feat: rework photo-viewer/asset-viewer - introduce adaptive-image.svelte

preload thumbs and previews

e2e/src/web/specs/photo-viewer.e2e-spec.ts

@@ -1,10 +1,7 @@
 import { AssetMediaResponseDto, LoginResponseDto } from '@immich/sdk';
-import { Page, expect, test } from '@playwright/test';
+import { expect, test } from '@playwright/test';
 import { utils } from 'src/utils';
 
-function imageLocator(page: Page) {
-  return page.getByAltText('Image taken').locator('visible=true');
-}
 test.describe('Photo Viewer', () => {
   let admin: LoginResponseDto;
   let asset: AssetMediaResponseDto;
@@ -26,31 +23,32 @@ test.describe('Photo Viewer', () => {
 
   test('loads original photo when zoomed', async ({ page }) => {
     await page.goto(`/photos/${asset.id}`);
-    await expect.poll(async () => await imageLocator(page).getAttribute('src')).toContain('thumbnail');
-    const box = await imageLocator(page).boundingBox();
+    await expect(page.getByTestId('thumbnail')).toHaveAttribute('src', /thumbnail/);
+    const box = await page.getByTestId('thumbnail').boundingBox();
     expect(box).toBeTruthy();
     const { x, y, width, height } = box!;
     await page.mouse.move(x + width / 2, y + height / 2);
     await page.mouse.wheel(0, -1);
-    await expect.poll(async () => await imageLocator(page).getAttribute('src')).toContain('original');
+    await expect(page.getByTestId('original')).toBeInViewport();
+    await expect(page.getByTestId('original')).toHaveAttribute('src', /original/);
   });
 
   test('loads fullsize image when zoomed and original is web-incompatible', async ({ page }) => {
     await page.goto(`/photos/${rawAsset.id}`);
-    await expect.poll(async () => await imageLocator(page).getAttribute('src')).toContain('thumbnail');
-    const box = await imageLocator(page).boundingBox();
+    await expect(page.getByTestId('thumbnail')).toHaveAttribute('src', /thumbnail/);
+    const box = await page.getByTestId('thumbnail').boundingBox();
     expect(box).toBeTruthy();
     const { x, y, width, height } = box!;
     await page.mouse.move(x + width / 2, y + height / 2);
     await page.mouse.wheel(0, -1);
-    await expect.poll(async () => await imageLocator(page).getAttribute('src')).toContain('fullsize');
+    await expect(page.getByTestId('original')).toHaveAttribute('src', /fullsize/);
   });
 
   test('reloads photo when checksum changes', async ({ page }) => {
     await page.goto(`/photos/${asset.id}`);
-    await expect.poll(async () => await imageLocator(page).getAttribute('src')).toContain('thumbnail');
-    const initialSrc = await imageLocator(page).getAttribute('src');
+    await expect(page.getByTestId('thumbnail')).toHaveAttribute('src', /thumbnail/);
+    const initialSrc = await page.getByTestId('thumbnail').getAttribute('src');
     await utils.replaceAsset(admin.accessToken, asset.id);
-    await expect.poll(async () => await imageLocator(page).getAttribute('src')).not.toBe(initialSrc);
+    await expect(page.getByTestId('preview')).not.toHaveAttribute('src', initialSrc!);
   });
 });

i18n/en.json

@@ -998,9 +998,11 @@
   "error_getting_places": "Error getting places",
   "error_loading_image": "Error loading image",
   "error_loading_partners": "Error loading partners: {error}",
+  "error_retrieving_asset_information": "Error retrieving asset information",
   "error_saving_image": "Error: {error}",
   "error_tag_face_bounding_box": "Error tagging face - cannot get bounding box coordinates",
   "error_title": "Error - Something went wrong",
+  "error_while_navigating": "Error while navigating to asset",
   "errors": {
     "cannot_navigate_next_asset": "Cannot navigate to the next asset",
     "cannot_navigate_previous_asset": "Cannot navigate to previous asset",

web/src/lib/actions/image-loader.svelte.ts

@@ -0,0 +1,196 @@
+import { cancelImageUrl } from '$lib/utils/sw-messaging';
+import type { ClassValue } from 'svelte/elements';
+
+/**
+ * Converts a ClassValue to a string suitable for className assignment.
+ * Handles strings, arrays, and objects similar to how clsx works.
+ */
+function classValueToString(value: ClassValue | undefined): string {
+  if (!value) {
+    return '';
+  }
+  if (typeof value === 'string') {
+    return value;
+  }
+  if (Array.isArray(value)) {
+    return value
+      .map((v) => classValueToString(v))
+      .filter(Boolean)
+      .join(' ');
+  }
+  // Object/dictionary case
+  return Object.entries(value)
+    .filter(([, v]) => v)
+    .map(([k]) => k)
+    .join(' ');
+}
+
+export interface ImageLoaderProperties {
+  imgClass?: ClassValue;
+  alt?: string;
+  draggable?: boolean;
+  role?: string;
+  style?: string;
+  title?: string | null;
+  loading?: 'lazy' | 'eager';
+  dataAttributes?: Record<string, string>;
+}
+export interface ImageSourceProperty {
+  src: string | undefined;
+}
+export interface ImageLoaderCallbacks {
+  onStart?: () => void;
+  onLoad?: () => void;
+  onError?: (error: Error) => void;
+  onElementCreated?: (element: HTMLImageElement) => void;
+}
+
+const updateImageAttributes = (img: HTMLImageElement, params: ImageLoaderProperties) => {
+  if (params.alt !== undefined) {
+    img.alt = params.alt;
+  }
+  if (params.draggable !== undefined) {
+    img.draggable = params.draggable;
+  }
+  if (params.imgClass) {
+    img.className = classValueToString(params.imgClass);
+  }
+  if (params.role) {
+    img.role = params.role;
+  }
+  if (params.style !== undefined) {
+    img.setAttribute('style', params.style);
+  }
+  if (params.title !== undefined && params.title !== null) {
+    img.title = params.title;
+  }
+  if (params.loading !== undefined) {
+    img.loading = params.loading;
+  }
+  if (params.dataAttributes) {
+    for (const [key, value] of Object.entries(params.dataAttributes)) {
+      img.setAttribute(key, value);
+    }
+  }
+};
+
+const cleanupImageElement = (
+  imgElement: HTMLImageElement,
+  currentSrc: string | undefined,
+  handleLoad: () => void,
+  handleError: () => void,
+) => {
+  cancelImageUrl(currentSrc);
+  if (imgElement) {
+    imgElement.removeEventListener('load', handleLoad);
+    imgElement.removeEventListener('error', handleError);
+    imgElement.remove();
+  }
+};
+
+const createImageElement = (
+  src: string | undefined,
+  properties: ImageLoaderProperties,
+  onLoad: () => void,
+  onError: () => void,
+  onStart?: () => void,
+  onElementCreated?: (imgElement: HTMLImageElement) => void,
+) => {
+  if (!src) {
+    return undefined;
+  }
+  const img = document.createElement('img');
+  updateImageAttributes(img, properties);
+
+  img.addEventListener('load', onLoad);
+  img.addEventListener('error', onError);
+
+  onStart?.();
+
+  if (src) {
+    img.src = src;
+    onElementCreated?.(img);
+  }
+
+  return img;
+};
+
+export function loadImage(
+  src: string,
+  properties: ImageLoaderProperties,
+  onLoad: () => void,
+  onError: () => void,
+  onStart?: () => void,
+) {
+  const img = createImageElement(src, properties, onLoad, onError, onStart);
+  if (!img) {
+    return () => void 0;
+  }
+  return () => cleanupImageElement(img, src, onLoad, onError);
+}
+
+export type LoadImageFunction = typeof loadImage;
+
+/**
+ * 1. Creates and appends an <img> element to the parent
+ * 2. Coordinates with service worker before src triggers fetch
+ * 3. Adds load/error listeners
+ * 4. Cancels SW request when element is removed from DOM
+ */
+export function imageLoader(
+  node: HTMLElement,
+  params: ImageSourceProperty & ImageLoaderProperties & ImageLoaderCallbacks,
+) {
+  let currentSrc = params.src;
+  let currentCallbacks = params;
+  let imgElement: HTMLImageElement | undefined = undefined;
+
+  const handleLoad = () => {
+    currentCallbacks.onLoad?.();
+  };
+
+  const handleError = () => {
+    currentCallbacks.onError?.(new Error(`Failed to load image: ${currentSrc}`));
+  };
+
+  const handleElementCreated = (img: HTMLImageElement) => {
+    if (img) {
+      node.append(img);
+      currentCallbacks.onElementCreated?.(img);
+    }
+  };
+
+  const createImage = () => {
+    imgElement = createImageElement(currentSrc, params, handleLoad, handleError, params.onStart, handleElementCreated);
+  };
+  createImage();
+
+  return {
+    update(newParams: ImageSourceProperty & ImageLoaderProperties & ImageLoaderCallbacks) {
+      // If src changed, recreate the image element
+      if (newParams.src !== currentSrc) {
+        cleanupImageElement(imgElement!, currentSrc, handleLoad, handleError);
+
+        currentSrc = newParams.src;
+        currentCallbacks = newParams;
+
+        createImage();
+        return;
+      }
+
+      currentCallbacks = newParams;
+
+      if (!imgElement) {
+        return;
+      }
+
+      updateImageAttributes(imgElement, newParams);
+    },
+
+    destroy() {
+      if (imgElement) {
+        cleanupImageElement(imgElement, currentSrc, handleLoad, handleError);
+      }
+    },
+  };
+}

