refactor(files): reorganize backend package layout

backend/src/main/java/com/yoyuzh/admin/AdminService.java

@@ -9,13 +9,13 @@ import com.yoyuzh.auth.RefreshTokenService;
 import com.yoyuzh.common.BusinessException;
 import com.yoyuzh.common.ErrorCode;
 import com.yoyuzh.common.PageResponse;
-import com.yoyuzh.files.FileBlobRepository;
-import com.yoyuzh.files.FileService;
-import com.yoyuzh.files.StoredFile;
-import com.yoyuzh.files.StoredFileRepository;
-import com.yoyuzh.files.StoragePolicy;
-import com.yoyuzh.files.StoragePolicyRepository;
-import com.yoyuzh.files.StoragePolicyService;
+import com.yoyuzh.files.core.FileBlobRepository;
+import com.yoyuzh.files.core.FileService;
+import com.yoyuzh.files.core.StoredFile;
+import com.yoyuzh.files.core.StoredFileRepository;
+import com.yoyuzh.files.policy.StoragePolicy;
+import com.yoyuzh.files.policy.StoragePolicyRepository;
+import com.yoyuzh.files.policy.StoragePolicyService;
 import com.yoyuzh.transfer.OfflineTransferSessionRepository;
 import lombok.RequiredArgsConstructor;
 import org.springframework.data.domain.Page;

backend/src/main/java/com/yoyuzh/admin/AdminStoragePolicyResponse.java

@@ -1,8 +1,8 @@
 package com.yoyuzh.admin;
 
-import com.yoyuzh.files.StoragePolicyCapabilities;
-import com.yoyuzh.files.StoragePolicyCredentialMode;
-import com.yoyuzh.files.StoragePolicyType;
+import com.yoyuzh.files.policy.StoragePolicyCapabilities;
+import com.yoyuzh.files.policy.StoragePolicyCredentialMode;
+import com.yoyuzh.files.policy.StoragePolicyType;
 
 import java.time.LocalDateTime;
 

backend/src/main/java/com/yoyuzh/api/v2/files/FileEventsV2Controller.java

@@ -2,7 +2,7 @@ package com.yoyuzh.api.v2.files;
 
 import com.yoyuzh.auth.CustomUserDetailsService;
 import com.yoyuzh.auth.User;
-import com.yoyuzh.files.FileEventService;
+import com.yoyuzh.files.events.FileEventService;
 import lombok.RequiredArgsConstructor;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
 import org.springframework.security.core.userdetails.UserDetails;

backend/src/main/java/com/yoyuzh/api/v2/files/FileSearchV2Controller.java

@@ -6,9 +6,9 @@ import com.yoyuzh.api.v2.ApiV2Response;
 import com.yoyuzh.auth.CustomUserDetailsService;
 import com.yoyuzh.auth.User;
 import com.yoyuzh.common.PageResponse;
-import com.yoyuzh.files.FileMetadataResponse;
-import com.yoyuzh.files.FileSearchQuery;
-import com.yoyuzh.files.FileSearchService;
+import com.yoyuzh.files.core.FileMetadataResponse;
+import com.yoyuzh.files.search.FileSearchQuery;
+import com.yoyuzh.files.search.FileSearchService;
 import lombok.RequiredArgsConstructor;
 import org.springframework.format.annotation.DateTimeFormat;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;

backend/src/main/java/com/yoyuzh/api/v2/files/PreparedUploadV2Response.java

@@ -0,0 +1,12 @@
+package com.yoyuzh.api.v2.files;
+
+import java.util.Map;
+
+public record PreparedUploadV2Response(
+        boolean direct,
+        String uploadUrl,
+        String method,
+        Map<String, String> headers,
+        String storageName
+) {
+}

backend/src/main/java/com/yoyuzh/api/v2/files/UploadSessionV2Controller.java

@@ -3,10 +3,11 @@ package com.yoyuzh.api.v2.files;
 import com.yoyuzh.api.v2.ApiV2Response;
 import com.yoyuzh.auth.CustomUserDetailsService;
 import com.yoyuzh.auth.User;
-import com.yoyuzh.files.UploadSession;
-import com.yoyuzh.files.UploadSessionCreateCommand;
-import com.yoyuzh.files.UploadSessionPartCommand;
-import com.yoyuzh.files.UploadSessionService;
+import com.yoyuzh.files.upload.UploadSession;
+import com.yoyuzh.files.upload.UploadSessionCreateCommand;
+import com.yoyuzh.files.upload.UploadSessionPartCommand;
+import com.yoyuzh.files.upload.UploadSessionService;
+import com.yoyuzh.files.storage.PreparedUpload;
 import jakarta.validation.Valid;
 import lombok.RequiredArgsConstructor;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
@@ -77,10 +78,26 @@ public class UploadSessionV2Controller {
         return ApiV2Response.success(toResponse(session));
     }
 
+    @GetMapping("/{sessionId}/parts/{partIndex}/prepare")
+    public ApiV2Response<PreparedUploadV2Response> preparePartUpload(@AuthenticationPrincipal UserDetails userDetails,
+                                                                     @PathVariable String sessionId,
+                                                                     @PathVariable int partIndex) {
+        User user = userDetailsService.loadDomainUser(userDetails.getUsername());
+        PreparedUpload preparedUpload = uploadSessionService.prepareOwnedPartUpload(user, sessionId, partIndex);
+        return ApiV2Response.success(new PreparedUploadV2Response(
+                preparedUpload.direct(),
+                preparedUpload.uploadUrl(),
+                preparedUpload.method(),
+                preparedUpload.headers(),
+                preparedUpload.storageName()
+        ));
+    }
+
     private UploadSessionV2Response toResponse(UploadSession session) {
         return new UploadSessionV2Response(
                 session.getSessionId(),
                 session.getObjectKey(),
+                session.getMultipartUploadId() != null,
                 session.getTargetPath(),
                 session.getFilename(),
                 session.getContentType(),

backend/src/main/java/com/yoyuzh/api/v2/files/UploadSessionV2Response.java

@@ -5,6 +5,7 @@ import java.time.LocalDateTime;
 public record UploadSessionV2Response(
         String sessionId,
         String objectKey,
+        boolean multipartUpload,
         String path,
         String filename,
         String contentType,

backend/src/main/java/com/yoyuzh/api/v2/shares/ShareV2Controller.java

@@ -4,14 +4,15 @@ import com.yoyuzh.api.v2.ApiV2Response;
 import com.yoyuzh.auth.CustomUserDetailsService;
 import com.yoyuzh.auth.User;
 import com.yoyuzh.common.PageResponse;
-import com.yoyuzh.files.FileMetadataResponse;
-import com.yoyuzh.files.ShareV2Service;
+import com.yoyuzh.files.core.FileMetadataResponse;
+import com.yoyuzh.files.share.ShareV2Service;
 import jakarta.validation.Valid;
 import jakarta.validation.constraints.Max;
 import jakarta.validation.constraints.Min;
 import lombok.RequiredArgsConstructor;
 import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Sort;
+import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
 import org.springframework.security.core.userdetails.UserDetails;
 import org.springframework.web.bind.annotation.DeleteMapping;
@@ -43,6 +44,12 @@ public class ShareV2Controller {
         return ApiV2Response.success(shareV2Service.getShare(token));
     }
 
+    @GetMapping(value = "/{token}", params = "download")
+    public ResponseEntity<?> downloadShare(@PathVariable String token,
+                                           @RequestParam(required = false) String password) {
+        return shareV2Service.downloadSharedFile(token, password);
+    }
+
     @PostMapping("/{token}/verify-password")
     public ApiV2Response<ShareV2Response> verifyPassword(@PathVariable String token,
                                                           @Valid @RequestBody VerifySharePasswordV2Request request) {

backend/src/main/java/com/yoyuzh/api/v2/shares/ShareV2Response.java

@@ -1,6 +1,6 @@
 package com.yoyuzh.api.v2.shares;
 
-import com.yoyuzh.files.FileMetadataResponse;
+import com.yoyuzh.files.core.FileMetadataResponse;
 
 import java.time.LocalDateTime;
 

backend/src/main/java/com/yoyuzh/api/v2/tasks/BackgroundTaskResponse.java

@@ -1,7 +1,7 @@
 package com.yoyuzh.api.v2.tasks;
 
-import com.yoyuzh.files.BackgroundTaskStatus;
-import com.yoyuzh.files.BackgroundTaskType;
+import com.yoyuzh.files.tasks.BackgroundTaskStatus;
+import com.yoyuzh.files.tasks.BackgroundTaskType;
 
 import java.time.LocalDateTime;
 

backend/src/main/java/com/yoyuzh/api/v2/tasks/BackgroundTaskV2Controller.java

@@ -4,9 +4,9 @@ import com.yoyuzh.api.v2.ApiV2Response;
 import com.yoyuzh.auth.CustomUserDetailsService;
 import com.yoyuzh.auth.User;
 import com.yoyuzh.common.PageResponse;
-import com.yoyuzh.files.BackgroundTask;
-import com.yoyuzh.files.BackgroundTaskService;
-import com.yoyuzh.files.BackgroundTaskType;
+import com.yoyuzh.files.tasks.BackgroundTask;
+import com.yoyuzh.files.tasks.BackgroundTaskService;
+import com.yoyuzh.files.tasks.BackgroundTaskType;
 import jakarta.validation.Valid;
 import jakarta.validation.constraints.Max;
 import jakarta.validation.constraints.Min;
@@ -63,6 +63,13 @@ public class BackgroundTaskV2Controller {
         return ApiV2Response.success(toResponse(backgroundTaskService.cancelOwnedTask(user, id)));
     }
 
+    @PostMapping("/{id}/retry")
+    public ApiV2Response<BackgroundTaskResponse> retry(@AuthenticationPrincipal UserDetails userDetails,
+                                                       @PathVariable Long id) {
+        User user = userDetailsService.loadDomainUser(userDetails.getUsername());
+        return ApiV2Response.success(toResponse(backgroundTaskService.retryOwnedTask(user, id)));
+    }
+
     @PostMapping("/archive")
     public ApiV2Response<BackgroundTaskResponse> createArchiveTask(@AuthenticationPrincipal UserDetails userDetails,
                                                                    @Valid @RequestBody CreateBackgroundTaskRequest request) {

backend/src/main/java/com/yoyuzh/auth/AuthService.java

@@ -9,8 +9,8 @@ import com.yoyuzh.auth.dto.UpdateUserProfileRequest;
 import com.yoyuzh.auth.dto.UserProfileResponse;
 import com.yoyuzh.common.BusinessException;
 import com.yoyuzh.common.ErrorCode;
-import com.yoyuzh.files.FileService;
-import com.yoyuzh.files.InitiateUploadResponse;
+import com.yoyuzh.files.core.FileService;
+import com.yoyuzh.files.upload.InitiateUploadResponse;
 import com.yoyuzh.files.storage.FileContentStorage;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;

backend/src/main/java/com/yoyuzh/auth/DevBootstrapDataInitializer.java

@@ -1,7 +1,7 @@
 package com.yoyuzh.auth;
 
-import com.yoyuzh.files.FileService;
-import com.yoyuzh.files.StoredFileRepository;
+import com.yoyuzh.files.core.FileService;
+import com.yoyuzh.files.core.StoredFileRepository;
 import lombok.RequiredArgsConstructor;
 import org.springframework.boot.CommandLineRunner;
 import org.springframework.context.annotation.Profile;

backend/src/main/java/com/yoyuzh/files/BackgroundTaskHandler.java

@@ -1,8 +0,0 @@
-package com.yoyuzh.files;
-
-public interface BackgroundTaskHandler {
-
-    boolean supports(BackgroundTaskType type);
-
-    BackgroundTaskHandlerResult handle(BackgroundTask task);
-}

backend/src/main/java/com/yoyuzh/files/BackgroundTaskRepository.java

@@ -1,35 +0,0 @@
-package com.yoyuzh.files;
-
-import org.springframework.data.domain.Page;
-import org.springframework.data.domain.Pageable;
-import org.springframework.data.jpa.repository.JpaRepository;
-import org.springframework.data.jpa.repository.Modifying;
-import org.springframework.data.jpa.repository.Query;
-import org.springframework.data.repository.query.Param;
-
-import java.time.LocalDateTime;
-import java.util.List;
-import java.util.Optional;
-
-public interface BackgroundTaskRepository extends JpaRepository<BackgroundTask, Long> {
-
-    Page<BackgroundTask> findByUserIdOrderByCreatedAtDesc(Long userId, Pageable pageable);
-
-    Optional<BackgroundTask> findByIdAndUserId(Long id, Long userId);
-
-    List<BackgroundTask> findByStatusOrderByCreatedAtAsc(BackgroundTaskStatus status, Pageable pageable);
-
-    @Modifying
-    @Query("""
-            update BackgroundTask task
-            set task.status = :runningStatus,
-                task.errorMessage = null,
-                task.updatedAt = :updatedAt
-            where task.id = :id
-              and task.status = :queuedStatus
-            """)
-    int claimQueuedTask(@Param("id") Long id,
-                        @Param("queuedStatus") BackgroundTaskStatus queuedStatus,
-                        @Param("runningStatus") BackgroundTaskStatus runningStatus,
-                        @Param("updatedAt") LocalDateTime updatedAt);
-}

backend/src/main/java/com/yoyuzh/files/BackgroundTaskService.java

@@ -1,314 +0,0 @@
-package com.yoyuzh.files;
-
-import com.fasterxml.jackson.core.JsonProcessingException;
-import com.fasterxml.jackson.core.type.TypeReference;
-import com.fasterxml.jackson.databind.ObjectMapper;
-import com.yoyuzh.api.v2.ApiV2ErrorCode;
-import com.yoyuzh.api.v2.ApiV2Exception;
-import com.yoyuzh.auth.User;
-import jakarta.transaction.Transactional;
-import lombok.RequiredArgsConstructor;
-import org.springframework.data.domain.Page;
-import org.springframework.data.domain.PageRequest;
-import org.springframework.data.domain.Pageable;
-import org.springframework.stereotype.Service;
-import org.springframework.util.StringUtils;
-
-import java.time.LocalDateTime;
-import java.util.LinkedHashMap;
-import java.util.List;
-import java.util.Locale;
-import java.util.Map;
-import java.util.Optional;
-import java.util.UUID;
-
-@Service
-@RequiredArgsConstructor
-public class BackgroundTaskService {
-
-    private static final List<String> ARCHIVE_EXTENSIONS = List.of(
-            ".zip", ".jar", ".war", ".7z", ".rar", ".tar", ".gz", ".tgz", ".bz2", ".xz"
-    );
-    private static final List<String> MEDIA_EXTENSIONS = List.of(
-            ".jpg", ".jpeg", ".png", ".gif", ".webp", ".bmp", ".svg",
-            ".mp4", ".mov", ".mkv", ".webm", ".avi",
-            ".mp3", ".wav", ".flac", ".aac", ".ogg", ".m4a"
-    );
-
-    private final BackgroundTaskRepository backgroundTaskRepository;
-    private final StoredFileRepository storedFileRepository;
-    private final ObjectMapper objectMapper;
-
-    @Transactional
-    public BackgroundTask createQueuedFileTask(User user,
-                                               BackgroundTaskType type,
-                                               Long fileId,
-                                               String requestedPath,
-                                               String correlationId) {
-        StoredFile file = storedFileRepository.findByIdAndUserIdAndDeletedAtIsNull(fileId, user.getId())
-                .orElseThrow(() -> new ApiV2Exception(ApiV2ErrorCode.FILE_NOT_FOUND, "file not found"));
-        String logicalPath = buildLogicalPath(file);
-        if (!logicalPath.equals(normalizeLogicalPath(requestedPath))) {
-            throw new ApiV2Exception(ApiV2ErrorCode.BAD_REQUEST, "task path does not match file path");
-        }
-        validateTaskTarget(type, file);
-
-        Map<String, Object> publicState = fileState(file, logicalPath);
-        Map<String, Object> privateState = new LinkedHashMap<>(publicState);
-        privateState.put("taskType", type.name());
-        return createQueuedTask(user, type, publicState, privateState, correlationId);
-    }
-
-    @Transactional
-    public BackgroundTask createQueuedTask(User user,
-                                           BackgroundTaskType type,
-                                           Map<String, Object> publicState,
-                                           Map<String, Object> privateState,
-                                           String correlationId) {
-        BackgroundTask task = new BackgroundTask();
-        task.setUserId(user.getId());
-        task.setType(type);
-        task.setStatus(BackgroundTaskStatus.QUEUED);
-        task.setPublicStateJson(toJson(publicState));
-        task.setPrivateStateJson(toJson(privateState));
-        task.setCorrelationId(normalizeCorrelationId(correlationId));
-        return backgroundTaskRepository.save(task);
-    }
-
-    public Page<BackgroundTask> listOwnedTasks(User user, Pageable pageable) {
-        return backgroundTaskRepository.findByUserIdOrderByCreatedAtDesc(user.getId(), pageable);
-    }
-
-    public BackgroundTask getOwnedTask(User user, Long id) {
-        return backgroundTaskRepository.findByIdAndUserId(id, user.getId())
-                .orElseThrow(() -> new ApiV2Exception(ApiV2ErrorCode.FILE_NOT_FOUND, "task not found"));
-    }
-
-    @Transactional
-    public BackgroundTask cancelOwnedTask(User user, Long id) {
-        BackgroundTask task = getOwnedTask(user, id);
-        if (task.isTerminal()) {
-            return task;
-        }
-
-        if (task.getStatus() == BackgroundTaskStatus.QUEUED || task.getStatus() == BackgroundTaskStatus.RUNNING) {
-            task.setStatus(BackgroundTaskStatus.CANCELLED);
-            task.setFinishedAt(LocalDateTime.now());
-            task.setErrorMessage(null);
-            return backgroundTaskRepository.save(task);
-        }
-
-        return task;
-    }
-
-    @Transactional
-    public BackgroundTask markRunning(User user, Long id) {
-        BackgroundTask task = getOwnedTask(user, id);
-        if (task.isTerminal()) {
-            return task;
-        }
-        task.setStatus(BackgroundTaskStatus.RUNNING);
-        return backgroundTaskRepository.save(task);
-    }
-
-    @Transactional
-    public BackgroundTask markCompleted(User user, Long id) {
-        BackgroundTask task = getOwnedTask(user, id);
-        if (task.isTerminal()) {
-            return task;
-        }
-        task.setStatus(BackgroundTaskStatus.COMPLETED);
-        task.setFinishedAt(LocalDateTime.now());
-        task.setErrorMessage(null);
-        return backgroundTaskRepository.save(task);
-    }
-
-    @Transactional
-    public BackgroundTask markFailed(User user, Long id, String errorMessage) {
-        BackgroundTask task = getOwnedTask(user, id);
-        if (task.isTerminal()) {
-            return task;
-        }
-        task.setStatus(BackgroundTaskStatus.FAILED);
-        task.setFinishedAt(LocalDateTime.now());
-        task.setErrorMessage(StringUtils.hasText(errorMessage) ? errorMessage.trim() : "task failed");
-        return backgroundTaskRepository.save(task);
-    }
-
-    public List<Long> findQueuedTaskIds(int limit) {
-        if (limit <= 0) {
-            return List.of();
-        }
-
-        return backgroundTaskRepository.findByStatusOrderByCreatedAtAsc(
-                        BackgroundTaskStatus.QUEUED,
-                        PageRequest.of(0, limit)
-                )
-                .stream()
-                .map(BackgroundTask::getId)
-                .toList();
-    }
-
-    @Transactional
-    public Optional<BackgroundTask> claimQueuedTask(Long id) {
-        int claimed = backgroundTaskRepository.claimQueuedTask(
-                id,
-                BackgroundTaskStatus.QUEUED,
-                BackgroundTaskStatus.RUNNING,
-                LocalDateTime.now()
-        );
-        if (claimed != 1) {
-            return Optional.empty();
-        }
-        return backgroundTaskRepository.findById(id);
-    }
-
-    @Transactional
-    public BackgroundTask markWorkerTaskCompleted(Long id, Map<String, Object> publicStatePatch) {
-        BackgroundTask task = backgroundTaskRepository.findById(id)
-                .orElseThrow(() -> new ApiV2Exception(ApiV2ErrorCode.FILE_NOT_FOUND, "task not found"));
-        if (task.isTerminal() || task.getStatus() != BackgroundTaskStatus.RUNNING) {
-            return task;
-        }
-
-        Map<String, Object> nextPublicState = parseJsonObject(task.getPublicStateJson());
-        if (publicStatePatch != null) {
-            nextPublicState.putAll(publicStatePatch);
-        }
-        task.setPublicStateJson(toJson(nextPublicState));
-        task.setStatus(BackgroundTaskStatus.COMPLETED);
-        task.setFinishedAt(LocalDateTime.now());
-        task.setErrorMessage(null);
-        return backgroundTaskRepository.save(task);
-    }
-
-    @Transactional
-    public BackgroundTask markWorkerTaskFailed(Long id, String errorMessage) {
-        BackgroundTask task = backgroundTaskRepository.findById(id)
-                .orElseThrow(() -> new ApiV2Exception(ApiV2ErrorCode.FILE_NOT_FOUND, "task not found"));
-        if (task.isTerminal()) {
-            return task;
-        }
-
-        task.setStatus(BackgroundTaskStatus.FAILED);
-        task.setFinishedAt(LocalDateTime.now());
-        task.setErrorMessage(StringUtils.hasText(errorMessage) ? errorMessage.trim() : "task failed");
-        return backgroundTaskRepository.save(task);
-    }
-
-    private String normalizeCorrelationId(String correlationId) {
-        if (StringUtils.hasText(correlationId)) {
-            return correlationId.trim();
-        }
-        return UUID.randomUUID().toString().replace("-", "");
-    }
-
-    private void validateTaskTarget(BackgroundTaskType type, StoredFile file) {
-        if (type == BackgroundTaskType.ARCHIVE) {
-            return;
-        }
-        if (file.isDirectory()) {
-            throw new ApiV2Exception(ApiV2ErrorCode.BAD_REQUEST, "task target type is not supported");
-        }
-        if (type == BackgroundTaskType.EXTRACT && !isArchiveLike(file)) {
-            throw new ApiV2Exception(ApiV2ErrorCode.BAD_REQUEST, "extract task only supports archive files");
-        }
-        if (type == BackgroundTaskType.MEDIA_META && !isMediaLike(file)) {
-            throw new ApiV2Exception(ApiV2ErrorCode.BAD_REQUEST, "media metadata task only supports media files");
-        }
-    }
-
-    private Map<String, Object> fileState(StoredFile file, String logicalPath) {
-        Map<String, Object> state = new LinkedHashMap<>();
-        state.put("fileId", file.getId());
-        state.put("path", logicalPath);
-        state.put("filename", file.getFilename());
-        state.put("directory", file.isDirectory());
-        state.put("contentType", file.getContentType());
-        state.put("size", file.getSize());
-        return state;
-    }
-
-    private boolean isArchiveLike(StoredFile file) {
-        String contentType = normalizeContentType(file.getContentType());
-        if (contentType.contains("zip")
-                || contentType.contains("x-tar")
-                || contentType.contains("gzip")
-                || contentType.contains("x-7z")
-                || contentType.contains("x-rar")
-                || contentType.contains("java-archive")) {
-            return true;
-        }
-        return hasExtension(file.getFilename(), ARCHIVE_EXTENSIONS);
-    }
-
-    private boolean isMediaLike(StoredFile file) {
-        String contentType = normalizeContentType(file.getContentType());
-        if (contentType.startsWith("image/") || contentType.startsWith("video/") || contentType.startsWith("audio/")) {
-            return true;
-        }
-        return hasExtension(file.getFilename(), MEDIA_EXTENSIONS);
-    }
-
-    private boolean hasExtension(String filename, List<String> extensions) {
-        if (!StringUtils.hasText(filename)) {
-            return false;
-        }
-        String normalized = filename.toLowerCase(Locale.ROOT);
-        return extensions.stream().anyMatch(normalized::endsWith);
-    }
-
-    private String normalizeContentType(String contentType) {
-        if (!StringUtils.hasText(contentType)) {
-            return "";
-        }
-        return contentType.trim().toLowerCase(Locale.ROOT);
-    }
-
-    private String buildLogicalPath(StoredFile file) {
-        String parent = normalizeLogicalPath(file.getPath());
-        if ("/".equals(parent)) {
-            return "/" + file.getFilename();
-        }
-        return parent + "/" + file.getFilename();
-    }
-
-    private String normalizeLogicalPath(String path) {
-        if (!StringUtils.hasText(path)) {
-            return "/";
-        }
-        String normalized = path.trim().replace('\\', '/');
-        while (normalized.contains("//")) {
-            normalized = normalized.replace("//", "/");
-        }
-        if (!normalized.startsWith("/")) {
-            normalized = "/" + normalized;
-        }
-        while (normalized.length() > 1 && normalized.endsWith("/")) {
-            normalized = normalized.substring(0, normalized.length() - 1);
-        }
-        return normalized;
-    }
-
-    private String toJson(Map<String, Object> value) {
-        Map<String, Object> safeValue = value == null ? new LinkedHashMap<>() : new LinkedHashMap<>(value);
-        try {
-            return objectMapper.writeValueAsString(safeValue);
-        } catch (JsonProcessingException ex) {
-            throw new IllegalStateException("Failed to serialize background task state", ex);
-        }
-    }
-
-    private Map<String, Object> parseJsonObject(String value) {
-        if (!StringUtils.hasText(value)) {
-            return new LinkedHashMap<>();
-        }
-
-        try {
-            return objectMapper.readValue(value, new TypeReference<LinkedHashMap<String, Object>>() {
-            });
-        } catch (JsonProcessingException ex) {
-            throw new IllegalStateException("Failed to parse background task state", ex);
-        }
-    }
-}

