diff --git a/src/main-window.ui b/src/main-window.ui
index b86dd08..efc50d8 100644
--- a/src/main-window.ui
+++ b/src/main-window.ui
@@ -26,154 +26,155 @@
     <property name="content">
       <object class="AdwToastOverlay" id="toast_overlay">
         <property name="child">
-          <object class="GtkPaned" id="main_pane">
-        <property name="orientation">horizontal</property>
-        <property name="position">180</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>
+          <object class="AdwOverlaySplitView" id="split_view">
+            <property name="min-sidebar-width">200</property>
+            <property name="max-sidebar-width">320</property>
 
-        <!-- LEFT: Sidebar Panel with AdwToolbarView -->
-        <property name="start-child">
-          <object class="AdwToolbarView">
-            <property name="width-request">200</property>
+            <!-- LEFT: Sidebar Panel with AdwToolbarView -->
+            <property name="sidebar">
+              <object class="AdwToolbarView">
 
-            <!-- Sidebar Header Bar -->
-            <child type="top">
-              <object class="AdwHeaderBar">
-                <property name="show-end-title-buttons">False</property>
-                <property name="show-start-title-buttons">False</property>
-                <property name="title-widget">
-                  <object class="GtkLabel">
-                    <property name="label">Projects</property>
-                    <style>
-                      <class name="title"/>
-                    </style>
-                  </object>
-                </property>
-                <child type="start">
-                  <object class="GtkWindowControls">
-                    <property name="side">start</property>
-                  </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>
-                <child type="end">
-                  <object class="GtkMenuButton" id="import_menu_button">
-                    <property name="icon-name">papyrus-vertical-symbolic</property>
-                    <property name="tooltip-text">Import</property>
-                    <property name="menu-model">import_menu</property>
-                    <style>
-                      <class name="flat"/>
-                    </style>
-                  </object>
-                </child>
-              </object>
-            </child>
-
-            <!-- Sidebar Content -->
-            <property name="content">
-              <object class="GtkBox">
-                <property name="orientation">vertical</property>
-
-                <!-- Projects List -->
-                <child>
-                  <object class="GtkScrolledWindow">
-                    <property name="vexpand">True</property>
-                    <child>
-                      <object class="GtkListBox" id="projects_listbox">
+                <!-- Sidebar Header Bar -->
+                <child type="top">
+                  <object class="AdwHeaderBar">
+                    <property name="show-end-title-buttons">False</property>
+                    <property name="show-start-title-buttons">False</property>
+                    <property name="title-widget">
+                      <object class="GtkLabel">
+                        <property name="label">Projects</property>
                         <style>
-                          <class name="navigation-sidebar"/>
+                          <class name="title"/>
+                        </style>
+                      </object>
+                    </property>
+                    <child type="start">
+                      <object class="GtkWindowControls">
+                        <property name="side">start</property>
+                      </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>
+                    <child type="end">
+                      <object class="GtkMenuButton" id="import_menu_button">
+                        <property name="icon-name">papyrus-vertical-symbolic</property>
+                        <property name="tooltip-text">Import</property>
+                        <property name="menu-model">import_menu</property>
+                        <style>
+                          <class name="flat"/>
                         </style>
                       </object>
                     </child>
                   </object>
                 </child>
+
+                <!-- Sidebar Content -->
+                <property name="content">
+                  <object class="GtkBox">
+                    <property name="orientation">vertical</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>
+                  </object>
+                </property>
               </object>
             </property>
-          </object>
-        </property>
 
-        <!-- RIGHT: Main Content Panel with AdwToolbarView -->
-        <property name="end-child">
-          <object class="AdwToolbarView">
+            <!-- RIGHT: Main Content Panel with AdwToolbarView -->
+            <property name="content">
+              <object class="AdwToolbarView">
 
-            <!-- Main Header Bar -->
-            <child type="top">
-              <object class="AdwHeaderBar">
-                <property name="show-title">False</property>
-                <property name="show-start-title-buttons">False</property>
-                <property name="show-end-title-buttons">False</property>
+                <!-- Main Header Bar -->
+                <child type="top">
+                  <object class="AdwHeaderBar">
+                    <property name="show-title">False</property>
+                    <property name="show-start-title-buttons">False</property>
+                    <property name="show-end-title-buttons">False</property>
 
-                <!-- Left side buttons -->
-                <child type="start">
-                  <object class="GtkButton" id="save_request_button">
-                    <property name="icon-name">document-save-symbolic</property>
-                    <property name="tooltip-text">Save Current Request (Ctrl+S)</property>
-                    <signal name="clicked" handler="on_save_request_clicked"/>
-                    <style>
-                      <class name="flat"/>
-                    </style>
-                  </object>
-                </child>
+                    <!-- Sidebar toggle (only visible when collapsed) -->
+                    <child type="start">
+                      <object class="GtkToggleButton" id="sidebar_toggle_button">
+                        <property name="icon-name">view-sidebar-symbolic</property>
+                        <property name="tooltip-text">Show Sidebar</property>
+                        <style>
+                          <class name="flat"/>
+                        </style>
+                        <binding name="visible">
+                          <lookup name="collapsed">split_view</lookup>
+                        </binding>
+                      </object>
+                    </child>
 
