diff --git a/src/App.jsx b/src/App.jsx
index 3beb3a1..c935f3b 100644
--- a/src/App.jsx
+++ b/src/App.jsx
@@ -606,7 +606,8 @@ export default function App() {
               {q.tw !== null && q.tw !== undefined && <> · {q.tw ? '→ motion' : '● location'}</>}
             </Hideable>
 
-            {nounForm(q.noun, q.cas) !== q.noun.w && (
+            {/* Pronoun questions have no noun at all, so this must be guarded. */}
+            {q.noun && nounForm(q.noun, q.cas) !== q.noun.w && (
               <div style={{...S.secondaryContext, marginTop:-10}}>
                 <button style={{...S.ruleBtn, marginLeft:0}} onClick={()=>setNounInfo(q)}>
                   ⓘ why {nounForm(q.noun, q.cas)}?
diff --git a/src/engine.test.js b/src/engine.test.js
index 09f82a7..02305ed 100644
--- a/src/engine.test.js
+++ b/src/engine.test.js
@@ -942,3 +942,58 @@ describe('no repeats within a round', () => {
     }
   });
 });
+
+// ── What the screens are allowed to assume ──────────────────
+// A question that is missing a field its screen dereferences does not fail
+// gracefully — React unmounts and the learner gets a blank page. That has now
+// happened twice, so the contract is written down here rather than left
+// implicit in the JSX.
+
+describe('question field contract', () => {
+  // The article / possessive / pronoun screen is shared by four types. Only
+  // pronoun questions have no noun, which is why every noun access on that
+  // screen has to be guarded.
+  const NEEDS_NOUN = ['article','chunk','poss','wechselContext','adjective','adjClass','verbSentence'];
+  const NO_NOUN    = ['pronoun','prep','contraction','verbCase'];
+
+  it('every question carries the fields its screen reads', () => {
+    for (const lv of LEVELS) {
+      for (const q of runSession(lv.id, 120)) {
+        expect([...NEEDS_NOUN, ...NO_NOUN], `unknown question type ${q.type}`).toContain(q.type);
+
+        if (NEEDS_NOUN.includes(q.type)) {
+          expect(q.noun, `${q.type} (level ${lv.id}) has no noun`).toBeTruthy();
+          expect(q.noun.g, `${q.type} noun has no gender`).toBeTruthy();
+          expect(q.noun.w).toBeTruthy();
+          expect(q.noun.en).toBeTruthy();
+        }
+        // every type needs something to show and something to grade
+        expect(q.ans, `${q.type} (level ${lv.id}) has no answer`).toBeTruthy();
+        if (q.sentence) expect(q.sentence).toContain('_____');
+      }
+    }
+  });
+
+  it('pronoun questions have a pronoun and deliberately no noun', () => {
+    for (const id of [14, 15, 16, 17]) {
+      for (const q of runSession(id, 120)) {
+        expect(q.pron, 'pronoun question has no pron').toBeTruthy();
+        expect(q.pron.nom).toBeTruthy();
+        expect(q.pron.en).toBeTruthy();
+        expect(q.pron.tag).toBeTruthy();
+        // this is the one the blank screen came from
+        expect(q.noun, 'pronoun questions must stay noun-less so the guard is real').toBeUndefined();
+      }
+    }
+  });
+
+  it('verbCase questions carry the verb, not a noun', () => {
+    for (const id of [30, 31]) {
+      for (const q of runSession(id, 120)) {
+        expect(q.verb?.de).toBeTruthy();
+        expect(q.verb?.en).toBeTruthy();
+        expect(q.noun).toBeUndefined();
+      }
+    }
+  });
+});