diff --git a/src/main/java/com/teamEWSN/gitdeun/common/exception/ErrorCode.java b/src/main/java/com/teamEWSN/gitdeun/common/exception/ErrorCode.java
index 1f432bd..a0cd2ed 100644
--- a/src/main/java/com/teamEWSN/gitdeun/common/exception/ErrorCode.java
+++ b/src/main/java/com/teamEWSN/gitdeun/common/exception/ErrorCode.java
@@ -23,6 +23,7 @@ public enum ErrorCode {
     USER_NOT_FOUND_BY_EMAIL(HttpStatus.NOT_FOUND, "ACCOUNT-002", "해당 이메일의 회원을 찾을 수 없습니다."),
     ACCOUNT_ALREADY_LINKED(HttpStatus.CONFLICT, "ACCOUNT-003", "이미 다른 사용자와 연동된 소셜 계정입니다."),
     SOCIAL_CONNECTION_NOT_FOUND(HttpStatus.NOT_FOUND, "ACCOUNT-004", "연동된 소셜 계정 정보를 찾을 수 없습니다."),
+    USER_SETTING_NOT_FOUND_BY_ID(HttpStatus.NOT_FOUND, "ACCOUNT-005", "해당 아이디의 설정을 찾을 수 없습니다."),
 
     // 소셜 로그인 관련
     OAUTH_PROCESSING_ERROR(HttpStatus.INTERNAL_SERVER_ERROR, "OAUTH-001", "소셜 로그인 처리 중 오류가 발생했습니다."),
@@ -31,7 +32,7 @@ public enum ErrorCode {
     OAUTH_COMMUNICATION_FAILED(HttpStatus.BAD_GATEWAY, "OAUTH-004", "소셜 플랫폼과의 통신에 실패했습니다."),
     SOCIAL_TOKEN_REFRESH_FAILED(HttpStatus.INTERNAL_SERVER_ERROR, "OAUTH-005", "소셜 플랫폼의 토큰 갱신에 실패했습니다."),
     SOCIAL_ACCOUNT_CONNECT_FAILED(HttpStatus.INTERNAL_SERVER_ERROR, "OAUTH-006", "소셜 계정 연동에 실패했습니다."),
-    GITHUB_TOKEN_REFRESH_NOT_SUPPORTED(HttpStatus.BAD_REQUEST, "OAUTH-007", "GitHub 토큰 갱신은 지원하지 않습니다. 재인증이 필요합니다."),
+    SOCIAL_TOKEN_REFRESH_NOT_SUPPORTED(HttpStatus.BAD_REQUEST, "OAUTH-007", "리프레시 토큰 갱신은 지원하지 않습니다. 재인증이 필요합니다."),
 
     // S3 파일 관련
     // Client Errors (4xx)
diff --git a/src/main/java/com/teamEWSN/gitdeun/common/oauth/entity/CustomOAuth2User.java b/src/main/java/com/teamEWSN/gitdeun/common/oauth/dto/CustomOAuth2User.java
similarity index 95%
rename from src/main/java/com/teamEWSN/gitdeun/common/oauth/entity/CustomOAuth2User.java
rename to src/main/java/com/teamEWSN/gitdeun/common/oauth/dto/CustomOAuth2User.java
index a79f1e1..ea70964 100644
--- a/src/main/java/com/teamEWSN/gitdeun/common/oauth/entity/CustomOAuth2User.java
+++ b/src/main/java/com/teamEWSN/gitdeun/common/oauth/dto/CustomOAuth2User.java
@@ -1,4 +1,4 @@
-package com.teamEWSN.gitdeun.common.oauth.entity;
+package com.teamEWSN.gitdeun.common.oauth.dto;
 
 import com.teamEWSN.gitdeun.user.entity.Role;
 import lombok.Getter;
diff --git a/src/main/java/com/teamEWSN/gitdeun/common/oauth/dto/GitHubEmailDto.java b/src/main/java/com/teamEWSN/gitdeun/common/oauth/dto/GitHubEmailDto.java
new file mode 100644
index 0000000..05176c5
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/common/oauth/dto/GitHubEmailDto.java
@@ -0,0 +1,17 @@
+package com.teamEWSN.gitdeun.common.oauth.dto;
+
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class GitHubEmailDto {
+
+    private String email;
+    private boolean primary;
+    private boolean verified;
+    private String visibility;
+}
diff --git a/src/main/java/com/teamEWSN/gitdeun/common/oauth/dto/OAuth2UserDto.java b/src/main/java/com/teamEWSN/gitdeun/common/oauth/dto/OAuth2UserDto.java
deleted file mode 100644
index f0cf9ad..0000000
--- a/src/main/java/com/teamEWSN/gitdeun/common/oauth/dto/OAuth2UserDto.java
+++ /dev/null
@@ -1,16 +0,0 @@
-package com.teamEWSN.gitdeun.common.oauth.dto;
-
-import lombok.Builder;
-import lombok.Getter;
-import lombok.ToString;
-
-@ToString
-@Getter
-@Builder
-public class OAuth2UserDto {
-    private String nickname;
-    private String name;
-    private String email;
-    private String role;
-    private String profileImage;
-}
diff --git a/src/main/java/com/teamEWSN/gitdeun/common/oauth/entity/SocialConnection.java b/src/main/java/com/teamEWSN/gitdeun/common/oauth/entity/SocialConnection.java
index 9b1ce2f..ccbb3da 100644
--- a/src/main/java/com/teamEWSN/gitdeun/common/oauth/entity/SocialConnection.java
+++ b/src/main/java/com/teamEWSN/gitdeun/common/oauth/entity/SocialConnection.java
@@ -1,7 +1,7 @@
 package com.teamEWSN.gitdeun.common.oauth.entity;
 
 import com.teamEWSN.gitdeun.common.converter.CryptoConverter;
-import com.teamEWSN.gitdeun.common.util.BaseEntity;
+import com.teamEWSN.gitdeun.common.util.AuditedEntity;
 import com.teamEWSN.gitdeun.user.entity.User;
 import jakarta.persistence.*;
 import lombok.*;
@@ -10,7 +10,7 @@
 @Getter
 @NoArgsConstructor(access = AccessLevel.PROTECTED)
 @Table(name = "social_connection")
-public class SocialConnection extends BaseEntity {
+public class SocialConnection extends AuditedEntity {
 
     @Id
     @GeneratedValue(strategy = GenerationType.IDENTITY)
diff --git a/src/main/java/com/teamEWSN/gitdeun/common/oauth/handler/CustomOAuth2SuccessHandler.java b/src/main/java/com/teamEWSN/gitdeun/common/oauth/handler/CustomOAuth2SuccessHandler.java
index 03dc0aa..d96969f 100644
--- a/src/main/java/com/teamEWSN/gitdeun/common/oauth/handler/CustomOAuth2SuccessHandler.java
+++ b/src/main/java/com/teamEWSN/gitdeun/common/oauth/handler/CustomOAuth2SuccessHandler.java
@@ -3,16 +3,18 @@
 import com.teamEWSN.gitdeun.common.cookie.CookieUtil;
 import com.teamEWSN.gitdeun.common.jwt.JwtToken;
 import com.teamEWSN.gitdeun.common.jwt.JwtTokenProvider;
-import com.teamEWSN.gitdeun.common.oauth.entity.CustomOAuth2User;
+import com.teamEWSN.gitdeun.common.oauth.service.OAuthStateService;
+import com.teamEWSN.gitdeun.user.service.AuthService;
 import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpServletResponse;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.security.core.Authentication;
+import org.springframework.security.oauth2.client.authentication.OAuth2AuthenticationToken;
+import org.springframework.security.oauth2.core.user.OAuth2User;
 import org.springframework.security.web.authentication.SimpleUrlAuthenticationSuccessHandler;
 import org.springframework.stereotype.Component;
-import org.springframework.web.util.UriComponentsBuilder;
 
 import java.io.IOException;
 
@@ -22,6 +24,8 @@
 public class CustomOAuth2SuccessHandler extends SimpleUrlAuthenticationSuccessHandler {
 
     private final JwtTokenProvider jwtTokenProvider;
+    private final OAuthStateService oAuthStateService;
+    private final AuthService authService;
     private final CookieUtil cookieUtil;
 
