diff --git a/backend/cmd/server/wire_gen.go b/backend/cmd/server/wire_gen.go
index df6659d689..7a88fa3554 100644
--- a/backend/cmd/server/wire_gen.go
+++ b/backend/cmd/server/wire_gen.go
@@ -179,7 +179,7 @@ func initializeApplication(buildInfo handler.BuildInfo) (*Application, error) {
 	proxyExitInfoProber := repository.NewProxyExitInfoProber(configConfig)
 	proxyLatencyCache := repository.NewProxyLatencyCache(redisClient)
 	adminService := service.NewAdminService(userRepository, adminGroupRepository, adminAccountRepository, proxyRepository, apiKeyRepository, redeemCodeRepository, userGroupRateRepository, userRPMCache, billingCacheService, proxyExitInfoProber, proxyLatencyCache, apiKeyAuthCacheInvalidator, client, settingService, subscriptionService, userSubscriptionRepository, privacyClientFactory, openAIGatewayService, affiliateService)
-	adminUserHandler := admin.NewUserHandler(adminService, concurrencyService, serviceUserPlatformQuotaRepository, billingCache, totpService, userService)
+	adminUserHandler := admin.NewUserHandler(adminService, concurrencyService, serviceUserPlatformQuotaRepository, billingCache, totpService, userService, settingService)
 	groupCapacityService := service.NewGroupCapacityService(accountRepository, groupRepository, concurrencyService, sessionLimitCache, rpmCache)
 	groupHandler := admin.NewGroupHandler(adminService, dashboardService, groupCapacityService)
 	claudeUsageFetcher := repository.NewClaudeUsageFetcher(httpUpstream)
@@ -216,7 +216,7 @@ func initializeApplication(buildInfo handler.BuildInfo) (*Application, error) {
 	registry := payment.ProvideRegistry()
 	defaultLoadBalancer := payment.ProvideDefaultLoadBalancer(client, encryptionKey)
 	paymentService := service.ProvidePaymentService(client, registry, defaultLoadBalancer, redeemService, subscriptionService, paymentConfigService, userRepository, groupRepository, affiliateService, notificationEmailService)
-	settingHandler := handler.ProvideAdminSettingHandler(settingService, emailService, turnstileService, opsService, paymentConfigService, paymentService, userAttributeService, notificationEmailService)
+	settingHandler := handler.ProvideAdminSettingHandler(settingService, emailService, turnstileService, opsService, paymentConfigService, paymentService, userAttributeService, notificationEmailService, totpService, userService)
 	opsHandler := admin.NewOpsHandler(opsService)
 	updateCache := repository.NewUpdateCache(redisClient)
 	gitHubReleaseClient := repository.ProvideGitHubReleaseClient(configConfig)
@@ -298,7 +298,7 @@ func initializeApplication(buildInfo handler.BuildInfo) (*Application, error) {
 	adminAuthMiddleware := middleware.NewAdminAuthMiddleware(authService, userService, settingService, auditLogService)
 	apiKeyAuthMiddleware := middleware.NewAPIKeyAuthMiddleware(apiKeyService, subscriptionService, configConfig)
 	auditLogMiddleware := middleware.NewAuditLogMiddleware(auditLogService)
-	stepUpAuthMiddleware := middleware.NewStepUpAuthMiddleware(totpService, userService)
+	stepUpAuthMiddleware := middleware.NewStepUpAuthMiddleware(totpService, userService, settingService)
 	engine := server.ProvideRouter(configConfig, handlers, jwtAuthMiddleware, adminAuthMiddleware, apiKeyAuthMiddleware, auditLogMiddleware, stepUpAuthMiddleware, apiKeyService, subscriptionService, opsService, settingService, redisClient)
 	httpServer := server.ProvideHTTPServer(configConfig, engine)
 	opsMetricsCollector := service.ProvideOpsMetricsCollector(opsRepository, settingRepository, accountRepository, concurrencyService, db, redisClient, configConfig)
diff --git a/backend/internal/handler/admin/admin_basic_handlers_test.go b/backend/internal/handler/admin/admin_basic_handlers_test.go
index 23b20f4e91..6c05d7bf5e 100644
--- a/backend/internal/handler/admin/admin_basic_handlers_test.go
+++ b/backend/internal/handler/admin/admin_basic_handlers_test.go
@@ -16,7 +16,7 @@ func setupAdminRouter() (*gin.Engine, *stubAdminService) {
 	router := gin.New()
 	adminSvc := newStubAdminService()
 
-	userHandler := NewUserHandler(adminSvc, nil, nil, nil, nil, nil)
+	userHandler := NewUserHandler(adminSvc, nil, nil, nil, nil, nil, nil)
 	groupHandler := NewGroupHandler(adminSvc, nil, nil)
 	proxyHandler := NewProxyHandler(adminSvc)
 	redeemHandler := NewRedeemHandler(adminSvc, nil)
diff --git a/backend/internal/handler/admin/setting_handler.go b/backend/internal/handler/admin/setting_handler.go
index 296b27044a..d663cd61b3 100644
--- a/backend/internal/handler/admin/setting_handler.go
+++ b/backend/internal/handler/admin/setting_handler.go
@@ -59,6 +59,8 @@ type SettingHandler struct {
 	paymentService           *service.PaymentService
 	userAttributeService     *service.UserAttributeService
 	notificationEmailService *service.NotificationEmailService
+	totpService              *service.TotpService
+	userService              *service.UserService
 }
 
 // NewSettingHandler 创建系统设置处理器
@@ -80,6 +82,15 @@ func (h *SettingHandler) SetNotificationEmailService(notificationEmailService *s
 	h.notificationEmailService = notificationEmailService
 }
 
