diff --git a/internal/handlers/kobo.go b/internal/handlers/kobo.go
index 9bd2f36..3872e0a 100644
--- a/internal/handlers/kobo.go
+++ b/internal/handlers/kobo.go
@@ -54,43 +54,449 @@ func (h *KoboHandler) mapContentIdToBookhoardUUID(ctx echo.Context, contentId st
 			})
 			return uuid.UUID(mediaItem.ID.Bytes), nil, "sha256_match"
 		}
-		case "last-read-place", "reading-position":
+	}
+
+	// Step 3: Try to parse as UUID directly
+	if parsedUUID, err := uuid.Parse(contentId); err == nil {
+		// Check if this UUID exists in media_items
+		mediaItem, err := h.db.GetMediaItem(ctx.Request().Context(), pgtype.UUID{Bytes: parsedUUID, Valid: true})
+		if err == nil {
+			// Create device catalog entry
+			_, _ = h.db.CreateDeviceCatalog(ctx.Request().Context(), database.CreateDeviceCatalogParams{
+				DeviceID:       pgtype.UUID{Bytes: deviceID, Valid: true},
+				MediaItemID:    pgtype.UUID{Bytes: mediaItem.ID.Bytes, Valid: true},
+				BookhoardUuid:  pgtype.UUID{Bytes: mediaItem.ID.Bytes, Valid: true},
+				KoboContentID:  contentId,
+				ContentIDType:  pgtype.Text{String: "bookhoard_uuid", Valid: true},
+				Available:      pgtype.Bool{Bool: true, Valid: true},
+				DeliveryDate:   pgtype.Timestamptz{Time: time.Now(), Valid: true},
+				DeliveryMethod: pgtype.Text{String: "sync", Valid: true},
+			})
+			return parsedUUID, nil, "uuid_match"
+		}
+	}
+
+	// Step 4: Not found - return error for unlinked book
+	return uuid.Nil, fmt.Errorf("unlinked book: ContentId %s not found", contentId), "unlinked"
+}
+
+// mapBookhoardUUIDToKoboContentId maps Bookhoard UUID to Kobo ContentId
+// Creates new entry in device_catalogs if not exists
+func (h *KoboHandler) mapBookhoardUUIDToKoboContentId(c echo.Context, bookhoardUUID uuid.UUID, deviceID uuid.UUID) (string, error) {
+	// Check if catalog entry already exists
+	catalog, err := h.db.GetDeviceCatalogByBookhoardUUID(c.Request().Context(), database.GetDeviceCatalogByBookhoardUUIDParams{
+		DeviceID:      pgtype.UUID{Bytes: deviceID, Valid: true},
+		BookhoardUuid: pgtype.UUID{Bytes: bookhoardUUID, Valid: true},
+	})
+	if err == nil && catalog.ID.Valid {
+		return catalog.KoboContentID, nil
+	}
+
+	// Get media item to check for existing Kobo content ID
+	mediaItem, err := h.db.GetMediaItem(c.Request().Context(), pgtype.UUID{Bytes: bookhoardUUID, Valid: true})
+	if err != nil {
+		return "", err
+	}
+
+	// Generate Kobo ContentId based on priority:
+	// 1. Use existing kobo_content_id from media_items
+	// 2. Use existing entitlement_id from media_items
+	// 3. Generate new "kobo_" prefixed UUID
+	var koboContentId string
+	contentIdType := "bookhoard_generated"
+
+	if mediaItem.KoboContentID.Valid && mediaItem.KoboContentID.String != "" {
+		koboContentId = mediaItem.KoboContentID.String
+		contentIdType = "kobo_metadata"
+	} else if mediaItem.EntitlementID.Valid && mediaItem.EntitlementID.String != "" {
+		koboContentId = mediaItem.EntitlementID.String
+		contentIdType = "entitlement_id"
+	} else {
+		koboContentId = "kobo_" + uuid.New().String()
+		contentIdType = "kobo_generated"
+	}
+
+	// Create device catalog entry
+	_, err = h.db.CreateDeviceCatalog(c.Request().Context(), database.CreateDeviceCatalogParams{
+		DeviceID:       pgtype.UUID{Bytes: deviceID, Valid: true},
+		MediaItemID:    pgtype.UUID{Bytes: bookhoardUUID, Valid: true},
+		BookhoardUuid:  pgtype.UUID{Bytes: bookhoardUUID, Valid: true},
+		KoboContentID:  koboContentId,
+		ContentIDType:  pgtype.Text{String: contentIdType, Valid: true},
+		Available:      pgtype.Bool{Bool: true, Valid: true},
