I need to improve my auto-login system, applied to WordPress websites installed on different domains. The system is fully functional. Currently, the user logs in the main website and move between the other standalone domains without re-authenticating. The missing piece is the opposite flow: I want the user to be able to land on any network site first, sign in there, and still gain seamless access everywhere else—without opening a separate window or forcing a manual jump to the main site. I’m open to either of the following approaches (or a smarter alternative you can propose): - On network sites, once successfully logged in, a quiet notification should be sent to the main site, which would then perform the login without the user needing to navigate to it. And that's all. or - Embed the main site’s login form directly on every network domain (iframe or similar), then refresh the current page once the credentials are validated. I already have a simple template for that, no issues here... The task would be to enable that communication. A popup window is not an option. Please outline, in just a few lines, which method you’d choose, WordPress actions/filters, hand-off secure. If you’ve tackled multi-domain SSO or JWT/OAuth flows before, let me know; Deliverable: a drop-in script plus some concise setup notes that let me reproduce the behaviour on staging, then roll it out to production with confidence. Tight budget, so clear, efficient solutions win.