diff --git a/trinityal/tests/SwapChain.cpp b/trinityal/tests/SwapChain.cpp
index 312c25c08..97dc42ab0 100644
--- a/trinityal/tests/SwapChain.cpp
+++ b/trinityal/tests/SwapChain.cpp
@@ -118,6 +118,145 @@ TEST_F( SwapChain, CanPresentSwapChain )
 	}
 }
 
+namespace
+{
+// Win32 occlusion check (DXGI-independent): true if the window is minimized, or every sampled point is
+// covered by another opaque top-level window. Mirrors the validated Python prototype: sample 5 points
+// (centre + 4 inset corners), and at each find the topmost OPAQUE window (skipping see-through overlays:
+// WS_EX_LAYERED / WS_EX_TRANSPARENT / WS_EX_TOOLWINDOW, e.g. the Alt+Tab switcher).
+bool PointTopIsWindow( HWND target, int px, int py )
+{
+	struct Ctx
+	{
+		int px, py;
+		HWND result;
+	} ctx = { px, py, nullptr };
+	::EnumWindows(
+		[]( HWND hwnd, LPARAM lp ) -> BOOL {
+			Ctx* c = reinterpret_cast<Ctx*>( lp );
+			if( !::IsWindowVisible( hwnd ) || ::IsIconic( hwnd ) )
+				return TRUE;
+			if( ::GetWindowLongW( hwnd, GWL_EXSTYLE ) & ( WS_EX_LAYERED | WS_EX_TRANSPARENT | WS_EX_TOOLWINDOW ) )
+				return TRUE;
+			RECT r;
+			if( !::GetWindowRect( hwnd, &r ) )
+				return TRUE;
+			if( c->px >= r.left && c->px < r.right && c->py >= r.top && c->py < r.bottom )
+			{
+				c->result = hwnd; // topmost opaque window covering this point
+				return FALSE;
+			}
+			return TRUE;
+		},
+		reinterpret_cast<LPARAM>( &ctx ) );
+	return ctx.result == target;
+}
+
+bool IsWindowOccluded( HWND hwnd )
+{
+	if( !hwnd )
+		return false;
+	if( ::IsIconic( hwnd ) )
+		return true; // minimized
+	RECT r;
+	if( !::GetWindowRect( hwnd, &r ) )
+		return false;
+	const int w = r.right - r.left;
+	const int h = r.bottom - r.top;
+	if( w <= 0 || h <= 0 )
+		return true;
+	const double fx[5] = { 0.5, 0.12, 0.88, 0.12, 0.88 };
+	const double fy[5] = { 0.5, 0.12, 0.12, 0.88, 0.88 };
+	for( int i = 0; i < 5; ++i )
+	{
+		if( PointTopIsWindow( hwnd, r.left + int( fx[i] * w ), r.top + int( fy[i] * h ) ) )
+			return false; // our window is visible at this point
+	}
+	return true; // every sampled point covered by another opaque window
+}
+}
+
+// Interactive occlusion probe: presents the primary swapchain (bound to the visible 640x480 window) in a
+// loop and logs the DXGI Present HRESULT + fps. Cover / minimize / half-cover the window and read the log;
+// DXGI_STATUS_OCCLUDED should appear only when the window is fully covered or minimized.
+//   TrinityALTest_dx12_internal.exe --interactive --gtest_filter=SwapChain.OcclusionThrottleProbe
+TEST_F( SwapChain, OcclusionThrottleProbe )
+{
+	ENSURE_GPU_OR_SKIP
+
+	FILE* log = nullptr;
+	fopen_s( &log, "occlusion_throttle_test.log", "w" );
+	if( log )
+	{
+		fprintf( log, "-- WINDOW_HIDDEN throttle demo: covered/minimized -> Win32-occlusion-gated throttle "
+					  "(20ms sleep + render 1/50, matching TriDevice::Throttle + ShouldSkipFrame). "
+					  "Click window + press a key to exit --\n" );
+		fflush( log );
+	}
+
+	LARGE_INTEGER freq;
+	QueryPerformanceFrequency( &freq );
+	LARGE_INTEGER lastLog;
+	QueryPerformanceCounter( &lastLog );
+	int frame = 0; // loop iterations
+	int renders = 0; // actual renders since last log
+	unsigned skip = 0;
+	uint32_t g = 0;
+
+	auto body = [&] {
+		const bool occluded = IsWindowOccluded( (HWND)WithWindow::GetWindowHandle() );
+
+		// Emulate TriDevice::ShouldSkipFrame() for WINDOW_HIDDEN: render only 1 frame in 50.
+		bool doRender = true;
+		if( occluded )
+			doRender = ( ( skip++ % 50 ) == 0 );
+		else
+			skip = 0;
+
+		if( doRender )
+		{
+			ASSERT_HRESULT_SUCCEEDED( renderContext->BeginScene() );
+			ASSERT_HRESULT_SUCCEEDED( renderContext->PushDepthStencil() );
+			ASSERT_HRESULT_SUCCEEDED( renderContext->SetDepthStencil( Tr2TextureAL() ) );
+			ASSERT_HRESULT_SUCCEEDED( renderContext->PushRenderTarget() );
+			ASSERT_HRESULT_SUCCEEDED( renderContext->SetRenderTarget( renderContext->GetDefaultBackBuffer() ) );
+			ASSERT_HRESULT_SUCCEEDED( renderContext->Clear( Tr2RenderContextEnum::CLEARFLAGS_TARGET, 0xff000000 | ( ( g & 0xff ) << 8 ), 1.0f ) );
+			ASSERT_HRESULT_SUCCEEDED( renderContext->PopRenderTarget() );
+			ASSERT_HRESULT_SUCCEEDED( renderContext->PopDepthStencil() );
+			ASSERT_HRESULT_SUCCEEDED( renderContext->EndScene() );
+			ASSERT_HRESULT_SUCCEEDED( renderContext->Present() );
+			++renders;
+		}
+
+		// Emulate TriDevice::Throttle() sleep for WINDOW_HIDDEN (20ms).
+		if( occluded )
+			::Sleep( 20 );
+
+		++frame;
+		++g;
+
+		if( frame % 30 == 0 && log )
+		{
+			LARGE_INTEGER now;
+			QueryPerformanceCounter( &now );
+			const double elapsed = double( now.QuadPart - lastLog.QuadPart ) / double( freq.QuadPart );
+			lastLog = now;
+			const double loopFps = elapsed > 0.0 ? 30.0 / elapsed : 0.0;
+			const double renderFps = elapsed > 0.0 ? renders / elapsed : 0.0;
+			renders = 0;
+			fprintf( log, "frame %6d | %-8s throttle=%-3s | loopFps=%9.1f | renderFps=%8.1f\n", frame, occluded ? "OCCLUDED" : "visible", occluded ? "ON" : "off", loopFps, renderFps );
+			fflush( log );
+		}
+	};
+
+	RunLoop( body );
+
+	if( log )
+	{
+		fclose( log );
+	}
+}
+
 TEST_F( SwapChain, CanRecreateSwapChain )
 {
 	ENSURE_GPU_OR_SKIP