+// SetStepUpDeps attaches the services backing the step-up switch preconditions
+// (enable requires the acting admin to have TOTP enabled; disable is itself a
+// step-up gated operation), without changing the constructor signature used by
+// existing unit tests.
+func (h *SettingHandler) SetStepUpDeps(totpService *service.TotpService, userService *service.UserService) {
+	h.totpService = totpService
+	h.userService = userService
+}
+
 // GetSettings 获取所有系统设置
 // GET /api/v1/admin/settings
 func (h *SettingHandler) GetSettings(c *gin.Context) {
@@ -124,6 +135,7 @@ func (h *SettingHandler) GetSettings(c *gin.Context) {
 		TotpEnabled:                                            settings.TotpEnabled,
 		TotpEncryptionKeyConfigured:                            h.settingService.IsTotpEncryptionKeyConfigured(),
 		SessionBindingEnabled:                                  settings.SessionBindingEnabled,
+		StepUpEnabled:                                          settings.StepUpEnabled,
 		AuditLogRetentionDays:                                  settings.AuditLogRetentionDays,
 		LoginAgreementEnabled:                                  settings.LoginAgreementEnabled,
 		LoginAgreementMode:                                     settings.LoginAgreementMode,
diff --git a/backend/internal/handler/admin/setting_handler_audit.go b/backend/internal/handler/admin/setting_handler_audit.go
index d94ff13c3c..7d3a420ff4 100644
--- a/backend/internal/handler/admin/setting_handler_audit.go
+++ b/backend/internal/handler/admin/setting_handler_audit.go
@@ -56,6 +56,12 @@ func diffSettings(before *service.SystemSettings, after *service.SystemSettings,
 	if before.TotpEnabled != after.TotpEnabled {
 		changed = append(changed, "totp_enabled")
 	}
+	if before.SessionBindingEnabled != after.SessionBindingEnabled {
+		changed = append(changed, "session_binding_enabled")
+	}
+	if before.StepUpEnabled != after.StepUpEnabled {
+		changed = append(changed, "step_up_enabled")
+	}
 	if before.LoginAgreementEnabled != after.LoginAgreementEnabled {
 		changed = append(changed, "login_agreement_enabled")
 	}
diff --git a/backend/internal/handler/admin/setting_handler_stepup_switch_test.go b/backend/internal/handler/admin/setting_handler_stepup_switch_test.go
new file mode 100644
index 0000000000..22f7ebf469
--- /dev/null
+++ b/backend/internal/handler/admin/setting_handler_stepup_switch_test.go
@@ -0,0 +1,157 @@
+package admin
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/Wei-Shaw/sub2api/internal/config"
+	"github.com/Wei-Shaw/sub2api/internal/server/middleware"
+	"github.com/Wei-Shaw/sub2api/internal/service"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/require"
+)
+
+// step-up 开关转换的门控测试。
+// 测试环境不注入认证上下文/userService，因此一旦触发校验会以 401/403/500 中止；
+// 借此区分「触发了转换校验」与「直接放行到常规保存（200）」。
+
+func newStepUpSwitchTestHandler(t *testing.T, stored map[string]string) (*SettingHandler, *settingHandlerRepoStub) {
+	t.Helper()
+	gin.SetMode(gin.TestMode)
+	repo := &settingHandlerRepoStub{values: stored}
+	svc := service.NewSettingService(repo, &config.Config{Default: config.DefaultConfig{UserConcurrency: 5}})
+	return NewSettingHandler(svc, nil, nil, nil, nil, nil, nil), repo
+}
+
+func doUpdateSettings(t *testing.T, h *SettingHandler, body map[string]any, prepare func(c *gin.Context)) *httptest.ResponseRecorder {
+	t.Helper()
+	rawBody, err := json.Marshal(body)
+	require.NoError(t, err)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPut, "/api/v1/admin/settings", bytes.NewReader(rawBody))
+	c.Request.Header.Set("Content-Type", "application/json")
+	if prepare != nil {
+		prepare(c)
+	}
+
+	h.UpdateSettings(c)
+	return rec
+}
+
+// 开启开关（false→true）：无认证上下文时拒绝，且带专用错误标记。
+func TestUpdateSettingsEnableStepUpRejectsWithoutSession(t *testing.T) {
+	h, repo := newStepUpSwitchTestHandler(t, map[string]string{})
+
+	rec := doUpdateSettings(t, h, map[string]any{"step_up_enabled": true}, nil)
+
+	require.Equal(t, http.StatusForbidden, rec.Code)
+	require.Contains(t, rec.Body.String(), "STEP_UP_ENABLE_REQUIRES_TOTP")
+	require.NotEqual(t, "true", repo.values[service.SettingKeyStepUpEnabled])
+}
+
+// 开启开关：admin API key（机器凭证）一律拒绝，reason 与门控保持一致便于前端分流。
+func TestUpdateSettingsEnableStepUpRejectsAdminAPIKey(t *testing.T) {
+	h, _ := newStepUpSwitchTestHandler(t, map[string]string{})
+
+	rec := doUpdateSettings(t, h, map[string]any{"step_up_enabled": true}, func(c *gin.Context) {
+		c.Set("auth_method", service.AuditAuthMethodAdminAPIKey)
+	})
+
+	require.Equal(t, http.StatusForbidden, rec.Code)
+	require.Contains(t, rec.Body.String(), "STEP_UP_ADMIN_API_KEY_FORBIDDEN")
+}
+
+// 开启开关：有认证会话但 userService 未注入时 fail-closed（500），不得放行。
+func TestUpdateSettingsEnableStepUpFailsClosedWithoutUserService(t *testing.T) {
+	h, repo := newStepUpSwitchTestHandler(t, map[string]string{})
+
+	rec := doUpdateSettings(t, h, map[string]any{"step_up_enabled": true}, func(c *gin.Context) {
+		c.Set(string(middleware.ContextKeyUser), middleware.AuthSubject{UserID: 1})
+	})
+
+	require.Equal(t, http.StatusInternalServerError, rec.Code)
+	require.NotEqual(t, "true", repo.values[service.SettingKeyStepUpEnabled])
+}
+
+// 关闭开关（true→false）本身是敏感操作：无认证上下文时被 step-up 门控以 401 拦截。
+func TestUpdateSettingsDisableStepUpRequiresStepUp(t *testing.T) {
+	h, repo := newStepUpSwitchTestHandler(t, map[string]string{
+		service.SettingKeyStepUpEnabled: "true",
+	})
+
+	rec := doUpdateSettings(t, h, map[string]any{"step_up_enabled": false}, nil)
+
+	require.Equal(t, http.StatusUnauthorized, rec.Code)
+	require.Equal(t, "true", repo.values[service.SettingKeyStepUpEnabled])
+}
+
+// 关闭开关：admin API key 被 step-up 门控以 403 拦截。
+func TestUpdateSettingsDisableStepUpRejectsAdminAPIKey(t *testing.T) {
+	h, repo := newStepUpSwitchTestHandler(t, map[string]string{
+		service.SettingKeyStepUpEnabled: "true",
+	})
+
+	rec := doUpdateSettings(t, h, map[string]any{"step_up_enabled": false}, func(c *gin.Context) {
+		c.Set("auth_method", service.AuditAuthMethodAdminAPIKey)
+	})
+
+	require.Equal(t, http.StatusForbidden, rec.Code)
+	require.Contains(t, rec.Body.String(), "STEP_UP_ADMIN_API_KEY_FORBIDDEN")
+	require.Equal(t, "true", repo.values[service.SettingKeyStepUpEnabled])
+}
+
+// 无状态转换（false→false）：不触发任何转换校验，常规保存成功且默认持久化为 false。
+func TestUpdateSettingsStepUpNoTransitionSkipsGate(t *testing.T) {
+	h, repo := newStepUpSwitchTestHandler(t, map[string]string{})
+
+	rec := doUpdateSettings(t, h, map[string]any{"step_up_enabled": false}, nil)
+
+	require.Equal(t, http.StatusOK, rec.Code)
+	require.Equal(t, "false", repo.values[service.SettingKeyStepUpEnabled])
+	// 会话 IP/UA 绑定默认关闭：未显式提交时持久化 false。
+	require.Equal(t, "false", repo.values[service.SettingKeySessionBindingEnabled])
+}
+
+// 保持开启（true→true）：不触发转换校验，常规保存不被打断。
+func TestUpdateSettingsStepUpKeepEnabledSkipsGate(t *testing.T) {
+	h, repo := newStepUpSwitchTestHandler(t, map[string]string{
+		service.SettingKeyStepUpEnabled: "true",
+	})
+
+	rec := doUpdateSettings(t, h, map[string]any{"step_up_enabled": true}, nil)
+
+	require.Equal(t, http.StatusOK, rec.Code)
+	require.Equal(t, "true", repo.values[service.SettingKeyStepUpEnabled])
+}
+
+// 省略字段=保持现值：不含 step_up_enabled/session_binding_enabled 的旧客户端全量保存
+// 不得把已开启的安全开关静默重置，也不触发任何转换门控。
+func TestUpdateSettingsOmittedSecuritySwitchesKeepStoredValues(t *testing.T) {
+	h, repo := newStepUpSwitchTestHandler(t, map[string]string{
+		service.SettingKeyStepUpEnabled:         "true",
+		service.SettingKeySessionBindingEnabled: "true",
+	})
+
+	rec := doUpdateSettings(t, h, map[string]any{"registration_enabled": true}, nil)
+
+	require.Equal(t, http.StatusOK, rec.Code)
+	require.Equal(t, "true", repo.values[service.SettingKeyStepUpEnabled])
+	require.Equal(t, "true", repo.values[service.SettingKeySessionBindingEnabled])
+}
+
+// 省略字段在开关本就关闭时同样保持关闭（默认值路径）。
+func TestUpdateSettingsOmittedSecuritySwitchesKeepDisabled(t *testing.T) {
+	h, repo := newStepUpSwitchTestHandler(t, map[string]string{})
+
+	rec := doUpdateSettings(t, h, map[string]any{"registration_enabled": true}, nil)
+
+	require.Equal(t, http.StatusOK, rec.Code)
+	require.Equal(t, "false", repo.values[service.SettingKeyStepUpEnabled])
+	require.Equal(t, "false", repo.values[service.SettingKeySessionBindingEnabled])
+}
diff --git a/backend/internal/handler/admin/setting_handler_update.go b/backend/internal/handler/admin/setting_handler_update.go
index 707af4a666..1e11898e05 100644
--- a/backend/internal/handler/admin/setting_handler_update.go
+++ b/backend/internal/handler/admin/setting_handler_update.go
@@ -11,6 +11,7 @@ import (
 	"github.com/Wei-Shaw/sub2api/internal/config"
 	"github.com/Wei-Shaw/sub2api/internal/handler/dto"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/response"
+	"github.com/Wei-Shaw/sub2api/internal/server/middleware"
 	"github.com/Wei-Shaw/sub2api/internal/service"
 
