diff --git a/backend/cmd/adminctl/main.go b/backend/cmd/adminctl/main.go
index 020d4e51..4fd536ce 100644
--- a/backend/cmd/adminctl/main.go
+++ b/backend/cmd/adminctl/main.go
@@ -28,6 +28,10 @@ type createSuperAdminConfig struct {
 	UpdatePassword bool
 }
 
+type clearOrphanUserTenantMembershipsConfig struct {
+	DryRun bool
+}
+
 func main() {
 	loadEnv()
 	logger.Init(logger.Config{
@@ -47,6 +51,11 @@ func main() {
 			slog.Error("create-super-admin failed", "error", err)
 			os.Exit(1)
 		}
+	case "clear-orphan-user-tenant-memberships":
+		if err := runClearOrphanUserTenantMemberships(os.Args[2:]); err != nil {
+			slog.Error("clear-orphan-user-tenant-memberships failed", "error", err)
+			os.Exit(1)
+		}
 	default:
 		printUsage()
 		os.Exit(2)
@@ -107,6 +116,37 @@ func runCreateSuperAdmin(args []string) error {
 	return nil
 }
 
+func runClearOrphanUserTenantMemberships(args []string) error {
+	config, err := resolveClearOrphanUserTenantMembershipsConfig(args)
+	if err != nil {
+		return err
+	}
+
+	db, err := openDB()
+	if err != nil {
+		return err
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+
+	if config.DryRun {
+		count, err := repository.CountOrphanUserTenantMemberships(ctx, db)
+		if err != nil {
+			return err
+		}
+		fmt.Printf("orphan user tenant memberships dry-run: count=%d\n", count)
+		return nil
+	}
+
+	affected, err := repository.ClearOrphanUserTenantMemberships(ctx, db)
+	if err != nil {
+		return err
+	}
+	fmt.Printf("orphan user tenant memberships cleared: count=%d\n", affected)
+	return nil
+}
+
 func resolveCreateSuperAdminConfig(args []string) (createSuperAdminConfig, error) {
 	fs := flag.NewFlagSet("create-super-admin", flag.ContinueOnError)
 	fs.SetOutput(os.Stderr)
@@ -135,6 +175,19 @@ func resolveCreateSuperAdminConfig(args []string) (createSuperAdminConfig, error
 	return config, nil
 }
 
+func resolveClearOrphanUserTenantMembershipsConfig(args []string) (clearOrphanUserTenantMembershipsConfig, error) {
+	fs := flag.NewFlagSet("clear-orphan-user-tenant-memberships", flag.ContinueOnError)
+	fs.SetOutput(os.Stderr)
+
+	config := clearOrphanUserTenantMembershipsConfig{}
+	fs.BoolVar(&config.DryRun, "dry-run", false, "count orphan memberships without updating users")
+
+	if err := fs.Parse(args); err != nil {
+		return config, err
+	}
+	return config, nil
+}
+
 func openDB() (*gorm.DB, error) {
 	dsn := fmt.Sprintf(
 		"host=%s user=%s password=%s dbname=%s port=%s sslmode=disable TimeZone=Asia/Seoul",
@@ -173,4 +226,5 @@ func getenv(key string, fallback string) string {
 func printUsage() {
 	fmt.Fprintln(os.Stderr, "usage:")
 	fmt.Fprintln(os.Stderr, "  adminctl create-super-admin [--email EMAIL] [--password PASSWORD] [--name NAME] [--update-password]")
+	fmt.Fprintln(os.Stderr, "  adminctl clear-orphan-user-tenant-memberships [--dry-run]")
 }
diff --git a/backend/cmd/adminctl/main_test.go b/backend/cmd/adminctl/main_test.go
index 0eb4c5f7..7d2551c9 100644
--- a/backend/cmd/adminctl/main_test.go
+++ b/backend/cmd/adminctl/main_test.go
@@ -60,3 +60,14 @@ func TestResolveCreateSuperAdminConfigRequiresEmailAndPassword(t *testing.T) {
 		t.Fatal("expected error")
 	}
 }
+
+func TestResolveClearOrphanUserTenantMembershipsConfig(t *testing.T) {
+	config, err := resolveClearOrphanUserTenantMembershipsConfig([]string{"--dry-run"})
+	if err != nil {
+		t.Fatalf("resolveClearOrphanUserTenantMembershipsConfig returned error: %v", err)
+	}
+
+	if !config.DryRun {
+		t.Fatal("dry-run flag was not set")
+	}
+}
diff --git a/backend/internal/bootstrap/admin_account.go b/backend/internal/bootstrap/admin_account.go
index ddb33a02..3940d15e 100644
--- a/backend/internal/bootstrap/admin_account.go
+++ b/backend/internal/bootstrap/admin_account.go
@@ -139,7 +139,6 @@ func buildSuperAdminBrokerUser(email, name string) *domain.BrokerUser {
 		Attributes: map[string]interface{}{
 			"department":      "Admin",
 			"affiliationType": "internal",
-			"companyCode":     "",
 			"grade":           "",
 			"role":            domain.RoleSuperAdmin,
 		},
diff --git a/backend/internal/bootstrap/bootstrap.go b/backend/internal/bootstrap/bootstrap.go
index c49ab2ae..d4422168 100644
--- a/backend/internal/bootstrap/bootstrap.go
+++ b/backend/internal/bootstrap/bootstrap.go
@@ -37,6 +37,9 @@ func migrateSchemas(db *gorm.DB) error {
 	if err := dropLegacyTenantDomainUniqueIndex(db); err != nil {
 		return err
 	}
+	if err := dropLegacyUserCompanyColumns(db); err != nil {
+		return err
+	}
 
 	// Add all domain models here
 	return db.AutoMigrate(
@@ -61,6 +64,21 @@ func migrateSchemas(db *gorm.DB) error {
 	)
 }
 
+func dropLegacyUserCompanyColumns(db *gorm.DB) error {
+	if !db.Migrator().HasTable(&domain.User{}) {
+		return nil
+	}
+	for _, column := range []string{"company_code", "company_codes"} {
+		if !db.Migrator().HasColumn(&domain.User{}, column) {
+			continue
+		}
+		if err := db.Migrator().DropColumn(&domain.User{}, column); err != nil {
+			return fmt.Errorf("failed to drop legacy users.%s column: %w", column, err)
+		}
+	}
+	return nil
+}
+
 func dropLegacyTenantDomainUniqueIndex(db *gorm.DB) error {
 	if !db.Migrator().HasTable(&domain.TenantDomain{}) {
 		return nil
diff --git a/backend/internal/bootstrap/kratos_seed.go b/backend/internal/bootstrap/kratos_seed.go
index bca52dfc..8c5c0503 100644
--- a/backend/internal/bootstrap/kratos_seed.go
+++ b/backend/internal/bootstrap/kratos_seed.go
@@ -34,7 +34,6 @@ func SeedAdminIdentity(idp domain.IdentityProvider) (string, error) {
 		Attributes: map[string]interface{}{
 			"department":      "Admin",
 			"affiliationType": "internal",
-			"companyCode":     "",
 			"grade":           "",
 			"role":            "super_admin", // Explicitly set role for Kratos traits
 		},
diff --git a/backend/internal/domain/auth_models.go b/backend/internal/domain/auth_models.go
index 234003b2..999a2229 100644
--- a/backend/internal/domain/auth_models.go
+++ b/backend/internal/domain/auth_models.go
@@ -60,6 +60,7 @@ type SignupRequest struct {
 	Name            string  `json:"name"`
 	Phone           string  `json:"phone"`
 	AffiliationType string  `json:"affiliationType"` // "AFFILIATE" or "GENERAL"
+	TenantSlug      string  `json:"tenantSlug,omitempty"`
 	CompanyCode     string  `json:"companyCode,omitempty"`
 	Department      string  `json:"department"`
 	Metadata        JSONMap `json:"metadata,omitempty"`
@@ -117,5 +118,6 @@ type PasswordChangeRequest struct {
 
 type CheckLoginIDRequest struct {
 	LoginID     string `json:"loginId"`
+	TenantSlug  string `json:"tenantSlug,omitempty"`
 	CompanyCode string `json:"companyCode,omitempty"`
 }
diff --git a/backend/internal/domain/user.go b/backend/internal/domain/user.go
index 34550c84..6088c5d8 100644
--- a/backend/internal/domain/user.go
+++ b/backend/internal/domain/user.go
@@ -59,8 +59,8 @@ type User struct {
 	Phone           string         `gorm:"column:phone" json:"phone"`
 	Role            string         `gorm:"column:role;default:'user';not null" json:"role"` // super_admin, tenant_admin, rp_admin, user
 	AffiliationType string         `gorm:"column:affiliation_type" json:"affiliationType"`
-	CompanyCode     string         `gorm:"column:company_code;index" json:"companyCode"`
-	CompanyCodes    pq.StringArray `gorm:"column:company_codes;type:text[]" json:"companyCodes"`
+	CompanyCode     string         `gorm:"-" json:"companyCode,omitempty"`
+	CompanyCodes    pq.StringArray `gorm:"-" json:"companyCodes,omitempty"`
 	TenantID        *string        `gorm:"column:tenant_id;type:uuid;index" json:"tenantId,omitempty"`
 	Tenant          *Tenant        `gorm:"foreignKey:TenantID" json:"tenant,omitempty"`
 	RelyingPartyID  *string        `gorm:"column:relying_party_id;type:uuid;index" json:"relyingPartyId,omitempty"` // RP Admin용
diff --git a/backend/internal/handler/auth_handler.go b/backend/internal/handler/auth_handler.go
index e9420cf3..9c842e03 100644
--- a/backend/internal/handler/auth_handler.go
+++ b/backend/internal/handler/auth_handler.go
@@ -704,8 +704,12 @@ func (h *AuthHandler) Signup(c *fiber.Ctx) error {
 		return errorJSON(c, fiber.StatusInternalServerError, "Identity provider unavailable")
 	}
 
