fix: 채팅방 마지막 메시지 메타데이터 동기화

src/main/java/gg/agit/konect/domain/chat/repository/ChatRoomRepository.java

@@ -2,9 +2,11 @@
 
 import static gg.agit.konect.global.code.ApiResponseCode.NOT_FOUND_CHAT_ROOM;
 
+import java.time.LocalDateTime;
 import java.util.List;
 import java.util.Optional;
 
+import org.springframework.data.jpa.repository.Modifying;
 import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.Repository;
 import org.springframework.data.repository.query.Param;
@@ -19,6 +21,30 @@ public interface ChatRoomRepository extends Repository<ChatRoom, Integer> {
 
     ChatRoom save(ChatRoom chatRoom);
 
+    @Modifying(flushAutomatically = true)
+    @Query("""
+        UPDATE ChatRoom cr
+        SET cr.lastMessageContent = :content,
+            cr.lastMessageSentAt = :sentAt
+        WHERE cr.id = :roomId
+          AND NOT EXISTS (
+              SELECT 1
+              FROM ChatMessage cm
+              WHERE cm.chatRoom.id = :roomId
+                AND cm.id <> :messageId
+                AND (
+                    cm.createdAt > :sentAt
+                    OR (cm.createdAt = :sentAt AND cm.id > :messageId)
+                )
+          )
+        """)
+    int updateLastMessageIfLatest(
+        @Param("roomId") Integer roomId,
+        @Param("messageId") Integer messageId,
+        @Param("content") String content,
+        @Param("sentAt") LocalDateTime sentAt
+    );
+
     @Query("""
         SELECT DISTINCT cr
         FROM ChatRoom cr

src/main/java/gg/agit/konect/domain/chat/service/ChatService.java

@@ -746,7 +746,7 @@ private ChatMessageDetailResponse sendDirectMessage(
             senderMember.restoreDirectRoom();
         }
 
-        chatRoom.updateLastMessage(chatMessage.getContent(), chatMessage.getCreatedAt());
+        syncLastMessage(chatRoom, chatMessage);
         members.stream()
             .filter(member -> !member.getUserId().equals(userId))
             .filter(ChatRoomMember::hasLeft)
@@ -828,7 +828,7 @@ private ChatMessageDetailResponse sendClubMessageByRoomId(Integer roomId, Intege
         ensureRoomMember(room, sender, member.getCreatedAt());
 
         ChatMessage message = chatMessageRepository.save(ChatMessage.of(room, sender, content));
-        room.updateLastMessage(message.getContent(), message.getCreatedAt());
+        syncLastMessage(room, message);
         updateClubMessageLastReadAt(roomId, userId, message.getCreatedAt());
 
         List<ChatRoomMember> members = chatRoomMemberRepository.findByChatRoomId(roomId);
@@ -909,7 +909,7 @@ private ChatMessageDetailResponse sendGroupMessageByRoomId(Integer roomId, Integ
         }
 
         ChatMessage message = chatMessageRepository.save(ChatMessage.of(room, sender, content));
-        room.updateLastMessage(message.getContent(), message.getCreatedAt());
+        syncLastMessage(room, message);
         updateLastReadAt(roomId, userId, message.getCreatedAt());
 
         List<ChatRoomMember> members = chatRoomMemberRepository.findByChatRoomId(roomId);
@@ -1210,6 +1210,20 @@ private void publishAdminChatEventIfNeeded(boolean isSystemAdminRoom, User sende
         }
     }
 
