From 1a560c64c7ddb0666a211d071d0dad4f17996aad Mon Sep 17 00:00:00 2001
From: "Calum H. (IMB11)" <contact@cal.engineer>
Date: Fri, 28 Aug 2026 12:04:52 +0100
Subject: [PATCH] fix: screenshots page lag + better virtualization pass

---
 .../components/ui/screenshots-page/card.vue   | 119 ++++++++++--
 .../components/ui/screenshots-page/group.vue  |  76 ++++++--
 .../components/ui/screenshots-page/index.vue  | 166 +++++++++++------
 .../ui/screenshots-page/section.vue           |  37 +++-
 apps/app/src/api/instance.rs                  |  30 ++-
 .../instance/screenshots/reconciliation.rs    | 173 ++++++++----------
 6 files changed, 413 insertions(+), 188 deletions(-)

diff --git a/apps/app-frontend/src/components/ui/screenshots-page/card.vue b/apps/app-frontend/src/components/ui/screenshots-page/card.vue
index adf1222ef8..f1de4c6532 100644
--- a/apps/app-frontend/src/components/ui/screenshots-page/card.vue
+++ b/apps/app-frontend/src/components/ui/screenshots-page/card.vue
@@ -3,11 +3,16 @@
 <script setup lang="ts">
 import { KeyboardSensor, PointerSensor, useDraggable } from '@dnd-kit/vue'
 import { CheckIcon, ClipboardCopyIcon, EditIcon, MoreHorizontalIcon } from '@modrinth/assets'
-import { defineMessages, IconButton, useFormatDateTime, useVIntl } from '@modrinth/ui'
-import { computed, onMounted, ref, watch } from 'vue'
+import {
+	defineMessages,
+	IconButton,
+	useDebugLogger,
+	useFormatDateTime,
+	useVIntl,
+} from '@modrinth/ui'
+import { computed, onBeforeUnmount, onMounted, ref, watch } from 'vue'
 
 import type { InstanceScreenshot } from '@/helpers/instance'
-const loadedScreenshotUrls = new Set<string>()
 
 const props = defineProps<{
 	screenshot: InstanceScreenshot
@@ -29,9 +34,12 @@ const emit = defineEmits<{
 
 const card = ref<HTMLElement>()
 const image = ref<HTMLImageElement>()
-const loaded = ref(loadedScreenshotUrls.has(props.screenshot.url))
+const imageReady = ref(false)
 const { formatMessage } = useVIntl()
+const debugImage = useDebugLogger('Screenshots:Card')
 const formatTime = useFormatDateTime({ dateStyle: 'medium', timeStyle: 'short' })
+let loadStartedAt = performance.now()
+let loadGeneration = 0
 const messages = defineMessages({
 	select: { id: 'app.screenshots.select', defaultMessage: 'Select {name}' },
 	deselect: { id: 'app.screenshots.deselect', defaultMessage: 'Deselect {name}' },
@@ -69,19 +77,86 @@ function activate(event: MouseEvent | KeyboardEvent) {
 	emit('activate', event)
 }
 
-function markImageLoaded() {
-	loadedScreenshotUrls.add(props.screenshot.url)
-	loaded.value = true
+async function markImageLoaded() {
+	const loadedImage = image.value
+	const loadedUrl = props.screenshot.url
+	const generation = loadGeneration
+	if (!loadedImage) return
+
+	try {
+		await loadedImage.decode()
+	} catch {
+		if (!loadedImage.complete || loadedImage.naturalWidth === 0) return
+	}
+
+	await new Promise<void>((resolve) => {
+		window.requestAnimationFrame(() => window.requestAnimationFrame(() => resolve()))
+	})
+
+	if (
+		generation !== loadGeneration ||
+		image.value !== loadedImage ||
+		props.screenshot.url !== loadedUrl
+	) {
+		return
+	}
+
+	const wasReady = imageReady.value
+	imageReady.value = true
+	if (!wasReady) {
+		debugImage('image loaded', {
+			id: props.screenshot.id,
+			fileName: props.screenshot.file_name,
+			url: props.screenshot.url,
+			loadDurationMs: performance.now() - loadStartedAt,
+			naturalWidth: image.value?.naturalWidth,
+			naturalHeight: image.value?.naturalHeight,
+		})
+	}
+}
+
+function markImageFailed(event: Event) {
+	debugImage('image failed', {
+		id: props.screenshot.id,
+		fileName: props.screenshot.file_name,
+		url: props.screenshot.url,
+		loadDurationMs: performance.now() - loadStartedAt,
+		event,
+	})
 }
 
 onMounted(() => {
+	debugImage('mounted', {
+		id: props.screenshot.id,
+		fileName: props.screenshot.file_name,
+		url: props.screenshot.url,
+		complete: image.value?.complete,
+	})
 	if (image.value?.complete && image.value.naturalWidth > 0) markImageLoaded()
 })
 
