diff --git a/lib/block-supports/layout.php b/lib/block-supports/layout.php
index 0734936b2610b..a50e1fb883717 100644
--- a/lib/block-supports/layout.php
+++ b/lib/block-supports/layout.php
@@ -477,7 +477,7 @@ function gutenberg_restore_group_inner_container( $block_content, $block ) {
 		preg_quote( $tag_name, '/' )
 	);
 	if (
-		WP_Theme_JSON_Resolver_Gutenberg::theme_has_support() ||
+		wp_theme_has_theme_json() ||
 		1 === preg_match( $group_with_inner_container_regex, $block_content ) ||
 		( isset( $block['attrs']['layout']['type'] ) && 'flex' === $block['attrs']['layout']['type'] )
 	) {
@@ -542,7 +542,7 @@ function gutenberg_restore_image_outer_container( $block_content, $block ) {
 )/iUx";
 
 	if (
-		WP_Theme_JSON_Resolver::theme_has_support() ||
+		wp_theme_has_theme_json() ||
 		0 === preg_match( $image_with_align, $block_content, $matches )
 	) {
 		return $block_content;
diff --git a/lib/client-assets.php b/lib/client-assets.php
index f1b94c0d46abf..ea199750fa10b 100644
--- a/lib/client-assets.php
+++ b/lib/client-assets.php
@@ -318,7 +318,7 @@ function gutenberg_register_packages_styles( $styles ) {
 	);
 
 	// Only load the default layout and margin styles for themes without theme.json file.
-	if ( ! WP_Theme_JSON_Resolver_Gutenberg::theme_has_support() ) {
+	if ( ! wp_theme_has_theme_json() ) {
 		$wp_edit_blocks_dependencies[] = 'wp-editor-classic-layout-styles';
 	}
 
diff --git a/lib/compat/wordpress-6.0/block-patterns.php b/lib/compat/wordpress-6.0/block-patterns.php
index 6ba5a15035530..c42ec73152219 100644
--- a/lib/compat/wordpress-6.0/block-patterns.php
+++ b/lib/compat/wordpress-6.0/block-patterns.php
@@ -15,7 +15,7 @@ function _register_remote_theme_patterns() {
 			return;
 		}
 
-		if ( ! WP_Theme_JSON_Resolver_Gutenberg::theme_has_support() ) {
+		if ( ! wp_theme_has_theme_json() ) {
 			return;
 		}
 
diff --git a/lib/compat/wordpress-6.0/class-wp-theme-json-resolver-6-0.php b/lib/compat/wordpress-6.0/class-wp-theme-json-resolver-6-0.php
index b85e8e335037a..45779d395e629 100644
--- a/lib/compat/wordpress-6.0/class-wp-theme-json-resolver-6-0.php
+++ b/lib/compat/wordpress-6.0/class-wp-theme-json-resolver-6-0.php
@@ -86,7 +86,7 @@ public static function get_theme_data( $deprecated = array(), $options = array()
 		 * and merge the static::$theme upon that.
 		 */
 		$theme_support_data = WP_Theme_JSON_Gutenberg::get_from_editor_settings( get_default_block_editor_settings() );
-		if ( ! static::theme_has_support() ) {
+		if ( ! wp_theme_has_theme_json() ) {
 			if ( ! isset( $theme_support_data['settings']['color'] ) ) {
 				$theme_support_data['settings']['color'] = array();
 			}
diff --git a/lib/compat/wordpress-6.0/get-global-styles-and-settings.php b/lib/compat/wordpress-6.0/get-global-styles-and-settings.php
index 1dfafe9f7631d..9ed3e891182cb 100644
--- a/lib/compat/wordpress-6.0/get-global-styles-and-settings.php
+++ b/lib/compat/wordpress-6.0/get-global-styles-and-settings.php
@@ -85,7 +85,7 @@ function gutenberg_get_global_styles_svg_filters() {
 		}
 	}
 
-	$supports_theme_json = WP_Theme_JSON_Resolver_Gutenberg::theme_has_support();
+	$supports_theme_json = wp_theme_has_theme_json();
 
