diff --git a/docs/modernization/build-inventory.md b/docs/modernization/build-inventory.md
index 9d2e9dd..0df10db 100644
--- a/docs/modernization/build-inventory.md
+++ b/docs/modernization/build-inventory.md
@@ -446,8 +446,8 @@ Known local toolchain state:
   platform clipboard bridges.
 - `pp_platform_api` exposes the SDK-free `PlatformServices` interface for
   clipboard text, cursor visibility, virtual-keyboard visibility, external
-  file display, file sharing, picker callbacks, and prepared-file
-  save/download handoff; Windows live app execution now uses injected
+  file display, file sharing, native app/window close, picker callbacks, and
+  prepared-file save/download handoff; Windows live app execution now uses injected
   `WindowsPlatformServices` from
   `src/platform_windows/windows_platform_services.*` in `pp_platform_windows`,
   while non-Windows platforms still reach retained platform bridges through
diff --git a/docs/modernization/debt.md b/docs/modernization/debt.md
index cba1de7..7d73ef7 100644
--- a/docs/modernization/debt.md
+++ b/docs/modernization/debt.md
@@ -35,7 +35,7 @@ agent or engineer to remove them without reconstructing context from chat.
 | DEBT-0014 | Open | Modernization | `windows-clangcl-asan` now configures as a headless Ninja/clang-cl preset and uses the release MSVC runtime required by ASan, but local builds still fail because installed clang-cl 18.1.8 is paired with VS 2026-preview STL headers that require Clang 20 or newer | Sanitizer validation should be local and repeatable, but this machine's compiler/header pairing is incompatible | `cmake --fresh --preset windows-clangcl-asan`; `cmake --build --preset windows-clangcl-asan --target pp_foundation` | Install/use Clang 20+ with the VS 2026 STL, or point the preset at a compatible VS 2022 toolchain, then make `platform-build.ps1 -Presets windows-clangcl-asan` pass for the headless matrix |
 | DEBT-0015 | Open | Modernization | Cursor visibility requests now consume pure `pp_app_core` planning through `pano_cli plan-cursor-visibility`, `App::show_cursor`/`App::hide_cursor` dispatch through `PlatformServices` without platform guards, and Windows live execution uses injected `WindowsPlatformServices`, but macOS cursor execution still reaches the retained fallback adapter | Keep canvas cursor behavior stable while platform shells are extracted incrementally | `pp_app_core_document_platform_io_tests`; `pano_cli plan-cursor-visibility --visible`; `ctest --preset desktop-fast --build-config Debug` | Cursor visibility execution is owned by injected `pp_platform_*` services for every supported platform |
 | DEBT-0016 | Open | Modernization | Clipboard get/set requests now consume pure `pp_app_core` planning through `pano_cli plan-clipboard-read` and `pano_cli plan-clipboard-write`, and Windows live execution uses injected `WindowsPlatformServices`, but Apple/Android clipboard execution still reaches retained fallback adapter branches from `App::clipboard_get_text` and `App::clipboard_set_text` | Keep picker/color text clipboard behavior stable while platform shells are extracted incrementally | `pp_app_core_document_platform_io_tests`; `pano_cli plan-clipboard-write --text #ff00aa`; `ctest --preset desktop-fast --build-config Debug` | Clipboard execution is owned by injected `pp_platform_*` services for every supported platform |
-| DEBT-0017 | Open | Modernization | `App::clipboard_get_text`, `App::clipboard_set_text`, `App::show_cursor`, `App::hide_cursor`, `App::showKeyboard`, `App::hideKeyboard`, `App::display_file`, `App::share_file`, `App::pick_image`, `App::pick_file`, the non-writer `App::pick_file_save`, `App::pick_dir`, and prepared-file save/download handoff now call the SDK-free `pp::platform::PlatformServices` interface, and Windows injects `WindowsPlatformServices` from `src/platform_windows/windows_platform_services.*`; non-Windows live implementations still use `src/platform_legacy/legacy_platform_services.*`, a named fallback adapter that forwards to retained Apple/Android/Linux/Web bridge functions and retained no-op branches | Preserve behavior while moving platform execution behind a testable service boundary before platform shell implementations are injected | `pp_platform_api_tests`; `pp_app_core_document_platform_io_tests`; `ctest --preset desktop-fast --build-config Debug`; `powershell -ExecutionPolicy Bypass -File scripts\automation\package-smoke.ps1 -Preset windows-msvc-default -Configuration Debug` | Replace `src/platform_legacy/legacy_platform_services.*` with injected `pp_platform_*` service implementations owned by each non-Windows platform shell |
+| DEBT-0017 | Open | Modernization | `App::clipboard_get_text`, `App::clipboard_set_text`, `App::show_cursor`, `App::hide_cursor`, `App::showKeyboard`, `App::hideKeyboard`, `App::display_file`, `App::share_file`, native app/window close, `App::pick_image`, `App::pick_file`, the non-writer `App::pick_file_save`, `App::pick_dir`, and prepared-file save/download handoff now call the SDK-free `pp::platform::PlatformServices` interface, and Windows injects `WindowsPlatformServices` from `src/platform_windows/windows_platform_services.*`; non-Windows live implementations still use `src/platform_legacy/legacy_platform_services.*`, a named fallback adapter that forwards to retained Apple/Android/Linux/Web bridge functions and retained no-op branches | Preserve behavior while moving platform execution behind a testable service boundary before platform shell implementations are injected | `pp_platform_api_tests`; `pp_app_core_document_platform_io_tests`; `ctest --preset desktop-fast --build-config Debug`; `powershell -ExecutionPolicy Bypass -File scripts\automation\package-smoke.ps1 -Preset windows-msvc-default -Configuration Debug` | Replace `src/platform_legacy/legacy_platform_services.*` with injected `pp_platform_*` service implementations owned by each non-Windows platform shell |
 
