diff --git a/.github/ISSUE_TEMPLATE/Enhancement.md b/.github/ISSUE_TEMPLATE/Enhancement.md
new file mode 100644
index 000000000..c87b3c3d1
--- /dev/null
+++ b/.github/ISSUE_TEMPLATE/Enhancement.md
@@ -0,0 +1,20 @@
+---
+name: '🔥Enhancement Issue'
+about: '기존 기능을 개선합니다.'
+title: '[domain] - issue title'
+labels: 'enhancement'
+assignees: ''
+
+---
+
+### 📝 기존 기능
+<!--기존 기능의 한계점 혹은 개선이 필요한 이유 설명-->
+- 
+
+### 🔨 개선 이유 및 개선 사항
+<!-- 개선사항 설명-->
+- 
+
+### ✏️ 작업할 내용
+<!--실질적 작업 내용 설명-->
+- [ ]
\ No newline at end of file
diff --git a/.github/ISSUE_TEMPLATE/NewFeature.md b/.github/ISSUE_TEMPLATE/NewFeature.md
new file mode 100644
index 000000000..a14741165
--- /dev/null
+++ b/.github/ISSUE_TEMPLATE/NewFeature.md
@@ -0,0 +1,16 @@
+---
+name: '✨New Feature'
+about: '새로운 기능을 추가합니다.'
+title: '[domain] - issue title'
+labels: 'feature'
+assignees: ''
+
+---
+
+### 🎯 새로운 기능
+<!--새로운 기능 설명-->
+- 
+
+### ✏️ 작업할 내용
+<!--실질적 작업 내용 설명-->
+- [ ]
\ No newline at end of file
diff --git a/.github/ISSUE_TEMPLATE/Refactor.md b/.github/ISSUE_TEMPLATE/Refactor.md
new file mode 100644
index 000000000..207e8c66b
--- /dev/null
+++ b/.github/ISSUE_TEMPLATE/Refactor.md
@@ -0,0 +1,18 @@
+---
+name: '♻️Refactoring issue'
+about: '리펙토링 이슈를 추가합니다.'
+title: '[domain] - issue title'
+labels: 'refactor'
+assignees: ''
+
+---
+
+### ♿️ 리펙토링 배경
+<!--리펙토링을 하게 된 이유 작성-->
+-
+<!--리펙토링 대상 코드/도메인 설명-->
+- 
+
+### 🚚️ 작업할 내용
+<!--작업 내용 설명-->
+- [ ]
\ No newline at end of file
diff --git a/.github/pull_request_template.md b/.github/pull_request_template.md
new file mode 100644
index 000000000..ffd8caa8d
--- /dev/null
+++ b/.github/pull_request_template.md
@@ -0,0 +1,15 @@
+### 💻 작업 내용
+<!-- 진행한 작업 내용에 대해 작성해주세요. -->
+- 
+
+### ✨ 리뷰 포인트
+<!-- (ex) query 가 너무 복잡한 것 같은데 이 위주로 봐주세요. -->
+
+### 📝 메모
+<!-- PR 관련 전달사항이 있다면 이곳에 작성해주세요. -->
+
+### 🎯 관련 이슈
+<!-- pr이 merge 되면 이슈가 자동으로 close 되도록 합니다. 만약 자동 close 를 하지 않고 이슈만 링크한다면 closed 키워드를 삭제해주세요.-->
+closed #이슈번호
+
+<!-- @claude -->
\ No newline at end of file
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 000000000..9abdd7716
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,71 @@
+name: CI pipeline
+
+on:
+  pull_request:
+    branches:
+      - develop
+      - main
+  workflow_dispatch:
+jobs:
+  #################################################
+  # 단위 테스트
+  #################################################
+  unit-test:
+    runs-on: ubuntu-24.04
+    permissions:
+      contents: read
+      statuses: write
+
+    steps:
+      # 1) 소스 체크아웃
+      - name: Checkout branch HEAD
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.head_ref }}
+          fetch-depth: 0
+          persist-credentials: true
