diff --git a/client/auth.go b/client/auth.go
index 40b9af9f..f1d482e1 100644
--- a/client/auth.go
+++ b/client/auth.go
@@ -22,15 +22,38 @@ type LoginRequest struct {
 // role in each, so callers can build a tenant switcher UI without a
 // follow-up request.
 type LoginResponse struct {
-	Success      bool             `json:"success"`
-	Message      string           `json:"message,omitempty"`
-	User         *AuthUser        `json:"user,omitempty"`
-	ActiveTenant *AuthTenant      `json:"active_tenant,omitempty"`
+	Success bool      `json:"success"`
+	Message string    `json:"message,omitempty"`
+	User    *AuthUser `json:"user,omitempty"`
+	// ActiveTenant is the tenant whose ID is encoded in the JWT. Use
+	// this field; Tenant is preserved as a compatibility alias only.
+	ActiveTenant *AuthTenant `json:"active_tenant,omitempty"`
+	// Tenant is a deprecated alias kept so SDK callers compiled against
+	// the pre-RBAC release continue to find the field by name. The
+	// server emits active_tenant; this field is populated on the client
+	// side by GetTenant() and will be removed in a future major release.
+	//
+	// Deprecated: use ActiveTenant.
+	Tenant       *AuthTenant      `json:"-"`
 	Memberships  []AuthMembership `json:"memberships,omitempty"`
 	Token        string           `json:"token,omitempty"`
 	RefreshToken string           `json:"refresh_token,omitempty"`
 }
 
+// GetTenant returns the active tenant, preferring ActiveTenant and
+// falling back to the deprecated Tenant alias. SDK code should prefer
+// reading ActiveTenant directly; this helper exists to keep callers that
+// only know about the old field name compiling and working.
+func (r *LoginResponse) GetTenant() *AuthTenant {
+	if r == nil {
+		return nil
+	}
+	if r.ActiveTenant != nil {
+		return r.ActiveTenant
+	}
+	return r.Tenant
+}
+
 // AuthMembership pairs a tenant ID with the user's role in that tenant.
 // Mirrors types.Membership on the server.
 type AuthMembership struct {
@@ -97,6 +120,9 @@ func (c *Client) Login(ctx context.Context, req LoginRequest) (*LoginResponse, e
 	if err := parseResponse(resp, &out); err != nil {
 		return nil, err
 	}
+	// 后端已将 tenant 字段重命名为 active_tenant；为照顾仍读取旧字段名的下游
+	// 调用者，在反序列化后镜像一份到 Tenant 上。两者总是指向同一指针。
+	out.Tenant = out.ActiveTenant
 	return &out, nil
 }
 
diff --git a/frontend/src/stores/auth.ts b/frontend/src/stores/auth.ts
index 4f0d161e..22899cac 100644
--- a/frontend/src/stores/auth.ts
+++ b/frontend/src/stores/auth.ts
@@ -59,6 +59,13 @@ export const useAuthStore = defineStore('auth', () => {
   // (defaulting to '' when memberships have not been loaded). Used by
   // role-aware UI gating; PR 2 wires backend enforcement, PR 3 uses
   // this for menu/button visibility.
+  //
+  // SECURITY: This value is read from localStorage (`weknora_memberships`)
+  // and therefore MUST be treated as UI-rendering-only — any user can
+  // tamper with localStorage and grant themselves "owner" here. All real
+  // authorisation decisions live on the server (auth middleware resolves
+  // the role from tenant_members on every request). Never branch
+  // security-sensitive logic on this value alone.
   const currentTenantRole = computed(() => {
     const tid = tenant.value?.id ? String(tenant.value.id) : ''
     if (!tid) return ''
diff --git a/internal/application/repository/tenant.go b/internal/application/repository/tenant.go
index b5978279..dfb7a2d5 100644
--- a/internal/application/repository/tenant.go
+++ b/internal/application/repository/tenant.go
@@ -45,6 +45,27 @@ func (r *tenantRepository) GetTenantByID(ctx context.Context, id uint64) (*types
 	return &tenant, nil
 }
 
+// GetTenantsByIDs batches GetTenantByID with a single IN-list query.
+// Returns a map keyed by tenant ID; missing rows are simply absent from
+// the map (no error). An empty input slice short-circuits to an empty map
+// without hitting the database.
+func (r *tenantRepository) GetTenantsByIDs(ctx context.Context, ids []uint64) (map[uint64]*types.Tenant, error) {
+	if len(ids) == 0 {
+		return map[uint64]*types.Tenant{}, nil
+	}
+	var tenants []*types.Tenant
+	if err := r.db.WithContext(ctx).Where("id IN ?", ids).Find(&tenants).Error; err != nil {
+		return nil, err
+	}
+	out := make(map[uint64]*types.Tenant, len(tenants))
+	for _, t := range tenants {
+		if t != nil {
+			out[t.ID] = t
+		}
+	}
+	return out, nil
+}
+
 // ListTenants lists all tenants
 func (r *tenantRepository) ListTenants(ctx context.Context) ([]*types.Tenant, error) {
 	var tenants []*types.Tenant
diff --git a/internal/application/repository/tenant_member.go b/internal/application/repository/tenant_member.go
index 97817e79..b8c7a782 100644
--- a/internal/application/repository/tenant_member.go
+++ b/internal/application/repository/tenant_member.go
@@ -115,13 +115,24 @@ func (r *tenantMemberRepository) CountActiveOwners(ctx context.Context, tenantID
 }
 
 // HasAnyMembers reports whether the tenant has at least one active
-// membership row.
+// membership row. Uses a LIMIT 1 SELECT (instead of COUNT(*)) so the query
+// short-circuits after the first match — important because this is on the
+// auth middleware's hot path for users without a cached membership.
 func (r *tenantMemberRepository) HasAnyMembers(ctx context.Context, tenantID uint64) (bool, error) {
-	var count int64
+	var probe struct {
+		ID uint64
+	}
 	err := r.db.WithContext(ctx).
 		Model(&types.TenantMember{}).
+		Select("id").
 		Where("tenant_id = ? AND status = ?", tenantID, types.TenantMemberStatusActive).
 		Limit(1).
-		Count(&count).Error
-	return count > 0, err
+		Take(&probe).Error
+	if err != nil {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			return false, nil
+		}
+		return false, err
+	}
+	return true, nil
 }
diff --git a/internal/application/service/tenant.go b/internal/application/service/tenant.go
index 1e115e30..5e4201b3 100644
--- a/internal/application/service/tenant.go
+++ b/internal/application/service/tenant.go
@@ -118,6 +118,11 @@ func (s *tenantService) GetTenantByID(ctx context.Context, id uint64) (*types.Te
 	return tenant, nil
 }
 
