more on this

17 files changed, 465 insertions, 73 deletions

diff --git a/internal/api/handlers_media.go b/internal/api/handlers_media.go
index 1469342..3863ab0 100644
--- a/internal/api/handlers_media.go
+++ b/internal/api/handlers_media.go
@@ -30,7 +30,7 @@ func (s *Server) handleListSets(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, sets)
 }
 
-func (s *Server) handleSetCover(w http.ResponseWriter, r *http.Request) {
+func (s *Server) handleGetSetCover(w http.ResponseWriter, r *http.Request) {
 	if !requireService(w, s.mediaSvc) {
 		return
 	}
@@ -39,7 +39,34 @@ func (s *Server) handleSetCover(w http.ResponseWriter, r *http.Request) {
 		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid set id"})
 		return
 	}
-	if err := s.mediaSvc.RegenerateSetCover(r.Context(), setID, userIDFromContext(r)); err != nil {
+	folder := r.URL.Query().Get("folder")
+	fr, err := s.mediaSvc.GetSetCover(r.Context(), setID, folder, userIDFromContext(r))
+	if err != nil {
+		if errors.Is(err, service.ErrNotFound) {
+			writeJSON(w, http.StatusNotFound, map[string]string{"error": "not found"})
+			return
+		}
+		if errors.Is(err, service.ErrForbidden) {
+			writeJSON(w, http.StatusForbidden, map[string]string{"error": "forbidden"})
+			return
+		}
+		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+		return
+	}
+	http.ServeFile(w, r, fr.Path)
+}
+
+func (s *Server) handlePostSetCover(w http.ResponseWriter, r *http.Request) {
+	if !requireService(w, s.mediaSvc) {
+		return
+	}
+	setID := pathID(r, "id")
+	if setID == 0 {
+		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid set id"})
+		return
+	}
+	folder := r.URL.Query().Get("folder")
+	if err := s.mediaSvc.RegenerateSetCover(r.Context(), setID, folder, userIDFromContext(r)); err != nil {
 		if errors.Is(err, service.ErrNotFound) {
 			writeJSON(w, http.StatusNotFound, map[string]string{"error": "not found"})
 			return
@@ -54,6 +81,28 @@ func (s *Server) handleSetCover(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
 }
 
+func (s *Server) handleBrowseSet(w http.ResponseWriter, r *http.Request) {
+	if !requireService(w, s.mediaSvc) {
+		return
+	}
+	setID := pathID(r, "id")
+	if setID == 0 {
+		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid set id"})
+		return
+	}
+	parent := r.URL.Query().Get("parent")
+	result, err := s.mediaSvc.BrowseSet(r.Context(), setID, userIDFromContext(r), parent)
+	if err != nil {
+		if errors.Is(err, service.ErrForbidden) {
+			writeJSON(w, http.StatusForbidden, map[string]string{"error": "forbidden"})
+			return
+		}
+		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+		return
+	}
+	writeJSON(w, http.StatusOK, result)
+}
+
 func (s *Server) handleUpload(w http.ResponseWriter, r *http.Request) {
 	if !requireService(w, s.mediaSvc) {
 		return
diff --git a/internal/api/handlers_more_test.go b/internal/api/handlers_more_test.go
index 23e94c7..e5d8529 100644
--- a/internal/api/handlers_more_test.go
+++ b/internal/api/handlers_more_test.go
@@ -339,7 +339,7 @@ func TestServer_SetCover(t *testing.T) {
 			var ms service.MediaService
 			if !tt.svcNil {
 				ms = &service.MockMediaService{
-					RegenerateSetCoverFunc: func(ctx context.Context, setID, userID int64) error {
+					RegenerateSetCoverFunc: func(ctx context.Context, setID int64, folder string, userID int64) error {
 						return tt.svcErr
 					},
 				}
diff --git a/internal/api/server.go b/internal/api/server.go
index 6c15c78..1855148 100644
--- a/internal/api/server.go
+++ b/internal/api/server.go
@@ -112,7 +112,9 @@ func (s *Server) routes() {
 
 	// Sets
 	s.mux.Handle("GET /api/sets", s.mw.RequireSession(http.HandlerFunc(s.handleListSets)))
-	s.mux.Handle("POST /api/sets/{id}/cover", s.mw.RequireSession(http.HandlerFunc(s.handleSetCover)))
+	s.mux.Handle("GET /api/sets/{id}/browse", s.mw.RequireSession(http.HandlerFunc(s.handleBrowseSet)))
+	s.mux.Handle("GET /api/sets/{id}/cover", s.mw.RequireSession(http.HandlerFunc(s.handleGetSetCover)))
+	s.mux.Handle("POST /api/sets/{id}/cover", s.mw.RequireSession(http.HandlerFunc(s.handlePostSetCover)))
 	s.mux.Handle("POST /api/sets/{id}/upload", s.mw.RequireSession(http.HandlerFunc(s.handleUpload)))
 
