diff --git a/src/lib/client/cache/previews.ts b/src/lib/client/cache/previews.ts
index d8ae889..736c273 100644
--- a/src/lib/client/cache/previews.ts
+++ b/src/lib/client/cache/previews.ts
@@ -8,7 +8,7 @@ import { documentPreviewFallbackUrl, documentPreviewPresignUrl } from '@/lib/cli
 
 const inMemoryPreviewUrlCache = new Map<string, string>();
 const inFlightPreviewPrime = new Map<string, Promise<string | null>>();
-const PREVIEW_CACHE_SCHEMA_VERSION = 3;
+const PREVIEW_CACHE_SCHEMA_VERSION = 4;
 
 function revokeIfBlobUrl(url: string | null | undefined): void {
   if (!url) return;
diff --git a/src/lib/server/documents/previews-blobstore.ts b/src/lib/server/documents/previews-blobstore.ts
index 01d9ecd..aa2d973 100644
--- a/src/lib/server/documents/previews-blobstore.ts
+++ b/src/lib/server/documents/previews-blobstore.ts
@@ -10,10 +10,10 @@ import { getS3Client, getS3Config, getS3ProxyClient } from '@/lib/server/storage
 const SAFE_NAMESPACE_REGEX = /^[a-zA-Z0-9._-]{1,128}$/;
 const DEFAULT_NAMESPACE_SEGMENT = '_default';
 
-export const DOCUMENT_PREVIEW_VARIANT = 'card-480-jpeg';
-export const DOCUMENT_PREVIEW_FILE_NAME = 'card-480.jpg';
+export const DOCUMENT_PREVIEW_VARIANT = 'card-400-jpeg';
+export const DOCUMENT_PREVIEW_FILE_NAME = 'card-400.jpg';
 export const DOCUMENT_PREVIEW_CONTENT_TYPE = 'image/jpeg';
-export const DOCUMENT_PREVIEW_WIDTH = 480;
+export const DOCUMENT_PREVIEW_WIDTH = 400;
 
 function sanitizeNamespace(namespace: string | null): string | null {
   if (!namespace) return null;
diff --git a/src/lib/server/documents/previews.ts b/src/lib/server/documents/previews.ts
index 8f4414c..9e7000a 100644
--- a/src/lib/server/documents/previews.ts
+++ b/src/lib/server/documents/previews.ts
@@ -1,7 +1,4 @@
 import { randomUUID } from 'crypto';
-import { mkdtemp, rm, writeFile } from 'fs/promises';
-import { tmpdir } from 'os';
-import { join } from 'path';
 import { and, eq, inArray, lt, or, sql } from 'drizzle-orm';
 import { db } from '@/db';
 import { documentPreviews } from '@/db/schema';
@@ -290,31 +287,17 @@ async function markPreviewFailed(docId: string, namespaceKey: string, error: unk
 }
 
 async function generateAndStorePreview(doc: PreviewSourceDocument, namespace: string | null): Promise<void> {
-  let workDir: string | null = null;
-  try {
-    const sourceBytes = await getDocumentBlob(doc.id, namespace);
-    workDir = await mkdtemp(join(tmpdir(), 'openreader-preview-'));
-    const sourcePath = join(workDir, 'source');
-    await writeFile(sourcePath, sourceBytes);
-
-    let rendered;
-    if (doc.type === 'pdf') {
-      rendered = await renderPdfFirstPageToJpeg(sourceBytes, DOCUMENT_PREVIEW_WIDTH);
-    } else if (doc.type === 'epub') {
-      rendered = await renderEpubCoverToJpeg(sourceBytes, DOCUMENT_PREVIEW_WIDTH);
-    } else {
-      throw new Error(`Unsupported preview type: ${doc.type}`);
-    }
-
-    // Replace-in-place semantics: clear old preview objects for this document
-    // prefix before writing the current variant so stale files don't linger.
-    await deleteDocumentPreviewArtifacts(doc.id, namespace).catch(() => undefined);
-    await putDocumentPreviewBuffer(doc.id, rendered.bytes, namespace);
-  } finally {
-    if (workDir) {
-      await rm(workDir, { recursive: true, force: true }).catch(() => {});
-    }
+  const sourceBytes = await getDocumentBlob(doc.id, namespace);
+  let rendered;
+  if (doc.type === 'pdf') {
+    rendered = await renderPdfFirstPageToJpeg(sourceBytes, DOCUMENT_PREVIEW_WIDTH);
+  } else if (doc.type === 'epub') {
+    rendered = await renderEpubCoverToJpeg(sourceBytes, DOCUMENT_PREVIEW_WIDTH);
+  } else {
+    throw new Error(`Unsupported preview type: ${doc.type}`);
   }
+  // Hot path: overwrite current variant key directly to avoid prefix list/delete latency.
+  await putDocumentPreviewBuffer(doc.id, rendered.bytes, namespace);
 }
 
 function pendingResult(status: PreviewStatus, lastError: string | null): EnsureDocumentPreviewResult {