new flat KV structure

internal/api/server.go

@@ -8,13 +8,16 @@ import (
 	"time"
 
 	"github.com/gorilla/mux"
+	"github.com/metazla/meta-core/internal/cache"
 	"github.com/metazla/meta-core/internal/config"
 	"github.com/metazla/meta-core/internal/discovery"
+	"github.com/metazla/meta-core/internal/events"
 	"github.com/metazla/meta-core/internal/leader"
 	"github.com/metazla/meta-core/internal/mounts"
 	"github.com/metazla/meta-core/internal/storage"
 	"github.com/metazla/meta-core/internal/watcher"
 	"github.com/metazla/meta-core/internal/watchers"
+	"github.com/metazla/meta-core/internal/webdav"
 )
 
 // Server is the HTTP API server for meta-core
@@ -33,6 +36,11 @@ type Server struct {
 	watchersManager   *watchers.Manager
 	watchersPoller    *watchers.Poller
 	watchersHandlers  *watchers.Handlers
+	cacheManager      *cache.Manager
+	cacheHandlers     *cache.Handlers
+	cacheInvalidator  *cache.Invalidator
+	metaPublisher     *events.MetaPublisher
+	webdavHandler     *webdav.Handler
 	router            *mux.Router
 	server            *http.Server
 }
@@ -100,6 +108,18 @@ func NewServer(
 		mountsManager.SetPoller(s.mountPoller)
 	}
 
+	// Initialize cache manager
+	cacheManager, err := cache.NewManager(cfg)
+	if err != nil {
+		log.Printf("[API] Warning: failed to initialize cache manager: %v", err)
+	} else {
+		s.cacheManager = cacheManager
+		s.cacheHandlers = cache.NewHandlers(cacheManager)
+		s.webdavHandler = webdav.NewHandler(cfg, cacheManager)
+
+		// Cache invalidator will be initialized in Start() after Redis is connected
+	}
+
 	s.setupRoutes()
 	return s
 }
@@ -179,6 +199,19 @@ func (s *Server) setupRoutes() {
 		log.Println("[API] Watchers management routes registered at /api/watchers/*")
 	}
 
+	// Cache management routes (if cache initialized)
+	if s.cacheHandlers != nil {
+		s.cacheHandlers.RegisterRoutes(s.router)
+		log.Println("[API] Cache management routes registered at /api/cache/*")
+	}
+
+	// WebDAV handler (if cache initialized)
+	if s.webdavHandler != nil {
+		s.router.PathPrefix("/webdav/").Handler(s.webdavHandler)
+		s.router.PathPrefix("/webdav").Handler(s.webdavHandler)
+		log.Println("[API] WebDAV routes registered at /webdav/*")
+	}
+
 	// Add middleware
 	s.router.Use(loggingMiddleware)
 	s.router.Use(corsMiddleware)
@@ -218,6 +251,30 @@ func (s *Server) Start() error {
 		}
 	}
 
+	// Start cache manager (if initialized)
+	if s.cacheManager != nil {
+		if err := s.cacheManager.Start(); err != nil {
+			log.Printf("[API] Warning: failed to start cache manager: %v", err)
+		}
+
+		// Initialize cache invalidator now that Redis is connected
+		if s.storage != nil && s.storage.IsConnected() {
+			s.cacheInvalidator = cache.NewInvalidator(s.cacheManager, s.storage.GetRedisClient())
+			if err := s.cacheInvalidator.Start(); err != nil {
+				log.Printf("[API] Warning: failed to start cache invalidator: %v", err)
+			}
+		}
+	}
+
+	// Start meta publisher (if storage is connected)
+	// Publishes keyspace notifications to meta:events stream
+	if s.storage != nil && s.storage.IsConnected() {
+		s.metaPublisher = events.NewMetaPublisher(s.storage.GetRedisClient())
+		if err := s.metaPublisher.Start(); err != nil {
+			log.Printf("[API] Warning: failed to start meta publisher: %v", err)
+		}
+	}
+
 	return nil
 }
 
@@ -237,6 +294,27 @@ func (s *Server) Stop() error {
 		}
 	}
 
+	// Stop meta publisher
+	if s.metaPublisher != nil {
+		if err := s.metaPublisher.Stop(); err != nil {
+			log.Printf("[API] Warning: failed to stop meta publisher: %v", err)
+		}
+	}
+
+	// Stop cache invalidator
+	if s.cacheInvalidator != nil {
+		if err := s.cacheInvalidator.Stop(); err != nil {
+			log.Printf("[API] Warning: failed to stop cache invalidator: %v", err)
+		}
+	}
+
+	// Stop cache manager
+	if s.cacheManager != nil {
+		if err := s.cacheManager.Stop(); err != nil {
+			log.Printf("[API] Warning: failed to stop cache manager: %v", err)
+		}
+	}
+
 	if s.server == nil {
 		return nil
 	}

internal/cache/handlers.go

@@ -0,0 +1,73 @@
+package cache
+
+import (
+	"encoding/json"
+	"log"
+	"net/http"
+
+	"github.com/gorilla/mux"
+)
+
+// Handlers provides HTTP handlers for cache management
+type Handlers struct {
+	manager *Manager
+}
+
+// NewHandlers creates new cache handlers
+func NewHandlers(manager *Manager) *Handlers {
+	return &Handlers{
+		manager: manager,
+	}
+}
+
+// RegisterRoutes registers cache management routes
+func (h *Handlers) RegisterRoutes(router *mux.Router) {
+	router.HandleFunc("/api/cache/stats", h.handleStats).Methods("GET")
+	router.HandleFunc("/api/cache/clear", h.handleClear).Methods("POST")
+	router.HandleFunc("/api/cache/invalidate", h.handleInvalidate).Methods("DELETE")
+}
+
+// handleStats returns cache statistics
+func (h *Handlers) handleStats(w http.ResponseWriter, r *http.Request) {
+	stats := h.manager.Stats()
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(stats)
+}
+
+// handleClear clears the entire cache
+func (h *Handlers) handleClear(w http.ResponseWriter, r *http.Request) {
+	if err := h.manager.Clear(); err != nil {
+		log.Printf("[CacheHandlers] Error clearing cache: %v", err)
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(map[string]interface{}{
+		"success": true,
+		"message": "Cache cleared",
+	})
+}
+
+// handleInvalidate invalidates a specific path
+func (h *Handlers) handleInvalidate(w http.ResponseWriter, r *http.Request) {
+	path := r.URL.Query().Get("path")
+	if path == "" {
+		http.Error(w, "path query parameter required", http.StatusBadRequest)
+		return
+	}
+
+	if err := h.manager.Invalidate(path); err != nil {
+		log.Printf("[CacheHandlers] Error invalidating path %s: %v", path, err)
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(map[string]interface{}{
+		"success": true,
+		"message": "Path invalidated",
+		"path":    path,
+	})
+}

internal/cache/index.go

@@ -0,0 +1,242 @@
+package cache
+
+import (
+	"container/list"
+	"sync"
+	"time"
+)
+
+// LRUIndex maintains an in-memory LRU index of cache entries
+type LRUIndex struct {
+	mu       sync.RWMutex
+	entries  map[string]*list.Element // path -> list element
+	lruList  *list.List               // LRU order (front = most recent)
+	maxSize  int64                    // Maximum total size in bytes
+	currSize int64                    // Current total size in bytes
+
+	// Stats
+	hitCount      int64
+	missCount     int64
+	evictionCount int64
+}
+
+// lruEntry wraps CacheEntry for the linked list
+type lruEntry struct {
+	entry *CacheEntry
+}
+
+// NewLRUIndex creates a new LRU index
+func NewLRUIndex(maxSizeGB int) *LRUIndex {
+	return &LRUIndex{
+		entries: make(map[string]*list.Element),
+		lruList: list.New(),
+		maxSize: int64(maxSizeGB) * 1024 * 1024 * 1024, // GB to bytes
+	}
+}
+
+// Get retrieves a cache entry and updates its LRU position
+// Returns nil if not found
+func (idx *LRUIndex) Get(path string) *CacheEntry {
+	idx.mu.Lock()
+	defer idx.mu.Unlock()
+
+	elem, exists := idx.entries[path]
+	if !exists {
+		idx.missCount++
+		return nil
+	}
+
+	// Move to front (most recently used)
+	idx.lruList.MoveToFront(elem)
+
+	// Update last accessed time
+	entry := elem.Value.(*lruEntry).entry
+	entry.LastAccessed = time.Now()
+
+	idx.hitCount++
+	return entry
+}
+
+// Put adds or updates a cache entry
+func (idx *LRUIndex) Put(entry *CacheEntry) {
+	idx.mu.Lock()
+	defer idx.mu.Unlock()
+
+	if elem, exists := idx.entries[entry.OriginalPath]; exists {
+		// Update existing entry
+		oldEntry := elem.Value.(*lruEntry).entry
+		idx.currSize -= oldEntry.Size
+		idx.currSize += entry.Size
+
+		elem.Value.(*lruEntry).entry = entry
+		idx.lruList.MoveToFront(elem)
+	} else {
+		// Add new entry
+		le := &lruEntry{entry: entry}
+		elem := idx.lruList.PushFront(le)
+		idx.entries[entry.OriginalPath] = elem
+		idx.currSize += entry.Size
+	}
+}
+
+// Remove removes a cache entry by path
+// Returns the removed entry or nil if not found
+func (idx *LRUIndex) Remove(path string) *CacheEntry {
+	idx.mu.Lock()
+	defer idx.mu.Unlock()
+
+	elem, exists := idx.entries[path]
+	if !exists {
+		return nil
+	}
+
+	entry := elem.Value.(*lruEntry).entry
+	idx.lruList.Remove(elem)
+	delete(idx.entries, path)
+	idx.currSize -= entry.Size
+
+	return entry
+}
+
+// GetLRUEntry returns the least recently used entry without removing it
+// Returns nil if the index is empty
+func (idx *LRUIndex) GetLRUEntry() *CacheEntry {
+	idx.mu.RLock()
+	defer idx.mu.RUnlock()
+
+	back := idx.lruList.Back()
+	if back == nil {
+		return nil
+	}
+
+	return back.Value.(*lruEntry).entry
+}
+
+// PopLRUEntry removes and returns the least recently used entry
+// Returns nil if the index is empty
+func (idx *LRUIndex) PopLRUEntry() *CacheEntry {
+	idx.mu.Lock()
+	defer idx.mu.Unlock()
+
+	back := idx.lruList.Back()
+	if back == nil {
+		return nil
+	}
+
+	entry := back.Value.(*lruEntry).entry
+	idx.lruList.Remove(back)
+	delete(idx.entries, entry.OriginalPath)
+	idx.currSize -= entry.Size
+	idx.evictionCount++
+
+	return entry
+}
+
+// GetExpiredEntries returns all entries that have exceeded the TTL
+func (idx *LRUIndex) GetExpiredEntries(ttl time.Duration) []*CacheEntry {
+	idx.mu.RLock()
+	defer idx.mu.RUnlock()
+
+	var expired []*CacheEntry
+	cutoff := time.Now().Add(-ttl)
+
+	for elem := idx.lruList.Back(); elem != nil; elem = elem.Prev() {
+		entry := elem.Value.(*lruEntry).entry
+		if entry.CachedAt.Before(cutoff) {
+			expired = append(expired, entry)
+		}
+	}
+
+	return expired
+}
+
+// Size returns the current total size of cached files
+func (idx *LRUIndex) Size() int64 {
+	idx.mu.RLock()
+	defer idx.mu.RUnlock()
+	return idx.currSize
+}
+
+// Count returns the number of entries in the index
+func (idx *LRUIndex) Count() int {
+	idx.mu.RLock()
+	defer idx.mu.RUnlock()
+	return len(idx.entries)
+}
+
+// MaxSize returns the maximum cache size
+func (idx *LRUIndex) MaxSize() int64 {
+	return idx.maxSize
+}
+
+// NeedsEviction returns true if the cache size exceeds the maximum
+func (idx *LRUIndex) NeedsEviction() bool {
+	idx.mu.RLock()
+	defer idx.mu.RUnlock()
+	return idx.currSize > idx.maxSize
+}
+
+// Stats returns cache statistics
+func (idx *LRUIndex) Stats() *CacheStats {
+	idx.mu.RLock()
+	defer idx.mu.RUnlock()
+
+	total := idx.hitCount + idx.missCount
+	var hitRate float64
+	if total > 0 {
+		hitRate = float64(idx.hitCount) / float64(total) * 100
+	}
+
+	return &CacheStats{
+		Enabled:       true,
+		TotalSize:     idx.currSize,
+		MaxSize:       idx.maxSize,
+		EntryCount:    len(idx.entries),
+		HitCount:      idx.hitCount,
+		MissCount:     idx.missCount,
+		EvictionCount: idx.evictionCount,
+		HitRate:       hitRate,
+	}
+}
+
+// GetAllEntries returns all cache entries (for persistence)
+func (idx *LRUIndex) GetAllEntries() map[string]*CacheEntry {
+	idx.mu.RLock()
+	defer idx.mu.RUnlock()
+
+	result := make(map[string]*CacheEntry, len(idx.entries))
+	for path, elem := range idx.entries {
+		result[path] = elem.Value.(*lruEntry).entry
+	}
+	return result
+}
+
+// LoadFromMap loads entries from a map (for loading persisted index)
+func (idx *LRUIndex) LoadFromMap(entries map[string]*CacheEntry) {
+	idx.mu.Lock()
+	defer idx.mu.Unlock()
+
+	// Clear existing entries
+	idx.lruList.Init()
+	idx.entries = make(map[string]*list.Element)
+	idx.currSize = 0
+
+	// Load entries sorted by LastAccessed (oldest first for proper LRU order)
+	// For simplicity, we just add them in arbitrary order - the access pattern will sort them
+	for _, entry := range entries {
+		le := &lruEntry{entry: entry}
+		elem := idx.lruList.PushBack(le) // Add to back (oldest)
+		idx.entries[entry.OriginalPath] = elem
+		idx.currSize += entry.Size
+	}
+}
+
+// Clear removes all entries from the index
+func (idx *LRUIndex) Clear() {
+	idx.mu.Lock()
+	defer idx.mu.Unlock()
+
+	idx.lruList.Init()
+	idx.entries = make(map[string]*list.Element)
+	idx.currSize = 0
+}