+	if strings.TrimSpace(req.CompanyCode) != "" {
+		return errorJSON(c, fiber.StatusBadRequest, "companyCode is deprecated; use tenantSlug")
+	}
+
 	// 소속이 비어 있는 일반 가입자는 PERSONAL tenant를 자동 생성해 대표소속을 보장합니다.
-	companyCode := ""
+	tenantSlug := strings.TrimSpace(req.TenantSlug)
 	var tenantID *string
 
 	parts := strings.Split(req.Email, "@")
@@ -726,33 +730,28 @@ func (h *AuthHandler) Signup(c *fiber.Ctx) error {
 		slog.Info("[Signup] Forcing AffiliationType to GENERAL", "email", req.Email)
 	}
 
-	// If user provided a CompanyCode, verify it exists and is a family affiliate
-	if req.CompanyCode != "" {
-		// [Security] Cross-check: If domain is NOT internal, they cannot provide a CompanyCode
+	if tenantSlug != "" {
+		// [Security] Cross-check: If domain is NOT internal, they cannot provide a tenantSlug
 		if !isInternal {
-			slog.Warn("[Signup] Security violation: non-internal email providing CompanyCode", "email", req.Email)
+			slog.Warn("[Signup] Security violation: non-internal email providing tenantSlug", "email", req.Email)
 			return errorJSON(c, fiber.StatusForbidden, "Only affiliate members can join an organization.")
 		}
 
-		// Verify the selected company code exists and is indeed a family company
-		if !affiliateSlugs[strings.ToLower(req.CompanyCode)] {
+		if !affiliateSlugs[strings.ToLower(tenantSlug)] {
 			return errorJSON(c, fiber.StatusForbidden, "The selected organization is not a valid family affiliate.")
 		}
 
-		tenant, err := h.TenantService.GetTenantBySlug(c.Context(), req.CompanyCode)
+		tenant, err := h.TenantService.GetTenantBySlug(c.Context(), tenantSlug)
 		if err == nil && tenant != nil {
 			if tenant.Status == domain.TenantStatusActive {
-				// We no longer strictly cross-check if the chosen tenant owns the email domain.
-				// Being an 'isInternal' (family) email is enough to join ANY family affiliate.
-
 				slog.Info("[Signup] Assigning tenant by manual slug", "email", req.Email, "tenant", tenant.Slug)
-				companyCode = tenant.Slug
+				tenantSlug = tenant.Slug
 				tenantID = &tenant.ID
 			} else {
 				return errorJSON(c, fiber.StatusForbidden, "The specified organization is not active.")
 			}
 		} else {
-			slog.Warn("[Signup] Attempted to join non-existent organization", "slug", req.CompanyCode, "email", req.Email)
+			slog.Warn("[Signup] Attempted to join non-existent organization", "slug", tenantSlug, "email", req.Email)
 			return errorJSON(c, fiber.StatusNotFound, "The specified organization code was not found.")
 		}
 	} else {
@@ -770,7 +769,7 @@ func (h *AuthHandler) Signup(c *fiber.Ctx) error {
 		if err != nil {
 			return errorJSON(c, fiber.StatusServiceUnavailable, "failed to create personal tenant")
 		}
-		companyCode = tenant.Slug
+		tenantSlug = tenant.Slug
 		tenantID = &tenant.ID
 	}
 
@@ -789,7 +788,6 @@ func (h *AuthHandler) Signup(c *fiber.Ctx) error {
 	attributes := map[string]interface{}{
 		"department":      req.Department,
 		"affiliationType": req.AffiliationType,
-		"companyCode":     companyCode,
 		"grade":           "",
 		"role":            domain.RoleUser,
 	}
@@ -844,7 +842,6 @@ func (h *AuthHandler) Signup(c *fiber.Ctx) error {
 		Phone:           normalizedPhone,
 		Role:            "user",
 		AffiliationType: req.AffiliationType,
-		CompanyCode:     companyCode,
 		Department:      req.Department,
 		Status:          "active",
 		CreatedAt:       time.Now(),
@@ -7508,7 +7505,6 @@ func (h *AuthHandler) mapKratosIdentityToProfile(identityID string, traits map[s
 	phone, _ := traits["phone_number"].(string)
 	dept, _ := traits["department"].(string)
 	affType, _ := traits["affiliationType"].(string)
-	compCode, _ := traits["companyCode"].(string)
 	role, _ := traits["role"].(string)
 	tenantID, _ := traits["tenant_id"].(string)
 	relyingPartyID, _ := traits["relying_party_id"].(string)
@@ -7520,7 +7516,6 @@ func (h *AuthHandler) mapKratosIdentityToProfile(identityID string, traits map[s
 		Phone:           h.formatPhoneForDisplay(phone),
 		Department:      dept,
 		AffiliationType: affType,
-		CompanyCode:     compCode,
 		Role:            domain.NormalizeRole(role),
 		Metadata:        make(map[string]any),
 	}
@@ -7591,16 +7586,6 @@ func (h *AuthHandler) mapKratosTraitsToLocalUser(identityID string, traits map[s
 		localUser.AffiliationType = affType
 	}
 
-	companyCode := extractTraitString(traits, "companyCode")
-	if companyCode == "" {
-		companyCode = extractTraitString(traits, "company_code")
-	}
-	if companyCode != "" {
-		localUser.CompanyCode = companyCode
-	}
-	if companyCodes := extractTraitStringArray(traits, "companyCodes"); len(companyCodes) > 0 {
-		localUser.CompanyCodes = pq.StringArray(companyCodes)
-	}
 	if tenantID := extractTraitString(traits, "tenant_id"); tenantID != "" {
 		localUser.TenantID = &tenantID
 	}
diff --git a/backend/internal/handler/auth_handler_profile_cache_test.go b/backend/internal/handler/auth_handler_profile_cache_test.go
index c33b07b4..0ef112b6 100644
--- a/backend/internal/handler/auth_handler_profile_cache_test.go
+++ b/backend/internal/handler/auth_handler_profile_cache_test.go
@@ -209,7 +209,7 @@ func TestUpdateMe_SyncsLocalReadModelFields(t *testing.T) {
 	require.Equal(t, "New Name", userRepo.updated.Name)
 	require.Equal(t, "+821087654321", userRepo.updated.Phone)
 	require.Equal(t, "New Dept", userRepo.updated.Department)
-	require.Equal(t, "saman", userRepo.updated.CompanyCode)
+	require.Empty(t, userRepo.updated.CompanyCode)
 	require.NotNil(t, userRepo.updated.TenantID)
 	require.Equal(t, "11111111-1111-1111-1111-111111111111", *userRepo.updated.TenantID)
 }
diff --git a/backend/internal/handler/auth_handler_signup_test.go b/backend/internal/handler/auth_handler_signup_test.go
index 3a479bdd..76085df3 100644
--- a/backend/internal/handler/auth_handler_signup_test.go
+++ b/backend/internal/handler/auth_handler_signup_test.go
@@ -5,7 +5,6 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
-	"errors"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -78,7 +77,7 @@ func (m *MockIdpForSignup) UpdateUserPassword(loginID, newPassword string, r *ht
 	return nil
 }
 
-func TestSignup_CompanyCodeValidation(t *testing.T) {
+func TestSignup_TenantSlugValidation(t *testing.T) {
 	app := fiber.New()
 	mockTenantSvc := new(MockTenantService)
 	mockRedis := new(MockRedisForSignup)
@@ -99,7 +98,7 @@ func TestSignup_CompanyCodeValidation(t *testing.T) {
 	})
 	mockRedis.On("Get", mock.Anything).Return(string(verifiedState), nil)
 
-	t.Run("Fail - Tenant not found for CompanyCode", func(t *testing.T) {
+	t.Run("Rejects legacy CompanyCode", func(t *testing.T) {
 		reqBody := domain.SignupRequest{
 			Email:         "user@gmail.com",
 			Password:      "StrongPass123!",
@@ -110,25 +109,21 @@ func TestSignup_CompanyCodeValidation(t *testing.T) {
 		}
 		body, _ := json.Marshal(reqBody)
 
-		mockTenantSvc.On("GetTenantByDomain", mock.Anything, "gmail.com").Return(nil, nil).Once()
-		mockTenantSvc.On("ProvisionTenantByDomain", mock.Anything, "gmail.com").Return(nil, errors.New("not found")).Maybe()
-		mockTenantSvc.On("GetTenantBySlug", mock.Anything, "new-slug").Return(nil, nil).Once()
-
 		req := httptest.NewRequest("POST", "/signup", bytes.NewReader(body))
 		req.Header.Set("Content-Type", "application/json")
 		resp, _ := app.Test(req)
 
-		assert.Equal(t, http.StatusForbidden, resp.StatusCode)
+		assert.Equal(t, http.StatusBadRequest, resp.StatusCode)
 	})
 
-	t.Run("Active Company Code", func(t *testing.T) {
+	t.Run("Active Tenant Slug", func(t *testing.T) {
 		reqBody := domain.SignupRequest{
 			Email:         "user@hanmaceng.co.kr",
 			Password:      "StrongPass123!",
 			Name:          "Test User",
 			Phone:         "010-1234-5678",
 			TermsAccepted: true,
-			CompanyCode:   "hanmac",
+			TenantSlug:    "hanmac",
 		}
 		body, _ := json.Marshal(reqBody)
 
diff --git a/backend/internal/handler/tenant_handler.go b/backend/internal/handler/tenant_handler.go
index 34c61e4e..cf909220 100644
--- a/backend/internal/handler/tenant_handler.go
+++ b/backend/internal/handler/tenant_handler.go
@@ -2386,14 +2386,6 @@ func mapOrgContextMemberAssignments(user domain.User, tenantByID, tenantBySlug m
 		tenant := tenantBySlug[strings.ToLower(user.Tenant.Slug)]
 		addTenant(tenant, tenant.ID != "", nil)
 	}
-	if user.CompanyCode != "" {
-		tenant := tenantBySlug[strings.ToLower(strings.TrimSpace(user.CompanyCode))]
-		addTenant(tenant, tenant.ID != "", nil)
-	}
-	for _, companyCode := range user.CompanyCodes {
-		tenant := tenantBySlug[strings.ToLower(strings.TrimSpace(companyCode))]
-		addTenant(tenant, tenant.ID != "", nil)
-	}
 	return assignments
 }
 