backend/src/main/java/com/yoyuzh/files/BackgroundTaskWorker.java

@@ -1,61 +0,0 @@
-package com.yoyuzh.files;
-
-import org.springframework.scheduling.annotation.Scheduled;
-import org.springframework.stereotype.Component;
-
-import java.util.List;
-
-@Component
-public class BackgroundTaskWorker {
-
-    private static final int DEFAULT_BATCH_SIZE = 5;
-
-    private final BackgroundTaskService backgroundTaskService;
-    private final List<BackgroundTaskHandler> handlers;
-
-    public BackgroundTaskWorker(BackgroundTaskService backgroundTaskService,
-                                List<BackgroundTaskHandler> handlers) {
-        this.backgroundTaskService = backgroundTaskService;
-        this.handlers = List.copyOf(handlers);
-    }
-
-    @Scheduled(
-            fixedDelayString = "${app.background-tasks.worker.fixed-delay-ms:30000}",
-            initialDelayString = "${app.background-tasks.worker.initial-delay-ms:30000}"
-    )
-    public void runScheduledBatch() {
-        processQueuedTasks(DEFAULT_BATCH_SIZE);
-    }
-
-    public int processQueuedTasks(int maxTasks) {
-        int processedCount = 0;
-        for (Long taskId : backgroundTaskService.findQueuedTaskIds(maxTasks)) {
-            var claimedTask = backgroundTaskService.claimQueuedTask(taskId);
-            if (claimedTask.isEmpty()) {
-                continue;
-            }
-
-            execute(claimedTask.get());
-            processedCount += 1;
-        }
-        return processedCount;
-    }
-
-    private void execute(BackgroundTask task) {
-        try {
-            BackgroundTaskHandler handler = findHandler(task);
-            BackgroundTaskHandlerResult result = handler.handle(task);
-            backgroundTaskService.markWorkerTaskCompleted(task.getId(), result.publicStatePatch());
-        } catch (Exception ex) {
-            String message = ex.getMessage() == null ? ex.getClass().getSimpleName() : ex.getMessage();
-            backgroundTaskService.markWorkerTaskFailed(task.getId(), message);
-        }
-    }
-
-    private BackgroundTaskHandler findHandler(BackgroundTask task) {
-        return handlers.stream()
-                .filter(handler -> handler.supports(task.getType()))
-                .findFirst()
-                .orElseThrow(() -> new IllegalStateException("No background task handler for " + task.getType()));
-    }
-}

backend/src/main/java/com/yoyuzh/files/core/CopyFileRequest.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import jakarta.validation.constraints.NotBlank;
 

backend/src/main/java/com/yoyuzh/files/core/DownloadUrlResponse.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 public record DownloadUrlResponse(String url) {
 }

backend/src/main/java/com/yoyuzh/files/core/FileBlob.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;

backend/src/main/java/com/yoyuzh/files/core/FileBlobBackfillService.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import com.yoyuzh.files.storage.FileContentStorage;
 import lombok.RequiredArgsConstructor;

backend/src/main/java/com/yoyuzh/files/core/FileBlobRepository.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.data.jpa.repository.Query;

backend/src/main/java/com/yoyuzh/files/core/FileController.java

@@ -1,8 +1,14 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import com.yoyuzh.auth.CustomUserDetailsService;
 import com.yoyuzh.common.ApiResponse;
 import com.yoyuzh.common.PageResponse;
+import com.yoyuzh.files.share.CreateFileShareLinkResponse;
+import com.yoyuzh.files.share.FileShareDetailsResponse;
+import com.yoyuzh.files.share.ImportSharedFileRequest;
+import com.yoyuzh.files.upload.CompleteUploadRequest;
+import com.yoyuzh.files.upload.InitiateUploadRequest;
+import com.yoyuzh.files.upload.InitiateUploadResponse;
 import io.swagger.v3.oas.annotations.Operation;
 import jakarta.validation.Valid;
 import lombok.RequiredArgsConstructor;

backend/src/main/java/com/yoyuzh/files/core/FileEntity.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import com.yoyuzh.auth.User;
 import jakarta.persistence.Column;

backend/src/main/java/com/yoyuzh/files/core/FileEntityBackfillService.java

@@ -1,5 +1,6 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
+import com.yoyuzh.files.policy.StoragePolicyService;
 import lombok.RequiredArgsConstructor;
 import org.springframework.boot.CommandLineRunner;
 import org.springframework.core.annotation.Order;

backend/src/main/java/com/yoyuzh/files/core/FileEntityRepository.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import org.springframework.data.jpa.repository.JpaRepository;
 

backend/src/main/java/com/yoyuzh/files/core/FileEntityType.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 public enum FileEntityType {
     VERSION,

backend/src/main/java/com/yoyuzh/files/core/FileMetadataResponse.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import java.time.LocalDateTime;
 

backend/src/main/java/com/yoyuzh/files/core/FileService.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import com.yoyuzh.admin.AdminMetricsService;
 import com.yoyuzh.auth.User;
@@ -6,8 +6,18 @@ import com.yoyuzh.common.BusinessException;
 import com.yoyuzh.common.ErrorCode;
 import com.yoyuzh.common.PageResponse;
 import com.yoyuzh.config.FileStorageProperties;
+import com.yoyuzh.files.events.FileEventService;
+import com.yoyuzh.files.events.FileEventType;
+import com.yoyuzh.files.policy.StoragePolicyService;
+import com.yoyuzh.files.share.CreateFileShareLinkResponse;
+import com.yoyuzh.files.share.FileShareDetailsResponse;
+import com.yoyuzh.files.share.FileShareLink;
+import com.yoyuzh.files.share.FileShareLinkRepository;
 import com.yoyuzh.files.storage.FileContentStorage;
 import com.yoyuzh.files.storage.PreparedUpload;
+import com.yoyuzh.files.upload.CompleteUploadRequest;
+import com.yoyuzh.files.upload.InitiateUploadRequest;
+import com.yoyuzh.files.upload.InitiateUploadResponse;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
@@ -20,6 +30,7 @@ import org.springframework.transaction.annotation.Transactional;
 import org.springframework.util.StringUtils;
 import org.springframework.web.multipart.MultipartFile;
 
+import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.net.URI;
@@ -41,6 +52,7 @@ import java.util.Set;
 import java.util.UUID;
 import java.util.Locale;
 import java.util.zip.ZipEntry;
+import java.util.zip.ZipInputStream;
 import java.util.zip.ZipOutputStream;
 
 @Service
@@ -566,36 +578,49 @@ public class FileService {
         });
     }
 
-    private ResponseEntity<byte[]> downloadDirectory(User user, StoredFile directory) {
-        String logicalPath = buildLogicalPath(directory);
-        String archiveName = directory.getFilename() + ".zip";
-        List<StoredFile> descendants = storedFileRepository.findByUserIdAndPathEqualsOrDescendant(user.getId(), logicalPath)
-                .stream()
-                .sorted(Comparator.comparing(StoredFile::getPath).thenComparing(StoredFile::getFilename))
-                .toList();
+    @Transactional
+    public void importExternalFilesAtomically(User recipient,
+                                              List<String> directories,
+                                              List<ExternalFileImport> files) {
+        importExternalFilesAtomically(recipient, directories, files, null);
+    }
 
-        byte[] archiveBytes;
-        try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
-             ZipOutputStream zipOutputStream = new ZipOutputStream(outputStream, StandardCharsets.UTF_8)) {
-            Set<String> createdEntries = new LinkedHashSet<>();
-            writeDirectoryEntry(zipOutputStream, createdEntries, directory.getFilename() + "/");
+    @Transactional
+    public void importExternalFilesAtomically(User recipient,
+                                              List<String> directories,
+                                              List<ExternalFileImport> files,
+                                              ExternalImportProgressListener progressListener) {
+        List<String> normalizedDirectories = normalizeExternalImportDirectories(directories);
+        List<ExternalFileImport> normalizedFiles = normalizeExternalImportFiles(files);
+        validateExternalImportBatch(recipient, normalizedDirectories, normalizedFiles);
 
-            for (StoredFile descendant : descendants) {
-                String entryName = buildZipEntryName(directory.getFilename(), logicalPath, descendant);
-                if (descendant.isDirectory()) {
-                    writeDirectoryEntry(zipOutputStream, createdEntries, entryName + "/");
-                    continue;
-                }
-
-                ensureParentDirectoryEntries(zipOutputStream, createdEntries, entryName);
-                writeFileEntry(zipOutputStream, createdEntries, entryName,
-                        fileContentStorage.readBlob(getRequiredBlob(descendant).getObjectKey()));
+        List<String> writtenBlobObjectKeys = new ArrayList<>();
+        int totalDirectoryCount = normalizedDirectories.size();
+        int totalFileCount = normalizedFiles.size();
+        int processedDirectoryCount = 0;
+        int processedFileCount = 0;
+        try {
+            for (String directory : normalizedDirectories) {
+                mkdir(recipient, directory);
+                processedDirectoryCount += 1;
+                reportExternalImportProgress(progressListener, processedFileCount, totalFileCount,
+                        processedDirectoryCount, totalDirectoryCount);
             }
-            zipOutputStream.finish();
-            archiveBytes = outputStream.toByteArray();
-        } catch (IOException ex) {
-            throw new BusinessException(ErrorCode.UNKNOWN, "目录压缩失败");
+            for (ExternalFileImport file : normalizedFiles) {
+                storeExternalImportFile(recipient, file, writtenBlobObjectKeys);
+                processedFileCount += 1;
+                reportExternalImportProgress(progressListener, processedFileCount, totalFileCount,
+                        processedDirectoryCount, totalDirectoryCount);
+            }
+        } catch (RuntimeException ex) {
+            cleanupWrittenBlobs(writtenBlobObjectKeys, ex);
+            throw ex;
         }
+    }
+
+    private ResponseEntity<byte[]> downloadDirectory(User user, StoredFile directory) {
+        String archiveName = directory.getFilename() + ".zip";
+        byte[] archiveBytes = buildArchiveBytes(directory);
 
         return ResponseEntity.ok()
                 .header(HttpHeaders.CONTENT_DISPOSITION,
@@ -604,6 +629,63 @@ public class FileService {
                 .body(archiveBytes);
     }
 
+    public byte[] buildArchiveBytes(StoredFile source) {
+        return buildArchiveBytes(source, null);
+    }
+
+    public byte[] buildArchiveBytes(StoredFile source, ArchiveBuildProgressListener progressListener) {
+        try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+             ZipOutputStream zipOutputStream = new ZipOutputStream(outputStream, StandardCharsets.UTF_8)) {
+            Set<String> createdEntries = new LinkedHashSet<>();
+            ArchiveBuildProgressState progressState = createArchiveBuildProgressState(source, progressListener);
+            reportArchiveProgress(progressState);
+            if (source.isDirectory()) {
+                writeDirectoryArchiveEntries(zipOutputStream, createdEntries, source, progressState);
+            } else {
+                writeFileArchiveEntry(zipOutputStream, createdEntries, source.getFilename(), source, progressState);
+            }
+            zipOutputStream.finish();
+            return outputStream.toByteArray();
+        } catch (IOException ex) {
+            throw new BusinessException(ErrorCode.UNKNOWN, "目录压缩失败");
+        }
+    }
+
+    public ZipCompatibleArchive readZipCompatibleArchive(StoredFile source) {
+        byte[] archiveBytes = fileContentStorage.readBlob(getRequiredBlob(source).getObjectKey());
+        try (ZipInputStream zipInputStream = new ZipInputStream(
+                new ByteArrayInputStream(archiveBytes),
+                StandardCharsets.UTF_8)) {
+            List<ZipCompatibleArchiveEntry> entries = new ArrayList<>();
+            Map<String, Boolean> seenEntries = new HashMap<>();
+            ZipEntry entry = zipInputStream.getNextEntry();
+            while (entry != null) {
+                String relativePath = normalizeZipCompatibleEntryPath(entry.getName());
+                if (StringUtils.hasText(relativePath)) {
+                    boolean directory = entry.isDirectory() || entry.getName().endsWith("/");
+                    Boolean existingType = seenEntries.putIfAbsent(relativePath, directory);
+                    if (existingType != null) {
+                        throw new BusinessException(ErrorCode.UNKNOWN, "压缩包内容不合法");
+                    }
+                    entries.add(new ZipCompatibleArchiveEntry(
+                            relativePath,
+                            directory,
+                            directory ? new byte[0] : zipInputStream.readAllBytes()
+                    ));
+                }
+                entry = zipInputStream.getNextEntry();
+            }
+            if (entries.isEmpty() && !hasZipCompatibleSignature(archiveBytes)) {
+                throw new BusinessException(ErrorCode.UNKNOWN, "压缩包读取失败");
+            }
+            return new ZipCompatibleArchive(entries, detectCommonRootDirectoryName(entries));
+        } catch (BusinessException ex) {
+            throw ex;
+        } catch (IOException ex) {
+            throw new BusinessException(ErrorCode.UNKNOWN, "压缩包读取失败");
+        }
+    }
+
     private boolean shouldUsePublicPackageDownload(StoredFile storedFile) {
         return fileContentStorage.supportsDirectDownload()
                 && StringUtils.hasText(packageDownloadBaseUrl)
@@ -854,6 +936,62 @@ public class FileService {
         ensureWithinStorageQuota(user, size);
     }
 
+    private List<String> normalizeExternalImportDirectories(List<String> directories) {
+        if (directories == null || directories.isEmpty()) {
+            return List.of();
+        }
+        return directories.stream()
+                .map(this::normalizeDirectoryPath)
+                .distinct()
+                .sorted(Comparator.comparingInt(String::length).thenComparing(String::compareTo))
+                .toList();
+    }
+
+    private List<ExternalFileImport> normalizeExternalImportFiles(List<ExternalFileImport> files) {
+        if (files == null || files.isEmpty()) {
+            return List.of();
+        }
+        return files.stream()
+                .map(file -> new ExternalFileImport(
+                        normalizeDirectoryPath(file.path()),
+                        normalizeLeafName(file.filename()),
+                        StringUtils.hasText(file.contentType()) ? file.contentType().trim() : "application/octet-stream",
+                        file.content() == null ? new byte[0] : file.content()
+                ))
+                .toList();
+    }
+
+    private void validateExternalImportBatch(User recipient,
+                                             List<String> directories,
+                                             List<ExternalFileImport> files) {
+        ensureWithinStorageQuota(recipient, files.stream().mapToLong(ExternalFileImport::size).sum());
+
+        Set<String> plannedTargets = new LinkedHashSet<>();
+        for (String directory : directories) {
+            if ("/".equals(directory)) {
+                continue;
+            }
+            if (!plannedTargets.add(directory)) {
+                continue;
+            }
+            String parentPath = extractParentPath(directory);
+            String directoryName = extractLeafName(directory);
+            if (storedFileRepository.existsByUserIdAndPathAndFilename(recipient.getId(), parentPath, directoryName)) {
+                throw new BusinessException(ErrorCode.UNKNOWN, "解压目标已存在");
+            }
+        }
+
+        for (ExternalFileImport file : files) {
+            String logicalPath = buildTargetLogicalPath(file.path(), file.filename());
+            if (plannedTargets.contains(logicalPath) || !plannedTargets.add(logicalPath)) {
+                throw new BusinessException(ErrorCode.UNKNOWN, "解压目标已存在");
+            }
+            if (storedFileRepository.existsByUserIdAndPathAndFilename(recipient.getId(), file.path(), file.filename())) {
+                throw new BusinessException(ErrorCode.UNKNOWN, "同目录下文件已存在");
+            }
+        }
+    }
+
     private void ensureWithinStorageQuota(User user, long additionalBytes) {
         if (additionalBytes <= 0) {
             return;
@@ -900,6 +1038,25 @@ public class FileService {
         }
     }
 
+    private void storeExternalImportFile(User recipient,
+                                         ExternalFileImport file,
+                                         List<String> writtenBlobObjectKeys) {
+        validateUpload(recipient, file.path(), file.filename(), file.size());
+        ensureDirectoryHierarchy(recipient, file.path());
+        String objectKey = createBlobObjectKey();
+        writtenBlobObjectKeys.add(objectKey);
+        fileContentStorage.storeBlob(objectKey, file.contentType(), file.content());
+        FileBlob blob = createAndSaveBlob(objectKey, file.contentType(), file.size());
+        saveFileMetadata(
+                recipient,
+                file.path(),
+                file.filename(),
+                file.contentType(),
+                file.size(),
+                blob
+        );
+    }
+
     private void moveToRecycleBin(List<StoredFile> filesToRecycle, Long recycleRootId) {
         if (filesToRecycle.isEmpty()) {
             return;
@@ -1071,6 +1228,37 @@ public class FileService {
         return savedFile;
     }
 
+    private void writeDirectoryArchiveEntries(ZipOutputStream zipOutputStream,
+                                              Set<String> createdEntries,
+                                              StoredFile directory,
+                                              ArchiveBuildProgressState progressState) throws IOException {
+        String logicalPath = buildLogicalPath(directory);
+        List<StoredFile> descendants = storedFileRepository.findByUserIdAndPathEqualsOrDescendant(directory.getUser().getId(), logicalPath)
+                .stream()
+                .sorted(Comparator.comparing(StoredFile::getPath).thenComparing(StoredFile::getFilename))
+                .toList();
+        writeDirectoryEntry(zipOutputStream, createdEntries, directory.getFilename() + "/", progressState);
+
+        for (StoredFile descendant : descendants) {
+            String entryName = buildZipEntryName(directory.getFilename(), logicalPath, descendant);
+            if (descendant.isDirectory()) {
+                writeDirectoryEntry(zipOutputStream, createdEntries, entryName + "/", progressState);
+                continue;
+            }
+            writeFileArchiveEntry(zipOutputStream, createdEntries, entryName, descendant, progressState);
+        }
+    }
+
+    private void writeFileArchiveEntry(ZipOutputStream zipOutputStream,
+                                       Set<String> createdEntries,
+                                       String entryName,
+                                       StoredFile file,
+                                       ArchiveBuildProgressState progressState) throws IOException {
+        ensureParentDirectoryEntries(zipOutputStream, createdEntries, entryName, progressState);
+        writeFileEntry(zipOutputStream, createdEntries, entryName, progressState,
+                fileContentStorage.readBlob(getRequiredBlob(file).getObjectKey()));
+    }
+
     private String buildZipEntryName(String rootDirectoryName, String rootLogicalPath, StoredFile storedFile) {
         StringBuilder entryName = new StringBuilder(rootDirectoryName).append('/');
         if (!storedFile.getPath().equals(rootLogicalPath)) {
@@ -1080,24 +1268,153 @@ public class FileService {
         return entryName.toString();
     }
 
-    private void ensureParentDirectoryEntries(ZipOutputStream zipOutputStream, Set<String> createdEntries, String entryName) throws IOException {
+    private String normalizeZipCompatibleEntryPath(String entryName) {
+        String normalized = entryName == null ? "" : entryName.trim().replace("\\", "/");
+        if (!StringUtils.hasText(normalized)) {
+            return "";
+        }
+        if (normalized.startsWith("/")) {
+            throw new BusinessException(ErrorCode.UNKNOWN, "压缩包内容不合法");
+        }
+        while (normalized.endsWith("/")) {
+            normalized = normalized.substring(0, normalized.length() - 1);
+        }
+        if (!StringUtils.hasText(normalized)) {
+            return "";
+        }
+
+        StringBuilder sanitized = new StringBuilder();
+        for (String segment : normalized.split("/")) {
+            if (!StringUtils.hasText(segment) || ".".equals(segment) || "..".equals(segment)) {
+                throw new BusinessException(ErrorCode.UNKNOWN, "压缩包内容不合法");
+            }
+            if (sanitized.length() > 0) {
+                sanitized.append('/');
+            }
+            sanitized.append(normalizeLeafName(segment));
+        }
+        return sanitized.toString();
+    }
+
+    private String detectCommonRootDirectoryName(List<ZipCompatibleArchiveEntry> entries) {
+        String candidate = null;
+        boolean hasNestedEntry = false;
+        boolean hasDirectoryCandidate = false;
+        for (ZipCompatibleArchiveEntry entry : entries) {
+            String relativePath = entry.relativePath();
+            int slashIndex = relativePath.indexOf('/');
+            String topSegment = slashIndex >= 0 ? relativePath.substring(0, slashIndex) : relativePath;
+            if (candidate == null) {
+                candidate = topSegment;
+            } else if (!candidate.equals(topSegment)) {
+                return null;
+            }
+            if (slashIndex >= 0) {
+                hasNestedEntry = true;
+            }
+            if (entry.directory() && candidate.equals(relativePath)) {
+                hasDirectoryCandidate = true;
+            }
+            if (!entry.directory() && candidate.equals(relativePath)) {
+                return null;
+            }
+        }
+        if (!hasNestedEntry && !hasDirectoryCandidate) {
+            return null;
+        }
+        return candidate;
+    }
+
+    private boolean hasZipCompatibleSignature(byte[] archiveBytes) {
+        if (archiveBytes == null || archiveBytes.length < 4) {
+            return false;
+        }
+        return archiveBytes[0] == 'P'
+                && archiveBytes[1] == 'K'
+                && (archiveBytes[2] == 3 || archiveBytes[2] == 5 || archiveBytes[2] == 7)
+                && (archiveBytes[3] == 4 || archiveBytes[3] == 6 || archiveBytes[3] == 8);
+    }
+
+    public ArchiveSourceSummary summarizeArchiveSource(StoredFile source) {
+        if (!source.isDirectory()) {
+            return new ArchiveSourceSummary(1, 0);
+        }
+        String logicalPath = buildLogicalPath(source);
+        List<StoredFile> descendants = storedFileRepository.findByUserIdAndPathEqualsOrDescendant(source.getUser().getId(), logicalPath);
+        int directoryCount = 1 + (int) descendants.stream().filter(StoredFile::isDirectory).count();
+        int fileCount = (int) descendants.stream().filter(file -> !file.isDirectory()).count();
+        return new ArchiveSourceSummary(fileCount, directoryCount);
+    }
+
+    private ArchiveBuildProgressState createArchiveBuildProgressState(StoredFile source,
+                                                                      ArchiveBuildProgressListener progressListener) {
+        if (progressListener == null) {
+            return null;
+        }
+        ArchiveSourceSummary summary = summarizeArchiveSource(source);
+        return new ArchiveBuildProgressState(progressListener, summary.fileCount(), summary.directoryCount());
+    }
+
+    private void reportArchiveProgress(ArchiveBuildProgressState progressState) {
+        if (progressState == null) {
+            return;
+        }
+        progressState.listener.onProgress(new ArchiveBuildProgress(
+                progressState.processedFileCount,
+                progressState.totalFileCount,
+                progressState.processedDirectoryCount,
+                progressState.totalDirectoryCount
+        ));
+    }
+
+    private void reportExternalImportProgress(ExternalImportProgressListener progressListener,
+                                              int processedFileCount,
+                                              int totalFileCount,
+                                              int processedDirectoryCount,
+                                              int totalDirectoryCount) {
+        if (progressListener == null) {
+            return;
+        }
+        progressListener.onProgress(new ExternalImportProgress(
+                processedFileCount,
+                totalFileCount,
+                processedDirectoryCount,
+                totalDirectoryCount
+        ));
+    }
+
+    private void ensureParentDirectoryEntries(ZipOutputStream zipOutputStream,
+                                              Set<String> createdEntries,
+                                              String entryName,
+                                              ArchiveBuildProgressState progressState) throws IOException {
         int slashIndex = entryName.indexOf('/');
         while (slashIndex >= 0) {
-            writeDirectoryEntry(zipOutputStream, createdEntries, entryName.substring(0, slashIndex + 1));
+            writeDirectoryEntry(zipOutputStream, createdEntries, entryName.substring(0, slashIndex + 1), progressState);
             slashIndex = entryName.indexOf('/', slashIndex + 1);
         }
     }
 
-    private void writeDirectoryEntry(ZipOutputStream zipOutputStream, Set<String> createdEntries, String entryName) throws IOException {
+    private void writeDirectoryEntry(ZipOutputStream zipOutputStream,
+                                     Set<String> createdEntries,
+                                     String entryName,
+                                     ArchiveBuildProgressState progressState) throws IOException {
         if (!createdEntries.add(entryName)) {
             return;
         }
 
         zipOutputStream.putNextEntry(new ZipEntry(entryName));
         zipOutputStream.closeEntry();
+        if (progressState != null) {
+            progressState.processedDirectoryCount += 1;
+            reportArchiveProgress(progressState);
+        }
     }
 
