From 68fc8fabab0c13e1b4d6cfc800939c16cf050554 Mon Sep 17 00:00:00 2001
From: Sebastian Stehle <sebastian@squidex.io>
Date: Tue, 24 Mar 2026 22:32:32 +0100
Subject: [PATCH] Fix path base.

---
 .../PathBaseMiddlewareExtensions.cs           | 47 +++++++++++++++++++
 backend/src/Squidex.Web/Resources.cs          |  1 -
 backend/src/Squidex/Startup.cs                |  2 +-
 3 files changed, 48 insertions(+), 2 deletions(-)
 create mode 100644 backend/src/Squidex.Web/PathBaseMiddlewareExtensions.cs

diff --git a/backend/src/Squidex.Web/PathBaseMiddlewareExtensions.cs b/backend/src/Squidex.Web/PathBaseMiddlewareExtensions.cs
new file mode 100644
index 000000000..00fd99dc4
--- /dev/null
+++ b/backend/src/Squidex.Web/PathBaseMiddlewareExtensions.cs
@@ -0,0 +1,47 @@
+// ==========================================================================
+//  Squidex Headless CMS
+// ==========================================================================
+//  Copyright (c) Squidex UG (haftungsbeschraenkt)
+//  All rights reserved. Licensed under the MIT license.
+// ==========================================================================
+
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.DependencyInjection;
+using Squidex.Hosting;
+
+namespace Squidex.Web;
+
+public static class PathBaseMiddlewareExtensions
+{
+    public static IApplicationBuilder UseFallbackPathBase(this IApplicationBuilder app)
+    {
+        var urlGenerator = app.ApplicationServices.GetRequiredService<IUrlGenerator>();
+
+        var configuredBase = urlGenerator.BuildBasePath();
+        if (string.IsNullOrWhiteSpace(configuredBase))
+        {
+            return app;
+        }
+
+        var pathBase = new PathString(configuredBase);
+
+        return app.Use(async (context, next) =>
+        {
+            if (context.Request.PathBase.HasValue)
+            {
+                await next();
+                return;
+            }
+
+            context.Request.PathBase = pathBase;
+
+            if (context.Request.Path.StartsWithSegments(pathBase, StringComparison.Ordinal, out var remainder))
+            {
+                context.Request.Path = remainder;
+            }
+
+            await next();
+        });
+    }
+}
diff --git a/backend/src/Squidex.Web/Resources.cs b/backend/src/Squidex.Web/Resources.cs
index 69030ab51..76f50e228 100644
--- a/backend/src/Squidex.Web/Resources.cs
+++ b/backend/src/Squidex.Web/Resources.cs
@@ -170,7 +170,6 @@ public sealed class Resources(ApiController controller)
         var url = Controller.Url(action, values);
 
         var basePath = Controller.HttpContext.Request.PathBase;
-
         if (url.StartsWith(Controller.HttpContext.Request.PathBase, StringComparison.OrdinalIgnoreCase))
         {
             url = url[basePath.Value!.Length..];
diff --git a/backend/src/Squidex/Startup.cs b/backend/src/Squidex/Startup.cs
index d41aacc67..d19ebd7bb 100644
--- a/backend/src/Squidex/Startup.cs
+++ b/backend/src/Squidex/Startup.cs
@@ -73,7 +73,7 @@ public sealed class Startup(IConfiguration config)
     {
         app.UseWebSockets();
         app.UseCookiePolicy();
-        app.UseDefaultPathBase();
+        app.UseFallbackPathBase();
         app.UseDefaultForwardRules();
         app.UseSquidexLogging();
         app.UseSquidexLocalization();