diff --git a/src/lib/exporter/modernVideoExporter.fallback.test.ts b/src/lib/exporter/modernVideoExporter.fallback.test.ts
index 9f62e935..c781ca1d 100644
--- a/src/lib/exporter/modernVideoExporter.fallback.test.ts
+++ b/src/lib/exporter/modernVideoExporter.fallback.test.ts
@@ -311,6 +311,19 @@ describe("ModernVideoExporter native fallback routing", () => {
 			processedFrameCount: number;
 			totalExportStartTimeMs: number;
 			mediaSourceRetryAttempted: boolean;
+			effectiveDurationSec: number;
+			runtimeDiagnostics: {
+				appVersion: string;
+				userAgent: string;
+				logicalProcessors: number;
+				deviceMemoryGb: number;
+			};
+			backpressureProfile: {
+				name: string;
+				maxDecodeQueue: number;
+				maxPendingFrames: number;
+				maxEncodeQueue: number;
+			};
 		};
 		exporter.sourceVideoInfo = mocks.videoInfo;
 		exporter.renderBackend = "webgpu";
@@ -319,6 +332,19 @@ describe("ModernVideoExporter native fallback routing", () => {
 		exporter.processedFrameCount = 314;
 		exporter.totalExportStartTimeMs = 1;
 		exporter.mediaSourceRetryAttempted = true;
+		exporter.effectiveDurationSec = 10;
+		exporter.runtimeDiagnostics = {
+			appVersion: "1.4.0",
+			userAgent: "RecordlyTest/1.0 Electron/43.1.0",
+			logicalProcessors: 12,
+			deviceMemoryGb: 8,
+		};
+		exporter.backpressureProfile = {
+			name: "webcodecs-balanced-plus",
+			maxDecodeQueue: 12,
+			maxPendingFrames: 32,
+			maxEncodeQueue: 72,
+		};
 
 		const report = exporter.buildLightningExportError(
 			new Error(
@@ -328,9 +354,17 @@ describe("ModernVideoExporter native fallback routing", () => {
 
 		expect(report).toContain("Failure code: VIDEO_DECODE_ENCODING_ERROR");
 		expect(report).toContain("Failure stage: Input video decoding");
+		expect(report).toContain("Output: 1200x570 @ 60 FPS; 8.00 Mbps; mode=default");
+		expect(report).toContain("Recordly version: 1.4.0");
+		expect(report).toContain("Runtime: RecordlyTest/1.0 Electron/43.1.0");
+		expect(report).toContain("Hardware capacity: 12 logical processors; 8 GB device memory");
 		expect(report).toContain("Source: h264 1920x1080 @ 30.000 FPS; 1.000s");
-		expect(report).toContain("Progress at failure: 314 rendered frames after");
+		expect(report).toContain("Source audio: none");
+		expect(report).toContain("Progress at failure: 314/600 (52.3%) rendered frames after");
 		expect(report).toContain("Media source retry: attempted with a fresh source");
+		expect(report).toContain(
+			"Pipeline tuning: webcodecs-balanced-plus; decode queue=12; pending frames=32; encode queue=72",
+		);
 		expect(report).toContain("If only this recording fails");
 		expect(report).not.toContain("Windows Lightning exports can use WebCodecs or FFmpeg");
 	});
diff --git a/src/lib/exporter/modernVideoExporter.ts b/src/lib/exporter/modernVideoExporter.ts
index af4b3169..1bedbb7b 100644
--- a/src/lib/exporter/modernVideoExporter.ts
+++ b/src/lib/exporter/modernVideoExporter.ts
@@ -161,6 +161,13 @@ interface VideoExporterConfig extends ExportConfig {
 	preferredEncoderPath?: SupportedMp4EncoderPath | null;
 }
 