 	// Media
diff --git a/internal/scanner/scanner.go b/internal/scanner/scanner.go
index 569f181..15d0d53 100644
--- a/internal/scanner/scanner.go
+++ b/internal/scanner/scanner.go
@@ -152,6 +152,7 @@ func (s *FSScanner) scanSet(ctx context.Context, root, setPath string, progress
 		if err != nil {
 			return fmt.Errorf("rel path for %q: %w", path, err)
 		}
+		relPath = filepath.ToSlash(relPath)
 		if _, alreadyExists := existing[relPath]; alreadyExists {
 			return nil
 		}
diff --git a/internal/service/media_browse.go b/internal/service/media_browse.go
index 2a60516..79c9da1 100644
--- a/internal/service/media_browse.go
+++ b/internal/service/media_browse.go
@@ -7,6 +7,7 @@ import (
 	mrand "math/rand"
 	"os"
 	"path/filepath"
+	"sort"
 	"strings"
 
 	"codeberg.org/snonux/player/internal/model"
@@ -182,7 +183,7 @@ func (s *mediaService) RegenerateThumbnail(ctx context.Context, mediaID, userID
 	return nil
 }
 
-func (s *mediaService) RegenerateSetCover(ctx context.Context, setID, userID int64) error {
+func (s *mediaService) RegenerateSetCover(ctx context.Context, setID int64, folder string, userID int64) error {
 	if err := s.verifySetModifyAccess(ctx, setID, userID); err != nil {
 		return err
 	}
@@ -200,9 +201,25 @@ func (s *mediaService) RegenerateSetCover(ctx context.Context, setID, userID int
 		return fmt.Errorf("list media: %w", err)
 	}
 
+	prefix := filepath.ToSlash(strings.Trim(folder, "/"))
 	var candidates []model.Media
 	for _, m := range media {
-		if m.Type == model.MediaTypeVideo && m.DeletedAt == nil {
+		if m.DeletedAt != nil {
+			continue
+		}
+		rel := filepath.ToSlash(m.RelPath)
+		if prefix != "" {
+			if !strings.HasPrefix(rel, prefix+"/") {
+				continue
+			}
+			suffix := strings.TrimPrefix(rel, prefix+"/")
+			if strings.Contains(suffix, "/") {
+				continue
+			}
+		} else if strings.Contains(rel, "/") {
+			continue
+		}
+		if m.Type == model.MediaTypeVideo {
 			candidates = append(candidates, m)
 		}
 	}
@@ -215,7 +232,11 @@ func (s *mediaService) RegenerateSetCover(ctx context.Context, setID, userID int
 		candidate = candidates[mrand.Intn(len(candidates))]
 	}
 
-	coverPath := filepath.Join(filepath.Clean(filepath.Join(s.mediaRoot, set.RootPath)), ".cover.jpg")
+	baseDir := filepath.Join(s.mediaRoot, filepath.FromSlash(set.RootPath))
+	if prefix != "" {
+		baseDir = filepath.Join(baseDir, filepath.FromSlash(prefix))
+	}
+	coverPath := filepath.Join(filepath.Clean(baseDir), ".cover.jpg")
 	meta, err := s.prober.Probe(ctx, candidate.AbsPath)
 	if err != nil {
 		return fmt.Errorf("probe cover candidate: %w", err)
@@ -225,13 +246,41 @@ func (s *mediaService) RegenerateSetCover(ctx context.Context, setID, userID int
 		return fmt.Errorf("generate cover: %w", err)
 	}
 
-	set.CoverThumbnailPath = coverPath
-	if err := s.store.UpdateSet(ctx, set); err != nil {
-		return fmt.Errorf("update set: %w", err)
-	}
 	return nil
 }
 
