diff --git a/packages/app/src/attachments/utils.ts b/packages/app/src/attachments/utils.ts
index 448b706d2..f6a78f6a0 100644
--- a/packages/app/src/attachments/utils.ts
+++ b/packages/app/src/attachments/utils.ts
@@ -55,9 +55,10 @@ export function parseImageDataUrl(
     if (!parsed.mimeType.toLowerCase().startsWith("image/")) {
       return null;
     }
+    const fingerprint = `${parsed.mimeType}\0${parsed.base64.length}\0${parsed.base64.slice(0, 64)}\0${parsed.base64.slice(-64)}`;
     return {
       ...parsed,
-      cacheKey: `data-image:${parsed.mimeType}:${parsed.base64.length}:${hashString(parsed.base64)}`,
+      cacheKey: `data-image:${parsed.mimeType}:${parsed.base64.length}:${hashString(fingerprint)}`,
     };
   } catch {
     return null;
@@ -80,13 +81,18 @@ export function getFileNameFromPath(path: string | null | undefined): string | n
 }
 
 export function createPreviewAttachmentId(input: {
-  base64: string;
   mimeType: string;
   path?: string | null;
+  size?: number | null;
+  modifiedAt?: string | null;
+  contentLength?: number | null;
 }): string {
   const path = input.path?.trim() ?? "";
-  const hash = hashString(`${input.mimeType}\0${path}\0${input.base64}`);
-  return `preview_${input.base64.length}_${hash}`;
+  const size = Number.isFinite(input.size) ? String(input.size) : "";
+  const modifiedAt = input.modifiedAt?.trim() ?? "";
+  const contentLength = Number.isFinite(input.contentLength) ? String(input.contentLength) : "";
+  const hash = hashString(`${input.mimeType}\0${path}\0${size}\0${modifiedAt}\0${contentLength}`);
+  return `preview_${size || contentLength || "unknown"}_${hash}`;
 }
 
 export async function blobToBase64(blob: Blob): Promise<string> {
diff --git a/packages/app/src/components/file-pane.tsx b/packages/app/src/components/file-pane.tsx
index d0bff6a59..2a11d8cb0 100644
--- a/packages/app/src/components/file-pane.tsx
+++ b/packages/app/src/components/file-pane.tsx
@@ -76,9 +76,11 @@ async function createFilePanePreview(file: ExplorerFile | null): Promise<{
   const { content: _content, ...imageFile } = file;
   const imageAttachment = await persistAttachmentFromBase64({
     id: createPreviewAttachmentId({
-      base64: file.content,
       mimeType: file.mimeType ?? "image/png",
       path: file.path,
+      size: file.size,
+      modifiedAt: file.modifiedAt,
+      contentLength: file.content.length,
     }),
     base64: file.content,
     mimeType: file.mimeType,
diff --git a/packages/app/src/components/message.tsx b/packages/app/src/components/message.tsx
index b137b8254..06da47460 100644
--- a/packages/app/src/components/message.tsx
+++ b/packages/app/src/components/message.tsx
@@ -635,9 +635,11 @@ function AssistantMarkdownImage({
 
       return await persistAttachmentFromBase64({
         id: createPreviewAttachmentId({
-          base64: file.content,
           mimeType: file.mimeType ?? "image/png",
           path: file.path || resolution.path,
+          size: file.size,
+          modifiedAt: file.modifiedAt,
+          contentLength: file.content.length,
         }),
         base64: file.content,
         mimeType: file.mimeType,
@@ -655,7 +657,10 @@ function AssistantMarkdownImage({
       }
 
       return await persistAttachmentFromDataUrl({
-        id: createPreviewAttachmentId(dataImage),
+        id: createPreviewAttachmentId({
+          mimeType: dataImage.mimeType,
+          contentLength: dataImage.base64.length,
+        }),
         dataUrl: source,
         mimeType: dataImage.mimeType,
       });