diff --git a/assets/js/calculator.js b/assets/js/calculator.js
old mode 100644
new mode 100755
index 7bc1147..52cdb6f
--- a/assets/js/calculator.js
+++ b/assets/js/calculator.js
@@ -15,6 +15,8 @@
 
 	/* ── Constants ────────────────────────────────────────────────────── */
 
+	// Must match PRC_Math::SYRINGE_UNITS_PER_ML in class-prc-math.php
+	// and prcConfig.syringeUnits in class-prc-shortcode.php.
 	var SYRINGE_UNITS_PER_ML = 100;
 
 	/* ── State ────────────────────────────────────────────────────────── */
diff --git a/includes/class-prc-math.php b/includes/class-prc-math.php
old mode 100644
new mode 100755
index 25fb02e..1d5e8bd
--- a/includes/class-prc-math.php
+++ b/includes/class-prc-math.php
@@ -25,6 +25,10 @@ class PRC_Math {
 
 	/**
 	 * Standard insulin syringe size in units (100 IU = 1 mL).
+	 *
+	 * Mirrored in: assets/js/calculator.js (SYRINGE_UNITS_PER_ML)
+	 * and prcConfig.syringeUnits (class-prc-shortcode.php).
+	 * All three MUST stay in sync.
 	 */
 	private const SYRINGE_UNITS_PER_ML = 100;
 
diff --git a/includes/class-prc-preset-provider.php b/includes/class-prc-preset-provider.php
old mode 100644
new mode 100755
index 9d477d7..a1b08cb
--- a/includes/class-prc-preset-provider.php
+++ b/includes/class-prc-preset-provider.php
@@ -85,6 +85,13 @@ class PRC_Preset_Provider {
 	 * @return array<int, array<string, mixed>>
 	 */
 	private function build_presets_from_pr_core(): array {
+		// Why class_exists: PR_CORE_VERSION constant may be defined but classes
+		// could fail to autoload (e.g. fatal error in PR Core bootstrap).
+		// Fall back to empty array so the caller merges in defaults gracefully.
+		if ( ! class_exists( 'PR_Core_Peptide_Repository' ) || ! class_exists( 'PR_Core_Dosing_Repository' ) ) {
+			return [];
+		}
+
 		$peptide_repo = new PR_Core_Peptide_Repository();
 		$dosing_repo  = new PR_Core_Dosing_Repository();
 
diff --git a/includes/frontend/class-prc-shortcode.php b/includes/frontend/class-prc-shortcode.php
old mode 100644
new mode 100755
index 41e13e8..acaa522
--- a/includes/frontend/class-prc-shortcode.php
+++ b/includes/frontend/class-prc-shortcode.php
@@ -93,13 +93,13 @@ class PRC_Shortcode {
 			true
 		);
 
-		// Pass presets and config to JS.
+		// Pass presets and config to JS — all REST endpoints are public-read,
+		// so no nonce is needed. The restUrl is provided for future use.
 		$provider = new PRC_Preset_Provider();
 		wp_localize_script( 'prc-calculator', 'prcConfig', [
 			'presets'      => $provider->get_all_presets(),
 			'restUrl'      => esc_url_raw( rest_url( 'prc/v1' ) ),
-			'nonce'        => wp_create_nonce( 'wp_rest' ),
-			'syringeUnits' => 100,
+			'syringeUnits' => 100, // Must match PRC_Math::SYRINGE_UNITS_PER_ML and calculator.js SYRINGE_UNITS_PER_ML.
 			'i18n'         => [
 				'selectPeptide'  => __( 'Select a peptide…', 'peptide-reconstitution-calculator' ),
 				'customEntry'    => __( 'Custom / Manual Entry', 'peptide-reconstitution-calculator' ),