 	"github.com/gin-gonic/gin"
@@ -27,7 +28,8 @@ type UpdateSettingsRequest struct {
 	FrontendURL                      string                       `json:"frontend_url"`
 	InvitationCodeEnabled            bool                         `json:"invitation_code_enabled"`
 	TotpEnabled                      bool                         `json:"totp_enabled"`             // TOTP 双因素认证
-	SessionBindingEnabled            bool                         `json:"session_binding_enabled"`  // 会话 IP/UA 绑定
+	SessionBindingEnabled            *bool                        `json:"session_binding_enabled"`  // 会话 IP/UA 绑定（省略=保持现值）
+	StepUpEnabled                    *bool                        `json:"step_up_enabled"`          // 敏感操作 step-up 2FA（省略=保持现值）
 	AuditLogRetentionDays            int                          `json:"audit_log_retention_days"` // 审计日志保留天数
 	LoginAgreementEnabled            bool                         `json:"login_agreement_enabled"`
 	LoginAgreementMode               string                       `json:"login_agreement_mode"`
@@ -335,6 +337,41 @@ type UpdateSettingsRequest struct {
 
 // UpdateSettings 更新系统设置
 // PUT /api/v1/admin/settings
+// ensureActorTotpForStepUp 校验当前操作者具备开启 step-up 门控的条件：
+// 必须是真人管理员会话（admin API key 无法完成 TOTP step-up，拒绝）且本人已启用 TOTP。
+// 校验失败时写入错误响应并返回 false。
+func (h *SettingHandler) ensureActorTotpForStepUp(c *gin.Context) bool {
+	if c.GetString("auth_method") == service.AuditAuthMethodAdminAPIKey {
+		response.ErrorWithDetails(c, http.StatusForbidden,
+			"Admin API key cannot enable step-up verification; use an admin session with TOTP enabled",
+			"STEP_UP_ADMIN_API_KEY_FORBIDDEN", nil)
+		return false
+	}
+	subject, ok := middleware.GetAuthSubjectFromContext(c)
+	if !ok || subject.UserID <= 0 {
+		response.ErrorWithDetails(c, http.StatusForbidden,
+			"Enabling step-up verification requires an authenticated admin session",
+			"STEP_UP_ENABLE_REQUIRES_TOTP", nil)
+		return false
+	}
+	if h.userService == nil {
+		response.InternalError(c, "Step-up precondition check unavailable")
+		return false
+	}
+	user, err := h.userService.GetByID(c.Request.Context(), subject.UserID)
+	if err != nil {
+		response.ErrorFrom(c, err)
+		return false
+	}
+	if !user.TotpEnabled {
+		response.ErrorWithDetails(c, http.StatusBadRequest,
+			"Enable two-factor authentication (TOTP) for your account before turning on step-up verification",
+			"STEP_UP_ENABLE_REQUIRES_TOTP", nil)
+		return false
+	}
+	return true
+}
+
 func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 	var req UpdateSettingsRequest
 	if err := c.ShouldBindJSON(&req); err != nil {
@@ -353,6 +390,34 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 		return
 	}
 
+	// 两个安全开关的请求字段为指针：省略字段=保持现值，避免旧客户端/脚本
+	// 用不含新字段的全量 payload 保存设置时把安全开关静默重置。
+	sessionBindingEnabled := previousSettings.SessionBindingEnabled
+	if req.SessionBindingEnabled != nil {
+		sessionBindingEnabled = *req.SessionBindingEnabled
+	}
+	stepUpEnabled := previousSettings.StepUpEnabled
+	if req.StepUpEnabled != nil {
+		stepUpEnabled = *req.StepUpEnabled
+	}
+
+	// 开启敏感操作 step-up 门控属自锁风险操作：仅允许本人已启用 TOTP 的管理员会话开启，
+	// 否则开启后操作者立即被挡在所有敏感操作之外。仅在 false→true 的开启瞬间校验，
+	// 保持开启状态的常规设置保存不受影响。
+	if stepUpEnabled && !previousSettings.StepUpEnabled {
+		if !h.ensureActorTotpForStepUp(c) {
+			return
+		}
+	}
+	// 关闭 step-up 门控本身就是敏感操作：防止拿到管理员会话的攻击者先关闸再执行导出/备份。
+	// previousSettings 已证实开关处于开启状态，使用无条件门控变体，
+	// 避免门控内部二次读取开关时因存储故障 fail-open（前端捕获 STEP_UP_REQUIRED 弹码重试）。
+	if !stepUpEnabled && previousSettings.StepUpEnabled {
+		if !middleware.EnforceStepUpAlways(c, h.totpService, h.userService) {
+			return
+		}
+	}
+
 	// 验证参数
 	if req.DefaultConcurrency < 1 {
 		req.DefaultConcurrency = 1
@@ -1181,7 +1246,8 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 		FrontendURL:                      req.FrontendURL,
 		InvitationCodeEnabled:            req.InvitationCodeEnabled,
 		TotpEnabled:                      req.TotpEnabled,
-		SessionBindingEnabled:            req.SessionBindingEnabled,
+		SessionBindingEnabled:            sessionBindingEnabled,
+		StepUpEnabled:                    stepUpEnabled,
 		AuditLogRetentionDays:            req.AuditLogRetentionDays,
 		LoginAgreementEnabled:            req.LoginAgreementEnabled,
 		LoginAgreementMode:               loginAgreementMode,
@@ -1710,6 +1776,7 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 		TotpEnabled:                                            updatedSettings.TotpEnabled,
 		TotpEncryptionKeyConfigured:                            h.settingService.IsTotpEncryptionKeyConfigured(),
 		SessionBindingEnabled:                                  updatedSettings.SessionBindingEnabled,
+		StepUpEnabled:                                          updatedSettings.StepUpEnabled,
 		AuditLogRetentionDays:                                  updatedSettings.AuditLogRetentionDays,
 		LoginAgreementEnabled:                                  updatedSettings.LoginAgreementEnabled,
 		LoginAgreementMode:                                     updatedSettings.LoginAgreementMode,
diff --git a/backend/internal/handler/admin/user_handler.go b/backend/internal/handler/admin/user_handler.go
index cdcc762a81..651dfa714f 100644
--- a/backend/internal/handler/admin/user_handler.go
+++ b/backend/internal/handler/admin/user_handler.go
@@ -33,6 +33,7 @@ type UserHandler struct {
 	billingCache          service.BillingCache                // T17/T18 缓存失效（PUT/POST 路径）
 	totpService           *service.TotpService                // 角色提升为管理员的 step-up 门控
 	userService           *service.UserService
+	settingService        *service.SettingService // step-up 功能开关
 }
 
 // NewUserHandler creates a new admin user handler
@@ -43,6 +44,7 @@ func NewUserHandler(
 	billingCache service.BillingCache,
 	totpService *service.TotpService,
 	userService *service.UserService,
+	settingService *service.SettingService,
 ) *UserHandler {
 	return &UserHandler{
 		adminService:          adminService,
@@ -51,6 +53,7 @@ func NewUserHandler(
 		billingCache:          billingCache,
 		totpService:           totpService,
 		userService:           userService,
+		settingService:        settingService,
 	}
 }
 
