fix: explicit store update in evaluateAnswer, remove mutation through reference

apps/api/src/gameSessionStore/GameSessionStore.ts

@@ -7,5 +7,6 @@ export interface GameSessionStore {
     ttlMs: number,
   ): Promise<void>;
   get(sessionId: string): Promise<GameSessionData | null>;
+  update(sessionId: string, data: GameSessionData): Promise<void>;
   delete(sessionId: string): Promise<void>;
-}
+}

apps/api/src/gameSessionStore/InMemoryGameSessionStore.ts

@@ -24,6 +24,13 @@ export class InMemoryGameSessionStore implements GameSessionStore {
     return Promise.resolve(entry.data);
   }
 
+  update(sessionId: string, data: GameSessionData): Promise<void> {
+    const entry = this.sessions.get(sessionId);
+    if (!entry) return Promise.resolve();
+    this.sessions.set(sessionId, { data, expiresAt: entry.expiresAt });
+    return Promise.resolve();
+  }
+
   delete(sessionId: string): Promise<void> {
     this.sessions.delete(sessionId);
     return Promise.resolve();

apps/api/src/services/gameService.ts

@@ -96,10 +96,16 @@ export const evaluateAnswer = async (
     throw new NotFoundError(`Question not found: ${submission.questionId}`);
   }
 
-  session.answers.delete(submission.questionId);
+  const updatedAnswers = new Map(session.answers);
+  updatedAnswers.delete(submission.questionId);
 
-  if (session.answers.size === 0) {
+  if (updatedAnswers.size === 0) {
     await store.delete(submission.sessionId);
+  } else {
+    await store.update(submission.sessionId, {
+      answers: updatedAnswers,
+      userId: session.userId,
+    });
   }
 
   return {