diff --git a/src/wp-includes/interactivity-api/class-wp-interactivity-api.php b/src/wp-includes/interactivity-api/class-wp-interactivity-api.php
index 8a2bc3467566a..e621bc5c2393a 100644
--- a/src/wp-includes/interactivity-api/class-wp-interactivity-api.php
+++ b/src/wp-includes/interactivity-api/class-wp-interactivity-api.php
@@ -401,9 +401,9 @@ public function register_script_modules() {
 	 * @since 6.9.0 Adds support for client-side navigation in script modules.
 	 */
 	public function add_hooks() {
-		add_filter( 'script_module_data_@wordpress/interactivity', array( $this, 'filter_script_module_interactivity_data' ) );
-		add_filter( 'script_module_data_@wordpress/interactivity-router', array( $this, 'filter_script_module_interactivity_router_data' ) );
-		add_filter( 'wp_script_attributes', array( $this, 'add_load_on_client_navigation_attribute_to_script_modules' ) );
+		add_filter( 'script_module_data_@wordpress/interactivity', 'wp_interactivity_script_module_data' );
+		add_filter( 'script_module_data_@wordpress/interactivity-router', 'wp_interactivity_router_script_module_data' );
+		add_filter( 'wp_script_attributes', 'wp_interactivity_script_module_attributes' );
 	}
 
 	/**
@@ -1516,7 +1516,7 @@ private function data_wp_router_region_processor( WP_Interactivity_API_Directive
 			wp_enqueue_style( 'wp-interactivity-router-animations' );
 
 			// Adds the necessary markup to the footer.
-			add_action( 'wp_footer', array( $this, 'print_router_markup' ) );
+			add_action( 'wp_footer', 'wp_interactivity_print_router_markup' );
 		}
 	}
 
diff --git a/src/wp-includes/interactivity-api/interactivity-api.php b/src/wp-includes/interactivity-api/interactivity-api.php
index 105f3f6f29c18..7de5d77191e41 100644
--- a/src/wp-includes/interactivity-api/interactivity-api.php
+++ b/src/wp-includes/interactivity-api/interactivity-api.php
@@ -138,3 +138,56 @@ function wp_interactivity_get_context( ?string $store_namespace = null ): array
 function wp_interactivity_get_element(): ?array {
 	return wp_interactivity()->get_element();
 }
+
+/**
+ * Filters the data for the `@wordpress/interactivity` script module.
+ *
+ * @since 7.2.0
+ *
+ * @see WP_Interactivity_API::filter_script_module_interactivity_data()
+ *
+ * @param array $data Data to filter.
+ * @return array Data for the Interactivity API script module.
+ */
+function wp_interactivity_script_module_data( array $data ): array {
+	return wp_interactivity()->filter_script_module_interactivity_data( $data );
+}
+
+/**
+ * Filters the data for the `@wordpress/interactivity-router` script module.
+ *
+ * @since 7.2.0
+ *
+ * @see WP_Interactivity_API::filter_script_module_interactivity_router_data()
+ *
+ * @param array $data Data to filter.
+ * @return array Data for the Interactivity Router script module.
+ */
+function wp_interactivity_router_script_module_data( array $data ): array {
+	return wp_interactivity()->filter_script_module_interactivity_router_data( $data );
+}
+
+/**
+ * Adds the `data-wp-router-options` attribute to script modules that support client-side navigation.
+ *
+ * @since 7.2.0
+ *
+ * @see WP_Interactivity_API::add_load_on_client_navigation_attribute_to_script_modules()
+ *
+ * @param array<string, string|true>|mixed $attributes The script tag attributes.
+ * @return array The modified script tag attributes.
+ */
+function wp_interactivity_script_module_attributes( $attributes ) {
+	return wp_interactivity()->add_load_on_client_navigation_attribute_to_script_modules( $attributes );
+}
+
+/**
+ * Outputs markup for the `@wordpress/interactivity-router` script module.
+ *
+ * @since 7.2.0
+ *
+ * @see WP_Interactivity_API::print_router_markup()
+ */
+function wp_interactivity_print_router_markup(): void {
+	wp_interactivity()->print_router_markup();
+}
diff --git a/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php
index 9d5a4024fc6c9..21ff26a787bd2 100644
--- a/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php
+++ b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php
@@ -19,12 +19,28 @@ class Tests_Interactivity_API_WpInteractivityAPI extends WP_UnitTestCase {
 	 */
 	protected $interactivity;
 
+	/**
+	 * Original global WP_Interactivity_API instance.
+	 *
+	 * @var WP_Interactivity_API|null
+	 */
+	protected $original_wp_interactivity;
+
 	/**
 	 * Set up.
 	 */
 	public function set_up() {
+		global $wp_interactivity;
 		parent::set_up();
 		$this->interactivity = new WP_Interactivity_API();
+
+		/*
+		 * The hooks added by `add_hooks()` operate on the global instance, so the
+		 * test instance must be the global one for those hooks to see its data.
+		 */
+		$this->original_wp_interactivity = $wp_interactivity;
+		$wp_interactivity                = $this->interactivity;
+
 		wp_default_script_modules();
 		$this->interactivity->add_hooks();
 	}
@@ -33,9 +49,10 @@ public function set_up() {
 	 * Tear down.
 	 */
 	public function tear_down() {
-		global $wp_script_modules;
+		global $wp_script_modules, $wp_interactivity;
 		parent::tear_down();
 		$wp_script_modules = null;
+		$wp_interactivity  = $this->original_wp_interactivity;
 	}
 
 	public function charset_iso_8859_1() {
@@ -2363,4 +2380,27 @@ public function test_add_client_navigation_support_to_script_module() {
 		$this->assertSame( 'unmarked-module-js-module', $p->get_attribute( 'id' ) );
 		$this->assertNull( $p->get_attribute( 'data-wp-router-options' ) );
 	}
+
+	/**
+	 * Tests that the callbacks added by `add_hooks()` read the current global
+	 * WP_Interactivity_API instance when they run.
+	 *
+	 * @ticket 66100
+	 * @covers WP_Interactivity_API::add_hooks
+	 */
+	public function test_add_hooks_callbacks_read_the_current_global_instance() {
+		global $wp_interactivity;
+
+		// set_up() registered the hooks on the instance that is the global.
+		$wp_interactivity = new WP_Interactivity_API();
+		wp_interactivity_state( 'test-hooks-global', array( 'value' => 'from-current-global' ) );
+
+		$data = apply_filters( 'script_module_data_@wordpress/interactivity', array() ); // phpcs:ignore WordPress.NamingConventions.ValidHookName.UseUnderscores
+
+		$this->assertSame(
+			array( 'state' => array( 'test-hooks-global' => array( 'value' => 'from-current-global' ) ) ),
+			$data,
+			'The filter callbacks added by add_hooks() must read the current global WP_Interactivity_API instance.'
+		);
+	}
 }