diff --git a/src/app/api/documents/blob/upload/finalize/route.ts b/src/app/api/documents/blob/upload/finalize/route.ts
index ea82ce4..8ab877f 100644
--- a/src/app/api/documents/blob/upload/finalize/route.ts
+++ b/src/app/api/documents/blob/upload/finalize/route.ts
@@ -10,6 +10,7 @@ import {
   headDocumentBlob,
   headTempDocumentBlob,
   isMissingBlobError,
+  isPreconditionFailed,
   isValidTempUploadToken,
   putTempDocumentFinalizeReceipt,
 } from '@/lib/server/documents/blobstore';
@@ -138,13 +139,18 @@ async function finalizeOne(input: {
     await headDocumentBlob(documentId, input.namespace);
   } catch (error) {
     if (!isMissingBlobError(error)) throw error;
-    await copyTempDocumentBlobToDocument(
-      input.upload.token,
-      input.userId,
-      documentId,
-      input.namespace,
-      temp.contentType,
-    );
+    try {
+      await copyTempDocumentBlobToDocument(
+        input.upload.token,
+        input.userId,
+        documentId,
+        input.namespace,
+        temp.contentType,
+        { ifNoneMatch: true },
+      );
+    } catch (copyError) {
+      if (!isPreconditionFailed(copyError)) throw copyError;
+    }
   }
 
   const canonicalHead = await headDocumentBlob(documentId, input.namespace);
@@ -194,14 +200,13 @@ export async function POST(req: NextRequest) {
       return NextResponse.json({ error: 'No valid uploads provided' }, { status: 400 });
     }
 
-    const stored: BaseDocument[] = [];
-    for (const upload of uploads) {
-      stored.push(await finalizeOne({
+    const stored = await Promise.all(
+      uploads.map((upload) => finalizeOne({
         upload,
         userId,
         namespace,
-      }));
-    }
+      })),
+    );
 
     return NextResponse.json({ stored });
   } catch (error) {
diff --git a/src/lib/server/documents/blobstore.ts b/src/lib/server/documents/blobstore.ts
index b8fa988..36316c9 100644
--- a/src/lib/server/documents/blobstore.ts
+++ b/src/lib/server/documents/blobstore.ts
@@ -73,6 +73,12 @@ export function isValidDocumentId(id: string): boolean {
   return DOCUMENT_ID_REGEX.test(id);
 }
 
+export function isPreconditionFailed(error: unknown): boolean {
+  if (!error || typeof error !== 'object') return false;
+  const maybe = error as { name?: string; $metadata?: { httpStatusCode?: number } };
+  return maybe.$metadata?.httpStatusCode === 412 || maybe.name === 'PreconditionFailed';
+}
+
 export function isValidTempUploadToken(token: string): boolean {
   return TEMP_UPLOAD_TOKEN_REGEX.test(token);
 }
@@ -455,6 +461,7 @@ export async function copyTempDocumentBlobToDocument(
   documentId: string,
   namespace: string | null,
   contentType: string,
+  options?: { ifNoneMatch?: boolean },
 ): Promise<void> {
   const cfg = getS3Config();
   const client = getS3ProxyClient();
@@ -466,6 +473,7 @@ export async function copyTempDocumentBlobToDocument(
       ContentType: contentType,
       MetadataDirective: 'REPLACE',
       ServerSideEncryption: 'AES256',
+      ...(options?.ifNoneMatch ? { IfNoneMatch: '*' } : {}),
     }),
   );
 }
diff --git a/src/lib/server/documents/register-upload.ts b/src/lib/server/documents/register-upload.ts
index 6fe134e..f63daea 100644
--- a/src/lib/server/documents/register-upload.ts
+++ b/src/lib/server/documents/register-upload.ts
@@ -27,6 +27,14 @@ export async function registerUploadedDocument(input: RegisterUploadedDocumentIn
   const reusableParsedPdf = input.type === 'pdf'
     ? await findReusableParsedPdfResult(input.documentId)
     : null;
+  const parsedJsonKey = reusableParsedPdf?.parsedJsonKey ?? null;
+  const parseState = input.type === 'pdf'
+    ? stringifyDocumentParseState(
+      reusableParsedPdf
+        ? { status: 'ready', progress: null, updatedAt: Date.now(), parserVersion: PDF_PARSER_VERSION }
+        : { status: 'pending', progress: null, updatedAt: Date.now(), parserVersion: PDF_PARSER_VERSION },
+    )
+    : null;
 
   await db
     .insert(documents)
@@ -38,14 +46,8 @@ export async function registerUploadedDocument(input: RegisterUploadedDocumentIn
       size: input.size,
       lastModified: input.lastModified,
       filePath: input.documentId,
-      parseState: input.type === 'pdf'
-        ? stringifyDocumentParseState(
-          reusableParsedPdf
-            ? { status: 'ready', progress: null, updatedAt: Date.now(), parserVersion: PDF_PARSER_VERSION }
-            : { status: 'pending', progress: null, updatedAt: Date.now(), parserVersion: PDF_PARSER_VERSION },
-        )
-        : null,
-      parsedJsonKey: reusableParsedPdf?.parsedJsonKey ?? null,
+      parseState,
+      parsedJsonKey,
     })
     .onConflictDoUpdate({
       target: [documents.id, documents.userId],
@@ -55,14 +57,8 @@ export async function registerUploadedDocument(input: RegisterUploadedDocumentIn
         size: input.size,
         lastModified: input.lastModified,
         filePath: input.documentId,
-        parseState: input.type === 'pdf'
-          ? stringifyDocumentParseState(
-            reusableParsedPdf
-              ? { status: 'ready', progress: null, updatedAt: Date.now(), parserVersion: PDF_PARSER_VERSION }
-              : { status: 'pending', progress: null, updatedAt: Date.now(), parserVersion: PDF_PARSER_VERSION },
-          )
-          : null,
-        parsedJsonKey: reusableParsedPdf?.parsedJsonKey ?? null,
+        parseState,
+        parsedJsonKey,
       },
     });