web/src/lib/components/asset-viewer/adaptive-image.svelte

@@ -0,0 +1,246 @@
+<script lang="ts">
+  import { imageLoader } from '$lib/actions/image-loader.svelte';
+  import { thumbhash } from '$lib/actions/thumbhash';
+  import { zoomImageAction } from '$lib/actions/zoom-image';
+  import BrokenAsset from '$lib/components/assets/broken-asset.svelte';
+  import { SlideshowLook, SlideshowState } from '$lib/stores/slideshow.store';
+  import { photoZoomState, photoZoomTransform, resetZoomState } from '$lib/stores/zoom-image.store';
+  import { AdaptiveImageLoader } from '$lib/utils/adaptive-image-loader.svelte';
+  import { getDimensions } from '$lib/utils/asset-utils';
+  import { scaleToFit } from '$lib/utils/layout-utils';
+  import { getAltText } from '$lib/utils/thumbnail-util';
+  import { toTimelineAsset } from '$lib/utils/timeline-util';
+  import type { AssetResponseDto, SharedLinkResponseDto } from '@immich/sdk';
+  import { LoadingSpinner } from '@immich/ui';
+  import { onDestroy, untrack, type Snippet } from 'svelte';
+
+  interface Props {
+    asset: AssetResponseDto;
+    sharedLink?: SharedLinkResponseDto;
+    zoomDisabled?: boolean;
+    imageClass?: string;
+    container: {
+      width: number;
+      height: number;
+    };
+    slideshowState: SlideshowState;
+    slideshowLook: SlideshowLook;
+    onImageReady?: () => void;
+    onError?: () => void;
+    imgElement?: HTMLImageElement;
+    overlays?: Snippet;
+  }
+
+  let {
+    imgElement = $bindable<HTMLImageElement | undefined>(),
+    asset,
+    sharedLink,
+    zoomDisabled = false,
+    imageClass = '',
+    container,
+    slideshowState,
+    slideshowLook,
+    onImageReady,
+    onError,
+    overlays,
+  }: Props = $props();
+
+  let previousLoader = $state<AdaptiveImageLoader>();
+  let previousAssetId: string | undefined;
+  let previousSharedLinkId: string | undefined;
+
+  const adaptiveImageLoader = $derived.by(() => {
+    if (previousAssetId === asset.id && previousSharedLinkId === sharedLink?.id) {
+      return previousLoader!;
+    }
+
+    return untrack(() => {
+      previousAssetId = asset.id;
+      previousSharedLinkId = sharedLink?.id;
+
+      previousLoader?.destroy();
+      resetZoomState();
+      const loader = new AdaptiveImageLoader(asset, sharedLink, {
+        currentZoomFn: () => $photoZoomState.currentZoom,
+        onImageReady,
+        onError,
+      });
+      previousLoader = loader;
+      return loader;
+    });
+  });
+  onDestroy(() => adaptiveImageLoader.destroy());
+
+  const imageDimensions = $derived.by(() => {
+    if ((asset.width ?? 0) > 0 && (asset.height ?? 0) > 0) {
+      return { width: asset.width!, height: asset.height! };
+    }
+
+    if (asset.exifInfo?.exifImageHeight && asset.exifInfo.exifImageWidth) {
+      return getDimensions(asset.exifInfo) as { width: number; height: number };
+    }
+
+    return { width: 1, height: 1 };
+  });
+
+  const scaledDimensions = $derived(scaleToFit(imageDimensions, container));
+
+  const renderDimensions = $derived.by(() => {
+    const { width, height } = scaledDimensions;
+    return {
+      width: width + 'px',
+      height: height + 'px',
+      left: (container.width - width) / 2 + 'px',
+      top: (container.height - height) / 2 + 'px',
+    };
+  });
+
+  const loadState = $derived(adaptiveImageLoader.adaptiveLoaderState);
+  const imageAltText = $derived(loadState.previewUrl ? $getAltText(toTimelineAsset(asset)) : '');
+  const thumbnailUrl = $derived(loadState.thumbnailUrl);
+  const previewUrl = $derived(loadState.previewUrl);
+  const originalUrl = $derived(loadState.originalUrl);
+  const showSpinner = $derived(!asset.thumbhash && loadState.quality === 'basic');
+  const showBrokenAsset = $derived(loadState.hasError && loadState.quality !== 'loading-original');
+
+  // Effect: Upgrade to original when user zooms in
+  $effect(() => {
+    if ($photoZoomState.currentZoom > 1 && loadState.quality === 'preview') {
+      void adaptiveImageLoader.triggerOriginal();
+    }
+  });
+  let thumbnailElement = $state<HTMLImageElement>();
+  let previewElement = $state<HTMLImageElement>();
+  let originalElement = $state<HTMLImageElement>();
+
+  // Effect: Synchronize highest quality element as main imgElement
+  $effect(() => {
+    imgElement = originalElement ?? previewElement ?? thumbnailElement;
+  });
+</script>
+
+<div
+  class="relative h-full w-full"
+  style:left={renderDimensions.left}
+  style:top={renderDimensions.top}
+  style:width={renderDimensions.width}
+  style:height={renderDimensions.height}
+>
+  {#if asset.thumbhash}
+    <!-- Thumbhash / spinner layer  -->
+    <div style:transform-origin="0px 0px" style:transform={$photoZoomTransform} class="h-full w-full absolute">
+      <canvas use:thumbhash={{ base64ThumbHash: asset.thumbhash }} class="h-full w-full absolute -z-2"></canvas>
+    </div>
+  {:else if showSpinner}
+    <div id="spinner" class="absolute flex h-full items-center justify-center">
+      <LoadingSpinner />
+    </div>
+  {/if}
+
+  <div
+    use:imageLoader={{
+      src: thumbnailUrl,
+      onStart: () => adaptiveImageLoader.onThumbnailStart(),
+      onLoad: () => adaptiveImageLoader.onThumbnailLoad(),
+      onError: () => adaptiveImageLoader.onThumbnailError(),
+      onElementCreated: (el) => (thumbnailElement = el),
+      imgClass: ['absolute h-full', 'w-full'],
+      alt: '',
+      role: 'presentation',
+      dataAttributes: {
+        'data-testid': 'thumbnail',
+      },
+    }}
+  ></div>
+
+  {#if showBrokenAsset}
+    <div class="h-full w-full absolute">
+      <BrokenAsset class="text-xl h-full w-full" />
+    </div>
+  {:else}
+    <!-- Slideshow blurred background -->
+    {#if thumbnailUrl && slideshowState !== SlideshowState.None && slideshowLook === SlideshowLook.BlurredBackground}
+      <img
+        src={thumbnailUrl}
+        alt=""
+        role="presentation"
+        class="-z-1 absolute top-0 start-0 object-cover h-full w-full blur-lg"
+        draggable="false"
+      />
+    {/if}
+
+    <div
+      class="absolute top-0"
+      style:transform-origin="0px 0px"
+      style:transform={$photoZoomTransform}
+      style:width={renderDimensions.width}
+      style:height={renderDimensions.height}
+    >
+      <div
+        use:imageLoader={{
+          src: previewUrl,
+          onStart: () => adaptiveImageLoader.onPreviewStart(),
+          onLoad: () => adaptiveImageLoader.onPreviewLoad(),
+          onError: () => adaptiveImageLoader.onPreviewError(),
+          onElementCreated: (el) => (previewElement = el),
+          imgClass: ['h-full', 'w-full', { imageClass }],
+          alt: imageAltText,
+          draggable: false,
+          dataAttributes: {
+            'data-testid': 'preview',
+          },
+        }}
+      ></div>
+
+      {@render overlays?.()}
+    </div>
+
+    <div
+      class="absolute top-0"
+      style:transform-origin="0px 0px"
+      style:transform={$photoZoomTransform}
+      style:width={renderDimensions.width}
+      style:height={renderDimensions.height}
+    >
+      <div
+        use:imageLoader={{
+          src: originalUrl,
+          onStart: () => adaptiveImageLoader.onOriginalStart(),
+          onLoad: () => adaptiveImageLoader.onOriginalLoad(),
+          onError: () => adaptiveImageLoader.onOriginalError(),
+          onElementCreated: (el) => (originalElement = el),
+          imgClass: ['h-full', 'w-full', { imageClass }],
+          alt: imageAltText,
+          draggable: false,
+          dataAttributes: {
+            'data-testid': 'original',
+          },
+        }}
+      ></div>
+
+      {@render overlays?.()}
+    </div>
+
+    <!-- Use placeholder empty image to zoomImage so it can monitor mouse-wheel events and update zoom state -->
+    <div
+      class="absolute top-0"
+      use:zoomImageAction={{ disabled: zoomDisabled }}
+      style:width={renderDimensions.width}
+      style:height={renderDimensions.height}
+    >
+      <img alt="" class="absolute h-full w-full hidden" draggable="false" />
+    </div>
+  {/if}
+</div>
+
+<style>
+  @keyframes delayedVisibility {
+    to {
+      visibility: visible;
+    }
+  }
+  #spinner {
+    visibility: hidden;
+    animation: 0s linear 0.4s forwards delayedVisibility;
+  }
+</style>

web/src/lib/components/asset-viewer/asset-viewer.svelte

@@ -1,6 +1,7 @@
 <script lang="ts">
   import { goto } from '$app/navigation';
   import { focusTrap } from '$lib/actions/focus-trap';
+  import { loadImage } from '$lib/actions/image-loader.svelte';
   import type { Action, OnAction, PreAction } from '$lib/components/asset-viewer/actions/action';
   import NextAssetAction from '$lib/components/asset-viewer/actions/next-asset-action.svelte';
   import PreviousAssetAction from '$lib/components/asset-viewer/actions/previous-asset-action.svelte';
@@ -11,25 +12,25 @@
   import { assetViewerManager } from '$lib/managers/asset-viewer-manager.svelte';
   import { authManager } from '$lib/managers/auth-manager.svelte';
   import { editManager, EditToolType } from '$lib/managers/edit/edit-manager.svelte';
-  import { preloadManager } from '$lib/managers/PreloadManager.svelte';
+  import { eventManager } from '$lib/managers/event-manager.svelte';
   import { Route } from '$lib/route';
   import { assetViewingStore } from '$lib/stores/asset-viewing.store';
   import { ocrManager } from '$lib/stores/ocr.svelte';
   import { alwaysLoadOriginalVideo } from '$lib/stores/preferences.store';
   import { SlideshowNavigation, SlideshowState, slideshowStore } from '$lib/stores/slideshow.store';
   import { user } from '$lib/stores/user.store';
-  import { getAssetJobMessage, getAssetUrl, getSharedLink, handlePromiseError } from '$lib/utils';
+  import { getAssetJobMessage, getSharedLink, handlePromiseError } from '$lib/utils';
   import type { OnUndoDelete } from '$lib/utils/actions';
+  import { AdaptiveImageLoader } from '$lib/utils/adaptive-image-loader.svelte';
   import { navigateToAsset } from '$lib/utils/asset-utils';
   import { handleError } from '$lib/utils/handle-error';
   import { InvocationTracker } from '$lib/utils/invocationTracker';
   import { SlideshowHistory } from '$lib/utils/slideshow-history';
-  import { preloadImageUrl } from '$lib/utils/sw-messaging';
+
   import { toTimelineAsset } from '$lib/utils/timeline-util';
   import {
     AssetJobName,
     AssetTypeEnum,
-    getAllAlbums,
     getAssetInfo,
     getStack,
     runAssetJobs,
@@ -98,7 +99,6 @@
     stopProgress: stopSlideshowProgress,
     slideshowNavigation,
     slideshowState,
-    slideshowTransition,
   } = slideshowStore;
   const stackThumbnailSize = 60;
   const stackSelectedThumbnailSize = 65;
@@ -106,12 +106,11 @@
   const asset = $derived(cursor.current);
   const nextAsset = $derived(cursor.nextAsset);
   const previousAsset = $derived(cursor.previousAsset);
-  let appearsInAlbums: AlbumResponseDto[] = $state([]);
+
   let sharedLink = getSharedLink();
   let previewStackedAsset: AssetResponseDto | undefined = $state();
   let isShowEditor = $state(false);
   let fullscreenElement = $state<Element>();
-  let unsubscribes: (() => void)[] = [];
   let stack: StackResponseDto | null = $state(null);
 
   let zoomToggle = $state(() => void 0);
@@ -126,93 +125,138 @@
       return;
     }
 