+onBeforeUnmount(() => {
+	loadGeneration += 1
+	debugImage('unmounted', {
+		id: props.screenshot.id,
+		fileName: props.screenshot.file_name,
+		url: props.screenshot.url,
+		loaded: imageReady.value,
+	})
+})
+
 watch(
 	() => props.screenshot.url,
-	(url) => {
-		loaded.value = loadedScreenshotUrls.has(url)
+	(url, previousUrl) => {
+		loadGeneration += 1
+		loadStartedAt = performance.now()
+		imageReady.value = false
+		debugImage('source changed', {
+			id: props.screenshot.id,
+			fileName: props.screenshot.file_name,
+			previousUrl,
+			url,
+		})
 	},
 )
 </script>
@@ -91,7 +166,7 @@ watch(
 		ref="card"
 		role="button"
 		tabindex="0"
-		class="group relative aspect-video min-w-0 cursor-pointer overflow-hidden rounded-xl border border-solid border-surface-5 bg-surface-2 p-0 text-left shadow-sm transition-[filter] hover:brightness-110 focus-visible:outline focus-visible:outline-2 focus-visible:outline-brand"
+		class="group relative isolate aspect-video min-w-0 cursor-pointer overflow-hidden rounded-xl border border-solid border-surface-5 bg-surface-2 p-0 text-left shadow-sm transition-[filter] hover:brightness-110 focus-visible:outline focus-visible:outline-2 focus-visible:outline-brand"
 		:class="{
 			'!border-contrast brightness-110': selected,
 			'!border-brand ring-2 ring-brand animate-pulse': highlighted,
@@ -115,7 +190,7 @@ watch(
 	>
 		<button
 			type="button"
-			class="selection-button group/selection absolute right-0.5 top-0 z-[2] flex size-[50px] cursor-pointer items-start justify-center border-0 bg-transparent p-0 pt-4"
+			class="selection-button group/selection absolute right-0.5 top-0 z-[3] flex size-[50px] cursor-pointer items-start justify-center border-0 bg-transparent p-0 pt-4"
 			:aria-label="
 				formatMessage(selected ? messages.deselect : messages.select, {
 					name: screenshot.file_name,
@@ -134,19 +209,25 @@ watch(
 				<CheckIcon v-if="selected" class="relative size-4 invert [stroke-width:3]" />
 			</span>
 		</button>
-		<div v-if="!loaded" class="absolute inset-0 animate-pulse bg-surface-3" />
 		<img
 			ref="image"
 			:src="screenshot.url"
 			:alt="screenshot.file_name"
-			loading="lazy"
+			loading="eager"
+			decoding="async"
 			draggable="false"
-			class="h-full w-full object-cover transition duration-200"
-			:class="loaded ? 'opacity-100' : 'opacity-0'"
+			class="screenshot-card-fade absolute inset-0 z-[1] h-full w-full object-cover"
+			:class="imageReady ? 'opacity-100' : 'opacity-0'"
 			@load="markImageLoaded"
+			@error="markImageFailed"
 		/>
 		<div
-			class="absolute inset-x-0 bottom-0 flex items-end justify-between gap-2 bg-gradient-to-t from-surface-1 to-transparent p-3 pt-[120px] text-contrast opacity-0 transition-opacity duration-200 group-hover:opacity-100 group-focus-within:opacity-100"
+			aria-hidden="true"
+			class="pointer-events-none absolute inset-0 bg-button-bg"
+			:class="{ 'animate-pulse': !imageReady }"
+		/>
+		<div
+			class="absolute inset-x-0 bottom-0 z-[2] flex items-end justify-between gap-2 bg-gradient-to-t from-surface-1 to-transparent p-3 pt-[120px] text-contrast opacity-0 transition-opacity duration-200 group-hover:opacity-100 group-focus-within:opacity-100"
 		>
 			<div class="min-w-0">
 				<div v-tooltip="screenshot.file_name" class="truncate text-sm font-semibold">
@@ -193,3 +274,9 @@ watch(
 		</div>
 	</article>
 </template>
+
+<style scoped>
+.screenshot-card-fade {
+	transition: opacity 350ms ease-in-out;
+}
+</style>
diff --git a/apps/app-frontend/src/components/ui/screenshots-page/group.vue b/apps/app-frontend/src/components/ui/screenshots-page/group.vue
index 2a5c1c2997..358126f221 100644
--- a/apps/app-frontend/src/components/ui/screenshots-page/group.vue
+++ b/apps/app-frontend/src/components/ui/screenshots-page/group.vue
@@ -1,7 +1,7 @@
 <script setup lang="ts">
 import { useDroppable } from '@dnd-kit/vue'
-import { defineMessages, useVIntl } from '@modrinth/ui'
-import { computed, onBeforeUnmount, ref, watch } from 'vue'
+import { defineMessages, useDebugLogger, useVIntl } from '@modrinth/ui'
+import { computed, nextTick, onBeforeUnmount, onMounted, ref, watch } from 'vue'
 
 import type { InstanceScreenshot } from '@/helpers/instance'
 
