diff --git a/shared/OpenIddict.Extensions/OpenIddictHelpers.cs b/shared/OpenIddict.Extensions/OpenIddictHelpers.cs
index 3d814499..f7dd1287 100644
--- a/shared/OpenIddict.Extensions/OpenIddictHelpers.cs
+++ b/shared/OpenIddict.Extensions/OpenIddictHelpers.cs
@@ -85,18 +85,6 @@ internal static class OpenIddictHelpers
         }
     }
 
-    /// <summary>
-    /// Computes an absolute URI from the specified <paramref name="left"/> and <paramref name="right"/> URIs.
-    /// Note: if the <paramref name="right"/> URI is already absolute, it is directly returned.
-    /// </summary>
-    /// <param name="left">The left part.</param>
-    /// <param name="right">The right part.</param>
-    /// <returns>An absolute URI from the specified <paramref name="left"/> and <paramref name="right"/>.</returns>
-    /// <exception cref="InvalidOperationException"><paramref name="left"/> is not an absolute URI.</exception>
-    [return: NotNullIfNotNull(nameof(right))]
-    public static Uri? CreateAbsoluteUri(Uri? left, string? right)
-        => CreateAbsoluteUri(left, !string.IsNullOrEmpty(right) ? new Uri(right, UriKind.RelativeOrAbsolute) : null);
-
     /// <summary>
     /// Computes an absolute URI from the specified <paramref name="left"/> and <paramref name="right"/> URIs.
     /// Note: if the <paramref name="right"/> URI is already absolute, it is directly returned.
diff --git a/src/OpenIddict.Client.SystemIntegration/OpenIddictClientSystemIntegrationHandlers.cs b/src/OpenIddict.Client.SystemIntegration/OpenIddictClientSystemIntegrationHandlers.cs
index 9b619793..309c7c6c 100644
--- a/src/OpenIddict.Client.SystemIntegration/OpenIddictClientSystemIntegrationHandlers.cs
+++ b/src/OpenIddict.Client.SystemIntegration/OpenIddictClientSystemIntegrationHandlers.cs
@@ -1236,7 +1236,7 @@ public static partial class OpenIddictClientSystemIntegrationHandlers
             // Ensure the authentication demand is tracked by the OpenIddict client system integration
             // marshal and resolve the corresponding request forgery protection. If it can't be found,
             // this may indicate a session fixation attack: in this case, reject the authentication demand.
-            if (!_marshal.TryGetRequestForgeryProtection(context.Nonce, out string? protection))
+            if (!_marshal.TryGetRequestForgeryProtection(context.Nonce, out string? result))
             {
                 context.Reject(
                     error: Errors.InvalidRequest,
@@ -1246,7 +1246,7 @@ public static partial class OpenIddictClientSystemIntegrationHandlers
                 return ValueTask.CompletedTask;
             }
 
-            context.RequestForgeryProtection = protection;
+            context.RequestForgeryProtection = result;
 
             return ValueTask.CompletedTask;
         }
diff --git a/src/OpenIddict.Client.SystemIntegration/OpenIddictClientSystemIntegrationMarshal.cs b/src/OpenIddict.Client.SystemIntegration/OpenIddictClientSystemIntegrationMarshal.cs
index 6584c090..b8dbc371 100644
--- a/src/OpenIddict.Client.SystemIntegration/OpenIddictClientSystemIntegrationMarshal.cs
+++ b/src/OpenIddict.Client.SystemIntegration/OpenIddictClientSystemIntegrationMarshal.cs
@@ -115,19 +115,19 @@ public sealed class OpenIddictClientSystemIntegrationMarshal
     /// Tries to resolve the request forgery protection associated with the specified authentication demand.
     /// </summary>
     /// <param name="nonce">The nonce, used as a unique identifier.</param>
-    /// <param name="protection">The request forgery protection associated with the specified authentication demand.</param>
+    /// <param name="result">The request forgery protection associated with the specified authentication demand.</param>
     /// <returns><see langword="true"/> if the operation could be validated, <see langword="false"/> otherwise.</returns>
-    internal bool TryGetRequestForgeryProtection(string nonce, [NotNullWhen(true)] out string? protection)
+    internal bool TryGetRequestForgeryProtection(string nonce, [NotNullWhen(true)] out string? result)
     {
         ArgumentException.ThrowIfNullOrEmpty(nonce);
 
         if (_tracker.TryGetValue(nonce, out var operation))
         {
-            protection = operation.Value.RequestForgeryProtection;
+            result = operation.Value.RequestForgeryProtection;
             return true;
         }
 