 ## Closed Debt
 
diff --git a/docs/modernization/roadmap.md b/docs/modernization/roadmap.md
index 9d0770a..748e15d 100644
--- a/docs/modernization/roadmap.md
+++ b/docs/modernization/roadmap.md
@@ -482,6 +482,10 @@ writes the temporary/exported payload.
 `App::show_cursor`, `App::hide_cursor`, `App::showKeyboard`, and
 `App::hideKeyboard` now dispatch through the active service without local
 platform guards; unsupported platforms rely on their service no-op behavior.
+The unsaved-document close prompt now requests native app/window close through
+`PlatformServices`, with Windows implemented by `WindowsPlatformServices` and
+macOS/Linux still handled by the legacy adapter until those platform shells
+are injected.
 `pano_cli plan-cloud-upload` exposes the app-core cloud upload decision used by
 the live cloud upload command for missing-canvas, new-document warning, publish
 prompt, and dirty-document save-before-upload states before legacy UI, canvas,
@@ -995,11 +999,12 @@ Results:
 - `pp_platform_api_tests` passed, covering the SDK-free `PlatformServices`
   interface for clipboard read/write, empty clipboard writes, cursor
   visibility dispatch, virtual-keyboard visibility dispatch, external file
-  display dispatch, file sharing dispatch, picker callback dispatch, and
-  prepared-file save/download callback dispatch. The live Windows app now
-  consumes this interface through an injected `WindowsPlatformServices`
-  instance isolated in `src/platform_windows/windows_platform_services.*`;
-  other platforms still use the legacy fallback adapter, now isolated in
+  display dispatch, file sharing dispatch, native app/window close dispatch,
+  picker callback dispatch, and prepared-file save/download callback dispatch.
+  The live Windows app now consumes this interface through an injected
+  `WindowsPlatformServices` instance isolated in
+  `src/platform_windows/windows_platform_services.*`; other platforms still
+  use the legacy fallback adapter, now isolated in
   `src/platform_legacy/legacy_platform_services.*` instead of being owned by
   `app_events.cpp`.
 - `panopainter_validate_shaders` passed, validating 25 shader programs and 7
diff --git a/src/app.cpp b/src/app.cpp
index bbcf890..ba3cb00 100644
--- a/src/app.cpp
+++ b/src/app.cpp
@@ -27,7 +27,6 @@ bool async_lock_try();
 void async_lock();
 void win32_async_swap();
 void async_unlock();
-void destroy_window();
 void win32_renderdoc_frame_start();
 void win32_renderdoc_frame_end();
 #elif __LINUX__
@@ -273,16 +272,7 @@ bool App::request_close()
         m->m_message->set_text("Do you want to close without saving?");
         m->btn_ok->m_text->set_text("Yes");
         m->btn_ok->on_click = [this](Node*) {
-#ifdef _WIN32
-            destroy_window();
-            //PostQuitMessage(0);
-#elif __OSX__
-            dispatch_async(dispatch_get_main_queue(), ^{
-                [osx_view close];
-            });
-#elif __LINUX__
-            glfwSetWindowShouldClose(glfw_window, GLFW_TRUE);
-#endif
+            request_app_close();
             Canvas::I->m_unsaved = false;
         };
         m->btn_cancel->m_text->set_text("No");
diff --git a/src/app.h b/src/app.h
index 3b54367..8e13d9e 100644
--- a/src/app.h
+++ b/src/app.h
@@ -189,6 +189,7 @@ public:
     void pick_dir(std::function<void(std::string path)> callback);
     void display_file(std::string path);
     void share_file(std::string path);
+    void request_app_close();
     void save_prepared_file(
         std::string path,
         std::string suggested_name,
diff --git a/src/app_events.cpp b/src/app_events.cpp
index 9747740..41b5630 100644
--- a/src/app_events.cpp
+++ b/src/app_events.cpp
@@ -214,6 +214,11 @@ void App::share_file(std::string path)
     active_platform_services().share_file(path);
 }
 
