diff --git a/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI.csproj b/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI.csproj
index 2231cba0..017c195d 100644
--- a/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI.csproj
+++ b/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI.csproj
@@ -9,6 +9,16 @@
   <ItemGroup>
     <ProjectReference Include="..\EnvelopeGenerator.WebUI.Client\EnvelopeGenerator.WebUI.Client.csproj" />
     <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.Server" Version="8.0.22" />
+    <PackageReference Include="Yarp.ReverseProxy" Version="2.1.0" />
+    <PackageReference Include="DevExpress.Blazor" Version="25.2.3" />
+    <PackageReference Include="DevExpress.Blazor.PdfViewer" Version="25.2.3" />
+    <PackageReference Include="DevExpress.Blazor.Reporting.Viewer" Version="25.2.3" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Content Update="yarp.json">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
   </ItemGroup>
 
 </Project>
diff --git a/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/Program.cs b/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/Program.cs
index 8dfc98c8..19799648 100644
--- a/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/Program.cs
+++ b/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/Program.cs
@@ -1,12 +1,31 @@
 using EnvelopeGenerator.WebUI.Components;
+using DevExpress.Blazor;
 
 var builder = WebApplication.CreateBuilder(args);
 
+// Load YARP configuration
+builder.Configuration.AddJsonFile("yarp.json", optional: false, reloadOnChange: true);
+
 // Add services to the container.
 builder.Services.AddRazorComponents()
     .AddInteractiveServerComponents()
     .AddInteractiveWebAssemblyComponents();
 
+// YARP Reverse Proxy
+builder.Services.AddReverseProxy()
+    .LoadFromConfig(builder.Configuration.GetSection("ReverseProxy"));
+
+// DevExpress Server-Side Services (CRITICAL for DxPdfViewer)
+builder.Services.AddDevExpressBlazor(configure => configure.BootstrapVersion = BootstrapVersion.v5);
+builder.Services.AddDevExpressServerSideBlazorPdfViewer();
+// builder.Services.AddDevExpressBlazorReportViewer();  // Will be enabled after Options migration
+
+// Configuration Options (will be enabled in Phase 5 after Options migration)
+// builder.Services.Configure<EnvelopeGenerator.WebUI.Client.Options.ApiOptions>(
+//     builder.Configuration.GetSection("ApiOptions"));
+// builder.Services.Configure<EnvelopeGenerator.WebUI.Client.Options.PdfViewerOptions>(
+//     builder.Configuration.GetSection("PdfViewerOptions"));
+
 var app = builder.Build();
 
 // Configure the HTTP request pipeline.
@@ -26,9 +45,13 @@ app.UseHttpsRedirection();
 app.UseStaticFiles();
 app.UseAntiforgery();
 
+// Blazor routing (BEFORE YARP - important order!)
 app.MapRazorComponents<App>()
     .AddInteractiveServerRenderMode()
     .AddInteractiveWebAssemblyRenderMode()
     .AddAdditionalAssemblies(typeof(EnvelopeGenerator.WebUI.Client._Imports).Assembly);
 
+// YARP proxy (AFTER Blazor - catch-all for /api/*)
+app.MapReverseProxy();
+
 app.Run();
diff --git a/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/appsettings.json b/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/appsettings.json
index 10f68b8c..46430479 100644
--- a/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/appsettings.json
+++ b/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/appsettings.json
@@ -5,5 +5,14 @@
       "Microsoft.AspNetCore": "Warning"
     }
   },
-  "AllowedHosts": "*"
+  "AllowedHosts": "*",
+  "ApiOptions": {
+    "BaseUrl": ""
+  },
+  "PdfViewerOptions": {
+    "ThumbnailBaseScale": 0.75,
+    "ThumbnailEnableHiDPI": true,
+    "MainCanvasEnableHiDPI": true,
+    "ZoomStepPercentage": 5
+  }
 }
diff --git a/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/yarp.json b/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/yarp.json
new file mode 100644
index 00000000..63b6fb2e
--- /dev/null
+++ b/EnvelopeGenerator.WebUI/EnvelopeGenerator.WebUI/yarp.json
@@ -0,0 +1,39 @@
+{
+  "ReverseProxy": {
+    "Routes": {
+      "api-route": {
+        "ClusterId": "api-cluster",
+        "Match": {
+          "Path": "/api/{**catch-all}"
+        }
+      },
+      "swagger-route": {
+        "ClusterId": "api-cluster",
+        "Match": {
+          "Path": "/swagger/{**catch-all}"
+        }
+      },
+      "openapi-route": {
+        "ClusterId": "api-cluster",
+        "Match": {
+          "Path": "/openapi/{**catch-all}"
+        }
+      },
+      "scalar-route": {
+        "ClusterId": "api-cluster",
+        "Match": {
+          "Path": "/scalar/{**catch-all}"
+        }
+      }
+    },
+    "Clusters": {
+      "api-cluster": {
+        "Destinations": {
+          "api-destination": {
+            "Address": "https://localhost:8088"
+          }
+        }
+      }
+    }
+  }
+}