diff --git a/docs/backlog.md b/docs/backlog.md
index eac1a58..b5f723b 100644
--- a/docs/backlog.md
+++ b/docs/backlog.md
@@ -168,6 +168,14 @@
       форматирование по колонкам??? для hex\bytes\rgba - пример в placeholder
 - [ ] прикрутить кастомный color picker, добавить прозрачность (range?)
 - [ ] обновить страницу kit или сделать storybook
+- [ ] **проверить `cachedDataUrl` (WeakMap-кэш превью) в реальной работе** — GC
+      срабатывает недетерминированно, поэтому освобождение base64-строк (≈1.3×
+      бинарного размера картинки на каждый тайл) не гарантировано своевременно.
+      Проверить на длинной сессии с большими картинками (несколько ранов подряд,
+      смена инструментов): растёт ли heap в DevTools → Memory после повторных
+      ранов и уходит ли после принудительной сборки. Если записи копятся —
+      заменить на ограниченный LRU или явную инвалидацию при
+      `resetForHost`/новом ране (`web/src/lib/core/io.ts`, `cachedDataUrl`)
 - [ ] `PreviewTile`: высота плитки задана только `min-height: clamp(...)`,
       поэтому она не следует за пропорциями результата — широкий результат
       уезжает в узкую полосу, а высокий упирается в `max-height: 100vh`. Нужно,
diff --git a/web/src/lib/components/schema/PartsGrid.svelte b/web/src/lib/components/schema/PartsGrid.svelte
index fbaa27c..fe28ba7 100644
--- a/web/src/lib/components/schema/PartsGrid.svelte
+++ b/web/src/lib/components/schema/PartsGrid.svelte
@@ -1,5 +1,5 @@
 <script lang="ts">
-	import { toDataUrl } from "$lib/core/io";
+	import { cachedDataUrl } from "$lib/core/io";
 	import type { ToolImageFile } from "$lib/registry";
 
 	interface Props {
@@ -8,7 +8,7 @@
 	let { files }: Props = $props();
 
 	const parts = $derived(
-		files.map((file) => ({ name: file.name, url: toDataUrl(file.image) })),
+		files.map((file) => ({ name: file.name, url: cachedDataUrl(file.image) })),
 	);
 </script>
 
diff --git a/web/src/lib/components/schema/SchemaResultTile.svelte b/web/src/lib/components/schema/SchemaResultTile.svelte
index f6b6490..93608be 100644
--- a/web/src/lib/components/schema/SchemaResultTile.svelte
+++ b/web/src/lib/components/schema/SchemaResultTile.svelte
@@ -1,5 +1,5 @@
 <script lang="ts">
-	import { toDataUrl } from "$lib/core/io";
+	import { cachedDataUrl } from "$lib/core/io";
 	import type { PixelImage } from "$lib/core/types";
 	import { t } from "$lib/i18n/t";
 	import type { FileResult, ResultKind, ResultNote } from "$lib/registry";
@@ -41,7 +41,7 @@
 	}: Props = $props();
 
 	const shown = $derived(maskOn && mask ? mask : result);
-	const resultUrl = $derived(shown ? toDataUrl(shown) : null);
+	const resultUrl = $derived(shown ? cachedDataUrl(shown) : null);
 	const resultDims = $derived(
 		resultKind === "image" && result
 			? `${result.width} × ${result.height}`
diff --git a/web/src/lib/components/schema/SchemaSourceTile.svelte b/web/src/lib/components/schema/SchemaSourceTile.svelte
index d23e3af..5b8e85a 100644
--- a/web/src/lib/components/schema/SchemaSourceTile.svelte
+++ b/web/src/lib/components/schema/SchemaSourceTile.svelte
@@ -1,5 +1,5 @@
 <script lang="ts">
-	import { toDataUrl } from "$lib/core/io";
+	import { cachedDataUrl } from "$lib/core/io";
 	import type { PixelImage } from "$lib/core/types";
 	import { t } from "$lib/i18n/t";
 	import type { InputMode, ToolImageFile } from "$lib/registry";
@@ -33,7 +33,7 @@
 		onuploadmany,
 	}: Props = $props();
 
-	const sourceUrl = $derived(source ? toDataUrl(source) : null);
+	const sourceUrl = $derived(source ? cachedDataUrl(source) : null);
 	const sourceDims = $derived(
 		source
 			? `${source.width} × ${source.height}` +
diff --git a/web/src/lib/components/schema/SchemaToolView.svelte b/web/src/lib/components/schema/SchemaToolView.svelte
index 2f9feaf..959c71b 100644
--- a/web/src/lib/components/schema/SchemaToolView.svelte
+++ b/web/src/lib/components/schema/SchemaToolView.svelte
@@ -5,7 +5,7 @@
 	import { Star } from "@lucide/svelte";
 	import { DragDropProvider } from "@dnd-kit/svelte";
 	import { debounce } from "$lib/core/debounce";
-	import { toDataUrl } from "$lib/core/io";
+	import { cachedDataUrl } from "$lib/core/io";
 	import type { PixelImage } from "$lib/core/types";
 	import {
 		chainStepTitle,
@@ -301,7 +301,7 @@
 					{#if inSet.length > 1}
 						<PartsGrid files={inSet} />
 					{:else if input}
-						<img src={toDataUrl(input)} alt="" />
+						<img src={cachedDataUrl(input)} alt="" />
 					{:else}
 						<span class="empty">{t("resultCard.noResult")}</span>
 					{/if}
@@ -344,7 +344,7 @@
 						<PartsGrid files={outSet} />
 					{:else if out}
 						<img
-							src={toDataUrl(
+							src={cachedDataUrl(
 								masks.maskOn[i] && masks.masks[i]
 									? (masks.masks[i] as PixelImage)
 									: out,
diff --git a/web/src/lib/core/io.ts b/web/src/lib/core/io.ts
index f53a7bf..599d297 100644
--- a/web/src/lib/core/io.ts
+++ b/web/src/lib/core/io.ts
@@ -82,6 +82,21 @@ export function toBase64(img: PixelImage): string {
 	return toDataUrl(img).slice("data:image/png;base64,".length);
 }
 
+const dataUrlCache = new WeakMap<PixelImage, string>();
+
+// Display helper: PNG-encode on the main thread is expensive and templates
+// re-render often with the same image (layout branch swaps, toggles). Results
+// are treated as immutable -- a re-run produces new objects -- so an
+// identity-keyed cache cannot go stale.
+export function cachedDataUrl(img: PixelImage): string {
+	let url = dataUrlCache.get(img);
+	if (url === undefined) {
+		url = toDataUrl(img);
+		dataUrlCache.set(img, url);
+	}
+	return url;
+}
+
 export async function decodeTextImage(text: string): Promise<PixelImage> {
 	const cleaned = text.trim().replace(/^data:[^,]*,/, "");
 	if (cleaned.length === 0) {