diff --git a/src/backend/apigateway-server/src/main/resources/application-local.yml b/src/backend/apigateway-server/src/main/resources/application-local.yml
index a3a332aa..262946f5 100644
--- a/src/backend/apigateway-server/src/main/resources/application-local.yml
+++ b/src/backend/apigateway-server/src/main/resources/application-local.yml
@@ -29,6 +29,14 @@ spring:
             - RemoveRequestHeader=Cookie
             - RewritePath=/users/(?<segment>.*), /$\{segment}
 
+        - id: chat-server-swagger
+          uri: lb://CHAT-SERVER
+          predicates:
+            - Path=/chats/swagger-ui/**, /chats/v3/api-docs/**, /chats/swagger-resources/**, /chats/webjars/**
+          filters:
+            - RemoveRequestHeader=Cookie
+            - RewritePath=/chats/(?<segment>.*), /$\{segment}
+
         - id: guild-server
           uri: lb://GUILD-SERVER
           predicates:
@@ -108,6 +116,15 @@ spring:
             - RemoveRequestHeader=Cookie
             - RewritePath=/signalings/(?<segment>.*), /$\{segment}
 
+        - id: chat-server
+          uri: lb://CHAT-SERVER
+          predicates:
+            - Path=/chats/**
+          filters:
+            - RemoveRequestHeader=Cookie
+            - RewritePath=/chats/(?<segment>.*), /$\{segment}
+            - AuthorizationHeaderFilter
+
       default-filters:
         - DedupeResponseHeader=Access-Control-Allow-Origin Access-Control-Allow-Credentials
       globalcors:
diff --git a/src/backend/apigateway-server/src/main/resources/application-prod.yml b/src/backend/apigateway-server/src/main/resources/application-prod.yml
index d700e371..73ae727f 100644
--- a/src/backend/apigateway-server/src/main/resources/application-prod.yml
+++ b/src/backend/apigateway-server/src/main/resources/application-prod.yml
@@ -29,6 +29,14 @@ spring:
             - RemoveRequestHeader=Cookie
             - RewritePath=/users/(?<segment>.*), /$\{segment}
 
+        - id: chat-server-swagger
+          uri: lb://CHAT-SERVER
+          predicates:
+            - Path=/guilds/swagger-ui/**, /guilds/v3/api-docs/**, /guilds/swagger-resources/**, /guilds/webjars/**
+          filters:
+            - RemoveRequestHeader=Cookie
+            - RewritePath=/guilds/(?<segment>.*), /$\{segment}
+
         - id: guild-server
           uri: lb://GUILD-SERVER
           predicates:
@@ -108,6 +116,15 @@ spring:
             - RemoveRequestHeader=Cookie
             - RewritePath=/signalings/(?<segment>.*), /$\{segment}
 
+        - id: chat-server
+          uri: lb://CHAT-SERVER
+          predicates:
+            - Path=/chats/**
+          filters:
+            - RemoveRequestHeader=Cookie
+            - RewritePath=/users/(?<segment>.*), /$\{segment}
+            - AuthorizationHeaderFilter
+
       default-filters:
         - DedupeResponseHeader=Access-Control-Allow-Origin Access-Control-Allow-Credentials
       globalcors:
diff --git a/src/backend/chat-server/build.gradle.kts b/src/backend/chat-server/build.gradle.kts
index 892e325d..c9f5380f 100644
--- a/src/backend/chat-server/build.gradle.kts
+++ b/src/backend/chat-server/build.gradle.kts
@@ -57,6 +57,9 @@ dependencies {
     implementation("org.springframework.kafka:spring-kafka")
 
     implementation("org.springframework.boot:spring-boot-starter-data-mongodb")
+
+    // Swagger
+    implementation("org.springdoc:springdoc-openapi-starter-webmvc-ui:2.7.0")
 }
 
 dependencyManagement {
diff --git a/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/controller/DirectController.kt b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/controller/DirectController.kt
index e7ff7cc6..96841d21 100644
--- a/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/controller/DirectController.kt
+++ b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/controller/DirectController.kt
@@ -1,5 +1,6 @@
 package com.asyncgate.chat_server.controller
 
