feat: decouple --lang preference from TUI display language (#1132)

2026-07-03 14:02:43 +08:00 · 2026-05-28 18:55:40 +08:00
parent 3cd84fca90
commit 3b770558e5
20 changed files with 898 additions and 107 deletions
--- a/cmd/auth/login.go
+++ b/cmd/auth/login.go
@@ -16,6 +16,7 @@ import (
 	larkauth "github.com/larksuite/cli/internal/auth"
 	"github.com/larksuite/cli/internal/cmdutil"
 	"github.com/larksuite/cli/internal/core"
+	"github.com/larksuite/cli/internal/i18n"
 	"github.com/larksuite/cli/internal/output"
 	"github.com/larksuite/cli/internal/registry"
 	"github.com/larksuite/cli/shortcuts"
@@ -121,7 +122,7 @@ func authLoginRun(opts *LoginOptions) error {
 	}

 	// Determine UI language from saved config
-	lang := "zh"
+	var lang i18n.Lang
 	if multi, _ := core.LoadMultiAppConfig(); multi != nil {
 		if app := multi.FindApp(config.ProfileName); app != nil {
 			lang = app.Lang
@@ -177,7 +178,7 @@ func authLoginRun(opts *LoginOptions) error {

 	if !hasAnyOption {
 		if !opts.JSON && f.IOStreams.IsTerminal {
-			result, err := runInteractiveLogin(f.IOStreams, lang, msg, config.Brand)
+			result, err := runInteractiveLogin(f.IOStreams, lang.Base(), msg, config.Brand)
 			if err != nil {
 				return err
 			}
--- a/cmd/auth/login_messages.go
+++ b/cmd/auth/login_messages.go
@@ -3,6 +3,8 @@

 package auth

+import "github.com/larksuite/cli/internal/i18n"
+
 type loginMsg struct {
 	// Interactive UI (login_interactive.go)
 	SelectDomains   string
@@ -115,8 +117,8 @@ var loginMsgEn = &loginMsg{
 }

 // getLoginMsg returns the login message bundle for the given language.
-func getLoginMsg(lang string) *loginMsg {
-	if lang == "en" {
+func getLoginMsg(lang i18n.Lang) *loginMsg {
+	if lang.IsEnglish() {
 		return loginMsgEn
 	}
 	return loginMsgZh
--- a/cmd/auth/login_messages_test.go
+++ b/cmd/auth/login_messages_test.go
@@ -8,6 +8,8 @@ import (
 	"reflect"
 	"strings"
 	"testing"
+
+	"github.com/larksuite/cli/internal/i18n"
 )

 func TestGetLoginMsg_Zh(t *testing.T) {
@@ -31,7 +33,7 @@ func TestGetLoginMsg_En(t *testing.T) {
 }

 func TestGetLoginMsg_DefaultsToZh(t *testing.T) {
-	for _, lang := range []string{"", "fr", "ja", "unknown"} {
+	for _, lang := range []i18n.Lang{"", "fr_fr", "ja_jp", "unknown"} {
 		msg := getLoginMsg(lang)
 		if msg != loginMsgZh {
 			t.Errorf("getLoginMsg(%q) should default to zh", lang)
@@ -61,7 +63,7 @@ func assertLoginMsgAllFieldsNonEmpty(t *testing.T, msg *loginMsg, label string)
 }

 func TestLoginMsg_FormatStrings(t *testing.T) {
-	for _, lang := range []string{"zh", "en"} {
+	for _, lang := range []i18n.Lang{i18n.LangZhCN, i18n.LangEnUS} {
 		msg := getLoginMsg(lang)

 		// LoginSuccess should contain two %s placeholders (userName, openId)
@@ -102,10 +104,10 @@ func TestLoginMsg_FormatStrings(t *testing.T) {
 // --device-code split-flow, and (c) non-streaming harnesses must end the turn
 // after presenting the URL instead of blocking in the same turn.
 func TestAgentTimeoutHint_CarriesKeyInfo(t *testing.T) {
-	for _, lang := range []string{"zh", "en"} {
+	for _, lang := range []i18n.Lang{i18n.LangZhCN, i18n.LangEnUS} {
 		hint := getLoginMsg(lang).AgentTimeoutHint
 		for _, want := range []string{"--no-wait", "--device-code", "turn"} {
-			if lang == "zh" && want == "turn" {
+			if lang == i18n.LangZhCN && want == "turn" {
 				want = "本轮"
 			}
 			if !strings.Contains(hint, want) {
--- a/cmd/config/bind.go
+++ b/cmd/config/bind.go
@@ -14,6 +14,7 @@ import (

 	"github.com/larksuite/cli/internal/cmdutil"
 	"github.com/larksuite/cli/internal/core"
+	"github.com/larksuite/cli/internal/i18n"
 	"github.com/larksuite/cli/internal/keychain"
 	"github.com/larksuite/cli/internal/output"
 	"github.com/larksuite/cli/internal/validate"
@@ -37,8 +38,10 @@ type BindOptions struct {
 	// this flag because its own prompts already require human confirmation.
 	Force bool

-	Lang         string
-	langExplicit bool // true when --lang was explicitly passed
+	Lang         string // raw --lang (string for cobra); normalized to canonical/"" in validateBindFlags
+	langExplicit bool   // true when --lang was explicitly passed
+
+	UILang i18n.Lang // TUI display language (picker-only); intentionally separate from --lang

 	// Brand holds the resolved Lark product brand ("feishu" | "lark") for
 	// the account being bound. Populated after resolveAccount; TUI stages
@@ -55,7 +58,7 @@ type BindOptions struct {

 // NewCmdConfigBind creates the config bind subcommand.
 func NewCmdConfigBind(f *cmdutil.Factory, runF func(*BindOptions) error) *cobra.Command {
-	opts := &BindOptions{Factory: f}
+	opts := &BindOptions{Factory: f, UILang: i18n.LangZhCN}

 	cmd := &cobra.Command{
 		Use:   "bind",
@@ -102,7 +105,7 @@ Interactive terminal use: run with no flags to enter the TUI form.`,
 	cmd.Flags().StringVar(&opts.AppID, "app-id", "", "App ID to bind (required for OpenClaw multi-account)")
 	cmd.Flags().StringVar(&opts.Identity, "identity", "", "identity preset (bot-only|user-default); defaults to bot-only in flag mode (safer: no impersonation)")
 	cmd.Flags().BoolVar(&opts.Force, "force", false, "confirm a risky transition (currently: bot-only → user-default identity change in flag mode)")
-	cmd.Flags().StringVar(&opts.Lang, "lang", "zh", "language for interactive prompts (zh|en)")
+	cmd.Flags().StringVar(&opts.Lang, "lang", "", "language preference (e.g. zh or zh_cn)")
 	cmdutil.SetRisk(cmd, "write")

 	return cmd
@@ -147,7 +150,7 @@ func configBindRun(opts *BindOptions) error {
 	if err := warnIdentityEscalation(opts, existing.ConfigBytes); err != nil {
 		return err
 	}
-	applyPreferences(appConfig, opts)
+	applyPreferences(appConfig, opts, priorLang(existing.ConfigBytes))
 	noticeUserDefaultRisk(opts)

 	return commitBinding(opts, appConfig, existing.ConfigBytes, source, targetConfigPath)
@@ -202,16 +205,18 @@ func finalizeSource(opts *BindOptions) (string, error) {

 	// TUI: prompt for language before any downstream prompts. The source
 	// selection itself may still be skipped entirely if --source or the
-	// env already pinned it.
+	// env already pinned it. Picker offers 2 options (中文 / English) and
+	// drives BOTH opts.Lang (preference) and opts.UILang (TUI rendering).
 	if opts.IsTUI && !opts.langExplicit {
-		lang, err := promptLangSelection("")
+		lang, err := promptLangSelection()
 		if err != nil {
 			if err == huh.ErrUserAborted {
 				return "", output.ErrBare(1)
 			}
-			return "", err
+			return "", output.Errorf(output.ExitInternal, "internal", "language selection failed: %v", err)
 		}
-		opts.Lang = lang
+		opts.Lang = string(lang)
+		opts.UILang = lang
 	}

 	if explicit != "" {
@@ -245,7 +250,7 @@ func reconcileExistingBinding(opts *BindOptions, source, configPath string) (exi
 			return existingBinding{}, err
 		}
 		if action == "cancel" {
-			msg := getBindMsg(opts.Lang)
+			msg := getBindMsg(opts.UILang)
 			fmt.Fprintln(opts.Factory.IOStreams.ErrOut, msg.ConflictCancelled)
 			return existingBinding{Cancelled: true}, nil
 		}
@@ -329,7 +334,7 @@ func warnIdentityEscalation(opts *BindOptions, previousConfigBytes []byte) error
 	if !hasStrictBotLock(previousConfigBytes) {
 		return nil
 	}
-	msg := getBindMsg(opts.Lang)
+	msg := getBindMsg(opts.UILang)
 	return output.ErrWithHint(output.ExitValidation, "bind",
 		msg.IdentityEscalationMessage, msg.IdentityEscalationHint)
 }
@@ -347,14 +352,23 @@ func noticeUserDefaultRisk(opts *BindOptions) {
 	if opts.IsTUI || opts.Identity != "user-default" {
 		return
 	}
-	msg := getBindMsg(opts.Lang)
+	msg := getBindMsg(opts.UILang)
 	fmt.Fprintln(opts.Factory.IOStreams.ErrOut, "⚠️ "+msg.IdentityEscalationMessage)
 }

