Add category view, pagination, and persist login across deployments

- Add 2-panel category view: sidebar tree + filtered item list
- Category counts use DISTINCT with descendant inclusion
- Hide empty categories, show category badges on item cards
- Add client-side pagination (10 items/page) for both views
- Persist access token in localStorage to survive page refresh
- Fix token refresh retry on backend restart

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitignore

@@ -67,3 +67,4 @@ oracle_data/
 # Claude Code
 # ========================
 .claude/
+cookies.txt

CLAUDE.md

@@ -19,6 +19,8 @@
 
 - 빌드: `cd backend && export JAVA_HOME=/opt/homebrew/Cellar/openjdk/25.0.2/libexec/openjdk.jdk/Contents/Home && set -a && source ../.env && set +a && mvn package -q -DskipTests`
 - 컴파일만: `cd backend && export JAVA_HOME=/opt/homebrew/Cellar/openjdk/25.0.2/libexec/openjdk.jdk/Contents/Home && set -a && source ../.env && set +a && mvn compile`
+- 프론트엔드 빌드/배포: `cd sundol-frontend && bash build.sh` (환경변수 검증 포함)
+- 프론트엔드 빌드 전 `.env`에 `NEXT_PUBLIC_GOOGLE_CLIENT_ID`, `NEXT_PUBLIC_API_URL` 필수. 없으면 Google OAuth 로그인 깨짐.
 - 배포 시 반드시 `git push origin main` 포함
 
 # DB 접속 (Oracle Autonomous DB - SQLcl)

docs/crawling-guide.md

@@ -0,0 +1,223 @@
+# 웹 크롤링 & YouTube 자막 추출 가이드
+
+## 아키텍처 개요
+
+```
+┌─────────────────────────────────────────────────────┐
+│                Spring Boot Application               │
+│                                                      │
+│  ┌──────────────────────────────────────────────┐   │
+│  │         PlaywrightBrowserService              │   │
+│  │  (싱글톤 Chromium 브라우저, 앱 기동 시 1회)    │   │
+│  │  - @PostConstruct: 브라우저 launch            │   │
+│  │  - @PreDestroy: 브라우저 close                │   │
+│  │  - 탭(Page) 단위로 작업 수행                   │   │
+│  │  - 브라우저 죽으면 자동 재시작                  │   │
+│  └──────────┬───────────────┬────────────────────┘   │
+│             │               │                        │
+│  ┌──────────▼──────┐  ┌────▼──────────────────┐     │
+│  │ WebCrawlerService│  │YouTubeTranscriptService│    │
+│  │ (일반 웹페이지)   │  │ (YouTube 자막)         │    │
+│  └─────────────────┘  └───────────────────────┘     │
+└─────────────────────────────────────────────────────┘
+```
+
+## 1. PlaywrightBrowserService (싱글톤 브라우저)
+
+### 핵심 설계
+
+- **싱글톤 패턴**: 앱 기동 시 Chromium을 한 번 띄우고 종료 시까지 유지
+- **탭 기반 작업**: 각 크롤링 요청마다 새 탭(`Page`)을 열고, 완료 후 `about:blank`로 이동 (브라우저 창 유지)
+- **자동 복구**: `ensureBrowserAlive()`로 브라우저 crash 시 자동 재시작
+- **쿠키 로딩**: `cookies.txt`에서 YouTube/Google 쿠키를 읽어 봇 차단 우회
+
+### 왜 싱글톤인가?
+
+| 항목 | 매번 브라우저 생성 | 싱글톤 브라우저 |
+|------|-------------------|----------------|
+| 기동 시간 | 요청마다 2~3초 | 최초 1회만 |
+| 메모리 | 매번 할당/해제 | 안정적 유지 |
+| 쿠키/세션 | 매번 재로딩 | 유지됨 |
+| VNC 디버깅 | 창이 뜨고 사라짐 | 항상 떠있어 관찰 가능 |
+
+### 주요 메서드
+
+```java
+// 새 탭 열기 (호출자가 사용 후 about:blank 또는 close)
+Page openPage(String url, int timeoutMs)
+Page openPage(String url)  // 기본 30초
+
+// 브라우저 페이지 내에서 JS fetch 실행 (쿠키/세션 유지)
+String fetchInPage(Page page, String url)
+```
+
+### 탭 정리 방식
+
+```java
+// page.close() 대신 about:blank로 이동 → 브라우저 창이 유지됨
+try {
+    page.navigate("about:blank");
+} catch (Exception ignored) {
+    page.close();  // about:blank 실패 시에만 탭 닫기
+}
+```
+
+### 쿠키 파일 형식 (`cookies.txt`)
+
+Netscape 쿠키 형식 (탭 구분):
+
+```
+.youtube.com	/	FALSE	TRUE	1780000000	COOKIE_NAME	COOKIE_VALUE
+```
+
+필드 순서: `domain`, `path`, `hostOnly(무시)`, `secure`, `expiry(무시)`, `name`, `value`
+
+YouTube/Google 도메인 쿠키만 로드됨.
+
+## 2. WebCrawlerService (일반 웹페이지 크롤링)
+
+### 3단계 Fallback 전략
+
+```
+1차: Jsoup (경량 HTML 파서)
+  ↓ 실패 또는 유효하지 않은 콘텐츠
+2차: Jina Reader API (외부 서비스)
+  ↓ 실패 또는 유효하지 않은 콘텐츠
+3차: Playwright (싱글톤 브라우저 탭)
+```
+
+### 1차: Jsoup
+
+- Java 기반 HTML 파서, 가장 빠르고 가벼움
+- JavaScript 렌더링 불가 → SPA 사이트에서는 빈 콘텐츠 반환
+- `nav, footer, header, script, style` 등 불필요 요소 제거 후 본문 추출
+
+### 2차: Jina Reader
+
+- `https://r.jina.ai/{URL}` 형태로 외부 서비스 호출
+- JavaScript 렌더링 지원, Markdown/텍스트 형식 반환
+- API 키 설정 시 인증 헤더 추가 가능
+
+### 3차: Playwright
+
+- 싱글톤 브라우저에서 새 탭으로 페이지 로드
+- JavaScript 렌더링 완료 후 `NETWORKIDLE` 대기
+- `page.evaluate()`로 DOM에서 직접 본문 텍스트 추출:
+
+```javascript
+() => {
+  // 불필요 요소 제거
+  ['nav','footer','header','script','style','.ad','#cookie-banner','.sidebar','.comments']
+    .forEach(sel => document.querySelectorAll(sel).forEach(el => el.remove()));
+  // 본문 영역 우선, 없으면 body 전체
+  const article = document.querySelector('article, main, .post-content, .article-body, .entry-content');
+  return (article || document.body).innerText;
+}
+```
+
+### 유효성 검증
+
+모든 단계에서 `isValidContent()` 검증:
+- 최소 100자 이상
+- 에러 페이지 패턴 감지 (403, captcha, "checking your browser" 등)
+
+## 3. YouTubeTranscriptService (YouTube 자막 추출)
+
+### 2단계 Fallback 전략
+
+```
+1차: youtube-transcript-api 라이브러리
+  ↓ 실패 (봇 차단 등)
+2차: Playwright (싱글톤 브라우저)
+  ├─ 방법 A: 자막 패널 DOM 추출
+  └─ 방법 B: Caption URL + fmt=json3
+```
+
+### 1차: youtube-transcript-api
+
+- `io.github.thoroldvix` 라이브러리 사용
+- 수동 자막(manual) 우선, 없으면 자동 생성(generated) 시도
+- 언어 우선순위: `ko` → `en`
+- **한계**: YouTube가 서버 IP를 봇으로 판정하면 실패
+
+### 2차: Playwright Fallback
+
+#### 방법 A: 자막 패널 DOM 추출 (우선)
+
+YouTube 페이지에서 '스크립트 표시' 버튼을 클릭하여 자막 패널을 열고 DOM에서 텍스트를 직접 추출한다.
+
+**흐름**:
+1. YouTube 동영상 페이지 로드 (NETWORKIDLE 대기)
+2. 2초 대기 후 '스크립트 표시' / 'Show transcript' 버튼 탐색 및 클릭
+3. 버튼 못 찾으면 설명란 '더보기' 펼치기 → 다시 탐색
+4. 3초 대기 (자막 패널 로드)
+5. `ytd-transcript-segment-renderer .segment-text` 등 CSS 셀렉터로 자막 텍스트 추출
+
+**장점**: 브라우저의 쿠키/세션이 완전히 유지되어 봇 차단 우회 가능
+
+#### 방법 B: Caption URL + fmt=json3 (보조)
+
+방법 A가 실패하면 HTML에서 `captionTracks`를 파싱하여 caption URL을 추출하고, `&fmt=json3` 파라미터를 추가하여 JSON 형식으로 자막을 요청한다.
+
+**왜 fmt=json3인가?**
+- 기본 XML 형식(`fmt` 없음)은 서명된 URL이 서버 IP에 바인딩되어 빈 응답을 반환하는 경우가 있음
+- `fmt=json3`은 `{"events":[{"segs":[{"utf8":"text"}]}]}` 형식으로 반환
+
+**Caption URL 추출 과정**:
+1. `page.content()`로 HTML 획득
+2. `"captionTracks":\s*\[(.*?)]` 정규식으로 JSON 추출
+3. 언어 우선순위에 따라 URL 선택 (ko → en → 첫 번째)
+4. `\u0026` → `&` 디코딩
+5. `&fmt=json3` 추가
+6. `page.evaluate(fetch())` — 브라우저 내 JS fetch로 요청 (쿠키 유지)
+
+### 언어 선택 로직
+
+```
+captionTracks JSON에서:
+  1. languageCode가 "ko"로 시작하는 트랙 → 최우선
+  2. languageCode가 "en"으로 시작하는 트랙 → 차선
+  3. 첫 번째 트랙 → 최후
+```
+
+## 4. DISPLAY 환경변수와 Head 모드
+
+Playwright가 head 모드(`setHeadless(false)`)로 실행되려면 X Window 디스플레이가 필요하다.
+
+| 환경 | DISPLAY 값 | 설명 |
+|------|-----------|------|
+| VNC 디버깅 | `:1` | VNC 접속 시 브라우저 보임 |
+| 운영 (백그라운드) | `:99` | Xvfb 가상 프레임버퍼 |
+
+설정 위치: `start-backend.sh`의 `export DISPLAY=:1` (또는 `:99`)
+
+## 5. 트러블슈팅
+
+### YouTube 자막이 안 가져와질 때
+
+1. **로그 확인**: `pm2 logs sundol-backend --lines 50`
+2. **"봇 판정"**: youtube-transcript-api 실패 → Playwright fallback 정상 동작하는지 확인
+3. **쿠키 만료**: `cookies.txt`의 쿠키가 오래되면 YouTube가 차단. 브라우저에서 새 쿠키 export 필요
+4. **자막 패널 버튼 변경**: YouTube UI 업데이트로 버튼 텍스트/셀렉터가 바뀌면 `extractTranscriptFromPanel()` 수정 필요
+
+### Playwright 브라우저가 죽었을 때
+
+- `ensureBrowserAlive()`가 자동 재시작
+- 로그에서 `Playwright 브라우저가 죽어있습니다. 재시작합니다.` 확인
+- 수동 재시작: `pm2 restart sundol-backend`
+
+### 크롤링이 빈 결과를 반환할 때
+
+1. Jsoup: JavaScript 렌더링이 필요한 SPA 사이트인지 확인
+2. Jina Reader: API 키 유효한지, rate limit 걸렸는지 확인
+3. Playwright: 해당 사이트가 Cloudflare 등 봇 차단을 하는지 확인
+
+## 6. 관련 파일
+
+| 파일 | 역할 |
+|------|------|
+| `PlaywrightBrowserService.java` | 싱글톤 브라우저 관리 |
+| `WebCrawlerService.java` | 일반 웹 크롤링 (3단계 fallback) |
+| `YouTubeTranscriptService.java` | YouTube 자막 추출 (2단계 fallback) |
+| `cookies.txt` | YouTube/Google 쿠키 (봇 차단 우회) |
+| `start-backend.sh` | DISPLAY 환경변수 설정 |

docs/operation-manual.md

@@ -0,0 +1,182 @@
+# Sundol 운영 매뉴얼
+
+## 프로세스 구성
+
+pm2로 3개 프로세스를 관리한다.
+
+| id | name | 설명 |
+|----|------|------|
+| 0 | pdf-ocr | PDF OCR 서비스 |
+| 1 | sundol-backend | Spring Boot 백엔드 |
+| 2 | sundol-frontend | Next.js 프론트엔드 |
+
+## pm2 기본 명령어
+
+```bash
+# 프로세스 목록 확인
+pm2 list
+
+# 로그 확인
+pm2 logs sundol-backend
+pm2 logs sundol-frontend
+pm2 logs pdf-ocr
+
+# 특정 프로세스 재시작
+pm2 restart sundol-backend
+pm2 restart sundol-frontend
+pm2 restart pdf-ocr
+
+# 전체 재시작
+pm2 restart all
+
+# 프로세스 중지
+pm2 stop sundol-backend
+
+# 프로세스 삭제
+pm2 delete sundol-backend
+```
+
+## 백엔드 시작 스크립트
+
+파일: `start-backend.sh`
+
+```bash
+#!/bin/bash
+set -a
+source /home/opc/sundol/.env
+set +a
+
+JAVA_HOME=${JAVA_HOME:-/usr/lib/jvm/java-21}
+export JAVA_HOME
+
+# Playwright 브라우저 경로
+export PLAYWRIGHT_BROWSERS_PATH=/home/opc/.cache/ms-playwright
+export PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD=1
+
+# Playwright head 모드용 디스플레이
+# :99 = Xvfb 가상 디스플레이 (브라우저 안 보임)
+# :1  = VNC 디스플레이 (VNC에서 브라우저 보임)
+export DISPLAY=:99
+
+# Xvfb 가상 디스플레이 시작 (DISPLAY=:99일 때만 필요)
+if ! pgrep -x Xvfb > /dev/null; then
+    Xvfb :99 -screen 0 1280x720x24 -nolisten tcp &
+    sleep 1
+fi
+
+BACKEND_DIR=/home/opc/sundol/sundol-backend
+exec $JAVA_HOME/bin/java -cp "$BACKEND_DIR/target/classes:$BACKEND_DIR/target/dependency/*" com.sundol.SundolApplication
+```
+
+### DISPLAY 설정 가이드
+
+| DISPLAY 값 | 용도 |
+|-------------|------|
+| `:99` | Xvfb 가상 디스플레이. 브라우저가 백그라운드에서 동작 (기본값) |
+| `:1` | VNC 디스플레이. VNC 접속 시 Playwright 브라우저가 화면에 보임 (디버깅용) |
+
+VNC에서 Playwright 브라우저를 직접 보려면:
+1. `start-backend.sh`에서 `export DISPLAY=:1`로 변경
+2. `pm2 restart sundol-backend`
+
+## 백엔드 빌드
+
+```bash
+cd /home/opc/sundol/sundol-backend
+export JAVA_HOME=/usr/lib/jvm/java-21
+set -a && source /home/opc/sundol/.env && set +a
+mvn package -q -DskipTests
+```
+
+> 컴파일만: `mvn compile` (위 환경변수 동일)
+
+## 프론트엔드 빌드/배포
+
+```bash
+cd /home/opc/sundol/sundol-frontend
+bash build.sh
+```
+
+> `.env`에 `NEXT_PUBLIC_GOOGLE_CLIENT_ID`, `NEXT_PUBLIC_API_URL` 필수.
+
+## 배포 절차
+
+1. 코드 변경 및 빌드
+2. `pm2 restart sundol-backend` (또는 sundol-frontend)
+3. `pm2 logs sundol-backend` 로 정상 기동 확인
+4. `git push origin main`
+
+## DB 접속 (Oracle Autonomous DB)
+
+```bash
+set -a && source /home/opc/sundol/.env && set +a
+/home/opc/sqlcl/bin/sql ${ORACLE_USERNAME}/${ORACLE_PASSWORD}@${ORACLE_TNS_NAME}?TNS_ADMIN=${ORACLE_WALLET_PATH}
+```
+
+## Playwright 관련
+
+- 브라우저 경로: `/home/opc/.cache/ms-playwright`
+- WebCrawlerService: Playwright head 모드 (`setHeadless(false)`)
+- YouTubeTranscriptService: Playwright head 모드 (`setHeadless(false)`)
+- head 모드 사용 시 DISPLAY 환경변수 필수
+
+## Playwright 의존 라이브러리
+
+Playwright Chromium 실행에 필요한 시스템 라이브러리:
+
+```bash
+sudo dnf install -y libicu woff2 harfbuzz-icu libjpeg-turbo libwebp enchant2 hyphen libffi
+```
+
+> `libx264`는 WebKit 전용이므로 Chromium만 사용할 경우 불필요.
+> 로그에 `validateDependenciesLinux` 에러가 나오면 위 패키지 설치 확인.
+
+### Xvfb vs VNC 디스플레이
+
+| 모드 | DISPLAY | 설명 |
+|------|---------|------|
+| Xvfb (운영) | `:99` | 가상 프레임버퍼. 화면 없이 백그라운드 동작 |
+| VNC (디버깅) | `:1` | VNC 접속 시 브라우저가 화면에 보임 |
+
+Xvfb 모드로 되돌리려면 `start-backend.sh`에서:
+```bash
+export DISPLAY=:99
+if ! pgrep -x Xvfb > /dev/null; then
+    Xvfb :99 -screen 0 1280x720x24 -nolisten tcp &
+    sleep 1
+fi
+```
+
+## 트러블슈팅
+
+### 백엔드가 안 뜰 때
+
+```bash
+pm2 logs sundol-backend --lines 50
+```
+
+### Playwright 브라우저가 안 열릴 때
+
+```bash
+# DISPLAY 확인
+echo $DISPLAY
+
+# Xvfb 실행 여부 확인
+pgrep -x Xvfb
+
+# VNC 실행 여부 확인
+vncserver -list
+
+# Playwright 브라우저 설치 확인
+ls /home/opc/.cache/ms-playwright/
+```
+
+### pm2 프로세스가 계속 재시작될 때
+
+```bash
+# 재시작 횟수 확인 (↺ 컬럼)
+pm2 list
+
+# 에러 로그 확인
+pm2 logs sundol-backend --err --lines 100
+```

docs/setup-xwindow.md

@@ -0,0 +1,174 @@
+# X Window + XFCE + VNC 설치 매뉴얼
+
+OCI(Oracle Cloud Infrastructure) Oracle Linux 9 환경 기준.
+
+## 1. 사전 확인
+
+```bash
+# Xorg 설치 여부 확인
+which Xorg
+rpm -q xorg-x11-server-Xorg
+
+# DISPLAY 환경변수 확인 (비어있으면 X 서버 미실행 상태)
+echo $DISPLAY
+```
+
+## 2. EPEL 저장소 설치
+
+```bash
+sudo dnf install -y epel-release
+```
+
+## 3. XFCE 데스크톱 환경 설치
+
+```bash
+sudo dnf groupinstall -y "Xfce"
+```
+
+> GNOME 대비 경량이라 서버 환경에 적합.
+
+## 4. 기본 타겟을 GUI 모드로 변경
+
+```bash
+sudo systemctl set-default graphical.target
+```
+
+> 되돌리려면: `sudo systemctl set-default multi-user.target`
+
+## 5. TigerVNC 서버 설치
+
+SSH 원격 접속 환경에서는 VNC를 통해 GUI에 접근한다.
+
+```bash
+sudo dnf install -y tigervnc-server
+```
+
+## 6. VNC 비밀번호 설정
+
+```bash
+vncpasswd
+```
+
+> VNC 비밀번호는 최대 8자까지만 유효.
+
+## 7. VNC 시작 스크립트 설정
+
+```bash
+mkdir -p ~/.vnc
+
+cat > ~/.vnc/xstartup << 'EOF'
+#!/bin/bash
+exec startxfce4
+EOF
+
+chmod +x ~/.vnc/xstartup
+```
+
+## 8. VNC 서버 시작
+
+```bash
+vncserver :1 -geometry 1920x1080 -depth 24
+```
+
+- `:1` = 포트 5901
+- `:2` = 포트 5902 (추가 세션 필요 시)
+
+### VNC 서버 중지
+
+```bash
+vncserver -kill :1
+```
+
+## 9. 방화벽 포트 개방
+
+```bash
+sudo firewall-cmd --permanent --add-port=5901/tcp
+sudo firewall-cmd --reload
+```
+
+### OCI 보안 목록 설정
+
+OCI 콘솔에서 해당 서브넷의 Security List에 인바운드 규칙 추가:
+- **Source**: 접속할 IP (또는 0.0.0.0/0)
+- **Protocol**: TCP
+- **Destination Port**: 5901
+
+## 10. 클라이언트에서 VNC 접속
+
+### Mac
+
+기본 내장 Screen Sharing 사용:
+
+```bash
+# Finder에서 Cmd+K → 아래 주소 입력
+vnc://공인IP:5901
+
+# 또는 터미널에서
+open vnc://공인IP:5901
+```
+
+### Windows
+
+- RealVNC Viewer, TigerVNC Viewer 등 VNC 클라이언트 설치
+- 주소: `공인IP:5901`
+
+## 11. Chrome 브라우저 설치
+
+```bash
+# Google Chrome 저장소 추가
+cat << 'EOF' | sudo tee /etc/yum.repos.d/google-chrome.repo
+[google-chrome]
+name=google-chrome
+baseurl=https://dl.google.com/linux/chrome/rpm/stable/x86_64
+enabled=1
+gpgcheck=1
+gpgkey=https://dl.google.com/linux/linux_signing_key.pub
+EOF
+
+# 설치
+sudo dnf install -y google-chrome-stable
+```
+
+## 12. 한글 폰트 설치
+
+브라우저 등에서 한글이 깨지는 경우 CJK 폰트를 설치한다.
+
+```bash
+sudo dnf install -y google-noto-sans-cjk-ttc-fonts google-noto-serif-cjk-ttc-fonts
+
+# 폰트 캐시 갱신
+fc-cache -fv
+```
+
+> 설치 후 Chrome 등 브라우저를 재시작해야 반영됨.
+
+## 트러블슈팅
+
+### VNC 접속이 안 될 때
+
+```bash
+# VNC 서버 실행 확인
+vncserver -list
+
+# 로그 확인
+cat ~/.vnc/*.log
+
+# 방화벽 확인
+sudo firewall-cmd --list-ports
+```
+
+### 화면이 회색/빈 화면일 때
+
+`~/.vnc/xstartup` 파일 내용이 올바른지 확인:
+
+```bash
+cat ~/.vnc/xstartup
+# exec startxfce4 가 있어야 함
+```
+
+VNC 서버 재시작:
+
+```bash
+vncserver -kill :1
+vncserver :1 -geometry 1920x1080 -depth 24
+```

docs/troubleshooting.md

@@ -0,0 +1,309 @@
+# 트러블슈팅 가이드
+
+## 1. 프론트엔드 502 Bad Gateway
+
+### 증상
+- 브라우저에서 `502 Bad Gateway nginx/1.20.1` 표시
+
+### 원인
+Next.js standalone 빌드 시 `server.js`가 `sundol-frontend/` 서브디렉토리에 생성되는 경우가 있음.
+PM2가 `.next/standalone/server.js`를 찾지만 실제 파일은 `.next/standalone/sundol-frontend/server.js`에 위치.
+
+### 확인 방법
+```bash
+pm2 list  # sundol-frontend 상태 확인 (errored 여부)
+pm2 logs sundol-frontend --err --lines 20  # 에러 로그 확인
+# "Cannot find module .../standalone/server.js" 에러가 나면 이 문제
+```
+
+### 해결
+```bash
+# server.js 심볼릭 링크 생성
+ln -sf /home/opc/sundol/sundol-frontend/.next/standalone/sundol-frontend/server.js \
+       /home/opc/sundol/sundol-frontend/.next/standalone/server.js
+
+pm2 restart sundol-frontend
+```
+
+> `build.sh`에 이미 자동 처리 로직 포함되어 있음. 문제가 반복되면 build.sh 확인.
+
+---
+
+## 2. 프론트엔드 static 파일 404
+
+### 증상
+- 페이지는 로드되지만 CSS/JS가 404
+- 브라우저 콘솔에 `_next/static/chunks/...js net::ERR_ABORTED 404` 다수 표시
+
+### 원인
+standalone 빌드에서 `.next/static` 심볼릭 링크가 올바른 위치에 걸리지 않음.
+`server.js`가 `standalone/sundol-frontend/` 안에서 실행되므로 static도 그 안에 있어야 함.
+
+### 해결
+```bash
+# 중첩 디렉토리에도 static 링크 생성
+ln -sf /home/opc/sundol/sundol-frontend/.next/static \
+       /home/opc/sundol/sundol-frontend/.next/standalone/sundol-frontend/.next/static
+
+pm2 restart sundol-frontend
+```
+
+> `build.sh`에 자동 처리 로직 포함되어 있음.
+
+---
+
+## 3. 브라우저 로그인 모달 (HTTP Basic Auth 팝업)
+
+### 증상
+- 페이지 리프레시 시 브라우저 기본 로그인 팝업(username/password)이 뜸
+- 특히 JWT 토큰이 만료되었거나 없을 때 발생
+
+### 원인
+Spring Security가 401 응답에 `WWW-Authenticate: Basic` 헤더를 포함.
+브라우저가 이 헤더를 감지하면 자동으로 Basic Auth 로그인 다이얼로그를 표시.
+
+### 해결
+`SecurityConfig.java`에 커스텀 `authenticationEntryPoint` 설정:
+
+```java
+.exceptionHandling(exceptions -> exceptions
+    .authenticationEntryPoint((exchange, ex) -> {
+        exchange.getResponse().setStatusCode(HttpStatus.UNAUTHORIZED);
+        return exchange.getResponse().setComplete();
+    })
+)
+```
+
+이렇게 하면 `WWW-Authenticate` 헤더 없이 401만 반환되어 브라우저 팝업이 뜨지 않음.
+프론트엔드의 axios 인터셉터가 401을 감지하여 자동으로 토큰 갱신 처리.
+
+---
+
+## 4. YouTube 자막 가져오기 실패 (Caption XML 0 chars)
+
+### 증상
+- YouTube 트랜스크립트 가져오기 시 "자막 텍스트를 파싱할 수 없습니다" 에러
+- 로그에 `Caption XML fetched: 0 chars` 표시
+
+### 원인
+YouTube timedtext API의 caption URL이 서명 기반으로, 브라우저 세션 외부에서 요청하면 빈 응답 반환.
+`HttpURLConnection`이나 `context.request().get()`으로는 쿠키/세션이 유지되지 않음.
+
+### 해결
+두 가지 방법으로 fallback 처리:
+
+1. **방법 A (우선)**: YouTube 페이지에서 '스크립트 표시' 패널을 열어 DOM에서 직접 텍스트 추출
+2. **방법 B**: caption URL에 `&fmt=json3` 추가 후 `page.evaluate(fetch())`로 브라우저 내에서 요청
+
+자세한 내용은 [crawling-guide.md](crawling-guide.md) 참조.
+
+---
+
+## 5. Playwright 브라우저 창이 사라짐
+
+### 증상
+- VNC에서 Playwright Chromium 창이 보이다가 사라짐
+
+### 원인
+`page.close()` 호출 시 마지막 탭이 닫히면 브라우저 창이 빈 상태가 됨.
+
+### 해결
+`page.close()` 대신 `page.navigate("about:blank")`으로 변경하여 탭을 유지:
+
+```java
+try {
+    page.navigate("about:blank");
+} catch (Exception ignored) {
+    page.close();
+}
+```
+
+---
+
+## 6. Playwright 의존 라이브러리 누락 경고
+
+### 증상
+- 백엔드 로그에 `Host system is missing dependencies to run browsers` 경고
+- `libicudata.so.66`, `libwoff2dec.so.1.0.2` 등 누락 표시
+
+### 원인
+Playwright가 WebKit 브라우저용 의존성까지 검사함. Chromium만 사용하면 대부분 문제없음.
+
+### 확인
+```bash
+# Chromium 실행 가능 여부 직접 테스트
+/home/opc/.cache/ms-playwright/chromium-1161/chrome-linux/chrome --version
+```
+
+### 해결 (경고 제거하려면)
+```bash
+sudo dnf install -y libicu woff2 harfbuzz-icu libjpeg-turbo libwebp enchant2 hyphen libffi
+```
+
+> `libx264`는 WebKit 전용이므로 Chromium만 사용 시 불필요.
+
+---
+
+## 7. Git Push 인증 실패
+
+### 증상
+- `git push origin main` 시 `could not read Username` 에러
+
+### 원인
+`.netrc`이나 `.git-credentials`에 인증 정보가 없음.
+
+### 해결
+`.env`의 `GIT_USER`, `GIT_PASSWORD` 사용 (비밀번호에 특수문자 포함 시 URL 인코딩 필요):
+
+```bash
+set -a && source /home/opc/sundol/.env && set +a
+ENCODED_PW=$(python3 -c "import urllib.parse; print(urllib.parse.quote('$GIT_PASSWORD', safe=''))")
+git push "https://${GIT_USER}:${ENCODED_PW}@gittea.cloud-handson.com/joungmin/sundol.git" main
+```
+
+---
+
+## 8. LLM 구조화 내용이 잘림
+
+### 증상
+- 지식 정리(구조화) 결과가 중간에 끊김
+
+### 원인
+OCI GenAI의 `maxTokens`가 4096으로 제한되어 있어 긴 콘텐츠 정리 시 응답이 잘림.
+
+### 해결
+한 번에 전체를 정리하지 않고, 나눠서 요청하는 방식으로 변경:
+
+1. **1차 호출**: Abstract + 목차만 생성
+2. **2차~ 호출**: 목차 항목별로 상세 정리 요청 (각각 maxTokens 4096 내에서 충분)
+3. **최종 조합**: 모든 결과를 합침
+
+각 섹션 완료 시 DB에 중간 저장하여 프론트엔드에서 실시간 확인 가능.
+
+---
+
+## 9. VNC 접속 안 됨
+
+### 증상
+- VNC 클라이언트에서 접속 불가
+
+### 확인
+```bash
+# VNC 서버 실행 확인
+vncserver -list
+
+# 방화벽 확인
+sudo firewall-cmd --list-ports
+
+# OCI 보안 목록에서 TCP 5901 인바운드 허용 여부 확인
+```
+
+### 해결
+```bash
+# VNC 서버 재시작
+vncserver -kill :1
+vncserver :1 -geometry 1920x1080 -depth 24
+
+# 방화벽 포트 열기
+sudo firewall-cmd --permanent --add-port=5901/tcp
+sudo firewall-cmd --reload
+```
+
+자세한 내용은 [setup-xwindow.md](setup-xwindow.md) 참조.
+
+---
+
+## 10. VNC 접속 시 스크린 락(화면 잠금) 걸림
+
+### 증상
+- VNC로 접속하면 검은 화면에 로그인 다이얼로그가 뜸
+- 잠시 자리를 비운 뒤 접속하면 사용자 비밀번호를 요구
+
+### 원인
+XFCE 스크린세이버가 기본 활성화되어 있어, 일정 시간 비활성 후 화면을 잠금.
+
+### 해결
+
+```bash
+export DISPLAY=:1
+
+# 스크린세이버 비활성화
+xfconf-query -c xfce4-screensaver -p /saver/enabled --create -t bool -s false
+
+# 화면 잠금 비활성화
+xfconf-query -c xfce4-screensaver -p /lock/enabled --create -t bool -s false
+xfconf-query -c xfce4-screensaver -p /lock/saver-activation/enabled --create -t bool -s false
+
+# 모니터 절전(DPMS) 비활성화
+xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/dpms-enabled --create -t bool -s false
+xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/lock-screen-suspend-hibernate --create -t bool -s false
+
+# 잠금 명령 제거
+xfconf-query -c xfce4-session -p /general/LockCommand --create -t string -s ""
+
+# 실행 중인 screensaver 프로세스 종료
+ps aux | grep -E 'xfce4-screensaver|screensaver-dialog' | grep -v grep | awk '{print $2}' | xargs kill 2>/dev/null
+```
+
+---
+
+## 11. YouTube 자막 추출 시 광고 때문에 실패
+
+### 증상
+- Playwright로 YouTube 페이지 로드 후 자막 패널이 열리지 않음
+- VNC에서 보면 광고가 재생 중
+
+### 원인
+YouTube 동영상 앞에 프리롤 광고가 삽입되면 본 영상 UI(자막 패널 등)가 활성화되지 않음.
+
+### 해결
+코드에 `waitForAdsToFinish()` 로직이 포함되어 있음:
+- 최대 60초간 2초 간격으로 광고 상태 확인
+- 스킵 버튼(`.ytp-skip-ad-button` 등)이 나타나면 자동 클릭
+- 광고가 끝나면 자막 추출 진행
+
+수동으로 확인하려면 VNC에서 Playwright 브라우저 창을 직접 관찰.
+
+---
+
+## 12. 백엔드 재시작 시 로그인이 풀림
+
+### 증상
+- 백엔드(`pm2 restart sundol-backend`) 후 프론트엔드에서 로그인 화면으로 튕김
+- 로그에 `User logged out: null` 표시
+
+### 원인
+1. 백엔드 재시작 중 프론트엔드가 API 호출 → 연결 실패(네트워크 에러)
+2. axios 인터셉터가 401로 인식 → refresh 시도 → 서버 아직 안 떠서 실패
+3. `onRefreshFailed` 콜백 → 자동 로그아웃 실행
+
+### 해결
+프론트엔드 axios 인터셉터에서 refresh 실패 시 네트워크 에러이면 3초 후 최대 2회 재시도:
+
+```typescript
+const attemptRefresh = async (retryCount: number): Promise<string> => {
+  try {
+    const res = await api.post<LoginResponse>("/api/auth/refresh");
+    return res.data.accessToken;
+  } catch (err) {
+    const isNetworkError = !((err as AxiosError).response);
+    if (isNetworkError && retryCount < 2) {
+      await new Promise((r) => setTimeout(r, 3000));
+      return attemptRefresh(retryCount + 1);
+    }
+    throw err;
+  }
+};
+```
+
+백엔드 logout에도 userId null 체크 추가:
+```java
+if (userId == null) {
+    log.warn("Logout called with null userId, ignoring");
+    return;
+}
+```
+
+### 예방
+- 백엔드 재시작 시 기동 완료까지 약 10~25초 소요
+- 프론트엔드는 네트워크 에러 시 최대 9초(3초 × 3회) 대기 후 재시도

docs/youtube-transcript-guide.md

@@ -0,0 +1,207 @@
+# YouTube 트랜스크립트 추출 가이드
+
+## 아키텍처
+
+```
+┌──────────────────────────────────────────────────┐
+│              사용자 Chrome 브라우저                │
+│  (VNC에서 직접 YouTube 로그인된 상태)              │
+│  --remote-debugging-port=9222                     │
+│  --remote-allow-origins=*                         │
+└──────────────┬───────────────────────────────────┘
+               │ CDP (Chrome DevTools Protocol)
+┌──────────────▼───────────────────────────────────┐
+│         PlaywrightBrowserService                  │
+│  playwright.chromium().connectOverCDP()            │
+│  → 사용자 Chrome의 세션/쿠키를 그대로 사용          │
+└──────────────┬───────────────────────────────────┘
+               │
+┌──────────────▼───────────────────────────────────┐
+│        YouTubeTranscriptService                   │
+│  1차: youtube-transcript-api 라이브러리            │
+│  2차: Playwright → 사용자 Chrome 탭으로 추출       │
+└──────────────────────────────────────────────────┘
+```
+
+## 핵심: 왜 사용자 Chrome인가?
+
+### Playwright 자체 브라우저의 한계
+- Playwright가 실행하는 Chromium에는 `--enable-automation` 플래그가 붙음
+- YouTube가 이를 감지하여 **봇으로 판정** → 자막 API 차단
+- 쿠키를 로드해도, 직접 로그인을 시도해도 차단됨
+- Google 로그인 자체가 "안전하지 않은 브라우저"로 거부됨
+
+### 사용자 Chrome + CDP 방식
+- VNC에서 일반 Chrome으로 YouTube에 로그인
+- 백엔드가 CDP로 해당 Chrome에 연결하여 새 탭을 열어 작업
+- **로그인 세션이 그대로 유지**되므로 봇 판정 우회
+- Chrome 자체는 종료하지 않고 연결만 관리
+
+## Chrome 실행 방법
+
+### 필수 옵션
+```bash
+DISPLAY=:1 google-chrome \
+  --remote-debugging-port=9222 \
+  --remote-allow-origins=* \
+  --user-data-dir=/tmp/chrome-debug-profile \
+  --no-default-browser-check \
+  "https://www.youtube.com"
+```
+
+| 옵션 | 설명 |
+|------|------|
+| `--remote-debugging-port=9222` | CDP 접속 포트 |
+| `--remote-allow-origins=*` | CDP WebSocket 연결 허용 |
+| `--user-data-dir` | 프로필 디렉토리 (기본과 다른 경로 필요) |
+
+### Chrome 프로필 복사 (기존 로그인 유지)
+```bash
+cp -r /home/opc/.config/google-chrome /tmp/chrome-debug-profile
+```
+
+### CDP 연결 확인
+```bash
+curl -s http://localhost:9222/json/version | python3 -m json.tool
+```
+
+## YouTube 로그인
+
+1. VNC로 접속 (`vnc://공인IP:5901`)
+2. Chrome에서 YouTube가 열려있는지 확인
+3. YouTube에 Google 계정으로 로그인
+4. 로그인 상태 유지 — Chrome을 닫지 않음
+
+> Chrome을 닫으면 CDP 연결이 끊기고 백엔드가 재연결을 시도함.
+> Chrome을 다시 시작하면 다시 로그인 필요.
+
+## 트랜스크립트 추출 흐름
+
+### 1차: youtube-transcript-api 라이브러리
+```
+videoId → TranscriptApi.listTranscripts()
+  → 수동 자막(ko, en) 우선
+  → 자동 생성 자막 fallback
+```
+- 서버 IP가 봇으로 판정되면 실패 (대부분 실패)
+
+### 2차: Playwright + 사용자 Chrome
+```
+1. 사용자 Chrome에 새 탭 열기 (DOMCONTENTLOADED, 60초 타임아웃)
+2. DOM 렌더링 대기 (3초)
+3. 동영상 재생 시작 (playVideo)
+   - 쿠키 동의 팝업 닫기
+   - 마우스 호버 → 재생 버튼 클릭
+4. 광고 대기 (waitForAdsToFinish, 최대 60초)
+   - 스킵 버튼 자동 클릭
+   - 광고 끝날 때까지 반복 확인
+5. 실제 영상 재생 확인 (waitForVideoPlaying, 최대 15초)
+   - video.currentTime > 0.5 확인
+   - 일시정지면 재시도
+6. ytInitialPlayerResponse에서 자막 URL 추출 + fetch (fetchTranscriptFromPageJs)
+7. 실패 시 자막 패널 열기 (extractTranscriptFromPanel)
+   - 'Show transcript' 버튼 클릭
+   - 자막 세그먼트 DOM에서 텍스트 추출
+   - 최대 30초 반복 확인
+8. 완료 후 about:blank로 이동 (탭 유지)
+```
+
+## 광고 처리
+
+### 감지 방법
+- `#movie_player.ad-showing` 클래스 확인 (가장 신뢰할 수 있음)
+- `.ytp-ad-player-overlay` 오버레이 확인
+- 광고 텍스트 배지 확인 (`.ytp-ad-text`)
+
+### 스킵 버튼 셀렉터
+```css
+.ytp-skip-ad-button,
+.ytp-ad-skip-button,
+.ytp-ad-skip-button-modern,
+.ytp-ad-skip-button-container button
+```
+
+### 주의사항
+- 광고 스킵 후 두 번째 광고가 나올 수 있음 → `no_ad` 상태 확인까지 반복
+- 광고 중에는 `NETWORKIDLE`에 도달하지 못함 → `DOMCONTENTLOADED` 사용
+
+## 쿠키 관리
+
+### CDP 방식에서는 쿠키 파일 불필요
+- 사용자 Chrome에 직접 연결하므로 `cookies.txt` 불필요
+- Chrome 세션의 쿠키가 자동으로 사용됨
+
+### Chrome 쿠키 수동 export (참고용)
+Chrome을 `--remote-debugging-port=9222`로 실행 후:
+```python
+import json, websocket, urllib.request
+
+tabs = json.loads(urllib.request.urlopen("http://localhost:9222/json").read())
+ws_url = tabs[0]["webSocketDebuggerUrl"]
+ws = websocket.create_connection(ws_url)
+ws.send(json.dumps({"id": 1, "method": "Network.getAllCookies"}))
+result = json.loads(ws.recv())
+cookies = result["result"]["cookies"]
+ws.close()
+```
+
+> Chrome의 쿠키 DB(`~/.config/google-chrome/Default/Cookies`)는 암호화되어 있어 직접 읽기 어려움.
+> CDP를 통해 복호화된 쿠키를 가져오는 것이 가장 확실한 방법.
+
+## PM2 + Chrome 자동 시작
+
+Chrome이 서버 재부팅 시에도 자동 시작되도록:
+```bash
+# pm2로 Chrome 관리하지 않음 (GUI 앱이라 적합하지 않음)
+# 대신 VNC 시작 시 자동 실행하도록 ~/.vnc/xstartup에 추가:
+```
+
+`~/.vnc/xstartup`:
+```bash
+#!/bin/bash
+exec startxfce4 &
+
+# Chrome을 CDP 모드로 자동 시작
+sleep 5
+google-chrome --remote-debugging-port=9222 \
+  --remote-allow-origins=* \
+  --user-data-dir=/tmp/chrome-debug-profile \
+  --no-default-browser-check \
+  "https://www.youtube.com" &
+```
+
+## 트러블슈팅
+
+### Chrome CDP 연결 실패
+```
+Chrome CDP 연결 실패: Chrome이 --remote-debugging-port=9222로 실행 중인지 확인하세요.
+```
+→ Chrome 재시작:
+```bash
+DISPLAY=:1 google-chrome --remote-debugging-port=9222 --remote-allow-origins=* \
+  --user-data-dir=/tmp/chrome-debug-profile --no-default-browser-check "https://www.youtube.com" &
+```
+
+### 자막 패널이 ghost-cards만 표시
+- YouTube가 자막 데이터 로드를 차단한 상태
+- Chrome에서 YouTube 로그인이 풀렸는지 VNC에서 확인
+- 로그인 상태라면 Chrome 재시작 후 다시 로그인
+
+### "안전하지 않은 브라우저" 로그인 거부
+- Playwright 자체 브라우저에서 발생 (정상)
+- **사용자 Chrome**에서만 로그인 가능
+- CDP 방식으로 전환하면 해결
+
+### 광고 중에 페이지가 닫힘
+- YouTube 페이지 로드 시 `NETWORKIDLE` 사용하면 광고 때문에 타임아웃
+- **`DOMCONTENTLOADED`** + 60초 타임아웃으로 변경하여 해결
+
+## 관련 파일
+
+| 파일 | 역할 |
+|------|------|
+| `PlaywrightBrowserService.java` | 사용자 Chrome에 CDP 연결, 탭 관리 |
+| `YouTubeTranscriptService.java` | 자막 추출 로직 (API → Playwright fallback) |
+| `youtube-transcript-extract.js` | 자막 패널 DOM 추출 JS |
+| `youtube-transcript-from-page.js` | ytInitialPlayerResponse 기반 자막 추출 JS |
+| `~/.vnc/xstartup` | VNC 시작 시 Chrome 자동 실행 |

ecosystem.config.cjs

@@ -7,6 +7,7 @@ module.exports = {
       cwd: "/home/opc/sundol",
       env: {
         JAVA_HOME: "/usr/lib/jvm/java-21",
+        PLAYWRIGHT_NODEJS_PATH: "/home/opc/.playwright-driver/driver/linux/node",
       },
     },
     {
@@ -17,6 +18,8 @@ module.exports = {
       env: {
         PORT: 3000,
         HOSTNAME: "0.0.0.0",
+        NEXT_PUBLIC_API_URL: "https://sundol.cloud-handson.com",
+        NEXT_PUBLIC_GOOGLE_CLIENT_ID: "906390686133-vpqsisodkg6uqui469hg8dhupbejoa0d.apps.googleusercontent.com",
       },
     },
   ],

start-backend.sh

@@ -6,4 +6,14 @@ set +a
 JAVA_HOME=${JAVA_HOME:-/usr/lib/jvm/java-21}
 export JAVA_HOME
 