+// GetTenantsByIDs batches GetTenantByID; returns a map keyed by tenant ID.
+func (s *tenantService) GetTenantsByIDs(ctx context.Context, ids []uint64) (map[uint64]*types.Tenant, error) {
+	return s.repo.GetTenantsByIDs(ctx, ids)
+}
+
 // ListTenants retrieves a list of all tenants
 func (s *tenantService) ListTenants(ctx context.Context) ([]*types.Tenant, error) {
 	tenants, err := s.repo.ListTenants(ctx)
diff --git a/internal/application/service/tenant_member_test.go b/internal/application/service/tenant_member_test.go
new file mode 100644
index 00000000..5f300339
--- /dev/null
+++ b/internal/application/service/tenant_member_test.go
@@ -0,0 +1,292 @@
+package service
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/Tencent/WeKnora/internal/types"
+	"github.com/Tencent/WeKnora/internal/types/interfaces"
+)
+
+// fakeTenantMemberRepo is an in-memory implementation of
+// interfaces.TenantMemberRepository for unit tests. It is intentionally
+// not safe for concurrent use; tests should drive it sequentially.
+type fakeTenantMemberRepo struct {
+	rows []*types.TenantMember
+	// nextID is incremented on Create to populate the surrogate PK.
+	nextID uint64
+	// failGet, failHasAny etc. let tests inject transient errors on the
+	// matching method to exercise error paths.
+	failGet           error
+	failHasAny        error
+	failCountOwners   error
+	failUpdateRole    error
+	failSoftDelete    error
+	failCreate        error
+}
+
+func newFakeRepo() *fakeTenantMemberRepo { return &fakeTenantMemberRepo{} }
+
+func (r *fakeTenantMemberRepo) Create(ctx context.Context, m *types.TenantMember) error {
+	if r.failCreate != nil {
+		return r.failCreate
+	}
+	r.nextID++
+	m.ID = r.nextID
+	// Mirror the partial unique index on (user_id, tenant_id) for
+	// active rows so tests can exercise duplicate-insert behaviour.
+	for _, e := range r.rows {
+		if e.UserID == m.UserID && e.TenantID == m.TenantID && e.DeletedAt.Valid == false {
+			return errors.New("duplicate active membership")
+		}
+	}
+	cp := *m
+	r.rows = append(r.rows, &cp)
+	return nil
+}
+
+func (r *fakeTenantMemberRepo) Get(ctx context.Context, userID string, tenantID uint64) (*types.TenantMember, error) {
+	if r.failGet != nil {
+		return nil, r.failGet
+	}
+	for _, e := range r.rows {
+		if e.UserID == userID && e.TenantID == tenantID && !e.DeletedAt.Valid {
+			cp := *e
+			return &cp, nil
+		}
+	}
+	return nil, nil
+}
+
+func (r *fakeTenantMemberRepo) ListByUser(ctx context.Context, userID string) ([]*types.TenantMember, error) {
+	var out []*types.TenantMember
+	for _, e := range r.rows {
+		if e.UserID == userID && !e.DeletedAt.Valid {
+			cp := *e
+			out = append(out, &cp)
+		}
+	}
+	return out, nil
+}
+
+func (r *fakeTenantMemberRepo) ListByTenant(ctx context.Context, tenantID uint64) ([]*types.TenantMember, error) {
+	var out []*types.TenantMember
+	for _, e := range r.rows {
+		if e.TenantID == tenantID && !e.DeletedAt.Valid {
+			cp := *e
+			out = append(out, &cp)
+		}
+	}
+	return out, nil
+}
+
+func (r *fakeTenantMemberRepo) UpdateRole(ctx context.Context, userID string, tenantID uint64, role types.TenantRole) error {
+	if r.failUpdateRole != nil {
+		return r.failUpdateRole
+	}
+	for _, e := range r.rows {
+		if e.UserID == userID && e.TenantID == tenantID && !e.DeletedAt.Valid {
+			e.Role = role
+			return nil
+		}
+	}
+	return errors.New("not found")
+}
+
+func (r *fakeTenantMemberRepo) SoftDelete(ctx context.Context, userID string, tenantID uint64) error {
+	if r.failSoftDelete != nil {
+		return r.failSoftDelete
+	}
+	for _, e := range r.rows {
+		if e.UserID == userID && e.TenantID == tenantID && !e.DeletedAt.Valid {
+			e.DeletedAt.Valid = true
+			return nil
+		}
+	}
+	return errors.New("not found")
+}
+
+func (r *fakeTenantMemberRepo) CountActiveOwners(ctx context.Context, tenantID uint64) (int64, error) {
+	if r.failCountOwners != nil {
+		return 0, r.failCountOwners
+	}
+	var n int64
+	for _, e := range r.rows {
+		if e.TenantID == tenantID && !e.DeletedAt.Valid &&
+			e.Role == types.TenantRoleOwner && e.Status == types.TenantMemberStatusActive {
+			n++
+		}
+	}
+	return n, nil
+}
+
+func (r *fakeTenantMemberRepo) HasAnyMembers(ctx context.Context, tenantID uint64) (bool, error) {
+	if r.failHasAny != nil {
+		return false, r.failHasAny
+	}
+	for _, e := range r.rows {
+		if e.TenantID == tenantID && !e.DeletedAt.Valid && e.Status == types.TenantMemberStatusActive {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+// Compile-time guard so the test stays in sync with the interface.
+var _ interfaces.TenantMemberRepository = (*fakeTenantMemberRepo)(nil)
+
+func newServiceWithRepo() (interfaces.TenantMemberService, *fakeTenantMemberRepo) {
+	r := newFakeRepo()
+	return NewTenantMemberService(r), r
+}
+
+func TestTenantMemberService_AddMember_RejectsInvalidRole(t *testing.T) {
+	svc, _ := newServiceWithRepo()
+	_, err := svc.AddMember(context.Background(), "u1", 1, types.TenantRole("nonsense"), nil)
+	if !errors.Is(err, ErrInvalidTenantRole) {
+		t.Fatalf("want ErrInvalidTenantRole, got %v", err)
+	}
+}
+
+func TestTenantMemberService_AddMember_RejectsDuplicate(t *testing.T) {
+	svc, _ := newServiceWithRepo()
+	ctx := context.Background()
+	if _, err := svc.AddMember(ctx, "u1", 1, types.TenantRoleContributor, nil); err != nil {
+		t.Fatalf("first AddMember: %v", err)
+	}
+	_, err := svc.AddMember(ctx, "u1", 1, types.TenantRoleContributor, nil)
+	if !errors.Is(err, ErrMembershipAlreadyExists) {
+		t.Fatalf("want ErrMembershipAlreadyExists, got %v", err)
+	}
+}
+
+func TestTenantMemberService_EnsureOwner_Idempotent(t *testing.T) {
+	svc, repo := newServiceWithRepo()
+	ctx := context.Background()
+	first, err := svc.EnsureOwner(ctx, "u1", 1)
+	if err != nil {
+		t.Fatalf("first EnsureOwner: %v", err)
+	}
+	second, err := svc.EnsureOwner(ctx, "u1", 1)
+	if err != nil {
+		t.Fatalf("second EnsureOwner: %v", err)
+	}
+	if first.ID != second.ID {
+		t.Fatalf("EnsureOwner not idempotent: %d vs %d", first.ID, second.ID)
+	}
+	if len(repo.rows) != 1 {
+		t.Fatalf("want exactly 1 row after idempotent EnsureOwner, got %d", len(repo.rows))
+	}
+}
+
+func TestTenantMemberService_UpdateRole_BlocksDemotingLastOwner(t *testing.T) {
+	svc, _ := newServiceWithRepo()
+	ctx := context.Background()
+	if _, err := svc.EnsureOwner(ctx, "owner", 1); err != nil {
+		t.Fatalf("seed: %v", err)
+	}
+	err := svc.UpdateRole(ctx, "owner", 1, types.TenantRoleAdmin)
+	if !errors.Is(err, ErrLastOwner) {
+		t.Fatalf("want ErrLastOwner when demoting last owner, got %v", err)
+	}
+}
+
+func TestTenantMemberService_UpdateRole_AllowsDemotionWhenOtherOwnerExists(t *testing.T) {
+	svc, _ := newServiceWithRepo()
+	ctx := context.Background()
+	if _, err := svc.EnsureOwner(ctx, "owner1", 1); err != nil {
+		t.Fatalf("seed1: %v", err)
+	}
+	if _, err := svc.AddMember(ctx, "owner2", 1, types.TenantRoleOwner, nil); err != nil {
+		t.Fatalf("seed2: %v", err)
+	}
+	if err := svc.UpdateRole(ctx, "owner1", 1, types.TenantRoleAdmin); err != nil {
+		t.Fatalf("UpdateRole: %v", err)
