diff --git a/frontend/app/content.js b/frontend/app/content.js
index 3e16164..a99322c 100644
--- a/frontend/app/content.js
+++ b/frontend/app/content.js
@@ -9,7 +9,7 @@ export const profileContent = {
   en: {
     locale: "en",
     htmlLang: "en",
-    alternateHref: "/pt/",
+    alternateHref: "/pt?lang=pt",
     alternateLabel: "PT",
     currentLabel: "EN",
     navAria: "Primary navigation",
@@ -139,7 +139,7 @@ export const profileContent = {
   pt: {
     locale: "pt",
     htmlLang: "pt-BR",
-    alternateHref: "/",
+    alternateHref: "/?lang=en",
     alternateLabel: "EN",
     currentLabel: "PT",
     navAria: "Navegação principal",
diff --git a/frontend/middleware.js b/frontend/middleware.js
new file mode 100644
index 0000000..6f0c5cb
--- /dev/null
+++ b/frontend/middleware.js
@@ -0,0 +1,124 @@
+import { NextResponse } from "next/server";
+
+const LOCALE_COOKIE = "rs_locale";
+const SUPPORTED_LOCALES = new Set(["en", "pt"]);
+const PUBLIC_FILE = /\.(?:ico|png|jpg|jpeg|svg|webp|avif|gif|txt|xml|json|webmanifest|css|js|map|woff2?)$/i;
+const RESERVED_PREFIXES = [
+  "/_next",
+  "/_a2a",
+  "/.well-known",
+  "/api",
+  "/auth",
+  "/invoke",
+  "/mcp",
+  "/message:send",
+  "/message:stream",
+  "/tasks",
+  "/answers",
+  "/input-requests",
+  "/scope-grants",
+  "/scope-denials",
+];
+
+function isReservedPath(pathname) {
+  if (PUBLIC_FILE.test(pathname)) {
+    return true;
+  }
+  return RESERVED_PREFIXES.some(
+    (prefix) => pathname === prefix || pathname.startsWith(`${prefix}/`),
+  );
+}
+
+function normalizeLocale(value) {
+  const locale = String(value || "").trim().toLowerCase();
+  if (SUPPORTED_LOCALES.has(locale)) {
+    return locale;
+  }
+  return null;
+}
+
+function localeFromCountry(request) {
+  const country = (
+    request.headers.get("x-vercel-ip-country")
+    || request.headers.get("cf-ipcountry")
+    || request.headers.get("x-country-code")
+    || ""
+  ).trim().toUpperCase();
+  if (country === "BR" || country === "PT") {
+    return "pt";
+  }
+  return null;
+}
+
+function localeFromAcceptLanguage(request) {
+  const header = request.headers.get("accept-language") || "";
+  const ranked = header
+    .split(",")
+    .map((part) => {
+      const [tag, ...params] = part.trim().split(";");
+      const q = params
+        .map((param) => param.trim())
+        .find((param) => param.startsWith("q="));
+      const weight = q ? Number.parseFloat(q.slice(2)) : 1;
+      return {
+        language: tag.toLowerCase().split("-")[0],
+        weight: Number.isFinite(weight) ? weight : 1,
+      };
+    })
+    .filter((item) => SUPPORTED_LOCALES.has(item.language))
+    .sort((a, b) => b.weight - a.weight);
+  return ranked[0]?.language || null;
+}
+
+function preferredLocale(request) {
+  return (
+    normalizeLocale(request.cookies.get(LOCALE_COOKIE)?.value)
+    || localeFromAcceptLanguage(request)
+    || localeFromCountry(request)
+    || "en"
+  );
+}
+
+function withLocaleCookie(response, locale) {
+  response.cookies.set(LOCALE_COOKIE, locale, {
+    path: "/",
+    maxAge: 60 * 60 * 24 * 365,
+    sameSite: "lax",
+  });
+  return response;
+}
+
+export function middleware(request) {
+  const url = request.nextUrl;
+  const { pathname, searchParams } = url;
+
+  if (isReservedPath(pathname)) {
+    return NextResponse.next();
+  }
+
+  const requestedLocale = normalizeLocale(searchParams.get("lang"));
+  if (requestedLocale) {
+    const cleanUrl = url.clone();
+    cleanUrl.searchParams.delete("lang");
+    const response =
+      cleanUrl.toString() === url.toString()
+        ? NextResponse.next()
+        : NextResponse.redirect(cleanUrl);
+    return withLocaleCookie(response, requestedLocale);
+  }
+
+  if (pathname === "/") {
+    const locale = preferredLocale(request);
+    if (locale === "pt") {
+      const redirectUrl = url.clone();
+      redirectUrl.pathname = "/pt/";
+      return NextResponse.redirect(redirectUrl);
+    }
+  }
+
+  return NextResponse.next();
+}
+
+export const config = {
+  matcher: ["/:path*"],
+};