src/main/kotlin/kr/co/vividnext/sodalive/chat/room/controller/ChatRoomController.kt

@@ -91,12 +91,13 @@ class ChatRoomController(
     @GetMapping("/{chatRoomId}/enter")
     fun enterChatRoom(
         @AuthenticationPrincipal(expression = "#this == 'anonymousUser' ? null : member") member: Member?,
-        @PathVariable chatRoomId: Long
+        @PathVariable chatRoomId: Long,
+        @RequestParam(required = false) characterImageId: Long?
     ) = run {
         if (member == null) throw SodaException("로그인 정보를 확인해주세요.")
         if (member.auth == null) throw SodaException("본인인증을 하셔야 합니다.")
 
-        val response = chatRoomService.enterChatRoom(member, chatRoomId)
+        val response = chatRoomService.enterChatRoom(member, chatRoomId, characterImageId)
         ApiResponse.ok(response)
     }
 

src/main/kotlin/kr/co/vividnext/sodalive/chat/room/dto/ChatRoomDto.kt

@@ -182,7 +182,8 @@ data class ChatRoomEnterResponse(
     val messages: List<ChatMessageItemDto>,
     val hasMoreMessages: Boolean,
     val totalRemaining: Int,
-    val nextRechargeAtEpoch: Long?
+    val nextRechargeAtEpoch: Long?,
+    val bgImageUrl: String? = null
 )
 
 /**

src/main/kotlin/kr/co/vividnext/sodalive/chat/room/service/ChatRoomService.kt

@@ -298,7 +298,7 @@ class ChatRoomService(
     }
 
     @Transactional
-    fun enterChatRoom(member: Member, chatRoomId: Long): ChatRoomEnterResponse {
+    fun enterChatRoom(member: Member, chatRoomId: Long, characterImageId: Long? = null): ChatRoomEnterResponse {
         val room = chatRoomRepository.findById(chatRoomId).orElseThrow {
             SodaException("채팅방을 찾을 수 없습니다.")
         }
@@ -340,13 +340,45 @@ class ChatRoomService(
         // 입장 시 Lazy refill 적용 후 상태 반환
         val quotaStatus = chatQuotaService.applyRefillOnEnterAndGetStatus(member.id!!)
 
+        // 선택적 캐릭터 이미지 서명 URL 생성 처리
+        val signedUrl: String? = try {
+            if (characterImageId != null) {
+                val img = characterImageService.getById(characterImageId)
+                // 동일 캐릭터 소속 및 활성 검증
+                if (img.chatCharacter.id == character.id && img.isActive) {
+                    val owned =
+                        (img.imagePriceCan == 0L) || characterImageService.isOwnedImageByMember(img.id!!, member.id!!)
+                    if (owned) {
+                        val expiration = 5L * 60L * 1000L // 5분
+                        imageCloudFront.generateSignedURL(img.imagePath, expiration)
+                    } else {
+                        null
+                    }
+                } else {
+                    null
+                }
+            } else {
+                null
+            }
+        } catch (e: Exception) {
+            // 문제가 있어도 입장 자체는 가능해야 하므로 로그만 남기고 null 반환
+            log.warn(
+                "[chat] enter: signed url generation failed. roomId={}, imageId={}, reason={}",
+                room.id,
+                characterImageId,
+                e.message
+            )
+            null
+        }
+
         return ChatRoomEnterResponse(
             roomId = room.id!!,
             character = characterDto,
             messages = items,
             hasMoreMessages = hasMore,
             totalRemaining = quotaStatus.totalRemaining,
-            nextRechargeAtEpoch = quotaStatus.nextRechargeAtEpochMillis
+            nextRechargeAtEpoch = quotaStatus.nextRechargeAtEpochMillis,
+            bgImageUrl = signedUrl
         )
     }