+    private void syncLastMessage(ChatRoom room, ChatMessage message) {
+        // 채팅방 목록은 chat_room.last_message_*를 직접 조회하므로
+        // 동시 전송에서도 가장 최신 메시지만 메타데이터를 덮어쓰도록 DB 조건을 같이 건다.
+        int updated = chatRoomRepository.updateLastMessageIfLatest(
+            room.getId(),
+            message.getId(),
+            message.getContent(),
+            message.getCreatedAt()
+        );
+        if (updated > 0) {
+            room.updateLastMessage(message.getContent(), message.getCreatedAt());
+        }
+    }
+
     private ChatRoomMember getRoomMember(Integer roomId, Integer userId) {
         return chatRoomMemberRepository.findByChatRoomIdAndUserId(roomId, userId)
             .orElseThrow(() -> CustomException.of(FORBIDDEN_CHAT_ROOM_ACCESS));

src/main/java/gg/agit/konect/domain/user/service/UserService.java

@@ -131,12 +131,24 @@ private void sendWelcomeMessage(User newUser) {
             ChatMessage chatMessage = chatMessageRepository.save(
                 ChatMessage.of(chatRoom, operator, DEFAULT_WELCOME_MESSAGE)
             );
-            chatRoom.updateLastMessage(chatMessage.getContent(), chatMessage.getCreatedAt());
+            syncLastMessage(chatRoom, chatMessage);
         } catch (Exception e) {
             log.warn("회원가입 환영 메시지 전송 실패. userId={}", newUser.getId(), e);
         }
     }
 
+    private void syncLastMessage(ChatRoom chatRoom, ChatMessage chatMessage) {
+        int updated = chatRoomRepository.updateLastMessageIfLatest(
+            chatRoom.getId(),
+            chatMessage.getId(),
+            chatMessage.getContent(),
+            chatMessage.getCreatedAt()
+        );
+        if (updated > 0) {
+            chatRoom.updateLastMessage(chatMessage.getContent(), chatMessage.getCreatedAt());
+        }
+    }
+
     private UnRegisteredUser findUnregisteredUser(String email, String providerId, Provider provider) {
         if (StringUtils.hasText(providerId)) {
             if (unRegisteredUserRepository.existsByProviderIdAndProvider(providerId, provider)) {

src/main/resources/db/migration/V70__backfill_chat_room_last_message_metadata.sql

@@ -0,0 +1,24 @@
+-- 채팅방 목록/관리 쿼리는 chat_room.last_message_*를 직접 사용하므로
+-- 기존 메시지 이력이 있는 방도 최신 메시지 메타데이터를 다시 맞춰 준다.
+-- MAX(created_at)으로 최신 메시지를 고르고, 같은 시각이면 id로 타이브레이크한다.
+UPDATE chat_room cr
+LEFT JOIN (
+    SELECT
+        cm1.chat_room_id,
+        cm1.content,
+        cm1.created_at
+    FROM chat_message cm1
+    JOIN (
+        SELECT chat_room_id, MAX(created_at) AS max_created_at
+        FROM chat_message
+        GROUP BY chat_room_id
+    ) cm2 ON cm2.chat_room_id = cm1.chat_room_id AND cm2.max_created_at = cm1.created_at
+    WHERE cm1.id = (
+        SELECT MAX(id)
+        FROM chat_message
+        WHERE chat_room_id = cm1.chat_room_id
+          AND created_at = cm2.max_created_at
+    )
+) latest_msg ON latest_msg.chat_room_id = cr.id
+SET cr.last_message_content = latest_msg.content,
+    cr.last_message_sent_at = latest_msg.created_at;

src/test/java/gg/agit/konect/integration/domain/chat/ChatApiTest.java

@@ -718,6 +718,35 @@ void sendMessageSuccess() throws Exception {
                 .containsExactly("안녕하세요");
         }
 