-        protection = null;
+        result = null;
         return false;
     }
 
diff --git a/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationHandlers.Discovery.cs b/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationHandlers.Discovery.cs
index d85628e1..c80b4abb 100644
--- a/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationHandlers.Discovery.cs
+++ b/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationHandlers.Discovery.cs
@@ -21,6 +21,7 @@ public static partial class OpenIddictClientWebIntegrationHandlers
              */
             AmendIssuer.Descriptor,
             AmendGrantTypes.Descriptor,
+            AmendResponseModes.Descriptor,
             AmendCodeChallengeMethods.Descriptor,
             AmendScopes.Descriptor,
             AmendClientAuthenticationMethods.Descriptor,
@@ -157,6 +158,42 @@ public static partial class OpenIddictClientWebIntegrationHandlers
             }
         }
 
+        /// <summary>
+        /// Contains the logic responsible for amending the supported response modes for the providers that require it.
+        /// </summary>
+        public sealed class AmendResponseModes : IOpenIddictClientHandler<HandleConfigurationResponseContext>
+        {
+            /// <summary>
+            /// Gets the default descriptor definition assigned to this handler.
+            /// </summary>
+            public static OpenIddictClientHandlerDescriptor Descriptor { get; }
+                = OpenIddictClientHandlerDescriptor.CreateBuilder<HandleConfigurationResponseContext>()
+                    .UseSingletonHandler<AmendResponseModes>()
+                    .SetOrder(ExtractGrantTypes.Descriptor.Order + 500)
+                    .SetType(OpenIddictClientHandlerType.BuiltIn)
+                    .Build();
+
+            /// <inheritdoc/>
+            public ValueTask HandleAsync(HandleConfigurationResponseContext context)
+            {
+                ArgumentNullException.ThrowIfNull(context);
+
+                // Note: some providers don't list the response modes they support, which prevents the OpenIddict
+                // client from using them (unless they are assumed to be enabled by default, like the query or
+                // fragment response modes). To work around that, the list of supported response modes is amended
+                // to include the known supported modes for the providers that require it.
+
+                // Note: Vercel supports the "query" response mode but exclusively lists
+                // the "web_message.opener" mode in its server configuration metadata.
+                if (context.Registration.ProviderType is ProviderTypes.Vercel)
+                {
+                    context.Configuration.ResponseModesSupported.Add(ResponseModes.Query);
+                }
+
+                return ValueTask.CompletedTask;
+            }
+        }
+
         /// <summary>
         /// Contains the logic responsible for amending the supported
         /// code challenge methods for the providers that require it.
@@ -169,7 +206,7 @@ public static partial class OpenIddictClientWebIntegrationHandlers
             public static OpenIddictClientHandlerDescriptor Descriptor { get; }
                 = OpenIddictClientHandlerDescriptor.CreateBuilder<HandleConfigurationResponseContext>()
                     .UseSingletonHandler<AmendCodeChallengeMethods>()
-                    .SetOrder(ExtractCodeChallengeMethods.Descriptor.Order + 500)
+                    .SetOrder(AmendResponseModes.Descriptor.Order + 500)
                     .SetType(OpenIddictClientHandlerType.BuiltIn)
                     .Build();
 
@@ -395,7 +432,7 @@ public static partial class OpenIddictClientWebIntegrationHandlers
                 else if (context.Registration.ProviderType is ProviderTypes.Auth0)
                 {
                     context.Configuration.EndSessionEndpoint ??= OpenIddictHelpers.CreateAbsoluteUri(
-                        context.Registration.Issuer, "oidc/logout");
+                        context.Registration.Issuer, new Uri("oidc/logout", UriKind.Relative));
                 }
 