internal/cache/invalidator.go

@@ -0,0 +1,166 @@
+package cache
+
+import (
+	"context"
+	"log"
+	"sync"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+)
+
+const (
+	// EventsStream is the Redis Stream name for file events
+	EventsStream = "file:events"
+
+	// ConsumerGroup is the consumer group name for cache invalidation
+	ConsumerGroup = "cache-invalidator"
+
+	// ConsumerName identifies this consumer in the group
+	ConsumerName = "meta-core-cache"
+)
+
+// Invalidator subscribes to Redis Stream for file events and invalidates cache
+type Invalidator struct {
+	manager      *Manager
+	redisClient  *redis.Client
+	ctx          context.Context
+	cancel       context.CancelFunc
+	wg           sync.WaitGroup
+	lastID       string
+}
+
+// NewInvalidator creates a new cache invalidator
+func NewInvalidator(manager *Manager, redisClient *redis.Client) *Invalidator {
+	ctx, cancel := context.WithCancel(context.Background())
+	return &Invalidator{
+		manager:     manager,
+		redisClient: redisClient,
+		ctx:         ctx,
+		cancel:      cancel,
+		lastID:      "$", // Start from new messages
+	}
+}
+
+// Start starts listening to the Redis Stream
+func (inv *Invalidator) Start() error {
+	if inv.manager == nil || !inv.manager.Enabled() {
+		log.Println("[CacheInvalidator] Cache disabled, not starting invalidator")
+		return nil
+	}
+
+	if inv.redisClient == nil {
+		log.Println("[CacheInvalidator] Redis client not available, not starting invalidator")
+		return nil
+	}
+
+	// Try to create consumer group (ignore error if already exists)
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	err := inv.redisClient.XGroupCreateMkStream(ctx, EventsStream, ConsumerGroup, "$").Err()
+	if err != nil && err.Error() != "BUSYGROUP Consumer Group name already exists" {
+		// Log but don't fail - we can still use XREAD
+		log.Printf("[CacheInvalidator] Note: consumer group creation: %v (using XREAD fallback)", err)
+	}
+
+	inv.wg.Add(1)
+	go inv.listen()
+
+	log.Println("[CacheInvalidator] Started listening on file:events stream")
+	return nil
+}
+
+// Stop stops the invalidator
+func (inv *Invalidator) Stop() error {
+	log.Println("[CacheInvalidator] Stopping...")
+	inv.cancel()
+	inv.wg.Wait()
+	return nil
+}
+
+// listen reads from the Redis Stream and processes events
+func (inv *Invalidator) listen() {
+	defer inv.wg.Done()
+
+	for {
+		select {
+		case <-inv.ctx.Done():
+			return
+		default:
+			inv.readEvents()
+		}
+	}
+}
+
+// readEvents reads and processes a batch of events
+func (inv *Invalidator) readEvents() {
+	ctx, cancel := context.WithTimeout(inv.ctx, 5*time.Second)
+	defer cancel()
+
+	// Use XREAD with BLOCK for efficient waiting
+	streams, err := inv.redisClient.XRead(ctx, &redis.XReadArgs{
+		Streams: []string{EventsStream, inv.lastID},
+		Count:   100,
+		Block:   2 * time.Second,
+	}).Result()
+
+	if err != nil {
+		if err == context.Canceled || err == context.DeadlineExceeded || err == redis.Nil {
+			return // Normal timeout or shutdown
+		}
+		log.Printf("[CacheInvalidator] Error reading stream: %v", err)
+		time.Sleep(1 * time.Second) // Backoff on error
+		return
+	}
+
+	for _, stream := range streams {
+		for _, msg := range stream.Messages {
+			inv.processEvent(msg)
+			inv.lastID = msg.ID
+		}
+	}
+}
+
+// processEvent processes a single file event
+func (inv *Invalidator) processEvent(msg redis.XMessage) {
+	eventType, _ := msg.Values["type"].(string)
+	path, _ := msg.Values["path"].(string)
+
+	switch eventType {
+	case "delete":
+		// File deleted - invalidate cache
+		if path != "" {
+			log.Printf("[CacheInvalidator] Invalidating deleted file: %s", path)
+			inv.manager.Invalidate(path)
+		}
+
+	case "change":
+		// File changed - invalidate cache
+		if path != "" {
+			log.Printf("[CacheInvalidator] Invalidating changed file: %s", path)
+			inv.manager.Invalidate(path)
+		}
+
+	case "rename":
+		// File renamed - invalidate old path
+		oldPath, _ := msg.Values["oldPath"].(string)
+		if oldPath != "" {
+			log.Printf("[CacheInvalidator] Invalidating renamed file (old): %s", oldPath)
+			inv.manager.Invalidate(oldPath)
+		}
+		// Also invalidate new path in case it was cached before
+		if path != "" {
+			inv.manager.Invalidate(path)
+		}
+
+	case "reset":
+		// Full reset - clear entire cache
+		log.Println("[CacheInvalidator] Reset event received - clearing cache")
+		inv.manager.Clear()
+
+	case "add":
+		// New file - nothing to invalidate
+		// (file wouldn't be in cache yet)
+	}
+}