+
+      # 1-2) race condition 대비용 pull
+      - name: Ensure latest commit
+        run: |
+          git pull --ff-only origin "${{ github.head_ref }}"
+
+      # 2) JDK 설치 + Gradle 캐싱
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: 17
+          cache: 'gradle'
+
+      # 3) Gradle Wrapper 권한 부여
+      - name: Grant execute permission for gradlew
+        run: chmod +x ./gradlew
+
+      # 4) 단위 테스트
+      - name: Run unit tests
+        run: ./gradlew --no-daemon test
+
+      # 테스트 리포트 업로드
+      - name: Upload Test Report (HTML)
+        uses: actions/upload-artifact@v4
+        with:
+          name: junit-report
+          path: build/reports/tests/test/**/*.html
+      - name: Upload Test Report (XML)
+        uses: actions/upload-artifact@v4
+        with:
+          name: junit-xml-report
+          path: build/test-results/test/**/*.xml
+
+      # 5) 빌드(JAR 파일 생성)
+      - name: Build jar
+        run: ./gradlew --no-daemon build -x test --stacktrace
+
+      # 빌드 실패 시 로그 업로드
+      - name: Upload Build Logs on failure
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: build-logs
+          path: build/reports/
\ No newline at end of file
diff --git a/.github/workflows/code-review.yml b/.github/workflows/code-review.yml
new file mode 100644
index 000000000..0433fdca2
--- /dev/null
+++ b/.github/workflows/code-review.yml
@@ -0,0 +1,24 @@
+name: Claude Auto PR Review
+on:
+  pull_request:
+    types: [opened, reopened]
+
+permissions:
+  contents: read
+  pull-requests: write
+  checks: write
+  id-token: write
+
+jobs:
+  review:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Simple LLM Code Review
+        uses: codingbaraGo/simple-llm-code-review@latest
+        with:
+          anthropic-api-key: ${{ secrets.ANTHROPIC_API_KEY }}
+          language: korean
\ No newline at end of file
diff --git a/src/main/java/app/db/UserRepository.java b/src/main/java/app/db/UserRepository.java
new file mode 100644
index 000000000..d87b525d1
--- /dev/null
+++ b/src/main/java/app/db/UserRepository.java
@@ -0,0 +1,11 @@
+package app.db;
+
+import app.model.User;
+import database.ConnectionManager;
+import database.CrudRepository;
+
+public class UserRepository extends CrudRepository<User> {
+    public UserRepository(ConnectionManager connectionManager) {
+        super(connectionManager, User.class);
+    }
+}
diff --git a/src/main/java/app/handler/RegisterWithPost.java b/src/main/java/app/handler/RegisterWithPost.java
index 066683b9b..410dc497d 100644
--- a/src/main/java/app/handler/RegisterWithPost.java
+++ b/src/main/java/app/handler/RegisterWithPost.java
@@ -1,7 +1,8 @@
 package app.handler;
 