 // applyPreferences expands the chosen identity preset into the underlying
 // StrictMode + DefaultAs on the AppConfig. Always writes both fields so the
 // profile's intent survives later changes to global strict-mode settings.
-func applyPreferences(appConfig *core.AppConfig, opts *BindOptions) {
+// preferredLang resolves the language to persist: the requested value when set,
+// otherwise the prior one — so an unset --lang never clears a stored preference.
+func preferredLang(requested, prior i18n.Lang) i18n.Lang {
+	if requested != "" {
+		return requested
+	}
+	return prior
+}
+
+func applyPreferences(appConfig *core.AppConfig, opts *BindOptions, prior i18n.Lang) {
 	switch opts.Identity {
 	case "bot-only":
 		sm := core.StrictModeBot
@@ -365,9 +379,22 @@ func applyPreferences(appConfig *core.AppConfig, opts *BindOptions) {
 		appConfig.StrictMode = &sm
 		appConfig.DefaultAs = core.AsUser
 	}
-	if opts.Lang != "" {
-		appConfig.Lang = opts.Lang
+	appConfig.Lang = preferredLang(i18n.Lang(opts.Lang), prior)
+}
+
+// priorLang returns the language preference recorded in a previous config, or
+// "" if there is none / the bytes don't parse.
+func priorLang(previousConfigBytes []byte) i18n.Lang {
+	var multi core.MultiAppConfig
+	if json.Unmarshal(previousConfigBytes, &multi) != nil {
+		return ""
 	}
+	for _, app := range multi.Apps {
+		if app.Lang != "" {
+			return app.Lang
+		}
+	}
+	return ""
 }

 // commitBinding finalizes the bind: atomic write of the new workspace config,
@@ -393,7 +420,10 @@ func commitBinding(opts *BindOptions, appConfig *core.AppConfig, previousConfigB
 	}

 	replaced := previousConfigBytes != nil
-	msg := getBindMsg(opts.Lang)
+	// uiMsg renders human-facing TUI text (stderr success banner). Follows
+	// opts.UILang — zh by default; picker can flip it to en. --lang does
+	// not influence the TUI language.
+	uiMsg := getBindMsg(opts.UILang)
 	display := sourceDisplayName(source)

 	if replaced {
@@ -401,7 +431,11 @@ func commitBinding(opts *BindOptions, appConfig *core.AppConfig, previousConfigB
 	}

 	fmt.Fprintln(opts.Factory.IOStreams.ErrOut,
-		fmt.Sprintf(msg.BindSuccessHeader, display)+"\n"+msg.BindSuccessNotice)
+		fmt.Sprintf(uiMsg.BindSuccessHeader, display)+"\n"+uiMsg.BindSuccessNotice)
+
+	if opts.langExplicit && opts.Lang != "" {
+		fmt.Fprintln(opts.Factory.IOStreams.ErrOut, fmt.Sprintf(uiMsg.LangPreferenceSet, opts.Lang))
+	}

 	// TUI mode is a human sitting at a terminal; the BindSuccess notice on
 	// stderr is enough and a machine-readable JSON dump on stdout is just
@@ -419,12 +453,17 @@ func commitBinding(opts *BindOptions, appConfig *core.AppConfig, previousConfigB
 		"replaced":    replaced,
 		"identity":    opts.Identity,
 	}
-	brand := brandDisplay(string(appConfig.Brand), opts.Lang)
+	// JSON "message" follows the effective preference on disk (appConfig.Lang),
+	// not the raw --lang value: when --lang is omitted on re-bind, preferredLang
+	// has already inherited the prior preference into appConfig.Lang, and the
+	// message should respect that inherited choice. stderr above follows UILang.
+	prefMsg := getBindMsg(appConfig.Lang)
+	brand := brandDisplay(string(appConfig.Brand), appConfig.Lang)
 	switch opts.Identity {
 	case "bot-only":
-		envelope["message"] = fmt.Sprintf(msg.MessageBotOnly, appConfig.AppId, display, brand)
+		envelope["message"] = fmt.Sprintf(prefMsg.MessageBotOnly, appConfig.AppId, display, brand)
 	case "user-default":
-		envelope["message"] = fmt.Sprintf(msg.MessageUserDefault, appConfig.AppId, display, display)
+		envelope["message"] = fmt.Sprintf(prefMsg.MessageUserDefault, appConfig.AppId, display, display)
 	}

 	resultJSON, _ := json.Marshal(envelope)
@@ -461,7 +500,7 @@ func cleanupKeychainFromData(kc keychain.KeychainAccess, data []byte, keep *core

 // tuiSelectSource prompts user to choose bind source.
 func tuiSelectSource(opts *BindOptions) (string, error) {
-	msg := getBindMsg(opts.Lang)
+	msg := getBindMsg(opts.UILang)
 	var source string

 	// Pre-select based on detected env signals
@@ -486,7 +525,7 @@ func tuiSelectSource(opts *BindOptions) (string, error) {
 		huh.NewGroup(
 			huh.NewSelect[string]().
 				Title(msg.SelectSource).
-				Description(fmt.Sprintf(msg.SelectSourceDesc, brandDisplay(opts.Brand, opts.Lang))).
+				Description(fmt.Sprintf(msg.SelectSourceDesc, brandDisplay(opts.Brand, opts.UILang))).
 				Options(
 					huh.NewOption(fmt.Sprintf(msg.SourceOpenClaw, openclawPath), "openclaw"),
 					huh.NewOption(fmt.Sprintf(msg.SourceHermes, hermesEnvPath), "hermes"),
@@ -508,7 +547,7 @@ func tuiSelectSource(opts *BindOptions) (string, error) {
 // tuiSelectApp prompts the user to choose from multiple account candidates.
 // Invoked only via selectCandidate's tuiPrompt callback, and only in TUI mode.
 func tuiSelectApp(opts *BindOptions, source string, candidates []Candidate) (*Candidate, error) {
-	msg := getBindMsg(opts.Lang)
+	msg := getBindMsg(opts.UILang)
 	options := make([]huh.Option[int], 0, len(candidates))
 	for i, c := range candidates {
 		label := c.AppID
@@ -522,7 +561,7 @@ func tuiSelectApp(opts *BindOptions, source string, candidates []Candidate) (*Ca
 	form := huh.NewForm(
 		huh.NewGroup(
 			huh.NewSelect[int]().
-				Title(fmt.Sprintf(msg.SelectAccount, sourceDisplayName(source), brandDisplay(opts.Brand, opts.Lang))).
+				Title(fmt.Sprintf(msg.SelectAccount, sourceDisplayName(source), brandDisplay(opts.Brand, opts.UILang))).
 				Options(options...).
 				Value(&selected),
 		),
@@ -539,7 +578,7 @@ func tuiSelectApp(opts *BindOptions, source string, candidates []Candidate) (*Ca

 // tuiConflictPrompt shows existing binding and asks user to Force or Cancel.
 func tuiConflictPrompt(opts *BindOptions, source, configPath string) (string, error) {
-	msg := getBindMsg(opts.Lang)
+	msg := getBindMsg(opts.UILang)

 	// Build existing binding summary
 	existingSummary := fmt.Sprintf(msg.ConflictDesc, source, "?", "?", configPath)
@@ -591,6 +630,11 @@ func validateBindFlags(opts *BindOptions) error {
 			return output.ErrValidation("invalid --identity %q; valid values: bot-only, user-default", opts.Identity)
 		}
 	}
+	lang, err := cmdutil.ParseLangFlag(opts.Lang)
+	if err != nil {
+		return err
+	}
+	opts.Lang = string(lang)
 	return nil
 }

@@ -606,8 +650,8 @@ func validateBindFlags(opts *BindOptions) error {
 // DescriptionFunc approach breaks here because a longer description on
 // hover pushes options out of the field's initial viewport.
 func tuiSelectIdentity(opts *BindOptions) (string, error) {
-	msg := getBindMsg(opts.Lang)
-	brand := brandDisplay(opts.Brand, opts.Lang)
+	msg := getBindMsg(opts.UILang)
+	brand := brandDisplay(opts.Brand, opts.UILang)
 	botLabel := msg.IdentityBotOnly + "\n" + indent(fmt.Sprintf(msg.IdentityBotOnlyDesc, brand))
 	userLabel := msg.IdentityUserDefault + "\n" + indent(fmt.Sprintf(msg.IdentityUserDefaultDesc, brand, brand))
 	var value string
--- a/cmd/config/bind_messages.go
+++ b/cmd/config/bind_messages.go
@@ -3,6 +3,8 @@

 package config

+import "github.com/larksuite/cli/internal/i18n"
+
 // bindMsg holds all TUI text for config bind, supporting zh/en via --lang.
 //
 // Brand-aware strings use a %s slot where the UI-friendly product name
@@ -84,6 +86,11 @@ type bindMsg struct {
 	// require in-flow human confirmation.
 	IdentityEscalationMessage string
 	IdentityEscalationHint    string
+
+	// LangPreferenceSet is printed to stderr after a successful bind when the
+	// user explicitly passed --lang. Format: language code. Not printed when
+	// --lang was not explicit (i.e., the cobra default zh stayed in effect).
+	LangPreferenceSet string
 }

 var bindMsgZh = &bindMsg{
@@ -116,6 +123,8 @@ var bindMsgZh = &bindMsg{

 	IdentityEscalationMessage: "你正在从应用身份切换到用户身份 —— 切换后 AI 将以你的名义在飞书中执行所有操作（读写文档、搜索消息、修改日程等）。⚠️ 请勿将此机器人分享给他人或拉入群聊中使用，以免泄露你的飞书数据。",
 	IdentityEscalationHint:    "若用户确认切换，附加 --force 重新运行：`lark-cli config bind --identity user-default --force`",
+
+	LangPreferenceSet: "语言偏好已设置：%s",
 }

 var bindMsgEn = &bindMsg{
@@ -150,10 +159,13 @@ var bindMsgEn = &bindMsg{

 	IdentityEscalationMessage: "you are switching from bot-only to user-default — the AI will then act under your Feishu identity for all operations (docs, messages, calendar, etc.). ⚠️ Don't share this bot with others or add it to group chats. It has access to your personal Feishu data.",
 	IdentityEscalationHint:    "if the user confirms the switch, re-run with --force: `lark-cli config bind --identity user-default --force`",
+
+	LangPreferenceSet: "Language preference set to: %s",
 }

