feat(desktop): show download progress and diagnostics on splash (#3273)

fluxer_desktop/src/main/Bootstrap.ts

@@ -92,12 +92,15 @@ const SPLASH_STATUS_BY_UPDATER_STATUS: Readonly<Record<ModuleUpdaterStatus, Spla
 
 function toSplashState(state: ModuleUpdaterSplashState): SplashState {
 	return {
-		status: SPLASH_STATUS_BY_UPDATER_STATUS[state.status],
+		status: state.stalled ? 'download-stalled' : SPLASH_STATUS_BY_UPDATER_STATUS[state.status],
 		requiredSecurityUpdate: state.requiredSecurityUpdate,
 		current: state.current,
 		total: state.total,
 		progress: state.progress,
 		seconds: state.seconds,
+		receivedBytes: state.receivedBytes,
+		totalBytes: state.totalBytes,
+		bytesPerSecond: state.bytesPerSecond,
 		message: state.detail,
 	};
 }
@@ -259,7 +262,7 @@ async function refuseUnsupportedBuild(reason: string): Promise<never> {
 }
 
 async function runModuleBootstrap(): Promise<void> {
-	const {app} = await import('electron');
+	const {app, clipboard, session, shell} = await import('electron');
 	const {BUILD_CHANNEL} = await import('@electron/common/BuildChannel');
 	const {createChildLogger} = await import('@electron/common/Logger');
 	const {loadDesktopConfig} = await import('@electron/common/DesktopConfig');
@@ -288,11 +291,14 @@ async function runModuleBootstrap(): Promise<void> {
 	const {resolveShellUpdatePlan, ShellUpdateCapability} = await import('@electron/main/ShellUpdateCapability');
 	const {armBlockedShellUpdate} = await import('@electron/main/ShellUpdateSplash');
 	const {UpdateServerRetry} = await import('@electron/main/UpdateServerRetry');
+	const {buildSplashDiagnosticsText} = await import('@electron/main/SplashDiagnostics');
 	const {
 		closeSplashWindow,
 		focusSplashWindow,
 		markSplashLaunching,
+		onSplashCopyDiagnostics,
 		onSplashNetworkOnline,
+		onSplashOpenLogs,
 		onSplashQuit,
 		onSplashRetry,
 		openSplashWindow,
@@ -373,6 +379,72 @@ async function runModuleBootstrap(): Promise<void> {
 		updateServerRetry.networkReturned();
 	});
 
+	const splashOpenedAt = Date.now();
+	let diagnosticsSource: {
+		readonly store: ModuleStoreInstance;
+		readonly updater: ModuleUpdaterInstance;
+	} | null = null;
+	const resolveLogsPath = (): string | null => {
+		try {
+			return app.getPath('logs');
+		} catch {
+			return null;
+		}
+	};
+	const collectSplashDiagnostics = async (): Promise<string> => {
+		const updaterDiagnostics = diagnosticsSource?.updater.diagnostics() ?? null;
+		const packageOrigin = updaterDiagnostics?.packageOrigin ?? resolveDesktopPackageOrigin();
+		let proxyRoute: string | null = null;
+		try {
+			proxyRoute = await session.defaultSession.resolveProxy(packageOrigin);
+		} catch (error) {
+			logger.warn('Failed to resolve the proxy route for diagnostics', error);
+		}
+		const state = updaterDiagnostics?.state ?? null;
+		return buildSplashDiagnosticsText({
+			generatedAt: Date.now(),
+			splashOpenedAt,
+			appVersion: app.getVersion(),
+			channel: BUILD_CHANNEL,
+			platform: process.platform,
+			arch: process.arch,
+			osVersion: process.getSystemVersion(),
+			electronVersion: process.versions.electron ?? 'unknown',
+			logsPath: resolveLogsPath(),
+			userDataPath: userDataConfig.base,
+			packageOrigin,
+			proxyRoute,
+			splashStatus: state == null ? null : (toSplashState(state).status ?? null),
+			updaterStatus: state?.status ?? null,
+			pendingModule: state?.moduleName ?? null,
+			receivedBytes: state?.receivedBytes ?? null,
+			totalBytes: state?.totalBytes ?? null,
+			bytesPerSecond: state?.bytesPerSecond ?? null,
+			committed: diagnosticsSource?.store.getCommitted() ?? {},
+			lastError: updaterDiagnostics?.lastError ?? null,
+			lastErrorAt: updaterDiagnostics?.lastErrorAt ?? null,
+		});
+	};
+	onSplashOpenLogs(() => {
+		const logsPath = resolveLogsPath();
+		if (logsPath == null) return;
+		void shell.openPath(logsPath).then((failure) => {
+			if (failure.length > 0) {
+				logger.warn('Failed to open the logs folder from the splash', {failure});
+			}
+		});
+	});
+	onSplashCopyDiagnostics(() => {
+		void collectSplashDiagnostics()
+			.then((text) => {
+				clipboard.writeText(text);
+				logger.info('Copied updater diagnostics from the splash');
+			})
+			.catch((error: unknown) => {
+				logger.error('Failed to copy updater diagnostics', error);
+			});
+	});
+
 	const showBlockedSplash = (status: SplashStatus, message: string | null = null): void => {
 		openSplashWindow();
 		setSplashState({status, action: SplashAction.RETRY, message});
@@ -432,6 +504,7 @@ async function runModuleBootstrap(): Promise<void> {
 				});
 			},
 		});
+		diagnosticsSource = {store, updater};
 
 		const runModuleUpdateAttempt = async (): Promise<ModuleLaunchPermit | null> => {
 			let outcome: ModuleUpdaterOutcome;

fluxer_desktop/src/main/ModuleDownloadRate.ts

@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+const RATE_SMOOTHING_WINDOW_MS = 3000;
+const RATE_MIN_SAMPLE_MS = 200;
+
+export class ModuleDownloadRate {
+	private lastBytes: number | null = null;
+	private lastAt = 0;
+	private rate: number | null = null;
+
+	public reset(): void {
+		this.lastBytes = null;
+		this.lastAt = 0;
+		this.rate = null;
+	}
+
+	public sample(bytes: number, at: number): number | null {
+		if (this.lastBytes == null || bytes < this.lastBytes) {
+			this.lastBytes = bytes;
+			this.lastAt = at;
+			this.rate = null;
+			return null;
+		}
+		const elapsed = at - this.lastAt;
+		if (elapsed < RATE_MIN_SAMPLE_MS) {
+			return this.rate;
+		}
+		const instant = ((bytes - this.lastBytes) * 1000) / elapsed;
+		const weight = 1 - Math.exp(-elapsed / RATE_SMOOTHING_WINDOW_MS);
+		this.rate = this.rate == null ? instant : this.rate + (instant - this.rate) * weight;
+		this.lastBytes = bytes;
+		this.lastAt = at;
+		return this.rate;
+	}
+}

