diff --git a/includes/class-psa-directory-api.php b/includes/class-psa-directory-api.php
new file mode 100644
index 0000000..1abbad7
--- /dev/null
+++ b/includes/class-psa-directory-api.php
@@ -0,0 +1,159 @@
+<?php
+/**
+ * REST API endpoint for the browsable peptide directory.
+ *
+ * What: GET /v1/compounds — paginated, filterable compound listing with basic/full field sets.
+ * Who calls it: PSA_Directory::init() registers the REST route; frontend JS fetches data.
+ * Dependencies: PSA_Post_Type (meta fields, taxonomy), PSA_Directory (constants).
+ *
+ * @package PeptideSearchAI
+ * @since   4.5.0
+ * @see     includes/class-psa-directory.php    — Shortcode rendering, hook registration.
+ * @see     assets/js/psa-directory.js           — Frontend grid, filter, modal logic.
+ */
+declare( strict_types=1 );
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+class PSA_Directory_API {
+
+	/**
+	 * Register the /v1/compounds endpoint. Public (no auth) — rate limiting at server/CDN level.
+	 */
+	public static function register_rest_routes(): void {
+		register_rest_route( 'peptide-search-ai/v1', '/compounds', array(
+			'methods'             => 'GET',
+			'callback'            => array( __CLASS__, 'rest_compounds' ),
+			'permission_callback' => '__return_true',
+			'args'                => array(
+				'search'   => array( 'type' => 'string', 'sanitize_callback' => 'sanitize_text_field', 'default' => '' ),
+				'category' => array( 'type' => 'string', 'sanitize_callback' => 'sanitize_text_field', 'default' => '' ),
+				'fields'   => array( 'type' => 'string', 'enum' => array( 'basic', 'full' ), 'default' => 'full' ),
+				'page'     => array( 'type' => 'integer', 'default' => 1, 'minimum' => 1, 'sanitize_callback' => 'absint' ),
+				'per_page' => array( 'type' => 'integer', 'default' => PSA_Directory::PER_PAGE_DEFAULT, 'minimum' => 1, 'maximum' => PSA_Directory::PER_PAGE_MAX, 'sanitize_callback' => 'absint' ),
+			),
+		) );
+	}
+
+	/**
+	 * REST callback for GET /v1/compounds.
+	 * Supports search, category filtering, pagination, and basic/full field sets.
+	 *
+	 * @param WP_REST_Request $request The REST request.
+	 * @return WP_REST_Response
+	 */
+	public static function rest_compounds( $request ) {
+		$search   = $request->get_param( 'search' );
+		$category = $request->get_param( 'category' );
+		$fields   = $request->get_param( 'fields' );
+		$page     = max( 1, (int) $request->get_param( 'page' ) );
+		$per_page = min( PSA_Directory::PER_PAGE_MAX, max( 1, (int) $request->get_param( 'per_page' ) ) );
+
+		$query_args = array(
+			'post_type'      => 'peptide',
+			'post_status'    => 'publish',
+			'posts_per_page' => $per_page,
+			'paged'          => $page,
+			'orderby'        => 'title',
+			'order'          => 'ASC',
+		);
+
+		if ( ! empty( $search ) ) {
+			$query_args['s'] = $search;
+		}
+
+		if ( ! empty( $category ) ) {
+			$query_args['tax_query'] = array( array(
+				'taxonomy' => 'peptide_category',
+				'field'    => 'slug',
+				'terms'    => $category,
+			) );
+		}
+
+		$query    = new WP_Query( $query_args );
+		$post_ids = wp_list_pluck( $query->posts, 'ID' );
+		if ( ! empty( $post_ids ) ) {
+			update_meta_cache( 'post', $post_ids );
+		}
+
+		$compounds = array();
+		foreach ( $query->posts as $post ) {
+			$compounds[] = self::format_compound( $post, $fields );
+		}
+
+		$response = new WP_REST_Response( array(
+			'compounds'   => $compounds,
+			'total'       => (int) $query->found_posts,
+			'total_pages' => (int) $query->max_num_pages,
+			'page'        => $page,
+			'per_page'    => $per_page,
+		), 200 );
+
+		$response->header( 'X-WP-Total', (string) $query->found_posts );
+		$response->header( 'X-WP-TotalPages', (string) $query->max_num_pages );
+
+		return $response;
+	}
+
+	/**
+	 * Format a single compound for REST response.
+	 *
+	 * @param WP_Post $post   The peptide post.
