diff --git a/src/main-window.ui b/src/main-window.ui
index 9769c0f..2697a35 100644
--- a/src/main-window.ui
+++ b/src/main-window.ui
@@ -8,24 +8,107 @@
     <property name="default-width">1200</property>
     <property name="default-height">800</property>
     <property name="content">
-      <object class="AdwToolbarView">
+      <object class="GtkPaned" id="main_pane">
+        <property name="orientation">horizontal</property>
+        <property name="position">300</property>
+        <property name="shrink-start-child">False</property>
+        <property name="resize-start-child">True</property>
+        <property name="shrink-end-child">False</property>
+        <property name="resize-end-child">True</property>
+        <property name="wide-handle">False</property>
 
-        <!-- Header Bar -->
-        <child type="top">
-          <object class="AdwHeaderBar">
-            <child type="end">
-              <object class="GtkMenuButton">
-                <property name="primary">True</property>
-                <property name="icon-name">open-menu-symbolic</property>
-                <property name="tooltip-text" translatable="yes">Main Menu</property>
-                <property name="menu-model">primary_menu</property>
+        <!-- LEFT: Sidebar Panel with its own header -->
+        <property name="start-child">
+          <object class="GtkBox">
+            <property name="orientation">vertical</property>
+            <property name="width-request">200</property>
+
+            <!-- Sidebar Header Bar -->
+            <child>
+              <object class="AdwHeaderBar">
+                <property name="show-title">False</property>
+                <property name="show-end-title-buttons">False</property>
+                <property name="show-start-title-buttons">False</property>
+                <child type="start">
+                  <object class="GtkLabel">
+                    <property name="label">Projects</property>
+                    <style>
+                      <class name="heading"/>
+                    </style>
+                  </object>
+                </child>
+                <child type="end">
+                  <object class="GtkButton" id="add_project_button">
+                    <property name="icon-name">list-add-symbolic</property>
+                    <property name="tooltip-text">Add Project</property>
+                    <signal name="clicked" handler="on_add_project_clicked"/>
+                    <style>
+                      <class name="flat"/>
+                    </style>
+                  </object>
+                </child>
+              </object>
+            </child>
+
+            <!-- Sidebar Content -->
+            <child>
+              <object class="GtkBox">
+                <property name="orientation">vertical</property>
+                <property name="vexpand">True</property>
+
+                <!-- Projects List -->
+                <child>
+                  <object class="GtkScrolledWindow">
+                    <property name="vexpand">True</property>
+                    <child>
+                      <object class="GtkListBox" id="projects_listbox">
+                        <style>
+                          <class name="navigation-sidebar"/>
+                        </style>
+                      </object>
+                    </child>
+                  </object>
+                </child>
+
+                <!-- Save Current Request Button -->
+                <child>
+                  <object class="GtkButton" id="save_request_button">
+                    <property name="label">Save Current Request</property>
+                    <property name="margin-start">12</property>
+                    <property name="margin-end">12</property>
+                    <property name="margin-bottom">12</property>
+                    <signal name="clicked" handler="on_save_request_clicked"/>
+                    <style>
+                      <class name="suggested-action"/>
+                    </style>
+                  </object>
+                </child>
               </object>
             </child>
           </object>
-        </child>
+        </property>
 
-        <!-- Main Content -->
-        <property name="content">
+        <!-- RIGHT: Main Content Panel with its own header -->
+        <property name="end-child">
+          <object class="GtkBox">
+            <property name="orientation">vertical</property>
+
+            <!-- Main Header Bar -->
+            <child>
+              <object class="AdwHeaderBar">
+                <child type="end">
+                  <object class="GtkMenuButton">
+                    <property name="primary">True</property>
+                    <property name="icon-name">open-menu-symbolic</property>
+                    <property name="tooltip-text" translatable="yes">Main Menu</property>
+                    <property name="menu-model">primary_menu</property>
+                  </object>
+                </child>
+              </object>
+            </child>
+
+            <!-- Main Content -->
+            <child>
           <object class="GtkBox">
             <property name="orientation">vertical</property>
 
@@ -83,87 +166,8 @@
                 <property name="resize-start-child">True</property>
                 <property name="resize-end-child">True</property>
 
