diff --git a/docs/modernization/build-inventory.md b/docs/modernization/build-inventory.md
index 0df10db..f708f00 100644
--- a/docs/modernization/build-inventory.md
+++ b/docs/modernization/build-inventory.md
@@ -446,8 +446,9 @@ 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, native app/window close, picker callbacks, and
-  prepared-file save/download handoff; Windows live app execution now uses injected
+  file display, file sharing, native app/window close, per-frame platform
+  hooks, 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 7d73ef7..140d2d3 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`, 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 |
+| 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, per-frame platform hooks, `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 748e15d..30aa918 100644
--- a/docs/modernization/roadmap.md
+++ b/docs/modernization/roadmap.md
@@ -486,6 +486,10 @@ 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.
+The UI loop's per-frame platform hooks now dispatch through
+`PlatformServices`: Windows stylus timeout polling and FPS-title updates live
+in `WindowsPlatformServices`, while Linux FPS-title updates remain in the
+legacy adapter pending Phase 6 platform shell extraction.
 `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,
@@ -1000,8 +1004,9 @@ Results:
   interface for clipboard read/write, empty clipboard writes, cursor
   visibility dispatch, virtual-keyboard visibility dispatch, external file
   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
+  per-frame platform hook 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
diff --git a/src/app.cpp b/src/app.cpp
index ba3cb00..855179f 100644
--- a/src/app.cpp
+++ b/src/app.cpp
@@ -1123,10 +1123,7 @@ void App::ui_thread_main()
         float dt = std::chrono::duration<float>(t_now - t_start).count();
         t_start = t_now;
 
-#ifdef _WIN32
-        extern void win32_update_stylus(float dt);
-        win32_update_stylus(dt);
-#endif
+        update_platform_frame(dt);
 
         // increment timers
         t_frame += dt;
@@ -1134,13 +1131,7 @@ void App::ui_thread_main()
 
         if (t_fps_counter > 1.f)
         {
-#ifdef _WIN32
-            extern void win32_update_fps(int frames);
-            win32_update_fps(rendered_frames);
-#elif __LINUX__
-            extern void linux_update_fps(int frames);
-            linux_update_fps(rendered_frames);
-#endif
+            report_rendered_frames(rendered_frames);
             t_fps_counter = 0;
             rendered_frames = 0;
         }
diff --git a/src/app.h b/src/app.h
index 8e13d9e..baf4ad1 100644
--- a/src/app.h
+++ b/src/app.h
@@ -190,6 +190,8 @@ public:
     void display_file(std::string path);
     void share_file(std::string path);
     void request_app_close();
+    void update_platform_frame(float delta_time_seconds);
+    void report_rendered_frames(int frames);
     void save_prepared_file(
         std::string path,
         std::string suggested_name,
diff --git a/src/app_events.cpp b/src/app_events.cpp
index 41b5630..8eb6015 100644
--- a/src/app_events.cpp
+++ b/src/app_events.cpp
@@ -219,6 +219,16 @@ void App::request_app_close()
     active_platform_services().request_app_close();
 }
 
+void App::update_platform_frame(float delta_time_seconds)
+{
+    active_platform_services().update_platform_frame(delta_time_seconds);
+}
+
+void App::report_rendered_frames(int frames)
+{
+    active_platform_services().report_rendered_frames(frames);
+}
+
 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 6d6e134..d04c582 100644
--- a/src/platform_api/platform_services.h
+++ b/src/platform_api/platform_services.h
@@ -18,6 +18,8 @@ public:
     [[nodiscard]] virtual bool set_clipboard_text(std::string_view text) = 0;
     virtual void set_cursor_visible(bool visible) = 0;
     virtual void set_virtual_keyboard_visible(bool visible) = 0;
+    virtual void update_platform_frame(float delta_time_seconds) = 0;
+    virtual void report_rendered_frames(int frames) = 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;
diff --git a/src/platform_legacy/legacy_platform_services.cpp b/src/platform_legacy/legacy_platform_services.cpp
index b473bbd..310fdae 100644
--- a/src/platform_legacy/legacy_platform_services.cpp
+++ b/src/platform_legacy/legacy_platform_services.cpp
@@ -13,6 +13,7 @@ bool android_set_clipboard(const std::string& s);
 #elif __APPLE__
 #elif __LINUX__
 #include <tinyfiledialogs.h>
+void linux_update_fps(int frames);
 #elif __WEB__
 void webgl_pick_file(std::function<void(std::string)> callback);
 void webgl_pick_file_save(
@@ -87,6 +88,20 @@ public:
 #endif
     }
 