fluxer_desktop/src/main/ModulePackageInstaller.ts

@@ -14,7 +14,8 @@ import type {ModulePlanItem} from '@electron/main/ModuleUpdatePlanner';
 
 const MODULE_PACKAGE_HASH_MISMATCH_RETRIES = 1;
 const MODULE_PACKAGE_HEADER_TIMEOUT_MS = 30000;
-const MODULE_PACKAGE_STALL_TIMEOUT_MS = 60000;
+export const MODULE_PACKAGE_STALL_TIMEOUT_MS = 30000;
+const MODULE_PACKAGE_PROGRESS_INTERVAL_MS = 250;
 const TRANSIENT_HTTP_STATUS_FLOOR = 500;
 const TRANSIENT_PACKAGE_HTTP_STATUSES: ReadonlySet<number> = new Set([408, 425, 429]);
 const CAUSE_CHAIN_LIMIT = 8;
@@ -37,6 +38,8 @@ interface ModulePackageInstallProgress {
 	readonly total: number;
 	readonly moduleName: string;
 	readonly progress: number;
+	readonly receivedBytes: number;
+	readonly totalBytes: number;
 }
 
 export const ModulePackageInstallerReportType = Object.freeze({
@@ -77,6 +80,7 @@ interface ModulePackageInstallerOptions {
 	readonly packageOrigin: string;
 	readonly fetch: typeof globalThis.fetch;
 	readonly onProgress: (progress: ModulePackageInstallProgress) => void;
+	readonly now?: () => number;
 	readonly report: (report: ModulePackageInstallerReport) => void;
 }
 
@@ -92,6 +96,17 @@ export class ModulePackageFetchError extends Error {
 	}
 }
 
+export class ModulePackageStallError extends ModulePackageFetchError {
+	public constructor(moduleName: string, stallMs: number) {
+		super(moduleName, null, `package download stalled for ${stallMs}ms`);
+		this.name = 'ModulePackageStallError';
+	}
+}
+
+export function isModulePackageStall(error: unknown): boolean {
+	return findCause(error, ModulePackageStallError) != null;
+}
+
 class ModulePackageUrlPolicyError extends Error {
 	public readonly module: string;
 
@@ -168,6 +183,7 @@ export class ModulePackageInstaller {
 	private readonly packageOrigin: string;
 	private readonly fetchImplementation: typeof globalThis.fetch;
 	private readonly onProgress: (progress: ModulePackageInstallProgress) => void;
+	private readonly now: () => number;
 	private readonly reporter: (report: ModulePackageInstallerReport) => void;
 
 	public constructor(options: ModulePackageInstallerOptions) {
@@ -175,6 +191,7 @@ export class ModulePackageInstaller {
 		this.packageOrigin = options.packageOrigin;
 		this.fetchImplementation = options.fetch;
 		this.onProgress = options.onProgress;
+		this.now = options.now ?? Date.now;
 		this.reporter = options.report;
 	}
 
@@ -192,6 +209,8 @@ export class ModulePackageInstaller {
 					total,
 					moduleName: item.module,
 					progress: Math.round((current / total) * 100),
+					receivedBytes: item.entry.bytes,
+					totalBytes: item.entry.bytes,
 				});
 				return;
 			} catch (error) {
@@ -238,6 +257,8 @@ export class ModulePackageInstaller {
 			total,
 			moduleName: item.module,
 			progress: item.entry.bytes === 0 ? 0 : Math.floor((offset / item.entry.bytes) * 100),
+			receivedBytes: offset,
+			totalBytes: item.entry.bytes,
 		});
 		if (offset > 0 && offset === item.entry.bytes) {
 			return {offset, chunks: []};
@@ -339,18 +360,13 @@ export class ModulePackageInstaller {
 		let reader: ReadableStreamDefaultReader<Uint8Array> | null = null;
 		let received = start;
 		let reported = item.entry.bytes === 0 ? 0 : Math.floor((start / item.entry.bytes) * 100);
+		let reportedAt = this.now();
 		let completed = false;
 		let transferFailure: unknown = null;
 		let stall: NodeJS.Timeout | null = null;
 		const arm = (): void => {
 			stall = setTimeout(() => {
-				controller.abort(
-					new ModulePackageFetchError(
-						item.module,
-						null,
-						`package download stalled for ${MODULE_PACKAGE_STALL_TIMEOUT_MS}ms`,
-					),
-				);
+				controller.abort(new ModulePackageStallError(item.module, MODULE_PACKAGE_STALL_TIMEOUT_MS));
 			}, MODULE_PACKAGE_STALL_TIMEOUT_MS);
 		};
 		const disarm = (): void => {
@@ -378,14 +394,18 @@ export class ModulePackageInstaller {
 					);
 				}
 				const percent = item.entry.bytes === 0 ? 100 : Math.floor((received / item.entry.bytes) * 100);
-				if (percent > reported) {
+				const at = this.now();
+				if (percent > reported || at - reportedAt >= MODULE_PACKAGE_PROGRESS_INTERVAL_MS) {
 					reported = percent;
+					reportedAt = at;
 					this.onProgress({
 						phase: ModulePackageInstallPhase.DOWNLOADING,
 						current,
 						total,
 						moduleName: item.module,
 						progress: percent,
+						receivedBytes: received,
+						totalBytes: item.entry.bytes,
 					});
 				}
 				yield chunk.value;

fluxer_desktop/src/main/ModuleUpdater.ts

@@ -2,6 +2,7 @@
 
 import {createHash} from 'node:crypto';
 import {BUILD_CHANNEL} from '@electron/common/BuildChannel';
+import {ModuleDownloadRate} from '@electron/main/ModuleDownloadRate';
 import {
 	blockingModuleNames,
 	type DesktopLinuxSecurityMinimum,
@@ -16,6 +17,7 @@ import {
 import {
 	describeErrorChain,
 	isDeterministicPackageFailure,
+	isModulePackageStall,
 	isTransientServerStatus,
 	ModulePackageFetchError,
 	ModulePackageInstaller,
@@ -123,6 +125,17 @@ export interface ModuleUpdaterSplashState {
 	readonly seconds: number | null;
 	readonly moduleName: string | null;
 	readonly detail: string | null;
+	readonly receivedBytes: number | null;
+	readonly totalBytes: number | null;
+	readonly bytesPerSecond: number | null;
+	readonly stalled: boolean;
+}
+
+export interface ModuleUpdaterDiagnostics {
+	readonly state: ModuleUpdaterSplashState;
+	readonly packageOrigin: string;
+	readonly lastError: string | null;
+	readonly lastErrorAt: number | null;
 }
 
