fix(cloud): show owner model balance and enforce single owner (#2384)

* fix(cloud): show owner model balance and enforce single owner

* fix(migrations): create owner index idempotently

---------

Co-authored-by: dadachann <185672915+dadachann@users.noreply.github.com>

src/langbot/pkg/api/http/authz.py

@@ -19,7 +19,6 @@ class Permission(enum.StrEnum):
     WORKSPACE_VIEW = 'workspace.view'
     WORKSPACE_UPDATE = 'workspace.update'
     WORKSPACE_DELETE = 'workspace.delete'
-    OWNER_TRANSFER = 'owner.transfer'
     MEMBER_VIEW = 'member.view'
     MEMBER_INVITE = 'member.invite'
     MEMBER_UPDATE_ROLE = 'member.update_role'
@@ -49,7 +48,6 @@ _ROLE_PERMISSIONS: typing.Final = types.MappingProxyType(
             if permission
             not in {
                 Permission.WORKSPACE_DELETE,
-                Permission.OWNER_TRANSFER,
                 Permission.BILLING_LINK_MANAGE,
             }
         ),

src/langbot/pkg/api/http/controller/group.py

@@ -62,7 +62,6 @@ class AuthType(enum.Enum):
 
 _SUPPORT_ADMIN_DENIED_PERMISSIONS = frozenset(
     {
-        Permission.OWNER_TRANSFER.value,
         Permission.MEMBER_VIEW.value,
         Permission.MEMBER_INVITE.value,
         Permission.MEMBER_UPDATE_ROLE.value,

src/langbot/pkg/api/http/controller/groups/user.py

@@ -291,11 +291,19 @@ class UserRouterGroup(group.RouterGroup):
             # Workspace owner is already bound even when this Core has no local OAuth
             # token row (model billing uses the owner's control-plane API key).
             owner_space_bound = cloud_mode or owner_has_local_space_credentials
-            credits = (
-                await self.ap.space_service.get_credits(owner.user)
-                if owner is not None and owner.space_account_uuid
-                else None
-            )
+            if cloud_mode:
+                catalog_service = getattr(self.ap, 'cloud_model_catalog_service', None)
+                credits = (
+                    catalog_service.get_workspace_credits(access.workspace.uuid)
+                    if catalog_service is not None
+                    else None
+                )
+            else:
+                credits = (
+                    await self.ap.space_service.get_credits(owner.user)
+                    if owner is not None and owner.space_account_uuid
+                    else None
+                )
             return self.success(
                 data={
                     'credits': credits,

src/langbot/pkg/cloud/model_catalog.py

@@ -53,6 +53,7 @@ class CloudWorkspaceModelBilling(BaseModel):
     workspace_uuid: str = Field(min_length=36, max_length=36)
     owner_account_uuid: str | None = Field(default=None, min_length=36, max_length=36)
     api_key: SecretStr | None = None
+    credits: int | None = None
 
     @field_validator('workspace_uuid')
     @classmethod
@@ -149,6 +150,11 @@ class CloudModelCatalogSyncService:
         # convergence marker so a failed runtime reload is retried even when the
         # following database reconciliation is a no-op.
         self._runtime_reload_pending = False
+        self._workspace_credits: dict[str, int | None] = {}
+
+    def get_workspace_credits(self, workspace_uuid: str) -> int | None:
+        """Return the latest signed owner-credit projection for a Workspace."""
+        return self._workspace_credits.get(str(uuid.UUID(workspace_uuid)))
 
     async def initialize(self) -> None:
         await self.sync_once(reload_runtime=False)
@@ -198,6 +204,7 @@ class CloudModelCatalogSyncService:
                     self._runtime_reload_pending = True
                 for key in ('created', 'updated', 'deleted'):
                     summary[key] += counts[key]
+                self._workspace_credits[binding.workspace_uuid] = billing_by_workspace[binding.workspace_uuid].credits
         except Exception as exc:
             sync_error = exc
         finally:

src/langbot/pkg/entity/persistence/workspace.py

@@ -163,6 +163,13 @@ class WorkspaceMembership(Base):
     __table_args__ = (
         sqlalchemy.UniqueConstraint('workspace_uuid', 'account_uuid', name='uq_workspace_membership_account'),
         sqlalchemy.Index('ix_workspace_memberships_account_status', 'account_uuid', 'status'),
+        sqlalchemy.Index(
+            'uq_workspace_memberships_one_active_owner',
+            'workspace_uuid',
+            unique=True,
+            sqlite_where=sqlalchemy.text("role = 'owner' AND status = 'active'"),
+            postgresql_where=sqlalchemy.text("role = 'owner' AND status = 'active'"),
+        ),
         sqlalchemy.CheckConstraint(
             "role IN ('owner', 'admin', 'developer', 'operator', 'viewer')",
             name='ck_workspace_memberships_role',

