diff --git a/backend/iclouddrive/api/drive.go b/backend/iclouddrive/api/drive.go
index 1fe9d907a..73d23e39a 100644
--- a/backend/iclouddrive/api/drive.go
+++ b/backend/iclouddrive/api/drive.go
@@ -498,7 +498,7 @@ func (d *DriveService) CopyDocByItemID(ctx context.Context, itemID string) (*Dri
 }
 
 // CreateUpload creates an url for an upload.
-func (d *DriveService) CreateUpload(ctx context.Context, size int64, name string) (*UploadResponse, *http.Response, error) {
+func (d *DriveService) CreateUpload(ctx context.Context, size int64, name, zone string) (*UploadResponse, *http.Response, error) {
 	// first we need to request an upload url
 	values := map[string]any{
 		"filename":     name,
@@ -513,7 +513,7 @@ func (d *DriveService) CreateUpload(ctx context.Context, size int64, name string
 
 	opts := rest.Opts{
 		Method:       "POST",
-		Path:         "/ws/" + defaultZone + "/upload/web",
+		Path:         "/ws/" + zone + "/upload/web",
 		ExtraHeaders: d.icloud.Session.GetHeaders(map[string]string{}),
 		RootURL:      d.docsEndpoint,
 		Body:         body,
@@ -552,14 +552,14 @@ func (d *DriveService) Upload(ctx context.Context, in io.Reader, size int64, nam
 // ctx: the context.Context object for the request.
 // r: a pointer to the UpdateFileInfo struct containing the information for the file update.
 // Returns a pointer to the DriveItem struct representing the updated file, the http.Response object, and an error if any.
-func (d *DriveService) UpdateFile(ctx context.Context, r *UpdateFileInfo) (*DriveItem, *http.Response, error) {
+func (d *DriveService) UpdateFile(ctx context.Context, r *UpdateFileInfo, zone string) (*DriveItem, *http.Response, error) {
 	body, err := IntoReader(r)
 	if err != nil {
 		return nil, nil, err
 	}
 	opts := rest.Opts{
 		Method:       "POST",
-		Path:         "/ws/" + defaultZone + "/update/documents",
+		Path:         "/ws/" + zone + "/update/documents",
 		ExtraHeaders: d.icloud.Session.GetHeaders(map[string]string{}),
 		RootURL:      d.docsEndpoint,
 		Body:         body,
@@ -572,7 +572,7 @@ func (d *DriveService) UpdateFile(ctx context.Context, r *UpdateFileInfo) (*Driv
 
 	doc := responseInfo.Results[0].Document
 	item := DriveItem{
-		Drivewsid:    "FILE::com.apple.CloudDocs::" + doc.DocumentID,
+		Drivewsid:    ConstructDriveID(doc.DocumentID, zone, "FILE"),
 		Docwsid:      doc.DocumentID,
 		Itemid:       doc.ItemID,
 		Etag:         doc.Etag,
@@ -892,6 +892,18 @@ func DeconstructDriveID(id string) (docType, zone, docid string) {
 	return split[0], split[1], split[2]
 }
 
+// ZoneFromDriveID returns the zone a drive ID belongs to, or the default zone
+// for an ID that carries none. Items in an app container -- Obsidian, Pages,
+// Shortcuts -- live in that app's zone rather than com.apple.CloudDocs, and a
+// write addressed to the wrong zone cannot resolve its parent.
+func ZoneFromDriveID(id string) string {
+	_, zone, _ := DeconstructDriveID(id)
+	if zone == "" {
+		return defaultZone
+	}
+	return zone
+}
+
 // ConstructDriveID constructs a drive ID from the given components.
 func ConstructDriveID(id string, zone string, t string) string {
 	return strings.Join([]string{t, zone, id}, "::")
diff --git a/backend/iclouddrive/api/drive_test.go b/backend/iclouddrive/api/drive_test.go
new file mode 100644
index 000000000..112f3f765
--- /dev/null
+++ b/backend/iclouddrive/api/drive_test.go
@@ -0,0 +1,32 @@
+package api
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestZoneFromDriveID(t *testing.T) {
+	for _, test := range []struct {
+		name string
+		id   string
+		want string
+	}{
+		{"app container", "FOLDER::iCloud.md.obsidian::documents#o2v", "iCloud.md.obsidian"},
+		{"another app container", "FOLDER::com.apple.Pages::documents#7qt", "com.apple.Pages"},
+		{"ordinary folder", "FOLDER::com.apple.CloudDocs::B847FE2D", "com.apple.CloudDocs"},
+		{"file in a container", "FILE::iCloud.md.obsidian::abc123", "iCloud.md.obsidian"},
+		{"no zone", "root", defaultZone},
+		{"empty", "", defaultZone},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			assert.Equal(t, test.want, ZoneFromDriveID(test.id))
+		})
+	}
+}
+
+func TestZoneFromDriveIDRoundTrip(t *testing.T) {
+	id := ConstructDriveID("abc123", "iCloud.md.obsidian", "FILE")
+	assert.Equal(t, "FILE::iCloud.md.obsidian::abc123", id)
+	assert.Equal(t, "iCloud.md.obsidian", ZoneFromDriveID(id))
+}
diff --git a/backend/iclouddrive/iclouddrive.go b/backend/iclouddrive/iclouddrive.go
index 90be7a712..3c78e3bce 100644
--- a/backend/iclouddrive/iclouddrive.go
+++ b/backend/iclouddrive/iclouddrive.go
@@ -343,7 +343,7 @@ func (f *Fs) Copy(ctx context.Context, src fs.Object, remote string) (fs.Object,
 
 	var item *api.DriveItem
 	if err = f.pacer.Call(func() (bool, error) {
-		item, resp, err = f.service.UpdateFile(ctx, &r)
+		item, resp, err = f.service.UpdateFile(ctx, &r, api.ZoneFromDriveID(pathID))
 		return retryResultUnknown(ctx, resp, err)
 	}); err != nil {
 		return nil, err
@@ -949,7 +949,7 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 	// Create document
 	var uploadInfo *api.UploadResponse
 	if err = o.fs.pacer.Call(func() (bool, error) {
-		uploadInfo, resp, err = o.fs.service.CreateUpload(ctx, size, name)
+		uploadInfo, resp, err = o.fs.service.CreateUpload(ctx, size, name, api.ZoneFromDriveID(dirID))
 		return ignoreResultUnknown(ctx, resp, err)
 	}); err != nil {
 		return err
@@ -988,7 +988,7 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 	// Update metadata
 	var item *api.DriveItem
 	if err = o.fs.pacer.Call(func() (bool, error) {
-		item, resp, err = o.fs.service.UpdateFile(ctx, &r)
+		item, resp, err = o.fs.service.UpdateFile(ctx, &r, api.ZoneFromDriveID(dirID))
 		return ignoreResultUnknown(ctx, resp, err)
 	}); err != nil {
 		return err