-func getBindMsg(lang string) *bindMsg {
-	if lang == "en" {
+// getBindMsg picks the zh/en TUI bundle; non-English falls back to zh.
+func getBindMsg(lang i18n.Lang) *bindMsg {
+	if lang.IsEnglish() {
 		return bindMsgEn
 	}
 	return bindMsgZh
@@ -164,11 +176,11 @@ func getBindMsg(lang string) *bindMsg {
 // "feishu" (or empty / unknown) maps to "飞书" in zh and "Feishu" in en —
 // this is the safe default when the brand hasn't been resolved yet (for
 // example, on the pre-binding source-selection screen).
-func brandDisplay(brand, lang string) string {
+func brandDisplay(brand string, lang i18n.Lang) string {
 	if brand == "lark" || brand == "Lark" || brand == "LARK" {
 		return "Lark"
 	}
-	if lang == "en" {
+	if lang.IsEnglish() {
 		return "Feishu"
 	}
 	return "飞书"
--- a/cmd/config/bind_test.go
+++ b/cmd/config/bind_test.go
@@ -16,6 +16,7 @@ import (
 	"github.com/larksuite/cli/errs"
 	"github.com/larksuite/cli/internal/cmdutil"
 	"github.com/larksuite/cli/internal/core"
+	"github.com/larksuite/cli/internal/i18n"
 	"github.com/larksuite/cli/internal/output"
 )

@@ -120,14 +121,182 @@ func TestConfigBindCmd_LangDefault(t *testing.T) {
 	if err := cmd.Execute(); err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
-	if gotOpts.Lang != "zh" {
-		t.Errorf("Lang = %q, want default %q", gotOpts.Lang, "zh")
+	if gotOpts.Lang != "" {
+		t.Errorf("Lang = %q, want default %q (unset)", gotOpts.Lang, "")
 	}
 	if gotOpts.langExplicit {
 		t.Error("expected langExplicit=false when --lang not passed")
 	}
 }

+// TestConfigBindRun_InvalidLang verifies a non-empty --lang is strictly
+// validated: wrong case, typos, and removed codes all exit with
+// ExitValidation (code 2) and a message identifying the offending value.
+// (Empty is not invalid — see TestConfigBindRun_EmptyLangIsNoOp.)
+func TestConfigBindRun_InvalidLang(t *testing.T) {
+	saveWorkspace(t)
+	configDir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", configDir)
+	hermesHome := t.TempDir()
+	t.Setenv("HERMES_HOME", hermesHome)
+	if err := os.WriteFile(filepath.Join(hermesHome, ".env"), []byte("FEISHU_APP_ID=cli_abc\nFEISHU_APP_SECRET=secret\n"), 0600); err != nil {
+		t.Fatalf("write .env: %v", err)
+	}
+
+	cases := []struct {
+		name string
+		lang string
+	}{
+		{"wrong case ZH", "ZH"},
+		{"typo frr", "frr"},
+		{"removed code ar", "ar"},
+		{"unknown xx", "xx"},
+		{"hyphen form zh-CN", "zh-CN"},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			f, _, _, _ := cmdutil.TestFactory(t, nil)
+			err := configBindRun(&BindOptions{
+				Factory:      f,
+				Source:       "hermes",
+				Lang:         tc.lang,
+				langExplicit: true,
+			})
+			if err == nil {
+				t.Fatalf("expected validation error for --lang %q, got nil", tc.lang)
+			}
+			exitErr, ok := err.(*output.ExitError)
+			if !ok {
+				t.Fatalf("expected *output.ExitError, got %T: %v", err, err)
+			}
+			if exitErr.Code != output.ExitValidation {
+				t.Errorf("exit code = %d, want %d (validation)", exitErr.Code, output.ExitValidation)
+			}
+			if !strings.Contains(exitErr.Error(), "invalid --lang") {
+				t.Errorf("error message %q does not contain 'invalid --lang'", exitErr.Error())
+			}
+		})
+	}
+}
+
+// TestConfigBindRun_EmptyLangIsNoOp verifies that an empty --lang (omitted or
+// explicit "") is unset: it neither errors nor persists a language, while a
+// non-empty short code or Feishu locale both canonicalize to the same locale.
+func TestConfigBindRun_EmptyLangIsNoOp(t *testing.T) {
+	cases := []struct {
+		name     string
+		lang     string
+		explicit bool
+		wantLang i18n.Lang
+	}{
+		{"omitted", "", false, ""},
+		{"explicit empty", "", true, ""},
+		{"short code", "ja", true, i18n.LangJaJP},
+		{"feishu locale", "ja_jp", true, i18n.LangJaJP},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			saveWorkspace(t)
+			t.Setenv("LARKSUITE_CLI_CONFIG_DIR", t.TempDir())
+			hermesHome := t.TempDir()
+			t.Setenv("HERMES_HOME", hermesHome)
+			if err := os.WriteFile(filepath.Join(hermesHome, ".env"), []byte("FEISHU_APP_ID=cli_abc\nFEISHU_APP_SECRET=secret\n"), 0600); err != nil {
+				t.Fatalf("write .env: %v", err)
+			}
+
+			f, _, _, _ := cmdutil.TestFactory(t, nil)
+			if err := configBindRun(&BindOptions{
+				Factory:      f,
+				Source:       "hermes",
+				Lang:         tc.lang,
+				langExplicit: tc.explicit,
+			}); err != nil {
+				t.Fatalf("configBindRun(--lang %q) = %v, want nil", tc.lang, err)
+			}
+
+			multi, err := core.LoadMultiAppConfig()
+			if err != nil {
+				t.Fatalf("LoadMultiAppConfig: %v", err)
+			}
+			app := multi.CurrentAppConfig("")
+			if app == nil {
+				t.Fatal("no app persisted")
+			}
+			if app.Lang != tc.wantLang {
+				t.Errorf("persisted Lang = %q, want %q", app.Lang, tc.wantLang)
+			}
+		})
+	}
+}
+
+// TestConfigBindRun_OmitLangPreservesPrior guards against a re-bind without
+// --lang silently dropping a previously stored preference (appConfig is rebuilt
+// fresh, so commitBinding must inherit the prior Lang).
+func TestConfigBindRun_OmitLangPreservesPrior(t *testing.T) {
+	saveWorkspace(t)
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", t.TempDir())
+	hermesHome := t.TempDir()
+	t.Setenv("HERMES_HOME", hermesHome)
+	if err := os.WriteFile(filepath.Join(hermesHome, ".env"), []byte("FEISHU_APP_ID=cli_abc\nFEISHU_APP_SECRET=secret\n"), 0600); err != nil {
+		t.Fatalf("write .env: %v", err)
+	}
+
+	f1, _, _, _ := cmdutil.TestFactory(t, nil)
+	if err := configBindRun(&BindOptions{Factory: f1, Source: "hermes", Lang: "ja", langExplicit: true}); err != nil {
+		t.Fatalf("first bind (--lang ja): %v", err)
+	}
+	f2, _, _, _ := cmdutil.TestFactory(t, nil)
+	if err := configBindRun(&BindOptions{Factory: f2, Source: "hermes", Lang: "", langExplicit: false}); err != nil {
+		t.Fatalf("re-bind (no --lang): %v", err)
+	}
+
+	multi, err := core.LoadMultiAppConfig()
+	if err != nil {
+		t.Fatalf("LoadMultiAppConfig: %v", err)
+	}
+	if app := multi.CurrentAppConfig(""); app == nil || app.Lang != i18n.LangJaJP {
+		t.Errorf("Lang after re-bind = %v, want %q (preserved)", app, i18n.LangJaJP)
+	}
+}
+
+// TestConfigBindRun_EnvelopeMessageFollowsInheritedLang guards the JSON envelope
+// "message" field against regressing to opts.Lang: when --lang is omitted on
+// re-bind, the inherited preference (appConfig.Lang) must drive the message
+// language and the embedded brand display — otherwise an AI agent that set
+// English on first bind sees Chinese in every subsequent re-bind envelope.
+func TestConfigBindRun_EnvelopeMessageFollowsInheritedLang(t *testing.T) {
+	saveWorkspace(t)
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", t.TempDir())
+	hermesHome := t.TempDir()
+	t.Setenv("HERMES_HOME", hermesHome)
+	if err := os.WriteFile(filepath.Join(hermesHome, ".env"), []byte("FEISHU_APP_ID=cli_abc\nFEISHU_APP_SECRET=secret\n"), 0600); err != nil {
+		t.Fatalf("write .env: %v", err)
+	}
+
+	f1, _, _, _ := cmdutil.TestFactory(t, nil)
+	if err := configBindRun(&BindOptions{Factory: f1, Source: "hermes", Lang: "en", langExplicit: true}); err != nil {
+		t.Fatalf("first bind (--lang en): %v", err)
+	}
+
+	f2, stdout, _, _ := cmdutil.TestFactory(t, nil)
+	if err := configBindRun(&BindOptions{Factory: f2, Source: "hermes", Lang: "", langExplicit: false}); err != nil {
+		t.Fatalf("re-bind (no --lang): %v", err)
+	}
+
+	envelope := map[string]any{}
+	if err := json.Unmarshal(stdout.Bytes(), &envelope); err != nil {
+		t.Fatalf("invalid JSON output: %v", err)
+	}
+	msg, _ := envelope["message"].(string)
+	enMsg := getBindMsg(i18n.LangEnUS)
+	wantMsg := fmt.Sprintf(enMsg.MessageBotOnly, "cli_abc", "Hermes", brandDisplay("feishu", i18n.LangEnUS))
+	if msg != wantMsg {
+		t.Errorf("envelope.message = %q,\nwant %q (must follow inherited appConfig.Lang=en_us, not raw opts.Lang)", msg, wantMsg)
+	}
+}
+
 // ── Run function tests (aligned with TestConfigShowRun pattern) ──