+    void update_platform_frame(float delta_time_seconds) override
+    {
+        (void)delta_time_seconds;
+    }
+
+    void report_rendered_frames(int frames) override
+    {
+#ifdef __LINUX__
+        linux_update_fps(frames);
+#else
+        (void)frames;
+#endif
+    }
+
     void pick_image(pp::platform::PickedPathCallback callback) override
     {
 #ifdef __IOS__
diff --git a/src/platform_windows/windows_platform_services.cpp b/src/platform_windows/windows_platform_services.cpp
index 38f7632..9771148 100644
--- a/src/platform_windows/windows_platform_services.cpp
+++ b/src/platform_windows/windows_platform_services.cpp
@@ -8,6 +8,8 @@ extern std::deque<std::packaged_task<void()>> main_tasklist;
 extern std::mutex main_task_mutex;
 
 void destroy_window();
+void win32_update_fps(int frames);
+void win32_update_stylus(float dt);
 
 namespace {
 
@@ -168,6 +170,16 @@ public:
         (void)visible;
     }
 
+    void update_platform_frame(float delta_time_seconds) override
+    {
+        win32_update_stylus(delta_time_seconds);
+    }
+
+    void report_rendered_frames(int frames) override
+    {
+        win32_update_fps(frames);
+    }
+
     void display_file(std::string_view path) override
     {
         (void)path;
diff --git a/tests/platform_api/platform_services_tests.cpp b/tests/platform_api/platform_services_tests.cpp
index b9c2ce9..ad21ce7 100644
--- a/tests/platform_api/platform_services_tests.cpp
+++ b/tests/platform_api/platform_services_tests.cpp
@@ -40,6 +40,18 @@ public:
         keyboard_visible = visible;
     }
 
+    void update_platform_frame(float delta_time_seconds) override
+    {
+        ++platform_frame_updates;
+        last_platform_delta = delta_time_seconds;
+    }
+
+    void report_rendered_frames(int frames) override
+    {
+        ++frame_reports;
+        last_frame_report = frames;
+    }
+
     void display_file(std::string_view path) override
     {
         ++display_file_requests;
@@ -98,6 +110,8 @@ public:
     int clipboard_writes = 0;
     int cursor_updates = 0;
     int keyboard_updates = 0;
+    int platform_frame_updates = 0;
+    int frame_reports = 0;
     int display_file_requests = 0;
     int share_file_requests = 0;
     int app_close_requests = 0;
@@ -109,6 +123,8 @@ public:
     bool cursor_visible = false;
     bool keyboard_visible = false;
     bool prepared_file_saved = true;
+    float last_platform_delta = 0.0f;
+    int last_frame_report = 0;
     std::string displayed_path;
     std::string shared_path;
     std::string prepared_file_path;
@@ -161,6 +177,20 @@ void platform_services_dispatch_visibility_updates(pp::tests::Harness& harness)
     PP_EXPECT(harness, !fake.keyboard_visible);
 }
 
+void platform_services_dispatch_frame_hooks(pp::tests::Harness& harness)
+{
+    FakePlatformServices fake("unused");
+    pp::platform::PlatformServices& services = fake;
+
+    services.update_platform_frame(0.125f);
+    services.report_rendered_frames(42);
+
+    PP_EXPECT(harness, fake.platform_frame_updates == 1);
+    PP_EXPECT(harness, fake.last_platform_delta == 0.125f);
+    PP_EXPECT(harness, fake.frame_reports == 1);
+    PP_EXPECT(harness, fake.last_frame_report == 42);
+}
+
 void platform_services_dispatch_file_actions(pp::tests::Harness& harness)
 {
     FakePlatformServices fake("unused");
@@ -233,6 +263,7 @@ int main()
     harness.run("platform services dispatch clipboard reads and writes", platform_services_dispatch_clipboard_reads_and_writes);
     harness.run("platform services preserve empty clipboard writes", platform_services_preserve_empty_clipboard_writes);
     harness.run("platform services dispatch visibility updates", platform_services_dispatch_visibility_updates);
+    harness.run("platform services dispatch frame hooks", platform_services_dispatch_frame_hooks);
     harness.run("platform services dispatch file actions", platform_services_dispatch_file_actions);
     harness.run("platform services dispatch picker callbacks", platform_services_dispatch_picker_callbacks);
     harness.run("platform services dispatch prepared file save", platform_services_dispatch_prepared_file_save);