diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index d54746e..4f1fb61 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -836,11 +836,11 @@ function drupal_find_base_themes($themes, $key, $used_keys = array()) {
  * phase, and are executed (if they exist), in the following
  * order (HOOK indicates the profile, module, theme engine or theme name,
  * THEME_HOOK indicates the name of the specific theme hook called):
- * - HOOK_theme_prepare(&$variables, $context): Prepare a set of variables
+ * - HOOK_theme_prepare(&$variables, $hook): Prepare a set of variables
  *   for all theme hook implementations.
- * - HOOK_theme_prepare_THEME_HOOK(&$variables, $context): Prepare a set of
+ * - HOOK_theme_prepare_THEME_HOOK(&$variables): Prepare a set of
  *   variables for a specific theme hook implementation.
- * - HOOK_theme_prepare_alter(&$variables, $context): Alter a set of prepared
+ * - HOOK_theme_prepare_alter(&$variables, $hook): Alter a set of prepared
  *   variables for all theme hook implementations.
  * - HOOK_theme_prepare_THEME_HOOK_alter(&$variables, $context): Alter a set of
  *   prepared variables for a specific theme hook implementation.
@@ -881,10 +881,6 @@ function drupal_find_base_themes($themes, $key, $used_keys = array()) {
  *   to the function or template implementing the theme hook. Alternatively,
  *   this can be a renderable array, in which case, its properties are mapped to
  *   variables expected by the theme hook implementations.
- * @param array $context
- *   An associative array of data used as context in hook_theme_prepare(). This
- *   array is used internally and is not available as a "variable" in  theme
- *   functions or templates.
  *
  * @return string|false
  *   An HTML string representing the themed output or FALSE if the passed $hook
@@ -897,7 +893,7 @@ function drupal_find_base_themes($themes, $key, $used_keys = array()) {
  *
  * @throws Exception
  */
-function theme($hook, $variables = array(), $context = array()) {
+function theme($hook, $variables = array()) {
   static $default_attributes;
   // If called before all modules are loaded, we do not necessarily have a full
   // theme registry to work with, and therefore cannot process the theme
@@ -986,10 +982,6 @@ function theme($hook, $variables = array(), $context = array()) {
   elseif (!empty($info['render element'])) {
     $variables += array($info['render element'] => array());
   }
-  // Supply original caller info.
-  $variables += array(
-    'theme_hook_original' => $original_hook,
-  );

   // Set base hook for later use. For example if '#theme' => 'node__article'
   // is called, we run hook_theme_suggestions_node_alter() rather than
@@ -1002,6 +994,12 @@ function theme($hook, $variables = array(), $context = array()) {
     $base_theme_hook = $hook;
   }

+  // Supply original caller info.
+  $variables += array(
+    'theme_hook' => $base_theme_hook,
+    'theme_hook_original' => $original_hook,
+  );
+
   // Invoke hook_theme_suggestions_HOOK().
   $suggestions = Drupal::moduleHandler()->invokeAll('theme_suggestions_' . $base_theme_hook, array($variables));
   // If theme() was invoked with a direct theme suggestion like
@@ -1045,17 +1043,10 @@ function theme($hook, $variables = array(), $context = array()) {
     }
   }

-  // Provide default context.
-  $context += array(
-    'theme_hook' => $hook,
-    'original_theme_hook' => $original_hook,
-    'suggestions' => $suggestions,
-  );
-
-  // A list of hooks that we'll fire for the given theme hook.
+  // A list of hooks that will be invoked for the given theme hook.
   $prepare_hooks = array(
     'theme_prepare',
-    'theme_prepare_' . $hook,
+    'theme_prepare_' . $base_theme_hook,
   );
   // If the original theme hook is not the same as the base theme hook, then
   // invoke the original theme hook suggestion after the base theme hook.
@@ -1066,22 +1057,20 @@ function theme($hook, $variables = array(), $context = array()) {
   // Invokes hook_theme_prepare(), hook_theme_prepare_THEME_HOOK() for enabled
   // modules.
   foreach ($prepare_hooks as $prepare_hook) {
-    // Provide immutable context for each hook.
-    $context_clone = $context;
-    $variables = NestedArray::mergeDeep($variables, (array) Drupal::moduleHandler()->invokeAll($prepare_hook, array($context_clone)));
+    $variables = NestedArray::mergeDeep($variables, (array) Drupal::moduleHandler()->invokeAll($prepare_hook, array($variables, $base_theme_hook)));
   }