-import app.db.Database;
+import app.db.UserRepository;
 import app.model.User;
+import config.VariableConfig;
 import exception.ErrorCode;
 import exception.ServiceException;
 import http.HttpMethod;
@@ -14,19 +15,58 @@
 import web.response.RedirectResponse;
 
 public class RegisterWithPost extends SingleArgHandler<QueryParameters> {
+    private static final String EMAIL = "email";
+    private static final String NICKNAME = "nickname";
+    private static final String PASSWORD = "password";
+
     private static final Logger log = LoggerFactory.getLogger(RegisterWithPost.class);
 
-    public RegisterWithPost() {
+    private final UserRepository userRepository;
+
+    public RegisterWithPost(UserRepository userRepository) {
         super(HttpMethod.POST, "/user/create");
+        this.userRepository = userRepository;
     }
 
     @Override
     public HandlerResponse handle(QueryParameters params) {
-        String email = params.getQueryValue("email").orElseThrow(()-> new ServiceException(ErrorCode.MISSING_REGISTER_TOKEN, "email required"));
-        String nickname = params.getQueryValue("nickname").orElseThrow(()-> new ServiceException(ErrorCode.MISSING_REGISTER_TOKEN, "nickname required"));
-        String password = params.getQueryValue("password").orElseThrow(()-> new ServiceException(ErrorCode.MISSING_REGISTER_TOKEN, "password required"));
-        Database.addUser(new User(password, nickname, email, UserRole.MEMBER.toString()));
-        log.info("Registered - password:{}, nickname:{}, email:{}", password, nickname, email);
+        String email = getRequired(params, EMAIL);
+        String nickname = getRequired(params, NICKNAME);
+        String password = getRequired(params, PASSWORD);
+
+        validate(email, nickname, password);
+
+        User saved = userRepository.save(
+                new User(password, nickname, email, UserRole.MEMBER.toString()));
+
+        log.info("Registered id:{}, email:{}, nickname:{}, password:{}",
+                saved.getId(), email, nickname, password);
         return RedirectResponse.to("/login");
     }
+
+    private void validate(String email, String nickname, String password) {
+        validateDuplicate(email, nickname);
+        validateLength(email, VariableConfig.EMAIL_MIN, VariableConfig.EMAIL_MAX, ErrorCode.EMAIL_LENGTH_INVALID);
+        validateLength(nickname, VariableConfig.NICKNAME_MIN, VariableConfig.NICKNAME_MAX, ErrorCode.NICKNAME_LENGTH_INVALID);
+        validateLength(password, VariableConfig.PASSWORD_MIN, VariableConfig.PASSWORD_MAX, ErrorCode.PASSWORD_LENGTH_INVALID);
+    }
+
+    private String getRequired(QueryParameters params, String key) {
+        return params.getQueryValue(key)
+                .orElseThrow(() -> new ServiceException(ErrorCode.MISSING_REGISTER_TOKEN, key + " required"));
+    }
+
+    private void validateLength(String value, int min, int max, ErrorCode code) {
+        int len = value.length();
+        if (len < min || len > max)
+            throw new ServiceException(code);
+    }
+
+    private void validateDuplicate(String email, String nickname) {
+        if (!userRepository.findByColumn(EMAIL, email).isEmpty())
+            throw new ServiceException(ErrorCode.EMAIL_ALREADY_EXISTS);
+
+        if (!userRepository.findByColumn(NICKNAME, nickname).isEmpty())
+            throw new ServiceException(ErrorCode.NICKNAME_ALREADY_EXISTS);
+    }
 }
diff --git a/src/main/java/app/model/User.java b/src/main/java/app/model/User.java
index 936b915e6..7a1dd54bc 100644
--- a/src/main/java/app/model/User.java
+++ b/src/main/java/app/model/User.java
@@ -14,6 +14,9 @@ public User(String password, String nickname, String email, String userRole) {
         this.userRole = userRole;
     }
 
+    public User() {
+    }
+
     public Long getId() {
         return id;
     }
diff --git a/src/main/java/config/AppConfig.java b/src/main/java/config/AppConfig.java
index bc5c4a9cd..da4871a78 100644
--- a/src/main/java/config/AppConfig.java
+++ b/src/main/java/config/AppConfig.java
@@ -1,5 +1,6 @@
 package config;
 
+import app.db.UserRepository;
 import app.handler.*;
 import database.ConnectionManager;
 import database.H2DbManager;
@@ -120,8 +121,7 @@ public RegisterWithGet registerWithGet() {
     public RegisterWithPost registerWithPost() {
         return getOrCreate(
                 "registerWithPost",
-                RegisterWithPost::new
-        );
+                () -> new RegisterWithPost(userRepository()));
     }
 
     public LoginWithPost loginWithPost() {
@@ -233,8 +233,9 @@ public QueryParamsResolver queryParamsResolver() {
     }
 
     public MultipartFormResolver multipartFormResolver(){
-        return getOrCreate("multipartFormResolver", () ->
-                new MultipartFormResolver(multipartFormParser()));
+        return getOrCreate("multipartFormResolver",
+                () -> new MultipartFormResolver(multipartFormParser()));
+
     }
 