     @Value("${app.front-url}")
@@ -29,19 +33,22 @@ public class CustomOAuth2SuccessHandler extends SimpleUrlAuthenticationSuccessHa
 
     @Override
     public void onAuthenticationSuccess(HttpServletRequest request, HttpServletResponse response, Authentication authentication) throws IOException {
-
-        // 우리 서비스의 JWT 생성
+        OAuth2AuthenticationToken authToken = (OAuth2AuthenticationToken) authentication;
+        OAuth2User oAuth2User = (OAuth2User) authentication.getPrincipal();
+        String state = request.getParameter("state");
+
+        String purpose = oAuthStateService.consumeState(state); // "connect:42" 또는 null
+        if (purpose != null && purpose.startsWith("connect:")) {
+            Long userId = Long.parseLong(purpose.split(":")[1]);
+            authService.connectGithubAccount(oAuth2User, userId);
+            response.sendRedirect(frontUrl + "/oauth/callback#connected=true");
+            return;
+        }
+
+        // 일반 로그인 흐름
         JwtToken jwtToken = jwtTokenProvider.generateToken(authentication);
-        log.info("JWT가 발급되었습니다. Access Token: {}", jwtToken.getAccessToken());
-
-        // Refresh Token은 HttpOnly 쿠키에 저장
         cookieUtil.setCookie(response, "refreshToken", jwtToken.getRefreshToken(), jwtTokenProvider.getRefreshTokenExpired());
-
-        // Access Token은 쿼리 파라미터로 프론트엔드에 전달
-        String targetUrl = UriComponentsBuilder.fromUriString(frontUrl + "/oauth/callback")
-            .queryParam("accessToken", jwtToken.getAccessToken())
-            .build().toUriString();
-
+        String targetUrl = frontUrl + "/oauth/callback#accessToken=" + jwtToken.getAccessToken();
         getRedirectStrategy().sendRedirect(request, response, targetUrl);
     }
 }
diff --git a/src/main/java/com/teamEWSN/gitdeun/common/oauth/record/GoogleTokenResponse.java b/src/main/java/com/teamEWSN/gitdeun/common/oauth/record/GoogleTokenResponse.java
new file mode 100644
index 0000000..dceba76
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/common/oauth/record/GoogleTokenResponse.java
@@ -0,0 +1,12 @@
+package com.teamEWSN.gitdeun.common.oauth.record;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+public record GoogleTokenResponse(
+    @JsonProperty("access_token") String accessToken,
+    @JsonProperty("refresh_token") String refreshToken,
+    @JsonProperty("token_type") String tokenType,
+    @JsonProperty("expires_in") Long expiresIn,
+    @JsonProperty("scope") String scope,
+    @JsonProperty("id_token") String idToken
+) {}
diff --git a/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/CustomOAuth2UserService.java b/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/CustomOAuth2UserService.java
index cf9c64e..d9d2310 100644
--- a/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/CustomOAuth2UserService.java
+++ b/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/CustomOAuth2UserService.java
@@ -2,6 +2,7 @@
 
 import com.teamEWSN.gitdeun.common.exception.GlobalException;
 import com.teamEWSN.gitdeun.common.exception.ErrorCode;
+import com.teamEWSN.gitdeun.common.oauth.dto.GitHubEmailDto;
 import com.teamEWSN.gitdeun.common.oauth.dto.provider.GitHubResponseDto;
 import com.teamEWSN.gitdeun.common.oauth.dto.provider.GoogleResponseDto;
 import com.teamEWSN.gitdeun.common.oauth.dto.provider.OAuth2ResponseDto;
@@ -11,7 +12,7 @@
 import com.teamEWSN.gitdeun.user.entity.User;
 import com.teamEWSN.gitdeun.common.oauth.repository.SocialConnectionRepository;
 import com.teamEWSN.gitdeun.user.repository.UserRepository;
-import com.teamEWSN.gitdeun.common.oauth.entity.CustomOAuth2User;
+import com.teamEWSN.gitdeun.common.oauth.dto.CustomOAuth2User;
 import jakarta.transaction.Transactional;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
@@ -21,6 +22,8 @@
 import org.springframework.security.oauth2.core.user.OAuth2User;
 import org.springframework.stereotype.Service;
 
+import java.util.List;
+import java.util.Map;
 import java.util.UUID;
 
 
@@ -29,6 +32,8 @@
 @RequiredArgsConstructor
 public class CustomOAuth2UserService extends DefaultOAuth2UserService {
 
+    private final GitHubApiHelper gitHubApiHelper;
+    private final SocialTokenRefreshService socialTokenRefreshService;
     private final UserRepository userRepository;
     private final SocialConnectionRepository socialConnectionRepository;
 
@@ -44,61 +49,68 @@ public OAuth2User loadUser(OAuth2UserRequest userRequest) throws OAuth2Authentic
             throw new GlobalException(ErrorCode.OAUTH_COMMUNICATION_FAILED);
         }
 
-        User user = processUserInTransaction(oAuth2User, userRequest);
+        User user = processUser(oAuth2User, userRequest);
         return new CustomOAuth2User(user.getId(), user.getRole());
     }
 
     // @Transactional
-    public User processUserInTransaction(OAuth2User oAuth2User, OAuth2UserRequest userRequest) {
-        OAuth2ResponseDto oAuth2ResponseDto = getOAuth2ResponseDto(oAuth2User, userRequest);
-
-        // 이메일 정보가 없는 경우 예외 처리 (GitHub 등)
-        if (oAuth2ResponseDto.getEmail() == null) {
-            throw new GlobalException(ErrorCode.EMAIL_NOT_PROVIDED);
-        }
-
-        OauthProvider provider = OauthProvider.valueOf(oAuth2ResponseDto.getProvider().toUpperCase());
-        String providerId = oAuth2ResponseDto.getProviderId();
-        String accessToken = userRequest.getAccessToken().getTokenValue();
+    public User processUser(OAuth2User oAuth2User, OAuth2UserRequest userRequest) {
+        OAuth2ResponseDto dto = getOAuth2ResponseDto(oAuth2User, userRequest);
+        OauthProvider provider = OauthProvider.valueOf(dto.getProvider().toUpperCase());
+        String providerId   = dto.getProviderId();
+        String accessToken  = userRequest.getAccessToken().getTokenValue();
         String refreshToken = (String) userRequest.getAdditionalParameters().get("refresh_token");
 
+        /* ② 이미 연결된 계정 → 토큰 갱신 로직 추상화  */
         return socialConnectionRepository.findByProviderAndProviderId(provider, providerId)
-            .map(connection -> {
-                log.info("기존 소셜 계정 정보를 업데이트합니다: {}", provider);
-                connection.updateTokens(accessToken, refreshToken);
-                return connection.getUser();
+            .map(conn -> {
+                // provider 별 refresh 정책
+                socialTokenRefreshService.refreshSocialToken(conn, accessToken, refreshToken);
+                return conn.getUser();
             })
-            .orElseGet(() -> {
-                // 다른 사용자가 이미 해당 이메일을 사용 중인지 확인
-                userRepository.findByEmailAndDeletedAtIsNull(oAuth2ResponseDto.getEmail())
-                    .ifPresent(existingUser -> {
-                        // 이메일은 같지만, 소셜 연동 정보가 없는 경우 -> 계정 연동
-                        log.info("기존 회원 계정에 소셜 계정을 연동합니다: {}", provider);
-                        connectSocialAccount(existingUser, provider, providerId, accessToken, refreshToken);
-                    });
-                // 위에서 연동했거나, 완전 신규 유저인 경우를 처리
-                // 다시 이메일로 조회하여 최종 유저를 반환하거나 새로 생성
-                return userRepository.findByEmailAndDeletedAtIsNull(oAuth2ResponseDto.getEmail())
-                    .orElseGet(() -> {
-                        log.info("신규 회원 및 소셜 계정을 생성합니다: {}", provider);
-                        return createNewUser(oAuth2ResponseDto, provider, providerId, accessToken, refreshToken);
-                    });
-            });
+            .orElseGet(() -> createOrConnect(dto, provider, providerId, accessToken, refreshToken));
     }
 