+        @Test
+        @DisplayName("메시지를 전송하면 chat_room last message 메타데이터도 함께 갱신된다")
+        @Sql(
+            statements = CHAT_TEST_DATA_CLEANUP_SQL,
+            config = @SqlConfig(transactionMode = SqlConfig.TransactionMode.ISOLATED),
+            executionPhase = Sql.ExecutionPhase.AFTER_TEST_METHOD
+        )
+        void sendMessageUpdatesChatRoomLastMessageColumns() throws Exception {
+            // given
+            ChatRoom chatRoom = createDirectChatRoom(normalUser, targetUser);
+            mockLoginUser(normalUser.getId());
+
+            // when
+            performPost("/chats/rooms/" + chatRoom.getId() + "/messages", new ChatMessageSendRequest("메타데이터 확인"))
+                .andExpect(status().isOk());
+
+            // then
+            TestTransaction.flagForCommit();
+            TestTransaction.end();
+
+            transactionTemplate.execute(status -> {
+                clearPersistenceContext();
+                ChatRoom updatedRoom = chatRoomRepository.findById(chatRoom.getId()).orElseThrow();
+                assertThat(updatedRoom.getLastMessageContent()).isEqualTo("메타데이터 확인");
+                assertThat(updatedRoom.getLastMessageSentAt()).isNotNull();
+                return null;
+            });
+        }
+
         @Test
         @DisplayName("관리자가 문의방에 답변하면 실제 문의 사용자에게 알림을 보낸다")
         void adminReplySendsNotificationToInquiryUser() throws Exception {
@@ -910,6 +939,15 @@ void leaveDirectChatRoomAndShowOnlyNewMessages() throws Exception {
             performPost("/chats/rooms/" + chatRoom.getId() + "/messages", new ChatMessageSendRequest("다시 안녕"))
                 .andExpect(status().isOk());
 
+            transactionTemplate.execute(status -> {
+                clearPersistenceContext();
+                ChatRoomMember restoredMember = chatRoomMemberRepository
+                    .findByChatRoomIdAndUserId(chatRoom.getId(), normalUser.getId())
+                    .orElseThrow();
+                assertThat(restoredMember.hasLeft()).isFalse();
+                return null;
+            });
+
             mockLoginUser(normalUser.getId());
             performGet("/chats/rooms")
                 .andExpect(status().isOk())

src/test/java/gg/agit/konect/unit/domain/chat/service/ChatServiceTest.java

@@ -825,6 +825,9 @@ void sendMessageInDirectRoomSavesMessageAndSendsNotification() {
         given(chatRoomMemberRepository.findByChatRoomId(directRoom.getId()))
             .willReturn(List.of(senderMember, receiverMember));
         given(chatMessageRepository.save(any(ChatMessage.class))).willReturn(savedMessage);
+        given(chatRoomRepository.updateLastMessageIfLatest(
+            directRoom.getId(), savedMessage.getId(), savedMessage.getContent(), savedMessage.getCreatedAt()
+        )).willReturn(1);
         given(chatRoomMemberRepository.updateLastReadAtIfOlder(eq(directRoom.getId()), eq(senderId),
             any(LocalDateTime.class)))
             .willReturn(1);
@@ -843,6 +846,44 @@ void sendMessageInDirectRoomSavesMessageAndSendsNotification() {
             eq("hello"));
     }
 
