diff --git a/cmd/main-server.go b/cmd/main-server.go
index 65cbbe22..2cdea369 100644
--- a/cmd/main-server.go
+++ b/cmd/main-server.go
@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"os"
 	"runtime/debug"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -216,7 +217,7 @@ func HandleGetPtyOut(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte(fmt.Sprintf("invalid cmdid: %v", err)))
 		return
 	}
-	_, data, err := sstore.ReadFullPtyOutFile(r.Context(), sessionId, cmdId)
+	realOffset, data, err := sstore.ReadFullPtyOutFile(r.Context(), sessionId, cmdId)
 	if err != nil {
 		if errors.Is(err, fs.ErrNotExist) {
 			w.WriteHeader(http.StatusOK)
@@ -226,6 +227,7 @@ func HandleGetPtyOut(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte(fmt.Sprintf("error reading ptyout file: %v", err)))
 		return
 	}
+	w.Header().Set("X-PtyDataOffset", strconv.FormatInt(realOffset, 10))
 	w.WriteHeader(http.StatusOK)
 	w.Write(data)
 }
diff --git a/pkg/sstore/fileops.go b/pkg/sstore/fileops.go
index e5500260..f7de7a8b 100644
--- a/pkg/sstore/fileops.go
+++ b/pkg/sstore/fileops.go
@@ -50,6 +50,7 @@ func AppendToCmdPtyBlob(ctx context.Context, sessionId string, cmdId string, dat
 	return nil
 }
 
+// returns (offset, data, err)
 func ReadFullPtyOutFile(ctx context.Context, sessionId string, cmdId string) (int64, []byte, error) {
 	ptyOutFileName, err := scbase.PtyOutFile(sessionId, cmdId)
 	if err != nil {