@@ -27,7 +27,6 @@ const props = defineProps<{
 	highlightedScreenshotId?: string
 	copiedScreenshotIds: ReadonlySet<string>
 	forceOpen: boolean
-	animateEntry: boolean
 	hideHeader?: boolean
 	editableTitle?: boolean
 	startEditingTitle?: boolean
@@ -39,6 +38,7 @@ const props = defineProps<{
 const collapsed = defineModel<boolean>('collapsed', { required: true })
 const dropTarget = ref<HTMLElement>()
 const { formatMessage } = useVIntl()
+const debugLayout = useDebugLogger('Screenshots:Group')
 const messages = defineMessages({
 	emptyGroup: {
 		id: 'app.screenshots.group.empty',
@@ -60,14 +60,42 @@ const visibleGridStyle = computed(() =>
 		: { transform: `translateY(${props.virtualGridTop}px)` },
 )
 let unmountGridTimeout: ReturnType<typeof setTimeout> | undefined
+let resizeObserver: ResizeObserver | undefined
+
+async function logGeometry(reason: string) {
+	await nextTick()
+	const rect = dropTarget.value?.getBoundingClientRect()
+	debugLayout(reason, {
+		id: props.id,
+		title: props.title,
+		collapsed: collapsed.value,
+		shouldShowGrid: shouldShowGrid.value,
+		renderGrid: renderGrid.value,
+		screenshotCount: props.screenshots.length,
+		renderedCount: visibleScreenshots.value.length,
+		firstScreenshotId: visibleScreenshots.value.at(0)?.id,
+		lastScreenshotId: visibleScreenshots.value.at(-1)?.id,
+		virtualGridHeight: props.virtualGridHeight,
+		virtualGridTop: props.virtualGridTop,
+		actual: rect
+			? { top: rect.top, left: rect.left, width: rect.width, height: rect.height }
+			: undefined,
+	})
+}
 
 watch(
 	() => props.renderedScreenshots ?? props.screenshots,
 	(screenshots) => {
 		if (shouldShowGrid.value) visibleScreenshots.value = screenshots
+		void logGeometry('rendered screenshots changed')
 	},
 )
 
+watch(
+	() => [props.virtualGridHeight, props.virtualGridTop] as const,
+	() => void logGeometry('virtual grid geometry changed'),
+)
+
 watch(
 	shouldShowGrid,
 	(showGrid, previouslyShown) => {
@@ -75,6 +103,7 @@ watch(
 		if (showGrid) {
 			visibleScreenshots.value = props.renderedScreenshots ?? props.screenshots
 			renderGrid.value = true
+			void logGeometry('grid shown')
 			return
 		}
 		if (!previouslyShown) {
@@ -83,13 +112,41 @@ watch(
 		}
 		unmountGridTimeout = setTimeout(() => {
 			renderGrid.value = false
+			void logGeometry('grid unmounted after collapse')
 			unmountGridTimeout = undefined
 		}, 300)
 	},
 	{ flush: 'post' },
 )
 
+onMounted(() => {
+	debugLayout('mounted', { id: props.id, title: props.title })
+	void logGeometry('mounted geometry')
+	if (dropTarget.value) {
+		resizeObserver = new ResizeObserver(([entry]) => {
+			const rect = entry?.target.getBoundingClientRect()
+			debugLayout('actual size changed', {
+				id: props.id,
+				title: props.title,
+				width: rect?.width,
+				height: rect?.height,
+				expectedHeight:
+					(props.hideHeader ? 0 : 40) +
+					(shouldShowGrid.value ? 10 + (props.virtualGridHeight ?? 0) : 0) +
+					12,
+			})
+		})
+		resizeObserver.observe(dropTarget.value)
+	}
+})
+
 onBeforeUnmount(() => {
+	debugLayout('unmounted', {
+		id: props.id,
+		title: props.title,
+		renderedCount: visibleScreenshots.value.length,
+	})
+	resizeObserver?.disconnect()
 	if (unmountGridTimeout) clearTimeout(unmountGridTimeout)
 })
 
@@ -149,19 +206,10 @@ function getSelectionKey(screenshot: InstanceScreenshot) {
 				<slot name="actions" :start-editing="startEditing" />
 			</template>
 			<div v-if="renderGrid" class="relative min-h-[45px] w-full" :style="virtualGridStyle">
-				<TransitionGroup
-					tag="div"
+				<div
 					class="grid min-h-[45px] w-full grid-cols-1 gap-3 sm:grid-cols-2 2xl:grid-cols-4"
 					:class="{ 'absolute inset-x-0 top-0': virtualGridHeight !== undefined }"
 					:style="visibleGridStyle"
-					move-class="transition-transform duration-200 ease-out motion-reduce:transition-none"
-					:enter-active-class="
-						animateEntry
-							? 'transition-[opacity,transform] duration-[150ms] ease-out motion-reduce:transition-none'
-							: ''
-					"
-					:enter-from-class="animateEntry ? 'opacity-0' : ''"
-					enter-to-class="opacity-100 scale-100"
 				>
 					<ScreenshotCard
 						v-for="screenshot in visibleScreenshots"
@@ -188,7 +236,7 @@ function getSelectionKey(screenshot: InstanceScreenshot) {
 					>
 						{{ formatMessage(messages.emptyGroup) }}
 					</p>
-				</TransitionGroup>
+				</div>
 			</div>
 		</ScreenshotSection>
 	</div>
diff --git a/apps/app-frontend/src/components/ui/screenshots-page/index.vue b/apps/app-frontend/src/components/ui/screenshots-page/index.vue
index d845fe8b68..99296d7c6c 100644
--- a/apps/app-frontend/src/components/ui/screenshots-page/index.vue
+++ b/apps/app-frontend/src/components/ui/screenshots-page/index.vue
@@ -34,6 +34,7 @@ import {
 	type ImageViewerEditorSavePayload,
 	injectNotificationManager,
 	ReadyTransition,
+	useDebugLogger,
 	useFormatDateTime,
 	useReadyState,
 	useScrollViewport,
@@ -109,6 +110,7 @@ type ScreenshotDropData = {
 }
 
 type ScreenshotGroupLayout = {
+	id: string
 	group: ScreenshotGroupData
 	top: number
 	height: number
@@ -117,7 +119,7 @@ type ScreenshotGroupLayout = {
 	gridTop: number
 }
 
