diff --git a/cmd/joj3/conf/conf.go b/cmd/joj3/conf/conf.go
index 5d3478c..72fb036 100644
--- a/cmd/joj3/conf/conf.go
+++ b/cmd/joj3/conf/conf.go
@@ -13,28 +13,30 @@ import (
 	"github.com/koding/multiconfig"
 )
 
+type ConfStage struct {
+	Name     string
+	Group    string
+	Executor struct {
+		Name string
+		With struct {
+			Default stage.Cmd
+			Cases   []OptionalCmd
+		}
+	}
+	Parsers []struct {
+		Name string
+		With interface{}
+	}
+}
+
 type Conf struct {
 	Name    string `default:"unknown"`
 	LogPath string `default:""`
 	Stage   struct {
 		SandboxExecServer string `default:"localhost:5051"`
 		SandboxToken      string `default:""`
-		OutputPath        string `default:"stages_result.json"`
-		Stages            []struct {
-			Name     string
-			Group    string
-			Executor struct {
-				Name string
-				With struct {
-					Default stage.Cmd
-					Cases   []OptionalCmd
-				}
-			}
-			Parsers []struct {
-				Name string
-				With interface{}
-			}
-		}
+		OutputPath        string `default:"joj3_result.json"`
+		Stages            []ConfStage
 	}
 	Teapot struct {
 		LogPath         string `default:"/home/tt/.cache/joint-teapot-debug.log"`
@@ -45,6 +47,29 @@ type Conf struct {
 		SkipScoreboard  bool   `default:"false"`
 		SkipFailedTable bool   `default:"false"`
 	}
+	// TODO: remove the following backward compatibility fields
+	SandboxExecServer string `default:"localhost:5051"`
+	SandboxToken      string `default:""`
+	OutputPath        string `default:"joj3_result.json"`
+	GradingRepoName   string `default:""`
+	SkipTeapot        bool   `default:"true"`
+	ScoreboardPath    string `default:"scoreboard.csv"`
+	FailedTablePath   string `default:"failed-table.md"`
+	Stages            []struct {
+		Name     string
+		Group    string
+		Executor struct {
+			Name string
+			With struct {
+				Default stage.Cmd
+				Cases   []OptionalCmd
+			}
+		}
+		Parser struct {
+			Name string
+			With interface{}
+		}
+	}
 }
 
 type OptionalCmd struct {
@@ -134,6 +159,25 @@ func parseConfFile(path string) (conf Conf, err error) {
 		slog.Error("validate stages conf", "error", err)
 		return
 	}
+	// TODO: remove the following backward compatibility codes
+	conf.Stage.SandboxExecServer = conf.SandboxExecServer
+	conf.Stage.SandboxToken = conf.SandboxToken
+	conf.Stage.OutputPath = conf.OutputPath
+	conf.Stage.Stages = make([]ConfStage, len(conf.Stages))
+	for i, stage := range conf.Stages {
+		conf.Stage.Stages[i].Name = stage.Name
+		conf.Stage.Stages[i].Group = stage.Group
+		conf.Stage.Stages[i].Executor = stage.Executor
+		conf.Stage.Stages[i].Parsers = []struct {
+			Name string
+			With interface{}
+		}{
+			{
+				Name: stage.Parser.Name,
+				With: stage.Parser.With,
+			},
+		}
+	}
 	return
 }