+		DeliveryDate:   pgtype.Timestamptz{Time: time.Now(), Valid: true},
+		DeliveryMethod: pgtype.Text{String: "opds", Valid: true},
+	})
+
+	if err != nil {
+		return "", err
+	}
+
+	return koboContentId, nil
+}
+
+// getCollectionMetadataForBook retrieves collection names for a book
+func (h *KoboHandler) getCollectionMetadataForBook(c echo.Context, bookhoardUUID uuid.UUID, deviceID uuid.UUID) ([]string, error) {
+	device := c.Get("device").(database.Devices)
+	pgDeviceID := pgtype.UUID{Bytes: device.ID.Bytes, Valid: true}
+
+	// Get collections for this book
+	collections, err := h.db.GetCollectionsForBook(c.Request().Context(), pgtype.UUID{Bytes: bookhoardUUID, Valid: true})
+	if err != nil {
+		return []string{}, nil
+	}
+
+	var collectionNames []string
+
+	// For each collection, check if there's a device-specific shelf mapping
+	for _, collection := range collections {
+		mapping, err := h.db.GetDeviceShelfMapping(c.Request().Context(), database.GetDeviceShelfMappingParams{
+			DeviceID:     pgDeviceID,
+			CollectionID: pgtype.UUID{Bytes: collection.ID.Bytes, Valid: true},
+		})
+		if err == nil && mapping.ID.Valid && mapping.DeviceShelfName.Valid {
+			// Use device-specific shelf name
+			collectionNames = append(collectionNames, mapping.DeviceShelfName.String)
+		} else if collection.Name != "" {
+			// Fall back to collection name
+			collectionNames = append(collectionNames, collection.Name)
+		}
+	}
+
+	return collectionNames, nil
+}
+
+// looksLikeSHA256 checks if a string looks like a SHA-256 hash
+func looksLikeSHA256(s string) bool {
+	if len(s) != 64 {
+		return false
+	}
+	matched, _ := regexp.MatchString("^[0-9a-fA-F]{64}$", s)
+	return matched
+}
+
+// calculateFileSHA256 calculates SHA-256 hash of file path
+func calculateFileSHA256(filePath string) string {
+	hash := sha256.Sum256([]byte(filePath))
+	return hex.EncodeToString(hash[:])
+}
+
+type KoboDeviceInfo struct {
+	DeviceID     string `json:"DeviceId"`
+	Model        string `json:"Model"`
+	SerialNumber string `json:"SerialNumber"`
+	Firmware     string `json:"Firmware,omitempty"`
+}
+
+type KoboReadingSync struct {
+	ContentId            string  `json:"ContentId"`
+	PercentRead          float64 `json:"PercentRead"`
+	EntitlementId        string  `json:"EntitlementId"`
+	RemainingTimeMinutes int     `json:"RemainingTimeMinutes"`
+	FirstReadTime        string  `json:"FirstReadTime,omitempty"`
+	LastModified         string  `json:"LastModified"`
+	ContentType          string  `json:"ContentType,omitempty"`
+}
+
+type KoboBookmarkSync struct {
+	BookmarkId    string `json:"BookmarkId"`
+	ContentId     string `json:"ContentId"`
+	BookmarkText  string `json:"BookmarkText"`
+	BookmarkType  string `json:"BookmarkType"`
+	BookmarkTitle string `json:"BookmarkTitle"`
+	DateCreated   string `json:"DateCreated"`
+	Chapter       int    `json:"Chapter,omitempty"`
+	Hidden        bool   `json:"Hidden,omitempty"`
+}
+
+type KoboMarkupRequest struct {
+	ReadingSync  []KoboReadingSync  `json:"ReadingSync"`
+	BookmarkSync []KoboBookmarkSync `json:"BookmarkSync,omitempty"`
+}
+
+type KoboLibraryBook struct {
+	ContentId      string   `json:"ContentId"`
+	ContentType    string   `json:"ContentType"`
+	Title          string   `json:"Title"`
+	Author         string   `json:"Author"`
+	PercentRead    float64  `json:"PercentRead"`
+	PagesRemaining *int     `json:"PagesRemaining,omitempty"`
+	BookmarkCount  int      `json:"BookmarkCount"`
+	LastModified   string   `json:"LastModified"`
+	EntitlementId  string   `json:"EntitlementId,omitempty"`