-type VisibleScreenshotGroupLayout = ScreenshotGroupLayout & {
+type VirtualizedScreenshotGroupLayout = ScreenshotGroupLayout & {
 	renderedScreenshots: InstanceScreenshot[]
 	virtualGridTop: number
 }
@@ -126,7 +128,7 @@ const SCREENSHOT_GRID_GAP = 12
 const SCREENSHOT_GROUP_SPACING = 12
 const SCREENSHOT_GROUP_HEADER_HEIGHT = 40
 const SCREENSHOT_GROUP_CONTENT_SPACING = 10
-const SCREENSHOT_GROUP_OVERSCAN = 900
+const SCREENSHOT_GROUP_OVERSCAN = 2000
 const SCREENSHOT_GRID_MIN_HEIGHT = 45
 const FALLBACK_SCREENSHOT_CARD_WIDTH = 320
 
@@ -173,8 +175,6 @@ const selectedKeys = ref(new Set<string>())
 const copiedScreenshotIds = ref(new Set<string>())
 const copiedResetTimeouts = new Map<string, ReturnType<typeof setTimeout>>()
 const screenshotsPage = ref<HTMLElement>()
-const regrouping = ref(false)
-const screenshotsScrolling = ref(false)
 const screenshotToDelete = ref<InstanceScreenshot | null>(null)
 const deleteFromPreview = ref(false)
 const activeDrag = ref<ActiveScreenshotDrag | null>(null)
@@ -197,7 +197,8 @@ const route = useRoute()
 const router = useRouter()
 const { formatMessage } = useVIntl()
 const { addNotification, handleError } = injectNotificationManager()
-let screenshotsScrollIdleTimeout: ReturnType<typeof setTimeout> | undefined
+const debugLayout = useDebugLogger('Screenshots:Layout')
+let screenshotsScrollLogFrame: number | undefined
 const {
 	listContainer: screenshotListContainer,
 	containerOffset: screenshotListOffset,
@@ -206,12 +207,18 @@ const {
 	viewportHeight: screenshotViewportHeight,
 } = useScrollViewport({
 	onScroll: () => {
-		screenshotsScrolling.value = true
-		if (screenshotsScrollIdleTimeout) clearTimeout(screenshotsScrollIdleTimeout)
-		screenshotsScrollIdleTimeout = setTimeout(() => {
-			screenshotsScrolling.value = false
-			screenshotsScrollIdleTimeout = undefined
-		}, 120)
+		if (screenshotsScrollLogFrame === undefined) {
+			screenshotsScrollLogFrame = requestAnimationFrame(() => {
+				screenshotsScrollLogFrame = undefined
+				debugLayout('scroll', {
+					groupBy: groupBy.value,
+					relativeScrollTop: screenshotListScrollTop.value,
+					listOffset: screenshotListOffset.value,
+					viewportHeight: screenshotViewportHeight.value,
+					listWidth: screenshotListWidth.value,
+				})
+			})
+		}
 	},
 })
 const { width: screenshotListWidth } = useElementSize(screenshotListContainer)
@@ -546,19 +553,14 @@ const screenshotGroupLayouts = computed<ScreenshotGroupLayout[]>(() => {
 			(isOpen ? SCREENSHOT_GROUP_CONTENT_SPACING + gridHeight : 0) +
 			SCREENSHOT_GROUP_SPACING
 
-		layouts.push({ group, top, height, isOpen, gridHeight, gridTop })
+		layouts.push({ id: group.id, group, top, height, isOpen, gridHeight, gridTop })
 		top += height
 	}
 
 	return layouts
 })
 
-const screenshotListHeight = computed(() => {
-	const lastGroup = screenshotGroupLayouts.value[screenshotGroupLayouts.value.length - 1]
-	return lastGroup ? lastGroup.top + lastGroup.height : 0
-})
-
-const visibleScreenshotGroups = computed<VisibleScreenshotGroupLayout[]>(() => {
+const virtualizedScreenshotGroups = computed<VirtualizedScreenshotGroupLayout[]>(() => {
 	const hasViewport = Boolean(screenshotListContainer.value && screenshotScrollContainer.value)
 	const viewportStart = hasViewport
 		? Math.max(0, screenshotListScrollTop.value - SCREENSHOT_GROUP_OVERSCAN)
@@ -567,36 +569,90 @@ const visibleScreenshotGroups = computed<VisibleScreenshotGroupLayout[]>(() => {
 		? screenshotListScrollTop.value + screenshotViewportHeight.value + SCREENSHOT_GROUP_OVERSCAN
 		: SCREENSHOT_GROUP_OVERSCAN
 