+import com.asyncgate.chat_server.controller.docs.DirectControllerDocs
 import com.asyncgate.chat_server.domain.ReadStatus
 import com.asyncgate.chat_server.filter.JwtTokenProvider
 import com.asyncgate.chat_server.service.DirectService
@@ -20,7 +21,7 @@ import org.springframework.web.bind.annotation.ResponseBody
 class DirectController(
     private val directService: DirectService,
     private val jwtTokenProvider: JwtTokenProvider,
-) {
+) : DirectControllerDocs {
 
     @MessageMapping("/chat/direct/send-message")
     fun direct(@Payload directMessageCreate: DirectMessageCreate, message: Message<*>) {
@@ -36,7 +37,7 @@ class DirectController(
     }
 
     @MessageMapping("/chat/direct/typing")
-    fun typing(@Payload directTyping: DirectMessageTyping, message: Message<*>) {
+    fun typing(@Payload directTyping: DirectMessageTypingRequest, message: Message<*>) {
         val jwtToken = CustomSecurityContext.extractJwtTokenForStomp(message)
         val userId = jwtTokenProvider.extract(jwtToken)
         val directMessage = directTyping.toDomain(userId)
@@ -44,7 +45,7 @@ class DirectController(
     }
 
     @MessageMapping("/chat/direct/edit")
-    fun edit(@Payload directEdit: DirectMessageEdit, message: Message<*>) {
+    fun edit(@Payload directEdit: DirectMessageEditRequest, message: Message<*>) {
         val jwtToken = CustomSecurityContext.extractJwtTokenForStomp(message)
         val userId = jwtTokenProvider.extract(jwtToken)
         val directMessage = directEdit.toDomain(userId)
@@ -52,7 +53,7 @@ class DirectController(
     }
 
     @MessageMapping("/chat/direct/delete")
-    fun sendDeleteMessage(@Payload directDelete: DirectMessageDelete, message: Message<*>) {
+    fun sendDeleteMessage(@Payload directDelete: DirectMessageDeleteRequest, message: Message<*>) {
         val jwtToken = CustomSecurityContext.extractJwtTokenForStomp(message)
         val userId = jwtTokenProvider.extract(jwtToken)
         val directMessage = directDelete.toDomain(userId)
@@ -61,7 +62,7 @@ class DirectController(
 
     @ResponseBody
     @PostMapping("/chat/direct/file")
-    fun uploadFile(@ModelAttribute fileRequest: FileRequest, servletRequest: HttpServletRequest): SuccessResponse<FileUploadResponse> {
+    override fun uploadFile(@ModelAttribute fileRequest: FileRequest, servletRequest: HttpServletRequest): SuccessResponse<FileUploadResponse> {
         val jwtToken = CustomSecurityContext.extractJwtTokenForHttp(servletRequest)
         val userId = jwtTokenProvider.extract(jwtToken)
         val response = directService.upload(fileRequest, userId)
@@ -70,7 +71,7 @@ class DirectController(
 
     @ResponseBody
     @GetMapping("chat/direct")
-    fun readPaging(
+    override fun readPaging(
         @RequestParam("page", defaultValue = "0") page: Int,
         @RequestParam("size", defaultValue = "10") size: Int,
         @RequestParam("channel-id") channelId: String,
@@ -78,4 +79,17 @@ class DirectController(
         val response = directService.readPaging(channelId, page, size)
         return SuccessResponse.ok(response)
     }
+
+    // Just Docs
+    override fun directJustDocs(directMessageCreate: DirectMessageCreate, message: Message<*>) {
+    }
+
+    override fun typingJustDocs(directTyping: DirectMessageTypingRequest, message: Message<*>) {
+    }
+
+    override fun editJustDocs(directEdit: DirectMessageEditRequest, message: Message<*>) {
+    }
+
+    override fun sendDeleteMessageJustDocs(directDelete: DirectMessageDeleteRequest, message: Message<*>) {
+    }
 }
diff --git a/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/controller/DirectRequest.kt b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/controller/DirectRequest.kt
index a220b8d5..c68ba618 100644
--- a/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/controller/DirectRequest.kt
+++ b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/controller/DirectRequest.kt
@@ -4,21 +4,36 @@ import com.asyncgate.chat_server.domain.DirectMessage
 import com.asyncgate.chat_server.domain.DirectMessageType
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize
 import com.fasterxml.jackson.databind.annotation.JsonSerialize
+import io.swagger.v3.oas.annotations.media.Schema
 import org.springframework.web.multipart.MultipartFile
 import java.io.Serializable
 