 interface ModuleUpdaterReport {
@@ -289,6 +302,11 @@ export class ModuleUpdater {
 	private readonly random: () => number;
 	private readonly now: () => number;
 	private lastState: ModuleUpdaterSplashState;
+	private readonly packageOrigin: string;
+	private readonly downloadRate = new ModuleDownloadRate();
+	private downloadProgressed = false;
+	private lastError: string | null = null;
+	private lastErrorAt: number | null = null;
 	private ensureBlockedUntil = 0;
 	private startupUpdatePolicy: ModuleStartupUpdatePolicy;
 	private manifestObservationTail: Promise<void> = Promise.resolve();
@@ -303,6 +321,7 @@ export class ModuleUpdater {
 		const arch = resolveDesktopModuleArchitecture(options.arch ?? process.arch);
 		this.manifestFeed = {releaseChannel, platform: this.platform, arch};
 		const packageOrigin = (options.packageOrigin ?? resolveDesktopPackageOrigin()).replace(/\/+$/u, '');
+		this.packageOrigin = packageOrigin;
 		this.planner = new ModuleUpdatePlanner(this.store, shellVersion, options.hasOfflineRenderer ?? false);
 		this.onState = options.onState ?? (() => {});
 		this.reporter = options.report ?? (() => {});
@@ -323,10 +342,15 @@ export class ModuleUpdater {
 			store: this.store,
 			packageOrigin,
 			fetch: options.fetch,
+			now: () => this.now(),
 			onProgress: (progress) => {
 				switch (progress.phase) {
 					case ModulePackageInstallPhase.DOWNLOADING:
-						this.emit(ModuleUpdaterStatus.DOWNLOADING, progress);
+						this.recordDownloadProgress(progress.receivedBytes);
+						this.emit(ModuleUpdaterStatus.DOWNLOADING, {
+							...progress,
+							bytesPerSecond: this.downloadRate.sample(progress.receivedBytes, this.now()) ?? undefined,
+						});
 						break;
 					case ModulePackageInstallPhase.INSTALLING:
 						this.emit(ModuleUpdaterStatus.INSTALLING, progress);
@@ -346,9 +370,29 @@ export class ModuleUpdater {
 			seconds: null,
 			moduleName: null,
 			detail: null,
+			receivedBytes: null,
+			totalBytes: null,
+			bytesPerSecond: null,
+			stalled: false,
 		};
 	}
 
+	public diagnostics(): ModuleUpdaterDiagnostics {
+		return {
+			state: this.lastState,
+			packageOrigin: this.packageOrigin,
+			lastError: this.lastError,
+			lastErrorAt: this.lastErrorAt,
+		};
+	}
+
+	private recordDownloadProgress(receivedBytes: number): void {
+		const previous = this.lastState.status === ModuleUpdaterStatus.DOWNLOADING ? this.lastState.receivedBytes : null;
+		if (previous != null && receivedBytes > previous) {
+			this.downloadProgressed = true;
+		}
+	}
+
 	public getLastState(): ModuleUpdaterSplashState {
 		return this.lastState;
 	}
@@ -372,6 +416,8 @@ export class ModuleUpdater {
 		const backoff = new ModuleUpdaterBackoff(this.random);
 		for (;;) {
 			this.emit(ModuleUpdaterStatus.CHECKING);
+			this.downloadRate.reset();
+			this.downloadProgressed = false;
 			let fetched = false;
 			try {
 				const document = await this.manifestRepository.fetchLatest();
@@ -415,8 +461,13 @@ export class ModuleUpdater {
 				backoff.reset();
 			} catch (error) {
 				this.reportFailure(error);
+				this.lastError = describeErrorChain(error);
+				this.lastErrorAt = this.now();
 				const detail = isStorageFullError(error) ? 'Not enough disk space to install the update' : null;
 				const updateServerUnreachable = !isRejectedManifestError(error) && isUpdateServerUnreachable(error);
+				if (this.downloadProgressed) {
+					backoff.reset();
+				}
 				const delayMs = backoff.fail();
 				const exhausted = backoff.reachedCeiling || isRejectedManifestError(error);
 				if (exhausted || !fetched) {
@@ -441,9 +492,18 @@ export class ModuleUpdater {
 						});
 					}
 				}
+				const stalled = isModulePackageStall(error);
+				const position = stalled && this.lastState.status === ModuleUpdaterStatus.DOWNLOADING ? this.lastState : null;
 				this.emit(ModuleUpdaterStatus.RETRY_WAIT, {
 					seconds: Math.max(1, Math.round(delayMs / 1000)),
 					detail,
+					stalled,
+					current: position?.current ?? undefined,
+					total: position?.total ?? undefined,
+					progress: position?.progress ?? undefined,
+					moduleName: position?.moduleName ?? undefined,
+					receivedBytes: position?.receivedBytes ?? undefined,
+					totalBytes: position?.totalBytes ?? undefined,
 				});
 				await this.sleep(delayMs);
 			}
@@ -934,6 +994,10 @@ export class ModuleUpdater {
 			readonly seconds?: number;
 			readonly moduleName?: string;
 			readonly detail?: string | null;
+			readonly receivedBytes?: number;
+			readonly totalBytes?: number;
+			readonly bytesPerSecond?: number;
+			readonly stalled?: boolean;
 		} = {},
 	): void {
 		this.lastState = {
@@ -945,6 +1009,10 @@ export class ModuleUpdater {
 			seconds: patch.seconds ?? null,
 			moduleName: patch.moduleName ?? null,
 			detail: patch.detail ?? null,
+			receivedBytes: patch.receivedBytes ?? null,
+			totalBytes: patch.totalBytes ?? null,
+			bytesPerSecond: patch.bytesPerSecond ?? null,
+			stalled: patch.stalled === true,
 		};
 		this.onState(this.lastState);
 	}

fluxer_desktop/src/main/ShellUpdateCapability.test.mjs

@@ -391,6 +391,9 @@ describe('arming the blocked shell update', () => {
 				total: null,
 				progress: null,
 				seconds: null,
+				receivedBytes: null,
+				totalBytes: null,
+				bytesPerSecond: null,
 				action: {kind: 'quit', label: 'Quit'},
 				message: null,
 				versionLabel: null,
@@ -420,6 +423,9 @@ describe('arming the blocked shell update', () => {
 				total: null,
 				progress: null,
 				seconds: null,
+				receivedBytes: null,
+				totalBytes: null,
+				bytesPerSecond: null,
 				action: {kind: 'download', label: 'Download update'},
 				message: null,
 				versionLabel: null,
@@ -449,6 +455,9 @@ describe('arming the blocked shell update', () => {
 				total: null,
 				progress: null,
 				seconds: null,
+				receivedBytes: null,
+				totalBytes: null,
+				bytesPerSecond: null,
 				action: null,
 				message: SPLASH_MANUAL_UPDATE_MESSAGE,
 				versionLabel: 'Version 2026.823.1 available',

