diff --git a/backend/src/backend/api/platform/_deps.py b/backend/src/backend/api/platform/_deps.py
index 5732e6e..3657fe9 100644
--- a/backend/src/backend/api/platform/_deps.py
+++ b/backend/src/backend/api/platform/_deps.py
@@ -79,7 +79,22 @@ async def _is_system_admin(session: AsyncSession, user: Users) -> bool:
 
 
 async def _load_role_by_code(session: AsyncSession, role_code: str) -> Roles:
-    role = await session.scalar(select(Roles).where(Roles.role_code == role_code))
+    """Load a live platform-scoped role by code; 422 if missing.
+
+    之所以把 ``is_deleted == 0`` 和 ``role_scope == "platform"`` 写进 helper,
+    是因为本 helper 的所有调用方(``employees`` create/update / 两个 count
+    helper)都需要的是 platform 角色。Workspace 角色不应被赋值到
+    ``users.platform_role_id``,软删除的 role 也不应被新引用 —— 在 helper
+    层兜底一次,后续 schema 放宽 ``role_code`` 为 ``str`` 时不必每个端点
+    再补守卫。
+    """
+    role = await session.scalar(
+        select(Roles).where(
+            Roles.role_code == role_code,
+            Roles.is_deleted == 0,
+            Roles.role_scope == "platform",
+        )
+    )
     if role is None:
         raise HTTPException(
             status.HTTP_422_UNPROCESSABLE_ENTITY,
diff --git a/backend/src/backend/api/platform/employees.py b/backend/src/backend/api/platform/employees.py
index 7c14131..398cc06 100644
--- a/backend/src/backend/api/platform/employees.py
+++ b/backend/src/backend/api/platform/employees.py
@@ -26,6 +26,13 @@ from backend.api.platform._deps import (
     system_admin_context,
 )
 
+# 平台角色 code 的字符串约束:与 RoleCreate.role_code 一致。
+# 之所以从 Literal["admin","developer"] 放宽为 str,是因为 ``listPlatformRoles``
+# 现已返回用户自建的 platform 角色(``role_scope=="platform"`` 且 ``is_builtin==0``),
+# 前端 dialog 用 ``listPlatformRoles()`` 渲染选项,提交非内置 code 时会被 Pydantic
+# Literal 校验直接 422 拒掉。schema 不应枚举运行时数据;改用 ``_load_role_by_code``
+# 做存在性 + 平台作用域校验(并隐式排除 is_deleted=1)。
+
 router = APIRouter(prefix="/api/v1/platform", tags=["platform"])
 
 
@@ -42,7 +49,7 @@ class PlatformEmployeeCreate(BaseModel):
     display_name: str = Field(min_length=1, max_length=100)
     email: str | None = Field(default=None, max_length=255)
     password: str = Field(min_length=8, max_length=72)
-    role_code: Literal["admin", "developer"] | None = None
+    role_code: str | None = Field(default=None, min_length=2, max_length=64)
 
 
 # 修改平台用户资料、状态或平台角色的请求体。
@@ -52,7 +59,7 @@ class PlatformEmployeeUpdate(BaseModel):
     display_name: str | None = Field(default=None, min_length=1, max_length=100)
     email: str | None = Field(default=None, max_length=255)
     status: Literal["active", "disabled", "locked"] | None = None
-    role_code: Literal["admin", "developer"] | None = None
+    role_code: str | None = Field(default=None, min_length=2, max_length=64)
 
 
 # ---------------------------------------------------------------------------