 	$origins = array( 'default', 'theme', 'custom' );
 	if ( ! $supports_theme_json ) {
diff --git a/lib/compat/wordpress-6.1/block-editor-settings.php b/lib/compat/wordpress-6.1/block-editor-settings.php
index 3181329475df4..cafe91e787dc6 100644
--- a/lib/compat/wordpress-6.1/block-editor-settings.php
+++ b/lib/compat/wordpress-6.1/block-editor-settings.php
@@ -68,7 +68,7 @@ function gutenberg_get_block_editor_settings( $settings ) {
 			}
 		}
 
-		if ( WP_Theme_JSON_Resolver::theme_has_support() ) {
+		if ( wp_theme_has_theme_json() ) {
 			$block_classes = array(
 				'css'            => 'styles',
 				'__unstableType' => 'theme',
diff --git a/lib/compat/wordpress-6.1/get-global-styles-and-settings.php b/lib/compat/wordpress-6.1/get-global-styles-and-settings.php
index 1837aa04dbb20..35c540ce1c57a 100644
--- a/lib/compat/wordpress-6.1/get-global-styles-and-settings.php
+++ b/lib/compat/wordpress-6.1/get-global-styles-and-settings.php
@@ -83,7 +83,7 @@ function gutenberg_get_global_stylesheet( $types = array() ) {
 		}
 	}
 	$tree                = WP_Theme_JSON_Resolver_Gutenberg::get_merged_data();
-	$supports_theme_json = WP_Theme_JSON_Resolver_Gutenberg::theme_has_support();
+	$supports_theme_json = wp_theme_has_theme_json();
 	if ( empty( $types ) && ! $supports_theme_json ) {
 		$types = array( 'variables', 'presets', 'base-layout-styles' );
 	} elseif ( empty( $types ) ) {
diff --git a/lib/compat/wordpress-6.1/template-parts-screen.php b/lib/compat/wordpress-6.1/template-parts-screen.php
index d9b785100b8d9..c8b5958bedcd4 100644
--- a/lib/compat/wordpress-6.1/template-parts-screen.php
+++ b/lib/compat/wordpress-6.1/template-parts-screen.php
@@ -116,7 +116,7 @@ static function( $classes ) {
 		'styles'                    => get_block_editor_theme_styles(),
 		'defaultTemplateTypes'      => $indexed_template_types,
 		'defaultTemplatePartAreas'  => get_allowed_block_template_part_areas(),
-		'supportsLayout'            => WP_Theme_JSON_Resolver::theme_has_support(),
+		'supportsLayout'            => wp_theme_has_theme_json(),
 		'supportsTemplatePartsMode' => ! wp_is_block_theme() && current_theme_supports( 'block-template-parts' ),
 		'__unstableHomeTemplate'    => gutenberg_resolve_home_template(),
 	);
diff --git a/lib/compat/wordpress-6.2/default-filters.php b/lib/compat/wordpress-6.2/default-filters.php
new file mode 100644
index 0000000000000..ac1ce19b42551
--- /dev/null
+++ b/lib/compat/wordpress-6.2/default-filters.php
@@ -0,0 +1,27 @@
+<?php
+/**
+ * Sets up the default filters and actions for most
+ * of the WordPress hooks.
+ *
+ * If you need to remove a default hook, this file will
+ * give you the priority to use for removing the hook.
+ *
+ * Not all of the default hooks are found in this file.
+ * For instance, administration-related hooks are located in
+ * wp-admin/includes/admin-filters.php.
+ *
+ * If a hook should only be called from a specific context
+ * (admin area, multisite environment…), please move it
+ * to a more appropriate file instead.
+ *
+ * @package gutenberg
+ */
+
+/**
+ * Note for backport: we should also remove the existing filters:
+ *
+ * > add_action( 'switch_theme', array( 'WP_Theme_JSON_Resolver', 'clean_cached_data' ) );
+ * > add_action( 'start_previewing_theme', array( 'WP_Theme_JSON_Resolver', 'clean_cached_data' ) );
+ */
+add_action( 'switch_theme', 'wp_theme_clean_theme_json_cached_data' );
+add_action( 'start_previewing_theme', 'wp_theme_clean_theme_json_cached_data' );
diff --git a/lib/compat/wordpress-6.2/get-global-styles-and-settings.php b/lib/compat/wordpress-6.2/get-global-styles-and-settings.php
new file mode 100644
index 0000000000000..4dbd9d0ba8bde
--- /dev/null
+++ b/lib/compat/wordpress-6.2/get-global-styles-and-settings.php
@@ -0,0 +1,47 @@
+<?php
+/**
+ * API to interact with global settings & styles.
+ *
+ * @package gutenberg
+ */
+
+if ( ! function_exists( 'wp_theme_has_theme_json' ) ) {
+	/**
+	 * Whether a theme or its parent have a theme.json file.
+	 *
+	 * @param boolean $clear_cache Whether the cache should be cleared and theme support recomputed. Default is false.
+	 *
+	 * @return boolean
+	 */
+	function wp_theme_has_theme_json( $clear_cache = false ) {
+		static $theme_has_support = null;
+
+		if ( true === $clear_cache ) {
+			$theme_has_support = null;
+		}
+
+		if ( null !== $theme_has_support ) {
+			return $theme_has_support;
+		}
+
+		// Has the own theme a theme.json?
+		$theme_has_support = is_readable( get_stylesheet_directory() . '/theme.json' );
+
+		// Look up the parent if the child does not have a theme.json.
+		if ( ! $theme_has_support ) {
+			$theme_has_support = is_readable( get_template_directory() . '/theme.json' );
+		}
+
+		return $theme_has_support;
+	}
+}
+
+if ( ! function_exists( 'wp_theme_clean_theme_json_cached_data' ) ) {
+	/**
+	 * Clean theme.json related cached data.
+	 */
+	function wp_theme_clean_theme_json_cached_data() {
+		wp_theme_has_theme_json( true );
+		WP_Theme_JSON_Resolver_Gutenberg::clean_cached_data();
+	}
+}
diff --git a/lib/experimental/block-editor-settings-mobile.php b/lib/experimental/block-editor-settings-mobile.php
index b0da17e929667..91e3694c199f8 100644
--- a/lib/experimental/block-editor-settings-mobile.php
+++ b/lib/experimental/block-editor-settings-mobile.php
@@ -22,7 +22,7 @@ function gutenberg_get_block_editor_settings_mobile( $settings ) {
 		isset( $_GET['context'] ) &&
 		'mobile' === $_GET['context']
 	) {
-		if ( WP_Theme_JSON_Resolver_Gutenberg::theme_has_support() ) {
+		if ( wp_theme_has_theme_json() ) {
 			$settings['__experimentalStyles'] = gutenberg_get_global_styles();
 		}
 