+@Schema(description = "Direct 메시지 생성 요청 DTO")
 @JsonSerialize
 @JsonDeserialize
 data class DirectMessageCreate(
+    @Schema(description = "채널 ID, 다이렉트 채팅방 생성 후 id. DirectId와 같음", example = "channel-12345")
     val channelId: String,
+
+    @Schema(description = "프로필 이미지 URL", example = "http://example.com/image.png")
     val profileImage: String,
 
+    @Schema(description = "사용자 이름", example = "John Doe")
     val name: String,
+
+    @Schema(description = "메시지 내용", example = "Hello!")
     val content: String,
+
+    @Schema(description = "썸네일 URL", example = "http://example.com/thumbnail.png", nullable = true)
     val thumbnail: String? = null,
 
+    @Schema(description = "부모 메시지 ID", example = "msg-12345", nullable = true)
     val parentId: String? = null,
+
+    @Schema(description = "부모 메시지 작성자 이름", example = "Jane Doe", nullable = true)
     val parentName: String? = null,
+
+    @Schema(description = "부모 메시지 내용", example = "Previous message content", nullable = true)
     val parentContent: String? = null,
 ) : Serializable {
     fun toDomain(userId: String): DirectMessage {
@@ -37,12 +52,22 @@ data class DirectMessageCreate(
     }
 }
 
-data class DirectMessageEdit(
+@Schema(description = "Direct 메시지 수정 요청 DTO")
+@JsonSerialize
+@JsonDeserialize
+data class DirectMessageEditRequest(
+    @Schema(description = "메시지 ID", example = "msg-12345")
     val id: String,
+
+    @Schema(description = "채널 ID", example = "channel-12345")
     val channelId: String,
+
+    @Schema(description = "사용자 이름", example = "John Doe")
     val name: String,
+
+    @Schema(description = "메시지 내용", example = "Hello, edited!")
     val content: String,
-) {
+) : Serializable {
     fun toDomain(userId: String): DirectMessage {
         return DirectMessage(
             channelId = channelId,
@@ -54,10 +79,16 @@ data class DirectMessageEdit(
     }
 }
 
-data class DirectMessageDelete(
+@Schema(description = "Direct 메시지 삭제 요청 DTO")
+@JsonSerialize
+@JsonDeserialize
+data class DirectMessageDeleteRequest(
+    @Schema(description = "채널 ID", example = "channel-12345")
     val channelId: String,
+
+    @Schema(description = "메시지 ID", example = "msg-12345")
     val id: String,
-) {
+) : Serializable {
     fun toDomain(userId: String): DirectMessage {
         return DirectMessage(
             id = id,
@@ -68,11 +99,19 @@ data class DirectMessageDelete(
     }
 }
 
-data class DirectMessageTyping(
+@Schema(description = "Direct 메시지 타이핑 요청 DTO")
+@JsonSerialize
+@JsonDeserialize
+data class DirectMessageTypingRequest(
+    @Schema(description = "채널 ID", example = "channel-12345")
     val channelId: String,
+
+    @Schema(description = "타이핑 중 메시지 내용", example = "User is typing...")
     val content: String,
+
+    @Schema(description = "사용자 이름", example = "John Doe")
     val name: String,
-) {
+) : Serializable {
     fun toDomain(userId: String): DirectMessage {
         return DirectMessage(
             channelId = channelId,
@@ -83,16 +122,34 @@ data class DirectMessageTyping(
     }
 }
 