-	return screenshotGroupLayouts.value
-		.filter((layout) => layout.top + layout.height >= viewportStart && layout.top <= viewportEnd)
-		.map((layout) => {
-			if (!layout.isOpen || layout.group.screenshots.length === 0) {
-				return { ...layout, renderedScreenshots: [], virtualGridTop: 0 }
-			}
+	return screenshotGroupLayouts.value.map((layout) => {
+		const isInRenderRange = layout.top + layout.height >= viewportStart && layout.top <= viewportEnd
+		if (!layout.isOpen || layout.group.screenshots.length === 0) {
+			return { ...layout, renderedScreenshots: [], virtualGridTop: 0 }
+		}
+		if (!isInRenderRange) {
+			return { ...layout, renderedScreenshots: [], virtualGridTop: 0 }
+		}
 
-			const rowCount = Math.ceil(layout.group.screenshots.length / screenshotColumnCount.value)
-			const firstRow = Math.min(
-				rowCount,
-				Math.max(0, Math.floor((viewportStart - layout.gridTop) / screenshotRowHeight.value)),
-			)
-			const lastRow = Math.min(
-				rowCount,
-				Math.max(
-					firstRow,
-					Math.ceil(
-						(viewportEnd - layout.gridTop + SCREENSHOT_GRID_GAP) / screenshotRowHeight.value,
-					),
-				),
-			)
-			const firstScreenshot = firstRow * screenshotColumnCount.value
-			const lastScreenshot = lastRow * screenshotColumnCount.value
+		const rowCount = Math.ceil(layout.group.screenshots.length / screenshotColumnCount.value)
+		const firstRow = Math.min(
+			rowCount,
+			Math.max(0, Math.floor((viewportStart - layout.gridTop) / screenshotRowHeight.value)),
+		)
+		const lastRow = Math.min(
+			rowCount,
+			Math.max(
+				firstRow,
+				Math.ceil((viewportEnd - layout.gridTop + SCREENSHOT_GRID_GAP) / screenshotRowHeight.value),
+			),
+		)
+		const firstScreenshot = firstRow * screenshotColumnCount.value
+		const lastScreenshot = lastRow * screenshotColumnCount.value
 
-			return {
-				...layout,
-				renderedScreenshots: layout.group.screenshots.slice(firstScreenshot, lastScreenshot),
-				virtualGridTop: firstRow * screenshotRowHeight.value,
-			}
+		return {
+			...layout,
+			renderedScreenshots: layout.group.screenshots.slice(firstScreenshot, lastScreenshot),
+			virtualGridTop: firstRow * screenshotRowHeight.value,
+		}
+	})
+})
+
+watch(
+	[groupBy, screenshotListWidth, windowWidth, screenshotColumnCount, screenshotCardHeight],
+	([currentGroupBy, listWidth, currentWindowWidth, columns, cardHeight], previous) => {
+		debugLayout('responsive geometry changed', {
+			groupBy: currentGroupBy,
+			listWidth,
+			windowWidth: currentWindowWidth,
+			columns,
+			cardHeight,
+			previous,
 		})
+	},
+	{ immediate: true },
+)
+
+watch(
+	screenshotGroupLayouts,
+	(layouts) => {
+		debugLayout('group layouts changed', {
+			groupBy: groupBy.value,
+			groupCount: layouts.length,
+			totalHeight: layouts.at(-1) ? layouts.at(-1)!.top + layouts.at(-1)!.height : 0,
+			layouts: layouts.map((layout) => ({
+				id: layout.id,
+				top: layout.top,
+				height: layout.height,
+				gridTop: layout.gridTop,
+				gridHeight: layout.gridHeight,
+				isOpen: layout.isOpen,
+				screenshotCount: layout.group.screenshots.length,
+			})),
+		})
+	},
+	{ immediate: true },
+)
+
+watch(virtualizedScreenshotGroups, (groups) => {
+	debugLayout('render window changed', {
+		groupBy: groupBy.value,
+		relativeScrollTop: screenshotListScrollTop.value,
+		viewportHeight: screenshotViewportHeight.value,
+		renderedGroups: groups
+			.filter((group) => group.renderedScreenshots.length > 0)
+			.map((group) => ({
+				id: group.id,
+				top: group.top,
+				virtualGridTop: group.virtualGridTop,
+				renderedCount: group.renderedScreenshots.length,
+				firstScreenshotId: group.renderedScreenshots.at(0)?.id,
+				lastScreenshotId: group.renderedScreenshots.at(-1)?.id,
+			})),
+	})
 })
 
 const previewItems = computed(() =>
@@ -685,10 +741,8 @@ watch(groupBy, async (currentGroupBy, previousGroupBy) => {
 	if (currentGroupBy === previousGroupBy) return
 
 	const previousPositions = getScreenshotCardPositions()
-	regrouping.value = true
 	await nextTick()
 	animateScreenshotCardsFrom(previousPositions)
-	regrouping.value = false
 })
 