-exec $JAVA_HOME/bin/java -jar /home/opc/sundol/sundol-backend/target/sundol-backend-0.0.1-SNAPSHOT.jar
+# Playwright: use pre-installed browsers, skip auto-download
+export PLAYWRIGHT_BROWSERS_PATH=/home/opc/.cache/ms-playwright
+export PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD=1
+
+# Xvfb virtual display for Playwright head mode (YouTube transcript)
+# :99 = Xvfb (백그라운드), :1 = VNC (디버깅용)
+export DISPLAY=:1
+
+# Playwright driver-bundle requires exploded classpath (fat JAR extraction fails)
+BACKEND_DIR=/home/opc/sundol/sundol-backend
+exec $JAVA_HOME/bin/java -cp "$BACKEND_DIR/target/classes:$BACKEND_DIR/target/dependency/*" com.sundol.SundolApplication

sundol-backend/pom.xml

@@ -56,10 +56,12 @@
         <dependency>
             <groupId>com.oracle.database.security</groupId>
             <artifactId>osdt_cert</artifactId>
+            <version>21.18.0.0</version>
         </dependency>
         <dependency>
             <groupId>com.oracle.database.security</groupId>
             <artifactId>osdt_core</artifactId>
+            <version>21.18.0.0</version>
         </dependency>
 
         <!-- JWT -->
@@ -81,6 +83,13 @@
             <scope>runtime</scope>
         </dependency>
 
+        <!-- Google Auth Library -->
+        <dependency>
+            <groupId>com.google.auth</groupId>
+            <artifactId>google-auth-library-oauth2-http</artifactId>
+            <version>1.30.1</version>
+        </dependency>
+
         <!-- Lombok -->
         <dependency>
             <groupId>org.projectlombok</groupId>
@@ -95,6 +104,25 @@
             <version>1.18.3</version>
         </dependency>
 
+        <!-- YouTube Transcript API -->
+        <dependency>
+            <groupId>io.github.thoroldvix</groupId>
+            <artifactId>youtube-transcript-api</artifactId>
+            <version>0.4.0</version>
+        </dependency>
+
+        <!-- Playwright (headless browser, driver-bundle includes node runtime) -->
+        <dependency>
+            <groupId>com.microsoft.playwright</groupId>
+            <artifactId>playwright</artifactId>
+            <version>1.51.0</version>
+        </dependency>
+        <dependency>
+            <groupId>com.microsoft.playwright</groupId>
+            <artifactId>driver-bundle</artifactId>
+            <version>1.51.0</version>
+        </dependency>
+
         <!-- Jackson -->
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>

sundol-backend/src/main/java/com/sundol/config/SecurityConfig.java

@@ -9,6 +9,8 @@ import org.springframework.security.config.annotation.web.reactive.EnableWebFlux
 import org.springframework.security.config.web.server.SecurityWebFiltersOrder;
 import org.springframework.security.config.web.server.ServerHttpSecurity;
 import org.springframework.security.web.server.SecurityWebFilterChain;
+import org.springframework.security.web.server.ServerAuthenticationEntryPoint;
+import org.springframework.http.HttpStatus;
 import org.springframework.web.cors.CorsConfiguration;
 import org.springframework.web.cors.reactive.CorsConfigurationSource;
 import org.springframework.web.cors.reactive.UrlBasedCorsConfigurationSource;
@@ -41,6 +43,12 @@ public class SecurityConfig {
                 .addFilterAt(jwtAuthenticationFilter, SecurityWebFiltersOrder.AUTHENTICATION)
                 .httpBasic(ServerHttpSecurity.HttpBasicSpec::disable)
                 .formLogin(ServerHttpSecurity.FormLoginSpec::disable)
+                .exceptionHandling(exceptions -> exceptions
+                        .authenticationEntryPoint((exchange, ex) -> {
+                            exchange.getResponse().setStatusCode(HttpStatus.UNAUTHORIZED);
+                            return exchange.getResponse().setComplete();
+                        })
+                )
                 .build();
     }
 

sundol-backend/src/main/java/com/sundol/controller/AuthController.java

@@ -1,13 +1,19 @@
 package com.sundol.controller;
 
-import com.sundol.dto.LoginRequest;
 import com.sundol.dto.LoginResponse;
-import com.sundol.dto.RefreshRequest;
 import com.sundol.service.AuthService;
+import org.springframework.http.HttpCookie;
+import org.springframework.http.ResponseCookie;
 import org.springframework.http.ResponseEntity;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.http.server.reactive.ServerHttpResponse;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
 import org.springframework.web.bind.annotation.*;
 import reactor.core.publisher.Mono;
 
+import java.time.Duration;
+import java.util.Map;
+
 @RestController
 @RequestMapping("/api/auth")
 public class AuthController {
@@ -19,19 +25,63 @@ public class AuthController {
     }
 
     @PostMapping("/google")
-    public Mono<ResponseEntity<LoginResponse>> googleLogin(@RequestBody LoginRequest request) {
-        return authService.googleLogin(request.idToken())
-                .map(ResponseEntity::ok);
+    public Mono<ResponseEntity<LoginResponse>> googleLogin(
+            @RequestBody Map<String, String> body,
+            ServerHttpResponse response) {
+        String code = body.get("code");
+        return authService.googleLogin(code)
+                .map(loginResponse -> {
+                    // Set refresh token as HttpOnly cookie
+                    ResponseCookie cookie = ResponseCookie.from("refreshToken", loginResponse.refreshToken())
+                            .httpOnly(true)
+                            .secure(true)
+                            .path("/api/auth")
+                            .maxAge(Duration.ofDays(30))
+                            .sameSite("Strict")
+                            .build();
+                    response.addCookie(cookie);
+                    return ResponseEntity.ok(loginResponse);
+                });
     }
 
     @PostMapping("/refresh")
-    public Mono<ResponseEntity<LoginResponse>> refresh(@RequestBody RefreshRequest request) {
-        return authService.refresh(request.refreshToken())
-                .map(ResponseEntity::ok);
+    public Mono<ResponseEntity<LoginResponse>> refresh(ServerHttpRequest request, ServerHttpResponse response) {
+        HttpCookie cookie = request.getCookies().getFirst("refreshToken");
+        String refreshToken = cookie != null ? cookie.getValue() : null;
+
+        if (refreshToken == null) {
+            return Mono.just(ResponseEntity.status(401).build());
+        }
+
+        return authService.refresh(refreshToken)
+                .map(loginResponse -> {
+                    // Rotate cookie
+                    ResponseCookie newCookie = ResponseCookie.from("refreshToken", loginResponse.refreshToken())
+                            .httpOnly(true)
+                            .secure(true)
+                            .path("/api/auth")
+                            .maxAge(Duration.ofDays(30))
+                            .sameSite("Strict")
+                            .build();
+                    response.addCookie(newCookie);
+                    return ResponseEntity.ok(loginResponse);
+                });
     }
 
     @PostMapping("/logout")
-    public Mono<ResponseEntity<Void>> logout(@RequestAttribute("userId") String userId) {
+    public Mono<ResponseEntity<Void>> logout(
+            @AuthenticationPrincipal String userId,
+            ServerHttpResponse response) {
+        // Clear cookie
+        ResponseCookie cookie = ResponseCookie.from("refreshToken", "")
+                .httpOnly(true)
+                .secure(true)
+                .path("/api/auth")
+                .maxAge(0)
+                .sameSite("Strict")
+                .build();
+        response.addCookie(cookie);
+
         return authService.logout(userId)
                 .then(Mono.just(ResponseEntity.ok().<Void>build()));
     }

sundol-backend/src/main/java/com/sundol/controller/KnowledgeController.java

@@ -1,7 +1,11 @@
 package com.sundol.controller;
 
 import com.sundol.dto.IngestRequest;
+import com.sundol.repository.CategoryRepository;
 import com.sundol.service.KnowledgeService;
+import com.sundol.service.YouTubeTranscriptService;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
@@ -15,10 +19,18 @@ import java.util.Map;
 @RequestMapping("/api/knowledge")
 public class KnowledgeController {
 
-    private final KnowledgeService knowledgeService;
+    private static final Logger log = LoggerFactory.getLogger(KnowledgeController.class);
 
-    public KnowledgeController(KnowledgeService knowledgeService) {
+    private final KnowledgeService knowledgeService;
+    private final YouTubeTranscriptService youTubeTranscriptService;
+    private final CategoryRepository categoryRepository;
+
+    public KnowledgeController(KnowledgeService knowledgeService,
+                               YouTubeTranscriptService youTubeTranscriptService,
+                               CategoryRepository categoryRepository) {
         this.knowledgeService = knowledgeService;
+        this.youTubeTranscriptService = youTubeTranscriptService;
+        this.categoryRepository = categoryRepository;
     }
 
     @GetMapping
@@ -40,6 +52,19 @@ public class KnowledgeController {
                 .map(result -> ResponseEntity.status(HttpStatus.ACCEPTED).body(result));
     }
 
+    @GetMapping("/youtube-transcript")
+    public Mono<ResponseEntity<Map<String, Object>>> fetchYouTubeTranscript(
+            @AuthenticationPrincipal String userId,
+            @RequestParam String url) {
+        return Mono.fromCallable(() -> youTubeTranscriptService.fetchTranscript(url))
+                .map(transcript -> ResponseEntity.ok(Map.<String, Object>of("transcript", transcript)))
+                .onErrorResume(e -> {
+                    log.error("YouTube transcript error: {}", e.getMessage(), e);
+                    return Mono.just(ResponseEntity.status(HttpStatus.BAD_REQUEST)
+                            .body(Map.of("error", e.getMessage() != null ? e.getMessage() : "트랜스크립트를 가져올 수 없습니다")));
+                });
+    }
+
     @GetMapping("/{id}")
     public Mono<ResponseEntity<Map<String, Object>>> getById(
             @AuthenticationPrincipal String userId,
@@ -65,6 +90,38 @@ public class KnowledgeController {
                 .then(Mono.just(ResponseEntity.ok().<Void>build()));
     }
 
+    @PostMapping("/{id}/structure")
+    public Mono<ResponseEntity<Map<String, Object>>> structure(
+            @AuthenticationPrincipal String userId,
+            @PathVariable String id,
+            @RequestBody(required = false) Map<String, String> body) {
+        String modelId = body != null ? body.get("modelId") : null;
+        String englishLevel = body != null ? body.get("englishLevel") : null;
+        return knowledgeService.structureContent(userId, id, modelId, englishLevel)
+                .map(ResponseEntity::ok);
+    }
+
+    @GetMapping("/categories")
+    public Mono<ResponseEntity<Map<String, Object>>> categories(@AuthenticationPrincipal String userId) {
+        return Mono.fromCallable(() -> {
+            var categories = categoryRepository.findAllByUserWithCount(userId);
+            var uncategorized = categoryRepository.findUncategorizedItems(userId);
+            return ResponseEntity.ok(Map.<String, Object>of(
+                    "categories", categories,
+                    "uncategorized", uncategorized
+            ));
+        }).subscribeOn(reactor.core.scheduler.Schedulers.boundedElastic());
+    }
+
+    @GetMapping("/categories/{categoryId}/items")
+    public Mono<ResponseEntity<List<Map<String, Object>>>> itemsByCategory(
+            @AuthenticationPrincipal String userId,
+            @PathVariable String categoryId) {
+        return Mono.fromCallable(() -> categoryRepository.findItemsByCategoryId(userId, categoryId))
+                .subscribeOn(reactor.core.scheduler.Schedulers.boundedElastic())
+                .map(ResponseEntity::ok);
+    }
+
     @GetMapping("/{id}/chunks")
     public Mono<ResponseEntity<List<Map<String, Object>>>> getChunks(
             @AuthenticationPrincipal String userId,

sundol-backend/src/main/java/com/sundol/controller/ModelController.java

@@ -0,0 +1,30 @@
+package com.sundol.controller;
+
+import com.sundol.service.OciGenAiService;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.List;
+import java.util.Map;
+
+@RestController
+@RequestMapping("/api/models")
+public class ModelController {
+
+    private final OciGenAiService genAiService;
+
+    public ModelController(OciGenAiService genAiService) {
+        this.genAiService = genAiService;
+    }
+
+    @GetMapping
+    public ResponseEntity<Map<String, Object>> listModels() {
+        return ResponseEntity.ok(Map.of(
+            "models", OciGenAiService.AVAILABLE_MODELS,
+            "defaultModel", genAiService.getDefaultModel(),
+            "configured", genAiService.isConfigured()
+        ));
+    }
+}

sundol-backend/src/main/java/com/sundol/controller/UserController.java

@@ -0,0 +1,51 @@
+package com.sundol.controller;
+
+import com.sundol.repository.UserRepository;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.web.bind.annotation.*;
+import reactor.core.publisher.Mono;
+import reactor.core.scheduler.Schedulers;
+
+import java.util.Map;
+
+@RestController
+@RequestMapping("/api/users")
+public class UserController {
+
+    private final UserRepository userRepository;
+
+    public UserController(UserRepository userRepository) {
+        this.userRepository = userRepository;
+    }
+
+    @GetMapping("/me")
+    public Mono<ResponseEntity<Map<String, Object>>> me(@AuthenticationPrincipal String userId) {
+        return Mono.fromCallable(() -> {
+            Map<String, Object> user = userRepository.findById(userId);
+            if (user == null) {
+                return ResponseEntity.notFound().<Map<String, Object>>build();
+            }
+            // refresh_token은 응답에서 제외
+            user.remove("REFRESH_TOKEN");
+            return ResponseEntity.ok(user);
+        }).subscribeOn(Schedulers.boundedElastic());
+    }
+
+    @PatchMapping("/me")
+    public Mono<ResponseEntity<Map<String, Object>>> updateMe(
+            @AuthenticationPrincipal String userId,
+            @RequestBody Map<String, Object> updates) {
+        return Mono.fromCallable(() -> {
+            if (updates.containsKey("englishLevel")) {
+                String level = (String) updates.get("englishLevel");
+                if (level != null && level.matches("^(A1|A2|B1|B2|C1|C2)$")) {
+                    userRepository.updateEnglishLevel(userId, level);
+                }
+            }
+            Map<String, Object> user = userRepository.findById(userId);
+            if (user != null) user.remove("REFRESH_TOKEN");
+            return ResponseEntity.ok(user);
+        }).subscribeOn(Schedulers.boundedElastic());
+    }
+}

sundol-backend/src/main/java/com/sundol/dto/IngestRequest.java

@@ -1,3 +1,3 @@
 package com.sundol.dto;
 
-public record IngestRequest(String type, String url, String title, String rawText) {}
+public record IngestRequest(String type, String url, String title, String rawText, String modelId, String englishLevel) {}

sundol-backend/src/main/java/com/sundol/repository/CategoryRepository.java

@@ -0,0 +1,178 @@
+package com.sundol.repository;
+
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.stereotype.Repository;
+
+import java.util.List;
+import java.util.Map;
+
+@Repository
+public class CategoryRepository {
+
+    private final JdbcTemplate jdbcTemplate;
+
+    public CategoryRepository(JdbcTemplate jdbcTemplate) {
+        this.jdbcTemplate = jdbcTemplate;
+    }
+
+    /**
+     * full_path로 카테고리 조회. 없으면 null.
+     */
+    public Map<String, Object> findByUserAndPath(String userId, String fullPath) {
+        var results = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, name, RAWTOHEX(parent_id) AS parent_id, depth, full_path " +
+            "FROM categories WHERE user_id = HEXTORAW(?) AND full_path = ?",
+            userId, fullPath
+        );
+        return results.isEmpty() ? null : results.get(0);
+    }
+
+    /**
+     * 카테고리 생성. 이미 존재하면 기존 ID 반환.
+     * full_path 예: "건강/운동/웨이트트레이닝"
+     */
+    public String findOrCreate(String userId, String fullPath) {
+        Map<String, Object> existing = findByUserAndPath(userId, fullPath);
+        if (existing != null) {
+            return (String) existing.get("ID");
+        }
+
+        // 경로 파싱
+        String[] parts = fullPath.split("/");
+        int depth = parts.length;
+        String name = parts[parts.length - 1];
+
+        // 부모 카테고리 확보 (재귀)
+        String parentId = null;
+        if (depth > 1) {
+            String parentPath = fullPath.substring(0, fullPath.lastIndexOf('/'));
+            parentId = findOrCreate(userId, parentPath);
+        }
+
+        // 삽입
+        if (parentId != null) {
+            jdbcTemplate.update(
+                "INSERT INTO categories (id, user_id, name, parent_id, depth, full_path, created_at) " +
+                "VALUES (SYS_GUID(), HEXTORAW(?), ?, HEXTORAW(?), ?, ?, SYSTIMESTAMP)",
+                userId, name, parentId, depth, fullPath
+            );
+        } else {
+            jdbcTemplate.update(
+                "INSERT INTO categories (id, user_id, name, parent_id, depth, full_path, created_at) " +
+                "VALUES (SYS_GUID(), HEXTORAW(?), ?, NULL, ?, ?, SYSTIMESTAMP)",
+                userId, name, depth, fullPath
+            );
+        }
+
+        Map<String, Object> created = findByUserAndPath(userId, fullPath);
+        return (String) created.get("ID");
+    }
+
+    /**
+     * knowledge_item에 카테고리 매핑
+     */
+    public void linkCategory(String knowledgeItemId, String categoryId) {
+        // 중복 방지
+        Integer count = jdbcTemplate.queryForObject(
+            "SELECT COUNT(*) FROM knowledge_item_categories WHERE knowledge_item_id = HEXTORAW(?) AND category_id = HEXTORAW(?)",
+            Integer.class, knowledgeItemId, categoryId
+        );
+        if (count != null && count > 0) return;
+
+        jdbcTemplate.update(
+            "INSERT INTO knowledge_item_categories (knowledge_item_id, category_id) VALUES (HEXTORAW(?), HEXTORAW(?))",
+            knowledgeItemId, categoryId
+        );
+    }
+
+    /**
+     * knowledge_item의 카테고리 목록 조회
+     */
+    public List<Map<String, Object>> findByKnowledgeItemId(String knowledgeItemId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(c.id) AS id, c.name, c.depth, c.full_path " +
+            "FROM categories c " +
+            "JOIN knowledge_item_categories kic ON kic.category_id = c.id " +
+            "WHERE kic.knowledge_item_id = HEXTORAW(?) " +
+            "ORDER BY c.full_path",
+            knowledgeItemId
+        );
+    }
+
+    /**
+     * 사용자의 전체 카테고리 트리 조회
+     */
+    public List<Map<String, Object>> findAllByUser(String userId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, name, RAWTOHEX(parent_id) AS parent_id, depth, full_path " +
+            "FROM categories WHERE user_id = HEXTORAW(?) ORDER BY full_path",
+            userId
+        );
+    }
+
+    /**
+     * 카테고리 트리 + 해당 카테고리 및 하위 카테고리에 속한 고유 항목 수 조회
+     */
+    public List<Map<String, Object>> findAllByUserWithCount(String userId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(c.id) AS id, c.name, RAWTOHEX(c.parent_id) AS parent_id, c.depth, c.full_path, " +
+            "  (SELECT COUNT(DISTINCT kic.knowledge_item_id) " +
+            "   FROM knowledge_item_categories kic " +
+            "   JOIN categories c2 ON c2.id = kic.category_id " +
+            "   WHERE c2.user_id = HEXTORAW(?) AND (c2.full_path = c.full_path OR c2.full_path LIKE c.full_path || '/%')) AS item_count " +
+            "FROM categories c WHERE c.user_id = HEXTORAW(?) ORDER BY c.full_path",
+            userId, userId
+        );
+    }
+
+    /**
+     * 특정 카테고리 및 하위 카테고리에 속한 knowledge_items 조회.
+     * full_path LIKE 'parent_path%' 로 하위 카테고리를 포함한다.
+     */
+    public List<Map<String, Object>> findItemsByCategoryId(String userId, String categoryId) {
+        // 먼저 선택된 카테고리의 full_path를 가져옴
+        var catResult = jdbcTemplate.queryForList(
+            "SELECT full_path FROM categories WHERE RAWTOHEX(id) = ?", categoryId
+        );
+        if (catResult.isEmpty()) return List.of();
+        String fullPath = (String) catResult.get(0).get("FULL_PATH");
+
+        return jdbcTemplate.queryForList(
+            "SELECT DISTINCT RAWTOHEX(ki.id) AS id, ki.type, ki.title, ki.source_url, ki.status, ki.created_at, " +
+            "  (SELECT LISTAGG(c2.full_path, ', ') WITHIN GROUP (ORDER BY c2.full_path) " +
+            "   FROM knowledge_item_categories kic2 JOIN categories c2 ON c2.id = kic2.category_id " +
+            "   WHERE kic2.knowledge_item_id = ki.id) AS categories " +
+            "FROM knowledge_items ki " +
+            "JOIN knowledge_item_categories kic ON kic.knowledge_item_id = ki.id " +
+            "JOIN categories c ON c.id = kic.category_id " +
+            "WHERE ki.user_id = HEXTORAW(?) AND (c.full_path = ? OR c.full_path LIKE ?) " +
+            "ORDER BY ki.created_at DESC",
+            userId, fullPath, fullPath + "/%"
+        );
+    }
+
+    /**
+     * 카테고리가 없는 knowledge_items 조회
+     */
+    public List<Map<String, Object>> findUncategorizedItems(String userId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(ki.id) AS id, ki.type, ki.title, ki.source_url, ki.status, ki.created_at, " +
+            "  NULL AS categories " +
+            "FROM knowledge_items ki " +
+            "WHERE ki.user_id = HEXTORAW(?) " +
+            "AND NOT EXISTS (SELECT 1 FROM knowledge_item_categories kic WHERE kic.knowledge_item_id = ki.id) " +
+            "ORDER BY ki.created_at DESC",
+            userId
+        );
+    }
+
+    /**
+     * knowledge_item의 카테고리 매핑 전체 삭제
+     */
+    public void unlinkAll(String knowledgeItemId) {
+        jdbcTemplate.update(
+            "DELETE FROM knowledge_item_categories WHERE knowledge_item_id = HEXTORAW(?)",
+            knowledgeItemId
+        );
+    }
+}

sundol-backend/src/main/java/com/sundol/repository/ChatRepository.java

@@ -3,6 +3,9 @@ package com.sundol.repository;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.stereotype.Repository;
 
+import java.util.List;
+import java.util.Map;
+
 @Repository
 public class ChatRepository {
 
@@ -12,5 +15,75 @@ public class ChatRepository {
         this.jdbcTemplate = jdbcTemplate;
     }
 
-    // TODO: CRUD for chat_sessions, chat_messages
+    public String createSession(String userId, String title) {
+        jdbcTemplate.update(
+            "INSERT INTO chat_sessions (id, user_id, title, created_at, updated_at) " +
+            "VALUES (SYS_GUID(), HEXTORAW(?), ?, SYSTIMESTAMP, SYSTIMESTAMP)",
+            userId, title
+        );
+        var result = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id FROM chat_sessions WHERE user_id = HEXTORAW(?) " +
+            "ORDER BY created_at DESC FETCH FIRST 1 ROW ONLY",
+            userId
+        );
+        return (String) result.get(0).get("ID");
+    }
+
+    public List<Map<String, Object>> listSessions(String userId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, title, created_at, updated_at " +
+            "FROM chat_sessions WHERE user_id = HEXTORAW(?) ORDER BY updated_at DESC",
+            userId
+        );
+    }
+
+    public Map<String, Object> findSession(String userId, String sessionId) {
+        var results = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, title, created_at, updated_at " +
+            "FROM chat_sessions WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?)",
+            sessionId, userId
+        );
+        return results.isEmpty() ? null : results.get(0);
+    }
+
+    public void updateSessionTitle(String sessionId, String title) {
+        jdbcTemplate.update(
+            "UPDATE chat_sessions SET title = ?, updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+            title, sessionId
+        );
+    }
+
+    public void touchSession(String sessionId) {
+        jdbcTemplate.update(
+            "UPDATE chat_sessions SET updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+            sessionId
+        );
+    }
+
+    public void deleteSession(String userId, String sessionId) {
+        jdbcTemplate.update(
+            "DELETE FROM chat_messages WHERE session_id = (SELECT id FROM chat_sessions WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?))",
+            sessionId, userId
+        );
+        jdbcTemplate.update(
+            "DELETE FROM chat_sessions WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?)",
+            sessionId, userId
+        );
+    }
+
+    public void insertMessage(String sessionId, String role, String content, String sourceChunksJson, Integer tokensUsed) {
+        jdbcTemplate.update(
+            "INSERT INTO chat_messages (id, session_id, role, content, source_chunks, tokens_used, created_at) " +
+            "VALUES (SYS_GUID(), HEXTORAW(?), ?, ?, ?, ?, SYSTIMESTAMP)",
+            sessionId, role, content, sourceChunksJson, tokensUsed
+        );
+    }
+
+    public List<Map<String, Object>> getMessages(String sessionId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, role, content, source_chunks, tokens_used, created_at " +
+            "FROM chat_messages WHERE session_id = HEXTORAW(?) ORDER BY created_at ASC",
+            sessionId
+        );
+    }
 }

sundol-backend/src/main/java/com/sundol/repository/ChunkEmbeddingRepository.java

@@ -0,0 +1,87 @@
+package com.sundol.repository;
+
+import oracle.jdbc.OracleType;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.stereotype.Repository;
+
+import java.sql.PreparedStatement;
+import java.util.List;
+import java.util.Map;
+
+@Repository
+public class ChunkEmbeddingRepository {
+
+    private final JdbcTemplate jdbcTemplate;
+
+    public ChunkEmbeddingRepository(JdbcTemplate jdbcTemplate) {
+        this.jdbcTemplate = jdbcTemplate;
+    }
+
+    public void upsertEmbedding(String chunkId, String modelId, float[] embedding) {
+        jdbcTemplate.update(
+            "DELETE FROM knowledge_chunk_embeddings WHERE chunk_id = HEXTORAW(?) AND model_id = ?",
+            chunkId, modelId
+        );
+        jdbcTemplate.update(con -> {
+            PreparedStatement ps = con.prepareStatement(
+                "INSERT INTO knowledge_chunk_embeddings (id, chunk_id, model_id, embedding, created_at) " +
+                "VALUES (SYS_GUID(), HEXTORAW(?), ?, ?, SYSTIMESTAMP)"
+            );
+            ps.setString(1, chunkId);
+            ps.setString(2, modelId);
+            ps.setObject(3, embedding, OracleType.VECTOR);
+            return ps;
+        });
+    }
+
+    public List<Map<String, Object>> findByChunkId(String chunkId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, model_id, created_at " +
+            "FROM knowledge_chunk_embeddings WHERE chunk_id = HEXTORAW(?)",
+            chunkId
+        );
+    }
+
+    /**
+     * 벡터 유사도 검색. 사용자의 knowledge 항목 중 READY 상태인 것만 대상.
+     */
+    public List<Map<String, Object>> searchSimilar(String userId, float[] queryEmbedding, int topK) {
+        return jdbcTemplate.query(con -> {
+            PreparedStatement ps = con.prepareStatement(
+                "SELECT RAWTOHEX(c.id) AS chunk_id, c.content, c.chunk_index, c.token_count, " +
+                "       RAWTOHEX(ki.id) AS knowledge_item_id, ki.title, ki.type, ki.source_url, " +
+                "       VECTOR_DISTANCE(e.embedding, ?, COSINE) AS distance " +
+                "FROM knowledge_chunk_embeddings e " +
+                "JOIN knowledge_chunks c ON c.id = e.chunk_id " +
+                "JOIN knowledge_items ki ON ki.id = c.knowledge_item_id " +
+                "WHERE ki.user_id = HEXTORAW(?) AND ki.status = 'READY' " +
+                "ORDER BY distance ASC " +
+                "FETCH FIRST ? ROWS ONLY"
+            );
+            ps.setObject(1, queryEmbedding, OracleType.VECTOR);
+            ps.setString(2, userId);
+            ps.setInt(3, topK);
+            return ps;
+        }, (rs, rowNum) -> {
+            Map<String, Object> row = new java.util.HashMap<>();
+            row.put("CHUNK_ID", rs.getString("chunk_id"));
+            row.put("CONTENT", rs.getString("content"));
+            row.put("CHUNK_INDEX", rs.getInt("chunk_index"));
+            row.put("TOKEN_COUNT", rs.getInt("token_count"));
+            row.put("KNOWLEDGE_ITEM_ID", rs.getString("knowledge_item_id"));
+            row.put("TITLE", rs.getString("title"));
+            row.put("TYPE", rs.getString("type"));
+            row.put("SOURCE_URL", rs.getString("source_url"));
+            row.put("DISTANCE", rs.getDouble("distance"));
+            return row;
+        });
+    }
+
+    public void deleteByKnowledgeItemId(String knowledgeItemId) {
+        jdbcTemplate.update(
+            "DELETE FROM knowledge_chunk_embeddings WHERE chunk_id IN " +
+            "(SELECT id FROM knowledge_chunks WHERE knowledge_item_id = HEXTORAW(?))",
+            knowledgeItemId
+        );
+    }
+}

sundol-backend/src/main/java/com/sundol/repository/HabitRepository.java

@@ -3,6 +3,9 @@ package com.sundol.repository;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.stereotype.Repository;
 
+import java.util.List;
+import java.util.Map;
+
 @Repository
 public class HabitRepository {
 
@@ -12,5 +15,137 @@ public class HabitRepository {
         this.jdbcTemplate = jdbcTemplate;
     }
 
-    // TODO: CRUD for habits, habit_logs
+    public String insert(String userId, String name, String description, String habitType, String targetDays, String color) {
+        jdbcTemplate.update(
+            "INSERT INTO habits (id, user_id, name, description, habit_type, target_days, color, streak_current, streak_best, is_active, created_at, updated_at) " +
+            "VALUES (SYS_GUID(), HEXTORAW(?), ?, ?, ?, ?, ?, 0, 0, 1, SYSTIMESTAMP, SYSTIMESTAMP)",
+            userId, name, description, habitType, targetDays, color
+        );
+        var result = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id FROM habits WHERE user_id = HEXTORAW(?) ORDER BY created_at DESC FETCH FIRST 1 ROW ONLY",
+            userId
+        );
+        return (String) result.get(0).get("ID");
+    }
+
+    public List<Map<String, Object>> list(String userId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, name, description, habit_type, target_days, color, " +
+            "streak_current, streak_best, is_active, created_at, updated_at " +
+            "FROM habits WHERE user_id = HEXTORAW(?) AND is_active = 1 ORDER BY created_at ASC",
+            userId
+        );
+    }
+
+    public Map<String, Object> findById(String userId, String id) {
+        var results = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, name, description, habit_type, target_days, color, " +
+            "streak_current, streak_best, is_active, created_at, updated_at " +
+            "FROM habits WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?)",
+            id, userId
+        );
+        return results.isEmpty() ? null : results.get(0);
+    }
+
+    public void updateName(String id, String name) {
+        jdbcTemplate.update(
+            "UPDATE habits SET name = ?, updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+            name, id
+        );
+    }
+
+    public void updateStreak(String id, int current, int best) {
+        jdbcTemplate.update(
+            "UPDATE habits SET streak_current = ?, streak_best = ?, updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+            current, best, id
+        );
+    }
+
+    public void deactivate(String id) {
+        jdbcTemplate.update(
+            "UPDATE habits SET is_active = 0, updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+            id
+        );
+    }
+
+    public void delete(String userId, String id) {
+        jdbcTemplate.update(
+            "DELETE FROM habit_logs WHERE habit_id = (SELECT id FROM habits WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?))",
+            id, userId
+        );
+        jdbcTemplate.update(
+            "DELETE FROM habits WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?)",
+            id, userId
+        );
+    }
+
+    // --- Habit Logs ---
+
+    public void insertLog(String habitId, String note) {
+        jdbcTemplate.update(
+            "INSERT INTO habit_logs (id, habit_id, log_date, checked_in, note, created_at) " +
+            "VALUES (SYS_GUID(), HEXTORAW(?), TRUNC(SYSDATE), 1, ?, SYSTIMESTAMP)",
+            habitId, note
+        );
+    }
+
+    public boolean hasCheckedInToday(String habitId) {
+        Integer count = jdbcTemplate.queryForObject(
+            "SELECT COUNT(*) FROM habit_logs WHERE habit_id = HEXTORAW(?) AND log_date = TRUNC(SYSDATE) AND checked_in = 1",
+            Integer.class, habitId
+        );
+        return count != null && count > 0;
+    }
+
+    public List<Map<String, Object>> getLogs(String habitId, String from, String to) {
+        StringBuilder sql = new StringBuilder(
+            "SELECT RAWTOHEX(id) AS id, TO_CHAR(log_date, 'YYYY-MM-DD') AS log_date, checked_in, note, created_at " +
+            "FROM habit_logs WHERE habit_id = HEXTORAW(?)"
+        );
+        java.util.ArrayList<Object> params = new java.util.ArrayList<>();
+        params.add(habitId);
+
+        if (from != null && !from.isEmpty()) {
+            sql.append(" AND log_date >= TO_DATE(?, 'YYYY-MM-DD')");
+            params.add(from);
+        }
+        if (to != null && !to.isEmpty()) {
+            sql.append(" AND log_date <= TO_DATE(?, 'YYYY-MM-DD')");
+            params.add(to);
+        }
+        sql.append(" ORDER BY log_date DESC");
+
+        return jdbcTemplate.queryForList(sql.toString(), params.toArray());
+    }
+
+    /**
+     * 연속 체크인 일수 계산 (오늘부터 역순)
+     */
+    public int calculateCurrentStreak(String habitId) {
+        List<Map<String, Object>> logs = jdbcTemplate.queryForList(
+            "SELECT TO_CHAR(log_date, 'YYYY-MM-DD') AS log_date FROM habit_logs " +
+            "WHERE habit_id = HEXTORAW(?) AND checked_in = 1 ORDER BY log_date DESC",
+            habitId
+        );
+        if (logs.isEmpty()) return 0;
+
+        int streak = 0;
+        java.time.LocalDate expected = java.time.LocalDate.now();
+
+        for (Map<String, Object> log : logs) {
+            java.time.LocalDate logDate = java.time.LocalDate.parse((String) log.get("LOG_DATE"));
+            if (logDate.equals(expected)) {
+                streak++;
+                expected = expected.minusDays(1);
+            } else if (logDate.equals(expected.minusDays(1)) && streak == 0) {
+                // 어제까지 연속이면 (오늘 아직 안 한 경우)
+                expected = logDate;
+                streak++;
+                expected = expected.minusDays(1);
+            } else {
+                break;
+            }
+        }
+        return streak;
+    }
 }

sundol-backend/src/main/java/com/sundol/repository/KnowledgeChunkRepository.java

@@ -3,6 +3,9 @@ package com.sundol.repository;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.stereotype.Repository;
 
+import java.util.List;
+import java.util.Map;
+
 @Repository
 public class KnowledgeChunkRepository {
 
@@ -12,5 +15,34 @@ public class KnowledgeChunkRepository {
         this.jdbcTemplate = jdbcTemplate;
     }
 
-    // TODO: CRUD for knowledge_chunks, VECTOR_DISTANCE search
+    public void insertChunk(String knowledgeItemId, int chunkIndex, String content, int tokenCount) {
+        jdbcTemplate.update(
+            "INSERT INTO knowledge_chunks (id, knowledge_item_id, chunk_index, content, token_count, created_at) " +
+            "VALUES (SYS_GUID(), HEXTORAW(?), ?, ?, ?, SYSTIMESTAMP)",
+            knowledgeItemId, chunkIndex, content, tokenCount
+        );
+    }
+
+    public List<Map<String, Object>> findByKnowledgeItemId(String knowledgeItemId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, chunk_index, content, token_count, created_at " +
+            "FROM knowledge_chunks WHERE knowledge_item_id = HEXTORAW(?) ORDER BY chunk_index",
+            knowledgeItemId
+        );
+    }
+
+    public int countByKnowledgeItemId(String knowledgeItemId) {
+        Integer count = jdbcTemplate.queryForObject(
+            "SELECT COUNT(*) FROM knowledge_chunks WHERE knowledge_item_id = HEXTORAW(?)",
+            Integer.class, knowledgeItemId
+        );
+        return count != null ? count : 0;
+    }
+
+    public void deleteByKnowledgeItemId(String knowledgeItemId) {
+        jdbcTemplate.update(
+            "DELETE FROM knowledge_chunks WHERE knowledge_item_id = HEXTORAW(?)",
+            knowledgeItemId
+        );
+    }
 }

sundol-backend/src/main/java/com/sundol/repository/KnowledgeRepository.java

@@ -3,6 +3,10 @@ package com.sundol.repository;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.stereotype.Repository;
 