+@Schema(description = "파일 업로드 요청 DTO")
+@JsonSerialize
+@JsonDeserialize
 data class FileRequest(
+    @Schema(description = "업로드 이미지 파일", nullable = true)
     val image: MultipartFile? = null,
+
+    @Schema(description = "썸네일 이미지 파일", nullable = true)
     val thumbnail: MultipartFile? = null,
+
+    @Schema(description = "사용자 ID", example = "12345")
     val userId: Long,
+
+    @Schema(description = "사용자 이름", example = "John Doe")
     val name: String,
+
+    @Schema(description = "메시지 내용", example = "파일 메시지", nullable = true)
     val content: String? = null,
+
+    @Schema(description = "프로필 이미지 URL", example = "http://example.com/profile.png")
     val profileImage: String,
+
+    @Schema(description = "채널 ID", example = "channel-12345")
     val channelId: String,
+
+    @Schema(description = "메시지 타입", example = "FILE")
     val fileType: DirectMessageType,
-) {
+) : Serializable {
     fun toDomain(userId: String, type: DirectMessageType): DirectMessage {
         return DirectMessage(
             userId = userId,
diff --git a/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/controller/docs/DirectControllerDocs.kt b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/controller/docs/DirectControllerDocs.kt
new file mode 100644
index 00000000..912fd93d
--- /dev/null
+++ b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/controller/docs/DirectControllerDocs.kt
@@ -0,0 +1,165 @@
+package com.asyncgate.chat_server.controller.docs
+
+import com.asyncgate.chat_server.controller.DirectMessageCreate
+import com.asyncgate.chat_server.controller.DirectMessageDeleteRequest
+import com.asyncgate.chat_server.controller.DirectMessageEditRequest
+import com.asyncgate.chat_server.controller.DirectMessageTypingRequest
+import com.asyncgate.chat_server.controller.DirectPagingResponse
+import com.asyncgate.chat_server.controller.FileRequest
+import com.asyncgate.chat_server.controller.FileUploadResponse
+import com.asyncgate.chat_server.support.response.SuccessResponse
+import io.swagger.v3.oas.annotations.Operation
+import io.swagger.v3.oas.annotations.Parameter
+import io.swagger.v3.oas.annotations.media.Content
+import io.swagger.v3.oas.annotations.media.Schema
+import io.swagger.v3.oas.annotations.parameters.RequestBody
+import io.swagger.v3.oas.annotations.security.SecurityRequirement
+import io.swagger.v3.oas.annotations.tags.Tag
+import jakarta.servlet.http.HttpServletRequest
+import org.springframework.messaging.Message
+import org.springframework.messaging.handler.annotation.Payload
+import org.springframework.web.bind.annotation.GetMapping
+import org.springframework.web.bind.annotation.ModelAttribute
+import org.springframework.web.bind.annotation.PostMapping
+import org.springframework.web.bind.annotation.PutMapping
+import org.springframework.web.bind.annotation.RequestParam
+
+@Tag(name = "Direct Message API", description = "Direct 메시지 관련 API (WebSocket 기반)")
+@SecurityRequirement(name = "JWT TOKEN")
+interface DirectControllerDocs {
+
+    @Operation(
+        summary = "Direct 메시지 전송 (WebSocket)",
+        description = """
+            WebSocket을 통해 Direct 메시지를 전송합니다.  
+            **STOMP Destination:** `/chat/direct/send-message`  
+            
+            **Example JSON:**
+            ```json
+            {
+                "channelId": "channel-12345",
+                "profileImage": "http://example.com/image.png",
+                "name": "John Doe",
+                "content": "Hello!",
+                "thumbnail": "http://example.com/thumbnail.png"
+            }
+            ```
+        """
+    )
+    @PutMapping("/chat/direct/send-message")
+    fun directJustDocs(
+        @Parameter(description = "Direct 메시지 생성 DTO", required = true)
+        @Payload
+        directMessageCreate: DirectMessageCreate,
+        message: Message<*>,
