diff --git a/src/env.d.ts b/src/env.d.ts
index eca1d69..63e3eaf 100644
--- a/src/env.d.ts
+++ b/src/env.d.ts
@@ -30,3 +30,5 @@ interface ImportMetaEnv {
 interface ImportMeta {
   readonly env: ImportMetaEnv;
 }
+
+declare const process: { env: Record<string, string | undefined> };
diff --git a/src/pages/api/auth/signin.ts b/src/pages/api/auth/signin.ts
new file mode 100644
index 0000000..e661dc4
--- /dev/null
+++ b/src/pages/api/auth/signin.ts
@@ -0,0 +1,15 @@
+import type { APIRoute } from 'astro';
+import { serverClient } from '@/lib/supabase';
+
+export const GET: APIRoute = async ({ cookies, url, redirect }) => {
+  const appUrl = process.env.PUBLIC_APP_URL ?? import.meta.env.PUBLIC_APP_URL ?? url.origin;
+  const supabase = serverClient(cookies);
+
+  const { data, error } = await supabase.auth.signInWithOAuth({
+    provider: 'google',
+    options: { redirectTo: `${appUrl}/api/auth/callback` },
+  });
+
+  if (error || !data?.url) return redirect('/login?error=oauth');
+  return redirect(data.url);
+};
diff --git a/src/pages/login.astro b/src/pages/login.astro
index b3c364a..31a5b52 100644
--- a/src/pages/login.astro
+++ b/src/pages/login.astro
@@ -9,10 +9,7 @@ const errorMsg = errorParam === 'dominio'
     ? 'No se pudo completar la autenticación con Google. Inténtalo de nuevo.'
     : null;
 
-const appUrl = process.env.PUBLIC_APP_URL ?? import.meta.env.PUBLIC_APP_URL ?? url.origin;
-const supabaseUrl = process.env.PUBLIC_SUPABASE_URL ?? import.meta.env.PUBLIC_SUPABASE_URL;
-const redirectTo = `${appUrl}/api/auth/callback`;
-const googleAuthUrl = `${supabaseUrl}/auth/v1/authorize?provider=google&redirect_to=${encodeURIComponent(redirectTo)}`;
+const googleAuthUrl = '/api/auth/signin';
 ---
 <Layout title="Iniciar sesión — LabPréstamos UABC">
   <main id="main" class="min-h-screen grid place-items-center p-4">