+++ b/composer/Plugin/Scaffold/ScaffoldFilePath.php
@@ -15,6 +15,8 @@ use Composer\Util\Filesystem;
  * source files used to create them. Static factory methods named
  * destinationPath and sourcePath, respectively, are provided to create
  * ScaffoldFilePath objects.
+ *
+ * @internal
  */
 class ScaffoldFilePath {
 
diff --git a/composer/Plugin/Scaffold/ScaffoldOptions.php b/composer/Plugin/Scaffold/ScaffoldOptions.php
index 0a963c788d6..05cd864245d 100644
--- a/composer/Plugin/Scaffold/ScaffoldOptions.php
+++ b/composer/Plugin/Scaffold/ScaffoldOptions.php
@@ -8,6 +8,8 @@ namespace Drupal\Composer\Plugin\Scaffold;
  * Projects that describe scaffold files do so via their scaffold options. This
  * data is pulled from the 'drupal-scaffold' portion of the extras section of
  * the project data.
+ *
+ * @internal
  */
 class ScaffoldOptions {
 
diff --git a/composer/Plugin/VendorHardening/Config.php b/composer/Plugin/VendorHardening/Config.php
index 2d1cef5feab..d468b03d236 100644
--- a/composer/Plugin/VendorHardening/Config.php
+++ b/composer/Plugin/VendorHardening/Config.php
@@ -9,6 +9,8 @@ use Composer\Package\RootPackageInterface;
  *
  * Default configuration is merged with the root package's
  * extra:drupal-core-vendor-hardening configuration.
+ *
+ * @internal
  */
 class Config {
 
diff --git a/composer/Plugin/VendorHardening/FileSecurity.php b/composer/Plugin/VendorHardening/FileSecurity.php
index c8bcd6d328d..c6f5b90c5b7 100644
--- a/composer/Plugin/VendorHardening/FileSecurity.php
+++ b/composer/Plugin/VendorHardening/FileSecurity.php
@@ -8,6 +8,8 @@ namespace Drupal\Composer\Plugin\VendorHardening;
  * IMPORTANT: This file is duplicated at /lib/Drupal/Component/FileSecurity.
  * If any change is made here, the same change should be made in the duplicate.
  * See https://www.drupal.org/project/drupal/issues/3079481.
+ *
+ * @internal
  */
 class FileSecurity {
 
diff --git a/composer/Plugin/VendorHardening/VendorHardeningPlugin.php b/composer/Plugin/VendorHardening/VendorHardeningPlugin.php
index 373b0654c8c..c8e6182e113 100644
--- a/composer/Plugin/VendorHardening/VendorHardeningPlugin.php
+++ b/composer/Plugin/VendorHardening/VendorHardeningPlugin.php
@@ -21,6 +21,8 @@ use Composer\Util\Filesystem;
  * directory within an HTTP server's docroot.
  *
  * @see https://www.drupal.org/docs/develop/using-composer/using-drupals-vendor-cleanup-composer-plugin
+ *
+ * @internal
  */
 class VendorHardeningPlugin implements PluginInterface, EventSubscriberInterface {