diff --git a/core/backend/apps/assets/assets_client.py b/core/backend/apps/assets/assets_client.py
index d9d445c..38356e4 100644
--- a/core/backend/apps/assets/assets_client.py
+++ b/core/backend/apps/assets/assets_client.py
@@ -20,9 +20,15 @@ _ASSETS_ERROR_MESSAGES = {
     "RequestError": "素材审核服务暂时不可用,请稍后重试",
     "InvalidParameter": "素材参数无效",
     "NotFound": "素材不存在或已被删除",
+    "NotFound.asset_id": "素材不存在或已被删除",
+    "NotFound.group_id": "素材组不存在或已被删除",
     "Forbidden": "没有权限操作该素材(检查 AK/SK)",
 }
 
+_NOT_FOUND_CODES = frozenset({"NotFound", "NotFound.asset_id", "NotFound.group_id"})
+_ASSET_NOT_FOUND_CODES = frozenset({"NotFound", "NotFound.asset_id"})
+_GROUP_NOT_FOUND_CODES = frozenset({"NotFound", "NotFound.group_id"})
+
 
 class AssetsAPIError(Exception):
     def __init__(self, code, message, status_code=400):
@@ -33,6 +39,18 @@ class AssetsAPIError(Exception):
         super().__init__(f"[{code}] {message}")
 
 
+def is_not_found_code(code: str | None) -> bool:
+    return code in _NOT_FOUND_CODES
+
+
+def is_asset_not_found_code(code: str | None) -> bool:
+    return code in _ASSET_NOT_FOUND_CODES
+
+
+def is_group_not_found_code(code: str | None) -> bool:
+    return code in _GROUP_NOT_FOUND_CODES
+
+
 def is_enabled() -> bool:
     cfg = getattr(settings, "ASSETS_API", {}) or {}
     return bool(cfg.get("enabled") and cfg.get("access_key") and cfg.get("secret_key"))
diff --git a/core/backend/apps/assets/free_library.py b/core/backend/apps/assets/free_library.py
index 3668d49..9fc2a0d 100644
--- a/core/backend/apps/assets/free_library.py
+++ b/core/backend/apps/assets/free_library.py
@@ -32,6 +32,8 @@ _VIDEO_MAX = 50 * 1024 * 1024
 _AUDIO_MAX = 15 * 1024 * 1024
 DEFAULT_GROUP_NAME = "默认素材"
 DEFAULT_GROUP_MARKER = "__airshelf_free_asset_default__"
+OTHER_REMOTE_ASSET_MESSAGE = "该素材属于其他火山账号，请重新上传后再编辑"
+OTHER_REMOTE_GROUP_MESSAGE = "该素材组属于其他火山账号，请新建素材组后重新上传"
 
 
 def _serialize_asset(fa: FreeAsset) -> dict:
@@ -63,10 +65,7 @@ def _assets_api_unavailable() -> Response:
     return Response({"detail": "素材库服务未配置，请联系管理员"}, status=status.HTTP_503_SERVICE_UNAVAILABLE)
 
 
-def _get_or_create_default_group(*, team, user) -> FreeAssetGroup:
-    group = FreeAssetGroup.objects.filter(team=team, is_deleted=False, description=DEFAULT_GROUP_MARKER).first()
-    if group is not None:
-        return group
+def _create_default_group(*, team, user) -> FreeAssetGroup:
     remote_group_id = assets_client.create_asset_group(DEFAULT_GROUP_NAME, DEFAULT_GROUP_MARKER)
     return FreeAssetGroup.objects.create(
         team=team,
@@ -77,6 +76,19 @@ def _get_or_create_default_group(*, team, user) -> FreeAssetGroup:
     )
 
