diff --git a/src/layouts/Base.astro b/src/layouts/Base.astro
index 9993240..8c5b03b 100644
--- a/src/layouts/Base.astro
+++ b/src/layouts/Base.astro
@@ -24,9 +24,20 @@ interface Props {
   description?: string;
   /** Keep the page out of search engines (still reachable by URL). For share-only pages. */
   noindex?: boolean;
+  /** Client-side language auto-routing sends a default-locale page to the visitor's preferred
+   *  built locale. Turn OFF on pages that exist only in the default locale (event guides, 404,
+   *  offline, go-eu): they have no localized counterpart, so redirecting a non-English visitor
+   *  lands on a 404, and the 404 page re-running the script is what stacked /cs/cs/cs forever. */
+  autoRoute?: boolean;
 }
 
-const { title, lang = 'en', description: pageDescription, noindex = false } = Astro.props;
+const {
+  title,
+  lang = 'en',
+  description: pageDescription,
+  noindex = false,
+  autoRoute = true,
+} = Astro.props;
 const t = useTranslations(lang);
 // Every in-site link goes through localeHref: a two-way `lang === 'en' ? … : '/nl/…'` sent
 // every non-English visitor to Dutch, which made /fr/ a dead end on .be and put a Dutch
@@ -126,7 +137,7 @@ const orgLd = {
         }
       }
     </script>
-    {LOCALES.length > 1 && (
+    {LOCALES.length > 1 && autoRoute && (
       <script
         define:vars={{
           locales: LOCALES,
@@ -169,9 +180,16 @@ const orgLd = {
               const root = base.replace(/\/$/, '');
               let rel = location.pathname;
               if (root && rel.indexOf(root) === 0) rel = rel.slice(root.length) || '/';
-              location.replace(
-                root + '/' + target + (rel === '/' ? '/' : rel) + location.search + location.hash,
-              );
+              // Idempotency guard: never prepend a locale onto a path that already starts with a
+              // built locale. A default-locale page can be SERVED under /<lang>/x (the 404 page
+              // answers /cs/missing as lang=en), so without this the script would re-fire there
+              // and stack /cs/cs/cs into an infinite redirect loop.
+              const first = rel.split('/')[1] || '';
+              if (locales.indexOf(first) === -1) {
+                location.replace(
+                  root + '/' + target + (rel === '/' ? '/' : rel) + location.search + location.hash,
+                );
+              }
             }
           } catch (e) {}
         }
diff --git a/src/layouts/Guide.astro b/src/layouts/Guide.astro
index 102841f..c530665 100644
--- a/src/layouts/Guide.astro
+++ b/src/layouts/Guide.astro
@@ -17,7 +17,7 @@ const current = Astro.url.pathname.replace(/\/$/, '').split('/').pop();
 const others = guides.filter((g) => g.slug !== current);
 ---
 
-<Base lang="en" title={frontmatter.title}>
+<Base lang="en" title={frontmatter.title} autoRoute={false}>
   <section class="hero">
     <p class="guide-back"><a href="/events">Back to events</a></p>
     <h1 class="display page-title">{frontmatter.title}</h1>
diff --git a/src/pages/404.astro b/src/pages/404.astro
index 672e435..3168381 100644
--- a/src/pages/404.astro
+++ b/src/pages/404.astro
@@ -2,7 +2,7 @@
 import Base from '../layouts/Base.astro';
 ---
 
-<Base lang="en" title="404">
+<Base lang="en" title="404" autoRoute={false}>
   <section class="hero">
     <h1 class="display page-title">404</h1>
     <p>This page does not exist. / Deze pagina bestaat niet.</p>
diff --git a/src/pages/go-eu.astro b/src/pages/go-eu.astro
index 9677f85..6dcd17c 100644
--- a/src/pages/go-eu.astro
+++ b/src/pages/go-eu.astro
@@ -6,7 +6,7 @@ import Base from '../layouts/Base.astro';
 const title = 'Be fully EU';
 ---
 
-<Base lang="en" title={title} description="Run your AT Protocol presence on European, self-owned infrastructure.">
+<Base lang="en" title={title} description="Run your AT Protocol presence on European, self-owned infrastructure." autoRoute={false}>
   <section class="hero">
     <h1 class="display page-title">{title}</h1>
     <p>
diff --git a/src/pages/offline.astro b/src/pages/offline.astro
index a9ee19a..8c9a04c 100644
--- a/src/pages/offline.astro
+++ b/src/pages/offline.astro
@@ -2,7 +2,7 @@
 import Base from '../layouts/Base.astro';
 ---
 
-<Base lang="en" title="Offline">
+<Base lang="en" title="Offline" autoRoute={false}>
   <section class="hero">
     <h1 class="display page-title">Offline</h1>
     <p>You are offline and this page is not cached yet. / Je bent offline en deze pagina is nog niet opgeslagen.</p>