 func TestConfigBindRun_InvalidSource(t *testing.T) {
@@ -1474,10 +1643,14 @@ func TestGetBindMsg_En(t *testing.T) {
 	}
 }

-func TestGetBindMsg_UnknownLang_DefaultsToZh(t *testing.T) {
-	msg := getBindMsg("fr")
-	if want := "你想在哪个 Agent 中使用 lark-cli?"; msg.SelectSource != want {
-		t.Errorf("fr (default) SelectSource = %q, want %q", msg.SelectSource, want)
+func TestGetBindMsg_NonEnLang_FallsBackToZh(t *testing.T) {
+	// Only zh and en TUI bundles exist; any non-English language (canonical
+	// locale, short code, or unrecognized value) falls back to zh.
+	for _, lang := range []i18n.Lang{"fr_fr", "ja_jp", "ko", "unknown", ""} {
+		msg := getBindMsg(lang)
+		if want := "你想在哪个 Agent 中使用 lark-cli?"; msg.SelectSource != want {
+			t.Errorf("getBindMsg(%q) SelectSource = %q, want %q (zh fallback)", lang, msg.SelectSource, want)
+		}
 	}
 }

@@ -1640,3 +1813,36 @@ func TestHasStrictBotLock(t *testing.T) {
 		})
 	}
 }
+
+// TestConfigBindRun_LangExplicit_PrintsConfirmation covers the flag-mode
+// confirmation line: when --lang is explicit, bind prints "language preference
+// set" to stderr (rendered in the TUI language, embedding the preference value).
+func TestConfigBindRun_LangExplicit_PrintsConfirmation(t *testing.T) {
+	saveWorkspace(t)
+	configDir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", configDir)
+
+	hermesHome := t.TempDir()
+	t.Setenv("HERMES_HOME", hermesHome)
+	if err := os.WriteFile(filepath.Join(hermesHome, ".env"), []byte("FEISHU_APP_ID=cli_abc\nFEISHU_APP_SECRET=secret\n"), 0600); err != nil {
+		t.Fatalf("write .env: %v", err)
+	}
+
+	f, _, stderr, _ := cmdutil.TestFactory(t, nil)
+	err := configBindRun(&BindOptions{
+		Factory:      f,
+		Source:       "hermes",
+		Identity:     "bot-only",
+		Lang:         "en",
+		langExplicit: true,
+	})
+	if err != nil {
+		t.Fatalf("expected success, got error: %v", err)
+	}
+	// The short --lang en is canonicalized to en_us before the confirmation
+	// echoes it back; the TUI language stays zh (flag mode, no picker).
+	want := fmt.Sprintf(getBindMsg(i18n.LangZhCN).LangPreferenceSet, "en_us")
+	if got := stderr.String(); !strings.Contains(got, want) {
+		t.Errorf("stderr = %q, want it to contain confirmation %q", got, want)
+	}
+}
--- a/cmd/config/config_test.go
+++ b/cmd/config/config_test.go
@@ -16,6 +16,7 @@ import (
 	"github.com/larksuite/cli/internal/cmdutil"
 	"github.com/larksuite/cli/internal/core"
 	"github.com/larksuite/cli/internal/credential"
+	"github.com/larksuite/cli/internal/i18n"
 	"github.com/larksuite/cli/internal/keychain"
 	"github.com/larksuite/cli/internal/output"
 )
@@ -151,8 +152,9 @@ func TestConfigInitCmd_LangFlag(t *testing.T) {
 	if err := cmd.Execute(); err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
-	if gotOpts.Lang != "en" {
-		t.Errorf("expected Lang en, got %s", gotOpts.Lang)
+	// --lang en is canonicalized to en_us in RunE before runF captures opts.
+	if gotOpts.Lang != string(i18n.LangEnUS) {
+		t.Errorf("expected Lang en_us, got %s", gotOpts.Lang)
 	}
 	if !gotOpts.langExplicit {
 		t.Error("expected langExplicit=true when --lang is passed")
@@ -173,14 +175,82 @@ func TestConfigInitCmd_LangDefault(t *testing.T) {
 	if err := cmd.Execute(); err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
-	if gotOpts.Lang != "zh" {
-		t.Errorf("expected default Lang zh, got %s", gotOpts.Lang)
+	if gotOpts.Lang != "" {
+		t.Errorf("expected default Lang to be unset (\"\"), got %q", gotOpts.Lang)
 	}
 	if gotOpts.langExplicit {
 		t.Error("expected langExplicit=false when --lang is not passed")
 	}
 }