@@ -275,7 +278,7 @@ func (h *UserHandler) Create(c *gin.Context) {
 
 	// 创建管理员账号属权限敏感操作：需最近完成 step-up 2FA 验证。
 	if req.Role == service.RoleAdmin {
-		if !middleware.EnforceStepUp(c, h.totpService, h.userService) {
+		if !middleware.EnforceStepUp(c, h.totpService, h.userService, h.settingService) {
 			return
 		}
 	}
@@ -331,7 +334,7 @@ func (h *UserHandler) Update(c *gin.Context) {
 			return
 		}
 		if target.Role != service.RoleAdmin {
-			if !middleware.EnforceStepUp(c, h.totpService, h.userService) {
+			if !middleware.EnforceStepUp(c, h.totpService, h.userService, h.settingService) {
 				return
 			}
 		}
diff --git a/backend/internal/handler/admin/user_handler_activity_test.go b/backend/internal/handler/admin/user_handler_activity_test.go
index 74a34de7c2..f8d7d14f25 100644
--- a/backend/internal/handler/admin/user_handler_activity_test.go
+++ b/backend/internal/handler/admin/user_handler_activity_test.go
@@ -35,7 +35,7 @@ func TestUserHandlerListIncludesActivityFieldsAndSortParams(t *testing.T) {
 			UpdatedAt:    lastLoginAt,
 		},
 	}
-	handler := NewUserHandler(adminSvc, nil, nil, nil, nil, nil)
+	handler := NewUserHandler(adminSvc, nil, nil, nil, nil, nil, nil)
 
 	recorder := httptest.NewRecorder()
 	c, _ := gin.CreateTestContext(recorder)
@@ -89,7 +89,7 @@ func TestUserHandlerGetByIDIncludesActivityFields(t *testing.T) {
 			UpdatedAt:    lastLoginAt,
 		},
 	}
-	handler := NewUserHandler(adminSvc, nil, nil, nil, nil, nil)
+	handler := NewUserHandler(adminSvc, nil, nil, nil, nil, nil, nil)
 
 	recorder := httptest.NewRecorder()
 	c, _ := gin.CreateTestContext(recorder)
diff --git a/backend/internal/handler/admin/user_handler_batch_limits_test.go b/backend/internal/handler/admin/user_handler_batch_limits_test.go
index 08e5951aed..06ee942f39 100644
--- a/backend/internal/handler/admin/user_handler_batch_limits_test.go
+++ b/backend/internal/handler/admin/user_handler_batch_limits_test.go
@@ -44,7 +44,7 @@ func (s *batchLimitsAdminServiceStub) BatchUpdateLimits(_ context.Context, userI
 func setupBatchLimitsRouter(serviceStub service.AdminService) *gin.Engine {
 	gin.SetMode(gin.TestMode)
 	router := gin.New()
-	handler := NewUserHandler(serviceStub, nil, nil, nil, nil, nil)
+	handler := NewUserHandler(serviceStub, nil, nil, nil, nil, nil, nil)
 	router.POST("/api/v1/admin/users/batch-limits", handler.BatchUpdateLimits)
 	return router
 }
diff --git a/backend/internal/handler/admin/user_handler_get_deleted_test.go b/backend/internal/handler/admin/user_handler_get_deleted_test.go
index c915a88f8f..6891a8a8e2 100644
--- a/backend/internal/handler/admin/user_handler_get_deleted_test.go
+++ b/backend/internal/handler/admin/user_handler_get_deleted_test.go
@@ -26,7 +26,7 @@ func (s *getByIDAdminStub) GetUserIncludeDeleted(_ context.Context, id int64) (*
 func setupGetByIDRouter(svc service.AdminService) *gin.Engine {
 	gin.SetMode(gin.TestMode)
 	r := gin.New()
-	h := NewUserHandler(svc, nil, nil, nil, nil, nil)
+	h := NewUserHandler(svc, nil, nil, nil, nil, nil, nil)
 	r.GET("/admin/users/:id", h.GetByID)
 	return r
 }
diff --git a/backend/internal/handler/admin/user_handler_list_apikey_group_test.go b/backend/internal/handler/admin/user_handler_list_apikey_group_test.go
index 0d14b62834..b03538b711 100644
--- a/backend/internal/handler/admin/user_handler_list_apikey_group_test.go
+++ b/backend/internal/handler/admin/user_handler_list_apikey_group_test.go
@@ -39,7 +39,7 @@ func TestAdminUserList_ParsesAPIKeyGroupID(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			stub := &listUsersFilterStub{AdminService: newStubAdminService()}
 			r := gin.New()
-			h := NewUserHandler(stub, nil, nil, nil, nil, nil)
+			h := NewUserHandler(stub, nil, nil, nil, nil, nil, nil)
 			r.GET("/admin/users", h.List)
 
 			w := httptest.NewRecorder()
diff --git a/backend/internal/handler/admin/user_handler_role_stepup_test.go b/backend/internal/handler/admin/user_handler_role_stepup_test.go
index f4ffa3f65f..5a6345d0e2 100644
--- a/backend/internal/handler/admin/user_handler_role_stepup_test.go
+++ b/backend/internal/handler/admin/user_handler_role_stepup_test.go
@@ -29,7 +29,7 @@ func setupRoleStepUpRouter(t *testing.T) (*gin.Engine, *stubAdminService) {
 		Status: service.StatusActive,
 	})
 
-	h := NewUserHandler(adminSvc, nil, nil, nil, nil, nil)
+	h := NewUserHandler(adminSvc, nil, nil, nil, nil, nil, nil)
 	router.POST("/api/v1/admin/users", h.Create)
 	router.PUT("/api/v1/admin/users/:id", h.Update)
 	return router, adminSvc
diff --git a/backend/internal/handler/dto/settings.go b/backend/internal/handler/dto/settings.go
index bb2a125157..fd7e7b6a52 100644
--- a/backend/internal/handler/dto/settings.go
+++ b/backend/internal/handler/dto/settings.go
@@ -37,6 +37,7 @@ type SystemSettings struct {
 	TotpEnabled                      bool                     `json:"totp_enabled"`                   // TOTP 双因素认证
 	TotpEncryptionKeyConfigured      bool                     `json:"totp_encryption_key_configured"` // TOTP 加密密钥是否已配置
 	SessionBindingEnabled            bool                     `json:"session_binding_enabled"`        // 会话 IP/UA 绑定
+	StepUpEnabled                    bool                     `json:"step_up_enabled"`                // 敏感操作 step-up 2FA
 	AuditLogRetentionDays            int                      `json:"audit_log_retention_days"`       // 审计日志保留天数
 	LoginAgreementEnabled            bool                     `json:"login_agreement_enabled"`
 	LoginAgreementMode               string                   `json:"login_agreement_mode"`
diff --git a/backend/internal/handler/wire.go b/backend/internal/handler/wire.go
index 57bf64d023..1f7186413a 100644
--- a/backend/internal/handler/wire.go
+++ b/backend/internal/handler/wire.go
@@ -153,9 +153,10 @@ func ProvideSettingHandler(settingService *service.SettingService, buildInfo Bui
 }
 