+import java.sql.Clob;
+import java.util.List;
+import java.util.Map;
+
 @Repository
 public class KnowledgeRepository {
 
@@ -12,5 +16,113 @@ public class KnowledgeRepository {
         this.jdbcTemplate = jdbcTemplate;
     }
 
-    // TODO: CRUD for knowledge_items table
+    public String insert(String userId, String type, String title, String sourceUrl, String rawText) {
+        jdbcTemplate.update(
+            "INSERT INTO knowledge_items (id, user_id, type, title, source_url, raw_text, status, created_at, updated_at) " +
+            "VALUES (SYS_GUID(), HEXTORAW(?), ?, ?, ?, ?, 'PENDING', SYSTIMESTAMP, SYSTIMESTAMP)",
+            userId, type, title, sourceUrl, rawText
+        );
+        // Get the ID of the just-inserted row
+        var result = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id FROM knowledge_items WHERE user_id = HEXTORAW(?) ORDER BY created_at DESC FETCH FIRST 1 ROW ONLY",
+            userId
+        );
+        return (String) result.get(0).get("ID");
+    }
+
+    public List<Map<String, Object>> list(String userId, String type, String status, String search) {
+        StringBuilder sql = new StringBuilder(
+            "SELECT RAWTOHEX(ki.id) AS id, ki.type, ki.title, ki.source_url, ki.status, ki.created_at, ki.updated_at, " +
+            "  (SELECT LISTAGG(c.full_path, ', ') WITHIN GROUP (ORDER BY c.full_path) " +
+            "   FROM knowledge_item_categories kic JOIN categories c ON c.id = kic.category_id " +
+            "   WHERE kic.knowledge_item_id = ki.id) AS categories " +
+            "FROM knowledge_items ki WHERE ki.user_id = HEXTORAW(?)"
+        );
+        java.util.List<Object> params = new java.util.ArrayList<>();
+        params.add(userId);
+
+        if (type != null && !type.isEmpty()) {
+            sql.append(" AND ki.type = ?");
+            params.add(type);
+        }
+        if (status != null && !status.isEmpty()) {
+            sql.append(" AND ki.status = ?");
+            params.add(status);
+        }
+        if (search != null && !search.isEmpty()) {
+            sql.append(" AND UPPER(ki.title) LIKE UPPER(?)");
+            params.add("%" + search + "%");
+        }
+        sql.append(" ORDER BY ki.created_at DESC");
+
+        return jdbcTemplate.queryForList(sql.toString(), params.toArray());
+    }
+
+    public Map<String, Object> findById(String userId, String id) {
+        var results = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, RAWTOHEX(user_id) AS user_id, type, title, source_url, raw_text, structured_content, status, created_at, updated_at " +
+            "FROM knowledge_items WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?)",
+            id, userId
+        );
+        if (results.isEmpty()) return null;
+        return convertClobFields(results.get(0));
+    }
+
+    public Map<String, Object> findByIdInternal(String id) {
+        var results = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, RAWTOHEX(user_id) AS user_id, type, title, source_url, raw_text, structured_content, status, created_at, updated_at " +
+            "FROM knowledge_items WHERE RAWTOHEX(id) = ?",
+            id
+        );
+        if (results.isEmpty()) return null;
+        return convertClobFields(results.get(0));
+    }
+
+    /**
+     * CLOB 필드를 String으로 변환한다.
+     * Oracle JDBC는 4000바이트 이상의 CLOB을 java.sql.Clob 객체로 반환하므로
+     * API 응답 전에 String으로 변환해야 한다.
+     */
+    private Map<String, Object> convertClobFields(Map<String, Object> row) {
+        for (var entry : row.entrySet()) {
+            Object val = entry.getValue();
+            if (val instanceof Clob clob) {
+                try {
+                    entry.setValue(clob.getSubString(1, (int) clob.length()));
+                } catch (Exception e) {
+                    entry.setValue(null);
+                }
+            }
+        }
+        return row;
+    }
+
+    public void updateStatus(String id, String status) {
+        jdbcTemplate.update(
+            "UPDATE knowledge_items SET status = ?, updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+            status, id
+        );
+    }
+
+    public void updateTitle(String id, String title) {
+        jdbcTemplate.update(
+            "UPDATE knowledge_items SET title = ?, updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+            title, id
+        );
+    }
+
+    public void updateStructuredContent(String id, String structuredContent) {
+        jdbcTemplate.update(
+            "UPDATE knowledge_items SET structured_content = ?, updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+            new Object[]{ structuredContent, id },
+            new int[]{ java.sql.Types.CLOB, java.sql.Types.VARCHAR }
+        );
+    }
+
+    public void delete(String userId, String id) {
+        jdbcTemplate.update(
+            "DELETE FROM knowledge_items WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?)",
+            id, userId
+        );
+    }
 }

sundol-backend/src/main/java/com/sundol/repository/StudyCardRepository.java

@@ -3,6 +3,9 @@ package com.sundol.repository;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.stereotype.Repository;
 
+import java.util.List;
+import java.util.Map;
+
 @Repository
 public class StudyCardRepository {
 
@@ -12,5 +15,80 @@ public class StudyCardRepository {
         this.jdbcTemplate = jdbcTemplate;
     }
 
-    // TODO: CRUD for study_cards, SM-2 queries
+    public String insert(String userId, String knowledgeItemId, String front, String back) {
+        if (knowledgeItemId != null) {
+            jdbcTemplate.update(
+                "INSERT INTO study_cards (id, user_id, knowledge_item_id, front, back, ease_factor, interval_days, repetitions, next_review_at, created_at, updated_at) " +
+                "VALUES (SYS_GUID(), HEXTORAW(?), HEXTORAW(?), ?, ?, 2.50, 0, 0, SYSTIMESTAMP, SYSTIMESTAMP, SYSTIMESTAMP)",
+                userId, knowledgeItemId, front, back
+            );
+        } else {
+            jdbcTemplate.update(
+                "INSERT INTO study_cards (id, user_id, knowledge_item_id, front, back, ease_factor, interval_days, repetitions, next_review_at, created_at, updated_at) " +
+                "VALUES (SYS_GUID(), HEXTORAW(?), NULL, ?, ?, 2.50, 0, 0, SYSTIMESTAMP, SYSTIMESTAMP, SYSTIMESTAMP)",
+                userId, front, back
+            );
+        }
+        var result = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id FROM study_cards WHERE user_id = HEXTORAW(?) ORDER BY created_at DESC FETCH FIRST 1 ROW ONLY",
+            userId
+        );
+        return (String) result.get(0).get("ID");
+    }
+
+    public List<Map<String, Object>> getDueCards(String userId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(sc.id) AS id, RAWTOHEX(sc.knowledge_item_id) AS knowledge_item_id, " +
+            "sc.front, sc.back, sc.ease_factor, sc.interval_days, sc.repetitions, sc.next_review_at, " +
+            "ki.title AS knowledge_title " +
+            "FROM study_cards sc " +
+            "LEFT JOIN knowledge_items ki ON ki.id = sc.knowledge_item_id " +
+            "WHERE sc.user_id = HEXTORAW(?) AND sc.next_review_at <= SYSTIMESTAMP " +
+            "ORDER BY sc.next_review_at ASC",
+            userId
+        );
+    }
+
+    public List<Map<String, Object>> getByKnowledgeItem(String userId, String knowledgeItemId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, front, back, ease_factor, interval_days, repetitions, next_review_at, created_at " +
+            "FROM study_cards WHERE user_id = HEXTORAW(?) AND knowledge_item_id = HEXTORAW(?) ORDER BY created_at ASC",
+            userId, knowledgeItemId
+        );
+    }
+
+    public Map<String, Object> findById(String userId, String id) {
+        var results = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, RAWTOHEX(knowledge_item_id) AS knowledge_item_id, " +
+            "front, back, ease_factor, interval_days, repetitions, next_review_at, created_at, updated_at " +
+            "FROM study_cards WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?)",
+            id, userId
+        );
+        return results.isEmpty() ? null : results.get(0);
+    }
+
+    public void updateSm2(String id, double easeFactor, int intervalDays, int repetitions, int nextReviewDaysFromNow) {
+        jdbcTemplate.update(
+            "UPDATE study_cards SET ease_factor = ?, interval_days = ?, repetitions = ?, " +
+            "next_review_at = SYSTIMESTAMP + INTERVAL '1' DAY * ?, updated_at = SYSTIMESTAMP " +
+            "WHERE RAWTOHEX(id) = ?",
+            easeFactor, intervalDays, repetitions, nextReviewDaysFromNow, id
+        );
+    }
+
+    public int countDue(String userId) {
+        Integer count = jdbcTemplate.queryForObject(
+            "SELECT COUNT(*) FROM study_cards WHERE user_id = HEXTORAW(?) AND next_review_at <= SYSTIMESTAMP",
+            Integer.class, userId
+        );
+        return count != null ? count : 0;
+    }
+
+    public int countByKnowledgeItem(String knowledgeItemId) {
+        Integer count = jdbcTemplate.queryForObject(
+            "SELECT COUNT(*) FROM study_cards WHERE knowledge_item_id = HEXTORAW(?)",
+            Integer.class, knowledgeItemId
+        );
+        return count != null ? count : 0;
+    }
 }

sundol-backend/src/main/java/com/sundol/repository/TagRepository.java

@@ -3,6 +3,9 @@ package com.sundol.repository;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.stereotype.Repository;
 
+import java.util.List;
+import java.util.Map;
+
 @Repository
 public class TagRepository {
 
@@ -12,5 +15,83 @@ public class TagRepository {
         this.jdbcTemplate = jdbcTemplate;
     }
 
-    // TODO: CRUD for tags, knowledge_item_tags
+    public String insert(String userId, String name, String color) {
+        jdbcTemplate.update(
+            "INSERT INTO tags (id, user_id, name, color, created_at) " +
+            "VALUES (SYS_GUID(), HEXTORAW(?), ?, ?, SYSTIMESTAMP)",
+            userId, name, color
+        );
+        var result = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id FROM tags WHERE user_id = HEXTORAW(?) ORDER BY created_at DESC FETCH FIRST 1 ROW ONLY",
+            userId
+        );
+        return (String) result.get(0).get("ID");
+    }
+
+    public List<Map<String, Object>> list(String userId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(t.id) AS id, t.name, t.color, t.created_at, " +
+            "(SELECT COUNT(*) FROM knowledge_item_tags kit WHERE kit.tag_id = t.id) AS item_count " +
+            "FROM tags t WHERE t.user_id = HEXTORAW(?) ORDER BY t.name",
+            userId
+        );
+    }
+
+    public Map<String, Object> findById(String userId, String id) {
+        var results = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, name, color, created_at " +
+            "FROM tags WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?)",
+            id, userId
+        );
+        return results.isEmpty() ? null : results.get(0);
+    }
+
+    public void updateName(String id, String name) {
+        jdbcTemplate.update("UPDATE tags SET name = ? WHERE RAWTOHEX(id) = ?", name, id);
+    }
+
+    public void updateColor(String id, String color) {
+        jdbcTemplate.update("UPDATE tags SET color = ? WHERE RAWTOHEX(id) = ?", color, id);
+    }
+
+    public void delete(String userId, String id) {
+        jdbcTemplate.update(
+            "DELETE FROM knowledge_item_tags WHERE tag_id = (SELECT id FROM tags WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?))",
+            id, userId
+        );
+        jdbcTemplate.update(
+            "DELETE FROM tags WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?)",
+            id, userId
+        );
+    }
+
+    // --- Knowledge Item ↔ Tag 매핑 ---
+
+    public void tagItem(String knowledgeItemId, String tagId) {
+        Integer count = jdbcTemplate.queryForObject(
+            "SELECT COUNT(*) FROM knowledge_item_tags WHERE knowledge_item_id = HEXTORAW(?) AND tag_id = HEXTORAW(?)",
+            Integer.class, knowledgeItemId, tagId
+        );
+        if (count != null && count > 0) return;
+        jdbcTemplate.update(
+            "INSERT INTO knowledge_item_tags (knowledge_item_id, tag_id) VALUES (HEXTORAW(?), HEXTORAW(?))",
+            knowledgeItemId, tagId
+        );
+    }
+
+    public void untagItem(String knowledgeItemId, String tagId) {
+        jdbcTemplate.update(
+            "DELETE FROM knowledge_item_tags WHERE knowledge_item_id = HEXTORAW(?) AND tag_id = HEXTORAW(?)",
+            knowledgeItemId, tagId
+        );
+    }
+
+    public List<Map<String, Object>> getTagsForItem(String knowledgeItemId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(t.id) AS id, t.name, t.color " +
+            "FROM tags t JOIN knowledge_item_tags kit ON kit.tag_id = t.id " +
+            "WHERE kit.knowledge_item_id = HEXTORAW(?) ORDER BY t.name",
+            knowledgeItemId
+        );
+    }
 }

sundol-backend/src/main/java/com/sundol/repository/TodoRepository.java

@@ -3,6 +3,10 @@ package com.sundol.repository;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.stereotype.Repository;
 
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
 @Repository
 public class TodoRepository {
 
@@ -12,5 +16,134 @@ public class TodoRepository {
         this.jdbcTemplate = jdbcTemplate;
     }
 
-    // TODO: CRUD for todos table
+    public String insert(String userId, String title, String description, String priority, String dueDate, String parentId) {
+        if (parentId != null) {
+            jdbcTemplate.update(
+                "INSERT INTO todos (id, user_id, parent_id, title, description, status, priority, due_date, created_at, updated_at) " +
+                "VALUES (SYS_GUID(), HEXTORAW(?), HEXTORAW(?), ?, ?, 'PENDING', ?, " +
+                "CASE WHEN ? IS NOT NULL THEN TO_DATE(?, 'YYYY-MM-DD') ELSE NULL END, SYSTIMESTAMP, SYSTIMESTAMP)",
+                userId, parentId, title, description, priority, dueDate, dueDate
+            );
+        } else {
+            jdbcTemplate.update(
+                "INSERT INTO todos (id, user_id, parent_id, title, description, status, priority, due_date, created_at, updated_at) " +
+                "VALUES (SYS_GUID(), HEXTORAW(?), NULL, ?, ?, 'PENDING', ?, " +
+                "CASE WHEN ? IS NOT NULL THEN TO_DATE(?, 'YYYY-MM-DD') ELSE NULL END, SYSTIMESTAMP, SYSTIMESTAMP)",
+                userId, title, description, priority, dueDate, dueDate
+            );
+        }
+
+        var result = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id FROM todos WHERE user_id = HEXTORAW(?) ORDER BY created_at DESC FETCH FIRST 1 ROW ONLY",
+            userId
+        );
+        return (String) result.get(0).get("ID");
+    }
+
+    public List<Map<String, Object>> list(String userId, String status, String priority, String dueDate) {
+        StringBuilder sql = new StringBuilder(
+            "SELECT RAWTOHEX(id) AS id, RAWTOHEX(parent_id) AS parent_id, title, description, status, priority, " +
+            "TO_CHAR(due_date, 'YYYY-MM-DD') AS due_date, created_at, updated_at " +
+            "FROM todos WHERE user_id = HEXTORAW(?) AND parent_id IS NULL"
+        );
+        List<Object> params = new ArrayList<>();
+        params.add(userId);
+
+        if (status != null && !status.isEmpty()) {
+            sql.append(" AND status = ?");
+            params.add(status);
+        }
+        if (priority != null && !priority.isEmpty()) {
+            sql.append(" AND priority = ?");
+            params.add(priority);
+        }
+        if (dueDate != null && !dueDate.isEmpty()) {
+            sql.append(" AND due_date <= TO_DATE(?, 'YYYY-MM-DD')");
+            params.add(dueDate);
+        }
+        sql.append(" ORDER BY CASE priority WHEN 'HIGH' THEN 1 WHEN 'MEDIUM' THEN 2 WHEN 'LOW' THEN 3 END, created_at DESC");
+
+        return jdbcTemplate.queryForList(sql.toString(), params.toArray());
+    }
+
+    public Map<String, Object> findById(String userId, String id) {
+        var results = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, RAWTOHEX(parent_id) AS parent_id, title, description, status, priority, " +
+            "TO_CHAR(due_date, 'YYYY-MM-DD') AS due_date, created_at, updated_at " +
+            "FROM todos WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?)",
+            id, userId
+        );
+        return results.isEmpty() ? null : results.get(0);
+    }
+
+    public List<Map<String, Object>> findSubtasks(String userId, String parentId) {
+        return jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, RAWTOHEX(parent_id) AS parent_id, title, description, status, priority, " +
+            "TO_CHAR(due_date, 'YYYY-MM-DD') AS due_date, created_at, updated_at " +
+            "FROM todos WHERE parent_id = HEXTORAW(?) AND user_id = HEXTORAW(?) ORDER BY created_at ASC",
+            parentId, userId
+        );
+    }
+
+    public void updateStatus(String id, String status) {
+        jdbcTemplate.update(
+            "UPDATE todos SET status = ?, updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+            status, id
+        );
+    }
+
+    public void updateTitle(String id, String title) {
+        jdbcTemplate.update(
+            "UPDATE todos SET title = ?, updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+            title, id
+        );
+    }
+
+    public void updatePriority(String id, String priority) {
+        jdbcTemplate.update(
+            "UPDATE todos SET priority = ?, updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+            priority, id
+        );
+    }
+
+    public void updateDueDate(String id, String dueDate) {
+        if (dueDate != null && !dueDate.isEmpty()) {
+            jdbcTemplate.update(
+                "UPDATE todos SET due_date = TO_DATE(?, 'YYYY-MM-DD'), updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+                dueDate, id
+            );
+        } else {
+            jdbcTemplate.update(
+                "UPDATE todos SET due_date = NULL, updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+                id
+            );
+        }
+    }
+
+    public void delete(String userId, String id) {
+        // 서브태스크 먼저 삭제
+        jdbcTemplate.update(
+            "DELETE FROM todos WHERE parent_id = HEXTORAW(?) AND user_id = HEXTORAW(?)",
+            id, userId
+        );
+        jdbcTemplate.update(
+            "DELETE FROM todos WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?)",
+            id, userId
+        );
+    }
+
+    public int countByUser(String userId, String status) {
+        if (status != null) {
+            Integer count = jdbcTemplate.queryForObject(
+                "SELECT COUNT(*) FROM todos WHERE user_id = HEXTORAW(?) AND status = ?",
+                Integer.class, userId, status
+            );
+            return count != null ? count : 0;
+        }
+        Integer count = jdbcTemplate.queryForObject(
+            "SELECT COUNT(*) FROM todos WHERE user_id = HEXTORAW(?)",
+            Integer.class, userId
+        );
+        return count != null ? count : 0;
+    }
 }

sundol-backend/src/main/java/com/sundol/repository/UserRepository.java

@@ -3,6 +3,8 @@ package com.sundol.repository;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.stereotype.Repository;
 
+import java.util.Map;
+
 @Repository
 public class UserRepository {
 
@@ -12,5 +14,50 @@ public class UserRepository {
         this.jdbcTemplate = jdbcTemplate;
     }
 
-    // TODO: findByGoogleSub, upsert, updateRefreshToken
+    public Map<String, Object> findByGoogleSub(String googleSub) {
+        var results = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, email, display_name, avatar_url, google_sub, english_level FROM users WHERE google_sub = ?",
+            googleSub
+        );
+        return results.isEmpty() ? null : results.get(0);
+    }
+
+    public Map<String, Object> upsert(String email, String displayName, String avatarUrl, String googleSub) {
+        var existing = findByGoogleSub(googleSub);
+        if (existing != null) {
+            jdbcTemplate.update(
+                "UPDATE users SET display_name = ?, avatar_url = ?, updated_at = SYSTIMESTAMP WHERE google_sub = ?",
+                displayName, avatarUrl, googleSub
+            );
+            return findByGoogleSub(googleSub);
+        } else {
+            jdbcTemplate.update(
+                "INSERT INTO users (id, email, display_name, avatar_url, google_sub, created_at, updated_at) VALUES (SYS_GUID(), ?, ?, ?, ?, SYSTIMESTAMP, SYSTIMESTAMP)",
+                email, displayName, avatarUrl, googleSub
+            );
+            return findByGoogleSub(googleSub);
+        }
+    }
+
+    public void updateRefreshToken(String userId, String hashedRefreshToken) {
+        jdbcTemplate.update(
+            "UPDATE users SET refresh_token = ?, updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+            hashedRefreshToken, userId
+        );
+    }
+
+    public Map<String, Object> findById(String userId) {
+        var results = jdbcTemplate.queryForList(
+            "SELECT RAWTOHEX(id) AS id, email, display_name, avatar_url, google_sub, refresh_token, english_level FROM users WHERE RAWTOHEX(id) = ?",
+            userId
+        );
+        return results.isEmpty() ? null : results.get(0);
+    }
+
+    public void updateEnglishLevel(String userId, String englishLevel) {
+        jdbcTemplate.update(
+            "UPDATE users SET english_level = ?, updated_at = SYSTIMESTAMP WHERE RAWTOHEX(id) = ?",
+            englishLevel, userId
+        );
+    }
 }

sundol-backend/src/main/java/com/sundol/service/AuthService.java

@@ -1,34 +1,151 @@
 package com.sundol.service;
 
 import com.sundol.dto.LoginResponse;
+import com.sundol.exception.AppException;
 import com.sundol.repository.UserRepository;
 import com.sundol.security.JwtProvider;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Service;
+import org.springframework.web.reactive.function.client.WebClient;
 import reactor.core.publisher.Mono;
+import reactor.core.scheduler.Schedulers;
+
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.HexFormat;
+import java.util.Map;
 
 @Service
 public class AuthService {
 
+    private static final Logger log = LoggerFactory.getLogger(AuthService.class);
+
     private final UserRepository userRepository;
     private final JwtProvider jwtProvider;
+    private final WebClient webClient;
+
+    @Value("${google.client-id}")
+    private String googleClientId;
+
+    @Value("${google.client-secret}")
+    private String googleClientSecret;
+
+    @Value("${google.redirect-uri}")
+    private String googleRedirectUri;
 
     public AuthService(UserRepository userRepository, JwtProvider jwtProvider) {
         this.userRepository = userRepository;
         this.jwtProvider = jwtProvider;
+        this.webClient = WebClient.builder().build();
     }
 
-    public Mono<LoginResponse> googleLogin(String idToken) {
-        // TODO: Verify Google ID token, upsert user, issue JWT pair
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+    public Mono<LoginResponse> googleLogin(String code) {
+        // Exchange auth code for tokens via Google token endpoint
+        return webClient.post()
+                .uri("https://oauth2.googleapis.com/token")
+                .header("Content-Type", "application/x-www-form-urlencoded")
+                .bodyValue("code=" + code
+                        + "&client_id=" + googleClientId
+                        + "&client_secret=" + googleClientSecret
+                        + "&redirect_uri=" + googleRedirectUri
+                        + "&grant_type=authorization_code")
+                .retrieve()
+                .bodyToMono(Map.class)
+                .flatMap(tokenResponse -> {
+                    String accessToken = (String) tokenResponse.get("access_token");
+                    if (accessToken == null) {
+                        return Mono.error(new AppException(HttpStatus.UNAUTHORIZED, "Failed to exchange auth code"));
+                    }
+                    // Get user info from Google
+                    return webClient.get()
+                            .uri("https://www.googleapis.com/oauth2/v2/userinfo")
+                            .header("Authorization", "Bearer " + accessToken)
+                            .retrieve()
+                            .bodyToMono(Map.class);
+                })
+                .flatMap(userInfo -> Mono.fromCallable(() -> {
+                    String googleSub = (String) userInfo.get("id");
+                    String email = (String) userInfo.get("email");
+                    String name = (String) userInfo.get("name");
+                    String picture = (String) userInfo.get("picture");
+
+                    if (googleSub == null || email == null) {
+                        throw new AppException(HttpStatus.UNAUTHORIZED, "Invalid Google user info");
+                    }
+
+                    // Upsert user
+                    Map<String, Object> user = userRepository.upsert(email, name, picture, googleSub);
+                    String userId = (String) user.get("ID");
+
+                    // Create JWT pair
+                    String jwt = jwtProvider.createAccessToken(userId, email);
+                    String refreshToken = jwtProvider.createRefreshToken(userId, email);
+
+                    // Store hashed refresh token
+                    userRepository.updateRefreshToken(userId, sha256(refreshToken));
+
+                    log.info("User logged in: {} ({})", email, userId);
+                    return new LoginResponse(jwt, refreshToken);
+                }).subscribeOn(Schedulers.boundedElastic()));
     }
 
     public Mono<LoginResponse> refresh(String refreshToken) {
-        // TODO: Validate refresh token, issue new token pair
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            if (!jwtProvider.validateToken(refreshToken)) {
+                throw new AppException(HttpStatus.UNAUTHORIZED, "Invalid refresh token");
+            }
+
+            var claims = jwtProvider.parseToken(refreshToken);
+            String type = claims.get("type", String.class);
+            if (!"REFRESH".equals(type)) {
+                throw new AppException(HttpStatus.UNAUTHORIZED, "Not a refresh token");
+            }
+
+            String userId = claims.getSubject();
+            Map<String, Object> user = userRepository.findById(userId);
+            if (user == null) {
+                throw new AppException(HttpStatus.UNAUTHORIZED, "User not found");
+            }
+
+            // Verify stored hash matches
+            String storedHash = (String) user.get("REFRESH_TOKEN");
+            if (storedHash == null || !storedHash.equals(sha256(refreshToken))) {
+                throw new AppException(HttpStatus.UNAUTHORIZED, "Refresh token revoked");
+            }
+
+            String email = (String) user.get("EMAIL");
+
+            // Issue new pair (rotation)
+            String newAccessToken = jwtProvider.createAccessToken(userId, email);
+            String newRefreshToken = jwtProvider.createRefreshToken(userId, email);
+            userRepository.updateRefreshToken(userId, sha256(newRefreshToken));
+
+            return new LoginResponse(newAccessToken, newRefreshToken);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Void> logout(String userId) {
-        // TODO: Invalidate refresh token
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromRunnable(() -> {
+            if (userId == null) {
+                log.warn("Logout called with null userId, ignoring");
+                return;
+            }
+            userRepository.updateRefreshToken(userId, null);
+            log.info("User logged out: {}", userId);
+        }).subscribeOn(Schedulers.boundedElastic()).then();
+    }
+
+    private String sha256(String input) {
+        try {
+            MessageDigest md = MessageDigest.getInstance("SHA-256");
+            byte[] hash = md.digest(input.getBytes(StandardCharsets.UTF_8));
+            return HexFormat.of().formatHex(hash);
+        } catch (NoSuchAlgorithmException e) {
+            throw new RuntimeException(e);
+        }
     }
 }

sundol-backend/src/main/java/com/sundol/service/ChatService.java

@@ -1,43 +1,186 @@
 package com.sundol.service;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.sundol.exception.AppException;
 import com.sundol.repository.ChatRepository;
+import com.sundol.repository.ChunkEmbeddingRepository;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Service;
 import reactor.core.publisher.Mono;
+import reactor.core.scheduler.Schedulers;
 
 import java.util.List;
 import java.util.Map;
+import java.util.stream.Collectors;
 
 @Service
 public class ChatService {
 
-    private final ChatRepository chatRepository;
+    private static final Logger log = LoggerFactory.getLogger(ChatService.class);
+    private static final int RAG_TOP_K = 5;
 
-    public ChatService(ChatRepository chatRepository) {
+    private final ChatRepository chatRepository;
+    private final ChunkEmbeddingRepository embeddingRepository;
+    private final OciGenAiService genAiService;
+    private final ObjectMapper objectMapper;
+
+    public ChatService(
+            ChatRepository chatRepository,
+            ChunkEmbeddingRepository embeddingRepository,
+            OciGenAiService genAiService,
+            ObjectMapper objectMapper) {
         this.chatRepository = chatRepository;
+        this.embeddingRepository = embeddingRepository;
+        this.genAiService = genAiService;
+        this.objectMapper = objectMapper;
     }
 
     public Mono<List<Map<String, Object>>> listSessions(String userId) {
-        // TODO: List chat sessions for user
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> chatRepository.listSessions(userId))
+                .subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> createSession(String userId) {
-        // TODO: Create new chat session
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            String id = chatRepository.createSession(userId, "New Chat");
+            return chatRepository.findSession(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<List<Map<String, Object>>> getMessages(String userId, String sessionId) {
-        // TODO: Get messages for chat session
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            Map<String, Object> session = chatRepository.findSession(userId, sessionId);
+            if (session == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Chat session not found");
+            }
+            return chatRepository.getMessages(sessionId);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> sendMessage(String userId, String sessionId, String content) {
-        // TODO: RAG pipeline - embed query, search, build prompt, call OCI GenAI
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            Map<String, Object> session = chatRepository.findSession(userId, sessionId);
+            if (session == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Chat session not found");
+            }
+
+            // 1. 사용자 메시지 저장
+            chatRepository.insertMessage(sessionId, "user", content, null, null);
+
+            // 2. RAG: 쿼리 임베딩 → 유사 청크 검색
+            List<Map<String, Object>> relevantChunks = List.of();
+            String contextBlock = "";
+            if (genAiService.isConfigured()) {
+                try {
+                    List<float[]> embeddings = genAiService.embedTexts(List.of(content), "SEARCH_QUERY");
+                    relevantChunks = embeddingRepository.searchSimilar(userId, embeddings.get(0), RAG_TOP_K);
+
+                    if (!relevantChunks.isEmpty()) {
+                        contextBlock = relevantChunks.stream()
+                            .map(chunk -> {
+                                String title = (String) chunk.get("TITLE");
+                                String chunkContent = (String) chunk.get("CONTENT");
+                                String source = (String) chunk.get("SOURCE_URL");
+                                String header = title != null ? "[" + title + "]" : "[Untitled]";
+                                if (source != null) header += " (" + source + ")";
+                                return header + "\n" + chunkContent;
+                            })
+                            .collect(Collectors.joining("\n\n---\n\n"));
+                    }
+                } catch (Exception e) {
+                    log.warn("RAG search failed, proceeding without context", e);
+                }
+            }
+
+            // 3. 대화 히스토리 조회 (최근 20개)
+            List<Map<String, Object>> history = chatRepository.getMessages(sessionId);
+            int historyStart = Math.max(0, history.size() - 20);
+            List<Map<String, Object>> recentHistory = history.subList(historyStart, history.size());
+
+            // 4. LLM 프롬프트 구성
+            String systemMsg = buildSystemPrompt(contextBlock);
+            String userMsg = buildUserPrompt(recentHistory, content);
+
+            // 5. LLM 호출
+            String assistantResponse;
+            try {
+                assistantResponse = genAiService.chat(systemMsg, userMsg, null);
+            } catch (Exception e) {
+                log.error("LLM chat failed", e);
+                assistantResponse = "죄송합니다, 응답을 생성하는 중 오류가 발생했습니다.";
+            }
+
+            // 6. 응답 저장
+            String sourceChunksJson = null;
+            if (!relevantChunks.isEmpty()) {
+                try {
+                    List<Map<String, Object>> sources = relevantChunks.stream()
+                        .map(c -> Map.of(
+                            "knowledgeItemId", (Object) c.get("KNOWLEDGE_ITEM_ID"),
+                            "title", c.get("TITLE") != null ? c.get("TITLE") : "Untitled",
+                            "chunkIndex", c.get("CHUNK_INDEX"),
+                            "distance", c.get("DISTANCE")
+                        ))
+                        .toList();
+                    sourceChunksJson = objectMapper.writeValueAsString(sources);
+                } catch (Exception e) {
+                    log.warn("Failed to serialize source chunks", e);
+                }
+            }
+            chatRepository.insertMessage(sessionId, "assistant", assistantResponse, sourceChunksJson, null);
+
+            // 7. 첫 메시지면 세션 제목 업데이트
+            if (history.size() <= 1) {
+                String sessionTitle = content.length() > 50
+                        ? content.substring(0, 50) + "..." : content;
+                chatRepository.updateSessionTitle(sessionId, sessionTitle);
+            }
+            chatRepository.touchSession(sessionId);
+
+            return Map.of(
+                "role", (Object) "assistant",
+                "content", assistantResponse,
+                "sourceChunks", sourceChunksJson != null ? sourceChunksJson : "[]"
+            );
+        }).subscribeOn(Schedulers.boundedElastic());
+    }
+
+    private String buildSystemPrompt(String contextBlock) {
+        StringBuilder sb = new StringBuilder();
+        sb.append("You are SUNDOL, a helpful personal knowledge assistant. ");
+        sb.append("Answer questions based on the user's knowledge base. ");
+        sb.append("If the context contains relevant information, use it to answer accurately. ");
+        sb.append("If the context doesn't contain relevant information, say so honestly. ");
+        sb.append("Respond in the same language the user uses.");
+
+        if (!contextBlock.isBlank()) {
+            sb.append("\n\n--- Knowledge Context ---\n\n");
+            sb.append(contextBlock);
+            sb.append("\n\n--- End Context ---");
+        }
+
+        return sb.toString();
+    }
+
+    private String buildUserPrompt(List<Map<String, Object>> history, String currentMessage) {
+        StringBuilder sb = new StringBuilder();
+        // 최근 대화 히스토리를 포함하여 맥락 유지 (현재 메시지 제외)
+        for (int i = 0; i < history.size() - 1; i++) {
+            Map<String, Object> msg = history.get(i);
+            String role = (String) msg.get("ROLE");
+            Object contentObj = msg.get("CONTENT");
+            String content = contentObj != null ? contentObj.toString() : "";
+            sb.append(role.equals("user") ? "User: " : "Assistant: ");
+            sb.append(content).append("\n\n");
+        }
+        sb.append(currentMessage);
+        return sb.toString();
     }
 
     public Mono<Void> deleteSession(String userId, String sessionId) {
-        // TODO: Delete chat session and messages
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromRunnable(() -> chatRepository.deleteSession(userId, sessionId))
+                .subscribeOn(Schedulers.boundedElastic()).then();
     }
 }

sundol-backend/src/main/java/com/sundol/service/ChunkingService.java

@@ -0,0 +1,37 @@
+package com.sundol.service;
+
+import org.springframework.stereotype.Service;
+
+import java.util.ArrayList;
+import java.util.List;
+
+@Service
+public class ChunkingService {
+
+    private static final int CHUNK_SIZE_TOKENS = 500;
+    private static final int CHUNK_OVERLAP_TOKENS = 50;
+
+    public List<String> chunk(String text) {
+        if (text == null || text.isBlank()) {
+            return List.of();
+        }
+
+        String[] words = text.split("\\s+");
+        int chunkWords = (int) (CHUNK_SIZE_TOKENS * 0.75);
+        int overlapWords = (int) (CHUNK_OVERLAP_TOKENS * 0.75);
+
+        List<String> chunks = new ArrayList<>();
+        int i = 0;
+        while (i < words.length) {
+            int end = Math.min(i + chunkWords, words.length);
+            chunks.add(String.join(" ", java.util.Arrays.copyOfRange(words, i, end)));
+            i += chunkWords - overlapWords;
+        }
+        return chunks;
+    }
+
+    public int estimateTokenCount(String text) {
+        if (text == null || text.isBlank()) return 0;
+        return (int) (text.split("\\s+").length / 0.75);
+    }
+}

sundol-backend/src/main/java/com/sundol/service/HabitService.java

@@ -1,9 +1,12 @@
 package com.sundol.service;
 
 import com.sundol.dto.HabitRequest;
+import com.sundol.exception.AppException;
 import com.sundol.repository.HabitRepository;
+import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Service;
 import reactor.core.publisher.Mono;
+import reactor.core.scheduler.Schedulers;
 
 import java.util.List;
 import java.util.Map;
@@ -18,32 +21,85 @@ public class HabitService {
     }
 
     public Mono<List<Map<String, Object>>> list(String userId) {
-        // TODO: List habits for user
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            List<Map<String, Object>> habits = habitRepository.list(userId);
+            for (Map<String, Object> habit : habits) {
+                String habitId = (String) habit.get("ID");
+                habit.put("CHECKED_TODAY", habitRepository.hasCheckedInToday(habitId));
+            }
+            return habits;
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> create(String userId, HabitRequest request) {
-        // TODO: Create habit
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            String habitType = request.habitType() != null ? request.habitType() : "DAILY";
+            String color = request.color() != null ? request.color() : "#6366f1";
+            String id = habitRepository.insert(
+                    userId, request.name(), request.description(),
+                    habitType, request.targetDays(), color
+            );
+            return habitRepository.findById(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> update(String userId, String id, Map<String, Object> updates) {
-        // TODO: Update habit
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            Map<String, Object> habit = habitRepository.findById(userId, id);
+            if (habit == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Habit not found");
+            }
+            if (updates.containsKey("name")) {
+                habitRepository.updateName(id, (String) updates.get("name"));
+            }
+            return habitRepository.findById(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Void> delete(String userId, String id) {
-        // TODO: Delete habit and logs
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromRunnable(() -> {
+            Map<String, Object> habit = habitRepository.findById(userId, id);
+            if (habit == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Habit not found");
+            }
+            habitRepository.delete(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic()).then();
     }
 
     public Mono<Map<String, Object>> checkin(String userId, String id, String note) {
-        // TODO: Check in for today
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            Map<String, Object> habit = habitRepository.findById(userId, id);
+            if (habit == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Habit not found");
+            }
+            if (habitRepository.hasCheckedInToday(id)) {
+                throw new AppException(HttpStatus.CONFLICT, "Already checked in today");
+            }
+
+            habitRepository.insertLog(id, note);
+
+            // 스트릭 갱신
+            int currentStreak = habitRepository.calculateCurrentStreak(id);
+            Number bestStreakNum = (Number) habit.get("STREAK_BEST");
+            int bestStreak = bestStreakNum != null ? bestStreakNum.intValue() : 0;
+            if (currentStreak > bestStreak) {
+                bestStreak = currentStreak;
+            }
+            habitRepository.updateStreak(id, currentStreak, bestStreak);
+
+            Map<String, Object> updated = habitRepository.findById(userId, id);
+            updated.put("CHECKED_TODAY", true);
+            return updated;
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<List<Map<String, Object>>> getLogs(String userId, String id, String from, String to) {
-        // TODO: Get habit logs
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            Map<String, Object> habit = habitRepository.findById(userId, id);
+            if (habit == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Habit not found");
+            }
+            return habitRepository.getLogs(id, from, to);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 }