+// TestSaveInitConfig_OmitLangPreservesPrior guards the single-app replace path:
+// re-running init without --lang must inherit the prior preference, not clear it.
+func TestSaveInitConfig_OmitLangPreservesPrior(t *testing.T) {
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", t.TempDir())
+	f, _, _, _ := cmdutil.TestFactory(t, nil)
+
+	existing := &core.MultiAppConfig{Apps: []core.AppConfig{
+		{AppId: "cli_x", AppSecret: core.PlainSecret("s"), Brand: core.BrandFeishu, Lang: i18n.LangJaJP},
+	}}
+	if err := core.SaveMultiAppConfig(existing); err != nil {
+		t.Fatalf("seed config: %v", err)
+	}
+
+	if err := saveInitConfig("", existing, f, "cli_x", core.PlainSecret("s2"), core.BrandFeishu, ""); err != nil {
+		t.Fatalf("saveInitConfig (no --lang): %v", err)
+	}
+
+	got, err := core.LoadMultiAppConfig()
+	if err != nil {
+		t.Fatalf("LoadMultiAppConfig: %v", err)
+	}
+	if app := got.CurrentAppConfig(""); app == nil || app.Lang != i18n.LangJaJP {
+		t.Errorf("Lang after re-init = %v, want %q (preserved)", app, i18n.LangJaJP)
+	}
+}
+
+// TestConfigInitCmd_InvalidLang verifies a non-empty --lang on config init is
+// strictly validated the same way bind validates: wrong-case / typo / removed
+// codes / hyphen form all exit with ExitValidation. (Empty is a no-op.)
+func TestConfigInitCmd_InvalidLang(t *testing.T) {
+	clearAgentEnv(t)
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", t.TempDir())
+
+	cases := []struct {
+		name string
+		lang string
+	}{
+		{"wrong case ZH", "ZH"},
+		{"typo frr", "frr"},
+		{"removed code ar", "ar"},
+		{"unknown xx", "xx"},
+		{"hyphen form zh-CN", "zh-CN"},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			f, _, _, _ := cmdutil.TestFactory(t, nil)
+			cmd := NewCmdConfigInit(f, nil)
+			f.IOStreams.In = strings.NewReader("sec\n")
+			cmd.SetArgs([]string{"--lang", tc.lang, "--app-id", "x", "--app-secret-stdin"})
+			err := cmd.Execute()
+			if err == nil {
+				t.Fatalf("expected validation error for --lang %q, got nil", tc.lang)
+			}
+			exitErr, ok := err.(*output.ExitError)
+			if !ok {
+				t.Fatalf("expected *output.ExitError, got %T: %v", err, err)
+			}
+			if exitErr.Code != output.ExitValidation {
+				t.Errorf("exit code = %d, want %d (validation)", exitErr.Code, output.ExitValidation)
+			}
+			if !strings.Contains(exitErr.Error(), "invalid --lang") {
+				t.Errorf("error message %q does not contain 'invalid --lang'", exitErr.Error())
+			}
+		})
+	}
+}
+
 func TestHasAnyNonInteractiveFlag(t *testing.T) {
 	tests := []struct {
 		name string
@@ -412,3 +482,59 @@ func TestConfigBlockedByExternalProvider(t *testing.T) {
 		})
 	}
 }
+
+// TestValidateInitLang covers the --lang contract: empty (omitted or explicit)
+// is a no-op leaving Lang unset; a short code or Feishu locale canonicalizes to
+// the same locale; an unrecognized value errors.
+func TestValidateInitLang(t *testing.T) {
+	t.Run("empty is a no-op", func(t *testing.T) {
+		for _, explicit := range []bool{false, true} {
+			opts := &ConfigInitOptions{Lang: "", langExplicit: explicit}
+			if err := validateInitLang(opts); err != nil {
+				t.Fatalf("explicit=%v: expected nil error, got %v", explicit, err)
+			}
+			if opts.Lang != "" {
+				t.Errorf("explicit=%v: Lang = %q, want \"\" (unset)", explicit, opts.Lang)
+			}
+		}
+	})
+	t.Run("short and locale canonicalize alike", func(t *testing.T) {
+		for _, in := range []string{"ja", "ja_jp"} {
+			opts := &ConfigInitOptions{Lang: in, langExplicit: true}
+			if err := validateInitLang(opts); err != nil {
+				t.Fatalf("--lang %q: unexpected error %v", in, err)
+			}
+			if opts.Lang != string(i18n.LangJaJP) {
+				t.Errorf("--lang %q normalized to %q, want %q", in, opts.Lang, i18n.LangJaJP)
+			}
+		}
+	})
+}
+
+// TestPrintLangPreferenceConfirmation covers the confirmation helper: it prints
+// to stderr only when --lang explicitly set a non-empty preference.
+func TestPrintLangPreferenceConfirmation(t *testing.T) {
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", t.TempDir())
+	t.Run("explicit non-empty prints confirmation", func(t *testing.T) {
+		f, _, stderr, _ := cmdutil.TestFactory(t, nil)
+		printLangPreferenceConfirmation(&ConfigInitOptions{Factory: f, Lang: "en_us", UILang: i18n.LangZhCN, langExplicit: true})
+		got := stderr.String()
+		if !strings.Contains(got, "语言偏好") || !strings.Contains(got, "en_us") {
+			t.Errorf("stderr = %q, want confirmation mentioning the preference and en_us", got)
+		}
+	})
+	t.Run("implicit prints nothing", func(t *testing.T) {
+		f, _, stderr, _ := cmdutil.TestFactory(t, nil)
+		printLangPreferenceConfirmation(&ConfigInitOptions{Factory: f, Lang: "en_us", UILang: i18n.LangZhCN, langExplicit: false})
+		if got := stderr.String(); got != "" {
+			t.Errorf("stderr = %q, want empty when --lang is implicit", got)
+		}
+	})
+	t.Run("explicit empty prints nothing", func(t *testing.T) {
+		f, _, stderr, _ := cmdutil.TestFactory(t, nil)
+		printLangPreferenceConfirmation(&ConfigInitOptions{Factory: f, Lang: "", UILang: i18n.LangZhCN, langExplicit: true})
+		if got := stderr.String(); got != "" {
+			t.Errorf("stderr = %q, want empty when --lang is empty", got)
+		}
+	})
+}
--- a/cmd/config/init.go
+++ b/cmd/config/init.go
@@ -18,6 +18,7 @@ import (
 	"github.com/larksuite/cli/internal/auth"
 	"github.com/larksuite/cli/internal/cmdutil"
 	"github.com/larksuite/cli/internal/core"
+	"github.com/larksuite/cli/internal/i18n"
 	"github.com/larksuite/cli/internal/keychain"
 	"github.com/larksuite/cli/internal/output"
 )
@@ -31,9 +32,13 @@ type ConfigInitOptions struct {
 	AppSecretStdin bool   // read app-secret from stdin (avoids process list exposure)
 	Brand          string
 	New            bool
-	Lang           string
-	langExplicit   bool   // true when --lang was explicitly passed
-	ProfileName    string // when set, create/update a named profile instead of replacing Apps[0]
+
+	Lang         string // raw --lang (string for cobra); normalized to canonical/"" in validateInitLang
+	langExplicit bool   // true when --lang was explicitly passed
+
+	UILang i18n.Lang // TUI display language (picker-only); intentionally separate from --lang
+
+	ProfileName string // when set, create/update a named profile instead of replacing Apps[0]

 	// ForceInit overrides the agent-workspace guard. Without it, running
 	// init under OPENCLAW_HOME / HERMES_HOME refuses and points the caller
@@ -45,7 +50,7 @@ type ConfigInitOptions struct {

 // NewCmdConfigInit creates the config init subcommand.
 func NewCmdConfigInit(f *cmdutil.Factory, runF func(*ConfigInitOptions) error) *cobra.Command {
-	opts := &ConfigInitOptions{Factory: f}
+	opts := &ConfigInitOptions{Factory: f, UILang: i18n.LangZhCN}

 	cmd := &cobra.Command{
 		Use:   "init",
@@ -63,6 +68,9 @@ if the user explicitly wants a separate app inside the Agent workspace.`,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			opts.Ctx = cmd.Context()
 			opts.langExplicit = cmd.Flags().Changed("lang")
+			if err := validateInitLang(opts); err != nil {
+				return err
+			}
 			if err := guardAgentWorkspace(opts); err != nil {
 				return err
 			}
@@ -77,7 +85,7 @@ if the user explicitly wants a separate app inside the Agent workspace.`,
 	cmd.Flags().StringVar(&opts.AppID, "app-id", "", "App ID (non-interactive)")
 	cmd.Flags().BoolVar(&opts.AppSecretStdin, "app-secret-stdin", false, "Read App Secret from stdin to avoid process list exposure")
 	cmd.Flags().StringVar(&opts.Brand, "brand", "feishu", "feishu or lark (non-interactive, default feishu)")
-	cmd.Flags().StringVar(&opts.Lang, "lang", "zh", "language for interactive prompts (zh or en)")
+	cmd.Flags().StringVar(&opts.Lang, "lang", "", "language preference (e.g. zh or zh_cn)")
 	cmd.Flags().StringVar(&opts.ProfileName, "name", "", "create or update a named profile (append instead of replace)")
 	cmd.Flags().BoolVar(&opts.ForceInit, "force-init", false, "allow init inside an Agent workspace (OPENCLAW_HOME / HERMES_HOME); use config bind instead unless you really want a separate app")
 	cmdutil.SetRisk(cmd, "write")
@@ -85,6 +93,25 @@ if the user explicitly wants a separate app inside the Agent workspace.`,
 	return cmd
 }

+// printLangPreferenceConfirmation echoes the set preference to stderr, only
+// when --lang explicitly set a non-empty value.
+func printLangPreferenceConfirmation(opts *ConfigInitOptions) {
+	if !opts.langExplicit || opts.Lang == "" {
+		return
+	}
+	msg := getInitMsg(opts.UILang)
+	fmt.Fprintln(opts.Factory.IOStreams.ErrOut, fmt.Sprintf(msg.LangPreferenceSet, opts.Lang))
+}
+
+func validateInitLang(opts *ConfigInitOptions) error {
+	lang, err := cmdutil.ParseLangFlag(opts.Lang)
+	if err != nil {
+		return err
+	}
+	opts.Lang = string(lang)
+	return nil
+}
+
 // guardAgentWorkspace refuses 'config init' when run inside an OpenClaw or
 // Hermes Agent context, because the Agent has already provisioned an app
 // and 'config bind' is the right tool for hooking lark-cli into it.
@@ -132,7 +159,7 @@ func cleanupOldConfig(existing *core.MultiAppConfig, f *cmdutil.Factory, skipApp
 func saveAsOnlyApp(appId string, secret core.SecretInput, brand core.LarkBrand, lang string) error {
 	config := &core.MultiAppConfig{
 		Apps: []core.AppConfig{{
-			AppId: appId, AppSecret: secret, Brand: brand, Lang: lang, Users: []core.AppUser{},
+			AppId: appId, AppSecret: secret, Brand: brand, Lang: i18n.Lang(lang), Users: []core.AppUser{},
 		}},
 	}
 	return core.SaveMultiAppConfig(config)
@@ -146,7 +173,13 @@ func saveInitConfig(profileName string, existing *core.MultiAppConfig, f *cmduti
 		return saveAsProfile(existing, f.Keychain, profileName, appId, secret, brand, lang)
 	}
 	cleanupOldConfig(existing, f, appId)
-	return saveAsOnlyApp(appId, secret, brand, lang)
+	var prior i18n.Lang
+	if existing != nil {
+		if app := existing.CurrentAppConfig(""); app != nil {
+			prior = app.Lang
+		}
+	}
+	return saveAsOnlyApp(appId, secret, brand, string(preferredLang(i18n.Lang(lang), prior)))
 }

 // saveAsProfile appends or updates a named profile in the config.
@@ -167,11 +200,10 @@ func saveAsProfile(existing *core.MultiAppConfig, kc keychain.KeychainAccess, pr
 			}
 			multi.Apps[idx].Users = []core.AppUser{}
 		}
-		// Update existing profile
 		multi.Apps[idx].AppId = appId
 		multi.Apps[idx].AppSecret = secret
 		multi.Apps[idx].Brand = brand
-		multi.Apps[idx].Lang = lang
+		multi.Apps[idx].Lang = preferredLang(i18n.Lang(lang), multi.Apps[idx].Lang)
 	} else {
 		if findAppIndexByAppID(multi, profileName) >= 0 {
 			return fmt.Errorf("profile name %q conflicts with existing appId", profileName)
@@ -182,7 +214,7 @@ func saveAsProfile(existing *core.MultiAppConfig, kc keychain.KeychainAccess, pr
 			AppId:     appId,
 			AppSecret: secret,
 			Brand:     brand,
-			Lang:      lang,
+			Lang:      i18n.Lang(lang),
 			Users:     []core.AppUser{},
 		})
 	}
@@ -238,7 +270,7 @@ func updateExistingProfileWithoutSecret(existing *core.MultiAppConfig, profileNa

 	app.AppId = appID
 	app.Brand = brand
-	app.Lang = lang
+	app.Lang = preferredLang(i18n.Lang(lang), app.Lang)
 	return core.SaveMultiAppConfig(existing)
 }