+func (s *mediaService) GetSetCover(ctx context.Context, setID int64, folder string, userID int64) (*FileResult, error) {
+	if err := s.checkSetPermission(ctx, setID, userID, ""); err != nil {
+		return nil, err
+	}
+
+	set, err := s.store.GetSetByID(ctx, setID)
+	if err != nil {
+		return nil, fmt.Errorf("get set: %w", err)
+	}
+	if set == nil {
+		return nil, ErrNotFound
+	}
+
+	prefix := filepath.ToSlash(strings.Trim(folder, "/"))
+	baseDir := filepath.Join(s.mediaRoot, filepath.FromSlash(set.RootPath))
+	if prefix != "" {
+		baseDir = filepath.Join(baseDir, filepath.FromSlash(prefix))
+	}
+	coverPath := filepath.Join(filepath.Clean(baseDir), ".cover.jpg")
+
+	info, err := os.Stat(coverPath)
+	if err != nil {
+		return nil, fmt.Errorf("stat cover: %w", err)
+	}
+
+	return &FileResult{
+		Path:     coverPath,
+		FileName: filepath.Base(coverPath),
+		FileSize: info.Size(),
+	}, nil
+}
+
 func (s *mediaService) ToggleFavorite(ctx context.Context, userID, mediaID int64) (bool, error) {
 	if _, err := s.verifyAccess(ctx, mediaID, userID); err != nil {
 		return false, err
@@ -270,3 +319,94 @@ func (s *mediaService) RemoveTag(ctx context.Context, mediaID, userID int64, tag
 	}
 	return s.store.RemoveTag(ctx, mediaID, tag.ID)
 }
+
+// BrowseSet returns the immediate subfolders and media files inside
+// a specific folder (parent) of a set.
+// If a subfolder contains exactly one file and no further subfolders,
+// that file is "flattened" and shown at the current level instead of
+// presenting the folder.
+func (s *mediaService) BrowseSet(ctx context.Context, setID, userID int64, parent string) (*BrowseResult, error) {
+	if err := s.checkSetPermission(ctx, setID, userID, ""); err != nil {
+		return nil, err
+	}
+
+	parent = filepath.ToSlash(strings.Trim(parent, "/"))
+	media, err := s.store.ListMedia(ctx, repository.MediaFilter{SetID: &setID})
+	if err != nil {
+		return nil, fmt.Errorf("list media: %w", err)
+	}
+
+	set, err := s.store.GetSetByID(ctx, setID)
+	if err != nil {
+		return nil, fmt.Errorf("get set: %w", err)
+	}
+	if set == nil {
+		return nil, ErrNotFound
+	}
+
+	type folderContent struct {
+		files      []model.Media
+		subfolders map[string]struct{}
+	}
+	folderMap := make(map[string]*folderContent)
+	var items []model.Media
+
+	for _, m := range media {
+		if m.DeletedAt != nil {
+			continue
+		}
+		rel := filepath.ToSlash(m.RelPath)
+		prefix := ""
+		if parent != "" {
+			prefix = parent + "/"
+		}
+		if !strings.HasPrefix(rel, prefix) {
+			continue
+		}
+		suffix := strings.TrimPrefix(rel, prefix)
+		if suffix == "" {
+			continue
+		}
+		parts := strings.SplitN(suffix, "/", 2)
+		name := parts[0]
+		if len(parts) == 1 {
+			// File at the current level.
+			items = append(items, m)
+			continue
+		}
+		// Inside a subfolder — count what is in there.
+		fc, ok := folderMap[name]
+		if !ok {
+			fc = &folderContent{subfolders: make(map[string]struct{})}
+			folderMap[name] = fc
+		}
+		rest := parts[1]
+		subparts := strings.SplitN(rest, "/", 2)
+		if len(subparts) == 1 {
+			fc.files = append(fc.files, m)
+		} else {
+			fc.subfolders[subparts[0]] = struct{}{}
+		}
+	}
+
+	var folders []BrowseFolder
+	for name, fc := range folderMap {
+		total := len(fc.files) + len(fc.subfolders)
+		if total == 1 && len(fc.files) == 1 {
+			// Flatten: show the lone file at the current level.
+			items = append(items, fc.files[0])
+		} else {
+			subPath := filepath.Join(parent, name)
+			coverPath := filepath.Join(filepath.Clean(filepath.Join(s.mediaRoot, set.RootPath, filepath.FromSlash(subPath))), ".cover.jpg")
+			_, err := os.Stat(coverPath)
+			folders = append(folders, BrowseFolder{Name: name, HasCover: err == nil})
+		}
+	}
+	sort.Slice(folders, func(i, j int) bool { return folders[i].Name < folders[j].Name })
+
+	return &BrowseResult{
+		CurrentPath: parent,
+		Folders:     folders,
+		Media:       items,
+	}, nil
+}
diff --git a/internal/service/media_test.go b/internal/service/media_test.go
index cbf3de1..27f93dc 100644
--- a/internal/service/media_test.go
+++ b/internal/service/media_test.go
@@ -1329,7 +1329,7 @@ func TestMediaService_ViewerCannotMutate(t *testing.T) {
 			},
 		}
 		svc := NewMediaService(store, newMockClock(), "/tmp/media", nil, nil)
-		err := svc.RegenerateSetCover(ctx, 1, 2)
+		err := svc.RegenerateSetCover(ctx, 1, "", 2)
 		if !errors.Is(err, ErrForbidden) {
 			t.Fatalf("expected ErrForbidden, got %v", err)
 		}
@@ -1815,7 +1815,7 @@ func TestMediaService_RegenerateSetCover(t *testing.T) {