sundol-backend/src/main/java/com/sundol/service/IngestPipelineService.java

@@ -0,0 +1,571 @@
+package com.sundol.service;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.sundol.repository.CategoryRepository;
+import com.sundol.repository.ChunkEmbeddingRepository;
+import com.sundol.repository.KnowledgeChunkRepository;
+import com.sundol.repository.KnowledgeRepository;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Service;
+
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+@Service
+public class IngestPipelineService {
+
+    private static final Logger log = LoggerFactory.getLogger(IngestPipelineService.class);
+
+    private final KnowledgeRepository knowledgeRepository;
+    private final KnowledgeChunkRepository chunkRepository;
+    private final ChunkEmbeddingRepository embeddingRepository;
+    private final CategoryRepository categoryRepository;
+    private final com.sundol.repository.UserRepository userRepository;
+    private final ChunkingService chunkingService;
+    private final WebCrawlerService webCrawlerService;
+    private final OciGenAiService genAiService;
+    private final ObjectMapper objectMapper;
+
+    public IngestPipelineService(
+            KnowledgeRepository knowledgeRepository,
+            KnowledgeChunkRepository chunkRepository,
+            ChunkEmbeddingRepository embeddingRepository,
+            CategoryRepository categoryRepository,
+            com.sundol.repository.UserRepository userRepository,
+            ChunkingService chunkingService,
+            WebCrawlerService webCrawlerService,
+            OciGenAiService genAiService,
+            ObjectMapper objectMapper) {
+        this.knowledgeRepository = knowledgeRepository;
+        this.chunkRepository = chunkRepository;
+        this.embeddingRepository = embeddingRepository;
+        this.categoryRepository = categoryRepository;
+        this.userRepository = userRepository;
+        this.chunkingService = chunkingService;
+        this.webCrawlerService = webCrawlerService;
+        this.genAiService = genAiService;
+        this.objectMapper = objectMapper;
+    }
+
+    private static final int TITLE_MAX_LENGTH = 80;
+    private static final int TEXT_PREVIEW_LENGTH = 3000;
+    private static final int STRUCTURING_MIN_LENGTH = 1000;
+
+    /**
+     * LLM으로 콘텐츠를 구조화: Abstract + 목차 + 목차별 상세 정리.
+     * 1000자 이상일 때만 실행.
+     * 1차 호출: Abstract + 목차 생성, 2차~ 호출: 목차별 상세 정리, 최종 조합.
+     */
+    public String structureContent(String text, String modelId, String knowledgeItemId) {
+        return structureContent(text, modelId, knowledgeItemId, "B2");
+    }
+
+    public String structureContent(String text, String modelId, String knowledgeItemId, String englishLevel) {
+        if (!genAiService.isConfigured()) {
+            log.info("OCI GenAI not configured, skipping structuring");
+            return null;
+        }
+
+        if (text.length() < STRUCTURING_MIN_LENGTH) {
+            log.info("Content too short for structuring ({} chars), skipping", text.length());
+            return null;
+        }
+
+        try {
+            String content = text.length() > 30000 ? text.substring(0, 30000) : text;
+            boolean isEnglish = isEnglishContent(content);
+            String level = (englishLevel == null || englishLevel.isBlank()) ? "B2" : englishLevel;
+            log.info("Structuring content: isEnglish={}, englishLevel={}", isEnglish, level);
+
+            // === 1차 호출: Abstract + 목차 생성 ===
+            String tocSystemMsg = buildTocSystemMsg(isEnglish);
+            String tocUserMsg = "아래 원본 텍스트의 요약과 목차를 생성해주세요:\n\n" + content;
+            String tocResult = genAiService.chat(tocSystemMsg, tocUserMsg, modelId).strip();
+            log.info("Phase 1 - TOC generated: {} chars", tocResult.length());
+
+            // 1차 결과 중간 저장
+            if (knowledgeItemId != null) {
+                knowledgeRepository.updateStructuredContent(knowledgeItemId, tocResult);
+            }
+
+            // 목차 항목 파싱
+            List<String> tocItems = parseTocItems(tocResult);
+            if (tocItems.isEmpty()) {
+                log.warn("No TOC items parsed, returning TOC-only result");
+                return tocResult;
+            }
+            log.info("Parsed {} TOC items: {}", tocItems.size(), tocItems);
+
+            // === 2차~ 호출: 목차별 상세 정리 (잘리면 이어쓰기) ===
+            StringBuilder fullResult = new StringBuilder(tocResult).append("\n\n");
+            String sectionSystemMsg = buildSectionSystemMsg(isEnglish, level);
+
+            for (int i = 0; i < tocItems.size(); i++) {
+                String tocItem = tocItems.get(i);
+                int sectionNum = i + 1;
+                log.info("Phase 2 - Processing section {}: '{}'", sectionNum, tocItem);
+
+                try {
+                    String sectionUserMsg = "원본 텍스트에서 아래 섹션에 해당하는 내용을 상세히 정리해주세요.\n" +
+                            "응답이 잘릴 경우 문장 중간에 끊지 말고, 완성된 문장까지만 작성하세요.\n\n" +
+                            "## 정리할 섹션\n" + sectionNum + ". " + tocItem + "\n\n" +
+                            "## 원본 텍스트\n" + content;
+
+                    String sectionResult = genAiService.chat(sectionSystemMsg, sectionUserMsg, modelId).strip();
+                    fullResult.append(sectionResult).append("\n\n");
+                    log.info("Phase 2 - Section {} '{}' generated: {} chars", sectionNum, tocItem, sectionResult.length());
+
+                    // 응답이 잘린 것 같으면 이어쓰기 (최대 2회)
+                    for (int cont = 0; cont < 2; cont++) {
+                        if (sectionResult.length() < 3500) break;
+                        String lastChars = sectionResult.substring(Math.max(0, sectionResult.length() - 50));
+                        if (lastChars.endsWith(".") || lastChars.endsWith("다.") || lastChars.endsWith("니다.") ||
+                            lastChars.endsWith("음.") || lastChars.endsWith("임.") || lastChars.endsWith("함.") ||
+                            lastChars.endsWith("습니다.") || lastChars.endsWith("됩니다.")) {
+                            break;
+                        }
+
+                        log.info("Phase 2 - Section {} may be truncated, continuation {}", sectionNum, cont + 1);
+                        String contUserMsg = "이전 응답이 잘렸습니다. 아래 마지막 부분부터 이어서 작성해주세요.\n" +
+                                "이미 작성된 내용을 반복하지 마세요.\n\n" +
+                                "## 이전 응답의 마지막 200자\n" +
+                                sectionResult.substring(Math.max(0, sectionResult.length() - 200)) + "\n\n" +
+                                "## 정리할 섹션\n" + sectionNum + ". " + tocItem + "\n\n" +
+                                "## 원본 텍스트\n" + content;
+
+                        String contResult = genAiService.chat(sectionSystemMsg, contUserMsg, modelId).strip();
+                        if (contResult.isBlank()) break;
+
+                        fullResult.append(contResult).append("\n\n");
+                        sectionResult = contResult;
+                        log.info("Phase 2 - Section {} continuation {}: {} chars", sectionNum, cont + 1, contResult.length());
+
+                        if (knowledgeItemId != null) {
+                            knowledgeRepository.updateStructuredContent(knowledgeItemId, fullResult.toString().strip());
+                        }
+                    }
+                } catch (Exception e) {
+                    log.warn("Failed to process section {}: {}", sectionNum, e.getMessage());
+                    fullResult.append("# ").append(sectionNum).append(". ").append(tocItem).append("\n\n(정리 실패)\n\n");
+                }
+
+                // 섹션 완료마다 중간 저장
+                if (knowledgeItemId != null) {
+                    knowledgeRepository.updateStructuredContent(knowledgeItemId, fullResult.toString().strip());
+                }
+            }
+
+            String result = fullResult.toString().strip();
+            log.info("Structured content generated: {} chars ({} sections)", result.length(), tocItems.size());
+            return result;
+        } catch (Exception e) {
+            log.warn("Content structuring failed", e);
+            return null;
+        }
+    }
+
+    /**
+     * 영어 컨텐츠인지 판단한다 (ASCII 알파벳 비중 60% 이상).
+     */
+    private boolean isEnglishContent(String text) {
+        if (text == null || text.isBlank()) return false;
+        int alpha = 0, total = 0;
+        for (int i = 0; i < text.length(); i++) {
+            char c = text.charAt(i);
+            if (Character.isWhitespace(c)) continue;
+            total++;
+            if ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')) alpha++;
+        }
+        if (total == 0) return false;
+        double ratio = (double) alpha / total;
+        return ratio >= 0.6;
+    }
+
+    /**
+     * CEFR 레벨에 대한 설명을 반환한다 (TOEIC 매핑 포함).
+     */
+    private String cefrDescription(String level) {
+        return switch (level) {
+            case "A1" -> "A1 (TOEIC 120-225, 입문)";
+            case "A2" -> "A2 (TOEIC 225-550, 초급, 기초 회화)";
+            case "B1" -> "B1 (TOEIC 550-785, 중급, 일상 의사소통)";
+            case "B2" -> "B2 (TOEIC 785-945, 중상급, 업무 영어)";
+            case "C1" -> "C1 (TOEIC 945-990, 고급, 유창함)";
+            case "C2" -> "C2 (원어민 수준)";
+            default -> "B2 (TOEIC 785-945, 중상급)";
+        };
+    }
+
+    /**
+     * 1차 호출용 시스템 메시지 (Abstract + 목차).
+     */
+    private String buildTocSystemMsg(boolean isEnglish) {
+        StringBuilder sb = new StringBuilder();
+        sb.append("당신은 콘텐츠 분석 전문가입니다. 주어진 원본 텍스트를 분석하여 요약과 목차만 생성해주세요.\n\n");
+        sb.append("## 출력 형식 규칙\n");
+        sb.append("1. 한국어로 작성하세요 (원본이 영어여도).\n");
+        sb.append("2. 순수 Markdown 형식으로 작성하세요. 코드 블록(```)으로 감싸지 마세요.\n");
+        sb.append("3. 아래 구조를 정확히 따르세요:\n\n");
+        sb.append("# 요약 (Abstract)\n");
+        sb.append("(핵심 내용을 3~5문장으로 요약)\n\n");
+        sb.append("# 목차\n");
+        sb.append("1. 첫 번째 주제\n");
+        sb.append("2. 두 번째 주제\n");
+        sb.append("...\n\n");
+        sb.append("## 작성 규칙\n");
+        sb.append("- 목차는 원본 텍스트의 **서술 순서(흐름)**에 따라 나누세요. 주제별 분류가 아닙니다.\n");
+        sb.append("- 원본에서 앞부분에 나오는 내용이 1번, 뒷부분이 마지막 번호가 되어야 합니다.\n");
+        sb.append("- 각 목차 항목이 원본의 서로 다른 구간을 담당해야 합니다. 같은 내용이 여러 항목에 걸치면 안 됩니다.\n");
+        sb.append("- 목차 개수는 원본 길이에 비례하세요: 3000자 미만이면 3~5개, 3000~10000자이면 5~10개, 10000자 이상이면 8~15개.\n");
+        sb.append("- 목차 항목은 번호와 제목만 포함하세요. 상세 설명은 넣지 마세요.\n");
+        sb.append("- 원본에 없는 내용을 추가하지 마세요.\n");
+        sb.append("- 목차 항목 앞에 불릿 마커(`-`, `*`)를 붙이지 마세요. 숫자만 사용하세요.\n");
+        sb.append("- **금지**: 전체 요약, 결론, 마무리, 종합 정리 같은 성격의 섹션을 만들지 마세요. 각 섹션은 원본의 고유한 구간만 담당해야 합니다.\n");
+        return sb.toString();
+    }
+
+    /**
+     * 2차+ 호출용 시스템 메시지 (목차별 상세 정리).
+     * 영어 컨텐츠인 경우 영어 표현 학습 섹션 추가.
+     */
+    private String buildSectionSystemMsg(boolean isEnglish, String englishLevel) {
+        StringBuilder sb = new StringBuilder();
+        sb.append("당신은 콘텐츠 정리 전문가입니다. 주어진 원본 텍스트에서 지정된 섹션에 해당하는 내용만 상세히 정리해주세요.\n\n");
+
+        sb.append("## 출력 형식 규칙 (반드시 지킬 것)\n");
+        sb.append("1. 순수 Markdown 형식으로 작성하세요. 코드 블록(```)으로 감싸지 마세요.\n");
+        sb.append("2. 섹션 제목은 정확히 `# 번호. 제목` 형식으로 시작하세요. (예: `# 1. 첫 번째 주제`)\n");
+        sb.append("3. 하위 제목이 필요하면 `## 소제목` 또는 `### 세부제목`을 사용하세요.\n");
+        sb.append("4. 불릿 포인트는 `-`만 사용하세요. `*`는 사용하지 마세요.\n");
+        sb.append("5. 굵은 글씨는 `**텍스트**` 형식만 사용하세요.\n");
+        sb.append("6. 각 불릿 포인트는 한 줄로 시작하고, 들여쓰기는 2칸(공백 2개)으로 일관되게 하세요.\n");
+        sb.append("7. 빈 줄은 섹션/소제목 구분에만 사용하세요. 불릿 사이에 빈 줄을 넣지 마세요.\n");
+        sb.append("8. 한국어로 작성하세요 (원본이 영어여도).\n\n");
+
+        sb.append("## 내용 작성 규칙\n");
+        sb.append("- 원본 텍스트에 있는 내용만 정리하세요. 원본에 없는 내용을 절대 추가하지 마세요.\n");
+        sb.append("- 부연 설명, 해석, 의견을 추가하지 마세요. 요약과 정리만 하세요.\n");
+        sb.append("- 원본의 의미를 왜곡하지 마세요. 디테일을 살리되, 원본의 범위를 넘지 마세요.\n");
+        sb.append("- 해당 섹션이 담당하는 원본 구간의 내용만 정리하세요. 다른 섹션의 내용을 포함하지 마세요.\n");
+        sb.append("- 가독성을 위해 하위 항목, 굵은 글씨, 불릿 포인트를 적절히 활용하세요.\n");
+        sb.append("- 원본이 짧으면 정리도 짧게 하세요. 불필요하게 늘리지 마세요.\n");
+
+        if (isEnglish) {
+            sb.append("\n## 영어 학습 보조 (원본이 영어 컨텐츠임)\n");
+            sb.append("사용자의 영어 수준: **").append(cefrDescription(englishLevel)).append("**\n\n");
+            sb.append("이 섹션 정리 마지막에 다음 형식으로 영어 학습 박스를 추가하세요:\n\n");
+            sb.append("### 핵심 영어 표현\n");
+            sb.append("- **expression** (한글 번역) — 간단한 설명 또는 사용 맥락\n");
+            sb.append("  - 예문: \"Original English sentence from the text\" (한글 번역)\n\n");
+            sb.append("### 작성 규칙:\n");
+            sb.append("- 사용자의 수준(").append(englishLevel).append(")보다 약간 어려운 표현을 우선 추출하세요.\n");
+            sb.append("- 일상적인 단어(go, eat, see 등)는 추출하지 마세요.\n");
+            sb.append("- 학습할 가치가 있는 관용 표현, 숙어, 학술/전문 용어, 콜로케이션을 우선하세요.\n");
+            sb.append("- 섹션당 3~7개 표현을 추출하세요.\n");
+            sb.append("- 예문은 반드시 원본 텍스트에서 인용하세요.\n");
+            sb.append("- 추출할 만한 표현이 없으면 이 박스를 생략하세요.\n");
+        }
+
+        return sb.toString();
+    }
+
+    /**
+     * 목차 텍스트에서 항목들을 파싱한다.
+     * "1. 첫 번째 주제" 형태의 줄을 추출.
+     */
+    private List<String> parseTocItems(String tocText) {
+        List<String> items = new java.util.ArrayList<>();
+        java.util.regex.Pattern pattern = java.util.regex.Pattern.compile("^\\d+\\.\\s+(.+)$", java.util.regex.Pattern.MULTILINE);
+        java.util.regex.Matcher matcher = pattern.matcher(tocText);
+
+        // "# 목차" 이후의 내용만 파싱
+        int tocStart = tocText.indexOf("# 목차");
+        if (tocStart == -1) tocStart = tocText.indexOf("# Table of Contents");
+        if (tocStart == -1) tocStart = 0;
+        String tocSection = tocText.substring(tocStart);
+
+        // 목차 섹션 이후 다음 '#'이 나오기 전까지만 파싱
+        int nextSection = tocSection.indexOf("\n#", 2);
+        if (nextSection > 0) {
+            tocSection = tocSection.substring(0, nextSection);
+        }
+
+        matcher = pattern.matcher(tocSection);
+        while (matcher.find()) {
+            String item = matcher.group(1).strip();
+            if (!item.isBlank()) {
+                items.add(item);
+            }
+        }
+        return items;
+    }
+
+    /**
+     * LLM으로 내용 기반 제목 생성. 실패 시 텍스트 앞부분으로 폴백.
+     */
+    private String generateTitle(String text, String modelId) {
+        if (genAiService.isConfigured()) {
+            try {
+                String preview = text.length() > TEXT_PREVIEW_LENGTH
+                        ? text.substring(0, TEXT_PREVIEW_LENGTH) : text;
+
+                String systemMsg = "You are a helpful assistant that generates concise titles. " +
+                        "Respond with ONLY the title, nothing else. " +
+                        "The title should be in the same language as the content. " +
+                        "Keep it under 60 characters.";
+                String userMsg = "Generate a concise, descriptive title for the following content:\n\n" + preview;
+
+                String title = genAiService.chat(systemMsg, userMsg, modelId).strip();
+                // 따옴표 제거
+                title = title.replaceAll("^\"|\"$", "").replaceAll("^'|'$", "");
+                if (!title.isBlank() && title.length() <= TITLE_MAX_LENGTH) {
+                    log.info("LLM generated title: {}", title);
+                    return title;
+                }
+            } catch (Exception e) {
+                log.warn("LLM title generation failed, falling back to text truncation", e);
+            }
+        }
+        // Fallback: 텍스트 첫 줄
+        String firstLine = text.strip().split("\\r?\\n", 2)[0].strip();
+        if (firstLine.length() <= TITLE_MAX_LENGTH) {
+            return firstLine;
+        }
+        return firstLine.substring(0, TITLE_MAX_LENGTH - 3) + "...";
+    }
+
+    /**
+     * LLM으로 2~4 depth 카테고리 추출. 기존 카테고리 목록을 컨텍스트로 전달.
+     */
+    private List<String> extractCategoryPaths(String userId, String text, String modelId) {
+        if (!genAiService.isConfigured()) {
+            log.info("OCI GenAI not configured, skipping categorization");
+            return List.of();
+        }
+
+        try {
+            // 기존 카테고리 목록
+            List<Map<String, Object>> existing = categoryRepository.findAllByUser(userId);
+            String existingPaths = existing.stream()
+                    .map(c -> (String) c.get("FULL_PATH"))
+                    .collect(Collectors.joining("\n"));
+
+            String preview = text.length() > TEXT_PREVIEW_LENGTH
+                    ? text.substring(0, TEXT_PREVIEW_LENGTH) : text;
+
+            String systemMsg = "You are a categorization assistant. " +
+                    "Analyze the content and assign 1-3 hierarchical categories. " +
+                    "Each category should be 2-4 levels deep, separated by '/'. " +
+                    "Examples: '건강/운동/웨이트트레이닝', 'IT/AI/LLM', '요리/한식'. " +
+                    "Respond with ONLY a JSON array of category path strings. " +
+                    "No explanation, no markdown formatting. Just the JSON array.";
+
+            StringBuilder userMsg = new StringBuilder();
+            if (!existingPaths.isBlank()) {
+                userMsg.append("Existing categories (reuse these when appropriate):\n");
+                userMsg.append(existingPaths);
+                userMsg.append("\n\n");
+            }
+            userMsg.append("Categorize the following content:\n\n");
+            userMsg.append(preview);
+
+            String response = genAiService.chat(systemMsg, userMsg.toString(), modelId).strip();
+            // JSON 배열 파싱 — 마크다운 코드블록 제거
+            response = response.replaceAll("```json\\s*", "").replaceAll("```\\s*", "").strip();
+
+            List<String> paths = objectMapper.readValue(response, new TypeReference<>() {});
+            // 유효성 검증: 슬래시가 있고 빈 값 아닌 것만
+            return paths.stream()
+                    .filter(p -> p != null && !p.isBlank() && p.contains("/"))
+                    .map(String::strip)
+                    .toList();
+        } catch (Exception e) {
+            log.warn("LLM categorization failed", e);
+            return List.of();
+        }
+    }
+
+    /**
+     * 청크들을 임베딩하여 knowledge_chunk_embeddings 테이블에 저장.
+     */
+    private void embedChunks(String knowledgeItemId, List<String> chunkContents) {
+        if (!genAiService.isConfigured()) {
+            log.info("OCI GenAI not configured, skipping embedding");
+            return;
+        }
+        try {
+            // chunk ID 목록 조회
+            List<Map<String, Object>> storedChunks = chunkRepository.findByKnowledgeItemId(knowledgeItemId);
+            if (storedChunks.size() != chunkContents.size()) {
+                log.warn("Chunk count mismatch: stored={}, content={}", storedChunks.size(), chunkContents.size());
+            }
+
+            List<float[]> embeddings = genAiService.embedTexts(chunkContents, "SEARCH_DOCUMENT");
+
+            String embedModelId = "cohere.embed-v4.0";
+            for (int i = 0; i < Math.min(storedChunks.size(), embeddings.size()); i++) {
+                String chunkId = (String) storedChunks.get(i).get("ID");
+                embeddingRepository.upsertEmbedding(chunkId, embedModelId, embeddings.get(i));
+            }
+
+            log.info("Item {} embedded {} chunks", knowledgeItemId, embeddings.size());
+        } catch (Exception e) {
+            log.warn("Embedding failed for item {}, continuing pipeline", knowledgeItemId, e);
+        }
+    }
+
+    private void categorize(String knowledgeItemId, String userId, String text, String modelId) {
+        try {
+            List<String> categoryPaths = extractCategoryPaths(userId, text, modelId);
+            for (String path : categoryPaths) {
+                String categoryId = categoryRepository.findOrCreate(userId, path);
+                categoryRepository.linkCategory(knowledgeItemId, categoryId);
+            }
+            log.info("Item {} categorized with {} categories: {}", knowledgeItemId, categoryPaths.size(), categoryPaths);
+        } catch (Exception e) {
+            log.warn("Categorization failed for item {}, continuing pipeline", knowledgeItemId, e);
+        }
+    }
+
+    /**
+     * 수동 구조화 요청 (비동기). 프론트엔드 버튼에서 호출.
+     */
+    @Async
+    public void runStructuring(String knowledgeItemId, String text, String modelId, String englishLevel) {
+        try {
+            String structured = structureContent(text, modelId, knowledgeItemId, englishLevel);
+            if (structured != null && !structured.isBlank()) {
+                knowledgeRepository.updateStructuredContent(knowledgeItemId, structured);
+            }
+            knowledgeRepository.updateStatus(knowledgeItemId, "READY");
+            log.info("Manual structuring complete for item {}", knowledgeItemId);
+        } catch (Exception e) {
+            log.error("Manual structuring failed for item {}", knowledgeItemId, e);
+            knowledgeRepository.updateStatus(knowledgeItemId, "READY");
+        }
+    }
+
+    @Async
+    public void runPipeline(String knowledgeItemId, String modelId) {
+        try {
+            Map<String, Object> item = knowledgeRepository.findByIdInternal(knowledgeItemId);
+            if (item == null) {
+                log.error("Knowledge item not found: {}", knowledgeItemId);
+                return;
+            }
+
+            String type = (String) item.get("TYPE");
+            String sourceUrl = (String) item.get("SOURCE_URL");
+            Object rawTextObj = item.get("RAW_TEXT");
+            String rawText = rawTextObj != null ? rawTextObj.toString() : null;
+
+            // Step 1: Extract text
+            knowledgeRepository.updateStatus(knowledgeItemId, "EXTRACTING");
+            String extractedText;
+
+            switch (type) {
+                case "WEB" -> {
+                    extractedText = webCrawlerService.crawl(sourceUrl);
+                    // WEB은 페이지 제목을 우선 시도
+                    String title = (String) item.get("TITLE");
+                    if (title == null || title.isBlank()) {
+                        try {
+                            String pageTitle = webCrawlerService.extractTitle(sourceUrl);
+                            if (pageTitle != null && !pageTitle.isBlank()) {
+                                knowledgeRepository.updateTitle(knowledgeItemId, pageTitle);
+                                item.put("TITLE", pageTitle);
+                            }
+                        } catch (Exception e) {
+                            log.warn("Failed to extract title from {}", sourceUrl, e);
+                        }
+                    }
+                }
+                case "YOUTUBE" -> {
+                    if (rawText == null || rawText.isBlank()) {
+                        knowledgeRepository.updateStatus(knowledgeItemId, "FAILED");
+                        log.error("YouTube item has no raw text: {}", knowledgeItemId);
+                        return;
+                    }
+                    extractedText = rawText;
+                }
+                case "TEXT" -> {
+                    if (rawText == null || rawText.isBlank()) {
+                        knowledgeRepository.updateStatus(knowledgeItemId, "FAILED");
+                        log.error("Text item has no raw text: {}", knowledgeItemId);
+                        return;
+                    }
+                    extractedText = rawText;
+                }
+                default -> {
+                    knowledgeRepository.updateStatus(knowledgeItemId, "FAILED");
+                    log.error("Unknown type: {}", type);
+                    return;
+                }
+            }
+
+            // Auto-generate title if not set
+            String currentTitle = (String) item.get("TITLE");
+            if (currentTitle == null || currentTitle.isBlank()) {
+                String autoTitle = generateTitle(extractedText, modelId);
+                knowledgeRepository.updateTitle(knowledgeItemId, autoTitle);
+            }
+
+            // Step 2: Structure content (1000자 이상일 때만)
+            knowledgeRepository.updateStatus(knowledgeItemId, "STRUCTURING");
+            try {
+                // 사용자의 영어 수준 가져오기
+                String userId = (String) item.get("USER_ID");
+                String englishLevel = "B2";
+                try {
+                    Map<String, Object> user = userRepository.findById(userId);
+                    if (user != null && user.get("ENGLISH_LEVEL") != null) {
+                        englishLevel = (String) user.get("ENGLISH_LEVEL");
+                    }
+                } catch (Exception ignored) {}
+
+                String structured = structureContent(extractedText, modelId, knowledgeItemId, englishLevel);
+                if (structured != null && !structured.isBlank()) {
+                    knowledgeRepository.updateStructuredContent(knowledgeItemId, structured);
+                    log.info("Item {} structured: {} chars", knowledgeItemId, structured.length());
+                }
+            } catch (Exception e) {
+                log.warn("Structuring failed for item {}, continuing pipeline", knowledgeItemId, e);
+            }
+
+            // Step 3: Chunk
+            knowledgeRepository.updateStatus(knowledgeItemId, "CHUNKING");
+            List<String> chunks = chunkingService.chunk(extractedText);
+            log.info("Item {} chunked into {} pieces", knowledgeItemId, chunks.size());
+
+            for (int i = 0; i < chunks.size(); i++) {
+                String chunkContent = chunks.get(i);
+                int tokenCount = chunkingService.estimateTokenCount(chunkContent);
+                chunkRepository.insertChunk(knowledgeItemId, i, chunkContent, tokenCount);
+            }
+
+            // Step 4: Categorize
+            knowledgeRepository.updateStatus(knowledgeItemId, "CATEGORIZING");
+            categorize(knowledgeItemId, (String) item.get("USER_ID"), extractedText, modelId);
+
+            // Step 5: Embedding
+            knowledgeRepository.updateStatus(knowledgeItemId, "EMBEDDING");
+            embedChunks(knowledgeItemId, chunks);
+
+            // Done
+            knowledgeRepository.updateStatus(knowledgeItemId, "READY");
+            log.info("Pipeline complete for item {}: {} chunks stored", knowledgeItemId, chunks.size());
+
+        } catch (Exception e) {
+            log.error("Pipeline failed for item {}", knowledgeItemId, e);
+            try {
+                knowledgeRepository.updateStatus(knowledgeItemId, "FAILED");
+            } catch (Exception ex) {
+                log.error("Failed to update status to FAILED", ex);
+            }
+        }
+    }
+}

sundol-backend/src/main/java/com/sundol/service/KnowledgeService.java

@@ -1,9 +1,15 @@
 package com.sundol.service;
 
 import com.sundol.dto.IngestRequest;
+import com.sundol.exception.AppException;
+import com.sundol.repository.CategoryRepository;
+import com.sundol.repository.KnowledgeChunkRepository;
 import com.sundol.repository.KnowledgeRepository;
+import com.sundol.repository.UserRepository;
+import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Service;
 import reactor.core.publisher.Mono;
+import reactor.core.scheduler.Schedulers;
 
 import java.util.List;
 import java.util.Map;
@@ -12,38 +18,132 @@ import java.util.Map;
 public class KnowledgeService {
 
     private final KnowledgeRepository knowledgeRepository;
+    private final KnowledgeChunkRepository chunkRepository;
+    private final CategoryRepository categoryRepository;
+    private final UserRepository userRepository;
+    private final IngestPipelineService pipelineService;
 
-    public KnowledgeService(KnowledgeRepository knowledgeRepository) {
+    public KnowledgeService(
+            KnowledgeRepository knowledgeRepository,
+            KnowledgeChunkRepository chunkRepository,
+            CategoryRepository categoryRepository,
+            UserRepository userRepository,
+            IngestPipelineService pipelineService) {
         this.knowledgeRepository = knowledgeRepository;
+        this.chunkRepository = chunkRepository;
+        this.categoryRepository = categoryRepository;
+        this.userRepository = userRepository;
+        this.pipelineService = pipelineService;
+    }
+
+    private String resolveEnglishLevel(String userId, String requestLevel) {
+        if (requestLevel != null && requestLevel.matches("^(A1|A2|B1|B2|C1|C2)$")) {
+            return requestLevel;
+        }
+        try {
+            Map<String, Object> user = userRepository.findById(userId);
+            if (user != null && user.get("ENGLISH_LEVEL") != null) {
+                return (String) user.get("ENGLISH_LEVEL");
+            }
+        } catch (Exception ignored) {}
+        return "B2";
     }
 
     public Mono<List<Map<String, Object>>> list(String userId, String type, String status, String tag, String search) {
-        // TODO: Query knowledge items with filters
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> knowledgeRepository.list(userId, type, status, search))
+                .subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> ingest(String userId, IngestRequest request) {
-        // TODO: Create knowledge item, trigger async ingest pipeline
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            String id = knowledgeRepository.insert(
+                    userId, request.type(), request.title(), request.url(), request.rawText()
+            );
+            // Trigger async pipeline
+            pipelineService.runPipeline(id, request.modelId());
+
+            return Map.of(
+                    "id", (Object) id,
+                    "status", "PENDING"
+            );
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> getById(String userId, String id) {
-        // TODO: Get knowledge item by ID
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            Map<String, Object> item = knowledgeRepository.findById(userId, id);
+            if (item == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Knowledge item not found");
+            }
+            item.put("CATEGORIES", categoryRepository.findByKnowledgeItemId(id));
+            return item;
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> update(String userId, String id, Map<String, Object> updates) {
-        // TODO: Update knowledge item fields
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            Map<String, Object> item = knowledgeRepository.findById(userId, id);
+            if (item == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Knowledge item not found");
+            }
+            if (updates.containsKey("title")) {
+                knowledgeRepository.updateTitle(id, (String) updates.get("title"));
+            }
+            return knowledgeRepository.findById(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic());
+    }
+
+    public Mono<Map<String, Object>> structureContent(String userId, String id, String modelId, String englishLevel) {
+        return Mono.fromCallable(() -> {
+            Map<String, Object> item = knowledgeRepository.findById(userId, id);
+            if (item == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Knowledge item not found");
+            }
+
+            // raw_text 또는 청크에서 원본 텍스트 가져오기
+            Object rawTextObj = item.get("RAW_TEXT");
+            String text = rawTextObj != null ? rawTextObj.toString() : null;
+
+            if (text == null || text.isBlank()) {
+                // WEB 타입은 raw_text가 없을 수 있으므로 청크에서 조합
+                var chunks = chunkRepository.findByKnowledgeItemId(id);
+                if (!chunks.isEmpty()) {
+                    text = chunks.stream()
+                            .map(c -> c.get("CONTENT").toString())
+                            .collect(java.util.stream.Collectors.joining("\n\n"));
+                }
+            }
+
+            if (text == null || text.isBlank()) {
+                throw new AppException(HttpStatus.BAD_REQUEST, "No content to structure");
+            }
+
+            // STRUCTURING 상태로 변경 (프론트엔드 폴링에서 진행 중 표시)
+            knowledgeRepository.updateStatus(id, "STRUCTURING");
+
+            // 영어 수준 결정 (요청 값 > 사용자 프로필 > B2 기본)
+            String level = resolveEnglishLevel(userId, englishLevel);
+
+            // 비동기로 구조화 실행 (중간 결과는 pipelineService가 DB에 직접 저장)
+            final String finalText = text;
+            pipelineService.runStructuring(id, finalText, modelId, level);
+
+            return knowledgeRepository.findById(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Void> delete(String userId, String id) {
-        // TODO: Delete knowledge item and all chunks
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromRunnable(() -> knowledgeRepository.delete(userId, id))
+                .subscribeOn(Schedulers.boundedElastic()).then();
     }
 
     public Mono<List<Map<String, Object>>> getChunks(String userId, String id) {
-        // TODO: List chunks for knowledge item
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            Map<String, Object> item = knowledgeRepository.findById(userId, id);
+            if (item == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Knowledge item not found");
+            }
+            return chunkRepository.findByKnowledgeItemId(id);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 }

sundol-backend/src/main/java/com/sundol/service/OciGenAiService.java

@@ -0,0 +1,202 @@
+package com.sundol.service;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Service;
+
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+@Service
+public class OciGenAiService {
+
+    private static final Logger log = LoggerFactory.getLogger(OciGenAiService.class);
+
+    private final String apiKey;
+    private final String compartment;
+    private final String defaultModel;
+    private final String baseUrl;
+    private final ObjectMapper objectMapper;
+    private final HttpClient httpClient;
+
+    public static final List<Map<String, String>> AVAILABLE_MODELS = List.of(
+        Map.of("id", "google.gemini-2.5-pro", "name", "Gemini 2.5 Pro", "vendor", "Google"),
+        Map.of("id", "google.gemini-2.5-flash", "name", "Gemini 2.5 Flash", "vendor", "Google"),
+        Map.of("id", "google.gemini-2.5-flash-lite", "name", "Gemini 2.5 Flash Lite", "vendor", "Google"),
+        Map.of("id", "xai.grok-4.20-reasoning", "name", "Grok 4.20 Reasoning", "vendor", "xAI"),
+        Map.of("id", "xai.grok-4.20-non-reasoning", "name", "Grok 4.20 Non-Reasoning", "vendor", "xAI"),
+        Map.of("id", "xai.grok-4-1-fast-reasoning", "name", "Grok 4-1 Fast Reasoning", "vendor", "xAI"),
+        Map.of("id", "xai.grok-4-1-fast-non-reasoning", "name", "Grok 4-1 Fast Non-Reasoning", "vendor", "xAI"),
+        Map.of("id", "xai.grok-4", "name", "Grok 4", "vendor", "xAI"),
+        Map.of("id", "xai.grok-3", "name", "Grok 3", "vendor", "xAI"),
+        Map.of("id", "xai.grok-3-mini", "name", "Grok 3 Mini", "vendor", "xAI"),
+        Map.of("id", "openai.gpt-oss-120b", "name", "GPT-OSS 120B", "vendor", "OpenAI"),
+        Map.of("id", "openai.gpt-oss-20b", "name", "GPT-OSS 20B", "vendor", "OpenAI"),
+        Map.of("id", "cohere.command-a-03-2025", "name", "Command A", "vendor", "Cohere"),
+        Map.of("id", "cohere.command-a-reasoning", "name", "Command A Reasoning", "vendor", "Cohere"),
+        Map.of("id", "cohere.command-r-plus-08-2024", "name", "Command R+", "vendor", "Cohere"),
+        Map.of("id", "meta.llama-4-maverick-17b-128e-instruct-fp8", "name", "Llama 4 Maverick 17B", "vendor", "Meta"),
+        Map.of("id", "meta.llama-4-scout-17b-16e-instruct", "name", "Llama 4 Scout 17B", "vendor", "Meta")
+    );
+
+    public OciGenAiService(
+            @Value("${oci.genai.api-key:}") String apiKey,
+            @Value("${oci.genai.compartment:}") String compartment,
+            @Value("${oci.genai.model:google.gemini-2.5-flash}") String defaultModel,
+            @Value("${oci.genai.base-url:}") String baseUrl,
+            ObjectMapper objectMapper) {
+        this.apiKey = apiKey;
+        this.compartment = compartment;
+        this.defaultModel = defaultModel;
+        this.baseUrl = baseUrl;
+        this.objectMapper = objectMapper;
+        this.httpClient = HttpClient.newBuilder()
+                .connectTimeout(Duration.ofSeconds(30))
+                .build();
+    }
+
+    public boolean isConfigured() {
+        return apiKey != null && !apiKey.isBlank()
+                && compartment != null && !compartment.isBlank();
+    }
+
+    public String getDefaultModel() {
+        return defaultModel;
+    }
+
+    /**
+     * OCI GenAI Chat API 호출.
+     */
+    public String chat(String systemMessage, String userMessage, String modelId) throws Exception {
+        if (!isConfigured()) {
+            throw new IllegalStateException("OCI GenAI is not configured");
+        }
+        if (modelId == null || modelId.isBlank()) {
+            modelId = defaultModel;
+        }
+
+        Map<String, Object> payload = Map.of(
+            "compartmentId", compartment,
+            "servingMode", Map.of(
+                "servingType", "ON_DEMAND",
+                "modelId", modelId
+            ),
+            "chatRequest", Map.of(
+                "apiFormat", "GENERIC",
+                "messages", List.of(
+                    Map.of("role", "SYSTEM", "content", List.of(Map.of("type", "TEXT", "text", systemMessage))),
+                    Map.of("role", "USER", "content", List.of(Map.of("type", "TEXT", "text", userMessage)))
+                ),
+                "maxTokens", 4096,
+                "temperature", 0.3
+            )
+        );
+
+        String body = objectMapper.writeValueAsString(payload);
+
+        HttpRequest request = HttpRequest.newBuilder()
+                .uri(URI.create(baseUrl + "/chat"))
+                .header("Content-Type", "application/json")
+                .header("Authorization", "Bearer " + apiKey)
+                .POST(HttpRequest.BodyPublishers.ofString(body))
+                .timeout(Duration.ofSeconds(120))
+                .build();
+
+        HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());
+
+        if (response.statusCode() != 200) {
+            log.error("OCI GenAI error {} (model={}): {}", response.statusCode(), modelId,
+                    response.body().substring(0, Math.min(response.body().length(), 500)));
+            throw new RuntimeException("OCI GenAI returned " + response.statusCode());
+        }
+
+        JsonNode root = objectMapper.readTree(response.body());
+        JsonNode choices = root.path("chatResponse").path("choices");
+        if (choices.isArray() && !choices.isEmpty()) {
+            JsonNode content = choices.get(0).path("message").path("content");
+            if (content.isArray() && !content.isEmpty()) {
+                return content.get(0).path("text").asText("");
+            }
+        }
+
+        throw new RuntimeException("Unexpected OCI GenAI response structure");
+    }
+
+    private static final String EMBED_MODEL = "cohere.embed-v4.0";
+    private static final int EMBED_BATCH_SIZE = 96;
+
+    /**
+     * OCI GenAI Embed API 호출. 최대 96개씩 배치 처리.
+     * @param texts 임베딩할 텍스트 목록
+     * @param inputType SEARCH_DOCUMENT (저장 시) 또는 SEARCH_QUERY (검색 시)
+     * @return 각 텍스트에 대응하는 float[] 벡터 리스트
+     */
+    public List<float[]> embedTexts(List<String> texts, String inputType) throws Exception {
+        if (!isConfigured()) {
+            throw new IllegalStateException("OCI GenAI is not configured");
+        }
+
+        List<float[]> allEmbeddings = new ArrayList<>();
+
+        for (int start = 0; start < texts.size(); start += EMBED_BATCH_SIZE) {
+            int end = Math.min(start + EMBED_BATCH_SIZE, texts.size());
+            List<String> batch = texts.subList(start, end);
+
+            Map<String, Object> payload = Map.of(
+                "compartmentId", compartment,
+                "servingMode", Map.of(
+                    "servingType", "ON_DEMAND",
+                    "modelId", EMBED_MODEL
+                ),
+                "inputs", batch,
+                "inputType", inputType,
+                "truncate", "END"
+            );
+
+            String body = objectMapper.writeValueAsString(payload);
+
+            HttpRequest request = HttpRequest.newBuilder()
+                    .uri(URI.create(baseUrl + "/embedText"))
+                    .header("Content-Type", "application/json")
+                    .header("Authorization", "Bearer " + apiKey)
+                    .POST(HttpRequest.BodyPublishers.ofString(body))
+                    .timeout(Duration.ofSeconds(120))
+                    .build();
+
+            HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());
+
+            if (response.statusCode() != 200) {
+                log.error("OCI GenAI embed error {}: {}", response.statusCode(),
+                        response.body().substring(0, Math.min(response.body().length(), 500)));
+                throw new RuntimeException("OCI GenAI embed returned " + response.statusCode());
+            }
+
+            JsonNode root = objectMapper.readTree(response.body());
+            JsonNode embeddings = root.path("embeddings");
+            if (!embeddings.isArray()) {
+                throw new RuntimeException("Unexpected embed response: no embeddings array");
+            }
+
+            for (JsonNode embNode : embeddings) {
+                float[] vec = new float[embNode.size()];
+                for (int i = 0; i < embNode.size(); i++) {
+                    vec[i] = (float) embNode.get(i).asDouble();
+                }
+                allEmbeddings.add(vec);
+            }
+
+            log.debug("Embedded batch [{}-{}] of {} texts", start, end, texts.size());
+        }
+
+        return allEmbeddings;
+    }
+}

sundol-backend/src/main/java/com/sundol/service/PlaywrightBrowserService.java

@@ -0,0 +1,129 @@
+package com.sundol.service;
+
+import com.microsoft.playwright.*;
+import com.microsoft.playwright.options.WaitUntilState;
+import jakarta.annotation.PostConstruct;
+import jakarta.annotation.PreDestroy;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.stereotype.Service;
+
+import java.io.IOException;
+import java.util.List;
+
+/**
+ * 사용자 Chrome 브라우저에 CDP(Chrome DevTools Protocol)로 연결하여 사용.
+ * Chrome은 --remote-debugging-port=9222로 실행되어 있어야 한다.
+ * VNC에서 사용자가 직접 로그인한 세션을 그대로 사용하므로 봇 판정을 우회할 수 있다.
+ */
+@Service
+public class PlaywrightBrowserService {
+
+    private static final Logger log = LoggerFactory.getLogger(PlaywrightBrowserService.class);
+    private static final String CDP_URL = "http://localhost:9222";
+
+    private Playwright playwright;
+    private Browser browser;
+
+    @PostConstruct
+    public void init() {
+        try {
+            playwright = Playwright.create();
+            connectToChrome();
+            log.info("사용자 Chrome에 CDP 연결 완료");
+        } catch (Exception e) {
+            log.error("Chrome CDP 연결 실패: {}. Chrome이 --remote-debugging-port=9222로 실행 중인지 확인하세요.", e.getMessage());
+        }
+    }
+
+    private void connectToChrome() {
+        browser = playwright.chromium().connectOverCDP(CDP_URL);
+        log.info("CDP 연결: {} contexts, {} pages",
+                browser.contexts().size(),
+                browser.contexts().stream().mapToInt(c -> c.pages().size()).sum());
+    }
+
+    @PreDestroy
+    public void destroy() {
+        try {
+            // CDP 연결만 끊음 (Chrome 자체는 종료하지 않음)
+            if (browser != null) browser.close();
+            if (playwright != null) playwright.close();
+            log.info("Chrome CDP 연결 해제 완료");
+        } catch (Exception e) {
+            log.warn("CDP 연결 해제 중 오류: {}", e.getMessage());
+        }
+    }
+
+    /**
+     * 사용자 Chrome의 기본 컨텍스트를 가져온다.
+     */
+    private BrowserContext getDefaultContext() throws IOException {
+        ensureBrowserAlive();
+        List<BrowserContext> contexts = browser.contexts();
+        if (contexts.isEmpty()) {
+            throw new IOException("Chrome에 활성 컨텍스트가 없습니다.");
+        }
+        return contexts.get(0);
+    }
+
+    /**
+     * 새 탭을 열고 URL로 이동한다.
+     */
+    public Page openPage(String url, int timeoutMs, WaitUntilState waitUntil) throws IOException {
+        BrowserContext ctx = getDefaultContext();
+        Page page = ctx.newPage();
+        try {
+            page.navigate(url, new Page.NavigateOptions()
+                    .setTimeout(timeoutMs)
+                    .setWaitUntil(waitUntil));
+            return page;
+        } catch (Exception e) {
+            page.close();
+            throw new IOException("페이지 로드 실패 (" + url + "): " + e.getMessage(), e);
+        }
+    }
+
+    public Page openPage(String url, int timeoutMs) throws IOException {
+        return openPage(url, timeoutMs, WaitUntilState.NETWORKIDLE);
+    }
+
+    public Page openPage(String url) throws IOException {
+        return openPage(url, 30_000);
+    }
+
+    /**
+     * 브라우저 페이지 내에서 JavaScript fetch로 URL 내용을 가져온다.
+     */
+    public String fetchInPage(Page page, String url) throws IOException {
+        try {
+            Object result = page.evaluate("async (url) => {" +
+                    "  const res = await fetch(url, { credentials: 'include' });" +
+                    "  if (!res.ok) throw new Error('HTTP ' + res.status);" +
+                    "  return await res.text();" +
+                    "}", url);
+            return result != null ? result.toString() : "";
+        } catch (Exception e) {
+            throw new IOException("브라우저 내 fetch 실패 (" + url + "): " + e.getMessage(), e);
+        }
+    }
+
+    /**
+     * Chrome 연결이 끊겼으면 재연결한다.
+     */
+    private synchronized void ensureBrowserAlive() throws IOException {
+        if (browser != null && browser.isConnected()) {
+            return;
+        }
+        log.warn("Chrome CDP 연결이 끊겼습니다. 재연결합니다.");
+        try {
+            if (browser != null) {
+                try { browser.close(); } catch (Exception ignored) {}
+            }
+            connectToChrome();
+            log.info("Chrome CDP 재연결 완료");
+        } catch (Exception e) {
+            throw new IOException("Chrome CDP 재연결 실패. Chrome이 실행 중인지 확인하세요: " + e.getMessage(), e);
+        }
+    }
+}

sundol-backend/src/main/java/com/sundol/service/SearchService.java

@@ -1,8 +1,11 @@
 package com.sundol.service;
 