+	Revision       int      `json:"Revision"`
+	MimeType       string   `json:"MimeType"`
+	FileSize       int64    `json:"FileSize"`
+	Categories     []string `json:"Categories,omitempty"`
+	BookhoardUUID  string   `json:"BookhoardUUID,omitempty"`
+}
+
+type KoboLibraryResponse struct {
+	LibrarySync []KoboLibraryBook `json:"library_sync"`
+	TotalBooks  int               `json:"total_books"`
+	LastSync    string            `json:"last_sync"`
+}
+
+type KoboInitResponse struct {
+	Resources map[string]interface{} `json:"Resources"`
+	UserKey   string                 `json:"UserKey"`
+}
+
+type KoboSyncStatus struct {
+	Status          string `json:"Status"`
+	MarkupsSynced   int    `json:"MarkupsSynced"`
+	BookmarksSynced int    `json:"BookmarksSynced"`
+}
+
+type KoboServerSyncData struct {
+	ContentId    string             `json:"ContentId"`
+	PercentRead  float64            `json:"PercentRead"`
+	Bookmarks    []KoboBookmarkSync `json:"Bookmarks,omitempty"`
+	Highlights   []KoboBookmarkSync `json:"Highlights,omitempty"`
+	LastModified string             `json:"LastModified"`
+}
+
+type KoboServerSyncResponse struct {
+	BooksSynced    int `json:"BooksSynced"`
+	BookmarksSent  int `json:"BookmarksSent"`
+	HighlightsSent int `json:"HighlightsSent"`
+}
+
+type KoboAnalyticsTest struct {
+	ContentId        string  `json:"ContentId"`
+	ReadingEvent     string  `json:"ReadingEvent"`
+	RemainingTimeMin int     `json:"RemainingTimeMin"`
+	PercentRead      float64 `json:"PercentRead"`
+}
+
+func (h *KoboHandler) Initialization(c echo.Context) error {
+	device := c.Get("device").(database.Devices)
+	userID := device.UserID.Bytes
+	deviceID := device.ID.Bytes
+
+	pgUserID := pgtype.UUID{Bytes: userID, Valid: true}
+	deviceUUID := uuid.UUID(deviceID)
+
+	mediaItems, err := h.db.GetUserMediaItemsForSync(c.Request().Context(), pgUserID)
+	if err != nil {
+		return c.JSON(http.StatusInternalServerError, map[string]string{
+			"error": "failed to fetch library",
+		})
+	}
+
+	librarySync := []KoboLibraryBook{}
+	for _, item := range mediaItems {
+		bookhoardUUID := uuid.UUID(item.ID.Bytes)
+
+		progress, _ := h.db.GetUniversalProgress(c.Request().Context(), database.GetUniversalProgressParams{
+			MediaItemID: pgtype.UUID{Bytes: item.ID.Bytes, Valid: true},
+			UserID:      pgUserID,
+		})
+
+		percentRead := 0.0
+		lastModified := time.Now().Format(time.RFC3339)
+		var pagesRemaining *int
+
+		if progress.ID.Valid {
+			percentRead = progress.Percentage.Float64 * 100
+			if progress.LastReadAt.Valid {
+				lastModified = progress.LastReadAt.Time.Format(time.RFC3339)
+			}
+			if progress.TotalPages.Valid && progress.CurrentPage.Valid {
+				remaining := int(progress.TotalPages.Int32 - progress.CurrentPage.Int32)
+				pagesRemaining = &remaining
+			}
+		}
+
+		bookmarkCount := 0
+		annotations, _ := h.db.GetAnnotationsForBook(c.Request().Context(), database.GetAnnotationsForBookParams{
+			MediaItemID: pgtype.UUID{Bytes: item.ID.Bytes, Valid: true},
+			UserID:      pgUserID,
+		})
+		bookmarkCount = len(annotations)
+
+		author := ""
+		if item.Author.Valid {
+			author = item.Author.String
+		}
+
+		// Phase 6: Use ContentId mapping instead of direct UUID
+		koboContentId, err := h.mapBookhoardUUIDToKoboContentId(c, bookhoardUUID, deviceUUID)
+		if err != nil {
+			// Fallback to entitlement_id or generate new one
+			if item.EntitlementID.Valid && item.EntitlementID.String != "" {
+				koboContentId = item.EntitlementID.String
+			} else {
+				koboContentId = "kobo_" + bookhoardUUID.String()
+			}
+		}
+