 let handledFocus: string | undefined
@@ -1335,7 +1389,7 @@ watch(activeDropGroupId, (groupId) => {
 onBeforeUnmount(() => {
 	clearGroupHoverOpenTimeout()
 	if (revealTimeout) clearTimeout(revealTimeout)
-	if (screenshotsScrollIdleTimeout) clearTimeout(screenshotsScrollIdleTimeout)
+	if (screenshotsScrollLogFrame !== undefined) cancelAnimationFrame(screenshotsScrollLogFrame)
 	for (const timeout of copiedResetTimeouts.values()) clearTimeout(timeout)
 	copiedResetTimeouts.clear()
 })
@@ -1479,20 +1533,21 @@ onBeforeUnmount(() => {
 			>
 				<div
 					ref="screenshotListContainer"
-					class="relative w-full"
-					:style="{ height: `${screenshotListHeight}px`, overflowAnchor: 'none' }"
+					class="w-full"
+					:style="{
+						overflowAnchor: 'none',
+						visibility: screenshotListWidth > 0 ? 'visible' : 'hidden',
+					}"
 				>
 					<div
 						v-for="{
+							id,
 							group,
-							top,
 							gridHeight,
 							renderedScreenshots,
 							virtualGridTop,
-						} in visibleScreenshotGroups"
-						:key="group.id"
-						class="absolute inset-x-0 transition-transform duration-300 ease-in-out will-change-transform motion-reduce:transition-none"
-						:style="{ transform: `translateY(${top}px)` }"
+						} in virtualizedScreenshotGroups"
+						:key="id"
 					>
 						<ScreenshotGroupSection
 							:id="group.id"
@@ -1514,7 +1569,6 @@ onBeforeUnmount(() => {
 							:show-instance-name="isGlobal && groupBy !== 'instance'"
 							:highlighted-screenshot-id="highlightedScreenshotId"
 							:copied-screenshot-ids="copiedScreenshotIds"
-							:animate-entry="!regrouping && !screenshotsScrolling"
 							:force-open="search.length > 0"
 							:hide-header="groupBy === 'none'"
 							:editable-title="Boolean(group.customGroupId)"
diff --git a/apps/app-frontend/src/components/ui/screenshots-page/section.vue b/apps/app-frontend/src/components/ui/screenshots-page/section.vue
index b5872c4ddf..82f4fdf0df 100644
--- a/apps/app-frontend/src/components/ui/screenshots-page/section.vue
+++ b/apps/app-frontend/src/components/ui/screenshots-page/section.vue
@@ -6,9 +6,10 @@ import {
 	defineMessages,
 	InlineEditableText,
 	TagItem,
+	useDebugLogger,
 	useVIntl,
 } from '@modrinth/ui'
-import { nextTick, ref, watch } from 'vue'
+import { nextTick, onBeforeUnmount, onMounted, ref, watch } from 'vue'
 
 const props = withDefaults(
 	defineProps<{
@@ -37,6 +38,7 @@ const emit = defineEmits<{
 }>()
 
 const { formatMessage } = useVIntl()
+const debugLayout = useDebugLogger('Screenshots:Section')
 const accordion = ref<InstanceType<typeof Accordion>>()
 const titleInput = ref<InstanceType<typeof InlineEditableText>>()
 const titleModel = ref(props.title)
@@ -46,6 +48,11 @@ const messages = defineMessages({
 })
 
 function toggle() {
+	debugLayout('toggle requested', {
+		title: props.title,
+		count: props.count,
+		isOpen: accordion.value?.isOpen,
+	})
 	if (accordion.value?.isOpen) {
 		accordion.value.close()
 	} else {
@@ -53,6 +60,30 @@ function toggle() {
 	}
 }
 
+function handleOpen() {
+	debugLayout('opened', { title: props.title, count: props.count })
+	emit('update:collapsed', false)
+}
+
+function handleClose() {
+	debugLayout('closed', { title: props.title, count: props.count })
+	emit('update:collapsed', true)
+}
+
+onMounted(() => {
+	debugLayout('mounted', {
+		title: props.title,
+		count: props.count,
+		collapsed: props.collapsed,
+		hideHeader: props.hideHeader,
+		forceOpen: props.forceOpen,
+	})
+})
+
+onBeforeUnmount(() => {
+	debugLayout('unmounted', { title: props.title, count: props.count })
+})
+
 async function startTitleEditing() {
 	if (!props.editable) return
 	await titleInput.value?.startEditing()
@@ -127,8 +158,8 @@ watch(
 			:force-open="forceOpen"
 			overflow-visible
 			class="w-full"
-			@on-open="emit('update:collapsed', false)"
-			@on-close="emit('update:collapsed', true)"
+			@on-open="handleOpen"
+			@on-close="handleClose"
 		>
 			<div class="mt-2.5">
 				<slot />
diff --git a/apps/app/src/api/instance.rs b/apps/app/src/api/instance.rs
index 6cbb60b904..6188ecc555 100644
--- a/apps/app/src/api/instance.rs
+++ b/apps/app/src/api/instance.rs
@@ -2,7 +2,7 @@ use crate::api::Result;
 use dashmap::DashMap;
 use path_util::SafeRelativeUtf8UnixPathBuf;
 use serde::{Deserialize, Serialize};
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::path::{Path, PathBuf};
 use tauri::{AppHandle, Manager, Runtime};
 use tauri_plugin_fs::FsExt;
@@ -906,13 +906,25 @@ fn serialize_screenshots<R: Runtime>(
     app_handle: &AppHandle<R>,
     screenshots: Vec<theseus::instance::InstanceScreenshot>,
 ) -> Result<Vec<InstanceScreenshot>> {
-    let mut result = Vec::with_capacity(screenshots.len());
-
-    for screenshot in screenshots {
-        result.push(serialize_screenshot(app_handle, screenshot)?);
+    let screenshot_directories = screenshots
+        .iter()
+        .filter_map(|screenshot| screenshot.path.parent())
+        .collect::<HashSet<_>>();
+    for directory in screenshot_directories {
+        app_handle
+            .asset_protocol_scope()
+            .allow_directory(directory, false)
+            .map_err(|error| std::io::Error::other(error.to_string()))?;
+        app_handle
+            .fs_scope()
+            .allow_directory(directory, false)
+            .map_err(|error| std::io::Error::other(error.to_string()))?;
     }
 