fluxer_desktop/src/main/SplashDiagnostics.ts

@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+export interface SplashDiagnosticsInput {
+	readonly generatedAt: number;
+	readonly splashOpenedAt: number | null;
+	readonly appVersion: string;
+	readonly channel: string;
+	readonly platform: string;
+	readonly arch: string;
+	readonly osVersion: string;
+	readonly electronVersion: string;
+	readonly logsPath: string | null;
+	readonly userDataPath: string;
+	readonly packageOrigin: string;
+	readonly proxyRoute: string | null;
+	readonly splashStatus: string | null;
+	readonly updaterStatus: string | null;
+	readonly pendingModule: string | null;
+	readonly receivedBytes: number | null;
+	readonly totalBytes: number | null;
+	readonly bytesPerSecond: number | null;
+	readonly committed: Readonly<Record<string, string>>;
+	readonly lastError: string | null;
+	readonly lastErrorAt: number | null;
+}
+
+const SHA_PREFIX_LENGTH = 12;
+const SECRET_HEADER_PATTERN =
+	/\b(authorization|cookie|token|secret|password)\b\s*[:=]\s*(?:(?:bearer|basic)\s+)?[^\s&]+/giu;
+const SECRET_QUERY_PATTERN = /([?&])([^=&#\s]+)=([^&#\s]*)/gu;
+const SECRET_USERINFO_PATTERN = /[^\s:@/]+:[^\s@/]+@/gu;
+
+export function redactDiagnosticText(value: string): string {
+	return value
+		.replace(SECRET_HEADER_PATTERN, (_match, key: string) => `${key}=…`)
+		.replace(SECRET_QUERY_PATTERN, (_match, separator: string, key: string) => `${separator}${key}=…`)
+		.replace(SECRET_USERINFO_PATTERN, '…@');
+}
+
+function formatTime(value: number | null): string {
+	return value == null ? 'none' : new Date(value).toISOString();
+}
+
+function formatBytes(value: number | null): string {
+	return value == null ? 'unknown' : `${value} bytes`;
+}
+
+export function buildSplashDiagnosticsText(input: SplashDiagnosticsInput): string {
+	const committed = Object.entries(input.committed)
+		.sort(([left], [right]) => left.localeCompare(right))
+		.map(([name, sha]) => `  ${name} ${sha.slice(0, SHA_PREFIX_LENGTH)}`);
+	const lines = [
+		'Fluxer desktop updater diagnostics',
+		`Generated: ${formatTime(input.generatedAt)}`,
+		`Splash opened: ${formatTime(input.splashOpenedAt)}`,
+		`App version: ${input.appVersion} (${input.channel})`,
+		`Platform: ${input.platform} ${input.arch}, OS ${input.osVersion}, Electron ${input.electronVersion}`,
+		`Logs: ${input.logsPath ?? 'unknown'}`,
+		`User data: ${input.userDataPath}`,
+		`Package origin: ${input.packageOrigin}`,
+		`Proxy route: ${input.proxyRoute ?? 'unknown'}`,
+		`Splash status: ${input.splashStatus ?? 'unknown'}`,
+		`Updater status: ${input.updaterStatus ?? 'unknown'}`,
+		`Pending module: ${input.pendingModule ?? 'none'}`,
+		`Downloaded: ${formatBytes(input.receivedBytes)} of ${formatBytes(input.totalBytes)}`,
+		`Speed: ${input.bytesPerSecond == null ? 'unknown' : `${Math.round(input.bytesPerSecond)} bytes/s`}`,
+		`Last updater error: ${input.lastError ?? 'none'}`,
+		`Last updater error at: ${formatTime(input.lastErrorAt)}`,
+		'Committed modules:',
+		...(committed.length === 0 ? ['  none'] : committed),
+	];
+	return redactDiagnosticText(lines.join('\n'));
+}