-    private void writeFileEntry(ZipOutputStream zipOutputStream, Set<String> createdEntries, String entryName, byte[] content)
+    private void writeFileEntry(ZipOutputStream zipOutputStream,
+                                Set<String> createdEntries,
+                                String entryName,
+                                ArchiveBuildProgressState progressState,
+                                byte[] content)
             throws IOException {
         if (!createdEntries.add(entryName)) {
             return;
@@ -1106,6 +1423,10 @@ public class FileService {
         zipOutputStream.putNextEntry(new ZipEntry(entryName));
         zipOutputStream.write(content);
         zipOutputStream.closeEntry();
+        if (progressState != null) {
+            progressState.processedFileCount += 1;
+            reportArchiveProgress(progressState);
+        }
     }
 
     private void recordFileEvent(User user,
@@ -1170,6 +1491,16 @@ public class FileService {
         }
     }
 
+    private void cleanupWrittenBlobs(List<String> writtenBlobObjectKeys, RuntimeException ex) {
+        for (String objectKey : writtenBlobObjectKeys) {
+            try {
+                fileContentStorage.deleteBlob(objectKey);
+            } catch (RuntimeException cleanupEx) {
+                ex.addSuppressed(cleanupEx);
+            }
+        }
+    }
+
     private FileBlob createAndSaveBlob(String objectKey, String contentType, long size) {
         FileBlob blob = new FileBlob();
         blob.setObjectKey(objectKey);
@@ -1248,4 +1579,57 @@ public class FileService {
     private interface BlobWriteOperation<T> {
         T run();
     }
+
+    public static record ZipCompatibleArchive(List<ZipCompatibleArchiveEntry> entries, String commonRootDirectoryName) {
+    }
+
+    public static record ZipCompatibleArchiveEntry(String relativePath, boolean directory, byte[] content) {
+    }
+
+    public static record ExternalFileImport(String path, String filename, String contentType, byte[] content) {
+        public long size() {
+            return content == null ? 0L : content.length;
+        }
+    }
+
+    public record ArchiveSourceSummary(int fileCount, int directoryCount) {
+    }
+
+    public record ArchiveBuildProgress(int processedFileCount,
+                                       int totalFileCount,
+                                       int processedDirectoryCount,
+                                       int totalDirectoryCount) {
+    }
+
+    @FunctionalInterface
+    public interface ArchiveBuildProgressListener {
+        void onProgress(ArchiveBuildProgress progress);
+    }
+
+    public record ExternalImportProgress(int processedFileCount,
+                                         int totalFileCount,
+                                         int processedDirectoryCount,
+                                         int totalDirectoryCount) {
+    }
+
+    @FunctionalInterface
+    public interface ExternalImportProgressListener {
+        void onProgress(ExternalImportProgress progress);
+    }
+
+    private static final class ArchiveBuildProgressState {
+        private final ArchiveBuildProgressListener listener;
+        private final int totalFileCount;
+        private final int totalDirectoryCount;
+        private int processedFileCount;
+        private int processedDirectoryCount;
+
+        private ArchiveBuildProgressState(ArchiveBuildProgressListener listener,
+                                          int totalFileCount,
+                                          int totalDirectoryCount) {
+            this.listener = listener;
+            this.totalFileCount = totalFileCount;
+            this.totalDirectoryCount = totalDirectoryCount;
+        }
+    }
 }

backend/src/main/java/com/yoyuzh/files/core/MkdirRequest.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import jakarta.validation.constraints.NotBlank;
 

backend/src/main/java/com/yoyuzh/files/core/MoveFileRequest.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import jakarta.validation.constraints.NotBlank;
 

backend/src/main/java/com/yoyuzh/files/core/RecycleBinItemResponse.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import java.time.LocalDateTime;
 

backend/src/main/java/com/yoyuzh/files/core/RenameFileRequest.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import jakarta.validation.constraints.NotBlank;
 

backend/src/main/java/com/yoyuzh/files/core/StoredFile.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import com.yoyuzh.auth.User;
 import jakarta.persistence.Column;

backend/src/main/java/com/yoyuzh/files/core/StoredFileEntity.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;

backend/src/main/java/com/yoyuzh/files/core/StoredFileEntityRepository.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import org.springframework.data.jpa.repository.JpaRepository;
 

backend/src/main/java/com/yoyuzh/files/core/StoredFileRepository.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;

backend/src/main/java/com/yoyuzh/files/events/FileEvent.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.events;
 
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;

backend/src/main/java/com/yoyuzh/files/events/FileEventRepository.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.events;
 
 import org.springframework.data.jpa.repository.JpaRepository;
 

backend/src/main/java/com/yoyuzh/files/events/FileEventService.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.events;
 
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;

backend/src/main/java/com/yoyuzh/files/events/FileEventType.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.events;
 
 public enum FileEventType {
     CREATED,

backend/src/main/java/com/yoyuzh/files/policy/StoragePolicy.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.policy;
 
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;

backend/src/main/java/com/yoyuzh/files/policy/StoragePolicyCapabilities.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.policy;
 
 public record StoragePolicyCapabilities(
         boolean directUpload,

backend/src/main/java/com/yoyuzh/files/policy/StoragePolicyCredentialMode.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.policy;
 
 public enum StoragePolicyCredentialMode {
     NONE,

backend/src/main/java/com/yoyuzh/files/policy/StoragePolicyRepository.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.policy;
 
 import org.springframework.data.jpa.repository.JpaRepository;
 

backend/src/main/java/com/yoyuzh/files/policy/StoragePolicyService.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.policy;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.yoyuzh.config.FileStorageProperties;
@@ -57,7 +57,7 @@ public class StoragePolicyService implements CommandLineRunner {
         policy.setMaxSizeBytes(properties.getMaxFileSize());
         policy.setCapabilitiesJson(writeCapabilities(new StoragePolicyCapabilities(
                 true,
-                false,
+                true,
                 true,
                 true,
                 false,

backend/src/main/java/com/yoyuzh/files/policy/StoragePolicyType.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.policy;
 
 public enum StoragePolicyType {
     LOCAL,

backend/src/main/java/com/yoyuzh/files/search/FileMetadata.java

@@ -1,5 +1,6 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.search;
 
+import com.yoyuzh.files.core.StoredFile;
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
 import jakarta.persistence.FetchType;

backend/src/main/java/com/yoyuzh/files/search/FileMetadataRepository.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.search;
 
 import org.springframework.data.jpa.repository.JpaRepository;
 

backend/src/main/java/com/yoyuzh/files/search/FileSearchQuery.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.search;
 
 import java.time.LocalDateTime;
 

backend/src/main/java/com/yoyuzh/files/search/FileSearchService.java

@@ -1,9 +1,12 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.search;
 
 import com.yoyuzh.api.v2.ApiV2ErrorCode;
 import com.yoyuzh.api.v2.ApiV2Exception;
 import com.yoyuzh.auth.User;
 import com.yoyuzh.common.PageResponse;
+import com.yoyuzh.files.core.FileMetadataResponse;
+import com.yoyuzh.files.core.StoredFile;
+import com.yoyuzh.files.core.StoredFileRepository;
 import lombok.RequiredArgsConstructor;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;

backend/src/main/java/com/yoyuzh/files/share/CreateFileShareLinkResponse.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.share;
 
 import java.time.LocalDateTime;
 

backend/src/main/java/com/yoyuzh/files/share/FileShareDetailsResponse.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.share;
 
 import java.time.LocalDateTime;
 

backend/src/main/java/com/yoyuzh/files/share/FileShareLink.java

@@ -1,6 +1,7 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.share;
 
 import com.yoyuzh.auth.User;
+import com.yoyuzh.files.core.StoredFile;
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
 import jakarta.persistence.FetchType;

backend/src/main/java/com/yoyuzh/files/share/FileShareLinkRepository.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.share;
 
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;

backend/src/main/java/com/yoyuzh/files/share/ImportSharedFileRequest.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.share;
 
 import jakarta.validation.constraints.NotBlank;
 

backend/src/main/java/com/yoyuzh/files/share/ShareV2Service.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.share;
 
 import com.yoyuzh.api.v2.ApiV2ErrorCode;
 import com.yoyuzh.api.v2.ApiV2Exception;
@@ -7,10 +7,15 @@ import com.yoyuzh.api.v2.shares.ImportShareV2Request;
 import com.yoyuzh.api.v2.shares.ShareV2Response;
 import com.yoyuzh.api.v2.shares.VerifySharePasswordV2Request;
 import com.yoyuzh.auth.User;
+import com.yoyuzh.files.core.FileMetadataResponse;
+import com.yoyuzh.files.core.FileService;
+import com.yoyuzh.files.core.StoredFile;
+import com.yoyuzh.files.core.StoredFileRepository;
 import jakarta.transaction.Transactional;
 import lombok.RequiredArgsConstructor;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
+import org.springframework.http.ResponseEntity;
 import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.stereotype.Service;
 import org.springframework.util.StringUtils;
@@ -85,6 +90,17 @@ public class ShareV2Service {
         return importedFile;
     }
 
+    @Transactional
+    public ResponseEntity<?> downloadSharedFile(String token, String password) {
+        FileShareLink shareLink = getShareLink(token);
+        ensureShareNotExpired(shareLink);
+        ensureDownloadAllowed(shareLink);
+        ensurePasswordAccepted(shareLink, password);
+
+        shareLink.setDownloadCount(shareLink.getDownloadCountOrZero() + 1);
+        return fileService.download(shareLink.getOwner(), shareLink.getFile().getId());
+    }
+
     @Transactional
     public Page<ShareV2Response> listOwnedShares(User user, Pageable pageable) {
         return fileShareLinkRepository.findByOwnerIdOrderByCreatedAtDesc(user.getId(), pageable)
@@ -114,6 +130,18 @@ public class ShareV2Service {
             throw new ApiV2Exception(ApiV2ErrorCode.PERMISSION_DENIED, "import disabled");
         }
 
+        ensureQuotaAvailable(shareLink);
+    }
+
+    private void ensureDownloadAllowed(FileShareLink shareLink) {
+        if (!shareLink.isAllowDownloadEnabled()) {
+            throw new ApiV2Exception(ApiV2ErrorCode.PERMISSION_DENIED, "download disabled");
+        }
+
+        ensureQuotaAvailable(shareLink);
+    }
+
+    private void ensureQuotaAvailable(FileShareLink shareLink) {
         Integer maxDownloads = shareLink.getMaxDownloads();
         if (maxDownloads != null && shareLink.getDownloadCountOrZero() >= maxDownloads) {
             throw new ApiV2Exception(ApiV2ErrorCode.PERMISSION_DENIED, "share quota exceeded");

backend/src/main/java/com/yoyuzh/files/storage/FileContentStorage.java

@@ -48,6 +48,26 @@ public interface FileContentStorage {
 
     void deleteBlob(String objectKey);
 
+    default String createMultipartUpload(String objectKey, String contentType) {
+        throw new UnsupportedOperationException("Multipart upload is not supported by this storage");
+    }
+
+    default PreparedUpload prepareMultipartPartUpload(String objectKey,
+                                                      String uploadId,
+                                                      int partNumber,
+                                                      String contentType,
+                                                      long size) {
+        throw new UnsupportedOperationException("Multipart upload is not supported by this storage");
+    }
+
+    default void completeMultipartUpload(String objectKey, String uploadId, java.util.List<MultipartCompletedPart> parts) {
+        throw new UnsupportedOperationException("Multipart upload is not supported by this storage");
+    }
+
+    default void abortMultipartUpload(String objectKey, String uploadId) {
+        throw new UnsupportedOperationException("Multipart upload is not supported by this storage");
+    }
+
     String createBlobDownloadUrl(String objectKey, String filename);
 
     void createDirectory(Long userId, String logicalPath);

backend/src/main/java/com/yoyuzh/files/storage/MultipartCompletedPart.java

@@ -0,0 +1,7 @@
+package com.yoyuzh.files.storage;
+
+public record MultipartCompletedPart(
+        int partNumber,
+        String etag
+) {
+}

backend/src/main/java/com/yoyuzh/files/storage/S3FileContentStorage.java

@@ -9,22 +9,31 @@ import org.springframework.web.multipart.MultipartFile;
 import software.amazon.awssdk.core.ResponseBytes;
 import software.amazon.awssdk.core.sync.RequestBody;
 import software.amazon.awssdk.http.SdkHttpMethod;
+import software.amazon.awssdk.services.s3.model.AbortMultipartUploadRequest;
+import software.amazon.awssdk.services.s3.model.CompleteMultipartUploadRequest;
+import software.amazon.awssdk.services.s3.model.CompletedMultipartUpload;
+import software.amazon.awssdk.services.s3.model.CompletedPart;
 import software.amazon.awssdk.services.s3.model.CopyObjectRequest;
+import software.amazon.awssdk.services.s3.model.CreateMultipartUploadRequest;
 import software.amazon.awssdk.services.s3.model.DeleteObjectRequest;
 import software.amazon.awssdk.services.s3.model.GetObjectRequest;
 import software.amazon.awssdk.services.s3.model.HeadObjectRequest;
 import software.amazon.awssdk.services.s3.model.NoSuchKeyException;
 import software.amazon.awssdk.services.s3.model.PutObjectRequest;
 import software.amazon.awssdk.services.s3.model.S3Exception;
+import software.amazon.awssdk.services.s3.model.UploadPartRequest;
+import software.amazon.awssdk.services.s3.presigner.model.PresignedUploadPartRequest;
 import software.amazon.awssdk.services.s3.presigner.model.GetObjectPresignRequest;
 import software.amazon.awssdk.services.s3.presigner.model.PresignedGetObjectRequest;
 import software.amazon.awssdk.services.s3.presigner.model.PresignedPutObjectRequest;
 import software.amazon.awssdk.services.s3.presigner.model.PutObjectPresignRequest;
+import software.amazon.awssdk.services.s3.presigner.model.UploadPartPresignRequest;
 
 import java.io.IOException;
 import java.net.URLEncoder;
 import java.nio.charset.StandardCharsets;
 import java.time.Duration;
+import java.util.Comparator;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -160,6 +169,90 @@ public class S3FileContentStorage implements FileContentStorage {
         }
     }
 
+    @Override
+    public String createMultipartUpload(String objectKey, String contentType) {
+        S3FileRuntimeSession session = sessionProvider.currentSession();
+        CreateMultipartUploadRequest.Builder requestBuilder = CreateMultipartUploadRequest.builder()
+                .bucket(session.bucket())
+                .key(normalizeObjectKey(objectKey));
+        if (StringUtils.hasText(contentType)) {
+            requestBuilder.contentType(contentType);
+        }
+        try {
+            return session.s3Client().createMultipartUpload(requestBuilder.build()).uploadId();
+        } catch (S3Exception ex) {
+            throw new BusinessException(ErrorCode.UNKNOWN, "Multipart upload init failed");
+        }
+    }
+
+    @Override
+    public PreparedUpload prepareMultipartPartUpload(String objectKey,
+                                                     String uploadId,
+                                                     int partNumber,
+                                                     String contentType,
+                                                     long size) {
+        S3FileRuntimeSession session = sessionProvider.currentSession();
+        UploadPartRequest uploadPartRequest = UploadPartRequest.builder()
+                .bucket(session.bucket())
+                .key(normalizeObjectKey(objectKey))
+                .uploadId(uploadId)
+                .partNumber(partNumber)
+                .contentLength(size)
+                .build();
+        UploadPartPresignRequest presignRequest = UploadPartPresignRequest.builder()
+                .signatureDuration(Duration.ofSeconds(Math.max(1, properties.getTtlSeconds())))
+                .uploadPartRequest(uploadPartRequest)
+                .build();
+        PresignedUploadPartRequest presignedRequest = session.s3Presigner().presignUploadPart(presignRequest);
+        Map<String, String> headers = flattenSignedHeaders(presignedRequest.signedHeaders());
+        if (StringUtils.hasText(contentType)) {
+            headers.put("Content-Type", contentType);
+        }
+        return new PreparedUpload(
+                true,
+                presignedRequest.url().toString(),
+                resolveUploadMethod(presignedRequest),
+                headers,
+                objectKey
+        );
+    }
+
+    @Override
+    public void completeMultipartUpload(String objectKey, String uploadId, List<MultipartCompletedPart> parts) {
+        S3FileRuntimeSession session = sessionProvider.currentSession();
+        List<CompletedPart> completedParts = parts.stream()
+                .sorted(Comparator.comparingInt(MultipartCompletedPart::partNumber))
+                .map(part -> CompletedPart.builder()
+                        .partNumber(part.partNumber())
+                        .eTag(part.etag())
+                        .build())
+                .toList();
+        try {
+            session.s3Client().completeMultipartUpload(CompleteMultipartUploadRequest.builder()
+                    .bucket(session.bucket())
+                    .key(normalizeObjectKey(objectKey))
+                    .uploadId(uploadId)
+                    .multipartUpload(CompletedMultipartUpload.builder().parts(completedParts).build())
+                    .build());
+        } catch (S3Exception ex) {
+            throw new BusinessException(ErrorCode.UNKNOWN, "Multipart upload complete failed");
+        }
+    }
+
+    @Override
+    public void abortMultipartUpload(String objectKey, String uploadId) {
+        S3FileRuntimeSession session = sessionProvider.currentSession();
+        try {
+            session.s3Client().abortMultipartUpload(AbortMultipartUploadRequest.builder()
+                    .bucket(session.bucket())
+                    .key(normalizeObjectKey(objectKey))
+                    .uploadId(uploadId)
+                    .build());
+        } catch (S3Exception ex) {
+            throw new BusinessException(ErrorCode.UNKNOWN, "Multipart upload abort failed");
+        }
+    }
+
     @Override
     public String createBlobDownloadUrl(String objectKey, String filename) {
         return createDownloadUrl(sessionProvider.currentSession(), normalizeObjectKey(objectKey), filename);
@@ -330,6 +423,13 @@ public class S3FileContentStorage implements FileContentStorage {
         return presignedRequest.httpRequest().method() == SdkHttpMethod.PUT ? "PUT" : "POST";
     }
 
+    private String resolveUploadMethod(PresignedUploadPartRequest presignedRequest) {
+        if (presignedRequest.httpRequest() == null) {
+            return "PUT";
+        }
+        return presignedRequest.httpRequest().method() == SdkHttpMethod.PUT ? "PUT" : presignedRequest.httpRequest().method().name();
+    }
+
     private Map<String, String> resolveUploadHeaders(PresignedPutObjectRequest presignedRequest, String contentType) {
         Map<String, String> headers = flattenSignedHeaders(presignedRequest.signedHeaders());
         if (StringUtils.hasText(contentType)) {

backend/src/main/java/com/yoyuzh/files/tasks/ArchiveBackgroundTaskHandler.java

@@ -0,0 +1,164 @@
+package com.yoyuzh.files.tasks;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.yoyuzh.auth.User;
+import com.yoyuzh.auth.UserRepository;
+import com.yoyuzh.files.core.FileMetadataResponse;
+import com.yoyuzh.files.core.FileService;
+import com.yoyuzh.files.core.StoredFile;
+import com.yoyuzh.files.core.StoredFileRepository;
+import jakarta.transaction.Transactional;
+import org.springframework.stereotype.Component;
+import org.springframework.util.StringUtils;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+@Component
+@Transactional
+public class ArchiveBackgroundTaskHandler implements BackgroundTaskHandler {
+
+    private final StoredFileRepository storedFileRepository;
+    private final UserRepository userRepository;
+    private final FileService fileService;
+    private final ObjectMapper objectMapper;
+
+    public ArchiveBackgroundTaskHandler(StoredFileRepository storedFileRepository,
+                                        UserRepository userRepository,
+                                        FileService fileService,
+                                        ObjectMapper objectMapper) {
+        this.storedFileRepository = storedFileRepository;
+        this.userRepository = userRepository;
+        this.fileService = fileService;
+        this.objectMapper = objectMapper;
+    }
+
+    @Override
+    public boolean supports(BackgroundTaskType type) {
+        return type == BackgroundTaskType.ARCHIVE;
+    }
+
+    @Override
+    public BackgroundTaskHandlerResult handle(BackgroundTask task) {
+        return handle(task, publicStatePatch -> {
+        });
+    }
+
+    @Override
+    public BackgroundTaskHandlerResult handle(BackgroundTask task, BackgroundTaskProgressReporter progressReporter) {
+        Map<String, Object> state = parseState(task.getPrivateStateJson(), task.getPublicStateJson());
+        Long fileId = extractLong(state.get("fileId"));
+        String outputPath = extractText(state.get("outputPath"));
+        String outputFilename = extractText(state.get("outputFilename"));
+        if (fileId == null) {
+            throw new IllegalStateException("archive task missing fileId");
+        }
+        if (!StringUtils.hasText(outputPath) || !StringUtils.hasText(outputFilename)) {
+            throw new IllegalStateException("archive task missing output target");
+        }
+
+        StoredFile source = storedFileRepository.findByIdAndUserIdAndDeletedAtIsNull(fileId, task.getUserId())
+                .orElseThrow(() -> new IllegalStateException("archive task file not found"));
+        User user = userRepository.findById(task.getUserId())
+                .orElseThrow(() -> new IllegalStateException("archive task user not found"));
+
+        FileService.ArchiveSourceSummary summary = fileService.summarizeArchiveSource(source);
+        progressReporter.report(progressPatch(0, summary.fileCount(), 0, summary.directoryCount()));
+        byte[] archiveBytes = fileService.buildArchiveBytes(source, progress ->
+                progressReporter.report(progressPatch(
+                        progress.processedFileCount(),
+                        progress.totalFileCount(),
+                        progress.processedDirectoryCount(),
+                        progress.totalDirectoryCount()
+                )));
+        FileMetadataResponse archivedFile = fileService.importExternalFile(
+                user,
+                outputPath,
+                outputFilename,
+                "application/zip",
+                archiveBytes.length,
+                archiveBytes
+        );
+
+        Map<String, Object> publicStatePatch = new LinkedHashMap<>();
+        publicStatePatch.put("worker", "archive");
+        publicStatePatch.put("archivedFileId", archivedFile.id());
+        publicStatePatch.put("archivedFilename", archivedFile.filename());
+        publicStatePatch.put("archivedPath", archivedFile.path());
+        publicStatePatch.put("archiveSize", archiveBytes.length);
+        publicStatePatch.putAll(progressPatch(
+                summary.fileCount(),
+                summary.fileCount(),
+                summary.directoryCount(),
+                summary.directoryCount()
+        ));
+        return new BackgroundTaskHandlerResult(publicStatePatch);
+    }
+
+    private Map<String, Object> progressPatch(int processedFileCount,
+                                              int totalFileCount,
+                                              int processedDirectoryCount,
+                                              int totalDirectoryCount) {
+        Map<String, Object> patch = new LinkedHashMap<>();
+        patch.put("processedFileCount", processedFileCount);
+        patch.put("totalFileCount", totalFileCount);
+        patch.put("processedDirectoryCount", processedDirectoryCount);
+        patch.put("totalDirectoryCount", totalDirectoryCount);
+        patch.put("progressPercent", calculateProgressPercent(
+                processedFileCount,
+                totalFileCount,
+                processedDirectoryCount,
+                totalDirectoryCount
+        ));
+        return patch;
+    }
+
+    private int calculateProgressPercent(int processedFileCount,
+                                         int totalFileCount,
+                                         int processedDirectoryCount,
+                                         int totalDirectoryCount) {
+        int total = Math.max(0, totalFileCount) + Math.max(0, totalDirectoryCount);
+        int processed = Math.max(0, processedFileCount) + Math.max(0, processedDirectoryCount);
+        if (total <= 0) {
+            return 100;
+        }
+        return Math.min(100, (int) Math.floor((processed * 100.0d) / total));
+    }
+
+    private Map<String, Object> parseState(String privateStateJson, String publicStateJson) {
+        Map<String, Object> state = new LinkedHashMap<>(parseJsonObject(publicStateJson));
+        state.putAll(parseJsonObject(privateStateJson));
+        return state;
+    }
+
+    private Map<String, Object> parseJsonObject(String json) {
+        if (!StringUtils.hasText(json)) {
+            return Map.of();
+        }
+        try {
+            return objectMapper.readValue(json, new TypeReference<LinkedHashMap<String, Object>>() {
+            });
+        } catch (JsonProcessingException ex) {
+            throw new IllegalStateException("archive task state is invalid", ex);
+        }
+    }
+
+    private Long extractLong(Object value) {
+        if (value instanceof Number number) {
+            return number.longValue();
+        }
+        if (value instanceof String text && StringUtils.hasText(text)) {
+            return Long.parseLong(text.trim());
+        }
+        return null;
+    }
+
+    private String extractText(Object value) {
+        if (value instanceof String text && StringUtils.hasText(text)) {
+            return text.trim();
+        }
+        return null;
+    }
+}

backend/src/main/java/com/yoyuzh/files/tasks/BackgroundTask.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.tasks;
 
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
@@ -18,6 +18,7 @@ import java.time.LocalDateTime;
 @Table(name = "portal_background_task", indexes = {
         @Index(name = "idx_background_task_user_created_at", columnList = "user_id,created_at"),
         @Index(name = "idx_background_task_status_created_at", columnList = "status,created_at"),
+        @Index(name = "idx_background_task_status_lease_expires_at", columnList = "status,lease_expires_at"),
         @Index(name = "idx_background_task_correlation_id", columnList = "correlation_id")
 })
 public class BackgroundTask {
@@ -49,6 +50,24 @@ public class BackgroundTask {
     @Column(name = "error_message", length = 512)
     private String errorMessage;
 