-    if (asset.stack) {
-      stack = await getStack({ id: asset.stack.id });
+    if (!asset.stack) {
+      return;
     }
 
+    stack = await getStack({ id: asset.stack.id });
+
     if (!stack?.assets.some(({ id }) => id === asset.id)) {
       stack = null;
     }
 
-    untrack(() => {
-      if (stack && stack?.assets.length > 1) {
-        preloadImageUrl(getAssetUrl({ asset: stack.assets[1] }));
-      }
-    });
+    if (stack?.assets[1]) {
+      untrack(() => {
+        const loader = new AdaptiveImageLoader(stack!.assets[1], undefined, undefined, loadImage);
+        loader.start();
+      });
+    }
   };
 
   const handleFavorite = async () => {
-    if (album && album.isActivityEnabled) {
-      try {
-        await activityManager.toggleLike();
-      } catch (error) {
-        handleError(error, $t('errors.unable_to_change_favorite'));
-      }
-    }
-  };
-
-  onMount(async () => {
-    unsubscribes.push(
-      slideshowState.subscribe((value) => {
-        if (value === SlideshowState.PlaySlideshow) {
-          slideshowHistory.reset();
-          slideshowHistory.queue(toTimelineAsset(asset));
-          handlePromiseError(handlePlaySlideshow());
-        } else if (value === SlideshowState.StopSlideshow) {
-          handlePromiseError(handleStopSlideshow());
-        }
-      }),
-      slideshowNavigation.subscribe((value) => {
-        if (value === SlideshowNavigation.Shuffle) {
-          slideshowHistory.reset();
-          slideshowHistory.queue(toTimelineAsset(asset));
-        }
-      }),
-    );
-
-    if (!sharedLink) {
-      await handleGetAllAlbums();
-    }
-  });
-
-  onDestroy(() => {
-    for (const unsubscribe of unsubscribes) {
-      unsubscribe();
-    }
-
-    activityManager.reset();
-  });
-
-  const handleGetAllAlbums = async () => {
-    if (authManager.isSharedLink) {
+    if (!album || !album.isActivityEnabled) {
       return;
     }
 
     try {
-      appearsInAlbums = await getAllAlbums({ assetId: asset.id });
+      await activityManager.toggleLike();
     } catch (error) {
-      console.error('Error getting album that asset belong to', error);
+      handleError(error, $t('errors.unable_to_change_favorite'));
     }
   };
 
+  onMount(() => {
+    const slideshowStateUnsubscribe = slideshowState.subscribe((value) => {
+      if (value === SlideshowState.PlaySlideshow) {
+        slideshowHistory.reset();
+        slideshowHistory.queue(toTimelineAsset(asset));
+        handlePromiseError(handlePlaySlideshow());
+      } else if (value === SlideshowState.StopSlideshow) {
+        handlePromiseError(handleStopSlideshow());
+      }
+    });
+
+    const slideshowNavigationUnsubscribe = slideshowNavigation.subscribe((value) => {
+      if (value === SlideshowNavigation.Shuffle) {
+        slideshowHistory.reset();
+        slideshowHistory.queue(toTimelineAsset(asset));
+      }
+    });
+
+    return () => {
+      slideshowStateUnsubscribe();
+      slideshowNavigationUnsubscribe();
+    };
+  });
+
+  onDestroy(() => {
+    activityManager.reset();
+
+    destroyNextPreloader();
+    destroyPreviousPreloader();
+  });
+
   const closeViewer = () => {
     onClose?.(asset);
   };
 
   const closeEditor = async () => {
     if (editManager.hasAppliedEdits) {
-      console.log(asset);
       const refreshedAsset = await getAssetInfo({ id: asset.id });
-      console.log(refreshedAsset);
       onAssetChange?.(refreshedAsset);
       assetViewingStore.setAsset(refreshedAsset);
     }
     isShowEditor = false;
   };
 
-  const tracker = new InvocationTracker();
+  let nextPreloader: AdaptiveImageLoader | undefined;
+  let previousPreloader: AdaptiveImageLoader | undefined;
 
-  const navigateAsset = (order?: 'previous' | 'next', e?: Event) => {
+  const startPreloader = (asset: AssetResponseDto | undefined) => {
+    if (!asset) {
+      return;
+    }
+    const loader = new AdaptiveImageLoader(asset, undefined, undefined, loadImage);
+    loader.start();
+    return loader;
+  };
+
+  const destroyPreviousPreloader = () => {
+    previousPreloader?.destroy();
+    previousPreloader = undefined;
+  };
+
+  const destroyNextPreloader = () => {
+    nextPreloader?.destroy();
+    nextPreloader = undefined;
+  };
+
+  const cancelPreloadsBeforeNavigation = (direction: 'previous' | 'next') => {
+    if (direction === 'next') {
+      destroyPreviousPreloader();
+      return;
+    }
+    destroyNextPreloader();
+  };
+
+  const updatePreloadsAfterNavigation = (oldCursor: AssetCursor, newCursor: AssetCursor) => {
+    const movedForward = newCursor.current.id === oldCursor.nextAsset?.id;
+    const movedBackward = newCursor.current.id === oldCursor.previousAsset?.id;
+
+    const shouldDestroyPrevious = movedForward || !movedBackward;
+    const shouldDestroyNext = movedBackward || !movedForward;
+
+    if (shouldDestroyPrevious) {
+      destroyPreviousPreloader();
+    }
+
+    if (shouldDestroyNext) {
+      destroyNextPreloader();
+    }
+
+    if (movedForward) {
+      nextPreloader = startPreloader(newCursor.nextAsset);
+    } else if (movedBackward) {
+      previousPreloader = startPreloader(newCursor.previousAsset);
+    } else {
+      // Non-adjacent navigation (e.g., slideshow random)
+      previousPreloader = startPreloader(newCursor.previousAsset);
+      nextPreloader = startPreloader(newCursor.nextAsset);
+    }
+  };
+
+  const tracker = new InvocationTracker();
+  const navigateAsset = (order?: 'previous' | 'next') => {
     if (!order) {
       if ($slideshowState === SlideshowState.PlaySlideshow) {
         order = $slideshowNavigation === SlideshowNavigation.AscendingOrder ? 'previous' : 'next';
@@ -221,12 +265,12 @@
       }
     }
 
-    e?.stopPropagation();
-    preloadManager.cancel(asset);
     if (tracker.isActive()) {
       return;
     }
 
+    cancelPreloadsBeforeNavigation(order);
+
     void tracker.invoke(async () => {
       let hasNext = false;
 
@@ -244,14 +288,16 @@
           order === 'previous' ? await navigateToAsset(cursor.previousAsset) : await navigateToAsset(cursor.nextAsset);
       }
 
-      if ($slideshowState === SlideshowState.PlaySlideshow) {
-        if (hasNext) {
-          $restartSlideshowProgress = true;
-        } else {
-          await handleStopSlideshow();
-        }
+      if ($slideshowState !== SlideshowState.PlaySlideshow) {
+        return;
       }
-    });
+
+      if (hasNext) {
+        $restartSlideshowProgress = true;
+      } else {
+        await handleStopSlideshow();
+      }
+    }, $t('error_while_navigating'));
   };
 
   const showEditor = () => {
@@ -318,7 +364,7 @@
   const handleAction = async (action: Action) => {
     switch (action.type) {
       case AssetAction.ADD_TO_ALBUM: {
-        await handleGetAllAlbums();
+        eventManager.emit('AlbumAddAssets');
         break;
       }
       case AssetAction.REMOVE_ASSET_FROM_STACK: {
@@ -373,21 +419,42 @@
 
   const refresh = async () => {
     await refreshStack();
-    await handleGetAllAlbums();
     ocrManager.clear();
-    if (!sharedLink) {
-      if (previewStackedAsset) {
-        await ocrManager.getAssetOcr(previewStackedAsset.id);
-      }
-      await ocrManager.getAssetOcr(asset.id);
+    if (sharedLink) {
+      return;
     }
+
+    if (previewStackedAsset) {
+      await ocrManager.getAssetOcr(previewStackedAsset.id);
+    }
+    await ocrManager.getAssetOcr(asset.id);
   };
   $effect(() => {
     // eslint-disable-next-line @typescript-eslint/no-unused-expressions
     asset;
     untrack(() => handlePromiseError(refresh()));
-    preloadManager.preload(cursor.nextAsset);
-    preloadManager.preload(cursor.previousAsset);
+  });
+
+  let lastCursor = $state<AssetCursor>();
+
+  $effect(() => {
+    if (cursor.current.id === lastCursor?.current.id) {
+      return;
+    }
+    if (lastCursor) {
+      // After navigation completes, reconcile preloads with full state information
+      updatePreloadsAfterNavigation(lastCursor, cursor);
+    }
+    if (!lastCursor && cursor) {
+      // "first time" load, start preloads
+      if (cursor.nextAsset) {
+        nextPreloader = startPreloader(cursor.nextAsset);
+      }
+      if (cursor.previousAsset) {
+        previousPreloader = startPreloader(cursor.previousAsset);
+      }
+    }
+    lastCursor = cursor;
   });
 