-    private static OAuth2ResponseDto getOAuth2ResponseDto(OAuth2User oAuth2User, OAuth2UserRequest userRequest) {
+    // OAuth2 공급자로부터 받은 사용자 정보를 기반으로 OAuth2ResponseDto를 생성(인스턴스 메서드)
+    private OAuth2ResponseDto getOAuth2ResponseDto(OAuth2User oAuth2User, OAuth2UserRequest userRequest) {
         String registrationId = userRequest.getClientRegistration().getRegistrationId();
+        Map<String, Object> attr = oAuth2User.getAttributes();
 
-        OAuth2ResponseDto oAuth2ResponseDto;
         if (registrationId.equalsIgnoreCase("google")) {
-            oAuth2ResponseDto = new GoogleResponseDto(oAuth2User.getAttributes());
-        } else if (registrationId.equalsIgnoreCase("github")) {
-            oAuth2ResponseDto = new GitHubResponseDto(oAuth2User.getAttributes());
+            return new GoogleResponseDto(attr);
+        }
+        if (registrationId.equalsIgnoreCase("github")) {
+            /* ① 기본 프로필에 e-mail 없으면 /user/emails 호출 */
+            if (attr.get("email") == null) {
+                // accessToken 으로 GitHub 보조 API 호출
+                List<GitHubEmailDto> emails =
+                    gitHubApiHelper.getPrimaryEmails(userRequest.getAccessToken().getTokenValue());
+                attr.put("email",
+                    emails.stream().filter(GitHubEmailDto::isPrimary)
+                        .findFirst().map(GitHubEmailDto::getEmail).orElse(null));
+            }
+            return new GitHubResponseDto(attr);
         } else {
             // 지원하지 않는 소셜 로그인 제공자
             throw new GlobalException(ErrorCode.UNSUPPORTED_OAUTH_PROVIDER);
         }
-        return oAuth2ResponseDto;
+    }
+
+    /**
+     * 사용자가 존재하면 계정을 연결하고, 존재하지 않으면 새로 생성합니다.
+     */
+    private User createOrConnect(OAuth2ResponseDto response, OauthProvider provider, String providerId, String accessToken, String refreshToken) {
+        // 이메일로 기존 사용자를 찾습니다.
+        return userRepository.findByEmailAndDeletedAtIsNull(response.getEmail())
+            .map(user -> {
+                // 사용자가 존재하면, 새 소셜 계정을 연결
+                connectSocialAccount(user, provider, providerId, accessToken, refreshToken);
+                return user;
+            })
+            .orElseGet(() -> {
+                // 사용자가 존재하지 않으면, 새 사용자를 생성
+                return createNewUser(response, provider, providerId, accessToken, refreshToken);
+            });
     }
 
     private User createNewUser(OAuth2ResponseDto response, OauthProvider provider, String providerId, String accessToken, String refreshToken) {
diff --git a/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/GitHubApiHelper.java b/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/GitHubApiHelper.java
index 13f5ce0..c87661b 100644
--- a/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/GitHubApiHelper.java
+++ b/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/GitHubApiHelper.java
@@ -2,7 +2,7 @@
 
 import com.teamEWSN.gitdeun.common.exception.ErrorCode;
 import com.teamEWSN.gitdeun.common.exception.GlobalException;
-import com.teamEWSN.gitdeun.common.oauth.dto.provider.GitHubResponseDto;
+import com.teamEWSN.gitdeun.common.oauth.dto.GitHubEmailDto;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.beans.factory.annotation.Value;
@@ -10,13 +10,12 @@
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.stereotype.Component;
-import org.springframework.util.LinkedMultiValueMap;
-import org.springframework.util.MultiValueMap;
 import org.springframework.web.reactive.function.client.WebClient;
 import reactor.core.publisher.Mono;
 
 import java.nio.charset.StandardCharsets;
 import java.util.Base64;
+import java.util.List;
 import java.util.Map;
 
 @Slf4j
@@ -32,60 +31,28 @@ public class GitHubApiHelper {
     @Value("${spring.security.oauth2.client.registration.github.client-secret}")
     private String clientSecret;
 
-    @Value("${spring.security.oauth2.client.registration.github.redirect-uri}")
-    private String redirectUri;
 
     /**
-     * 인가 코드로 GitHub Access Token을 요청합니다.
-     * @param code GitHub에서 받은 인가 코드
-     * @return Access Token 문자열
-     */
-    public String getAccessToken(String code) {
-        String tokenUri = "https://github.com/login/oauth/access_token";
-
-        MultiValueMap<String, String> formData = new LinkedMultiValueMap<>();
-        formData.add("client_id", clientId);
-        formData.add("client_secret", clientSecret);
-        formData.add("code", code);
-        formData.add("redirect_uri", redirectUri);
-
-        Map<String, Object> response = webClient.post()
-            .uri(tokenUri)
-            .accept(MediaType.APPLICATION_JSON)
-            .bodyValue(formData)
-            .retrieve()
-            // 단순 map이 아닌 정확한 타입 정보를 런타임에도 잃어버리지 않도록 ParameterizedTypeReference를 사용
-            .bodyToMono(new ParameterizedTypeReference<Map<String, Object>>() {})
-            .block();
-
-        if (response == null || response.get("access_token") == null) {
-            log.error("GitHub Access Token 발급 실패: {}", response);
-            throw new GlobalException(ErrorCode.OAUTH_PROCESSING_ERROR);
-        }
-
-        return (String) response.get("access_token");
-    }
-
-    /**
-     * Access Token으로 GitHub 사용자 정보를 조회합니다.
+     * Access Token으로 사용자의 이메일 목록을 조회합니다.
+     * GitHub 기본 사용자 정보에 이메일이 포함되지 않은 경우 사용됩니다.
      * @param accessToken GitHub Access Token
-     * @return GitHub 사용자 정보를 담은 DTO
+     * @return 이메일 정보 DTO 리스트
      */
-    public GitHubResponseDto getUserInfo(String accessToken) {
-        String userInfoUri = "https://api.github.com/user";
+    public List<GitHubEmailDto> getPrimaryEmails(String accessToken) {
+        String emailsUri = "https://api.github.com/user/emails";
 
-        Map<String, Object> attributes = webClient.get()
-            .uri(userInfoUri)
-            .header(HttpHeaders.AUTHORIZATION, "token " + accessToken)
+        List<GitHubEmailDto> emails = webClient.get()
+            .uri(emailsUri)
+            .header(HttpHeaders.AUTHORIZATION, "Bearer " + accessToken)
             .retrieve()
-            .bodyToMono(new ParameterizedTypeReference<Map<String, Object>>() {})
+            .bodyToMono(new ParameterizedTypeReference<List<GitHubEmailDto>>() {})
             .block();
 
-        if (attributes == null) {
+        if (emails == null || emails.isEmpty()) {
+            log.error("GitHub 이메일 정보를 가져올 수 없습니다.");
             throw new GlobalException(ErrorCode.OAUTH_COMMUNICATION_FAILED);
         }
-
-        return new GitHubResponseDto(attributes);
+        return emails;
     }
 
 
diff --git a/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/GoogleApiHelper.java b/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/GoogleApiHelper.java
index cdfdb1d..7a0d3c8 100644
--- a/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/GoogleApiHelper.java
+++ b/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/GoogleApiHelper.java
@@ -1,16 +1,99 @@
 package com.teamEWSN.gitdeun.common.oauth.service;
 
+import com.teamEWSN.gitdeun.common.exception.ErrorCode;
+import com.teamEWSN.gitdeun.common.exception.GlobalException;
+import com.teamEWSN.gitdeun.common.oauth.record.GoogleTokenResponse;
 import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.http.MediaType;
 import org.springframework.stereotype.Component;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
+import org.springframework.web.reactive.function.BodyInserters;
 import org.springframework.web.reactive.function.client.WebClient;
+import org.springframework.web.reactive.function.client.WebClientResponseException;
 import reactor.core.publisher.Mono;
 
+
+@Slf4j
 @Component
 @RequiredArgsConstructor
 public class GoogleApiHelper {
 
     private final WebClient webClient;
 