+    @Column(name = "attempt_count", nullable = false)
+    private Integer attemptCount;
+
+    @Column(name = "max_attempts", nullable = false)
+    private Integer maxAttempts;
+
+    @Column(name = "next_run_at")
+    private LocalDateTime nextRunAt;
+
+    @Column(name = "lease_owner", length = 128)
+    private String leaseOwner;
+
+    @Column(name = "lease_expires_at")
+    private LocalDateTime leaseExpiresAt;
+
+    @Column(name = "heartbeat_at")
+    private LocalDateTime heartbeatAt;
+
     @Column(name = "created_at", nullable = false)
     private LocalDateTime createdAt;
 
@@ -70,6 +89,12 @@ public class BackgroundTask {
         if (status == null) {
             status = BackgroundTaskStatus.QUEUED;
         }
+        if (attemptCount == null) {
+            attemptCount = 0;
+        }
+        if (maxAttempts == null) {
+            maxAttempts = 1;
+        }
         if (publicStateJson == null) {
             publicStateJson = "{}";
         }
@@ -147,6 +172,54 @@ public class BackgroundTask {
         this.errorMessage = errorMessage;
     }
 
+    public Integer getAttemptCount() {
+        return attemptCount;
+    }
+
+    public void setAttemptCount(Integer attemptCount) {
+        this.attemptCount = attemptCount;
+    }
+
+    public Integer getMaxAttempts() {
+        return maxAttempts;
+    }
+
+    public void setMaxAttempts(Integer maxAttempts) {
+        this.maxAttempts = maxAttempts;
+    }
+
+    public LocalDateTime getNextRunAt() {
+        return nextRunAt;
+    }
+
+    public void setNextRunAt(LocalDateTime nextRunAt) {
+        this.nextRunAt = nextRunAt;
+    }
+
+    public String getLeaseOwner() {
+        return leaseOwner;
+    }
+
+    public void setLeaseOwner(String leaseOwner) {
+        this.leaseOwner = leaseOwner;
+    }
+
+    public LocalDateTime getLeaseExpiresAt() {
+        return leaseExpiresAt;
+    }
+
+    public void setLeaseExpiresAt(LocalDateTime leaseExpiresAt) {
+        this.leaseExpiresAt = leaseExpiresAt;
+    }
+
+    public LocalDateTime getHeartbeatAt() {
+        return heartbeatAt;
+    }
+
+    public void setHeartbeatAt(LocalDateTime heartbeatAt) {
+        this.heartbeatAt = heartbeatAt;
+    }
+
     public LocalDateTime getCreatedAt() {
         return createdAt;
     }

backend/src/main/java/com/yoyuzh/files/tasks/BackgroundTaskFailureCategory.java

@@ -0,0 +1,19 @@
+package com.yoyuzh.files.tasks;
+
+public enum BackgroundTaskFailureCategory {
+    UNSUPPORTED_INPUT(false),
+    DATA_STATE(false),
+    TRANSIENT_INFRASTRUCTURE(true),
+    RATE_LIMITED(true),
+    UNKNOWN(true);
+
+    private final boolean retryable;
+
+    BackgroundTaskFailureCategory(boolean retryable) {
+        this.retryable = retryable;
+    }
+
+    public boolean isRetryable() {
+        return retryable;
+    }
+}

backend/src/main/java/com/yoyuzh/files/tasks/BackgroundTaskHandler.java

@@ -0,0 +1,12 @@
+package com.yoyuzh.files.tasks;
+
+public interface BackgroundTaskHandler {
+
+    boolean supports(BackgroundTaskType type);
+
+    BackgroundTaskHandlerResult handle(BackgroundTask task);
+
+    default BackgroundTaskHandlerResult handle(BackgroundTask task, BackgroundTaskProgressReporter progressReporter) {
+        return handle(task);
+    }
+}

backend/src/main/java/com/yoyuzh/files/tasks/BackgroundTaskHandlerResult.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.tasks;
 
 import java.util.Map;
 

backend/src/main/java/com/yoyuzh/files/tasks/BackgroundTaskLeaseLostException.java

@@ -0,0 +1,8 @@
+package com.yoyuzh.files.tasks;
+
+class BackgroundTaskLeaseLostException extends RuntimeException {
+
+    BackgroundTaskLeaseLostException(Long taskId, String workerOwner) {
+        super("background task lease lost: taskId=" + taskId + ", workerOwner=" + workerOwner);
+    }
+}

backend/src/main/java/com/yoyuzh/files/tasks/BackgroundTaskProgressReporter.java

@@ -0,0 +1,9 @@
+package com.yoyuzh.files.tasks;
+
+import java.util.Map;
+
+@FunctionalInterface
+public interface BackgroundTaskProgressReporter {
+
+    void report(Map<String, Object> publicStatePatch);
+}

backend/src/main/java/com/yoyuzh/files/tasks/BackgroundTaskRepository.java

@@ -0,0 +1,103 @@
+package com.yoyuzh.files.tasks;
+
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.Pageable;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Modifying;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
+
+import java.time.LocalDateTime;
+import java.util.List;
+import java.util.Optional;
+
+public interface BackgroundTaskRepository extends JpaRepository<BackgroundTask, Long> {
+
+    Page<BackgroundTask> findByUserIdOrderByCreatedAtDesc(Long userId, Pageable pageable);
+
+    Optional<BackgroundTask> findByIdAndUserId(Long id, Long userId);
+
+    List<BackgroundTask> findByStatusOrderByCreatedAtAsc(BackgroundTaskStatus status, Pageable pageable);
+
+    List<BackgroundTask> findByStatusOrderByUpdatedAtAsc(BackgroundTaskStatus status);
+
+    @Query("""
+            select task.id from BackgroundTask task
+            where task.status = :status
+              and (task.nextRunAt is null or task.nextRunAt <= :now)
+            order by coalesce(task.nextRunAt, task.createdAt) asc, task.createdAt asc
+            """)
+    List<Long> findReadyTaskIdsByStatusOrder(@Param("status") BackgroundTaskStatus status,
+                                             @Param("now") LocalDateTime now,
+                                             Pageable pageable);
+
+    @Modifying
+    @Query("""
+            update BackgroundTask task
+            set task.status = :runningStatus,
+                task.errorMessage = null,
+                task.nextRunAt = null,
+                task.attemptCount = task.attemptCount + 1,
+                task.leaseOwner = :leaseOwner,
+                task.leaseExpiresAt = :leaseExpiresAt,
+                task.heartbeatAt = :heartbeatAt,
+                task.updatedAt = :updatedAt
+            where task.id = :id
+              and task.status = :queuedStatus
+            """)
+    int claimQueuedTask(@Param("id") Long id,
+                        @Param("queuedStatus") BackgroundTaskStatus queuedStatus,
+                        @Param("runningStatus") BackgroundTaskStatus runningStatus,
+                        @Param("leaseOwner") String leaseOwner,
+                        @Param("leaseExpiresAt") LocalDateTime leaseExpiresAt,
+                        @Param("heartbeatAt") LocalDateTime heartbeatAt,
+                        @Param("updatedAt") LocalDateTime updatedAt);
+
+    @Query("""
+            select task.id from BackgroundTask task
+            where task.status = :status
+              and (task.leaseExpiresAt is null or task.leaseExpiresAt <= :now)
+            order by coalesce(task.leaseExpiresAt, task.updatedAt, task.createdAt) asc
+            """)
+    List<Long> findExpiredRunningTaskIds(@Param("status") BackgroundTaskStatus status,
+                                         @Param("now") LocalDateTime now,
+                                         Pageable pageable);
+
+    @Modifying
+    @Query("""
+            update BackgroundTask task
+            set task.status = :queuedStatus,
+                task.errorMessage = null,
+                task.finishedAt = null,
+                task.nextRunAt = null,
+                task.leaseOwner = null,
+                task.leaseExpiresAt = null,
+                task.heartbeatAt = null,
+                task.updatedAt = :updatedAt
+            where task.id = :id
+              and task.status = :runningStatus
+              and (task.leaseExpiresAt is null or task.leaseExpiresAt <= :now)
+            """)
+    int requeueExpiredRunningTask(@Param("id") Long id,
+                                  @Param("runningStatus") BackgroundTaskStatus runningStatus,
+                                  @Param("queuedStatus") BackgroundTaskStatus queuedStatus,
+                                  @Param("now") LocalDateTime now,
+                                  @Param("updatedAt") LocalDateTime updatedAt);
+
+    @Modifying
+    @Query("""
+            update BackgroundTask task
+            set task.leaseExpiresAt = :leaseExpiresAt,
+                task.heartbeatAt = :heartbeatAt,
+                task.updatedAt = :updatedAt
+            where task.id = :id
+              and task.status = :runningStatus
+              and task.leaseOwner = :leaseOwner
+            """)
+    int refreshRunningTaskLease(@Param("id") Long id,
+                                @Param("runningStatus") BackgroundTaskStatus runningStatus,
+                                @Param("leaseOwner") String leaseOwner,
+                                @Param("leaseExpiresAt") LocalDateTime leaseExpiresAt,
+                                @Param("heartbeatAt") LocalDateTime heartbeatAt,
+                                @Param("updatedAt") LocalDateTime updatedAt);
+}

backend/src/main/java/com/yoyuzh/files/tasks/BackgroundTaskService.java

@@ -0,0 +1,683 @@
+package com.yoyuzh.files.tasks;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.yoyuzh.api.v2.ApiV2ErrorCode;
+import com.yoyuzh.api.v2.ApiV2Exception;
+import com.yoyuzh.auth.User;
+import com.yoyuzh.files.core.StoredFile;
+import com.yoyuzh.files.core.StoredFileRepository;
+import jakarta.transaction.Transactional;
+import lombok.RequiredArgsConstructor;
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Pageable;
+import org.springframework.stereotype.Service;
+import org.springframework.util.StringUtils;
+
+import java.time.LocalDateTime;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Optional;
+import java.util.UUID;
+
+@Service
+@RequiredArgsConstructor
+public class BackgroundTaskService {
+
+    static final String STATE_PHASE_KEY = "phase";
+    static final String STATE_ATTEMPT_COUNT_KEY = "attemptCount";
+    static final String STATE_MAX_ATTEMPTS_KEY = "maxAttempts";
+    static final String STATE_RETRY_SCHEDULED_KEY = "retryScheduled";
+    static final String STATE_NEXT_RETRY_AT_KEY = "nextRetryAt";
+    static final String STATE_RETRY_DELAY_SECONDS_KEY = "retryDelaySeconds";
+    static final String STATE_LAST_FAILURE_MESSAGE_KEY = "lastFailureMessage";
+    static final String STATE_LAST_FAILURE_AT_KEY = "lastFailureAt";
+    static final String STATE_FAILURE_CATEGORY_KEY = "failureCategory";
+    static final String STATE_WORKER_OWNER_KEY = "workerOwner";
+    static final String STATE_HEARTBEAT_AT_KEY = "heartbeatAt";
+    static final String STATE_LEASE_EXPIRES_AT_KEY = "leaseExpiresAt";
+    static final String STATE_STARTED_AT_KEY = "startedAt";
+
+    private static final List<String> ZIP_COMPATIBLE_EXTENSIONS = List.of(".zip", ".jar", ".war");
+    private static final List<String> MEDIA_EXTENSIONS = List.of(
+            ".jpg", ".jpeg", ".png", ".gif", ".webp", ".bmp", ".svg",
+            ".mp4", ".mov", ".mkv", ".webm", ".avi",
+            ".mp3", ".wav", ".flac", ".aac", ".ogg", ".m4a"
+    );
+    private static final List<String> RETRY_TRANSIENT_STATE_KEYS = List.of(
+            STATE_RETRY_SCHEDULED_KEY,
+            STATE_NEXT_RETRY_AT_KEY,
+            STATE_RETRY_DELAY_SECONDS_KEY,
+            STATE_LAST_FAILURE_MESSAGE_KEY,
+            STATE_LAST_FAILURE_AT_KEY,
+            STATE_FAILURE_CATEGORY_KEY
+    );
+    private static final List<String> RUNNING_TRANSIENT_STATE_KEYS = List.of(
+            STATE_WORKER_OWNER_KEY,
+            STATE_LEASE_EXPIRES_AT_KEY
+    );
+    private static final int EXPIRED_RUNNING_TASK_BATCH_SIZE = 100;
+
+    private final BackgroundTaskRepository backgroundTaskRepository;
+    private final StoredFileRepository storedFileRepository;
+    private final ObjectMapper objectMapper;
+
+    @Transactional
+    public BackgroundTask createQueuedFileTask(User user,
+                                               BackgroundTaskType type,
+                                               Long fileId,
+                                               String requestedPath,
+                                               String correlationId) {
+        StoredFile file = storedFileRepository.findByIdAndUserIdAndDeletedAtIsNull(fileId, user.getId())
+                .orElseThrow(() -> new ApiV2Exception(ApiV2ErrorCode.FILE_NOT_FOUND, "file not found"));
+        String logicalPath = buildLogicalPath(file);
+        if (!logicalPath.equals(normalizeLogicalPath(requestedPath))) {
+            throw new ApiV2Exception(ApiV2ErrorCode.BAD_REQUEST, "task path does not match file path");
+        }
+        validateTaskTarget(type, file);
+
+        Map<String, Object> publicState = fileState(file, logicalPath);
+        Map<String, Object> privateState = new LinkedHashMap<>(publicState);
+        privateState.put("taskType", type.name());
+        if (type == BackgroundTaskType.ARCHIVE) {
+            String outputPath = file.getPath();
+            String outputFilename = file.getFilename() + ".zip";
+            publicState.put("outputPath", outputPath);
+            publicState.put("outputFilename", outputFilename);
+            privateState.put("outputPath", outputPath);
+            privateState.put("outputFilename", outputFilename);
+        } else if (type == BackgroundTaskType.EXTRACT) {
+            String outputPath = file.getPath();
+            String outputDirectoryName = deriveExtractOutputDirectoryName(file.getFilename());
+            publicState.put("outputPath", outputPath);
+            publicState.put("outputDirectoryName", outputDirectoryName);
+            privateState.put("outputPath", outputPath);
+            privateState.put("outputDirectoryName", outputDirectoryName);
+        }
+        return createQueuedTask(user, type, publicState, privateState, correlationId);
+    }
+
+    @Transactional
+    public BackgroundTask createQueuedTask(User user,
+                                           BackgroundTaskType type,
+                                           Map<String, Object> publicState,
+                                           Map<String, Object> privateState,
+                                           String correlationId) {
+        BackgroundTask task = new BackgroundTask();
+        task.setUserId(user.getId());
+        task.setType(type);
+        task.setStatus(BackgroundTaskStatus.QUEUED);
+        task.setAttemptCount(0);
+        task.setMaxAttempts(resolveMaxAttempts(type));
+        task.setNextRunAt(null);
+        Map<String, Object> nextPublicState = new LinkedHashMap<>(publicState == null ? Map.of() : publicState);
+        nextPublicState.put(STATE_PHASE_KEY, "queued");
+        nextPublicState.putAll(retryStatePatch(task.getAttemptCount(), task.getMaxAttempts()));
+        task.setPublicStateJson(toJson(nextPublicState));
+        task.setPrivateStateJson(toJson(privateState));
+        task.setCorrelationId(normalizeCorrelationId(correlationId));
+        return backgroundTaskRepository.save(task);
+    }
+
+    public Page<BackgroundTask> listOwnedTasks(User user, Pageable pageable) {
+        return backgroundTaskRepository.findByUserIdOrderByCreatedAtDesc(user.getId(), pageable);
+    }
+
+    public BackgroundTask getOwnedTask(User user, Long id) {
+        return backgroundTaskRepository.findByIdAndUserId(id, user.getId())
+                .orElseThrow(() -> new ApiV2Exception(ApiV2ErrorCode.FILE_NOT_FOUND, "task not found"));
+    }
+
+    @Transactional
+    public BackgroundTask cancelOwnedTask(User user, Long id) {
+        BackgroundTask task = getOwnedTask(user, id);
+        if (task.isTerminal()) {
+            return task;
+        }
+
+        if (task.getStatus() == BackgroundTaskStatus.QUEUED || task.getStatus() == BackgroundTaskStatus.RUNNING) {
+            task.setStatus(BackgroundTaskStatus.CANCELLED);
+            task.setNextRunAt(null);
+            clearLease(task);
+            task.setPublicStateJson(mergePublicStateJson(
+                    task.getPublicStateJson(),
+                    Map.of(
+                            STATE_PHASE_KEY, "cancelled",
+                            STATE_ATTEMPT_COUNT_KEY, task.getAttemptCount(),
+                            STATE_MAX_ATTEMPTS_KEY, task.getMaxAttempts(),
+                            STATE_HEARTBEAT_AT_KEY, LocalDateTime.now().toString()
+                    ),
+                    removableStateKeys(RETRY_TRANSIENT_STATE_KEYS, RUNNING_TRANSIENT_STATE_KEYS)
+            ));
+            task.setFinishedAt(LocalDateTime.now());
+            task.setErrorMessage(null);
+            return backgroundTaskRepository.save(task);
+        }
+
+        return task;
+    }
+
+    @Transactional
+    public BackgroundTask retryOwnedTask(User user, Long id) {
+        BackgroundTask task = getOwnedTask(user, id);
+        if (task.getStatus() != BackgroundTaskStatus.FAILED) {
+            throw new ApiV2Exception(ApiV2ErrorCode.BAD_REQUEST, "only failed tasks can be retried");
+        }
+
+        task.setAttemptCount(0);
+        task.setNextRunAt(null);
+        clearLease(task);
+        task.setPublicStateJson(resetPublicStateForRetry(task.getPrivateStateJson(), task.getAttemptCount(), task.getMaxAttempts()));
+        task.setStatus(BackgroundTaskStatus.QUEUED);
+        task.setFinishedAt(null);
+        task.setErrorMessage(null);
+        return backgroundTaskRepository.save(task);
+    }
+
+    @Transactional
+    public BackgroundTask markRunning(User user, Long id) {
+        BackgroundTask task = getOwnedTask(user, id);
+        if (task.isTerminal()) {
+            return task;
+        }
+        task.setStatus(BackgroundTaskStatus.RUNNING);
+        task.setPublicStateJson(mergePublicStateJson(
+                task.getPublicStateJson(),
+                Map.of(
+                        STATE_PHASE_KEY, "running",
+                        STATE_ATTEMPT_COUNT_KEY, task.getAttemptCount(),
+                        STATE_MAX_ATTEMPTS_KEY, task.getMaxAttempts()
+                ),
+                List.of(STATE_RETRY_SCHEDULED_KEY, STATE_NEXT_RETRY_AT_KEY)
+        ));
+        return backgroundTaskRepository.save(task);
+    }
+
+    @Transactional
+    public BackgroundTask markCompleted(User user, Long id) {
+        BackgroundTask task = getOwnedTask(user, id);
+        if (task.isTerminal()) {
+            return task;
+        }
+        task.setStatus(BackgroundTaskStatus.COMPLETED);
+        task.setNextRunAt(null);
+        clearLease(task);
+        task.setPublicStateJson(mergePublicStateJson(
+                task.getPublicStateJson(),
+                Map.of(
+                        STATE_PHASE_KEY, "completed",
+                        STATE_ATTEMPT_COUNT_KEY, task.getAttemptCount(),
+                        STATE_MAX_ATTEMPTS_KEY, task.getMaxAttempts(),
+                        STATE_HEARTBEAT_AT_KEY, LocalDateTime.now().toString()
+                ),
+                removableStateKeys(RETRY_TRANSIENT_STATE_KEYS, RUNNING_TRANSIENT_STATE_KEYS)
+        ));
+        task.setFinishedAt(LocalDateTime.now());
+        task.setErrorMessage(null);
+        return backgroundTaskRepository.save(task);
+    }
+
+    @Transactional
+    public BackgroundTask markFailed(User user, Long id, String errorMessage) {
+        BackgroundTask task = getOwnedTask(user, id);
+        if (task.isTerminal()) {
+            return task;
+        }
+        task.setStatus(BackgroundTaskStatus.FAILED);
+        task.setNextRunAt(null);
+        clearLease(task);
+        task.setPublicStateJson(mergePublicStateJson(
+                task.getPublicStateJson(),
+                Map.of(
+                        STATE_PHASE_KEY, "failed",
+                        STATE_ATTEMPT_COUNT_KEY, task.getAttemptCount(),
+                        STATE_MAX_ATTEMPTS_KEY, task.getMaxAttempts(),
+                        STATE_LAST_FAILURE_MESSAGE_KEY, StringUtils.hasText(errorMessage) ? errorMessage.trim() : "task failed",
+                        STATE_LAST_FAILURE_AT_KEY, LocalDateTime.now().toString(),
+                        STATE_FAILURE_CATEGORY_KEY, BackgroundTaskFailureCategory.UNKNOWN.name(),
+                        STATE_HEARTBEAT_AT_KEY, LocalDateTime.now().toString()
+                ),
+                removableStateKeys(List.of(STATE_RETRY_SCHEDULED_KEY, STATE_NEXT_RETRY_AT_KEY), RUNNING_TRANSIENT_STATE_KEYS)
+        ));
+        task.setFinishedAt(LocalDateTime.now());
+        task.setErrorMessage(StringUtils.hasText(errorMessage) ? errorMessage.trim() : "task failed");
+        return backgroundTaskRepository.save(task);
+    }
+
+    @Transactional
+    public int requeueExpiredRunningTasks() {
+        LocalDateTime now = LocalDateTime.now();
+        int recovered = 0;
+        for (Long taskId : backgroundTaskRepository.findExpiredRunningTaskIds(
+                BackgroundTaskStatus.RUNNING,
+                now,
+                PageRequest.of(0, EXPIRED_RUNNING_TASK_BATCH_SIZE)
+        )) {
+            int requeued = backgroundTaskRepository.requeueExpiredRunningTask(
+                    taskId,
+                    BackgroundTaskStatus.RUNNING,
+                    BackgroundTaskStatus.QUEUED,
+                    now,
+                    now
+            );
+            if (requeued != 1) {
+                continue;
+            }
+            BackgroundTask task = backgroundTaskRepository.findById(taskId)
+                    .orElseThrow(() -> new ApiV2Exception(ApiV2ErrorCode.FILE_NOT_FOUND, "task not found"));
+            resetTaskToQueued(task);
+            backgroundTaskRepository.save(task);
+            recovered += 1;
+        }
+        return recovered;
+    }
+
+    public List<Long> findQueuedTaskIds(int limit) {
+        if (limit <= 0) {
+            return List.of();
+        }
+
+        return backgroundTaskRepository.findReadyTaskIdsByStatusOrder(
+                BackgroundTaskStatus.QUEUED,
+                LocalDateTime.now(),
+                PageRequest.of(0, limit)
+        );
+    }
+
+    @Transactional
+    public Optional<BackgroundTask> claimQueuedTask(Long id, String workerOwner, long leaseDurationSeconds) {
+        LocalDateTime now = LocalDateTime.now();
+        LocalDateTime leaseExpiresAt = now.plusSeconds(Math.max(30L, leaseDurationSeconds));
+        int claimed = backgroundTaskRepository.claimQueuedTask(
+                id,
+                BackgroundTaskStatus.QUEUED,
+                BackgroundTaskStatus.RUNNING,
+                workerOwner,
+                leaseExpiresAt,
+                now,
+                now
+        );
+        if (claimed != 1) {
+            return Optional.empty();
+        }
+        Optional<BackgroundTask> task = backgroundTaskRepository.findById(id);
+        task.ifPresent(claimedTask -> {
+            claimedTask.setLeaseOwner(workerOwner);
+            claimedTask.setLeaseExpiresAt(leaseExpiresAt);
+            claimedTask.setHeartbeatAt(now);
+            claimedTask.setPublicStateJson(mergePublicStateJson(
+                    claimedTask.getPublicStateJson(),
+                    runningStatePatch(claimedTask, workerOwner, now, leaseExpiresAt, true),
+                    RETRY_TRANSIENT_STATE_KEYS
+            ));
+        });
+        task.ifPresent(backgroundTaskRepository::save);
+        return task;
+    }
+
+    @Transactional
+    public BackgroundTask markWorkerTaskProgress(Long id,
+                                                 String workerOwner,
+                                                 Map<String, Object> publicStatePatch,
+                                                 long leaseDurationSeconds) {
+        LeaseTouch leaseTouch = refreshLease(id, workerOwner, leaseDurationSeconds);
+        BackgroundTask task = backgroundTaskRepository.findById(id)
+                .orElseThrow(() -> new ApiV2Exception(ApiV2ErrorCode.FILE_NOT_FOUND, "task not found"));
+        task.setLeaseOwner(workerOwner);
+        task.setLeaseExpiresAt(leaseTouch.leaseExpiresAt());
+        task.setHeartbeatAt(leaseTouch.now());
+        Map<String, Object> nextPatch = new LinkedHashMap<>(runningStatePatch(
+                task,
+                workerOwner,
+                leaseTouch.now(),
+                leaseTouch.leaseExpiresAt(),
+                false
+        ));
+        if (publicStatePatch != null) {
+            nextPatch.putAll(publicStatePatch);
+        }
+        task.setPublicStateJson(mergePublicStateJson(task.getPublicStateJson(), nextPatch));
+        return backgroundTaskRepository.save(task);
+    }
+
+    @Transactional
+    public BackgroundTask markWorkerTaskCompleted(Long id,
+                                                  String workerOwner,
+                                                  Map<String, Object> publicStatePatch,
+                                                  long leaseDurationSeconds) {
+        LeaseTouch leaseTouch = refreshLease(id, workerOwner, leaseDurationSeconds);
+        BackgroundTask task = backgroundTaskRepository.findById(id)
+                .orElseThrow(() -> new ApiV2Exception(ApiV2ErrorCode.FILE_NOT_FOUND, "task not found"));
+        Map<String, Object> nextPatch = new LinkedHashMap<>(publicStatePatch == null ? Map.of() : publicStatePatch);
+        nextPatch.put(STATE_PHASE_KEY, "completed");
+        nextPatch.put(STATE_ATTEMPT_COUNT_KEY, task.getAttemptCount());
+        nextPatch.put(STATE_MAX_ATTEMPTS_KEY, task.getMaxAttempts());
+        nextPatch.put(STATE_HEARTBEAT_AT_KEY, leaseTouch.now().toString());
+        task.setPublicStateJson(mergePublicStateJson(
+                task.getPublicStateJson(),
+                nextPatch,
+                removableStateKeys(RETRY_TRANSIENT_STATE_KEYS, RUNNING_TRANSIENT_STATE_KEYS)
+        ));
+        task.setStatus(BackgroundTaskStatus.COMPLETED);
+        task.setNextRunAt(null);
+        clearLease(task);
+        task.setFinishedAt(LocalDateTime.now());
+        task.setErrorMessage(null);
+        return backgroundTaskRepository.save(task);
+    }
+
+    @Transactional
+    public BackgroundTask markWorkerTaskFailed(Long id,
+                                               String workerOwner,
+                                               String errorMessage,
+                                               BackgroundTaskFailureCategory failureCategory,
+                                               long leaseDurationSeconds) {
+        LeaseTouch leaseTouch = refreshLease(id, workerOwner, leaseDurationSeconds);
+        BackgroundTask task = backgroundTaskRepository.findById(id)
+                .orElseThrow(() -> new ApiV2Exception(ApiV2ErrorCode.FILE_NOT_FOUND, "task not found"));
+        String normalizedErrorMessage = StringUtils.hasText(errorMessage) ? errorMessage.trim() : "task failed";
+        LocalDateTime now = leaseTouch.now();
+        if (failureCategory.isRetryable() && hasRemainingAttempts(task)) {
+            long retryDelaySeconds = resolveRetryDelaySeconds(task.getType(), failureCategory, task.getAttemptCount());
+            LocalDateTime nextRunAt = now.plusSeconds(retryDelaySeconds);
+            task.setStatus(BackgroundTaskStatus.QUEUED);
+            task.setNextRunAt(nextRunAt);
+            clearLease(task);
+            task.setFinishedAt(null);
+            task.setErrorMessage(null);
+            task.setPublicStateJson(mergePublicStateJson(
+                    task.getPublicStateJson(),
+                    Map.of(
+                            STATE_PHASE_KEY, "queued",
+                            STATE_ATTEMPT_COUNT_KEY, task.getAttemptCount(),
+                            STATE_MAX_ATTEMPTS_KEY, task.getMaxAttempts(),
+                            STATE_RETRY_SCHEDULED_KEY, true,
+                            STATE_NEXT_RETRY_AT_KEY, nextRunAt.toString(),
+                            STATE_RETRY_DELAY_SECONDS_KEY, retryDelaySeconds,
+                            STATE_LAST_FAILURE_MESSAGE_KEY, normalizedErrorMessage,
+                            STATE_LAST_FAILURE_AT_KEY, now.toString(),
+                            STATE_FAILURE_CATEGORY_KEY, failureCategory.name(),
+                            STATE_HEARTBEAT_AT_KEY, now.toString()
+                    ),
+                    RUNNING_TRANSIENT_STATE_KEYS
+            ));
+            return backgroundTaskRepository.save(task);
+        }
+
+        task.setNextRunAt(null);
+        clearLease(task);
+        task.setPublicStateJson(mergePublicStateJson(
+                task.getPublicStateJson(),
+                Map.of(
+                        STATE_PHASE_KEY, "failed",
+                        STATE_ATTEMPT_COUNT_KEY, task.getAttemptCount(),
+                        STATE_MAX_ATTEMPTS_KEY, task.getMaxAttempts(),
+                        STATE_LAST_FAILURE_MESSAGE_KEY, normalizedErrorMessage,
+                        STATE_LAST_FAILURE_AT_KEY, now.toString(),
+                        STATE_FAILURE_CATEGORY_KEY, failureCategory.name(),
+                        STATE_HEARTBEAT_AT_KEY, now.toString()
+                ),
+                removableStateKeys(List.of(STATE_RETRY_SCHEDULED_KEY, STATE_NEXT_RETRY_AT_KEY, STATE_RETRY_DELAY_SECONDS_KEY), RUNNING_TRANSIENT_STATE_KEYS)
+        ));
+        task.setStatus(BackgroundTaskStatus.FAILED);
+        task.setFinishedAt(now);
+        task.setErrorMessage(normalizedErrorMessage);
+        return backgroundTaskRepository.save(task);
+    }
+
+    private String normalizeCorrelationId(String correlationId) {
+        if (StringUtils.hasText(correlationId)) {
+            return correlationId.trim();
+        }
+        return UUID.randomUUID().toString().replace("-", "");
+    }
+
+    private void validateTaskTarget(BackgroundTaskType type, StoredFile file) {
+        if (type == BackgroundTaskType.ARCHIVE) {
+            return;
+        }
+        if (file.isDirectory()) {
+            throw new ApiV2Exception(ApiV2ErrorCode.BAD_REQUEST, "task target type is not supported");
+        }
+        if (type == BackgroundTaskType.EXTRACT && !isZipCompatibleArchive(file)) {
+            throw new ApiV2Exception(ApiV2ErrorCode.BAD_REQUEST, "extract task only supports zip-compatible archives");
+        }
+        if (type == BackgroundTaskType.MEDIA_META && !isMediaLike(file)) {
+            throw new ApiV2Exception(ApiV2ErrorCode.BAD_REQUEST, "media metadata task only supports media files");
+        }
+    }
+
+    private Map<String, Object> fileState(StoredFile file, String logicalPath) {
+        Map<String, Object> state = new LinkedHashMap<>();
+        state.put("fileId", file.getId());
+        state.put("path", logicalPath);
+        state.put("filename", file.getFilename());
+        state.put("directory", file.isDirectory());
+        state.put("contentType", file.getContentType());
+        state.put("size", file.getSize());
+        return state;
+    }
+
+    private boolean isZipCompatibleArchive(StoredFile file) {
+        String contentType = normalizeContentType(file.getContentType());
+        if (contentType.contains("zip") || contentType.contains("java-archive")) {
+            return true;
+        }
+        return hasExtension(file.getFilename(), ZIP_COMPATIBLE_EXTENSIONS);
+    }
+
+    private boolean isMediaLike(StoredFile file) {
+        String contentType = normalizeContentType(file.getContentType());
+        if (contentType.startsWith("image/") || contentType.startsWith("video/") || contentType.startsWith("audio/")) {
+            return true;
+        }
+        return hasExtension(file.getFilename(), MEDIA_EXTENSIONS);
+    }
+
+    private String deriveExtractOutputDirectoryName(String filename) {
+        if (!StringUtils.hasText(filename)) {
+            return "extracted";
+        }
+        String trimmed = filename.trim();
+        String lower = trimmed.toLowerCase(Locale.ROOT);
+        for (String extension : ZIP_COMPATIBLE_EXTENSIONS) {
+            if (lower.endsWith(extension) && trimmed.length() > extension.length()) {
+                return trimmed.substring(0, trimmed.length() - extension.length());
+            }
+        }
+        int lastDot = trimmed.lastIndexOf('.');
+        if (lastDot > 0) {
+            return trimmed.substring(0, lastDot);
+        }
+        return trimmed;
+    }
+
+    private boolean hasExtension(String filename, List<String> extensions) {
+        if (!StringUtils.hasText(filename)) {
+            return false;
+        }
+        String normalized = filename.toLowerCase(Locale.ROOT);
+        return extensions.stream().anyMatch(normalized::endsWith);
+    }
+
+    private String normalizeContentType(String contentType) {
+        if (!StringUtils.hasText(contentType)) {
+            return "";
+        }
+        return contentType.trim().toLowerCase(Locale.ROOT);
+    }
+
+    private String buildLogicalPath(StoredFile file) {
+        String parent = normalizeLogicalPath(file.getPath());
+        if ("/".equals(parent)) {
+            return "/" + file.getFilename();
+        }
+        return parent + "/" + file.getFilename();
+    }
+
+    private String normalizeLogicalPath(String path) {
+        if (!StringUtils.hasText(path)) {
+            return "/";
+        }
+        String normalized = path.trim().replace('\\', '/');
+        while (normalized.contains("//")) {
+            normalized = normalized.replace("//", "/");
+        }
+        if (!normalized.startsWith("/")) {
+            normalized = "/" + normalized;
+        }
+        while (normalized.length() > 1 && normalized.endsWith("/")) {
+            normalized = normalized.substring(0, normalized.length() - 1);
+        }
+        return normalized;
+    }
+
+    private String toJson(Map<String, Object> value) {
+        Map<String, Object> safeValue = value == null ? new LinkedHashMap<>() : new LinkedHashMap<>(value);
+        try {
+            return objectMapper.writeValueAsString(safeValue);
+        } catch (JsonProcessingException ex) {
+            throw new IllegalStateException("Failed to serialize background task state", ex);
+        }
+    }
+
+    private Map<String, Object> parseJsonObject(String value) {
+        if (!StringUtils.hasText(value)) {
+            return new LinkedHashMap<>();
+        }
+
+        try {
+            return objectMapper.readValue(value, new TypeReference<LinkedHashMap<String, Object>>() {
+            });
+        } catch (JsonProcessingException ex) {
+            throw new IllegalStateException("Failed to parse background task state", ex);
+        }
+    }
+
+    private String mergePublicStateJson(String currentValue, Map<String, Object> patch) {
+        return mergePublicStateJson(currentValue, patch, List.of());
+    }
+
+    private String mergePublicStateJson(String currentValue, Map<String, Object> patch, List<String> keysToRemove) {
+        Map<String, Object> nextPublicState = parseJsonObject(currentValue);
+        if (keysToRemove != null) {
+            keysToRemove.forEach(nextPublicState::remove);
+        }
+        if (patch != null) {
+            nextPublicState.putAll(patch);
+        }
+        return toJson(nextPublicState);
+    }
+
+    private String resetPublicStateForRetry(String privateStateJson, int attemptCount, int maxAttempts) {
+        Map<String, Object> nextPublicState = parseJsonObject(privateStateJson);
+        nextPublicState.remove("taskType");
+        nextPublicState.put(STATE_PHASE_KEY, "queued");
+        nextPublicState.putAll(retryStatePatch(attemptCount, maxAttempts));
+        return toJson(nextPublicState);
+    }
+
+    private void resetTaskToQueued(BackgroundTask task) {
+        task.setNextRunAt(null);
+        clearLease(task);
+        task.setPublicStateJson(resetPublicStateForRetry(task.getPrivateStateJson(), task.getAttemptCount(), task.getMaxAttempts()));
+        task.setStatus(BackgroundTaskStatus.QUEUED);
+        task.setFinishedAt(null);
+        task.setErrorMessage(null);
+    }
+
+    private int resolveMaxAttempts(BackgroundTaskType type) {
+        return switch (type) {
+            case ARCHIVE -> 4;
+            case EXTRACT -> 3;
+            case MEDIA_META -> 2;
+            default -> 1;
+        };
+    }
+
+    private Map<String, Object> retryStatePatch(int attemptCount, int maxAttempts) {
+        Map<String, Object> patch = new LinkedHashMap<>();
+        patch.put(STATE_ATTEMPT_COUNT_KEY, attemptCount);
+        patch.put(STATE_MAX_ATTEMPTS_KEY, maxAttempts);
+        return patch;
+    }
+
+    private boolean hasRemainingAttempts(BackgroundTask task) {
+        return task.getAttemptCount() != null
+                && task.getMaxAttempts() != null
+                && task.getAttemptCount() < task.getMaxAttempts();
+    }
+
+    private long resolveRetryDelaySeconds(BackgroundTaskType type,
+                                          BackgroundTaskFailureCategory failureCategory,
+                                          Integer attemptCount) {
+        int safeAttemptCount = attemptCount == null ? 1 : Math.max(1, attemptCount);
+        long baseDelaySeconds = switch (type) {
+            case ARCHIVE -> 30L;
+            case EXTRACT -> 45L;
+            case MEDIA_META -> 15L;
+            default -> 30L;
+        };
+        if (failureCategory == BackgroundTaskFailureCategory.RATE_LIMITED) {
+            baseDelaySeconds *= 4L;
+        } else if (failureCategory == BackgroundTaskFailureCategory.UNKNOWN) {
+            baseDelaySeconds *= 2L;
+        }
+        long delay = baseDelaySeconds * (1L << Math.min(safeAttemptCount - 1, 2));
+        return Math.min(delay, baseDelaySeconds * 4L);
+    }
+
+    private LeaseTouch refreshLease(Long id, String workerOwner, long leaseDurationSeconds) {
+        LocalDateTime now = LocalDateTime.now();
+        LocalDateTime leaseExpiresAt = now.plusSeconds(Math.max(30L, leaseDurationSeconds));
+        int refreshed = backgroundTaskRepository.refreshRunningTaskLease(
+                id,
+                BackgroundTaskStatus.RUNNING,
+                workerOwner,
+                leaseExpiresAt,
+                now,
+                now
+        );
+        if (refreshed != 1) {
+            throw new BackgroundTaskLeaseLostException(id, workerOwner);
+        }
+        return new LeaseTouch(now, leaseExpiresAt);
+    }
+
+    private Map<String, Object> runningStatePatch(BackgroundTask task,
+                                                  String workerOwner,
+                                                  LocalDateTime heartbeatAt,
+                                                  LocalDateTime leaseExpiresAt,
+                                                  boolean includeStartedAt) {
+        Map<String, Object> patch = new LinkedHashMap<>();
+        patch.put(STATE_PHASE_KEY, "running");
+        patch.put(STATE_ATTEMPT_COUNT_KEY, task.getAttemptCount());
+        patch.put(STATE_MAX_ATTEMPTS_KEY, task.getMaxAttempts());
+        patch.put(STATE_WORKER_OWNER_KEY, workerOwner);
+        patch.put(STATE_HEARTBEAT_AT_KEY, heartbeatAt.toString());
+        patch.put(STATE_LEASE_EXPIRES_AT_KEY, leaseExpiresAt.toString());
+        if (includeStartedAt) {
+            patch.put(STATE_STARTED_AT_KEY, heartbeatAt.toString());
+        }
+        return patch;
+    }
+
+    private List<String> removableStateKeys(List<String> primary, List<String> secondary) {
+        List<String> keys = new java.util.ArrayList<>(primary);
+        keys.addAll(secondary);
+        return keys;
+    }
+
+    private void clearLease(BackgroundTask task) {
+        task.setLeaseOwner(null);
+        task.setLeaseExpiresAt(null);
+        task.setHeartbeatAt(null);
+    }
+
+    private record LeaseTouch(LocalDateTime now, LocalDateTime leaseExpiresAt) {
+    }
+}