diff --git a/lib/experimental/class-wp-theme-json-resolver-gutenberg.php b/lib/experimental/class-wp-theme-json-resolver-gutenberg.php
index bab54c9410ac8..43ac5b3bc9ec4 100644
--- a/lib/experimental/class-wp-theme-json-resolver-gutenberg.php
+++ b/lib/experimental/class-wp-theme-json-resolver-gutenberg.php
@@ -73,7 +73,7 @@ public static function get_theme_data( $deprecated = array(), $settings = array(
 		 * and merge the static::$theme upon that.
 		 */
 		$theme_support_data = WP_Theme_JSON_Gutenberg::get_from_editor_settings( get_default_block_editor_settings() );
-		if ( ! static::theme_has_support() ) {
+		if ( ! wp_theme_has_theme_json() ) {
 			if ( ! isset( $theme_support_data['settings']['color'] ) ) {
 				$theme_support_data['settings']['color'] = array();
 			}
diff --git a/lib/load.php b/lib/load.php
index 65e8e3e2cb220..0db2d25761771 100644
--- a/lib/load.php
+++ b/lib/load.php
@@ -83,6 +83,8 @@ function gutenberg_is_experiment_enabled( $name ) {
 require __DIR__ . '/compat/wordpress-6.1/block-editor-settings.php';
 require __DIR__ . '/compat/wordpress-6.1/persisted-preferences.php';
 require __DIR__ . '/compat/wordpress-6.1/get-global-styles-and-settings.php';
+require __DIR__ . '/compat/wordpress-6.2/get-global-styles-and-settings.php';
+require __DIR__ . '/compat/wordpress-6.2/default-filters.php';
 require __DIR__ . '/compat/wordpress-6.1/class-wp-theme-json-data-gutenberg.php';
 require __DIR__ . '/compat/wordpress-6.1/class-wp-theme-json-6-1.php';
 require __DIR__ . '/compat/wordpress-6.1/class-wp-theme-json-resolver-6-1.php';
diff --git a/phpunit/class-wp-theme-json-resolver-test.php b/phpunit/class-wp-theme-json-resolver-test.php
index 14ce71f3b4ed5..3746d158f2016 100644
--- a/phpunit/class-wp-theme-json-resolver-test.php
+++ b/phpunit/class-wp-theme-json-resolver-test.php
@@ -125,19 +125,6 @@ public function test_translations_are_applied() {
 		);
 	}
 