+	 * @param string  $fields 'basic' for lightweight data, 'full' for everything.
+	 * @return array Formatted compound data.
+	 */
+	public static function format_compound( $post, string $fields = 'full' ): array {
+		$id = $post->ID;
+
+		$terms      = wp_get_object_terms( $id, 'peptide_category', array( 'fields' => 'all' ) );
+		$categories = array();
+		if ( ! is_wp_error( $terms ) ) {
+			foreach ( $terms as $term ) {
+				$categories[] = array( 'slug' => $term->slug, 'name' => $term->name );
+			}
+		}
+
+		$basic = array(
+			'id'         => $id,
+			'name'       => $post->post_title,
+			'slug'       => $post->post_name,
+			'url'        => get_permalink( $id ),
+			'categories' => $categories,
+			'half_life'  => get_post_meta( $id, 'psa_half_life', true ),
+			'stability'  => get_post_meta( $id, 'psa_stability', true ),
+			'source'     => get_post_meta( $id, 'psa_source', true ),
+			'extras'     => apply_filters( 'psa_directory_card_extras', '', $id ),
+		);
+
+		if ( 'basic' === $fields ) {
+			$basic['vial_size_mg'] = get_post_meta( $id, 'psa_vial_size_mg', true );
+			return $basic;
+		}
+
+		$full = array_merge( $basic, array(
+			'excerpt'               => wp_trim_words( $post->post_content, 30 ),
+			'description'           => wp_trim_words( $post->post_content, 80 ),
+			'sequence'              => get_post_meta( $id, 'psa_sequence', true ),
+			'molecular_weight'      => get_post_meta( $id, 'psa_molecular_weight', true ),
+			'molecular_formula'     => get_post_meta( $id, 'psa_molecular_formula', true ),
+			'aliases'               => get_post_meta( $id, 'psa_aliases', true ),
+			'mechanism'             => get_post_meta( $id, 'psa_mechanism', true ),
+			'research_apps'         => get_post_meta( $id, 'psa_research_apps', true ),
+			'safety_profile'        => get_post_meta( $id, 'psa_safety_profile', true ),
+			'dosage_info'           => get_post_meta( $id, 'psa_dosage_info', true ),
+			'references'            => get_post_meta( $id, 'psa_references', true ),
+			'pubchem_cid'           => get_post_meta( $id, 'psa_pubchem_cid', true ),
+			'solubility'            => get_post_meta( $id, 'psa_solubility', true ),
+			'vial_size_mg'          => get_post_meta( $id, 'psa_vial_size_mg', true ),
+			'storage_lyophilized'   => get_post_meta( $id, 'psa_storage_lyophilized', true ),
+			'storage_reconstituted' => get_post_meta( $id, 'psa_storage_reconstituted', true ),
+			'typical_dose_mcg'      => get_post_meta( $id, 'psa_typical_dose_mcg', true ),
+			'cycle_parameters'      => get_post_meta( $id, 'psa_cycle_parameters', true ),
+			'amino_acid_count'      => get_post_meta( $id, 'psa_amino_acid_count', true ),
+		) );
+
+		return apply_filters( 'psa_rest_compound_data', $full, $id );
+	}
+}
diff --git a/includes/class-psa-directory.php b/includes/class-psa-directory.php
index cef5c10..3a57d8c 100755
--- a/includes/class-psa-directory.php
+++ b/includes/class-psa-directory.php
@@ -1,15 +1,16 @@
 <?php
 /**
- * Browsable peptide directory — REST endpoint, shortcode, and data formatting.
+ * Browsable peptide directory — shortcode rendering and hook registration.
  *
- * What: Provides the [peptide_directory] shortcode and GET /v1/compounds REST endpoint.
- * Who calls it: WordPress shortcode parser, REST API router, main plugin file via PSA_Directory::init().
- * Dependencies: PSA_Post_Type (meta fields, taxonomy), PSA_Config.
+ * What: Provides the [peptide_directory] shortcode and delegates REST to PSA_Directory_API.
+ * Who calls it: WordPress shortcode parser, main plugin file via PSA_Directory::init().
+ * Dependencies: PSA_Directory_API (REST endpoint), frontend JS/CSS.
  *
  * @package PeptideSearchAI
- * @see     includes/class-psa-post-type.php   — CPT + taxonomy registration, meta keys
- * @see     includes/class-psa-search.php      — existing search shortcode (separate from directory)
- * @see     assets/js/psa-directory.js          — frontend grid, filter, modal logic
+ * @since   4.0.0
+ * @see     includes/class-psa-directory-api.php — REST endpoint and compound formatting.