+    @Value("${spring.security.oauth2.client.registration.google.client-id}")
+    private String googleClientId;
+
+    @Value("${spring.security.oauth2.client.registration.google.client-secret}")
+    private String googleClientSecret;
+
+
+    /**
+     * 토큰이 만료되었는지 확인
+     * @param accessToken 확인할 액세스 토큰
+     * @return 만료 여부 (true: 만료됨, false: 유효함)
+     */
+    protected boolean isExpired(String accessToken) {
+        // String validateUrl = "https://www.googleapis.com/oauth2/v1/tokeninfo";
+        try {
+            // 토큰 정보 요청
+            webClient.get()
+                .uri(uriBuilder -> uriBuilder
+                    .scheme("https")
+                    .host("www.googleapis.com")
+                    .path("/oauth2/v1/tokeninfo")
+                    .queryParam("access_token", accessToken)
+                    .build())
+                .retrieve()
+                .bodyToMono(String.class)
+                .block();
+
+            // 응답이 있으면 토큰이 유효함
+            return false; // 만료되지 않음
+        } catch (WebClientResponseException e) {
+            // 401, 400 등의 에러는 토큰이 만료되었거나 유효하지 않음
+            log.debug("토큰 검증 오류: {}", e.getMessage());
+            return true; // 만료됨
+        } catch (Exception e) {
+            // 기타 예외
+            log.error("토큰 검증 중 예상치 못한 오류: {}", e.getMessage());
+            return true; // 안전하게 만료로 취급
+        }
+    }
+
+    /**
+     * 리프레시 토큰으로 새 액세스 토큰 요청
+     * @param refreshToken 리프레시 토큰
+     * @return 새로운 토큰 응답 객체
+     */
+    protected GoogleTokenResponse refreshToken(String refreshToken) {
+        String tokenUrl = "https://oauth2.googleapis.com/token";
+
+        // 요청 바디 구성
+        MultiValueMap<String, String> formData = new LinkedMultiValueMap<>();
+        formData.add("client_id", googleClientId);
+        formData.add("client_secret", googleClientSecret);
+        formData.add("refresh_token", refreshToken);
+        formData.add("grant_type", "refresh_token");
+
+        try {
+            // 토큰 갱신 요청
+            return webClient.post()
+                .uri(tokenUrl)
+                .contentType(MediaType.APPLICATION_FORM_URLENCODED)
+                .body(BodyInserters.fromFormData(formData))
+                .retrieve()
+                .bodyToMono(GoogleTokenResponse.class)
+                .block();
+        } catch (Exception e) {
+            log.error("Google 토큰 갱신 실패: {}", e.getMessage());
+            throw new GlobalException(ErrorCode.SOCIAL_TOKEN_REFRESH_FAILED);
+        }
+    }
+
+
     public Mono<Void> revokeToken(String accessToken) {
         String revokeUrl = "https://accounts.google.com/o/oauth2/revoke";
         return webClient.post()
diff --git a/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/OAuthStateService.java b/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/OAuthStateService.java
new file mode 100644
index 0000000..cf776bb
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/OAuthStateService.java
@@ -0,0 +1,29 @@
+package com.teamEWSN.gitdeun.common.oauth.service;
+
+import lombok.RequiredArgsConstructor;
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.stereotype.Service;
+
+import java.time.Duration;
+import java.util.UUID;
+
+@Service
+@RequiredArgsConstructor
+public class OAuthStateService {
+
+    private final RedisTemplate<String, String> redisTemplate;
+    private static final Duration EXPIRATION = Duration.ofMinutes(3);
+
+    public String createState(String purpose) {
+        String state = UUID.randomUUID().toString();
+        redisTemplate.opsForValue().set("oauth:state:" + state, purpose, EXPIRATION);
+        return state;
+    }
+
+    public String consumeState(String state) {
+        String key = "oauth:state:" + state;
+        String purpose = redisTemplate.opsForValue().get(key);
+        redisTemplate.delete(key);
+        return purpose;
+    }
+}
diff --git a/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/SocialTokenRefreshService.java b/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/SocialTokenRefreshService.java
index d026f47..2d2a0f5 100644
--- a/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/SocialTokenRefreshService.java
+++ b/src/main/java/com/teamEWSN/gitdeun/common/oauth/service/SocialTokenRefreshService.java
@@ -1,34 +1,34 @@
 package com.teamEWSN.gitdeun.common.oauth.service;
 
-import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.teamEWSN.gitdeun.common.exception.GlobalException;
 import com.teamEWSN.gitdeun.common.exception.ErrorCode;
 import com.teamEWSN.gitdeun.common.oauth.entity.OauthProvider;
 import com.teamEWSN.gitdeun.common.oauth.entity.SocialConnection;
+import com.teamEWSN.gitdeun.common.oauth.record.GoogleTokenResponse;
 import com.teamEWSN.gitdeun.common.oauth.repository.SocialConnectionRepository;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
+import java.util.Optional;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.http.HttpHeaders;
-import org.springframework.http.MediaType;
 import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
 import org.springframework.web.reactive.function.client.WebClient;
 
-import org.springframework.util.LinkedMultiValueMap;
-import org.springframework.util.MultiValueMap;
-import org.springframework.web.reactive.function.BodyInserters;
-
 
 // 레포 및 마인드맵 호출 시 소셜로그인 토큰 갱신 호출
 @Slf4j
 @Service
+@Transactional
 @RequiredArgsConstructor
 public class SocialTokenRefreshService {
 
     private final SocialConnectionRepository socialConnectionRepository;
     private final WebClient webClient;
-    private final ObjectMapper objectMapper = new ObjectMapper(); // JSON 파싱을 위한 ObjectMapper
+    private final ObjectMapper objectMapper = new ObjectMapper(); // JSON 파싱을 위한 ObjectMapper'
+    private final GitHubApiHelper gitHubApiHelper;
+    private final GoogleApiHelper googleApiHelper;
 
     @Value("${spring.security.oauth2.client.registration.google.client-id}")
     private String googleClientId;
@@ -37,110 +37,57 @@ public class SocialTokenRefreshService {
     private String googleClientSecret;
 
 
-    // oauth 토큰 갱신
+    // 기존 refreshToken 기반 갱신(주기적/자동 갱신)
     public void refreshSocialToken(Long userId, OauthProvider provider) {
         SocialConnection connection = socialConnectionRepository.findByUserIdAndProvider(userId, provider)
             .orElseThrow(() -> new GlobalException(ErrorCode.SOCIAL_CONNECTION_NOT_FOUND));
 
         switch (provider) {
-            case GOOGLE -> refreshGoogleToken(connection);
+            case GOOGLE -> refreshGoogle(connection, Optional.empty(), Optional.empty());
             case GITHUB -> {
                 log.warn("GitHub는 토큰 갱신을 지원하지 않습니다. 재인증이 필요합니다.");
-                throw new GlobalException(ErrorCode.GITHUB_TOKEN_REFRESH_NOT_SUPPORTED);
+                throw new GlobalException(ErrorCode.SOCIAL_TOKEN_REFRESH_NOT_SUPPORTED);
             }
         }
+
+        // 갱신 후 저장 명시
+        socialConnectionRepository.save(connection);
     }
 
-    private void refreshGoogleToken(SocialConnection connection) {
-        if (connection.getRefreshToken() == null) {
-            throw new GlobalException(ErrorCode.INVALID_REFRESH_TOKEN);
+    // oauth 새로운 토큰 제공 시 갱신(로그인 콜백)
+    public void refreshSocialToken(SocialConnection conn,
+                                   String latestAccess, String latestRefresh) {
+        switch (conn.getProvider()) {
+            case GOOGLE -> refreshGoogle(conn, Optional.ofNullable(latestAccess),
+                Optional.ofNullable(latestRefresh));
+            // GitHub은 refresh 불가
+            case GITHUB -> conn.updateTokens(latestAccess, null);  // accessToken만 교체
         }
 
-        try {
-            // Google Token 갱신 API 호출
-            String tokenUrl = "https://oauth2.googleapis.com/token";
-
-
-            MultiValueMap<String, String> formData = new LinkedMultiValueMap<>();
-            formData.add("client_id", googleClientId);
-            formData.add("client_secret", googleClientSecret);
-            formData.add("refresh_token", connection.getRefreshToken());
-            formData.add("grant_type", "refresh_token");
-
-
-            String response = webClient.post()
-                .uri(tokenUrl)
-                .contentType(MediaType.APPLICATION_FORM_URLENCODED)
-                .bodyValue(BodyInserters.fromFormData(formData))
-                .retrieve()
-                .bodyToMono(String.class)
-                .block();   // 결과를 동기적으로 기다림
-
-            JsonNode tokenNode = objectMapper.readTree(response);
-
-            String newAccessToken = tokenNode.get("access_token").asText();
-            // 구글은 리프레시 토큰을 갱신하면 기존 리프레시 토큰을 다시 주지 않는 경우가 대부분
-            String newRefreshToken = tokenNode.has("refresh_token") ?
-                tokenNode.get("refresh_token").asText() : connection.getRefreshToken();
-
-            connection.updateTokens(newAccessToken, newRefreshToken);
-            socialConnectionRepository.save(connection);
+        socialConnectionRepository.save(conn);
+    }
 