-  // Invokes hook_theme_prepare(), hook_theme_prepare_THEME_ID() for the active
+  // Invokes hook_theme_prepare(), hook_theme_prepare_THEME_HOOK() for the active
   // theme, which takes precedence over modules.
   // @todo Replace with Drupal::themeHandler()->invoke() once implemented.
   // @see https://drupal.org/node/2029819
   foreach ($prepare_hooks as $prepare_hook) {
-    // Provide immutable context for each hook.
-    $context_clone = $context;
-    $variables = NestedArray::mergeDeep($variables, (array) Drupal::moduleHandler()->themeInvoke($prepare_hook, array($context_clone)));
+    $variables = NestedArray::mergeDeep($variables, (array) theme_invoke($prepare_hook, array($variables, $base_theme_hook)));
   }

-  // Invokes preprocess functions (deprecated).
+  // Invokes hook_preprocess() and hook_preprocess_HOOK() implementations. This
+  // phase is deprecated and is run in between hook_theme_prepare[_THEME_HOOK]()
+  // and hook_theme_prepare[_THEME_HOOK]_alter().
   if (isset($info['preprocess functions'])) {
     foreach ($info['preprocess functions'] as $preprocessor_function) {
       if (function_exists($preprocessor_function)) {
@@ -1095,9 +1084,7 @@ function theme($hook, $variables = array(), $context = array()) {
   // @todo Add Drupal::themeHandler()->alter() invocations once implemented.
   // @see https://drupal.org/node/2029819
   foreach ($prepare_hooks as $prepare_hook) {
-    // Provide immutable context for each hook.
-    $context_clone = $context;
-    Drupal::moduleHandler()->alter($prepare_hook, $variables, $context_clone);
+    Drupal::moduleHandler()->alter($prepare_hook, $variables, $base_theme_hook);
   }

   // Generate the output using either a function or a template.
@@ -1585,6 +1572,39 @@ function theme_disable($theme_list) {
 }

 /**
+ * Rudimentary and temporary method for invoking theme hooks.
+ *
+ * @param string $hook
+ *   The hook name to invoke.
+ * @param array $args
+ *   The array of arguments to pass to hook invocation.
+ *
+ * @return mixed
+ *   The value returned varies on which hook is invoked.
+ *
+ * @todo Remove once a proper Drupal::themeHandler() is created.
+ * @see https://drupal.org/node/2029819
+ */
+function theme_invoke($hook, $args = array()) {
+  // Allow the active theme to invoke hooks after the theme system has been
+  // initialized.
+  global $theme, $base_theme_info;
+  if (isset($theme)) {
+    $theme_keys = array();
+    foreach ($base_theme_info as $base) {
+      $theme_keys[] = $base->name;
+    }
+    $theme_keys[] = $theme;
+    foreach ($theme_keys as $theme_key) {
+      $function = $theme_key . '_' . $hook;
+      if (function_exists($function)) {
+        return call_user_func_array($function, $args);
+      }
+    }
+  }
+}
+
+/**
  * @addtogroup themeable
  * @{
  */
diff --git a/core/lib/Drupal/Core/Extension/ModuleHandler.php b/core/lib/Drupal/Core/Extension/ModuleHandler.php
index 96b332f..92cf2a4 100644
--- a/core/lib/Drupal/Core/Extension/ModuleHandler.php
+++ b/core/lib/Drupal/Core/Extension/ModuleHandler.php
@@ -273,31 +273,6 @@ public function invoke($module, $hook, $args = array()) {
   }