                 // While Huawei supports OpenID Connect discovery, the configuration
diff --git a/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationProviders.xml b/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationProviders.xml
index 4018dc5b..47f3ff7f 100644
--- a/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationProviders.xml
+++ b/src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationProviders.xml
@@ -798,9 +798,9 @@
   <Provider Name="ExactOnline" DisplayName="Exact Online" Id="7fbc91df-e1c0-4f7e-9c65-f86b1d173ab9"
             Documentation="https://support.exactonline.com/community/s/knowledge-base#All-All-DNO-Content-oauth-eol-oauth-dev-impleovervw">
     <Environment Issuer="{settings.Issuer}">
-      <Configuration AuthorizationEndpoint="{CreateAbsoluteUri(settings.Issuer, 'api/oauth2/auth')}"
-                     TokenEndpoint="{CreateAbsoluteUri(settings.Issuer, 'api/oauth2/token')}"
-                     UserInfoEndpoint="{CreateAbsoluteUri(settings.Issuer, 'api/v1/current/Me')}">
+      <Configuration AuthorizationEndpoint="{CreateAbsoluteUri(settings.Issuer, new Uri('api/oauth2/auth', UriKind.Relative))}"
+                     TokenEndpoint="{CreateAbsoluteUri(settings.Issuer, new Uri('api/oauth2/token', UriKind.Relative))}"
+                     UserInfoEndpoint="{CreateAbsoluteUri(settings.Issuer, new Uri('api/v1/current/Me', UriKind.Relative))}">
         <GrantType Value="authorization_code" />
         <GrantType Value="refresh_token" />
       </Configuration>
@@ -1517,9 +1517,9 @@
     -->
 
     <Environment Issuer="{settings.Issuer}">
-      <Configuration AuthorizationEndpoint="{CreateAbsoluteUri(settings.Issuer, 'oauth/authorize')}"
-                     TokenEndpoint="{CreateAbsoluteUri(settings.Issuer, 'oauth/token')}"
-                     UserInfoEndpoint="{CreateAbsoluteUri(settings.Issuer, 'api/v1/accounts/verify_credentials')}">
+      <Configuration AuthorizationEndpoint="{CreateAbsoluteUri(settings.Issuer, new Uri('oauth/authorize', UriKind.Relative))}"
+                     TokenEndpoint="{CreateAbsoluteUri(settings.Issuer, new Uri('oauth/token', UriKind.Relative))}"
+                     UserInfoEndpoint="{CreateAbsoluteUri(settings.Issuer, new Uri('api/v1/accounts/verify_credentials', UriKind.Relative))}">
         <GrantType Value="authorization_code" />
         <GrantType Value="client_credentials" />
         <GrantType Value="password" />
@@ -1696,9 +1696,9 @@
   <Provider Name="Nextcloud" Id="f256847d-c720-4b2f-bda0-69e8f4bceac2"
             Documentation="https://docs.nextcloud.com/server/latest/admin_manual/configuration_server/oauth2.html">
     <Environment Issuer="{settings.Issuer}">
-      <Configuration AuthorizationEndpoint="{CreateAbsoluteUri(settings.Issuer, 'index.php/apps/oauth2/authorize')}"
-                     TokenEndpoint="{CreateAbsoluteUri(settings.Issuer, 'index.php/apps/oauth2/api/v1/token')}"
-                     UserInfoEndpoint="{CreateAbsoluteUri(settings.Issuer, 'ocs/v2.php/cloud/user?format=json')}">
+      <Configuration AuthorizationEndpoint="{CreateAbsoluteUri(settings.Issuer, new Uri('index.php/apps/oauth2/authorize', UriKind.Relative))}"
+                     TokenEndpoint="{CreateAbsoluteUri(settings.Issuer, new Uri('index.php/apps/oauth2/api/v1/token', UriKind.Relative))}"
+                     UserInfoEndpoint="{CreateAbsoluteUri(settings.Issuer, new Uri('ocs/v2.php/cloud/user?format=json', UriKind.Relative))}">
         <GrantType Value="authorization_code" />
         <GrantType Value="refresh_token" />
       </Configuration>
@@ -2538,6 +2538,19 @@
     </Environment>
   </Provider>
 
+  <!--
+                                            ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄
+                                            ██ ███ ██ ▄▄▄██ ▄▄▀██ ▄▄▀██ ▄▄▄██ █████
+                                            ███ █ ███ ▄▄▄██ ▀▀▄██ █████ ▄▄▄██ █████
+                                            ███▄▀▄███ ▀▀▀██ ██ ██ ▀▀▄██ ▀▀▀██ ▀▀ ██
+                                            ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
+  -->
+
+  <Provider Name="Vercel" Id="f44fc1d8-8575-4271-aae5-3e6bdc030d46"
+            Documentation="https://vercel.com/docs/sign-in-with-vercel/getting-started">
+    <Environment Issuer="https://vercel.com/" />
+  </Provider>
+
   <!--
                                                ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄
                                                ██ ███ █ ▄▄▄██ ▄▄▀█▄ ▄██ ▄▀▄ █▄ ▄██