-import com.sundol.repository.KnowledgeChunkRepository;
+import com.sundol.repository.ChunkEmbeddingRepository;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.stereotype.Service;
 import reactor.core.publisher.Mono;
+import reactor.core.scheduler.Schedulers;
 
 import java.util.List;
 import java.util.Map;
@@ -10,14 +13,24 @@ import java.util.Map;
 @Service
 public class SearchService {
 
-    private final KnowledgeChunkRepository chunkRepository;
+    private static final Logger log = LoggerFactory.getLogger(SearchService.class);
 
-    public SearchService(KnowledgeChunkRepository chunkRepository) {
-        this.chunkRepository = chunkRepository;
+    private final ChunkEmbeddingRepository embeddingRepository;
+    private final OciGenAiService genAiService;
+
+    public SearchService(ChunkEmbeddingRepository embeddingRepository, OciGenAiService genAiService) {
+        this.embeddingRepository = embeddingRepository;
+        this.genAiService = genAiService;
     }
 
+    /**
+     * 시맨틱 검색: 쿼리를 임베딩 → VECTOR_DISTANCE로 유사 청크 검색
+     */
     public Mono<List<Map<String, Object>>> search(String userId, String query, int topK) {
-        // TODO: Embed query via OCI GenAI, VECTOR_DISTANCE search
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            List<float[]> embeddings = genAiService.embedTexts(List.of(query), "SEARCH_QUERY");
+            float[] queryVector = embeddings.get(0);
+            return embeddingRepository.searchSimilar(userId, queryVector, topK);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 }

sundol-backend/src/main/java/com/sundol/service/StudyCardService.java

@@ -1,8 +1,17 @@
 package com.sundol.service;
 
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.sundol.exception.AppException;
+import com.sundol.repository.KnowledgeChunkRepository;
+import com.sundol.repository.KnowledgeRepository;
 import com.sundol.repository.StudyCardRepository;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Service;
 import reactor.core.publisher.Mono;
+import reactor.core.scheduler.Schedulers;
 
 import java.util.List;
 import java.util.Map;
@@ -10,29 +19,137 @@ import java.util.Map;
 @Service
 public class StudyCardService {
 
-    private final StudyCardRepository studyCardRepository;
+    private static final Logger log = LoggerFactory.getLogger(StudyCardService.class);
 
-    public StudyCardService(StudyCardRepository studyCardRepository) {
+    private final StudyCardRepository studyCardRepository;
+    private final KnowledgeRepository knowledgeRepository;
+    private final KnowledgeChunkRepository chunkRepository;
+    private final OciGenAiService genAiService;
+    private final ObjectMapper objectMapper;
+
+    public StudyCardService(
+            StudyCardRepository studyCardRepository,
+            KnowledgeRepository knowledgeRepository,
+            KnowledgeChunkRepository chunkRepository,
+            OciGenAiService genAiService,
+            ObjectMapper objectMapper) {
         this.studyCardRepository = studyCardRepository;
+        this.knowledgeRepository = knowledgeRepository;
+        this.chunkRepository = chunkRepository;
+        this.genAiService = genAiService;
+        this.objectMapper = objectMapper;
     }
 
     public Mono<List<Map<String, Object>>> getDueCards(String userId) {
-        // TODO: Get cards due for review today
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> studyCardRepository.getDueCards(userId))
+                .subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<List<Map<String, Object>>> getByKnowledgeItem(String userId, String knowledgeItemId) {
-        // TODO: Get cards for a specific knowledge item
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> studyCardRepository.getByKnowledgeItem(userId, knowledgeItemId))
+                .subscribeOn(Schedulers.boundedElastic());
     }
 
+    /**
+     * Knowledge item의 청크들을 기반으로 LLM이 Q&A 카드를 자동 생성.
+     */
     public Mono<Map<String, Object>> generate(String userId, String knowledgeItemId) {
-        // TODO: Trigger AI card generation from knowledge item
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            Map<String, Object> item = knowledgeRepository.findById(userId, knowledgeItemId);
+            if (item == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Knowledge item not found");
+            }
+            if (!"READY".equals(item.get("STATUS"))) {
+                throw new AppException(HttpStatus.BAD_REQUEST, "Knowledge item is not ready yet");
+            }
+
+            List<Map<String, Object>> chunks = chunkRepository.findByKnowledgeItemId(knowledgeItemId);
+            if (chunks.isEmpty()) {
+                throw new AppException(HttpStatus.BAD_REQUEST, "No chunks available");
+            }
+
+            // 청크 내용을 합쳐서 LLM에 전달 (최대 4000자)
+            StringBuilder content = new StringBuilder();
+            for (Map<String, Object> chunk : chunks) {
+                Object c = chunk.get("CONTENT");
+                if (c != null) {
+                    content.append(c.toString()).append("\n\n");
+                }
+                if (content.length() > 4000) break;
+            }
+
+            String systemMsg =
+                "You are a study card generator. Create flashcards from the given content. " +
+                "Each card has a 'front' (question) and 'back' (answer). " +
+                "Generate 3-5 cards that test key concepts. " +
+                "Use the same language as the content. " +
+                "Respond with ONLY a JSON array: [{\"front\":\"question\",\"back\":\"answer\"},...]. " +
+                "No markdown, no explanation.";
+            String userMsg = "Generate study cards from this content:\n\n" + content;
+
+            String response = genAiService.chat(systemMsg, userMsg, null);
+            response = response.replaceAll("```json\\s*", "").replaceAll("```\\s*", "").strip();
+
+            List<Map<String, String>> cards = objectMapper.readValue(response, new TypeReference<>() {});
+
+            int created = 0;
+            for (Map<String, String> card : cards) {
+                String front = card.get("front");
+                String back = card.get("back");
+                if (front != null && back != null && !front.isBlank() && !back.isBlank()) {
+                    studyCardRepository.insert(userId, knowledgeItemId, front, back);
+                    created++;
+                }
+            }
+
+            log.info("Generated {} study cards for knowledge item {}", created, knowledgeItemId);
+            return Map.of("generated", (Object) created, "knowledgeItemId", knowledgeItemId);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
+    /**
+     * SM-2 알고리즘으로 카드 복습 결과 처리.
+     * rating: 0(완전 모름) ~ 5(완벽)
+     */
     public Mono<Map<String, Object>> review(String userId, String id, int rating) {
-        // TODO: Apply SM-2 algorithm and update card
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            Map<String, Object> card = studyCardRepository.findById(userId, id);
+            if (card == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Study card not found");
+            }
+
+            Number efNum = (Number) card.get("EASE_FACTOR");
+            Number ivNum = (Number) card.get("INTERVAL_DAYS");
+            Number repNum = (Number) card.get("REPETITIONS");
+
+            double easeFactor = efNum != null ? efNum.doubleValue() : 2.5;
+            int intervalDays = ivNum != null ? ivNum.intValue() : 0;
+            int repetitions = repNum != null ? repNum.intValue() : 0;
+
+            // SM-2 알고리즘
+            if (rating < 3) {
+                // 실패: 처음부터 다시
+                repetitions = 0;
+                intervalDays = 1;
+            } else {
+                // 성공
+                repetitions++;
+                if (repetitions == 1) {
+                    intervalDays = 1;
+                } else if (repetitions == 2) {
+                    intervalDays = 6;
+                } else {
+                    intervalDays = (int) Math.round(intervalDays * easeFactor);
+                }
+            }
+
+            // Ease Factor 갱신
+            easeFactor = easeFactor + (0.1 - (5 - rating) * (0.08 + (5 - rating) * 0.02));
+            if (easeFactor < 1.3) easeFactor = 1.3;
+
+            studyCardRepository.updateSm2(id, easeFactor, intervalDays, repetitions, intervalDays);
+
+            return studyCardRepository.findById(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 }

sundol-backend/src/main/java/com/sundol/service/TagService.java

@@ -1,9 +1,12 @@
 package com.sundol.service;
 
 import com.sundol.dto.TagRequest;
+import com.sundol.exception.AppException;
 import com.sundol.repository.TagRepository;
+import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Service;
 import reactor.core.publisher.Mono;
+import reactor.core.scheduler.Schedulers;
 
 import java.util.List;
 import java.util.Map;
@@ -18,22 +21,41 @@ public class TagService {
     }
 
     public Mono<List<Map<String, Object>>> list(String userId) {
-        // TODO: List tags for user
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> tagRepository.list(userId))
+                .subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> create(String userId, TagRequest request) {
-        // TODO: Create tag
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            String color = request.color() != null ? request.color() : "#6366f1";
+            String id = tagRepository.insert(userId, request.name(), color);
+            return tagRepository.findById(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> update(String userId, String id, TagRequest request) {
-        // TODO: Update tag
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            Map<String, Object> tag = tagRepository.findById(userId, id);
+            if (tag == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Tag not found");
+            }
+            if (request.name() != null) {
+                tagRepository.updateName(id, request.name());
+            }
+            if (request.color() != null) {
+                tagRepository.updateColor(id, request.color());
+            }
+            return tagRepository.findById(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Void> delete(String userId, String id) {
-        // TODO: Delete tag and remove from items
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromRunnable(() -> {
+            Map<String, Object> tag = tagRepository.findById(userId, id);
+            if (tag == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Tag not found");
+            }
+            tagRepository.delete(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic()).then();
     }
 }

sundol-backend/src/main/java/com/sundol/service/TodoService.java

@@ -1,9 +1,12 @@
 package com.sundol.service;
 
 import com.sundol.dto.TodoRequest;
+import com.sundol.exception.AppException;
 import com.sundol.repository.TodoRepository;
+import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Service;
 import reactor.core.publisher.Mono;
+import reactor.core.scheduler.Schedulers;
 
 import java.util.List;
 import java.util.Map;
@@ -18,27 +21,72 @@ public class TodoService {
     }
 
     public Mono<List<Map<String, Object>>> list(String userId, String status, String priority, String dueDate) {
-        // TODO: List todos with filters
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            List<Map<String, Object>> todos = todoRepository.list(userId, status, priority, dueDate);
+            // 각 todo에 서브태스크 개수 포함
+            for (Map<String, Object> todo : todos) {
+                String todoId = (String) todo.get("ID");
+                List<Map<String, Object>> subtasks = todoRepository.findSubtasks(userId, todoId);
+                todo.put("SUBTASK_COUNT", subtasks.size());
+                long doneCount = subtasks.stream()
+                        .filter(s -> "DONE".equals(s.get("STATUS")))
+                        .count();
+                todo.put("SUBTASK_DONE_COUNT", doneCount);
+            }
+            return todos;
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> create(String userId, TodoRequest request) {
-        // TODO: Create todo
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            String priority = request.priority() != null ? request.priority() : "MEDIUM";
+            String id = todoRepository.insert(
+                    userId, request.title(), request.description(),
+                    priority, request.dueDate(), request.parentId()
+            );
+            return todoRepository.findById(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> update(String userId, String id, Map<String, Object> updates) {
-        // TODO: Update todo fields
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            Map<String, Object> todo = todoRepository.findById(userId, id);
+            if (todo == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Todo not found");
+            }
+            if (updates.containsKey("status")) {
+                todoRepository.updateStatus(id, (String) updates.get("status"));
+            }
+            if (updates.containsKey("title")) {
+                todoRepository.updateTitle(id, (String) updates.get("title"));
+            }
+            if (updates.containsKey("priority")) {
+                todoRepository.updatePriority(id, (String) updates.get("priority"));
+            }
+            if (updates.containsKey("dueDate")) {
+                todoRepository.updateDueDate(id, (String) updates.get("dueDate"));
+            }
+            return todoRepository.findById(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Void> delete(String userId, String id) {
-        // TODO: Delete todo and subtasks
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromRunnable(() -> {
+            Map<String, Object> todo = todoRepository.findById(userId, id);
+            if (todo == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Todo not found");
+            }
+            todoRepository.delete(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic()).then();
     }
 
     public Mono<List<Map<String, Object>>> getSubtasks(String userId, String id) {
-        // TODO: List subtasks for todo
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        return Mono.fromCallable(() -> {
+            Map<String, Object> todo = todoRepository.findById(userId, id);
+            if (todo == null) {
+                throw new AppException(HttpStatus.NOT_FOUND, "Todo not found");
+            }
+            return todoRepository.findSubtasks(userId, id);
+        }).subscribeOn(Schedulers.boundedElastic());
     }
 }

sundol-backend/src/main/java/com/sundol/service/WebCrawlerService.java

@@ -0,0 +1,203 @@
+package com.sundol.service;
+
+import com.microsoft.playwright.Page;
+import org.jsoup.Jsoup;
+import org.jsoup.nodes.Document;
+import org.jsoup.nodes.Element;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Service;
+import org.springframework.web.reactive.function.client.WebClient;
+
+import java.io.IOException;
+import java.time.Duration;
+
+@Service
+public class WebCrawlerService {
+
+    private static final Logger log = LoggerFactory.getLogger(WebCrawlerService.class);
+    private static final String JINA_READER_BASE = "https://r.jina.ai/";
+    private static final int MIN_CONTENT_LENGTH = 100;
+    private static final java.util.List<String> ERROR_PATTERNS = java.util.List.of(
+            "access denied", "403 forbidden", "you don't have permission",
+            "error 403", "error 401", "unauthorized", "captcha",
+            "please enable javascript", "checking your browser",
+            "attention required", "just a moment",
+            "technical difficulty", "page not found", "404 not found"
+    );
+
+    private final WebClient webClient;
+    private final PlaywrightBrowserService browserService;
+
+    @Value("${jina.reader.api-key:}")
+    private String jinaApiKey;
+
+    public WebCrawlerService(PlaywrightBrowserService browserService) {
+        this.browserService = browserService;
+        this.webClient = WebClient.builder()
+                .codecs(configurer -> configurer.defaultCodecs().maxInMemorySize(5 * 1024 * 1024))
+                .build();
+    }
+
+    public String crawl(String url) throws IOException {
+        // 1차: Jsoup 시도
+        try {
+            String text = crawlWithJsoup(url);
+            if (isValidContent(text)) {
+                return text;
+            }
+            log.warn("Jsoup returned invalid content ({} chars), falling back to Jina Reader",
+                    text != null ? text.length() : 0);
+        } catch (Exception e) {
+            log.warn("Jsoup crawl failed for {}: {}, falling back to Jina Reader", url, e.getMessage());
+        }
+
+        // 2차: Jina Reader fallback
+        try {
+            String text = crawlWithJinaReader(url);
+            if (isValidContent(text)) {
+                return text;
+            }
+            log.warn("Jina Reader returned invalid content ({} chars), falling back to Playwright",
+                    text != null ? text.length() : 0);
+        } catch (Exception e) {
+            log.warn("Jina Reader failed for {}: {}, falling back to Playwright", url, e.getMessage());
+        }
+
+        // 3차: Playwright (싱글톤 브라우저 탭)
+        String playwrightText = crawlWithPlaywright(url);
+        if (!isValidContent(playwrightText)) {
+            throw new IOException("All crawl methods failed for " + url + " (error page detected from all 3 sources)");
+        }
+        return playwrightText;
+    }
+
+    private boolean isValidContent(String text) {
+        if (text == null || text.length() < MIN_CONTENT_LENGTH) {
+            return false;
+        }
+        // 에러 페이지 패턴 감지 (앞 500자만 검사)
+        String preview = text.substring(0, Math.min(text.length(), 500)).toLowerCase();
+        for (String pattern : ERROR_PATTERNS) {
+            if (preview.contains(pattern)) {
+                log.warn("Error page detected: content contains '{}'", pattern);
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private String crawlWithJsoup(String url) throws IOException {
+        log.info("Crawling with Jsoup: {}", url);
+        Document doc = Jsoup.connect(url)
+                .userAgent("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36")
+                .timeout(15_000)
+                .followRedirects(true)
+                .get();
+
+        // Remove non-content elements
+        doc.select("nav, footer, header, script, style, .ad, #cookie-banner, .sidebar, .comments").remove();
+
+        // Prefer article body
+        Element article = doc.selectFirst("article, main, .post-content, .article-body, .entry-content");
+        String text = (article != null ? article : doc.body()).text();
+
+        String title = doc.title();
+        log.info("Jsoup crawled '{}' - {} chars", title, text.length());
+        return text;
+    }
+
+    private String crawlWithJinaReader(String url) throws IOException {
+        log.info("Crawling with Jina Reader: {}", url);
+        try {
+            WebClient.RequestHeadersSpec<?> request = webClient.get()
+                    .uri(JINA_READER_BASE + url)
+                    .header("Accept", "text/plain");
+
+            if (jinaApiKey != null && !jinaApiKey.isBlank()) {
+                request = request.header("Authorization", "Bearer " + jinaApiKey);
+            }
+
+            String result = ((WebClient.RequestHeadersSpec<?>) request)
+                    .retrieve()
+                    .bodyToMono(String.class)
+                    .timeout(Duration.ofSeconds(30))
+                    .block();
+
+            if (result == null || result.isBlank()) {
+                throw new IOException("Jina Reader returned empty response for: " + url);
+            }
+
+            log.info("Jina Reader crawled {} - {} chars", url, result.length());
+            return result;
+        } catch (IOException e) {
+            throw e;
+        } catch (Exception e) {
+            throw new IOException("Jina Reader failed for " + url + ": " + e.getMessage(), e);
+        }
+    }
+
+    private String crawlWithPlaywright(String url) throws IOException {
+        log.info("Crawling with Playwright: {}", url);
+        Page page = browserService.openPage(url);
+        try {
+            // JS 실행으로 본문 텍스트 추출
+            String text = page.evaluate("() => {" +
+                    "  ['nav','footer','header','script','style','.ad','#cookie-banner','.sidebar','.comments']" +
+                    "    .forEach(sel => document.querySelectorAll(sel).forEach(el => el.remove()));" +
+                    "  const article = document.querySelector('article, main, .post-content, .article-body, .entry-content');" +
+                    "  return (article || document.body).innerText;" +
+                    "}").toString();
+
+            log.info("Playwright crawled {} - {} chars", url, text.length());
+
+            if (text == null || text.isBlank()) {
+                throw new IOException("Playwright returned empty content for: " + url);
+            }
+
+            return text;
+        } finally {
+            try {
+                page.navigate("about:blank");
+            } catch (Exception ignored) {
+                page.close();
+            }
+        }
+    }
+
+    public String extractTitle(String url) throws IOException {
+        // Jsoup으로 제목만 가져오기 (가벼움)
+        try {
+            Document doc = Jsoup.connect(url)
+                    .userAgent("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36")
+                    .timeout(10_000)
+                    .get();
+            return doc.title();
+        } catch (Exception e) {
+            log.warn("Title extraction via Jsoup failed for {}, trying Jina Reader", url);
+            // Jina Reader 응답에서 첫 줄을 제목으로 사용
+            try {
+                String content = crawlWithJinaReader(url);
+                String firstLine = content.strip().split("\\r?\\n", 2)[0].strip();
+                if (firstLine.startsWith("Title:")) {
+                    return firstLine.substring(6).strip();
+                }
+                return firstLine.length() > 80 ? firstLine.substring(0, 77) + "..." : firstLine;
+            } catch (Exception e2) {
+                log.warn("Jina Reader title extraction also failed, trying Playwright", e2);
+                // Playwright 싱글톤 브라우저로 제목 추출
+                Page page = browserService.openPage(url);
+                try {
+                    return page.title();
+                } finally {
+                    try {
+                        page.navigate("about:blank");
+                    } catch (Exception ignored2) {
+                        page.close();
+                    }
+                }
+            }
+        }
+    }
+}

sundol-backend/src/main/java/com/sundol/service/YouTubeTranscriptService.java

@@ -0,0 +1,590 @@
+package com.sundol.service;
+
+import com.microsoft.playwright.Page;
+import com.microsoft.playwright.options.WaitUntilState;
+import io.github.thoroldvix.api.TranscriptApiFactory;
+import io.github.thoroldvix.api.TranscriptContent;
+import io.github.thoroldvix.api.TranscriptList;
+import io.github.thoroldvix.api.Transcript;
+import io.github.thoroldvix.api.YoutubeTranscriptApi;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.stereotype.Service;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URLDecoder;
+import java.nio.charset.StandardCharsets;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
+@Service
+public class YouTubeTranscriptService {
+
+    private static final Logger log = LoggerFactory.getLogger(YouTubeTranscriptService.class);
+
+    private static final String[] PREFERRED_LANGS = {"ko", "en"};
+
+    private static final Pattern CAPTION_TRACK_PATTERN =
+            Pattern.compile("\"captionTracks\":\\s*\\[(.*?)]", Pattern.DOTALL);
+    private static final Pattern BASE_URL_PATTERN =
+            Pattern.compile("\"baseUrl\":\\s*\"(.*?)\"");
+    private static final Pattern LANG_PATTERN =
+            Pattern.compile("\"languageCode\":\\s*\"(.*?)\"");
+    private static final Pattern XML_TEXT_PATTERN =
+            Pattern.compile("<text[^>]*>(.*?)</text>", Pattern.DOTALL);
+
+    private final YoutubeTranscriptApi transcriptApi = TranscriptApiFactory.createDefault();
+    private final PlaywrightBrowserService browserService;
+    private final String extractTranscriptJs;
+    private final String transcriptFromPageJs;
+
+    public YouTubeTranscriptService(PlaywrightBrowserService browserService) {
+        this.browserService = browserService;
+        this.extractTranscriptJs = loadResource("youtube-transcript-extract.js");
+        this.transcriptFromPageJs = loadResource("youtube-transcript-from-page.js");
+    }
+
+    private String loadResource(String name) {
+        try (InputStream is = getClass().getClassLoader().getResourceAsStream(name)) {
+            if (is == null) throw new RuntimeException("Resource not found: " + name);
+            return new String(is.readAllBytes(), StandardCharsets.UTF_8);
+        } catch (IOException e) {
+            throw new RuntimeException("Failed to load resource: " + name, e);
+        }
+    }
+
+    public String fetchTranscript(String youtubeUrl) throws IOException {
+        String videoId = extractVideoId(youtubeUrl);
+        if (videoId == null) {
+            throw new IOException("유효하지 않은 YouTube URL입니다: " + youtubeUrl);
+        }
+
+        log.info("Fetching YouTube transcript for videoId: {}", videoId);
+
+        // 1차: youtube-transcript-api 라이브러리
+        try {
+            String transcript = fetchWithApi(videoId);
+            if (transcript != null && !transcript.isBlank()) {
+                log.info("Successfully fetched transcript via API: {} chars", transcript.length());
+                return transcript;
+            }
+        } catch (Exception e) {
+            log.warn("youtube-transcript-api failed for {}: {}", videoId, e.getMessage());
+        }
+
+        // 2차 fallback: Playwright head 모드 (싱글톤 브라우저 탭)
+        log.info("Falling back to Playwright for videoId: {}", videoId);
+        return fetchWithPlaywright(videoId);
+    }
+
+    private String fetchWithApi(String videoId) {
+        TranscriptList transcriptList;
+        try {
+            transcriptList = transcriptApi.listTranscripts(videoId);
+        } catch (Exception e) {
+            log.warn("Cannot list transcripts for {}: {}", videoId, e.getMessage());
+            return null;
+        }
+
+        // manual(수동 자막) 먼저 시도, 없으면 generated(자동 생성)
+        String result = fetchTranscriptByType(transcriptList, true);
+        if (result != null) return result;
+        return fetchTranscriptByType(transcriptList, false);
+    }
+
+    private String fetchTranscriptByType(TranscriptList list, boolean manual) {
+        Transcript picked;
+        try {
+            picked = manual ? list.findManualTranscript(PREFERRED_LANGS)
+                            : list.findGeneratedTranscript(PREFERRED_LANGS);
+        } catch (Exception e) {
+            return null;
+        }
+
+        try {
+            TranscriptContent content = picked.fetch();
+            String text = content.getContent().stream()
+                    .map(TranscriptContent.Fragment::getText)
+                    .collect(Collectors.joining(" "));
+            if (text.isBlank()) return null;
+            String label = manual ? "manual" : "generated";
+            log.info("Transcript source: {} ({})", label, picked.getLanguageCode());
+            return text;
+        } catch (Exception e) {
+            log.warn("Failed to fetch transcript for language {}: {}",
+                    picked.getLanguageCode(), e.getMessage());
+            return null;
+        }
+    }
+
+    private String fetchWithPlaywright(String videoId) throws IOException {
+        String watchUrl = "https://www.youtube.com/watch?v=" + videoId;
+
+        // YouTube는 광고 때문에 NETWORKIDLE에 도달하지 못할 수 있으므로 DOMCONTENTLOADED 사용
+        Page page = browserService.openPage(watchUrl, 60_000, WaitUntilState.DOMCONTENTLOADED);
+        try {
+            log.info("Playwright fetched YouTube page for videoId: {}", videoId);
+            // DOM 로드 후 추가 대기 (JS 렌더링)
+            page.waitForTimeout(3000);
+
+            // Step 0: 동영상 재생 시작 (봇 판정 우회)
+            playVideo(page);
+
+            // Step 1: 광고 대기 (최대 60초)
+            waitForAdsToFinish(page);
+
+            // Step 2: 실제 영상 재생 확인 (최대 15초)
+            waitForVideoPlaying(page);
+
+            // Step 3: 페이지 내 JS에서 ytInitialPlayerResponse로 자막 데이터 직접 추출
+            String transcript = fetchTranscriptFromPageJs(page);
+            if (transcript != null && !transcript.isBlank()) {
+                log.info("Successfully fetched transcript via page JS: {} chars", transcript.length());
+                return transcript;
+            }
+
+            // Step 4: 자막 패널 열어서 텍스트 추출 (확인 루프)
+            transcript = extractTranscriptFromPanel(page);
+            if (transcript != null && !transcript.isBlank()) {
+                log.info("Successfully fetched transcript via panel: {} chars", transcript.length());
+                return transcript;
+            }
+
+            throw new IOException("자막 텍스트를 가져올 수 없습니다.");
+        } finally {
+            try {
+                page.navigate("about:blank");
+            } catch (Exception ignored) {
+                page.close();
+            }
+        }
+    }
+
+    /**
+     * 페이지 내 ytInitialPlayerResponse에서 자막 데이터를 직접 추출한다.
+     * 브라우저 JS 컨텍스트에서 fetch하므로 쿠키/세션 유지.
+     */
+    private String fetchTranscriptFromPageJs(Page page) {
+        try {
+            Object result = page.evaluate(transcriptFromPageJs);
+            if (result == null) return null;
+
+            String resultStr = result.toString();
+            log.info("Page JS transcript result: {} chars", resultStr.length());
+
+            if (resultStr.startsWith("{")) {
+                // JSON 응답 파싱
+                var jsonNode = new com.fasterxml.jackson.databind.ObjectMapper().readTree(resultStr);
+                if (jsonNode.has("error")) {
+                    log.warn("Page JS transcript error: {}", jsonNode.get("error").asText());
+                    return null;
+                }
+                String type = jsonNode.has("type") ? jsonNode.get("type").asText() : "";
+                String data = jsonNode.has("data") ? jsonNode.get("data").asText() : "";
+                String lang = jsonNode.has("lang") ? jsonNode.get("lang").asText() : "";
+                log.info("Page JS transcript type={}, lang={}, data={} chars", type, lang, data.length());
+
+                if (data.isEmpty()) return null;
+
+                if ("json3".equals(type)) {
+                    return parseTranscriptJson(data);
+                } else if ("xml".equals(type)) {
+                    return parseTranscriptXml(data);
+                }
+                return null;
+            }
+            // 문자열 직접 반환된 경우
+            return resultStr.isBlank() ? null : resultStr;
+        } catch (Exception e) {
+            log.warn("fetchTranscriptFromPageJs failed: {}", e.getMessage());
+            return null;
+        }
+    }
+
+    /**
+     * 동영상 재생을 시작한다. 실제 사용자처럼 행동하여 봇 판정을 우회.
+     */
+    private void playVideo(Page page) {
+        try {
+            // 쿠키 동의 팝업 닫기
+            page.evaluate(
+                "() => { " +
+                "  var agreeBtn = document.querySelector('button[aria-label*=\"Accept\"], button[aria-label*=\"동의\"], tp-yt-paper-button[aria-label*=\"Agree\"]'); " +
+                "  if (agreeBtn) agreeBtn.click(); " +
+                "}"
+            );
+            page.waitForTimeout(1000);
+
+            // 마우스를 플레이어 위로 이동 (호버 효과)
+            page.evaluate(
+                "() => { " +
+                "  var player = document.querySelector('#movie_player, .html5-video-player'); " +
+                "  if (player) player.dispatchEvent(new MouseEvent('mouseover', {bubbles: true})); " +
+                "}"
+            );
+            page.waitForTimeout(500);
+
+            // 재생 버튼 클릭 또는 영상 영역 클릭
+            page.evaluate(
+                "() => { " +
+                "  var playBtn = document.querySelector('.ytp-play-button, .ytp-large-play-button'); " +
+                "  if (playBtn) { playBtn.click(); return 'play_clicked'; } " +
+                "  var video = document.querySelector('video'); " +
+                "  if (video) { video.play(); return 'video_play'; } " +
+                "  var player = document.querySelector('#movie_player'); " +
+                "  if (player) { player.click(); return 'player_clicked'; } " +
+                "  return 'nothing'; " +
+                "}"
+            );
+            log.info("Video play initiated");
+            page.waitForTimeout(2000);
+        } catch (Exception e) {
+            log.warn("playVideo error (non-fatal): {}", e.getMessage());
+        }
+    }
+
+    /**
+     * 실제 영상이 재생 중인지 확인한다. (최대 15초)
+     * 재생 시간이 변화하면 재생 중으로 판단.
+     */
+    private void waitForVideoPlaying(Page page) {
+        log.info("Waiting for video to start playing...");
+        try {
+            for (int i = 0; i < 5; i++) {
+                Object result = page.evaluate(
+                    "() => { " +
+                    "  var video = document.querySelector('video'); " +
+                    "  if (!video) return 'no_video'; " +
+                    "  if (video.paused) return 'paused:' + video.currentTime; " +
+                    "  return 'playing:' + video.currentTime; " +
+                    "}"
+                );
+                String status = result != null ? result.toString() : "unknown";
+                log.info("Video status: {}", status);
+
+                if (status.startsWith("playing:")) {
+                    // 재생 시간이 0보다 크면 실제 재생 중
+                    String timeStr = status.substring(8);
+                    try {
+                        double time = Double.parseDouble(timeStr);
+                        if (time > 0.5) {
+                            log.info("Video is playing at {}s", time);
+                            return;
+                        }
+                    } catch (NumberFormatException ignored) {}
+                }
+
+                if (status.startsWith("paused")) {
+                    // 일시정지 상태면 다시 재생 시도
+                    page.evaluate(
+                        "() => { " +
+                        "  var video = document.querySelector('video'); " +
+                        "  if (video) video.play(); " +
+                        "}"
+                    );
+                }
+
+                page.waitForTimeout(3000);
+            }
+            log.info("Video play wait finished");
+        } catch (Exception e) {
+            log.warn("waitForVideoPlaying error (non-fatal): {}", e.getMessage());
+        }
+    }
+
+    /**
+     * YouTube 광고가 재생 중이면 끝날 때까지 대기한다. (최대 60초)
+     * 스킵 버튼이 나타나면 클릭한다.
+     */
+    private void waitForAdsToFinish(Page page) {
+        log.info("Checking for YouTube ads...");
+        for (int i = 0; i < 30; i++) {  // 최대 60초 (2초 간격)
+            try {
+                Object adResult = page.evaluate(
+                    "() => { " +
+                    "  // 스킵 버튼 찾기 (여러 버전 대응) " +
+                    "  var skipBtns = document.querySelectorAll('.ytp-skip-ad-button, .ytp-ad-skip-button, .ytp-ad-skip-button-modern, .ytp-ad-skip-button-container button, [class*=\"skip\"][class*=\"ad\"] button'); " +
+                    "  for (var i = 0; i < skipBtns.length; i++) { " +
+                    "    if (skipBtns[i].offsetParent !== null) { skipBtns[i].click(); return 'skipped'; } " +
+                    "  } " +
+                    "  // 광고 재생 중 확인: #movie_player에 ad-showing 클래스 " +
+                    "  var player = document.querySelector('#movie_player'); " +
+                    "  if (player && player.classList.contains('ad-showing')) return 'ad_playing'; " +
+                    "  // 광고 오버레이 확인 " +
+                    "  var adOverlay = document.querySelector('.ytp-ad-player-overlay'); " +
+                    "  if (adOverlay && adOverlay.offsetHeight > 0) return 'ad_playing'; " +
+                    "  // video duration으로 확인 (광고는 보통 짧음) " +
+                    "  var video = document.querySelector('video'); " +
+                    "  if (video && video.duration > 0 && video.duration < 120 && !video.paused) { " +
+                    "    var adText = document.querySelector('.ytp-ad-text, .ytp-ad-preview-text, .ytp-ad-simple-ad-badge'); " +
+                    "    if (adText) return 'ad_playing'; " +
+                    "  } " +
+                    "  return 'no_ad'; " +
+                    "}"
+                );
+                String status = adResult != null ? adResult.toString() : "no_ad";
+
+                if ("skipped".equals(status)) {
+                    log.info("Ad skipped at attempt {}", i + 1);
+                    page.waitForTimeout(3000);
+                    continue;
+                }
+                if ("no_ad".equals(status)) {
+                    if (i == 0) {
+                        log.info("No ads detected");
+                    } else {
+                        log.info("Ads finished after {} attempts", i + 1);
+                    }
+                    return;
+                }
+                if (i % 5 == 0) log.info("Ad still playing, waiting... ({}s)", i * 2);
+                page.waitForTimeout(2000);
+            } catch (Exception e) {
+                log.warn("Ad check error: {}", e.getMessage());
+                return;
+            }
+        }
+        log.warn("Ad wait timeout (60s), proceeding anyway");
+    }
+
+    /**
+     * YouTube 페이지에서 '자막 표시' 패널을 열고 텍스트를 추출한다.
+     */
+    private String extractTranscriptFromPanel(Page page) {
+        try {
+            page.waitForTimeout(2000);
+
+            // Step 1: 설명란 펼치기
+            page.evaluate(
+                "() => { " +
+                "  var exp = document.querySelector('#expand, tp-yt-paper-button#expand, #description-inline-expander #expand'); " +
+                "  if (exp) exp.click(); " +
+                "}"
+            );
+            page.waitForTimeout(1500);
+
+            // Step 2: '스크립트 표시' / 'Show transcript' 버튼 찾아 클릭
+            Object result = page.evaluate(
+                "() => { " +
+                "  var keywords = ['Show transcript', 'transcript', '스크립트 표시', '자막 보기', '자막']; " +
+                "  var allBtns = document.querySelectorAll('button, ytd-button-renderer, tp-yt-paper-button'); " +
+                "  for (var i = 0; i < allBtns.length; i++) { " +
+                "    var t = (allBtns[i].innerText || allBtns[i].textContent || '').trim().toLowerCase(); " +
+                "    for (var j = 0; j < keywords.length; j++) { " +
+                "      if (t.indexOf(keywords[j].toLowerCase()) !== -1) { " +
+                "        allBtns[i].click(); " +
+                "        return 'clicked:' + t; " +
+                "      } " +
+                "    } " +
+                "  } " +
+                "  return 'not_found'; " +
+                "}"
+            );
+            log.info("Transcript panel button result: {}", result);
+
+            // 패널이 HIDDEN 상태일 수 있으므로 직접 visibility를 변경하고 데이터 로드 트리거
+            page.waitForTimeout(1500);
+            page.evaluate(
+                "() => { " +
+                "  var panel = document.querySelector('ytd-engagement-panel-section-list-renderer[target-id=\"engagement-panel-searchable-transcript\"]'); " +
+                "  if (panel) { " +
+                "    panel.setAttribute('visibility', 'ENGAGEMENT_PANEL_VISIBILITY_EXPANDED'); " +
+                "    panel.removeAttribute('hidden'); " +
+                "    panel.style.display = ''; " +
+                "  } " +
+                "}"
+            );
+            page.waitForTimeout(1000);
+
+            if (result != null && result.toString().startsWith("not_found")) {
+                // 대안: 동영상 메뉴(...) 버튼 → 스크립트 열기
+                page.evaluate(
+                    "() => { " +
+                    "  var menuBtn = document.querySelector('ytd-menu-renderer yt-icon-button button, #menu button'); " +
+                    "  if (menuBtn) menuBtn.click(); " +
+                    "}"
+                );
+                page.waitForTimeout(1000);
+                page.evaluate(
+                    "() => { " +
+                    "  var items = document.querySelectorAll('tp-yt-paper-item, ytd-menu-service-item-renderer'); " +
+                    "  for (var i = 0; i < items.length; i++) { " +
+                    "    var t = (items[i].innerText || '').toLowerCase(); " +
+                    "    if (t.indexOf('transcript') !== -1 || t.indexOf('스크립트') !== -1) { " +
+                    "      items[i].click(); " +
+                    "      return 'menu_clicked'; " +
+                    "    } " +
+                    "  } " +
+                    "  return 'not_found'; " +
+                    "}"
+                );
+            }
+
+            // Step 3: 자막 텍스트가 나타날 때까지 확인 루프 (최대 30초)
+            String transcript = null;
+            for (int attempt = 0; attempt < 15; attempt++) {
+                page.waitForTimeout(2000);
+
+                // 디버그: 트랜스크립트 패널 DOM 상태 확인
+                if (attempt == 0 || attempt == 3) {
+                    Object debugInfo = page.evaluate(
+                        "() => { " +
+                        "  var panel = document.querySelector('ytd-engagement-panel-section-list-renderer[target-id=\"engagement-panel-searchable-transcript\"]'); " +
+                        "  if (!panel) return 'panel:NOT_FOUND'; " +
+                        "  var vis = panel.getAttribute('visibility'); " +
+                        "  var segs = panel.querySelectorAll('[class*=\"segment\"], [class*=\"cue\"], yt-formatted-string'); " +
+                        "  var body = panel.querySelector('#body, #content'); " +
+                        "  var bodyHtml = body ? body.innerHTML.substring(0, 500) : 'no_body'; " +
+                        "  return 'panel:' + vis + ' segs:' + segs.length + ' html:' + bodyHtml; " +
+                        "}"
+                    );
+                    log.info("Debug transcript panel (attempt {}): {}", attempt + 1, debugInfo);
+                }
+
+                Object transcriptObj = page.evaluate(extractTranscriptJs);
+
+                transcript = transcriptObj != null ? transcriptObj.toString() : "";
+                if (!transcript.isBlank()) {
+                    log.info("Transcript from panel: {} chars (attempt {})", transcript.length(), attempt + 1);
+                    return transcript;
+                }
+
+                // 패널이 아직 안 열렸으면 다시 시도
+                if (attempt == 2 || attempt == 5 || attempt == 9) {
+                    log.info("Retrying panel open at attempt {}", attempt + 1);
+                    // 패널 visibility 강제 변경 + Show transcript 버튼 재클릭
+                    page.evaluate(
+                        "() => { " +
+                        "  var panel = document.querySelector('ytd-engagement-panel-section-list-renderer[target-id=\"engagement-panel-searchable-transcript\"]'); " +
+                        "  if (panel) { " +
+                        "    panel.setAttribute('visibility', 'ENGAGEMENT_PANEL_VISIBILITY_EXPANDED'); " +
+                        "    panel.removeAttribute('hidden'); " +
+                        "    panel.style.display = ''; " +
+                        "    var cont = panel.querySelector('ytd-continuation-item-renderer'); " +
+                        "    if (cont) cont.click(); " +
+                        "  } " +
+                        "  var keywords = ['Show transcript', 'transcript', '스크립트 표시', '자막 보기']; " +
+                        "  var allBtns = document.querySelectorAll('button, ytd-button-renderer, tp-yt-paper-button'); " +
+                        "  for (var i = 0; i < allBtns.length; i++) { " +
+                        "    var t = (allBtns[i].innerText || '').trim().toLowerCase(); " +
+                        "    for (var j = 0; j < keywords.length; j++) { " +
+                        "      if (t.indexOf(keywords[j].toLowerCase()) !== -1) { " +
+                        "        allBtns[i].click(); return 'retried'; " +
+                        "      } " +
+                        "    } " +
+                        "  } " +
+                        "}"
+                    );
+                }
+            }
+
+            log.info("Transcript panel extraction timed out after 30s");
+            return null;
+        } catch (Exception e) {
+            log.warn("Failed to extract transcript from panel: {}", e.getMessage());
+            return null;
+        }
+    }
+
+    /**
+     * YouTube timedtext API의 fmt=json3 응답을 파싱한다.
+     */
+    private String parseTranscriptJson(String json) {
+        try {
+            StringBuilder sb = new StringBuilder();
+            // json3 형식: {"events":[{"segs":[{"utf8":"text"}]},...]}
+            Pattern segPattern = Pattern.compile("\"utf8\":\\s*\"(.*?)\"");
+            Matcher matcher = segPattern.matcher(json);
+            while (matcher.find()) {
+                String text = matcher.group(1)
+                        .replace("\\n", " ")
+                        .replace("\\\"", "\"")
+                        .trim();
+                if (!text.isEmpty() && !text.equals("\n")) {
+                    if (sb.length() > 0) sb.append(" ");
+                    sb.append(text);
+                }
+            }
+            return sb.toString();
+        } catch (Exception e) {
+            log.warn("Failed to parse transcript JSON: {}", e.getMessage());
+            return null;
+        }
+    }
+
+    private String selectCaptionUrl(String captionTracksJson) {
+        String[] tracks = captionTracksJson.split("\\},\\s*\\{");
+
+        String koUrl = null;
+        String enUrl = null;
+        String firstUrl = null;
+
+        for (String track : tracks) {
+            Matcher urlMatcher = BASE_URL_PATTERN.matcher(track);
+            Matcher langMatcher = LANG_PATTERN.matcher(track);
+
+            if (urlMatcher.find()) {
+                String url = urlMatcher.group(1);
+                if (firstUrl == null) firstUrl = url;
+
+                if (langMatcher.find()) {
+                    String lang = langMatcher.group(1);
+                    if (lang.startsWith("ko") && koUrl == null) koUrl = url;
+                    if (lang.startsWith("en") && enUrl == null) enUrl = url;
+                }
+            }
+        }
+
+        if (koUrl != null) return koUrl;
+        if (enUrl != null) return enUrl;
+        return firstUrl;
+    }
+
+    private String parseTranscriptXml(String xml) {
+        StringBuilder sb = new StringBuilder();
+        Matcher matcher = XML_TEXT_PATTERN.matcher(xml);
+        while (matcher.find()) {
+            String text = matcher.group(1)
+                    .replace("&amp;", "&")
+                    .replace("&lt;", "<")
+                    .replace("&gt;", ">")
+                    .replace("&quot;", "\"")
+                    .replace("&#39;", "'")
+                    .replace("\n", " ")
+                    .trim();
+            if (!text.isEmpty()) {
+                if (sb.length() > 0) sb.append(" ");
+                sb.append(text);
+            }
+        }
+        return sb.toString();
+    }
+
+    private String extractVideoId(String url) {
+        if (url == null || url.isBlank()) return null;
+        try {
+            java.net.URI uri = new java.net.URI(url);
+            String host = uri.getHost();
+            if (host == null) return null;
+            if (host.equals("youtu.be")) {
+                String path = uri.getPath();
+                return path != null && path.length() > 1 ? path.substring(1) : null;
+            }
+            if (host.contains("youtube.com")) {
+                String query = uri.getQuery();
+                if (query == null) return null;
+                for (String param : query.split("&")) {
+                    String[] kv = param.split("=", 2);
+                    if (kv.length == 2 && kv[0].equals("v")) {
+                        return URLDecoder.decode(kv[1], StandardCharsets.UTF_8);
+                    }
+                }
+            }
+        } catch (Exception e) {
+            log.warn("Failed to parse YouTube URL: {}", url);
+        }
+        return null;
+    }
+}