-                <!-- START: Main Content Area -->
+                <!-- START: Request/Response Split -->
                 <property name="start-child">
-                  <!-- 3-Column Layout: Sidebar | Request | Response -->
-                  <object class="GtkPaned" id="main_pane">
-                <property name="orientation">horizontal</property>
-                <property name="position">250</property>
-                <property name="shrink-start-child">False</property>
-                <property name="resize-start-child">True</property>
-
-                <!-- START: Sidebar for Projects -->
-                <property name="start-child">
-                  <object class="GtkBox">
-                    <property name="orientation">vertical</property>
-                    <property name="width-request">200</property>
-
-                    <!-- Sidebar Header -->
-                    <child>
-                      <object class="GtkBox">
-                        <property name="orientation">horizontal</property>
-                        <property name="spacing">6</property>
-                        <property name="margin-start">12</property>
-                        <property name="margin-end">12</property>
-                        <property name="margin-top">6</property>
-                        <property name="margin-bottom">6</property>
-
-                        <child>
-                          <object class="GtkLabel">
-                            <property name="label">Projects</property>
-                            <property name="xalign">0</property>
-                            <property name="hexpand">True</property>
-                            <style>
-                              <class name="heading"/>
-                            </style>
-                          </object>
-                        </child>
-
-                        <child>
-                          <object class="GtkButton" id="add_project_button">
-                            <property name="icon-name">list-add-symbolic</property>
-                            <property name="tooltip-text">Add Project</property>
-                            <signal name="clicked" handler="on_add_project_clicked"/>
-                            <style>
-                              <class name="flat"/>
-                            </style>
-                          </object>
-                        </child>
-                      </object>
-                    </child>
-
-                    <!-- Projects List -->
-                    <child>
-                      <object class="GtkScrolledWindow">
-                        <property name="vexpand">True</property>
-                        <child>
-                          <object class="GtkListBox" id="projects_listbox">
-                            <style>
-                              <class name="navigation-sidebar"/>
-                            </style>
-                          </object>
-                        </child>
-                      </object>
-                    </child>
-
-                    <!-- Save Current Request Button -->
-                    <child>
-                      <object class="GtkButton" id="save_request_button">
-                        <property name="label">Save Current Request</property>
-                        <property name="margin-start">12</property>
-                        <property name="margin-end">12</property>
-                        <property name="margin-bottom">12</property>
-                        <signal name="clicked" handler="on_save_request_clicked"/>
-                        <style>
-                          <class name="suggested-action"/>
-                        </style>
-                      </object>
-                    </child>
-                  </object>
-                </property>
-
-                <!-- END: Request/Response Split -->
-                <property name="end-child">
                   <object class="GtkPaned" id="split_pane">
                     <property name="orientation">horizontal</property>
                     <property name="position">600</property>
@@ -237,8 +241,6 @@
                     </property>
                   </object>
                 </property>
-              </object>
-                </property>
 
                 <!-- END: History Panel -->
                 <property name="end-child">
@@ -287,6 +289,8 @@
               </object>
             </child>
           </object>
+            </child>
+          </object>
         </property>
       </object>
     </property>
diff --git a/src/window.ui b/src/window.ui
deleted file mode 100644
index caa0921..0000000
--- a/src/window.ui
+++ /dev/null
@@ -1,50 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<interface>
-  <requires lib="gtk" version="4.0"/>
-  <requires lib="Adw" version="1.0"/>
-  <template class="RosterWindow" parent="AdwApplicationWindow">
-    <property name="title" translatable="yes">Roster</property>
-    <property name="default-width">800</property>
-    <property name="default-height">600</property>
-    <property name="content">
-      <object class="AdwToolbarView">
-        <child type="top">
-          <object class="AdwHeaderBar">
-            <child type="end">
-              <object class="GtkMenuButton">
-                <property name="primary">True</property>
-                <property name="icon-name">open-menu-symbolic</property>
-                <property name="tooltip-text" translatable="yes">Main Menu</property>
-                <property name="menu-model">primary_menu</property>
-              </object>
-            </child>
-          </object>
-        </child>
-        <property name="content">
-          <object class="GtkLabel" id="label">
-            <property name="label" translatable="yes">Hello, World!</property>
-            <style>
-              <class name="title-1"/>
-            </style>
-          </object>
-        </property>
-      </object>
-    </property>
-  </template>
-  <menu id="primary_menu">
-    <section>
-      <item>
-        <attribute name="label" translatable="yes">_Preferences</attribute>
-        <attribute name="action">app.preferences</attribute>
-      </item>
-      <item>
-        <attribute name="label" translatable="yes">_Keyboard Shortcuts</attribute>
-        <attribute name="action">app.shortcuts</attribute>
-      </item>
-      <item>
-        <attribute name="label" translatable="yes">_About Roster</attribute>
-        <attribute name="action">app.about</attribute>
-      </item>
-    </section>
-  </menu>
-</interface>