backend/src/main/java/com/yoyuzh/files/tasks/BackgroundTaskStartupRecovery.java

@@ -0,0 +1,23 @@
+package com.yoyuzh.files.tasks;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.boot.context.event.ApplicationReadyEvent;
+import org.springframework.context.event.EventListener;
+import org.springframework.stereotype.Component;
+
+@Component
+@RequiredArgsConstructor
+@Slf4j
+public class BackgroundTaskStartupRecovery {
+
+    private final BackgroundTaskService backgroundTaskService;
+
+    @EventListener(ApplicationReadyEvent.class)
+    public void recoverOnStartup() {
+        int recovered = backgroundTaskService.requeueExpiredRunningTasks();
+        if (recovered > 0) {
+            log.warn("Recovered {} expired RUNNING background task leases back to QUEUED on startup", recovered);
+        }
+    }
+}

backend/src/main/java/com/yoyuzh/files/tasks/BackgroundTaskStatus.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.tasks;
 
 public enum BackgroundTaskStatus {
     QUEUED,

backend/src/main/java/com/yoyuzh/files/tasks/BackgroundTaskType.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.tasks;
 
 public enum BackgroundTaskType {
     ARCHIVE,

backend/src/main/java/com/yoyuzh/files/tasks/BackgroundTaskWorker.java

@@ -0,0 +1,167 @@
+package com.yoyuzh.files.tasks;
+
+import com.yoyuzh.common.BusinessException;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.stereotype.Component;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.net.ConnectException;
+import java.net.SocketTimeoutException;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+import java.util.concurrent.TimeoutException;
+
+@Component
+public class BackgroundTaskWorker {
+
+    private static final int DEFAULT_BATCH_SIZE = 5;
+    private static final long DEFAULT_LEASE_DURATION_SECONDS = 120L;
+
+    private final BackgroundTaskService backgroundTaskService;
+    private final List<BackgroundTaskHandler> handlers;
+    private final String workerOwner;
+
+    public BackgroundTaskWorker(BackgroundTaskService backgroundTaskService,
+                                List<BackgroundTaskHandler> handlers) {
+        this.backgroundTaskService = backgroundTaskService;
+        this.handlers = List.copyOf(handlers);
+        this.workerOwner = UUID.randomUUID().toString().replace("-", "");
+    }
+
+    @Scheduled(
+            fixedDelayString = "${app.background-tasks.worker.fixed-delay-ms:30000}",
+            initialDelayString = "${app.background-tasks.worker.initial-delay-ms:30000}"
+    )
+    public void runScheduledBatch() {
+        processQueuedTasks(DEFAULT_BATCH_SIZE);
+    }
+
+    public int processQueuedTasks(int maxTasks) {
+        backgroundTaskService.requeueExpiredRunningTasks();
+        int processedCount = 0;
+        for (Long taskId : backgroundTaskService.findQueuedTaskIds(maxTasks)) {
+            var claimedTask = backgroundTaskService.claimQueuedTask(taskId, workerOwner, DEFAULT_LEASE_DURATION_SECONDS);
+            if (claimedTask.isEmpty()) {
+                continue;
+            }
+
+            execute(claimedTask.get());
+            processedCount += 1;
+        }
+        return processedCount;
+    }
+
+    private void execute(BackgroundTask task) {
+        try {
+            backgroundTaskService.markWorkerTaskProgress(
+                    task.getId(),
+                    workerOwner,
+                    Map.of(BackgroundTaskService.STATE_PHASE_KEY, resolveRunningPhase(task.getType())),
+                    DEFAULT_LEASE_DURATION_SECONDS
+            );
+            BackgroundTaskHandler handler = findHandler(task);
+            BackgroundTaskHandlerResult result = handler.handle(task, publicStatePatch ->
+                    backgroundTaskService.markWorkerTaskProgress(
+                            task.getId(),
+                            workerOwner,
+                            publicStatePatch,
+                            DEFAULT_LEASE_DURATION_SECONDS
+                    ));
+            backgroundTaskService.markWorkerTaskCompleted(
+                    task.getId(),
+                    workerOwner,
+                    result.publicStatePatch(),
+                    DEFAULT_LEASE_DURATION_SECONDS
+            );
+        } catch (BackgroundTaskLeaseLostException ignored) {
+            // Another worker reclaimed the task after this worker stopped heartbeating.
+        } catch (Exception ex) {
+            String message = ex.getMessage() == null ? ex.getClass().getSimpleName() : ex.getMessage();
+            try {
+                backgroundTaskService.markWorkerTaskFailed(
+                        task.getId(),
+                        workerOwner,
+                        message,
+                        classifyFailure(ex),
+                        DEFAULT_LEASE_DURATION_SECONDS
+                );
+            } catch (BackgroundTaskLeaseLostException ignored) {
+                // Lease already moved to another worker; keep current worker from overwriting state.
+            }
+        }
+    }
+
+    private String resolveRunningPhase(BackgroundTaskType type) {
+        return switch (type) {
+            case ARCHIVE -> "archiving";
+            case EXTRACT -> "extracting";
+            case MEDIA_META -> "extracting-metadata";
+            default -> "running";
+        };
+    }
+
+    private BackgroundTaskHandler findHandler(BackgroundTask task) {
+        return handlers.stream()
+                .filter(handler -> handler.supports(task.getType()))
+                .findFirst()
+                .orElseThrow(() -> new IllegalStateException("No background task handler for " + task.getType()));
+    }
+
+    private BackgroundTaskFailureCategory classifyFailure(Throwable throwable) {
+        if (containsRateLimitSignal(throwable)) {
+            return BackgroundTaskFailureCategory.RATE_LIMITED;
+        }
+        Throwable current = throwable;
+        while (current != null) {
+            if (current instanceof BusinessException || current instanceof IllegalArgumentException) {
+                return BackgroundTaskFailureCategory.UNSUPPORTED_INPUT;
+            }
+            if (current instanceof IllegalStateException) {
+                return BackgroundTaskFailureCategory.DATA_STATE;
+            }
+            if (current instanceof SocketTimeoutException
+                    || current instanceof TimeoutException
+                    || current instanceof ConnectException
+                    || current instanceof IOException
+                    || current instanceof UncheckedIOException) {
+                return BackgroundTaskFailureCategory.TRANSIENT_INFRASTRUCTURE;
+            }
+            current = current.getCause();
+        }
+        if (containsTransientInfrastructureSignal(throwable)) {
+            return BackgroundTaskFailureCategory.TRANSIENT_INFRASTRUCTURE;
+        }
+        return BackgroundTaskFailureCategory.UNKNOWN;
+    }
+
+    private boolean containsRateLimitSignal(Throwable throwable) {
+        String message = collectMessages(throwable);
+        return message.contains("429")
+                || message.contains("too many requests")
+                || message.contains("rate limit")
+                || message.contains("throttle");
+    }
+
+    private boolean containsTransientInfrastructureSignal(Throwable throwable) {
+        String message = collectMessages(throwable);
+        return message.contains("timeout")
+                || message.contains("temporarily unavailable")
+                || message.contains("connection reset")
+                || message.contains("broken pipe")
+                || message.contains("connection refused");
+    }
+
+    private String collectMessages(Throwable throwable) {
+        StringBuilder builder = new StringBuilder();
+        Throwable current = throwable;
+        while (current != null) {
+            if (current.getMessage() != null) {
+                builder.append(current.getMessage().toLowerCase()).append(' ');
+            }
+            current = current.getCause();
+        }
+        return builder.toString();
+    }
+}