+ * @see     assets/js/psa-directory.js            — Frontend grid, filter, modal logic.
+ * @see     assets/css/psa-directory.css           — Directory-specific styles.
  */
 declare( strict_types=1 );
 
@@ -23,286 +24,71 @@ class PSA_Directory {
 	const PER_PAGE_DEFAULT = 12;
 	const PER_PAGE_MAX     = 100;
 
-	/**
-	 * Register hooks.
-	 */
+	/** Register hooks. */
 	public static function init(): void {
 		add_shortcode( 'peptide_directory', array( __CLASS__, 'render_shortcode' ) );
-		add_action( 'rest_api_init', array( __CLASS__, 'register_rest_routes' ) );
+		add_action( 'rest_api_init', array( 'PSA_Directory_API', 'register_rest_routes' ) );
 	}
 
-	// -------------------------------------------------------------------------
-	// REST API
-	// -------------------------------------------------------------------------
-
-	/**
-	 * Register the /v1/compounds endpoint for directory listing and cross-plugin data access.
-	 *
-	 * Public endpoint (no auth required) — serves the browsable directory.
-	 * Rate limiting should be handled at the server/CDN level.
-	 */
-	public static function register_rest_routes(): void {
-		register_rest_route(
-			'peptide-search-ai/v1',
-			'/compounds',
-			array(
-				'methods'             => 'GET',
-				'callback'            => array( __CLASS__, 'rest_compounds' ),
-				'permission_callback' => '__return_true',
-				'args'                => array(
-					'search'   => array(
-						'type'              => 'string',
-						'sanitize_callback' => 'sanitize_text_field',
-						'default'           => '',
-					),
-					'category' => array(
-						'type'              => 'string',
-						'sanitize_callback' => 'sanitize_text_field',
-						'default'           => '',
-					),
-					'fields'   => array(
-						'type'              => 'string',
-						'enum'              => array( 'basic', 'full' ),
-						'default'           => 'full',
-					),
-					'page'     => array(
-						'type'              => 'integer',
-						'default'           => 1,
-						'minimum'           => 1,
-						'sanitize_callback' => 'absint',
-					),
-					'per_page' => array(
-						'type'              => 'integer',
-						'default'           => self::PER_PAGE_DEFAULT,
-						'minimum'           => 1,
-						'maximum'           => self::PER_PAGE_MAX,
-						'sanitize_callback' => 'absint',
-					),
-				),
-			)
-		);
-	}
-
-	/**
-	 * REST callback for GET /v1/compounds.
-	 *
-	 * Supports search, category filtering, pagination, and basic/full field sets.
-	 *
-	 * @param WP_REST_Request $request The REST request.
-	 * @return WP_REST_Response
-	 */
-	public static function rest_compounds( $request ) {
-		$search   = $request->get_param( 'search' );
-		$category = $request->get_param( 'category' );
-		$fields   = $request->get_param( 'fields' );
-		$page     = max( 1, (int) $request->get_param( 'page' ) );
-		$per_page = min( self::PER_PAGE_MAX, max( 1, (int) $request->get_param( 'per_page' ) ) );
-
-		$query_args = array(
-			'post_type'      => 'peptide',
-			'post_status'    => 'publish',
-			'posts_per_page' => $per_page,
-			'paged'          => $page,
-			'orderby'        => 'title',
-			'order'          => 'ASC',
-		);
-
-		// Search filter: title and alias matching.
-		if ( ! empty( $search ) ) {
-			$query_args['s'] = $search;
-		}
-
-		// Category filter: taxonomy query.
-		if ( ! empty( $category ) ) {
-			$query_args['tax_query'] = array(
-				array(
-					'taxonomy' => 'peptide_category',
-					'field'    => 'slug',
-					'terms'    => $category,
-				),
-			);
-		}
-
-		$query = new WP_Query( $query_args );
-
-		// Prime caches for performance.
-		$post_ids = wp_list_pluck( $query->posts, 'ID' );
-		if ( ! empty( $post_ids ) ) {
-			update_meta_cache( 'post', $post_ids );
-		}
-
-		$compounds = array();
-		foreach ( $query->posts as $post ) {
-			$compounds[] = self::format_compound( $post, $fields );
-		}
-
-		$response_data = array(
-			'compounds'  => $compounds,
-			'total'      => (int) $query->found_posts,
-			'total_pages' => (int) $query->max_num_pages,
-			'page'       => $page,
-			'per_page'   => $per_page,
-		);
-
-		$response = new WP_REST_Response( $response_data, 200 );
-
-		// Pagination headers for client convenience.