internal/cache/manager.go

@@ -0,0 +1,494 @@
+package cache
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/metazla/meta-core/internal/config"
+)
+
+// Manager handles caching operations for WebDAV files
+type Manager struct {
+	config     *config.Config
+	index      *LRUIndex
+	filesPath  string
+	cachePath  string
+	ttl        time.Duration
+	enabled    bool
+
+	mu         sync.RWMutex
+	ctx        context.Context
+	cancel     context.CancelFunc
+	cleanupWg  sync.WaitGroup
+}
+
+// NewManager creates a new cache manager
+func NewManager(cfg *config.Config) (*Manager, error) {
+	if !cfg.CacheEnabled {
+		log.Println("[Cache] Caching is disabled")
+		return &Manager{
+			config:  cfg,
+			enabled: false,
+		}, nil
+	}
+
+	// Ensure cache directory exists
+	if err := os.MkdirAll(cfg.CacheDir(), 0755); err != nil {
+		return nil, fmt.Errorf("failed to create cache directory: %w", err)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	m := &Manager{
+		config:    cfg,
+		index:     NewLRUIndex(cfg.CacheMaxSizeGB),
+		filesPath: cfg.FilesPath,
+		cachePath: cfg.CacheDir(),
+		ttl:       time.Duration(cfg.CacheTTLSeconds) * time.Second,
+		enabled:   true,
+		ctx:       ctx,
+		cancel:    cancel,
+	}
+
+	// Load existing index from disk
+	if err := m.loadIndex(); err != nil {
+		log.Printf("[Cache] Warning: failed to load index: %v (starting fresh)", err)
+	}
+
+	return m, nil
+}
+
+// Start starts the cache manager (cleanup goroutine)
+func (m *Manager) Start() error {
+	if !m.enabled {
+		return nil
+	}
+
+	log.Printf("[Cache] Starting cache manager (max: %dGB, ttl: %v)",
+		m.config.CacheMaxSizeGB, m.ttl)
+
+	// Start cleanup goroutine
+	m.cleanupWg.Add(1)
+	go m.cleanupLoop()
+
+	return nil
+}
+
+// Stop stops the cache manager
+func (m *Manager) Stop() error {
+	if !m.enabled {
+		return nil
+	}
+
+	log.Println("[Cache] Stopping cache manager...")
+	m.cancel()
+	m.cleanupWg.Wait()
+
+	// Persist index
+	if err := m.saveIndex(); err != nil {
+		log.Printf("[Cache] Warning: failed to save index: %v", err)
+	}
+
+	return nil
+}
+
+// Enabled returns whether caching is enabled
+func (m *Manager) Enabled() bool {
+	return m.enabled
+}
+
+// Get retrieves a file from cache or fetches it from origin
+// Returns the cached file path and content type, or an error
+func (m *Manager) Get(path string) (string, string, error) {
+	if !m.enabled {
+		// Return original path if caching disabled
+		return filepath.Join(m.filesPath, path), "", nil
+	}
+
+	// Normalize path (remove leading slash if present)
+	path = strings.TrimPrefix(path, "/")
+
+	// Check cache
+	entry := m.index.Get(path)
+	if entry != nil {
+		// Verify cached file still exists
+		if _, err := os.Stat(entry.CachePath); err == nil {
+			log.Printf("[Cache] HIT: %s", path)
+			return entry.CachePath, entry.ContentType, nil
+		}
+		// Cached file missing, remove from index
+		m.index.Remove(path)
+	}
+
+	log.Printf("[Cache] MISS: %s", path)
+
+	// Fetch from origin and cache
+	cachedPath, contentType, err := m.fetchAndCache(path)
+	if err != nil {
+		return "", "", err
+	}
+
+	return cachedPath, contentType, nil
+}
+
+// GetOriginalPath returns the original file path (for when caching is bypassed)
+func (m *Manager) GetOriginalPath(path string) string {
+	path = strings.TrimPrefix(path, "/")
+	return filepath.Join(m.filesPath, path)
+}
+
+// fetchAndCache fetches a file from origin and caches it
+func (m *Manager) fetchAndCache(path string) (string, string, error) {
+	originPath := filepath.Join(m.filesPath, path)
+
+	// Check if origin file exists
+	info, err := os.Stat(originPath)
+	if err != nil {
+		return "", "", err
+	}
+
+	// Skip caching directories
+	if info.IsDir() {
+		return originPath, "", nil
+	}
+
+	// Generate cache path using SHA256 of original path with 2-char sharding
+	cachePath := m.getCachePath(path)
+
+	// Ensure cache subdirectory exists
+	cacheDir := filepath.Dir(cachePath)
+	if err := os.MkdirAll(cacheDir, 0755); err != nil {
+		return "", "", fmt.Errorf("failed to create cache dir: %w", err)
+	}
+
+	// Copy file to cache
+	src, err := os.Open(originPath)
+	if err != nil {
+		return "", "", err
+	}
+	defer src.Close()
+
+	dst, err := os.Create(cachePath)
+	if err != nil {
+		return "", "", err
+	}
+	defer dst.Close()
+
+	_, err = io.Copy(dst, src)
+	if err != nil {
+		os.Remove(cachePath)
+		return "", "", err
+	}
+
+	// Detect content type
+	contentType := detectContentType(originPath)
+
+	// Create cache entry
+	entry := &CacheEntry{
+		OriginalPath: path,
+		CachePath:    cachePath,
+		Size:         info.Size(),
+		CachedAt:     time.Now(),
+		LastAccessed: time.Now(),
+		ContentType:  contentType,
+	}
+
+	// Add to index
+	m.index.Put(entry)
+
+	// Trigger eviction if needed
+	m.evictIfNeeded()
+
+	log.Printf("[Cache] Cached: %s (%d bytes)", path, info.Size())
+
+	return cachePath, contentType, nil
+}
+
+// getCachePath generates a cache path using SHA256 with 2-char directory sharding
+func (m *Manager) getCachePath(path string) string {
+	hash := sha256.Sum256([]byte(path))
+	hexHash := hex.EncodeToString(hash[:])
+
+	// Use first 2 characters for sharding
+	shard := hexHash[:2]
+	filename := hexHash[2:]
+
+	return filepath.Join(m.cachePath, shard, filename)
+}
+
+// Invalidate removes a specific path from the cache
+func (m *Manager) Invalidate(path string) error {
+	if !m.enabled {
+		return nil
+	}
+
+	path = strings.TrimPrefix(path, "/")
+
+	entry := m.index.Remove(path)
+	if entry == nil {
+		return nil // Not in cache
+	}
+
+	// Remove cached file
+	if err := os.Remove(entry.CachePath); err != nil && !os.IsNotExist(err) {
+		log.Printf("[Cache] Warning: failed to remove cached file: %v", err)
+	}
+
+	log.Printf("[Cache] Invalidated: %s", path)
+	return nil
+}
+
+// Clear removes all entries from the cache
+func (m *Manager) Clear() error {
+	if !m.enabled {
+		return nil
+	}
+
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	// Get all entries before clearing
+	entries := m.index.GetAllEntries()
+
+	// Clear index
+	m.index.Clear()
+
+	// Remove all cached files
+	for _, entry := range entries {
+		if err := os.Remove(entry.CachePath); err != nil && !os.IsNotExist(err) {
+			log.Printf("[Cache] Warning: failed to remove cached file: %v", err)
+		}
+	}
+
+	// Remove empty shard directories
+	files, err := os.ReadDir(m.cachePath)
+	if err == nil {
+		for _, f := range files {
+			if f.IsDir() && len(f.Name()) == 2 {
+				dirPath := filepath.Join(m.cachePath, f.Name())
+				os.Remove(dirPath) // Only removes if empty
+			}
+		}
+	}
+
+	log.Printf("[Cache] Cleared %d entries", len(entries))
+	return nil
+}
+
+// Stats returns cache statistics
+func (m *Manager) Stats() *CacheStats {
+	if !m.enabled {
+		return &CacheStats{Enabled: false}
+	}
+
+	stats := m.index.Stats()
+	stats.TTLSeconds = m.config.CacheTTLSeconds
+	return stats
+}
+
+// evictIfNeeded evicts LRU entries until cache is under max size
+func (m *Manager) evictIfNeeded() {
+	for m.index.NeedsEviction() {
+		entry := m.index.PopLRUEntry()
+		if entry == nil {
+			break
+		}
+
+		// Remove cached file
+		if err := os.Remove(entry.CachePath); err != nil && !os.IsNotExist(err) {
+			log.Printf("[Cache] Warning: failed to remove evicted file: %v", err)
+		}
+
+		log.Printf("[Cache] Evicted (LRU): %s", entry.OriginalPath)
+	}
+}
+
+// cleanupLoop periodically cleans up expired entries
+func (m *Manager) cleanupLoop() {
+	defer m.cleanupWg.Done()
+
+	ticker := time.NewTicker(5 * time.Minute)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-m.ctx.Done():
+			return
+		case <-ticker.C:
+			m.cleanupExpired()
+			m.evictIfNeeded()
+
+			// Periodically save index
+			if err := m.saveIndex(); err != nil {
+				log.Printf("[Cache] Warning: failed to save index: %v", err)
+			}
+		}
+	}
+}
+
+// cleanupExpired removes entries that have exceeded TTL
+func (m *Manager) cleanupExpired() {
+	expired := m.index.GetExpiredEntries(m.ttl)
+
+	for _, entry := range expired {
+		m.index.Remove(entry.OriginalPath)
+
+		if err := os.Remove(entry.CachePath); err != nil && !os.IsNotExist(err) {
+			log.Printf("[Cache] Warning: failed to remove expired file: %v", err)
+		}
+
+		log.Printf("[Cache] Expired (TTL): %s", entry.OriginalPath)
+	}
+
+	if len(expired) > 0 {
+		log.Printf("[Cache] Cleaned up %d expired entries", len(expired))
+	}
+}
+
+// loadIndex loads the cache index from disk
+func (m *Manager) loadIndex() error {
+	indexPath := m.config.CacheIndexPath()
+
+	data, err := os.ReadFile(indexPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil // No index file yet
+		}
+		return err
+	}
+
+	var idx CacheIndex
+	if err := json.Unmarshal(data, &idx); err != nil {
+		return err
+	}
+
+	// Validate and load entries
+	validEntries := make(map[string]*CacheEntry)
+	for path, entry := range idx.Entries {
+		// Verify cached file still exists
+		if _, err := os.Stat(entry.CachePath); err == nil {
+			validEntries[path] = entry
+		}
+	}
+
+	m.index.LoadFromMap(validEntries)
+
+	log.Printf("[Cache] Loaded %d entries from index", len(validEntries))
+	return nil
+}
+
+// saveIndex persists the cache index to disk
+func (m *Manager) saveIndex() error {
+	indexPath := m.config.CacheIndexPath()
+
+	idx := &CacheIndex{
+		Version:   1,
+		Entries:   m.index.GetAllEntries(),
+		Stats:     m.index.Stats(),
+		UpdatedAt: time.Now(),
+	}
+
+	data, err := json.MarshalIndent(idx, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	// Write atomically using temp file
+	tmpPath := indexPath + ".tmp"
+	if err := os.WriteFile(tmpPath, data, 0644); err != nil {
+		return err
+	}
+
+	return os.Rename(tmpPath, indexPath)
+}
+
+// detectContentType detects the content type based on file extension
+func detectContentType(path string) string {
+	ext := strings.ToLower(filepath.Ext(path))
+
+	// Common media types
+	switch ext {
+	case ".mp4":
+		return "video/mp4"
+	case ".mkv":
+		return "video/x-matroska"
+	case ".avi":
+		return "video/x-msvideo"
+	case ".webm":
+		return "video/webm"
+	case ".mov":
+		return "video/quicktime"
+	case ".mp3":
+		return "audio/mpeg"
+	case ".flac":
+		return "audio/flac"
+	case ".wav":
+		return "audio/wav"
+	case ".aac":
+		return "audio/aac"
+	case ".jpg", ".jpeg":
+		return "image/jpeg"
+	case ".png":
+		return "image/png"
+	case ".gif":
+		return "image/gif"
+	case ".webp":
+		return "image/webp"
+	case ".srt":
+		return "text/plain"
+	case ".vtt":
+		return "text/vtt"
+	case ".ass", ".ssa":
+		return "text/x-ssa"
+	case ".nfo":
+		return "text/plain"
+	case ".txt":
+		return "text/plain"
+	case ".json":
+		return "application/json"
+	case ".xml":
+		return "application/xml"
+	default:
+		return "application/octet-stream"
+	}
+}
+
+// ServeFile serves a file through the cache, handling HTTP response
+func (m *Manager) ServeFile(w http.ResponseWriter, r *http.Request, path string) error {
+	cachedPath, contentType, err := m.Get(path)
+	if err != nil {
+		return err
+	}
+
+	// Open the file (cached or original)
+	file, err := os.Open(cachedPath)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	stat, err := file.Stat()
+	if err != nil {
+		return err
+	}
+
+	// Set content type if detected
+	if contentType != "" {
+		w.Header().Set("Content-Type", contentType)
+	}
+
+	// Use http.ServeContent for proper range support
+	http.ServeContent(w, r, filepath.Base(path), stat.ModTime(), file)
+	return nil
+}