     public MultipartFormParser multipartFormParser(){
@@ -250,10 +251,7 @@ public ExceptionHandlerMapping exceptionHandlerMapping() {
                         List.of(
                                 serviceExceptionHandler(),
                                 errorExceptionHandler(),
-                                unhandledErrorHandler()
-                        )
-                )
-        );
+                                unhandledErrorHandler())));
     }
 
     public ServiceExceptionHandler serviceExceptionHandler() {
@@ -325,8 +323,13 @@ public H2DbManager h2DbManager(){
     }
 
     public DdlGenerator ddlGenerator(){
-        return getOrCreate(DdlGenerator.class.getSimpleName(), () ->
-                new DdlGenerator(connectionManager()));
+        return getOrCreate(DdlGenerator.class.getSimpleName(),
+                () -> new DdlGenerator(connectionManager()));
+    }
+
+    public UserRepository userRepository(){
+        return getOrCreate(UserRepository.class.getSimpleName(),
+                ()-> new UserRepository(connectionManager()));
     }
 }
 
diff --git a/src/main/java/config/DdlGenerator.java b/src/main/java/config/DdlGenerator.java
index 3dfb27dbf..0d06d7d7b 100644
--- a/src/main/java/config/DdlGenerator.java
+++ b/src/main/java/config/DdlGenerator.java
@@ -57,7 +57,7 @@ private String buildDdlForEntity(Class<?> entityClass, String tableName) {
                 continue;
             }
 
-            String columnName = field.getName();
+            String columnName = toColumnName(field.getName());
             Class<?> fieldType = field.getType();
 
             if (!firstColumn) {
@@ -108,4 +108,9 @@ private String toTableName(Class<?> clazz) {
         }
         return name;
     }
+
+    private String toColumnName(String str){
+        String snake = str.replaceAll("(?<!^)([A-Z])", "_$1");
+        return snake.toLowerCase();
+    }
 }
diff --git a/src/main/java/config/VariableConfig.java b/src/main/java/config/VariableConfig.java
index 3b74e0c23..962ef6ffd 100644
--- a/src/main/java/config/VariableConfig.java
+++ b/src/main/java/config/VariableConfig.java
@@ -12,4 +12,11 @@ public class VariableConfig {
 
     public static final long IDLE_MS = 30*60*100;
     public static final long ABSOLUTE_MS = 180*60*100;
+
+    public static final int EMAIL_MAX = 50;
+    public static final int EMAIL_MIN = 4;
+    public static final int NICKNAME_MAX = 12;
+    public static final int NICKNAME_MIN = 4;
+    public static final int PASSWORD_MAX = 16;
+    public static final int PASSWORD_MIN = 4;
 }
diff --git a/src/main/java/database/CrudRepository.java b/src/main/java/database/CrudRepository.java
index 55c67cfe4..efdac2690 100644
--- a/src/main/java/database/CrudRepository.java
+++ b/src/main/java/database/CrudRepository.java
@@ -43,10 +43,10 @@ public T save(T entity) {
                 if (Modifier.isStatic(field.getModifiers())) {
                     continue;
                 }
-                if ("id".equals(field.getName())) {
+                if ("id".equals(toColumnName(field.getName()))) {
                     continue;
                 }
-                sqlBuilder.append(field.getName()).append(", ");
+                sqlBuilder.append(toColumnName(field.getName())).append(", ");
                 placeholder.append("?, ");
                 insertFields.add(field);
             }
@@ -128,7 +128,7 @@ public List<T> findAll() {
     }
 
     public List<T> findByColumn(String columnName, Object value) {
-        String sql = "SELECT * FROM " + tableName + " WHERE " + columnName + " = ?";
+        String sql = "SELECT * FROM " + tableName + " WHERE " + toColumnName(columnName) + " = ?";
 
         try (Connection conn = connectionManager.getConnection();
              PreparedStatement pstmt = conn.prepareStatement(sql)) {
@@ -145,7 +145,7 @@ public List<T> findByColumn(String columnName, Object value) {
             }
 
         } catch (SQLException e) {
-            throw new ErrorException("엔티티 조회 중 오류 (column=" + columnName + ", value=" + value + ")", e);
+            throw new ErrorException("엔티티 조회 중 오류 (column=" + toColumnName(columnName) + ", value=" + value + ")", e);
         }
     }
 