-		$response->header( 'X-WP-Total', (string) $query->found_posts );
-		$response->header( 'X-WP-TotalPages', (string) $query->max_num_pages );
-
-		return $response;
-	}
-
-	/**
-	 * Format a single compound for REST response.
-	 *
-	 * @param WP_Post $post   The peptide post.
-	 * @param string  $fields 'basic' for lightweight data, 'full' for everything.
-	 * @return array Formatted compound data.
-	 */
-	public static function format_compound( $post, string $fields = 'full' ): array {
-		$post_id = $post->ID;
-
-		// Get category terms.
-		$terms      = wp_get_object_terms( $post_id, 'peptide_category', array( 'fields' => 'all' ) );
-		$categories = array();
-		if ( ! is_wp_error( $terms ) ) {
-			foreach ( $terms as $term ) {
-				$categories[] = array(
-					'slug' => $term->slug,
-					'name' => $term->name,
-				);
-			}
-		}
-
-		$basic = array(
-			'id'         => $post_id,
-			'name'       => $post->post_title,
-			'slug'       => $post->post_name,
-			'url'        => get_permalink( $post_id ),
-			'categories' => $categories,
-			'half_life'  => get_post_meta( $post_id, 'psa_half_life', true ),
-			'stability'  => get_post_meta( $post_id, 'psa_stability', true ),
-			'source'     => get_post_meta( $post_id, 'psa_source', true ),
-		);
-
-		// Allow other plugins to add data to directory cards (e.g., observation count).
-		$basic['extras'] = apply_filters( 'psa_directory_card_extras', '', $post_id );
-
-		if ( 'basic' === $fields ) {
-			// Lightweight response for cross-plugin use.
-			$basic['vial_size_mg'] = get_post_meta( $post_id, 'psa_vial_size_mg', true );
-			return $basic;
-		}
-
-		// Full response: merge in all meta for detail modal.
-		$full = array_merge(
-			$basic,
-			array(
-				'excerpt'              => wp_trim_words( $post->post_content, 30 ),
-				'description'          => wp_trim_words( $post->post_content, 80 ),
-				'sequence'             => get_post_meta( $post_id, 'psa_sequence', true ),
-				'molecular_weight'     => get_post_meta( $post_id, 'psa_molecular_weight', true ),
-				'molecular_formula'    => get_post_meta( $post_id, 'psa_molecular_formula', true ),
-				'aliases'              => get_post_meta( $post_id, 'psa_aliases', true ),
-				'mechanism'            => get_post_meta( $post_id, 'psa_mechanism', true ),
-				'research_apps'        => get_post_meta( $post_id, 'psa_research_apps', true ),
-				'safety_profile'       => get_post_meta( $post_id, 'psa_safety_profile', true ),
-				'dosage_info'          => get_post_meta( $post_id, 'psa_dosage_info', true ),
-				'references'           => get_post_meta( $post_id, 'psa_references', true ),
-				'pubchem_cid'          => get_post_meta( $post_id, 'psa_pubchem_cid', true ),
-				'solubility'           => get_post_meta( $post_id, 'psa_solubility', true ),
-				'vial_size_mg'         => get_post_meta( $post_id, 'psa_vial_size_mg', true ),
-				'storage_lyophilized'  => get_post_meta( $post_id, 'psa_storage_lyophilized', true ),
-				'storage_reconstituted' => get_post_meta( $post_id, 'psa_storage_reconstituted', true ),
-				'typical_dose_mcg'     => get_post_meta( $post_id, 'psa_typical_dose_mcg', true ),
-				'cycle_parameters'     => get_post_meta( $post_id, 'psa_cycle_parameters', true ),
-				'amino_acid_count'     => get_post_meta( $post_id, 'psa_amino_acid_count', true ),
-			)
-		);
-
-		// Allow other plugins (e.g., Peptide Community) to enrich the compound data.
-		$full = apply_filters( 'psa_rest_compound_data', $full, $post_id );
-
-		return $full;
-	}
-
-	// -------------------------------------------------------------------------
-	// Shortcode
-	// -------------------------------------------------------------------------
-
 	/**
 	 * Render the [peptide_directory] shortcode.