 			return &model.Metadata{Duration: 60}, nil
 		}}
 		svc := NewMediaService(store, newMockClock(), tmpDir, thumbGen, prober)
-		if err := svc.RegenerateSetCover(ctx, 1, 1); err != nil {
+		if err := svc.RegenerateSetCover(ctx, 1, "", 1); err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
 	})
@@ -1832,7 +1832,7 @@ func TestMediaService_RegenerateSetCover(t *testing.T) {
 			return &model.Metadata{Duration: 60}, nil
 		}}
 		svc := NewMediaService(store, newMockClock(), tmpDir, thumbGen, prober)
-		if err := svc.RegenerateSetCover(ctx, 1, 2); err != nil {
+		if err := svc.RegenerateSetCover(ctx, 1, "", 2); err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
 	})
@@ -1841,7 +1841,7 @@ func TestMediaService_RegenerateSetCover(t *testing.T) {
 		set := &model.Set{ID: 1, RootPath: "music", Permissions: []model.SetPermission{{SetID: 1, UserID: 2, Role: model.RoleViewer}}}
 		store := makeStore(1, nil, set)
 		svc := NewMediaService(store, newMockClock(), "/tmp/media", nil, nil)
-		err := svc.RegenerateSetCover(ctx, 1, 2)
+		err := svc.RegenerateSetCover(ctx, 1, "", 2)
 		if !errors.Is(err, ErrForbidden) {
 			t.Fatalf("expected ErrForbidden, got %v", err)
 		}
@@ -1850,7 +1850,7 @@ func TestMediaService_RegenerateSetCover(t *testing.T) {
 	t.Run("set not found", func(t *testing.T) {
 		store := makeStore(1, nil, nil)
 		svc := NewMediaService(store, newMockClock(), "/tmp/media", nil, nil)
-		err := svc.RegenerateSetCover(ctx, 1, 1)
+		err := svc.RegenerateSetCover(ctx, 1, "", 1)
 		if !errors.Is(err, ErrNotFound) {
 			t.Fatalf("expected ErrNotFound, got %v", err)
 		}
@@ -1861,7 +1861,7 @@ func TestMediaService_RegenerateSetCover(t *testing.T) {
 		media := []model.Media{{ID: 1, SetID: 1, AbsPath: "/tmp/song.mp3", Type: model.MediaTypeAudio}}
 		store := makeStore(1, media, set)
 		svc := NewMediaService(store, newMockClock(), "/tmp/media", nil, nil)
-		err := svc.RegenerateSetCover(ctx, 1, 1)
+		err := svc.RegenerateSetCover(ctx, 1, "", 1)
 		if err == nil {
 			t.Fatal("expected error")
 		}
@@ -1878,7 +1878,7 @@ func TestMediaService_RegenerateSetCover(t *testing.T) {
 			return nil, errors.New("probe err")
 		}}
 		svc := NewMediaService(store, newMockClock(), tmpDir, nil, prober)
-		err := svc.RegenerateSetCover(ctx, 1, 1)
+		err := svc.RegenerateSetCover(ctx, 1, "", 1)
 		if err == nil {
 			t.Fatal("expected error")
 		}
@@ -1898,28 +1898,7 @@ func TestMediaService_RegenerateSetCover(t *testing.T) {
 			return &model.Metadata{Duration: 60}, nil
 		}}
 		svc := NewMediaService(store, newMockClock(), tmpDir, thumbGen, prober)
-		err := svc.RegenerateSetCover(ctx, 1, 1)
-		if err == nil {
-			t.Fatal("expected error")
-		}
-	})
-
-	t.Run("update set failure", func(t *testing.T) {
-		tmpDir := t.TempDir()
-		videoPath := filepath.Join(tmpDir, "video.mp4")
-		_ = os.WriteFile(videoPath, []byte("fake"), 0o644)
-		set := &model.Set{ID: 1, RootPath: "music"}
-		media := []model.Media{{ID: 1, SetID: 1, AbsPath: videoPath, Type: model.MediaTypeVideo}}
-		store := makeStore(1, media, set)
-		store.SetRepo.UpdateSetFunc = func(ctx context.Context, s *model.Set) error {
-			return errors.New("update err")
-		}
-		thumbGen := &mockThumbGenerator{}
-		prober := &mockProber{ProbeFunc: func(ctx context.Context, path string) (*model.Metadata, error) {
-			return &model.Metadata{Duration: 60}, nil
-		}}
-		svc := NewMediaService(store, newMockClock(), tmpDir, thumbGen, prober)
-		err := svc.RegenerateSetCover(ctx, 1, 1)
+		err := svc.RegenerateSetCover(ctx, 1, "", 1)
 		if err == nil {
 			t.Fatal("expected error")
 		}
diff --git a/internal/service/mock.go b/internal/service/mock.go
index 82a25de..50e2e53 100644
--- a/internal/service/mock.go
+++ b/internal/service/mock.go
@@ -30,7 +30,9 @@ type MockMediaService struct {
 	DownloadMediaFunc       func(ctx context.Context, mediaID, userID int64) (*FileResult, error)
 	GetThumbnailFunc        func(ctx context.Context, mediaID, userID int64) (*FileResult, error)
 	RegenerateThumbnailFunc func(ctx context.Context, mediaID, userID int64) error
-	RegenerateSetCoverFunc  func(ctx context.Context, setID, userID int64) error
+	RegenerateSetCoverFunc  func(ctx context.Context, setID int64, folder string, userID int64) error
+	BrowseSetFunc           func(ctx context.Context, setID, userID int64, parent string) (*BrowseResult, error)
+	GetSetCoverFunc         func(ctx context.Context, setID int64, folder string, userID int64) (*FileResult, error)
 	ToggleFavoriteFunc      func(ctx context.Context, userID, mediaID int64) (bool, error)