sundol-backend/src/main/resources/application.yml

@@ -12,12 +12,26 @@ jwt:
   access-token-expiry: ${JWT_ACCESS_TOKEN_EXPIRY:900000}
   refresh-token-expiry: ${JWT_REFRESH_TOKEN_EXPIRY:604800000}
 
+google:
+  client-id: ${GOOGLE_CLIENT_ID}
+  client-secret: ${GOOGLE_CLIENT_SECRET}
+  redirect-uri: ${GOOGLE_REDIRECT_URI:https://sundol.cloud-handson.com/login/callback}
+
 cors:
   origin: ${CORS_ORIGIN:http://localhost:3000}
 
 oci:
   compartment-id: ${OCI_COMPARTMENT_ID:}
   region: ${OCI_REGION:ap-seoul-1}
+  genai:
+    api-key: ${OCI_GENAI_API_KEY:}
+    compartment: ${OCI_GENAI_COMPARTMENT:}
+    model: ${OCI_GENAI_MODEL:google.gemini-2.5-flash}
+    base-url: ${OCI_GENAI_BASE_URL:https://inference.generativeai.us-chicago-1.oci.oraclecloud.com/20231130/actions}
+
+jina:
+  reader:
+    api-key: ${JINA_READER_API_KEY:}
 
 logging:
   level:

sundol-backend/src/main/resources/youtube-transcript-extract.js

@@ -0,0 +1,33 @@
+() => {
+  var selectors = [
+    'ytd-transcript-segment-renderer .segment-text',
+    'yt-formatted-string.segment-text',
+    '#segments-container yt-formatted-string',
+    'ytd-transcript-segment-list-renderer .segment-text',
+    'ytd-transcript-segment-renderer yt-formatted-string',
+    'ytd-engagement-panel-section-list-renderer yt-formatted-string.ytd-transcript-segment-renderer'
+  ];
+  for (var s = 0; s < selectors.length; s++) {
+    try {
+      var segs = document.querySelectorAll(selectors[s]);
+      if (segs.length > 0) {
+        var texts = [];
+        for (var i = 0; i < segs.length; i++) {
+          var txt = segs[i].textContent.trim();
+          if (txt.length > 0) texts.push(txt);
+        }
+        if (texts.length > 0) return texts.join(' ');
+      }
+    } catch(e) {}
+  }
+  // 최후 수단: engagement panel 내 모든 텍스트
+  var panel = document.querySelector('ytd-engagement-panel-section-list-renderer[target-id="engagement-panel-searchable-transcript"]');
+  if (panel) {
+    var body = panel.querySelector('#body, #content');
+    if (body) {
+      var allText = body.innerText.trim();
+      if (allText.length > 100) return allText;
+    }
+  }
+  return '';
+}

sundol-backend/src/main/resources/youtube-transcript-from-page.js

@@ -0,0 +1,72 @@
+() => {
+  try {
+    // 방법 1: ytInitialPlayerResponse에서 직접 자막 데이터 추출
+    var playerResponse = null;
+    if (typeof ytInitialPlayerResponse !== 'undefined') {
+      playerResponse = ytInitialPlayerResponse;
+    }
+    if (!playerResponse) {
+      // 페이지 소스에서 추출 시도
+      var scripts = document.querySelectorAll('script');
+      for (var i = 0; i < scripts.length; i++) {
+        var text = scripts[i].textContent;
+        if (text && text.indexOf('ytInitialPlayerResponse') !== -1) {
+          var match = text.match(/ytInitialPlayerResponse\s*=\s*(\{.*?\});/s);
+          if (match) {
+            try { playerResponse = JSON.parse(match[1]); } catch(e) {}
+          }
+        }
+      }
+    }
+
+    if (!playerResponse) return JSON.stringify({error: 'no_player_response'});
+
+    // captionTracks 추출
+    var captions = playerResponse.captions;
+    if (!captions) return JSON.stringify({error: 'no_captions'});
+
+    var renderer = captions.playerCaptionsTracklistRenderer;
+    if (!renderer) return JSON.stringify({error: 'no_renderer'});
+
+    var tracks = renderer.captionTracks;
+    if (!tracks || tracks.length === 0) return JSON.stringify({error: 'no_tracks'});
+
+    // 언어 우선순위: ko > en > 첫 번째
+    var selectedTrack = null;
+    for (var t = 0; t < tracks.length; t++) {
+      if (tracks[t].languageCode === 'ko') { selectedTrack = tracks[t]; break; }
+    }
+    if (!selectedTrack) {
+      for (var t = 0; t < tracks.length; t++) {
+        if (tracks[t].languageCode === 'en') { selectedTrack = tracks[t]; break; }
+      }
+    }
+    if (!selectedTrack) selectedTrack = tracks[0];
+
+    var baseUrl = selectedTrack.baseUrl;
+    if (!baseUrl) return JSON.stringify({error: 'no_base_url'});
+
+    // fmt=json3 추가
+    if (baseUrl.indexOf('fmt=') === -1) {
+      baseUrl += '&fmt=json3';
+    }
+
+    // 브라우저 내에서 fetch로 자막 데이터 가져오기
+    return fetch(baseUrl, {credentials: 'include'})
+      .then(function(res) { return res.text(); })
+      .then(function(text) {
+        if (!text || text.length === 0) {
+          // fmt=json3 실패 시 fmt 없이 재시도 (XML)
+          var xmlUrl = baseUrl.replace('&fmt=json3', '');
+          return fetch(xmlUrl, {credentials: 'include'})
+            .then(function(res2) { return res2.text(); })
+            .then(function(xmlText) {
+              return JSON.stringify({type: 'xml', data: xmlText, lang: selectedTrack.languageCode});
+            });
+        }
+        return JSON.stringify({type: 'json3', data: text, lang: selectedTrack.languageCode});
+      });
+  } catch(e) {
+    return JSON.stringify({error: e.message});
+  }
+}

sundol-frontend/build.sh

@@ -0,0 +1,58 @@
+#!/bin/bash
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+cd "$SCRIPT_DIR"
+
+# .env 로드
+ENV_FILE="$SCRIPT_DIR/../.env"
+if [ -f "$ENV_FILE" ]; then
+    set -a && source "$ENV_FILE" && set +a
+fi
+
+# 필수 환경변수 검증
+echo "=== [0/3] 환경변수 검증 ==="
+REQUIRED_VARS=("NEXT_PUBLIC_GOOGLE_CLIENT_ID" "NEXT_PUBLIC_API_URL")
+for var in "${REQUIRED_VARS[@]}"; do
+    if [ -z "${!var}" ]; then
+        echo "ERROR: $var 가 .env에 설정되어 있지 않습니다. 빌드를 중단합니다."
+        exit 1
+    fi
+    echo "  $var = ${!var:0:20}..."
+done
+
+echo "=== [1/3] Next.js 빌드 ==="
+npx next build
+
+echo "=== [2/3] 심볼릭 링크 생성 ==="
+STANDALONE_DIR="$SCRIPT_DIR/.next/standalone"
+
+# static 링크
+STATIC_SRC="$SCRIPT_DIR/.next/static"
+STATIC_DST="$STANDALONE_DIR/.next/static"
+mkdir -p "$STANDALONE_DIR/.next"
+if [ -L "$STATIC_DST" ] || [ -e "$STATIC_DST" ]; then
+    rm -rf "$STATIC_DST"
+fi
+ln -s "$STATIC_SRC" "$STATIC_DST"
+echo "링크 생성 완료: $STATIC_DST -> $STATIC_SRC"
+
+# standalone output이 subdirectory에 생성되는 경우 대응
+if [ -d "$STANDALONE_DIR/sundol-frontend" ]; then
+    # server.js 링크
+    if [ ! -f "$STANDALONE_DIR/server.js" ] && [ -f "$STANDALONE_DIR/sundol-frontend/server.js" ]; then
+        ln -sf "$STANDALONE_DIR/sundol-frontend/server.js" "$STANDALONE_DIR/server.js"
+        echo "server.js 링크 생성 완료"
+    fi
+    # nested static 링크
+    NESTED_STATIC="$STANDALONE_DIR/sundol-frontend/.next/static"
+    if [ ! -L "$NESTED_STATIC" ] && [ ! -e "$NESTED_STATIC" ]; then
+        ln -s "$STATIC_SRC" "$NESTED_STATIC"
+        echo "nested static 링크 생성 완료"
+    fi
+fi
+
+echo "=== [3/3] PM2 재시작 ==="
+pm2 restart sundol-frontend
+
+echo "=== 빌드 완료 ==="

sundol-frontend/next-env.d.ts

@@ -0,0 +1,6 @@
+/// <reference types="next" />
+/// <reference types="next/image-types/global" />
+/// <reference path="./.next/types/routes.d.ts" />
+
+// NOTE: This file should not be edited
+// see https://nextjs.org/docs/app/api-reference/config/typescript for more information.

sundol-frontend/package.json

@@ -9,23 +9,23 @@
     "lint": "next lint"
   },
   "dependencies": {
+    "axios": "^1.7.9",
+    "lucide-react": "^0.469.0",
     "next": "^15.3.1",
     "react": "^19.1.0",
     "react-dom": "^19.1.0",
-    "axios": "^1.7.9",
-    "zustand": "^5.0.3",
-    "react-markdown": "^9.0.3",
-    "lucide-react": "^0.469.0"
+    "react-markdown": "^9.1.0",
+    "zustand": "^5.0.3"
   },
   "devDependencies": {
-    "typescript": "^5.7.3",
+    "@eslint/eslintrc": "^3",
+    "@tailwindcss/postcss": "^4.1.0",
     "@types/node": "^22.10.0",
     "@types/react": "^19.1.0",
     "@types/react-dom": "^19.1.0",
-    "@tailwindcss/postcss": "^4.1.0",
-    "tailwindcss": "^4.1.0",
     "eslint": "^9.17.0",
     "eslint-config-next": "^15.3.1",
-    "@eslint/eslintrc": "^3"
+    "tailwindcss": "^4.1.0",
+    "typescript": "^5.7.3"
   }
 }

sundol-frontend/src/app/chat/page.tsx

@@ -1,16 +1,297 @@
 "use client";
 
+import { useEffect, useState, useRef } from "react";
 import AuthGuard from "@/components/auth-guard";
 import NavBar from "@/components/nav-bar";
+import { useApi } from "@/lib/use-api";
+
+interface Session {
+  ID: string;
+  TITLE: string;
+  CREATED_AT: string;
+  UPDATED_AT: string;
+}
+
+interface Message {
+  ID: string;
+  ROLE: string;
+  CONTENT: string;
+  SOURCE_CHUNKS: string | null;
+  CREATED_AT: string;
+}
+
+interface SourceChunk {
+  knowledgeItemId: string;
+  title: string;
+  chunkIndex: number;
+  distance: number;
+}
 
 export default function ChatPage() {
+  const { request } = useApi();
+  const [sessions, setSessions] = useState<Session[]>([]);
+  const [activeSessionId, setActiveSessionId] = useState<string | null>(null);
+  const [messages, setMessages] = useState<Message[]>([]);
+  const [input, setInput] = useState("");
+  const [sending, setSending] = useState(false);
+  const [loadingSessions, setLoadingSessions] = useState(true);
+  const messagesEndRef = useRef<HTMLDivElement>(null);
+
+  const scrollToBottom = () => {
+    messagesEndRef.current?.scrollIntoView({ behavior: "smooth" });
+  };
+
+  useEffect(() => {
+    scrollToBottom();
+  }, [messages]);
+
+  // Load sessions
+  useEffect(() => {
+    request<Session[]>({ method: "GET", url: "/api/chat/sessions" })
+      .then(setSessions)
+      .catch((err) => console.error("Failed to load sessions:", err))
+      .finally(() => setLoadingSessions(false));
+  }, []);
+
+  // Load messages when session changes
+  useEffect(() => {
+    if (!activeSessionId) {
+      setMessages([]);
+      return;
+    }
+    request<Message[]>({ method: "GET", url: `/api/chat/sessions/${activeSessionId}/messages` })
+      .then(setMessages)
+      .catch((err) => console.error("Failed to load messages:", err));
+  }, [activeSessionId]);
+
+  const handleNewSession = async () => {
+    try {
+      const session = await request<Session>({ method: "POST", url: "/api/chat/sessions" });
+      setSessions((prev) => [session, ...prev]);
+      setActiveSessionId(session.ID);
+    } catch (err) {
+      console.error("Failed to create session:", err);
+    }
+  };
+
+  const handleDeleteSession = async (sessionId: string) => {
+    try {
+      await request({ method: "DELETE", url: `/api/chat/sessions/${sessionId}` });
+      setSessions((prev) => prev.filter((s) => s.ID !== sessionId));
+      if (activeSessionId === sessionId) {
+        setActiveSessionId(null);
+        setMessages([]);
+      }
+    } catch (err) {
+      console.error("Failed to delete session:", err);
+    }
+  };
+
+  const handleSend = async () => {
+    if (!input.trim() || sending || !activeSessionId) return;
+
+    const userMessage = input.trim();
+    setInput("");
+    setSending(true);
+
+    // Optimistic UI: add user message immediately
+    const tempUserMsg: Message = {
+      ID: "temp-user",
+      ROLE: "user",
+      CONTENT: userMessage,
+      SOURCE_CHUNKS: null,
+      CREATED_AT: new Date().toISOString(),
+    };
+    setMessages((prev) => [...prev, tempUserMsg]);
+
+    try {
+      const response = await request<{ role: string; content: string; sourceChunks: string }>({
+        method: "POST",
+        url: `/api/chat/sessions/${activeSessionId}/messages`,
+        data: { content: userMessage },
+      });
+
+      const assistantMsg: Message = {
+        ID: "temp-assistant-" + Date.now(),
+        ROLE: "assistant",
+        CONTENT: response.content,
+        SOURCE_CHUNKS: response.sourceChunks,
+        CREATED_AT: new Date().toISOString(),
+      };
+      setMessages((prev) => [...prev, assistantMsg]);
+
+      // Refresh sessions for updated title
+      request<Session[]>({ method: "GET", url: "/api/chat/sessions" })
+        .then(setSessions)
+        .catch(() => {});
+    } catch (err) {
+      console.error("Failed to send message:", err);
+      const errorMsg: Message = {
+        ID: "temp-error",
+        ROLE: "assistant",
+        CONTENT: "메시지 전송에 실패했습니다.",
+        SOURCE_CHUNKS: null,
+        CREATED_AT: new Date().toISOString(),
+      };
+      setMessages((prev) => [...prev, errorMsg]);
+    } finally {
+      setSending(false);
+    }
+  };
+
+  const parseSourceChunks = (json: string | null): SourceChunk[] => {
+    if (!json) return [];
+    try {
+      return JSON.parse(json);
+    } catch {
+      return [];
+    }
+  };
+
   return (
     <AuthGuard>
       <NavBar />
-      <main className="max-w-7xl mx-auto px-4 py-8">
-        <h1 className="text-2xl font-bold mb-6">AI Chat</h1>
-        <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)] min-h-[60vh] flex items-center justify-center">
-          <p className="text-[var(--color-text-muted)]">Start a new conversation to ask questions about your knowledge base.</p>
+      <main className="max-w-7xl mx-auto px-4 py-4 h-[calc(100vh-64px)] flex gap-4">
+        {/* Sidebar: Sessions */}
+        <div className="w-64 flex-shrink-0 flex flex-col">
+          <button
+            onClick={handleNewSession}
+            className="w-full px-4 py-2 mb-3 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] rounded-lg text-sm transition-colors"
+          >
+            + New Chat
+          </button>
+          <div className="flex-1 overflow-y-auto space-y-1">
+            {loadingSessions ? (
+              <p className="text-sm text-[var(--color-text-muted)] px-2">Loading...</p>
+            ) : sessions.length === 0 ? (
+              <p className="text-sm text-[var(--color-text-muted)] px-2">No conversations yet</p>
+            ) : (
+              sessions.map((s) => (
+                <div
+                  key={s.ID}
+                  className={`group flex items-center rounded-lg px-3 py-2 text-sm cursor-pointer transition-colors ${
+                    activeSessionId === s.ID
+                      ? "bg-[var(--color-primary)]/20 text-[var(--color-primary)]"
+                      : "hover:bg-[var(--color-bg-hover)] text-[var(--color-text-muted)]"
+                  }`}
+                  onClick={() => setActiveSessionId(s.ID)}
+                >
+                  <span className="flex-1 truncate">{s.TITLE || "New Chat"}</span>
+                  <button
+                    onClick={(e) => {
+                      e.stopPropagation();
+                      handleDeleteSession(s.ID);
+                    }}
+                    className="hidden group-hover:block text-red-400 hover:text-red-300 ml-2 text-xs"
+                  >
+                    ✕
+                  </button>
+                </div>
+              ))
+            )}
+          </div>
+        </div>
+
+        {/* Main Chat Area */}
+        <div className="flex-1 flex flex-col min-w-0">
+          {!activeSessionId ? (
+            <div className="flex-1 flex items-center justify-center">
+              <div className="text-center">
+                <h2 className="text-xl font-bold mb-2">AI Chat</h2>
+                <p className="text-[var(--color-text-muted)] mb-4">
+                  Knowledge base를 기반으로 질문하세요.
+                </p>
+                <button
+                  onClick={handleNewSession}
+                  className="px-6 py-2 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] rounded-lg transition-colors"
+                >
+                  Start a new chat
+                </button>
+              </div>
+            </div>
+          ) : (
+            <>
+              {/* Messages */}
+              <div className="flex-1 overflow-y-auto space-y-4 py-4">
+                {messages.length === 0 && (
+                  <p className="text-center text-[var(--color-text-muted)] mt-20">
+                    Knowledge base에 대해 질문해보세요.
+                  </p>
+                )}
+                {messages.map((msg) => (
+                  <div
+                    key={msg.ID}
+                    className={`flex ${msg.ROLE === "user" ? "justify-end" : "justify-start"}`}
+                  >
+                    <div
+                      className={`max-w-[75%] rounded-xl px-4 py-3 ${
+                        msg.ROLE === "user"
+                          ? "bg-[var(--color-primary)] text-white"
+                          : "bg-[var(--color-bg-card)] border border-[var(--color-border)]"
+                      }`}
+                    >
+                      <p className="whitespace-pre-wrap text-sm">{msg.CONTENT}</p>
+                      {/* Source chunks */}
+                      {msg.ROLE === "assistant" && (() => {
+                        const sources = parseSourceChunks(msg.SOURCE_CHUNKS);
+                        if (sources.length === 0) return null;
+                        return (
+                          <div className="mt-2 pt-2 border-t border-[var(--color-border)]">
+                            <p className="text-xs text-[var(--color-text-muted)] mb-1">참조:</p>
+                            <div className="flex flex-wrap gap-1">
+                              {sources.map((src, i) => (
+                                <a
+                                  key={i}
+                                  href={`/knowledge/${src.knowledgeItemId}`}
+                                  className="text-xs px-2 py-0.5 rounded bg-[var(--color-bg-hover)] text-[var(--color-text-muted)] hover:text-[var(--color-primary)]"
+                                >
+                                  {src.title}
+                                </a>
+                              ))}
+                            </div>
+                          </div>
+                        );
+                      })()}
+                    </div>
+                  </div>
+                ))}
+                {sending && (
+                  <div className="flex justify-start">
+                    <div className="bg-[var(--color-bg-card)] border border-[var(--color-border)] rounded-xl px-4 py-3">
+                      <div className="flex gap-1">
+                        <div className="w-2 h-2 bg-[var(--color-text-muted)] rounded-full animate-bounce" style={{ animationDelay: "0ms" }} />
+                        <div className="w-2 h-2 bg-[var(--color-text-muted)] rounded-full animate-bounce" style={{ animationDelay: "150ms" }} />
+                        <div className="w-2 h-2 bg-[var(--color-text-muted)] rounded-full animate-bounce" style={{ animationDelay: "300ms" }} />
+                      </div>
+                    </div>
+                  </div>
+                )}
+                <div ref={messagesEndRef} />
+              </div>
+
+              {/* Input */}
+              <div className="py-3">
+                <div className="flex gap-2">
+                  <input
+                    type="text"
+                    value={input}
+                    onChange={(e) => setInput(e.target.value)}
+                    onKeyDown={(e) => e.key === "Enter" && !e.shiftKey && handleSend()}
+                    placeholder="메시지를 입력하세요..."
+                    disabled={sending}
+                    className="flex-1 px-4 py-3 rounded-xl bg-[var(--color-bg-card)] border border-[var(--color-border)] focus:border-[var(--color-primary)] focus:outline-none disabled:opacity-50"
+                  />
+                  <button
+                    onClick={handleSend}
+                    disabled={!input.trim() || sending}
+                    className="px-6 py-3 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] disabled:opacity-40 disabled:cursor-not-allowed rounded-xl transition-colors"
+                  >
+                    전송
+                  </button>
+                </div>
+              </div>
+            </>
+          )}
         </div>
       </main>
     </AuthGuard>

sundol-frontend/src/app/dashboard/page.tsx

@@ -1,33 +1,81 @@
 "use client";
 
+import { useEffect, useState } from "react";
+import Link from "next/link";
 import AuthGuard from "@/components/auth-guard";
 import NavBar from "@/components/nav-bar";
+import { useApi } from "@/lib/use-api";
+
+interface DashData {
+  knowledgeCount: number;
+  dueCards: number;
+  activeTodos: number;
+  habitStreaks: number;
+  chatSessions: number;
+  tags: number;
+}
 
 export default function DashboardPage() {
+  const { request } = useApi();
+  const [data, setData] = useState<DashData | null>(null);
+
+  useEffect(() => {
+    Promise.all([
+      request<unknown[]>({ method: "GET", url: "/api/knowledge" }).catch(() => []),
+      request<unknown[]>({ method: "GET", url: "/api/study-cards/due" }).catch(() => []),
+      request<unknown[]>({ method: "GET", url: "/api/todos?status=PENDING" }).catch(() => []),
+      request<{ STREAK_CURRENT?: number }[]>({ method: "GET", url: "/api/habits" }).catch(() => []),
+      request<unknown[]>({ method: "GET", url: "/api/chat/sessions" }).catch(() => []),
+      request<unknown[]>({ method: "GET", url: "/api/tags" }).catch(() => []),
+    ]).then(([knowledge, dueCards, todos, habits, sessions, tags]) => {
+      const activeStreaks = (habits as { STREAK_CURRENT?: number }[]).filter(
+        (h) => h.STREAK_CURRENT && h.STREAK_CURRENT > 0
+      ).length;
+      setData({
+        knowledgeCount: knowledge.length,
+        dueCards: dueCards.length,
+        activeTodos: todos.length,
+        habitStreaks: activeStreaks,
+        chatSessions: sessions.length,
+        tags: tags.length,
+      });
+    });
+  }, []);
+
+  const cards: { title: string; value: string; description: string; href: string; color: string }[] = data
+    ? [
+        { title: "Knowledge Items", value: String(data.knowledgeCount), description: "수집된 항목", href: "/knowledge", color: "text-blue-400" },
+        { title: "Due Study Cards", value: String(data.dueCards), description: "복습 대기 카드", href: "/study", color: "text-purple-400" },
+        { title: "Active Todos", value: String(data.activeTodos), description: "진행중인 할 일", href: "/todos", color: "text-yellow-400" },
+        { title: "Habit Streaks", value: String(data.habitStreaks), description: "활성 연속 기록", href: "/habits", color: "text-green-400" },
+        { title: "Chat Sessions", value: String(data.chatSessions), description: "대화 세션", href: "/chat", color: "text-cyan-400" },
+        { title: "Tags", value: String(data.tags), description: "태그 수", href: "#", color: "text-indigo-400" },
+      ]
+    : [];
+
   return (
     <AuthGuard>
       <NavBar />
       <main className="max-w-7xl mx-auto px-4 py-8">
         <h1 className="text-2xl font-bold mb-6">Dashboard</h1>
-        <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-6">
-          <DashCard title="Knowledge Items" value="-" description="Total ingested items" />
-          <DashCard title="Due Study Cards" value="-" description="Cards due for review" />
-          <DashCard title="Active Todos" value="-" description="Pending tasks" />
-          <DashCard title="Habit Streaks" value="-" description="Current active streaks" />
-          <DashCard title="Chat Sessions" value="-" description="Active conversations" />
-          <DashCard title="Tags" value="-" description="Knowledge categories" />
-        </div>
+        {!data ? (
+          <p className="text-[var(--color-text-muted)]">Loading...</p>
+        ) : (
+          <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-6">
+            {cards.map((card) => (
+              <Link
+                key={card.title}
+                href={card.href}
+                className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)] hover:border-[var(--color-primary)] transition-colors"
+              >
+                <h3 className="text-sm text-[var(--color-text-muted)] mb-1">{card.title}</h3>
+                <p className={`text-3xl font-bold mb-1 ${card.color}`}>{card.value}</p>
+                <p className="text-sm text-[var(--color-text-muted)]">{card.description}</p>
+              </Link>
+            ))}
+          </div>
+        )}
       </main>
     </AuthGuard>
   );
 }
-
-function DashCard({ title, value, description }: { title: string; value: string; description: string }) {
-  return (
-    <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)]">
-      <h3 className="text-sm text-[var(--color-text-muted)] mb-1">{title}</h3>
-      <p className="text-3xl font-bold mb-1">{value}</p>
-      <p className="text-sm text-[var(--color-text-muted)]">{description}</p>
-    </div>
-  );
-}

sundol-frontend/src/app/habits/page.tsx

@@ -1,22 +1,203 @@
 "use client";
 
+import { useEffect, useState } from "react";
 import AuthGuard from "@/components/auth-guard";
 import NavBar from "@/components/nav-bar";
+import { useApi } from "@/lib/use-api";
+
+interface Habit {
+  ID: string;
+  NAME: string;
+  DESCRIPTION: string | null;
+  HABIT_TYPE: string;
+  COLOR: string;
+  STREAK_CURRENT: number;
+  STREAK_BEST: number;
+  CHECKED_TODAY: boolean;
+}
+
+const COLORS = ["#6366f1", "#ec4899", "#f59e0b", "#10b981", "#3b82f6", "#8b5cf6", "#ef4444"];
 
 export default function HabitsPage() {
+  const { request } = useApi();
+  const [habits, setHabits] = useState<Habit[]>([]);
+  const [loading, setLoading] = useState(true);
+
+  // Add form
+  const [showAdd, setShowAdd] = useState(false);
+  const [newName, setNewName] = useState("");
+  const [newColor, setNewColor] = useState(COLORS[0]);
+
+  const fetchHabits = async () => {
+    try {
+      const data = await request<Habit[]>({ method: "GET", url: "/api/habits" });
+      setHabits(data);
+    } catch (err) {
+      console.error("Failed to load habits:", err);
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  useEffect(() => {
+    fetchHabits();
+  }, []);
+
+  const handleAdd = async () => {
+    if (!newName.trim()) return;
+    try {
+      await request({
+        method: "POST",
+        url: "/api/habits",
+        data: { name: newName.trim(), habitType: "DAILY", color: newColor },
+      });
+      setNewName("");
+      setShowAdd(false);
+      fetchHabits();
+    } catch (err) {
+      console.error("Failed to create habit:", err);
+    }
+  };
+
+  const handleCheckin = async (habitId: string) => {
+    try {
+      await request({ method: "POST", url: `/api/habits/${habitId}/checkin`, data: {} });
+      fetchHabits();
+    } catch (err) {
+      console.error("Failed to check in:", err);
+    }
+  };
+
+  const handleDelete = async (habitId: string) => {
+    if (!confirm("이 습관을 삭제하시겠습니까?")) return;
+    try {
+      await request({ method: "DELETE", url: `/api/habits/${habitId}` });
+      fetchHabits();
+    } catch (err) {
+      console.error("Failed to delete habit:", err);
+    }
+  };
+
+  // 오늘 요일 (월~일 한글)
+  const today = new Date();
+  const weekDays = ["일", "월", "화", "수", "목", "금", "토"];
+
   return (
     <AuthGuard>
       <NavBar />
-      <main className="max-w-7xl mx-auto px-4 py-8">
+      <main className="max-w-3xl mx-auto px-4 py-8">
         <div className="flex justify-between items-center mb-6">
-          <h1 className="text-2xl font-bold">Habits</h1>
-          <button className="px-4 py-2 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] rounded-lg transition-colors">
+          <div>
+            <h1 className="text-2xl font-bold">Habits</h1>
+            <p className="text-sm text-[var(--color-text-muted)]">
+              {today.toLocaleDateString("ko-KR", { month: "long", day: "numeric", weekday: "long" })}
+            </p>
+          </div>
+          <button
+            onClick={() => setShowAdd(!showAdd)}
+            className="px-4 py-2 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] rounded-lg transition-colors text-sm"
+          >
             + Add Habit
           </button>
         </div>
-        <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)]">
-          <p className="text-[var(--color-text-muted)]">No habits tracked yet. Start building good habits.</p>
-        </div>
+
+        {/* Add form */}
+        {showAdd && (
+          <div className="bg-[var(--color-bg-card)] rounded-xl p-4 border border-[var(--color-border)] mb-4 space-y-3">
+            <input
+              type="text"
+              value={newName}
+              onChange={(e) => setNewName(e.target.value)}
+              onKeyDown={(e) => e.key === "Enter" && handleAdd()}
+              placeholder="습관 이름 (예: 물 2L 마시기)"
+              autoFocus
+              className="w-full px-3 py-2 rounded-lg bg-[var(--color-bg-hover)] border border-[var(--color-border)] focus:border-[var(--color-primary)] focus:outline-none"
+            />
+            <div className="flex items-center gap-3">
+              <span className="text-sm text-[var(--color-text-muted)]">색상:</span>
+              <div className="flex gap-2">
+                {COLORS.map((c) => (
+                  <button
+                    key={c}
+                    onClick={() => setNewColor(c)}
+                    className={`w-6 h-6 rounded-full transition-transform ${newColor === c ? "scale-125 ring-2 ring-white" : ""}`}
+                    style={{ backgroundColor: c }}
+                  />
+                ))}
+              </div>
+              <button
+                onClick={handleAdd}
+                disabled={!newName.trim()}
+                className="ml-auto px-4 py-1.5 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] disabled:opacity-40 rounded-lg text-sm transition-colors"
+              >
+                추가
+              </button>
+            </div>
+          </div>
+        )}
+
+        {/* Habit list */}
+        {loading ? (
+          <p className="text-[var(--color-text-muted)]">Loading...</p>
+        ) : habits.length === 0 ? (
+          <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)]">
+            <p className="text-[var(--color-text-muted)]">아직 습관이 없습니다. 새로운 습관을 만들어보세요.</p>
+          </div>
+        ) : (
+          <div className="space-y-3">
+            {habits.map((habit) => (
+              <div
+                key={habit.ID}
+                className="bg-[var(--color-bg-card)] rounded-xl p-4 border border-[var(--color-border)] hover:border-[var(--color-primary)] transition-colors"
+              >
+                <div className="flex items-center gap-4">
+                  {/* Check-in button */}
+                  <button
+                    onClick={() => !habit.CHECKED_TODAY && handleCheckin(habit.ID)}
+                    disabled={habit.CHECKED_TODAY}
+                    className={`w-12 h-12 rounded-xl flex items-center justify-center flex-shrink-0 transition-all ${
+                      habit.CHECKED_TODAY
+                        ? "opacity-90"
+                        : "opacity-50 hover:opacity-100 hover:scale-105"
+                    }`}
+                    style={{ backgroundColor: habit.COLOR || "#6366f1" }}
+                  >
+                    {habit.CHECKED_TODAY ? (
+                      <svg className="w-6 h-6 text-white" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={3}>
+                        <path strokeLinecap="round" strokeLinejoin="round" d="M5 13l4 4L19 7" />
+                      </svg>
+                    ) : (
+                      <span className="text-white text-lg font-bold">+</span>
+                    )}
+                  </button>
+
+                  {/* Info */}
+                  <div className="flex-1 min-w-0">
+                    <h3 className="font-medium">{habit.NAME}</h3>
+                    <div className="flex items-center gap-4 mt-1">
+                      <span className="text-sm" style={{ color: habit.COLOR || "#6366f1" }}>
+                        {habit.STREAK_CURRENT > 0 ? `${habit.STREAK_CURRENT}일 연속` : "시작 전"}
+                      </span>
+                      {habit.STREAK_BEST > 0 && (
+                        <span className="text-xs text-[var(--color-text-muted)]">
+                          최고: {habit.STREAK_BEST}일
+                        </span>
+                      )}
+                    </div>
+                  </div>
+
+                  {/* Delete */}
+                  <button
+                    onClick={() => handleDelete(habit.ID)}
+                    className="text-xs text-red-400 hover:text-red-300 px-2"
+                  >
+                    ✕
+                  </button>
+                </div>
+              </div>
+            ))}
+          </div>
+        )}
       </main>
     </AuthGuard>
   );

sundol-frontend/src/app/knowledge/[id]/page.tsx

@@ -0,0 +1,436 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import { useParams, useRouter } from "next/navigation";
+import AuthGuard from "@/components/auth-guard";
+import NavBar from "@/components/nav-bar";
+import { useApi } from "@/lib/use-api";
+import ReactMarkdown from "react-markdown";
+
+interface Category {
+  ID: string;
+  NAME: string;
+  DEPTH: number;
+  FULL_PATH: string;
+}
+
+interface KnowledgeItem {
+  ID: string;
+  TYPE: string;
+  TITLE: string;
+  SOURCE_URL: string;
+  RAW_TEXT: string;
+  STRUCTURED_CONTENT: string | null;
+  STATUS: string;
+  CREATED_AT: string;
+  UPDATED_AT: string;
+  CATEGORIES: Category[];
+}
+
+interface Chunk {
+  ID: string;
+  CHUNK_INDEX: number;
+  CONTENT: string;
+  TOKEN_COUNT: number;
+}
+
+const statusColors: Record<string, string> = {
+  PENDING: "bg-yellow-500/20 text-yellow-400",
+  EXTRACTING: "bg-blue-500/20 text-blue-400",
+  CHUNKING: "bg-purple-500/20 text-purple-400",
+  CATEGORIZING: "bg-indigo-500/20 text-indigo-400",
+  STRUCTURING: "bg-orange-500/20 text-orange-400",
+  EMBEDDING: "bg-cyan-500/20 text-cyan-400",
+  READY: "bg-green-500/20 text-green-400",
+  FAILED: "bg-red-500/20 text-red-400",
+};
+
+const typeLabels: Record<string, string> = {
+  YOUTUBE: "YouTube",
+  WEB: "Web",
+  TEXT: "Text",
+};
+
+function extractYouTubeVideoId(url: string): string | null {
+  try {
+    const u = new URL(url);
+    if (u.hostname === "youtu.be") return u.pathname.slice(1);
+    if (u.hostname.includes("youtube.com")) return u.searchParams.get("v");
+  } catch {
+    // invalid URL
+  }
+  return null;
+}
+
+export default function KnowledgeDetailPage() {
+  const { request } = useApi();
+  const router = useRouter();
+  const params = useParams();
+  const id = params.id as string;
+
+  const [item, setItem] = useState<KnowledgeItem | null>(null);
+  const [chunks, setChunks] = useState<Chunk[]>([]);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState<string | null>(null);
+  const [editingTitle, setEditingTitle] = useState(false);
+  const [titleDraft, setTitleDraft] = useState("");
+  const [showChunks, setShowChunks] = useState(false);
+  const [deleting, setDeleting] = useState(false);
+  const [generating, setGenerating] = useState(false);
+  const [structuring, setStructuring] = useState(false);
+  const [showStructured, setShowStructured] = useState(true);
+
+  const fetchItem = async () => {
+    try {
+      const data = await request<KnowledgeItem>({ method: "GET", url: `/api/knowledge/${id}` });
+      setItem(data);
+    } catch (err: unknown) {
+      const msg = err instanceof Error ? err.message : "Failed to load";
+      setError(msg);
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  const fetchChunks = async () => {
+    try {
+      const data = await request<Chunk[]>({ method: "GET", url: `/api/knowledge/${id}/chunks` });
+      setChunks(data);
+    } catch (err) {
+      console.error("Failed to load chunks:", err);
+    }
+  };
+
+  useEffect(() => {
+    fetchItem();
+  }, [id]);
+
+  // Poll while processing
+  useEffect(() => {
+    if (!item) return;
+    const processing = ["PENDING", "EXTRACTING", "STRUCTURING", "CHUNKING", "CATEGORIZING", "EMBEDDING"].includes(item.STATUS);
+    if (!processing) return;
+    const interval = setInterval(fetchItem, 3000);
+    return () => clearInterval(interval);
+  }, [item?.STATUS]);
+
+  const handleSaveTitle = async () => {
+    if (!titleDraft.trim()) return;
+    try {
+      const updated = await request<KnowledgeItem>({
+        method: "PATCH",
+        url: `/api/knowledge/${id}`,
+        data: { title: titleDraft.trim() },
+      });
+      setItem(updated);
+      setEditingTitle(false);
+    } catch (err) {
+      console.error("Failed to update title:", err);
+    }
+  };
+
+  const handleDelete = async () => {
+    if (!confirm("정말 삭제하시겠습니까?")) return;
+    setDeleting(true);
+    try {
+      await request({ method: "DELETE", url: `/api/knowledge/${id}` });
+      router.push("/knowledge");
+    } catch (err) {
+      console.error("Failed to delete:", err);
+      setDeleting(false);
+    }
+  };
+
+  const handleToggleChunks = () => {
+    if (!showChunks && chunks.length === 0) {
+      fetchChunks();
+    }
+    setShowChunks(!showChunks);
+  };
+
+  if (loading) {
+    return (
+      <AuthGuard>
+        <NavBar />
+        <main className="max-w-4xl mx-auto px-4 py-8">
+          <p className="text-[var(--color-text-muted)]">Loading...</p>
+        </main>
+      </AuthGuard>
+    );
+  }
+
+  if (error || !item) {
+    return (
+      <AuthGuard>
+        <NavBar />
+        <main className="max-w-4xl mx-auto px-4 py-8">
+          <p className="text-red-400">{error || "Item not found"}</p>
+          <button
+            onClick={() => router.push("/knowledge")}
+            className="mt-4 text-sm text-[var(--color-primary)] hover:underline"
+          >
+            ← Back to Knowledge
+          </button>
+        </main>
+      </AuthGuard>
+    );
+  }
+
+  const videoId = item.TYPE === "YOUTUBE" && item.SOURCE_URL ? extractYouTubeVideoId(item.SOURCE_URL) : null;
+
+  return (
+    <AuthGuard>
+      <NavBar />
+      <main className="max-w-4xl mx-auto px-4 py-8">
+        {/* Back link */}
+        <button
+          onClick={() => router.push("/knowledge")}
+          className="text-sm text-[var(--color-text-muted)] hover:text-[var(--color-primary)] mb-4 inline-block"
+        >
+          ← Back to Knowledge
+        </button>
+
+        {/* Header */}
+        <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)] mb-6">
+          <div className="flex items-center gap-3 mb-3">
+            <span className="text-xs px-2 py-0.5 rounded bg-[var(--color-bg-hover)] text-[var(--color-text-muted)]">
+              {typeLabels[item.TYPE] || item.TYPE}
+            </span>
+            <span className={`text-xs px-2 py-0.5 rounded ${statusColors[item.STATUS] || ""}`}>
+              {item.STATUS}
+            </span>
+          </div>
+
+          {/* Title (editable) */}
+          {editingTitle ? (
+            <div className="flex gap-2 mb-3">
+              <input
+                type="text"
+                value={titleDraft}
+                onChange={(e) => setTitleDraft(e.target.value)}
+                onKeyDown={(e) => e.key === "Enter" && handleSaveTitle()}
+                className="flex-1 px-3 py-1 rounded-lg bg-[var(--color-bg-hover)] border border-[var(--color-border)] focus:border-[var(--color-primary)] focus:outline-none text-lg font-bold"
+                autoFocus
+              />
+              <button
+                onClick={handleSaveTitle}
+                className="px-3 py-1 text-sm bg-[var(--color-primary)] rounded-lg"
+              >
+                저장
+              </button>
+              <button
+                onClick={() => setEditingTitle(false)}
+                className="px-3 py-1 text-sm bg-[var(--color-bg-hover)] border border-[var(--color-border)] rounded-lg"
+              >
+                취소
+              </button>
+            </div>
+          ) : (
+            <h1
+              className="text-xl font-bold mb-3 cursor-pointer hover:text-[var(--color-primary)] transition-colors"
+              onClick={() => {
+                setTitleDraft(item.TITLE || "");
+                setEditingTitle(true);
+              }}
+              title="클릭하여 제목 수정"
+            >
+              {item.TITLE || "Untitled"}
+            </h1>
+          )}
+
+          {/* Source URL */}
+          {item.SOURCE_URL && (
+            <p className="text-sm text-[var(--color-text-muted)] mb-3 break-all">
+              <a href={item.SOURCE_URL} target="_blank" rel="noopener noreferrer" className="hover:text-[var(--color-primary)]">
+                {item.SOURCE_URL}
+              </a>
+            </p>
+          )}
+
+          {/* Meta */}
+          <div className="flex gap-4 text-xs text-[var(--color-text-muted)]">
+            <span>생성: {new Date(item.CREATED_AT).toLocaleString("ko-KR")}</span>
+            <span>수정: {new Date(item.UPDATED_AT).toLocaleString("ko-KR")}</span>
+          </div>
+        </div>
+
+        {/* YouTube Embed */}
+        {videoId && (
+          <div className="rounded-xl overflow-hidden border border-[var(--color-border)] mb-6">
+            <div className="relative w-full" style={{ paddingBottom: "56.25%" }}>
+              <iframe
+                className="absolute inset-0 w-full h-full"
+                src={`https://www.youtube.com/embed/${videoId}`}
+                allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"
+                allowFullScreen
+              />
+            </div>
+          </div>
+        )}
+
+        {/* Processing indicator */}
+        {/* Categories */}
+        {item.CATEGORIES && item.CATEGORIES.length > 0 && (
+          <div className="flex flex-wrap gap-2 mb-6">
+            {item.CATEGORIES.map((cat) => (
+              <span
+                key={cat.ID}
+                className="text-xs px-2.5 py-1 rounded-full bg-[var(--color-primary)]/15 text-[var(--color-primary)] border border-[var(--color-primary)]/30"
+              >
+                {cat.FULL_PATH}
+              </span>
+            ))}
+          </div>
+        )}
+
+        {["PENDING", "EXTRACTING", "STRUCTURING", "CHUNKING", "CATEGORIZING", "EMBEDDING"].includes(item.STATUS) && (
+          <div className="bg-blue-500/10 border border-blue-500/30 rounded-xl p-4 mb-6 flex items-center gap-3">
+            <div className="w-4 h-4 border-2 border-blue-400 border-t-transparent rounded-full animate-spin" />
+            <span className="text-sm text-blue-400">
+              {item.STATUS === "PENDING" && "파이프라인 대기 중..."}
+              {item.STATUS === "EXTRACTING" && "텍스트 추출 중..."}
+              {item.STATUS === "STRUCTURING" && "내용 정리 중..."}
+              {item.STATUS === "CHUNKING" && "청킹 처리 중..."}
+              {item.STATUS === "CATEGORIZING" && "카테고리 분류 중..."}
+              {item.STATUS === "EMBEDDING" && "벡터 임베딩 중..."}
+            </span>
+          </div>
+        )}
+
+        {/* Structured Content */}
+        {item.STRUCTURED_CONTENT && (
+          <div className="mb-6">
+            <button
+              onClick={() => setShowStructured(!showStructured)}
+              className="text-sm text-[var(--color-primary)] hover:underline mb-3"
+            >
+              {showStructured ? "▼ 정리된 내용 숨기기" : "▶ 정리된 내용 보기"}
+            </button>
+            {showStructured && (
+              <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)] max-w-none">
+                <div className="structured-content text-sm leading-relaxed">
+                  <ReactMarkdown
+                    components={{
+                      h1: ({children}) => <h1 className="text-xl font-bold mt-6 mb-3">{children}</h1>,
+                      h2: ({children}) => <h2 className="text-lg font-bold mt-5 mb-2">{children}</h2>,
+                      h3: ({children}) => <h3 className="text-base font-bold mt-4 mb-2">{children}</h3>,
+                      p: ({children}) => <p className="mb-3">{children}</p>,
+                      ul: ({children}) => <ul className="list-disc ml-5 mb-3 space-y-1">{children}</ul>,
+                      ol: ({children}) => <ol className="list-decimal ml-5 mb-3 space-y-1">{children}</ol>,
+                      li: ({children}) => <li className="leading-relaxed">{children}</li>,
+                      strong: ({children}) => <strong className="font-bold">{children}</strong>,
+                      blockquote: ({children}) => <blockquote className="border-l-2 border-[var(--color-primary)] pl-4 my-3 italic text-[var(--color-text-muted)]">{children}</blockquote>,
+                      code: ({children}) => <code className="bg-[var(--color-bg-hover)] px-1.5 py-0.5 rounded text-xs">{children}</code>,
+                    }}
+                  >
+                    {item.STRUCTURED_CONTENT}
+                  </ReactMarkdown>
+                </div>
+              </div>
+            )}
+          </div>
+        )}
+
+        {/* Chunks toggle */}
+        {item.STATUS === "READY" && (
+          <div className="mb-6">
+            <button
+              onClick={handleToggleChunks}
+              className="text-sm text-[var(--color-primary)] hover:underline"
+            >
+              {showChunks ? "▼ 청크 숨기기" : "▶ 청크 보기"}
+            </button>
+
+            {showChunks && (
+              <div className="mt-3 space-y-3">
+                {chunks.length === 0 ? (
+                  <p className="text-sm text-[var(--color-text-muted)]">Loading chunks...</p>
+                ) : (
+                  chunks.map((chunk) => (
+                    <div
+                      key={chunk.ID}
+                      className="bg-[var(--color-bg-card)] rounded-lg p-4 border border-[var(--color-border)]"
+                    >
+                      <div className="flex justify-between items-center mb-2">
+                        <span className="text-xs text-[var(--color-text-muted)]">
+                          Chunk #{chunk.CHUNK_INDEX}
+                        </span>
+                        <span className="text-xs text-[var(--color-text-muted)]">
+                          ~{chunk.TOKEN_COUNT} tokens
+                        </span>
+                      </div>
+                      <p className="text-sm whitespace-pre-wrap">{chunk.CONTENT}</p>
+                    </div>
+                  ))
+                )}
+              </div>
+            )}
+          </div>
+        )}
+
+        {/* Actions */}
+        <div className="pt-4 border-t border-[var(--color-border)] flex items-center gap-4">
+          {item.STATUS === "READY" && (
+            <>
+              <button
+                onClick={async () => {
+                  setStructuring(true);
+                  setShowStructured(true);
+                  try {
+                    // 비동기 요청: 서버가 STRUCTURING 상태로 변경 후 백그라운드 처리
+                    // 폴링이 자동으로 진행 상태를 갱신함
+                    await request({
+                      method: "POST",
+                      url: `/api/knowledge/${id}/structure`,
+                      data: {},
+                    });
+                    // 완료 후 최종 상태 갱신
+                    await fetchItem();
+                  } catch (err) {
+                    console.error("Failed to structure:", err);
+                    alert("내용 정리에 실패했습니다.");
+                    await fetchItem();
+                  } finally {
+                    setStructuring(false);
+                  }
+                }}
+                disabled={structuring}
+                className="text-sm text-[var(--color-primary)] hover:underline disabled:opacity-40"
+              >
+                {structuring ? "정리 중..." : item.STRUCTURED_CONTENT ? "다시 정리하기" : "내용 정리하기"}
+              </button>
+              <button
+                onClick={async () => {
+                  setGenerating(true);
+                  try {
+                    const result = await request<{ generated: number }>({
+                      method: "POST",
+                      url: `/api/study-cards/generate/${id}`,
+                    });
+                    alert(`${result.generated}개의 스터디 카드가 생성되었습니다.`);
+                  } catch (err) {
+                    console.error("Failed to generate cards:", err);
+                    alert("카드 생성에 실패했습니다.");
+                  } finally {
+                    setGenerating(false);
+                  }
+                }}
+                disabled={generating}
+                className="text-sm text-[var(--color-primary)] hover:underline disabled:opacity-40"
+              >
+                {generating ? "카드 생성 중..." : "스터디 카드 생성"}
+              </button>
+            </>
+          )}
+          <button
+            onClick={handleDelete}
+            disabled={deleting}
+            className="text-sm text-red-400 hover:text-red-300 disabled:opacity-40"
+          >
+            {deleting ? "삭제 중..." : "삭제"}
+          </button>
+        </div>
+      </main>
+    </AuthGuard>
+  );
+}

sundol-frontend/src/app/knowledge/add/page.tsx

@@ -0,0 +1,276 @@
+"use client";
+
+import { useState, useMemo, useEffect } from "react";
+import { useRouter } from "next/navigation";
+import AuthGuard from "@/components/auth-guard";
+import NavBar from "@/components/nav-bar";
+import { useApi } from "@/lib/use-api";
+
+type KnowledgeType = "TEXT" | "WEB" | "YOUTUBE";
+
+interface ModelInfo {
+  id: string;
+  name: string;
+  vendor: string;
+}
+
+function extractYouTubeVideoId(url: string): string | null {
+  try {
+    const u = new URL(url);
+    if (u.hostname === "youtu.be") return u.pathname.slice(1);
+    if (u.hostname.includes("youtube.com")) return u.searchParams.get("v");
+  } catch {
+    // invalid URL
+  }
+  return null;
+}
+
+export default function KnowledgeAddPage() {
+  const { request } = useApi();
+  const router = useRouter();
+
+  const [type, setType] = useState<KnowledgeType>("TEXT");
+  const [title, setTitle] = useState("");
+  const [url, setUrl] = useState("");
+  const [rawText, setRawText] = useState("");
+  const [modelId, setModelId] = useState("");
+  const [models, setModels] = useState<ModelInfo[]>([]);
+  const [submitting, setSubmitting] = useState(false);
+  const [fetchingTranscript, setFetchingTranscript] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+
+  useEffect(() => {
+    request<{ models: ModelInfo[]; defaultModel: string; configured: boolean }>({
+      method: "GET",
+      url: "/api/models",
+    }).then((data) => {
+      setModels(data.models);
+      setModelId(data.defaultModel);
+    }).catch((err) => {
+      console.error("Failed to load models:", err);
+    });
+  }, []);
+
+  const videoId = useMemo(() => (type === "YOUTUBE" ? extractYouTubeVideoId(url) : null), [type, url]);
+
+  const canFetchTranscript = type === "YOUTUBE" && videoId !== null && !fetchingTranscript;
+
+  const handleFetchTranscript = async () => {
+    if (!canFetchTranscript) return;
+    setError(null);
+    setFetchingTranscript(true);
+    try {
+      const data = await request<{ transcript?: string; error?: string }>({
+        method: "GET",
+        url: `/api/knowledge/youtube-transcript?url=${encodeURIComponent(url.trim())}`,
+      });
+      if (data.error) {
+        setError(data.error);
+      } else if (data.transcript) {
+        setRawText(data.transcript);
+      }
+    } catch (err: unknown) {
+      const msg = err instanceof Error ? err.message : "트랜스크립트를 가져올 수 없습니다";
+      setError(msg);
+    } finally {
+      setFetchingTranscript(false);
+    }
+  };
+
+  const canSubmit =
+    !submitting &&
+    ((type === "TEXT" && rawText.trim().length > 0) ||
+      (type === "WEB" && url.trim().length > 0) ||
+      (type === "YOUTUBE" && url.trim().length > 0 && rawText.trim().length > 0));
+
+  const handleSubmit = async () => {
+    setError(null);
+    setSubmitting(true);
+    try {
+      await request({
+        method: "POST",
+        url: "/api/knowledge/ingest",
+        data: {
+          type,
+          title: title.trim() || null,
+          url: type !== "TEXT" ? url.trim() : null,
+          rawText: type !== "WEB" ? rawText.trim() : null,
+          modelId: modelId || null,
+        },
+      });
+      router.push("/knowledge");
+    } catch (err: unknown) {
+      const msg = err instanceof Error ? err.message : "Failed to submit";
+      setError(msg);
+      setSubmitting(false);
+    }
+  };
+
+  const types: { value: KnowledgeType; label: string }[] = [
+    { value: "TEXT", label: "Text" },
+    { value: "WEB", label: "Web" },
+    { value: "YOUTUBE", label: "YouTube" },
+  ];
+
+  // 벤더별 그룹화
+  const groupedModels = useMemo(() => {
+    const groups: Record<string, ModelInfo[]> = {};
+    for (const m of models) {
+      if (!groups[m.vendor]) groups[m.vendor] = [];
+      groups[m.vendor].push(m);
+    }
+    return groups;
+  }, [models]);
+
+  return (
+    <AuthGuard>
+      <NavBar />
+      <main className="max-w-3xl mx-auto px-4 py-8">
+        <h1 className="text-2xl font-bold mb-6">Add Knowledge</h1>
+
+        {/* Type Tabs */}
+        <div className="flex gap-2 mb-6">
+          {types.map((t) => (
+            <button
+              key={t.value}
+              onClick={() => {
+                setType(t.value);
+                setUrl("");
+                setRawText("");
+                setError(null);
+              }}
+              className={`px-4 py-2 rounded-lg text-sm font-medium transition-colors ${
+                type === t.value
+                  ? "bg-[var(--color-primary)] text-white"
+                  : "bg-[var(--color-bg-card)] text-[var(--color-text-muted)] border border-[var(--color-border)] hover:border-[var(--color-primary)]"
+              }`}
+            >
+              {t.label}
+            </button>
+          ))}
+        </div>
+
+        <div className="space-y-4">
+          {/* Title */}
+          <div>
+            <label className="block text-sm text-[var(--color-text-muted)] mb-1">
+              제목 (비워두면 AI가 자동 생성)
+            </label>
+            <input
+              type="text"
+              value={title}
+              onChange={(e) => setTitle(e.target.value)}
+              placeholder="비워두면 내용 기반으로 자동 생성"
+              className="w-full px-3 py-2 rounded-lg bg-[var(--color-bg-card)] border border-[var(--color-border)] focus:border-[var(--color-primary)] focus:outline-none"
+            />
+          </div>
+
+          {/* URL (WEB / YOUTUBE) */}
+          {type !== "TEXT" && (
+            <div>
+              <label className="block text-sm text-[var(--color-text-muted)] mb-1">URL</label>
+              <input
+                type="url"
+                value={url}
+                onChange={(e) => setUrl(e.target.value)}
+                placeholder={type === "YOUTUBE" ? "https://www.youtube.com/watch?v=..." : "https://example.com/article"}
+                className="w-full px-3 py-2 rounded-lg bg-[var(--color-bg-card)] border border-[var(--color-border)] focus:border-[var(--color-primary)] focus:outline-none"
+              />
+            </div>
+          )}
+
+          {/* YouTube Embed */}
+          {type === "YOUTUBE" && videoId && (
+            <div className="rounded-lg overflow-hidden border border-[var(--color-border)]">
+              <div className="relative w-full" style={{ paddingBottom: "56.25%" }}>
+                <iframe
+                  className="absolute inset-0 w-full h-full"
+                  src={`https://www.youtube.com/embed/${videoId}`}
+                  allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"
+                  allowFullScreen
+                />
+              </div>
+            </div>
+          )}
+
+          {/* Fetch Transcript Button (YOUTUBE) */}
+          {type === "YOUTUBE" && videoId && (
+            <button
+              onClick={handleFetchTranscript}
+              disabled={!canFetchTranscript}
+              className="w-full px-4 py-2 bg-[var(--color-bg-card)] border border-[var(--color-border)] hover:border-[var(--color-primary)] disabled:opacity-40 disabled:cursor-not-allowed rounded-lg transition-colors text-sm font-medium"
+            >
+              {fetchingTranscript ? "트랜스크립트 가져오는 중..." : "트랜스크립트 자동 가져오기"}
+            </button>
+          )}
+
+          {/* Text Input (TEXT / YOUTUBE) */}
+          {type !== "WEB" && (
+            <div>
+              <label className="block text-sm text-[var(--color-text-muted)] mb-1">
+                {type === "YOUTUBE" ? "Transcript / 내용 붙여넣기" : "텍스트 입력"}
+              </label>
+              <textarea
+                value={rawText}
+                onChange={(e) => setRawText(e.target.value)}
+                placeholder={
+                  type === "YOUTUBE"
+                    ? "영상의 transcript나 내용을 여기에 붙여넣으세요..."
+                    : "텍스트를 직접 입력하세요..."
+                }
+                rows={12}
+                className="w-full px-3 py-2 rounded-lg bg-[var(--color-bg-card)] border border-[var(--color-border)] focus:border-[var(--color-primary)] focus:outline-none resize-y"
+              />
+            </div>
+          )}
+
+          {/* Model Selection */}
+          {models.length > 0 && (
+            <div>
+              <label className="block text-sm text-[var(--color-text-muted)] mb-1">
+                AI 모델
+              </label>
+              <select
+                value={modelId}
+                onChange={(e) => setModelId(e.target.value)}
+                className="w-full px-3 py-2 rounded-lg bg-[var(--color-bg-card)] border border-[var(--color-border)] focus:border-[var(--color-primary)] focus:outline-none"
+              >
+                {Object.entries(groupedModels).map(([vendor, vendorModels]) => (
+                  <optgroup key={vendor} label={vendor}>
+                    {vendorModels.map((m) => (
+                      <option key={m.id} value={m.id}>
+                        {m.name}
+                      </option>
+                    ))}
+                  </optgroup>
+                ))}
+              </select>
+            </div>
+          )}
+
+          {/* Error */}
+          {error && (
+            <p className="text-sm text-red-400">{error}</p>
+          )}
+
+          {/* Actions */}
+          <div className="flex gap-3 pt-2">
+            <button
+              onClick={handleSubmit}
+              disabled={!canSubmit}
+              className="px-6 py-2 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] disabled:opacity-40 disabled:cursor-not-allowed rounded-lg transition-colors"
+            >
+              {submitting ? "처리 중..." : "추가"}
+            </button>
+            <button
+              onClick={() => router.push("/knowledge")}
+              className="px-6 py-2 bg-[var(--color-bg-card)] border border-[var(--color-border)] hover:border-[var(--color-primary)] rounded-lg transition-colors"
+            >
+              취소
+            </button>
+          </div>
+        </div>
+      </main>
+    </AuthGuard>
+  );
+}

sundol-frontend/src/app/knowledge/page.tsx

@@ -1,23 +1,475 @@
 "use client";
 
+import { useEffect, useState } from "react";
+import Link from "next/link";
 import AuthGuard from "@/components/auth-guard";
 import NavBar from "@/components/nav-bar";
+import { useApi } from "@/lib/use-api";
+
+interface KnowledgeItem {
+  ID: string;
+  TYPE: string;
+  TITLE: string;
+  SOURCE_URL: string;
+  STATUS: string;
+  CREATED_AT: string;
+  CATEGORIES?: string;
+}
+
+interface Category {
+  ID: string;
+  NAME: string;
+  PARENT_ID: string | null;
+  DEPTH: number;
+  FULL_PATH: string;
+  ITEM_COUNT: number;
+}
+
+interface CategoryTree extends Category {
+  children: CategoryTree[];
+}
+
+const statusColors: Record<string, string> = {
+  PENDING: "bg-yellow-500/20 text-yellow-400",
+  EXTRACTING: "bg-blue-500/20 text-blue-400",
+  STRUCTURING: "bg-orange-500/20 text-orange-400",
+  CHUNKING: "bg-purple-500/20 text-purple-400",
+  CATEGORIZING: "bg-indigo-500/20 text-indigo-400",
+  EMBEDDING: "bg-cyan-500/20 text-cyan-400",
+  READY: "bg-green-500/20 text-green-400",
+  FAILED: "bg-red-500/20 text-red-400",
+};
+
+const typeLabels: Record<string, string> = {
+  YOUTUBE: "YouTube",
+  WEB: "Web",
+  TEXT: "Text",
+};
+
+function buildTree(categories: Category[]): CategoryTree[] {
+  const map = new Map<string, CategoryTree>();
+  const roots: CategoryTree[] = [];
+
+  for (const cat of categories) {
+    map.set(cat.ID, { ...cat, children: [] });
+  }
+
+  for (const cat of categories) {
+    const node = map.get(cat.ID)!;
+    if (cat.PARENT_ID && map.has(cat.PARENT_ID)) {
+      map.get(cat.PARENT_ID)!.children.push(node);
+    } else {
+      roots.push(node);
+    }
+  }
+
+  // 항목이 0개인 카테고리 제거
+  function prune(nodes: CategoryTree[]): CategoryTree[] {
+    return nodes
+      .map((n) => ({ ...n, children: prune(n.children) }))
+      .filter((n) => n.ITEM_COUNT > 0 || n.children.length > 0);
+  }
+
+  return prune(roots);
+}
+
+// ITEM_COUNT는 백엔드에서 하위 카테고리 포함 고유 항목 수를 이미 계산함
+
+function CategoryNode({
+  node,
+  selectedId,
+  onSelect,
+  expanded,
+  onToggle,
+}: {
+  node: CategoryTree;
+  selectedId: string | null;
+  onSelect: (id: string, path: string) => void;
+  expanded: Set<string>;
+  onToggle: (id: string) => void;
+}) {
+  const isExpanded = expanded.has(node.ID);
+  const isSelected = selectedId === node.ID;
+  const hasChildren = node.children.length > 0;
+  const totalCount = node.ITEM_COUNT;
+
+  return (
+    <div>
+      <div
+        className={`flex items-center gap-1 px-2 py-1.5 rounded-lg cursor-pointer text-sm transition-colors ${
+          isSelected
+            ? "bg-[var(--color-primary)]/20 text-[var(--color-primary)]"
+            : "hover:bg-[var(--color-bg-hover)] text-[var(--color-text-muted)]"
+        }`}
+        style={{ paddingLeft: `${(node.DEPTH - 1) * 16 + 8}px` }}
+        onClick={() => {
+          onSelect(node.ID, node.FULL_PATH);
+          if (hasChildren) onToggle(node.ID);
+        }}
+      >
+        <span className="w-4 text-center text-xs">
+          {hasChildren ? (isExpanded ? "▼" : "▶") : "·"}
+        </span>
+        <span className="flex-1 truncate">{node.NAME}</span>
+        {totalCount > 0 && (
+          <span className="text-xs px-1.5 py-0.5 rounded-full bg-[var(--color-bg-hover)]">
+            {totalCount}
+          </span>
+        )}
+      </div>
+      {isExpanded && hasChildren && (
+        <div>
+          {node.children.map((child) => (
+            <CategoryNode
+              key={child.ID}
+              node={child}
+              selectedId={selectedId}
+              onSelect={onSelect}
+              expanded={expanded}
+              onToggle={onToggle}
+            />
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}
 
 export default function KnowledgePage() {
+  const { request } = useApi();
+  const [items, setItems] = useState<KnowledgeItem[]>([]);
+  const [loading, setLoading] = useState(true);
+  const [viewMode, setViewMode] = useState<"list" | "category">("category");
+  const [currentPage, setCurrentPage] = useState(1);
+  const PAGE_SIZE = 10;
+
+  // 카테고리 뷰 상태
+  const [categoryTree, setCategoryTree] = useState<CategoryTree[]>([]);
+  const [uncategorized, setUncategorized] = useState<KnowledgeItem[]>([]);
+  const [selectedCategoryId, setSelectedCategoryId] = useState<string | null>("__all__");
+  const [selectedCategoryPath, setSelectedCategoryPath] = useState<string>("전체");
+  const [categoryItems, setCategoryItems] = useState<KnowledgeItem[]>([]);
+  const [expanded, setExpanded] = useState<Set<string>>(new Set());
+  const [catLoading, setCatLoading] = useState(false);
+
+  const fetchItems = async () => {
+    try {
+      const data = await request<KnowledgeItem[]>({ method: "GET", url: "/api/knowledge" });
+      setItems(data);
+    } catch (err) {
+      console.error("Failed to load knowledge items:", err);
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  const fetchCategories = async () => {
+    try {
+      const data = await request<{ categories: Category[]; uncategorized: KnowledgeItem[] }>({
+        method: "GET",
+        url: "/api/knowledge/categories",
+      });
+      const tree = buildTree(data.categories);
+      setCategoryTree(tree);
+      setUncategorized(data.uncategorized);
+      // 최상위 카테고리를 펼침
+      setExpanded(new Set(tree.map((n) => n.ID)));
+    } catch (err) {
+      console.error("Failed to load categories:", err);
+    }
+  };
+
+  const fetchCategoryItems = async (categoryId: string) => {
+    setCatLoading(true);
+    try {
+      const data = await request<KnowledgeItem[]>({
+        method: "GET",
+        url: `/api/knowledge/categories/${categoryId}/items`,
+      });
+      setCategoryItems(data);
+    } catch (err) {
+      console.error("Failed to load category items:", err);
+    } finally {
+      setCatLoading(false);
+    }
+  };
+
+  const handleSelectCategory = (id: string, path: string) => {
+    setSelectedCategoryId(id);
+    setSelectedCategoryPath(path);
+    setCurrentPage(1);
+    fetchCategoryItems(id);
+  };
+
+  const handleSelectUncategorized = () => {
+    setSelectedCategoryId("__uncategorized__");
+    setSelectedCategoryPath("미분류");
+    setCategoryItems(uncategorized as KnowledgeItem[]);
+    setCurrentPage(1);
+  };
+
+  const handleSelectAll = () => {
+    setSelectedCategoryId("__all__");
+    setSelectedCategoryPath("전체");
+    setCategoryItems(items);
+    setCurrentPage(1);
+  };
+
+  const handleToggle = (id: string) => {
+    setExpanded((prev) => {
+      const next = new Set(prev);
+      if (next.has(id)) next.delete(id);
+      else next.add(id);
+      return next;
+    });
+  };
+
+  useEffect(() => {
+    fetchItems();
+    fetchCategories();
+    const interval = setInterval(fetchItems, 5000);
+    return () => clearInterval(interval);
+  }, []);
+
+  // 카테고리 뷰에서 표시할 항목 결정
+  const allDisplayItems =
+    viewMode === "list"
+      ? items
+      : selectedCategoryId === "__all__"
+      ? items
+      : selectedCategoryId === "__uncategorized__"
+      ? uncategorized
+      : categoryItems;
+
+  const totalPages = Math.max(1, Math.ceil(allDisplayItems.length / PAGE_SIZE));
+  const displayItems = allDisplayItems.slice((currentPage - 1) * PAGE_SIZE, currentPage * PAGE_SIZE);
+
   return (
     <AuthGuard>
       <NavBar />
       <main className="max-w-7xl mx-auto px-4 py-8">
         <div className="flex justify-between items-center mb-6">
-          <h1 className="text-2xl font-bold">Knowledge</h1>
-          <button className="px-4 py-2 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] rounded-lg transition-colors">
+          <div className="flex items-center gap-4">
+            <h1 className="text-2xl font-bold">Knowledge</h1>
+            <div className="flex gap-1 bg-[var(--color-bg-card)] rounded-lg p-0.5 border border-[var(--color-border)]">
+              <button
+                onClick={() => setViewMode("list")}
+                className={`px-3 py-1 text-xs rounded-md transition-colors ${
+                  viewMode === "list"
+                    ? "bg-[var(--color-primary)] text-white"
+                    : "text-[var(--color-text-muted)] hover:text-white"
+                }`}
+              >
+                목록
+              </button>
+              <button
+                onClick={() => { setViewMode("category"); fetchCategories(); }}
+                className={`px-3 py-1 text-xs rounded-md transition-colors ${
+                  viewMode === "category"
+                    ? "bg-[var(--color-primary)] text-white"
+                    : "text-[var(--color-text-muted)] hover:text-white"
+                }`}
+              >
+                카테고리
+              </button>
+            </div>
+          </div>
+          <Link
+            href="/knowledge/add"
+            className="px-4 py-2 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] rounded-lg transition-colors"
+          >
             + Add Knowledge
-          </button>
-        </div>
-        <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)]">
-          <p className="text-[var(--color-text-muted)]">No knowledge items yet. Add your first item to get started.</p>
+          </Link>
         </div>
+
+        {loading ? (
+          <p className="text-[var(--color-text-muted)]">Loading...</p>
+        ) : viewMode === "list" ? (
+          /* 목록 뷰 */
+          items.length === 0 ? (
+            <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)]">
+              <p className="text-[var(--color-text-muted)]">No knowledge items yet. Add your first item to get started.</p>
+            </div>
+          ) : (
+            <>
+              <div className="space-y-3">
+                {displayItems.map((item) => (
+                  <KnowledgeItemCard key={item.ID} item={item} />
+                ))}
+              </div>
+              {totalPages > 1 && <Pagination currentPage={currentPage} totalPages={totalPages} onPageChange={setCurrentPage} />}
+            </>
+          )
+        ) : (
+          /* 카테고리 뷰 — 2단 레이아웃 */
+          <div className="flex gap-4" style={{ minHeight: "60vh" }}>
+            {/* 왼쪽: 카테고리 트리 */}
+            <div className="w-64 shrink-0 bg-[var(--color-bg-card)] rounded-xl border border-[var(--color-border)] p-3 overflow-y-auto" style={{ maxHeight: "75vh" }}>
+              {/* 전체 보기 */}
+              <div
+                className={`flex items-center gap-1 px-2 py-1.5 rounded-lg cursor-pointer text-sm transition-colors mb-1 ${
+                  selectedCategoryId === "__all__"
+                    ? "bg-[var(--color-primary)]/20 text-[var(--color-primary)]"
+                    : "hover:bg-[var(--color-bg-hover)] text-[var(--color-text-muted)]"
+                }`}
+                onClick={handleSelectAll}
+              >
+                <span className="w-4 text-center text-xs">*</span>
+                <span className="flex-1">전체</span>
+                <span className="text-xs px-1.5 py-0.5 rounded-full bg-[var(--color-bg-hover)]">{items.length}</span>
+              </div>
+
+              {/* 카테고리 트리 */}
+              {categoryTree.map((node) => (
+                <CategoryNode
+                  key={node.ID}
+                  node={node}
+                  selectedId={selectedCategoryId}
+                  onSelect={handleSelectCategory}
+                  expanded={expanded}
+                  onToggle={handleToggle}
+                />
+              ))}
+
+              {/* 미분류 */}
+              {uncategorized.length > 0 && (
+                <div
+                  className={`flex items-center gap-1 px-2 py-1.5 rounded-lg cursor-pointer text-sm transition-colors mt-2 ${
+                    selectedCategoryId === "__uncategorized__"
+                      ? "bg-[var(--color-primary)]/20 text-[var(--color-primary)]"
+                      : "hover:bg-[var(--color-bg-hover)] text-[var(--color-text-muted)]"
+                  }`}
+                  onClick={handleSelectUncategorized}
+                >
+                  <span className="w-4 text-center text-xs">?</span>
+                  <span className="flex-1">미분류</span>
+                  <span className="text-xs px-1.5 py-0.5 rounded-full bg-[var(--color-bg-hover)]">{uncategorized.length}</span>
+                </div>
+              )}
+            </div>
+
+            {/* 오른쪽: 선택된 카테고리의 항목 목록 */}
+            <div className="flex-1 min-w-0">
+              {/* 브레드크럼 */}
+              <div className="text-sm text-[var(--color-text-muted)] mb-3">
+                {selectedCategoryPath.split("/").map((part, i, arr) => (
+                  <span key={i}>
+                    {i > 0 && <span className="mx-1">{">"}</span>}
+                    <span className={i === arr.length - 1 ? "text-white" : ""}>{part}</span>
+                  </span>
+                ))}
+              </div>
+
+              {catLoading ? (
+                <p className="text-[var(--color-text-muted)]">Loading...</p>
+              ) : (displayItems as KnowledgeItem[]).length === 0 ? (
+                <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)]">
+                  <p className="text-[var(--color-text-muted)]">
+                    {selectedCategoryId === "__all__"
+                      ? "등록된 지식이 없습니다."
+                      : "이 카테고리에 항목이 없습니다."}
+                  </p>
+                </div>
+              ) : (
+                <>
+                  <div className="space-y-3">
+                    {(displayItems as KnowledgeItem[]).map((item) => (
+                      <KnowledgeItemCard key={item.ID} item={item} />
+                    ))}
+                  </div>
+                  {totalPages > 1 && <Pagination currentPage={currentPage} totalPages={totalPages} onPageChange={setCurrentPage} />}
+                </>
+              )}
+            </div>
+          </div>
+        )}
       </main>
     </AuthGuard>
   );
 }
+
+function KnowledgeItemCard({ item }: { item: KnowledgeItem }) {
+  return (
+    <Link
+      href={`/knowledge/${item.ID}`}
+      className="block bg-[var(--color-bg-card)] rounded-xl p-4 border border-[var(--color-border)] hover:border-[var(--color-primary)] transition-colors"
+    >
+      <div className="flex items-center justify-between">
+        <div className="flex-1 min-w-0">
+          <div className="flex items-center gap-3 mb-1">
+            <span className="text-xs px-2 py-0.5 rounded bg-[var(--color-bg-hover)] text-[var(--color-text-muted)]">
+              {typeLabels[item.TYPE] || item.TYPE}
+            </span>
+            <span className={`text-xs px-2 py-0.5 rounded ${statusColors[item.STATUS] || ""}`}>
+              {item.STATUS}
+            </span>
+          </div>
+          <h3 className="font-medium truncate">
+            {item.TITLE || item.SOURCE_URL || "Untitled"}
+          </h3>
+          {item.CATEGORIES && (
+            <div className="flex flex-wrap gap-1 mt-1">
+              {item.CATEGORIES.split(", ").map((cat, i) => (
+                <span key={i} className="text-xs px-1.5 py-0.5 rounded bg-[var(--color-primary)]/10 text-[var(--color-primary)]">
+                  {cat}
+                </span>
+              ))}
+            </div>
+          )}
+        </div>
+        <span className="text-sm text-[var(--color-text-muted)] ml-4 whitespace-nowrap">
+          {new Date(item.CREATED_AT).toLocaleDateString()}
+        </span>
+      </div>
+    </Link>
+  );
+}
+
+function Pagination({ currentPage, totalPages, onPageChange }: { currentPage: number; totalPages: number; onPageChange: (page: number) => void }) {
+  const pages: number[] = [];
+  const start = Math.max(1, currentPage - 2);
+  const end = Math.min(totalPages, currentPage + 2);
+  for (let i = start; i <= end; i++) pages.push(i);
+
+  return (
+    <div className="flex items-center justify-center gap-1 mt-6">
+      <button
+        onClick={() => onPageChange(currentPage - 1)}
+        disabled={currentPage <= 1}
+        className="px-3 py-1.5 text-sm rounded-lg bg-[var(--color-bg-card)] border border-[var(--color-border)] disabled:opacity-30 hover:bg-[var(--color-bg-hover)]"
+      >
+        이전
+      </button>
+      {start > 1 && (
+        <>
+          <button onClick={() => onPageChange(1)} className="px-3 py-1.5 text-sm rounded-lg hover:bg-[var(--color-bg-hover)]">1</button>
+          {start > 2 && <span className="px-1 text-[var(--color-text-muted)]">...</span>}
+        </>
+      )}
+      {pages.map((p) => (
+        <button
+          key={p}
+          onClick={() => onPageChange(p)}
+          className={`px-3 py-1.5 text-sm rounded-lg ${
+            p === currentPage ? "bg-[var(--color-primary)] text-white" : "hover:bg-[var(--color-bg-hover)]"
+          }`}
+        >
+          {p}
+        </button>
+      ))}
+      {end < totalPages && (
+        <>
+          {end < totalPages - 1 && <span className="px-1 text-[var(--color-text-muted)]">...</span>}
+          <button onClick={() => onPageChange(totalPages)} className="px-3 py-1.5 text-sm rounded-lg hover:bg-[var(--color-bg-hover)]">{totalPages}</button>
+        </>
+      )}
+      <button
+        onClick={() => onPageChange(currentPage + 1)}
+        disabled={currentPage >= totalPages}
+        className="px-3 py-1.5 text-sm rounded-lg bg-[var(--color-bg-card)] border border-[var(--color-border)] disabled:opacity-30 hover:bg-[var(--color-bg-hover)]"
+      >
+        다음
+      </button>
+    </div>
+  );
+}

sundol-frontend/src/app/login/callback/page.tsx

@@ -0,0 +1,64 @@
+"use client";
+
+import { useEffect, useRef } from "react";
+import { useRouter, useSearchParams } from "next/navigation";
+import { Suspense } from "react";
+import { api } from "@/lib/api";
+import { useAuth } from "@/lib/auth-context";
+
+function CallbackHandler() {
+  const router = useRouter();
+  const searchParams = useSearchParams();
+  const { login } = useAuth();
+  const processed = useRef(false);
+
+  useEffect(() => {
+    if (processed.current) return;
+    processed.current = true;
+
+    const code = searchParams.get("code");
+    const error = searchParams.get("error");
+
+    if (error) {
+      console.error("OAuth error:", error);
+      router.replace("/login");
+      return;
+    }
+
+    if (!code) {
+      router.replace("/login");
+      return;
+    }
+
+    api.post("/api/auth/google", { code })
+      .then((res) => {
+        login(res.data);
+        router.replace("/dashboard");
+      })
+      .catch((err) => {
+        console.error("Login failed:", err);
+        router.replace("/login");
+      });
+  }, [searchParams, login, router]);
+
+  return (
+    <div className="flex items-center justify-center min-h-screen">
+      <div className="text-center">
+        <div className="animate-spin rounded-full h-8 w-8 border-b-2 border-white mx-auto mb-4"></div>
+        <p className="text-[var(--color-text-muted)]">Signing in...</p>
+      </div>
+    </div>
+  );
+}
+
+export default function CallbackPage() {
+  return (
+    <Suspense fallback={
+      <div className="flex items-center justify-center min-h-screen">
+        <p className="text-[var(--color-text-muted)]">Loading...</p>
+      </div>
+    }>
+      <CallbackHandler />
+    </Suspense>
+  );
+}

sundol-frontend/src/app/login/page.tsx

@@ -1,25 +1,32 @@
 "use client";
 