src/langbot/pkg/persistence/alembic/versions/0019_single_workspace_owner.py

@@ -0,0 +1,80 @@
+"""enforce one active owner per Workspace
+
+Revision ID: 0019_single_workspace_owner
+Revises: 0018_merge_launch_replay
+Create Date: 2026-08-02
+"""
+
+from __future__ import annotations
+
+import sqlalchemy as sa
+from alembic import op
+
+revision = '0019_single_workspace_owner'
+down_revision = '0018_merge_launch_replay'
+branch_labels = None
+depends_on = None
+
+_INDEX_NAME = 'uq_workspace_memberships_one_active_owner'
+
+
+def upgrade() -> None:
+    conn = op.get_bind()
+    inspector = sa.inspect(conn)
+    if 'workspace_memberships' not in inspector.get_table_names():
+        return
+
+    # Ownership transfer used to promote a second member without demoting the
+    # original owner. Preserve the Workspace creator where possible and demote
+    # every historical extra owner before installing the database invariant.
+    op.execute(
+        sa.text(
+            """
+            WITH ranked_owners AS (
+                SELECT membership.uuid,
+                       ROW_NUMBER() OVER (
+                           PARTITION BY membership.workspace_uuid
+                           ORDER BY
+                               CASE
+                                   WHEN membership.account_uuid = workspace.created_by_account_uuid THEN 0
+                                   ELSE 1
+                               END,
+                               COALESCE(membership.joined_at, membership.created_at),
+                               membership.uuid
+                       ) AS owner_rank
+                FROM workspace_memberships AS membership
+                JOIN workspaces AS workspace
+                  ON workspace.uuid = membership.workspace_uuid
+                WHERE membership.role = 'owner'
+                  AND membership.status = 'active'
+            )
+            UPDATE workspace_memberships
+               SET role = 'admin'
+             WHERE uuid IN (
+                 SELECT uuid
+                   FROM ranked_owners
+                  WHERE owner_rank > 1
+             )
+            """
+        )
+    )
+    # Fresh installations may already have this index because SQLAlchemy
+    # metadata is created before Alembic advances the revision marker.
+    op.execute(
+        sa.text(
+            'CREATE UNIQUE INDEX IF NOT EXISTS '
+            'uq_workspace_memberships_one_active_owner '
+            'ON workspace_memberships (workspace_uuid) '
+            "WHERE role = 'owner' AND status = 'active'"
+        )
+    )
+
+
+def downgrade() -> None:
+    conn = op.get_bind()
+    inspector = sa.inspect(conn)
+    if 'workspace_memberships' not in inspector.get_table_names():
+        return
+    index_names = {index['name'] for index in inspector.get_indexes('workspace_memberships')}
+    if _INDEX_NAME in index_names:
+        op.drop_index(_INDEX_NAME, table_name='workspace_memberships')

src/langbot/pkg/workspace/collaboration.py

@@ -606,6 +606,8 @@ class WorkspaceCollaborationService:
     ) -> WorkspaceMembership:
         if role not in {item.value for item in MembershipRole}:
             raise MembershipPermissionError('Unknown Workspace role')
+        if role == MembershipRole.OWNER.value:
+            raise MembershipPermissionError('Workspace ownership cannot be transferred')
 
         async def operation(active_session: AsyncSession) -> WorkspaceMembership:
             await self._require_active_workspace(active_session, workspace_uuid)
@@ -617,8 +619,8 @@ class WorkspaceCollaborationService:
                 target_account_uuid,
             )
             self._require_can_manage_target(persisted_actor, target, new_role=role)
-            if target.role == MembershipRole.OWNER.value and role != MembershipRole.OWNER.value:
-                await self._require_another_owner(active_session, workspace_uuid, target.account_uuid)
+            if target.role == MembershipRole.OWNER.value:
+                raise LastOwnerError('The Workspace owner cannot be removed or demoted')
             target.role = role
             await active_session.flush()
             return target
@@ -644,7 +646,7 @@ class WorkspaceCollaborationService:
             )
             self._require_can_manage_target(persisted_actor, target)
             if target.role == MembershipRole.OWNER.value:
-                await self._require_another_owner(active_session, workspace_uuid, target.account_uuid)
+                raise LastOwnerError('The Workspace owner cannot be removed or demoted')
             target.status = MembershipStatus.REMOVED.value
             await active_session.flush()
             return target
@@ -751,26 +753,6 @@ class WorkspaceCollaborationService:
             raise WorkspaceNotFoundError('Workspace not found')
         return persisted_actor
 
-    async def _require_another_owner(
-        self,
-        session: AsyncSession,
-        workspace_uuid: str,
-        excluded_account_uuid: str,
-    ) -> None:
-        owners = (
-            await session.scalars(
-                sqlalchemy.select(WorkspaceMembership)
-                .where(
-                    WorkspaceMembership.workspace_uuid == workspace_uuid,
-                    WorkspaceMembership.status == MembershipStatus.ACTIVE.value,
-                    WorkspaceMembership.role == MembershipRole.OWNER.value,
-                )
-                .with_for_update()
-            )
-        ).all()
-        if not any(owner.account_uuid != excluded_account_uuid for owner in owners):
-            raise LastOwnerError('The last Workspace owner cannot be removed or demoted')
-
     def _require_actor_workspace(self, actor: WorkspaceMembership, workspace_uuid: str) -> None:
         if actor.workspace_uuid != workspace_uuid or actor.status != MembershipStatus.ACTIVE.value:
             raise WorkspaceNotFoundError('Workspace not found')