@@ -2596,7 +2588,6 @@ func (h *TenantHandler) GetPublicOrgChart(c *fiber.Ctx) error {
 	sharedRootID := findRoot(link.TenantID)
 	var filteredTenants []domain.Tenant
 	var tenantIDs []string
-	var slugs []string
 
 	for _, t := range allTenants {
 		if findRoot(t.ID) == sharedRootID {
@@ -2606,16 +2597,15 @@ func (h *TenantHandler) GetPublicOrgChart(c *fiber.Ctx) error {
 	filteredTenants = filterPublicTenants(filteredTenants)
 	for _, t := range filteredTenants {
 		tenantIDs = append(tenantIDs, t.ID)
-		slugs = append(slugs, t.Slug)
 	}
 
 	type publicUserSummary struct {
-		ID          string `json:"id"`
-		Name        string `json:"name"`
-		Position    string `json:"position"`
-		JobTitle    string `json:"jobTitle"`
-		CompanyCode string `json:"companyCode"`
-		Status      string `json:"status"`
+		ID         string `json:"id"`
+		Name       string `json:"name"`
+		Position   string `json:"position"`
+		JobTitle   string `json:"jobTitle"`
+		TenantSlug string `json:"tenantSlug"`
+		Status     string `json:"status"`
 	}
 
 	var publicUsers []publicUserSummary
@@ -2629,29 +2619,12 @@ func (h *TenantHandler) GetPublicOrgChart(c *fiber.Ctx) error {
 			continue
 		}
 		seen[u.ID] = true
-		cc := u.CompanyCode
-		if cc == "" && u.Tenant != nil {
-			cc = u.Tenant.Slug
+		tenantSlug := ""
+		if u.Tenant != nil {
+			tenantSlug = u.Tenant.Slug
 		}
 		publicUsers = append(publicUsers, publicUserSummary{
-			ID: u.ID, Name: u.Name, Position: u.Position, JobTitle: u.JobTitle, CompanyCode: cc, Status: u.Status,
-		})
-	}
-
-	// Fetch users by Slugs
-	var usersBySlug []domain.User
-	h.DB.Where("company_code IN ?", slugs).Preload("Tenant").Find(&usersBySlug)
-	for _, u := range usersBySlug {
-		if u.Status != "active" || seen[u.ID] {
-			continue
-		}
-		seen[u.ID] = true
-		cc := u.CompanyCode
-		if cc == "" && u.Tenant != nil {
-			cc = u.Tenant.Slug
-		}
-		publicUsers = append(publicUsers, publicUserSummary{
-			ID: u.ID, Name: u.Name, Position: u.Position, JobTitle: u.JobTitle, CompanyCode: cc, Status: u.Status,
+			ID: u.ID, Name: u.Name, Position: u.Position, JobTitle: u.JobTitle, TenantSlug: tenantSlug, Status: u.Status,
 		})
 	}
 
diff --git a/backend/internal/handler/tenant_handler_test.go b/backend/internal/handler/tenant_handler_test.go
index 6e34c078..00ec15b6 100644
--- a/backend/internal/handler/tenant_handler_test.go
+++ b/backend/internal/handler/tenant_handler_test.go
@@ -690,8 +690,8 @@ func TestTenantHandler_GetOrgContextJSONDefaultsToHanmacFamilyForApiKey(t *testi
 	require.Equal(t, "기술기획", firstUser["jobTitle"])
 	teamSSO := tenantsPayload[3].(map[string]any)
 	ssoMembers := teamSSO["members"].([]any)
-	require.Len(t, ssoMembers, 2)
-	appointmentOnly := ssoMembers[1].(map[string]any)
+	require.Len(t, ssoMembers, 1)
+	appointmentOnly := ssoMembers[0].(map[string]any)
 	require.Equal(t, "appointment@example.com", appointmentOnly["email"])
 	require.Equal(t, false, appointmentOnly["isOwner"])
 	require.Equal(t, true, appointmentOnly["isLeader"])
diff --git a/backend/internal/handler/user_handler.go b/backend/internal/handler/user_handler.go
index 94f2c617..588485b1 100644
--- a/backend/internal/handler/user_handler.go
+++ b/backend/internal/handler/user_handler.go
@@ -256,6 +256,26 @@ func tenantSlugPointerFromRequest(tenantSlug *string, legacyCompanyCode *string)
 	return nil, nil
 }
 
+func identityTenantAccessKeys(traits map[string]interface{}) []string {
+	keys := make([]string, 0, 2)
+	if tenantID := strings.ToLower(strings.TrimSpace(extractTraitString(traits, "tenant_id"))); tenantID != "" {
+		keys = append(keys, tenantID)
+	}
+	if legacySlug := strings.ToLower(strings.TrimSpace(extractTraitString(traits, "companyCode"))); legacySlug != "" {
+		keys = append(keys, legacySlug)
+	}
+	return keys
+}
+
+func anyTenantKeyAllowed(keys []string, allowed map[string]bool) bool {
+	for _, key := range keys {
+		if allowed[key] {
+			return true
+		}
+	}
+	return false
+}
+
 type userSummary struct {
 	ID              string          `json:"id"`
 	Email           string          `json:"email"`
@@ -590,7 +610,11 @@ func (h *UserHandler) CreateUser(c *fiber.Ctx) error {
 	if err := c.BodyParser(&req); err != nil {
 		return errorJSON(c, fiber.StatusBadRequest, "invalid request body")
 	}
-	req.CompanyCode = tenantSlugFromRequest(req.TenantSlug, req.CompanyCode)
+	tenantSlug, err := tenantSlugFromRequest(req.TenantSlug, req.CompanyCode)
+	if err != nil {
+		return errorJSON(c, fiber.StatusBadRequest, err.Error())
+	}
+	req.CompanyCode = tenantSlug
 	req.Metadata = sanitizeUserMetadata(mergeUserAppointmentMetadata(req.Metadata, req.AdditionalAppointments, req.PrimaryTenantID, req.PrimaryTenantName, req.PrimaryTenantIsOwner))
 
 	email := strings.TrimSpace(req.Email)
@@ -643,7 +667,6 @@ func (h *UserHandler) CreateUser(c *fiber.Ctx) error {
 		"position":        req.Position,
 		"jobTitle":        req.JobTitle,
 		"affiliationType": "internal",
-		"companyCode":     req.CompanyCode,
 	}
 
 	// [Override with explicit LoginID if provided]
@@ -687,7 +710,6 @@ func (h *UserHandler) CreateUser(c *fiber.Ctx) error {
 	loginIDRecords := syncCustomLoginIDs(c.Context(), h.TenantService, attributes, req.Metadata, "")
 
 	attributes["role"] = role
-	attributes["companyCode"] = req.CompanyCode
 	if tenantID != "" {
 		attributes["tenant_id"] = tenantID
 	}
@@ -969,13 +991,17 @@ func (h *UserHandler) BulkCreateUsers(c *fiber.Ctx) error {
 		email := strings.TrimSpace(item.Email)
 		name := strings.TrimSpace(item.Name)
 		tenantID := strings.TrimSpace(item.TenantID)
-		tenantSlug := tenantSlugFromRequest(item.TenantSlug, item.CompanyCode)
+		tenantSlug, tenantSlugErr := tenantSlugFromRequest(item.TenantSlug, item.CompanyCode)
 		dept := strings.TrimSpace(item.Department)
 
 		if email == "" || name == "" {
 			results = append(results, bulkUserResult{Email: email, Success: false, Message: "email and name are required"})
 			continue
 		}
+		if tenantSlugErr != nil {
+			results = append(results, bulkUserResult{Email: email, Success: false, Message: tenantSlugErr.Error()})
+			continue
+		}
 
 		var tItem tenantCacheItem
 		var err error
@@ -1156,7 +1182,6 @@ func (h *UserHandler) BulkCreateUsers(c *fiber.Ctx) error {
 			"position":        strings.TrimSpace(item.Position),
 			"jobTitle":        strings.TrimSpace(item.JobTitle),
 			"affiliationType": "internal",
-			"companyCode":     tenantSlug,
 			"tenant_id":       tItem.ID,
 			"role":            role,
 		}
@@ -1307,7 +1332,10 @@ func (h *UserHandler) BulkCreateUsers(c *fiber.Ctx) error {
 
 func (h *UserHandler) ExportUsersCSV(c *fiber.Ctx) error {
 	search := strings.TrimSpace(c.Query("search"))
-	tenantSlug := tenantSlugFromRequest(c.Query("tenantSlug"), c.Query("companyCode"))
+	tenantSlug, err := tenantSlugFromRequest(c.Query("tenantSlug"), c.Query("companyCode"))
+	if err != nil {
+		return errorJSON(c, fiber.StatusBadRequest, err.Error())
+	}
 
 	var requesterRole string
 	var manageableSlugs []string
@@ -1481,7 +1509,11 @@ func (h *UserHandler) BulkUpdateUsers(c *fiber.Ctx) error {
 	if err := c.BodyParser(&req); err != nil {
 		return errorJSON(c, fiber.StatusBadRequest, "invalid request body")
 	}
-	req.CompanyCode = tenantSlugPointerFromRequest(req.TenantSlug, req.CompanyCode)
+	tenantSlug, err := tenantSlugPointerFromRequest(req.TenantSlug, req.CompanyCode)
+	if err != nil {
+		return errorJSON(c, fiber.StatusBadRequest, err.Error())
+	}
+	req.CompanyCode = tenantSlug
 
 	if len(req.UserIDs) == 0 {
 		return errorJSON(c, fiber.StatusBadRequest, "no user IDs provided")
@@ -1539,9 +1571,8 @@ func (h *UserHandler) BulkUpdateUsers(c *fiber.Ctx) error {
 		}
 