   const onAssetReplace = async ({ oldAssetId, newAssetId }: { oldAssetId: string; newAssetId: string }) => {
@@ -498,15 +565,7 @@
   <!-- Asset Viewer -->
   <div class="z-[-1] relative col-start-1 col-span-4 row-start-1 row-span-full">
     {#if viewerKind === 'StackPhotoViewer'}
-      <PhotoViewer
-        bind:zoomToggle
-        bind:copyImage
-        cursor={{ ...cursor, current: previewStackedAsset! }}
-        onPreviousAsset={() => navigateAsset('previous')}
-        onNextAsset={() => navigateAsset('next')}
-        haveFadeTransition={false}
-        {sharedLink}
-      />
+      <PhotoViewer bind:zoomToggle bind:copyImage cursor={{ ...cursor, current: previewStackedAsset! }} {sharedLink} />
     {:else if viewerKind === 'StackVideoViewer'}
       <VideoViewer
         assetId={previewStackedAsset!.id}
@@ -536,15 +595,7 @@
     {:else if viewerKind === 'CropArea'}
       <CropArea {asset} />
     {:else if viewerKind === 'PhotoViewer'}
-      <PhotoViewer
-        bind:zoomToggle
-        bind:copyImage
-        {cursor}
-        onPreviousAsset={() => navigateAsset('previous')}
-        onNextAsset={() => navigateAsset('next')}
-        {sharedLink}
-        haveFadeTransition={$slideshowState !== SlideshowState.None && $slideshowTransition}
-      />
+      <PhotoViewer bind:zoomToggle bind:copyImage {cursor} {sharedLink} />
     {:else if viewerKind === 'VideoViewer'}
       <VideoViewer
         assetId={asset.id}
@@ -592,7 +643,7 @@
       class="row-start-1 row-span-4 w-90 overflow-y-auto transition-all dark:border-l dark:border-s-immich-dark-gray bg-light"
       translate="yes"
     >
-      <DetailPanel {asset} currentAlbum={album} albums={appearsInAlbums} />
+      <DetailPanel {asset} currentAlbum={album} />
     </div>
   {/if}
 

web/src/lib/components/asset-viewer/detail-panel.svelte

@@ -7,6 +7,7 @@
   import { timeToLoadTheMap } from '$lib/constants';
   import { assetViewerManager } from '$lib/managers/asset-viewer-manager.svelte';
   import { authManager } from '$lib/managers/auth-manager.svelte';
+  import { eventManager } from '$lib/managers/event-manager.svelte';
   import { featureFlagsManager } from '$lib/managers/feature-flags-manager.svelte';
   import AssetChangeDateModal from '$lib/modals/AssetChangeDateModal.svelte';
   import { Route } from '$lib/route';
@@ -17,9 +18,16 @@
   import { getAssetThumbnailUrl, getPeopleThumbnailUrl } from '$lib/utils';
   import { delay, getDimensions } from '$lib/utils/asset-utils';
   import { getByteUnitString } from '$lib/utils/byte-units';
+  import { handleError } from '$lib/utils/handle-error';
   import { fromISODateTime, fromISODateTimeUTC, toTimelineAsset } from '$lib/utils/timeline-util';
   import { getParentPath } from '$lib/utils/tree-utils';
-  import { AssetMediaSize, getAssetInfo, type AlbumResponseDto, type AssetResponseDto } from '@immich/sdk';
+  import {
+    AssetMediaSize,
+    getAllAlbums,
+    getAssetInfo,
+    type AlbumResponseDto,
+    type AssetResponseDto,
+  } from '@immich/sdk';
   import { Icon, IconButton, LoadingSpinner, modalManager } from '@immich/ui';
   import {
     mdiCalendar,
@@ -34,6 +42,7 @@
     mdiPlus,
   } from '@mdi/js';
   import { DateTime } from 'luxon';
+  import { onDestroy, untrack } from 'svelte';
   import { t } from 'svelte-i18n';
   import { slide } from 'svelte/transition';
   import ImageThumbnail from '../assets/thumbnail/image-thumbnail.svelte';
@@ -43,11 +52,10 @@
 
   interface Props {
     asset: AssetResponseDto;
-    albums?: AlbumResponseDto[];
     currentAlbum?: AlbumResponseDto | null;
   }
 
-  let { asset, albums = [], currentAlbum = null }: Props = $props();
+  let { asset, currentAlbum = null }: Props = $props();
 
   let showAssetPath = $state(false);
   let showEditFaces = $state(false);
@@ -74,14 +82,43 @@
   let previousId: string | undefined = $state();
   let previousRoute = $derived(currentAlbum?.id ? Route.viewAlbum(currentAlbum) : Route.photos());
 
+  let albums = $state<AlbumResponseDto[]>([]);
+
+  const refreshAlbums = async () => {
+    if (authManager.isSharedLink) {
+      return;
+    }
+
+    try {
+      albums = await getAllAlbums({ assetId: asset.id });
+    } catch (error) {
+      handleError(error, 'Error getting asset album membership');
+    }
+  };
+
+  eventManager.on('AlbumAddAssets', () => void refreshAlbums());
+  onDestroy(() => {
+    eventManager.off('AlbumAddAssets', () => void refreshAlbums());
+  });
+
+  $effect(() => {
+    // eslint-disable-next-line @typescript-eslint/no-unused-expressions
+    asset;
+    untrack(() => void refreshAlbums());
+  });
+
   $effect(() => {
     if (!previousId) {
       previousId = asset.id;
+      return;
     }
-    if (asset.id !== previousId) {
-      showEditFaces = false;
-      previousId = asset.id;
+
+    if (asset.id === previousId) {
+      return;
     }
+
+    showEditFaces = false;
+    previousId = asset.id;
   });
 
   const getMegapixel = (width: number, height: number): number | undefined => {

web/src/lib/components/asset-viewer/photo-viewer.svelte

@@ -1,51 +1,40 @@
 <script lang="ts">
   import { shortcuts } from '$lib/actions/shortcut';
-  import { zoomImageAction } from '$lib/actions/zoom-image';
+  import AdaptiveImage from '$lib/components/asset-viewer/adaptive-image.svelte';
   import FaceEditor from '$lib/components/asset-viewer/face-editor/face-editor.svelte';
   import OcrBoundingBox from '$lib/components/asset-viewer/ocr-bounding-box.svelte';
-  import BrokenAsset from '$lib/components/assets/broken-asset.svelte';
-  import { assetViewerFadeDuration } from '$lib/constants';
   import { castManager } from '$lib/managers/cast-manager.svelte';
-  import { preloadManager } from '$lib/managers/PreloadManager.svelte';
   import { photoViewerImgElement } from '$lib/stores/assets-store.svelte';
   import { isFaceEditMode } from '$lib/stores/face-edit.svelte';
   import { ocrManager } from '$lib/stores/ocr.svelte';
   import { boundingBoxesArray } from '$lib/stores/people.store';
-  import { SlideshowLook, SlideshowState, slideshowLookCssMapping, slideshowStore } from '$lib/stores/slideshow.store';
+  import { SlideshowState, slideshowLookCssMapping, slideshowStore } from '$lib/stores/slideshow.store';
   import { photoZoomState } from '$lib/stores/zoom-image.store';
-  import { getAssetUrl, targetImageSize as getTargetImageSize, handlePromiseError } from '$lib/utils';
+  import { handlePromiseError } from '$lib/utils';
   import { canCopyImageToClipboard, copyImageToClipboard } from '$lib/utils/asset-utils';
   import { handleError } from '$lib/utils/handle-error';
   import { getOcrBoundingBoxes } from '$lib/utils/ocr-utils';
   import { getBoundingBox } from '$lib/utils/people-utils';
-  import { getAltText } from '$lib/utils/thumbnail-util';
-  import { toTimelineAsset } from '$lib/utils/timeline-util';
-  import { AssetMediaSize, type SharedLinkResponseDto } from '@immich/sdk';
-  import { LoadingSpinner, toastManager } from '@immich/ui';
-  import { onDestroy, untrack } from 'svelte';
-  import { useSwipe, type SwipeCustomEvent } from 'svelte-gestures';
+  import { type SharedLinkResponseDto } from '@immich/sdk';
+  import { toastManager } from '@immich/ui';
+  import { onDestroy } from 'svelte';
   import { t } from 'svelte-i18n';
-  import { fade } from 'svelte/transition';
   import type { AssetCursor } from './asset-viewer.svelte';
 
   interface Props {
     cursor: AssetCursor;
-    element?: HTMLDivElement | undefined;
-    haveFadeTransition?: boolean;
-    sharedLink?: SharedLinkResponseDto | undefined;
-    onPreviousAsset?: (() => void) | null;
-    onNextAsset?: (() => void) | null;
+    element?: HTMLDivElement;
+    sharedLink?: SharedLinkResponseDto;
+    onReady?: () => void;
     copyImage?: () => Promise<void>;
-    zoomToggle?: (() => void) | null;
+    zoomToggle?: () => void;
   }
 
   let {
     cursor,
     element = $bindable(),
-    haveFadeTransition = true,
-    sharedLink = undefined,
-    onPreviousAsset = null,
-    onNextAsset = null,
+    sharedLink,
+    onReady,
     copyImage = $bindable(),
     zoomToggle = $bindable(),
   }: Props = $props();
@@ -53,20 +42,6 @@
   const { slideshowState, slideshowLook } = slideshowStore;
   const asset = $derived(cursor.current);
 
-  let imageLoaded: boolean = $state(false);
-  let originalImageLoaded: boolean = $state(false);
-  let imageError: boolean = $state(false);
-
-  let loader = $state<HTMLImageElement>();
-
-  photoZoomState.set({
-    currentRotation: 0,
-    currentZoom: 1,
-    enable: true,
-    currentPositionX: 0,
-    currentPositionY: 0,
-  });
-
   onDestroy(() => {
     $boundingBoxesArray = [];
   });
@@ -115,29 +90,11 @@
     handlePromiseError(copyImage());
   };
 
-  const onSwipe = (event: SwipeCustomEvent) => {
-    if ($photoZoomState.currentZoom > 1) {
-      return;
-    }
-
-    if (ocrManager.showOverlay) {
-      return;
-    }
-
-    if (onNextAsset && event.detail.direction === 'left') {
-      onNextAsset();
-    }
-
-    if (onPreviousAsset && event.detail.direction === 'right') {
-      onPreviousAsset();
-    }
-  };
-
-  const targetImageSize = $derived(getTargetImageSize(asset, originalImageLoaded || $photoZoomState.currentZoom > 1));
+  let currentPreviewUrl = $state<string>();
 
   $effect(() => {
-    if (imageLoaderUrl) {
-      void cast(imageLoaderUrl);
+    if (currentPreviewUrl) {
+      void cast(currentPreviewUrl);
     }
   });
 
@@ -155,35 +112,11 @@
     }
   };
 
-  const onload = () => {
-    imageLoaded = true;
-    originalImageLoaded = targetImageSize === AssetMediaSize.Fullsize || targetImageSize === 'original';
-  };
-
-  const onerror = () => {
-    imageError = imageLoaded = true;
-  };
-
-  onDestroy(() => preloadManager.cancelPreloadUrl(imageLoaderUrl));
-
-  let imageLoaderUrl = $derived(
-    getAssetUrl({ asset, sharedLink, forceOriginal: originalImageLoaded || $photoZoomState.currentZoom > 1 }),
-  );
-
   let containerWidth = $state(0);
   let containerHeight = $state(0);
-
-  let lastUrl: string | undefined;
-
-  $effect(() => {
-    if (lastUrl && lastUrl !== imageLoaderUrl) {
-      untrack(() => {
-        imageLoaded = false;
-        originalImageLoaded = false;
-        imageError = false;
-      });
-    }
-    lastUrl = imageLoaderUrl;
+  const container = $derived({
+    width: containerWidth,
+    height: containerHeight,
   });
 </script>
 