+		mimeType := item.MimeType.String
+		if !item.MimeType.Valid {
+			mimeType = ""
+		}
+
+		fileSize := int64(0)
+		if item.FileSize.Valid {
+			fileSize = item.FileSize.Int64
+		}
+
+		revision := 1
+		if item.RevisionNumber.Valid {
+			revision = int(item.RevisionNumber.Int32)
+		}
+
+		contentType := "6"
+		if strings.Contains(mimeType, "pdf") {
+			contentType = "5"
+		}
+
+		// Phase 6: Get collection metadata for this book
+		collections, _ := h.getCollectionMetadataForBook(c, bookhoardUUID, deviceUUID)
+
+		librarySync = append(librarySync, KoboLibraryBook{
+			ContentId:      koboContentId,
+			ContentType:    contentType,
+			Title:          item.Title,
+			Author:         author,
+			PercentRead:    percentRead,
+			PagesRemaining: pagesRemaining,
+			BookmarkCount:  bookmarkCount,
+			LastModified:   lastModified,
+			EntitlementId:  koboContentId,
+			Revision:       revision,
+			MimeType:       mimeType,
+			FileSize:       fileSize,
+			Categories:     collections,
+			BookhoardUUID:  bookhoardUUID.String(),
+		})
+	}
+
+	return c.JSON(http.StatusOK, KoboLibraryResponse{
+		LibrarySync: librarySync,
+		TotalBooks:  len(librarySync),
+		LastSync:    time.Now().Format(time.RFC3339),
+	})
+}
+
+func (h *KoboHandler) LibrarySync(c echo.Context) error {
+	return h.Initialization(c)
+}
+
+func (h *KoboHandler) Markup(c echo.Context) error {
+	device := c.Get("device").(database.Devices)
+	userID := device.UserID.Bytes
+	deviceID := device.ID.Bytes
+
+	pgUserID := pgtype.UUID{Bytes: userID, Valid: true}
+	deviceUUID := uuid.UUID(deviceID)
+
+	var req KoboMarkupRequest
+	if err := c.Bind(&req); err != nil {
+		return c.JSON(http.StatusBadRequest, map[string]string{
+			"error": "invalid request format",
+		})
+	}
+
+	markupsSynced := 0
+	bookmarksSynced := 0
+	unlinkedBooks := 0
+
+	for _, readingSync := range req.ReadingSync {
+		// Phase 6: Use ContentId mapping with fallback logic
+		bookhoardUUID, err, _ := h.mapContentIdToBookhoardUUID(c, readingSync.ContentId, deviceUUID)
+		if err != nil || bookhoardUUID == uuid.Nil {
+			// Unlinked book detected
+			unlinkedBooks++
+			// TODO: Create unlinked book entry for manual resolution
+			continue
+		}
+
+		pgMediaUUID := pgtype.UUID{Bytes: bookhoardUUID, Valid: true}
+
+		percentage := readingSync.PercentRead / 100.0
+
+		_, err = h.db.UpdateUniversalProgress(c.Request().Context(), database.UpdateUniversalProgressParams{
+			MediaItemID:    pgMediaUUID,
+			UserID:         pgUserID,
+			Percentage:     pgtype.Float8{Float64: percentage, Valid: true},
+			LastSyncDevice: pgtype.Text{String: "kobo", Valid: true},
+			LastSyncSource: pgtype.Text{String: "kobo", Valid: true},
+		})
+
+		if err == nil {
+			markupsSynced++
+
+			h.connManager.BroadcastProgressUpdate(
+				bookhoardUUID,
+				percentage,
+				wsync.SourceDevice{
+					ID:   uuid.UUID(userID).String(),
+					Name: device.DeviceName,
+					Type: "kobo",
+				},
+			)
+		}
+	}
+
+	for _, bookmarkSync := range req.BookmarkSync {
+		// Phase 6: Use ContentId mapping with fallback logic
+		bookhoardUUID, err, _ := h.mapContentIdToBookhoardUUID(c, bookmarkSync.ContentId, deviceUUID)
+		if err != nil || bookhoardUUID == uuid.Nil {
+			// Unlinked book - skip
+			continue
+		}
+
+		pgMediaUUID := pgtype.UUID{Bytes: bookhoardUUID, Valid: true}
+
+		switch bookmarkSync.BookmarkType {
+		case "annotation":
+			if bookmarkSync.BookmarkText != "" {
+				h.db.CreateMediaHighlight(c.Request().Context(), database.CreateMediaHighlightParams{
+					MediaItemID:   pgMediaUUID,
+					UserID:        pgUserID,