+interface ExportRuntimeDiagnostics {
+	appVersion?: string;
+	userAgent?: string;
+	logicalProcessors?: number;
+	deviceMemoryGb?: number;
+}
+
 type NativeAudioPlan =
 	| {
 			audioMode: "none";
@@ -369,6 +376,7 @@ export class ModernVideoExporter {
 	private displayedRenderFps = 0;
 	private sourceVideoInfo: DecodedVideoInfo | null = null;
 	private mediaSourceRetryAttempted = false;
+	private runtimeDiagnostics: ExportRuntimeDiagnostics = {};
 
 	constructor(config: VideoExporterConfig) {
 		this.config = config;
@@ -378,6 +386,7 @@ export class ModernVideoExporter {
 		let useFallbackMediaSource = false;
 		let retriedWithFallbackMediaSource = false;
 		this.mediaSourceRetryAttempted = false;
+		this.runtimeDiagnostics = await this.collectRuntimeDiagnostics();
 
 		while (true) {
 			let shouldRetryWithFallbackMediaSource = false;
@@ -971,6 +980,36 @@ export class ModernVideoExporter {
 		return normalizeLightningRuntimePlatform(navigator.platform || navigator.userAgent || "");
 	}
 
+	private async collectRuntimeDiagnostics(): Promise<ExportRuntimeDiagnostics> {
+		const diagnostics: ExportRuntimeDiagnostics = {};
+		if (typeof navigator !== "undefined") {
+			const navigatorWithMemory = navigator as Navigator & { deviceMemory?: number };
+			if (navigator.userAgent) diagnostics.userAgent = navigator.userAgent;
+			if (navigator.hardwareConcurrency > 0) {
+				diagnostics.logicalProcessors = navigator.hardwareConcurrency;
+			}
+			if (
+				typeof navigatorWithMemory.deviceMemory === "number" &&
+				navigatorWithMemory.deviceMemory > 0
+			) {
+				diagnostics.deviceMemoryGb = navigatorWithMemory.deviceMemory;
+			}
+		}
+
+		try {
+			if (
+				typeof window !== "undefined" &&
+				typeof window.electronAPI?.getAppVersion === "function"
+			) {
+				diagnostics.appVersion = await window.electronAPI.getAppVersion();
+			}
+		} catch {
+			// Environment diagnostics must never prevent an export attempt.
+		}
+
+		return diagnostics;
+	}
+
 	private getLightningErrorGuidance(message: string): string[] {
 		const guidance = new Set<string>();
 		const platform = this.getPlatformLabel();
@@ -1049,13 +1088,36 @@ export class ModernVideoExporter {
 			`Reason: ${message}`,
 			`Platform: ${this.getPlatformLabel()}`,
 			`Requested backend mode: ${this.config.backendPreference ?? "auto"}`,
-			`Output: ${this.config.width}x${this.config.height} @ ${this.config.frameRate} FPS`,
+			`Output: ${this.config.width}x${this.config.height} @ ${this.config.frameRate} FPS; ${(this.config.bitrate / 1_000_000).toFixed(2)} Mbps; mode=${this.config.encodingMode ?? "default"}`,
 		];
 
+		if (this.runtimeDiagnostics.appVersion) {
+			lines.push(`Recordly version: ${this.runtimeDiagnostics.appVersion}`);
+		}
+		if (this.runtimeDiagnostics.userAgent) {
+			lines.push(`Runtime: ${this.runtimeDiagnostics.userAgent}`);
+		}
+		const hardwareParts = [
+			this.runtimeDiagnostics.logicalProcessors
+				? `${this.runtimeDiagnostics.logicalProcessors} logical processors`
+				: null,
+			this.runtimeDiagnostics.deviceMemoryGb
+				? `${this.runtimeDiagnostics.deviceMemoryGb} GB device memory`
+				: null,
+		].filter((value): value is string => Boolean(value));
+		if (hardwareParts.length > 0) {
+			lines.push(`Hardware capacity: ${hardwareParts.join("; ")}`);
+		}
+
 		if (this.sourceVideoInfo) {
 			lines.push(
 				`Source: ${this.sourceVideoInfo.codec} ${this.sourceVideoInfo.width}x${this.sourceVideoInfo.height} @ ${this.sourceVideoInfo.frameRate.toFixed(3)} FPS; ${this.sourceVideoInfo.duration.toFixed(3)}s`,
 			);
+			lines.push(
+				this.sourceVideoInfo.hasAudio
+					? `Source audio: ${this.sourceVideoInfo.audioCodec ?? "unknown codec"}${this.sourceVideoInfo.audioSampleRate ? ` @ ${this.sourceVideoInfo.audioSampleRate} Hz` : ""}`
+					: "Source audio: none",
+			);
 		}
 