-            log.info("Google 토큰 갱신 완료: userId={}", connection.getUser().getId());
 
-        } catch (Exception e) {
-            log.error("Google 토큰 갱신 실패: userId={}, error={}",
-                connection.getUser().getId(), e.getMessage());
-            throw new GlobalException(ErrorCode.SOCIAL_TOKEN_REFRESH_FAILED);
+    private void refreshGoogle(SocialConnection conn,
+                                 Optional<String> latestAccessOpt,
+                                 Optional<String> latestRefreshOpt) {
+        // 1. latestAccess가 주어지고 유효하면 교체
+        if (latestAccessOpt.isPresent() && !googleApiHelper.isExpired(latestAccessOpt.get())) {
+            String newRefresh = latestRefreshOpt.orElse(conn.getRefreshToken());
+            conn.updateTokens(latestAccessOpt.get(), newRefresh);
+            return;
         }
-    }
 
-    /**
-     * 토큰 유효성 검증
-     */
-    public boolean isTokenValid(String accessToken, OauthProvider provider) {
-        try {
-            return switch (provider) {
-                case GOOGLE -> validateGoogleToken(accessToken);
-                case GITHUB -> validateGitHubToken(accessToken);
-            };
-        } catch (Exception e) {
-            log.error("토큰 유효성 검증 실패: provider={}, error={}", provider, e.getMessage());
-            return false;
+        // 2. refreshToken 기반 재발급 (latestRefresh가 있으면 그것 사용, 없으면 기존)
+        String refreshToUse = latestRefreshOpt.orElse(conn.getRefreshToken());
+        if (refreshToUse == null) {
+            throw new GlobalException(ErrorCode.INVALID_REFRESH_TOKEN);
         }
-    }
 
-    private boolean validateGoogleToken(String accessToken) {
-        String validateUrl = "https://www.googleapis.com/oauth2/v1/tokeninfo";
-
-        try {
-            webClient.get()
-                .uri(uriBuilder -> uriBuilder
-                    .path(validateUrl)
-                    .queryParam("access_token", accessToken)
-                    .build())
-                .retrieve()
-                .bodyToMono(String.class)
-                .block();
-            return true;
-        } catch (Exception e) {
-            return false;
-        }
-    }
+        GoogleTokenResponse res = googleApiHelper.refreshToken(refreshToUse);
 
-    private boolean validateGitHubToken(String accessToken) {
-        String validateUrl = "https://api.github.com/user";
-
-        try {
-            webClient.get()
-                .uri(validateUrl)
-                .header(HttpHeaders.AUTHORIZATION, "token " + accessToken)
-                .retrieve()
-                .bodyToMono(String.class)
-                .block();
-            return true;
-        } catch (Exception e) {
-            return false;
-        }
+        String newRefresh = (res.refreshToken() != null) ? res.refreshToken() : conn.getRefreshToken();
+        conn.updateTokens(res.accessToken(), newRefresh);
     }
+
 }
diff --git a/src/main/java/com/teamEWSN/gitdeun/common/util/AuditedEntity.java b/src/main/java/com/teamEWSN/gitdeun/common/util/AuditedEntity.java
new file mode 100644
index 0000000..3b04b77
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/common/util/AuditedEntity.java
@@ -0,0 +1,24 @@
+package com.teamEWSN.gitdeun.common.util;
+
+import jakarta.persistence.Column;
+import jakarta.persistence.EntityListeners;
+import jakarta.persistence.MappedSuperclass;
+import lombok.Getter;
+import lombok.Setter;
+import org.springframework.data.annotation.CreatedDate;
+import org.springframework.data.annotation.LastModifiedDate;
+import org.springframework.data.jpa.domain.support.AuditingEntityListener;
+
+import java.time.LocalDateTime;
+
+@EntityListeners(AuditingEntityListener.class)
+@Getter
+@Setter
+@MappedSuperclass
+public class AuditedEntity extends CreatedEntity {
+
+  @LastModifiedDate
+  @Column(name = "updated_at", nullable = false, columnDefinition = "DATETIME(0)")
+  private LocalDateTime updatedAt;
+
+}
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/common/util/BaseEntity.java b/src/main/java/com/teamEWSN/gitdeun/common/util/CreatedEntity.java
similarity index 80%
rename from src/main/java/com/teamEWSN/gitdeun/common/util/BaseEntity.java
rename to src/main/java/com/teamEWSN/gitdeun/common/util/CreatedEntity.java
index e2dcb5b..dc5a3f7 100644
--- a/src/main/java/com/teamEWSN/gitdeun/common/util/BaseEntity.java
+++ b/src/main/java/com/teamEWSN/gitdeun/common/util/CreatedEntity.java
@@ -15,14 +15,9 @@
 @Getter
 @Setter
 @MappedSuperclass
-public class BaseEntity {
+public class CreatedEntity {
 
   @CreatedDate
   @Column(name = "created_at", nullable = false, updatable = false, columnDefinition = "DATETIME(0)")
   private LocalDateTime createdAt;
-
-  @LastModifiedDate
-  @Column(name = "updated_at", nullable = false, columnDefinition = "DATETIME(0)")
-  private LocalDateTime updatedAt;
-
 }
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/repo/controller/RepoController.java b/src/main/java/com/teamEWSN/gitdeun/repo/controller/RepoController.java
new file mode 100644
index 0000000..b903ef3
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/repo/controller/RepoController.java
@@ -0,0 +1,5 @@
+package com.teamEWSN.gitdeun.repo.controller;
+
+public class RepoController {
+    
+}
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/repo/dto/RepoDto.java b/src/main/java/com/teamEWSN/gitdeun/repo/dto/RepoDto.java
new file mode 100644
index 0000000..9c8714f
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/repo/dto/RepoDto.java
@@ -0,0 +1,5 @@
+package com.teamEWSN.gitdeun.repo.dto;
+
+public class RepoDto {
+    
+}
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/repo/entity/Repo.java b/src/main/java/com/teamEWSN/gitdeun/repo/entity/Repo.java
new file mode 100644
index 0000000..c527d3f
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/repo/entity/Repo.java
@@ -0,0 +1,5 @@
+package com.teamEWSN.gitdeun.repo.entity;
+
+public class Repo {
+    
+}
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/repo/repository/RepoRepository.java b/src/main/java/com/teamEWSN/gitdeun/repo/repository/RepoRepository.java
new file mode 100644
index 0000000..7d3b49b
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/repo/repository/RepoRepository.java
@@ -0,0 +1,5 @@
+package com.teamEWSN.gitdeun.repo.repository;
+
+public class RepoRepository {
+    
+}
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/repo/service/RepoService.java b/src/main/java/com/teamEWSN/gitdeun/repo/service/RepoService.java
new file mode 100644
index 0000000..9eaf262
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/repo/service/RepoService.java
@@ -0,0 +1,5 @@
+package com.teamEWSN.gitdeun.repo.service;
+
+public class RepoService {
+    
+}
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/repository/controller/RepositoryController.java b/src/main/java/com/teamEWSN/gitdeun/repository/controller/RepositoryController.java
deleted file mode 100644
index ced6177..0000000
--- a/src/main/java/com/teamEWSN/gitdeun/repository/controller/RepositoryController.java
+++ /dev/null
@@ -1,5 +0,0 @@
-package com.teamEWSN.gitdeun.repository.controller;
-
-public class RepositoryController {
-    
-}
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/repository/dto/RepositoryDto.java b/src/main/java/com/teamEWSN/gitdeun/repository/dto/RepositoryDto.java
deleted file mode 100644
index 603d314..0000000
--- a/src/main/java/com/teamEWSN/gitdeun/repository/dto/RepositoryDto.java
+++ /dev/null
@@ -1,5 +0,0 @@
-package com.teamEWSN.gitdeun.repository.dto;
-
-public class RepositoryDto {
-    
-}
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/repository/entity/Repository.java b/src/main/java/com/teamEWSN/gitdeun/repository/entity/Repository.java
deleted file mode 100644
index 2d51bbe..0000000
--- a/src/main/java/com/teamEWSN/gitdeun/repository/entity/Repository.java
+++ /dev/null
@@ -1,5 +0,0 @@
-package com.teamEWSN.gitdeun.repository.entity;
-
-public class Repository {
-    
-}
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/repository/repository/RepositoryRepository.java b/src/main/java/com/teamEWSN/gitdeun/repository/repository/RepositoryRepository.java
deleted file mode 100644
index 6abc5b4..0000000
--- a/src/main/java/com/teamEWSN/gitdeun/repository/repository/RepositoryRepository.java
+++ /dev/null
@@ -1,5 +0,0 @@
-package com.teamEWSN.gitdeun.repository.repository;
-
-public class RepositoryRepository {
-    
-}
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/repository/service/RepositoryService.java b/src/main/java/com/teamEWSN/gitdeun/repository/service/RepositoryService.java
deleted file mode 100644
index 28097f8..0000000
--- a/src/main/java/com/teamEWSN/gitdeun/repository/service/RepositoryService.java
+++ /dev/null
@@ -1,5 +0,0 @@
-package com.teamEWSN.gitdeun.repository.service;
-
-public class RepositoryService {
-    
-}
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/user/controller/AuthController.java b/src/main/java/com/teamEWSN/gitdeun/user/controller/AuthController.java
index 5d06c4b..acc86dd 100644
--- a/src/main/java/com/teamEWSN/gitdeun/user/controller/AuthController.java
+++ b/src/main/java/com/teamEWSN/gitdeun/user/controller/AuthController.java
@@ -3,29 +3,41 @@
 import com.teamEWSN.gitdeun.common.cookie.CookieUtil;
 import com.teamEWSN.gitdeun.common.jwt.CustomUserDetails;
 import com.teamEWSN.gitdeun.common.jwt.JwtToken;
+import com.teamEWSN.gitdeun.common.oauth.service.OAuthStateService;
 import com.teamEWSN.gitdeun.user.dto.UserTokenResponseDto;
 import com.teamEWSN.gitdeun.user.service.AuthService;
 import jakarta.servlet.http.HttpServletResponse;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.beans.factory.annotation.Value;
-import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
 import org.springframework.web.bind.annotation.*;
 