+					SelectionText: bookmarkSync.BookmarkText,
+					StartPosition: pgtype.Text{String: bookmarkSync.BookmarkId, Valid: true},
+					EndPosition:   pgtype.Text{String: bookmarkSync.BookmarkId, Valid: true},
+					Color:         pgtype.Text{String: "#ffff00", Valid: true},
+				})
+				bookmarksSynced++
+			}
+		case "bookmark":
+			if bookmarkSync.BookmarkText != "" {
+				h.db.CreateMediaNote(c.Request().Context(), database.CreateMediaNoteParams{
+					MediaItemID: pgMediaUUID,
+					UserID:      pgUserID,
+					Content:     bookmarkSync.BookmarkText,
+					Position:    pgtype.Text{String: bookmarkSync.BookmarkId, Valid: true},
+				})
+				bookmarksSynced++
+			}
+		case "last-read-place":
 			if bookmarkSync.BookmarkId != "" {
-				// Extract position data from BookmarkId
-				var epubcfi, chapter string
-				
+				var epubcfi string
+
 				if strings.HasPrefix(bookmarkSync.BookmarkId, "epubcfi(") {
 					epubcfi = strings.TrimPrefix(bookmarkSync.BookmarkId, "epubcfi(")
 					epubcfi = strings.TrimSuffix(epubcfi, ")")
 				}
-				
-				// Update reading_progress with precise position
+
 				_, err = h.db.UpdateUniversalProgress(c.Request().Context(), database.UpdateUniversalProgressParams{
-					MediaItemID:      pgMediaUUID,
-					UserID:           pgUserID,
+					MediaItemID:     pgMediaUUID,
+					UserID:          pgUserID,
 					Epubcfi:         pgtype.Text{String: epubcfi, Valid: true},
 					Chapter:         pgtype.Int4{Int32: int32(bookmarkSync.Chapter), Valid: true},
 					ChapterProgress: pgtype.Float8{Float64: 0.5, Valid: true},
-					DeviceSyncData:  pgtype.JSONB{
-						Bytes: []byte(fmt.Sprintf(`{"kobo_bookmark_id": "%s", "hidden": %v}`, 
-							bookmarkSync.BookmarkId, bookmarkSync.Hidden)),
-						Valid: true,
-					},
-					LastSyncDevice:   pgtype.Text{String: "kobo", Valid: true},
-					LastSyncSource:   pgtype.Text{String: "kobo", Valid: true},
+					LastSyncDevice:  pgtype.Text{String: "kobo", Valid: true},
+					LastSyncSource:  pgtype.Text{String: "kobo", Valid: true},
 				})
 				if err != nil {
 					fmt.Printf("Failed to store last-read-place: %v", err)
 				}
 				bookmarksSynced++
 			}
-		default:
-			fmt.Printf("Unknown bookmark type: %s", bookmarkSync.BookmarkType)
-		}
-			}
-		default:
-			fmt.Printf("Unknown bookmark type: %s", bookmarkSync.BookmarkType)
 		}
+	}
 
 	_, err := h.db.UpdateDeviceLastSync(c.Request().Context(), device.ID)
 	if err != nil {
@@ -137,7 +543,7 @@ func (h *KoboHandler) Bookmark(c echo.Context) error {
 	for _, bookmarkSync := range req.BookmarkSync {
 		// Phase 6: Use ContentId mapping with fallback logic
 		bookhoardUUID, err, _ := h.mapContentIdToBookhoardUUID(c, bookmarkSync.ContentId, deviceUUID)
-		if err != nil {
+		if err != nil || bookhoardUUID == uuid.Nil {
 			// Unlinked book - skip
 			continue
 		}
@@ -203,7 +609,7 @@ func (h *KoboHandler) AnalyticsGettests(c echo.Context) error {
 		// Phase 6: Use ContentId mapping with fallback logic
 		bookhoardUUID, err, _ := h.mapContentIdToBookhoardUUID(c, test.ContentId, deviceUUID)
 		if err != nil || bookhoardUUID == uuid.Nil {
-			// Unlinked book or invalid UUID - skip
+			// Unlinked book - skip
 			continue
 		}
 
@@ -280,7 +686,7 @@ func (h *KoboHandler) SyncFromServer(c echo.Context) error {
 		// Phase 6: Use ContentId mapping with fallback logic
 		bookhoardUUID, err, _ := h.mapContentIdToBookhoardUUID(c, syncData.ContentId, deviceUUID)
 		if err != nil || bookhoardUUID == uuid.Nil {
-			// Unlinked book or invalid UUID - skip
+			// Unlinked book - skip
 			continue
 		}