diff --git a/frontend/src/lib/document/transcription/useTranscriptionBlocks.svelte.ts b/frontend/src/lib/document/transcription/useTranscriptionBlocks.svelte.ts
index 3a601f1a..da864ad8 100644
--- a/frontend/src/lib/document/transcription/useTranscriptionBlocks.svelte.ts
+++ b/frontend/src/lib/document/transcription/useTranscriptionBlocks.svelte.ts
@@ -119,7 +119,11 @@ export function createTranscriptionBlocks(
 		const res = await fetchImpl(`/api/documents/${documentId()}/transcription-blocks/review-all`, {
 			method: 'PUT'
 		});
-		if (!res.ok) return;
+		if (!res.ok) {
+			const body = await res.json().catch(() => ({}));
+			// Never render body.message — route through getErrorMessage() to prevent leaking backend internals
+			throw new Error((body as { code?: string })?.code ?? 'INTERNAL_ERROR');
+		}
 		const updated = (await res.json()) as { id: string; reviewed: boolean }[];
 		for (const b of updated) {
 			const existing = blocks.find((x) => x.id === b.id);