+import java.util.Map;
+
 @Slf4j
 @RestController
-@RequestMapping("/api/oauth")
+@RequestMapping("/api/auth")
 @RequiredArgsConstructor
 public class AuthController {
 
     @Value("${jwt.refresh-expired}")
     private Long refreshTokenExpired;
 
+    private final OAuthStateService oAuthStateService;
     private final AuthService authService;
     private final CookieUtil cookieUtil;
 
+    @Value("${app.front-url}")
+    private String frontUrl;
+
+    // 깃허브 연동 흐름 구분 조회
+    @GetMapping("/connect/github/state")
+    public ResponseEntity<Map<String, String>> generateStateForGithubConnect(@AuthenticationPrincipal CustomUserDetails user) {
+        String state = oAuthStateService.createState("connect:" + user.getId());
+        return ResponseEntity.ok(Map.of("state", state));
+    }
 
     // 로그아웃 API
     @PostMapping("/logout")
@@ -54,14 +66,30 @@ public ResponseEntity<UserTokenResponseDto> refreshAccessToken(
         return ResponseEntity.ok(new UserTokenResponseDto(newJwtToken.getAccessToken()));
     }
 
-    @GetMapping("/connect/github/callback")
-    public ResponseEntity<Void> connectGithubAccountCallback(
-        @RequestParam("code") String code,
-        @AuthenticationPrincipal CustomUserDetails userDetails
-    ) {
-        authService.connectGithubAccount(userDetails.getId(), code);
-
-        return ResponseEntity.ok().build();
-    }
+//    /**
+//     * GitHub의 모든 OAuth 콜백을 처리하는 단일 엔드포인트
+//     * @param code GitHub에서 제공하는 Authorization Code
+//     * @param userDetails 현재 로그인된 사용자 정보. 비로그인 상태면 null.
+//     * @return 로그인 또는 계정 연동 흐름에 따라 적절한 경로로 포워딩 또는 리디렉션
+//     */
+//    @GetMapping("/github/callback")
+//    public ResponseEntity<?> githubCallback(
+//        @RequestParam("code") String code,
+//        @AuthenticationPrincipal CustomUserDetails userDetails,
+//        HttpServletResponse response // 쿠키 설정을 위해 필요
+//    ) {
+//
+//        if (userDetails != null) {
+//            // "계정 연동" 흐름
+//            authService.connectGithubAccount(userDetails.getId(), code);
+//            // 성공했다는 응답 전달
+//            return ResponseEntity.ok().body(Map.of("status", "success", "message", "계정 연동 성공!"));
+//
+//        } else {
+//            // "최초 로그인" 흐름
+//            GithubLoginResponseDto loginResponse = authService.loginWithGithub(code, response);
+//            return ResponseEntity.ok(loginResponse);
+//        }
+//    }
 
 }
diff --git a/src/main/java/com/teamEWSN/gitdeun/user/controller/UserSettingController.java b/src/main/java/com/teamEWSN/gitdeun/user/controller/UserSettingController.java
new file mode 100644
index 0000000..8c26416
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/user/controller/UserSettingController.java
@@ -0,0 +1,48 @@
+package com.teamEWSN.gitdeun.user.controller;
+
+import com.teamEWSN.gitdeun.common.jwt.CustomUserDetails;
+import com.teamEWSN.gitdeun.user.dto.UserSettingResponseDto;
+import com.teamEWSN.gitdeun.user.dto.UserSettingUpdateRequestDto;
+import com.teamEWSN.gitdeun.user.service.UserSettingService;
+import jakarta.validation.Valid;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.web.bind.annotation.*;
+
+@Slf4j
+@RestController
+@RequestMapping("/api/settings")
+@RequiredArgsConstructor
+public class UserSettingController {
+    private final UserSettingService userSettingService;
+
+    /**
+     * 현재 로그인된 사용자의 설정을 조회합니다.
+     * @param userDetails 인증된 사용자 정보
+     * @return 현재 설정 정보를 담은 응답
+     */
+    @GetMapping
+    public ResponseEntity<UserSettingResponseDto> getUserSettings(
+        @AuthenticationPrincipal CustomUserDetails userDetails
+    ) {
+        UserSettingResponseDto responseDto = userSettingService.getSettings(userDetails.getId());
+        return ResponseEntity.ok(responseDto);
+    }
+
+    /**
+     * 현재 로그인된 사용자의 설정을 변경합니다.
+     * @param userDetails 인증된 사용자 정보
+     * @param requestDto 변경할 설정 정보를 담은 요청 DTO
+     * @return 변경된 설정 정보를 담은 응답
+     */
+    @PatchMapping // 리소스의 일부만 변경하므로 PATCH가 더 적합합니다.
+    public ResponseEntity<UserSettingResponseDto> updateUserSettings(
+        @AuthenticationPrincipal CustomUserDetails userDetails,
+        @Valid @RequestBody UserSettingUpdateRequestDto requestDto
+    ) {
+        UserSettingResponseDto responseDto = userSettingService.updateSettings(userDetails.getId(), requestDto);
+        return ResponseEntity.ok(responseDto);
+    }
+}
diff --git a/src/main/java/com/teamEWSN/gitdeun/user/dto/UserResponseDto.java b/src/main/java/com/teamEWSN/gitdeun/user/dto/UserResponseDto.java
index c05807e..cdf4d13 100644
--- a/src/main/java/com/teamEWSN/gitdeun/user/dto/UserResponseDto.java
+++ b/src/main/java/com/teamEWSN/gitdeun/user/dto/UserResponseDto.java
@@ -4,7 +4,6 @@
 import lombok.Builder;
 import lombok.Getter;
 
-import java.time.LocalDate;
 