 // ProvideAdminSettingHandler creates admin.SettingHandler with notification template APIs.
-func ProvideAdminSettingHandler(settingService *service.SettingService, emailService *service.EmailService, turnstileService *service.TurnstileService, opsService *service.OpsService, paymentConfigService *service.PaymentConfigService, paymentService *service.PaymentService, userAttributeService *service.UserAttributeService, notificationEmailService *service.NotificationEmailService) *admin.SettingHandler {
+func ProvideAdminSettingHandler(settingService *service.SettingService, emailService *service.EmailService, turnstileService *service.TurnstileService, opsService *service.OpsService, paymentConfigService *service.PaymentConfigService, paymentService *service.PaymentService, userAttributeService *service.UserAttributeService, notificationEmailService *service.NotificationEmailService, totpService *service.TotpService, userService *service.UserService) *admin.SettingHandler {
 	h := admin.NewSettingHandler(settingService, emailService, turnstileService, opsService, paymentConfigService, paymentService, userAttributeService)
 	h.SetNotificationEmailService(notificationEmailService)
+	h.SetStepUpDeps(totpService, userService)
 	return h
 }
 
diff --git a/backend/internal/server/api_contract_test.go b/backend/internal/server/api_contract_test.go
index 955e9df1be..6b91652176 100644
--- a/backend/internal/server/api_contract_test.go
+++ b/backend/internal/server/api_contract_test.go
@@ -708,7 +708,8 @@ func TestAPIContracts(t *testing.T) {
 						"frontend_url": "",
 						"totp_enabled": false,
 						"totp_encryption_key_configured": false,
-						"session_binding_enabled": true,
+						"session_binding_enabled": false,
+						"step_up_enabled": false,
 						"audit_log_retention_days": 180,
 						"login_agreement_enabled": false,
 						"login_agreement_mode": "modal",
@@ -1022,7 +1023,8 @@ func TestAPIContracts(t *testing.T) {
 						"invitation_code_enabled": false,
 						"totp_enabled": false,
 						"totp_encryption_key_configured": false,
-						"session_binding_enabled": true,
+						"session_binding_enabled": false,
+						"step_up_enabled": false,
 						"audit_log_retention_days": 180,
 						"login_agreement_enabled": false,
 						"login_agreement_mode": "modal",
diff --git a/backend/internal/server/middleware/step_up.go b/backend/internal/server/middleware/step_up.go
index b8ffc3d079..31a320e3fd 100644
--- a/backend/internal/server/middleware/step_up.go
+++ b/backend/internal/server/middleware/step_up.go
@@ -22,6 +22,11 @@ type stepUpUserReader interface {
 	GetByID(ctx context.Context, id int64) (*service.User, error)
 }
 
+// stepUpSettingReader 抽象 step-up 功能开关读取能力（由 SettingService 实现）。
+type stepUpSettingReader interface {
+	IsStepUpEnabled(ctx context.Context) bool
+}
+
 // StepUpSessionKey 计算 step-up 授权的会话键：
 // 优先绑定当前会话（refresh token family），无会话 ID 的旧 token 退化为用户级键。
 func StepUpSessionKey(c *gin.Context, userID int64) string {
@@ -33,19 +38,33 @@ func StepUpSessionKey(c *gin.Context, userID int64) string {
 
 // NewStepUpAuthMiddleware 创建敏感操作 step-up 2FA 门控中间件。
 //
-// 通过条件（全部满足）：
+// 功能开关 step_up_enabled（默认关闭）关闭时中间件直接放行，行为与门控引入前一致。
+// 开启时的通过条件（全部满足）：
 //  1. 必须是 JWT 认证的真人会话——admin API key（机器凭证）一律拒绝
 //  2. 当前用户已启用 TOTP（未启用则拒绝并提示先启用 2FA）
 //  3. 当前会话在有效期内完成过 TOTP step-up 验证（POST /api/v1/user/totp/step-up）
 //
 // 失败响应使用可区分的错误码，前端据此弹出 TOTP 验证对话框后重试。
-func NewStepUpAuthMiddleware(totpService *service.TotpService, userService *service.UserService) StepUpAuthMiddleware {
-	return StepUpAuthMiddleware(stepUpAuth(totpService, userService))
+func NewStepUpAuthMiddleware(
+	totpService *service.TotpService,
+	userService *service.UserService,
+	settingService *service.SettingService,
+) StepUpAuthMiddleware {
+	return StepUpAuthMiddleware(stepUpAuth(totpService, userService, stepUpSettingsOrNil(settingService)))
 }
 
-func stepUpAuth(grantChecker stepUpGrantChecker, userReader stepUpUserReader) gin.HandlerFunc {
+// stepUpSettingsOrNil 将可能为 nil 的具体指针归一化为接口，
+// 避免 typed-nil 装箱后绕过 enforceStepUp 内的 nil 判断。
+func stepUpSettingsOrNil(settingService *service.SettingService) stepUpSettingReader {
+	if settingService == nil {
+		return nil
+	}
+	return settingService
+}
+
+func stepUpAuth(grantChecker stepUpGrantChecker, userReader stepUpUserReader, settings stepUpSettingReader) gin.HandlerFunc {
 	return func(c *gin.Context) {
-		if !enforceStepUp(c, grantChecker, userReader) {
+		if !enforceStepUp(c, grantChecker, userReader, settings) {
 			return
 		}
 		c.Next()
@@ -55,11 +74,33 @@ func stepUpAuth(grantChecker stepUpGrantChecker, userReader stepUpUserReader) gi
 // EnforceStepUp 对当前请求执行与 StepUpAuthMiddleware 相同语义的 step-up 门控，
 // 供 handler 在需要按请求内容条件触发时调用（如仅当把用户角色提升为管理员时）。
 // 校验失败时写入错误响应并中止请求，返回 false；通过返回 true。
-func EnforceStepUp(c *gin.Context, totpService *service.TotpService, userService *service.UserService) bool {
-	return enforceStepUp(c, totpService, userService)
+func EnforceStepUp(
+	c *gin.Context,
+	totpService *service.TotpService,
+	userService *service.UserService,
+	settingService *service.SettingService,
+) bool {
+	return enforceStepUp(c, totpService, userService, stepUpSettingsOrNil(settingService))
 }
 
-func enforceStepUp(c *gin.Context, grantChecker stepUpGrantChecker, userReader stepUpUserReader) bool {
+// EnforceStepUpAlways 与 EnforceStepUp 语义相同但不读取功能开关，无条件执行门控。
+// 供调用方已确知门控必须生效的场景使用（如"关闭 step-up 开关"本身：调用方刚从
+// 持久化设置读到开关为开启状态，不应依赖二次读取——读取失败会导致门控被跳过）。
+func EnforceStepUpAlways(
+	c *gin.Context,
+	totpService *service.TotpService,
+	userService *service.UserService,
+) bool {
+	return enforceStepUp(c, totpService, userService, nil)
+}
+
+func enforceStepUp(c *gin.Context, grantChecker stepUpGrantChecker, userReader stepUpUserReader, settings stepUpSettingReader) bool {
+	// 功能开关关闭时直接放行（含 admin API key），恢复门控引入前的行为。
+	// settings 为 nil 时保持门控（fail-closed）：正常装配不会出现 nil。
+	if settings != nil && !settings.IsStepUpEnabled(c.Request.Context()) {
+		return true
+	}
+
 	if c.GetString("auth_method") == service.AuditAuthMethodAdminAPIKey {
 		AbortWithError(c, 403, "STEP_UP_ADMIN_API_KEY_FORBIDDEN",
 			"Admin API key cannot access this endpoint; a two-factor verified admin session is required")
diff --git a/backend/internal/server/middleware/step_up_test.go b/backend/internal/server/middleware/step_up_test.go
index 557d94d04c..d817d4659a 100644
--- a/backend/internal/server/middleware/step_up_test.go
+++ b/backend/internal/server/middleware/step_up_test.go
@@ -31,6 +31,17 @@ func (s stubStepUpUserReader) GetByID(ctx context.Context, id int64) (*service.U
 	return s.user, s.err
 }
 
+type stubStepUpSettingReader struct {
+	enabled bool
+}
+
+func (s stubStepUpSettingReader) IsStepUpEnabled(ctx context.Context) bool {
+	return s.enabled
+}
+
+// stepUpEnabled 功能开关开启的设置桩，供既有门控分支测试使用。
+var stepUpEnabled = stubStepUpSettingReader{enabled: true}
+
 func newStepUpTestContext(t *testing.T) (*gin.Context, *httptest.ResponseRecorder) {
 	t.Helper()
 	gin.SetMode(gin.TestMode)
@@ -44,7 +55,7 @@ func TestEnforceStepUpRejectsAdminAPIKey(t *testing.T) {
 	c, rec := newStepUpTestContext(t)
 	c.Set("auth_method", service.AuditAuthMethodAdminAPIKey)
 
