diff --git a/internal/executor/sandbox/executor.go b/internal/executor/sandbox/executor.go
index c7d3e5c..47a89a4 100644
--- a/internal/executor/sandbox/executor.go
+++ b/internal/executor/sandbox/executor.go
@@ -7,6 +7,7 @@ import (
 
 	"github.com/criyle/go-judge/pb"
 	"github.com/joint-online-judge/JOJ3/internal/stage"
+	"google.golang.org/protobuf/encoding/protojson"
 	"google.golang.org/protobuf/proto"
 )
 
@@ -42,7 +43,14 @@ func (e *Sandbox) Run(cmds []stage.Cmd) ([]stage.ExecutorResult, error) {
 		slog.Debug("sandbox execute", "i", i, "pbCmd size", proto.Size(pbCmd))
 	}
 	pbReq := &pb.Request{Cmd: pbCmds}
-	slog.Info("sandbox execute", "pbReq size", proto.Size(pbReq))
+	pbReqBytes, err := protojson.Marshal(pbReq)
+	if err != nil {
+		slog.Error("failed to marshal json", "error", err)
+	}
+	slog.Info("sandbox execute",
+		"pbReq size", proto.Size(pbReq),
+		"pbReqBytes size", len(pbReqBytes),
+	)
 	pbRet, err := e.execClient.Exec(context.TODO(), pbReq)
 	if err != nil {
 		return nil, err