+    )
+
+    @Operation(
+        summary = "Direct 메시지 타이핑 (WebSocket)",
+        description = """
+            사용자의 타이핑 상태를 WebSocket으로 전송합니다.  
+            **STOMP Destination:** `/chat/direct/typing`
+            
+            **Example JSON:**
+            ```json
+            {
+                "channelId": "channel-12345",
+                "name": "John Doe",
+                "content": "Typing..."
+            }
+            ```
+        """
+    )
+    @PutMapping("/chat/direct/typing")
+    fun typingJustDocs(
+        @Parameter(description = "타이핑 상태 DTO", required = true)
+        @Payload
+        directTyping: DirectMessageTypingRequest,
+        message: Message<*>,
+    )
+
+    @Operation(
+        summary = "Direct 메시지 수정 (WebSocket)",
+        description = """
+            WebSocket을 통해 Direct 메시지를 수정합니다.  
+            **STOMP Destination:** `/chat/direct/edit`
+            
+            **Example JSON:**
+            ```json
+            {
+                "id": "msg-12345",
+                "channelId": "channel-12345",
+                "name": "John Doe",
+                "content": "Edited message"
+            }
+            ```
+        """
+    )
+    @PutMapping("/chat/direct/edit")
+    fun editJustDocs(
+        @Parameter(description = "메시지 수정 DTO", required = true)
+        @Payload
+        directEdit: DirectMessageEditRequest,
+        message: Message<*>,
+    )
+
+    @Operation(
+        summary = "Direct 메시지 삭제 (WebSocket)",
+        description = """
+            WebSocket을 통해 Direct 메시지를 삭제합니다.  
+            **STOMP Destination:** `/chat/direct/delete`
+            
+            **Example JSON:**
+            ```json
+            {
+                "channelId": "channel-12345",
+                "id": "msg-67890"
+            }
+            ```
+        """
+    )
+    @PutMapping("/chat/direct/delete")
+    fun sendDeleteMessageJustDocs(
+        @Parameter(description = "메시지 삭제 DTO", required = true)
+        @Payload
+        directDelete: DirectMessageDeleteRequest,
+        message: Message<*>,
+    )
+
+    @Operation(
+        summary = "Direct 파일 업로드 (HTTP)",
+        description = "HTTP를 통해 파일을 업로드하고 Direct 메시지를 전송합니다.",
+        requestBody = RequestBody(
+            content = [
+                Content(
+                    mediaType = "multipart/form-data",
+                    schema = Schema(implementation = FileRequest::class)
+                )
+            ]
+        )
+    )
+    @PostMapping("/chat/direct/file")
+    fun uploadFile(
+        @Parameter(description = "파일 업로드 DTO", required = true)
+        @ModelAttribute
+        fileRequest: FileRequest,
+        servletRequest: HttpServletRequest,
+    ): SuccessResponse<FileUploadResponse>
+
+    @Operation(
+        summary = "Direct 메시지 페이징 조회 (HTTP)",
+        description = "채널에 속한 Direct 메시지를 페이징하여 조회합니다."
+    )
+    @GetMapping("/chat/direct")
+    fun readPaging(
+        @Parameter(description = "페이지 번호", example = "0")
+        @RequestParam("page", defaultValue = "0")
+        page: Int,
+        @Parameter(description = "페이지 크기", example = "10")
+        @RequestParam("size", defaultValue = "10")
+        size: Int,
+        @Parameter(description = "채널 ID", example = "channel-12345")
+        @RequestParam("channel-id")
+        channelId: String,
+    ): SuccessResponse<DirectPagingResponse>
+}
diff --git a/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/filter/StompInterceptor.kt b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/filter/StompInterceptor.kt
index 907d1d0a..6ea7cc6e 100644
--- a/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/filter/StompInterceptor.kt
+++ b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/filter/StompInterceptor.kt
@@ -1,5 +1,7 @@
 package com.asyncgate.chat_server.filter
 