   /**
-   * Rudimentary and temporary method for invoking theme hooks.
-   *
-   * @todo Remove once a proper Drupal::themeHandler() is created.
-   * @see https://drupal.org/node/2029819
-   */
-  public function themeInvoke($hook, $args = array()) {
-    // Allow the active theme to invoke hooks after the theme system has been
-    // initialized.
-    global $theme, $base_theme_info;
-    if (isset($theme)) {
-      $theme_keys = array();
-      foreach ($base_theme_info as $base) {
-        $theme_keys[] = $base->name;
-      }
-      $theme_keys[] = $theme;
-      foreach ($theme_keys as $theme_key) {
-        $function = $theme_key . '_' . $hook;
-        if (function_exists($function)) {
-          return call_user_func_array($function, $args);
-        }
-      }
-    }
-  }
-
-  /**
    * Implements \Drupal\Core\Extension\ModuleHandlerInterface::invokeAll().
    */
   public function invokeAll($hook, $args = array()) {
diff --git a/core/modules/system/theme.api.php b/core/modules/system/theme.api.php
index 29ae59d..b8e24fe 100644
--- a/core/modules/system/theme.api.php
+++ b/core/modules/system/theme.api.php
@@ -109,7 +109,7 @@ function hook_form_system_theme_settings_alter(&$form, &$form_state) {
  * @see hook_theme_prepare()
  */
 function hook_preprocess(&$variables, $hook) {
-  // This hook has been deprecated, do not use it. Please use instead:
+  // This hook has been deprecated, do not use it. Use the following instead:
   // hook_theme_prepare().

   static $hooks;
@@ -158,11 +158,11 @@ function hook_preprocess(&$variables, $hook) {
  *   The variables array (modify in place).
  *
  * @deprecated
- * @see hook_theme_prepare_SUGGESTION()
+ * @see hook_theme_prepare_THEME_HOOK()
  */
 function hook_preprocess_HOOK(&$variables) {
-  // This hook has been deprecated, do not use it. Please use instead:
-  // hook_theme_prepare_SUGGESTION().
+  // This hook has been deprecated, do not use it. Use the following instead:
+  // hook_theme_prepare_THEME_HOOK().

   // This example is from rdf_preprocess_image(). It adds an RDF attribute
   // to the image hook's variables.
@@ -170,22 +170,25 @@ function hook_preprocess_HOOK(&$variables) {
 }

 /**
- * Prepares theme variables for templates.
+ * Prepares variables for theme functions and templates.
  *
- * This hook allows modules to prepare theme variables for theme templates.
- * It is called for all theme hooks implemented as templates, but not for theme
- * hooks implemented as functions. hook_preprocess_HOOK() can be used to
- * preprocess variables for a specific theme hook, whether implemented as a
- * template or function.
+ * This hook allows any module or theme to prepare variables for any theme hook.
+ * hook_theme_prepare_THEME_HOOK() can be used to prepare variables for a
+ * specific theme hook.
  *
  * For more detailed information, see theme().
  *
- * @param array $context
- *   The immutable context array.
+ * @param array $variables
+ *   The associative array of variables, passed by reference (modify in place).
+ * @param string $hook
+ *   The name of the theme hook called.
+ *
+ * @see hook_theme_prepare_alter()
+ * @see hook_theme_prepare_THEME_HOOK()
+ * @see hook_theme_prepare_THEME_HOOK_alter()
  */
-function hook_theme_prepare($context) {
+function hook_theme_prepare(&$variables, $hook) {
   static $hooks;
-  $variables = array();

   // Add contextual links to the variables, if the user has permission.
   if (!user_access('access contextual links')) {
@@ -196,9 +199,6 @@ function hook_theme_prepare($context) {
     $hooks = theme_get_registry();
   }

-  // Retrieve the original theme hook from context.
-  $hook = $context['original_theme_hook'];
-
   // Determine the primary theme function argument.
   if (isset($hooks[$hook]['variables'])) {
     $keys = array_keys($hooks[$hook]['variables']);
@@ -218,59 +218,67 @@ function hook_theme_prepare($context) {
       $variables['attributes']['class'][] = 'contextual-links-region';
     }
   }
-
-  return $variables;
 }