+void App::request_app_close()
+{
+    active_platform_services().request_app_close();
+}
+
 void App::save_prepared_file(
     std::string path,
     std::string suggested_name,
diff --git a/src/platform_api/platform_services.h b/src/platform_api/platform_services.h
index fc1c9d5..6d6e134 100644
--- a/src/platform_api/platform_services.h
+++ b/src/platform_api/platform_services.h
@@ -20,6 +20,7 @@ public:
     virtual void set_virtual_keyboard_visible(bool visible) = 0;
     virtual void display_file(std::string_view path) = 0;
     virtual void share_file(std::string_view path) = 0;
+    virtual void request_app_close() = 0;
     virtual void pick_image(PickedPathCallback callback) = 0;
     virtual void pick_file(std::vector<std::string> file_types, PickedPathCallback callback) = 0;
     virtual void pick_save_file(std::vector<std::string> file_types, PickedPathCallback callback) = 0;
diff --git a/src/platform_legacy/legacy_platform_services.cpp b/src/platform_legacy/legacy_platform_services.cpp
index 8fa4990..b473bbd 100644
--- a/src/platform_legacy/legacy_platform_services.cpp
+++ b/src/platform_legacy/legacy_platform_services.cpp
@@ -205,6 +205,17 @@ public:
 #endif
     }
 
+    void request_app_close() override
+    {
+#ifdef __OSX__
+        dispatch_async(dispatch_get_main_queue(), ^{
+            [App::I->osx_view close];
+        });
+#elif __LINUX__
+        glfwSetWindowShouldClose(App::I->glfw_window, GLFW_TRUE);
+#endif
+    }
+
     void save_prepared_file(
         std::string_view path,
         std::string_view suggested_name,
diff --git a/src/platform_windows/windows_platform_services.cpp b/src/platform_windows/windows_platform_services.cpp
index 9b8a219..38f7632 100644
--- a/src/platform_windows/windows_platform_services.cpp
+++ b/src/platform_windows/windows_platform_services.cpp
@@ -7,6 +7,8 @@ extern HWND hWnd;
 extern std::deque<std::packaged_task<void()>> main_tasklist;
 extern std::mutex main_task_mutex;
 
+void destroy_window();
+
 namespace {
 
 void show_cursor(bool visible)
@@ -176,6 +178,11 @@ public:
         (void)path;
     }
 
+    void request_app_close() override
+    {
+        destroy_window();
+    }
+
     void pick_image(pp::platform::PickedPathCallback callback) override
     {
         const std::string path = open_file("Image Files (*.jpg, *.png)\0*.jpg;*.png");
diff --git a/tests/platform_api/platform_services_tests.cpp b/tests/platform_api/platform_services_tests.cpp
index 2aa69df..b9c2ce9 100644
--- a/tests/platform_api/platform_services_tests.cpp
+++ b/tests/platform_api/platform_services_tests.cpp
@@ -52,6 +52,11 @@ public:
         shared_path.assign(path);
     }
 
+    void request_app_close() override
+    {
+        ++app_close_requests;
+    }
+
     void pick_image(pp::platform::PickedPathCallback callback) override
     {
         ++pick_image_requests;
@@ -95,6 +100,7 @@ public:
     int keyboard_updates = 0;
     int display_file_requests = 0;
     int share_file_requests = 0;
+    int app_close_requests = 0;
     int pick_image_requests = 0;
     int pick_file_requests = 0;
     int pick_save_file_requests = 0;
@@ -162,9 +168,11 @@ void platform_services_dispatch_file_actions(pp::tests::Harness& harness)
 
     services.display_file("D:/Paint/export.png");
     services.share_file("D:/Paint/demo.ppi");
+    services.request_app_close();
 
     PP_EXPECT(harness, fake.display_file_requests == 1);
     PP_EXPECT(harness, fake.share_file_requests == 1);
+    PP_EXPECT(harness, fake.app_close_requests == 1);
     PP_EXPECT(harness, fake.displayed_path == "D:/Paint/export.png");
     PP_EXPECT(harness, fake.shared_path == "D:/Paint/demo.ppi");
 }