+	}
+}
+
+func TestTenantMemberService_UpdateRole_NoopOnSameRole(t *testing.T) {
+	svc, _ := newServiceWithRepo()
+	ctx := context.Background()
+	if _, err := svc.EnsureOwner(ctx, "owner", 1); err != nil {
+		t.Fatalf("seed: %v", err)
+	}
+	// 把"还是 Owner"作为 no-op 处理，必须不触发 ErrLastOwner（同一角色不算降级）。
+	if err := svc.UpdateRole(ctx, "owner", 1, types.TenantRoleOwner); err != nil {
+		t.Fatalf("UpdateRole same role should be a no-op, got %v", err)
+	}
+}
+
+func TestTenantMemberService_UpdateRole_RejectsInvalidRole(t *testing.T) {
+	svc, _ := newServiceWithRepo()
+	ctx := context.Background()
+	if _, err := svc.EnsureOwner(ctx, "owner", 1); err != nil {
+		t.Fatalf("seed: %v", err)
+	}
+	if err := svc.UpdateRole(ctx, "owner", 1, types.TenantRole("nope")); !errors.Is(err, ErrInvalidTenantRole) {
+		t.Fatalf("want ErrInvalidTenantRole, got %v", err)
+	}
+}
+
+func TestTenantMemberService_UpdateRole_ReturnsNotFound(t *testing.T) {
+	svc, _ := newServiceWithRepo()
+	if err := svc.UpdateRole(context.Background(), "ghost", 1, types.TenantRoleAdmin); !errors.Is(err, ErrMembershipNotFound) {
+		t.Fatalf("want ErrMembershipNotFound, got %v", err)
+	}
+}
+
+func TestTenantMemberService_RemoveMember_BlocksLastOwner(t *testing.T) {
+	svc, _ := newServiceWithRepo()
+	ctx := context.Background()
+	if _, err := svc.EnsureOwner(ctx, "owner", 1); err != nil {
+		t.Fatalf("seed: %v", err)
+	}
+	if err := svc.RemoveMember(ctx, "owner", 1); !errors.Is(err, ErrLastOwner) {
+		t.Fatalf("want ErrLastOwner, got %v", err)
+	}
+}
+
+func TestTenantMemberService_RemoveMember_AllowsContributorRemoval(t *testing.T) {
+	svc, _ := newServiceWithRepo()
+	ctx := context.Background()
+	if _, err := svc.EnsureOwner(ctx, "owner", 1); err != nil {
+		t.Fatalf("seed owner: %v", err)
+	}
+	if _, err := svc.AddMember(ctx, "contrib", 1, types.TenantRoleContributor, nil); err != nil {
+		t.Fatalf("seed contributor: %v", err)
+	}
+	if err := svc.RemoveMember(ctx, "contrib", 1); err != nil {
+		t.Fatalf("RemoveMember: %v", err)
+	}
+	got, _ := svc.GetMembership(ctx, "contrib", 1)
+	if got != nil {
+		t.Fatalf("contributor should be soft-deleted, got %+v", got)
+	}
+}
+
+func TestTenantMemberService_RemoveMember_ReturnsNotFound(t *testing.T) {
+	svc, _ := newServiceWithRepo()
+	if err := svc.RemoveMember(context.Background(), "ghost", 1); !errors.Is(err, ErrMembershipNotFound) {
+		t.Fatalf("want ErrMembershipNotFound, got %v", err)
+	}
+}
+
+func TestTenantRole_HasPermission(t *testing.T) {
+	cases := []struct {
+		caller   types.TenantRole
+		required types.TenantRole
+		want     bool
+	}{
+		{types.TenantRoleOwner, types.TenantRoleAdmin, true},
+		{types.TenantRoleAdmin, types.TenantRoleOwner, false},
+		{types.TenantRoleContributor, types.TenantRoleViewer, true},
+		{types.TenantRoleViewer, types.TenantRoleContributor, false},
+		{types.TenantRole("bogus"), types.TenantRoleViewer, false},
+	}
+	for _, c := range cases {
+		if got := c.caller.HasPermission(c.required); got != c.want {
+			t.Errorf("HasPermission(%s, %s) = %v, want %v", c.caller, c.required, got, c.want)
+		}
+	}
+}
diff --git a/internal/application/service/user.go b/internal/application/service/user.go
index 6127636d..396d74b4 100644
--- a/internal/application/service/user.go
+++ b/internal/application/service/user.go
@@ -240,13 +240,21 @@ func (s *userService) Login(ctx context.Context, req *types.LoginRequest) (*type
 // part of the dependency graph), this falls back to a single synthesized
 // row built from User.TenantID + the active tenant so callers always get
 // at least one entry.
+func (s *userService) BuildLoginMemberships(
+	ctx context.Context,
+	user *types.User,
+	activeTenant *types.Tenant,
+) []types.Membership {
+	return s.buildMembershipsForUser(ctx, user, activeTenant)
+}
+
 func (s *userService) buildMembershipsForUser(
 	ctx context.Context,
 	user *types.User,
 	activeTenant *types.Tenant,
 ) []types.Membership {
 	if user == nil {
-		return nil
+		return []types.Membership{}
 	}
 	if s.memberService == nil {
 		return synthFallbackMembership(user, activeTenant)
@@ -259,6 +267,27 @@ func (s *userService) buildMembershipsForUser(
 	if len(rows) == 0 {
 		return synthFallbackMembership(user, activeTenant)
 	}
+	// 收集需要批量查询名称的 tenant id（跳过 activeTenant 因为它已经在手）。
+	needsLookup := make([]uint64, 0, len(rows))
+	for _, m := range rows {
+		if m == nil || m.Status != types.TenantMemberStatusActive {
+			continue
+		}
+		if activeTenant != nil && m.TenantID == activeTenant.ID {
+			continue
+		}
+		needsLookup = append(needsLookup, m.TenantID)
+	}
+	tenantByID := map[uint64]*types.Tenant{}
+	if len(needsLookup) > 0 {
+		if found, terr := s.tenantService.GetTenantsByIDs(ctx, needsLookup); terr == nil {
+			tenantByID = found
+		} else {
+			logger.Warnf(ctx, "Failed to batch-load tenants for memberships (user=%s): %v",
+				user.ID, terr)
+		}
+	}
+
 	out := make([]types.Membership, 0, len(rows))
 	for _, m := range rows {
 		if m == nil || m.Status != types.TenantMemberStatusActive {
@@ -267,7 +296,7 @@ func (s *userService) buildMembershipsForUser(
 		name := ""
 		if activeTenant != nil && m.TenantID == activeTenant.ID {
 			name = activeTenant.Name
-		} else if t, err := s.tenantService.GetTenantByID(ctx, m.TenantID); err == nil && t != nil {
+		} else if t, ok := tenantByID[m.TenantID]; ok && t != nil {
 			name = t.Name
 		}
 		out = append(out, types.Membership{
@@ -287,9 +316,21 @@ func (s *userService) buildMembershipsForUser(
 // populated yet (e.g. during the rollout window where the migration has
 // run but the auth middleware's auto-promotion hasn't fired) so the
 // response shape stays consistent.
+//
+// The fallback role is intentionally TenantRoleViewer (least privilege):
+// the login response only feeds UI rendering, and the backend re-derives
+// the real role from tenant_members on every request. If membership data
+// is temporarily unavailable, showing a Viewer UI is preferable to
+// granting a misleading Owner UI that would surface admin controls the
+// backend will then 403. Once the membership row appears (via the auth
+// middleware's home-tenant auto-promotion or an admin invitation) the
+// next /auth/me-style refresh will upgrade the UI to the real role.
 func synthFallbackMembership(user *types.User, activeTenant *types.Tenant) []types.Membership {
 	if user == nil || user.TenantID == 0 {
-		return nil
+		// Always return a non-nil slice so the login response carries an
+		// empty array rather than `null`, preserving the documented
+		// "always populated" contract on LoginResponse.Memberships.
+		return []types.Membership{}
 	}
 	name := ""
 	if activeTenant != nil && activeTenant.ID == user.TenantID {
@@ -298,7 +339,7 @@ func synthFallbackMembership(user *types.User, activeTenant *types.Tenant) []typ
 	return []types.Membership{{
 		TenantID:   user.TenantID,
 		TenantName: name,
-		Role:       types.TenantRoleOwner, // safe default for legacy single-tenant users
+		Role:       types.TenantRoleViewer,
 	}}
 }
 