@@ -193,49 +126,28 @@
     { shortcut: { key: 's' }, onShortcut: onPlaySlideshow, preventDefault: true },
     { shortcut: { key: 'c', ctrl: true }, onShortcut: onCopyShortcut, preventDefault: false },
     { shortcut: { key: 'c', meta: true }, onShortcut: onCopyShortcut, preventDefault: false },
-    { shortcut: { key: 'z' }, onShortcut: zoomToggle, preventDefault: false },
   ]}
 />
-{#if imageError}
-  <div id="broken-asset" class="h-full w-full">
-    <BrokenAsset class="text-xl h-full w-full" />
-  </div>
-{/if}
-<img bind:this={loader} style="display:none" src={imageLoaderUrl} alt="" aria-hidden="true" {onload} {onerror} />
+
 <div
   bind:this={element}
   class="relative h-full w-full select-none"
   bind:clientWidth={containerWidth}
   bind:clientHeight={containerHeight}
 >
-  {#if !imageLoaded}
-    <div id="spinner" class="flex h-full items-center justify-center">
-      <LoadingSpinner />
-    </div>
-  {:else if !imageError}
-    <div
-      use:zoomImageAction={{ disabled: isOcrActive }}
-      {...useSwipe(onSwipe)}
-      class="h-full w-full"
-      transition:fade={{ duration: haveFadeTransition ? assetViewerFadeDuration : 0 }}
-    >
-      {#if $slideshowState !== SlideshowState.None && $slideshowLook === SlideshowLook.BlurredBackground}
-        <img
-          src={imageLoaderUrl}
-          alt=""
-          class="-z-1 absolute top-0 start-0 object-cover h-full w-full blur-lg"
-          draggable="false"
-        />
-      {/if}
-      <img
-        bind:this={$photoViewerImgElement}
-        src={imageLoaderUrl}
-        alt={$getAltText(toTimelineAsset(asset))}
-        class="h-full w-full {$slideshowState === SlideshowState.None
-          ? 'object-contain'
-          : slideshowLookCssMapping[$slideshowLook]}"
-        draggable="false"
-      />
+  <AdaptiveImage
+    {asset}
+    {sharedLink}
+    {container}
+    zoomDisabled={isOcrActive}
+    imageClass={$slideshowState === SlideshowState.None ? 'object-contain' : slideshowLookCssMapping[$slideshowLook]}
+    slideshowState={$slideshowState}
+    slideshowLook={$slideshowLook}
+    onImageReady={() => onReady?.()}
+    onError={() => onReady?.()}
+    bind:imgElement={$photoViewerImgElement}
+  >
+    {#snippet overlays()}
       <!-- eslint-disable-next-line svelte/require-each-key -->
       {#each getBoundingBox($boundingBoxesArray, $photoZoomState, $photoViewerImgElement) as boundingbox}
         <div
@@ -247,23 +159,10 @@
       {#each ocrBoxes as ocrBox (ocrBox.id)}
         <OcrBoundingBox {ocrBox} />
       {/each}
-    </div>
+    {/snippet}
+  </AdaptiveImage>
 
-    {#if isFaceEditMode.value}
-      <FaceEditor htmlElement={$photoViewerImgElement} {containerWidth} {containerHeight} assetId={asset.id} />
-    {/if}
+  {#if isFaceEditMode.value}
+    <FaceEditor htmlElement={$photoViewerImgElement} {containerWidth} {containerHeight} assetId={asset.id} />
   {/if}
 </div>
-
-<style>
-  @keyframes delayedVisibility {
-    to {
-      visibility: visible;
-    }
-  }
-  #broken-asset,
-  #spinner {
-    visibility: hidden;
-    animation: 0s linear 0.4s forwards delayedVisibility;
-  }
-</style>

web/src/lib/components/assets/thumbnail/image-thumbnail.svelte

@@ -1,9 +1,8 @@
 <script lang="ts">
+  import { imageLoader } from '$lib/actions/image-loader.svelte';
   import BrokenAsset from '$lib/components/assets/broken-asset.svelte';
-  import { preloadManager } from '$lib/managers/PreloadManager.svelte';
   import { Icon } from '@immich/ui';
   import { mdiEyeOffOutline } from '@mdi/js';
-  import type { ActionReturn } from 'svelte/action';
   import type { ClassValue } from 'svelte/elements';
 
   interface Props {
@@ -54,16 +53,6 @@
     onComplete?.(true);
   };
 
-  function mount(elem: HTMLImageElement): ActionReturn {
-    if (elem.complete) {
-      loaded = true;
-      onComplete?.(false);
-    }
-    return {
-      destroy: () => preloadManager.cancelPreloadUrl(url),
-    };
-  }
-
   let optionalClasses = $derived(
     [
       curve && 'rounded-xl',
@@ -76,26 +65,28 @@
       .filter(Boolean)
       .join(' '),
   );
+
+  let style = $derived(
+    `width: ${widthStyle}; height: ${heightStyle ?? ''}; filter: ${hidden ? 'grayscale(50%)' : 'none'}; opacity: ${hidden ? '0.5' : '1'};`,
+  );
 </script>
 
 {#if errored}
   <BrokenAsset class={optionalClasses} width={widthStyle} height={heightStyle} />
 {:else}
-  <img
-    use:mount
-    onload={setLoaded}
-    onerror={setErrored}
-    style:width={widthStyle}
-    style:height={heightStyle}
-    style:filter={hidden ? 'grayscale(50%)' : 'none'}
-    style:opacity={hidden ? '0.5' : '1'}
-    src={url}
-    alt={loaded || errored ? altText : ''}
-    {title}
-    class={['object-cover', optionalClasses, imageClass]}
-    draggable="false"
-    loading={preload ? 'eager' : 'lazy'}
-  />
+  <div
+    use:imageLoader={{
+      src: url,
+      onLoad: setLoaded,
+      onError: setErrored,
+      imgClass: ['object-cover', optionalClasses, imageClass],
+      style,
+      alt: loaded || errored ? altText : '',
+      draggable: false,
+      title,
+      loading: preload ? 'eager' : 'lazy',
+    }}
+  ></div>
 {/if}
 
 {#if hidden}

web/src/lib/components/timeline/TimelineAssetViewer.svelte

@@ -11,10 +11,12 @@
   import { handlePromiseError } from '$lib/utils';
   import { updateStackedAssetInTimeline, updateUnstackedAssetInTimeline } from '$lib/utils/actions';
   import { navigateToAsset } from '$lib/utils/asset-utils';
+  import { handleErrorAsync } from '$lib/utils/handle-error';
   import { navigate } from '$lib/utils/navigation';
   import { toTimelineAsset } from '$lib/utils/timeline-util';
   import { type AlbumResponseDto, type AssetResponseDto, type PersonResponseDto, getAssetInfo } from '@immich/sdk';
   import { onDestroy, onMount, untrack } from 'svelte';
+  import { t } from 'svelte-i18n';
 
   let { asset: viewingAsset, gridScrollTarget } = assetViewingStore;
 
@@ -38,28 +40,27 @@
     person,
   }: Props = $props();
 
-  const getNextAsset = async (currentAsset: AssetResponseDto, preload: boolean = true) => {
-    const earlierTimelineAsset = await timelineManager.getEarlierAsset(currentAsset);
-    if (earlierTimelineAsset) {
-      const asset = await assetCacheManager.getAsset({ ...authManager.params, id: earlierTimelineAsset.id });
-      if (preload) {
-        // also pre-cache an extra one, to pre-cache these assetInfos for the next nav after this one is complete
-        void getNextAsset(asset, false);
-      }
-      return asset;
-    }
+  const getAsset = (id: string) => {
+    return handleErrorAsync(
+      () => assetCacheManager.getAsset({ ...authManager.params, id }),
+      $t('error_retrieving_asset_information'),
+    );
   };
 
-  const getPreviousAsset = async (currentAsset: AssetResponseDto, preload: boolean = true) => {
-    const laterTimelineAsset = await timelineManager.getLaterAsset(currentAsset);
-    if (laterTimelineAsset) {
-      const asset = await assetCacheManager.getAsset({ ...authManager.params, id: laterTimelineAsset.id });
-      if (preload) {
-        // also pre-cache an extra one, to pre-cache these assetInfos for the next nav after this one is complete
-        void getPreviousAsset(asset, false);
-      }
-      return asset;
+  const getNextAsset = async (currentAsset: AssetResponseDto) => {
+    const earlierTimelineAsset = await timelineManager.getEarlierAsset(currentAsset);
+    if (!earlierTimelineAsset) {
+      return;
     }
+    return getAsset(earlierTimelineAsset.id);
+  };
+
+  const getPreviousAsset = async (currentAsset: AssetResponseDto) => {
+    const laterTimelineAsset = await timelineManager.getLaterAsset(currentAsset);
+    if (!laterTimelineAsset) {
+      return;
+    }
+    return getAsset(laterTimelineAsset.id);
   };
 
   let assetCursor = $state<AssetCursor>({
@@ -87,10 +88,12 @@
 
   const handleRandom = async () => {
     const randomAsset = await timelineManager.getRandomAsset();
-    if (randomAsset) {
-      await navigate({ targetRoute: 'current', assetId: randomAsset.id });
-      return { id: randomAsset.id };
+    if (!randomAsset) {
+      return;
     }
+
+    await navigate({ targetRoute: 'current', assetId: randomAsset.id });
+    return { id: randomAsset.id };
   };
 
   const handleClose = async (asset: { id: string }) => {
@@ -180,12 +183,14 @@
   };
   const handleUndoDelete = async (assets: TimelineAsset[]) => {
     timelineManager.upsertAssets(assets);
-    if (assets.length > 0) {
-      const restoredAsset = assets[0];
-      const asset = await getAssetInfo({ ...authManager.params, id: restoredAsset.id });
-      assetViewingStore.setAsset(asset);
-      await navigate({ targetRoute: 'current', assetId: restoredAsset.id });
+    if (assets.length === 0) {
+      return;
     }
+
+    const restoredAsset = assets[0];
+    const asset = await getAssetInfo({ ...authManager.params, id: restoredAsset.id });
+    assetViewingStore.setAsset(asset);
+    await navigate({ targetRoute: 'current', assetId: restoredAsset.id });
   };
 