-	public function test_switching_themes_recalculates_data() {
-		// The "default" theme doesn't have theme.json support.
-		switch_theme( 'default' );
-		$default = WP_Theme_JSON_Resolver_Gutenberg::theme_has_support();
-
-		// Switch to a theme that does have support.
-		switch_theme( 'block-theme' );
-		$has_theme_json_support = WP_Theme_JSON_Resolver_Gutenberg::theme_has_support();
-
-		$this->assertFalse( $default );
-		$this->assertTrue( $has_theme_json_support );
-	}
-
 	public function test_add_theme_supports_are_loaded_for_themes_without_theme_json() {
 		switch_theme( 'default' );
 		$color_palette = array(
@@ -165,7 +152,7 @@ public function test_add_theme_supports_are_loaded_for_themes_without_theme_json
 		remove_theme_support( 'custom-line-height' );
 		remove_theme_support( 'editor-color-palette' );
 
-		$this->assertFalse( WP_Theme_JSON_Resolver_Gutenberg::theme_has_support() );
+		$this->assertFalse( wp_theme_has_theme_json() );
 		$this->assertTrue( $settings['typography']['lineHeight'] );
 		$this->assertSame( $color_palette, $settings['color']['palette']['theme'] );
 	}
diff --git a/phpunit/data/themedir1/block-theme-child-no-theme-json/style.css b/phpunit/data/themedir1/block-theme-child-no-theme-json/style.css
new file mode 100644
index 0000000000000..344441288258e
--- /dev/null
+++ b/phpunit/data/themedir1/block-theme-child-no-theme-json/style.css
@@ -0,0 +1,8 @@
+/*
+Theme Name: Block Theme Child with no theme.json
+Theme URI: https://wordpress.org/
+Description: For testing purposes only.
+Template: block-theme
+Version: 1.0.0
+Text Domain: block-theme-child-no-theme-json
+*/
diff --git a/phpunit/data/themedir1/default-child-no-theme-json/style.css b/phpunit/data/themedir1/default-child-no-theme-json/style.css
new file mode 100644
index 0000000000000..8f971990d9fec
--- /dev/null
+++ b/phpunit/data/themedir1/default-child-no-theme-json/style.css
@@ -0,0 +1,8 @@
+/*
+Theme Name: Default Child Theme with no theme.json
+Theme URI: https://wordpress.org/
+Description: For testing purposes only.
+Template: default
+Version: 1.0.0
+Text Domain: default-child-no-theme-json
+*/
diff --git a/phpunit/data/themedir1/default/style.css b/phpunit/data/themedir1/default/style.css
new file mode 100644
index 0000000000000..e73392422dd64
--- /dev/null
+++ b/phpunit/data/themedir1/default/style.css
@@ -0,0 +1,13 @@
+/*
+Theme Name: WordPress Default
+Theme URI: http://wordpress.org/
+Description: The default WordPress theme based on the famous <a href="http://binarybonsai.com/kubrick/">Kubrick</a>.
+Version: 1.6
+Author: Michael Heilemann
+Author URI: http://binarybonsai.com/
+
+This is just a stub to test the loading of the above metadata.
+*/
+
+
+
diff --git a/phpunit/wp-theme-json-test.php b/phpunit/wp-theme-json-test.php
new file mode 100644
index 0000000000000..0d92d33faf88d
--- /dev/null
+++ b/phpunit/wp-theme-json-test.php
@@ -0,0 +1,120 @@
+<?php
+/**
+ * Tests theme.json related public APIs.
+ *
+ * @package Gutenberg
+ */
+
+class WP_Theme_Json_Test extends WP_UnitTestCase {
+
+	public function set_up() {
+		parent::set_up();