@@ -396,9 +437,25 @@ func (s *userService) LoginWithOIDC(ctx context.Context, code, redirectURI strin
 		return nil, fmt.Errorf("failed to generate local tokens: %w", err)
 	}
 
+	// 拉取 tenant + memberships，让 OIDC 登录的返回结构与本地登录一致，
+	// 前端无须为 OIDC 单独走一次 /auth/me 才能拿到角色。
+	var tenant *types.Tenant
+	if user.TenantID > 0 {
+		if t, terr := s.tenantService.GetTenantByID(ctx, user.TenantID); terr == nil {
+			tenant = t
+		} else {
+			logger.Warnf(ctx, "OIDC login: failed to load tenant %d for user %s: %v",
+				user.TenantID, user.ID, terr)
+		}
+	}
+	memberships := s.buildMembershipsForUser(ctx, user, tenant)
+
 	return &types.OIDCCallbackResponse{
 		Success:      true,
 		Message:      "登录成功",
+		User:         user,
+		Tenant:       tenant,
+		Memberships:  memberships,
 		Token:        accessToken,
 		RefreshToken: refreshToken,
 		IsNewUser:    isNewUser,
diff --git a/internal/handler/auth.go b/internal/handler/auth.go
index 1972501a..1ab5cb56 100644
--- a/internal/handler/auth.go
+++ b/internal/handler/auth.go
@@ -444,11 +444,15 @@ func (h *AuthHandler) GetCurrentUser(c *gin.Context) {
 	}
 	userInfo := user.ToUserInfo()
 	userInfo.CanAccessAllTenants = user.CanAccessAllTenants && h.configInfo.Tenant.EnableCrossTenantAccess
+	// 同步返回当前用户的 memberships，让前端在页面刷新（仅命中 /auth/me）
+	// 后也能恢复 currentTenantRole，避免角色信息只在 login 那一刻可用。
+	memberships := h.userService.BuildLoginMemberships(ctx, user, tenant)
 	c.JSON(http.StatusOK, gin.H{
 		"success": true,
 		"data": gin.H{
-			"user":   userInfo,
-			"tenant": tenant,
+			"user":        userInfo,
+			"tenant":      tenant,
+			"memberships": memberships,
 		},
 	})
 }
diff --git a/internal/middleware/auth.go b/internal/middleware/auth.go
index 9a81742f..9e142668 100644
--- a/internal/middleware/auth.go
+++ b/internal/middleware/auth.go
@@ -12,6 +12,7 @@ import (
 	"strings"
 