@@ -283,29 +315,27 @@ func configInitRun(opts *ConfigInitOptions) error {
 			return output.Errorf(output.ExitInternal, "internal", "failed to save config: %v", err)
 		}
 		output.PrintSuccess(f.IOStreams.ErrOut, fmt.Sprintf("Configuration saved to %s", core.GetConfigPath()))
+		printLangPreferenceConfirmation(opts)
 		output.PrintJson(f.IOStreams.Out, map[string]interface{}{"appId": opts.AppID, "appSecret": "****", "brand": brand})
 		return nil
 	}

-	// For interactive modes, prompt language selection if --lang was not explicitly set
+	// For interactive modes, prompt language selection if --lang was not explicitly set.
+	// Picker offers 2 options (中文 / English) and drives BOTH opts.Lang
+	// (preference) and opts.UILang (TUI rendering).
 	if f.IOStreams.IsTerminal && !opts.langExplicit && !opts.hasAnyNonInteractiveFlag() {
-		savedLang := ""
-		if existing != nil {
-			if app := existing.CurrentAppConfig(""); app != nil {
-				savedLang = app.Lang
-			}
-		}
-		lang, err := promptLangSelection(savedLang)
+		lang, err := promptLangSelection()
 		if err != nil {
 			if err == huh.ErrUserAborted {
 				return output.ErrBare(1)
 			}
-			return err
+			return output.Errorf(output.ExitInternal, "internal", "language selection failed: %v", err)
 		}
-		opts.Lang = lang
+		opts.Lang = string(lang)
+		opts.UILang = lang
 	}

-	msg := getInitMsg(opts.Lang)
+	msg := getInitMsg(opts.UILang)

 	// Mode 3: Create new app directly (--new)
 	if opts.New {
@@ -324,6 +354,7 @@ func configInitRun(opts *ConfigInitOptions) error {
 		if err := saveInitConfig(opts.ProfileName, existing, f, result.AppID, secret, result.Brand, opts.Lang); err != nil {
 			return output.Errorf(output.ExitInternal, "internal", "failed to save config: %v", err)
 		}
+		printLangPreferenceConfirmation(opts)
 		output.PrintJson(f.IOStreams.Out, map[string]interface{}{"appId": result.AppID, "appSecret": "****", "brand": result.Brand})
 		return nil
 	}
@@ -366,6 +397,7 @@ func configInitRun(opts *ConfigInitOptions) error {
 		if result.Mode == "existing" {
 			output.PrintSuccess(f.IOStreams.ErrOut, fmt.Sprintf(msg.ConfigSaved, result.AppID))
 		}
+		printLangPreferenceConfirmation(opts)
 		return nil
 	}

@@ -452,5 +484,6 @@ func configInitRun(opts *ConfigInitOptions) error {
 		return output.Errorf(output.ExitInternal, "internal", "failed to save config: %v", err)
 	}
 	output.PrintSuccess(f.IOStreams.ErrOut, fmt.Sprintf("Configuration saved to %s", core.GetConfigPath()))
+	printLangPreferenceConfirmation(opts)
 	return nil
 }
--- a/cmd/config/init_messages.go
+++ b/cmd/config/init_messages.go
@@ -7,6 +7,7 @@ import (
 	"github.com/charmbracelet/huh"

 	"github.com/larksuite/cli/internal/cmdutil"
+	"github.com/larksuite/cli/internal/i18n"
 )

 type initMsg struct {
@@ -26,6 +27,10 @@ type initMsg struct {
 	DetectedLarkTenant   string
 	AppCreated           string
 	ConfigSaved          string
+
+	// LangPreferenceSet is printed to stderr after a successful init when the
+	// user explicitly passed --lang. Format: language code.
+	LangPreferenceSet string
 }

 var initMsgZh = &initMsg{
@@ -43,6 +48,7 @@ var initMsgZh = &initMsg{
 	DetectedLarkTenant:   "[lark-cli] 检测到 Lark 租户，切换端点重试...",
 	AppCreated:           "应用配置成功! App ID: %s",
 	ConfigSaved:          "应用配置成功! App ID: %s",
+	LangPreferenceSet:    "语言偏好已设置：%s",
 }

 var initMsgEn = &initMsg{
@@ -60,29 +66,27 @@ var initMsgEn = &initMsg{
 	DetectedLarkTenant:   "[lark-cli] Detected Lark tenant, switching endpoint...",
 	AppCreated:           "App configured! App ID: %s",
 	ConfigSaved:          "App configured! App ID: %s",
+	LangPreferenceSet:    "Language preference set to: %s",
 }

-func getInitMsg(lang string) *initMsg {
-	if lang == "en" {
+// getInitMsg picks the zh/en TUI bundle; non-English falls back to zh.
+func getInitMsg(lang i18n.Lang) *initMsg {
+	if lang.IsEnglish() {
 		return initMsgEn
 	}
 	return initMsgZh
 }

-// promptLangSelection shows an interactive language picker and returns the chosen lang code.
-// savedLang is used as the pre-selected default (from existing config).
-func promptLangSelection(savedLang string) (string, error) {
-	lang := savedLang
-	if lang != "en" {
-		lang = "zh"
-	}
+// promptLangSelection shows the 中文/English picker and returns the chosen locale.
+func promptLangSelection() (i18n.Lang, error) {
+	lang := i18n.LangZhCN
 	form := huh.NewForm(
 		huh.NewGroup(
-			huh.NewSelect[string]().
+			huh.NewSelect[i18n.Lang]().
 				Title("Language / 语言").
 				Options(
-					huh.NewOption("中文", "zh"),
-					huh.NewOption("English", "en"),
+					huh.NewOption("中文", i18n.LangZhCN),
+					huh.NewOption("English", i18n.LangEnUS),
 				).
 				Value(&lang),
 		),
--- a/cmd/config/init_messages_test.go
+++ b/cmd/config/init_messages_test.go
@@ -6,6 +6,8 @@ package config
 import (
 	"fmt"
 	"testing"
+
+	"github.com/larksuite/cli/internal/i18n"
 )

 func TestGetInitMsg_Zh(t *testing.T) {
@@ -29,7 +31,7 @@ func TestGetInitMsg_En(t *testing.T) {
 }

 func TestGetInitMsg_DefaultsToZh(t *testing.T) {
-	for _, lang := range []string{"", "fr", "ja", "unknown"} {
+	for _, lang := range []i18n.Lang{"", "unknown", "xyz", "invalid"} {
 		msg := getInitMsg(lang)
 		if msg != initMsgZh {
 			t.Errorf("getInitMsg(%q) should default to zh", lang)
@@ -62,6 +64,7 @@ func assertAllFieldsNonEmpty(t *testing.T, msg *initMsg, label string) {
 		"DetectedLarkTenant":   msg.DetectedLarkTenant,
 		"AppCreated":           msg.AppCreated,
 		"ConfigSaved":          msg.ConfigSaved,
+		"LangPreferenceSet":    msg.LangPreferenceSet,
 	}
 	for name, val := range fields {
 		if val == "" {
@@ -71,7 +74,7 @@ func assertAllFieldsNonEmpty(t *testing.T, msg *initMsg, label string) {
 }

 func TestInitMsg_FormatStrings(t *testing.T) {
-	for _, lang := range []string{"zh", "en"} {
+	for _, lang := range []i18n.Lang{i18n.LangZhCN, i18n.LangEnUS} {
 		msg := getInitMsg(lang)
 		// AppCreated and ConfigSaved should contain %s for App ID
 		got := fmt.Sprintf(msg.AppCreated, "cli_test123")
@@ -84,3 +87,37 @@ func TestInitMsg_FormatStrings(t *testing.T) {
 		}
 	}
 }
+
+func TestGetInitMsg_BilingualCollapse(t *testing.T) {
+	// The TUI is bilingual (zh + en). Only English-bucket languages return the
+	// English struct — by canonical locale ("en_us") or legacy short ("en").
+	// Everything else (zh, the other codes, invalid, "") returns Chinese.
+	tests := []struct {
+		lang       i18n.Lang
+		shouldBeEn bool
+	}{
+		{i18n.LangZhCN, false},
+		{i18n.LangEnUS, true},
+		{"en", true}, // legacy short value
+		{i18n.LangJaJP, false},
+		{"fr_fr", false},
+		{"invalid", false},
+		{"", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(string(tt.lang), func(t *testing.T) {
+			msg := getInitMsg(tt.lang)
+			if msg == nil {
+				t.Fatal("getInitMsg returned nil")
+			}
+			want := initMsgZh
+			if tt.shouldBeEn {
+				want = initMsgEn
+			}
+			if msg != want {
+				t.Errorf("getInitMsg(%q) returned wrong struct", tt.lang)
+			}
+		})
+	}
+}
--- a/cmd/profile/add.go
+++ b/cmd/profile/add.go
@@ -14,6 +14,7 @@ import (

 	"github.com/larksuite/cli/internal/cmdutil"
 	"github.com/larksuite/cli/internal/core"
+	"github.com/larksuite/cli/internal/i18n"
 	"github.com/larksuite/cli/internal/output"
 )