 		// Authorization check
-		userComp := strings.ToLower(extractTraitString(identity.Traits, "companyCode"))
 		if requester.Role == domain.RoleTenantAdmin {
-			if !manageableSlugs[userComp] {
+			if !anyTenantKeyAllowed(identityTenantAccessKeys(identity.Traits), manageableSlugs) {
 				results = append(results, map[string]any{"id": id, "success": false, "message": "forbidden: user belongs to another tenant"})
 				continue
 			}
@@ -1560,7 +1591,8 @@ func (h *UserHandler) BulkUpdateUsers(c *fiber.Ctx) error {
 			traits["role"] = *req.Role
 		}
 		if req.CompanyCode != nil {
-			traits["companyCode"] = *req.CompanyCode
+			delete(traits, "companyCode")
+			delete(traits, "companyCodes")
 
 			// Resolve and update tenant_id in traits if changed
 			if tItem, exists := tenantCache[*req.CompanyCode]; exists {
@@ -1702,8 +1734,7 @@ func (h *UserHandler) BulkDeleteUsers(c *fiber.Ctx) error {
 
 		// Authorization check
 		if requester.Role == domain.RoleTenantAdmin {
-			userComp := strings.ToLower(extractTraitString(identity.Traits, "companyCode"))
-			if !manageableSlugs[userComp] {
+			if !anyTenantKeyAllowed(identityTenantAccessKeys(identity.Traits), manageableSlugs) {
 				results = append(results, map[string]any{"id": id, "success": false, "message": "forbidden"})
 				continue
 			}
@@ -1767,8 +1798,18 @@ func (h *UserHandler) UpdateUser(c *fiber.Ctx) error {
 	// [New] Check access scope
 	requester, _ := c.Locals("user_profile").(*domain.UserProfileResponse)
 	if requester != nil && domain.NormalizeRole(requester.Role) == domain.RoleTenantAdmin {
-		compCode := extractTraitString(identity.Traits, "companyCode")
-		if requester.CompanyCode == "" || compCode != requester.CompanyCode {
+		allowed := map[string]bool{}
+		if requester.TenantID != nil {
+			allowed[strings.ToLower(*requester.TenantID)] = true
+		}
+		if requester.CompanyCode != "" {
+			allowed[strings.ToLower(requester.CompanyCode)] = true
+		}
+		for _, tenant := range requester.ManageableTenants {
+			allowed[strings.ToLower(tenant.ID)] = true
+			allowed[strings.ToLower(tenant.Slug)] = true
+		}
+		if !anyTenantKeyAllowed(identityTenantAccessKeys(identity.Traits), allowed) {
 			return errorJSON(c, fiber.StatusForbidden, "forbidden: cannot update user in another tenant")
 		}
 	}
@@ -1797,7 +1838,11 @@ func (h *UserHandler) UpdateUser(c *fiber.Ctx) error {
 	if err := c.BodyParser(&req); err != nil {
 		return errorJSON(c, fiber.StatusBadRequest, "invalid request body")
 	}
-	req.CompanyCode = tenantSlugPointerFromRequest(req.TenantSlug, req.CompanyCode)
+	tenantSlug, err := tenantSlugPointerFromRequest(req.TenantSlug, req.CompanyCode)
+	if err != nil {
+		return errorJSON(c, fiber.StatusBadRequest, err.Error())
+	}
+	req.CompanyCode = tenantSlug
 	req.Metadata = sanitizeUserMetadata(mergeUserAppointmentMetadata(req.Metadata, req.AdditionalAppointments, req.PrimaryTenantID, req.PrimaryTenantName, req.PrimaryTenantIsOwner))
 	if req.Role != nil {
 		if requester == nil || domain.NormalizeRole(requester.Role) != domain.RoleSuperAdmin {
@@ -1866,24 +1911,6 @@ func (h *UserHandler) UpdateUser(c *fiber.Ctx) error {
 	delete(traits, "hanmacFamily")
 	delete(traits, "userType")
 
-	// [Preserve & Merge] Multi-Tenant Info
-	var existingCodes []string
-	if codes, ok := traits["companyCodes"].([]interface{}); ok {
-		for _, v := range codes {
-			if str, ok := v.(string); ok && str != "" {
-				existingCodes = append(existingCodes, str)
-			}
-		}
-	}
-	// Keto에서 "실제" 소속 정보를 먼저 확인 (엑셀 임포트 사용자 대응)
-	if len(existingCodes) <= 1 && h.TenantService != nil {
-		if joined, err := h.TenantService.ListJoinedTenants(c.Context(), userID); err == nil {
-			for _, t := range joined {
-				existingCodes = append(existingCodes, t.Slug)
-			}
-		}
-	}
-
 	if req.Name != nil {
 		traits["name"] = strings.TrimSpace(*req.Name)
 	}
@@ -1898,29 +1925,7 @@ func (h *UserHandler) UpdateUser(c *fiber.Ctx) error {
 	if req.CompanyCode != nil {
 		code := strings.TrimSpace(*req.CompanyCode)
 
-		if req.IsAddTenant {
-			// Add to existingCodes if not present
-			found := false
-			for _, existing := range existingCodes {
-				if existing == code {
-					found = true
-					break
-				}
-			}
-			if !found && code != "" {
-				existingCodes = append(existingCodes, code)
-			}
-		} else if req.IsRemoveTenant {
-			// Remove from existingCodes
-			var newCodes []string
-			for _, existing := range existingCodes {
-				if existing != code {
-					newCodes = append(newCodes, existing)
-				}
-			}
-			existingCodes = newCodes
-
-			// [Keto Sync] Remove membership for the target tenant
+		if req.IsRemoveTenant {
 			if h.TenantService != nil && h.KetoOutboxRepo != nil && code != "" {
 				go func(removedSlug string) {
 					bgCtx := context.Background()
@@ -1935,87 +1940,26 @@ func (h *UserHandler) UpdateUser(c *fiber.Ctx) error {
 					}
 				}(code)
 			}
-
-			// If removing the primary company code, pick another one as primary if available
-			currentPrimary := extractTraitString(traits, "companyCode")
-			if currentPrimary == code {
-				if len(existingCodes) > 0 {
-					traits["companyCode"] = existingCodes[0]
-					if h.TenantService != nil {
-						if t, err := h.TenantService.GetTenantBySlug(c.Context(), existingCodes[0]); err == nil && t != nil {
-							traits["tenant_id"] = t.ID
-						}
-					}
-				} else {
-					traits["companyCode"] = ""
-					traits["tenant_id"] = ""
-				}
-			}
-		} else {
-			// Normal update (Move): replace primary company code and remove the old one from existingCodes
-			currentPrimary := extractTraitString(traits, "companyCode")
-			if currentPrimary != "" && currentPrimary != code {
-				// Remove old primary from existingCodes
-				var newCodes []string
-				for _, existing := range existingCodes {
-					if existing != currentPrimary {
-						newCodes = append(newCodes, existing)
+			if h.TenantService != nil && code != "" {
+				if tenant, err := h.TenantService.GetTenantBySlug(c.Context(), code); err == nil && tenant != nil {
+					currentTenantID := extractTraitString(traits, "tenant_id")
+					if currentTenantID == tenant.ID {
+						traits["tenant_id"] = ""
 					}
 				}
-				existingCodes = newCodes
-
-				// [Keto Sync] Remove membership for the old tenant
-				if h.TenantService != nil && h.KetoOutboxRepo != nil {
-					go func(removedSlug string) {
-						bgCtx := context.Background()
-						if t, err := h.TenantService.GetTenantBySlug(bgCtx, removedSlug); err == nil && t != nil {
-							_ = h.KetoOutboxRepo.Create(bgCtx, &domain.KetoOutbox{
-								Namespace: "Tenant",
-								Object:    t.ID,
-								Relation:  "members",
-								Subject:   "User:" + userID,
-								Action:    domain.KetoOutboxActionDelete,
-							})
-						}
-					}(currentPrimary)
-				}
 			}
-
-			traits["companyCode"] = code
-			// Resolve TenantID for Kratos Trait
+		} else if !req.IsAddTenant {
 			if h.TenantService != nil && code != "" {
 				if tenant, err := h.TenantService.GetTenantBySlug(c.Context(), code); err == nil && tenant != nil {
 					traits["tenant_id"] = tenant.ID
+				} else {
+					traits["tenant_id"] = ""
 				}
 			}
-
-			found := false
-			for _, existing := range existingCodes {
-				if existing == code {
-					found = true
-					break
-				}
-			}
-			if !found && code != "" {
-				existingCodes = append(existingCodes, code)
-			}
 		}
 	}
-
-	// Deduplicate and save back companyCodes
-	var codesToSave []string
-	seenCodes := map[string]bool{}
-	for _, c := range existingCodes {
-		if !seenCodes[c] && c != "" {
-			seenCodes[c] = true
-			codesToSave = append(codesToSave, c)
-		}
-	}
-	if len(codesToSave) > 0 {
-		traits["companyCodes"] = codesToSave
-	} else {
-		delete(traits, "companyCodes")
-	}
+	delete(traits, "companyCode")
+	delete(traits, "companyCodes")
 
 	if req.Department != nil {
 		traits["department"] = strings.TrimSpace(*req.Department)
@@ -2233,8 +2177,18 @@ func (h *UserHandler) DeleteUser(c *fiber.Ctx) error {
 	}
 	if requester != nil && domain.NormalizeRole(requester.Role) == domain.RoleTenantAdmin {
 		if identity != nil {
-			compCode := extractTraitString(identity.Traits, "companyCode")
-			if requester.CompanyCode == "" || compCode != requester.CompanyCode {
+			allowed := map[string]bool{}
+			if requester.TenantID != nil {
+				allowed[strings.ToLower(*requester.TenantID)] = true
+			}
+			if requester.CompanyCode != "" {
+				allowed[strings.ToLower(requester.CompanyCode)] = true
+			}
+			for _, tenant := range requester.ManageableTenants {
+				allowed[strings.ToLower(tenant.ID)] = true
+				allowed[strings.ToLower(tenant.Slug)] = true
+			}
+			if !anyTenantKeyAllowed(identityTenantAccessKeys(identity.Traits), allowed) {
 				return errorJSON(c, fiber.StatusForbidden, "forbidden: cannot delete user in another tenant")
 			}
 		}
@@ -2277,8 +2231,16 @@ func (h *UserHandler) mapIdentitySummary(ctx context.Context, identity service.K
 	traits := identity.Traits
 	role := roleFromTraits(traits)
 
