Remove stale @Gtk.Template.Callback from on_add_project_clicked

src/main-window.ui

@@ -3,7 +3,13 @@
   <requires lib="gtk" version="4.0"/>
   <requires lib="Adw" version="1.0"/>
 
-  <menu id="import_menu">
+  <menu id="sidebar_menu">
+    <section>
+      <item>
+        <attribute name="label">Add Project</attribute>
+        <attribute name="action">win.add-project</attribute>
+      </item>
+    </section>
     <section>
       <item>
         <attribute name="label">Import from OpenAPI / Swagger</attribute>
@@ -18,27 +24,36 @@
         <attribute name="action">win.import-http-file</attribute>
       </item>
     </section>
+    <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>
 
   <template class="RosterWindow" parent="AdwApplicationWindow">
     <property name="default-width">1200</property>
     <property name="default-height">800</property>
+    <property name="width-request">470</property>
     <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">
+            <property name="sidebar">
               <object class="AdwToolbarView">
-            <property name="width-request">200</property>
 
                 <!-- Sidebar Header Bar -->
                 <child type="top">
@@ -59,20 +74,11 @@
                       </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>
+                      <object class="GtkMenuButton" id="sidebar_hamburger_button">
+                        <property name="primary">True</property>
+                        <property name="icon-name">open-menu-symbolic</property>
+                        <property name="tooltip-text">Menu</property>
+                        <property name="menu-model">sidebar_menu</property>
                         <style>
                           <class name="flat"/>
                         </style>
@@ -105,7 +111,7 @@
             </property>
 
             <!-- RIGHT: Main Content Panel with AdwToolbarView -->
-        <property name="end-child">
+            <property name="content">
               <object class="AdwToolbarView">
 
                 <!-- Main Header Bar -->
@@ -115,6 +121,20 @@
                     <property name="show-start-title-buttons">False</property>
                     <property name="show-end-title-buttons">False</property>
 
+                    <!-- Sidebar toggle (only visible when collapsed) -->
+                    <child type="start">
+                      <object class="GtkToggleButton" id="sidebar_toggle_button">
+                        <property name="icon-name">sidebar-show-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>
+
                     <!-- Left side buttons -->
                     <child type="start">
                       <object class="GtkButton" id="save_request_button">
@@ -126,7 +146,6 @@
                         </style>
                       </object>
                     </child>
-
                     <child type="start">
                       <object class="GtkButton" id="export_request_button">
                         <property name="icon-name">export-symbolic</property>
@@ -138,13 +157,15 @@
                       </object>
                     </child>
 
+                    <!-- Window controls: separate end child so it's always rightmost -->
+                    <child type="end">
+                      <object class="GtkWindowControls">
+                        <property name="side">end</property>
+                      </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>
@@ -153,25 +174,6 @@
                         </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>
-                      </object>
-                    </child>
-                  </object>
-                </child>
                   </object>
                 </child>
 
@@ -256,22 +258,14 @@
         </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">
-    <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>

src/request_tab_widget.py

@@ -115,6 +115,7 @@ class RequestTabWidget(Gtk.Box):
         self.url_entry = Gtk.Entry()
         self.url_entry.set_placeholder_text("Enter URL...")
         self.url_entry.set_hexpand(True)
+        self.url_entry.add_css_class("url-entry")
         self.url_box.append(self.url_entry)
 
         # Send Button
@@ -131,10 +132,10 @@ class RequestTabWidget(Gtk.Box):
         split_pane = Gtk.Paned(orientation=Gtk.Orientation.HORIZONTAL)
         split_pane.set_vexpand(True)
         split_pane.set_position(UI_PANE_REQUEST_RESPONSE_POSITION)
-        split_pane.set_shrink_start_child(False)
-        split_pane.set_shrink_end_child(False)
-        split_pane.set_resize_start_child(True)
-        split_pane.set_resize_end_child(True)
+        split_pane.set_shrink_start_child(True)   # request can collapse to 0
+        split_pane.set_shrink_end_child(False)    # response stays
+        split_pane.set_resize_start_child(True)   # request gives up space first
+        split_pane.set_resize_end_child(False)    # response keeps its size
 
         # Request Panel
         request_box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)
@@ -165,6 +166,7 @@ class RequestTabWidget(Gtk.Box):
 
         # Response Panel
         response_box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)
+        response_box.set_size_request(250, -1)
 
         # Stack switcher (placed in bottom bar together with status info)
         response_switcher = Gtk.StackSwitcher()

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
@@ -63,14 +63,12 @@ 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()
-    add_project_button = Gtk.Template.Child()
-
-    import_menu_button = Gtk.Template.Child()
 
     # History (hidden but kept for compatibility)
     history_listbox = Gtk.Template.Child()
@@ -102,6 +100,14 @@ 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()
@@ -204,6 +210,11 @@ class RosterWindow(Adw.ApplicationWindow):
                 font-weight: 600;
             }
 
+            /* URL entry can shrink to near-zero so the Send button stays visible */
+            entry.url-entry {
+                min-width: 0;
+            }
+
             /* Method chips in sidebar request list */
             .method-chip {
                 border-radius: 4px;
@@ -508,6 +519,10 @@ class RosterWindow(Adw.ApplicationWindow):
         self.add_action(action)
         self.get_application().set_accels_for_action("win.send-request", ["<Control>Return"])
 
+        action = Gio.SimpleAction.new("add-project", None)
+        action.connect("activate", lambda a, p: self.on_add_project_clicked(None))
+        self.add_action(action)
+
         action = Gio.SimpleAction.new("import-openapi", None)
         action.connect("activate", lambda a, p: self.on_import_openapi_clicked(None))
         self.add_action(action)
@@ -949,7 +964,6 @@ class RosterWindow(Adw.ApplicationWindow):
             item.connect('manage-environments-requested', self._on_manage_environments, project)
             self.projects_listbox.append(item)
 
-    @Gtk.Template.Callback()
     def on_add_project_clicked(self, button):
         """Show dialog to create project."""
         dialog = Adw.AlertDialog()