internal/cache/types.go

@@ -0,0 +1,48 @@
+package cache
+
+import (
+	"time"
+)
+
+// CacheEntry represents a cached file
+type CacheEntry struct {
+	OriginalPath string    `json:"originalPath"` // Relative to /files/
+	CachePath    string    `json:"cachePath"`    // Path in /meta-core/cache/
+	Size         int64     `json:"size"`
+	CachedAt     time.Time `json:"cachedAt"`
+	LastAccessed time.Time `json:"lastAccessed"`
+	ContentType  string    `json:"contentType"`
+}
+
+// CacheStats provides cache statistics
+type CacheStats struct {
+	Enabled       bool    `json:"enabled"`
+	TotalSize     int64   `json:"totalSize"`     // Current cache size in bytes
+	MaxSize       int64   `json:"maxSize"`       // Maximum cache size in bytes
+	EntryCount    int     `json:"entryCount"`    // Number of cached entries
+	HitCount      int64   `json:"hitCount"`      // Number of cache hits
+	MissCount     int64   `json:"missCount"`     // Number of cache misses
+	EvictionCount int64   `json:"evictionCount"` // Number of evictions
+	HitRate       float64 `json:"hitRate"`       // Hit rate percentage
+	TTLSeconds    int     `json:"ttlSeconds"`    // TTL in seconds
+}
+
+// CacheIndex is the persistent index structure
+type CacheIndex struct {
+	Version   int                    `json:"version"`
+	Entries   map[string]*CacheEntry `json:"entries"` // keyed by OriginalPath
+	Stats     *CacheStats            `json:"stats"`
+	UpdatedAt time.Time              `json:"updatedAt"`
+}
+
+// NewCacheIndex creates a new empty cache index
+func NewCacheIndex() *CacheIndex {
+	return &CacheIndex{
+		Version: 1,
+		Entries: make(map[string]*CacheEntry),
+		Stats: &CacheStats{
+			Enabled: true,
+		},
+		UpdatedAt: time.Now(),
+	}
+}

internal/config/config.go

@@ -39,6 +39,12 @@ type Config struct {
 
 	// Mount configuration
 	MountsDir string // Path to mounts configuration (default: /meta-core/mounts)
+
+	// Cache configuration
+	CacheEnabled    bool   // Enable WebDAV caching (default: true)
+	CachePath       string // Path to cache directory (default: /meta-core/cache)
+	CacheMaxSizeGB  int    // Maximum cache size in GB (default: 100)
+	CacheTTLSeconds int    // Cache entry TTL in seconds (default: 3600)
 }
 
 // Load creates a Config from environment variables
@@ -66,6 +72,12 @@ func Load() *Config {
 	// Set mounts directory
 	cfg.MountsDir = cfg.MetaCorePath + "/mounts"
 
+	// Set cache configuration
+	cfg.CacheEnabled = getEnvBool("CACHE_ENABLED", true)
+	cfg.CachePath = getEnv("CACHE_PATH", cfg.MetaCorePath+"/cache")
+	cfg.CacheMaxSizeGB = getEnvInt("CACHE_MAX_SIZE_GB", 100)
+	cfg.CacheTTLSeconds = getEnvInt("CACHE_TTL_SECONDS", 3600)
+
 	return cfg
 }
 
@@ -99,6 +111,16 @@ func (c *Config) MountsErrorDir() string {
 	return c.MountsDir + "/errors"
 }
 
+// CacheDir returns the path to the cache directory
+func (c *Config) CacheDir() string {
+	return c.CachePath
+}
+
+// CacheIndexPath returns the path to the cache index file
+func (c *Config) CacheIndexPath() string {
+	return c.CachePath + "/cache-index.json"
+}
+
 // WatchersFilePath returns the path to the watchers configuration file
 func (c *Config) WatchersFilePath() string {
 	return c.MetaCorePath + "/watchers.json"

internal/events/meta_publisher.go

@@ -0,0 +1,139 @@
+package events
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+)
+
+const (
+	// MetaEventsStream is the Redis stream name for metadata events
+	MetaEventsStream = "meta:events"
+	// StreamMaxLen is the maximum stream length (approximate)
+	StreamMaxLen = 10000
+)
+
+// MetaPublisher subscribes to Redis keyspace notifications
+// and publishes metadata change events to the meta:events stream
+type MetaPublisher struct {
+	client  *redis.Client
+	ctx     context.Context
+	cancel  context.CancelFunc
+	wg      sync.WaitGroup
+	running bool
+	mu      sync.RWMutex
+}
+
+// NewMetaPublisher creates a new MetaPublisher
+func NewMetaPublisher(client *redis.Client) *MetaPublisher {
+	ctx, cancel := context.WithCancel(context.Background())
+	return &MetaPublisher{
+		client: client,
+		ctx:    ctx,
+		cancel: cancel,
+	}
+}
+
+// Start begins subscribing to keyspace notifications
+func (p *MetaPublisher) Start() error {
+	p.mu.Lock()
+	if p.running {
+		p.mu.Unlock()
+		return nil
+	}
+	p.running = true
+	p.mu.Unlock()
+
+	p.wg.Add(1)
+	go p.subscribeLoop()
+
+	log.Println("[MetaPublisher] Started - listening for keyspace notifications")
+	return nil
+}
+
+// Stop stops the publisher
+func (p *MetaPublisher) Stop() error {
+	p.mu.Lock()
+	if !p.running {
+		p.mu.Unlock()
+		return nil
+	}
+	p.running = false
+	p.mu.Unlock()
+
+	p.cancel()
+	p.wg.Wait()
+
+	log.Println("[MetaPublisher] Stopped")
+	return nil
+}
+
+// IsRunning returns true if the publisher is running
+func (p *MetaPublisher) IsRunning() bool {
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+	return p.running
+}
+
+// subscribeLoop subscribes to keyspace notifications and publishes events
+func (p *MetaPublisher) subscribeLoop() {
+	defer p.wg.Done()
+
+	// Subscribe to all file:* keyspace events
+	// Pattern: __keyspace@0__:file:*
+	pattern := "__keyspace@0__:file:*"
+	pubsub := p.client.PSubscribe(p.ctx, pattern)
+	defer pubsub.Close()
+
+	log.Printf("[MetaPublisher] Subscribed to pattern: %s", pattern)
+
+	ch := pubsub.Channel()
+	for {
+		select {
+		case <-p.ctx.Done():
+			return
+		case msg := <-ch:
+			if msg == nil {
+				continue
+			}
+			// msg.Channel: __keyspace@0__:file:midhash256:abc123/tmdb
+			// msg.Payload: set, del, expire, etc.
+			p.publishEvent(msg.Channel, msg.Payload)
+		}
+	}
+}
+
+// publishEvent publishes a keyspace event to the meta:events stream
+func (p *MetaPublisher) publishEvent(channel, operation string) {
+	// Extract key from channel: __keyspace@0__:file:xxx/field -> file:xxx/field
+	key := strings.TrimPrefix(channel, "__keyspace@0__:")
+
+	// Skip index key and non-file keys
+	if strings.Contains(key, "__index__") || !strings.HasPrefix(key, "file:") {
+		return
+	}
+
+	// Build event fields
+	fields := map[string]interface{}{
+		"type": operation, // "set", "del", "expire"
+		"key":  key,       // "file:midhash256:abc123/tmdb"
+		"ts":   fmt.Sprintf("%d", time.Now().UnixMilli()),
+	}
+
+	// Add to stream
+	_, err := p.client.XAdd(p.ctx, &redis.XAddArgs{
+		Stream: MetaEventsStream,
+		MaxLen: StreamMaxLen,
+		Approx: true,
+		Values: fields,
+	}).Result()
+
+	if err != nil {
+		log.Printf("[MetaPublisher] Error publishing event: %v", err)
+	}
+}

internal/leader/redis.go

@@ -57,6 +57,11 @@ func (rm *RedisManager) Start() error {
 		"--dbfilename", "dump.rdb",
 		"--save", "60", "1", // Save after 60 seconds if at least 1 key changed
 		"--loglevel", "warning",
+		// Enable keyspace notifications for meta:events stream
+		// K = Keyspace events (publish to __keyspace@0__:keyname)
+		// g = Generic commands (DEL, EXPIRE, RENAME)
+		// $ = String commands (SET, MSET, etc.)
+		"--notify-keyspace-events", "Kg$",
 	}
 
 	rm.cmd = exec.Command("redis-server", args...)

internal/storage/client.go

@@ -97,9 +97,9 @@ func (c *Client) buildKey(key string) string {
 	return key
 }
 
-// buildHashKey constructs the Redis Hash key for a file
-func (c *Client) buildHashKey(hashID string) string {
-	return c.buildKey(fmt.Sprintf("file:%s", hashID))
+// buildKeyPrefix constructs the prefix for a file's flat keys
+func (c *Client) buildKeyPrefix(hashID string) string {
+	return c.buildKey(fmt.Sprintf("file:%s/", hashID))
 }
 
 // buildIndexKey constructs the key for the file index set
@@ -108,7 +108,7 @@ func (c *Client) buildIndexKey() string {
 }
 
 // GetMetadataFlat retrieves all metadata for a file as a flat map
-// Uses Redis Hash: HGETALL file:{hashId}
+// Uses flat keys: SCAN file:{hashId}/* then MGET
 func (c *Client) GetMetadataFlat(hashID string) (map[string]string, error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
@@ -120,10 +120,34 @@ func (c *Client) GetMetadataFlat(hashID string) (map[string]string, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancel()
 
-	hashKey := c.buildHashKey(hashID)
-	result, err := c.client.HGetAll(ctx, hashKey).Result()
-	if err != nil {
-		return nil, fmt.Errorf("hgetall failed: %w", err)
+	prefix := c.buildKeyPrefix(hashID)
+	result := make(map[string]string)
+
+	// Scan for all keys with this prefix
+	var cursor uint64
+	for {
+		keys, nextCursor, err := c.client.Scan(ctx, cursor, prefix+"*", 1000).Result()
+		if err != nil {
+			return nil, fmt.Errorf("scan failed: %w", err)
+		}
+
+		if len(keys) > 0 {
+			values, err := c.client.MGet(ctx, keys...).Result()
+			if err != nil {
+				return nil, fmt.Errorf("mget failed: %w", err)
+			}
+			for i, key := range keys {
+				field := strings.TrimPrefix(key, prefix)
+				if values[i] != nil {
+					result[field] = values[i].(string)
+				}
+			}
+		}
+
+		cursor = nextCursor
+		if cursor == 0 {
+			break
+		}
 	}
 
 	if len(result) == 0 {
@@ -133,8 +157,8 @@ func (c *Client) GetMetadataFlat(hashID string) (map[string]string, error) {
 	return result, nil
 }
 
-// SetMetadataFlat stores metadata for a file using Redis Hash
-// Uses Redis Hash: HMSET file:{hashId} prop1 val1 prop2 val2...
+// SetMetadataFlat stores metadata for a file using flat keys
+// Uses pipeline SET for each key: file:{hashId}/{property}
 func (c *Client) SetMetadataFlat(hashID string, metadata map[string]string) error {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
@@ -150,11 +174,15 @@ func (c *Client) SetMetadataFlat(hashID string, metadata map[string]string) erro
 	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancel()
 
-	hashKey := c.buildHashKey(hashID)
+	prefix := c.buildKeyPrefix(hashID)
+	pipe := c.client.Pipeline()
 
-	// Use HMSET to set all fields at once
-	if err := c.client.HMSet(ctx, hashKey, metadata).Err(); err != nil {
-		return fmt.Errorf("hmset failed: %w", err)
+	for field, value := range metadata {
+		pipe.Set(ctx, prefix+field, value, 0)
+	}
+
+	if _, err := pipe.Exec(ctx); err != nil {
+		return fmt.Errorf("pipeline exec failed: %w", err)
 	}
 
