diff --git a/package-lock.json b/package-lock.json
index 9c5725c..5fe57c7 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
     "name": "pages",
-    "version": "0.0.3",
+    "version": "0.0.5",
     "lockfileVersion": 3,
     "requires": true,
     "packages": {
         "": {
             "name": "pages",
-            "version": "0.0.3",
+            "version": "0.0.5",
             "license": "MIT",
             "devDependencies": {
                 "@eslint/js": "^10.0.1",
diff --git a/pages/chat/main.ts b/pages/chat/main.ts
index e5c2193..72e98bd 100644
--- a/pages/chat/main.ts
+++ b/pages/chat/main.ts
@@ -26,8 +26,8 @@ const i18n = {
         attrTargetUrlDefault: 'app.doctorina.com',
         attrChildren: 'Child <code>&lt;p&gt;</code> elements: 1 = static placeholder, 2+ = typing animation',
         attrChildrenDefault: 'None',
-        attrParams: 'JSON object of extra query parameters (e.g. UTM tags)',
-        attrParamsDefault: 'None',
+        attrParams: 'JSON object of extra query parameters (e.g. UTM tags). Overrides defaults.',
+        attrParamsDefault: 'utm_medium=user_message',
         examples: 'Examples',
         exBasicTitle: 'Basic Usage',
         exBasicDesc: 'Minimal setup — just add the container and the script:',
@@ -63,8 +63,8 @@ const i18n = {
         attrTargetUrlDefault: 'app.doctorina.com',
         attrChildren: 'Elementos hijos <code>&lt;p&gt;</code>: 1 = placeholder estático, 2+ = animación de escritura',
         attrChildrenDefault: 'Ninguno',
-        attrParams: 'Objeto JSON con parámetros extra (ej. etiquetas UTM)',
-        attrParamsDefault: 'Ninguno',
+        attrParams: 'Objeto JSON con parámetros extra (ej. etiquetas UTM). Sobrescribe los valores predeterminados.',
+        attrParamsDefault: 'utm_medium=user_message',
         examples: 'Ejemplos',
         exBasicTitle: 'Uso básico',
         exBasicDesc: 'Configuración mínima — solo agrega el contenedor y el script:',
@@ -100,8 +100,8 @@ const i18n = {
         attrTargetUrlDefault: 'app.doctorina.com',
         attrChildren: 'Дочерние элементы <code>&lt;p&gt;</code>: 1 = статический placeholder, 2+ = анимация печатания',
         attrChildrenDefault: 'Нет',
-        attrParams: 'JSON-объект с дополнительными query-параметрами (напр. UTM-метки)',
-        attrParamsDefault: 'Нет',
+        attrParams: 'JSON-объект с дополнительными query-параметрами (напр. UTM-метки). Перекрывает значения по умолчанию.',
+        attrParamsDefault: 'utm_medium=user_message',
         examples: 'Примеры',
         exBasicTitle: 'Базовое подключение',
         exBasicDesc: 'Минимальная настройка — только контейнер и скрипт:',
@@ -147,7 +147,7 @@ const SNIPPET_PLACEHOLDER = `<div id="doctorina-chat">
 <script defer src="${WIDGET_HOST}/widget/doctorina-chat.js"></script>`;
 
 const SNIPPET_PARAMS = `<div id="doctorina-chat"
-     data-params='{"utm_source":"website","utm_campaign":"spring"}'>
+     data-params='{"utm_source":"landing","utm_campaign":"spring"}'>
 </div>
 <script defer src="${WIDGET_HOST}/widget/doctorina-chat.js"></script>`;
 
diff --git a/src/widget/tab-opener.ts b/src/widget/tab-opener.ts
index 83713f6..329263a 100644
--- a/src/widget/tab-opener.ts
+++ b/src/widget/tab-opener.ts
@@ -1,18 +1,26 @@
 import type { WidgetConfig } from './config';
 
+// The widget *is* the user-message medium — every redirect is the user pressing Send.
+// Embedders override by passing utm_medium in data-params.
+const DEFAULT_PARAMS: Readonly<Record<string, string>> = Object.freeze({
+  utm_medium: 'user_message',
+});
+
 function normalizeMessage(raw: string): string {
   return raw.trim().replace(/\s+/g, ' ');
 }
 
+function effectiveParams(config: WidgetConfig): Record<string, string> {
+  return { ...DEFAULT_PARAMS, ...(config.params ?? {}) };
+}
+
 function buildTargetUrl(config: WidgetConfig, message?: string): string {
   const url = new URL(config.targetUrl);
   url.searchParams.set('auto_accept_policies', '1');
   url.searchParams.set('referrer', window.location.href);
 
-  if (config.params) {
-    for (const [key, value] of Object.entries(config.params)) {
-      url.searchParams.set(key, value);
-    }
+  for (const [key, value] of Object.entries(effectiveParams(config))) {
+    url.searchParams.set(key, value);
   }
 
   if (message) {
@@ -43,9 +51,7 @@ export function openTarget(config: WidgetConfig, message: string): void {
     if (text) {
       payload.message = text;
     }
-    if (config.params) {
-      payload.params = config.params;
-    }
+    payload.params = effectiveParams(config);
     newTab.name = JSON.stringify(payload);
     newTab.location.href = buildTargetUrl(config);
   } else {