   const handleUpdateOrUpload = (asset: AssetResponseDto) => {

web/src/lib/managers/ImageManager.svelte.ts

@@ -0,0 +1,41 @@
+import { getAssetUrlForKind, ImageKinds, type ImageKind } from '$lib/utils';
+import { cancelImageUrl } from '$lib/utils/sw-messaging';
+import { type AssetResponseDto } from '@immich/sdk';
+
+class ImageManager {
+  preload(asset: AssetResponseDto | undefined, kind: ImageKind = 'preview') {
+    if (!asset) {
+      return;
+    }
+
+    const url = getAssetUrlForKind(asset, kind);
+    if (!url) {
+      return;
+    }
+
+    const img = new Image();
+    img.src = url;
+  }
+
+  cancel(asset: AssetResponseDto | undefined, kind: ImageKind | 'all' = 'preview') {
+    if (!asset) {
+      return;
+    }
+
+    const kinds = kind === 'all' ? (Object.keys(ImageKinds) as ImageKind[]) : [kind];
+    for (const k of kinds) {
+      const url = getAssetUrlForKind(asset, k);
+      if (url) {
+        cancelImageUrl(url);
+      }
+    }
+  }
+
+  cancelPreloadUrl(url: string | undefined) {
+    if (url) {
+      cancelImageUrl(url);
+    }
+  }
+}
+
+export const imageManager = new ImageManager();

web/src/lib/managers/PreloadManager.svelte.ts

@@ -1,38 +0,0 @@
-import { getAssetUrl } from '$lib/utils';
-import { cancelImageUrl, preloadImageUrl } from '$lib/utils/sw-messaging';
-import { AssetTypeEnum, type AssetResponseDto } from '@immich/sdk';
-
-class PreloadManager {
-  preload(asset: AssetResponseDto | undefined) {
-    if (globalThis.isSecureContext) {
-      preloadImageUrl(getAssetUrl({ asset }));
-      return;
-    }
-    if (!asset || asset.type !== AssetTypeEnum.Image) {
-      return;
-    }
-    const img = new Image();
-    const url = getAssetUrl({ asset });
-    if (!url) {
-      return;
-    }
-    img.src = url;
-  }
-
-  cancel(asset: AssetResponseDto | undefined) {
-    if (!globalThis.isSecureContext || !asset) {
-      return;
-    }
-    const url = getAssetUrl({ asset });
-    cancelImageUrl(url);
-  }
-
-  cancelPreloadUrl(url: string | undefined) {
-    if (!globalThis.isSecureContext) {
-      return;
-    }
-    cancelImageUrl(url);
-  }
-}
-
-export const preloadManager = new PreloadManager();

web/src/lib/stores/assets-store.svelte.ts

@@ -1,4 +1,4 @@
 import { writable } from 'svelte/store';
 
-export const photoViewerImgElement = writable<HTMLImageElement | null>(null);
+export const photoViewerImgElement = writable<HTMLImageElement>();
 export const isSelectingAllAssets = writable(false);

web/src/lib/utils.ts

@@ -31,6 +31,15 @@ import { mdiCogRefreshOutline, mdiDatabaseRefreshOutline, mdiHeadSyncOutline, md
 import { init, register, t } from 'svelte-i18n';
 import { derived, get } from 'svelte/store';
 
+export const ImageKinds = {
+  thumbnail: true,
+  preview: true,
+  fullsize: true,
+  original: true,
+} as const;
+
+export type ImageKind = keyof typeof ImageKinds;
+
 interface DownloadRequestOptions<T = unknown> {
   method?: 'GET' | 'POST' | 'PUT' | 'DELETE';
   url: string;
@@ -195,18 +204,32 @@ const createUrl = (path: string, parameters?: Record<string, unknown>) => {
 
 type AssetUrlOptions = { id: string; cacheKey?: string | null; edited?: boolean };
 
+export const getAssetUrlForKind = (asset: AssetResponseDto, kind: ImageKind) => {
+  switch (kind) {
+    case 'preview': {
+      return getAssetThumbnailUrl({ id: asset.id, size: AssetMediaSize.Preview, cacheKey: asset.thumbhash });
+    }
+    case 'thumbnail': {
+      return getAssetThumbnailUrl({ id: asset.id, size: AssetMediaSize.Thumbnail, cacheKey: asset.thumbhash });
+    }
+    case 'fullsize': {
+      return getAssetThumbnailUrl({ id: asset.id, size: AssetMediaSize.Fullsize, cacheKey: asset.thumbhash });
+    }
+    case 'original': {
+      return getAssetOriginalUrl({ id: asset.id, cacheKey: asset.thumbhash });
+    }
+  }
+};
+
 export const getAssetUrl = ({
   asset,
   sharedLink,
   forceOriginal = false,
 }: {
-  asset: AssetResponseDto | undefined;
+  asset: AssetResponseDto;
   sharedLink?: SharedLinkResponseDto;
   forceOriginal?: boolean;
 }) => {
-  if (!asset) {
-    return;
-  }
   const id = asset.id;
   const cacheKey = asset.thumbhash;
   if (sharedLink && (!sharedLink.allowDownload || !sharedLink.showMetadata)) {

web/src/lib/utils/adaptive-image-loader.svelte.ts

@@ -0,0 +1,202 @@
+import type { LoadImageFunction } from '$lib/actions/image-loader.svelte';
+import { imageManager } from '$lib/managers/ImageManager.svelte';
+import { getAssetUrl, getAssetUrlForKind } from '$lib/utils';
+import { type AssetResponseDto, type SharedLinkResponseDto } from '@immich/sdk';
+
+/**
+ * Quality levels for progressive image loading
+ */
+type ImageQuality =
+  | 'basic'
+  | 'loading-thumbnail'
+  | 'thumbnail'
+  | 'loading-preview'
+  | 'preview'
+  | 'loading-original'
+  | 'original';
+
+export interface ImageLoaderState {
+  previewUrl?: string;
+  thumbnailUrl?: string;
+  originalUrl?: string;
+  quality: ImageQuality;
+  hasError: boolean;
+  thumbnailImage: ImageStatus;
+  previewImage: ImageStatus;
+  originalImage: ImageStatus;
+}
+enum ImageStatus {
+  Unloaded = 'Unloaded',
+  Success = 'Success',
+  Error = 'Error',
+}
+
+/**
+ * Coordinates adaptive loading of a single asset image:
+ * thumbhash → thumbnail → preview → original (on zoom)
+ *
+ */
+export class AdaptiveImageLoader {
+  private state = $state<ImageLoaderState>({
+    quality: 'basic',
+    hasError: false,
+    thumbnailImage: ImageStatus.Unloaded,
+    previewImage: ImageStatus.Unloaded,
+    originalImage: ImageStatus.Unloaded,
+  });
+
+  private readonly currentZoomFn?: () => number;
+  private readonly onImageReady?: () => void;
+  private readonly onError?: () => void;
+  private readonly imageLoader?: LoadImageFunction;
+  private readonly destroyFunctions: (() => void)[] = [];
+  readonly thumbnailUrl: string;
+  readonly previewUrl: string;
+  readonly originalUrl: string;
+  asset: AssetResponseDto;
+  constructor(
+    asset: AssetResponseDto,
+    sharedLink: SharedLinkResponseDto | undefined,
+    callbacks?: {
+      currentZoomFn: () => number;
+      onImageReady?: () => void;
+      onError?: () => void;
+    },
+    imageLoader?: LoadImageFunction,
+  ) {
+    this.asset = asset;
+    this.currentZoomFn = callbacks?.currentZoomFn;
+    this.onImageReady = callbacks?.onImageReady;
+    this.onError = callbacks?.onError;
+    this.imageLoader = imageLoader;
+
+    this.thumbnailUrl = getAssetUrlForKind(asset, 'thumbnail');
+    this.previewUrl = getAssetUrl({ asset, sharedLink });
+    this.originalUrl = getAssetUrl({ asset, sharedLink, forceOriginal: true });
+    this.state.thumbnailUrl = this.thumbnailUrl;
+  }
+
+  start() {
+    if (!this.imageLoader) {
+      throw new Error('Start requires imageLoader to be specified');
+    }
+    this.destroyFunctions.push(
+      this.imageLoader(
+        this.thumbnailUrl,
+        {},
+        () => this.onThumbnailLoad(),
+        () => this.onThumbnailError(),
+        () => this.onThumbnailStart(),
+      ),
+    );
+  }
+
+  get adaptiveLoaderState(): ImageLoaderState {
+    return this.state;
+  }
+
+  onThumbnailStart() {
+    this.state.quality = 'loading-thumbnail';
+  }
+
+  onThumbnailLoad() {
+    this.state.quality = 'thumbnail';
+    this.state.thumbnailImage = ImageStatus.Success;
+    this.onImageReady?.();
+    this.triggerMainImage();
+  }
+
+  onThumbnailError() {
+    this.state.thumbnailUrl = undefined;
+    this.state.thumbnailImage = ImageStatus.Error;
+    this.triggerMainImage();
+  }
+
+  triggerMainImage() {
+    const wantsOriginal = (this.currentZoomFn?.() ?? 1) > 1;
+    return wantsOriginal ? this.triggerOriginal() : this.triggerPreview();
+  }
+
+  triggerPreview() {
+    if (!this.previewUrl) {
+      // no preview, try original?
+      this.triggerOriginal();
+      return false;
+    }
+    this.state.previewUrl = this.previewUrl;
+    if (this.imageLoader) {
+      this.destroyFunctions.push(
+        this.imageLoader(
+          this.previewUrl,
+          {},
+          () => this.onPreviewLoad(),
+          () => this.onPreviewError(),
+          () => this.onPreviewStart(),
+        ),
+      );
+    }
+  }
+
+  onPreviewStart() {
+    this.state.quality = 'loading-preview';
+  }
+
+  onPreviewLoad() {
+    this.state.quality = 'preview';
+    this.state.previewImage = ImageStatus.Success;
+    this.onImageReady?.();
+  }
+
+  onPreviewError() {
+    this.state.previewImage = ImageStatus.Error;
+    this.state.previewUrl = undefined;
+    // TODO: maybe try original, but only if preview's error isnt due to cancelation
+  }
+
+  triggerOriginal() {
+    if (!this.originalUrl) {
+      this.onError?.();
+      return false;
+    }
+    this.state.originalUrl = this.originalUrl;
+
+    if (this.imageLoader) {
+      this.destroyFunctions.push(
+        this.imageLoader(
+          this.originalUrl,
+          {},
+          () => this.onOriginalLoad(),
+          () => this.onOriginalError(),
+          () => this.onOriginalStart(),
+        ),
+      );
+    }
+  }
+
+  onOriginalStart() {
+    this.state.quality = 'loading-original';
+  }
+
+  onOriginalLoad() {
+    this.state.quality = 'original';
+    this.state.originalImage = ImageStatus.Success;
+    this.onImageReady?.();
+  }
+
+  onOriginalError() {
+    this.state.originalImage = ImageStatus.Error;
+    this.state.originalUrl = undefined;
+  }
+
+  destroy(): void {
+    if (this.imageLoader) {
+      for (const destroy of this.destroyFunctions) {
+        destroy();
+      }
+      return;
+    }
+    imageManager.cancelPreloadUrl(this.thumbnailUrl);
+    imageManager.cancelPreloadUrl(this.previewUrl);
+    imageManager.cancelPreloadUrl(this.originalUrl);
+  }
+}

web/src/lib/utils/handle-error.ts

@@ -19,12 +19,17 @@ export function getServerErrorMessage(error: unknown) {
   return data?.message || error.message;
 }
 