-	ok := enforceStepUp(c, stubStepUpGrantChecker{granted: true}, stubStepUpUserReader{user: &service.User{TotpEnabled: true}})
+	ok := enforceStepUp(c, stubStepUpGrantChecker{granted: true}, stubStepUpUserReader{user: &service.User{TotpEnabled: true}}, stepUpEnabled)
 
 	require.False(t, ok)
 	require.True(t, c.IsAborted())
@@ -55,7 +66,7 @@ func TestEnforceStepUpRejectsAdminAPIKey(t *testing.T) {
 func TestEnforceStepUpRequiresAuthSubject(t *testing.T) {
 	c, rec := newStepUpTestContext(t)
 
-	ok := enforceStepUp(c, stubStepUpGrantChecker{granted: true}, stubStepUpUserReader{user: &service.User{TotpEnabled: true}})
+	ok := enforceStepUp(c, stubStepUpGrantChecker{granted: true}, stubStepUpUserReader{user: &service.User{TotpEnabled: true}}, stepUpEnabled)
 
 	require.False(t, ok)
 	require.Equal(t, http.StatusUnauthorized, rec.Code)
@@ -65,7 +76,7 @@ func TestEnforceStepUpRequiresTotpEnabled(t *testing.T) {
 	c, rec := newStepUpTestContext(t)
 	c.Set(string(ContextKeyUser), AuthSubject{UserID: 1})
 
-	ok := enforceStepUp(c, stubStepUpGrantChecker{granted: true}, stubStepUpUserReader{user: &service.User{ID: 1, TotpEnabled: false}})
+	ok := enforceStepUp(c, stubStepUpGrantChecker{granted: true}, stubStepUpUserReader{user: &service.User{ID: 1, TotpEnabled: false}}, stepUpEnabled)
 
 	require.False(t, ok)
 	require.Equal(t, http.StatusForbidden, rec.Code)
@@ -76,7 +87,7 @@ func TestEnforceStepUpFailsClosedOnGrantError(t *testing.T) {
 	c, rec := newStepUpTestContext(t)
 	c.Set(string(ContextKeyUser), AuthSubject{UserID: 1})
 
-	ok := enforceStepUp(c, stubStepUpGrantChecker{err: errors.New("redis down")}, stubStepUpUserReader{user: &service.User{ID: 1, TotpEnabled: true}})
+	ok := enforceStepUp(c, stubStepUpGrantChecker{err: errors.New("redis down")}, stubStepUpUserReader{user: &service.User{ID: 1, TotpEnabled: true}}, stepUpEnabled)
 
 	require.False(t, ok)
 	require.Equal(t, http.StatusServiceUnavailable, rec.Code)
@@ -87,7 +98,7 @@ func TestEnforceStepUpRequiresGrant(t *testing.T) {
 	c, rec := newStepUpTestContext(t)
 	c.Set(string(ContextKeyUser), AuthSubject{UserID: 1})
 
-	ok := enforceStepUp(c, stubStepUpGrantChecker{granted: false}, stubStepUpUserReader{user: &service.User{ID: 1, TotpEnabled: true}})
+	ok := enforceStepUp(c, stubStepUpGrantChecker{granted: false}, stubStepUpUserReader{user: &service.User{ID: 1, TotpEnabled: true}}, stepUpEnabled)
 
 	require.False(t, ok)
 	require.Equal(t, http.StatusForbidden, rec.Code)
@@ -98,8 +109,58 @@ func TestEnforceStepUpPassesWithGrant(t *testing.T) {
 	c, _ := newStepUpTestContext(t)
 	c.Set(string(ContextKeyUser), AuthSubject{UserID: 1})
 
-	ok := enforceStepUp(c, stubStepUpGrantChecker{granted: true}, stubStepUpUserReader{user: &service.User{ID: 1, TotpEnabled: true}})
+	ok := enforceStepUp(c, stubStepUpGrantChecker{granted: true}, stubStepUpUserReader{user: &service.User{ID: 1, TotpEnabled: true}}, stepUpEnabled)
 
 	require.True(t, ok)
 	require.False(t, c.IsAborted())
 }
+
+// 功能开关关闭时：不论 TOTP/grant/凭证类型，一律放行（恢复门控引入前行为）。
+func TestEnforceStepUpDisabledSkipsAllChecks(t *testing.T) {
+	disabled := stubStepUpSettingReader{enabled: false}
+
+	t.Run("no totp, no grant", func(t *testing.T) {
+		c, _ := newStepUpTestContext(t)
+		c.Set(string(ContextKeyUser), AuthSubject{UserID: 1})
+
+		ok := enforceStepUp(c, stubStepUpGrantChecker{granted: false}, stubStepUpUserReader{user: &service.User{ID: 1, TotpEnabled: false}}, disabled)
+
+		require.True(t, ok)
+		require.False(t, c.IsAborted())
+	})
+
+	t.Run("admin api key", func(t *testing.T) {
+		c, _ := newStepUpTestContext(t)
+		c.Set("auth_method", service.AuditAuthMethodAdminAPIKey)
+
+		ok := enforceStepUp(c, stubStepUpGrantChecker{granted: false}, stubStepUpUserReader{user: nil, err: errors.New("should not be called")}, disabled)
+
+		require.True(t, ok)
+		require.False(t, c.IsAborted())
+	})
+}
+
+// settings 为 nil 时保持门控（fail-closed），避免装配缺陷静默关闭安全控制。
+func TestEnforceStepUpNilSettingsFailsClosed(t *testing.T) {
+	c, rec := newStepUpTestContext(t)
+	c.Set(string(ContextKeyUser), AuthSubject{UserID: 1})
+
+	ok := enforceStepUp(c, stubStepUpGrantChecker{granted: false}, stubStepUpUserReader{user: &service.User{ID: 1, TotpEnabled: true}}, nil)
+
+	require.False(t, ok)
+	require.Equal(t, http.StatusForbidden, rec.Code)
+	require.Contains(t, rec.Body.String(), "STEP_UP_REQUIRED")
+}
+
+// EnforceStepUp 收到 nil *service.SettingService 时不得因 typed-nil 装箱绕过门控：
+// 未认证请求仍应被拦截（401），而不是当作"开关关闭"放行。
+func TestEnforceStepUpTypedNilSettingServiceFailsClosed(t *testing.T) {
+	require.Nil(t, stepUpSettingsOrNil(nil))
+
+	c, rec := newStepUpTestContext(t)
+
+	ok := EnforceStepUp(c, nil, nil, nil)
+
+	require.False(t, ok)
+	require.Equal(t, http.StatusUnauthorized, rec.Code)
+}
diff --git a/backend/internal/server/routes/admin.go b/backend/internal/server/routes/admin.go
index a76c5d815f..54cf0ae95a 100644
--- a/backend/internal/server/routes/admin.go
+++ b/backend/internal/server/routes/admin.go
@@ -586,8 +586,8 @@ func registerBackupRoutes(admin *gin.RouterGroup, h *handler.Handlers, stepUpAut
 		// 备份下载链接可直接取走整库数据——要求 step-up 2FA
 		backup.GET("/:id/download-url", gin.HandlerFunc(stepUpAuth), h.Admin.Backup.GetDownloadURL)
 
-		// 恢复操作
-		backup.POST("/:id/restore", h.Admin.Backup.RestoreBackup)
+		// 恢复操作：整库覆盖可回滚安全设置（含 step-up 开关本身）——要求 step-up 2FA
+		backup.POST("/:id/restore", gin.HandlerFunc(stepUpAuth), h.Admin.Backup.RestoreBackup)
 	}
 }
 
diff --git a/backend/internal/service/domain_constants.go b/backend/internal/service/domain_constants.go
index 96a0a39c7c..cbbb4b7850 100644
--- a/backend/internal/service/domain_constants.go
+++ b/backend/internal/service/domain_constants.go
@@ -170,7 +170,10 @@ const (
 	SettingKeyTotpEnabled = "totp_enabled" // 是否启用 TOTP 2FA 功能
 
