diff --git a/.astro/settings.json b/.astro/settings.json
index 934e7f9..27baba6 100644
--- a/.astro/settings.json
+++ b/.astro/settings.json
@@ -1,5 +1,5 @@
 {
 	"_variables": {
-		"lastUpdateCheck": 1772339173160
+		"lastUpdateCheck": 1775922065555
 	}
 }
\ No newline at end of file
diff --git a/.env.example b/.env.example
index dc761b2..d8fa78e 100644
--- a/.env.example
+++ b/.env.example
@@ -1,2 +1 @@
-# .env
-VITE_GA_MEASUREMENT_ID=G-XXXXXXXXXX
+PUBLIC_GA_MEASUREMENT_ID=G-XXXXXXXXXX
diff --git a/src/components/BaseHead.astro b/src/components/BaseHead.astro
index bcf9b3c..3a5bafe 100644
--- a/src/components/BaseHead.astro
+++ b/src/components/BaseHead.astro
@@ -55,7 +55,23 @@ const esURL = lang === 'es' ? canonicalURL.href : (alternateUrl ?? new URL('/es/
 <!-- Fonts -->
 <link rel="preconnect" href="https://fonts.googleapis.com" />
 <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
-<link
-  href="https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&display=swap"
-  rel="stylesheet"
-/>
+
+{
+  import.meta.env.PUBLIC_GA_MEASUREMENT_ID && (
+    <>
+      <script
+        is:inline
+        async
+        src={`https://www.googletagmanager.com/gtag/js?id=${import.meta.env.PUBLIC_GA_MEASUREMENT_ID}`}
+      />
+      <script is:inline define:vars={{ id: import.meta.env.PUBLIC_GA_MEASUREMENT_ID }}>
+        window.dataLayer = window.dataLayer || [];
+        window.gtag = function () {
+          window.dataLayer.push(arguments);
+        };
+        gtag('js', new Date());
+        gtag('config', id);
+      </script>
+    </>
+  )
+}
diff --git a/src/components/HeaderInteractive.tsx b/src/components/HeaderInteractive.tsx
index d0d48c2..325cdd9 100644
--- a/src/components/HeaderInteractive.tsx
+++ b/src/components/HeaderInteractive.tsx
@@ -46,6 +46,12 @@ const HeaderInteractive = ({ navItems, logoSrc, lang, altLangHref }: Props) => {
 
   const altLang = lang === 'es' ? 'EN' : 'ES';
 