@@ -40,7 +41,7 @@ func NewCmdProfileAdd(f *cmdutil.Factory) *cobra.Command {
 	cmd.Flags().StringVar(&appID, "app-id", "", "App ID (required)")
 	cmd.Flags().BoolVar(&appSecretStdin, "app-secret-stdin", false, "read App Secret from stdin")
 	cmd.Flags().StringVar(&brand, "brand", "feishu", "feishu or lark")
-	cmd.Flags().StringVar(&lang, "lang", "zh", "language for interactive prompts (zh or en)")
+	cmd.Flags().StringVar(&lang, "lang", "", "language preference (e.g. zh or zh_cn)")
 	cmd.Flags().BoolVar(&use, "use", false, "switch to this profile after adding")

 	_ = cmd.MarkFlagRequired("name")
@@ -55,6 +56,12 @@ func profileAddRun(f *cmdutil.Factory, name, appID string, appSecretStdin bool,
 		return output.ErrValidation("%v", err)
 	}

+	langPref, err := cmdutil.ParseLangFlag(lang)
+	if err != nil {
+		return err
+	}
+	lang = string(langPref)
+
 	// Read secret from stdin
 	if !appSecretStdin {
 		return output.ErrValidation("app secret must be provided via stdin: use --app-secret-stdin and pipe the secret")
@@ -115,7 +122,7 @@ func profileAddRun(f *cmdutil.Factory, name, appID string, appSecretStdin bool,
 		AppId:     appID,
 		AppSecret: secret,
 		Brand:     parsedBrand,
-		Lang:      lang,
+		Lang:      i18n.Lang(lang),
 		Users:     []core.AppUser{},
 	})

--- a/cmd/profile/profile_test.go
+++ b/cmd/profile/profile_test.go
@@ -13,6 +13,7 @@ import (

 	"github.com/larksuite/cli/internal/cmdutil"
 	"github.com/larksuite/cli/internal/core"
+	"github.com/larksuite/cli/internal/i18n"
 	"github.com/larksuite/cli/internal/output"
 	"github.com/larksuite/cli/internal/vfs"
 )
@@ -51,6 +52,56 @@ func TestProfileAddRun_InvalidExistingConfigReturnsError(t *testing.T) {
 	}
 }

+// TestProfileAddRun_Lang covers the unified --lang contract on profile add:
+// short codes and Feishu locales both canonicalize to the same stored locale,
+// empty stores no preference, and an unrecognized value errors.
+func TestProfileAddRun_Lang(t *testing.T) {
+	t.Run("short and locale canonicalize and persist alike", func(t *testing.T) {
+		for _, in := range []string{"ja", "ja_jp"} {
+			setupProfileConfigDir(t)
+			f, _, _, _ := cmdutil.TestFactory(t, nil)
+			f.IOStreams.In = strings.NewReader("secret\n")
+			if err := profileAddRun(f, "p", "app-p", true, "feishu", in, false); err != nil {
+				t.Fatalf("--lang %q: profileAddRun() error = %v", in, err)
+			}
+			saved, err := core.LoadMultiAppConfig()
+			if err != nil {
+				t.Fatalf("LoadMultiAppConfig() error = %v", err)
+			}
+			if app := saved.FindApp("p"); app == nil || app.Lang != i18n.LangJaJP {
+				t.Errorf("--lang %q: stored Lang = %v, want %q", in, app, i18n.LangJaJP)
+			}
+		}
+	})
+
+	t.Run("empty stores no preference", func(t *testing.T) {
+		setupProfileConfigDir(t)
+		f, _, _, _ := cmdutil.TestFactory(t, nil)
+		f.IOStreams.In = strings.NewReader("secret\n")
+		if err := profileAddRun(f, "p", "app-p", true, "feishu", "", false); err != nil {
+			t.Fatalf("profileAddRun() error = %v", err)
+		}
+		saved, _ := core.LoadMultiAppConfig()
+		if app := saved.FindApp("p"); app == nil || app.Lang != "" {
+			t.Errorf("stored Lang = %v, want \"\" (unset)", app)
+		}
+	})
+
+	t.Run("invalid lang errors", func(t *testing.T) {
+		setupProfileConfigDir(t)
+		f, _, _, _ := cmdutil.TestFactory(t, nil)
+		f.IOStreams.In = strings.NewReader("secret\n")
+		err := profileAddRun(f, "p", "app-p", true, "feishu", "ZH", false)
+		if err == nil {
+			t.Fatal("expected validation error for --lang ZH, got nil")
+		}
+		exitErr, ok := err.(*output.ExitError)
+		if !ok || exitErr.Code != output.ExitValidation {
+			t.Fatalf("expected ExitValidation, got %T: %v", err, err)
+		}
+	})
+}
+
 func TestProfileAddRun_UseAfterUpdatesCurrentAndPrevious(t *testing.T) {
 	setupProfileConfigDir(t)
 	multi := &core.MultiAppConfig{
--- a/internal/cmdutil/lang.go
+++ b/internal/cmdutil/lang.go
@@ -0,0 +1,27 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package cmdutil
+
+import (
+	"strings"
+
+	"github.com/larksuite/cli/internal/i18n"
+	"github.com/larksuite/cli/internal/output"
+)
+
+// ParseLangFlag validates and canonicalizes a --lang value, shared by config
+// and profile so every entry point honors one contract. Empty is unset (no-op);
+// a non-empty value must resolve via i18n.Parse or it errors.
+func ParseLangFlag(raw string) (i18n.Lang, error) {
+	if raw == "" {
+		return "", nil
+	}
+	lang, ok := i18n.Parse(raw)
+	if !ok {
+		return "", output.ErrValidation(
+			"invalid --lang %q; valid values: %s",
+			raw, strings.Join(i18n.Codes(), ", "))
+	}
+	return lang, nil
+}
--- a/internal/core/config.go
+++ b/internal/core/config.go
@@ -11,6 +11,7 @@ import (
 	"strings"
 	"unicode/utf8"

+	"github.com/larksuite/cli/internal/i18n"
 	"github.com/larksuite/cli/internal/keychain"
 	"github.com/larksuite/cli/internal/output"
 	"github.com/larksuite/cli/internal/validate"
@@ -41,7 +42,7 @@ type AppConfig struct {
 	AppId      string      `json:"appId"`
 	AppSecret  SecretInput `json:"appSecret"`
 	Brand      LarkBrand   `json:"brand"`
-	Lang       string      `json:"lang,omitempty"`
+	Lang       i18n.Lang   `json:"lang,omitempty"`
 	DefaultAs  Identity    `json:"defaultAs,omitempty"` // AsUser | AsBot | AsAuto
 	StrictMode *StrictMode `json:"strictMode,omitempty"`
 	Users      []AppUser   `json:"users"`
@@ -159,6 +160,7 @@ type CliConfig struct {
 	DefaultAs           Identity // AsUser | AsBot | AsAuto | "" (from config file)
 	UserOpenId          string
 	UserName            string
+	Lang                i18n.Lang
 	SupportedIdentities uint8 `json:"-"` // bitflag: 1=user, 2=bot; set by credential provider
 }

