diff --git a/docker-compose.prod.yml b/docker-compose.prod.yml
index 7d11d99..ec252d4 100644
--- a/docker-compose.prod.yml
+++ b/docker-compose.prod.yml
@@ -84,6 +84,36 @@ services:
     networks:
       - logit-network
 
+  # Logit MCP Server
+  logit-mcp:
+    build:
+      context: ../logit-mcp
+      dockerfile: Dockerfile
+    container_name: logit-mcp
+    restart: unless-stopped
+    expose:
+      - "8001"
+    env_file:
+      - ../logit-mcp/.env
+    environment:
+      - POSTGRES_SERVER=postgres
+      - POSTGRES_PORT=5432
+      - QDRANT_HOST=qdrant
+      - QDRANT_PORT=6333
+    depends_on:
+      postgres:
+        condition: service_healthy
+      qdrant:
+        condition: service_healthy
+    healthcheck:
+      test: ["CMD-SHELL", "curl -f http://localhost:8001/health || exit 1"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+      start_period: 15s
+    networks:
+      - logit-network
+
   # PostgreSQL Database
   postgres:
     image: postgres:16-alpine
diff --git a/scripts/deploy.sh b/scripts/deploy.sh
index 5e5fcb8..097cb04 100755
--- a/scripts/deploy.sh
+++ b/scripts/deploy.sh
@@ -79,20 +79,41 @@ update_caddyfile() {
 # Active upstream: app-${target}
 
 {\$DOMAIN:api.logit.ai.kr} {
-    # Reverse proxy to active app
-    reverse_proxy app-${target}:8000
+    reverse_proxy app-${target}:8000 {
+        health_uri      /health
+        health_interval 10s
+        health_timeout  5s
+    }
+
+    encode gzip
+
+    header {
+        X-Content-Type-Options nosniff
+        X-Frame-Options DENY
+        Referrer-Policy strict-origin-when-cross-origin
+    }
+
+    log {
+        output stdout
+        format console
+    }
+}
+
+mcp.logit.ai.kr {
+    reverse_proxy logit-mcp:8001 {
+        health_uri      /health
+        health_interval 10s
+        health_timeout  5s
+    }
 
-    # Enable compression
     encode gzip
 
-    # Security headers
     header {
         X-Content-Type-Options nosniff
         X-Frame-Options DENY
         Referrer-Policy strict-origin-when-cross-origin
     }
 
-    # Logging
     log {
         output stdout
         format console
diff --git a/src/auth/service.py b/src/auth/service.py
index 0af4cfc..e123749 100644
--- a/src/auth/service.py
+++ b/src/auth/service.py
@@ -131,16 +131,13 @@ async def _find_or_create_user(
     if existing_user:
         return existing_user, False
 
-    # 2) 동일 email이 다른 provider로 이미 가입되어 있는지 확인
+    # 2) 동일 email로 이미 가입된 사용자가 있으면 기존 계정으로 로그인
     email_user = await user_service.get_user_by_email(
         session=session, email=email
     )
 
     if email_user:
-        raise OAuthError(
-            f"This email is already registered with {email_user.oauth_provider.value}. "
-            f"Please sign in with {email_user.oauth_provider.value}."
-        )
+        return email_user, False
 
     try:
         new_user = await create_oauth_user(
@@ -275,12 +272,20 @@ async def _verify_google_id_token(id_token: str) -> dict:
     kid = unverified_header.get("kid")
     signing_key = await _find_jwks_key(kid, _get_google_jwks, "Google")
 
+    allowed_audiences = [
+        aud for aud in [
+            settings.GOOGLE_CLIENT_ID,
+            settings.GOOGLE_IOS_CLIENT_ID,
+            settings.GOOGLE_ANDROID_CLIENT_ID,
+        ] if aud
+    ]
+
     try:
         decoded = jwt.decode(
             id_token,
             signing_key.key,
             algorithms=["RS256"],
-            audience=settings.GOOGLE_CLIENT_ID,
+            audience=allowed_audiences,
             issuer=["https://accounts.google.com", "accounts.google.com"],
         )
     except jwt.PyJWTError as e:
@@ -318,7 +323,7 @@ async def google_mobile_auth_flow(id_token: str, session: AsyncSession) -> dict:
 
 
 async def _verify_apple_id_token(
-    id_token: str, platform: str, nonce: str | None = None
+    id_token: str, nonce: str | None = None,
 ) -> dict:
     """
     Apple id_token을 비동기 JWKS로 검증하고 디코딩된 페이로드를 반환합니다.
@@ -330,16 +335,16 @@ async def _verify_apple_id_token(
 
     kid = unverified_header.get("kid")
     signing_key = await _find_jwks_key(kid, _get_apple_jwks, "Apple")
-    audience = settings.APPLE_CLIENT_ID
-    if platform == "app":
-        audience = audience[:-3]
+    allowed_audiences = [settings.APPLE_CLIENT_ID]
+    if settings.APPLE_CLIENT_ID:
+        allowed_audiences.append(settings.APPLE_CLIENT_ID[:-3])  # bundle id (앱용)
 
     try:
         decoded = jwt.decode(
             id_token,
             signing_key.key,
             algorithms=["RS256"],
-            audience=audience,
+            audience=allowed_audiences,
             issuer="https://appleid.apple.com",
         )
     except jwt.PyJWTError as e:
@@ -416,7 +421,7 @@ async def apple_oauth_flow(
         if not id_token:
             raise OAuthError("No id_token in response from Apple")
 
-        decoded = await _verify_apple_id_token(id_token, "web", nonce=nonce)
+        decoded = await _verify_apple_id_token(id_token, nonce=nonce)
         apple_sub = decoded["sub"]
         email = decoded["email"]
 
@@ -450,7 +455,7 @@ async def apple_mobile_auth_flow(
     모바일용 Apple 로그인.
     네이티브 SDK에서 받은 id_token을 JWKS로 검증하고 JWT 토큰 발급.
     """
-    decoded = await _verify_apple_id_token(id_token, "app")
+    decoded = await _verify_apple_id_token(id_token)
     apple_sub = decoded["sub"]
     email = decoded["email"]
 
diff --git a/src/config.py b/src/config.py
index 410a1d4..0e6caf9 100644
--- a/src/config.py
+++ b/src/config.py
@@ -104,6 +104,8 @@ def SQLALCHEMY_DATABASE_URI(self) -> PostgresDsn:
     # OAuth - Google
     GOOGLE_CLIENT_ID: str | None = None
     GOOGLE_CLIENT_SECRET: str | None = None
+    GOOGLE_IOS_CLIENT_ID: str | None = None
+    GOOGLE_ANDROID_CLIENT_ID: str | None = None
 
     # OAuth - Apple
     APPLE_CLIENT_ID: str | None = None