fix: Server Expert AI JSON parsing and numeric type conversion

- Add response_format: { type: 'json_object' } for review mode to force JSON response
- Convert expectedDau and expectedConcurrent from string to number before API call
- Add enhanced KV session debugging with key names in logs

Fixes:
- AI returning plain text instead of JSON in review mode
- 400 error from recommend API due to string values in expected_users

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/server-agent.ts

@@ -25,17 +25,18 @@ export async function getServerSession(
 ): Promise<ServerSession | null> {
   try {
     const key = `${SESSION_KEY_PREFIX}${userId}`;
+    logger.info('세션 조회 시도', { userId, key });
     const data = await kv.get(key, 'json');
 
     if (!data) {
-      logger.info('세션 없음', { userId });
+      logger.info('세션 없음', { userId, key });
       return null;
     }
 
-    logger.info('세션 조회 성공', { userId, status: (data as ServerSession).status });
+    logger.info('세션 조회 성공', { userId, key, status: (data as ServerSession).status });
     return data as ServerSession;
   } catch (error) {
-    logger.error('세션 조회 실패', error as Error, { userId });
+    logger.error('세션 조회 실패', error as Error, { userId, key: `${SESSION_KEY_PREFIX}${userId}` });
     return null;
   }
 }
@@ -49,13 +50,16 @@ export async function saveServerSession(
     const key = `${SESSION_KEY_PREFIX}${userId}`;
     session.updatedAt = Date.now();
 
-    await kv.put(key, JSON.stringify(session), {
+    const sessionData = JSON.stringify(session);
+    logger.info('세션 저장 시도', { userId, key, status: session.status, dataLength: sessionData.length });
+
+    await kv.put(key, sessionData, {
       expirationTtl: SESSION_TTL,
     });
 
-    logger.info('세션 저장 성공', { userId, status: session.status });
+    logger.info('세션 저장 성공', { userId, key, status: session.status });
   } catch (error) {
-    logger.error('세션 저장 실패', error as Error, { userId });
+    logger.error('세션 저장 실패', error as Error, { userId, key: `${SESSION_KEY_PREFIX}${userId}` });
     throw error;
   }
 }
@@ -370,20 +374,31 @@ ${JSON.stringify(session.collectedInfo, null, 2)}
 
     // Loop to handle tool calls
     while (toolCallCount < MAX_TOOL_CALLS) {
+      // 검토 모드에서는 도구 없이 JSON 응답만 요청
+      const requestBody = isReviewMode
+        ? {
+            model: 'gpt-4o-mini',
+            messages,
+            response_format: { type: 'json_object' },
+            max_tokens: 500,
+            temperature: 0.5,
+          }
+        : {
+            model: 'gpt-4o-mini',
+            messages,
+            tools: serverExpertTools,
+            tool_choice: 'auto',
+            max_tokens: 800,
+            temperature: 0.7,
+          };
+
       const response = await fetch(getOpenAIUrl(env), {
         method: 'POST',
         headers: {
           'Content-Type': 'application/json',
           'Authorization': `Bearer ${env.OPENAI_API_KEY}`,
         },
-        body: JSON.stringify({
+        body: JSON.stringify(requestBody),
-          model: 'gpt-4o-mini',
-          messages,
-          tools: serverExpertTools,
-          tool_choice: 'auto',
-          max_tokens: 800,
-          temperature: 0.7,
-        }),
       });
 
       if (!response.ok) {
@@ -570,11 +585,14 @@ export async function processServerConsultation(
 
       // 동시접속자 우선 사용, 없으면 scale 기반 추론
       let expectedUsers = 10; // Default
-      if (session.collectedInfo.expectedConcurrent) {
+      const concurrent = Number(session.collectedInfo.expectedConcurrent) || 0;
-        expectedUsers = session.collectedInfo.expectedConcurrent;
+      const dau = Number(session.collectedInfo.expectedDau) || 0;
-      } else if (session.collectedInfo.expectedDau) {
+
+      if (concurrent > 0) {
+        expectedUsers = concurrent;
+      } else if (dau > 0) {
         // DAU가 있으면 10% 비율로 동시접속자 계산
-        expectedUsers = Math.ceil(session.collectedInfo.expectedDau * 0.1);
+        expectedUsers = Math.ceil(dau * 0.1);
       } else if (session.collectedInfo.scale) {
         expectedUsers = inferExpectedUsers(session.collectedInfo.scale);
       }