-export function handleError(error: unknown, message: string) {
-  if ((error as Error)?.name === 'AbortError') {
+export function standardizeError(error: unknown) {
+  return error instanceof Error ? error : new Error(String(error));
+}
+
+export function handleError(error: unknown, localizedMessage: string) {
+  const standardizedError = standardizeError(error);
+  if (standardizedError.name === 'AbortError') {
     return;
   }
 
-  console.error(`[handleError]: ${message}`, error, (error as Error)?.stack);
+  console.error(`[handleError]: ${standardizedError}`, error, standardizedError.stack);
 
   try {
     let serverMessage = getServerErrorMessage(error);
@@ -32,13 +37,22 @@ export function handleError(error: unknown, message: string) {
       serverMessage = `${String(serverMessage).slice(0, 75)}\n(Immich Server Error)`;
     }
 
-    const errorMessage = serverMessage || message;
+    const errorMessage = serverMessage || localizedMessage;
 
     toastManager.danger(errorMessage);
 
     return errorMessage;
   } catch (error) {
     console.error(error);
-    return message;
+    return localizedMessage;
+  }
+}
+
+export async function handleErrorAsync<T>(fn: () => Promise<T>, localizedMessage: string): Promise<T | undefined> {
+  try {
+    return await fn();
+  } catch (error: unknown) {
+    handleError(error, localizedMessage);
+    return undefined;
   }
 }

web/src/lib/utils/invocationTracker.ts

@@ -1,3 +1,5 @@
+import { handleError } from '$lib/utils/handle-error';
+
 /**
  * Tracks the state of asynchronous invocations to handle race conditions and stale operations.
  * This class helps manage concurrent operations by tracking which invocations are active
@@ -51,10 +53,12 @@ export class InvocationTracker {
     return this.invocationsStarted !== this.invocationsEnded;
   }
 
-  async invoke<T>(invocable: () => Promise<T>) {
+  async invoke<T>(invocable: () => Promise<T>, localizedMessage: string) {
     const invocation = this.startInvocation();
     try {
       return await invocable();
+    } catch (error: unknown) {
+      handleError(error, localizedMessage);
     } finally {
       invocation.endInvocation();
     }

web/src/lib/utils/layout-utils.ts

@@ -129,3 +129,19 @@ export type CommonPosition = {
   width: number;
   height: number;
 };
+
+// Scales dimensions to fit within a container (like object-fit: contain)
+export const scaleToFit = (
+  dimensions: { width: number; height: number },
+  container: { width: number; height: number },
+) => {
+  const scaleX = container.width / dimensions.width;
+  const scaleY = container.height / dimensions.height;
+
+  const scale = Math.min(scaleX, scaleY);
+
+  return {
+    width: dimensions.width * scale,
+    height: dimensions.height * scale,
+  };
+};

web/src/lib/utils/people-utils.ts

@@ -24,11 +24,11 @@ export interface boundingBox {
 export const getBoundingBox = (
   faces: Faces[],
   zoom: ZoomImageWheelState,
-  photoViewer: HTMLImageElement | null,
+  photoViewer: HTMLImageElement | undefined,
 ): boundingBox[] => {
   const boxes: boundingBox[] = [];
 
-  if (photoViewer === null) {
+  if (!photoViewer) {
     return boxes;
   }
   const clientHeight = photoViewer.clientHeight;
@@ -93,7 +93,7 @@ export const zoomImageToBase64 = async (
 
     image = img;
   }
-  if (image === null) {
+  if (!image) {
     return null;
   }
   const { boundingBoxX1: x1, boundingBoxX2: x2, boundingBoxY1: y1, boundingBoxY2: y2, imageWidth, imageHeight } = face;
@@ -121,11 +121,9 @@ export const zoomImageToBase64 = async (
   canvas.height = faceHeight;
 
   const context = canvas.getContext('2d');
-  if (context) {
-    context.drawImage(faceImage, coordinates.x1, coordinates.y1, faceWidth, faceHeight, 0, 0, faceWidth, faceHeight);
-
-    return canvas.toDataURL();
-  } else {
+  if (!context) {
     return null;
   }
+  context.drawImage(faceImage, coordinates.x1, coordinates.y1, faceWidth, faceHeight, 0, 0, faceWidth, faceHeight);
+  return canvas.toDataURL();
 };

web/src/lib/utils/sw-messaging.ts

@@ -1,14 +1,24 @@
-const broadcast = new BroadcastChannel('immich');
+import { ServiceWorkerMessenger } from './sw-messenger';
+
+const messenger = new ServiceWorkerMessenger();
+
+let isServiceWorkerEnabled = true;
+
+messenger.onAckTimeout(() => {
+  if (!isServiceWorkerEnabled) {
+    return;
+  }
+  console.error('[ServiceWorker] No communication detected. Auto-disabled service worker.');
+  isServiceWorkerEnabled = false;
+});
+
+const isValidSwContext = (url: string | undefined | null): url is string => {
+  return globalThis.isSecureContext && isServiceWorkerEnabled && !!url;
+};
 
 export function cancelImageUrl(url: string | undefined | null) {
-  if (!url) {
+  if (!isValidSwContext(url)) {
     return;
   }
-  broadcast.postMessage({ type: 'cancel', url });
-}
-export function preloadImageUrl(url: string | undefined | null) {
-  if (!url) {
-    return;
-  }
-  broadcast.postMessage({ type: 'preload', url });
+  void messenger.send('cancel', { url });
 }

web/src/lib/utils/sw-messenger.ts

@@ -0,0 +1,157 @@
+/**
+ * Low-level protocol for communicating with the service worker via postMessage.
+ *
+ * Protocol:
+ * 1. Main thread sends request: { type: string, requestId: string, ...data }
+ * 2. SW sends ack: { type: 'ack', requestId: string }
+ * 3. SW sends response (optional): { type: 'response', requestId: string, result?: any, error?: string }
+ */
+
+interface PendingRequest {
+  resolveAck: () => void;
+  resolveResponse?: (result: unknown) => void;
+  rejectResponse?: (error: Error) => void;
+  ackTimeout: ReturnType<typeof setTimeout>;
+  ackReceived: boolean;
+}
+
+export class ServiceWorkerMessenger {
+  readonly #pendingRequests = new Map<string, PendingRequest>();
+  readonly #ackTimeoutMs: number;
+  #requestCounter = 0;
+  #onTimeout?: (type: string, data: Record<string, unknown>) => void;
+  #messageHandler?: (event: MessageEvent) => void;
+
+  constructor(ackTimeoutMs = 5000) {
+    this.#ackTimeoutMs = ackTimeoutMs;
+
+    // Listen for messages from the service worker
+    if ('serviceWorker' in navigator) {
+      this.#messageHandler = (event) => {
+        this.#handleMessage(event.data);
+      };
+      navigator.serviceWorker.addEventListener('message', this.#messageHandler);
+    }
+  }
+
+  #handleMessage(data: unknown) {
+    if (typeof data !== 'object' || data === null) {
+      return;
+    }
+
+    const message = data as { requestId?: string; type?: string; error?: string; result?: unknown };
+    const requestId = message.requestId;
+    if (!requestId) {
+      return;
+    }
+
+    const pending = this.#pendingRequests.get(requestId);
+    if (!pending) {
+      return;
+    }
+
+    if (message.type === 'ack') {
+      pending.ackReceived = true;
+      clearTimeout(pending.ackTimeout);
+      pending.resolveAck();
+      return;
+    }
+
+    if (message.type === 'response') {
+      clearTimeout(pending.ackTimeout);
+      this.#pendingRequests.delete(requestId);
+
+      if (message.error) {
+        pending.rejectResponse?.(new Error(message.error));
+        return;
+      }
+
+      pending.resolveResponse?.(message.result);
+    }
+  }
+
+  /**
+   * Set a callback to be invoked when an ack timeout occurs.
+   * This can be used to detect and disable faulty service workers.
+   */
+  onAckTimeout(callback: (type: string, data: Record<string, unknown>) => void): void {
+    this.#onTimeout = callback;
+  }
+
+  /**
+   * Send a message to the service worker.
+   * - send(): waits for ack, resolves when acknowledged
+   * - request(): waits for response, throws on error/timeout
+   */
+  #sendInternal<T>(type: string, data: Record<string, unknown>, waitForResponse: boolean): Promise<T> {
+    const requestId = `${type}-${++this.#requestCounter}-${Date.now()}`;
+
+    const promise = new Promise<T>((resolve, reject) => {
+      const ackTimeout = setTimeout(() => {
+        const pending = this.#pendingRequests.get(requestId);
+        if (pending && !pending.ackReceived) {
+          this.#pendingRequests.delete(requestId);
+          console.warn(`[ServiceWorker] ${type} request not acknowledged:`, data);
+          this.#onTimeout?.(type, data);
+          // Only reject if we're waiting for a response
+          if (waitForResponse) {
+            reject(new Error(`Service worker did not acknowledge ${type} request`));
+          } else {
+            resolve(undefined as T);
+          }
+        }
+      }, this.#ackTimeoutMs);
+
+      this.#pendingRequests.set(requestId, {
+        resolveAck: waitForResponse ? () => {} : () => resolve(undefined as T),
+        resolveResponse: waitForResponse ? (result: unknown) => resolve(result as T) : undefined,
+        rejectResponse: waitForResponse ? reject : undefined,
+        ackTimeout,
+        ackReceived: false,
+      });
+
+      // Send message to the active service worker
+      // Feature detection is done in constructor and at call sites (sw-messaging.ts:isValidSwContext)
+      // eslint-disable-next-line compat/compat
+      navigator.serviceWorker.controller?.postMessage({
+        type,
+        requestId,
+        ...data,
+      });
+    });
+
+    return promise;
+  }
+
+  /**
+   * Send a one-way message to the service worker.
+   * Returns a promise that resolves after the service worker acknowledges receipt.
+   * Resolves even if no ack is received within the timeout period.
+   */
+  send(type: string, data: Record<string, unknown>): Promise<void> {
+    return this.#sendInternal<void>(type, data, false);
+  }
+
+  /**
+   * Send a request and wait for ack + response.
+   * Returns a promise that resolves with the response data or rejects on error/timeout.
+   */
+  request<T = void>(type: string, data: Record<string, unknown>): Promise<T> {
+    return this.#sendInternal<T>(type, data, true);
+  }
+
+  /**
+   * Clean up pending requests and remove event listener
+   */
+  close(): void {
+    for (const pending of this.#pendingRequests.values()) {
+      clearTimeout(pending.ackTimeout);
+    }
+    this.#pendingRequests.clear();
+
+    if (this.#messageHandler && 'serviceWorker' in navigator) {
+      navigator.serviceWorker.removeEventListener('message', this.#messageHandler);
+      this.#messageHandler = undefined;
+    }
+  }
+}

