diff --git a/index.html b/index.html
index a3f45e8..c0c3c66 100644
--- a/index.html
+++ b/index.html
@@ -27,8 +27,14 @@
             } else {
                 document.documentElement.setAttribute('data-theme', theme);
             }
+
+            // Reload Remarkbox iframe with new theme if it exists
+            var iframe = document.getElementById('remarkbox-iframe');
+            if (iframe && window.buildRbSrc) {
+                iframe.src = buildRbSrc();
+            }
         }
-        
+
         // Disable custom styling for uncloseai.js - use PicoCSS instead
         window.UNCLOSEAI_CUSTOM_STYLING = false;
     </script>
@@ -531,11 +537,30 @@ speech.ai.unturf.com {
             var thread_title = window.document.title;
             var thread_fragment = window.location.hash;
 
-            var rb_src = "https://my.remarkbox.com/embed" +
-                "?rb_owner_key=" + rb_owner_key +
-                "&thread_title=" + encodeURI(thread_title) +
-                "&thread_uri=" + encodeURIComponent(thread_uri) +
-                thread_fragment;
+            function getCurrentTheme() {
+                // Check if data-theme is set on documentElement
+                var theme = document.documentElement.getAttribute('data-theme');
+                if (theme) {
+                    return theme; // 'light' or 'dark'
+                }
+                // If auto, detect system preference
+                if (window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches) {
+                    return 'dark';
+                }
+                return 'light';
+            }
+
+            function buildRbSrc() {
+                var mode = getCurrentTheme();
+                return "https://my.remarkbox.com/embed" +
+                    "?rb_owner_key=" + rb_owner_key +
+                    "&thread_title=" + encodeURI(thread_title) +
+                    "&thread_uri=" + encodeURIComponent(thread_uri) +
+                    "&mode=" + mode +
+                    thread_fragment;
+            }
+
+            var rb_src = buildRbSrc();
 
             function create_remarkbox_iframe() {
                 var ifrm = document.createElement("iframe");