 	"github.com/Tencent/WeKnora/internal/config"
+	"github.com/Tencent/WeKnora/internal/logger"
 	"github.com/Tencent/WeKnora/internal/types"
 	"github.com/Tencent/WeKnora/internal/types/interfaces"
 	"github.com/gin-gonic/gin"
@@ -143,7 +144,8 @@ func Auth(
 				if !ok {
 					// 强制 RBAC 时，缺少 active membership 即拒绝；fail-open 路径已在
 					// resolveTenantRole 内部处理。
-					log.Printf("User %s has no active membership in tenant %d", user.ID, targetTenantID)
+					logger.Warnf(c.Request.Context(),
+						"User %s has no active membership in tenant %d", user.ID, targetTenantID)
 					c.JSON(http.StatusForbidden, gin.H{
 						"error": "Forbidden: not a member of the target tenant",
 					})
@@ -250,10 +252,17 @@ func Auth(
 //  2. Cross-tenant superuser switch (X-Tenant-ID with CanAccessAllTenants=true)
 //     → grant Admin in the target tenant. Org admins are intentionally not
 //     promoted to Owner; tenant deletion / API-key rotation should always
-//     stay with a real Owner inside the target tenant.
-//  3. No membership but the tenant currently has zero active members
-//     (an API-key-only orphan tenant gaining its first human member) →
-//     auto-promote the user to Owner.
+//     stay with a real Owner inside the target tenant. Cross-tenant access
+//     is also never allowed to trigger the orphan-tenant auto-promotion
+//     below — a superuser only visits, never claims ownership.
+//  3. No membership but the tenant currently has zero active members AND
+//     the caller is authenticating into their own home tenant (i.e.
+//     targetTenantID == user.TenantID and this is not a cross-tenant
+//     switch). This is the API-key-only orphan-tenant self-heal path:
+//     the registrant becomes Owner of the tenant their own user record
+//     points to. Any other path (cross-tenant switch, JWT minted for a
+//     foreign tenant, etc.) is intentionally excluded to avoid silent
+//     ownership grabs.
 //  4. Otherwise → return ok=false. Caller decides:
 //     - When EnableRBAC=true (or cfg unavailable): treat as 403.
 //     - When EnableRBAC=false: fail open with Admin so existing deployments
@@ -277,25 +286,38 @@ func resolveTenantRole(
 		return member.Role, true
 	}
 	if err != nil {
-		log.Printf("tenant_members lookup failed user=%s tenant=%d: %v", user.ID, targetTenantID, err)
-		// Fall through to the fail-open branch below; treat lookup errors
-		// the same as "no membership found" so a transient DB hiccup
-		// doesn't lock everyone out.
+		logger.Warnf(ctx, "tenant_members lookup failed user=%s tenant=%d: %v",
+			user.ID, targetTenantID, err)
+		// Fall through; treat lookup errors the same as "no membership
+		// found" so a transient DB hiccup doesn't lock everyone out.
 	}
 
-	// 2. 跨租户超管直通：CanAccessAllTenants 用户切到别的租户时不强制要求 membership
+	// 2. 跨租户超管直通：CanAccessAllTenants 用户切到别的租户时不强制要求 membership。
+	//    注意：这里只授予临时 Admin 角色，不写入 tenant_members，避免"看一眼别人租户"
+	//    意外升级为持久化所有权。
 	if crossTenantSwitch && user.CanAccessAllTenants {
 		return types.TenantRoleAdmin, true
 	}
 
-	// 3. 孤儿租户自愈：API-key-only 租户首个登录的人类用户自动成为 Owner
-	hasAny, anyErr := memberService.HasAnyMembers(ctx, targetTenantID)
-	if anyErr == nil && !hasAny {
-		if _, e := memberService.AddMember(ctx, user.ID, targetTenantID, types.TenantRoleOwner, nil); e == nil {
-			log.Printf("Auto-promoted user %s to Owner of orphan tenant %d", user.ID, targetTenantID)
-			return types.TenantRoleOwner, true
-		} else {
-			log.Printf("Failed to auto-promote user %s in tenant %d: %v", user.ID, targetTenantID, e)
+	// 3. 孤儿租户自愈：仅当用户登录的是自己的 home tenant、且该租户尚无任何活跃成员时
+	//    允许自动晋升为 Owner。跨租户 switch / JWT 指向他人租户的场景一律不进入此分支，
+	//    防止越权获得他人租户的 Owner 权限。
+	isHomeTenant := !crossTenantSwitch && targetTenantID == user.TenantID
+	if isHomeTenant {
+		hasAny, anyErr := memberService.HasAnyMembers(ctx, targetTenantID)
+		if anyErr == nil && !hasAny {
+			if _, e := memberService.AddMember(
+				ctx, user.ID, targetTenantID, types.TenantRoleOwner, nil,
+			); e == nil {
+				logger.Infof(ctx,
+					"[audit] Auto-promoted user %s to Owner of orphan tenant %d (home_tenant=true)",
+					user.ID, targetTenantID,
+				)
+				return types.TenantRoleOwner, true
+			} else {
+				logger.Warnf(ctx, "Failed to auto-promote user %s in tenant %d: %v",
+					user.ID, targetTenantID, e)
+			}
 		}
 	}
 
