diff --git a/apps/api/src/routes/tools.ts b/apps/api/src/routes/tools.ts
index 7018c8d..854616d 100644
--- a/apps/api/src/routes/tools.ts
+++ b/apps/api/src/routes/tools.ts
@@ -4,8 +4,11 @@ import { Hono } from 'hono';
 import {
 	CardsCreateInputSchema,
 	CardsSearchInputSchema,
+	cardContentHash,
+	maskRegionCount,
 	newReview,
 	subIndexCount,
+	subIndexCountForCloze,
 } from '@cards/domain';
 
 import { getDb, type CardsDb } from '../db/connection.ts';
@@ -55,8 +58,39 @@ export function toolsRouter(deps: ToolsDeps = {}): Hono<{ Variables: AuthVars }>
 				if (!deck) return c.json({ error: 'deck_not_found' }, 404);
 				if (deck.userId !== userId) return c.json({ error: 'deck_not_owned' }, 403);
 
+				// Text-abhängige Sub-Index-Counts identisch zum REST-Pfad
+				// (cards.ts POST). Cloze ohne Cluster + Image-Occlusion
+				// ohne Mask-Regions werden 422.
+				let count: number;
+				if (parsed.data.type === 'cloze') {
+					count = subIndexCountForCloze(parsed.data.fields.text ?? '');
+					if (count === 0) {
+						return c.json(
+							{ error: 'invalid_input', issues: ['cloze.text contains no {{cN::…}} clusters'] },
+							422
+						);
+					}
+				} else if (parsed.data.type === 'image-occlusion') {
+					count = maskRegionCount(parsed.data.fields.mask_regions ?? '');
+					if (count === 0) {
+						return c.json(
+							{
+								error: 'invalid_input',
+								issues: ['image-occlusion.mask_regions must be JSON array with >=1 region'],
+							},
+							422
+						);
+					}
+				} else {
+					count = subIndexCount(parsed.data.type);
+				}
+
 				const cardId = ulid();
 				const now = new Date();
+				const contentHash = await cardContentHash({
+					type: parsed.data.type,
+					fields: parsed.data.fields,
+				});
 				const [row] = await dbOf().transaction(async (tx) => {
 					const [card] = await tx
 						.insert(cards)
@@ -67,14 +101,12 @@ export function toolsRouter(deps: ToolsDeps = {}): Hono<{ Variables: AuthVars }>
 							type: parsed.data.type,
 							fields: parsed.data.fields,
 							mediaRefs: parsed.data.media_refs ?? [],
+							contentHash,
 							createdAt: now,
 							updatedAt: now,
 						})
 						.returning();
-					const initial = Array.from(
-						{ length: subIndexCount(parsed.data.type) },
-						(_, i) => i
-					).map((subIndex) => {
+					const initial = Array.from({ length: count }, (_, i) => i).map((subIndex) => {
 						const r = newReview({ userId, cardId, subIndex, now });
 						return {
 							cardId: r.card_id,