diff --git a/src/chat_tui/app.py b/src/chat_tui/app.py
index 993988b..9f2bbeb 100644
--- a/src/chat_tui/app.py
+++ b/src/chat_tui/app.py
@@ -116,17 +116,20 @@ class ChatApp(App[None]):
         self.messages.extend((user_message, agent_message))
 
         conversation = self.query_one("#conversation", VerticalScroll)
-        self._mount_message(conversation, user_message, "user-message")
-        self._mount_message(conversation, agent_message, "response-message")
+        self._mount_message(conversation, user_message)
+        self._mount_message(conversation, agent_message)
         conversation.scroll_end(animate=False)
 
     @staticmethod
     def _mount_message(
         conversation: VerticalScroll,
         message: ChatMessage,
-        style_class: str,
     ) -> None:
-        """메시지 역할을 라벨과 호환 가능한 구조적 스타일로 변환한다."""
+        """메시지 역할에서 라벨과 구조적 스타일을 일관되게 파생한다."""
+        style_class = {
+            MessageRole.USER: "user-message",
+            MessageRole.AGENT: "response-message",
+        }[message.role]
         text = f"{message.role.label}: {message.content}"
         conversation.mount(
             Label(text, classes=f"chat-message {style_class} {message.role.value}-role")
diff --git a/tests/test_app.py b/tests/test_app.py
index 6394c20..2bc2a3b 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -1,7 +1,7 @@
 import unittest
 from unittest.mock import patch
 
-from textual.widgets import Input, Label
+from textual.widgets import Input
 
 from chat_tui.app import (
     RESPONSE_MESSAGES,
@@ -78,13 +78,46 @@ class ChatAppTest(unittest.IsolatedAsyncioTestCase):
                     labels[1].classes,
                     frozenset({"chat-message", "response-message", "agent-role"}),
                 )
-                self.assertIn("사용자:", str(labels[0].renderable))
-                self.assertIn("에이전트:", str(labels[1].renderable))
+                self.assertEqual(
+                    str(labels[0].renderable),
+                    "사용자: 역할 확인",
+                )
+                self.assertEqual(
+                    str(labels[1].renderable),
+                    f"에이전트: {RESPONSE_MESSAGES[0]}",
+                )
                 self.assertIn("border-left", app.CSS)
                 self.assertIn("border-right", app.CSS)
                 self.assertIn("align: left middle", app.CSS)
                 self.assertIn("align: right middle", app.CSS)
 
+    async def test_rendering_styles_are_derived_from_message_roles(self) -> None:
+        app = ChatApp()
+        async with app.run_test() as pilot:
+            conversation = app.query_one("#conversation")
+            app._mount_message(
+                conversation,
+                ChatMessage(MessageRole.USER, "사용자 본문"),
+            )
+            app._mount_message(
+                conversation,
+                ChatMessage(MessageRole.AGENT, "에이전트 본문"),
+            )
+            await pilot.pause()
+
+            labels = list(app.query("#conversation Label"))
+            self.assertEqual(len(labels), 2)
+            self.assertEqual(
+                labels[0].classes,
+                frozenset({"chat-message", "user-message", "user-role"}),
+            )
+            self.assertEqual(
+                labels[1].classes,
+                frozenset({"chat-message", "response-message", "agent-role"}),
+            )
+            self.assertEqual(str(labels[0].renderable), "사용자: 사용자 본문")
+            self.assertEqual(str(labels[1].renderable), "에이전트: 에이전트 본문")
+
     async def test_response_selection_uses_standard_random_choice(self) -> None:
         app = ChatApp()
         with patch(
@@ -112,6 +145,7 @@ class ChatAppTest(unittest.IsolatedAsyncioTestCase):
                 self.assertEqual(app.selected_responses, [])
                 self.assertEqual(app.messages, [])
                 self.assertEqual(len(app.query("#conversation Label")), 0)
+                self.assertEqual(input_widget.value, "")
                 choice_mock.assert_not_called()
 
     async def test_empty_input_is_not_added(self) -> None: