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

@@ -7,6 +7,7 @@ import kr.co.vividnext.sodalive.common.SodaException
 import kr.co.vividnext.sodalive.member.Member
 import org.springframework.security.core.annotation.AuthenticationPrincipal
 import org.springframework.web.bind.annotation.GetMapping
+import org.springframework.web.bind.annotation.PathVariable
 import org.springframework.web.bind.annotation.PostMapping
 import org.springframework.web.bind.annotation.RequestBody
 import org.springframework.web.bind.annotation.RequestMapping
@@ -60,4 +61,21 @@ class ChatRoomController(
             ApiResponse.ok(response)
         }
     }
+
+    /**
+     * 세션 상태 조회 API
+     * - 채팅방 참여 여부 검증
+     * - 외부 API로 세션 상태 조회 후 active면 true, 아니면 false 반환
+     */
+    @GetMapping("/{chatRoomId}/session")
+    fun getChatSessionStatus(
+        @AuthenticationPrincipal(expression = "#this == 'anonymousUser' ? null : member") member: Member?,
+        @PathVariable chatRoomId: Long
+    ) = run {
+        if (member == null) throw SodaException("로그인 정보를 확인해주세요.")
+        if (member.auth == null) throw SodaException("본인인증을 하셔야 합니다.")
+
+        val isActive = chatRoomService.isMyRoomSessionActive(member, chatRoomId)
+        ApiResponse.ok(isActive)
+    }
 }

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

@@ -34,18 +34,20 @@ data class ChatRoomListQueryDto(
 )
 
 /**
- * 외부 API 채팅 세션 응답 DTO
+ * 외부 API 채팅 세션 생성 응답 DTO
  */
-data class ExternalChatSessionResponse(
+data class ExternalChatSessionCreateResponse(
     val success: Boolean,
     val message: String?,
-    val data: ExternalChatSessionData?
+    val data: ExternalChatSessionCreateData?
 )
 
 /**
- * 외부 API 채팅 세션 데이터 DTO
+ * 외부 API 채팅 세션 생성 데이터 DTO
+ * 공통: sessionId, status
+ * 생성 전용: userId, characterId, character, createdAt
  */
-data class ExternalChatSessionData(
+data class ExternalChatSessionCreateData(
     val sessionId: String,
     val userId: String,
     val characterId: String,
@@ -54,6 +56,24 @@ data class ExternalChatSessionData(
     val createdAt: String
 )
 
+/**
+ * 외부 API 채팅 세션 조회 응답 DTO
+ */
+data class ExternalChatSessionGetResponse(
+    val success: Boolean,
+    val message: String?,
+    val data: ExternalChatSessionGetData?
+)
+
+/**
+ * 외부 API 채팅 세션 조회 데이터 DTO
+ * 세션 조회에서 사용하는 공통 필드만 포함
+ */
+data class ExternalChatSessionGetData(
+    val sessionId: String,
+    val status: String
+)
+
 /**
  * 외부 API 캐릭터 데이터 DTO
  */

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

@@ -8,7 +8,8 @@ import kr.co.vividnext.sodalive.chat.room.ParticipantType
 import kr.co.vividnext.sodalive.chat.room.dto.ChatRoomListItemDto
 import kr.co.vividnext.sodalive.chat.room.dto.ChatRoomListQueryDto
 import kr.co.vividnext.sodalive.chat.room.dto.CreateChatRoomResponse
-import kr.co.vividnext.sodalive.chat.room.dto.ExternalChatSessionResponse
+import kr.co.vividnext.sodalive.chat.room.dto.ExternalChatSessionCreateResponse
+import kr.co.vividnext.sodalive.chat.room.dto.ExternalChatSessionGetResponse
 import kr.co.vividnext.sodalive.chat.room.repository.CharacterChatMessageRepository
 import kr.co.vividnext.sodalive.chat.room.repository.CharacterChatParticipantRepository
 import kr.co.vividnext.sodalive.chat.room.repository.CharacterChatRoomRepository
@@ -150,7 +151,10 @@ class ChatRoomService(
 
             // 응답 파싱
             val objectMapper = ObjectMapper()
-            val apiResponse = objectMapper.readValue(response.body, ExternalChatSessionResponse::class.java)
+            val apiResponse = objectMapper.readValue(
+                response.body,
+                ExternalChatSessionCreateResponse::class.java
+            )
 
             // success가 false이면 throw
             if (!apiResponse.success) {
@@ -195,4 +199,55 @@ class ChatRoomService(
             )
         }
     }
+
+    @Transactional(readOnly = true)
+    fun isMyRoomSessionActive(member: Member, chatRoomId: Long): Boolean {
+        val room = chatRoomRepository.findById(chatRoomId).orElseThrow {
+            SodaException("채팅방을 찾을 수 없습니다.")
+        }
+        val participant = participantRepository.findByChatRoomAndMemberAndIsActiveTrue(room, member)
+        if (participant == null) {
+            throw SodaException("잘못된 접근입니다")
+        }
+        return fetchSessionActive(room.sessionId)
+    }
+
+    private fun fetchSessionActive(sessionId: String): Boolean {
+        try {
+            val factory = SimpleClientHttpRequestFactory()
+            factory.setConnectTimeout(20000) // 20초
+            factory.setReadTimeout(20000) // 20초
+
+            val restTemplate = RestTemplate(factory)
+
+            val headers = HttpHeaders()
+            headers.set("x-api-key", apiKey)
+
+            val httpEntity = HttpEntity(null, headers)
+
+            val response = restTemplate.exchange(
+                "$apiUrl/api/session/$sessionId",
+                HttpMethod.GET,
+                httpEntity,
+                String::class.java
+            )
+
+            val objectMapper = ObjectMapper()
+            val apiResponse = objectMapper.readValue(
+                response.body,
+                ExternalChatSessionGetResponse::class.java
+            )
+
+            // success가 false이면 throw
+            if (!apiResponse.success) {
+                throw SodaException("오류가 발생했습니다. 다시 시도해 주세요.")
+            }
+
+            val status = apiResponse.data?.status
+            return status == "active"
+        } catch (e: Exception) {
+            e.printStackTrace()
+            throw SodaException("오류가 발생했습니다. 다시 시도해 주세요.")
+        }
+    }
 }