+	 * Outputs a container div populated by frontend JS via REST.
 	 *
-	 * Outputs a container div that the frontend JS populates with the card grid.
-	 * Passes REST endpoint URL and category data via wp_localize_script.
-	 *
-	 * @param array $atts Shortcode attributes (unused for now, reserved for future).
+	 * @param array $atts Shortcode attributes (reserved for future use).
 	 * @return string HTML output.
 	 */
 	public static function render_shortcode( $atts ): string {
-		// Get categories for filter buttons.
-		$terms = get_terms(
-			array(
-				'taxonomy'   => 'peptide_category',
-				'hide_empty' => false,
-				'orderby'    => 'name',
-				'order'      => 'ASC',
-			)
-		);
+		$terms = get_terms( array(
+			'taxonomy'   => 'peptide_category',
+			'hide_empty' => false,
+			'orderby'    => 'name',
+			'order'      => 'ASC',
+		) );
 
 		$categories = array();
 		if ( ! is_wp_error( $terms ) ) {
 			foreach ( $terms as $term ) {
-				$categories[] = array(
-					'slug' => $term->slug,
-					'name' => $term->name,
-				);
+				$categories[] = array( 'slug' => $term->slug, 'name' => $term->name );
 			}
 		}
 
-		// Localize script data for the directory JS.
-		wp_localize_script(
-			'psa-directory',
-			'psaDirectory',
-			array(
-				'restUrl'    => esc_url_raw( rest_url( 'peptide-search-ai/v1/compounds' ) ),
-				'nonce'      => wp_create_nonce( 'wp_rest' ),
-				'categories' => $categories,
-				'perPage'    => self::PER_PAGE_DEFAULT,
-				'i18n'       => array(
-					'title'        => __( 'Peptide Directory', 'peptide-search-ai' ),
-					'subtitle'     => __( 'Browse reagents with detailed research parameters.', 'peptide-search-ai' ),
-					'searchPlaceholder' => __( 'Search peptides...', 'peptide-search-ai' ),
-					'showAll'      => __( 'Show All', 'peptide-search-ai' ),
-					'loadMore'     => __( 'Load More', 'peptide-search-ai' ),
-					'loading'      => __( 'Loading...', 'peptide-search-ai' ),
-					'noResults'    => __( 'No peptides found matching your criteria.', 'peptide-search-ai' ),
-					'viewDetails'  => __( 'View Research Details', 'peptide-search-ai' ),
-					'viewFullPage' => __( 'View Full Page', 'peptide-search-ai' ),
-					'close'        => __( 'Close', 'peptide-search-ai' ),
-					'halfLife'     => __( 'Half-Life', 'peptide-search-ai' ),
-					'stability'    => __( 'Stability', 'peptide-search-ai' ),
-					'solubility'   => __( 'Solubility', 'peptide-search-ai' ),
-					'vialSize'     => __( 'Vial Size', 'peptide-search-ai' ),
-					'storageLyo'   => __( 'Storage (Lyophilized)', 'peptide-search-ai' ),
-					'storageRecon' => __( 'Storage (Reconstituted)', 'peptide-search-ai' ),
-					'molecularWeight' => __( 'Molecular Weight', 'peptide-search-ai' ),
-					'formula'      => __( 'Formula', 'peptide-search-ai' ),
-					'typicalDose'  => __( 'Typical Dose', 'peptide-search-ai' ),
-					'cycleParams'  => __( 'Cycle Parameters', 'peptide-search-ai' ),
-					'sequence'     => __( 'Sequence', 'peptide-search-ai' ),
-					'singleReagents'   => __( 'Single Reagents', 'peptide-search-ai' ),
-					'protocolModels'   => __( 'Protocol Models', 'peptide-search-ai' ),
-					'comingSoon'       => __( 'Coming Soon', 'peptide-search-ai' ),
-					'researchParams'   => __( 'Research Parameters', 'peptide-search-ai' ),
-					'communityObs'     => __( 'Community Observations', 'peptide-search-ai' ),
-					'pubchemLink'      => __( 'View on PubChem', 'peptide-search-ai' ),
-					'copySequence'     => __( 'Copy', 'peptide-search-ai' ),
-					'copied'           => __( 'Copied!', 'peptide-search-ai' ),
-				),
-			)
-		);
+		wp_localize_script( 'psa-directory', 'psaDirectory', array(
