Endpoint/Common/Services/UrlHelper.cs

@@ -18,5 +18,29 @@ public static class UrlHelper
     }
 
     public static string GetSubPath => CreateSubPath(Environment.GetEnvironmentVariable("ACTUAL_SUB_PATH"));
+
+    public static string GetSubPathWithoutFirstApiName
+    {
+        get
+        {
+            var path = GetSubPath;
+
+            if (string.IsNullOrEmpty(path) || path == "/")
+                return CreateSubPath(null);
+
+            var parts = path.Split('/', StringSplitOptions.RemoveEmptyEntries);
+
+            for (int i = 0; i < parts.Length; i++)
+            {
+                if (!parts[i].Equals("api", StringComparison.CurrentCultureIgnoreCase)) continue;
+
+                parts = parts.Take(i).Concat(parts.Skip(i + 1)).ToArray();
+                break;
+            }
+
+            return CreateSubPath(string.Join("/", parts));
+        }
+    }
+
     public static string GetSubPathSwagger => CreateSubPath(Environment.GetEnvironmentVariable("SWAGGER_SUB_PATH"));
 }

Endpoint/Controllers/Configuration/SetupController.cs

@@ -69,7 +69,7 @@ public partial class SetupController(
 
         Response.Cookies.Append("AuthToken", token, new CookieOptions
         {
-            Path = UrlHelper.GetSubPath + "api",
+            Path = UrlHelper.GetSubPathWithoutFirstApiName + "api",
             Domain = UrlHelper.CurrentDomain(ControllerContext.HttpContext),
             Secure = true,
             HttpOnly = true

Endpoint/Controllers/V1/AuthController.cs

@@ -29,7 +29,7 @@ public class AuthController(IOptionsSnapshot<Admin> user, AuthService auth, Pass
         var cookieOptions = new CookieOptions
         {
             Expires = expires,
-            Path = UrlHelper.GetSubPath + "api",
+            Path = UrlHelper.GetSubPathWithoutFirstApiName + "api",
             Domain = UrlHelper.CurrentDomain(ControllerContext.HttpContext),
             Secure = true,
             HttpOnly = true