 	// Add to index set
@@ -188,7 +216,7 @@ func (c *Client) GetAllHashIDs() ([]string, error) {
 }
 
 // GetProperty retrieves a single property value
-// Uses Redis Hash: HGET file:{hashId} {property}
+// Uses flat key: GET file:{hashId}/{property}
 func (c *Client) GetProperty(hashID, property string) (string, error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
@@ -200,8 +228,8 @@ func (c *Client) GetProperty(hashID, property string) (string, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 	defer cancel()
 
-	hashKey := c.buildHashKey(hashID)
-	result, err := c.client.HGet(ctx, hashKey, property).Result()
+	key := c.buildKeyPrefix(hashID) + property
+	result, err := c.client.Get(ctx, key).Result()
 	if err == redis.Nil {
 		return "", nil
 	}
@@ -209,7 +237,7 @@ func (c *Client) GetProperty(hashID, property string) (string, error) {
 }
 
 // SetProperty sets a single property value
-// Uses Redis Hash: HSET file:{hashId} {property} {value}
+// Uses flat key: SET file:{hashId}/{property} {value}
 func (c *Client) SetProperty(hashID, property, value string) error {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
@@ -221,11 +249,11 @@ func (c *Client) SetProperty(hashID, property, value string) error {
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 	defer cancel()
 
-	hashKey := c.buildHashKey(hashID)
+	key := c.buildKeyPrefix(hashID) + property
 
-	// Use HSET to set the field
-	if err := c.client.HSet(ctx, hashKey, property, value).Err(); err != nil {
-		return fmt.Errorf("hset failed: %w", err)
+	// Use SET to set the key
+	if err := c.client.Set(ctx, key, value, 0).Err(); err != nil {
+		return fmt.Errorf("set failed: %w", err)
 	}
 
 	// Add to index set
@@ -237,7 +265,7 @@ func (c *Client) SetProperty(hashID, property, value string) error {
 }
 
 // DeleteMetadata deletes all metadata for a file
-// Uses Redis Hash: DEL file:{hashId}
+// Uses SCAN + DEL for flat keys: file:{hashId}/*
 func (c *Client) DeleteMetadata(hashID string) (int64, error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
@@ -249,25 +277,37 @@ func (c *Client) DeleteMetadata(hashID string) (int64, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancel()
 
-	hashKey := c.buildHashKey(hashID)
+	prefix := c.buildKeyPrefix(hashID)
 
-	// Get field count before deletion
-	fieldCount, err := c.client.HLen(ctx, hashKey).Result()
-	if err != nil {
-		return 0, fmt.Errorf("hlen failed: %w", err)
-	}
+	// Scan and delete all keys with this prefix
+	var deletedCount int64
+	var cursor uint64
+	for {
+		keys, nextCursor, err := c.client.Scan(ctx, cursor, prefix+"*", 1000).Result()
+		if err != nil {
+			return deletedCount, fmt.Errorf("scan failed: %w", err)
+		}
 
-	// Delete the hash
-	if err := c.client.Del(ctx, hashKey).Err(); err != nil {
-		return 0, fmt.Errorf("del failed: %w", err)
+		if len(keys) > 0 {
+			deleted, err := c.client.Del(ctx, keys...).Result()
+			if err != nil {
+				return deletedCount, fmt.Errorf("del failed: %w", err)
+			}
+			deletedCount += deleted
+		}
+
+		cursor = nextCursor
+		if cursor == 0 {
+			break
+		}
 	}
 
 	// Remove from index set
 	if err := c.client.SRem(ctx, c.buildIndexKey(), hashID).Err(); err != nil {
-		return fieldCount, fmt.Errorf("srem index failed: %w", err)
+		return deletedCount, fmt.Errorf("srem index failed: %w", err)
 	}
 
-	return fieldCount, nil
+	return deletedCount, nil
 }
 
 // CountFiles returns the number of unique files stored
@@ -302,23 +342,23 @@ func (c *Client) LookupPathByCID(cid string) (string, error) {
 		return "", err
 	}
 
-	// For each hash, check poster and backdrop CIDs using Hash operations
+	// For each hash, check poster and backdrop CIDs using flat keys
 	for _, hashID := range hashIDs {
-		hashKey := c.buildHashKey(hashID)
+		prefix := c.buildKeyPrefix(hashID)
 
 		// Check poster
-		posterCID, err := c.client.HGet(ctx, hashKey, "poster").Result()
+		posterCID, err := c.client.Get(ctx, prefix+"poster").Result()
 		if err == nil && posterCID == cid {
-			posterPath, err := c.client.HGet(ctx, hashKey, "posterPath").Result()
+			posterPath, err := c.client.Get(ctx, prefix+"posterPath").Result()
 			if err == nil && posterPath != "" {
 				return posterPath, nil
 			}
 		}
 
 		// Check backdrop
-		backdropCID, err := c.client.HGet(ctx, hashKey, "backdrop").Result()
+		backdropCID, err := c.client.Get(ctx, prefix+"backdrop").Result()
 		if err == nil && backdropCID == cid {
-			backdropPath, err := c.client.HGet(ctx, hashKey, "backdropPath").Result()
+			backdropPath, err := c.client.Get(ctx, prefix+"backdropPath").Result()
 			if err == nil && backdropPath != "" {
 				return backdropPath, nil
 			}
@@ -341,7 +381,7 @@ func (c *Client) getAllHashIDsInternal(ctx context.Context) ([]string, error) {
 
 // MergeMetadataFlat merges new metadata into existing (PATCH semantics)
 // New keys are added, existing keys are updated, missing keys are NOT deleted
-// Uses Redis Hash: HMSET file:{hashId}
+// Uses pipeline SET for flat keys: file:{hashId}/{property}
 func (c *Client) MergeMetadataFlat(hashID string, metadata map[string]string) (int, error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
@@ -357,11 +397,15 @@ func (c *Client) MergeMetadataFlat(hashID string, metadata map[string]string) (i
 	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancel()
 
-	hashKey := c.buildHashKey(hashID)
+	prefix := c.buildKeyPrefix(hashID)
+	pipe := c.client.Pipeline()
 
-	// Use HMSET to merge fields
-	if err := c.client.HMSet(ctx, hashKey, metadata).Err(); err != nil {
-		return 0, fmt.Errorf("hmset failed: %w", err)
+	for field, value := range metadata {
+		pipe.Set(ctx, prefix+field, value, 0)
+	}
+
+	if _, err := pipe.Exec(ctx); err != nil {
+		return 0, fmt.Errorf("pipeline exec failed: %w", err)
 	}
 
 	// Add to index set
@@ -373,7 +417,7 @@ func (c *Client) MergeMetadataFlat(hashID string, metadata map[string]string) (i
 }
 
 // DeleteProperty deletes a single property
-// Uses Redis Hash: HDEL file:{hashId} {property}
+// Uses flat key: DEL file:{hashId}/{property}
 func (c *Client) DeleteProperty(hashID, property string) error {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
@@ -385,11 +429,11 @@ func (c *Client) DeleteProperty(hashID, property string) error {
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 	defer cancel()
 
-	hashKey := c.buildHashKey(hashID)
-	return c.client.HDel(ctx, hashKey, property).Err()
+	key := c.buildKeyPrefix(hashID) + property
+	return c.client.Del(ctx, key).Err()
 }
 
-// AddToSet adds a value to a set-type field (stored as pipe-delimited string in Hash field)
+// AddToSet adds a value to a set-type field (stored as pipe-delimited string in flat key)
 // Returns true if value was added, false if it already existed
 func (c *Client) AddToSet(hashID, property, value string) (bool, error) {
 	c.mu.Lock()
@@ -402,10 +446,10 @@ func (c *Client) AddToSet(hashID, property, value string) (bool, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 	defer cancel()
 
-	hashKey := c.buildHashKey(hashID)
+	key := c.buildKeyPrefix(hashID) + property
 
 	// Get current value
-	current, err := c.client.HGet(ctx, hashKey, property).Result()
+	current, err := c.client.Get(ctx, key).Result()
 	if err != nil && err != redis.Nil {
 		return false, err
 	}
@@ -427,8 +471,8 @@ func (c *Client) AddToSet(hashID, property, value string) (bool, error) {
 	values = append(values, value)
 	newValue := strings.Join(values, "|")
 
-	// Save back using HSET
-	if err := c.client.HSet(ctx, hashKey, property, newValue).Err(); err != nil {
+	// Save back using SET
+	if err := c.client.Set(ctx, key, newValue, 0).Err(); err != nil {
 		return false, err
 	}
 
@@ -440,7 +484,7 @@ func (c *Client) AddToSet(hashID, property, value string) (bool, error) {
 	return true, nil
 }
 
-// RemoveFromSet removes a value from a set-type field (stored in Hash)
+// RemoveFromSet removes a value from a set-type field (stored in flat key)
 // Returns true if value was removed, false if it didn't exist
 func (c *Client) RemoveFromSet(hashID, property, value string) (bool, error) {
 	c.mu.Lock()
@@ -453,12 +497,12 @@ func (c *Client) RemoveFromSet(hashID, property, value string) (bool, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 	defer cancel()
 
-	hashKey := c.buildHashKey(hashID)
+	key := c.buildKeyPrefix(hashID) + property
 
 	// Get current value
-	current, err := c.client.HGet(ctx, hashKey, property).Result()
+	current, err := c.client.Get(ctx, key).Result()
 	if err == redis.Nil {
-		return false, nil // Field doesn't exist
+		return false, nil // Key doesn't exist
 	}
 	if err != nil {
 		return false, err
@@ -482,13 +526,13 @@ func (c *Client) RemoveFromSet(hashID, property, value string) (bool, error) {
 		return false, nil
 	}
 
-	// Save back (or delete field if empty)
+	// Save back (or delete key if empty)
 	if len(newValues) == 0 {
-		return true, c.client.HDel(ctx, hashKey, property).Err()
+		return true, c.client.Del(ctx, key).Err()
 	}
 
 	newValue := strings.Join(newValues, "|")
-	return true, c.client.HSet(ctx, hashKey, property, newValue).Err()
+	return true, c.client.Set(ctx, key, newValue, 0).Err()
 }
 
