fix(export): keep Windows auto off static layout first

src/lib/exporter/backendPolicy.test.ts

@@ -27,8 +27,8 @@ describe("backendPolicy", () => {
 		expect(getDefaultLightningRenderBackend()).toBe("webgl");
 	});
 
-	it("puts visually compatible Windows auto exports on native static layout before Breeze", () => {
-		expect(shouldPreferNativeStaticLayoutBeforeBreeze("win32", "auto")).toBe(true);
+	it("keeps Windows auto exports on the streaming route by default", () => {
+		expect(shouldPreferNativeStaticLayoutBeforeBreeze("win32", "auto")).toBe(false);
 		expect(shouldPreferNativeStaticLayoutBeforeBreeze("darwin", "auto")).toBe(false);
 
 		expect(
@@ -38,16 +38,16 @@ describe("backendPolicy", () => {
 				nativeStaticLayoutAvailable: true,
 			}),
 		).toMatchObject({
-			selectedRoute: "native-static-layout",
+			selectedRoute: "breeze-stream",
 			decisions: [
-				{ route: "native-static-layout", status: "selected" },
-				{ route: "breeze-stream", status: "fallback" },
+				{ route: "native-static-layout", status: "rejected" },
+				{ route: "breeze-stream", status: "selected" },
 				{ route: "webcodecs", status: "fallback" },
 			],
 		});
 	});
 
-	it("documents the Breeze fallback when Windows static native is rejected", () => {
+	it("ignores native static skip reasons for Windows auto routing", () => {
 		expect(
 			planLightningExportRoutes({
 				backendPreference: "auto",
@@ -61,12 +61,12 @@ describe("backendPolicy", () => {
 				{
 					route: "native-static-layout",
 					status: "rejected",
-					reasons: ["unsupported-frame-overlay"],
+					reasons: ["platform-does-not-use-native-static-layout"],
 				},
 				{
 					route: "breeze-stream",
 					status: "selected",
-					reasons: ["windows-native-static-fallback"],
+					reasons: ["platform-prefers-native-streaming"],
 				},
 				{
 					route: "webcodecs",

src/lib/exporter/backendPolicy.ts

@@ -41,11 +41,19 @@ export interface LightningExportRoutePlan {
 	decisions: LightningExportRouteDecision[];
 }
 
+// Disabled while stabilizing v1.3.0: the Windows auto static-layout probe can
+// leave Lightning at "Preparing export..." before the stable streaming fallback.
+const WINDOWS_AUTO_STATIC_LAYOUT_FIRST_ENABLED = false;
+
 export function shouldPreferNativeStaticLayoutBeforeBreeze(
 	platform: LightningRuntimePlatform,
 	backendPreference: ExportBackendPreference,
 ): boolean {
-	return backendPreference === "auto" && platform === "win32";
+	return (
+		WINDOWS_AUTO_STATIC_LAYOUT_FIRST_ENABLED &&
+		backendPreference === "auto" &&
+		platform === "win32"
+	);
 }
 
 export function planLightningExportRoutes(options: {
@@ -92,7 +100,7 @@ export function planLightningExportRoutes(options: {
 			reasons: [
 				options.backendPreference === "breeze"
 					? "user-selected-breeze"
-					: "windows-native-static-fallback",
+					: "native-static-layout-not-auto-default",
 			],
 		});
 		decisions.push({

src/lib/exporter/modernVideoExporter.fallback.test.ts

@@ -118,7 +118,64 @@ describe("ModernVideoExporter native fallback routing", () => {
 		expect(mocks.muxerFinalize).toHaveBeenCalledTimes(1);
 	}, 15_000);
 