+  const handleLangSwitch = () => {
+    const targetLang = lang === 'es' ? 'en' : 'es';
+    localStorage.setItem('preferred_lang', targetLang);
+    sessionStorage.removeItem('lang_redirected');
+  };
+
   return (
     <header
       className={`fixed top-0 left-0 right-0 z-50 transition-all duration-300 ${
@@ -95,6 +101,7 @@ const HeaderInteractive = ({ navItems, logoSrc, lang, altLangHref }: Props) => {
             {/* Language switcher */}
             <a
               href={altLangHref}
+              onClick={handleLangSwitch}
               className={`text-sm px-3 py-1 rounded-full border transition-all duration-300 font-bold ${
                 isScrolled || isMenuOpen
                   ? 'text-foreground border-foreground/20 hover:border-primary hover:text-primary'
@@ -146,6 +153,7 @@ const HeaderInteractive = ({ navItems, logoSrc, lang, altLangHref }: Props) => {
             <div className="pt-6 border-t border-foreground/10">
               <a
                 href={altLangHref}
+                onClick={handleLangSwitch}
                 className="inline-flex items-center text-lg font-bold text-foreground hover:text-primary transition-colors"
                 aria-label={`Switch to ${altLang}`}
               >
diff --git a/src/components/LanguageDetector.astro b/src/components/LanguageDetector.astro
new file mode 100644
index 0000000..6249090
--- /dev/null
+++ b/src/components/LanguageDetector.astro
@@ -0,0 +1,55 @@
+---
+// src/components/LanguageDetector.astro
+// Client-side browser language detection with SEO-safe redirection.
+// Only performs automatic detection on the home page to avoid breaking
+// deep-linked / indexed pages. Manual preference (via header toggle)
+// is respected on ALL pages.
+import type { Lang } from '@/lib/i18n';
+
+interface Props {
+  lang: Lang;
+  alternateUrl?: string;
+}
+
+const { lang, alternateUrl } = Astro.props;
+---
+
+<script
+  define:vars={{ pageLang: lang, alternateUrl: alternateUrl ?? null }}
+>
+  (function detectLanguage() {
+    const PREFERRED_LANG_KEY = 'preferred_lang';
+    const REDIRECTED_KEY = 'lang_redirected';
+
+    // Never redirect if we already redirected this session (prevents loops)
+    if (sessionStorage.getItem(REDIRECTED_KEY)) return;
+
+    const storedPref = localStorage.getItem(PREFERRED_LANG_KEY);
+    const isHomePage =
+      window.location.pathname === '/' ||
+      window.location.pathname === '/es/' ||
+      window.location.pathname === '/es';
+
+    /** @type {'en' | 'es' | null} */
+    let targetLang = null;
+
+    if (storedPref === 'en' || storedPref === 'es') {
+      // User has explicitly chosen a language before — respect it everywhere
+      targetLang = storedPref;
+    } else if (isHomePage) {
+      // First visit, no preference saved — detect from browser, but ONLY on
+      // the home page to preserve SEO for deep-linked pages.
+      const browserLang = navigator.language || navigator.userLanguage || 'en';
+      targetLang = browserLang.startsWith('es') ? 'es' : 'en';
+
+      // Persist the detected preference so subsequent pages are consistent
+      localStorage.setItem(PREFERRED_LANG_KEY, targetLang);
+    }
+
+    // If we have a target and it differs from the current page, redirect
+    if (targetLang && targetLang !== pageLang && alternateUrl) {
+      sessionStorage.setItem(REDIRECTED_KEY, '1');
+      window.location.replace(alternateUrl);
+    }
+  })();
+</script>
diff --git a/src/layouts/BaseLayout.astro b/src/layouts/BaseLayout.astro
index 8e11d5c..0eaddc2 100644
--- a/src/layouts/BaseLayout.astro
+++ b/src/layouts/BaseLayout.astro
@@ -3,6 +3,7 @@
 import BaseHead from '@/components/BaseHead.astro';
 import Header from '@/components/Header.astro';
 import Footer from '@/components/Footer.astro';
+import LanguageDetector from '@/components/LanguageDetector.astro';
 import type { Lang } from '@/lib/i18n';
 import '@/index.css';
 
@@ -20,6 +21,7 @@ const { title, description, lang = 'en', alternateUrl } = Astro.props;
 <html lang={lang}>
   <head>
     <BaseHead title={title} description={description} lang={lang} alternateUrl={alternateUrl} />
+    <LanguageDetector lang={lang} alternateUrl={alternateUrl} />
   </head>
   <body class="min-h-screen bg-background flex flex-col">
     <Header lang={lang} />
diff --git a/src/lib/analytics.ts b/src/lib/analytics.ts
index 8040eb1..94e64e0 100644
--- a/src/lib/analytics.ts
+++ b/src/lib/analytics.ts
@@ -1,7 +1,7 @@
 // src/lib/analytics.ts
 // Utility for Google Analytics event tracking
 
-const GA_MEASUREMENT_ID = import.meta.env.VITE_GA_MEASUREMENT_ID;
+const GA_MEASUREMENT_ID = import.meta.env.PUBLIC_GA_MEASUREMENT_ID;
 
 export function trackEvent({
   action,
@@ -20,6 +20,8 @@ export function trackEvent({
       event_label: label,
       value: value,
     });
+  } else if (import.meta.env.DEV) {
+    console.log('[Analytics]', { action, category, label, value });
   }
 }
 
diff --git a/src/lib/i18n.ts b/src/lib/i18n.ts
index 8b7ce39..c930d06 100644
--- a/src/lib/i18n.ts
+++ b/src/lib/i18n.ts
@@ -5,6 +5,9 @@ const translations = { en, es } as const;
 
 export type Lang = 'en' | 'es';
 
+/** localStorage key for the user's explicitly chosen language */
+export const PREFERRED_LANG_KEY = 'preferred_lang' as const;
+
 export function getLang(url: URL): Lang {
   const [, lang] = url.pathname.split('/');
   if (lang === 'es') return 'es';