diff --git a/iridium_installer/ui/window.py b/iridium_installer/ui/window.py
index c848ccb..efbbb2f 100644
--- a/iridium_installer/ui/window.py
+++ b/iridium_installer/ui/window.py
@@ -287,6 +287,100 @@ class InstallerWindow(Adw.ApplicationWindow):
         # self.bottom_bar.set_visible(True)
         # self.next_button.set_label("Finish")
 
+    def on_next_clicked(self, button):
+        # Logic before transition
+        current_page_name = self.page_ids[self.current_page_index]
+
+        if current_page_name == "storage":
+            selected_disk = self.storage_page.get_selected_disk()
+            self.partitioning_page.load_partitions(selected_disk)
+
+        next_index = self.current_page_index + 1
+
+        if current_page_name == "install_mode":
+            mode = self.install_mode_page.get_mode()
+            if mode == "automatic":
+                # Skip partitioning page
+                next_index = self.page_ids.index("modules")
+            else:
+                # Go to partitioning page
+                next_index = self.page_ids.index("partitioning")
+
+        if current_page_name == "user":
+            # Prepare summary instead of installing immediately
+            disk = self.storage_page.get_selected_disk()
+            mode = self.install_mode_page.get_mode()
+            modules = self.modules_page.get_modules()
+            user_info = self.user_page.get_user_info()
+
+            partitions_config = {}
+            if mode == "manual":
+                partitions_config = self.partitioning_page.get_config()
+            elif mode == "automatic":
+                partitions = calculate_auto_partitions(disk)
+                partitions_config = {"partitions": partitions}
+
+            # Update summary page
+            self.summary_page.update_summary(
+                disk_info=disk,
+                mode=mode,
+                partitions=partitions_config,
+                user_info=user_info,
+                modules=modules,
+            )
+            # Proceed to summary page (which is next_index after user)
+
+        if current_page_name == "summary":
+            # THIS IS THE REAL INSTALL TRIGGER
+            print("Install process triggered!")
+            disk = self.storage_page.get_selected_disk()
+            mode = self.install_mode_page.get_mode()
+            modules = self.modules_page.get_modules()
+            user_info = self.user_page.get_user_info()
+
+            if self.mock_mode:
+                print("!!! MOCK MODE ENABLED - NO CHANGES WILL BE MADE !!!")
+                print(f"Target Disk: {disk}")
+                print(f"Mode: {mode}")
+                print(f"Modules: {modules}")
+                print(f"User: {user_info}")
+                print("Simulation complete.")
+                # Show success in UI even in mock
+                self.show_finish_page("Mock Installation Complete!")
+            else:
+                from ..backend.disk import auto_partition_disk, mount_partitions
+                from ..backend.os_install import install_minimal_os, configure_system
+                
+                # Simple progress UI transition
+                self.show_progress_page("Installing Iridium OS...")
+                
+                # We should really run this in a thread to keep UI responsive, 
+                # but for "barely bootable" requirement and simplicity:
+                try:
+                    # Step 1: Partitioning
+                    print("Step 1: Partitioning...")
+                    parts = auto_partition_disk(disk)
+                    
+                    # Step 2: Mounting
+                    print("Step 2: Mounting...")
+                    mount_root = "/mnt"
+                    mount_partitions(parts, mount_root)
+                    
+                    # Step 3: OS Installation
+                    print("Step 3: OS Installation...")
+                    install_minimal_os(mount_root)
+                    
+                    # Step 4: Configure
+                    print("Step 4: Configuration...")
+                    configure_system(mount_root, parts)
+                    
+                    self.show_finish_page("Installation Successful!")
+                except Exception as e:
+                    print(f"Installation failed: {e}")
+                    self.show_finish_page(f"Installation Failed: {e}", success=False)
+
+            return
+
         if next_index < len(self.page_ids):
             self.current_page_index = next_index
             self.stack.set_visible_child_name(self.page_ids[self.current_page_index])