In OutSystems, Single Sign-On (SSO) is natively enabled for all applications within the environment when they share the same User Provider module and authentication settings. However, if you need to restrict SSO to a specific application while keeping the overall SSO enabled, you would need to isolate the user provider for that specific app. Here's how you can achieve this:

1. Set up a Dedicated User Provider for the Application
   Instead of using the default/shared Users module as the User Provider for the specific app, you need to designate a new module that will act as the User Provider for this specific application. Here's how:

   • Create a new module in Service Studio and enable the Is User Provider property for that module.
   • Publish this module to your environment.

2. Link the Application to the Dedicated User Provider

   • Open the application’s module(s) in Service Studio.
   • Navigate to the module's Properties and change the User Provider property to the new dedicated User Provider module you just created.
   • Republish the application.

3. Customize Authentication and Users for the Specific App

   • In this new User Provider module, manage users specifically for this application (e.g., by storing and managing a separate set of users in the database or integrating with specific external identity providers if needed).
   • Configure the authentication settings for this module if you want to integrate it with an external identity provider (e.g., Azure AD B2C). Follow the steps in this guide How to Enable SSO for OutSystems IT User Accounts if you're using tools like Azure AD for SSO integration.

4. Ensure Separate Sessions (Optional)
   By using a separate User Provider, session sharing will be automatically disabled between the selected app and other apps in the environment. This ensures that SSO is isolated, and authenticating in one app does not authenticate the user in the other apps.

5. Validate and Test the Configuration

   • Test the application to ensure the SSO is enabled only within the desired app and that users are not automatically logged into other apps in the environment.
   • If necessary, confirm that session management and shared session variables are working as expected in your setup.

Keep in mind that these steps may require discussions with your IT and infrastructure teams, especially if external identity providers are involved. For additional details on working with User Providers and SSO, you can refer to the official OutSystems documentation Single Sign-On.