web/src/service-worker/broadcast-channel.ts

@@ -1,25 +0,0 @@
-import { handleCancel, handlePreload } from './request';
-
-export const installBroadcastChannelListener = () => {
-  const broadcast = new BroadcastChannel('immich');
-  // eslint-disable-next-line  unicorn/prefer-add-event-listener
-  broadcast.onmessage = (event) => {
-    if (!event.data) {
-      return;
-    }
-
-    const url = new URL(event.data.url, event.origin);
-
-    switch (event.data.type) {
-      case 'preload': {
-        handlePreload(url);
-        break;
-      }
-
-      case 'cancel': {
-        handleCancel(url);
-        break;
-      }
-    }
-  };
-};

web/src/service-worker/cache.ts

@@ -1,42 +0,0 @@
-import { version } from '$service-worker';
-
-const CACHE = `cache-${version}`;
-
-let _cache: Cache | undefined;
-const getCache = async () => {
-  if (_cache) {
-    return _cache;
-  }
-  _cache = await caches.open(CACHE);
-  return _cache;
-};
-
-export const get = async (key: string) => {
-  const cache = await getCache();
-  if (!cache) {
-    return;
-  }
-
-  return cache.match(key);
-};
-
-export const put = async (key: string, response: Response) => {
-  if (response.status !== 200) {
-    return;
-  }
-
-  const cache = await getCache();
-  if (!cache) {
-    return;
-  }
-
-  cache.put(key, response.clone());
-};
-
-export const prune = async () => {
-  for (const key of await caches.keys()) {
-    if (key !== CACHE) {
-      await caches.delete(key);
-    }
-  }
-};

web/src/service-worker/index.ts

@@ -2,9 +2,9 @@
 /// <reference no-default-lib="true"/>
 /// <reference lib="esnext" />
 /// <reference lib="webworker" />
-import { installBroadcastChannelListener } from './broadcast-channel';
-import { prune } from './cache';
-import { handleRequest } from './request';
+
+import { installMessageListener } from './messaging';
+import { handleFetch as handleAssetFetch } from './request';
 
 const ASSET_REQUEST_REGEX = /^\/api\/assets\/[a-f0-9-]+\/(original|thumbnail)/;
 
@@ -12,12 +12,10 @@ const sw = globalThis as unknown as ServiceWorkerGlobalScope;
 
 const handleActivate = (event: ExtendableEvent) => {
   event.waitUntil(sw.clients.claim());
-  event.waitUntil(prune());
 };
 
 const handleInstall = (event: ExtendableEvent) => {
   event.waitUntil(sw.skipWaiting());
-  // do not preload app resources
 };
 
 const handleFetch = (event: FetchEvent): void => {
@@ -28,7 +26,7 @@ const handleFetch = (event: FetchEvent): void => {
   // Cache requests for thumbnails
   const url = new URL(event.request.url);
   if (url.origin === self.location.origin && ASSET_REQUEST_REGEX.test(url.pathname)) {
-    event.respondWith(handleRequest(event.request));
+    event.respondWith(handleAssetFetch(event.request));
     return;
   }
 };
@@ -36,4 +34,4 @@ const handleFetch = (event: FetchEvent): void => {
 sw.addEventListener('install', handleInstall, { passive: true });
 sw.addEventListener('activate', handleActivate, { passive: true });
 sw.addEventListener('fetch', handleFetch, { passive: true });
-installBroadcastChannelListener();
+installMessageListener();

web/src/service-worker/messaging.ts

@@ -0,0 +1,53 @@
+/// <reference types="@sveltejs/kit" />
+/// <reference no-default-lib="true"/>
+/// <reference lib="esnext" />
+/// <reference lib="webworker" />
+
+import { handleCancel } from './request';
+
+const sw = globalThis as unknown as ServiceWorkerGlobalScope;
+
+/**
+ * Send acknowledgment for a request
+ */
+function sendAck(client: Client, requestId: string) {
+  client.postMessage({
+    type: 'ack',
+    requestId,
+  });
+}
+
+/**
+ * Handle 'cancel' request: cancel a pending request
+ */
+const handleCancelRequest = (client: Client, url: URL, requestId: string) => {
+  sendAck(client, requestId);
+  handleCancel(url);
+};
+
+export const installMessageListener = () => {
+  sw.addEventListener('message', (event) => {
+    if (!event.data?.requestId || !event.data?.type) {
+      return;
+    }
+
+    const requestId = event.data.requestId;
+
+    switch (event.data.type) {
+      case 'cancel': {
+        const url = event.data.url ? new URL(event.data.url, self.location.origin) : undefined;
+        if (!url) {
+          return;
+        }
+
+        const client = event.source;
+        if (!client) {
+          return;
+        }
+
+        handleCancelRequest(client, url, requestId);
+        break;
+      }
+    }
+  });
+};

web/src/service-worker/request.ts

@@ -1,73 +1,68 @@
-import { get, put } from './cache';
+/// <reference types="@sveltejs/kit" />
+/// <reference no-default-lib="true"/>
+/// <reference lib="esnext" />
+/// <reference lib="webworker" />
 
-const pendingRequests = new Map<string, AbortController>();
-
-const isURL = (request: URL | RequestInfo): request is URL => (request as URL).href !== undefined;
-const isRequest = (request: RequestInfo): request is Request => (request as Request).url !== undefined;
-
-const assertResponse = (response: Response) => {
-  if (!(response instanceof Response)) {
-    throw new TypeError('Fetch did not return a valid Response object');
-  }
+type PendingRequest = {
+  controller: AbortController;
+  promise: Promise<Response>;
+  cleanupTimeout?: ReturnType<typeof setTimeout>;
 };
 
-const getCacheKey = (request: URL | Request) => {
-  if (isURL(request)) {
-    return request.toString();
+const pendingRequests = new Map<string, PendingRequest>();
+
+const getRequestKey = (request: URL | Request): string => (request instanceof URL ? request.href : request.url);
+
+const CANCELATION_MESSAGE = 'Request canceled by application';
+const CLEANUP_TIMEOUT_MS = 5 * 60 * 1000; // 5 minutes
+
+export const handleFetch = (request: URL | Request): Promise<Response> => {
+  const requestKey = getRequestKey(request);
+  const existing = pendingRequests.get(requestKey);
+
+  if (existing) {
+    // Clone the response since response bodies can only be read once
+    // Each caller gets an independent clone they can consume
+    return existing.promise.then((response) => response.clone());
   }
 
-  if (isRequest(request)) {
-    return request.url;
-  }
+  const pendingRequest: PendingRequest = {
+    controller: new AbortController(),
+    promise: undefined as unknown as Promise<Response>,
+  };
+  pendingRequests.set(requestKey, pendingRequest);
 
-  throw new Error(`Invalid request: ${request}`);
-};
+  // NOTE: fetch returns after headers received, not the body
+  pendingRequest.promise = fetch(request, { signal: pendingRequest.controller.signal })
+    .catch((error: unknown) => {
+      const standardError = error instanceof Error ? error : new Error(String(error));
+      if (standardError.name === 'AbortError' || standardError.message === CANCELATION_MESSAGE) {
+        // dummy response avoids network errors in the console for these requests
+        return new Response(undefined, { status: 204 });
+      }
+      throw standardError;
+    })
+    .finally(() => {
+      // Schedule cleanup after timeout to allow response body streaming to complete
+      const cleanupTimeout = setTimeout(() => {
+        pendingRequests.delete(requestKey);
+      }, CLEANUP_TIMEOUT_MS);
+      pendingRequest.cleanupTimeout = cleanupTimeout;
+    });
 
-export const handlePreload = async (request: URL | Request) => {
-  try {
-    return await handleRequest(request);
-  } catch (error) {
-    console.error(`Preload failed: ${error}`);
-  }
-};
-
-export const handleRequest = async (request: URL | Request) => {
-  const cacheKey = getCacheKey(request);
-  const cachedResponse = await get(cacheKey);
-  if (cachedResponse) {
-    return cachedResponse;
-  }
-
-  try {
-    const cancelToken = new AbortController();
-    pendingRequests.set(cacheKey, cancelToken);
-    const response = await fetch(request, { signal: cancelToken.signal });
-
-    assertResponse(response);
-    put(cacheKey, response);
-
-    return response;
-  } catch (error) {
-    if (error.name === 'AbortError') {
-      // dummy response avoids network errors in the console for these requests
-      return new Response(undefined, { status: 204 });
-    }
-
-    console.log('Not an abort error', error);
-
-    throw error;
-  } finally {
-    pendingRequests.delete(cacheKey);
-  }
+  // Clone for the first caller to keep the original response unconsumed for future callers
+  return pendingRequest.promise.then((response) => response.clone());
 };
 
 export const handleCancel = (url: URL) => {
-  const cacheKey = getCacheKey(url);
-  const pendingRequest = pendingRequests.get(cacheKey);
-  if (!pendingRequest) {
-    return;
-  }
+  const requestKey = getRequestKey(url);
 
-  pendingRequest.abort();
-  pendingRequests.delete(cacheKey);
+  const pendingRequest = pendingRequests.get(requestKey);
+  if (pendingRequest) {
+    pendingRequest.controller.abort(CANCELATION_MESSAGE);
+    if (pendingRequest.cleanupTimeout) {
+      clearTimeout(pendingRequest.cleanupTimeout);
+    }
+    pendingRequests.delete(requestKey);
+  }
 };