Share credentials between native app and web site : <p>An application I'm working on allows users to log into an OAuth-enabled backend. The application is therefore privy only to the authentication tokens and user metadata, not to the user's credentials.</p>

<p>Within the application, users can hit links that open up links in a browser. These resources are also protected by OAuth, and the token obtained during login to the native app is also relevant to the web.</p>

<p>I would like the user's credentials to flow from the native app to the web browser in the standard OAuth manner (by including it as an <code>Authorization</code> header).</p>

<p>It seems that Android facilitates this through its <a href="https://developers.google.com/identity/smartlock-passwords/android/associate-apps-and-sites" rel="noreferrer">shared credentials</a> feature, but I cannot find an equivalent for iOS. I did find the <a href="https://developer.apple.com/reference/security/shared_web_credentials" rel="noreferrer">shared web credentials</a> feature, but that seems to require knowledge of the user's credentials.</p>

<p>How can I flow OAuth tokens from my native app through to web browsers that it opens?</p>