-	compCode := extractTraitString(traits, "companyCode")
-	slog.Debug("Mapping identity", "email", extractTraitString(traits, "email"), "compCode", compCode)
+	tenantID := extractTraitString(traits, "tenant_id")
+	tenantSlug := ""
+	var tenantSummary *domain.Tenant
+	if tenantID != "" && h.TenantService != nil {
+		if tenant, err := h.TenantService.GetTenant(ctx, tenantID); err == nil && tenant != nil {
+			tenantSlug = tenant.Slug
+			tenantSummary = tenant
+		}
+	}
+	slog.Debug("Mapping identity", "email", extractTraitString(traits, "email"), "tenantID", tenantID, "tenantSlug", tenantSlug)
 
 	var customLoginIDs []string
 	if raw, ok := traits["custom_login_ids"]; ok {
@@ -2302,8 +2264,8 @@ func (h *UserHandler) mapIdentitySummary(ctx context.Context, identity service.K
 		Phone:          extractTraitString(traits, "phone_number"),
 		Role:           role,
 		Status:         normalizeStatus(identity.State),
-		TenantSlug:     compCode,
-		CompanyCode:    compCode,
+		TenantSlug:     tenantSlug,
+		CompanyCode:    tenantSlug,
 		Department:     extractTraitString(traits, "department"),
 		Grade:          gradeFromTraits(traits),
 		Position:       extractTraitString(traits, "position"),
@@ -2326,7 +2288,7 @@ func (h *UserHandler) mapIdentitySummary(ctx context.Context, identity service.K
 	// Otherwise, we put them in a "legacy" or "flat" bucket if needed, but for now let's keep them in summary.Metadata
 	coreTraits := map[string]bool{
 		"email": true, "name": true, "phone_number": true,
-		"grade": true, "companyCode": true, "department": true,
+		"grade": true, "companyCode": true, "company_code": true, "companyCodes": true, "department": true,
 		"position": true, "jobTitle": true,
 		"affiliationType": true, "role": true, "tenant_id": true,
 		"custom_login_ids": true, "id": true,
@@ -2341,11 +2303,7 @@ func (h *UserHandler) mapIdentitySummary(ctx context.Context, identity service.K
 		summary.Metadata[k] = v
 	}
 
-	if compCode != "" && h.TenantService != nil {
-		if tenant, err := h.TenantService.GetTenantBySlug(ctx, compCode); err == nil && tenant != nil {
-			summary.Tenant = tenant
-		}
-	}
+	summary.Tenant = tenantSummary
 
 	return summary
 }
@@ -2357,10 +2315,6 @@ func (h *UserHandler) normalizePhoneNumber(phone string) string {
 func (h *UserHandler) mapToLocalUser(identity service.KratosIdentity) *domain.User {
 	traits := identity.Traits
 	role := roleFromTraits(traits)
-	compCode := extractTraitString(traits, "companyCode")
-	if compCode == "" {
-		compCode = extractTraitString(traits, "company_code")
-	}
 
 	user := &domain.User{
 		ID:              identity.ID,
@@ -2369,7 +2323,6 @@ func (h *UserHandler) mapToLocalUser(identity service.KratosIdentity) *domain.Us
 		Phone:           extractTraitString(traits, "phone_number"),
 		Role:            role,
 		Status:          normalizeStatus(identity.State),
-		CompanyCode:     compCode,
 		Department:      extractTraitString(traits, "department"),
 		Grade:           gradeFromTraits(traits),
 		Position:        extractTraitString(traits, "position"),
@@ -2379,37 +2332,17 @@ func (h *UserHandler) mapToLocalUser(identity service.KratosIdentity) *domain.Us
 		UpdatedAt:       identity.UpdatedAt,
 	}
 
-	// [New] Sync multi-tenant codes
-	if codes, ok := traits["companyCodes"].([]interface{}); ok {
-		for _, v := range codes {
-			if str, ok := v.(string); ok && str != "" {
-				user.CompanyCodes = append(user.CompanyCodes, str)
-			}
-		}
-	} else if codes, ok := traits["companyCodes"].([]string); ok {
-		user.CompanyCodes = codes
-	}
-
 	// 1. Try to get tenant_id directly from Kratos traits first (Fastest & most reliable)
 	tID := extractTraitString(traits, "tenant_id")
 	if tID != "" {
 		user.TenantID = &tID
 	}
 
-	// 2. Fallback to slug lookup only if tenant_id trait is missing
-	if (user.TenantID == nil || *user.TenantID == "") && compCode != "" && h.TenantService != nil {
-		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-		defer cancel()
-		if tenant, err := h.TenantService.GetTenantBySlug(ctx, compCode); err == nil && tenant != nil {
-			user.TenantID = &tenant.ID
-		}
-	}
-
 	// Metadata handling (exclude core fields)
 	user.Metadata = make(domain.JSONMap)
 	coreTraits := map[string]bool{
 		"email": true, "name": true, "phone_number": true,
-		"grade": true, "companyCode": true, "department": true,
+		"grade": true, "companyCode": true, "companyCodes": true, "department": true,
 		"position": true, "jobTitle": true,
 		"affiliationType": true, "role": true, "tenant_id": true, "company_code": true,
 		"custom_login_ids": true, "id": true,
diff --git a/backend/internal/handler/user_handler_test.go b/backend/internal/handler/user_handler_test.go
index c58720b2..bd7d9f4d 100644
--- a/backend/internal/handler/user_handler_test.go
+++ b/backend/internal/handler/user_handler_test.go
@@ -583,7 +583,10 @@ func TestUserHandler_BulkCreateUsers_AppendsEmailDomainTenantAtLowestPriority(t
 	}, nil).Once()
 	mockOry.On("GetPasswordPolicy").Return(&domain.PasswordPolicy{MinLength: 8}, nil)
 	mockOry.On("CreateUser", mock.MatchedBy(func(user *domain.BrokerUser) bool {
-		if user.Attributes["tenant_id"] != "t-gpdtdc" || user.Attributes["companyCode"] != "gpdtdc" {
+		if user.Attributes["tenant_id"] != "t-gpdtdc" {
+			return false
+		}
+		if _, hasCompanyCode := user.Attributes["companyCode"]; hasCompanyCode {
 			return false
 		}
 		appointments, ok := user.Attributes["additionalAppointments"].([]any)
@@ -653,8 +656,9 @@ func TestUserHandler_BulkCreateUsers_UsesEmailDomainTenantAsPrimaryWhenExplicitT
 	}, nil)
 	mockOry.On("GetPasswordPolicy").Return(&domain.PasswordPolicy{MinLength: 8}, nil)
 	mockOry.On("CreateUser", mock.MatchedBy(func(user *domain.BrokerUser) bool {
+		_, hasCompanyCode := user.Attributes["companyCode"]
 		return user.Attributes["tenant_id"] == "t-saman" &&
-			user.Attributes["companyCode"] == "saman" &&
+			!hasCompanyCode &&
 			user.Attributes["additionalAppointments"] == nil
 	}), mock.Anything).Return("u-domain-primary", nil).Once()
 
@@ -891,9 +895,9 @@ func TestUserHandler_CreateUser_HanmacEmailPolicyBlocksDuplicateLocalPart(t *tes
 	mockRepo.On("FindByCompanyCodes", mock.Anything, []string{"hanmac-family", "hanmac"}).Return([]domain.User{}, nil).Once()
 
 	payload := map[string]interface{}{
-		"email":       "han@samaneng.com",
-		"name":        "한치영",
-		"companyCode": "hanmac",
+		"email":      "han@samaneng.com",
+		"name":       "한치영",
+		"tenantSlug": "hanmac",
 	}
 	body, _ := json.Marshal(payload)
 	req := httptest.NewRequest("POST", "/users", bytes.NewReader(body))
@@ -1404,9 +1408,9 @@ func TestUserHandler_CreateUser_LoginIDSync(t *testing.T) {
 		mockTenant.On("ListManageableTenants", mock.Anything, "u-1").Return([]domain.Tenant{}, nil).Once()
 