 		if (this.totalExportStartTimeMs > 0) {
@@ -1063,8 +1125,13 @@ export class ModernVideoExporter {
 				0,
 				(this.getNowMs() - this.totalExportStartTimeMs) / 1000,
 			);
+			const expectedFrames = Math.ceil(this.effectiveDurationSec * this.config.frameRate);
+			const progressSuffix =
+				expectedFrames > 0
+					? `/${expectedFrames} (${Math.min(100, (this.processedFrameCount / expectedFrames) * 100).toFixed(1)}%)`
+					: "";
 			lines.push(
-				`Progress at failure: ${this.processedFrameCount} rendered frames after ${elapsedSeconds.toFixed(2)}s`,
+				`Progress at failure: ${this.processedFrameCount}${progressSuffix} rendered frames after ${elapsedSeconds.toFixed(2)}s`,
 			);
 		}
 
@@ -1082,6 +1149,12 @@ export class ModernVideoExporter {
 			);
 		}
 
+		if (this.backpressureProfile) {
+			lines.push(
+				`Pipeline tuning: ${this.backpressureProfile.name}; decode queue=${this.config.maxDecodeQueue ?? this.backpressureProfile.maxDecodeQueue}; pending frames=${this.config.maxPendingFrames ?? this.backpressureProfile.maxPendingFrames}; encode queue=${this.config.maxEncodeQueue ?? this.backpressureProfile.maxEncodeQueue}`,
+			);
+		}
+
 		if (this.lastNativeExportError && !message.includes(this.lastNativeExportError)) {
 			lines.push(`${NATIVE_EXPORT_ENGINE_NAME} fallback: ${this.lastNativeExportError}`);
 		}
diff --git a/src/lib/exporter/streamingDecoder.test.ts b/src/lib/exporter/streamingDecoder.test.ts
index d8e4de74..11805fd0 100644
--- a/src/lib/exporter/streamingDecoder.test.ts
+++ b/src/lib/exporter/streamingDecoder.test.ts
@@ -1,4 +1,4 @@
-import { beforeEach, describe, expect, it, vi } from "vitest";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import {
 	buildVideoDecodeFailure,
 	getDecodedFrameStartupOffsetUs,
@@ -91,6 +91,7 @@ const {
 	mockDemuxerGetMediaInfo,
 	mockDemuxerDestroy,
 	mockDemuxerGetDecoderConfig,
+	mockDemuxerRead,
 } = vi.hoisted(() => ({
 	mockDemuxerLoad: vi.fn(),
 	mockDemuxerGetMediaInfo: vi.fn(async () => ({
@@ -110,6 +111,7 @@ const {
 	})),
 	mockDemuxerDestroy: vi.fn(),
 	mockDemuxerGetDecoderConfig: vi.fn(),
+	mockDemuxerRead: vi.fn(),
 }));
 
 vi.mock("web-demuxer", () => ({
@@ -118,6 +120,7 @@ vi.mock("web-demuxer", () => ({
 		getMediaInfo = mockDemuxerGetMediaInfo;
 		destroy = mockDemuxerDestroy;
 		getDecoderConfig = mockDemuxerGetDecoderConfig;
+		read = mockDemuxerRead;
 	},
 }));
 
@@ -127,6 +130,80 @@ const mockGetLocalMediaUrl = vi.fn(async (filePath: string) => ({
 	url: `http://127.0.0.1:4321/video?path=${encodeURIComponent(filePath)}`,
 }));
 