 @Getter
 @Builder
diff --git a/src/main/java/com/teamEWSN/gitdeun/user/dto/UserSettingResponseDto.java b/src/main/java/com/teamEWSN/gitdeun/user/dto/UserSettingResponseDto.java
new file mode 100644
index 0000000..4f54f79
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/user/dto/UserSettingResponseDto.java
@@ -0,0 +1,17 @@
+package com.teamEWSN.gitdeun.user.dto;
+
+import com.teamEWSN.gitdeun.user.entity.UserSetting;
+import lombok.AccessLevel;
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+
+@Getter
+@AllArgsConstructor
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+public class UserSettingResponseDto {
+    private UserSetting.DisplayTheme theme;
+    private UserSetting.UserMode mode;
+    private boolean emailNotification;
+}
diff --git a/src/main/java/com/teamEWSN/gitdeun/user/dto/UserSettingUpdateRequestDto.java b/src/main/java/com/teamEWSN/gitdeun/user/dto/UserSettingUpdateRequestDto.java
new file mode 100644
index 0000000..d7683d3
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/user/dto/UserSettingUpdateRequestDto.java
@@ -0,0 +1,20 @@
+package com.teamEWSN.gitdeun.user.dto;
+
+import com.teamEWSN.gitdeun.user.entity.UserSetting;
+import jakarta.validation.constraints.NotNull;
+import lombok.AccessLevel;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@Getter
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+public class UserSettingUpdateRequestDto {
+    @NotNull(message = "테마를 선택해주세요.")
+    private UserSetting.DisplayTheme theme;
+
+    @NotNull(message = "모드를 선택해주세요.")
+    private UserSetting.UserMode mode;
+
+    @NotNull(message = "이메일 수신 여부를 선택해주세요.")
+    private Boolean emailNotification;
+}
diff --git a/src/main/java/com/teamEWSN/gitdeun/user/entity/User.java b/src/main/java/com/teamEWSN/gitdeun/user/entity/User.java
index 5e33ea3..0d0c532 100644
--- a/src/main/java/com/teamEWSN/gitdeun/user/entity/User.java
+++ b/src/main/java/com/teamEWSN/gitdeun/user/entity/User.java
@@ -1,7 +1,7 @@
 package com.teamEWSN.gitdeun.user.entity;
 
 import com.teamEWSN.gitdeun.common.oauth.entity.SocialConnection;
-import com.teamEWSN.gitdeun.common.util.BaseEntity;
+import com.teamEWSN.gitdeun.common.util.AuditedEntity;
 import jakarta.persistence.*;
 import lombok.*;
 
@@ -13,7 +13,7 @@
 @Getter
 @NoArgsConstructor(access = AccessLevel.PROTECTED)
 @Table(name = "users")
-public class User extends BaseEntity {
+public class User extends AuditedEntity {
     @Id
     @GeneratedValue(strategy = GenerationType.IDENTITY)
     private Long id;
diff --git a/src/main/java/com/teamEWSN/gitdeun/user/entity/UserSetting.java b/src/main/java/com/teamEWSN/gitdeun/user/entity/UserSetting.java
new file mode 100644
index 0000000..773133e
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/user/entity/UserSetting.java
@@ -0,0 +1,72 @@
+package com.teamEWSN.gitdeun.user.entity;
+
+import com.teamEWSN.gitdeun.user.dto.UserSettingUpdateRequestDto;
+import jakarta.persistence.Entity;
+import lombok.*;
+import jakarta.persistence.*;
+import org.hibernate.annotations.ColumnDefault;
+
+@Entity
+@Getter
+@Builder
+@AllArgsConstructor(access = AccessLevel.PRIVATE)
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+@Table(name = "user_settings")
+public class UserSetting {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @OneToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "user_id", nullable = false, unique = true)
+    private User user;
+
+    // 화면 테마 (LIGHT, DARK)
+    @Builder.Default
+    @Enumerated(EnumType.STRING)
+    @Column(nullable = false, length = 20)
+    @ColumnDefault("'LIGHT'")
+    private DisplayTheme theme = DisplayTheme.LIGHT;
+
+    // 사용자 모드 (GENERAL, DEVELOPER)
+    @Builder.Default
+    @Enumerated(EnumType.STRING)
+    @Column(nullable = false, length = 20)
+    @ColumnDefault("'GENERAL'")
+    private UserMode mode = UserMode.GENERAL;
+
+    @Builder.Default
+    @Column(name = "email_notification", nullable = false)
+    @ColumnDefault("true")
+    private boolean emailNotification = true;
+
+
+    public enum DisplayTheme {
+        LIGHT, DARK
+    }
+
+    public enum UserMode {
+        GENERAL, DEVELOPER
+    }
+
+    @Builder
+    private UserSetting(User user, DisplayTheme theme, UserMode mode, boolean emailNotification) {
+        this.user = user;
+        this.theme = theme;
+        this.mode = mode;
+        this.emailNotification = emailNotification;
+    }
+
+    public static UserSetting createDefault(User user) {
+        return UserSetting.builder()
+            .user(user)
+            .build();
+    }
+
+    public void update(UserSettingUpdateRequestDto dto) {
+        this.theme = dto.getTheme();
+        this.mode = dto.getMode();
+        this.emailNotification = dto.getEmailNotification();
+    }
+}
+
diff --git a/src/main/java/com/teamEWSN/gitdeun/user/mapper/UserSettingMapper.java b/src/main/java/com/teamEWSN/gitdeun/user/mapper/UserSettingMapper.java
new file mode 100644
index 0000000..916e774
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/user/mapper/UserSettingMapper.java
@@ -0,0 +1,13 @@
+package com.teamEWSN.gitdeun.user.mapper;
+
+import com.teamEWSN.gitdeun.user.dto.UserSettingResponseDto;
+import com.teamEWSN.gitdeun.user.entity.UserSetting;
+import org.mapstruct.Mapper;
+import org.mapstruct.ReportingPolicy;
+
+@Mapper(componentModel = "spring", unmappedTargetPolicy = ReportingPolicy.IGNORE)
+public interface UserSettingMapper {
+
+    UserSettingResponseDto toResponseDto(UserSetting userSetting);
+
+}
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/user/repository/UserSettingRepository.java b/src/main/java/com/teamEWSN/gitdeun/user/repository/UserSettingRepository.java
new file mode 100644
index 0000000..fb0228a
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/user/repository/UserSettingRepository.java
@@ -0,0 +1,14 @@
+package com.teamEWSN.gitdeun.user.repository;
+
+import com.teamEWSN.gitdeun.user.entity.UserSetting;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+
+import java.util.Optional;
+
+@Repository
+public interface UserSettingRepository extends JpaRepository<UserSetting, Long> {
+
+    // 사용자 ID로 설정 조회
+    Optional<UserSetting> findByUserId(Long userId);
+}
\ No newline at end of file
diff --git a/src/main/java/com/teamEWSN/gitdeun/user/service/AuthService.java b/src/main/java/com/teamEWSN/gitdeun/user/service/AuthService.java
index d17f8f6..4543ca7 100644
--- a/src/main/java/com/teamEWSN/gitdeun/user/service/AuthService.java
+++ b/src/main/java/com/teamEWSN/gitdeun/user/service/AuthService.java
@@ -6,11 +6,9 @@
 import com.teamEWSN.gitdeun.common.exception.GlobalException;
 import com.teamEWSN.gitdeun.common.cookie.CookieUtil;
 import com.teamEWSN.gitdeun.common.jwt.*;
-import com.teamEWSN.gitdeun.common.oauth.dto.provider.GitHubResponseDto;
 import com.teamEWSN.gitdeun.common.oauth.entity.OauthProvider;
 import com.teamEWSN.gitdeun.common.oauth.entity.SocialConnection;
 import com.teamEWSN.gitdeun.common.oauth.repository.SocialConnectionRepository;
-import com.teamEWSN.gitdeun.common.oauth.service.GitHubApiHelper;
 import com.teamEWSN.gitdeun.user.entity.User;
 import com.teamEWSN.gitdeun.user.repository.UserRepository;
 import jakarta.servlet.http.HttpServletResponse;
@@ -19,9 +17,12 @@
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
 import org.springframework.security.core.Authentication;
+import org.springframework.security.oauth2.core.user.OAuth2User;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import java.util.Objects;
+
 