-	it("tries Windows auto static-layout before starting the streaming native encoder", async () => {
+	it("keeps Windows auto exports on the streaming native route before static layout", async () => {
+		vi.stubGlobal("navigator", {
+			platform: "Win32",
+			userAgent: "Mozilla/5.0 (Windows NT 10.0; Win64; x64)",
+		});
+
+		const { ModernVideoExporter } = await import("./modernVideoExporter");
+		const nativeResult = {
+			success: true,
+			blob: new Blob([], { type: "video/mp4" }),
+		};
+		const exporter = new ModernVideoExporter({
+			videoUrl: "file:///recording.mp4",
+			width: 1920,
+			height: 1080,
+			frameRate: 30,
+			bitrate: 8_000_000,
+			wallpaper: "#101010",
+			padding: 0,
+			borderRadius: 0,
+			backgroundBlur: 0,
+			shadowIntensity: 0,
+			showShadow: false,
+			cropRegion: { x: 0, y: 0, width: 1, height: 1 },
+			experimentalNativeExport: true,
+			backendPreference: "auto",
+		} as never) as unknown as {
+			export: () => Promise<{ success: boolean; blob?: Blob; error?: string }>;
+			finishNativeVideoExport: () => Promise<unknown>;
+			loadNativeStaticLayoutVideoInfo: () => Promise<unknown>;
+			tryExportNativeStaticLayout: () => Promise<unknown>;
+			tryStartNativeVideoExport: () => Promise<boolean>;
+		};
+
+		const loadNativeStaticLayoutVideoInfo = vi.spyOn(
+			exporter,
+			"loadNativeStaticLayoutVideoInfo",
+		);
+		const tryExportNativeStaticLayout = vi.spyOn(exporter, "tryExportNativeStaticLayout");
+		const tryStartNativeVideoExport = vi
+			.spyOn(exporter, "tryStartNativeVideoExport")
+			.mockResolvedValue(true);
+		const finishNativeVideoExport = vi
+			.spyOn(exporter, "finishNativeVideoExport")
+			.mockResolvedValue(nativeResult);
+
+		const result = await exporter.export();
+
+		expect(result.success).toBe(true);
+		expect(result.blob).toBe(nativeResult.blob);
+		expect(tryStartNativeVideoExport).toHaveBeenCalledTimes(1);
+		expect(loadNativeStaticLayoutVideoInfo).not.toHaveBeenCalled();
+		expect(tryExportNativeStaticLayout).not.toHaveBeenCalled();
+		expect(mocks.streamingDecoderLoadMetadata).toHaveBeenCalledTimes(1);
+		expect(finishNativeVideoExport).toHaveBeenCalledTimes(1);
+	}, 15_000);
+
+	it("tries Windows auto static-layout first when NVIDIA CUDA is opted in", async () => {
 		vi.stubGlobal("navigator", {
 			platform: "Win32",
 			userAgent: "Mozilla/5.0 (Windows NT 10.0; Win64; x64)",
@@ -143,6 +200,7 @@ describe("ModernVideoExporter native fallback routing", () => {
 			showShadow: false,
 			cropRegion: { x: 0, y: 0, width: 1, height: 1 },
 			experimentalNativeExport: true,
+			experimentalNvidiaCudaExport: true,
 			backendPreference: "auto",
 		} as never) as unknown as {
 			export: () => Promise<{ success: boolean; blob?: Blob; error?: string }>;

src/lib/exporter/modernVideoExporter.ts

@@ -382,8 +382,12 @@ export class ModernVideoExporter {
 				const runtimePlatform = this.getRuntimePlatform();
 				let useNativeEncoder = false;
 				let triedNativeStaticLayoutWithProbe = false;
+				const shouldTryNativeStaticLayout =
+					backendPreference === "breeze" ||
+					this.config.experimentalNvidiaCudaExport === true;
 				let shouldDeferNativeEncoderStart =
 					backendPreference === "breeze" ||
+					this.config.experimentalNvidiaCudaExport === true ||
 					shouldPreferNativeStaticLayoutBeforeBreeze(runtimePlatform, backendPreference);
 				this.lastNativeExportError = null;
 
@@ -478,10 +482,7 @@ export class ModernVideoExporter {
 					maxInFlightNativeWrites: this.maxNativeWriteInFlight,
 				});
 
-				if (
-					(backendPreference === "auto" || backendPreference === "breeze") &&
-					!useNativeEncoder
-				) {
+				if (shouldTryNativeStaticLayout && !useNativeEncoder) {
 					const nativeVideoInfo = await this.loadNativeStaticLayoutVideoInfo();
 					if (nativeVideoInfo) {
 						triedNativeStaticLayoutWithProbe = true;
@@ -530,7 +531,7 @@ export class ModernVideoExporter {
 				const totalFrames = Math.ceil(effectiveDuration * this.config.frameRate);
 
 				if (
-					(backendPreference === "auto" || backendPreference === "breeze") &&
+					shouldTryNativeStaticLayout &&
 					!useNativeEncoder &&
 					!triedNativeStaticLayoutWithProbe
 				) {