 
+def _get_or_create_default_group(*, team, user) -> FreeAssetGroup:
+    group = FreeAssetGroup.objects.filter(team=team, is_deleted=False, description=DEFAULT_GROUP_MARKER).first()
+    if group is not None:
+        try:
+            assets_client.get_asset_group(group.remote_group_id)
+        except AssetsAPIError as exc:
+            if not assets_client.is_group_not_found_code(exc.code):
+                raise
+            return _create_default_group(team=team, user=user)
+        return group
+    return _create_default_group(team=team, user=user)
+
+
 def _upload_asset_to_group(request, *, team, group: FreeAssetGroup, image_only: bool = False) -> Response:
     upload = request.FILES.get("file")
     if upload is None:
@@ -138,6 +150,8 @@ def _upload_asset_to_group(request, *, team, group: FreeAssetGroup, image_only:
     try:
         remote_asset_id = assets_client.create_asset(group.remote_group_id, url, name=name, asset_type=asset_type)
     except AssetsAPIError as exc:
+        if assets_client.is_group_not_found_code(exc.code):
+            return Response({"detail": OTHER_REMOTE_GROUP_MESSAGE}, status=status.HTTP_400_BAD_REQUEST)
         return Response({"detail": exc.user_message}, status=status.HTTP_400_BAD_REQUEST)
 
     fa = FreeAsset.objects.create(
@@ -215,8 +229,9 @@ class FreeAssetGroupDetailView(APIView):
         try:
             assets_client.update_asset_group(group.remote_group_id, name=group.name, description=group.description)
         except AssetsAPIError as exc:
-            if exc.code != "NotFound":
-                return Response({"detail": exc.user_message}, status=status.HTTP_400_BAD_REQUEST)
+            if assets_client.is_group_not_found_code(exc.code):
+                return Response({"detail": OTHER_REMOTE_GROUP_MESSAGE}, status=status.HTTP_400_BAD_REQUEST)
+            return Response({"detail": exc.user_message}, status=status.HTTP_400_BAD_REQUEST)
         group.save(update_fields=update_fields)
         return Response({"group": _serialize_group(group)})
 
@@ -228,7 +243,7 @@ class FreeAssetGroupDetailView(APIView):
             assets_client.delete_asset_group(group.remote_group_id)
         except AssetsAPIError as exc:
             # 远程已不存在 → 幂等继续清本地;其它错误如实反馈
-            if exc.code != "NotFound":
+            if not assets_client.is_group_not_found_code(exc.code):
                 return Response({"detail": exc.user_message}, status=status.HTTP_400_BAD_REQUEST)
         group.is_deleted = True
         group.save(update_fields=["is_deleted", "updated_at"])
@@ -286,8 +301,9 @@ class FreeAssetDetailView(APIView):
         try:
             assets_client.update_asset(fa.remote_asset_id, name=name)
         except AssetsAPIError as exc:
-            if exc.code != "NotFound":
-                return Response({"detail": exc.user_message}, status=status.HTTP_400_BAD_REQUEST)
+            if assets_client.is_asset_not_found_code(exc.code):
+                return Response({"detail": OTHER_REMOTE_ASSET_MESSAGE}, status=status.HTTP_400_BAD_REQUEST)
+            return Response({"detail": exc.user_message}, status=status.HTTP_400_BAD_REQUEST)
         fa.name = name[:128]
         fa.save(update_fields=["name", "updated_at"])
         return Response({"asset": _serialize_asset(fa)})
@@ -299,7 +315,7 @@ class FreeAssetDetailView(APIView):
         try:
             assets_client.delete_asset(fa.remote_asset_id)
         except AssetsAPIError as exc:
-            if exc.code != "NotFound":
+            if not assets_client.is_asset_not_found_code(exc.code):
                 return Response({"detail": exc.user_message}, status=status.HTTP_400_BAD_REQUEST)
         fa.delete()
         return Response(status=status.HTTP_204_NO_CONTENT)
diff --git a/core/backend/apps/assets/tests.py b/core/backend/apps/assets/tests.py
index 7e4c60b..05719bd 100644
--- a/core/backend/apps/assets/tests.py
+++ b/core/backend/apps/assets/tests.py
@@ -3,11 +3,12 @@ from types import SimpleNamespace
 from unittest.mock import patch
 
 from django.core.files.uploadedfile import SimpleUploadedFile
-from django.test import TestCase
+from django.test import SimpleTestCase, TestCase
 from rest_framework.test import APIClient
 
 from apps.accounts.models import Team, TeamMember, User
 
+from . import assets_client
 from .models import Asset, FreeAsset, FreeAssetGroup, Model
 
 
@@ -152,6 +153,32 @@ class AssetTrashApiTests(TestCase):
         self.assertEqual(self.client.post(f"/api/assets/{self.live.id}/restore/").status_code, 404)
 