fluxer_desktop/src/main/SplashDownloadDiagnostics.test.mjs

@@ -0,0 +1,163 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import assert from 'node:assert/strict';
+import {describe, test} from 'node:test';
+import './LocalAppTestSupport.test.mjs';
+
+const {ModuleDownloadRate} = await import('@electron/main/ModuleDownloadRate');
+const {buildSplashDiagnosticsText, redactDiagnosticText} = await import('@electron/main/SplashDiagnostics');
+const {isModulePackageStall, ModulePackageFetchError, ModulePackageStallError, MODULE_PACKAGE_STALL_TIMEOUT_MS} =
+	await import('@electron/main/ModulePackageInstaller');
+const {serializeSplashState, SplashStatus} = await import('@electron/main/SplashWindow');
+
+function diagnosticsInput(overrides = {}) {
+	return {
+		generatedAt: Date.UTC(2026, 9, 8, 1, 0, 0),
+		splashOpenedAt: Date.UTC(2026, 9, 8, 0, 59, 0),
+		appVersion: '2026.1008.1',
+		channel: 'canary',
+		platform: 'win32',
+		arch: 'x64',
+		osVersion: '10.0.26100',
+		electronVersion: '44.4.1',
+		logsPath: 'C:\\Users\\u\\AppData\\Roaming\\fluxer_desktop_canary\\logs',
+		userDataPath: 'C:\\Users\\u\\AppData\\Roaming\\fluxercanary',
+		packageOrigin: 'https://pkgs.fluxer.com',
+		proxyRoute: 'PROXY 10.0.0.2:3128',
+		splashStatus: 'download-stalled',
+		updaterStatus: 'retry-wait',
+		pendingModule: 'fluxer_renderer',
+		receivedBytes: 42000000,
+		totalBytes: 146684915,
+		bytesPerSecond: 3100000,
+		committed: {fluxer_sourcemaps: 'b'.repeat(64), fluxer_renderer: 'a'.repeat(64)},
+		lastError: 'package download stalled for 30000ms',
+		lastErrorAt: Date.UTC(2026, 9, 8, 0, 59, 40),
+		...overrides,
+	};
+}
+
+describe('module download rate', () => {
+	test('reports nothing until a second sample and then the transfer rate', () => {
+		const rate = new ModuleDownloadRate();
+		assert.equal(rate.sample(0, 0), null);
+		assert.equal(rate.sample(1_000_000, 1000), 1_000_000);
+	});
+
+	test('smooths a sudden change instead of jumping to it', () => {
+		const rate = new ModuleDownloadRate();
+		rate.sample(0, 0);
+		rate.sample(1_000_000, 1000);
+		const smoothed = rate.sample(1_000_000 + 4_000_000, 2000);
+		assert.ok(smoothed > 1_000_000 && smoothed < 4_000_000, String(smoothed));
+	});
+
+	test('keeps the last rate for samples closer together than the minimum window', () => {
+		const rate = new ModuleDownloadRate();
+		rate.sample(0, 0);
+		const first = rate.sample(1_000_000, 1000);
+		assert.equal(rate.sample(1_100_000, 1050), first);
+	});
+
+	test('starts over when the byte count goes backwards or after a reset', () => {
+		const rate = new ModuleDownloadRate();
+		rate.sample(0, 0);
+		rate.sample(5_000_000, 1000);
+		assert.equal(rate.sample(100, 1500), null);
+		rate.reset();
+		assert.equal(rate.sample(0, 3000), null);
+	});
+});
+
+describe('package download stalls', () => {
+	test('a stall is a transient fetch failure the updater can name', () => {
+		const stall = new ModulePackageStallError('fluxer_renderer', MODULE_PACKAGE_STALL_TIMEOUT_MS);
+		assert.ok(stall instanceof ModulePackageFetchError);
+		assert.equal(stall.status, null);
+		assert.equal(isModulePackageStall(new Error('install failed', {cause: stall})), true);
+		assert.equal(isModulePackageStall(new ModulePackageFetchError('fluxer_renderer', 503, 'busy')), false);
+	});
+
+	test('gives up on a silent transfer after thirty seconds', () => {
+		assert.equal(MODULE_PACKAGE_STALL_TIMEOUT_MS, 30000);
+	});
+});
+
+describe('splash download state', () => {
+	test('carries byte counts and speed across the IPC boundary as whole numbers', () => {
+		const serialized = serializeSplashState({
+			status: SplashStatus.DOWNLOADING_UPDATES,
+			receivedBytes: 42_000_000.7,
+			totalBytes: 146_684_915,
+			bytesPerSecond: 3_100_000.4,
+		});
+		assert.equal(serialized.receivedBytes, 42_000_000);
+		assert.equal(serialized.totalBytes, 146_684_915);
+		assert.equal(serialized.bytesPerSecond, 3_100_000);
+	});
+
+	test('keeps the stalled status and drops byte values that are not numbers', () => {
+		const serialized = serializeSplashState({
+			status: SplashStatus.DOWNLOAD_STALLED,
+			seconds: 4,
+			receivedBytes: Number.NaN,
+			totalBytes: '9',
+			bytesPerSecond: Number.POSITIVE_INFINITY,
+		});
+		assert.equal(serialized.status, 'download-stalled');
+		assert.equal(serialized.receivedBytes, null);
+		assert.equal(serialized.totalBytes, null);
+		assert.equal(serialized.bytesPerSecond, null);
+	});
+});
+
+describe('splash diagnostics', () => {
+	test('lists what support needs to place a stuck download', () => {
+		const text = buildSplashDiagnosticsText(diagnosticsInput());
+		for (const expected of [
+			'App version: 2026.1008.1 (canary)',
+			'Platform: win32 x64, OS 10.0.26100, Electron 44.4.1',
+			'Package origin: https://pkgs.fluxer.com',
+			'Proxy route: PROXY 10.0.0.2:3128',
+			'Splash status: download-stalled',
+			'Pending module: fluxer_renderer',
+			'Downloaded: 42000000 bytes of 146684915 bytes',
+			'Speed: 3100000 bytes/s',
+			'Last updater error: package download stalled for 30000ms',
+			'Last updater error at: 2026-10-08T00:59:40.000Z',
+			'  fluxer_renderer aaaaaaaaaaaa',
+			'  fluxer_sourcemaps bbbbbbbbbbbb',
+		]) {
+			assert.ok(text.includes(expected), `missing ${expected}\n${text}`);
+		}
+		assert.ok(text.indexOf('fluxer_renderer aaaa') < text.indexOf('fluxer_sourcemaps bbbb'));
+	});
+
+	test('never carries query values or credential-looking pairs', () => {
+		const text = buildSplashDiagnosticsText(
+			diagnosticsInput({
+				lastError: 'failed to reach https://pkgs.fluxer.com/x?token=abc123&sig=zzz: authorization: Bearer secretvalue',
+				proxyRoute: 'PROXY user:pass@proxy:8080',
+			}),
+		);
+		assert.ok(!text.includes('abc123'));
+		assert.ok(!text.includes('zzz'));
+		assert.ok(!text.includes('secretvalue'));
+		assert.ok(!text.includes('user:pass'));
+		assert.ok(text.includes('?token=…&sig=…'));
+		assert.ok(text.includes('Proxy route: PROXY …@proxy:8080'));
+	});
+
+	test('redaction leaves plain diagnostic text alone', () => {
+		assert.equal(
+			redactDiagnosticText('Package origin: https://pkgs.fluxer.com'),
+			'Package origin: https://pkgs.fluxer.com',
+		);
+	});
+
+	test('says so when nothing is installed yet', () => {
+		const text = buildSplashDiagnosticsText(diagnosticsInput({committed: {}, lastError: null, lastErrorAt: null}));
+		assert.ok(text.includes('Committed modules:\n  none'));
+		assert.ok(text.includes('Last updater error: none'));
+	});
+});

fluxer_desktop/src/main/SplashWindow.test.mjs

@@ -533,6 +533,9 @@ describe('splash state serialisation', () => {
 				total: 7,
 				progress: 42.5,
 				seconds: null,
+				receivedBytes: null,
+				totalBytes: null,
+				bytesPerSecond: null,
 				action: null,
 				message: null,
 				versionLabel: null,
@@ -560,6 +563,9 @@ describe('splash state serialisation', () => {
 				total: null,
 				progress: 0,
 				seconds: 0,
+				receivedBytes: null,
+				totalBytes: null,
+				bytesPerSecond: null,
 				action: null,
 				message: null,
 				versionLabel: null,
@@ -820,6 +826,9 @@ describe('splash IPC', () => {
 					total: 5,
 					progress: 40,
 					seconds: null,
+					receivedBytes: null,
+					totalBytes: null,
+					bytesPerSecond: null,
 					action: null,
 					message: null,
 					versionLabel: null,
@@ -853,6 +862,9 @@ describe('splash IPC', () => {
 					total: null,
 					progress: null,
 					seconds: null,
+					receivedBytes: null,
+					totalBytes: null,
+					bytesPerSecond: null,
 					action: null,
 					message: null,
 					versionLabel: null,
@@ -1132,6 +1144,12 @@ function createPreloadHarness() {
 			timeouts.push({callback, delayMs});
 			return timeouts.length;
 		},
+		clearTimeout: (id) => {
+			const timer = timeouts[id - 1];
+			if (timer != null) {
+				timer.cleared = true;
+			}
+		},
 		window: {
 			addEventListener: (eventName, listener) => {
 				windowListeners.set(eventName, listener);
@@ -1209,8 +1227,8 @@ describe('splash preload rendering', () => {
 		assert.deepEqual(harness.sent, []);
 		assert.equal(harness.query('.splash-mark').decodeCalls, 1);
 		assert.deepEqual(harness.fontLoads, ['400 12px "Fluxer Sans"', '500 16px "Fluxer Sans"']);
-		assert.equal(harness.timeouts.length, 1);
-		assert.ok(harness.timeouts[0].delayMs <= 500);
+		const brandingWaits = harness.timeouts.filter((timer) => timer.delayMs <= 500);
+		assert.equal(brandingWaits.length, 1);
 
