diff --git a/backend/app/db/governance_seed.py b/backend/app/db/governance_seed.py
index caa6c3a..ae8e267 100644
--- a/backend/app/db/governance_seed.py
+++ b/backend/app/db/governance_seed.py
@@ -4,6 +4,7 @@ from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.domains.baigong.models import Capability
+from app.domains.baigong.service import PLATFORM_SCOPE
 
 _BUILTIN_CAPABILITIES = [
     # name, 描述, 执行类型, 执行器, 四维风险, 数据范围, 目的地, consent
@@ -71,7 +72,7 @@ async def _seed_capabilities(session: AsyncSession) -> None:
         session.add(
             Capability(
                 name=name,
-                owner_scope="local-user",
+                owner_scope=PLATFORM_SCOPE,
                 description=desc,
                 executor_type=executor_type,
                 executor_ref=ref,
@@ -89,3 +90,4 @@ async def _seed_capabilities(session: AsyncSession) -> None:
 async def ensure_governance_seed(session: AsyncSession) -> None:
     """启动幂等登记内置能力。"""
     await _seed_capabilities(session)
+    await session.commit()
diff --git a/backend/app/domains/baigong/service.py b/backend/app/domains/baigong/service.py
index 1a4c69c..17feaf4 100644
--- a/backend/app/domains/baigong/service.py
+++ b/backend/app/domains/baigong/service.py
@@ -26,10 +26,20 @@ from app.models.safety import AuditEvent, PendingConfirmationRecord
 from app.schemas.auth import CurrentUser
 
 
+# 内置能力挂平台作用域（全局可见可授契；自定义能力按 owner 隔离）
+PLATFORM_SCOPE = "__platform__"
+
+
+def _capability_visible(cap: Capability, owner_scope: str) -> bool:
+    return cap.owner_scope == owner_scope or (
+        cap.owner_scope == PLATFORM_SCOPE and cap.source == "builtin"
+    )
+
+
 async def _get_capability(capability_id: str, owner_scope: str) -> Capability:
     async with AsyncSessionLocal() as session:
         cap = await session.get(Capability, capability_id)
-        if cap is None or cap.owner_scope != owner_scope:
+        if cap is None or not _capability_visible(cap, owner_scope):
             raise AppError("not_found", "能力不存在。", status_code=404)
         session.expunge(cap)
         return cap
@@ -300,15 +310,24 @@ async def resolve_petition(petition_id: str, approved: bool) -> dict[str, Any]:
 
 async def list_capabilities(owner_scope: str) -> list[dict[str, Any]]:
     async with AsyncSessionLocal() as session:
-        caps = (
-            (
-                await session.execute(
-                    select(Capability).where(Capability.owner_scope == owner_scope)
+        caps = [
+            c
+            for c in (
+                (
+                    await session.execute(
+                        select(Capability).where(
+                            (Capability.owner_scope == owner_scope)
+                            | (
+                                (Capability.owner_scope == PLATFORM_SCOPE)
+                                & (Capability.source == "builtin")
+                            )
+                        )
+                    )
                 )
+                .scalars()
+                .all()
             )
-            .scalars()
-            .all()
-        )
+        ]
         mandates = (
             (
                 await session.execute(
diff --git a/backend/app/domains/mirror_tree/service.py b/backend/app/domains/mirror_tree/service.py
index 1b94d1a..e02806b 100644
--- a/backend/app/domains/mirror_tree/service.py
+++ b/backend/app/domains/mirror_tree/service.py
@@ -120,14 +120,15 @@ async def create_tree(*, character_id: str, owner_scope: str, title: str, defaul
 
 async def list_trees(owner_scope: str, character_id: str | None = None) -> list[MirrorTree]:
     async with AsyncSessionLocal() as session:
-        character_ids = [
-            c.id
-            for c in (
+        character_ids = list(
+            (
                 await session.execute(
                     select(Character.id).where(Character.owner_scope == owner_scope)
                 )
-            ).scalars()
-        ]
+            )
+            .scalars()
+            .all()
+        )
         if not character_ids:
             return []
         stmt = select(MirrorTree).where(