backend/src/main/java/com/yoyuzh/files/tasks/ExtractBackgroundTaskHandler.java

@@ -0,0 +1,356 @@
+package com.yoyuzh.files.tasks;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.yoyuzh.auth.User;
+import com.yoyuzh.auth.UserRepository;
+import com.yoyuzh.common.BusinessException;
+import com.yoyuzh.files.core.FileService;
+import com.yoyuzh.files.core.StoredFile;
+import com.yoyuzh.files.core.StoredFileRepository;
+import jakarta.transaction.Transactional;
+import org.springframework.stereotype.Component;
+import org.springframework.util.StringUtils;
+
+import java.net.URLConnection;
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+@Component
+@Transactional
+public class ExtractBackgroundTaskHandler implements BackgroundTaskHandler {
+
+    private final StoredFileRepository storedFileRepository;
+    private final UserRepository userRepository;
+    private final FileService fileService;
+    private final ObjectMapper objectMapper;
+
+    public ExtractBackgroundTaskHandler(StoredFileRepository storedFileRepository,
+                                        UserRepository userRepository,
+                                        FileService fileService,
+                                        ObjectMapper objectMapper) {
+        this.storedFileRepository = storedFileRepository;
+        this.userRepository = userRepository;
+        this.fileService = fileService;
+        this.objectMapper = objectMapper;
+    }
+
+    @Override
+    public boolean supports(BackgroundTaskType type) {
+        return type == BackgroundTaskType.EXTRACT;
+    }
+
+    @Override
+    public BackgroundTaskHandlerResult handle(BackgroundTask task) {
+        return handle(task, publicStatePatch -> {
+        });
+    }
+
+    @Override
+    public BackgroundTaskHandlerResult handle(BackgroundTask task, BackgroundTaskProgressReporter progressReporter) {
+        Map<String, Object> state = parseState(task.getPrivateStateJson(), task.getPublicStateJson());
+        Long fileId = extractLong(state.get("fileId"));
+        String outputPath = extractText(state.get("outputPath"));
+        String outputDirectoryName = extractText(state.get("outputDirectoryName"));
+        if (fileId == null) {
+            throw new IllegalStateException("extract task missing fileId");
+        }
+        if (!StringUtils.hasText(outputPath) || !StringUtils.hasText(outputDirectoryName)) {
+            throw new IllegalStateException("extract task missing output target");
+        }
+
+        StoredFile archive = storedFileRepository.findByIdAndUserIdAndDeletedAtIsNull(fileId, task.getUserId())
+                .orElseThrow(() -> new IllegalStateException("extract task file not found"));
+        if (archive.isDirectory()) {
+            throw new IllegalStateException("extract task only supports files");
+        }
+        User user = userRepository.findById(task.getUserId())
+                .orElseThrow(() -> new IllegalStateException("extract task user not found"));
+
+        ExtractPlan plan = parseArchivePlan(archive, outputPath, outputDirectoryName);
+        progressReporter.report(progressPatch(0, plan.files().size(), 0, plan.directories().size()));
+        executePlan(user, plan, progressReporter);
+
+        Map<String, Object> publicStatePatch = new LinkedHashMap<>();
+        publicStatePatch.put("worker", "extract");
+        publicStatePatch.put("extractedPath", plan.extractedPath());
+        publicStatePatch.put("extractedFileCount", plan.files().size());
+        publicStatePatch.put("extractedDirectoryCount", plan.directories().size());
+        publicStatePatch.putAll(progressPatch(
+                plan.files().size(),
+                plan.files().size(),
+                plan.directories().size(),
+                plan.directories().size()
+        ));
+        return new BackgroundTaskHandlerResult(publicStatePatch);
+    }
+
+    private void executePlan(User user, ExtractPlan plan, BackgroundTaskProgressReporter progressReporter) {
+        fileService.importExternalFilesAtomically(
+                user,
+                plan.directories(),
+                plan.files().stream()
+                        .map(file -> new FileService.ExternalFileImport(
+                                file.parentPath(),
+                                file.filename(),
+                                file.contentType(),
+                                file.content()
+                        ))
+                        .toList(),
+                progress -> progressReporter.report(progressPatch(
+                        progress.processedFileCount(),
+                        progress.totalFileCount(),
+                        progress.processedDirectoryCount(),
+                        progress.totalDirectoryCount()
+                ))
+        );
+    }
+
+    private Map<String, Object> progressPatch(int processedFileCount,
+                                              int totalFileCount,
+                                              int processedDirectoryCount,
+                                              int totalDirectoryCount) {
+        Map<String, Object> patch = new LinkedHashMap<>();
+        patch.put("processedFileCount", processedFileCount);
+        patch.put("totalFileCount", totalFileCount);
+        patch.put("processedDirectoryCount", processedDirectoryCount);
+        patch.put("totalDirectoryCount", totalDirectoryCount);
+        patch.put("progressPercent", calculateProgressPercent(
+                processedFileCount,
+                totalFileCount,
+                processedDirectoryCount,
+                totalDirectoryCount
+        ));
+        return patch;
+    }
+
+    private int calculateProgressPercent(int processedFileCount,
+                                         int totalFileCount,
+                                         int processedDirectoryCount,
+                                         int totalDirectoryCount) {
+        int total = Math.max(0, totalFileCount) + Math.max(0, totalDirectoryCount);
+        int processed = Math.max(0, processedFileCount) + Math.max(0, processedDirectoryCount);
+        if (total <= 0) {
+            return 100;
+        }
+        return Math.min(100, (int) Math.floor((processed * 100.0d) / total));
+    }
+
+    private ExtractPlan parseArchivePlan(StoredFile archive, String outputPath, String outputDirectoryName) {
+        FileService.ZipCompatibleArchive zipArchive;
+        try {
+            zipArchive = fileService.readZipCompatibleArchive(archive);
+        } catch (BusinessException ex) {
+            throw new IllegalStateException("extract task only supports zip-compatible archives", ex);
+        }
+
+        List<ZipItem> items = zipArchive.entries().stream()
+                .map(entry -> toZipItem(entry, zipArchive.commonRootDirectoryName()))
+                .filter(item -> StringUtils.hasText(item.path()))
+                .toList();
+        if (items.isEmpty()) {
+            throw new IllegalStateException("extract task archive is empty");
+        }
+
+        String normalizedOutputPath = normalizeDirectoryPath(outputPath);
+        if (shouldExtractSingleFileToParent(items, outputDirectoryName)) {
+            ZipItem fileItem = items.get(0);
+            return new ExtractPlan(
+                    List.of(),
+                    List.of(new ExtractedFile(
+                            normalizedOutputPath,
+                            outputDirectoryName,
+                            fileItem.contentType(),
+                            fileItem.content()
+                    )),
+                    normalizedOutputPath
+            );
+        }
+
+        String rootPath = joinPath(normalizedOutputPath, outputDirectoryName);
+        LinkedHashSet<String> directories = new LinkedHashSet<>();
+        directories.add(rootPath);
+        List<ExtractedFile> files = new ArrayList<>();
+        for (ZipItem item : items) {
+            if (item.directory()) {
+                directories.add(joinPath(rootPath, trimTrailingSlash(item.path())));
+                continue;
+            }
+            String relativeParent = extractParentPath(item.path());
+            String targetParent = StringUtils.hasText(relativeParent) ? joinPath(rootPath, relativeParent) : rootPath;
+            collectParentDirectories(directories, rootPath, relativeParent);
+            files.add(new ExtractedFile(
+                    targetParent,
+                    extractLeafName(item.path()),
+                    item.contentType(),
+                    item.content()
+            ));
+        }
+
+        return new ExtractPlan(List.copyOf(directories), List.copyOf(files), rootPath);
+    }
+
+    private void collectParentDirectories(LinkedHashSet<String> directories, String rootPath, String relativeParent) {
+        if (!StringUtils.hasText(relativeParent)) {
+            return;
+        }
+        String current = "";
+        for (String segment : relativeParent.split("/")) {
+            current = StringUtils.hasText(current) ? current + "/" + segment : segment;
+            directories.add(joinPath(rootPath, current));
+        }
+    }
+
+    private boolean shouldExtractSingleFileToParent(List<ZipItem> items, String outputDirectoryName) {
+        if (items.size() != 1) {
+            return false;
+        }
+        ZipItem item = items.get(0);
+        return !item.directory()
+                && !item.path().contains("/")
+                && outputDirectoryName.equals(item.path());
+    }
+
+    private ZipItem toZipItem(FileService.ZipCompatibleArchiveEntry entry, String commonRootDirectoryName) {
+        String path = stripCommonRootDirectory(entry.relativePath(), commonRootDirectoryName);
+        return new ZipItem(path, entry.directory(), entry.content(), guessContentType(path));
+    }
+
+    private String stripCommonRootDirectory(String relativePath, String commonRootDirectoryName) {
+        if (!StringUtils.hasText(relativePath) || !StringUtils.hasText(commonRootDirectoryName)) {
+            return relativePath;
+        }
+        String prefix = commonRootDirectoryName + "/";
+        if (relativePath.equals(commonRootDirectoryName)) {
+            return "";
+        }
+        if (relativePath.startsWith(prefix)) {
+            return relativePath.substring(prefix.length());
+        }
+        return relativePath;
+    }
+
+    private Map<String, Object> parseState(String privateStateJson, String publicStateJson) {
+        Map<String, Object> state = new LinkedHashMap<>(parseJsonObject(publicStateJson));
+        state.putAll(parseJsonObject(privateStateJson));
+        return state;
+    }
+
+    private Map<String, Object> parseJsonObject(String json) {
+        if (!StringUtils.hasText(json)) {
+            return Map.of();
+        }
+        try {
+            return objectMapper.readValue(json, new TypeReference<LinkedHashMap<String, Object>>() {
+            });
+        } catch (JsonProcessingException ex) {
+            throw new IllegalStateException("extract task state is invalid", ex);
+        }
+    }
+
+    private Long extractLong(Object value) {
+        if (value instanceof Number number) {
+            return number.longValue();
+        }
+        if (value instanceof String text && StringUtils.hasText(text)) {
+            return Long.parseLong(text.trim());
+        }
+        return null;
+    }
+
+    private String extractText(Object value) {
+        if (value instanceof String text && StringUtils.hasText(text)) {
+            return text.trim();
+        }
+        return null;
+    }
+
+    private String normalizeDirectoryPath(String path) {
+        if (!StringUtils.hasText(path)) {
+            return "/";
+        }
+        String normalized = path.trim().replace('\\', '/');
+        while (normalized.contains("//")) {
+            normalized = normalized.replace("//", "/");
+        }
+        if (!normalized.startsWith("/")) {
+            normalized = "/" + normalized;
+        }
+        while (normalized.length() > 1 && normalized.endsWith("/")) {
+            normalized = normalized.substring(0, normalized.length() - 1);
+        }
+        return normalized;
+    }
+
+    private String joinPath(String parent, String leaf) {
+        String normalizedParent = normalizeDirectoryPath(parent);
+        String normalizedLeaf = trimSlashes(leaf);
+        if (!StringUtils.hasText(normalizedLeaf)) {
+            return normalizedParent;
+        }
+        if ("/".equals(normalizedParent)) {
+            return "/" + normalizedLeaf;
+        }
+        return normalizedParent + "/" + normalizedLeaf;
+    }
+
+    private String trimSlashes(String value) {
+        String normalized = value == null ? "" : value.trim().replace('\\', '/');
+        while (normalized.startsWith("/")) {
+            normalized = normalized.substring(1);
+        }
+        while (normalized.endsWith("/")) {
+            normalized = normalized.substring(0, normalized.length() - 1);
+        }
+        return normalized;
+    }
+
+    private String trimTrailingSlash(String value) {
+        if (value == null) {
+            return "";
+        }
+        String normalized = value;
+        while (normalized.endsWith("/")) {
+            normalized = normalized.substring(0, normalized.length() - 1);
+        }
+        return normalized;
+    }
+
+    private String extractParentPath(String path) {
+        int separator = path.lastIndexOf('/');
+        if (separator < 0) {
+            return "";
+        }
+        return path.substring(0, separator);
+    }
+
+    private String extractLeafName(String path) {
+        int separator = path.lastIndexOf('/');
+        if (separator < 0) {
+            return path;
+        }
+        return path.substring(separator + 1);
+    }
+
+    private String guessContentType(String entryPath) {
+        String contentType = URLConnection.guessContentTypeFromName(entryPath);
+        if (StringUtils.hasText(contentType)) {
+            return contentType;
+        }
+        return "application/octet-stream";
+    }
+
+    private record ZipItem(String path, boolean directory, byte[] content, String contentType) {
+    }
+
+    private record ExtractedFile(String parentPath, String filename, String contentType, byte[] content) {
+    }
+
+    private record ExtractPlan(List<String> directories, List<ExtractedFile> files, String extractedPath) {
+    }
+}

backend/src/main/java/com/yoyuzh/files/tasks/MediaMetadataBackgroundTaskHandler.java

@@ -1,8 +1,13 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.tasks;
 
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.yoyuzh.files.core.FileBlob;
+import com.yoyuzh.files.core.StoredFile;
+import com.yoyuzh.files.core.StoredFileRepository;
+import com.yoyuzh.files.search.FileMetadata;
+import com.yoyuzh.files.search.FileMetadataRepository;
 import com.yoyuzh.files.storage.FileContentStorage;
 import jakarta.transaction.Transactional;
 import org.springframework.stereotype.Component;
@@ -48,6 +53,12 @@ public class MediaMetadataBackgroundTaskHandler implements BackgroundTaskHandler
 
     @Override
     public BackgroundTaskHandlerResult handle(BackgroundTask task) {
+        return handle(task, publicStatePatch -> {
+        });
+    }
+
+    @Override
+    public BackgroundTaskHandlerResult handle(BackgroundTask task, BackgroundTaskProgressReporter progressReporter) {
         Long fileId = readFileId(task);
         StoredFile file = storedFileRepository.findByIdAndUserIdAndDeletedAtIsNull(fileId, task.getUserId())
                 .orElseThrow(() -> new IllegalStateException("media metadata task file not found"));
@@ -62,6 +73,7 @@ public class MediaMetadataBackgroundTaskHandler implements BackgroundTaskHandler
 
         String contentType = firstText(file.getContentType(), blob.getContentType());
         long size = firstLong(file.getSize(), blob.getSize());
+        progressReporter.report(Map.of("metadataStage", "loading-content"));
         byte[] content = Optional.ofNullable(fileContentStorage.readBlob(blob.getObjectKey()))
                 .orElseThrow(() -> new IllegalStateException("media metadata task requires blob content"));
 
@@ -75,6 +87,7 @@ public class MediaMetadataBackgroundTaskHandler implements BackgroundTaskHandler
         upsertMetadata(file, MEDIA_SIZE, String.valueOf(size));
 
         try {
+            progressReporter.report(Map.of("metadataStage", "reading-image"));
             BufferedImage image = ImageIO.read(new ByteArrayInputStream(content));
             if (image != null) {
                 upsertMetadata(file, MEDIA_WIDTH, String.valueOf(image.getWidth()));
@@ -86,6 +99,7 @@ public class MediaMetadataBackgroundTaskHandler implements BackgroundTaskHandler
             throw new IllegalStateException("media metadata task failed to read image dimensions", ex);
         }
 
+        publicStatePatch.put("metadataStage", "completed");
         return new BackgroundTaskHandlerResult(publicStatePatch);
     }
 

backend/src/main/java/com/yoyuzh/files/tasks/NoopBackgroundTaskHandler.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.tasks;
 
 import org.springframework.stereotype.Component;
 
@@ -9,10 +9,7 @@ import java.util.Set;
 @Component
 public class NoopBackgroundTaskHandler implements BackgroundTaskHandler {
 
-    private static final Set<BackgroundTaskType> SUPPORTED_TYPES = Set.of(
-            BackgroundTaskType.ARCHIVE,
-            BackgroundTaskType.EXTRACT
-    );
+    private static final Set<BackgroundTaskType> SUPPORTED_TYPES = Set.of();
 
     @Override
     public boolean supports(BackgroundTaskType type) {

backend/src/main/java/com/yoyuzh/files/upload/CompleteUploadRequest.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.upload;
 
 import jakarta.validation.constraints.Min;
 import jakarta.validation.constraints.NotBlank;

backend/src/main/java/com/yoyuzh/files/upload/InitiateUploadRequest.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.upload;
 
 import jakarta.validation.constraints.Min;
 import jakarta.validation.constraints.NotBlank;

backend/src/main/java/com/yoyuzh/files/upload/InitiateUploadResponse.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.upload;
 
 import java.util.Map;
 

backend/src/main/java/com/yoyuzh/files/upload/UploadSession.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.upload;
 
 import com.yoyuzh.auth.User;
 import jakarta.persistence.Column;
@@ -55,6 +55,9 @@ public class UploadSession {
     @Column(name = "object_key", nullable = false, length = 512)
     private String objectKey;
 
+    @Column(name = "multipart_upload_id", length = 255)
+    private String multipartUploadId;
+
     @Column(name = "storage_policy_id")
     private Long storagePolicyId;
 
@@ -163,6 +166,14 @@ public class UploadSession {
         this.objectKey = objectKey;
     }
 
+    public String getMultipartUploadId() {
+        return multipartUploadId;
+    }
+
+    public void setMultipartUploadId(String multipartUploadId) {
+        this.multipartUploadId = multipartUploadId;
+    }
+
     public Long getStoragePolicyId() {
         return storagePolicyId;
     }

backend/src/main/java/com/yoyuzh/files/upload/UploadSessionCreateCommand.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.upload;
 
 public record UploadSessionCreateCommand(
         String path,

backend/src/main/java/com/yoyuzh/files/upload/UploadSessionPartCommand.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.upload;
 
 public record UploadSessionPartCommand(
         String etag,

backend/src/main/java/com/yoyuzh/files/upload/UploadSessionRepository.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.upload;
 
 import org.springframework.data.jpa.repository.JpaRepository;
 

backend/src/main/java/com/yoyuzh/files/upload/UploadSessionService.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.upload;
 
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -6,7 +6,13 @@ import com.yoyuzh.auth.User;
 import com.yoyuzh.common.BusinessException;
 import com.yoyuzh.common.ErrorCode;
 import com.yoyuzh.config.FileStorageProperties;
+import com.yoyuzh.files.core.FileService;
+import com.yoyuzh.files.core.StoredFileRepository;
+import com.yoyuzh.files.policy.StoragePolicy;
+import com.yoyuzh.files.policy.StoragePolicyService;
 import com.yoyuzh.files.storage.FileContentStorage;
+import com.yoyuzh.files.storage.MultipartCompletedPart;
+import com.yoyuzh.files.storage.PreparedUpload;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.scheduling.annotation.Scheduled;
 import org.springframework.stereotype.Service;
@@ -82,7 +88,8 @@ public class UploadSessionService {
         session.setContentType(command.contentType());
         session.setSize(command.size());
         session.setObjectKey(createBlobObjectKey());
-        session.setStoragePolicyId(storagePolicyService.ensureDefaultPolicy().getId());
+        StoragePolicy policy = storagePolicyService.ensureDefaultPolicy();
+        session.setStoragePolicyId(policy.getId());
         session.setChunkSize(DEFAULT_CHUNK_SIZE);
         session.setChunkCount(calculateChunkCount(command.size(), DEFAULT_CHUNK_SIZE));
         session.setUploadedPartsJson("[]");
@@ -91,6 +98,9 @@ public class UploadSessionService {
         session.setCreatedAt(now);
         session.setUpdatedAt(now);
         session.setExpiresAt(now.plusHours(SESSION_TTL_HOURS));
+        if (storagePolicyService.readCapabilities(policy).multipartUpload()) {
+            session.setMultipartUploadId(fileContentStorage.createMultipartUpload(session.getObjectKey(), session.getContentType()));
+        }
         return uploadSessionRepository.save(session);
     }
 
@@ -111,6 +121,26 @@ public class UploadSessionService {
         return uploadSessionRepository.save(session);
     }
 
+    @Transactional(readOnly = true)
+    public PreparedUpload prepareOwnedPartUpload(User user, String sessionId, int partIndex) {
+        UploadSession session = getOwnedSession(user, sessionId);
+        LocalDateTime now = LocalDateTime.ofInstant(clock.instant(), clock.getZone());
+        ensureSessionCanReceivePart(session, now);
+        if (!StringUtils.hasText(session.getMultipartUploadId())) {
+            throw new BusinessException(ErrorCode.UNKNOWN, "上传会话未启用 multipart");
+        }
+        if (partIndex < 0 || partIndex >= session.getChunkCount()) {
+            throw new BusinessException(ErrorCode.UNKNOWN, "分片序号不合法");
+        }
+        return fileContentStorage.prepareMultipartPartUpload(
+                session.getObjectKey(),
+                session.getMultipartUploadId(),
+                partIndex + 1,
+                session.getContentType(),
+                resolveChunkSize(session, partIndex)
+        );
+    }
+
     @Transactional
     public UploadSession recordUploadedPart(User user,
                                             String sessionId,
@@ -164,6 +194,13 @@ public class UploadSessionService {
         uploadSessionRepository.save(session);
 
         try {
+            if (StringUtils.hasText(session.getMultipartUploadId())) {
+                fileContentStorage.completeMultipartUpload(
+                        session.getObjectKey(),
+                        session.getMultipartUploadId(),
+                        toCompletedParts(session)
+                );
+            }
             fileService.completeUpload(user, new CompleteUploadRequest(
                     session.getTargetPath(),
                     session.getFilename(),
@@ -192,7 +229,11 @@ public class UploadSessionService {
         );
         for (UploadSession session : expiredSessions) {
             try {
-                fileContentStorage.deleteBlob(session.getObjectKey());
+                if (StringUtils.hasText(session.getMultipartUploadId())) {
+                    fileContentStorage.abortMultipartUpload(session.getObjectKey(), session.getMultipartUploadId());
+                } else {
+                    fileContentStorage.deleteBlob(session.getObjectKey());
+                }
             } catch (RuntimeException ignored) {
                 // Expiration is authoritative in the database even if remote object cleanup fails.
             }
@@ -253,6 +294,41 @@ public class UploadSessionService {
         }
     }
 
+    private List<MultipartCompletedPart> toCompletedParts(UploadSession session) {
+        List<UploadedPart> uploadedParts = readUploadedParts(session).stream()
+                .sorted(Comparator.comparingInt(UploadedPart::partIndex))
+                .toList();
+        if (uploadedParts.size() != session.getChunkCount()) {
+            throw new BusinessException(ErrorCode.UNKNOWN, "上传分片不完整");
+        }
+        for (int expectedIndex = 0; expectedIndex < session.getChunkCount(); expectedIndex++) {
+            UploadedPart part = uploadedParts.get(expectedIndex);
+            if (part.partIndex() != expectedIndex) {
+                throw new BusinessException(ErrorCode.UNKNOWN, "上传分片不完整");
+            }
+            if (!StringUtils.hasText(part.etag())) {
+                throw new BusinessException(ErrorCode.UNKNOWN, "上传分片标识缺失");
+            }
+            if (part.size() <= 0 || part.size() > resolveChunkSize(session, expectedIndex)) {
+                throw new BusinessException(ErrorCode.UNKNOWN, "上传分片大小不合法");
+            }
+        }
+        return uploadedParts.stream()
+                .map(part -> new MultipartCompletedPart(part.partIndex() + 1, part.etag()))
+                .toList();
+    }
+
+    private long resolveChunkSize(UploadSession session, int partIndex) {
+        if (partIndex < 0 || partIndex >= session.getChunkCount()) {
+            throw new BusinessException(ErrorCode.UNKNOWN, "分片序号不合法");
+        }
+        if (partIndex < session.getChunkCount() - 1) {
+            return session.getChunkSize();
+        }
+        long remaining = session.getSize() - session.getChunkSize() * (session.getChunkCount() - 1L);
+        return remaining > 0 ? remaining : session.getChunkSize();
+    }
+
     private record UploadedPart(int partIndex, String etag, long size, String uploadedAt) {
     }
 

backend/src/main/java/com/yoyuzh/files/upload/UploadSessionStatus.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.upload;
 
 public enum UploadSessionStatus {
     CREATED,

backend/src/main/java/com/yoyuzh/transfer/TransferController.java

@@ -5,8 +5,8 @@ import com.yoyuzh.auth.User;
 import com.yoyuzh.common.ApiResponse;
 import com.yoyuzh.common.BusinessException;
 import com.yoyuzh.common.ErrorCode;
-import com.yoyuzh.files.FileMetadataResponse;
-import com.yoyuzh.files.ImportSharedFileRequest;
+import com.yoyuzh.files.core.FileMetadataResponse;
+import com.yoyuzh.files.share.ImportSharedFileRequest;
 import io.swagger.v3.oas.annotations.Operation;
 import jakarta.validation.Valid;
 import lombok.RequiredArgsConstructor;

backend/src/main/java/com/yoyuzh/transfer/TransferService.java

@@ -5,8 +5,8 @@ import com.yoyuzh.auth.User;
 import com.yoyuzh.common.BusinessException;
 import com.yoyuzh.common.ErrorCode;
 import com.yoyuzh.config.FileStorageProperties;
-import com.yoyuzh.files.FileMetadataResponse;
-import com.yoyuzh.files.FileService;
+import com.yoyuzh.files.core.FileMetadataResponse;
+import com.yoyuzh.files.core.FileService;
 import com.yoyuzh.files.storage.FileContentStorage;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;

backend/src/test/java/com/yoyuzh/admin/AdminControllerIntegrationTest.java

@@ -4,10 +4,10 @@ import com.yoyuzh.PortalBackendApplication;
 import com.yoyuzh.admin.AdminMetricsStateRepository;
 import com.yoyuzh.auth.User;
 import com.yoyuzh.auth.UserRepository;
-import com.yoyuzh.files.FileBlob;
-import com.yoyuzh.files.FileBlobRepository;
-import com.yoyuzh.files.StoredFile;
-import com.yoyuzh.files.StoredFileRepository;
+import com.yoyuzh.files.core.FileBlob;
+import com.yoyuzh.files.core.FileBlobRepository;
+import com.yoyuzh.files.core.StoredFile;
+import com.yoyuzh.files.core.StoredFileRepository;
 import com.yoyuzh.transfer.OfflineTransferSessionRepository;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;

backend/src/test/java/com/yoyuzh/admin/AdminServiceTest.java

@@ -8,12 +8,12 @@ import com.yoyuzh.auth.UserRepository;
 import com.yoyuzh.auth.UserRole;
 import com.yoyuzh.common.BusinessException;
 import com.yoyuzh.common.PageResponse;
-import com.yoyuzh.files.FileBlobRepository;
-import com.yoyuzh.files.FileService;
-import com.yoyuzh.files.StoredFile;
-import com.yoyuzh.files.StoredFileRepository;
-import com.yoyuzh.files.StoragePolicyRepository;
-import com.yoyuzh.files.StoragePolicyService;
+import com.yoyuzh.files.core.FileBlobRepository;
+import com.yoyuzh.files.core.FileService;
+import com.yoyuzh.files.core.StoredFile;
+import com.yoyuzh.files.core.StoredFileRepository;
+import com.yoyuzh.files.policy.StoragePolicyRepository;
+import com.yoyuzh.files.policy.StoragePolicyService;
 import com.yoyuzh.transfer.OfflineTransferSessionRepository;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;

backend/src/test/java/com/yoyuzh/api/v2/files/FileSearchV2ControllerTest.java

@@ -4,9 +4,9 @@ import com.yoyuzh.api.v2.ApiV2ExceptionHandler;
 import com.yoyuzh.auth.CustomUserDetailsService;
 import com.yoyuzh.auth.User;
 import com.yoyuzh.common.PageResponse;
-import com.yoyuzh.files.FileMetadataResponse;
-import com.yoyuzh.files.FileSearchQuery;
-import com.yoyuzh.files.FileSearchService;
+import com.yoyuzh.files.core.FileMetadataResponse;
+import com.yoyuzh.files.search.FileSearchQuery;
+import com.yoyuzh.files.search.FileSearchService;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.springframework.core.MethodParameter;

backend/src/test/java/com/yoyuzh/api/v2/files/UploadSessionV2ControllerTest.java

@@ -2,9 +2,9 @@ package com.yoyuzh.api.v2.files;
 
 import com.yoyuzh.auth.CustomUserDetailsService;
 import com.yoyuzh.auth.User;
-import com.yoyuzh.files.UploadSession;
-import com.yoyuzh.files.UploadSessionService;
-import com.yoyuzh.files.UploadSessionStatus;
+import com.yoyuzh.files.upload.UploadSession;
+import com.yoyuzh.files.upload.UploadSessionService;
+import com.yoyuzh.files.upload.UploadSessionStatus;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.springframework.http.MediaType;
@@ -19,6 +19,7 @@ import org.springframework.web.method.support.HandlerMethodArgumentResolver;
 import org.springframework.web.method.support.ModelAndViewContainer;
 
 import java.time.LocalDateTime;
+import java.util.Map;
 
