diff --git a/src/lib/exporter/finalizationTimeout.test.ts b/src/lib/exporter/finalizationTimeout.test.ts
index 91728291..7193470a 100644
--- a/src/lib/exporter/finalizationTimeout.test.ts
+++ b/src/lib/exporter/finalizationTimeout.test.ts
@@ -189,4 +189,24 @@ describe("finalizationTimeout", () => {
 		expect(advanced.lastRenderProgress).toBe(100);
 		expect(advanced.lastAudioProgress).toBe(0.5);
 	});
+
+	it("ignores non-finite render progress without poisoning later updates", () => {
+		const invalid = advanceFinalizationProgress({
+			renderProgress: Number.NaN,
+			audioProgress: 0.25,
+			state: INITIAL_FINALIZATION_PROGRESS_STATE,
+		});
+		expect(invalid.progressed).toBe(true);
+		expect(invalid.lastRenderProgress).toBe(-1);
+		expect(invalid.lastAudioProgress).toBe(0.25);
+
+		const recovered = advanceFinalizationProgress({
+			renderProgress: 99,
+			audioProgress: 0.25,
+			state: invalid,
+		});
+		expect(recovered.progressed).toBe(true);
+		expect(recovered.lastRenderProgress).toBe(99);
+		expect(recovered.lastAudioProgress).toBe(0.25);
+	});
 });
diff --git a/src/lib/exporter/finalizationTimeout.ts b/src/lib/exporter/finalizationTimeout.ts
index 86b7e9dd..040409fd 100644
--- a/src/lib/exporter/finalizationTimeout.ts
+++ b/src/lib/exporter/finalizationTimeout.ts
@@ -75,12 +75,18 @@ export function advanceFinalizationProgress({
 	audioProgress?: number;
 	state: FinalizationProgressState;
 }): FinalizationProgressState & { progressed: boolean } {
-	const normalizedRenderProgress = Math.max(0, Math.min(renderProgress, 100));
+	const normalizedRenderProgress =
+		typeof renderProgress === "number" && Number.isFinite(renderProgress)
+			? Math.max(0, Math.min(renderProgress, 100))
+			: null;
 	const normalizedAudioProgress =
 		typeof audioProgress === "number" && Number.isFinite(audioProgress)
 			? Math.max(0, Math.min(audioProgress, 1))
 			: null;
-	const nextRenderProgress = Math.max(state.lastRenderProgress, normalizedRenderProgress);
+	const nextRenderProgress =
+		normalizedRenderProgress === null
+			? state.lastRenderProgress
+			: Math.max(state.lastRenderProgress, normalizedRenderProgress);
 	const nextAudioProgress =
 		normalizedAudioProgress === null
 			? state.lastAudioProgress
@@ -122,12 +128,17 @@ export async function withFinalizationTimeout<T>({
 				workload,
 			})
 		: null;
-	const watchdog: FinalizationProgressWatchdog | null =
-		progressAware && idleTimeoutMs !== null && idleTimeoutMs !== undefined
-			? {
-					refreshProgress: () => undefined,
-				}
-			: null;
+	const hasIdleWatchdog =
+		progressAware &&
+		typeof idleTimeoutMs === "number" &&
+		Number.isFinite(idleTimeoutMs) &&
+		idleTimeoutMs >= 0;
+	const resolvedIdleTimeoutMs = hasIdleWatchdog ? idleTimeoutMs : null;
+	const watchdog: FinalizationProgressWatchdog | null = hasIdleWatchdog
+		? {
+				refreshProgress: () => undefined,
+			}
+		: null;
 
 	try {
 		return await Promise.race([
@@ -136,16 +147,16 @@ export async function withFinalizationTimeout<T>({
 				const rejectWithMessage = (message: string) => {
 					reject(new Error(message));
 				};
-				if (watchdog && idleTimeoutMs !== null) {
+				if (watchdog && resolvedIdleTimeoutMs !== null) {
 					const refreshProgress = () => {
 						if (idleTimeoutId) {
 							clearTimeout(idleTimeoutId);
 						}
 						idleTimeoutId = setTimeout(() => {
 							rejectWithMessage(
-								`Export timed out during ${stage} after ${Math.ceil(idleTimeoutMs / 1000)} seconds without observable progress`,
+								`Export timed out during ${stage} after ${Math.ceil(resolvedIdleTimeoutMs / 1000)} seconds without observable progress`,
 							);
-						}, idleTimeoutMs);
+						}, resolvedIdleTimeoutMs);
 					};
 					watchdog.refreshProgress = refreshProgress;
 					onWatchdogChanged?.(watchdog);
diff --git a/src/lib/exporter/modernVideoExporter.ts b/src/lib/exporter/modernVideoExporter.ts
index 35db408d..622a4914 100644
--- a/src/lib/exporter/modernVideoExporter.ts
+++ b/src/lib/exporter/modernVideoExporter.ts
@@ -985,7 +985,6 @@ export class ModernVideoExporter {
 		}
 
 		const sessionId = this.nativeExportSessionId;
-		this.nativeExportSessionId = null;
 		console.log(`[VideoExporter] Finalizing ${NATIVE_EXPORT_ENGINE_NAME} export`, {
 			sessionId,
 			audioMode: audioPlan.audioMode,
@@ -1009,6 +1008,7 @@ export class ModernVideoExporter {
 			`${NATIVE_EXPORT_ENGINE_NAME} export finalization`,
 			audioPlan.audioMode === "none" ? "default" : "audio",
 		);
+		this.nativeExportSessionId = null;
 
 		if (!result.success) {
 			return {
diff --git a/src/lib/exporter/videoExporter.ts b/src/lib/exporter/videoExporter.ts
index ebcad040..c5c53c80 100644
--- a/src/lib/exporter/videoExporter.ts
+++ b/src/lib/exporter/videoExporter.ts
@@ -710,8 +710,6 @@ export class VideoExporter {
 		}
 
 		const sessionId = this.nativeExportSessionId;
-		this.nativeExportSessionId = null;
-
 		const result = await this.awaitWithFinalizationTimeout(
 			window.electronAPI.nativeVideoExportFinish(sessionId, {
 				audioMode: audioPlan.audioMode,
@@ -727,6 +725,7 @@ export class VideoExporter {
 			"native export finalization",
 			audioPlan.audioMode === "none" ? "default" : "audio",
 		);
+		this.nativeExportSessionId = null;
 
 		if (!result.success || !result.data) {
 			return {
@@ -1152,6 +1151,7 @@ export class VideoExporter {
 		}
 
 		this.muxer = null;
+		this.audioProcessor?.cancel();
 		this.audioProcessor = null;
 		this.activeFinalizationProgressWatchdog = null;
 		this.lastFinalizationRenderProgress =