@@ -264,6 +266,7 @@ func ResolveConfigFromMulti(raw *MultiAppConfig, kc keychain.KeychainAccess, pro
 		AppSecret:   secret,
 		Brand:       app.Brand,
 		DefaultAs:   app.DefaultAs,
+		Lang:        app.Lang,
 	}
 	if len(app.Users) > 0 {
 		cfg.UserOpenId = app.Users[0].UserOpenId
--- a/internal/i18n/lang.go
+++ b/internal/i18n/lang.go
@@ -0,0 +1,76 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package i18n
+
+// Lang is a Feishu locale (e.g. "zh_cn"); "" means unset.
+type Lang string
+
+const (
+	LangZhCN Lang = "zh_cn"
+	LangEnUS Lang = "en_us"
+	LangJaJP Lang = "ja_jp"
+	LangKoKR Lang = "ko_kr"
+	LangFrFR Lang = "fr_fr"
+	LangDeDE Lang = "de_de"
+	LangEsES Lang = "es_es"
+	LangItIT Lang = "it_it"
+	LangRuRU Lang = "ru_ru"
+	LangPtBR Lang = "pt_br"
+	LangThTH Lang = "th_th"
+	LangViVN Lang = "vi_vn"
+	LangIdID Lang = "id_id"
+	LangMsMY Lang = "ms_my"
+)
+
+type langEntry struct {
+	Code  Lang   // canonical Feishu locale
+	Short string // ISO 639-1 code, also accepted as input shorthand
+}
+
+// catalog is the single source of truth; order drives --help and error listing.
+var catalog = []langEntry{
+	{LangZhCN, "zh"}, {LangEnUS, "en"}, {LangJaJP, "ja"}, {LangKoKR, "ko"},
+	{LangFrFR, "fr"}, {LangDeDE, "de"}, {LangEsES, "es"}, {LangItIT, "it"},
+	{LangRuRU, "ru"}, {LangPtBR, "pt"}, {LangThTH, "th"}, {LangViVN, "vi"},
+	{LangIdID, "id"}, {LangMsMY, "ms"},
+}
+
+// find matches a short code or Feishu locale against the catalog (case-sensitive).
+func find(s string) (langEntry, bool) {
+	for _, e := range catalog {
+		if string(e.Code) == s || e.Short == s {
+			return e, true
+		}
+	}
+	return langEntry{}, false
+}
+
+// Parse resolves a short code or Feishu locale to its canonical Lang.
+// "" and unrecognized values return ("", false).
+func Parse(s string) (Lang, bool) {
+	e, ok := find(s)
+	return e.Code, ok
+}
+
+// IsEnglish reports whether l uses the English TUI bundle (robust to "en_us"
+// and legacy "en").
+func (l Lang) IsEnglish() bool {
+	e, _ := find(string(l))
+	return e.Code == LangEnUS
+}
+
+// Base returns the ISO 639-1 short code ("en_us" → "en"), or "" if unknown.
+func (l Lang) Base() string {
+	e, _ := find(string(l))
+	return e.Short
+}
+
+// Codes lists the canonical locales, for --help and error messages.
+func Codes() []string {
+	out := make([]string, len(catalog))
+	for i, e := range catalog {
+		out[i] = string(e.Code)
+	}
+	return out
+}
--- a/internal/i18n/lang_test.go
+++ b/internal/i18n/lang_test.go
@@ -0,0 +1,96 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package i18n
+
+import "testing"
+
+func TestParse(t *testing.T) {
+	tests := []struct {
+		in     string
+		want   Lang
+		wantOK bool
+	}{
+		{"zh", LangZhCN, true},    // short code
+		{"zh_cn", LangZhCN, true}, // canonical locale
+		{"en", LangEnUS, true},    // short code
+		{"en_us", LangEnUS, true}, // canonical locale
+		{"ja", LangJaJP, true},    // short code
+		{"pt", LangPtBR, true},    // pt → pt_br, not pt_pt
+		{"ms", LangMsMY, true},    // ms → ms_my
+		{"", "", false},           // unset
+		{"ZH", "", false},         // case-sensitive
+		{"zh-CN", "", false},      // hyphen form not accepted
+		{"zh_CN", "", false},      // case-sensitive region
+		{"ar", "", false},         // not in the supported set
+		{"xx", "", false},         // unknown
+	}
+	for _, tt := range tests {
+		t.Run(tt.in, func(t *testing.T) {
+			got, ok := Parse(tt.in)
+			if got != tt.want || ok != tt.wantOK {
+				t.Errorf("Parse(%q) = (%q, %v), want (%q, %v)", tt.in, got, ok, tt.want, tt.wantOK)
+			}
+		})
+	}
+}
+
+func TestIsEnglish(t *testing.T) {
+	tests := []struct {
+		lang Lang
+		want bool
+	}{
+		{LangEnUS, true},
+		{Lang("en"), true}, // legacy short value on disk stays robust
+		{LangZhCN, false},
+		{LangJaJP, false},
+		{Lang("zh"), false},
+		{Lang(""), false}, // unset → not English (zh bundle)
+		{Lang("garbage"), false},
+	}
+	for _, tt := range tests {
+		t.Run(string(tt.lang), func(t *testing.T) {
+			if got := tt.lang.IsEnglish(); got != tt.want {
+				t.Errorf("Lang(%q).IsEnglish() = %v, want %v", tt.lang, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestBase(t *testing.T) {
+	tests := []struct {
+		lang Lang
+		want string
+	}{
+		{LangEnUS, "en"},
+		{LangZhCN, "zh"},
+		{LangJaJP, "ja"},
+		{Lang("en"), "en"}, // legacy short value
+		{Lang("zh"), "zh"},
+		{Lang(""), ""},        // unset
+		{Lang("garbage"), ""}, // unknown
+	}
+	for _, tt := range tests {
+		t.Run(string(tt.lang), func(t *testing.T) {
+			if got := tt.lang.Base(); got != tt.want {
+				t.Errorf("Lang(%q).Base() = %q, want %q", tt.lang, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestCodes(t *testing.T) {
+	codes := Codes()
+	if len(codes) != 14 {
+		t.Fatalf("len(Codes()) = %d, want 14", len(codes))
+	}
+	if codes[0] != "zh_cn" {
+		t.Errorf("Codes()[0] = %q, want %q (catalog order)", codes[0], "zh_cn")
+	}
+	// Every code must round-trip through Parse to itself (canonical).
+	for _, c := range codes {
+		if got, ok := Parse(c); !ok || string(got) != c {
+			t.Errorf("Parse(%q) = (%q, %v), want (%q, true)", c, got, ok, c)
+		}
+	}
+}
--- a/shortcuts/common/runner.go
+++ b/shortcuts/common/runner.go
@@ -25,6 +25,7 @@ import (
 	"github.com/larksuite/cli/internal/cmdutil"
 	"github.com/larksuite/cli/internal/core"
 	"github.com/larksuite/cli/internal/credential"
+	"github.com/larksuite/cli/internal/i18n"
 	"github.com/larksuite/cli/internal/output"
 	"github.com/spf13/cobra"
 )
@@ -72,6 +73,13 @@ func (ctx *RuntimeContext) IsBot() bool {
 // UserOpenId returns the current user's open_id from config.
 func (ctx *RuntimeContext) UserOpenId() string { return ctx.Config.UserOpenId }

+// Lang returns the user's preference as a canonical locale, or "" if unset or
+// unrecognized; callers choose their own fallback.
+func (ctx *RuntimeContext) Lang() i18n.Lang {
+	lang, _ := i18n.Parse(string(ctx.Config.Lang))
+	return lang
+}
+
 // BotInfo holds bot identity metadata fetched lazily from /bot/v3/info.
 type BotInfo struct {
 	OpenID  string
--- a/shortcuts/common/runner_lang_test.go
+++ b/shortcuts/common/runner_lang_test.go
@@ -0,0 +1,33 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package common
+
+import (
+	"testing"
+
+	"github.com/larksuite/cli/internal/core"
+	"github.com/larksuite/cli/internal/i18n"
+)
+
+func TestRuntimeContext_Lang(t *testing.T) {
+	tests := []struct {
+		name   string
+		stored i18n.Lang
+		want   i18n.Lang
+	}{
+		{"canonical locale", i18n.LangJaJP, i18n.LangJaJP},
+		{"legacy short value normalizes", "ja", i18n.LangJaJP},
+		{"legacy short zh normalizes", "zh", i18n.LangZhCN},
+		{"unset stays empty", "", ""},
+		{"unrecognized stays empty", "klingon", ""},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ctx := &RuntimeContext{Config: &core.CliConfig{Lang: tt.stored}}
+			if got := ctx.Lang(); got != tt.want {
+				t.Errorf("Lang() with stored %q = %q, want %q", tt.stored, got, tt.want)
+			}
+		})
+	}
+}
--- a/shortcuts/mail/mail_signature.go
+++ b/shortcuts/mail/mail_signature.go
@@ -8,7 +8,7 @@ import (
 	"regexp"
 	"strings"

-	"github.com/larksuite/cli/internal/core"
+	"github.com/larksuite/cli/internal/i18n"
 	"github.com/larksuite/cli/internal/output"
 	"github.com/larksuite/cli/shortcuts/common"
 	"github.com/larksuite/cli/shortcuts/mail/signature"
@@ -154,26 +154,14 @@ func executeSignatureDetail(runtime *common.RuntimeContext, resp *signature.GetS
 }

 // resolveLang maps CLI config lang ("zh"/"en") to i18n key ("zh_cn"/"en_us").
+// resolveLang maps the preference to a locale the mail API accepts (it supports
+// only zh_cn / en_us / ja_jp; anything else falls back to zh_cn).
 func resolveLang(runtime *common.RuntimeContext) string {
-	multi, err := core.LoadMultiAppConfig()
-	if err != nil {
-		return "zh_cn"
-	}
-	cfg, err := runtime.Factory.Config()
-	if err != nil {
-		return "zh_cn"
-	}
-	app := multi.FindApp(cfg.ProfileName)
-	if app == nil {
-		return "zh_cn"
-	}
-	switch app.Lang {
-	case "en":
-		return "en_us"
-	case "ja":
-		return "ja_jp"
+	switch runtime.Lang() {
+	case i18n.LangEnUS, i18n.LangJaJP:
+		return string(runtime.Lang())
 	default:
-		return "zh_cn"
+		return string(i18n.LangZhCN)
 	}
 }

--- a/shortcuts/mail/mail_signature_lang_test.go
+++ b/shortcuts/mail/mail_signature_lang_test.go
@@ -0,0 +1,35 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package mail
+
+import (
+	"testing"
+
+	"github.com/larksuite/cli/internal/core"
+	"github.com/larksuite/cli/internal/i18n"
+	"github.com/larksuite/cli/shortcuts/common"
+)
+
+func TestResolveLang(t *testing.T) {
+	tests := []struct {
+		name   string
+		stored i18n.Lang
+		want   string
+	}{
+		{"english", i18n.LangEnUS, "en_us"},
+		{"japanese", i18n.LangJaJP, "ja_jp"},
+		{"chinese", i18n.LangZhCN, "zh_cn"},
+		{"legacy short en", "en", "en_us"},
+		{"unsupported-by-mail falls back to zh_cn", i18n.LangFrFR, "zh_cn"},
+		{"unset falls back to zh_cn", "", "zh_cn"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			rt := &common.RuntimeContext{Config: &core.CliConfig{Lang: tt.stored}}
+			if got := resolveLang(rt); got != tt.want {
+				t.Errorf("resolveLang(stored=%q) = %q, want %q", tt.stored, got, tt.want)
+			}
+		})
+	}
+}