 // GetMemoryInfo returns Redis memory usage information
@@ -540,12 +584,29 @@ func (c *Client) ClearAllMetadata() (int64, error) {
 
 	var deletedCount int64
 
-	// Delete each file's hash
+	// Delete each file's flat keys
 	for _, hashID := range hashIDs {
-		hashKey := c.buildHashKey(hashID)
-		if err := c.client.Del(ctx, hashKey).Err(); err != nil {
-			log.Printf("[Storage] Warning: failed to delete %s: %v", hashKey, err)
-			continue
+		prefix := c.buildKeyPrefix(hashID)
+
+		// Scan and delete all keys with this prefix
+		var cursor uint64
+		for {
+			keys, nextCursor, err := c.client.Scan(ctx, cursor, prefix+"*", 1000).Result()
+			if err != nil {
+				log.Printf("[Storage] Warning: failed to scan %s: %v", prefix, err)
+				break
+			}
+
+			if len(keys) > 0 {
+				if err := c.client.Del(ctx, keys...).Err(); err != nil {
+					log.Printf("[Storage] Warning: failed to delete keys for %s: %v", hashID, err)
+				}
+			}
+
+			cursor = nextCursor
+			if cursor == 0 {
+				break
+			}
 		}
 		deletedCount++
 	}
@@ -599,3 +660,42 @@ func (c *Client) XAdd(stream string, maxLen int64, fields map[string]interface{}
 
 	return id, nil
 }
+
+// ClearStream deletes a Redis stream entirely
+func (c *Client) ClearStream(stream string) error {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+
+	if c.client == nil {
+		return fmt.Errorf("not connected")
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	if err := c.client.Del(ctx, stream).Err(); err != nil {
+		return fmt.Errorf("del stream failed: %w", err)
+	}
+
+	return nil
+}
+
+// GetStreamLength returns the length of a Redis stream
+func (c *Client) GetStreamLength(stream string) (int64, error) {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+
+	if c.client == nil {
+		return 0, fmt.Errorf("not connected")
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	length, err := c.client.XLen(ctx, stream).Result()
+	if err != nil {
+		return 0, fmt.Errorf("xlen failed: %w", err)
+	}
+
+	return length, nil
+}

internal/watcher/dispatcher.go

@@ -66,6 +66,9 @@ func (d *Dispatcher) dispatchToStream(event FileEvent) {
 	if event.OldPath != "" {
 		fields["oldPath"] = event.OldPath
 	}
+	if event.WatcherID != "" {
+		fields["watcherId"] = event.WatcherID
+	}
 
 	// Publish to stream
 	_, err := client.XAdd(EventsStream, StreamMaxLen, fields)
@@ -73,3 +76,49 @@ func (d *Dispatcher) dispatchToStream(event FileEvent) {
 		log.Printf("[Dispatcher] Failed to publish to stream: %v", err)
 	}
 }
+
+// EmitReset clears the stream and emits a reset event
+// This is called when triggering a full rescan
+func (d *Dispatcher) EmitReset(watcherID string) error {
+	d.mu.RLock()
+	client := d.storageClient
+	d.mu.RUnlock()
+
+	if client == nil || !client.IsConnected() {
+		return fmt.Errorf("storage client not connected")
+	}
+
+	// Delete the stream to clear all historical events
+	if err := client.ClearStream(EventsStream); err != nil {
+		log.Printf("[Dispatcher] Warning: failed to clear stream: %v", err)
+		// Continue anyway - we'll emit the reset event
+	}
+
+	log.Printf("[Dispatcher] Cleared stream %s for reset", EventsStream)
+
+	// Emit reset event as the first message in the fresh stream
+	event := FileEvent{
+		Type:      EventTypeReset,
+		Path:      "",  // No specific path for reset
+		WatcherID: watcherID,
+		Timestamp: NowMS(),
+	}
+
+	// Dispatch synchronously for reset
+	d.dispatchToStream(event)
+
+	return nil
+}
+
+// GetStreamLength returns the current stream length
+func (d *Dispatcher) GetStreamLength() (int64, error) {
+	d.mu.RLock()
+	client := d.storageClient
+	d.mu.RUnlock()
+
+	if client == nil || !client.IsConnected() {
+		return 0, fmt.Errorf("storage client not connected")
+	}
+
+	return client.GetStreamLength(EventsStream)
+}

internal/watcher/state.go

@@ -0,0 +1,146 @@
+package watcher
+
+import (
+	"sync"
+)
+
+// FileState tracks the known state of a file
+type FileState struct {
+	Size      int64
+	MtimeNano int64
+	MidHash   string
+}
+
+// WatcherState tracks all files for a single watcher (in-memory)
+type WatcherState struct {
+	mu    sync.RWMutex
+	files map[string]*FileState // key: relative path
+}
+
+// NewWatcherState creates a new watcher state tracker
+func NewWatcherState() *WatcherState {
+	return &WatcherState{
+		files: make(map[string]*FileState),
+	}
+}
+
+// Get returns the file state for a given path, or nil if not tracked
+func (ws *WatcherState) Get(path string) *FileState {
+	ws.mu.RLock()
+	defer ws.mu.RUnlock()
+	return ws.files[path]
+}
+
+// Set updates or adds the file state for a given path
+func (ws *WatcherState) Set(path string, state *FileState) {
+	ws.mu.Lock()
+	defer ws.mu.Unlock()
+	ws.files[path] = state
+}
+
+// Delete removes a file from the tracked state
+func (ws *WatcherState) Delete(path string) {
+	ws.mu.Lock()
+	defer ws.mu.Unlock()
+	delete(ws.files, path)
+}
+
+// GetAll returns a snapshot of all tracked files
+// The returned map is a copy - safe to modify
+func (ws *WatcherState) GetAll() map[string]*FileState {
+	ws.mu.RLock()
+	defer ws.mu.RUnlock()
+
+	snapshot := make(map[string]*FileState, len(ws.files))
+	for path, state := range ws.files {
+		// Copy the state to avoid race conditions
+		stateCopy := *state
+		snapshot[path] = &stateCopy
+	}
+	return snapshot
+}
+
+// Clear removes all tracked files
+func (ws *WatcherState) Clear() {
+	ws.mu.Lock()
+	defer ws.mu.Unlock()
+	ws.files = make(map[string]*FileState)
+}
+
+// Count returns the number of tracked files
+func (ws *WatcherState) Count() int {
+	ws.mu.RLock()
+	defer ws.mu.RUnlock()
+	return len(ws.files)
+}
+
+// StateRegistry manages per-watcher state
+type StateRegistry struct {
+	mu     sync.RWMutex
+	states map[string]*WatcherState // key: watcher ID
+}
+
+// NewStateRegistry creates a new state registry
+func NewStateRegistry() *StateRegistry {
+	return &StateRegistry{
+		states: make(map[string]*WatcherState),
+	}
+}
+
+// GetOrCreate returns the state for a watcher, creating one if needed
+func (sr *StateRegistry) GetOrCreate(watcherID string) *WatcherState {
+	sr.mu.Lock()
+	defer sr.mu.Unlock()
+
+	state, exists := sr.states[watcherID]
+	if !exists {
+		state = NewWatcherState()
+		sr.states[watcherID] = state
+	}
+	return state
+}
+
+// Get returns the state for a watcher, or nil if not exists
+func (sr *StateRegistry) Get(watcherID string) *WatcherState {
+	sr.mu.RLock()
+	defer sr.mu.RUnlock()
+	return sr.states[watcherID]
+}
+
+// Clear removes the state for a watcher
+func (sr *StateRegistry) Clear(watcherID string) {
+	sr.mu.Lock()
+	defer sr.mu.Unlock()
+
+	if state, exists := sr.states[watcherID]; exists {
+		state.Clear()
+	}
+}
+
+// ClearAll removes all watcher states
+func (sr *StateRegistry) ClearAll() {
+	sr.mu.Lock()
+	defer sr.mu.Unlock()
+
+	for _, state := range sr.states {
+		state.Clear()
+	}
+}
+
+// Delete removes a watcher's state completely
+func (sr *StateRegistry) Delete(watcherID string) {
+	sr.mu.Lock()
+	defer sr.mu.Unlock()
+	delete(sr.states, watcherID)
+}
+
+// Count returns the number of files tracked for a watcher
+func (sr *StateRegistry) Count(watcherID string) int {
+	sr.mu.RLock()
+	defer sr.mu.RUnlock()
+
+	if state, exists := sr.states[watcherID]; exists {
+		return state.Count()
+	}
+	return 0
+}

internal/watcher/types.go

@@ -10,6 +10,7 @@ const (
 	EventTypeChange FileEventType = "change"
 	EventTypeDelete FileEventType = "delete"
 	EventTypeRename FileEventType = "rename"
+	EventTypeReset  FileEventType = "reset"
 )
 
 // FileEvent represents a file system event
@@ -20,6 +21,7 @@ type FileEvent struct {
 	Timestamp  int64         `json:"timestamp"`
 	MidHash256 string        `json:"midhash256,omitempty"` // midhash256 CID (SHA-256 of middle 1MB + file size)
 	OldPath    string        `json:"oldPath,omitempty"`    // For rename events
+	WatcherID  string        `json:"watcherId,omitempty"`  // For reset events
 }
 
 // PendingEvent tracks a file event that's being debounced
@@ -44,6 +46,14 @@ type ScanStatusResponse struct {
 	FileCount int    `json:"fileCount,omitempty"`
 }
 
+// DiffScanResult holds the results of a differential scan
+type DiffScanResult struct {
+	Added   int // Number of new files added
+	Changed int // Number of files with changed size/mtime
+	Deleted int // Number of files that no longer exist
+	Total   int // Total number of files currently tracked
+}
+
 // NowMS returns current time in milliseconds
 func NowMS() int64 {
 	return time.Now().UnixMilli()

internal/watcher/watcher.go

@@ -13,10 +13,11 @@ import (
 
 // Watcher provides file scanning and event dispatching
 type Watcher struct {
-	config     *config.Config
-	debouncer  *Debouncer
-	dispatcher *Dispatcher
-	filesPath  string
+	config        *config.Config
+	debouncer     *Debouncer
+	dispatcher    *Dispatcher
+	filesPath     string
+	stateRegistry *StateRegistry
 
 	mu          sync.RWMutex
 	eventBuffer []FileEvent
@@ -27,11 +28,12 @@ func NewWatcher(cfg *config.Config, dispatcher *Dispatcher) (*Watcher, error) {
 	debouncer := NewDebouncer(0) // No debouncing for polling-based scanning
 
 	w := &Watcher{
-		config:      cfg,
-		debouncer:   debouncer,
-		dispatcher:  dispatcher,
-		filesPath:   cfg.FilesPath,
-		eventBuffer: make([]FileEvent, 0, 1000),
+		config:        cfg,
+		debouncer:     debouncer,
+		dispatcher:    dispatcher,
+		filesPath:     cfg.FilesPath,
+		stateRegistry: NewStateRegistry(),
+		eventBuffer:   make([]FileEvent, 0, 1000),
 	}
 
 	return w, nil
@@ -110,6 +112,138 @@ func (w *Watcher) ScanDirectory(root string) int {
 	return count
 }
 