-    Ok(result)
+    screenshots
+        .into_iter()
+        .map(serialize_screenshot_data)
+        .collect()
 }
 
 fn serialize_screenshot<R: Runtime>(
@@ -927,6 +939,12 @@ fn serialize_screenshot<R: Runtime>(
         .fs_scope()
         .allow_file(&screenshot.path)
         .map_err(|error| std::io::Error::other(error.to_string()))?;
+    serialize_screenshot_data(screenshot)
+}
+
+fn serialize_screenshot_data(
+    screenshot: theseus::instance::InstanceScreenshot,
+) -> Result<InstanceScreenshot> {
     let mut url = super::utils::tauri_convert_file_src(&screenshot.path)?;
     url.query_pairs_mut()
         .append_pair("revision", &screenshot.modified_at.to_string());
diff --git a/packages/app-lib/src/api/instance/screenshots/reconciliation.rs b/packages/app-lib/src/api/instance/screenshots/reconciliation.rs
index 67882d497f..c77db13884 100644
--- a/packages/app-lib/src/api/instance/screenshots/reconciliation.rs
+++ b/packages/app-lib/src/api/instance/screenshots/reconciliation.rs
@@ -8,12 +8,15 @@ use crate::state::instances::adapters::sqlite::{
     screenshot_rows::{self, ScreenshotRow},
 };
 use crate::util::fetch::sha1_file_async;
-use crate::util::io::{self, IOError};
+use crate::util::io::IOError;
 use chrono::{DateTime, Utc};
+use futures::stream::{self, StreamExt, TryStreamExt};
 use std::collections::HashMap;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use uuid::Uuid;
 
+const SCREENSHOT_HASH_CONCURRENCY: usize = 8;
+
 pub(super) struct ScannedScreenshot {
     file_name: String,
     created_at: DateTime<Utc>,
@@ -109,7 +112,14 @@ pub(super) async fn scan_source_screenshots(
     }
 
     let screenshots_dir = source_screenshots_dir(state, source).await?;
-    let mut entries = match io::read_dir(&screenshots_dir).await {
+    tokio::task::spawn_blocking(move || scan_screenshots_dir(&screenshots_dir))
+        .await?
+}
+
+fn scan_screenshots_dir(
+    screenshots_dir: &Path,
+) -> crate::Result<Vec<ScannedScreenshot>> {
+    let entries = match std::fs::read_dir(screenshots_dir) {
         Ok(entries) => entries,
         Err(error) if error.kind() == std::io::ErrorKind::NotFound => {
             return Ok(Vec::new());
@@ -118,14 +128,11 @@ pub(super) async fn scan_source_screenshots(
     };
     let mut screenshots = Vec::new();
 
-    while let Some(entry) = entries
-        .next_entry()
-        .await
-        .map_err(|error| IOError::with_path(error, &screenshots_dir))?
-    {
+    for entry in entries {
+        let entry = entry
+            .map_err(|error| IOError::with_path(error, screenshots_dir))?;
         let file_type = entry
             .file_type()
-            .await
             .map_err(|error| IOError::with_path(error, entry.path()))?;
         if !file_type.is_file() {
             continue;
@@ -142,7 +149,6 @@ pub(super) async fn scan_source_screenshots(
         };
         let metadata = entry
             .metadata()
-            .await
             .map_err(|error| IOError::with_path(error, &path))?;
         let created_at = metadata
             .created()
@@ -179,53 +185,34 @@ pub(super) async fn reconcile_source_screenshots(
 ) -> crate::Result<Vec<InstanceScreenshot>> {
     let existing =
         screenshot_rows::list_screenshots(&source.id, &state.pool).await?;
-    let existing_by_name = existing
-        .iter()
-        .map(|row| (row.file_name.as_str(), row))
+    let mut unmatched_by_name = existing
+        .into_iter()
+        .map(|row| (row.file_name.clone(), row))
         .collect::<HashMap<_, _>>();
-    let metadata_matches = existing.len() == scanned.len()
-        && scanned.iter().all(|scanned| {
-            existing_by_name
-                .get(scanned.file_name.as_str())
-                .is_some_and(|row| {
-                    row.file_size == scanned.file_size
-                        && row.modified_at == scanned.modified_at
-                        && row.created_at
-                            == scanned.created_at.timestamp_millis()
-                })
-        });
-    let mut unmatched_by_hash =
-        HashMap::<(String, i64), Vec<ScreenshotRow>>::new();
     let mut resolved = Vec::with_capacity(scanned.len());
+    let mut needs_hash = Vec::new();
 