@@ -303,7 +325,7 @@ func resolveTenantRole(
 	if cfg != nil && cfg.Tenant != nil && cfg.Tenant.EnableRBAC {
 		return "", false
 	}
-	// fail-open 期间保持现有行为（每个登录用户在自己租户里都是“管理员”）。
+	// fail-open 期间保持现有行为（每个登录用户在自己租户里都是"管理员"）。
 	return types.TenantRoleAdmin, true
 }
 
diff --git a/internal/middleware/auth_role_test.go b/internal/middleware/auth_role_test.go
new file mode 100644
index 00000000..f5a38121
--- /dev/null
+++ b/internal/middleware/auth_role_test.go
@@ -0,0 +1,254 @@
+package middleware
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/Tencent/WeKnora/internal/config"
+	"github.com/Tencent/WeKnora/internal/types"
+	"github.com/Tencent/WeKnora/internal/types/interfaces"
+)
+
+// fakeMemberService is a hand-rolled stand-in for
+// interfaces.TenantMemberService. It backs Get/HasAnyMembers/AddMember
+// with two in-memory maps and lets each test seed exactly the rows it
+// cares about. Other interface methods are stubbed because resolveTenantRole
+// never touches them.
+type fakeMemberService struct {
+	members map[string]*types.TenantMember // key = userID + "|" + tenantID
+	// addCalls records every AddMember invocation so tests can assert
+	// that resolveTenantRole did (or didn't) attempt to auto-promote.
+	addCalls []struct {
+		UserID   string
+		TenantID uint64
+		Role     types.TenantRole
+	}
+	failGet     error
+	failHasAny  error
+	failAdd     error
+	// 阻止 auto-promote 把 hasAny 翻面：默认 AddMember 成功也会写入 members map。
+}
+
+func newFakeMemberService() *fakeMemberService {
+	return &fakeMemberService{members: map[string]*types.TenantMember{}}
+}
+
+func memberKey(u string, t uint64) string {
+	return u + "|" + uintToStr(t)
+}
+
+func uintToStr(t uint64) string {
+	// 简单数字转字符串，避免引入额外依赖。
+	if t == 0 {
+		return "0"
+	}
+	var buf [20]byte
+	i := len(buf)
+	for t > 0 {
+		i--
+		buf[i] = byte('0' + t%10)
+		t /= 10
+	}
+	return string(buf[i:])
+}
+
+func (f *fakeMemberService) seedActive(userID string, tenantID uint64, role types.TenantRole) {
+	f.members[memberKey(userID, tenantID)] = &types.TenantMember{
+		UserID:   userID,
+		TenantID: tenantID,
+		Role:     role,
+		Status:   types.TenantMemberStatusActive,
+	}
+}
+
+func (f *fakeMemberService) AddMember(
+	ctx context.Context, userID string, tenantID uint64, role types.TenantRole, invitedBy *string,
+) (*types.TenantMember, error) {
+	f.addCalls = append(f.addCalls, struct {
+		UserID   string
+		TenantID uint64
+		Role     types.TenantRole
+	}{userID, tenantID, role})
+	if f.failAdd != nil {
+		return nil, f.failAdd
+	}
+	m := &types.TenantMember{UserID: userID, TenantID: tenantID, Role: role, Status: types.TenantMemberStatusActive}
+	f.members[memberKey(userID, tenantID)] = m
+	return m, nil
+}
+
+func (f *fakeMemberService) EnsureOwner(
+	ctx context.Context, userID string, tenantID uint64,
+) (*types.TenantMember, error) {
+	if existing, ok := f.members[memberKey(userID, tenantID)]; ok {
+		return existing, nil
+	}
+	return f.AddMember(ctx, userID, tenantID, types.TenantRoleOwner, nil)
+}
+
+func (f *fakeMemberService) GetMembership(
+	ctx context.Context, userID string, tenantID uint64,
+) (*types.TenantMember, error) {
+	if f.failGet != nil {
+		return nil, f.failGet
+	}
+	m, ok := f.members[memberKey(userID, tenantID)]
+	if !ok {
+		return nil, nil
+	}
+	cp := *m
+	return &cp, nil
+}
+
+func (f *fakeMemberService) ListByUser(ctx context.Context, userID string) ([]*types.TenantMember, error) {
+	return nil, nil
+}
+func (f *fakeMemberService) ListByTenant(ctx context.Context, tenantID uint64) ([]*types.TenantMember, error) {
+	return nil, nil
+}
+func (f *fakeMemberService) HasAnyMembers(ctx context.Context, tenantID uint64) (bool, error) {
+	if f.failHasAny != nil {
+		return false, f.failHasAny
+	}
+	for _, m := range f.members {
+		if m.TenantID == tenantID && m.Status == types.TenantMemberStatusActive {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+func (f *fakeMemberService) UpdateRole(
+	ctx context.Context, userID string, tenantID uint64, newRole types.TenantRole,
+) error {
+	return nil
+}
+func (f *fakeMemberService) RemoveMember(ctx context.Context, userID string, tenantID uint64) error {
+	return nil
+}
+
+var _ interfaces.TenantMemberService = (*fakeMemberService)(nil)
+
+func cfgWithRBAC(enabled bool) *config.Config {
+	return &config.Config{Tenant: &config.TenantConfig{EnableRBAC: enabled}}
+}
+
+func TestResolveTenantRole_ActiveMembershipWins(t *testing.T) {
+	svc := newFakeMemberService()
+	svc.seedActive("u1", 10, types.TenantRoleContributor)
+
+	got, ok := resolveTenantRole(context.Background(), svc,
+		&types.User{ID: "u1", TenantID: 10}, 10, false, cfgWithRBAC(true))
+	if !ok || got != types.TenantRoleContributor {
+		t.Fatalf("got (%v, %v), want (contributor, true)", got, ok)
+	}
+	if len(svc.addCalls) != 0 {
+		t.Fatalf("must not auto-promote when membership exists, got %d AddMember calls", len(svc.addCalls))
+	}
+}
+
+func TestResolveTenantRole_CrossTenantSuperuserGetsAdmin_NoAutoPromote(t *testing.T) {
+	// 回归 H1：跨租户超管 switch 到他人租户时，绝对不能写入 tenant_members。
+	svc := newFakeMemberService()
+	user := &types.User{ID: "super", TenantID: 1, CanAccessAllTenants: true}
+
+	got, ok := resolveTenantRole(context.Background(), svc, user, 99, true, cfgWithRBAC(true))
+	if !ok || got != types.TenantRoleAdmin {
+		t.Fatalf("got (%v, %v), want (admin, true)", got, ok)
+	}
+	if len(svc.addCalls) != 0 {
+		t.Fatalf("cross-tenant superuser must not trigger auto-promote, got %+v", svc.addCalls)
+	}
+}
+
+func TestResolveTenantRole_AutoPromoteRequiresHomeTenant(t *testing.T) {
+	// 回归 H1：即便 target 是孤儿租户，只要不是用户自己的 home tenant，
+	// 就不能 auto-promote 为 Owner。
+	svc := newFakeMemberService() // 空 — 任何租户都是孤儿
+	user := &types.User{ID: "u1", TenantID: 1, CanAccessAllTenants: true}
+
+	got, ok := resolveTenantRole(context.Background(), svc, user, 42, true, cfgWithRBAC(true))
+	if !ok || got != types.TenantRoleAdmin {
+		t.Fatalf("cross-tenant superuser should still get visitor Admin, got (%v, %v)", got, ok)
+	}
+	if len(svc.addCalls) != 0 {
+		t.Fatalf("auto-promote must skip cross-tenant target, got %+v", svc.addCalls)
+	}
+}
+
+func TestResolveTenantRole_AutoPromoteHomeTenant(t *testing.T) {
+	// home tenant + 孤儿租户 + 非 switch → 允许 auto-promote 为 Owner。
+	svc := newFakeMemberService()
+	user := &types.User{ID: "u1", TenantID: 7}
+
+	got, ok := resolveTenantRole(context.Background(), svc, user, 7, false, cfgWithRBAC(true))
+	if !ok || got != types.TenantRoleOwner {
+		t.Fatalf("got (%v, %v), want (owner, true)", got, ok)
+	}
+	if len(svc.addCalls) != 1 || svc.addCalls[0].Role != types.TenantRoleOwner {
+		t.Fatalf("expected exactly one Owner AddMember call, got %+v", svc.addCalls)
+	}
+}
+
+func TestResolveTenantRole_AutoPromoteSkippedIfTenantHasMembers(t *testing.T) {
+	svc := newFakeMemberService()
+	// 同一 home tenant 已经有其它成员 — 不应自动晋升新登录者。
+	svc.seedActive("other", 7, types.TenantRoleOwner)
+	user := &types.User{ID: "u1", TenantID: 7}
+
+	got, ok := resolveTenantRole(context.Background(), svc, user, 7, false, cfgWithRBAC(true))
+	if ok {
+		t.Fatalf("RBAC enabled + no membership for u1 should be rejected, got role=%v", got)
+	}
+	if len(svc.addCalls) != 0 {
+		t.Fatalf("must not auto-promote into a tenant that already has members, got %+v", svc.addCalls)
+	}
+}
+
+func TestResolveTenantRole_FailOpenAdminWhenRBACDisabled(t *testing.T) {
+	svc := newFakeMemberService()
+	user := &types.User{ID: "u1", TenantID: 7}
+	// targetTenantID != home，所以不进 auto-promote 分支。
+	got, ok := resolveTenantRole(context.Background(), svc, user, 8, false, cfgWithRBAC(false))
+	if !ok || got != types.TenantRoleAdmin {
+		t.Fatalf("EnableRBAC=false should fail open Admin, got (%v, %v)", got, ok)
+	}
+}
+
+func TestResolveTenantRole_FailClosedWhenRBACEnabled(t *testing.T) {
+	svc := newFakeMemberService()
+	// 已有其它成员，自动晋升路径关闭；RBAC 启用 → 必须 403。
+	svc.seedActive("other", 8, types.TenantRoleOwner)
+	user := &types.User{ID: "u1", TenantID: 7}
+	if _, ok := resolveTenantRole(context.Background(), svc, user, 8, false, cfgWithRBAC(true)); ok {
+		t.Fatalf("EnableRBAC=true + no membership should be rejected")
+	}
+}
+
+func TestResolveTenantRole_LookupErrorFailsOpenWhenRBACDisabled(t *testing.T) {
+	// 短暂 DB 错误时，fail-open 模式不应锁死现有用户。这里 targetTenantID 故意
+	// 选与 home 不同的值，避免进入 home-tenant auto-promote 分支。
+	svc := newFakeMemberService()
+	svc.failGet = errors.New("transient db failure")
+	// 让 HasAnyMembers 返回 true，关闭孤儿租户自愈路径。
+	svc.seedActive("placeholder", 8, types.TenantRoleAdmin)
+	user := &types.User{ID: "u1", TenantID: 7}
+
+	got, ok := resolveTenantRole(context.Background(), svc, user, 8, false, cfgWithRBAC(false))
+	if !ok || got != types.TenantRoleAdmin {
+		t.Fatalf("transient lookup error under RBAC=false should fail open Admin, got (%v, %v)", got, ok)
+	}
+}
+
+func TestResolveTenantRole_DemotedUserCannotReclaimViaOrphan(t *testing.T) {
+	// 边界场景：管理员人为软删全部成员后，被踢出的用户不应在登录自己 home tenant 时
+	// 因 HasAnyMembers=false 而自动重新拿到 Owner。
+	// 当前实现的策略是 "home tenant + 孤儿 => Owner"，这是设计选择；本测试为这条
+	// 路径加锁，未来如果收紧策略需要同步更新。
+	svc := newFakeMemberService()
+	user := &types.User{ID: "demoted", TenantID: 5}
+	got, ok := resolveTenantRole(context.Background(), svc, user, 5, false, cfgWithRBAC(true))
+	if !ok || got != types.TenantRoleOwner {
+		t.Fatalf("current policy allows orphan-tenant self-heal on home tenant, got (%v, %v)", got, ok)
+	}
+}
diff --git a/internal/types/custom_agent.go b/internal/types/custom_agent.go
index 1774badf..c66c89e1 100644
--- a/internal/types/custom_agent.go
+++ b/internal/types/custom_agent.go
@@ -79,7 +79,15 @@ type CustomAgent struct {
 	// start chat sessions against this agent. Defaults to true so viewers
 	// can still consume published agents; admins toggle it off for agents
 	// whose tools should be restricted to contributors and above.
-	RunnableByViewer bool `yaml:"runnable_by_viewer" json:"runnable_by_viewer" gorm:"default:true"`
+	//
+	// Note: no GORM `default:true` tag here. With a plain `bool` field that
+	// tag causes GORM to treat Go's zero value (false) as "unspecified" and
+	// silently rewrite it to the DB default (true) on insert — preventing
+	// admins from ever creating an agent with viewer-runtime disabled. The
+	// column-level DEFAULT TRUE on the database side still covers rows
+	// inserted by raw SQL / migrations; GORM Create always writes the
+	// explicit struct value.
+	RunnableByViewer bool `yaml:"runnable_by_viewer" json:"runnable_by_viewer"`
 