+import com.asyncgate.chat_server.exception.ChatServerException
+import com.asyncgate.chat_server.exception.FailType
 import org.slf4j.Logger
 import org.slf4j.LoggerFactory
 import org.springframework.http.HttpStatus
@@ -8,6 +10,7 @@ import org.springframework.messaging.MessageChannel
 import org.springframework.messaging.simp.stomp.StompCommand
 import org.springframework.messaging.simp.stomp.StompHeaderAccessor
 import org.springframework.messaging.support.ChannelInterceptor
+import org.springframework.messaging.support.MessageBuilder
 import org.springframework.stereotype.Component
 import org.springframework.web.server.ResponseStatusException
 
@@ -44,11 +47,15 @@ class FilterChannelInterceptor(
                 log.error("🚨 [STOMP] Access Token is missing or improperly formatted!")
                 throw ResponseStatusException(HttpStatus.UNAUTHORIZED, "Access token is missing")
             }
-            if (!jwtTokenProvider.validate(jwtToken)) {
-                log.error("🚨 [STOMP] Access Token validation failed!")
-                throw ResponseStatusException(HttpStatus.UNAUTHORIZED)
+            try {
+                if (!jwtTokenProvider.validate(jwtToken)) {
+                    log.error("🚨 [STOMP] Access Token validation failed!")
+                    throw ResponseStatusException(HttpStatus.UNAUTHORIZED)
+                }
+                log.info("✅ [STOMP] CONNECT 요청 처리 완료")
+            } catch (e: ChatServerException) {
+                createErrorMessage(e.failType)
             }
-            log.info("✅ [STOMP] CONNECT 요청 처리 완료")
         }
         return message
     }
@@ -101,6 +108,18 @@ class FilterChannelInterceptor(
         // 시그널링 서버에 전달 (주석)
         // messageSender.signaling(stateTopic, stateRequest)
     }
+
+    /**
+     * STOMP ERROR 프레임 생성 메서드
+     */
+    private fun createErrorMessage(failType: FailType): Message<*> {
+        val errorAccessor = StompHeaderAccessor.create(StompCommand.ERROR)
+        errorAccessor.messageHeaders[StompHeaderAccessor.STOMP_MESSAGE_HEADER] = failType.message
+        errorAccessor.messageHeaders["errorCode"] = failType.errorCode
+        errorAccessor.messageHeaders["status"] = failType.status.value()
+
+        return MessageBuilder.createMessage(ByteArray(0), errorAccessor.messageHeaders)
+    }
 }
 
 data class LoginSessionRequest(
diff --git a/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/filter/WebSocketHandshakeInterceptor.kt b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/filter/WebSocketHandshakeInterceptor.kt
index 855ab606..b184669c 100644
--- a/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/filter/WebSocketHandshakeInterceptor.kt
+++ b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/filter/WebSocketHandshakeInterceptor.kt
@@ -1,5 +1,6 @@
 package com.asyncgate.chat_server.filter
 
+import com.asyncgate.chat_server.exception.ChatServerException
 import org.slf4j.Logger
 import org.slf4j.LoggerFactory
 import org.springframework.http.HttpStatus
@@ -60,13 +61,26 @@ class WebSocketHandshakeInterceptor(
         }
         val (_, jwtToken) = pair
 
-        if (!jwtTokenProvider.validate(jwtToken)) {
-            log.info("❌ WebSocket Handshake 실패: 유효하지 않은 JWT 토큰")
-            response.setStatusCode(HttpStatus.UNAUTHORIZED)
+        try {
+            if (!jwtTokenProvider.validate(jwtToken)) {
+                log.info("❌ WebSocket Handshake 실패: 유효하지 않은 JWT 토큰")
+                response.setStatusCode(HttpStatus.UNAUTHORIZED)
+                response.headers["WWW-Authenticate"] =
+                    "Bearer error=\"invalid_token\", error_description=\"invalid JWT token\""
+                return false
+            }
+        } catch (e: ChatServerException) {
+            log.info("❌ WebSocket Handshake 실패: {}", e.failType.message)
+            val message = e.failType.message
+            val status = e.failType.status
+
+            response.setStatusCode(status)
             response.headers["WWW-Authenticate"] =
-                "Bearer error=\"invalid_token\", error_description=\"invalid JWT token\""
+                "Bearer error=\"invalid_token\", error_description=\""
+
             return false
         }
+
         val userId = jwtTokenProvider.extract(jwtToken)
         log.info("✅ WebSocket Handshake 성공 - userId: $userId")
 
