test(frontend): normalize reveal guess fooled-player nullability

frontend/src/api/mappers.ts

@@ -131,10 +131,11 @@ function mapSessionDetail(payload: unknown): SessionDetailResponse {
       }),
       guesses: guessesRaw.map((guess, index) => {
         const record = asRecord(guess, `session_detail.reveal.guesses[${index}]`);
-        const fooledPlayerId = record.fooled_player_id;
-        if (fooledPlayerId !== null && !isNumber(fooledPlayerId)) {
+        const fooledPlayerIdRaw = record.fooled_player_id;
+        if (fooledPlayerIdRaw !== undefined && fooledPlayerIdRaw !== null && !isNumber(fooledPlayerIdRaw)) {
           throw new Error(`Invalid API contract: expected number|null at session_detail.reveal.guesses[${index}].fooled_player_id`);
         }
+        const fooledPlayerId = fooledPlayerIdRaw === undefined ? null : fooledPlayerIdRaw;
         const fooledPlayerNickname = record.fooled_player_nickname;
         if (fooledPlayerNickname !== undefined && !isString(fooledPlayerNickname)) {
           throw new Error(`Invalid API contract: expected string at session_detail.reveal.guesses[${index}].fooled_player_nickname`);

frontend/tests/angular-api-client.test.ts

@@ -283,6 +283,79 @@ describe('createAngularApiClient', () => {
     }
   });
 
+  it('normalizes omitted fooled_player_id to null in canonical reveal payload guesses', async () => {
+    const get = vi.fn<AngularHttpClientLike['get']>(async <T>(url: string) => {
+      if (url === '/lobby/sessions/ABCD12') {
+        return {
+          session: { code: 'ABCD12', status: 'reveal', host_id: 1, current_round: 1, players_count: 2 },
+          players: [
+            { id: 2, nickname: 'Maja', score: 10, is_connected: true },
+            { id: 3, nickname: 'Bo', score: 7, is_connected: true }
+          ],
+          round_question: {
+            id: 77,
+            round_number: 1,
+            prompt: 'Q?',
+            shown_at: '2026-03-01T18:00:00Z',
+            answers: [{ text: 'A' }, { text: 'B' }]
+          },
+          reveal: {
+            round_question_id: 77,
+            round_number: 1,
+            prompt: 'Q?',
+            correct_answer: 'A',
+            lies: [],
+            guesses: [
+              {
+                player_id: 3,
+                nickname: 'Bo',
+                selected_text: 'A',
+                is_correct: true,
+                created_at: '2026-03-01T18:00:15Z'
+              }
+            ]
+          },
+          phase_view_model: {
+            status: 'reveal',
+            round_number: 1,
+            players_count: 2,
+            constraints: {
+              min_players_to_start: 2,
+              max_players_mvp: 8,
+              min_players_reached: true,
+              max_players_allowed: true
+            },
+            host: {
+              can_start_round: false,
+              can_show_question: false,
+              can_mix_answers: false,
+              can_calculate_scores: false,
+              can_reveal_scoreboard: true,
+              can_start_next_round: false,
+              can_finish_game: false
+            },
+            player: {
+              can_join: true,
+              can_submit_lie: false,
+              can_submit_guess: false,
+              can_view_final_result: false
+            }
+          }
+        } as T;
+      }
+      throw { status: 404, error: { error: 'Not found' } };
+    });
+
+    const client = createAngularApiClient({ get, post: vi.fn() } as unknown as AngularHttpClientLike);
+    const session = await client.getSession('abcd12');
+
+    expect(session.ok).toBe(true);
+    if (session.ok) {
+      expect(session.data.reveal?.guesses[0].fooled_player_id).toBeNull();
+      expect(session.data.reveal?.guesses[0]).not.toHaveProperty('fooled_player_nickname');
+    }
+  });
+
   it('maps host/player gameplay endpoints through typed response mappers', async () => {
     const get = vi.fn<AngularHttpClientLike['get']>(async <T>(url: string) => {
       if (url === '/lobby/sessions/ABCD12/scoreboard') {