diff --git a/scripts/qa-wind-engine-switch.mjs b/scripts/qa-wind-engine-switch.mjs
index ac155feba..f9b6c7e05 100644
--- a/scripts/qa-wind-engine-switch.mjs
+++ b/scripts/qa-wind-engine-switch.mjs
@@ -81,7 +81,7 @@ await strict.run({}, async (b) => {
   });
   await p.waitForFunction(
     () =>
-      window.qaWind.getDiagnostics().surface?.ready &&
+      window.qaWind.getDiagnostics().imageryActive &&
       window.qaWind.getDiagnostics().gpu?.ready,
   );
   await p.evaluate(() => window.qaWind.setParams({ inspect: true }));
diff --git a/src/data/bhoteKoshiEvent.js b/src/data/bhoteKoshiEvent.js
index bff2e169e..5e32285f0 100644
--- a/src/data/bhoteKoshiEvent.js
+++ b/src/data/bhoteKoshiEvent.js
@@ -1010,6 +1010,7 @@ export function createBhoteKoshiEventLayer({
   imageryProviderFactory = DEFAULT_IMAGERY_PROVIDER_FACTORY,
   terrainSampler = DEFAULT_TERRAIN_SAMPLER,
   mediaLoader = DEFAULT_MEDIA_LOADER,
+  imageLoader = DEFAULT_MEDIA_LOADER,
   evidenceFrameFactory = createEvidenceFrame,
   evidenceFrameUpdater = updateEvidenceFrame,
   videoFactory = DEFAULT_VIDEO_FACTORY,
@@ -1022,6 +1023,9 @@ export function createBhoteKoshiEventLayer({
   let _native = null;
   let _nativeFlood = null;
   let _providers = null;
+  // The before and after images, decoded once for every engine the event
+  // is drawn on (as Cesium's providers were kept across switches).
+  let _imageryImages = null;
   const cameraForScene = () => _engine?.camera ?? _viewer?.camera;
   const canvasForScene = () => _engine?.host.canvas ?? _viewer?.scene?.canvas;
   let _dataManager = null;
@@ -1183,12 +1187,21 @@ export function createBhoteKoshiEventLayer({
   async function createImagery(event, current = () => true) {
     if (_native) {
       // The engine's display draws the images through engine.imagery.
+      _imageryImages ??= Promise.all(
+        [event.imagery.before.path, event.imagery.after.path].map((path) =>
+          imageLoader(eventAsset(path)),
+        ),
+      );
+      let images;
+      try {
+        images = await _imageryImages;
+      } catch {
+        _imageryImages = null;
+        throw new Error('Bhote Koshi imagery unavailable');
+      }
       await _native.loadImages(
         event.imagery.rectangle,
-        [
-          eventAsset(event.imagery.before.path),
-          eventAsset(event.imagery.after.path),
-        ],
+        images,
         'Vantor WorldView Open Data · CC BY-NC 4.0',
       );
       if (_enabled && current()) setSplit(_split);
@@ -3793,6 +3806,7 @@ export function createBhoteKoshiEventLayer({
     _nativeFlood = null;
     _native?.clear();
     _providers = null;
+    _imageryImages = null;
     if (_floodDataSource && _viewer)
       _viewer.dataSources.remove(_floodDataSource, true);
     _floodDataSource = null;
diff --git a/src/layers/bhoteKoshi/render/display.js b/src/layers/bhoteKoshi/render/display.js
index 05b3ab820..2172bb1db 100644
--- a/src/layers/bhoteKoshi/render/display.js
+++ b/src/layers/bhoteKoshi/render/display.js
@@ -44,11 +44,11 @@ export function createBhoteKoshiDisplay(engine) {
       };
     },
     /**
-     * The before and after images over `box` (degrees); resolves once both
-     * draw, rejects when one would not load (unless replaced or cleared
-     * first).
+     * The before and after images over `box` (degrees), each a URL or an
+     * image already decoded; resolves once both draw, rejects when one
+     * would not load (unless replaced or cleared first).
      */
-    async loadImages(box, urls, credit = null) {
+    async loadImages(box, images, credit = null) {
       if (destroyed) return;
       clear();
       const load = loads;
@@ -60,7 +60,7 @@ export function createBhoteKoshiDisplay(engine) {
       };
       // Each layer stages its image over an empty one, which tells whether
       // the image loaded.
-      layers = urls.map((_url, index) =>
+      layers = images.map((_image, index) =>
         engine.imagery.createLayer({
           id: `${id}-${SIDES[index]}`,
           order: IMAGERY_ORDER,
@@ -75,7 +75,9 @@ export function createBhoteKoshiDisplay(engine) {
           layer.setSource(
             {
               kind: 'image',
-              url: urls[index],
+              ...(typeof images[index] === 'string'
+                ? { url: images[index] }
+                : { image: images[index] }),
               rectangle,
               ...(credit ? { credit } : {}),
             },