+// ScanDirectoryDiff scans a directory and only emits events for differences
+// Returns the count of added, changed, and deleted files
+func (w *Watcher) ScanDirectoryDiff(root string, watcherID string) DiffScanResult {
+	result := DiffScanResult{}
+	state := w.stateRegistry.GetOrCreate(watcherID)
+
+	// Get snapshot of known files
+	knownFiles := state.GetAll()
+	seenFiles := make(map[string]bool)
+
+	filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return nil
+		}
+
+		// Skip directories
+		if info.IsDir() {
+			return nil
+		}
+
+		// Skip hidden files
+		if strings.HasPrefix(filepath.Base(path), ".") {
+			return nil
+		}
+
+		// Get relative path
+		relPath, err := filepath.Rel(w.filesPath, path)
+		if err != nil {
+			relPath = path
+		}
+		relPath = filepath.ToSlash(relPath)
+		seenFiles[relPath] = true
+
+		// Check current file state
+		currentMtime := info.ModTime().UnixNano()
+		currentSize := info.Size()
+
+		prevState := knownFiles[relPath]
+
+		if prevState == nil {
+			// New file - emit add event
+			event := FileEvent{
+				Type:      EventTypeAdd,
+				Path:      relPath,
+				Size:      currentSize,
+				Timestamp: NowMS(),
+			}
+
+			// Compute midhash256
+			if hash, err := ComputeMidHash256(path); err == nil {
+				event.MidHash256 = hash
+			}
+
+			// Dispatch event
+			w.dispatcher.Dispatch(event)
+
+			// Update state
+			state.Set(relPath, &FileState{
+				Size:      currentSize,
+				MtimeNano: currentMtime,
+				MidHash:   event.MidHash256,
+			})
+
+			result.Added++
+		} else if prevState.Size != currentSize || prevState.MtimeNano != currentMtime {
+			// File changed - emit change event
+			event := FileEvent{
+				Type:      EventTypeChange,
+				Path:      relPath,
+				Size:      currentSize,
+				Timestamp: NowMS(),
+			}
+
+			// Compute midhash256
+			if hash, err := ComputeMidHash256(path); err == nil {
+				event.MidHash256 = hash
+			}
+
+			// Dispatch event
+			w.dispatcher.Dispatch(event)
+
+			// Update state
+			state.Set(relPath, &FileState{
+				Size:      currentSize,
+				MtimeNano: currentMtime,
+				MidHash:   event.MidHash256,
+			})
+
+			result.Changed++
+		}
+		// If file exists and hasn't changed, do nothing
+
+		return nil
+	})
+
+	// Check for deleted files (in known but not seen)
+	for relPath := range knownFiles {
+		if !seenFiles[relPath] {
+			// File deleted - emit delete event
+			event := FileEvent{
+				Type:      EventTypeDelete,
+				Path:      relPath,
+				Timestamp: NowMS(),
+			}
+
+			w.dispatcher.Dispatch(event)
+			state.Delete(relPath)
+			result.Deleted++
+		}
+	}
+
+	result.Total = state.Count()
+	return result
+}
+
+// ClearState clears the tracked state for a watcher
+func (w *Watcher) ClearState(watcherID string) {
+	w.stateRegistry.Clear(watcherID)
+}
+
+// ClearEventBuffer clears the in-memory event buffer
+func (w *Watcher) ClearEventBuffer() {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	w.eventBuffer = make([]FileEvent, 0, 1000)
+}
+
+// GetStateRegistry returns the state registry for external access
+func (w *Watcher) GetStateRegistry() *StateRegistry {
+	return w.stateRegistry
+}
+
 // ScanMountPath scans a specific mount path and returns file count
 // This is used by the mount poller to scan individual mounts
 func (w *Watcher) ScanMountPath(mountPath string) (int, error) {

internal/watchers/handlers.go

@@ -26,10 +26,12 @@ func (h *Handlers) RegisterRoutes(r *mux.Router) {
 	r.HandleFunc("/api/watchers", h.handleList).Methods("GET")
 	r.HandleFunc("/api/watchers", h.handleCreate).Methods("POST")
 	r.HandleFunc("/api/watchers/scan-all", h.handleScanAll).Methods("POST")
+	r.HandleFunc("/api/watchers/reset-all", h.handleResetAll).Methods("POST")
 	r.HandleFunc("/api/watchers/{id}", h.handleGet).Methods("GET")
 	r.HandleFunc("/api/watchers/{id}", h.handleUpdate).Methods("PUT")
 	r.HandleFunc("/api/watchers/{id}", h.handleDelete).Methods("DELETE")
 	r.HandleFunc("/api/watchers/{id}/scan", h.handleScan).Methods("POST")
+	r.HandleFunc("/api/watchers/{id}/reset", h.handleReset).Methods("POST")
 }
 
 // handleList handles GET /api/watchers
@@ -176,6 +178,44 @@ func (h *Handlers) handleScanAll(w http.ResponseWriter, r *http.Request) {
 	})
 }
 
+// handleReset handles POST /api/watchers/{id}/reset
+func (h *Handlers) handleReset(w http.ResponseWriter, r *http.Request) {
+	vars := mux.Vars(r)
+	id := vars["id"]
+
+	fileCount, err := h.poller.TriggerReset(id)
+	if err != nil {
+		if err.Error() == "watcher not found: "+id {
+			writeError(w, http.StatusNotFound, err.Error())
+		} else {
+			writeError(w, http.StatusInternalServerError, err.Error())
+		}
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]interface{}{
+		"status":    "ok",
+		"message":   "Reset complete",
+		"watcherId": id,
+		"fileCount": fileCount,
+	})
+}
+
+// handleResetAll handles POST /api/watchers/reset-all
+func (h *Handlers) handleResetAll(w http.ResponseWriter, r *http.Request) {
+	totalCount, err := h.poller.TriggerResetAll()
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]interface{}{
+		"status":     "ok",
+		"message":    "All watchers reset",
+		"totalFiles": totalCount,
+	})
+}
+
 // Helper functions
 
 func writeJSON(w http.ResponseWriter, status int, data interface{}) {

internal/watchers/poller.go

@@ -203,7 +203,7 @@ func (p *Poller) stopPoller(poller *watcherPoller) {
 	}
 }
 
-// runPollScan executes a scan for a watcher
+// runPollScan executes a differential scan for a watcher
 func (p *Poller) runPollScan(watcherID, path string) {
 	if p.scanner == nil {
 		return
@@ -216,22 +216,26 @@ func (p *Poller) runPollScan(watcherID, path string) {
 	}
 	p.mu.Unlock()
 
-	// Perform scan
-	fileCount := p.scanner.ScanDirectory(path)
+	// Perform differential scan
+	result := p.scanner.ScanDirectoryDiff(path, watcherID)
 
 	// Update status
 	p.mu.Lock()
 	if status, exists := p.status[watcherID]; exists {
 		status.LastScan = NowMS()
-		status.FileCount = fileCount
+		status.FileCount = result.Total
 		status.IsScanning = false
 	}
 	p.mu.Unlock()
 
-	log.Printf("[WatcherPoller] Poll scan complete for watcher %s: %d files", watcherID, fileCount)
+	// Only log if there were changes
+	if result.Added > 0 || result.Changed > 0 || result.Deleted > 0 {
+		log.Printf("[WatcherPoller] Diff scan for %s: +%d ~%d -%d (total: %d)",
+			watcherID, result.Added, result.Changed, result.Deleted, result.Total)
+	}
 }
 
-// TriggerScan triggers an immediate scan for a watcher
+// TriggerScan triggers an immediate differential scan for a watcher
 func (p *Poller) TriggerScan(watcherID string) (int, error) {
 	w, err := p.manager.Get(watcherID)
 	if err != nil {
@@ -251,19 +255,22 @@ func (p *Poller) TriggerScan(watcherID string) (int, error) {
 	}
 	p.mu.Unlock()
 
-	// Perform scan
-	fileCount := p.scanner.ScanDirectory(w.Path)
+	// Perform differential scan
+	result := p.scanner.ScanDirectoryDiff(w.Path, watcherID)
 
 	// Update status
 	p.mu.Lock()
 	if status, exists := p.status[watcherID]; exists {
 		status.LastScan = NowMS()
-		status.FileCount = fileCount
+		status.FileCount = result.Total
 		status.IsScanning = false
 	}
 	p.mu.Unlock()
 
-	return fileCount, nil
+	log.Printf("[WatcherPoller] Triggered scan for %s: +%d ~%d -%d (total: %d)",
+		watcherID, result.Added, result.Changed, result.Deleted, result.Total)
+
+	return result.Total, nil
 }
 
 // TriggerScanAll triggers scans for all enabled watchers
@@ -285,6 +292,90 @@ func (p *Poller) TriggerScanAll() (int, error) {
 	return totalCount, nil
 }
 
+// TriggerReset performs a full reset for a watcher:
+// 1. Clears the Redis stream and emits a reset event
+// 2. Clears the watcher's state
+// 3. Performs a full scan (all files are "new")
+func (p *Poller) TriggerReset(watcherID string) (int, error) {
+	w, err := p.manager.Get(watcherID)
+	if err != nil {
+		return 0, err
+	}
+
+	if p.scanner == nil || p.dispatcher == nil {
+		return 0, nil
+	}
+
+	log.Printf("[WatcherPoller] Triggering reset for watcher %s", watcherID)
+
+	// Mark as scanning
+	p.mu.Lock()
+	if status, exists := p.status[watcherID]; exists {
+		status.IsScanning = true
+	} else {
+		p.status[watcherID] = &RuntimeStatus{IsScanning: true}
+	}
+	p.mu.Unlock()
+
+	// Step 1: Emit reset event (this clears the stream first)
+	if err := p.dispatcher.EmitReset(watcherID); err != nil {
+		log.Printf("[WatcherPoller] Warning: failed to emit reset for %s: %v", watcherID, err)
+	}
+
+	// Step 2: Clear the watcher's state
+	p.scanner.ClearState(watcherID)
+
+	// Step 3: Clear event buffer
+	p.scanner.ClearEventBuffer()
+
+	// Step 4: Perform full scan (all files are now "new" since state is cleared)
+	result := p.scanner.ScanDirectoryDiff(w.Path, watcherID)
+
+	// Update status
+	p.mu.Lock()
+	if status, exists := p.status[watcherID]; exists {
+		status.LastScan = NowMS()
+		status.FileCount = result.Total
+		status.IsScanning = false
+	}
+	p.mu.Unlock()
+
+	log.Printf("[WatcherPoller] Reset complete for %s: %d files", watcherID, result.Total)
+
+	return result.Total, nil
+}
+
+// TriggerResetAll performs a full reset for all enabled watchers
+func (p *Poller) TriggerResetAll() (int, error) {
+	watchers := p.manager.List()
+	totalCount := 0
+	isFirst := true
+
+	for _, w := range watchers {
+		if w.Enabled {
+			// Only emit reset event once (for the first watcher)
+			// Subsequent watchers just clear state and rescan
+			if isFirst {
+				count, err := p.TriggerReset(w.ID)
+				if err != nil {
+					log.Printf("[WatcherPoller] Failed to reset watcher %s: %v", w.ID, err)
+					continue
+				}
+				totalCount += count
+				isFirst = false
+			} else {
+				// Clear state and rescan without clearing stream again
+				p.scanner.ClearState(w.ID)
+				result := p.scanner.ScanDirectoryDiff(w.Path, w.ID)
+				totalCount += result.Total
+				log.Printf("[WatcherPoller] Reset scan for %s: %d files", w.ID, result.Total)
+			}
+		}
+	}
+
+	return totalCount, nil
+}
+
 // GetStatus returns the runtime status for a watcher
 func (p *Poller) GetStatus(watcherID string) *RuntimeStatus {
 	p.mu.RLock()

