diff --git a/app/services/auth.js b/app/services/auth.js
index 9b2ee4b77a..9a3e2d0bb0 100644
--- a/app/services/auth.js
+++ b/app/services/auth.js
@@ -93,6 +93,33 @@ export default Service.extend({
     window.addEventListener('focus', () => this.checkAuth());
   },
 
+  /**
+   * Sets a domain-wide ( .travis-ci.com ) cookie indicating whether the user
+   * is currently signed in (1) or signed out (0). The cookie is consumed by
+   * the marketing / WordPress site to perform automatic redirects.
+   *
+   * Note: Cookie cannot be marked HttpOnly because it must be readable by
+   * client-side JavaScript on marketing pages.
+   */
+  setSharedLoginCookie(isLoggedIn) {
+    try {
+      const host = window.location.hostname;
+      const cfg = config.loginStateCookie || {};
+      const name = cfg.name;
+      const days = cfg.expiryDays || 90;
+      const expires = new Date(Date.now() + days * 864e5).toUTCString();
+      const domainPart = /travis-ci\.com$/.test(host) ? '; Domain=.travis-ci.com' : '';
+      const securePart = window.location.protocol === 'https:' ? '; Secure' : '';
+      const value = isLoggedIn ? '1' : '0'; // (1=logged in,0=out)
+      document.cookie = `${name}=${value}; Expires=${expires}; Path=/${domainPart}${securePart}; SameSite=Lax`;
+    } catch (e) {}
+  },
+
+  clearSharedLoginCookie() {
+    this.setSharedLoginCookie(false);
+  },
+
+
   checkAuth() {
     if (!this.currentUser || !this.storage)
       return;
@@ -141,6 +168,7 @@ export default Service.extend({
         this.router.transitionTo('signin');
       } catch (e) {}
     }
+    this.clearSharedLoginCookie();
   },
 
   afterSignOut(callback) {
@@ -198,6 +226,7 @@ export default Service.extend({
           this.set('state', STATE.SIGNED_IN);
           Travis.trigger('user:signed_in', currentUser);
           Travis.trigger('user:refreshed', currentUser);
+          this.setSharedLoginCookie(true);
         })
         .catch(error => {
           if (!didCancel(error)) {
diff --git a/config/environment.js b/config/environment.js
index b352500ef9..8f73fcb2f0 100644
--- a/config/environment.js
+++ b/config/environment.js
@@ -53,6 +53,12 @@ module.exports = function (environment) {
     plans,
     screens,
     tailwind,
+    // login state cookie (used by marketing site for redirect decisions)
+    loginStateCookie: {
+      name: 'logged_in_to_app',
+      expiryDays:
+        parseInt(process.env.LOGGED_IN_TO_APP_COOKIE_EXPIRY, 10) || 90,
+    },
     EmberENV: {
       FEATURES: {
         // Here you can enable experimental features on an ember canary build
diff --git a/tests/acceptance/profile/billing-test.js b/tests/acceptance/profile/billing-test.js
index dfea88b32e..14f566328e 100644
--- a/tests/acceptance/profile/billing-test.js
+++ b/tests/acceptance/profile/billing-test.js
@@ -446,7 +446,7 @@ module('Acceptance | profile/billing', function (hooks) {
   test('view billing on a manual plan with no invoices', async function (assert) {
     this.subscription.source = 'manual';
     this.subscription.status = undefined;
-    this.subscription.valid_to = new Date(2025, 7, 16).toISOString();
+    this.subscription.valid_to = new Date(2099, 1, 1).toISOString();
 
     await profilePage.visit();
     await profilePage.billing.visit();