 @Slf4j
 @Service
@@ -33,7 +34,6 @@ public class AuthService {
     private final BlacklistService blacklistService;
     private final UserService userService;
     private final CookieUtil cookieUtil;
-    private final GitHubApiHelper gitHubApiHelper;
     private final UserRepository userRepository;
     private final SocialConnectionRepository socialConnectionRepository;
 
@@ -49,7 +49,6 @@ public class AuthService {
     @Value("${spring.security.oauth2.client.registration.github.redirect-uri}")
     private String githubRedirectUri;
 
-
     // 로그 아웃
     @Transactional
     public void logout(String accessToken, String refreshToken, HttpServletResponse response) {
@@ -89,47 +88,36 @@ private Authentication createAuthentication(User user) {
 
 
     // 구글 -> Github 계정 연동
-    @Transactional
-    public void connectGithubAccount(Long userId, String code) {
+    public void connectGithubAccount(OAuth2User githubUser, Long userId) {
         User user = userRepository.findById(userId)
             .orElseThrow(() -> new GlobalException(ErrorCode.USER_NOT_FOUND_BY_ID));
 
-        // GitHubApiHelper를 통해 Access Token 요청
-        String accessToken = gitHubApiHelper.getAccessToken(code);
-
-        // GitHubApiHelper를 통해 사용자 정보 요청
-        GitHubResponseDto githubResponse = gitHubApiHelper.getUserInfo(accessToken);
+        String providerId = Objects.requireNonNull(githubUser.getAttribute("id")).toString();
+        String accessToken = githubUser.getAttribute("access_token");
+        String refreshToken = githubUser.getAttribute("refresh_token");
 
-        String providerId = githubResponse.getProviderId();
-        OauthProvider provider = OauthProvider.GITHUB;
-
-        // 이미 다른 계정에 연동되어 있는지 확인
-        socialConnectionRepository.findByProviderAndProviderId(provider, providerId)
+        // 이미 다른 계정에 연동되어 있는지, 동일 사용자에 의해 이미 연동되는지 확인
+        socialConnectionRepository.findByProviderAndProviderId(OauthProvider.GITHUB, providerId)
             .ifPresent(connection -> {
                 if (!connection.getUser().getId().equals(userId)) {
                     throw new GlobalException(ErrorCode.ACCOUNT_ALREADY_LINKED);
+                } else {
+                    log.info("이미 현재 사용자와 연동된 GitHub 계정입니다: {}", providerId);
+                    return;
                 }
             });
 
-        // 현재 사용자에 대한 중복 연동 확인 (이미 연동되어 있으면 추가 로직 없음)
-        boolean alreadyLinked = user.getSocialConnections().stream()
-            .anyMatch(conn -> conn.getProvider() == provider && conn.getProviderId().equals(providerId));
-
-        if (alreadyLinked) {
-            log.info("이미 현재 사용자와 연동된 GitHub 계정입니다: {}", providerId);
-            return; // 이미 연동되었으므로 여기서 종료
-        }
 
         // 신규 소셜 연동 정보 생성 및 저장
-        SocialConnection newConnection = SocialConnection.builder()
+        SocialConnection connection = SocialConnection.builder()
             .user(user)
-            .provider(provider)
+            .provider(OauthProvider.GITHUB)
             .providerId(providerId)
             .accessToken(accessToken)
-            .refreshToken(null)
+            .refreshToken(refreshToken)
             .build();
 
-        socialConnectionRepository.save(newConnection);
-        log.info("사용자(ID:{})에게 GitHub 계정(ProviderId:{}) 연동이 완료되었습니다.", userId, providerId);
+        socialConnectionRepository.save(connection);
     }
+
 }
diff --git a/src/main/java/com/teamEWSN/gitdeun/user/service/UserSettingService.java b/src/main/java/com/teamEWSN/gitdeun/user/service/UserSettingService.java
new file mode 100644
index 0000000..a3a00ad
--- /dev/null
+++ b/src/main/java/com/teamEWSN/gitdeun/user/service/UserSettingService.java
@@ -0,0 +1,61 @@
+package com.teamEWSN.gitdeun.user.service;
+
+import com.teamEWSN.gitdeun.common.exception.ErrorCode;
+import com.teamEWSN.gitdeun.common.exception.GlobalException;
+import com.teamEWSN.gitdeun.user.dto.UserSettingResponseDto;
+import com.teamEWSN.gitdeun.user.dto.UserSettingUpdateRequestDto;
+import com.teamEWSN.gitdeun.user.entity.User;
+import com.teamEWSN.gitdeun.user.entity.UserSetting;
+import com.teamEWSN.gitdeun.user.mapper.UserSettingMapper;
+import com.teamEWSN.gitdeun.user.repository.UserRepository;
+import com.teamEWSN.gitdeun.user.repository.UserSettingRepository;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+@Service
+@RequiredArgsConstructor
+public class UserSettingService {
+
+    private final UserSettingRepository userSettingRepository;
+    private final UserRepository userRepository;
+    private final UserSettingMapper userSettingMapper;
+
+    /**
+     * 사용자 ID로 설정 정보 조회
+     * 설정이 없는 경우 기본값을 생성하고 저장한 뒤 반환합니다.
+     * @param userId 조회할 사용자의 ID
+     * @return 사용자의 설정 정보 DTO
+     */
+    @Transactional
+    public UserSettingResponseDto getSettings(Long userId) {
+        UserSetting userSetting = userSettingRepository.findByUserId(userId)
+            .orElseGet(() -> {
+                // 설정이 없는 경우, 기본 설정을 생성
+                User user = userRepository.findById(userId)
+                    .orElseThrow(() -> new GlobalException(ErrorCode.USER_NOT_FOUND_BY_ID));
+                UserSetting defaultSetting = UserSetting.createDefault(user);
+                return userSettingRepository.save(defaultSetting);
+            });
+
+        return userSettingMapper.toResponseDto(userSetting);
+    }
+
+    /**
+     * 사용자 설정 업데이트
+     * @param userId 업데이트할 사용자의 ID
+     * @param requestDto 업데이트할 설정 내용
+     * @return 업데이트된 사용자의 설정 정보 DTO
+     */
+    @Transactional // 쓰기 작업을 위한 @Transactional
+    public UserSettingResponseDto updateSettings(Long userId, UserSettingUpdateRequestDto requestDto) {
+        UserSetting userSetting = userSettingRepository.findByUserId(userId)
+            .orElseThrow(() -> new GlobalException(ErrorCode.USER_SETTING_NOT_FOUND_BY_ID));
+
+        // 엔티티의 update 메서드를 사용하여 상태 변경
+        userSetting.update(requestDto);
+
+        return userSettingMapper.toResponseDto(userSetting);
+    }
+}
+
diff --git a/src/main/resources/application-dev.yml b/src/main/resources/application-dev.yml
index 69e048c..5f65fb5 100644
--- a/src/main/resources/application-dev.yml
+++ b/src/main/resources/application-dev.yml
@@ -9,11 +9,11 @@ spring:
       client:
         registration:
           google:
-            redirect-uri: http://localhost:8080/login/oauth2/code/google
+            redirect-uri: http://localhost:8080/login/oauth2/code/google  # /oauth2/authorization/google 로그인 시작 URL
           github:
             client-id: ${GITHUB_DEV_CLIENT_ID}
             client-secret: ${GITHUB_DEV_CLIENT_SECRET}
-            redirect-uri: http://localhost:8080/login/oauth2/code/github
+            redirect-uri: http://localhost:8080/api/auth/github/callback
 #      provider:
 #        google:
 #          authorization-uri: https://accounts.google.com/o/oauth2/v2/auth
diff --git a/src/main/resources/application-prod.yml b/src/main/resources/application-prod.yml
index a8081ce..fbd1c5f 100644
--- a/src/main/resources/application-prod.yml
+++ b/src/main/resources/application-prod.yml
@@ -17,7 +17,7 @@ spring:
           github:
             client-id: ${GITHUB_PROD_CLIENT_ID}
             client-secret: ${GITHUB_PROD_CLIENT_SECRET}
-            redirect-uri: https://api.gitdeun.site/login/oauth2/code/github
+            redirect-uri: https://api.gitdeun.site/api/auth/github/callback
 
 
 jwt: