Add error logging and improve HTTP handling for YouTube transcript fetching

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)

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 +6,17 @@ 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)
+export DISPLAY=:99
+if ! pgrep -x Xvfb > /dev/null; then
+    Xvfb :99 -screen 0 1280x720x24 -nolisten tcp &
+    sleep 1
+fi
+
+# 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/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) {
+    public Mono<ResponseEntity<LoginResponse>> googleLogin(
-        return authService.googleLogin(request.idToken())
+            @RequestBody Map<String, String> body,
-                .map(ResponseEntity::ok);
+            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) {
+    public Mono<ResponseEntity<LoginResponse>> refresh(ServerHttpRequest request, ServerHttpResponse response) {
-        return authService.refresh(request.refreshToken())
+        HttpCookie cookie = request.getCookies().getFirst("refreshToken");
-                .map(ResponseEntity::ok);
+        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

@@ -2,6 +2,9 @@ package com.sundol.controller;
 
 import com.sundol.dto.IngestRequest;
 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 +18,15 @@ 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;
+
+    public KnowledgeController(KnowledgeService knowledgeService,
+                               YouTubeTranscriptService youTubeTranscriptService) {
         this.knowledgeService = knowledgeService;
+        this.youTubeTranscriptService = youTubeTranscriptService;
     }
 
     @GetMapping
@@ -40,6 +48,19 @@ 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,

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/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) {}

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

@@ -0,0 +1,122 @@
+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
+        );
+    }
+
+    /**
+     * 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 +3,9 @@ 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 KnowledgeRepository {
 
@@ -12,5 +15,80 @@ 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(id) AS id, type, title, source_url, status, created_at, updated_at FROM knowledge_items WHERE user_id = HEXTORAW(?)"
+        );
+        java.util.List<Object> params = new java.util.ArrayList<>();
+        params.add(userId);
+
+        if (type != null && !type.isEmpty()) {
+            sql.append(" AND type = ?");
+            params.add(type);
+        }
+        if (status != null && !status.isEmpty()) {
+            sql.append(" AND status = ?");
+            params.add(status);
+        }
+        if (search != null && !search.isEmpty()) {
+            sql.append(" AND UPPER(title) LIKE UPPER(?)");
+            params.add("%" + search + "%");
+        }
+        sql.append(" ORDER BY 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, status, created_at, updated_at " +
+            "FROM knowledge_items WHERE RAWTOHEX(id) = ? AND user_id = HEXTORAW(?)",
+            id, userId
+        );
+        return results.isEmpty() ? null : 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, status, created_at, updated_at " +
+            "FROM knowledge_items WHERE RAWTOHEX(id) = ?",
+            id
+        );
+        return results.isEmpty() ? null : results.get(0);
+    }
+
+    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 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 +14,43 @@ 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 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 FROM users WHERE RAWTOHEX(id) = ?",
+            userId
+        );
+        return results.isEmpty() ? null : results.get(0);
+    }
 }

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

@@ -1,34 +1,147 @@
 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) {
+    public Mono<LoginResponse> googleLogin(String code) {
-        // TODO: Verify Google ID token, upsert user, issue JWT pair
+        // Exchange auth code for tokens via Google token endpoint
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+        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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromRunnable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> chatRepository.listSessions(userId))
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+                .subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> createSession(String userId) {
-        // TODO: Create new chat session
+        return Mono.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromRunnable(() -> chatRepository.deleteSession(userId, sessionId))
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+                .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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromRunnable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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 +1,278 @@
+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 ChunkingService chunkingService;
+    private final WebCrawlerService webCrawlerService;
+    private final OciGenAiService genAiService;
+    private final ObjectMapper objectMapper;
+
+    public IngestPipelineService(
+            KnowledgeRepository knowledgeRepository,
+            KnowledgeChunkRepository chunkRepository,
+            ChunkEmbeddingRepository embeddingRepository,
+            CategoryRepository categoryRepository,
+            ChunkingService chunkingService,
+            WebCrawlerService webCrawlerService,
+            OciGenAiService genAiService,
+            ObjectMapper objectMapper) {
+        this.knowledgeRepository = knowledgeRepository;
+        this.chunkRepository = chunkRepository;
+        this.embeddingRepository = embeddingRepository;
+        this.categoryRepository = categoryRepository;
+        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;
+
+    /**
+     * 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);
+        }
+    }
+
+    @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: 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 3: Categorize
+            knowledgeRepository.updateStatus(knowledgeItemId, "CATEGORIZING");
+            categorize(knowledgeItemId, (String) item.get("USER_ID"), extractedText, modelId);
+
+            // Step 4: 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 +1,14 @@
 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 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 +17,77 @@ import java.util.Map;
 public class KnowledgeService {
 
     private final KnowledgeRepository knowledgeRepository;
+    private final KnowledgeChunkRepository chunkRepository;
+    private final CategoryRepository categoryRepository;
+    private final IngestPipelineService pipelineService;
 
-    public KnowledgeService(KnowledgeRepository knowledgeRepository) {
+    public KnowledgeService(
+            KnowledgeRepository knowledgeRepository,
+            KnowledgeChunkRepository chunkRepository,
+            CategoryRepository categoryRepository,
+            IngestPipelineService pipelineService) {
         this.knowledgeRepository = knowledgeRepository;
+        this.chunkRepository = chunkRepository;
+        this.categoryRepository = categoryRepository;
+        this.pipelineService = pipelineService;
     }
 
     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.fromCallable(() -> knowledgeRepository.list(userId, type, status, search))
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+                .subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> ingest(String userId, IngestRequest request) {
-        // TODO: Create knowledge item, trigger async ingest pipeline
+        return Mono.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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<Void> delete(String userId, String id) {
-        // TODO: Delete knowledge item and all chunks
+        return Mono.fromRunnable(() -> knowledgeRepository.delete(userId, id))
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+                .subscribeOn(Schedulers.boundedElastic()).then();
     }
 
     public Mono<List<Map<String, Object>>> getChunks(String userId, String id) {
-        // TODO: List chunks for knowledge item
+        return Mono.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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/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) {
+    private final ChunkEmbeddingRepository embeddingRepository;
-        this.chunkRepository = chunkRepository;
+    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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> studyCardRepository.getDueCards(userId))
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+                .subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<List<Map<String, Object>>> getByKnowledgeItem(String userId, String knowledgeItemId) {
-        // TODO: Get cards for a specific knowledge item
+        return Mono.fromCallable(() -> studyCardRepository.getByKnowledgeItem(userId, knowledgeItemId))
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+                .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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> tagRepository.list(userId))
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+                .subscribeOn(Schedulers.boundedElastic());
     }
 
     public Mono<Map<String, Object>> create(String userId, TagRequest request) {
-        // TODO: Create tag
+        return Mono.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromRunnable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromRunnable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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.fromCallable(() -> {
-        return Mono.error(new UnsupportedOperationException("Not implemented yet"));
+            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 +1,223 @@
+package com.sundol.service;
+
+import com.microsoft.playwright.Browser;
+import com.microsoft.playwright.BrowserType;
+import com.microsoft.playwright.Page;
+import com.microsoft.playwright.Playwright;
+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;
+
+    @Value("${jina.reader.api-key:}")
+    private String jinaApiKey;
+
+    public WebCrawlerService() {
+        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 headless browser (최후의 수단)
+        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);
+        try (Playwright playwright = Playwright.create()) {
+            BrowserType.LaunchOptions launchOptions = new BrowserType.LaunchOptions()
+                    .setHeadless(true)
+                    .setArgs(java.util.List.of(
+                            "--no-sandbox",
+                            "--disable-setuid-sandbox",
+                            "--disable-dev-shm-usage",
+                            "--disable-gpu"
+                    ));
+
+            try (Browser browser = playwright.chromium().launch(launchOptions)) {
+                Browser.NewContextOptions contextOptions = new Browser.NewContextOptions()
+                        .setUserAgent("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36");
+
+                var context = browser.newContext(contextOptions);
+                Page page = context.newPage();
+
+                page.navigate(url, new Page.NavigateOptions()
+                        .setTimeout(30_000)
+                        .setWaitUntil(com.microsoft.playwright.options.WaitUntilState.NETWORKIDLE));
+
+                // 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;
+            }
+        } catch (IOException e) {
+            throw e;
+        } catch (Exception e) {
+            throw new IOException("Playwright failed for " + url + ": " + e.getMessage(), e);
+        }
+    }
+
+    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);
+                // Playwright로 제목 추출
+                try (Playwright playwright = Playwright.create()) {
+                    try (Browser browser = playwright.chromium().launch(
+                            new BrowserType.LaunchOptions().setHeadless(true)
+                                    .setArgs(java.util.List.of("--no-sandbox", "--disable-setuid-sandbox")))) {
+                        Page page = browser.newPage();
+                        page.navigate(url, new Page.NavigateOptions().setTimeout(30_000));
+                        return page.title();
+                    }
+                } catch (Exception e3) {
+                    throw new IOException("All title extraction methods failed for: " + url, e3);
+                }
+            }
+        }
+    }
+}

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

@@ -0,0 +1,295 @@
+package com.sundol.service;
+
+import com.microsoft.playwright.*;
+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.net.URLDecoder;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+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();
+
+    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
+        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;
+
+        String html;
+        try (Playwright playwright = Playwright.create()) {
+            BrowserType.LaunchOptions launchOptions = new BrowserType.LaunchOptions()
+                    .setHeadless(false)
+                    .setArgs(List.of(
+                            "--no-sandbox",
+                            "--disable-setuid-sandbox",
+                            "--disable-dev-shm-usage"
+                    ));
+
+            try (Browser browser = playwright.chromium().launch(launchOptions)) {
+                BrowserContext context = browser.newContext(new Browser.NewContextOptions()
+                        .setUserAgent("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36")
+                        .setLocale("ko-KR"));
+
+                // YouTube 쿠키 로딩 (봇 차단 우회)
+                loadCookies(context);
+
+                Page page = context.newPage();
+
+                page.navigate(watchUrl, new Page.NavigateOptions()
+                        .setTimeout(30_000)
+                        .setWaitUntil(WaitUntilState.NETWORKIDLE));
+
+                html = page.content();
+                log.info("Playwright fetched YouTube page: {} chars", html.length());
+
+                context.close();
+            }
+        } catch (Exception e) {
+            throw new IOException("YouTube 페이지를 가져올 수 없습니다 (Playwright): " + e.getMessage(), e);
+        }
+
+        // captionTracks JSON 추출
+        Matcher captionMatcher = CAPTION_TRACK_PATTERN.matcher(html);
+        if (!captionMatcher.find()) {
+            throw new IOException("이 영상에는 자막(caption)이 없습니다.");
+        }
+
+        String captionTracksJson = captionMatcher.group(1);
+        String captionUrl = selectCaptionUrl(captionTracksJson);
+        if (captionUrl == null) {
+            throw new IOException("자막 트랙 URL을 추출할 수 없습니다.");
+        }
+
+        captionUrl = captionUrl.replace("\\u0026", "&");
+        log.info("Fetching caption XML from: {}", captionUrl);
+
+        // 자막 XML 가져오기
+        log.info("Attempting to fetch caption XML...");
+        String xml;
+        try {
+            var conn = (java.net.HttpURLConnection) new java.net.URI(captionUrl).toURL().openConnection();
+            conn.setRequestProperty("User-Agent", "Mozilla/5.0");
+            conn.setConnectTimeout(15_000);
+            conn.setReadTimeout(15_000);
+            int responseCode = conn.getResponseCode();
+            log.info("Caption XML response code: {}", responseCode);
+            if (responseCode != 200) {
+                String errorBody = new String(conn.getErrorStream().readAllBytes(), StandardCharsets.UTF_8);
+                log.error("Caption XML error response: {}", errorBody);
+                throw new IOException("자막 XML 응답 코드: " + responseCode);
+            }
+            xml = new String(conn.getInputStream().readAllBytes(), StandardCharsets.UTF_8);
+            log.info("Caption XML fetched: {} chars", xml.length());
+        } catch (Exception e) {
+            log.error("Failed to fetch caption XML: {}", e.getMessage(), e);
+            throw new IOException("자막 XML을 가져올 수 없습니다: " + e.getMessage(), e);
+        }
+
+        String transcript = parseTranscriptXml(xml);
+        log.info("Parsed transcript: {} chars (blank={})", transcript.length(), transcript.isBlank());
+        if (transcript.isBlank()) {
+            log.error("Transcript XML content (first 500 chars): {}", xml.substring(0, Math.min(500, xml.length())));
+            throw new IOException("자막 텍스트를 파싱할 수 없습니다.");
+        }
+
+        log.info("Successfully fetched transcript via Playwright: {} chars", transcript.length());
+        return transcript;
+    }
+
+    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 void loadCookies(BrowserContext context) {
+        Path cookieFile = Path.of(System.getProperty("user.dir"), "cookies.txt");
+        if (!Files.exists(cookieFile)) {
+            log.warn("cookies.txt not found at: {}", cookieFile);
+            return;
+        }
+
+        try {
+            List<String> lines = Files.readAllLines(cookieFile);
+            List<com.microsoft.playwright.options.Cookie> cookies = new ArrayList<>();
+            for (String line : lines) {
+                if (line.startsWith("#") || line.isBlank()) continue;
+                String[] parts = line.split("\t");
+                if (parts.length < 7) continue;
+                String domain = parts[0];
+                if (!domain.contains("youtube") && !domain.contains("google")) continue;
+                cookies.add(new com.microsoft.playwright.options.Cookie(parts[5], parts[6])
+                        .setDomain(domain)
+                        .setPath(parts[2])
+                        .setSecure("TRUE".equalsIgnoreCase(parts[3]))
+                        .setHttpOnly(false));
+            }
+            if (!cookies.isEmpty()) {
+                context.addCookies(cookies);
+                log.info("Loaded {} YouTube cookies", cookies.size());
+            }
+        } catch (Exception e) {
+            log.warn("Failed to load cookies: {}", e.getMessage());
+        }
+    }
+
+    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-frontend/build.sh

@@ -0,0 +1,41 @@
+#!/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 = ${!var:0:20}..."
+done
+
+echo "=== [1/3] Next.js 빌드 ==="
+npx next build
+
+echo "=== [2/3] 심볼릭 링크 생성 ==="
+STATIC_SRC="$SCRIPT_DIR/.next/static"
+STATIC_DST="$SCRIPT_DIR/.next/standalone/.next/static"
+
+if [ -L "$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"
+
+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/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">
+      <main className="max-w-7xl mx-auto px-4 py-4 h-[calc(100vh-64px)] flex gap-4">
-        <h1 className="text-2xl font-bold mb-6">AI Chat</h1>
+        {/* Sidebar: Sessions */}
-        <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)] min-h-[60vh] flex items-center justify-center">
+        <div className="w-64 flex-shrink-0 flex flex-col">
-          <p className="text-[var(--color-text-muted)]">Start a new conversation to ask questions about your knowledge base.</p>
+          <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">
+        {!data ? (
-          <DashCard title="Knowledge Items" value="-" description="Total ingested items" />
+          <p className="text-[var(--color-text-muted)]">Loading...</p>
-          <DashCard title="Due Study Cards" value="-" description="Cards due for review" />
+        ) : (
-          <DashCard title="Active Todos" value="-" description="Pending tasks" />
+          <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-6">
-          <DashCard title="Habit Streaks" value="-" description="Current active streaks" />
+            {cards.map((card) => (
-          <DashCard title="Chat Sessions" value="-" description="Active conversations" />
+              <Link
-          <DashCard title="Tags" value="-" description="Knowledge categories" />
+                key={card.title}
-        </div>
+                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>
+          <div>
-          <button className="px-4 py-2 bg-[var(--color-primary)] hover:bg-[var(--color-primary-hover)] rounded-lg transition-colors">
+            <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>
+        {/* Add form */}
-        </div>
+        {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 +1,367 @@
+"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";
+
+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;
+  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",
+  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 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", "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", "CHUNKING", "CATEGORIZING"].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 === "CHUNKING" && "청킹 처리 중..."}
+              {item.STATUS === "CATEGORIZING" && "카테고리 분류 중..."}
+              {item.STATUS === "EMBEDDING" && "벡터 임베딩 중..."}
+            </span>
+          </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 () => {
+                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