@@ -167,10 +167,10 @@ public void update(T entity) {
             if (Modifier.isStatic(field.getModifiers())) {
                 continue;
             }
-            if ("id".equals(field.getName())) {
+            if ("id".equals(toColumnName(field.getName()))) {
                 continue;
             }
-            sql.append(field.getName()).append(" = ?, ");
+            sql.append(toColumnName(field.getName())).append(" = ?, ");
             updateFields.add(field);
         }
 
@@ -264,7 +264,7 @@ private T mapRow(ResultSet resultSet) {
                     continue;
                 }
 
-                String columnName = field.getName();
+                String columnName = toColumnName(field.getName());
                 field.setAccessible(true);
 
                 Class<?> fieldType = field.getType();
@@ -311,4 +311,9 @@ private String toTableName(Class<?> clazz) {
         }
         return name;
     }
+
+    private String toColumnName(String str){
+        String snake = str.replaceAll("(?<!^)([A-Z])", "_$1");
+        return snake.toLowerCase();
+    }
 }
diff --git a/src/main/java/exception/ErrorCode.java b/src/main/java/exception/ErrorCode.java
index 2a541fdc9..56f2d4fec 100644
--- a/src/main/java/exception/ErrorCode.java
+++ b/src/main/java/exception/ErrorCode.java
@@ -9,6 +9,13 @@ public enum ErrorCode {
             HttpStatus.BAD_REQUEST, "400_MISSING_REGISTER_TOKEN", "회원가입에 필요한 토큰이 누락되었습니다."),
     LOGIN_FAILED(
             HttpStatus.BAD_REQUEST, "400_LOGIN_FAILED", "아이디 혹은 비밀번호가 잘못되었습니다."),
+    EMAIL_LENGTH_INVALID(HttpStatus.BAD_REQUEST, "400_EMAIL_LENGTH_INVALID", "이메일은 4 ~ 50글자 사이여야합니다."),
+    NICKNAME_LENGTH_INVALID(HttpStatus.BAD_REQUEST, "400_NICKNAME_LENGTH_INVALID", "닉네임은 4 ~ 12글자 사이여야합니다."),
+    PASSWORD_LENGTH_INVALID(HttpStatus.BAD_REQUEST, "400_PASSWORD_LENGTH_INVALID", "비밀번호는 4 ~ 16글자 사이여야합니다."),
+
+
+    EMAIL_ALREADY_EXISTS(HttpStatus.CONFLICT, "409_EMAIL_ALREADY_EXISTS", "이미 가입된 Email입니다."),
+    NICKNAME_ALREADY_EXISTS(HttpStatus.CONFLICT, "409_NICKNAME_ALREADY_EXISTS", "이미 사용중인 닉네임입니다."),
 
     /* Internal Error */
     INTERNAL_ERROR(HttpStatus.INTERNAL_SERVER_ERROR, "500_INTERNAL", "서버 내부 오류가 발생했습니다."),
diff --git a/src/main/java/exception/handler/ErrorExceptionHandler.java b/src/main/java/exception/handler/ErrorExceptionHandler.java
index 82c0eea19..47c306a83 100644
--- a/src/main/java/exception/handler/ErrorExceptionHandler.java
+++ b/src/main/java/exception/handler/ErrorExceptionHandler.java
@@ -24,11 +24,11 @@ public boolean support(Throwable e) {
     @Override
     public void handle(Throwable t, Socket connection) {
         ErrorException error = (ErrorException) t;
-        logger.debug(error.getThrowable().toString());
+        logger.debug("{} - {}", error.getMessage(), error.getThrowable().toString());
         ErrorCode errorCode = error.getErrorCode();
         HttpStatus status = errorCode.getStatus();
 
-        String body = toJson(errorCode.getCode(), error.getMessage());
+        String body = toJson(errorCode.getCode(), errorCode.getMessage());
         byte[] bodyBytes = body.getBytes(StandardCharsets.UTF_8);
 
         StringBuilder sb = new StringBuilder();