-    if metadata_matches {
-        let mut existing_by_name = existing
-            .into_iter()
-            .map(|row| (row.file_name.clone(), row))
-            .collect::<HashMap<_, _>>();
-        for scanned in scanned {
-            let row = existing_by_name.remove(&scanned.file_name).ok_or_else(
-                || {
-                    crate::ErrorKind::InputError(
-                        "Screenshot index changed during reconciliation"
-                            .to_string(),
-                    )
-                },
-            )?;
-            resolved.push(ResolvedScreenshot {
-                scanned,
-                row,
-                is_new: false,
-                changed: false,
-            });
+    for scanned in scanned {
+        match unmatched_by_name.remove(&scanned.file_name) {
+            Some(row)
+                if row.file_size == scanned.file_size
+                    && row.modified_at == scanned.modified_at
+                    && row.created_at
+                        == scanned.created_at.timestamp_millis() =>
+            {
+                resolved.push(ResolvedScreenshot {
+                    scanned,
+                    row,
+                    is_new: false,
+                    changed: false,
+                });
+            }
+            matched => needs_hash.push((scanned, matched)),
         }
-    } else {
-        let mut unmatched_by_name = existing
-            .into_iter()
-            .map(|row| (row.file_name.clone(), row))
-            .collect::<HashMap<_, _>>();
-        let mut hashed = Vec::with_capacity(scanned.len());
-        for mut scanned in scanned {
+    }
+
+    let hashed = stream::iter(needs_hash.into_iter().map(
+        |(mut scanned, matched)| async move {
             let (file_size, content_hash) =
                 sha1_file_async(&scanned.path).await?;
             scanned.file_size = i64::try_from(file_size).map_err(|_| {
@@ -233,54 +220,54 @@ pub(super) async fn reconcile_source_screenshots(
                     "Screenshot is too large to index".to_string(),
                 )
             })?;
-            hashed.push((scanned, content_hash));
-        }
+            Ok::<_, crate::Error>((scanned, content_hash, matched))
+        },
+    ))
+    .buffer_unordered(SCREENSHOT_HASH_CONCURRENCY)
+    .try_collect::<Vec<_>>()
+    .await?;
 
-        let mut renamed_or_new = Vec::new();
-        for (scanned, content_hash) in hashed {
-            if let Some(row) = unmatched_by_name.remove(&scanned.file_name) {
-                resolved.push(resolve_scanned_screenshot(
-                    source,
-                    scanned,
-                    content_hash,
-                    Some(row),
-                ));
-            } else {
-                renamed_or_new.push((scanned, content_hash));
-            }
-        }
+    let mut unmatched_by_hash =
+        HashMap::<(String, i64), Vec<ScreenshotRow>>::new();
+    for row in unmatched_by_name.into_values() {
+        unmatched_by_hash
+            .entry((row.content_hash.clone(), row.file_size))
+            .or_default()
+            .push(row);
+    }
 
-        for row in unmatched_by_name.into_values() {
-            unmatched_by_hash
-                .entry((row.content_hash.clone(), row.file_size))
-                .or_default()
-                .push(row);
-        }
-
-        for (scanned, content_hash) in renamed_or_new {
-            let hash_key = (content_hash.clone(), scanned.file_size);
-            let matched =
-                unmatched_by_hash.get_mut(&hash_key).and_then(|rows| {
-                    if rows.is_empty() {
-                        return None;
-                    }
-                    let created_at = scanned.created_at.timestamp_millis();
-                    let index = rows
-                        .iter()
-                        .position(|row| {
-                            row.modified_at == scanned.modified_at
-                                && row.created_at == created_at
-                        })
-                        .unwrap_or(rows.len() - 1);
-                    Some(rows.swap_remove(index))
-                });
+    for (scanned, content_hash, matched_by_name) in hashed {
+        if let Some(row) = matched_by_name {
             resolved.push(resolve_scanned_screenshot(
                 source,
                 scanned,
                 content_hash,
-                matched,
+                Some(row),
             ));
+            continue;
         }
+
+        let hash_key = (content_hash.clone(), scanned.file_size);
+        let matched = unmatched_by_hash.get_mut(&hash_key).and_then(|rows| {
+            if rows.is_empty() {
+                return None;
+            }
+            let created_at = scanned.created_at.timestamp_millis();
+            let index = rows
+                .iter()
+                .position(|row| {
+                    row.modified_at == scanned.modified_at
+                        && row.created_at == created_at
+                })
+                .unwrap_or(rows.len() - 1);
+            Some(rows.swap_remove(index))
+        });
+        resolved.push(resolve_scanned_screenshot(
+            source,
+            scanned,
+            content_hash,
+            matched,
+        ));
     }
 
     let mut tx = state.pool.begin().await?;