The client that wants to login always needs to execute a browser (or at least a render and JavaScript engine). See this (stalled) proposal to make it more compatible with non-browser&#x2F;simpler agents: <a href="https:&#x2F;&#x2F;groups.google.com&#x2F;d&#x2F;msg&#x2F;mozilla.dev.identity&#x2F;L2ETKkdMv8g&#x2F;q3ffwFaJgl0J" rel="nofollow">https:&#x2F;&#x2F;groups.google.com&#x2F;d&#x2F;msg&#x2F;mozilla.dev.identity&#x2F;L2ETKkd...</a>