 	AssignTagFunc           func(ctx context.Context, mediaID, userID int64, tagName string) error
 	RemoveTagFunc           func(ctx context.Context, mediaID, userID int64, tagName string) error
@@ -90,12 +92,24 @@ func (m *MockMediaService) RegenerateThumbnail(ctx context.Context, mediaID, use
 	}
 	return nil
 }
-func (m *MockMediaService) RegenerateSetCover(ctx context.Context, setID, userID int64) error {
+func (m *MockMediaService) RegenerateSetCover(ctx context.Context, setID int64, folder string, userID int64) error {
 	if m.RegenerateSetCoverFunc != nil {
-		return m.RegenerateSetCoverFunc(ctx, setID, userID)
+		return m.RegenerateSetCoverFunc(ctx, setID, folder, userID)
 	}
 	return nil
 }
+func (m *MockMediaService) BrowseSet(ctx context.Context, setID, userID int64, parent string) (*BrowseResult, error) {
+	if m.BrowseSetFunc != nil {
+		return m.BrowseSetFunc(ctx, setID, userID, parent)
+	}
+	return nil, nil
+}
+func (m *MockMediaService) GetSetCover(ctx context.Context, setID int64, folder string, userID int64) (*FileResult, error) {
+	if m.GetSetCoverFunc != nil {
+		return m.GetSetCoverFunc(ctx, setID, folder, userID)
+	}
+	return nil, errors.New("not implemented")
+}
 func (m *MockMediaService) ToggleFavorite(ctx context.Context, userID, mediaID int64) (bool, error) {
 	if m.ToggleFavoriteFunc != nil {
 		return m.ToggleFavoriteFunc(ctx, userID, mediaID)
@@ -168,6 +182,9 @@ func (m *MockMediaService) GetSharedMedia(ctx context.Context, token string) (*G
 	}
 	return nil, errors.New("not implemented")
 }
+func (m *MockMediaService) GetSharedThumbnail(ctx context.Context, token string) (*FileResult, error) {
+	return nil, errors.New("not implemented")
+}
 func (m *MockMediaService) GetNote(ctx context.Context, mediaID, userID int64) (*model.Note, error) {
 	if m.GetNoteFunc != nil {
 		return m.GetNoteFunc(ctx, mediaID, userID)
diff --git a/internal/service/mock_test.go b/internal/service/mock_test.go
index d9e20d2..c7c3fdc 100644
--- a/internal/service/mock_test.go
+++ b/internal/service/mock_test.go
@@ -25,7 +25,7 @@ func TestMockMediaService_Defaults(t *testing.T) {
 	m.SoftDeleteMedia(ctx, 1, 1)
 	m.RestoreMedia(ctx, 1, 1)
 	m.RegenerateThumbnail(ctx, 1, 1)
-	m.RegenerateSetCover(ctx, 1, 1)
+	m.RegenerateSetCover(ctx, 1, "", 1)
 	m.GetNote(ctx, 1, 1)
 	m.UpsertNote(ctx, &model.Note{MediaID: 1, UserID: 1, Content: "hi"})
 	m.DeleteNote(ctx, 1, 1)
@@ -64,7 +64,7 @@ func TestMockMediaService_WithFuncs(t *testing.T) {
 		DownloadMediaFunc:       func(ctx context.Context, mediaID, userID int64) (*FileResult, error) { return nil, nil },
 		GetThumbnailFunc:        func(ctx context.Context, mediaID, userID int64) (*FileResult, error) { return nil, nil },
 		RegenerateThumbnailFunc: func(ctx context.Context, mediaID, userID int64) error { return nil },
-		RegenerateSetCoverFunc:  func(ctx context.Context, setID, userID int64) error { return nil },
+		RegenerateSetCoverFunc:  func(ctx context.Context, setID int64, folder string, userID int64) error { return nil },
 		ToggleFavoriteFunc:      func(ctx context.Context, userID, mediaID int64) (bool, error) { return false, nil },
 		AssignTagFunc:           func(ctx context.Context, mediaID, userID int64, tagName string) error { return nil },
 		RemoveTagFunc:           func(ctx context.Context, mediaID, userID int64, tagName string) error { return nil },
@@ -88,7 +88,7 @@ func TestMockMediaService_WithFuncs(t *testing.T) {
 	m.DownloadMedia(ctx, 1, 1)
 	m.GetThumbnail(ctx, 1, 1)
 	m.RegenerateThumbnail(ctx, 1, 1)
-	m.RegenerateSetCover(ctx, 1, 1)
+	m.RegenerateSetCover(ctx, 1, "", 1)
 	m.ToggleFavorite(ctx, 1, 1)
 	m.AssignTag(ctx, 1, 1, "rock")
 	m.RemoveTag(ctx, 1, 1, "rock")
diff --git a/internal/service/service.go b/internal/service/service.go
index fd96b25..aa3d715 100644
--- a/internal/service/service.go
+++ b/internal/service/service.go
@@ -19,7 +19,9 @@ type MediaBrowseService interface {
 	DownloadMedia(ctx context.Context, mediaID, userID int64) (*FileResult, error)
 	GetThumbnail(ctx context.Context, mediaID, userID int64) (*FileResult, error)
 	RegenerateThumbnail(ctx context.Context, mediaID, userID int64) error
-	RegenerateSetCover(ctx context.Context, setID, userID int64) error
+	RegenerateSetCover(ctx context.Context, setID int64, folder string, userID int64) error
+	BrowseSet(ctx context.Context, setID, userID int64, parent string) (*BrowseResult, error)
+	GetSetCover(ctx context.Context, setID int64, folder string, userID int64) (*FileResult, error)
 }
 