internal/webdav/handler.go

@@ -0,0 +1,389 @@
+package webdav
+
+import (
+	"encoding/json"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+
+	"github.com/metazla/meta-core/internal/cache"
+	"github.com/metazla/meta-core/internal/config"
+	"golang.org/x/net/webdav"
+)
+
+// Handler handles WebDAV requests with caching support
+type Handler struct {
+	config       *config.Config
+	cacheManager *cache.Manager
+	filesPath    string
+	webdavFS     webdav.Handler
+}
+
+// NewHandler creates a new WebDAV handler with caching support
+func NewHandler(cfg *config.Config, cacheManager *cache.Manager) *Handler {
+	h := &Handler{
+		config:       cfg,
+		cacheManager: cacheManager,
+		filesPath:    cfg.FilesPath,
+	}
+
+	// Create standard WebDAV handler for write operations
+	h.webdavFS = webdav.Handler{
+		FileSystem: webdav.Dir(cfg.FilesPath),
+		LockSystem: webdav.NewMemLS(),
+		Logger: func(r *http.Request, err error) {
+			if err != nil {
+				log.Printf("[WebDAV] %s %s: %v", r.Method, r.URL.Path, err)
+			}
+		},
+	}
+
+	return h
+}
+
+// ServeHTTP handles WebDAV requests
+func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	// Remove /webdav prefix to get the file path
+	path := strings.TrimPrefix(r.URL.Path, "/webdav")
+	if path == "" {
+		path = "/"
+	}
+
+	log.Printf("[WebDAV] %s %s", r.Method, path)
+
+	switch r.Method {
+	case "GET", "HEAD":
+		h.handleRead(w, r, path)
+	case "PUT":
+		h.handlePut(w, r, path)
+	case "DELETE":
+		h.handleDelete(w, r, path)
+	case "MKCOL":
+		h.handleMkcol(w, r, path)
+	case "COPY", "MOVE":
+		h.handleCopyMove(w, r, path)
+	case "PROPFIND":
+		h.handlePropfind(w, r, path)
+	case "OPTIONS":
+		h.handleOptions(w, r)
+	default:
+		// Pass to standard WebDAV handler
+		h.webdavFS.ServeHTTP(w, r)
+	}
+}
+
+// handleRead handles GET and HEAD requests with caching
+func (h *Handler) handleRead(w http.ResponseWriter, r *http.Request, path string) {
+	fullPath := filepath.Join(h.filesPath, path)
+
+	// Check if it's a directory
+	info, err := os.Stat(fullPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			http.Error(w, "Not found", http.StatusNotFound)
+		} else {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
+		return
+	}
+
+	if info.IsDir() {
+		// Return directory listing as JSON
+		h.handleDirListing(w, r, fullPath, path)
+		return
+	}
+
+	// Serve file through cache
+	if err := h.cacheManager.ServeFile(w, r, path); err != nil {
+		if os.IsNotExist(err) {
+			http.Error(w, "Not found", http.StatusNotFound)
+		} else {
+			log.Printf("[WebDAV] Error serving file: %v", err)
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
+	}
+}
+
+// handleDirListing returns a directory listing as JSON
+func (h *Handler) handleDirListing(w http.ResponseWriter, r *http.Request, fullPath, relPath string) {
+	entries, err := os.ReadDir(fullPath)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	type dirEntry struct {
+		Name  string `json:"name"`
+		Type  string `json:"type"`
+		MTime string `json:"mtime"`
+		Size  int64  `json:"size,omitempty"`
+	}
+
+	var result []dirEntry
+	for _, entry := range entries {
+		info, err := entry.Info()
+		if err != nil {
+			continue
+		}
+
+		entryType := "file"
+		if entry.IsDir() {
+			entryType = "directory"
+		}
+
+		result = append(result, dirEntry{
+			Name:  entry.Name(),
+			Type:  entryType,
+			MTime: info.ModTime().Format("2006-01-02T15:04:05Z"),
+			Size:  info.Size(),
+		})
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(result)
+}
+
+// handlePut handles PUT requests (file upload)
+func (h *Handler) handlePut(w http.ResponseWriter, r *http.Request, path string) {
+	fullPath := filepath.Join(h.filesPath, path)
+
+	// Ensure parent directory exists
+	if err := os.MkdirAll(filepath.Dir(fullPath), 0755); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	// Create/overwrite file
+	file, err := os.Create(fullPath)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	defer file.Close()
+
+	// Copy request body to file
+	_, err = io.Copy(file, r.Body)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	// Invalidate cache for this path
+	h.cacheManager.Invalidate(path)
+
+	w.WriteHeader(http.StatusCreated)
+}
+
+// handleDelete handles DELETE requests
+func (h *Handler) handleDelete(w http.ResponseWriter, r *http.Request, path string) {
+	fullPath := filepath.Join(h.filesPath, path)
+
+	// Check if exists
+	_, err := os.Stat(fullPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			http.Error(w, "Not found", http.StatusNotFound)
+		} else {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
+		return
+	}
+
+	// Remove file or directory
+	if err := os.RemoveAll(fullPath); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	// Invalidate cache
+	h.cacheManager.Invalidate(path)
+
+	w.WriteHeader(http.StatusNoContent)
+}
+
+// handleMkcol handles MKCOL requests (create directory)
+func (h *Handler) handleMkcol(w http.ResponseWriter, r *http.Request, path string) {
+	fullPath := filepath.Join(h.filesPath, path)
+
+	// Check if already exists
+	if _, err := os.Stat(fullPath); err == nil {
+		http.Error(w, "Already exists", http.StatusMethodNotAllowed)
+		return
+	}
+
+	// Create directory
+	if err := os.MkdirAll(fullPath, 0755); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	w.WriteHeader(http.StatusCreated)
+}
+
+// handleCopyMove handles COPY and MOVE requests
+func (h *Handler) handleCopyMove(w http.ResponseWriter, r *http.Request, path string) {
+	// Get destination from header
+	dest := r.Header.Get("Destination")
+	if dest == "" {
+		http.Error(w, "Destination header required", http.StatusBadRequest)
+		return
+	}
+
+	// Parse destination URL to get path
+	destPath := strings.TrimPrefix(dest, "/webdav")
+	if strings.HasPrefix(dest, "http") {
+		// Full URL provided - extract path
+		parts := strings.SplitN(dest, "/webdav", 2)
+		if len(parts) == 2 {
+			destPath = parts[1]
+		}
+	}
+
+	srcFullPath := filepath.Join(h.filesPath, path)
+	destFullPath := filepath.Join(h.filesPath, destPath)
+
+	// Check if source exists
+	if _, err := os.Stat(srcFullPath); err != nil {
+		if os.IsNotExist(err) {
+			http.Error(w, "Source not found", http.StatusNotFound)
+		} else {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
+		return
+	}
+
+	// Ensure destination directory exists
+	if err := os.MkdirAll(filepath.Dir(destFullPath), 0755); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	if r.Method == "MOVE" {
+		// Move file
+		if err := os.Rename(srcFullPath, destFullPath); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		// Invalidate cache for both paths
+		h.cacheManager.Invalidate(path)
+		h.cacheManager.Invalidate(destPath)
+	} else {
+		// Copy file
+		if err := copyFile(srcFullPath, destFullPath); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+	}
+
+	w.WriteHeader(http.StatusCreated)
+}
+
+// handlePropfind handles PROPFIND requests
+func (h *Handler) handlePropfind(w http.ResponseWriter, r *http.Request, path string) {
+	fullPath := filepath.Join(h.filesPath, path)
+
+	info, err := os.Stat(fullPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			http.Error(w, "Not found", http.StatusNotFound)
+		} else {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
+		return
+	}
+
+	depth := r.Header.Get("Depth")
+	if depth == "" {
+		depth = "infinity"
+	}
+
+	// Build XML response
+	w.Header().Set("Content-Type", "application/xml; charset=utf-8")
+	w.WriteHeader(http.StatusMultiStatus)
+
+	w.Write([]byte(`<?xml version="1.0" encoding="utf-8"?>` + "\n"))
+	w.Write([]byte(`<D:multistatus xmlns:D="DAV:">` + "\n"))
+
+	// Add entry for the requested resource
+	h.writePropfindEntry(w, path, info)
+
+	// If directory and depth > 0, add children
+	if info.IsDir() && depth != "0" {
+		entries, err := os.ReadDir(fullPath)
+		if err == nil {
+			for _, entry := range entries {
+				childInfo, err := entry.Info()
+				if err != nil {
+					continue
+				}
+				childPath := filepath.Join(path, entry.Name())
+				h.writePropfindEntry(w, childPath, childInfo)
+			}
+		}
+	}
+
+	w.Write([]byte(`</D:multistatus>` + "\n"))
+}
+
+// writePropfindEntry writes a single PROPFIND response entry
+func (h *Handler) writePropfindEntry(w http.ResponseWriter, path string, info os.FileInfo) {
+	href := "/webdav" + path
+	if info.IsDir() && !strings.HasSuffix(href, "/") {
+		href += "/"
+	}
+
+	resourceType := ""
+	if info.IsDir() {
+		resourceType = "<D:collection/>"
+	}
+
+	w.Write([]byte(`  <D:response>` + "\n"))
+	w.Write([]byte(`    <D:href>` + href + `</D:href>` + "\n"))
+	w.Write([]byte(`    <D:propstat>` + "\n"))
+	w.Write([]byte(`      <D:prop>` + "\n"))
+	w.Write([]byte(`        <D:resourcetype>` + resourceType + `</D:resourcetype>` + "\n"))
+	if !info.IsDir() {
+		w.Write([]byte(`        <D:getcontentlength>` + formatInt64(info.Size()) + `</D:getcontentlength>` + "\n"))
+	}
+	w.Write([]byte(`        <D:getlastmodified>` + info.ModTime().Format("Mon, 02 Jan 2006 15:04:05 GMT") + `</D:getlastmodified>` + "\n"))
+	w.Write([]byte(`      </D:prop>` + "\n"))
+	w.Write([]byte(`      <D:status>HTTP/1.1 200 OK</D:status>` + "\n"))
+	w.Write([]byte(`    </D:propstat>` + "\n"))
+	w.Write([]byte(`  </D:response>` + "\n"))
+}
+
+// handleOptions handles OPTIONS requests
+func (h *Handler) handleOptions(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Allow", "OPTIONS, GET, HEAD, PUT, DELETE, MKCOL, COPY, MOVE, PROPFIND")
+	w.Header().Set("DAV", "1, 2")
+	w.Header().Set("MS-Author-Via", "DAV")
+	w.WriteHeader(http.StatusOK)
+}
+
+// copyFile copies a file from src to dst
+func copyFile(src, dst string) error {
+	srcFile, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer srcFile.Close()
+
+	dstFile, err := os.Create(dst)
+	if err != nil {
+		return err
+	}
+	defer dstFile.Close()
+
+	_, err = io.Copy(dstFile, srcFile)
+	return err
+}
+
+// formatInt64 formats an int64 as a string
+func formatInt64(n int64) string {
+	return strconv.FormatInt(n, 10)
+}