+describe("StreamingVideoDecoder decode failures", () => {
+	beforeEach(() => {
+		vi.restoreAllMocks();
+		mockDemuxerLoad.mockResolvedValue(undefined);
+		mockDemuxerGetDecoderConfig.mockResolvedValue({
+			codec: "avc1.640034",
+			codedWidth: 1920,
+			codedHeight: 1080,
+		});
+		mockDemuxerRead.mockReturnValue(
+			new ReadableStream({
+				start(controller) {
+					controller.enqueue({
+						type: "key",
+						timestamp: 0,
+						duration: 33_333,
+						byteLength: 4,
+					});
+					controller.close();
+				},
+			}),
+		);
+		Object.assign(globalThis, {
+			window: {
+				location: { href: "http://localhost:5173/" },
+				electronAPI: {
+					readLocalFile: mockReadLocalFile,
+					getLocalMediaUrl: mockGetLocalMediaUrl,
+				},
+			},
+		});
+	});
+
+	afterEach(() => {
+		vi.unstubAllGlobals();
+	});
+
+	it("does not emit frozen remaining frames after a decoder error", async () => {
+		const frame = { timestamp: 0, close: vi.fn() } as unknown as VideoFrame;
+		class FailingVideoDecoder {
+			state: CodecState = "unconfigured";
+			decodeQueueSize = 0;
+			constructor(
+				private readonly callbacks: {
+					output: (decodedFrame: VideoFrame) => void;
+					error: (error: DOMException) => void;
+				},
+			) {}
+			configure() {
+				this.state = "configured";
+			}
+			decode() {
+				this.callbacks.output(frame);
+				this.callbacks.error(new DOMException("bad frame", "EncodingError"));
+			}
+			async flush() {}
+			close() {
+				this.state = "closed";
+			}
+		}
+		vi.stubGlobal("VideoDecoder", FailingVideoDecoder);
+
+		const decoder = new StreamingVideoDecoder();
+		await decoder.loadMetadata("/tmp/failing.mp4");
+		const onFrame = vi.fn(async () => {});
+
+		await expect(decoder.decodeAll(30, undefined, undefined, onFrame)).rejects.toThrow(
+			"[VIDEO_DECODE_ENCODING_ERROR]",
+		);
+		expect(onFrame).not.toHaveBeenCalled();
+		expect(frame.close).toHaveBeenCalledTimes(1);
+	});
+});
+
 describe("StreamingVideoDecoder local media loading", () => {
 	beforeEach(() => {
 		vi.restoreAllMocks();
diff --git a/src/lib/exporter/streamingDecoder.ts b/src/lib/exporter/streamingDecoder.ts
index 17956aef..ee59a0ac 100644
--- a/src/lib/exporter/streamingDecoder.ts
+++ b/src/lib/exporter/streamingDecoder.ts
@@ -36,6 +36,7 @@ interface VideoDecodeFailureContext {
 	decodeQueueSize?: number;
 }
 
+/** Maps WebCodecs failures to stable support-facing identifiers. */
 export function getVideoDecodeFailureCode(error: unknown): string {
 	const name = error instanceof DOMException ? error.name : "";
 	switch (name) {
@@ -64,6 +65,7 @@ function describeUnknownError(error: unknown): string {
 	return String(error);
 }
 
+/** Builds a decode error with codec, source, chunk, and decoder-state context. */
 export function buildVideoDecodeFailure(error: unknown, context: VideoDecodeFailureContext): Error {
 	const details = [`codec=${context.decoderConfig.codec}`];
 	const failureCode = getVideoDecodeFailureCode(error);
@@ -105,6 +107,7 @@ export function buildVideoDecodeFailure(error: unknown, context: VideoDecodeFail
 	return failure;
 }
 
+/** Keeps the original decoder failure when cleanup triggers secondary errors. */
 export function preserveFirstVideoDecodeFailure(
 	existingError: Error | null,
 	error: unknown,
@@ -630,7 +633,7 @@ export class StreamingVideoDecoder {
 		}
 
 		// Flush remaining output frames for the last decoded frame.
-		if (heldFrame && segmentIdx < segments.length) {
+		if (!decodeError && heldFrame && segmentIdx < segments.length) {
 			while (!this.cancelled && segmentIdx < segments.length) {
 				const segment = segments[segmentIdx];
 				if (heldFrameSec < segment.startSec - epsilonSec) {