 // MediaWriteService handles mutations such as upload, soft-delete and restore.
@@ -29,6 +31,19 @@ type MediaWriteService interface {
 	UploadMedia(ctx context.Context, setID, userID int64, filename string, data io.Reader, size int64) (*model.Media, error)
 }
 
+// BrowseFolder is a named folder within a set's directory tree.
+type BrowseFolder struct {
+	Name       string `json:"name"`
+	HasCover   bool   `json:"has_cover"`
+}
+
+// BrowseResult is the content of one directory inside a set.
+type BrowseResult struct {
+	CurrentPath string        `json:"current_path"`
+	Folders     []BrowseFolder `json:"folders"`
+	Media       []model.Media   `json:"media"`
+}
+
 // GetSharedMediaResult wraps media metadata needed to render a share page.
 	type GetSharedMediaResult struct {
 		Media      *model.Media `json:"media"`
diff --git a/web/css/layout.css b/web/css/layout.css
index 7f0e19e..e52a083 100644
--- a/web/css/layout.css
+++ b/web/css/layout.css
@@ -103,6 +103,31 @@ body {
   max-width: 100%;
 }
 
+/* Breadcrumb bar */
+.breadcrumb-bar {
+  display: flex;
+  align-items: center;
+  gap: 0.35rem;
+  flex-wrap: wrap;
+  margin-bottom: 0.75rem;
+  font-size: 0.85rem;
+}
+.breadcrumb-bar.hidden { display: none !important; }
+.breadcrumb-bar button {
+  background: transparent;
+  border: none;
+  color: var(--accent);
+  padding: 0.15rem 0.25rem;
+  cursor: pointer;
+  font: inherit;
+  border-radius: var(--radius-sm);
+}
+.breadcrumb-bar button:hover { background: var(--accent-soft); }
+.breadcrumb-bar .breadcrumb-sep { color: var(--text-muted); user-select: none; }
+
+/* Folder card placeholder */
+.folder-card .thumb-wrap .placeholder { font-size: 3rem; }
+
 /* Media grid */
 .media-grid {
   display: grid;
diff --git a/web/css/player.css b/web/css/player.css
index 7c7b189..5628dfd 100644
--- a/web/css/player.css
+++ b/web/css/player.css
@@ -15,6 +15,9 @@
 .page.has-sidebar .player {
   inset: auto 0 0 var(--sidebar-width);
 }
+.page.has-sidebar .player.collapsed {
+  inset: auto auto 0 0;
+}
 .player.is-fullscreen {
   inset: 0;
   background: var(--player-stage-bg);
diff --git a/web/index.html b/web/index.html
index e2b58a4..c5a124f 100644
--- a/web/index.html
+++ b/web/index.html
@@ -63,6 +63,9 @@
       <p class="text-muted text-sm">Press <kbd>s</kbd> to browse sets, <kbd>/</kbd> to search, or <kbd>?</kbd> for help.</p>
     </div>
 