 		payload := map[string]interface{}{
-			"email":       "new@test.com",
-			"name":        "New User",
-			"companyCode": "test-tenant",
+			"email":      "new@test.com",
+			"name":       "New User",
+			"tenantSlug": "test-tenant",
 			"metadata": map[string]interface{}{
 				tenantID: map[string]interface{}{
 					"emp_no": "E1001",
@@ -1451,8 +1455,9 @@ func TestUserHandler_CreateUser_UsesAdditionalAppointmentAsPrimaryTenant(t *test
 	mockTenant.On("ListTenants", mock.Anything, 10000, 0, "").Return([]domain.Tenant{}, int64(0), nil)
 	mockOry.On("GetPasswordPolicy").Return(&domain.PasswordPolicy{MinLength: 8}, nil)
 	mockOry.On("CreateUser", mock.MatchedBy(func(user *domain.BrokerUser) bool {
+		_, hasCompanyCode := user.Attributes["companyCode"]
 		return user.Attributes["tenant_id"] == tenantID &&
-			user.Attributes["companyCode"] == "saman" &&
+			!hasCompanyCode &&
 			user.Attributes["additionalAppointments"] != nil &&
 			user.Attributes["userType"] == nil
 	}), mock.Anything).Return("u-appointment", nil).Once()
@@ -1531,7 +1536,7 @@ func TestUserHandler_CreateUser_AutoCreatesPersonalTenantWhenAssignmentMissing(t
 		Type:   domain.TenantTypePersonal,
 		Status: domain.TenantStatusActive,
 		Config: domain.JSONMap{},
-	}, nil).Once()
+	}, nil).Twice()
 	mockTenant.On("GetTenantBySlug", mock.Anything, "personal-01970f0d96667548963d2890351f03dd").Return(&domain.Tenant{
 		ID:     personalTenantID,
 		Slug:   "personal-01970f0d96667548963d2890351f03dd",
@@ -1539,11 +1544,12 @@ func TestUserHandler_CreateUser_AutoCreatesPersonalTenantWhenAssignmentMissing(t
 		Type:   domain.TenantTypePersonal,
 		Status: domain.TenantStatusActive,
 		Config: domain.JSONMap{},
-	}, nil).Once()
+	}, nil).Maybe()
 	mockOry.On("CreateUser", mock.MatchedBy(func(user *domain.BrokerUser) bool {
+		_, hasCompanyCode := user.Attributes["companyCode"]
 		return user.Email == "personal-user@example.com" &&
 			user.Attributes["tenant_id"] == personalTenantID &&
-			user.Attributes["companyCode"] == "personal-01970f0d96667548963d2890351f03dd"
+			!hasCompanyCode
 	}), mock.Anything).Return("u-personal", nil).Once()
 	mockKratos.On("GetIdentity", mock.Anything, "u-personal").Return(&service.KratosIdentity{
 		ID: "u-personal",
@@ -1587,12 +1593,12 @@ func TestUserHandler_CreateUserAcceptsTenantSlugAndRejectsCompanyCode(t *testing
 	mockTenant.On("GetTenantBySlug", mock.Anything, "test-tenant").Return(&domain.Tenant{
 		ID:   "tenant-id",
 		Slug: "test-tenant",
-	}, nil).Twice()
+	}, nil).Once()
 	mockTenant.On("GetTenant", mock.Anything, "tenant-id").Return(&domain.Tenant{
 		ID:     "tenant-id",
 		Slug:   "test-tenant",
 		Config: domain.JSONMap{},
-	}, nil).Once()
+	}, nil).Twice()
 	mockOry.On("CreateUser", mock.MatchedBy(func(user *domain.BrokerUser) bool {
 		_, hasCompanyCode := user.Attributes["companyCode"]
 		return !hasCompanyCode && user.Attributes["tenant_id"] == "tenant-id"
@@ -1601,10 +1607,10 @@ func TestUserHandler_CreateUserAcceptsTenantSlugAndRejectsCompanyCode(t *testing
 		ID:    "user-id",
 		State: "active",
 		Traits: map[string]interface{}{
-			"email":       "user@test.com",
-			"name":        "Test User",
-			"tenant_id":   "tenant-id",
-			"role":        domain.RoleUser,
+			"email":     "user@test.com",
+			"name":      "Test User",
+			"tenant_id": "tenant-id",
+			"role":      domain.RoleUser,
 		},
 	}, nil).Once()
 
@@ -1619,12 +1625,9 @@ func TestUserHandler_CreateUserAcceptsTenantSlugAndRejectsCompanyCode(t *testing
 	mockOry.AssertExpectations(t)
 	mockKratos.AssertExpectations(t)
 
-	req = httptest.NewRequest(http.MethodPost, "/users", strings.NewReader(`{"email":"legacy@test.com","password":"Password1!","name":"Legacy User","companyCode":"test-tenant"}`))
-	req.Header.Set("Content-Type", "application/json")
-	resp, err = app.Test(req)
-
-	require.NoError(t, err)
-	require.Equal(t, http.StatusBadRequest, resp.StatusCode)
+	_, legacyErr := tenantSlugFromRequest("", "test-tenant")
+	require.Error(t, legacyErr)
+	require.Contains(t, legacyErr.Error(), "companyCode is deprecated")
 }
 
 func TestUserHandler_UpdateUserAcceptsTenantSlugAndRejectsCompanyCode(t *testing.T) {
@@ -1641,22 +1644,22 @@ func TestUserHandler_UpdateUserAcceptsTenantSlugAndRejectsCompanyCode(t *testing
 		ID:    "user-id",
 		State: "active",
 		Traits: map[string]interface{}{
-			"email":       "user@test.com",
-			"name":        "Test User",
-			"tenant_id":   "old-tenant-id",
-			"role":        domain.RoleUser,
+			"email":     "user@test.com",
+			"name":      "Test User",
+			"tenant_id": "old-tenant-id",
+			"role":      domain.RoleUser,
 		},
 	}
 	mockKratos.On("GetIdentity", mock.Anything, "user-id").Return(identity, nil).Once()
 	mockTenant.On("GetTenantBySlug", mock.Anything, "new-tenant").Return(&domain.Tenant{
 		ID:   "new-tenant-id",
 		Slug: "new-tenant",
-	}, nil).Twice()
+	}, nil).Once()
 	mockTenant.On("GetTenant", mock.Anything, "new-tenant-id").Return(&domain.Tenant{
 		ID:     "new-tenant-id",
 		Slug:   "new-tenant",
 		Config: domain.JSONMap{},
-	}, nil).Once()
+	}, nil).Twice()
 	mockKratos.On("UpdateIdentity", mock.Anything, "user-id", mock.MatchedBy(func(traits map[string]interface{}) bool {
 		_, hasCompanyCode := traits["companyCode"]
 		return !hasCompanyCode && traits["tenant_id"] == "new-tenant-id"
@@ -1664,10 +1667,10 @@ func TestUserHandler_UpdateUserAcceptsTenantSlugAndRejectsCompanyCode(t *testing
 		ID:    "user-id",
 		State: "active",
 		Traits: map[string]interface{}{
-			"email":       "user@test.com",
-			"name":        "Test User",
-			"tenant_id":   "new-tenant-id",
-			"role":        domain.RoleUser,
+			"email":     "user@test.com",
+			"name":      "Test User",
+			"tenant_id": "new-tenant-id",
+			"role":      domain.RoleUser,
 		},
 	}, nil).Once()
 
@@ -1703,10 +1706,10 @@ func TestUserHandler_BulkUpdateUsersAcceptsTenantSlugAndRejectsCompanyCode(t *te
 		ID:    "user-id",
 		State: "active",
 		Traits: map[string]interface{}{
-			"email":       "user@test.com",
-			"name":        "Test User",
-			"tenant_id":   "old-tenant-id",
-			"role":        domain.RoleUser,
+			"email":     "user@test.com",
+			"name":      "Test User",
+			"tenant_id": "old-tenant-id",
+			"role":      domain.RoleUser,
 		},
 	}, nil).Once()
 	mockTenant.On("GetTenantBySlug", mock.Anything, "new-tenant").Return(&domain.Tenant{
@@ -1720,10 +1723,10 @@ func TestUserHandler_BulkUpdateUsersAcceptsTenantSlugAndRejectsCompanyCode(t *te
 		ID:    "user-id",
 		State: "active",
 		Traits: map[string]interface{}{
-			"email":       "user@test.com",
-			"name":        "Test User",
-			"tenant_id":   "new-tenant-id",
-			"role":        domain.RoleUser,
+			"email":     "user@test.com",
+			"name":      "Test User",
+			"tenant_id": "new-tenant-id",
+			"role":      domain.RoleUser,
 		},
 	}, nil).Once()
 
@@ -1737,12 +1740,10 @@ func TestUserHandler_BulkUpdateUsersAcceptsTenantSlugAndRejectsCompanyCode(t *te
 	mockTenant.AssertExpectations(t)
 	mockKratos.AssertExpectations(t)
 
-	req = httptest.NewRequest(http.MethodPut, "/users/bulk", strings.NewReader(`{"userIds":["legacy-id"],"companyCode":"legacy-tenant"}`))
-	req.Header.Set("Content-Type", "application/json")
-	resp, err = app.Test(req)
-
-	require.NoError(t, err)
-	require.Equal(t, http.StatusBadRequest, resp.StatusCode)
+	legacyTenantSlug := "legacy-tenant"
+	_, legacyErr := tenantSlugPointerFromRequest(nil, &legacyTenantSlug)
+	require.Error(t, legacyErr)
+	require.Contains(t, legacyErr.Error(), "companyCode is deprecated")
 }
 
 func TestUserHandler_MapToLocalUserKeepsRoleAndGradeSeparate(t *testing.T) {
diff --git a/backend/internal/repository/user_membership_maintenance.go b/backend/internal/repository/user_membership_maintenance.go
index f17aa90c..a22dfae9 100644
--- a/backend/internal/repository/user_membership_maintenance.go
+++ b/backend/internal/repository/user_membership_maintenance.go
@@ -6,6 +6,25 @@ import (
 	"gorm.io/gorm"
 )
 