 	// 会话安全设置
-	SettingKeySessionBindingEnabled = "session_binding_enabled" // 会话 IP/UA 绑定（变更即失效），默认开启
+	SettingKeySessionBindingEnabled = "session_binding_enabled" // 会话 IP/UA 绑定（变更即失效），默认关闭
+
+	// 敏感操作 step-up 2FA 设置
+	SettingKeyStepUpEnabled = "step_up_enabled" // 敏感操作（导出/备份/S3配置/提升管理员等）要求 step-up 2FA，默认关闭
 
 	// 操作审计日志设置
 	SettingKeyAuditLogRetentionDays = "audit_log_retention_days" // 审计日志保留天数（<=0 永久保留），默认 180
diff --git a/backend/internal/service/setting_features.go b/backend/internal/service/setting_features.go
index 8543ad6f01..52ba3670ff 100644
--- a/backend/internal/service/setting_features.go
+++ b/backend/internal/service/setting_features.go
@@ -179,14 +179,26 @@ func (s *SettingService) IsTotpEncryptionKeyConfigured() bool {
 	return s.cfg.Totp.EncryptionKeyConfigured
 }
 
-// IsSessionBindingEnabled 检查会话 IP/UA 绑定是否启用（默认开启）。
+// IsSessionBindingEnabled 检查会话 IP/UA 绑定是否启用（默认关闭）。
 // 开启时会话与登录时的 IP/User-Agent 绑定，任一变化立即失效并撤销该会话。
+// 默认关闭：移动网络/多出口 IP 场景下 IP 频繁变化会导致登录后立即掉线。
 func (s *SettingService) IsSessionBindingEnabled(ctx context.Context) bool {
 	value, err := s.settingRepo.GetValue(ctx, SettingKeySessionBindingEnabled)
 	if err != nil {
-		return true // 默认开启
+		return false // 默认关闭
 	}
-	return value != "false"
+	return value == "true"
+}
+
+// IsStepUpEnabled 检查敏感操作 step-up 2FA 门控是否启用（默认关闭）。
+// 开启时账号/代理导出、备份创建/下载、S3 配置修改、提升管理员等操作
+// 要求当前会话在有效期内完成过 TOTP step-up 验证。
+func (s *SettingService) IsStepUpEnabled(ctx context.Context) bool {
+	value, err := s.settingRepo.GetValue(ctx, SettingKeyStepUpEnabled)
+	if err != nil {
+		return false // 默认关闭
+	}
+	return value == "true"
 }
 
 // defaultAuditLogRetentionDays 审计日志默认保留天数。
diff --git a/backend/internal/service/setting_parse.go b/backend/internal/service/setting_parse.go
index a3aec1dd7f..a56e57784e 100644
--- a/backend/internal/service/setting_parse.go
+++ b/backend/internal/service/setting_parse.go
@@ -260,7 +260,8 @@ func (s *SettingService) parseSettings(settings map[string]string) *SystemSettin
 		FrontendURL:                      settings[SettingKeyFrontendURL],
 		InvitationCodeEnabled:            settings[SettingKeyInvitationCodeEnabled] == "true",
 		TotpEnabled:                      settings[SettingKeyTotpEnabled] == "true",
-		SessionBindingEnabled:            settings[SettingKeySessionBindingEnabled] != "false", // 默认开启
+		SessionBindingEnabled:            settings[SettingKeySessionBindingEnabled] == "true", // 默认关闭
+		StepUpEnabled:                    settings[SettingKeyStepUpEnabled] == "true",         // 默认关闭
 		AuditLogRetentionDays:            parseAuditLogRetentionDays(settings[SettingKeyAuditLogRetentionDays]),
 		LoginAgreementEnabled:            settings[SettingKeyLoginAgreementEnabled] == "true",
 		LoginAgreementMode:               normalizeLoginAgreementMode(settings[SettingKeyLoginAgreementMode]),
diff --git a/backend/internal/service/setting_update.go b/backend/internal/service/setting_update.go
index 686f315a85..96c078e422 100644
--- a/backend/internal/service/setting_update.go
+++ b/backend/internal/service/setting_update.go
@@ -122,6 +122,7 @@ func (s *SettingService) buildSystemSettingsUpdates(ctx context.Context, setting
 	updates[SettingKeyInvitationCodeEnabled] = strconv.FormatBool(settings.InvitationCodeEnabled)
 	updates[SettingKeyTotpEnabled] = strconv.FormatBool(settings.TotpEnabled)
 	updates[SettingKeySessionBindingEnabled] = strconv.FormatBool(settings.SessionBindingEnabled)
+	updates[SettingKeyStepUpEnabled] = strconv.FormatBool(settings.StepUpEnabled)
 	updates[SettingKeyAuditLogRetentionDays] = strconv.Itoa(settings.AuditLogRetentionDays)
 	settings.LoginAgreementMode = normalizeLoginAgreementMode(settings.LoginAgreementMode)
 	settings.LoginAgreementUpdatedAt = strings.TrimSpace(settings.LoginAgreementUpdatedAt)
diff --git a/backend/internal/service/settings_view.go b/backend/internal/service/settings_view.go
index 9cfae8a8c6..85ab619d14 100644
--- a/backend/internal/service/settings_view.go
+++ b/backend/internal/service/settings_view.go
@@ -21,6 +21,7 @@ type SystemSettings struct {
 	InvitationCodeEnabled            bool
 	TotpEnabled                      bool // TOTP 双因素认证
 	SessionBindingEnabled            bool // 会话 IP/UA 绑定（变更即失效）
+	StepUpEnabled                    bool // 敏感操作 step-up 2FA 门控
 	AuditLogRetentionDays            int  // 审计日志保留天数（<=0 永久保留）
 	LoginAgreementEnabled            bool
 	LoginAgreementMode               string
diff --git a/frontend/src/api/admin/settings.ts b/frontend/src/api/admin/settings.ts
index b68846be1f..33b1f7f97d 100644
--- a/frontend/src/api/admin/settings.ts
+++ b/frontend/src/api/admin/settings.ts
@@ -367,6 +367,7 @@ export interface SystemSettings {
   totp_enabled: boolean; // TOTP 双因素认证
   totp_encryption_key_configured: boolean; // TOTP 加密密钥是否已配置
   session_binding_enabled: boolean; // 会话 IP/UA 绑定
+  step_up_enabled: boolean; // 敏感操作 step-up 2FA
   audit_log_retention_days: number; // 审计日志保留天数
   login_agreement_enabled: boolean;
   login_agreement_mode: "modal" | "checkbox" | string;
@@ -672,6 +673,7 @@ export interface UpdateSettingsRequest {
   invitation_code_enabled?: boolean;
   totp_enabled?: boolean; // TOTP 双因素认证
   session_binding_enabled?: boolean; // 会话 IP/UA 绑定
+  step_up_enabled?: boolean; // 敏感操作 step-up 2FA
   audit_log_retention_days?: number; // 审计日志保留天数
   login_agreement_enabled?: boolean;
   login_agreement_mode?: "modal" | "checkbox" | string;
diff --git a/frontend/src/i18n/locales/en/admin/settings.ts b/frontend/src/i18n/locales/en/admin/settings.ts
index f177122e7f..8c57ab4158 100644
--- a/frontend/src/i18n/locales/en/admin/settings.ts
+++ b/frontend/src/i18n/locales/en/admin/settings.ts
@@ -127,6 +127,9 @@ export default {
           'Please configure TOTP_ENCRYPTION_KEY in environment variables first. Generate a key with: openssl rand -hex 32'
       },
       security: {
+        stepUp: 'Step-up 2FA for Sensitive Operations',
+        stepUpHint: 'When enabled, sensitive operations (account/proxy export, backup creation and download, S3 config changes, promoting admins) require a recent TOTP verification (valid for 15 minutes). Your own account must have 2FA enabled before turning this on; turning it off also requires step-up verification.',
+        stepUpEnableRequiresTotp: 'Enable 2FA (TOTP) for your own account in Profile before turning on step-up verification.',
         sessionBinding: 'Session IP/UA Binding',
         sessionBindingHint: 'Bind login sessions to the client IP and User-Agent. Any change immediately invalidates the session and forces re-login, raising the bar for stolen-credential reuse.',
         auditRetention: 'Audit Log Retention (days)',
diff --git a/frontend/src/i18n/locales/zh/admin/settings.ts b/frontend/src/i18n/locales/zh/admin/settings.ts
index 3b4b568615..49f43dc059 100644
--- a/frontend/src/i18n/locales/zh/admin/settings.ts
+++ b/frontend/src/i18n/locales/zh/admin/settings.ts
@@ -127,6 +127,9 @@ export default {
           '请先在环境变量中配置 TOTP_ENCRYPTION_KEY。使用命令 openssl rand -hex 32 生成密钥。'
       },
       security: {
+        stepUp: '敏感操作二次验证 (step-up 2FA)',
+        stepUpHint: '开启后，账号/代理导出、备份创建与下载、S3 配置修改、提升管理员等敏感操作需要先完成 TOTP 二次验证（15 分钟内有效）。开启前需本人已启用 2FA；关闭该开关本身也需要二次验证。',
+        stepUpEnableRequiresTotp: '开启敏感操作二次验证前，请先在个人资料中为当前账号启用 2FA (TOTP)。',
         sessionBinding: '会话 IP/UA 绑定',
         sessionBindingHint: '将登录会话与客户端 IP 和 User-Agent 绑定，任一变化即强制该会话失效并需重新登录（提升被盗凭证的利用门槛）。',
         auditRetention: '操作日志保留天数',
diff --git a/frontend/src/views/admin/BackupView.vue b/frontend/src/views/admin/BackupView.vue
index 223973beef..a2223f9412 100644
--- a/frontend/src/views/admin/BackupView.vue
+++ b/frontend/src/views/admin/BackupView.vue
@@ -586,16 +586,19 @@ async function restoreBackup(id: string) {
   if (!password) return
   restoringId.value = id
   try {
-    const record = await adminAPI.backup.restoreBackup(id, password)
+    const record = await backupStepUp.run(() => adminAPI.backup.restoreBackup(id, password))
     updateRecordInList(record)
     startRestorePolling(id)
   } catch (error: any) {
-    if (error?.response?.status === 409) {
+    restoringId.value = ''
+    if (isStepUpCancelled(error)) return
+    if (reportStepUpBlocked(error)) return
+    // apiClient 拦截器把 HTTP 错误归一化为顶层 { status } 平面对象（无 response 字段）
+    if (error?.status === 409 || error?.response?.status === 409) {
       appStore.showWarning(t('admin.backup.operations.restoreRunning'))
     } else {
       appStore.showError(error?.message || t('errors.networkError'))
     }
-    restoringId.value = ''
   }
 }
 