diff --git a/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/repository/DirectMessageMongoRepository.kt b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/repository/DirectMessageMongoRepository.kt
index 087d4c5d..4194b6d1 100644
--- a/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/repository/DirectMessageMongoRepository.kt
+++ b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/repository/DirectMessageMongoRepository.kt
@@ -10,6 +10,6 @@ interface DirectMessageMongoRepository : MongoRepository<DirectMessageEntity, St
     @Query("{ '_id': ?0, 'isDeleted': false }")
     fun findActiveById(id: String): DirectMessageEntity?
 
-    @Query("{ 'channelId': ?0, 'isDeleted': false }")
+    @Query(value = "{ 'channelId': ?0, 'isDeleted': false }", sort = "{ 'createdAt': -1 }")
     fun findByChannelId(channelId: String, pageable: Pageable): Page<DirectMessageEntity>
 }
diff --git a/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/repository/DirectMessageRepository.kt b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/repository/DirectMessageRepository.kt
index 7356223b..5989e33c 100644
--- a/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/repository/DirectMessageRepository.kt
+++ b/src/backend/chat-server/src/main/kotlin/com/asyncgate/chat_server/repository/DirectMessageRepository.kt
@@ -8,6 +8,7 @@ import com.asyncgate.chat_server.support.utility.toDomain
 import com.asyncgate.chat_server.support.utility.toEntity
 import org.springframework.data.domain.Page
 import org.springframework.data.domain.PageImpl
+import org.springframework.data.domain.Sort
 import org.springframework.stereotype.Repository
 
 interface DirectMessageRepository {
@@ -42,7 +43,7 @@ class DirectMessageRepositoryImpl(
     }
 
     override fun findByChannelId(channelId: String, page: Int, size: Int): Page<DirectMessage> {
-        val pageable = org.springframework.data.domain.PageRequest.of(page, size)
+        val pageable = org.springframework.data.domain.PageRequest.of(page, size, Sort.by(Sort.Direction.DESC, "createdAt"))
         val data = directMessageMongoRepository.findByChannelId(channelId, pageable)
         val content = data.map { it.toDomain() }.toList()
         return PageImpl(content, pageable, data.totalElements)
diff --git a/src/backend/chat-server/src/main/resources/application-local.yml b/src/backend/chat-server/src/main/resources/application-local.yml
index e03ba8a7..da453f99 100644
--- a/src/backend/chat-server/src/main/resources/application-local.yml
+++ b/src/backend/chat-server/src/main/resources/application-local.yml
@@ -47,3 +47,14 @@ management:
 logging:
   level:
     com.asyncgate.chat_server: DEBUG
+    
+springdoc:
+  api-docs:
+    path: /v3/api-docs
+  swagger-ui:
+    path: /swagger-ui.html
+    config-url: /chats/v3/api-docs/swagger-config
+    url: /chats/v3/api-docs
+    operationsSorter: method
+    tagsSorter: alpha
+    tryItOutEnabled: true
diff --git a/src/backend/chat-server/src/main/resources/application-prod.yml b/src/backend/chat-server/src/main/resources/application-prod.yml
index e03ba8a7..a0a5a59c 100644
--- a/src/backend/chat-server/src/main/resources/application-prod.yml
+++ b/src/backend/chat-server/src/main/resources/application-prod.yml
@@ -47,3 +47,14 @@ management:
 logging:
   level:
     com.asyncgate.chat_server: DEBUG
+
+springdoc:
+  api-docs:
+    path: /v3/api-docs
+  swagger-ui:
+    path: /swagger-ui.html
+    config-url: /chats/v3/api-docs/swagger-config
+    url: /chats/v3/api-docs
+    operationsSorter: method
+    tagsSorter: alpha
+    tryItOutEnabled: true