+			'restUrl'    => esc_url_raw( rest_url( 'peptide-search-ai/v1/compounds' ) ),
+			'nonce'      => wp_create_nonce( 'wp_rest' ),
+			'categories' => $categories,
+			'perPage'    => self::PER_PAGE_DEFAULT,
+			'i18n'       => array(
+				'title'            => __( 'Peptide Directory', 'peptide-search-ai' ),
+				'subtitle'         => __( 'Browse reagents with detailed research parameters.', 'peptide-search-ai' ),
+				'searchPlaceholder' => __( 'Search peptides...', 'peptide-search-ai' ),
+				'showAll'          => __( 'Show All', 'peptide-search-ai' ),
+				'loadMore'         => __( 'Load More', 'peptide-search-ai' ),
+				'loading'          => __( 'Loading...', 'peptide-search-ai' ),
+				'noResults'        => __( 'No peptides found matching your criteria.', 'peptide-search-ai' ),
+				'viewDetails'      => __( 'View Research Details', 'peptide-search-ai' ),
+				'viewFullPage'     => __( 'View Full Page', 'peptide-search-ai' ),
+				'close'            => __( 'Close', 'peptide-search-ai' ),
+				'halfLife'         => __( 'Half-Life', 'peptide-search-ai' ),
+				'stability'        => __( 'Stability', 'peptide-search-ai' ),
+				'solubility'       => __( 'Solubility', 'peptide-search-ai' ),
+				'vialSize'         => __( 'Vial Size', 'peptide-search-ai' ),
+				'storageLyo'       => __( 'Storage (Lyophilized)', 'peptide-search-ai' ),
+				'storageRecon'     => __( 'Storage (Reconstituted)', 'peptide-search-ai' ),
+				'molecularWeight'  => __( 'Molecular Weight', 'peptide-search-ai' ),
+				'formula'          => __( 'Formula', 'peptide-search-ai' ),
+				'typicalDose'      => __( 'Typical Dose', 'peptide-search-ai' ),
+				'cycleParams'      => __( 'Cycle Parameters', 'peptide-search-ai' ),
+				'sequence'         => __( 'Sequence', 'peptide-search-ai' ),
+				'singleReagents'   => __( 'Single Reagents', 'peptide-search-ai' ),
+				'protocolModels'   => __( 'Protocol Models', 'peptide-search-ai' ),
+				'comingSoon'       => __( 'Coming Soon', 'peptide-search-ai' ),
+				'researchParams'   => __( 'Research Parameters', 'peptide-search-ai' ),
+				'communityObs'     => __( 'Community Observations', 'peptide-search-ai' ),
+				'pubchemLink'      => __( 'View on PubChem', 'peptide-search-ai' ),
+				'copySequence'     => __( 'Copy', 'peptide-search-ai' ),
+				'copied'           => __( 'Copied!', 'peptide-search-ai' ),
+			),
+		) );
 
 		ob_start();
 		?>
@@ -314,4 +100,15 @@ class PSA_Directory {
 		<?php
 		return ob_get_clean();
 	}
+
+	// ── Backward-compatible proxies (REST moved to PSA_Directory_API) ───
+
+	/** @see PSA_Directory_API::register_rest_routes() */
+	public static function register_rest_routes(): void { PSA_Directory_API::register_rest_routes(); }
+
+	/** @see PSA_Directory_API::rest_compounds() */
+	public static function rest_compounds( $request ) { return PSA_Directory_API::rest_compounds( $request ); }
+
+	/** @see PSA_Directory_API::format_compound() */
+	public static function format_compound( $post, string $fields = 'full' ): array { return PSA_Directory_API::format_compound( $post, $fields ); }
 }
diff --git a/peptide-search-ai.php b/peptide-search-ai.php
index 5142a8d..4acb4c5 100755
--- a/peptide-search-ai.php
+++ b/peptide-search-ai.php
@@ -37,6 +37,7 @@ require_once PSA_PLUGIN_DIR . 'includes/class-psa-admin-page.php';
 require_once PSA_PLUGIN_DIR . 'includes/class-psa-admin.php';
 require_once PSA_PLUGIN_DIR . 'includes/class-psa-batch-enrichment.php';
 require_once PSA_PLUGIN_DIR . 'includes/class-psa-template.php';
+require_once PSA_PLUGIN_DIR . 'includes/class-psa-directory-api.php';
 require_once PSA_PLUGIN_DIR . 'includes/class-psa-directory.php';
 require_once PSA_PLUGIN_DIR . 'includes/class-psa-upgrade.php';