 		await harness.settle();
 		assert.deepEqual(harness.sent, []);
@@ -1713,6 +1731,9 @@ describe('splash preload contract', () => {
 			total: null,
 			progress: null,
 			seconds: null,
+			receivedBytes: null,
+			totalBytes: null,
+			bytesPerSecond: null,
 			action: null,
 			message: null,
 			versionLabel: null,

fluxer_desktop/src/main/SplashWindow.ts

@@ -27,6 +27,8 @@ export const DESKTOP_SPLASH_RETRY_NOW_CHANNEL = 'desktop-splash:retry-now';
 export const DESKTOP_SPLASH_QUIT_CHANNEL = 'desktop-splash:quit';
 export const DESKTOP_SPLASH_OPEN_DOWNLOAD_CHANNEL = 'desktop-splash:open-download';
 export const DESKTOP_SPLASH_NETWORK_ONLINE_CHANNEL = 'desktop-splash:network-online';
+export const DESKTOP_SPLASH_OPEN_LOGS_CHANNEL = 'desktop-splash:open-logs';
+export const DESKTOP_SPLASH_COPY_DIAGNOSTICS_CHANNEL = 'desktop-splash:copy-diagnostics';
 
 export const SplashLayout = Object.freeze({
 	SPLASH: 'splash',
@@ -41,6 +43,7 @@ export const SplashStatus = Object.freeze({
 	INSTALLING_UPDATES: 'installing-updates',
 	VERIFYING: 'verifying',
 	UPDATE_FAILURE: 'update-failure',
+	DOWNLOAD_STALLED: 'download-stalled',
 	SHELL_UPDATE_DOWNLOADING: 'shell-update-downloading',
 	SHELL_UPDATE_RESTARTING: 'shell-update-restarting',
 	BLOCKED_UPDATE_REQUIRED: 'blocked-update-required',
@@ -91,6 +94,9 @@ export interface SplashState {
 	readonly total?: number | null;
 	readonly progress?: number | null;
 	readonly seconds?: number | null;
+	readonly receivedBytes?: number | null;
+	readonly totalBytes?: number | null;
+	readonly bytesPerSecond?: number | null;
 	readonly action?: SplashActionDescriptor | null;
 	readonly message?: string | null;
 	readonly versionLabel?: string | null;
@@ -105,6 +111,9 @@ export interface SerializedSplashState {
 	readonly total: number | null;
 	readonly progress: number | null;
 	readonly seconds: number | null;
+	readonly receivedBytes: number | null;
+	readonly totalBytes: number | null;
+	readonly bytesPerSecond: number | null;
 	readonly action: SplashActionDescriptor | null;
 	readonly message: string | null;
 	readonly versionLabel: string | null;
@@ -123,6 +132,8 @@ const retryListeners = new Set<SplashListener>();
 const quitListeners = new Set<SplashListener>();
 const networkOnlineListeners = new Set<SplashListener>();
 const openDownloadListeners = new Set<SplashDownloadListener>();
+const openLogsListeners = new Set<SplashListener>();
+const copyDiagnosticsListeners = new Set<SplashListener>();
 
 let splashWindow: BrowserWindow | null = null;
 let splashIpcRegistered = false;
@@ -196,6 +207,9 @@ export function serializeSplashState(state: SplashState): SerializedSplashState
 		total: toSplashCount(state.total),
 		progress: toSplashProgress(state.progress),
 		seconds: toSplashCount(state.seconds),
+		receivedBytes: toSplashCount(state.receivedBytes),
+		totalBytes: toSplashCount(state.totalBytes),
+		bytesPerSecond: toSplashCount(state.bytesPerSecond),
 		action: toSplashAction(state.action),
 		message: toSplashText(state.message, SPLASH_MESSAGE_MAX_LENGTH),
 		versionLabel: toSplashText(state.versionLabel, SPLASH_VERSION_LABEL_MAX_LENGTH),
@@ -294,6 +308,14 @@ function registerSplashIpc(): void {
 		if (!isSplashSender(event)) return;
 		emitSplashDownloadListeners(toSplashDownloadValue(value));
 	});
+	ipcMain.on(DESKTOP_SPLASH_OPEN_LOGS_CHANNEL, (event) => {
+		if (!isSplashSender(event)) return;
+		emitSplashListeners(openLogsListeners);
+	});
+	ipcMain.on(DESKTOP_SPLASH_COPY_DIAGNOSTICS_CHANNEL, (event) => {
+		if (!isSplashSender(event)) return;
+		emitSplashListeners(copyDiagnosticsListeners);
+	});
 }
 
 function registerSplashDiagnostics(window: BrowserWindow): void {
@@ -391,6 +413,8 @@ export function closeSplashWindow(): void {
 	quitListeners.clear();
 	networkOnlineListeners.clear();
 	openDownloadListeners.clear();
+	openLogsListeners.clear();
+	copyDiagnosticsListeners.clear();
 	if (readyWatchdog != null) {
 		clearTimeout(readyWatchdog);
 		readyWatchdog = null;
@@ -450,3 +474,11 @@ export function onSplashNetworkOnline(listener: SplashListener): () => void {
 export function onSplashOpenDownload(listener: SplashDownloadListener): () => void {
 	return addSplashListener(openDownloadListeners, listener);
 }
+
+export function onSplashOpenLogs(listener: SplashListener): () => void {
+	return addSplashListener(openLogsListeners, listener);
+}
+
+export function onSplashCopyDiagnostics(listener: SplashListener): () => void {
+	return addSplashListener(copyDiagnosticsListeners, listener);
+}

fluxer_desktop/src/preload/splash.cjs

@@ -8,6 +8,8 @@ const SPLASH_RETRY_CHANNEL = 'desktop-splash:retry-now';
 const SPLASH_QUIT_CHANNEL = 'desktop-splash:quit';
 const SPLASH_OPEN_DOWNLOAD_CHANNEL = 'desktop-splash:open-download';
 const SPLASH_NETWORK_ONLINE_CHANNEL = 'desktop-splash:network-online';
+const SPLASH_OPEN_LOGS_CHANNEL = 'desktop-splash:open-logs';
+const SPLASH_COPY_DIAGNOSTICS_CHANNEL = 'desktop-splash:copy-diagnostics';
 