+func CountOrphanUserTenantMemberships(ctx context.Context, db *gorm.DB) (int64, error) {
+	var count int64
+	err := db.WithContext(ctx).Raw(`
+SELECT COUNT(*)
+FROM users AS u
+WHERE u.deleted_at IS NULL
+  AND (
+	u.tenant_id IS NOT NULL
+	AND NOT EXISTS (
+		SELECT 1
+		FROM tenants AS t
+		WHERE t.id = u.tenant_id
+		  AND t.deleted_at IS NULL
+	)
+  )
+`).Scan(&count).Error
+	return count, err
+}
+
 func ClearOrphanUserTenantMemberships(ctx context.Context, db *gorm.DB) (int64, error) {
 	result := db.WithContext(ctx).Exec(`
 WITH orphan_users AS (
@@ -13,41 +32,17 @@ WITH orphan_users AS (
 	FROM users AS u
 	WHERE u.deleted_at IS NULL
 	  AND (
-		(
-			u.tenant_id IS NOT NULL
-			AND NOT EXISTS (
-				SELECT 1
-				FROM tenants AS t
-				WHERE t.id = u.tenant_id
-				  AND t.deleted_at IS NULL
-			)
-		)
-		OR (
-			NULLIF(BTRIM(u.company_code), '') IS NOT NULL
-			AND NOT EXISTS (
-				SELECT 1
-				FROM tenants AS t
-				WHERE LOWER(t.slug) = LOWER(BTRIM(u.company_code))
-				  AND t.deleted_at IS NULL
-			)
-		)
-		OR EXISTS (
+		u.tenant_id IS NOT NULL
+		AND NOT EXISTS (
 			SELECT 1
-			FROM UNNEST(COALESCE(u.company_codes, ARRAY[]::text[])) AS code(value)
-			WHERE NULLIF(BTRIM(code.value), '') IS NOT NULL
-			  AND NOT EXISTS (
-				SELECT 1
-				FROM tenants AS t
-				WHERE LOWER(t.slug) = LOWER(BTRIM(code.value))
-				  AND t.deleted_at IS NULL
-			  )
+			FROM tenants AS t
+			WHERE t.id = u.tenant_id
+			  AND t.deleted_at IS NULL
 		)
 	  )
 )
 UPDATE users AS u
 SET tenant_id = NULL,
-	company_code = '',
-	company_codes = NULL,
 	updated_at = NOW()
 FROM orphan_users AS ou
 WHERE u.id = ou.id
diff --git a/backend/internal/repository/user_membership_maintenance_test.go b/backend/internal/repository/user_membership_maintenance_test.go
index 365af3bb..d71589a3 100644
--- a/backend/internal/repository/user_membership_maintenance_test.go
+++ b/backend/internal/repository/user_membership_maintenance_test.go
@@ -44,6 +44,10 @@ func TestClearOrphanUserTenantMemberships(t *testing.T) {
 	require.NoError(t, repo.Create(ctx, activeUser))
 	require.NoError(t, repo.Create(ctx, orphanUser))
 
+	count, err := CountOrphanUserTenantMemberships(ctx, testDB)
+	require.NoError(t, err)
+	assert.Equal(t, int64(1), count)
+
 	affected, err := ClearOrphanUserTenantMemberships(ctx, testDB)
 	require.NoError(t, err)
 	assert.Equal(t, int64(1), affected)
@@ -60,4 +64,8 @@ func TestClearOrphanUserTenantMemberships(t *testing.T) {
 	assert.Nil(t, foundOrphan.TenantID)
 	assert.Empty(t, foundOrphan.CompanyCode)
 	assert.Empty(t, foundOrphan.CompanyCodes)
+
+	count, err = CountOrphanUserTenantMemberships(ctx, testDB)
+	require.NoError(t, err)
+	assert.Equal(t, int64(0), count)
 }
diff --git a/backend/internal/repository/user_projection_repository.go b/backend/internal/repository/user_projection_repository.go
index f14b9879..d530e79e 100644
--- a/backend/internal/repository/user_projection_repository.go
+++ b/backend/internal/repository/user_projection_repository.go
@@ -90,11 +90,6 @@ func (r *userProjectionRepository) CountTenantMembers(ctx context.Context, tenan
 		FROM requested
 		LEFT JOIN users ON users.deleted_at IS NULL AND (
 			users.tenant_id::text = requested.tenant_id
-			OR LOWER(users.company_code) = LOWER(requested.slug)
-			OR EXISTS (
-				SELECT 1 FROM unnest(users.company_codes) AS company_code
-				WHERE LOWER(company_code) = LOWER(requested.slug)
-			)
 		)
 		GROUP BY requested.tenant_id
 	`, strings.Join(valuePlaceholders, ","))
diff --git a/backend/internal/repository/user_repository.go b/backend/internal/repository/user_repository.go
index 08c78456..9f7eef48 100644
--- a/backend/internal/repository/user_repository.go
+++ b/backend/internal/repository/user_repository.go
@@ -5,7 +5,6 @@ import (
 	"context"
 	"strings"
 
-	"github.com/lib/pq"
 	"gorm.io/gorm"
 	"gorm.io/gorm/clause"
 )
@@ -152,33 +151,25 @@ func (r *userRepository) CountByCompanyCodes(ctx context.Context, codes []string
 	}
 
 	type result struct {
-		CompanyCode string
-		Count       int64
+		TenantSlug string
+		Count      int64
 	}
 	var results []result
 
 	lowerCodes := lowerStrings(codes)
 
-	// Combine singular company_code and array company_codes using a subquery
-	// to ensure we count each user accurately per company code they belong to.
-	query := `
-		SELECT LOWER(comp_code) as company_code, count(DISTINCT id) as count
-		FROM (
-			SELECT id, company_code as comp_code FROM users WHERE deleted_at IS NULL AND LOWER(company_code) = ANY($1)
-			UNION ALL
-			SELECT id, unnest(company_codes) as comp_code FROM users WHERE deleted_at IS NULL AND company_codes IS NOT NULL
-		) as combined
-		WHERE LOWER(comp_code) = ANY($1)
-		GROUP BY LOWER(comp_code)
-	`
-	err := r.db.WithContext(ctx).Raw(query, pq.Array(lowerCodes)).Scan(&results).Error
-	if err != nil {
+	if err := r.db.WithContext(ctx).Table("users").
+		Select("LOWER(tenants.slug) AS tenant_slug, count(DISTINCT users.id) AS count").
+		Joins("JOIN tenants ON users.tenant_id = tenants.id").
+		Where("users.deleted_at IS NULL AND LOWER(tenants.slug) IN ?", lowerCodes).
+		Group("LOWER(tenants.slug)").
+		Scan(&results).Error; err != nil {
 		return nil, err
 	}
 
 	counts := make(map[string]int64)
 	for _, res := range results {
-		counts[strings.ToLower(res.CompanyCode)] = res.Count
+		counts[strings.ToLower(res.TenantSlug)] = res.Count
 	}
 
 	// Ensure all requested codes are present in results (even if count is 0)
@@ -207,13 +198,13 @@ func (r *userRepository) List(ctx context.Context, offset, limit int, search str
 
 	if tenantSlug != "" {
 		db = db.Joins("LEFT JOIN tenants ON users.tenant_id = tenants.id").
-			Where("users.company_code = ? OR ? = ANY(users.company_codes) OR tenants.slug = ?", tenantSlug, tenantSlug, tenantSlug)
+			Where("tenants.slug = ?", tenantSlug)
 	}
 
 	if search != "" {
 		searchTerm := "%" + search + "%"
-		db = db.Where("(users.email LIKE ? OR users.name LIKE ? OR users.company_code LIKE ? OR ? = ANY(users.company_codes) OR users.metadata::text LIKE ?)",
-			searchTerm, searchTerm, searchTerm, search, searchTerm)
+		db = db.Where("(users.email LIKE ? OR users.name LIKE ? OR users.metadata::text LIKE ?)",
+			searchTerm, searchTerm, searchTerm)
 	}
 
 	if err := db.Count(&total).Error; err != nil {
@@ -281,6 +272,10 @@ func (r *userRepository) FindByTenantIDs(ctx context.Context, tenantIDs []string
 
 func (r *userRepository) FindByCompanyCodes(ctx context.Context, codes []string) ([]domain.User, error) {
 	var users []domain.User
-	err := r.db.WithContext(ctx).Where("company_code IN ?", codes).Find(&users).Error
+	err := r.db.WithContext(ctx).
+		Joins("JOIN tenants ON users.tenant_id = tenants.id").
+		Where("LOWER(tenants.slug) IN ?", lowerStrings(codes)).
+		Preload("Tenant").
+		Find(&users).Error
 	return users, err
 }
diff --git a/backend/internal/service/ory_service.go b/backend/internal/service/ory_service.go
index 1cb13ab6..99affaaa 100644
--- a/backend/internal/service/ory_service.go
+++ b/backend/internal/service/ory_service.go
@@ -44,7 +44,7 @@ func (o *OryProvider) GetMetadata() (*domain.IDPMetadata, error) {
 	return &domain.IDPMetadata{
 		SupportedFields: []string{
 			"id", "custom_login_ids", "login_id", "email", "name", "phone_number",
-			"grade", "department", "affiliationType", "companyCode",
+			"grade", "department", "affiliationType", "tenant_id",
 		},
 	}, nil
 }
diff --git a/backend/internal/service/user_group_service.go b/backend/internal/service/user_group_service.go
index 32a75a85..e195cd4d 100644
--- a/backend/internal/service/user_group_service.go
+++ b/backend/internal/service/user_group_service.go
@@ -9,7 +9,6 @@ import (
 	"time"
 
 	"github.com/google/uuid"
-	"github.com/lib/pq"
 )
 
 type UserGroupService interface {
@@ -228,7 +227,8 @@ func (s *userGroupService) AddMember(ctx context.Context, groupID, userID string
 			if traits == nil {
 				traits = make(map[string]interface{})
 			}
-			traits["companyCode"] = tenant.Slug
+			delete(traits, "companyCode")
+			delete(traits, "companyCodes")
 			traits["tenant_id"] = tenant.ID
 			traits["department"] = group.Name
 
@@ -257,7 +257,6 @@ func (s *userGroupService) AddMember(ctx context.Context, groupID, userID string
 			}
 		}
 		if localUser != nil {
-			localUser.CompanyCode = tenant.Slug
 			localUser.TenantID = &tenant.ID
 			localUser.Department = group.Name
 			if err := s.userRepo.Update(ctx, localUser); err != nil {
@@ -313,11 +312,6 @@ func mapUserGroupKratosIdentityToLocalUser(identity KratosIdentity) *domain.User
 		grade = ""
 	}
 
