diff --git a/core/lib/Drupal/Core/Config/Action/Attribute/ConfigAction.php b/core/lib/Drupal/Core/Config/Action/Attribute/ConfigAction.php
index 27445a1da0a62c7e4ddefa2a0a1b41797641d206..d8df99cf100cc8441e6384bfad65e9a6ea08b8ac 100644
--- a/core/lib/Drupal/Core/Config/Action/Attribute/ConfigAction.php
+++ b/core/lib/Drupal/Core/Config/Action/Attribute/ConfigAction.php
@@ -15,6 +15,9 @@
  *
  * @ingroup config_action_api
  *
+ * @internal
+ *   This API is experimental.
+ *
  * @see \Drupal\Core\Config\Action\ConfigActionPluginInterface
  * @see \Drupal\Core\Config\Action\ConfigActionManager
  * @see plugin_api
diff --git a/core/lib/Drupal/Core/Config/Action/ConfigActionManager.php b/core/lib/Drupal/Core/Config/Action/ConfigActionManager.php
index b830ee75763600790e8df347cdf3eddb51b42e73..c08d341ac3218b307d1abeda9ff0521003f07e5b 100644
--- a/core/lib/Drupal/Core/Config/Action/ConfigActionManager.php
+++ b/core/lib/Drupal/Core/Config/Action/ConfigActionManager.php
@@ -45,6 +45,9 @@
  * - \Drupal\Core\Config\Action\Plugin\ConfigAction\SimpleConfigUpdate allows
  *   you to update simple configuration using a config action.
  * @}
+ *
+ * @internal
+ *   This API is experimental.
  */
 class ConfigActionManager extends DefaultPluginManager {
 
diff --git a/core/lib/Drupal/Core/Config/Action/ConfigActionPluginInterface.php b/core/lib/Drupal/Core/Config/Action/ConfigActionPluginInterface.php
index 143ce3a3d2ba23430487eb7b9389406be848801e..fb174b67e3c00dd111d4c47184258d61652bd3e6 100644
--- a/core/lib/Drupal/Core/Config/Action/ConfigActionPluginInterface.php
+++ b/core/lib/Drupal/Core/Config/Action/ConfigActionPluginInterface.php
@@ -2,6 +2,10 @@
 
 namespace Drupal\Core\Config\Action;
 
+/**
+ * @internal
+ *   This API is experimental.
+ */
 interface ConfigActionPluginInterface {
 
   /**
diff --git a/core/lib/Drupal/Core/Config/Action/DuplicateConfigActionIdException.php b/core/lib/Drupal/Core/Config/Action/DuplicateConfigActionIdException.php
index 7f6bdd3f0eb94d4656ea1fdd322082912879d9e4..9ba0ca8ff729667531bd54335633c226b3b97220 100644
--- a/core/lib/Drupal/Core/Config/Action/DuplicateConfigActionIdException.php
+++ b/core/lib/Drupal/Core/Config/Action/DuplicateConfigActionIdException.php
@@ -4,6 +4,9 @@
 
 /**
  * Exception thrown if there are conflicting shorthand action IDs.
+ *
+ * @internal
+ *   This API is experimental.
  */
 class DuplicateConfigActionIdException extends \RuntimeException {
 }
diff --git a/core/lib/Drupal/Core/Config/Action/Plugin/ConfigAction/Deriver/PermissionsPerBundleDeriver.php b/core/lib/Drupal/Core/Config/Action/Plugin/ConfigAction/Deriver/PermissionsPerBundleDeriver.php
index 4d47e5bc561341680785de0c645a2b80e31c1f41..0b30e51480598f749c023a8bf9280e546fb92606 100644
--- a/core/lib/Drupal/Core/Config/Action/Plugin/ConfigAction/Deriver/PermissionsPerBundleDeriver.php
+++ b/core/lib/Drupal/Core/Config/Action/Plugin/ConfigAction/Deriver/PermissionsPerBundleDeriver.php
@@ -10,6 +10,10 @@
 use Symfony\Component\DependencyInjection\Container;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
+/**
+ * @internal
+ *   This API is experimental.
+ */
 final class PermissionsPerBundleDeriver extends DeriverBase implements ContainerDeriverInterface {
 
   public function __construct(
diff --git a/core/lib/Drupal/Core/Config/Checkpoint/Checkpoint.php b/core/lib/Drupal/Core/Config/Checkpoint/Checkpoint.php
index 96fa4983178914758bfd00ae4d941a324f98bb7d..46e1247f728ed9487040a30df7b3d9b6bf1c5d39 100644
--- a/core/lib/Drupal/Core/Config/Checkpoint/Checkpoint.php
+++ b/core/lib/Drupal/Core/Config/Checkpoint/Checkpoint.php
@@ -6,6 +6,9 @@
 