 const SPLASH_MOUNT_ID = 'splash-mount';
 const SPLASH_MARK_SIZE = 88;
@@ -23,6 +25,10 @@ const SPLASH_OPTION_LABEL_MAX_LENGTH = 48;
 const SPLASH_OPTION_BUTTON_LABEL_MAX_LENGTH = 24;
 const SPLASH_OPTION_MAX_COUNT = 8;
 const SPLASH_OPTION_VALUE_PATTERN = /^[a-z0-9_]{1,32}$/;
+const DIAGNOSTICS_REVEAL_MS = 30000;
+const DIAGNOSTICS_COPIED_MS = 2000;
+const BYTES_PER_MEGABYTE = 1000000;
+const BYTES_PER_KILOBYTE = 1000;
 
 const SplashLayout = Object.freeze({
 	SPLASH: 'splash',
@@ -35,6 +41,7 @@ const SplashStatus = Object.freeze({
 	INSTALLING_UPDATES: 'installing-updates',
 	VERIFYING: 'verifying',
 	UPDATE_FAILURE: 'update-failure',
+	DOWNLOAD_STALLED: 'download-stalled',
 	SHELL_UPDATE_DOWNLOADING: 'shell-update-downloading',
 	SHELL_UPDATE_RESTARTING: 'shell-update-restarting',
 	BLOCKED_UPDATE_REQUIRED: 'blocked-update-required',
@@ -53,9 +60,21 @@ const KNOWN_LAYOUTS = new Set(Object.values(SplashLayout));
 const KNOWN_STATUSES = new Set(Object.values(SplashStatus));
 const PROGRESS_STATUSES = new Set([
 	SplashStatus.DOWNLOADING_UPDATES,
+	SplashStatus.DOWNLOAD_STALLED,
 	SplashStatus.INSTALLING_UPDATES,
 	SplashStatus.SHELL_UPDATE_DOWNLOADING,
 ]);
+const DIAGNOSTICS_STATUSES = new Set([
+	SplashStatus.UPDATE_FAILURE,
+	SplashStatus.DOWNLOAD_STALLED,
+	SplashStatus.BLOCKED_UPDATE_REQUIRED,
+	SplashStatus.BLOCKED_UPDATE_UNREACHABLE,
+	SplashStatus.BLOCKED_SECURITY_UPDATE_REQUIRED,
+	SplashStatus.BLOCKED_SHELL_UPDATE,
+	SplashStatus.BLOCKED_UNSUPPORTED_BUILD,
+	SplashStatus.UNREACHABLE_LAUNCH,
+]);
+const DIAGNOSTICS_HIDDEN_STATUSES = new Set([SplashStatus.LAUNCHING, SplashStatus.SHELL_UPDATE_RESTARTING]);
 const ACTION_CHANNELS = new Map([
 	['retry', SPLASH_RETRY_CHANNEL],
 	['download', SPLASH_OPEN_DOWNLOAD_CHANNEL],
@@ -68,6 +87,9 @@ let renderedLayout = null;
 let renderedManualSignature = null;
 let countdownTimer = null;
 let selectedOption = null;
+let splashStartedAt = Date.now();
+let diagnosticsRevealTimer = null;
+let diagnosticsCopiedTimer = null;
 
 function toCount(value) {
 	if (typeof value !== 'number' || !Number.isFinite(value)) return null;
@@ -128,6 +150,9 @@ function normalizeState(payload) {
 			total: null,
 			progress: null,
 			seconds: null,
+			receivedBytes: null,
+			totalBytes: null,
+			bytesPerSecond: null,
 			action: null,
 			message: null,
 			versionLabel: null,
@@ -142,6 +167,9 @@ function normalizeState(payload) {
 		total: toCount(payload.total),
 		progress: typeof payload.progress === 'number' && Number.isFinite(payload.progress) ? payload.progress : null,
 		seconds: toCount(payload.seconds),
+		receivedBytes: toCount(payload.receivedBytes),
+		totalBytes: toCount(payload.totalBytes),
+		bytesPerSecond: toCount(payload.bytesPerSecond),
 		action: normalizeAction(payload.action),
 		message: toText(payload.message, SPLASH_MESSAGE_MAX_LENGTH),
 		versionLabel: toText(payload.versionLabel, SPLASH_VERSION_LABEL_MAX_LENGTH),
@@ -161,6 +189,8 @@ function getStatusText(state) {
 				: `Installing update ${state.current ?? 0} of ${state.total ?? 0}…`;
 		case SplashStatus.VERIFYING:
 			return state.requiredSecurityUpdate ? 'Verifying required security update…' : 'Verifying files…';
+		case SplashStatus.DOWNLOAD_STALLED:
+			return `Download stalled. Retrying in ${state.seconds ?? 0} sec…`;
 		case SplashStatus.UPDATE_FAILURE:
 			return state.requiredSecurityUpdate
 				? `Required security update failed. Retrying in ${state.seconds ?? 0} sec…`
@@ -204,9 +234,39 @@ function shouldShowProgress(state) {
 	return state.progress !== null && PROGRESS_STATUSES.has(state.status);
 }
 
-function toProgressPercent(progress) {
-	if (progress === null) return 0;
-	return Math.min(100, Math.max(0, progress));
+function toProgressPercent(state) {
+	if (state.receivedBytes !== null && state.totalBytes !== null && state.totalBytes > 0) {
+		return Math.min(100, Math.max(0, (state.receivedBytes / state.totalBytes) * 100));
+	}
+	if (state.progress === null) return 0;
+	return Math.min(100, Math.max(0, state.progress));
+}
+
+function formatMegabytes(bytes) {
+	const megabytes = bytes / BYTES_PER_MEGABYTE;
+	return megabytes >= 10 ? String(Math.round(megabytes)) : megabytes.toFixed(1);
+}
+
+function formatSpeed(bytesPerSecond) {
+	if (bytesPerSecond >= BYTES_PER_MEGABYTE) {
+		return `${(bytesPerSecond / BYTES_PER_MEGABYTE).toFixed(1)} MB/s`;
+	}
+	return `${Math.max(0, Math.round(bytesPerSecond / BYTES_PER_KILOBYTE))} KB/s`;
+}
+
+function getMetricsText(state) {
+	if (state.status !== SplashStatus.DOWNLOADING_UPDATES && state.status !== SplashStatus.DOWNLOAD_STALLED) return '';
+	if (state.receivedBytes === null || state.totalBytes === null || state.totalBytes === 0) return '';
+	const amount = `${formatMegabytes(state.receivedBytes)} of ${formatMegabytes(state.totalBytes)} MB`;
+	if (state.status !== SplashStatus.DOWNLOADING_UPDATES || state.bytesPerSecond === null) return amount;
+	return `${amount}, ${formatSpeed(state.bytesPerSecond)}`;
+}
+
+function shouldShowDiagnostics(state) {
+	if (state.layout !== SplashLayout.SPLASH) return false;
+	if (DIAGNOSTICS_HIDDEN_STATUSES.has(state.status)) return false;
+	if (DIAGNOSTICS_STATUSES.has(state.status)) return true;
+	return Date.now() - splashStartedAt >= DIAGNOSTICS_REVEAL_MS;
 }
 
