Add passkey option on TOTP page and auto-trigger passkey for TOTP users

When a user has both passkeys and TOTP configured, auto-trigger the
passkey flow on login to save them from the password→TOTP path. Also
add a "Use Passkey Instead" button on the TOTP verification page as
an escape hatch for users who end up there.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/controllers/sessions_controller.rb

@@ -147,6 +147,10 @@ class SessionsController < ApplicationController
       nil
     end
 
+    # Pass data to the view for passkey option
+    @user_has_webauthn = user&.can_authenticate_with_webauthn?
+    @pending_email = user&.email_address
+
     # Just render the form
   end
 

app/controllers/webauthn_controller.rb

@@ -148,7 +148,8 @@ class WebauthnController < ApplicationController
     # Only return minimal necessary info - no user_id or preferred_method
     render json: {
       has_webauthn: user.can_authenticate_with_webauthn?,
-      requires_webauthn: user.require_webauthn?
+      requires_webauthn: user.require_webauthn?,
+      has_totp: user.totp_enabled?
     }
   end
 

app/javascript/controllers/webauthn_controller.js

@@ -49,8 +49,9 @@ export default class extends Controller {
           }
         });
 
-        // Auto-trigger passkey authentication if required
-        if (data.requires_webauthn) {
+        // Auto-trigger passkey authentication if required, or if user has both
+        // webauthn and TOTP (to save them from the password→TOTP flow)
+        if (data.requires_webauthn || (data.has_webauthn && data.has_totp)) {
           setTimeout(() => this.authenticate(), 100);
         }
       } else {
@@ -289,6 +290,10 @@ export default class extends Controller {
     if (!emailInput) {
       emailInput = document.querySelector('input[name="user[email_address]"]');
     }
+    // Fallback to hidden webauthn_email field (e.g., on TOTP verification page)
+    if (!emailInput) {
+      emailInput = document.querySelector('input[name="webauthn_email"]');
+    }
     return emailInput ? emailInput.value.trim() : "";
   }
 

app/views/sessions/verify_totp.html.erb

@@ -34,6 +34,31 @@
       </div>
     <% end %>
 
+    <% if @user_has_webauthn %>
+      <div data-controller="webauthn" data-webauthn-check-url-value="/webauthn/check">
+        <input type="hidden" name="webauthn_email" value="<%= @pending_email %>">
+        <div class="mt-4">
+          <div class="relative my-4">
+            <div class="absolute inset-0 flex items-center">
+              <div class="w-full border-t border-gray-300"></div>
+            </div>
+            <div class="relative flex justify-center text-sm">
+              <span class="px-2 bg-white text-gray-500">Or</span>
+            </div>
+          </div>
+          <button type="button"
+                  data-action="click->webauthn#authenticate"
+                  class="w-full rounded-md px-3.5 py-2.5 bg-green-600 hover:bg-green-500 text-white font-medium cursor-pointer flex items-center justify-center">
+            <svg class="w-5 h-5 mr-2" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+              <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M15 7a2 2 0 012 2m4 0a6 6 0 01-7.743 5.743L11 17H9v2H7v2H4a1 1 0 01-1-1v-2.586a1 1 0 01.293-.707l5.964-5.964A6 6 0 1121 9z" />
+            </svg>
+            Use Passkey Instead
+          </button>
+          <div data-webauthn-target="error" class="mt-2 text-sm text-red-600" style="display: none;"></div>
+        </div>
+      </div>
+    <% end %>
+
     <div class="mt-6">
       <div class="relative">
         <div class="absolute inset-0 flex items-center">