 /**
  * A value object to store information about a checkpoint.
+ *
+ * @internal
+ *   This API is experimental.
  */
 final class Checkpoint {
 
diff --git a/core/lib/Drupal/Core/Config/Checkpoint/CheckpointExistsException.php b/core/lib/Drupal/Core/Config/Checkpoint/CheckpointExistsException.php
index 320022f29f5de04db263618f9f5f0131389162f7..123ece5f533be4c9cd9b9cb23834a5fcb6c18cee 100644
--- a/core/lib/Drupal/Core/Config/Checkpoint/CheckpointExistsException.php
+++ b/core/lib/Drupal/Core/Config/Checkpoint/CheckpointExistsException.php
@@ -4,6 +4,9 @@
 
 /**
  * Thrown when trying to add a checkpoint with an ID that already exists.
+ *
+ * @internal
+ *   This API is experimental.
  */
 final class CheckpointExistsException extends \RuntimeException {
 }
diff --git a/core/lib/Drupal/Core/Config/Checkpoint/CheckpointListInterface.php b/core/lib/Drupal/Core/Config/Checkpoint/CheckpointListInterface.php
index ef60e217c45741f909ec44f17597a8770c6f3eae..5a2c569e2c8d768a5af5308ac2acd12b3f223694 100644
--- a/core/lib/Drupal/Core/Config/Checkpoint/CheckpointListInterface.php
+++ b/core/lib/Drupal/Core/Config/Checkpoint/CheckpointListInterface.php
@@ -5,6 +5,9 @@
 /**
  * Maintains a list of checkpoints.
  *
+ * @internal
+ *   This API is experimental.
+ *
  * @see \Drupal\Core\Config\Checkpoint\Checkpoint
  *
  * @phpstan-extends \IteratorAggregate<string, \Drupal\Core\Config\Checkpoint\Checkpoint>
diff --git a/core/lib/Drupal/Core/Config/Checkpoint/CheckpointStorage.php b/core/lib/Drupal/Core/Config/Checkpoint/CheckpointStorage.php
index 4cb6e10d460a37dabf5c93cb1ffc40019d0f4a64..bca2e0601a1dc1ee48f7000c653ba5147161ad0e 100644
--- a/core/lib/Drupal/Core/Config/Checkpoint/CheckpointStorage.php
+++ b/core/lib/Drupal/Core/Config/Checkpoint/CheckpointStorage.php
@@ -28,6 +28,9 @@
  * This class cannot be used to checkpoint another storage since it relies on
  * events triggered by the configuration system in order to work. It is the
  * responsibility of the caller to construct this class with the active storage.
+ *
+ * @internal
+ *   This API is experimental.
  */
 final class CheckpointStorage implements CheckpointStorageInterface, EventSubscriberInterface, LoggerAwareInterface {
 
diff --git a/core/lib/Drupal/Core/Config/Checkpoint/CheckpointStorageInterface.php b/core/lib/Drupal/Core/Config/Checkpoint/CheckpointStorageInterface.php
index 1539cd18d5737784e5229809406fd5bb2643988f..837033b022ad58b5dd68fe0aa755fe6fa55e08f9 100644
--- a/core/lib/Drupal/Core/Config/Checkpoint/CheckpointStorageInterface.php
+++ b/core/lib/Drupal/Core/Config/Checkpoint/CheckpointStorageInterface.php
@@ -6,6 +6,9 @@
 
 /**
  * Provides an interface for checkpoint storages.
+ *
+ * @internal
+ *   This API is experimental.
  */
 interface CheckpointStorageInterface extends StorageInterface {
 
diff --git a/core/lib/Drupal/Core/Config/Checkpoint/LinearHistory.php b/core/lib/Drupal/Core/Config/Checkpoint/LinearHistory.php
index 65bd02501a46fb9f1d3d8519881c0ca765189d6e..34047523d62378437779e1d31e941e683170e8ac 100644
--- a/core/lib/Drupal/Core/Config/Checkpoint/LinearHistory.php
+++ b/core/lib/Drupal/Core/Config/Checkpoint/LinearHistory.php
@@ -9,6 +9,9 @@
 