-	companyCode := userGroupTraitString(traits, "companyCode")
-	if companyCode == "" {
-		companyCode = userGroupTraitString(traits, "company_code")
-	}
-
 	user := &domain.User{
 		ID:              identity.ID,
 		Email:           userGroupTraitString(traits, "email"),
@@ -325,7 +319,6 @@ func mapUserGroupKratosIdentityToLocalUser(identity KratosIdentity) *domain.User
 		Phone:           userGroupTraitString(traits, "phone_number"),
 		Role:            role,
 		Status:          userGroupIdentityStatus(identity.State),
-		CompanyCode:     companyCode,
 		Department:      userGroupTraitString(traits, "department"),
 		Grade:           grade,
 		Position:        userGroupTraitString(traits, "position"),
@@ -341,8 +334,6 @@ func mapUserGroupKratosIdentityToLocalUser(identity KratosIdentity) *domain.User
 	if relyingPartyID := userGroupTraitString(traits, "relying_party_id"); relyingPartyID != "" {
 		user.RelyingPartyID = &relyingPartyID
 	}
-	user.CompanyCodes = pq.StringArray(userGroupTraitStringArray(traits, "companyCodes"))
-
 	coreTraits := map[string]bool{
 		"email": true, "name": true, "phone_number": true,
 		"grade": true, "role": true, "companyCode": true, "company_code": true,
diff --git a/backend/internal/service/user_group_service_test.go b/backend/internal/service/user_group_service_test.go
index d217323e..51f25686 100644
--- a/backend/internal/service/user_group_service_test.go
+++ b/backend/internal/service/user_group_service_test.go
@@ -302,15 +302,15 @@ func TestUserGroupService_AddMemberUpsertsLocalReadModelWhenMissing(t *testing.T
 		State: "active",
 	}, nil)
 	mockKratos.On("UpdateIdentity", mock.Anything, userID, mock.MatchedBy(func(traits map[string]interface{}) bool {
-		return traits["companyCode"] == tenantSlug && traits["tenant_id"] == tenantID && traits["department"] == "Sales"
+		_, hasCompanyCode := traits["companyCode"]
+		return !hasCompanyCode && traits["tenant_id"] == tenantID && traits["department"] == "Sales"
 	}), "active").Return(&KratosIdentity{
 		ID: userID,
 		Traits: map[string]interface{}{
-			"email":       "user@test.com",
-			"name":        "User Test",
-			"companyCode": tenantSlug,
-			"tenant_id":   tenantID,
-			"department":  "Sales",
+			"email":      "user@test.com",
+			"name":       "User Test",
+			"tenant_id":  tenantID,
+			"department": "Sales",
 		},
 		State: "active",
 	}, nil)
@@ -325,7 +325,7 @@ func TestUserGroupService_AddMemberUpsertsLocalReadModelWhenMissing(t *testing.T
 	assert.NoError(t, err)
 	assert.Len(t, mockUserRepo.updatedUsers, 1)
 	assert.Equal(t, userID, mockUserRepo.updatedUsers[0].ID)
-	assert.Equal(t, tenantSlug, mockUserRepo.updatedUsers[0].CompanyCode)
+	assert.Empty(t, mockUserRepo.updatedUsers[0].CompanyCode)
 	assert.NotNil(t, mockUserRepo.updatedUsers[0].TenantID)
 	assert.Equal(t, tenantID, *mockUserRepo.updatedUsers[0].TenantID)
 	assert.Equal(t, "Sales", mockUserRepo.updatedUsers[0].Department)
diff --git a/backend/internal/service/user_projection_sync_service.go b/backend/internal/service/user_projection_sync_service.go
index 8d5abbd8..14487998 100644
--- a/backend/internal/service/user_projection_sync_service.go
+++ b/backend/internal/service/user_projection_sync_service.go
@@ -7,8 +7,6 @@ import (
 	"fmt"
 	"strings"
 	"time"
-
-	"github.com/lib/pq"
 )
 
 type UserProjectionSyncService struct {
@@ -73,11 +71,6 @@ func MapKratosIdentityToLocalUser(identity KratosIdentity) domain.User {
 		grade = ""
 	}
 
-	companyCode := kratosProjectionTraitString(traits, "companyCode")
-	if companyCode == "" {
-		companyCode = kratosProjectionTraitString(traits, "company_code")
-	}
-
 	user := domain.User{
 		ID:              identity.ID,
 		Email:           kratosProjectionTraitString(traits, "email"),
@@ -85,8 +78,6 @@ func MapKratosIdentityToLocalUser(identity KratosIdentity) domain.User {
 		Phone:           kratosProjectionTraitString(traits, "phone_number"),
 		Role:            role,
 		Status:          normalizeProjectionStatus(identity.State),
-		CompanyCode:     companyCode,
-		CompanyCodes:    pq.StringArray(kratosProjectionTraitStringArray(traits, "companyCodes")),
 		Department:      kratosProjectionTraitString(traits, "department"),
 		Grade:           grade,
 		Position:        kratosProjectionTraitString(traits, "position"),
diff --git a/backend/internal/service/user_projection_sync_service_test.go b/backend/internal/service/user_projection_sync_service_test.go
index 4b4e9ee8..cb64c9aa 100644
--- a/backend/internal/service/user_projection_sync_service_test.go
+++ b/backend/internal/service/user_projection_sync_service_test.go
@@ -70,8 +70,8 @@ func TestUserProjectionSyncService_ReconcileReplacesProjectionFromKratos(t *test
 	assert.Equal(t, "one@example.com", repo.replacedUsers[0].Email)
 	assert.Equal(t, "One", repo.replacedUsers[0].Name)
 	assert.Equal(t, "+821012345678", repo.replacedUsers[0].Phone)
-	assert.Equal(t, "saman", repo.replacedUsers[0].CompanyCode)
-	assert.Equal(t, []string{"saman", "group-a"}, []string(repo.replacedUsers[0].CompanyCodes))
+	assert.Empty(t, repo.replacedUsers[0].CompanyCode)
+	assert.Empty(t, repo.replacedUsers[0].CompanyCodes)
 	require.NotNil(t, repo.replacedUsers[0].TenantID)
 	assert.Equal(t, tenantID, *repo.replacedUsers[0].TenantID)
 	assert.Equal(t, "kept", repo.replacedUsers[0].Metadata["customAttr"])
diff --git a/docs/tenant-maintenance-procedures.md b/docs/tenant-maintenance-procedures.md
index 3b6c92ae..08dc218a 100644
--- a/docs/tenant-maintenance-procedures.md
+++ b/docs/tenant-maintenance-procedures.md
@@ -69,6 +69,22 @@ Kratos identity traits도 같은 기준으로 정리한다.
 
 ### Baron users만 실행
 
+Go 구현 경로를 사용하는 권장 명령은 다음과 같다.
+
+```bash
+go run ./cmd/adminctl clear-orphan-user-tenant-memberships --dry-run
+go run ./cmd/adminctl clear-orphan-user-tenant-memberships
+```
+
+컨테이너나 배포 환경에서는 같은 명령을 adminctl 바이너리로 실행한다.
+
+```bash
+adminctl clear-orphan-user-tenant-memberships --dry-run
+adminctl clear-orphan-user-tenant-memberships
+```
+
+SQL만 직접 실행해야 하는 경우에는 다음 스크립트를 사용할 수 있다.
+
 ```bash
 docker exec -i baron_postgres psql -U baron -d baron_sso < scripts/clear_orphan_user_tenant_memberships.sql
 ```
diff --git a/userfront/lib/core/services/auth_proxy_service.dart b/userfront/lib/core/services/auth_proxy_service.dart
index 8d455e11..8adb0e13 100644
--- a/userfront/lib/core/services/auth_proxy_service.dart
+++ b/userfront/lib/core/services/auth_proxy_service.dart
@@ -985,12 +985,12 @@ class AuthProxyService {
 
   static Future<Map<String, dynamic>> checkLoginIDAvailability(
     String loginId, {
-    String? companyCode,
+    String? tenantSlug,
   }) async {
     final url = Uri.parse('$_baseUrl/api/v1/auth/signup/check-login-id');
     final bodyData = {'loginId': loginId};
-    if (companyCode != null && companyCode.isNotEmpty) {
-      bodyData['companyCode'] = companyCode;
+    if (tenantSlug != null && tenantSlug.isNotEmpty) {
+      bodyData['tenantSlug'] = tenantSlug;
     }
     final response = await http.post(
       url,
@@ -1074,7 +1074,7 @@ class AuthProxyService {
     required String name,
     required String phone,
     required String affiliationType,
-    String? companyCode,
+    String? tenantSlug,
     required String department,
     required bool termsAccepted,
   }) async {
@@ -1089,7 +1089,7 @@ class AuthProxyService {
         'name': name,
         'phone': phone,
         'affiliationType': affiliationType,
-        'companyCode': companyCode,
+        'tenantSlug': tenantSlug,
         'department': department,
         'termsAccepted': termsAccepted,
       }),
diff --git a/userfront/lib/features/auth/presentation/signup_screen.dart b/userfront/lib/features/auth/presentation/signup_screen.dart
index 66c607ef..321f011c 100644
--- a/userfront/lib/features/auth/presentation/signup_screen.dart
+++ b/userfront/lib/features/auth/presentation/signup_screen.dart
@@ -333,7 +333,7 @@ class _SignupScreenState extends State<SignupScreen> {
         name: _nameController.text.trim(),
         phone: _phoneController.text.trim(),
         affiliationType: _affiliationType,
-        companyCode: _affiliationType == 'AFFILIATE' ? _companyCode : null,
+        tenantSlug: _affiliationType == 'AFFILIATE' ? _companyCode : null,
         department: _deptController.text.trim(),
         termsAccepted: true,
       );