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.eq;
@@ -69,6 +70,7 @@ class UploadSessionV2ControllerTest {
                 .andExpect(jsonPath("$.data.sessionId").value("session-1"))
                 .andExpect(jsonPath("$.data.objectKey").value("blobs/session-1"))
                 .andExpect(jsonPath("$.data.status").value("CREATED"))
+                .andExpect(jsonPath("$.data.multipartUpload").value(true))
                 .andExpect(jsonPath("$.data.chunkSize").value(8388608))
                 .andExpect(jsonPath("$.data.chunkCount").value(3));
     }
@@ -85,7 +87,8 @@ class UploadSessionV2ControllerTest {
                 .andExpect(status().isOk())
                 .andExpect(jsonPath("$.code").value(0))
                 .andExpect(jsonPath("$.data.sessionId").value("session-1"))
-                .andExpect(jsonPath("$.data.status").value("CREATED"));
+                .andExpect(jsonPath("$.data.status").value("CREATED"))
+                .andExpect(jsonPath("$.data.multipartUpload").value(true));
     }
 
     @Test
@@ -127,6 +130,29 @@ class UploadSessionV2ControllerTest {
                 .andExpect(jsonPath("$.data.status").value("UPLOADING"));
     }
 
+    @Test
+    void shouldPrepareMultipartPartUploadWithV2Envelope() throws Exception {
+        User user = createUser(7L);
+        when(userDetailsService.loadDomainUser("alice")).thenReturn(user);
+        when(uploadSessionService.prepareOwnedPartUpload(user, "session-1", 1))
+                .thenReturn(new com.yoyuzh.files.storage.PreparedUpload(
+                        true,
+                        "https://upload.example.com/session-1/part-2",
+                        "PUT",
+                        Map.of("Content-Type", "video/mp4"),
+                        "blobs/session-1"
+                ));
+
+        mockMvc.perform(get("/api/v2/files/upload-sessions/session-1/parts/1/prepare")
+                        .with(user(userDetails())))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.code").value(0))
+                .andExpect(jsonPath("$.data.direct").value(true))
+                .andExpect(jsonPath("$.data.uploadUrl").value("https://upload.example.com/session-1/part-2"))
+                .andExpect(jsonPath("$.data.method").value("PUT"))
+                .andExpect(jsonPath("$.data.headers['Content-Type']").value("video/mp4"));
+    }
+
     private UserDetails userDetails() {
         return org.springframework.security.core.userdetails.User
                 .withUsername("alice")
@@ -172,6 +198,7 @@ class UploadSessionV2ControllerTest {
         session.setContentType("video/mp4");
         session.setSize(20L * 1024 * 1024);
         session.setObjectKey("blobs/session-1");
+        session.setMultipartUploadId("upload-123");
         session.setChunkSize(8L * 1024 * 1024);
         session.setChunkCount(3);
         session.setStatus(UploadSessionStatus.CREATED);

backend/src/test/java/com/yoyuzh/api/v2/shares/ShareV2ControllerIntegrationTest.java

@@ -4,12 +4,12 @@ import com.jayway.jsonpath.JsonPath;
 import com.yoyuzh.PortalBackendApplication;
 import com.yoyuzh.auth.User;
 import com.yoyuzh.auth.UserRepository;
-import com.yoyuzh.files.FileBlob;
-import com.yoyuzh.files.FileBlobRepository;
-import com.yoyuzh.files.FileShareLink;
-import com.yoyuzh.files.FileShareLinkRepository;
-import com.yoyuzh.files.StoredFile;
-import com.yoyuzh.files.StoredFileRepository;
+import com.yoyuzh.files.core.FileBlob;
+import com.yoyuzh.files.core.FileBlobRepository;
+import com.yoyuzh.files.share.FileShareLink;
+import com.yoyuzh.files.share.FileShareLinkRepository;
+import com.yoyuzh.files.core.StoredFile;
+import com.yoyuzh.files.core.StoredFileRepository;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -30,6 +30,8 @@ import static org.springframework.security.test.web.servlet.request.SecurityMock
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.delete;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.header;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
 
@@ -274,6 +276,120 @@ class ShareV2ControllerIntegrationTest {
                 .andExpect(jsonPath("$.code").value(2404));
     }
 
+    @Test
+    void shouldDownloadSharedFileAndCountQuota() throws Exception {
+        String createResponse = mockMvc.perform(post("/api/v2/shares")
+                        .with(user("alice"))
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("""
+                                {
+                                  "fileId": %d,
+                                  "maxDownloads": 1,
+                                  "allowDownload": true
+                                }
+                                """.formatted(sharedFileId)))
+                .andExpect(status().isOk())
+                .andReturn()
+                .getResponse()
+                .getContentAsString();
+        String token = JsonPath.read(createResponse, "$.data.token");
+
+        mockMvc.perform(get("/api/v2/shares/{token}", token)
+                        .with(anonymous())
+                        .param("download", "1"))
+                .andExpect(status().isOk())
+                .andExpect(header().string("Content-Disposition", "attachment; filename*=UTF-8''notes.txt"))
+                .andExpect(content().contentType("text/plain"))
+                .andExpect(content().bytes("hello".getBytes(StandardCharsets.UTF_8)));
+
+        mockMvc.perform(get("/api/v2/shares/{token}", token)
+                        .with(anonymous())
+                        .param("download", "1"))
+                .andExpect(status().isForbidden())
+                .andExpect(jsonPath("$.code").value(2403));
+
+        mockMvc.perform(get("/api/v2/shares/{token}", token).with(anonymous()))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.data.downloadCount").value(1));
+    }
+
+    @Test
+    void shouldRejectDownloadWhenSharePolicyBlocksIt() throws Exception {
+        String passwordResponse = mockMvc.perform(post("/api/v2/shares")
+                        .with(user("alice"))
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("""
+                                {
+                                  "fileId": %d,
+                                  "password": "Share123",
+                                  "allowDownload": true
+                                }
+                                """.formatted(sharedFileId)))
+                .andExpect(status().isOk())
+                .andReturn()
+                .getResponse()
+                .getContentAsString();
+        String passwordToken = JsonPath.read(passwordResponse, "$.data.token");
+
+        mockMvc.perform(get("/api/v2/shares/{token}", passwordToken)
+                        .with(anonymous())
+                        .param("download", "1"))
+                .andExpect(status().isBadRequest())
+                .andExpect(jsonPath("$.code").value(2400));
+
+        mockMvc.perform(get("/api/v2/shares/{token}", passwordToken)
+                        .with(anonymous())
+                        .param("download", "1")
+                        .param("password", "Share123"))
+                .andExpect(status().isOk())
+                .andExpect(content().bytes("hello".getBytes(StandardCharsets.UTF_8)));
+
+        String disabledResponse = mockMvc.perform(post("/api/v2/shares")
+                        .with(user("alice"))
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("""
+                                {
+                                  "fileId": %d,
+                                  "allowDownload": false
+                                }
+                                """.formatted(sharedFileId)))
+                .andExpect(status().isOk())
+                .andReturn()
+                .getResponse()
+                .getContentAsString();
+        String disabledToken = JsonPath.read(disabledResponse, "$.data.token");
+
+        mockMvc.perform(get("/api/v2/shares/{token}", disabledToken)
+                        .with(anonymous())
+                        .param("download", "1"))
+                .andExpect(status().isForbidden())
+                .andExpect(jsonPath("$.code").value(2403));
+
+        String expiredResponse = mockMvc.perform(post("/api/v2/shares")
+                        .with(user("alice"))
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("""
+                                {
+                                  "fileId": %d,
+                                  "allowDownload": true
+                                }
+                                """.formatted(sharedFileId)))
+                .andExpect(status().isOk())
+                .andReturn()
+                .getResponse()
+                .getContentAsString();
+        String expiredToken = JsonPath.read(expiredResponse, "$.data.token");
+        FileShareLink expiredShare = fileShareLinkRepository.findByToken(expiredToken).orElseThrow();
+        expiredShare.setExpiresAt(LocalDateTime.now().minusMinutes(1));
+        fileShareLinkRepository.save(expiredShare);
+
+        mockMvc.perform(get("/api/v2/shares/{token}", expiredToken)
+                        .with(anonymous())
+                        .param("download", "1"))
+                .andExpect(status().isNotFound())
+                .andExpect(jsonPath("$.code").value(2404));
+    }
+
     @Test
     void shouldDenyDeletingOtherUsersShare() throws Exception {
         String createResponse = mockMvc.perform(post("/api/v2/shares")

backend/src/test/java/com/yoyuzh/api/v2/tasks/BackgroundTaskV2ControllerIntegrationTest.java

@@ -1,16 +1,22 @@
 package com.yoyuzh.api.v2.tasks;
 
+import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.jayway.jsonpath.JsonPath;
 import com.yoyuzh.PortalBackendApplication;
 import com.yoyuzh.auth.User;
 import com.yoyuzh.auth.UserRepository;
-import com.yoyuzh.files.BackgroundTask;
-import com.yoyuzh.files.BackgroundTaskRepository;
-import com.yoyuzh.files.BackgroundTaskStatus;
-import com.yoyuzh.files.BackgroundTaskType;
-import com.yoyuzh.files.StoredFile;
-import com.yoyuzh.files.StoredFileRepository;
+import com.yoyuzh.files.tasks.BackgroundTask;
+import com.yoyuzh.files.tasks.BackgroundTaskRepository;
+import com.yoyuzh.files.tasks.BackgroundTaskStatus;
+import com.yoyuzh.files.tasks.BackgroundTaskStartupRecovery;
+import com.yoyuzh.files.tasks.BackgroundTaskType;
+import com.yoyuzh.files.tasks.BackgroundTaskWorker;
+import com.yoyuzh.files.core.FileBlob;
+import com.yoyuzh.files.core.FileBlobRepository;
+import com.yoyuzh.files.core.StoredFile;
+import com.yoyuzh.files.core.StoredFileRepository;
+import com.yoyuzh.files.storage.FileContentStorage;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -19,10 +25,17 @@ import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.http.MediaType;
 import org.springframework.test.web.servlet.MockMvc;
 
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import java.time.LocalDateTime;
+import java.util.Map;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipOutputStream;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.not;
 import static org.springframework.security.test.web.servlet.request.SecurityMockMvcRequestPostProcessors.anonymous;
 import static org.springframework.security.test.web.servlet.request.SecurityMockMvcRequestPostProcessors.user;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.delete;
@@ -55,23 +68,39 @@ class BackgroundTaskV2ControllerIntegrationTest {
     @Autowired
     private BackgroundTaskRepository backgroundTaskRepository;
 
+    @Autowired
+    private BackgroundTaskWorker backgroundTaskWorker;
+
+    @Autowired
+    private BackgroundTaskStartupRecovery backgroundTaskStartupRecovery;
+
+    @Autowired
+    private FileBlobRepository fileBlobRepository;
+
+    @Autowired
+    private FileContentStorage fileContentStorage;
+
     @Autowired
     private StoredFileRepository storedFileRepository;
 
     @Autowired
     private ObjectMapper objectMapper;
 
+    private Long aliceId;
     private Long archiveDirectoryId;
     private Long archiveFileId;
     private Long extractFileId;
+    private Long invalidExtractFileId;
+    private Long unsupportedExtractFileId;
     private Long mediaFileId;
     private Long foreignFileId;
     private Long deletedFileId;
 
     @BeforeEach
-    void setUp() {
+    void setUp() throws Exception {
         backgroundTaskRepository.deleteAll();
         storedFileRepository.deleteAll();
+        fileBlobRepository.deleteAll();
         userRepository.deleteAll();
 
         User alice = new User();
@@ -80,7 +109,8 @@ class BackgroundTaskV2ControllerIntegrationTest {
         alice.setPhoneNumber("13800138000");
         alice.setPasswordHash("encoded-password");
         alice.setCreatedAt(LocalDateTime.now());
-        userRepository.save(alice);
+        alice = userRepository.save(alice);
+        aliceId = alice.getId();
 
         User bob = new User();
         bob.setUsername("bob");
@@ -91,11 +121,62 @@ class BackgroundTaskV2ControllerIntegrationTest {
         bob = userRepository.save(bob);
 
         archiveDirectoryId = storedFileRepository.save(createFile(alice, "/docs", "archive", true, null, 0L, null)).getId();
-        archiveFileId = storedFileRepository.save(createFile(alice, "/docs", "archive-source.txt", false, "text/plain", 12L, null)).getId();
-        extractFileId = storedFileRepository.save(createFile(alice, "/docs", "extract.zip", false, "application/zip", 32L, null)).getId();
+        storedFileRepository.save(createBlobBackedFile(
+                alice,
+                "/docs/archive",
+                "nested.txt",
+                "text/plain",
+                "archive-nested",
+                "nested-content".getBytes(StandardCharsets.UTF_8)
+        ));
+        archiveFileId = storedFileRepository.save(createBlobBackedFile(
+                alice,
+                "/docs",
+                "archive-source.txt",
+                "text/plain",
+                "archive-source",
+                "archive-source".getBytes(StandardCharsets.UTF_8)
+        )).getId();
+        extractFileId = storedFileRepository.save(createBlobBackedFile(
+                alice,
+                "/docs",
+                "extract.zip",
+                "application/zip",
+                "extract-source",
+                createZipArchive(Map.of(
+                        "extract/", "",
+                        "extract/nested/", "",
+                        "extract/notes.txt", "hello",
+                        "extract/nested/todo.txt", "world"
+                ))
+        )).getId();
+        invalidExtractFileId = storedFileRepository.save(createBlobBackedFile(
+                alice,
+                "/docs",
+                "broken.zip",
+                "application/zip",
+                "broken-extract",
+                "not-a-zip".getBytes(StandardCharsets.UTF_8)
+        )).getId();
+        unsupportedExtractFileId = storedFileRepository.save(createFile(alice, "/docs", "backup.7z", false, "application/x-7z-compressed", 64L, null)).getId();
         mediaFileId = storedFileRepository.save(createFile(alice, "/docs", "media.png", false, "image/png", 24L, null)).getId();
-        foreignFileId = storedFileRepository.save(createFile(bob, "/docs", "foreign.zip", false, "application/zip", 32L, null)).getId();
-        deletedFileId = storedFileRepository.save(createFile(alice, "/docs", "deleted.zip", false, "application/zip", 32L, LocalDateTime.now())).getId();
+        foreignFileId = storedFileRepository.save(createBlobBackedFile(
+                bob,
+                "/docs",
+                "foreign.zip",
+                "application/zip",
+                "foreign-zip",
+                createZipArchive(Map.of("foreign.txt", "blocked"))
+        )).getId();
+        deletedFileId = storedFileRepository.save(createBlobBackedFile(
+                alice,
+                "/docs",
+                "deleted.zip",
+                "application/zip",
+                "deleted-zip",
+                createZipArchive(Map.of("deleted.txt", "gone")),
+                LocalDateTime.now()
+        )).getId();
     }
 
     @Test
@@ -132,6 +213,9 @@ class BackgroundTaskV2ControllerIntegrationTest {
                 .andExpect(jsonPath("$.data.publicStateJson", containsString("\"fileId\":" + archiveDirectoryId)))
                 .andExpect(jsonPath("$.data.publicStateJson", containsString("\"path\":\"/docs/archive\"")))
                 .andExpect(jsonPath("$.data.publicStateJson", containsString("\"directory\":true")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"phase\":\"queued\"")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"attemptCount\":0")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"maxAttempts\":4")))
                 .andReturn()
                 .getResponse()
                 .getContentAsString();
@@ -148,6 +232,11 @@ class BackgroundTaskV2ControllerIntegrationTest {
                 .andExpect(status().isOk())
                 .andExpect(jsonPath("$.data.type").value("EXTRACT"))
                 .andExpect(jsonPath("$.data.status").value("QUEUED"))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"outputPath\":\"/docs\"")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"outputDirectoryName\":\"extract\"")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"phase\":\"queued\"")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"attemptCount\":0")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"maxAttempts\":3")))
                 .andReturn()
                 .getResponse()
                 .getContentAsString();
@@ -164,6 +253,9 @@ class BackgroundTaskV2ControllerIntegrationTest {
                 .andExpect(status().isOk())
                 .andExpect(jsonPath("$.data.type").value("MEDIA_META"))
                 .andExpect(jsonPath("$.data.status").value("QUEUED"))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"phase\":\"queued\"")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"attemptCount\":0")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"maxAttempts\":2")))
                 .andReturn()
                 .getResponse()
                 .getContentAsString();
@@ -187,11 +279,13 @@ class BackgroundTaskV2ControllerIntegrationTest {
 
         mockMvc.perform(delete("/api/v2/tasks/{id}", extractId).with(user("alice")))
                 .andExpect(status().isOk())
-                .andExpect(jsonPath("$.data.status").value("CANCELLED"));
+                .andExpect(jsonPath("$.data.status").value("CANCELLED"))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"phase\":\"cancelled\"")));
 
         BackgroundTask cancelled = backgroundTaskRepository.findById(extractId).orElseThrow();
         assertThat(cancelled.getStatus()).isEqualTo(BackgroundTaskStatus.CANCELLED);
         assertThat(cancelled.getFinishedAt()).isNotNull();
+        assertThat(cancelled.getPublicStateJson()).contains("\"phase\":\"cancelled\"");
     }
 
     @Test
@@ -216,6 +310,289 @@ class BackgroundTaskV2ControllerIntegrationTest {
 
         mockMvc.perform(delete("/api/v2/tasks/{id}", taskId).with(user("bob")))
                 .andExpect(status().isNotFound());
+
+        mockMvc.perform(post("/api/v2/tasks/{id}/retry", taskId).with(user("bob")))
+                .andExpect(status().isNotFound());
+    }
+
+    @Test
+    void shouldRejectExtractTaskForNonZipCompatibleArchive() throws Exception {
+        mockMvc.perform(post("/api/v2/tasks/extract")
+                        .with(user("alice"))
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("""
+                                {
+                                  "fileId": %d,
+                                  "path": "/docs/backup.7z"
+                                }
+                                """.formatted(unsupportedExtractFileId)))
+                .andExpect(status().isBadRequest());
+    }
+
+    @Test
+    void shouldCompleteArchiveTaskThroughWorkerAndExposeTerminalState() throws Exception {
+        String response = mockMvc.perform(post("/api/v2/tasks/archive")
+                        .with(user("alice"))
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("""
+                                {
+                                  "fileId": %d,
+                                  "path": "/docs/archive-source.txt"
+                                }
+                                """.formatted(archiveFileId)))
+                .andExpect(status().isOk())
+                .andReturn()
+                .getResponse()
+                .getContentAsString();
+        Long taskId = ((Number) JsonPath.read(response, "$.data.id")).longValue();
+
+        int processedCount = backgroundTaskWorker.processQueuedTasks(5);
+
+        assertThat(processedCount).isEqualTo(1);
+        String taskResponse = mockMvc.perform(get("/api/v2/tasks/{id}", taskId).with(user("alice")))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.data.status").value("COMPLETED"))
+                .andReturn()
+                .getResponse()
+                .getContentAsString();
+
+        Map<String, Object> publicState = readPublicState(taskResponse);
+        assertThat(publicState).containsEntry("worker", "archive");
+        assertThat(publicState).containsEntry("archivedFilename", "archive-source.txt.zip");
+        assertThat(publicState).containsEntry("archivedPath", "/docs");
+        assertThat(publicState).containsEntry("phase", "completed");
+        assertThat(publicState).containsEntry("attemptCount", 1);
+        assertThat(publicState).containsEntry("maxAttempts", 4);
+        assertThat(publicState).containsEntry("processedFileCount", 1);
+        assertThat(publicState).containsEntry("totalFileCount", 1);
+        assertThat(publicState).containsEntry("processedDirectoryCount", 0);
+        assertThat(publicState).containsEntry("totalDirectoryCount", 0);
+        assertThat(publicState).containsEntry("progressPercent", 100);
+        assertThat(publicState.get("heartbeatAt")).isNotNull();
+        assertThat(publicState).doesNotContainKey("workerOwner");
+        assertThat(publicState).doesNotContainKey("leaseExpiresAt");
+        assertThat(publicState.get("archivedFileId")).isNotNull();
+        assertThat(publicState.get("archiveSize")).isNotNull();
+
+        BackgroundTask completed = backgroundTaskRepository.findById(taskId).orElseThrow();
+        assertThat(completed.getStatus()).isEqualTo(BackgroundTaskStatus.COMPLETED);
+        assertThat(completed.getFinishedAt()).isNotNull();
+        assertThat(completed.getErrorMessage()).isNull();
+        assertThat(storedFileRepository.findByUserIdAndPathAndFilename(aliceId, "/docs", "archive-source.txt.zip")).isPresent();
+    }
+
+    @Test
+    void shouldCompleteExtractTaskThroughWorkerAndExposeTerminalState() throws Exception {
+        String response = mockMvc.perform(post("/api/v2/tasks/extract")
+                        .with(user("alice"))
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("""
+                                {
+                                  "fileId": %d,
+                                  "path": "/docs/extract.zip"
+                                }
+                                """.formatted(extractFileId)))
+                .andExpect(status().isOk())
+                .andReturn()
+                .getResponse()
+                .getContentAsString();
+        Long taskId = ((Number) JsonPath.read(response, "$.data.id")).longValue();
+
+        int processedCount = backgroundTaskWorker.processQueuedTasks(5);
+
+        assertThat(processedCount).isEqualTo(1);
+        String taskResponse = mockMvc.perform(get("/api/v2/tasks/{id}", taskId).with(user("alice")))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.data.status").value("COMPLETED"))
+                .andReturn()
+                .getResponse()
+                .getContentAsString();
+
+        Map<String, Object> publicState = readPublicState(taskResponse);
+        assertThat(publicState).containsEntry("worker", "extract");
+        assertThat(publicState).containsEntry("extractedPath", "/docs/extract");
+        assertThat(publicState).containsEntry("extractedFileCount", 2);
+        assertThat(publicState).containsEntry("extractedDirectoryCount", 2);
+        assertThat(publicState).containsEntry("phase", "completed");
+        assertThat(publicState).containsEntry("attemptCount", 1);
+        assertThat(publicState).containsEntry("maxAttempts", 3);
+        assertThat(publicState).containsEntry("processedFileCount", 2);
+        assertThat(publicState).containsEntry("totalFileCount", 2);
+        assertThat(publicState).containsEntry("processedDirectoryCount", 2);
+        assertThat(publicState).containsEntry("totalDirectoryCount", 2);
+        assertThat(publicState).containsEntry("progressPercent", 100);
+        assertThat(publicState.get("heartbeatAt")).isNotNull();
+        assertThat(publicState).doesNotContainKey("workerOwner");
+        assertThat(publicState).doesNotContainKey("leaseExpiresAt");
+
+        BackgroundTask completed = backgroundTaskRepository.findById(taskId).orElseThrow();
+        assertThat(completed.getStatus()).isEqualTo(BackgroundTaskStatus.COMPLETED);
+        assertThat(completed.getFinishedAt()).isNotNull();
+        assertThat(completed.getErrorMessage()).isNull();
+        assertThat(storedFileRepository.findByUserIdAndPathAndFilename(aliceId, "/docs/extract", "notes.txt")).isPresent();
+        assertThat(storedFileRepository.findByUserIdAndPathAndFilename(aliceId, "/docs/extract/nested", "todo.txt")).isPresent();
+    }
+
+    @Test
+    void shouldMarkExtractTaskFailedWhenWorkerHitsInvalidArchiveContent() throws Exception {
+        String response = mockMvc.perform(post("/api/v2/tasks/extract")
+                        .with(user("alice"))
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("""
+                                {
+                                  "fileId": %d,
+                                  "path": "/docs/broken.zip"
+                                }
+                                """.formatted(invalidExtractFileId)))
+                .andExpect(status().isOk())
+                .andReturn()
+                .getResponse()
+                .getContentAsString();
+        Long taskId = ((Number) JsonPath.read(response, "$.data.id")).longValue();
+
+        int processedCount = backgroundTaskWorker.processQueuedTasks(5);
+
+        assertThat(processedCount).isEqualTo(1);
+        mockMvc.perform(get("/api/v2/tasks/{id}", taskId).with(user("alice")))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.data.status").value("FAILED"))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"phase\":\"failed\"")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"attemptCount\":1")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"maxAttempts\":3")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"failureCategory\":\"DATA_STATE\"")))
+                .andExpect(jsonPath("$.data.errorMessage").value("extract task only supports zip-compatible archives"));
+
+        BackgroundTask failed = backgroundTaskRepository.findById(taskId).orElseThrow();
+        assertThat(failed.getStatus()).isEqualTo(BackgroundTaskStatus.FAILED);
+        assertThat(failed.getFinishedAt()).isNotNull();
+        assertThat(failed.getErrorMessage()).isEqualTo("extract task only supports zip-compatible archives");
+    }
+
+    @Test
+    void shouldRetryFailedTaskAndResetStateToQueued() throws Exception {
+        String response = mockMvc.perform(post("/api/v2/tasks/extract")
+                        .with(user("alice"))
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("""
+                                {
+                                  "fileId": %d,
+                                  "path": "/docs/broken.zip"
+                                }
+                                """.formatted(invalidExtractFileId)))
+                .andExpect(status().isOk())
+                .andReturn()
+                .getResponse()
+                .getContentAsString();
+        Long taskId = ((Number) JsonPath.read(response, "$.data.id")).longValue();
+        backgroundTaskWorker.processQueuedTasks(5);
+
+        String retryResponse = mockMvc.perform(post("/api/v2/tasks/{id}/retry", taskId).with(user("alice")))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.data.status").value("QUEUED"))
+                .andExpect(jsonPath("$.data.errorMessage").doesNotExist())
+                .andExpect(jsonPath("$.data.finishedAt").doesNotExist())
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"phase\":\"queued\"")))
+                .andReturn()
+                .getResponse()
+                .getContentAsString();
+
+        Map<String, Object> publicState = readPublicState(retryResponse);
+        assertThat(publicState).containsEntry("phase", "queued");
+        assertThat(publicState).containsEntry("outputPath", "/docs");
+        assertThat(publicState).containsEntry("outputDirectoryName", "broken");
+        assertThat(publicState).containsEntry("attemptCount", 0);
+        assertThat(publicState).containsEntry("maxAttempts", 3);
+        assertThat(publicState).doesNotContainKey("worker");
+        assertThat(publicState).doesNotContainKey("processedFileCount");
+        assertThat(publicState).doesNotContainKey("totalFileCount");
+
+        BackgroundTask retried = backgroundTaskRepository.findById(taskId).orElseThrow();
+        assertThat(retried.getStatus()).isEqualTo(BackgroundTaskStatus.QUEUED);
+        assertThat(retried.getFinishedAt()).isNull();
+        assertThat(retried.getErrorMessage()).isNull();
+    }
+
+    @Test
+    void shouldRejectRetryForNonFailedTask() throws Exception {
+        String response = mockMvc.perform(post("/api/v2/tasks/archive")
+                        .with(user("alice"))
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("""
+                                {
+                                  "fileId": %d,
+                                  "path": "/docs/archive-source.txt"
+                                }
+                                """.formatted(archiveFileId)))
+                .andExpect(status().isOk())
+                .andReturn()
+                .getResponse()
+                .getContentAsString();
+        Long taskId = ((Number) JsonPath.read(response, "$.data.id")).longValue();
+
+        mockMvc.perform(post("/api/v2/tasks/{id}/retry", taskId).with(user("alice")))
+                .andExpect(status().isBadRequest());
+    }
+
+    @Test
+    void shouldRecoverOnlyExpiredRunningTaskBackToQueuedOnStartup() throws Exception {
+        BackgroundTask expired = new BackgroundTask();
+        expired.setType(BackgroundTaskType.EXTRACT);
+        expired.setStatus(BackgroundTaskStatus.RUNNING);
+        expired.setUserId(aliceId);
+        expired.setCorrelationId("recover-1");
+        expired.setAttemptCount(1);
+        expired.setMaxAttempts(3);
+        expired.setLeaseOwner("worker-stale");
+        expired.setLeaseExpiresAt(LocalDateTime.now().minusMinutes(2));
+        expired.setHeartbeatAt(LocalDateTime.now().minusMinutes(3));
+        expired.setPublicStateJson("""
+                {"fileId":%d,"path":"/docs/extract.zip","phase":"extracting","worker":"extract","workerOwner":"worker-stale","attemptCount":1,"maxAttempts":3}
+                """.formatted(extractFileId));
+        expired.setPrivateStateJson("""
+                {"fileId":%d,"path":"/docs/extract.zip","taskType":"EXTRACT","outputPath":"/docs","outputDirectoryName":"extract"}
+                """.formatted(extractFileId));
+        expired.setErrorMessage("stale worker");
+        expired.setFinishedAt(LocalDateTime.now());
+        expired = backgroundTaskRepository.save(expired);
+
+        BackgroundTask fresh = new BackgroundTask();
+        fresh.setType(BackgroundTaskType.EXTRACT);
+        fresh.setStatus(BackgroundTaskStatus.RUNNING);
+        fresh.setUserId(aliceId);
+        fresh.setCorrelationId("recover-2");
+        fresh.setAttemptCount(1);
+        fresh.setMaxAttempts(3);
+        fresh.setLeaseOwner("worker-live");
+        fresh.setLeaseExpiresAt(LocalDateTime.now().plusMinutes(5));
+        fresh.setHeartbeatAt(LocalDateTime.now());
+        fresh.setPublicStateJson("""
+                {"fileId":%d,"path":"/docs/extract.zip","phase":"extracting","worker":"extract","workerOwner":"worker-live","attemptCount":1,"maxAttempts":3}
+                """.formatted(extractFileId));
+        fresh.setPrivateStateJson("""
+                {"fileId":%d,"path":"/docs/extract.zip","taskType":"EXTRACT","outputPath":"/docs","outputDirectoryName":"extract"}
+                """.formatted(extractFileId));
+        fresh = backgroundTaskRepository.save(fresh);
+
+        backgroundTaskStartupRecovery.recoverOnStartup();
+
+        mockMvc.perform(get("/api/v2/tasks/{id}", expired.getId()).with(user("alice")))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.data.status").value("QUEUED"))
+                .andExpect(jsonPath("$.data.errorMessage").doesNotExist())
+                .andExpect(jsonPath("$.data.finishedAt").doesNotExist())
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"phase\":\"queued\"")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"attemptCount\":1")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"maxAttempts\":3")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"outputPath\":\"/docs\"")))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"outputDirectoryName\":\"extract\"")))
+                .andExpect(jsonPath("$.data.publicStateJson", not(containsString("\"worker\""))))
+                .andExpect(jsonPath("$.data.publicStateJson", not(containsString("\"workerOwner\""))))
+                .andExpect(jsonPath("$.data.publicStateJson", not(containsString("\"leaseExpiresAt\""))));
+
+        mockMvc.perform(get("/api/v2/tasks/{id}", fresh.getId()).with(user("alice")))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.data.status").value("RUNNING"))
+                .andExpect(jsonPath("$.data.publicStateJson", containsString("\"workerOwner\":\"worker-live\"")));
     }
 