 /**
  * A chronological list of Checkpoint objects.
+ *
+ * @internal
+ *   This API is experimental.
  */
 final class LinearHistory implements CheckpointListInterface {
 
diff --git a/core/lib/Drupal/Core/Config/Checkpoint/NoCheckpointsException.php b/core/lib/Drupal/Core/Config/Checkpoint/NoCheckpointsException.php
index 9a26a2c6ed2020e263e7e93c4ebb59441804cc51..4ebda97426092bb447391c3fb84f288938455dc5 100644
--- a/core/lib/Drupal/Core/Config/Checkpoint/NoCheckpointsException.php
+++ b/core/lib/Drupal/Core/Config/Checkpoint/NoCheckpointsException.php
@@ -4,6 +4,9 @@
 
 /**
  * Thrown when using the checkpoint storage with no checkpoints.
+ *
+ * @internal
+ *   This API is experimental.
  */
 final class NoCheckpointsException extends \RuntimeException {
 
diff --git a/core/lib/Drupal/Core/Config/Checkpoint/UnknownCheckpointException.php b/core/lib/Drupal/Core/Config/Checkpoint/UnknownCheckpointException.php
index 1d6dd928f2aa4f575b5322693769f5672c2543df..029585e30bd10ebefcd6a0f639c845e49432c3b4 100644
--- a/core/lib/Drupal/Core/Config/Checkpoint/UnknownCheckpointException.php
+++ b/core/lib/Drupal/Core/Config/Checkpoint/UnknownCheckpointException.php
@@ -4,6 +4,9 @@
 
 /**
  * Thrown when trying to access a checkpoint that does not exist.
+ *
+ * @internal
+ *   This API is experimental.
  */
 final class UnknownCheckpointException extends \RuntimeException {
 }
diff --git a/core/lib/Drupal/Core/DefaultContent/ImportException.php b/core/lib/Drupal/Core/DefaultContent/ImportException.php
index cf8327f4c06c86e24a728edd1c77e4e926e57294..ef358b9994bafc9944e7cfebc8762e05d1f10592 100644
--- a/core/lib/Drupal/Core/DefaultContent/ImportException.php
+++ b/core/lib/Drupal/Core/DefaultContent/ImportException.php
@@ -4,6 +4,9 @@
 
 /**
  * Exception thrown when there is an error importing content.
+ *
+ * @internal
+ *   This API is experimental.
  */
 final class ImportException extends \RuntimeException {
 }
diff --git a/core/lib/Drupal/Core/Recipe/InvalidConfigException.php b/core/lib/Drupal/Core/Recipe/InvalidConfigException.php
index cbf61a3de67520af6cc833b22eea63f7e0318329..0c92a42f55cd758bc33106960dc478d9264bbecc 100644
--- a/core/lib/Drupal/Core/Recipe/InvalidConfigException.php
+++ b/core/lib/Drupal/Core/Recipe/InvalidConfigException.php
@@ -9,6 +9,9 @@
 
 /**
  * Thrown if config created or changed by a recipe fails validation.
+ *
+ * @internal
+ *   This API is experimental.
  */
 final class InvalidConfigException extends \RuntimeException {
 
diff --git a/core/lib/Drupal/Core/Recipe/RecipePreExistingConfigException.php b/core/lib/Drupal/Core/Recipe/RecipePreExistingConfigException.php
index ce0bd543bc4c80dc68f2db0daf2384a629d66435..cdd9eb0b1804d9c67671683881b830563298b5c5 100644
--- a/core/lib/Drupal/Core/Recipe/RecipePreExistingConfigException.php
+++ b/core/lib/Drupal/Core/Recipe/RecipePreExistingConfigException.php
@@ -4,6 +4,9 @@
 
 /**
  * Exception thrown when a recipe has configuration that exists already.
+ *
+ * @internal
+ *   This API is experimental.
  */
 class RecipePreExistingConfigException extends \RuntimeException {