 function createNode(tagName, className) {
@@ -267,18 +327,55 @@ function buildSplashLayout(mount) {
 	text.appendChild(createNode('span', 'splash-status'));
 	text.appendChild(createNode('span', 'splash-detail'));
 	text.appendChild(createProgressPlaceholder());
+	text.appendChild(createNode('span', 'splash-metrics'));
 	text.appendChild(createNode('div', 'splash-action-slot'));
 	inner.appendChild(media);
 	inner.appendChild(text);
 	splash.appendChild(inner);
+	splash.appendChild(buildDiagnosticsRow());
 	mount.replaceChildren(splash);
 }
 
+function buildDiagnosticsRow() {
+	const row = createNode('div', 'splash-diagnostics');
+	const openLogs = createNode('button', 'splash-diagnostics-link');
+	openLogs.setAttribute('data-action', 'open-logs');
+	openLogs.textContent = 'Open logs';
+	openLogs.addEventListener('click', () => {
+		ipcRenderer.send(SPLASH_OPEN_LOGS_CHANNEL);
+	});
+	const copy = createNode('button', 'splash-diagnostics-link');
+	copy.setAttribute('data-action', 'copy-diagnostics');
+	copy.textContent = 'Copy diagnostics';
+	copy.addEventListener('click', () => {
+		ipcRenderer.send(SPLASH_COPY_DIAGNOSTICS_CHANNEL);
+		copy.textContent = 'Copied';
+		if (diagnosticsCopiedTimer != null) clearTimeout(diagnosticsCopiedTimer);
+		diagnosticsCopiedTimer = setTimeout(() => {
+			diagnosticsCopiedTimer = null;
+			copy.textContent = 'Copy diagnostics';
+		}, DIAGNOSTICS_COPIED_MS);
+	});
+	row.appendChild(openLogs);
+	row.appendChild(copy);
+	return row;
+}
+
+function reconcileDiagnostics(mount, state) {
+	const row = mount.querySelector('.splash-diagnostics');
+	if (row == null) return;
+	if (shouldShowDiagnostics(state)) {
+		row.classList.add('is-visible');
+	} else {
+		row.classList.remove('is-visible');
+	}
+}
+
 function reconcileProgress(mount, state) {
 	const existing = mount.querySelector('.progress, .progress-placeholder');
 	if (existing == null) return;
 	if (shouldShowProgress(state)) {
-		const percent = toProgressPercent(state.progress);
+		const percent = toProgressPercent(state);
 		const complete = existing.querySelector('.complete');
 		if (complete != null) {
 			complete.style.width = `${percent}%`;
@@ -426,8 +523,13 @@ function render() {
 	if (detailNode != null) {
 		detailNode.textContent = state.message ?? '';
 	}
+	const metricsNode = mount.querySelector('.splash-metrics');
+	if (metricsNode != null) {
+		metricsNode.textContent = getMetricsText(state) || NON_BREAKING_SPACE;
+	}
 	reconcileProgress(mount, state);
 	reconcileAction(mount, state);
+	reconcileDiagnostics(mount, state);
 }
 
 function hasCountdown(state) {
@@ -491,6 +593,11 @@ function afterNextPaint(callback) {
 }
 
 window.addEventListener('DOMContentLoaded', () => {
+	splashStartedAt = Date.now();
+	diagnosticsRevealTimer = setTimeout(() => {
+		diagnosticsRevealTimer = null;
+		render();
+	}, DIAGNOSTICS_REVEAL_MS);
 	render();
 	const mount = document.getElementById(SPLASH_MOUNT_ID);
 	const branded = mount == null ? Promise.resolve() : waitForBranding(mount);
@@ -507,4 +614,6 @@ window.addEventListener('online', () => {
 
 window.addEventListener('beforeunload', () => {
 	stopCountdown();
+	if (diagnosticsRevealTimer != null) clearTimeout(diagnosticsRevealTimer);
+	if (diagnosticsCopiedTimer != null) clearTimeout(diagnosticsCopiedTimer);
 });

fluxer_desktop/src/splash/index.css

@@ -101,6 +101,15 @@ html {
 				font-variant-numeric: tabular-nums;
 			}
 
+			&.splash-metrics {
+				margin-top: 8px;
+				height: 16px;
+				line-height: 16px;
+				font-weight: 400;
+				white-space: nowrap;
+				font-variant-numeric: tabular-nums;
+			}
+
 			&.splash-detail {
 				max-width: 280px;
 				margin: 6px auto 0;
@@ -179,6 +188,38 @@ html {
 	background: var(--brand-bright);
 }
 
+.splash-diagnostics {
+	position: absolute;
+	left: 0;
+	right: 0;
+	bottom: 14px;
+	display: flex;
+	justify-content: center;
+	gap: 14px;
+	visibility: hidden;
+}
+
+.splash-diagnostics.is-visible {
+	visibility: visible;
+}
+
+.splash-diagnostics-link {
+	-webkit-app-region: no-drag;
+	background: none;
+	border: none;
+	padding: 2px 0;
+	color: var(--muted);
+	font-family: var(--primary-font);
+	font-size: 11px;
+	font-weight: 400;
+	cursor: pointer;
+	text-decoration: none;
+}
+
+.splash-diagnostics-link:hover {
+	color: var(--white);
+}
+
 #splash:has(.splash-inner-dl) {
 	align-items: stretch;
 	padding-bottom: 0;

fluxer_desktop/src/splash/index.html

@@ -15,9 +15,14 @@
 					<div class="splash-text">
 						<span class="splash-status">Checking for updates…</span>
 						<div class="progress-placeholder">&nbsp;</div>
+						<span class="splash-metrics">&nbsp;</span>
 						<div class="splash-action-slot"></div>
 					</div>
 				</div>
+				<div class="splash-diagnostics">
+					<button class="splash-diagnostics-link" data-action="open-logs">Open logs</button>
+					<button class="splash-diagnostics-link" data-action="copy-diagnostics">Copy diagnostics</button>
+				</div>
 			</div>
 		</div>
 	</body>