+    <!-- Breadcrumb bar for folder navigation -->
+    <div id="breadcrumb-bar" class="breadcrumb-bar hidden"></div>
+
     <!-- Media grid: hidden until a set is loaded or search is active -->
     <div id="media-grid" class="media-grid hidden" tabindex="0" aria-label="Media grid"></div>
   </div>
@@ -113,11 +116,12 @@
         <tr><td><kbd>k</kbd> <kbd>j</kbd></td><td>Navigate media list (vim-style)</td></tr>
         <tr><td><kbd>←</kbd> <kbd>→</kbd></td><td>Switch sets / pages</td></tr>
         <tr><td><kbd>h</kbd> <kbd>l</kbd></td><td>Switch sets / pages (vim-style)</td></tr>
-        <tr><td><kbd>Enter</kbd></td><td>Open selected media</td></tr>
+        <tr><td><kbd>Enter</kbd></td><td>Open selected media / enter folder</td></tr>
         <tr><td><kbd>Space</kbd> <kbd>p</kbd></td><td>Play / pause</td></tr>
         <tr><td><kbd>f</kbd></td><td>Toggle fullscreen</td></tr>
         <tr><td><kbd>c</kbd></td><td>Collapse / expand player stage</td></tr>
         <tr><td><kbd>Esc</kbd></td><td>Exit fullscreen, deselect item</td></tr>
+        <tr><td><kbd>Backspace</kbd></td><td>Go up one folder</td></tr>
         <tr><td><kbd>r</kbd></td><td>Toggle shuffle</td></tr>
         <tr><td><kbd>s</kbd></td><td>Toggle sets sidebar</td></tr>
         <tr><td><kbd>/</kbd></td><td>Focus search bar</td></tr>
diff --git a/web/js/api.js b/web/js/api.js
index dc8ee8d..8e80a0d 100644
--- a/web/js/api.js
+++ b/web/js/api.js
@@ -58,7 +58,18 @@ export const API = {
   tags: () => api('/api/tags'),
   download: (id) => api(`/api/media/${id}/download`),
   regenThumbnail: (id) => api(`/api/media/${id}/thumbnail`, { method: 'POST' }),
-  regenCover: (setId) => api(`/api/sets/${setId}/cover`, { method: 'POST' }),
+  browse: (setId, parent) => {
+    const params = new URLSearchParams();
+    if (parent) params.set('parent', parent);
+    const s = params.toString();
+    return api(`/api/sets/${setId}/browse${s ? '?' + s : ''}`);
+  },
+  regenCover: (setId, folder = '') => {
+    const params = new URLSearchParams();
+    if (folder) params.set('folder', folder);
+    const s = params.toString();
+    return api(`/api/sets/${setId}/cover${s ? '?' + s : ''}`, { method: 'POST' });
+  },
   upload: (setId, formData) => api(`/api/sets/${setId}/upload`, { method: 'POST', body: formData }),
   addTag: (id, tag) => api(`/api/media/${id}/tags`, { method: 'POST', body: { tag } }),
   removeTag: (id, tag) => api(`/api/media/${id}/tags/${encodeURIComponent(tag)}`, { method: 'DELETE' }),
diff --git a/web/js/app.js b/web/js/app.js
index 2d0e15d..2bd6aef 100644
--- a/web/js/app.js
+++ b/web/js/app.js
@@ -73,6 +73,7 @@ async function initApp() {
   initSearch({
     onChange: (q) => {
       state.filters.search = q;
+      state.folderPath = '';
       loadMedia();
     },
     input: document.getElementById('search-input'),
@@ -96,7 +97,13 @@ async function initApp() {
     toggleSetSelect: () => toggleSetSelection(),
     enter: () => {
       const el = currentElement();
-      if (el) { selectByElement(el); playSelected(); }
+      if (!el) return;
+      selectByElement(el);
+      if (el.classList.contains('folder-card')) {
+        enterFolder(el.dataset.name);
+      } else {
+        playSelected();
+      }
     },
     playPause: () => togglePlay(),
     fullscreen: () => toggleFullscreen(),
@@ -110,6 +117,7 @@ async function initApp() {
     download: downloadSelected,
     help: toggleHelp,
     toolbar: toggleToolbar,
+    backspace: () => { navigateBack(); },
     sidebar: toggleSidebar,
     upload: () => showUpload(),
     focusMinDuration: () => focusFilter('filter-min-duration'),
@@ -122,15 +130,16 @@ async function initApp() {
   initHelp();
 
   // Filters
-  document.getElementById('filter-type')?.addEventListener('change', (e) => { state.filters.type = e.target.value; loadMedia(); });
+  document.getElementById('filter-type')?.addEventListener('change', (e) => { state.filters.type = e.target.value; state.folderPath = ''; loadMedia(); });
   document.getElementById('filter-favorites')?.addEventListener('click', (e) => {
     state.filters.favorites = !state.filters.favorites;
     e.target.classList.toggle('active', state.filters.favorites);
+    state.folderPath = '';
     loadMedia();
   });
-  document.getElementById('filter-tags')?.addEventListener('change', (e) => { state.filters.tags = e.target.value; loadMedia(); });
-  document.getElementById('filter-min-duration')?.addEventListener('change', (e) => { state.filters.minDuration = e.target.value; loadMedia(); });
-  document.getElementById('filter-max-duration')?.addEventListener('change', (e) => { state.filters.maxDuration = e.target.value; loadMedia(); });
+  document.getElementById('filter-tags')?.addEventListener('change', (e) => { state.filters.tags = e.target.value; state.folderPath = ''; loadMedia(); });
+  document.getElementById('filter-min-duration')?.addEventListener('change', (e) => { state.filters.minDuration = e.target.value; state.folderPath = ''; loadMedia(); });
+  document.getElementById('filter-max-duration')?.addEventListener('change', (e) => { state.filters.maxDuration = e.target.value; state.folderPath = ''; loadMedia(); });
   document.getElementById('filter-toggle')?.addEventListener('click', () => {
     document.getElementById('filter-advanced')?.classList.toggle('hidden');
   });
@@ -162,6 +171,15 @@ async function initApp() {
     if (el) { selectByElement(el); playSelected(); }
   });
 