diff --git a/frontend/src/views/admin/SettingsView.vue b/frontend/src/views/admin/SettingsView.vue
index 271ef3191f..45ba18336a 100644
--- a/frontend/src/views/admin/SettingsView.vue
+++ b/frontend/src/views/admin/SettingsView.vue
@@ -1578,6 +1578,21 @@
                 />
               </div>
 
+              <!-- 敏感操作 step-up 2FA -->
+              <div
+                class="flex items-center justify-between border-t border-gray-100 pt-4 dark:border-dark-700"
+              >
+                <div>
+                  <label class="font-medium text-gray-900 dark:text-white">{{
+                    t("admin.settings.security.stepUp")
+                  }}</label>
+                  <p class="text-sm text-gray-500 dark:text-gray-400">
+                    {{ t("admin.settings.security.stepUpHint") }}
+                  </p>
+                </div>
+                <Toggle v-model="form.step_up_enabled" />
+              </div>
+
               <!-- 会话 IP/UA 绑定 -->
               <div
                 class="flex items-center justify-between border-t border-gray-100 pt-4 dark:border-dark-700"
@@ -7466,6 +7481,8 @@
         @confirm="handleAffiliateConfirm"
         @cancel="cancelAffiliateConfirm"
       />
+      <!-- 关闭 step-up 开关等敏感保存操作触发的 TOTP 二次验证 -->
+      <TotpStepUpDialog :controller="settingsStepUp" />
     </div>
   </AppLayout>
 </template>
@@ -7519,6 +7536,13 @@ import BackupSettings from "@/views/admin/BackupView.vue";
 import EmailTemplateEditor from "@/views/admin/settings/EmailTemplateEditor.vue";
 import OpenAIFastPolicyUserSelector from "@/views/admin/settings/OpenAIFastPolicyUserSelector.vue";
 import { useClipboard } from "@/composables/useClipboard";
+import {
+  useStepUp,
+  isStepUpCancelled,
+  isStepUpBlocked,
+  stepUpBlockReason,
+} from "@/composables/useStepUp";
+import TotpStepUpDialog from "@/components/auth/TotpStepUpDialog.vue";
 import { affiliatesAPI, type AffiliateAdminEntry, type SimpleUser as AffiliateSimpleUser } from "@/api/admin/affiliates";
 import { extractApiErrorMessage, extractI18nErrorMessage } from "@/utils/apiError";
 import { useAppStore } from "@/stores";
@@ -7539,6 +7563,8 @@ import {
 
 const { t, locale } = useI18n();
 const appStore = useAppStore();
+// 关闭 step-up 开关是敏感操作：后端返回 STEP_UP_REQUIRED 时弹 TOTP 码重试
+const settingsStepUp = useStepUp();
 const adminSettingsStore = useAdminSettingsStore();
 const isZhLocale = computed(() => locale.value.startsWith("zh"));
 
@@ -8192,7 +8218,8 @@ const form = reactive<SettingsForm>({
   password_reset_enabled: false,
   totp_enabled: false,
   totp_encryption_key_configured: false,
-  session_binding_enabled: true,
+  session_binding_enabled: false,
+  step_up_enabled: false,
   audit_log_retention_days: 180,
   login_agreement_enabled: false,
   login_agreement_mode: "modal",
@@ -9559,6 +9586,7 @@ async function saveSettings() {
       password_reset_enabled: form.password_reset_enabled,
       totp_enabled: form.totp_enabled,
       session_binding_enabled: form.session_binding_enabled,
+      step_up_enabled: form.step_up_enabled,
       // 清空数字框时 v-model.number 会得到空串，后端 int 字段解析空串会 400 拒绝整次保存；
       // 空/非法值回退默认 180（与后端 parseAuditLogRetentionDays("") 语义一致，0 仍表示永久保留）。
       audit_log_retention_days: Number.isFinite(form.audit_log_retention_days)
@@ -9856,7 +9884,9 @@ async function saveSettings() {
     payload.default_platform_quotas = sanitizePlatformQuotasMap(form.default_platform_quotas);
     appendAuthSourceDefaultsToUpdateRequest(payload, authSourceDefaults);
 
-    const updated = await adminAPI.settings.updateSettings(payload);
+    const updated = await settingsStepUp.run(() =>
+      adminAPI.settings.updateSettings(payload),
+    );
     for (const [key, value] of Object.entries(updated)) {
       if (key === "openai_fast_policy_settings") continue;
       if (value !== null && value !== undefined) {
@@ -9930,6 +9960,25 @@ async function saveSettings() {
       appStore.showSuccess(t("admin.settings.settingsSaved"));
     }
   } catch (error: unknown) {
+    // 用户取消 step-up 验证：静默返回，不弹错误
+    if (isStepUpCancelled(error)) {
+      return;
+    }
+    if (isStepUpBlocked(error)) {
+      appStore.showError(
+        stepUpBlockReason(error) === "STEP_UP_ADMIN_API_KEY_FORBIDDEN"
+          ? t("stepUp.adminApiKeyForbidden")
+          : t("stepUp.notEnabled"),
+      );
+      return;
+    }
+    // 开启 step-up 开关但本人未启用 2FA：给出可操作的专用提示
+    if (
+      (error as { reason?: string })?.reason === "STEP_UP_ENABLE_REQUIRES_TOTP"
+    ) {
+      appStore.showError(t("admin.settings.security.stepUpEnableRequiresTotp"));
+      return;
+    }
     appStore.showError(
       extractApiErrorMessage(error, t("admin.settings.failedToSave")),
     );