 	// Agent configuration
 	Config CustomAgentConfig `yaml:"config" json:"config" gorm:"type:json"`
diff --git a/internal/types/interfaces/tenant.go b/internal/types/interfaces/tenant.go
index 5fbef292..0e864122 100644
--- a/internal/types/interfaces/tenant.go
+++ b/internal/types/interfaces/tenant.go
@@ -12,6 +12,10 @@ type TenantService interface {
 	CreateTenant(ctx context.Context, tenant *types.Tenant) (*types.Tenant, error)
 	// GetTenantByID gets a tenant by ID
 	GetTenantByID(ctx context.Context, id uint64) (*types.Tenant, error)
+	// GetTenantsByIDs batches GetTenantByID for multiple IDs in a single
+	// query. Returns a map keyed by tenant ID for O(1) lookup at the
+	// call site; missing tenants are simply absent from the map.
+	GetTenantsByIDs(ctx context.Context, ids []uint64) (map[uint64]*types.Tenant, error)
 	// ListTenants lists all tenants
 	ListTenants(ctx context.Context) ([]*types.Tenant, error)
 	// UpdateTenant updates a tenant
@@ -38,6 +42,8 @@ type TenantRepository interface {
 	CreateTenant(ctx context.Context, tenant *types.Tenant) error
 	// GetTenantByID gets a tenant by ID
 	GetTenantByID(ctx context.Context, id uint64) (*types.Tenant, error)
+	// GetTenantsByIDs batches GetTenantByID; see TenantService.GetTenantsByIDs.
+	GetTenantsByIDs(ctx context.Context, ids []uint64) (map[uint64]*types.Tenant, error)
 	// ListTenants lists all tenants
 	ListTenants(ctx context.Context) ([]*types.Tenant, error)
 	// SearchTenants searches tenants with pagination and filters
diff --git a/internal/types/interfaces/user.go b/internal/types/interfaces/user.go
index 70ca0441..1a4d907e 100644
--- a/internal/types/interfaces/user.go
+++ b/internal/types/interfaces/user.go
@@ -34,6 +34,12 @@ type UserService interface {
 	ValidatePassword(ctx context.Context, userID string, password string) error
 	// GenerateTokens generates access and refresh tokens for user
 	GenerateTokens(ctx context.Context, user *types.User) (accessToken, refreshToken string, err error)
+	// BuildLoginMemberships projects the user's tenant memberships into
+	// the login-response shape. activeTenant is reused (without an extra
+	// lookup) for the matching row's TenantName. The slice is guaranteed
+	// non-nil so callers can serialise it as an empty JSON array when the
+	// membership table is unavailable.
+	BuildLoginMemberships(ctx context.Context, user *types.User, activeTenant *types.Tenant) []types.Membership
 	// SwitchTenant issues a new token pair scoped to targetTenantID and
 	// returns the corresponding LoginResponse. The caller's previous
 	// refresh token (passed in for revocation) is invalidated. Membership
diff --git a/internal/types/user.go b/internal/types/user.go
index e0aad641..16dbe214 100644
--- a/internal/types/user.go
+++ b/internal/types/user.go
@@ -78,13 +78,21 @@ type OIDCConfigResponse struct {
 }
 