-import { useState } from "react";
+import { useEffect } from "react";
 import { useRouter } from "next/navigation";
 import { useAuth } from "@/lib/auth-context";
 
+const GOOGLE_CLIENT_ID = process.env.NEXT_PUBLIC_GOOGLE_CLIENT_ID || "";
+const REDIRECT_URI = `${typeof window !== "undefined" ? window.location.origin : ""}/login/callback`;
+
 export default function LoginPage() {
   const router = useRouter();
-  const { login } = useAuth();
-  const [isLoading, setIsLoading] = useState(false);
+  const { isAuthenticated, isLoading } = useAuth();
 
-  const handleGoogleLogin = async () => {
-    setIsLoading(true);
-    try {
-      // TODO: Implement Google OAuth flow
-      // For now, placeholder
-      alert("Google OAuth not configured yet");
-    } catch (error) {
-      console.error("Login failed:", error);
-    } finally {
-      setIsLoading(false);
+  useEffect(() => {
+    if (!isLoading && isAuthenticated) {
+      router.replace("/dashboard");
     }
+  }, [isAuthenticated, isLoading, router]);
+
+  const handleGoogleLogin = () => {
+    const params = new URLSearchParams({
+      client_id: GOOGLE_CLIENT_ID,
+      redirect_uri: REDIRECT_URI,
+      response_type: "code",
+      scope: "openid email profile",
+      access_type: "offline",
+      prompt: "consent",
+    });
+    window.location.href = `https://accounts.google.com/o/oauth2/v2/auth?${params.toString()}`;
   };
 
   return (
@@ -33,8 +40,7 @@ export default function LoginPage() {
         </div>
         <button
           onClick={handleGoogleLogin}
-          disabled={isLoading}
-          className="w-full py-3 px-4 bg-white text-gray-800 rounded-lg font-medium hover:bg-gray-100 transition-colors disabled:opacity-50 flex items-center justify-center gap-3"
+          className="w-full py-3 px-4 bg-white text-gray-800 rounded-lg font-medium hover:bg-gray-100 transition-colors flex items-center justify-center gap-3"
         >
           <svg className="w-5 h-5" viewBox="0 0 24 24">
             <path fill="#4285F4" d="M22.56 12.25c0-.78-.07-1.53-.2-2.25H12v4.26h5.92a5.06 5.06 0 0 1-2.2 3.32v2.77h3.57c2.08-1.92 3.28-4.74 3.28-8.1z"/>
@@ -42,7 +48,7 @@ export default function LoginPage() {
             <path fill="#FBBC05" d="M5.84 14.09c-.22-.66-.35-1.36-.35-2.09s.13-1.43.35-2.09V7.07H2.18C1.43 8.55 1 10.22 1 12s.43 3.45 1.18 4.93l2.85-2.22.81-.62z"/>
             <path fill="#EA4335" d="M12 5.38c1.62 0 3.06.56 4.21 1.64l3.15-3.15C17.45 2.09 14.97 1 12 1 7.7 1 3.99 3.47 2.18 7.07l3.66 2.84c.87-2.6 3.3-4.53 6.16-4.53z"/>
           </svg>
-          {isLoading ? "Signing in..." : "Sign in with Google"}
+          Sign in with Google
         </button>
       </div>
     </div>

sundol-frontend/src/app/settings/page.tsx

@@ -0,0 +1,123 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import AuthGuard from "@/components/auth-guard";
+import NavBar from "@/components/nav-bar";
+import { useApi } from "@/lib/use-api";
+
+interface UserProfile {
+  ID: string;
+  EMAIL: string;
+  DISPLAY_NAME: string;
+  AVATAR_URL: string;
+  ENGLISH_LEVEL: string;
+}
+
+const ENGLISH_LEVELS = [
+  { value: "A1", label: "A1 - 입문 (TOEIC 120~225)" },
+  { value: "A2", label: "A2 - 초급 (TOEIC 225~550, 기초 회화)" },
+  { value: "B1", label: "B1 - 중급 (TOEIC 550~785, 일상 의사소통)" },
+  { value: "B2", label: "B2 - 중상급 (TOEIC 785~945, 업무 영어)" },
+  { value: "C1", label: "C1 - 고급 (TOEIC 945~990, 유창함)" },
+  { value: "C2", label: "C2 - 원어민 수준" },
+];
+
+export default function SettingsPage() {
+  const { request } = useApi();
+  const [profile, setProfile] = useState<UserProfile | null>(null);
+  const [loading, setLoading] = useState(true);
+  const [saving, setSaving] = useState(false);
+  const [savedMsg, setSavedMsg] = useState("");
+
+  useEffect(() => {
+    (async () => {
+      try {
+        const data = await request<UserProfile>({ method: "GET", url: "/api/users/me" });
+        setProfile(data);
+      } catch (err) {
+        console.error("Failed to load profile:", err);
+      } finally {
+        setLoading(false);
+      }
+    })();
+  }, []);
+
+  const handleEnglishLevelChange = async (newLevel: string) => {
+    if (!profile) return;
+    setSaving(true);
+    setSavedMsg("");
+    try {
+      const updated = await request<UserProfile>({
+        method: "PATCH",
+        url: "/api/users/me",
+        data: { englishLevel: newLevel },
+      });
+      setProfile(updated);
+      setSavedMsg("저장되었습니다");
+      setTimeout(() => setSavedMsg(""), 2000);
+    } catch (err) {
+      console.error("Failed to update level:", err);
+      alert("저장에 실패했습니다");
+    } finally {
+      setSaving(false);
+    }
+  };
+
+  if (loading) {
+    return (
+      <AuthGuard>
+        <NavBar />
+        <main className="max-w-2xl mx-auto px-4 py-8">
+          <p className="text-[var(--color-text-muted)]">Loading...</p>
+        </main>
+      </AuthGuard>
+    );
+  }
+
+  return (
+    <AuthGuard>
+      <NavBar />
+      <main className="max-w-2xl mx-auto px-4 py-8">
+        <h1 className="text-2xl font-bold mb-6">설정</h1>
+
+        {/* 프로필 정보 */}
+        <section className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)] mb-6">
+          <h2 className="text-lg font-semibold mb-4">프로필</h2>
+          <div className="space-y-3 text-sm">
+            <div className="flex">
+              <span className="w-24 text-[var(--color-text-muted)]">이름</span>
+              <span>{profile?.DISPLAY_NAME || "-"}</span>
+            </div>
+            <div className="flex">
+              <span className="w-24 text-[var(--color-text-muted)]">이메일</span>
+              <span>{profile?.EMAIL || "-"}</span>
+            </div>
+          </div>
+        </section>
+
+        {/* 영어 학습 수준 */}
+        <section className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)]">
+          <h2 className="text-lg font-semibold mb-2">영어 학습 수준</h2>
+          <p className="text-sm text-[var(--color-text-muted)] mb-4">
+            영어 컨텐츠를 정리할 때 추출할 학습 표현의 난이도를 결정합니다.
+          </p>
+          <select
+            value={profile?.ENGLISH_LEVEL || "B2"}
+            onChange={(e) => handleEnglishLevelChange(e.target.value)}
+            disabled={saving}
+            className="w-full px-3 py-2 rounded-lg bg-[var(--color-bg-hover)] border border-[var(--color-border)] focus:border-[var(--color-primary)] focus:outline-none disabled:opacity-50"
+          >
+            {ENGLISH_LEVELS.map((level) => (
+              <option key={level.value} value={level.value}>
+                {level.label}
+              </option>
+            ))}
+          </select>
+          {savedMsg && (
+            <p className="text-sm text-green-400 mt-2">{savedMsg}</p>
+          )}
+        </section>
+      </main>
+    </AuthGuard>
+  );
+}

sundol-frontend/src/app/study/page.tsx

@@ -1,17 +1,177 @@
 "use client";
 
+import { useEffect, useState } from "react";
 import AuthGuard from "@/components/auth-guard";
 import NavBar from "@/components/nav-bar";
+import { useApi } from "@/lib/use-api";
+
+interface StudyCard {
+  ID: string;
+  KNOWLEDGE_ITEM_ID: string | null;
+  KNOWLEDGE_TITLE: string | null;
+  FRONT: string;
+  BACK: string;
+  EASE_FACTOR: number;
+  INTERVAL_DAYS: number;
+  REPETITIONS: number;
+}
+
+const ratingButtons = [
+  { value: 0, label: "모름", color: "bg-red-600 hover:bg-red-500" },
+  { value: 1, label: "거의 모름", color: "bg-red-500 hover:bg-red-400" },
+  { value: 2, label: "어려움", color: "bg-orange-500 hover:bg-orange-400" },
+  { value: 3, label: "보통", color: "bg-yellow-500 hover:bg-yellow-400" },
+  { value: 4, label: "쉬움", color: "bg-green-500 hover:bg-green-400" },
+  { value: 5, label: "완벽", color: "bg-green-600 hover:bg-green-500" },
+];
 
 export default function StudyPage() {
+  const { request } = useApi();
+  const [cards, setCards] = useState<StudyCard[]>([]);
+  const [loading, setLoading] = useState(true);
+  const [currentIndex, setCurrentIndex] = useState(0);
+  const [showBack, setShowBack] = useState(false);
+  const [reviewing, setReviewing] = useState(false);
+
+  const fetchDueCards = async () => {
+    try {
+      const data = await request<StudyCard[]>({ method: "GET", url: "/api/study-cards/due" });
+      setCards(data);
+      setCurrentIndex(0);
+      setShowBack(false);
+    } catch (err) {
+      console.error("Failed to load cards:", err);
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  useEffect(() => {
+    fetchDueCards();
+  }, []);
+
+  const handleReview = async (rating: number) => {
+    if (reviewing || !cards[currentIndex]) return;
+    setReviewing(true);
+    try {
+      await request({
+        method: "POST",
+        url: `/api/study-cards/${cards[currentIndex].ID}/review`,
+        data: { rating },
+      });
+
+      if (currentIndex + 1 < cards.length) {
+        setCurrentIndex(currentIndex + 1);
+        setShowBack(false);
+      } else {
+        // 모든 카드 완료
+        setCards([]);
+      }
+    } catch (err) {
+      console.error("Failed to review card:", err);
+    } finally {
+      setReviewing(false);
+    }
+  };
+
+  const currentCard = cards[currentIndex];
+
   return (
     <AuthGuard>
       <NavBar />
-      <main className="max-w-7xl mx-auto px-4 py-8">
-        <h1 className="text-2xl font-bold mb-6">Study Cards</h1>
-        <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)] flex items-center justify-center min-h-[40vh]">
-          <p className="text-[var(--color-text-muted)]">No cards due for review. Generate cards from your knowledge items.</p>
+      <main className="max-w-2xl mx-auto px-4 py-8">
+        <div className="flex justify-between items-center mb-6">
+          <h1 className="text-2xl font-bold">Study Cards</h1>
+          {cards.length > 0 && (
+            <span className="text-sm text-[var(--color-text-muted)]">
+              {currentIndex + 1} / {cards.length}
+            </span>
+          )}
         </div>
+
+        {loading ? (
+          <p className="text-[var(--color-text-muted)]">Loading...</p>
+        ) : cards.length === 0 ? (
+          <div className="bg-[var(--color-bg-card)] rounded-xl p-8 border border-[var(--color-border)] text-center">
+            <p className="text-lg mb-2">
+              {currentIndex > 0 ? "복습 완료!" : "복습할 카드가 없습니다."}
+            </p>
+            <p className="text-[var(--color-text-muted)] text-sm">
+              Knowledge 항목에서 카드를 생성해보세요.
+            </p>
+          </div>
+        ) : currentCard ? (
+          <div>
+            {/* Source */}
+            {currentCard.KNOWLEDGE_TITLE && (
+              <p className="text-xs text-[var(--color-text-muted)] mb-2">
+                출처: {currentCard.KNOWLEDGE_TITLE}
+              </p>
+            )}
+
+            {/* Card */}
+            <div
+              className="bg-[var(--color-bg-card)] rounded-xl border border-[var(--color-border)] min-h-[300px] flex flex-col cursor-pointer"
+              onClick={() => !showBack && setShowBack(true)}
+            >
+              {/* Front */}
+              <div className="flex-1 flex items-center justify-center p-8">
+                <div className="text-center">
+                  <p className="text-xs text-[var(--color-text-muted)] mb-3">Question</p>
+                  <p className="text-lg whitespace-pre-wrap">{currentCard.FRONT}</p>
+                </div>
+              </div>
+
+              {/* Back (revealed) */}
+              {showBack && (
+                <div className="border-t border-[var(--color-border)] flex-1 flex items-center justify-center p-8 bg-[var(--color-bg-hover)]">
+                  <div className="text-center">
+                    <p className="text-xs text-[var(--color-text-muted)] mb-3">Answer</p>
+                    <p className="text-lg whitespace-pre-wrap">{currentCard.BACK}</p>
+                  </div>
+                </div>
+              )}
+            </div>
+
+            {/* Actions */}
+            {!showBack ? (
+              <div className="mt-4 text-center">
+                <button
+                  onClick={() => setShowBack(true)}
+                  className="px-8 py-3 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] rounded-xl transition-colors"
+                >
+                  정답 보기
+                </button>
+              </div>
+            ) : (
+              <div className="mt-4">
+                <p className="text-sm text-[var(--color-text-muted)] text-center mb-3">
+                  얼마나 잘 알고 있나요?
+                </p>
+                <div className="grid grid-cols-3 gap-2">
+                  {ratingButtons.map((btn) => (
+                    <button
+                      key={btn.value}
+                      onClick={() => handleReview(btn.value)}
+                      disabled={reviewing}
+                      className={`${btn.color} text-white py-2 rounded-lg text-sm font-medium transition-colors disabled:opacity-40`}
+                    >
+                      {btn.label}
+                    </button>
+                  ))}
+                </div>
+              </div>
+            )}
+
+            {/* Progress bar */}
+            <div className="mt-4 h-1 bg-[var(--color-bg-hover)] rounded-full overflow-hidden">
+              <div
+                className="h-full bg-[var(--color-primary)] transition-all"
+                style={{ width: `${((currentIndex) / cards.length) * 100}%` }}
+              />
+            </div>
+          </div>
+        ) : null}
       </main>
     </AuthGuard>
   );

sundol-frontend/src/app/todos/page.tsx

@@ -1,22 +1,367 @@
 "use client";
 
+import { useEffect, useState } from "react";
 import AuthGuard from "@/components/auth-guard";
 import NavBar from "@/components/nav-bar";
+import { useApi } from "@/lib/use-api";
+
+interface Todo {
+  ID: string;
+  PARENT_ID: string | null;
+  TITLE: string;
+  DESCRIPTION: string | null;
+  STATUS: string;
+  PRIORITY: string;
+  DUE_DATE: string | null;
+  SUBTASK_COUNT: number;
+  SUBTASK_DONE_COUNT: number;
+}
+
+interface Subtask {
+  ID: string;
+  TITLE: string;
+  STATUS: string;
+}
+
+const priorityColors: Record<string, string> = {
+  HIGH: "text-red-400",
+  MEDIUM: "text-yellow-400",
+  LOW: "text-green-400",
+};
+
+const priorityLabels: Record<string, string> = {
+  HIGH: "높음",
+  MEDIUM: "보통",
+  LOW: "낮음",
+};
 
 export default function TodosPage() {
+  const { request } = useApi();
+  const [todos, setTodos] = useState<Todo[]>([]);
+  const [loading, setLoading] = useState(true);
+  const [filter, setFilter] = useState<"ALL" | "PENDING" | "DONE">("ALL");
+
+  // Add form
+  const [showAdd, setShowAdd] = useState(false);
+  const [newTitle, setNewTitle] = useState("");
+  const [newPriority, setNewPriority] = useState("MEDIUM");
+  const [newDueDate, setNewDueDate] = useState("");
+
+  // Subtasks
+  const [expandedId, setExpandedId] = useState<string | null>(null);
+  const [subtasks, setSubtasks] = useState<Subtask[]>([]);
+  const [newSubtask, setNewSubtask] = useState("");
+
+  const fetchTodos = async () => {
+    try {
+      const status = filter === "ALL" ? undefined : filter;
+      const params = new URLSearchParams();
+      if (status) params.set("status", status);
+      const data = await request<Todo[]>({ method: "GET", url: `/api/todos?${params}` });
+      setTodos(data);
+    } catch (err) {
+      console.error("Failed to load todos:", err);
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  useEffect(() => {
+    fetchTodos();
+  }, [filter]);
+
+  const handleAdd = async () => {
+    if (!newTitle.trim()) return;
+    try {
+      await request({
+        method: "POST",
+        url: "/api/todos",
+        data: {
+          title: newTitle.trim(),
+          priority: newPriority,
+          dueDate: newDueDate || null,
+        },
+      });
+      setNewTitle("");
+      setNewDueDate("");
+      setShowAdd(false);
+      fetchTodos();
+    } catch (err) {
+      console.error("Failed to create todo:", err);
+    }
+  };
+
+  const handleToggleStatus = async (todo: Todo) => {
+    const newStatus = todo.STATUS === "DONE" ? "PENDING" : "DONE";
+    try {
+      await request({
+        method: "PATCH",
+        url: `/api/todos/${todo.ID}`,
+        data: { status: newStatus },
+      });
+      fetchTodos();
+      if (expandedId === todo.ID) fetchSubtasks(todo.ID);
+    } catch (err) {
+      console.error("Failed to update todo:", err);
+    }
+  };
+
+  const handleDelete = async (id: string) => {
+    try {
+      await request({ method: "DELETE", url: `/api/todos/${id}` });
+      if (expandedId === id) setExpandedId(null);
+      fetchTodos();
+    } catch (err) {
+      console.error("Failed to delete todo:", err);
+    }
+  };
+
+  const fetchSubtasks = async (todoId: string) => {
+    try {
+      const data = await request<Subtask[]>({ method: "GET", url: `/api/todos/${todoId}/subtasks` });
+      setSubtasks(data);
+    } catch (err) {
+      console.error("Failed to load subtasks:", err);
+    }
+  };
+
+  const handleExpand = (todoId: string) => {
+    if (expandedId === todoId) {
+      setExpandedId(null);
+      return;
+    }
+    setExpandedId(todoId);
+    fetchSubtasks(todoId);
+  };
+
+  const handleAddSubtask = async () => {
+    if (!newSubtask.trim() || !expandedId) return;
+    try {
+      await request({
+        method: "POST",
+        url: "/api/todos",
+        data: { title: newSubtask.trim(), priority: "MEDIUM", parentId: expandedId },
+      });
+      setNewSubtask("");
+      fetchSubtasks(expandedId);
+      fetchTodos();
+    } catch (err) {
+      console.error("Failed to create subtask:", err);
+    }
+  };
+
+  const handleToggleSubtask = async (subtask: Subtask) => {
+    const newStatus = subtask.STATUS === "DONE" ? "PENDING" : "DONE";
+    try {
+      await request({
+        method: "PATCH",
+        url: `/api/todos/${subtask.ID}`,
+        data: { status: newStatus },
+      });
+      if (expandedId) fetchSubtasks(expandedId);
+      fetchTodos();
+    } catch (err) {
+      console.error("Failed to update subtask:", err);
+    }
+  };
+
+  const isOverdue = (dueDate: string | null) => {
+    if (!dueDate) return false;
+    return new Date(dueDate) < new Date(new Date().toDateString());
+  };
+
   return (
     <AuthGuard>
       <NavBar />
-      <main className="max-w-7xl mx-auto px-4 py-8">
+      <main className="max-w-3xl mx-auto px-4 py-8">
         <div className="flex justify-between items-center mb-6">
           <h1 className="text-2xl font-bold">Todos</h1>
-          <button className="px-4 py-2 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] rounded-lg transition-colors">
+          <button
+            onClick={() => setShowAdd(!showAdd)}
+            className="px-4 py-2 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] rounded-lg transition-colors text-sm"
+          >
             + Add Todo
           </button>
         </div>
-        <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)]">
-          <p className="text-[var(--color-text-muted)]">No todos yet. Create your first task.</p>
+
+        {/* Add form */}
+        {showAdd && (
+          <div className="bg-[var(--color-bg-card)] rounded-xl p-4 border border-[var(--color-border)] mb-4 space-y-3">
+            <input
+              type="text"
+              value={newTitle}
+              onChange={(e) => setNewTitle(e.target.value)}
+              onKeyDown={(e) => e.key === "Enter" && handleAdd()}
+              placeholder="할 일 입력..."
+              autoFocus
+              className="w-full px-3 py-2 rounded-lg bg-[var(--color-bg-hover)] border border-[var(--color-border)] focus:border-[var(--color-primary)] focus:outline-none"
+            />
+            <div className="flex gap-3 items-center">
+              <select
+                value={newPriority}
+                onChange={(e) => setNewPriority(e.target.value)}
+                className="px-3 py-1.5 rounded-lg bg-[var(--color-bg-hover)] border border-[var(--color-border)] text-sm focus:outline-none"
+              >
+                <option value="HIGH">높음</option>
+                <option value="MEDIUM">보통</option>
+                <option value="LOW">낮음</option>
+              </select>
+              <input
+                type="date"
+                value={newDueDate}
+                onChange={(e) => setNewDueDate(e.target.value)}
+                className="px-3 py-1.5 rounded-lg bg-[var(--color-bg-hover)] border border-[var(--color-border)] text-sm focus:outline-none"
+              />
+              <button
+                onClick={handleAdd}
+                disabled={!newTitle.trim()}
+                className="px-4 py-1.5 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] disabled:opacity-40 rounded-lg text-sm transition-colors"
+              >
+                추가
+              </button>
+            </div>
+          </div>
+        )}
+
+        {/* Filters */}
+        <div className="flex gap-2 mb-4">
+          {(["ALL", "PENDING", "DONE"] as const).map((f) => (
+            <button
+              key={f}
+              onClick={() => setFilter(f)}
+              className={`px-3 py-1 rounded-lg text-sm transition-colors ${
+                filter === f
+                  ? "bg-[var(--color-primary)] text-white"
+                  : "bg-[var(--color-bg-card)] text-[var(--color-text-muted)] border border-[var(--color-border)]"
+              }`}
+            >
+              {f === "ALL" ? "전체" : f === "PENDING" ? "진행중" : "완료"}
+            </button>
+          ))}
         </div>
+
+        {/* Todo list */}
+        {loading ? (
+          <p className="text-[var(--color-text-muted)]">Loading...</p>
+        ) : todos.length === 0 ? (
+          <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)]">
+            <p className="text-[var(--color-text-muted)]">
+              {filter === "ALL" ? "아직 할 일이 없습니다." : filter === "PENDING" ? "진행중인 할 일이 없습니다." : "완료된 할 일이 없습니다."}
+            </p>
+          </div>
+        ) : (
+          <div className="space-y-2">
+            {todos.map((todo) => (
+              <div key={todo.ID}>
+                <div className="bg-[var(--color-bg-card)] rounded-xl p-4 border border-[var(--color-border)] hover:border-[var(--color-primary)] transition-colors">
+                  <div className="flex items-center gap-3">
+                    {/* Checkbox */}
+                    <button
+                      onClick={() => handleToggleStatus(todo)}
+                      className={`w-5 h-5 rounded border-2 flex-shrink-0 flex items-center justify-center transition-colors ${
+                        todo.STATUS === "DONE"
+                          ? "bg-[var(--color-primary)] border-[var(--color-primary)]"
+                          : "border-[var(--color-border)] hover:border-[var(--color-primary)]"
+                      }`}
+                    >
+                      {todo.STATUS === "DONE" && (
+                        <svg className="w-3 h-3 text-white" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={3}>
+                          <path strokeLinecap="round" strokeLinejoin="round" d="M5 13l4 4L19 7" />
+                        </svg>
+                      )}
+                    </button>
+
+                    {/* Content */}
+                    <div className="flex-1 min-w-0">
+                      <div className="flex items-center gap-2">
+                        <span className={`${todo.STATUS === "DONE" ? "line-through text-[var(--color-text-muted)]" : ""}`}>
+                          {todo.TITLE}
+                        </span>
+                        <span className={`text-xs ${priorityColors[todo.PRIORITY]}`}>
+                          {priorityLabels[todo.PRIORITY]}
+                        </span>
+                      </div>
+                      <div className="flex items-center gap-3 mt-1">
+                        {todo.DUE_DATE && (
+                          <span className={`text-xs ${isOverdue(todo.DUE_DATE) && todo.STATUS !== "DONE" ? "text-red-400" : "text-[var(--color-text-muted)]"}`}>
+                            {todo.DUE_DATE}
+                          </span>
+                        )}
+                        {todo.SUBTASK_COUNT > 0 && (
+                          <span className="text-xs text-[var(--color-text-muted)]">
+                            {todo.SUBTASK_DONE_COUNT}/{todo.SUBTASK_COUNT} subtasks
+                          </span>
+                        )}
+                      </div>
+                    </div>
+
+                    {/* Actions */}
+                    <button
+                      onClick={() => handleExpand(todo.ID)}
+                      className="text-xs text-[var(--color-text-muted)] hover:text-[var(--color-primary)] px-2"
+                    >
+                      {expandedId === todo.ID ? "▼" : "▶"}
+                    </button>
+                    <button
+                      onClick={() => handleDelete(todo.ID)}
+                      className="text-xs text-red-400 hover:text-red-300 px-1"
+                    >
+                      ✕
+                    </button>
+                  </div>
+                </div>
+
+                {/* Subtasks */}
+                {expandedId === todo.ID && (
+                  <div className="ml-8 mt-1 space-y-1">
+                    {subtasks.map((st) => (
+                      <div
+                        key={st.ID}
+                        className="flex items-center gap-3 bg-[var(--color-bg-card)] rounded-lg px-3 py-2 border border-[var(--color-border)]"
+                      >
+                        <button
+                          onClick={() => handleToggleSubtask(st)}
+                          className={`w-4 h-4 rounded border-2 flex-shrink-0 flex items-center justify-center transition-colors ${
+                            st.STATUS === "DONE"
+                              ? "bg-[var(--color-primary)] border-[var(--color-primary)]"
+                              : "border-[var(--color-border)] hover:border-[var(--color-primary)]"
+                          }`}
+                        >
+                          {st.STATUS === "DONE" && (
+                            <svg className="w-2.5 h-2.5 text-white" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={3}>
+                              <path strokeLinecap="round" strokeLinejoin="round" d="M5 13l4 4L19 7" />
+                            </svg>
+                          )}
+                        </button>
+                        <span className={`text-sm flex-1 ${st.STATUS === "DONE" ? "line-through text-[var(--color-text-muted)]" : ""}`}>
+                          {st.TITLE}
+                        </span>
+                      </div>
+                    ))}
+                    {/* Add subtask */}
+                    <div className="flex gap-2">
+                      <input
+                        type="text"
+                        value={newSubtask}
+                        onChange={(e) => setNewSubtask(e.target.value)}
+                        onKeyDown={(e) => e.key === "Enter" && handleAddSubtask()}
+                        placeholder="서브태스크 추가..."
+                        className="flex-1 px-3 py-1.5 rounded-lg bg-[var(--color-bg-card)] border border-[var(--color-border)] focus:border-[var(--color-primary)] focus:outline-none text-sm"
+                      />
+                      <button
+                        onClick={handleAddSubtask}
+                        disabled={!newSubtask.trim()}
+                        className="px-3 py-1.5 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] disabled:opacity-40 rounded-lg text-xs transition-colors"
+                      >
+                        추가
+                      </button>
+                    </div>
+                  </div>
+                )}
+              </div>
+            ))}
+          </div>
+        )}
       </main>
     </AuthGuard>
   );

sundol-frontend/src/components/nav-bar.tsx

@@ -11,6 +11,7 @@ const navItems = [
   { href: "/study", label: "Study" },
   { href: "/todos", label: "Todos" },
   { href: "/habits", label: "Habits" },
+  { href: "/settings", label: "Settings" },
 ];
 
 export default function NavBar() {

sundol-frontend/src/lib/api.ts

@@ -1,10 +1,110 @@
-import axios from "axios";
+import axios, { AxiosError, InternalAxiosRequestConfig } from "axios";
 
 export const api = axios.create({
   baseURL: process.env.NEXT_PUBLIC_API_URL || "http://localhost:8080",
   withCredentials: true,
 });
 
+// --- 공통 토큰 refresh 로직 (mutex 패턴) ---
+
+let isRefreshing = false;
+let pendingQueue: {
+  resolve: (token: string) => void;
+  reject: (error: unknown) => void;
+}[] = [];
+
+// auth-context에서 주입하는 콜백
+let onTokenRefreshed: ((token: string) => void) | null = null;
+let onRefreshFailed: (() => void) | null = null;
+
+export function setAuthCallbacks(
+  onRefreshed: (token: string) => void,
+  onFailed: () => void
+) {
+  onTokenRefreshed = onRefreshed;
+  onRefreshFailed = onFailed;
+}
+
+function processQueue(token: string | null, error: unknown) {
+  pendingQueue.forEach(({ resolve, reject }) => {
+    if (token) {
+      resolve(token);
+    } else {
+      reject(error);
+    }
+  });
+  pendingQueue = [];
+}
+
+api.interceptors.response.use(
+  (response) => response,
+  async (error: AxiosError) => {
+    const originalRequest = error.config as InternalAxiosRequestConfig & { _retry?: boolean };
+
+    // 401이 아니거나, refresh 요청 자체가 실패한 경우, 이미 retry한 경우 → 그냥 throw
+    if (
+      error.response?.status !== 401 ||
+      originalRequest.url?.includes("/api/auth/") ||
+      originalRequest._retry
+    ) {
+      return Promise.reject(error);
+    }
+
+    // 이미 refresh 진행 중이면 큐에 대기
+    if (isRefreshing) {
+      return new Promise((resolve, reject) => {
+        pendingQueue.push({
+          resolve: (token: string) => {
+            originalRequest._retry = true;
+            originalRequest.headers["Authorization"] = `Bearer ${token}`;
+            resolve(api.request(originalRequest));
+          },
+          reject,
+        });
+      });
+    }
+
+    // refresh 시작
+    isRefreshing = true;
+    originalRequest._retry = true;
+
+    const attemptRefresh = async (retryCount: number): Promise<string> => {
+      try {
+        const res = await api.post<LoginResponse>("/api/auth/refresh");
+        return res.data.accessToken;
+      } catch (err) {
+        const isNetworkError = !((err as AxiosError).response);
+        if (isNetworkError && retryCount < 2) {
+          // 네트워크 에러(서버 재시작 등)면 3초 후 재시도
+          await new Promise((r) => setTimeout(r, 3000));
+          return attemptRefresh(retryCount + 1);
+        }
+        throw err;
+      }
+    };
+
+    try {
+      const newToken = await attemptRefresh(0);
+
+      api.defaults.headers.common["Authorization"] = `Bearer ${newToken}`;
+      onTokenRefreshed?.(newToken);
+
+      // 대기 중인 요청들 처리
+      processQueue(newToken, null);
+
+      // 원래 요청 retry
+      originalRequest.headers["Authorization"] = `Bearer ${newToken}`;
+      return api.request(originalRequest);
+    } catch (refreshError) {
+      processQueue(null, refreshError);
+      onRefreshFailed?.();
+      return Promise.reject(refreshError);
+    } finally {
+      isRefreshing = false;
+    }
+  }
+);
+
 // Types
 export interface LoginResponse {
   accessToken: string;

sundol-frontend/src/lib/auth-context.tsx

@@ -1,7 +1,7 @@
 "use client";
 
-import React, { createContext, useContext, useState, useCallback, useEffect } from "react";
-import { api, LoginResponse } from "./api";
+import React, { createContext, useContext, useState, useCallback, useEffect, useRef } from "react";
+import { api, LoginResponse, setAuthCallbacks } from "./api";
 
 interface AuthContextType {
   isAuthenticated: boolean;
@@ -22,23 +22,53 @@ const AuthContext = createContext<AuthContextType>({
 });
 
 export function AuthProvider({ children }: { children: React.ReactNode }) {
-  const [accessToken, setAccessToken] = useState<string | null>(null);
+  const [accessToken, setAccessTokenState] = useState<string | null>(null);
   const [isLoading, setIsLoading] = useState(true);
+  const logoutRef = useRef<() => void>(() => {});
+
+  // localStorage와 동기화하는 setter
+  const setAccessToken = useCallback((token: string | null) => {
+    setAccessTokenState(token);
+    if (token) {
+      localStorage.setItem("accessToken", token);
+    } else {
+      localStorage.removeItem("accessToken");
+    }
+  }, []);
+
+  // interceptor 콜백 등록
+  useEffect(() => {
+    setAuthCallbacks(
+      (token: string) => setAccessToken(token),
+      () => logoutRef.current()
+    );
+  }, [setAccessToken]);
 
   useEffect(() => {
-    // Try to restore session from refresh token cookie
-    const tryRefresh = async () => {
+    const restoreSession = async () => {
+      // 1차: localStorage에서 복원
+      const stored = localStorage.getItem("accessToken");
+      if (stored) {
+        setAccessTokenState(stored);
+        api.defaults.headers.common["Authorization"] = `Bearer ${stored}`;
+        setIsLoading(false);
+        return;
+      }
+
+      // 2차: refresh token cookie로 복원
       try {
         const res = await api.post<LoginResponse>("/api/auth/refresh");
-        setAccessToken(res.data.accessToken);
+        const token = res.data.accessToken;
+        setAccessToken(token);
+        api.defaults.headers.common["Authorization"] = `Bearer ${token}`;
       } catch {
         // No valid session
       } finally {
         setIsLoading(false);
       }
     };
-    tryRefresh();
-  }, []);
+    restoreSession();
+  }, [setAccessToken]);
 
   useEffect(() => {
     if (accessToken) {
@@ -50,7 +80,7 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
 
   const login = useCallback((response: LoginResponse) => {
     setAccessToken(response.accessToken);
-  }, []);
+  }, [setAccessToken]);
 
   const logout = useCallback(async () => {
     try {
@@ -60,7 +90,12 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
     }
     setAccessToken(null);
     window.location.href = "/login";
-  }, []);
+  }, [setAccessToken]);
+
+  // ref로 최신 logout 유지 (interceptor에서 사용)
+  useEffect(() => {
+    logoutRef.current = logout;
+  }, [logout]);
 
   return (
     <AuthContext.Provider

sundol-frontend/src/lib/use-api.ts

@@ -1,35 +1,16 @@
 "use client";
 
 import { useCallback } from "react";
-import { api, LoginResponse } from "./api";
-import { useAuth } from "./auth-context";
+import { api } from "./api";
 import { AxiosRequestConfig } from "axios";
 
 export function useApi() {
-  const { setAccessToken, logout } = useAuth();
-
   const request = useCallback(
     async <T>(config: AxiosRequestConfig): Promise<T> => {
-      try {
-        const response = await api.request<T>(config);
-        return response.data;
-      } catch (error: any) {
-        if (error.response?.status === 401) {
-          try {
-            const refreshRes = await api.post<LoginResponse>("/api/auth/refresh");
-            setAccessToken(refreshRes.data.accessToken);
-            api.defaults.headers.common["Authorization"] = `Bearer ${refreshRes.data.accessToken}`;
-            const retryResponse = await api.request<T>(config);
-            return retryResponse.data;
-          } catch {
-            logout();
-            throw error;
-          }
-        }
-        throw error;
-      }
+      const response = await api.request<T>(config);
+      return response.data;
     },
-    [setAccessToken, logout]
+    []
   );
 
   return { request };