+  // Folder navigation
+  document.getElementById('media-grid')?.addEventListener('click', (e) => {
+    const folder = e.target.closest('.folder-card');
+    if (folder) {
+      e.stopPropagation();
+      enterFolder(folder.dataset.name);
+    }
+  });
+
   // Tags modal close
   document.getElementById('tags-close')?.addEventListener('click', closeTagsModal);
   document.getElementById('tags-modal')?.addEventListener('click', (e) => { if (e.target === document.getElementById('tags-modal')) closeTagsModal(); });
@@ -186,6 +204,7 @@ function renderSets() {
       const id = parseInt(row.dataset.id, 10);
       state.selectedSetIds = [id];
       state.selectedSetId = id;
+      state.folderPath = '';
       updateSetRowsUI();
       loadMedia();
     });
@@ -229,6 +248,7 @@ function toggleSetSelection() {
   } else {
     state.selectedSetId = null;
   }
+  state.folderPath = '';
   updateSetRowsUI();
   loadMedia();
 }
@@ -244,6 +264,7 @@ function setSetByDelta(dx) {
   const nextIdx = (idx + dx + state.sets.length) % state.sets.length;
   state.selectedSetId = state.sets[nextIdx].id;
   state.selectedSetIds = [state.selectedSetId];
+  state.folderPath = '';
   setActiveSet(state.selectedSetId);
   loadMedia();
 }
@@ -255,31 +276,154 @@ async function loadMedia() {
   grid.classList.remove('hidden');
   hint?.classList.add('hidden');
   grid.innerHTML = '<p class="text-muted text-sm grid-full">Loading...</p>';
+
+  const resultCount = document.getElementById('result-count');
+  const breadcrumb = document.getElementById('breadcrumb-bar');
+
   try {
     const setIds = state.selectedSetIds.length > 1 ? state.selectedSetIds.join(',') : '';
-    const singleSetId = state.selectedSetIds.length === 1 ? String(state.selectedSetIds[0]) : (state.selectedSetId ?? '');
-    const params = {
-      set_id: setIds ? '' : singleSetId,
-      set_ids: setIds,
-      type: state.filters.type,
-      search: state.filters.search,
-      favorites: state.filters.favorites ? 'true' : '',
-      tags: state.filters.tags || '',
-      min_duration: state.filters.minDuration ? String(parseFloat(state.filters.minDuration) * 60) : '',
-      max_duration: state.filters.maxDuration ? String(parseFloat(state.filters.maxDuration) * 60) : '',
-      sort: isShuffle() ? 'random' : 'name',
-      limit: '200',
-    };
-    const data = await API.media(params);
-    const list = Array.isArray(data) ? data : data?.media || [];
-    setMedia(list);
-    renderGrid(list);
-    document.getElementById('result-count').textContent = `${list.length} items`;
+    const singleSetId = state.selectedSetIds.length === 1 ? state.selectedSetIds[0] : null;
+
+    // When viewing a single set with no filters/search, use the browse endpoint
+    // so that subfolders are presented as folders to navigate into.
+    if (singleSetId && !setIds && !state.filters.search && !state.filters.type && !state.filters.favorites && !state.filters.tags && !state.filters.minDuration && !state.filters.maxDuration) {
+      const data = await API.browse(singleSetId, state.folderPath);
+      updateBreadcrumb(data.current_path);
+      setMedia(data.media || []);
+      renderBrowse(data);
+      const total = (data.media?.length || 0) + (data.folders?.length || 0);
+      resultCount.textContent = `${total} items`;
+    } else {
+      breadcrumb?.classList.add('hidden');
+      const params = {
+        set_id: setIds ? '' : String(singleSetId || state.selectedSetId || ''),
+        set_ids: setIds,
+        type: state.filters.type,
+        search: state.filters.search,
+        favorites: state.filters.favorites ? 'true' : '',
+        tags: state.filters.tags || '',
+        min_duration: state.filters.minDuration ? String(parseFloat(state.filters.minDuration) * 60) : '',
+        max_duration: state.filters.maxDuration ? String(parseFloat(state.filters.maxDuration) * 60) : '',
+        sort: isShuffle() ? 'random' : 'name',
+        limit: '200',
+      };
+      const data = await API.media(params);
+      const list = Array.isArray(data) ? data : data?.media || [];
+      setMedia(list);