WordPress-React Native SSO Setup

I run multiple WordPress sites and a React Native mobile app that should feel like one ecosystem. I need one secure sign-in that automatically works across all three properties and logs the user out everywhere when they choose to sign off.

I’m open to your expert recommendation proposal—so long as the solution remains lightweight, secure, and easy for my team to maintain later.

Here’s what success looks like:
• A single authentication flow that lets a user log in on any of the WordPress sites or the app and arrive at the others already authenticated
• Centralised session handling that survives token refreshes and password changes
• A clean logout that invalidates sessions across every platform
• Brief technical documentation explaining how to extend or troubleshoot the setup

I need this delivered ASAP. When you reply, include a concise yet detailed project proposal outlining:
• the protocol, plugins, or libraries you’d use
• a step-by-step implementation schedule through to production hand-off
• any prerequisites or changes I must prepare on my side

Once a user can pass the four-point live test—sign in on one platform, remain authenticated on the other two, and fully log out everywhere—I'll consider the job complete and release payment. I’m ready to start as soon as I find the right approach.