@@ -1,22 +1,112 @@
 "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;
+}
+
+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",
+  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",
+};
 
 export default function KnowledgePage() {
+  const { request } = useApi();
+  const [items, setItems] = useState<KnowledgeItem[]>([]);
+  const [loading, setLoading] = useState(true);
+
+  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);
+    }
+  };
+
+  useEffect(() => {
+    fetchItems();
+    // Poll for status updates every 5 seconds
+    const interval = setInterval(fetchItems, 5000);
+    return () => clearInterval(interval);
+  }, []);
+
   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">
+          <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>
+          </Link>
-        </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>
         </div>
+
+        {loading ? (
+          <p className="text-[var(--color-text-muted)]">Loading...</p>
+        ) : 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">
+            {items.map((item) => (
+              <Link
+                key={item.ID}
+                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.SOURCE_URL && (
+                      <p className="text-sm text-[var(--color-text-muted)] truncate mt-1">{item.SOURCE_URL}</p>
+                    )}
+                  </div>
+                  <span className="text-sm text-[var(--color-text-muted)] ml-4 whitespace-nowrap">
+                    {new Date(item.CREATED_AT).toLocaleDateString()}
+                  </span>
+                </div>
+              </Link>
+            ))}
+          </div>
+        )}
       </main>
     </AuthGuard>
   );

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 { isAuthenticated, isLoading } = useAuth();
-  const [isLoading, setIsLoading] = useState(false);
 
-  const handleGoogleLogin = async () => {
+  useEffect(() => {
-    setIsLoading(true);
+    if (!isLoading && isAuthenticated) {
-    try {
+      router.replace("/dashboard");
-      // TODO: Implement Google OAuth flow
-      // For now, placeholder
-      alert("Google OAuth not configured yet");
-    } catch (error) {
-      console.error("Login failed:", error);
-    } finally {
-      setIsLoading(false);
     }
+  }, [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 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 disabled:opacity-50 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/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">
+      <main className="max-w-2xl mx-auto px-4 py-8">
-        <h1 className="text-2xl font-bold mb-6">Study Cards</h1>
+        <div className="flex justify-between items-center mb-6">
-        <div className="bg-[var(--color-bg-card)] rounded-xl p-6 border border-[var(--color-border)] flex items-center justify-center min-h-[40vh]">
+          <h1 className="text-2xl font-bold">Study Cards</h1>
-          <p className="text-[var(--color-text-muted)]">No cards due for review. Generate cards from your knowledge items.</p>
+          {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/lib/api.ts

@@ -1,10 +1,96 @@
-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;
+
+    try {
+      const res = await api.post<LoginResponse>("/api/auth/refresh");
+      const newToken = res.data.accessToken;
+
+      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 React, { createContext, useContext, useState, useCallback, useEffect, useRef } from "react";
-import { api, LoginResponse } from "./api";
+import { api, LoginResponse, setAuthCallbacks } from "./api";
 
 interface AuthContextType {
   isAuthenticated: boolean;
@@ -24,13 +24,24 @@ const AuthContext = createContext<AuthContextType>({
 export function AuthProvider({ children }: { children: React.ReactNode }) {
   const [accessToken, setAccessToken] = useState<string | null>(null);
   const [isLoading, setIsLoading] = useState(true);
+  const logoutRef = useRef<() => void>(() => {});
+
+  // interceptor 콜백 등록
+  useEffect(() => {
+    setAuthCallbacks(
+      (token: string) => setAccessToken(token),
+      () => logoutRef.current()
+    );
+  }, []);
 
   useEffect(() => {
     // Try to restore session from refresh token cookie
     const tryRefresh = async () => {
       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 {
@@ -62,6 +73,11 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
     window.location.href = "/login";
   }, []);
 
+  // ref로 최신 logout 유지 (interceptor에서 사용)
+  useEffect(() => {
+    logoutRef.current = logout;
+  }, [logout]);
+
   return (
     <AuthContext.Provider
       value={{

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

@@ -1,35 +1,16 @@
 "use client";
 
 import { useCallback } from "react";
-import { api, LoginResponse } from "./api";
+import { api } from "./api";
-import { useAuth } from "./auth-context";
 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);
-        const response = await api.request<T>(config);
+      return response.data;
-        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;
-      }
     },
-    [setAccessToken, logout]
+    []
   );
 
   return { request };