+    @Test
+    @DisplayName("sendMessage는 이미 더 최신 메시지가 있으면 room 마지막 메시지 메타데이터를 덮어쓰지 않는다")
+    void sendMessageDoesNotOverwriteRoomMetadataWhenNewerMessageAlreadyExists() {
+        Integer senderId = 10;
+        Integer receiverId = 20;
+        User sender = createUser(senderId, "보낸이", UserRole.USER);
+        User receiver = createUser(receiverId, "받는이", UserRole.USER);
+        ChatRoom directRoom = createRoom(1, ChatType.DIRECT, LocalDateTime.of(2026, 4, 11, 10, 0));
+        ChatRoomMember senderMember = createRoomMember(directRoom, sender, false,
+            LocalDateTime.of(2026, 4, 11, 10, 0));
+        ChatRoomMember receiverMember = createRoomMember(directRoom, receiver, false,
+            LocalDateTime.of(2026, 4, 11, 10, 0));
+        ChatMessage savedMessage = createMessage(100, directRoom, sender, "older",
+            LocalDateTime.of(2026, 4, 11, 10, 1));
+
+        ReflectionTestUtils.setField(directRoom, "lastMessageContent", "newer");
+        ReflectionTestUtils.setField(directRoom, "lastMessageSentAt", LocalDateTime.of(2026, 4, 11, 10, 2));
+
+        given(chatRoomRepository.findById(directRoom.getId())).willReturn(Optional.of(directRoom));
+        given(userRepository.getById(senderId)).willReturn(sender);
+        given(chatRoomMemberRepository.findByChatRoomIdAndUserId(directRoom.getId(), senderId))
+            .willReturn(Optional.of(senderMember));
+        given(chatRoomMemberRepository.findByChatRoomId(directRoom.getId()))
+            .willReturn(List.of(senderMember, receiverMember));
+        given(chatMessageRepository.save(any(ChatMessage.class))).willReturn(savedMessage);
+        given(chatRoomRepository.updateLastMessageIfLatest(
+            directRoom.getId(), savedMessage.getId(), savedMessage.getContent(), savedMessage.getCreatedAt()
+        )).willReturn(0);
+        given(chatRoomMemberRepository.updateLastReadAtIfOlder(eq(directRoom.getId()), eq(senderId),
+            any(LocalDateTime.class)))
+            .willReturn(1);
+
+        chatService.sendMessage(senderId, directRoom.getId(), new ChatMessageSendRequest("older"));
+
+        assertThat(directRoom.getLastMessageContent()).isEqualTo("newer");
+        assertThat(directRoom.getLastMessageSentAt()).isEqualTo(LocalDateTime.of(2026, 4, 11, 10, 2));
+    }
+
     @Test
     @DisplayName("sendMessage는 group room에서 메시지를 저장하고 그룹 알림을 보낸다")
     void sendMessageInGroupRoomSavesMessageAndSendsGroupNotification() {
@@ -860,6 +901,9 @@ void sendMessageInGroupRoomSavesMessageAndSendsGroupNotification() {
         given(chatRoomMemberRepository.findByChatRoomIdAndUserId(groupRoom.getId(), senderId))
             .willReturn(Optional.of(senderMember));
         given(chatMessageRepository.save(any(ChatMessage.class))).willReturn(savedMessage);
+        given(chatRoomRepository.updateLastMessageIfLatest(
+            groupRoom.getId(), savedMessage.getId(), savedMessage.getContent(), savedMessage.getCreatedAt()
+        )).willReturn(1);
         given(chatRoomMemberRepository.updateLastReadAtIfOlder(eq(groupRoom.getId()), eq(senderId),
             any(LocalDateTime.class)))
             .willReturn(1);
@@ -926,6 +970,9 @@ void sendMessageInClubRoomSavesMessageAndSendsGroupNotification() {
         given(chatRoomMemberRepository.findByChatRoomIdAndUserId(clubRoom.getId(), senderId))
             .willReturn(Optional.of(senderRoomMember));
         given(chatMessageRepository.save(any(ChatMessage.class))).willReturn(savedMessage);
+        given(chatRoomRepository.updateLastMessageIfLatest(
+            clubRoom.getId(), savedMessage.getId(), savedMessage.getContent(), savedMessage.getCreatedAt()
+        )).willReturn(1);
         given(chatRoomMemberRepository.updateLastReadAtIfOlder(eq(clubRoom.getId()), eq(senderId),
             any(LocalDateTime.class)))
             .willReturn(1);
@@ -972,6 +1019,9 @@ void sendMessageAdminBypassesMembershipInSystemAdminRoom() {
         given(chatRoomMemberRepository.findByChatRoomId(systemAdminRoom.getId()))
             .willReturn(List.of(systemAdminMember, targetMember));
         given(chatMessageRepository.save(any(ChatMessage.class))).willReturn(savedMessage);
+        given(chatRoomRepository.updateLastMessageIfLatest(
+            systemAdminRoom.getId(), savedMessage.getId(), savedMessage.getContent(), savedMessage.getCreatedAt()
+        )).willReturn(1);
 
         // when
         ChatMessageDetailResponse response = chatService.sendMessage(adminId, systemAdminRoom.getId(),