+		$this->theme_root = realpath( __DIR__ . '/data/themedir1' );
+
+		$this->orig_theme_dir = $GLOBALS['wp_theme_directories'];
+
+		// /themes is necessary as theme.php functions assume /themes is the root if there is only one root.
+		$GLOBALS['wp_theme_directories'] = array( WP_CONTENT_DIR . '/themes', $this->theme_root );
+
+		add_filter( 'theme_root', array( $this, 'filter_set_theme_root' ) );
+		add_filter( 'stylesheet_root', array( $this, 'filter_set_theme_root' ) );
+		add_filter( 'template_root', array( $this, 'filter_set_theme_root' ) );
+		$this->queries = array();
+		// Clear caches.
+		wp_clean_themes_cache();
+		unset( $GLOBALS['wp_themes'] );
+	}
+
+	public function tear_down() {
+		$GLOBALS['wp_theme_directories'] = $this->orig_theme_dir;
+		wp_clean_themes_cache();
+		unset( $GLOBALS['wp_themes'] );
+		parent::tear_down();
+	}
+
+	public function filter_set_theme_root() {
+		return $this->theme_root;
+	}
+
+	/**
+	 * Test that it reports correctly themes that have a theme.json.
+	 *
+	 * @group theme_json
+	 *
+	 * @covers wp_theme_has_theme_json
+	 */
+	public function test_theme_has_theme_json() {
+		switch_theme( 'block-theme' );
+		$this->assertTrue( wp_theme_has_theme_json() );
+	}
+
+	/**
+	 * Test that it reports correctly themes that do not have a theme.json.
+	 *
+	 * @group theme_json
+	 *
+	 * @covers wp_theme_has_theme_json
+	 */
+	public function test_theme_has_no_theme_json() {
+		switch_theme( 'default' );
+		$this->assertFalse( wp_theme_has_theme_json() );
+	}
+
+	/**
+	 * Test it reports correctly child themes that have a theme.json.
+	 *
+	 * @group theme_json
+	 *
+	 * @covers wp_theme_has_theme_json
+	 */
+	public function test_child_theme_has_theme_json() {
+		switch_theme( 'block-theme-child' );
+		$this->assertTrue( wp_theme_has_theme_json() );
+	}
+
+	/**
+	 * Test that it reports correctly child themes that do not have a theme.json
+	 * and the parent does.
+	 *
+	 * @group theme_json
+	 *
+	 * @covers wp_theme_has_theme_json
+	 */
+	public function test_child_theme_has_not_theme_json_but_parent_has() {
+		switch_theme( 'block-theme-child-no-theme-json' );
+		$this->assertTrue( wp_theme_has_theme_json() );
+	}
+
+	/**
+	 * Test that it reports correctly child themes that do not have a theme.json
+	 * and the parent does not either.
+	 *
+	 * @group theme_json
+	 *
+	 * @covers wp_theme_has_theme_json
+	 */
+	public function test_neither_child_or_parent_themes_have_theme_json() {
+		switch_theme( 'default-child-no-theme-json' );
+		$this->assertFalse( wp_theme_has_theme_json() );
+	}
+
+	/**
+	 * Test that switching themes recalculates theme support.
+	 *
+	 * @group theme_json
+	 *
+	 * @covers wp_theme_has_theme_json
+	 */
+	public function test_switching_themes_recalculates_support() {
+		// The "default" theme doesn't have theme.json support.
+		switch_theme( 'default' );
+		$default = wp_theme_has_theme_json();
+
+		// Switch to a theme that does have support.
+		switch_theme( 'block-theme' );
+		$block_theme = wp_theme_has_theme_json();
+
+		$this->assertFalse( $default );
+		$this->assertTrue( $block_theme );
+	}
+}