diff --git a/includes/pmid.php b/includes/pmid.php
deleted file mode 100644
index e6a371e..0000000
--- a/includes/pmid.php
+++ /dev/null
@@ -1,175 +0,0 @@
-<?php
-/**
- * PubMed/PMID resolver REST endpoint and cache helpers.
- *
- * @package BibliographyBuilder
- */
-
-if ( ! defined( 'ABSPATH' ) ) {
-	exit;
-}
-
-/**
- * Build a bounded cache key for PMID resolver responses.
- *
- * @param string $pmid PubMed ID.
- * @return string
- */
-function bibliography_builder_get_pmid_cache_key( $pmid ) {
-	return 'bibliography_builder_pmid_' . md5( (string) $pmid );
-}
-
-/**
- * Read a cached PMID resolver response when WordPress transients are available.
- *
- * @param string $pmid PubMed ID.
- * @return array|null
- */
-function bibliography_builder_get_cached_pmid_response( $pmid ) {
-	if ( ! function_exists( 'get_transient' ) ) {
-		return null;
-	}
-
-	$cached = get_transient( bibliography_builder_get_pmid_cache_key( $pmid ) );
-
-	return is_array( $cached ) ? $cached : null;
-}
-
-/**
- * Cache a PMID resolver response when WordPress transients are available.
- *
- * @param string $pmid  PubMed ID.
- * @param array  $value Cache payload.
- * @param int    $ttl   Cache TTL in seconds.
- * @return void
- */
-function bibliography_builder_set_cached_pmid_response( $pmid, $value, $ttl ) {
-	if ( ! function_exists( 'set_transient' ) ) {
-		return;
-	}
-
-	set_transient( bibliography_builder_get_pmid_cache_key( $pmid ), $value, $ttl );
-}
-
-/**
- * Permission callback for editor-only PMID resolver requests.
- *
- * @return true|WP_Error
- */
-function bibliography_builder_rest_pmid_permissions_check() {
-	if ( current_user_can( 'edit_posts' ) ) {
-		return true;
-	}
-
-	return new WP_Error(
-		'bibliography_builder_pmid_forbidden',
-		__( 'Sorry, you are not allowed to resolve PubMed citations.', 'borges-bibliography-builder' ),
-		array( 'status' => 403 )
-	);
-}
-
-/**
- * REST callback that resolves a PubMed ID to CSL-JSON.
- *
- * NCBI's CSL endpoint does not currently emit browser CORS headers, so editor
- * requests are proxied through WordPress using a fixed URL and numeric PMID.
- *
- * @param WP_REST_Request $request REST request.
- * @return WP_REST_Response|WP_Error
- */
-function bibliography_builder_rest_resolve_pmid( WP_REST_Request $request ) {
-	$pmid = isset( $request['pmid'] ) ? (string) $request['pmid'] : '';
-
-	if ( ! preg_match( '/^\d{1,8}$/', $pmid ) ) {
-		return new WP_Error(
-			'bibliography_builder_pmid_invalid',
-			__( 'Invalid PubMed ID.', 'borges-bibliography-builder' ),
-			array( 'status' => 400 )
-		);
-	}
-
-	$cached = bibliography_builder_get_cached_pmid_response( $pmid );
-
-	if ( isset( $cached['type'] ) && 'success' === $cached['type'] && isset( $cached['data'] ) && is_array( $cached['data'] ) ) {
-		return rest_ensure_response( $cached['data'] );
-	}
-
-	if ( isset( $cached['type'] ) && 'not_found' === $cached['type'] ) {
-		return new WP_Error(
-			'bibliography_builder_pmid_not_found',
-			__( 'The PubMed ID could not be resolved.', 'borges-bibliography-builder' ),
-			array( 'status' => 404 )
-		);
-	}
-
-	$url      = add_query_arg(
-		array(
-			'format' => 'csl',
-			'id'     => $pmid,
-		),
-		BIBLIOGRAPHY_BUILDER_PUBMED_CSL_API
-	);
-	$response = wp_remote_get(
-		$url,
-		array(
-			'timeout'     => BIBLIOGRAPHY_BUILDER_PUBMED_TIMEOUT,
-			'redirection' => 3,
-		)
-	);
-
-	if ( is_wp_error( $response ) ) {
-		return new WP_Error(
-			'bibliography_builder_pmid_upstream_error',
-			__( 'The PubMed citation service could not be reached.', 'borges-bibliography-builder' ),
-			array( 'status' => 502 )
-		);
-	}
-
-	$status = (int) wp_remote_retrieve_response_code( $response );
-
-	if ( $status < 200 || $status >= 300 ) {
-		if ( 404 === $status ) {
-			bibliography_builder_set_cached_pmid_response(
-				$pmid,
-				array( 'type' => 'not_found' ),
-				BIBLIOGRAPHY_BUILDER_PUBMED_NOT_FOUND_TTL
-			);
-
-			return new WP_Error(
-				'bibliography_builder_pmid_not_found',
-				__( 'The PubMed ID could not be resolved.', 'borges-bibliography-builder' ),
-				array( 'status' => 404 )
-			);
-		}
-
-		return new WP_Error(
-			'bibliography_builder_pmid_upstream_error',
-			__( 'The PubMed citation service returned an error.', 'borges-bibliography-builder' ),
-			array(
-				'status'          => 502,
-				'upstream_status' => $status,
-			)
-		);
-	}
-
-	$decoded = json_decode( wp_remote_retrieve_body( $response ), true );
-
-	if ( ! is_array( $decoded ) || empty( $decoded ) ) {
-		return new WP_Error(
-			'bibliography_builder_pmid_invalid_response',
-			__( 'The PubMed citation service returned an invalid response.', 'borges-bibliography-builder' ),
-			array( 'status' => 502 )
-		);
-	}
-
-	bibliography_builder_set_cached_pmid_response(
-		$pmid,
-		array(
-			'type' => 'success',
-			'data' => $decoded,
-		),
-		BIBLIOGRAPHY_BUILDER_PUBMED_SUCCESS_TTL
-	);
-
-	return rest_ensure_response( $decoded );
-}