function et_theme_builder_api_save() {
	et_builder_security_check( 'theme_builder', 'edit_others_posts', 'et_theme_builder_api_save', 'nonce' );

	// phpcs:disable WordPress.Security.NonceVerification.Missing -- Nonce is done in `et_builder_security_check`.
	$_                   = et_();
	$live                = '1' === $_->array_get( $_POST, 'live', '0' );
	$first_request       = '1' === $_->array_get( $_POST, 'first_request', '1' );
	$last_request        = '1' === $_->array_get( $_POST, 'last_request', '1' );
	$templates           = wp_unslash( $_->array_get( $_POST, 'templates', array() ) );
	$processed_templates = wp_unslash( $_->array_get( $_POST, 'processed_templates', array() ) );
	$library_tb_id       = (int) $_->array_get( $_POST, 'library_theme_builder_id', 0 );
	$library_item_id     = (int) $_->array_get( $_POST, 'library_item_id', 0 );
	$theme_builder_id    = $library_tb_id ? $library_tb_id : et_theme_builder_get_theme_builder_post_id( $live, true );
	$has_default         = '1' === $_->array_get( $_POST, 'hasDefault', '0' );
	$updated_ids         = array();
	// phpcs:enable

	// Remove this action as it not necessary when we're saving entire TB.
	// save_post_cb is a heavy operation and significanlty slows down the saving of TB.
	// We remove static page resources after TB save below in this function.
	remove_action( 'save_post', array( 'ET_Core_PageResource', 'save_post_cb' ), 10, 3 );

	$templates_to_process = array();

	// Populate the templates.
	foreach ( $templates as $index => $template ) {
		$templates_to_process[ $_->array_get( $template, 'id', 'unsaved_' . $index ) ] = $template;
	}

	$affected_templates = array();

	// Update or insert templates.
	foreach ( $templates_to_process as $template ) {
		$raw_post_id = $_->array_get( $template, 'id', 0 );
		$post_id     = is_numeric( $raw_post_id ) ? (int) $raw_post_id : 0;
		$new_post_id = et_theme_builder_store_template( $theme_builder_id, $template, ! $has_default );

		if ( ! $new_post_id ) {
			continue;
		}

		$is_default = get_post_meta( $new_post_id, '_et_default', true ) === '1';

		if ( $is_default ) {
			$has_default = true;
		}

		// Add template ID into $affected_templates for later use
		// to Add mapping template ID to theme builder ID
		// and delete existing template mapping.
		$affected_templates[] = array(
			'raw'         => $raw_post_id,
			'normalized'  => $post_id,
			'new_post_id' => $new_post_id,
		);
	}

	foreach ( $affected_templates as $template_pair ) {
		if ( $template_pair['normalized'] !== $template_pair['new_post_id'] ) {
			$updated_ids[ $template_pair['raw'] ] = $template_pair['new_post_id'];
		}
	}

	if ( $last_request ) {
		$existing_templates = get_post_meta( $theme_builder_id, '_et_template', false );

		if ( $existing_templates ) {
			// Store existing template mapping as backup to avoid data lost
			// when user interrupting the saving process before completed.
			update_option( 'et_tb_templates_backup_' . $theme_builder_id, $existing_templates );
		}

		// Delete existing template mapping.
		delete_post_meta( $theme_builder_id, '_et_template' );

		$processed_templates = array_merge( $processed_templates, $affected_templates );

		// Insert new template mapping.
		foreach ( $processed_templates as $template_pair ) {
			add_post_meta( $theme_builder_id, '_et_template', $template_pair['new_post_id'] );
		}

		// Delete existing template mapping backup.
		delete_option( 'et_tb_templates_backup_' . $theme_builder_id );

		if ( $live ) {
			et_theme_builder_trash_draft_and_unused_posts();
		}

		et_theme_builder_clear_wp_cache( 'all' );

		// Clear all CSS cache files when Theme Builder templates are saved.
		// Theme builder CSS files include layout IDs in the filename (e.g., et-core-unified-tb-285804-tb-285806-279784.min),
		// so we need to clear all CSS files to ensure files with these layout IDs are removed.
		ET_Core_PageResource::remove_static_resources( 'all', 'all' );
	}

	// Edit Template and Edit Preset: Save the templates into local library.
	if ( $library_tb_id && $library_item_id ) {
		et_theme_builder_update_library_item( $library_item_id, $templates );
	}

	// Add this action back.
	add_action( 'save_post', array( 'ET_Core_PageResource', 'save_post_cb' ), 10, 3 );

	wp_send_json_success(
		array(
			'updatedTemplateIds'     => (object) $updated_ids,
			'processedTemplatesData' => (object) $affected_templates,
			'hasDefault'             => $has_default ? '1' : '0',
		)
	);
}