 /**
- * Alters the prepared theme variables used in templates.
+ * Alters the prepared variables used in theme functions and templates.
  *
- * This hook allows any module or theme to add new variables or reorder/remove
- * existing variables provided by earlier invocations of hook_theme_prepare() or
- * hook_theme_prepare_THEME_HOOK().
+ * This hook allows any module or theme to alter existing variables provided by
+ * earlier invocations of hook_theme_prepare() or
+ * hook_theme_prepare_THEME_HOOK(). This hook should only be used when it is
+ * needed to override or add to the $variables array for a theme hook it did not
+ * define.
  *
  * For more detailed information, see theme().
  *
  * @param array $variables
- *   The variables array (modify in place).
- * @param array $context
- *   The immutable context array.
+ *   The associative array of variables, passed by reference (modify in place).
+ * @param string $hook
+ *   The name of the theme hook called.
+ *
+ * @see hook_theme_prepare()
+ * @see hook_theme_prepare_THEME_HOOK()
+ * @see hook_theme_prepare_THEME_HOOK_alter()
  */
-function hook_theme_prepare_alter(&$variables, $context) {
-  // Replace the name of the user whom authored the node.
-  if ($context['theme_hook'] === 'node') {
+function hook_theme_prepare_alter(&$variables, $hook) {
+  // Replace the name of the user whom authored article nodes.
+  if ($hook === 'node__article') {
     $variables['name'] = t('Anonymous Unicorn');
   }
 }

 /**
- * Prepares variables used in templates for a specific theme suggestion.
+ * Prepares variables for a specific theme hook or theme hook suggestion.
  *
- * This hook allows modules to prepare theme variables for a specific theme
- * suggestion. It should only be used when it is needed to override or add to
- * theme preparation for a theme hook it did not define.
+ * This hook allow any module or theme to prepare theme variables for a specific
+ * theme hook or theme hook suggestion.
  *
  * THEME_HOOK can be either the base theme hook or a more specific suggestion
  * using the double-underscore ('__') notation.
  *
  * For more detailed information, see theme().
  *
- * @param array $context
- *   The immutable context array.
+ * @param array $variables
+ *   The associative array of variables, passed by reference (modify in place).
+ *
+ * @see rdf_preprocess_image()
+ * @see hook_theme_prepare_THEME_HOOK_alter()
+ * @see hook_theme_prepare_alter()
+ * @see hook_theme_prepare()
  */
-function hook_theme_prepare_THEME_HOOK($context) {
-  // This example is from rdf_theme_prepare_image(). It adds an RDF attribute
+function hook_theme_prepare_THEME_HOOK(&$variables) {
+  // This example is from rdf_preprocess_image(). It adds an RDF attribute
   // to the image hook's variables.
   $variables['attributes']['typeof'] = array('foaf:Image');
-  return $variables;
 }

 /**
- * Alters prepared variables used in templates for a specific theme suggestion.
+ * Alters prepared variables for a specific theme hook or theme hook suggestion.
  *
- * This hook allows any module or theme to add new variables or reorder/remove
- * existing variables provided by earlier invocations of hook_theme_prepare() or
- * hook_theme_prepare_THEME_HOOK().
+ * This hook allows any module or theme to alter existing variables provided by
+ * earlier invocations of hook_theme_prepare() or
+ * hook_theme_prepare_THEME_HOOK(). It should only be used when it is needed
+ * to override or add to the theme variable for a theme hook it did not define.
  *
  * THEME_HOOK can be either the base theme hook or a more specific suggestion
  * using the double-underscore ('__') notation.
@@ -278,12 +286,16 @@ function hook_theme_prepare_THEME_HOOK($context) {
  * For more detailed information, see theme().
  *
  * @param array $variables
- *   The variables array (modify in place).
- * @param array $context
- *   The immutable context array.
+ *   The associative array of variables, passed by reference (modify in place).
+ *
+ * @see hook_theme_prepare_THEME_HOOK()
+ * @see hook_theme_prepare_alter()
+ * @see hook_theme_prepare()
  */
-function hook_theme_prepare_THEME_HOOK_alter(&$variables, $context) {
-  // Replace the name of the user whom authored the node.
+function hook_theme_prepare_THEME_HOOK_alter(&$variables) {
+  // Replace the name of the user whom authored article nodes; assuming
+  // THEME_HOOK was "node__article" and placed in node.module, the function name
+  // would read: node_theme_prepare_node__article_alter.
   $variables['name'] = t('Anonymous Unicorn');
 }