 type OIDCCallbackResponse struct {
-	Success      bool    `json:"success"`
-	Message      string  `json:"message,omitempty"`
-	User         *User   `json:"user,omitempty"`
-	Tenant       *Tenant `json:"tenant,omitempty"`
-	Token        string  `json:"token,omitempty"`
-	RefreshToken string  `json:"refresh_token,omitempty"`
-	IsNewUser    bool    `json:"is_new_user,omitempty"`
+	Success bool   `json:"success"`
+	Message string `json:"message,omitempty"`
+	User    *User  `json:"user,omitempty"`
+	// Tenant carries the active tenant for the issued token. The field
+	// name is preserved for backward compatibility with existing frontend
+	// OIDC callback handling; LoginResponse uses ActiveTenant for the
+	// same data.
+	Tenant *Tenant `json:"tenant,omitempty"`
+	// Memberships mirrors LoginResponse.Memberships so the OIDC flow
+	// produces the same role information available to password logins.
+	// Always populated (length >= 1 for an authenticated user).
+	Memberships  []Membership `json:"memberships"`
+	Token        string       `json:"token,omitempty"`
+	RefreshToken string       `json:"refresh_token,omitempty"`
+	IsNewUser    bool         `json:"is_new_user,omitempty"`
 }
 
 type OIDCUserInfo struct {
@@ -113,8 +121,11 @@ type LoginResponse struct {
 	// Memberships lists every tenant the user can authenticate into,
 	// along with their role in each. Always populated (length 1 for users
 	// who only belong to their home tenant) so frontends can render a
-	// tenant switcher without a follow-up request.
-	Memberships  []Membership `json:"memberships,omitempty"`
+	// tenant switcher without a follow-up request. Serialised without
+	// omitempty so the field is always present as a JSON array (possibly
+	// empty) — the "always populated" contract relies on the server side
+	// guaranteeing a non-nil slice.
+	Memberships  []Membership `json:"memberships"`
 	Token        string       `json:"token,omitempty"`
 	RefreshToken string       `json:"refresh_token,omitempty"`
 }
diff --git a/migrations/versioned/000043_tenant_rbac.down.sql b/migrations/versioned/000043_tenant_rbac.down.sql
index 2e625f0c..3d8a4fb4 100644
--- a/migrations/versioned/000043_tenant_rbac.down.sql
+++ b/migrations/versioned/000043_tenant_rbac.down.sql
@@ -1,7 +1,23 @@
 -- Migration 000043 down: revert tenant RBAC schema additions.
--- Note: this drops role information unrecoverably; only intended for
--- development rollbacks, not production.
-DO $$ BEGIN RAISE NOTICE '[Migration 000043 down] Reverting tenant RBAC...'; END $$;
+--
+-- DANGER: This drops the tenant_members table and the creator_id /
+--         runnable_by_viewer columns. All role assignments, KB ownership
+--         metadata, and viewer-runtime flags are lost UNRECOVERABLY.
+--         Only intended for development rollbacks, never for production.
+--
+-- Operators who really need to run this in a non-dev environment must set
+-- the session-level GUC `weknora.allow_destructive_migration` to 'true'
+-- first (e.g. `SET weknora.allow_destructive_migration = 'true';`).
+-- Otherwise the migration aborts before touching any data.
+DO $$
+BEGIN
+    IF coalesce(current_setting('weknora.allow_destructive_migration', true), 'false') <> 'true' THEN
+        RAISE EXCEPTION
+            '[Migration 000043 down] BLOCKED: refuse to drop tenant_members / creator_id / runnable_by_viewer. '
+            'Set weknora.allow_destructive_migration = ''true'' in this session to override.';
+    END IF;
+    RAISE WARNING '[Migration 000043 down] Reverting tenant RBAC — role data will be lost';
+END $$;
 
 ALTER TABLE custom_agents DROP COLUMN IF EXISTS runnable_by_viewer;