diff --git a/go/service/chat_local.go b/go/service/chat_local.go
index <HASH>..<HASH> 100644
--- a/go/service/chat_local.go
+++ b/go/service/chat_local.go
@@ -841,8 +841,9 @@ func (h *chatLocalHandler) PostAttachmentLocal(ctx context.Context, arg chat1.Po
 	if arg.Preview != nil {
 		g.Go(func() error {
 			chatUI.ChatAttachmentPreviewUploadStart(ctx)
-			// add .preview suffix to object key
-			params.ObjectKey += ".preview"
+			// add preview suffix to object key (P in hex)
+			// the s3path in gregor is expecting hex here
+			params.ObjectKey += "50"
 			prev, err := h.uploadAsset(ctx, arg.SessionID, params, *arg.Preview, nil)
 			chatUI.ChatAttachmentPreviewUploadDone(ctx)
 			if err == nil {
Change preview suffix to hex