-                <child type="start">
-                  <object class="GtkButton" id="export_request_button">
-                    <property name="icon-name">export-symbolic</property>
-                    <property name="tooltip-text">Export as cURL</property>
-                    <signal name="clicked" handler="on_export_request_clicked"/>
-                    <style>
-                      <class name="flat"/>
-                    </style>
-                  </object>
-                </child>
-
-                <!-- Right side buttons -->
-                <child type="end">
-                  <object class="GtkBox">
-                    <property name="spacing">6</property>
-
-                    <!-- New Request Button -->
-                    <child>
-                      <object class="GtkButton" id="new_request_button">
-                        <property name="icon-name">list-add-symbolic</property>
-                        <property name="tooltip-text">New Request (Ctrl+T)</property>
+                    <!-- Left side buttons -->
+                    <child type="start">
+                      <object class="GtkButton" id="save_request_button">
+                        <property name="icon-name">document-save-symbolic</property>
+                        <property name="tooltip-text">Save Current Request (Ctrl+S)</property>
+                        <signal name="clicked" handler="on_save_request_clicked"/>
+                        <style>
+                          <class name="flat"/>
+                        </style>
+                      </object>
+                    </child>
+                    <child type="start">
+                      <object class="GtkButton" id="export_request_button">
+                        <property name="icon-name">export-symbolic</property>
+                        <property name="tooltip-text">Export as cURL</property>
+                        <signal name="clicked" handler="on_export_request_clicked"/>
                         <style>
                           <class name="flat"/>
                         </style>
                       </object>
                     </child>
 
-                    <!-- Main Menu -->
-                    <child>
-                      <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>
-
-                    <!-- Window Controls -->
-                    <child>
-                      <object class="GtkWindowControls">
-                        <property name="side">end</property>
+                    <!-- Right side buttons -->
+                    <child type="end">
+                      <object class="GtkBox">
+                        <property name="spacing">6</property>
+                        <child>
+                          <object class="GtkButton" id="new_request_button">
+                            <property name="icon-name">list-add-symbolic</property>
+                            <property name="tooltip-text">New Request (Ctrl+T)</property>
+                            <style>
+                              <class name="flat"/>
+                            </style>
+                          </object>
+                        </child>
+                        <child>
+                          <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>
+                        <child>
+                          <object class="GtkWindowControls">
+                            <property name="side">end</property>
+                          </object>
+                        </child>
                       </object>
                     </child>
                   </object>
                 </child>
-              </object>
-            </child>
 
             <!-- Tab Bar as separate top bar -->
             <child type="top">
@@ -256,6 +257,14 @@
         </property>
       </object>
     </property>
+
+    <!-- Collapse sidebar when window is narrow -->
+    <child>
+      <object class="AdwBreakpoint">
+        <condition>max-width: 700sp</condition>
+        <setter object="split_view" property="collapsed">True</setter>
+      </object>
+    </child>
   </template>
 
   <menu id="primary_menu">
diff --git a/src/window.py b/src/window.py
index 081ba91..9078d43 100644
--- a/src/window.py
+++ b/src/window.py
@@ -19,7 +19,7 @@
 
 import gi
 gi.require_version('GtkSource', '5')
-from gi.repository import Adw, Gtk, GLib, Gio, GtkSource
+from gi.repository import Adw, Gtk, GLib, Gio, GtkSource, GObject
 from typing import Dict, Optional
 import logging
 from .models import HttpRequest, HttpResponse, HistoryEntry, RequestTab
@@ -63,8 +63,9 @@ class RosterWindow(Adw.ApplicationWindow):
     tab_view = Gtk.Template.Child()
     tab_bar = Gtk.Template.Child()
 
-    # Panes
-    main_pane = Gtk.Template.Child()
+    # Split view
+    split_view = Gtk.Template.Child()
+    sidebar_toggle_button = Gtk.Template.Child()
 
     # Sidebar widgets
     projects_listbox = Gtk.Template.Child()
@@ -102,6 +103,14 @@ class RosterWindow(Adw.ApplicationWindow):
         # Setup custom CSS
         self._setup_custom_css()
 
+        # Bind sidebar toggle button to split view (bidirectional)
+        self.split_view.bind_property(
+            'show-sidebar',
+            self.sidebar_toggle_button,
+            'active',
+            GObject.BindingFlags.BIDIRECTIONAL | GObject.BindingFlags.SYNC_CREATE
+        )
+
         # Setup UI
         self._setup_tab_system()
         self._load_projects()