diff --git a/packages/layout-engine/pm-adapter/src/utilities.test.ts b/packages/layout-engine/pm-adapter/src/utilities.test.ts
index c9b231da1d..1218404f3b 100644
--- a/packages/layout-engine/pm-adapter/src/utilities.test.ts
+++ b/packages/layout-engine/pm-adapter/src/utilities.test.ts
@@ -836,6 +836,40 @@ describe('Media Utilities', () => {
       const result = hydrateImageBlocks(blocks, mediaFiles);
       expect(result[0].src).toBe('data:image/png;base64,iVBORw0KGgoAAAANS');
     });
+
+    it('handles Uint8Array media values from persistence layers', () => {
+      const blocks: FlowBlock[] = [
+        {
+          kind: 'image',
+          id: '1',
+          src: 'media/image.png',
+          runs: [],
+        },
+      ];
+      // Persistence layers (e.g., Y.js binary encoding) may return Uint8Array
+      const base64String = 'iVBORw0KGgoAAAANS';
+      const mediaFiles = { 'media/image.png': new TextEncoder().encode(base64String) };
+
+      const result = hydrateImageBlocks(blocks, mediaFiles);
+      expect(result[0].src).toBe('data:image/png;base64,iVBORw0KGgoAAAANS');
+    });
+
+    it('handles Uint8Array data URI values from persistence layers', () => {
+      const blocks: FlowBlock[] = [
+        {
+          kind: 'image',
+          id: '1',
+          src: 'media/image.png',
+          runs: [],
+        },
+      ];
+      // Data URI stored as Uint8Array
+      const dataUri = 'data:image/png;base64,iVBORw0KGgoAAAANS';
+      const mediaFiles = { 'media/image.png': new TextEncoder().encode(dataUri) };
+
+      const result = hydrateImageBlocks(blocks, mediaFiles);
+      expect(result[0].src).toBe('data:image/png;base64,iVBORw0KGgoAAAANS');
+    });
   });
 
   describe('hydrateImageBlocks - ShapeGroup image hydration', () => {
diff --git a/packages/layout-engine/pm-adapter/src/utilities.ts b/packages/layout-engine/pm-adapter/src/utilities.ts
index 978a1621b7..1af7679a7f 100644
--- a/packages/layout-engine/pm-adapter/src/utilities.ts
+++ b/packages/layout-engine/pm-adapter/src/utilities.ts
@@ -954,7 +954,7 @@ export function inferExtensionFromPath(value?: string | null): string | undefine
  * // Matches via candidate path: word/media/rId3.png
  * ```
  */
-export function hydrateImageBlocks(blocks: FlowBlock[], mediaFiles?: Record<string, string>): FlowBlock[] {
+export function hydrateImageBlocks(blocks: FlowBlock[], mediaFiles?: Record<string, string | Uint8Array>): FlowBlock[] {
   if (!mediaFiles || Object.keys(mediaFiles).length === 0) {
     return blocks;
   }
@@ -963,7 +963,9 @@ export function hydrateImageBlocks(blocks: FlowBlock[], mediaFiles?: Record<stri
   Object.entries(mediaFiles).forEach(([key, value]) => {
     const normalized = normalizeMediaKey(key);
     if (normalized) {
-      normalizedMedia.set(normalized, value);
+      // Handle Uint8Array values from persistence layers (e.g., Y.js binary encoding)
+      const stringValue = value instanceof Uint8Array ? new TextDecoder().decode(value) : value;
+      normalizedMedia.set(normalized, stringValue);
     }
   });