     @Test
@@ -274,4 +651,54 @@ class BackgroundTaskV2ControllerIntegrationTest {
         file.setDeletedAt(deletedAt);
         return file;
     }
+
+    private StoredFile createBlobBackedFile(User user,
+                                            String path,
+                                            String filename,
+                                            String contentType,
+                                            String objectKeySuffix,
+                                            byte[] content) {
+        return createBlobBackedFile(user, path, filename, contentType, objectKeySuffix, content, null);
+    }
+
+    private StoredFile createBlobBackedFile(User user,
+                                            String path,
+                                            String filename,
+                                            String contentType,
+                                            String objectKeySuffix,
+                                            byte[] content,
+                                            LocalDateTime deletedAt) {
+        String objectKey = "blobs/test-background-task/" + objectKeySuffix;
+        fileContentStorage.storeBlob(objectKey, contentType, content);
+
+        FileBlob blob = new FileBlob();
+        blob.setObjectKey(objectKey);
+        blob.setContentType(contentType);
+        blob.setSize((long) content.length);
+        blob = fileBlobRepository.save(blob);
+
+        StoredFile file = createFile(user, path, filename, false, contentType, (long) content.length, deletedAt);
+        file.setBlob(blob);
+        return file;
+    }
+
+    private byte[] createZipArchive(Map<String, String> entries) throws IOException {
+        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+        try (ZipOutputStream zipOutputStream = new ZipOutputStream(outputStream, StandardCharsets.UTF_8)) {
+            for (Map.Entry<String, String> entry : entries.entrySet()) {
+                zipOutputStream.putNextEntry(new ZipEntry(entry.getKey()));
+                if (!entry.getKey().endsWith("/")) {
+                    zipOutputStream.write(entry.getValue().getBytes(StandardCharsets.UTF_8));
+                }
+                zipOutputStream.closeEntry();
+            }
+        }
+        return outputStream.toByteArray();
+    }
+
+    private Map<String, Object> readPublicState(String taskResponse) throws Exception {
+        String publicStateJson = JsonPath.read(taskResponse, "$.data.publicStateJson");
+        return objectMapper.readValue(publicStateJson, new TypeReference<Map<String, Object>>() {
+        });
+    }
 }

backend/src/test/java/com/yoyuzh/auth/AuthServiceTest.java

@@ -7,8 +7,8 @@ import com.yoyuzh.auth.dto.UpdateUserAvatarRequest;
 import com.yoyuzh.auth.dto.UpdateUserPasswordRequest;
 import com.yoyuzh.auth.dto.UpdateUserProfileRequest;
 import com.yoyuzh.common.BusinessException;
-import com.yoyuzh.files.FileService;
-import com.yoyuzh.files.InitiateUploadResponse;
+import com.yoyuzh.files.core.FileService;
+import com.yoyuzh.files.upload.InitiateUploadResponse;
 import com.yoyuzh.files.storage.FileContentStorage;
 import com.yoyuzh.files.storage.PreparedUpload;
 import org.junit.jupiter.api.Test;

backend/src/test/java/com/yoyuzh/auth/AuthSingleDeviceIntegrationTest.java

@@ -39,7 +39,7 @@ class AuthSingleDeviceIntegrationTest {
     private UserRepository userRepository;
 
     @Autowired
-    private com.yoyuzh.files.StoredFileRepository storedFileRepository;
+    private com.yoyuzh.files.core.StoredFileRepository storedFileRepository;
 
     @Autowired
     private RefreshTokenRepository refreshTokenRepository;

backend/src/test/java/com/yoyuzh/auth/DevBootstrapDataInitializerTest.java

@@ -1,7 +1,7 @@
 package com.yoyuzh.auth;
 
-import com.yoyuzh.files.FileService;
-import com.yoyuzh.files.StoredFileRepository;
+import com.yoyuzh.files.core.FileService;
+import com.yoyuzh.files.core.StoredFileRepository;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.InjectMocks;

backend/src/test/java/com/yoyuzh/files/BackgroundTaskServiceTest.java

@@ -1,246 +0,0 @@
-package com.yoyuzh.files;
-
-import com.fasterxml.jackson.databind.ObjectMapper;
-import com.yoyuzh.api.v2.ApiV2Exception;
-import com.yoyuzh.auth.User;
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.extension.ExtendWith;
-import org.mockito.Mock;
-import org.mockito.junit.jupiter.MockitoExtension;
-
-import java.util.List;
-import java.util.Map;
-import java.util.Optional;
-
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatThrownBy;
-import static org.mockito.ArgumentMatchers.any;
-import static org.mockito.ArgumentMatchers.eq;
-import static org.mockito.Mockito.when;
-
-@ExtendWith(MockitoExtension.class)
-class BackgroundTaskServiceTest {
-
-    @Mock
-    private BackgroundTaskRepository backgroundTaskRepository;
-
-    @Mock
-    private StoredFileRepository storedFileRepository;
-
-    private BackgroundTaskService backgroundTaskService;
-
-    @BeforeEach
-    void setUp() {
-        backgroundTaskService = new BackgroundTaskService(backgroundTaskRepository, storedFileRepository, new ObjectMapper());
-    }
-
-    @Test
-    void shouldRejectTaskCreationForForeignFile() {
-        User user = createUser(7L);
-        when(storedFileRepository.findByIdAndUserIdAndDeletedAtIsNull(99L, 7L)).thenReturn(Optional.empty());
-
-        assertThatThrownBy(() -> backgroundTaskService.createQueuedFileTask(
-                user,
-                BackgroundTaskType.ARCHIVE,
-                99L,
-                "/docs/foreign.txt",
-                null
-        )).isInstanceOf(ApiV2Exception.class)
-                .hasMessage("file not found");
-    }
-
-    @Test
-    void shouldRejectTaskCreationForDeletedFile() {
-        User user = createUser(7L);
-        when(storedFileRepository.findByIdAndUserIdAndDeletedAtIsNull(100L, 7L)).thenReturn(Optional.empty());
-
-        assertThatThrownBy(() -> backgroundTaskService.createQueuedFileTask(
-                user,
-                BackgroundTaskType.ARCHIVE,
-                100L,
-                "/docs/deleted.txt",
-                null
-        )).isInstanceOf(ApiV2Exception.class)
-                .hasMessage("file not found");
-    }
-
-    @Test
-    void shouldRejectTaskCreationWhenRequestedPathDoesNotMatchFile() {
-        User user = createUser(7L);
-        StoredFile file = createStoredFile(11L, user, "/docs", "real.txt", false, "text/plain", 3L);
-        when(storedFileRepository.findByIdAndUserIdAndDeletedAtIsNull(11L, 7L)).thenReturn(Optional.of(file));
-
-        assertThatThrownBy(() -> backgroundTaskService.createQueuedFileTask(
-                user,
-                BackgroundTaskType.ARCHIVE,
-                11L,
-                "/docs/fake.txt",
-                null
-        )).isInstanceOf(ApiV2Exception.class)
-                .hasMessage("task path does not match file path");
-    }
-
-    @Test
-    void shouldRejectExtractTaskForDirectory() {
-        User user = createUser(7L);
-        StoredFile directory = createStoredFile(12L, user, "/", "bundle", true, null, 0L);
-        when(storedFileRepository.findByIdAndUserIdAndDeletedAtIsNull(12L, 7L)).thenReturn(Optional.of(directory));
-
-        assertThatThrownBy(() -> backgroundTaskService.createQueuedFileTask(
-                user,
-                BackgroundTaskType.EXTRACT,
-                12L,
-                "/bundle",
-                null
-        )).isInstanceOf(ApiV2Exception.class)
-                .hasMessage("task target type is not supported");
-    }
-
-    @Test
-    void shouldRejectMediaMetadataTaskForNonMediaFile() {
-        User user = createUser(7L);
-        StoredFile file = createStoredFile(13L, user, "/docs", "notes.txt", false, "text/plain", 9L);
-        when(storedFileRepository.findByIdAndUserIdAndDeletedAtIsNull(13L, 7L)).thenReturn(Optional.of(file));
-
-        assertThatThrownBy(() -> backgroundTaskService.createQueuedFileTask(
-                user,
-                BackgroundTaskType.MEDIA_META,
-                13L,
-                "/docs/notes.txt",
-                null
-        )).isInstanceOf(ApiV2Exception.class)
-                .hasMessage("media metadata task only supports media files");
-    }
-
-    @Test
-    void shouldCreateTaskStateFromServerFilePath() {
-        User user = createUser(7L);
-        StoredFile file = createStoredFile(14L, user, "/docs", "photo.png", false, "image/png", 15L);
-        when(storedFileRepository.findByIdAndUserIdAndDeletedAtIsNull(14L, 7L)).thenReturn(Optional.of(file));
-        when(backgroundTaskRepository.save(any(BackgroundTask.class))).thenAnswer(invocation -> invocation.getArgument(0));
-
-        BackgroundTask task = backgroundTaskService.createQueuedFileTask(
-                user,
-                BackgroundTaskType.MEDIA_META,
-                14L,
-                "/docs/photo.png",
-                "media-1"
-        );
-
-        assertThat(task.getPublicStateJson()).contains("\"fileId\":14");
-        assertThat(task.getPublicStateJson()).contains("\"path\":\"/docs/photo.png\"");
-        assertThat(task.getPublicStateJson()).contains("\"filename\":\"photo.png\"");
-        assertThat(task.getPublicStateJson()).contains("\"directory\":false");
-        assertThat(task.getPublicStateJson()).contains("\"contentType\":\"image/png\"");
-        assertThat(task.getPublicStateJson()).contains("\"size\":15");
-        assertThat(task.getPrivateStateJson()).contains("\"taskType\":\"MEDIA_META\"");
-    }
-
-    @Test
-    void shouldClaimQueuedTaskOnlyWhenRepositoryTransitionSucceeds() {
-        BackgroundTask task = createTask(1L, BackgroundTaskStatus.RUNNING);
-        when(backgroundTaskRepository.claimQueuedTask(
-                eq(1L),
-                eq(BackgroundTaskStatus.QUEUED),
-                eq(BackgroundTaskStatus.RUNNING),
-                any()
-        )).thenReturn(1);
-        when(backgroundTaskRepository.findById(1L)).thenReturn(Optional.of(task));
-
-        Optional<BackgroundTask> result = backgroundTaskService.claimQueuedTask(1L);
-
-        assertThat(result).containsSame(task);
-    }
-
-    @Test
-    void shouldNotClaimTaskWhenRepositoryTransitionWasSkipped() {
-        when(backgroundTaskRepository.claimQueuedTask(
-                eq(2L),
-                eq(BackgroundTaskStatus.QUEUED),
-                eq(BackgroundTaskStatus.RUNNING),
-                any()
-        )).thenReturn(0);
-
-        Optional<BackgroundTask> result = backgroundTaskService.claimQueuedTask(2L);
-
-        assertThat(result).isEmpty();
-    }
-
-    @Test
-    void shouldCompleteRunningWorkerTaskAndMergePublicState() {
-        BackgroundTask task = createTask(3L, BackgroundTaskStatus.RUNNING);
-        task.setPublicStateJson("{\"fileId\":11}");
-        when(backgroundTaskRepository.findById(3L)).thenReturn(Optional.of(task));
-        when(backgroundTaskRepository.save(any(BackgroundTask.class))).thenAnswer(invocation -> invocation.getArgument(0));
-
-        BackgroundTask result = backgroundTaskService.markWorkerTaskCompleted(3L, Map.of("worker", "noop"));
-
-        assertThat(result.getStatus()).isEqualTo(BackgroundTaskStatus.COMPLETED);
-        assertThat(result.getFinishedAt()).isNotNull();
-        assertThat(result.getErrorMessage()).isNull();
-        assertThat(result.getPublicStateJson()).contains("\"fileId\":11");
-        assertThat(result.getPublicStateJson()).contains("\"worker\":\"noop\"");
-    }
-
-    @Test
-    void shouldRecordWorkerFailureMessage() {
-        BackgroundTask task = createTask(4L, BackgroundTaskStatus.RUNNING);
-        when(backgroundTaskRepository.findById(4L)).thenReturn(Optional.of(task));
-        when(backgroundTaskRepository.save(any(BackgroundTask.class))).thenAnswer(invocation -> invocation.getArgument(0));
-
-        BackgroundTask result = backgroundTaskService.markWorkerTaskFailed(4L, "media parser unavailable");
-
-        assertThat(result.getStatus()).isEqualTo(BackgroundTaskStatus.FAILED);
-        assertThat(result.getFinishedAt()).isNotNull();
-        assertThat(result.getErrorMessage()).isEqualTo("media parser unavailable");
-    }
-
-    @Test
-    void shouldFindQueuedTaskIdsInCreatedOrderLimit() {
-        BackgroundTask first = createTask(5L, BackgroundTaskStatus.QUEUED);
-        BackgroundTask second = createTask(6L, BackgroundTaskStatus.QUEUED);
-        when(backgroundTaskRepository.findByStatusOrderByCreatedAtAsc(eq(BackgroundTaskStatus.QUEUED), any()))
-                .thenReturn(List.of(first, second));
-
-        List<Long> result = backgroundTaskService.findQueuedTaskIds(2);
-
-        assertThat(result).containsExactly(5L, 6L);
-    }
-
-    private BackgroundTask createTask(Long id, BackgroundTaskStatus status) {
-        BackgroundTask task = new BackgroundTask();
-        task.setId(id);
-        task.setType(BackgroundTaskType.MEDIA_META);
-        task.setStatus(status);
-        task.setUserId(7L);
-        task.setPublicStateJson("{}");
-        task.setPrivateStateJson("{}");
-        return task;
-    }
-
-    private User createUser(Long id) {
-        User user = new User();
-        user.setId(id);
-        user.setUsername("alice");
-        return user;
-    }
-
-    private StoredFile createStoredFile(Long id,
-                                        User user,
-                                        String path,
-                                        String filename,
-                                        boolean directory,
-                                        String contentType,
-                                        Long size) {
-        StoredFile file = new StoredFile();
-        file.setId(id);
-        file.setUser(user);
-        file.setPath(path);
-        file.setFilename(filename);
-        file.setDirectory(directory);
-        file.setContentType(contentType);
-        file.setSize(size);
-        return file;
-    }
-}

backend/src/test/java/com/yoyuzh/files/BackgroundTaskWorkerTest.java

@@ -1,83 +0,0 @@
-package com.yoyuzh.files;
-
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.extension.ExtendWith;
-import org.mockito.Mock;
-import org.mockito.junit.jupiter.MockitoExtension;
-
-import java.util.List;
-import java.util.Map;
-import java.util.Optional;
-
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.mockito.Mockito.never;
-import static org.mockito.Mockito.verify;
-import static org.mockito.Mockito.when;
-
-@ExtendWith(MockitoExtension.class)
-class BackgroundTaskWorkerTest {
-
-    @Mock
-    private BackgroundTaskService backgroundTaskService;
-    @Mock
-    private BackgroundTaskHandler backgroundTaskHandler;
-
-    private BackgroundTaskWorker backgroundTaskWorker;
-
-    @BeforeEach
-    void setUp() {
-        backgroundTaskWorker = new BackgroundTaskWorker(backgroundTaskService, List.of(backgroundTaskHandler));
-    }
-
-    @Test
-    void shouldClaimAndCompleteQueuedTaskThroughNoopHandler() {
-        BackgroundTask task = createTask(1L, BackgroundTaskType.ARCHIVE, BackgroundTaskStatus.RUNNING);
-        when(backgroundTaskService.findQueuedTaskIds(5)).thenReturn(List.of(1L));
-        when(backgroundTaskService.claimQueuedTask(1L)).thenReturn(Optional.of(task));
-        when(backgroundTaskHandler.supports(BackgroundTaskType.ARCHIVE)).thenReturn(true);
-        when(backgroundTaskHandler.handle(task)).thenReturn(new BackgroundTaskHandlerResult(Map.of("worker", "noop")));
-
-        int processedCount = backgroundTaskWorker.processQueuedTasks(5);
-
-        assertThat(processedCount).isEqualTo(1);
-        verify(backgroundTaskHandler).handle(task);
-        verify(backgroundTaskService).markWorkerTaskCompleted(1L, Map.of("worker", "noop"));
-    }
-
-    @Test
-    void shouldSkipTaskThatWasNotClaimed() {
-        when(backgroundTaskService.findQueuedTaskIds(5)).thenReturn(List.of(1L));
-        when(backgroundTaskService.claimQueuedTask(1L)).thenReturn(Optional.empty());
-
-        int processedCount = backgroundTaskWorker.processQueuedTasks(5);
-
-        assertThat(processedCount).isZero();
-        verify(backgroundTaskHandler, never()).handle(org.mockito.ArgumentMatchers.any());
-    }
-
-    @Test
-    void shouldMarkTaskFailedWhenHandlerThrows() {
-        BackgroundTask task = createTask(2L, BackgroundTaskType.MEDIA_META, BackgroundTaskStatus.RUNNING);
-        when(backgroundTaskService.findQueuedTaskIds(5)).thenReturn(List.of(2L));
-        when(backgroundTaskService.claimQueuedTask(2L)).thenReturn(Optional.of(task));
-        when(backgroundTaskHandler.supports(BackgroundTaskType.MEDIA_META)).thenReturn(true);
-        when(backgroundTaskHandler.handle(task)).thenThrow(new IllegalStateException("media parser unavailable"));
-
-        int processedCount = backgroundTaskWorker.processQueuedTasks(5);
-
-        assertThat(processedCount).isEqualTo(1);
-        verify(backgroundTaskService).markWorkerTaskFailed(2L, "media parser unavailable");
-    }
-
-    private BackgroundTask createTask(Long id, BackgroundTaskType type, BackgroundTaskStatus status) {
-        BackgroundTask task = new BackgroundTask();
-        task.setId(id);
-        task.setType(type);
-        task.setStatus(status);
-        task.setUserId(7L);
-        task.setPublicStateJson("{}");
-        task.setPrivateStateJson("{}");
-        return task;
-    }
-}

backend/src/test/java/com/yoyuzh/files/core/FileBlobBackfillServiceTest.java

@@ -1,4 +1,4 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import com.yoyuzh.auth.User;
 import com.yoyuzh.files.storage.FileContentStorage;

backend/src/test/java/com/yoyuzh/files/core/FileEntityBackfillServiceTest.java

@@ -1,6 +1,10 @@
-package com.yoyuzh.files;
+package com.yoyuzh.files.core;
 
 import com.yoyuzh.auth.User;
+import com.yoyuzh.files.policy.StoragePolicy;
+import com.yoyuzh.files.policy.StoragePolicyCredentialMode;
+import com.yoyuzh.files.policy.StoragePolicyService;
+import com.yoyuzh.files.policy.StoragePolicyType;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;