 
+class AssetsClientErrorCodeTests(SimpleTestCase):
+    def test_not_found_helpers_cover_volcano_variants(self):
+        self.assertTrue(assets_client.is_not_found_code("NotFound"))
+        self.assertTrue(assets_client.is_not_found_code("NotFound.asset_id"))
+        self.assertTrue(assets_client.is_not_found_code("NotFound.group_id"))
+        self.assertFalse(assets_client.is_not_found_code("Forbidden"))
+        self.assertFalse(assets_client.is_not_found_code(None))
+
+        self.assertTrue(assets_client.is_asset_not_found_code("NotFound"))
+        self.assertTrue(assets_client.is_asset_not_found_code("NotFound.asset_id"))
+        self.assertFalse(assets_client.is_asset_not_found_code("NotFound.group_id"))
+
+        self.assertTrue(assets_client.is_group_not_found_code("NotFound"))
+        self.assertTrue(assets_client.is_group_not_found_code("NotFound.group_id"))
+        self.assertFalse(assets_client.is_group_not_found_code("NotFound.asset_id"))
+
+    def test_not_found_variant_messages_are_not_generic(self):
+        asset_error = assets_client.AssetsAPIError("NotFound.asset_id", "remote asset missing")
+        group_error = assets_client.AssetsAPIError("NotFound.group_id", "remote group missing")
+        unknown_error = assets_client.AssetsAPIError("Unknown", "unknown")
+
+        self.assertNotEqual(asset_error.user_message, unknown_error.user_message)
+        self.assertNotEqual(group_error.user_message, unknown_error.user_message)
+        self.assertNotEqual(asset_error.user_message, group_error.user_message)
+
+
 class FreeAssetQuickUploadTests(TestCase):
     """人物素材库快捷上传:自动默认组,但底层仍走 FreeAssetGroup / FreeAsset。"""
 
@@ -187,10 +214,11 @@ class FreeAssetQuickUploadTests(TestCase):
         self.assertEqual(res.json()["group"]["id"], str(group.id))
 
     @patch("apps.assets.free_library.assets_client.is_enabled", return_value=True)
+    @patch("apps.assets.free_library.assets_client.get_asset_group", return_value={"Id": "Group-1"})
     @patch("apps.assets.free_library.assets_client.create_asset_group", return_value="Group-1")
     @patch("apps.assets.free_library.assets_client.create_asset", side_effect=["Asset-1", "Asset-2"])
     @patch("apps.assets.free_library.TosStorage")
-    def test_quick_upload_reuses_default_group(self, storage_cls, create_asset, create_group, _enabled):
+    def test_quick_upload_reuses_default_group(self, storage_cls, create_asset, create_group, get_group, _enabled):
         storage = storage_cls.return_value
         storage.upload_fileobj.return_value = self.stored
         storage.public_url.return_value = "http://tos/a.png"
@@ -202,8 +230,40 @@ class FreeAssetQuickUploadTests(TestCase):
         self.assertEqual(FreeAssetGroup.objects.filter(team=self.team).count(), 1)
         self.assertEqual(FreeAsset.objects.filter(group__team=self.team).count(), 2)
         create_group.assert_called_once()
+        get_group.assert_called_once_with("Group-1")
         self.assertEqual(create_asset.call_count, 2)
 
+    @patch("apps.assets.free_library.assets_client.is_enabled", return_value=True)
+    @patch(
+        "apps.assets.free_library.assets_client.get_asset_group",
+        side_effect=assets_client.AssetsAPIError("NotFound.group_id", "old group not visible"),
+    )
+    @patch("apps.assets.free_library.assets_client.create_asset_group", return_value="Group-2")
+    @patch("apps.assets.free_library.assets_client.create_asset", return_value="Asset-2")
+    @patch("apps.assets.free_library.TosStorage")
+    def test_quick_upload_replaces_old_default_group(self, storage_cls, create_asset, create_group, get_group, _enabled):
+        old_group = FreeAssetGroup.objects.create(
+            team=self.team,
+            created_by=self.user,
+            name="默认素材",
+            description="__airshelf_free_asset_default__",
+            remote_group_id="Old-Group",
+        )
+        storage = storage_cls.return_value
+        storage.upload_fileobj.return_value = self.stored
+        storage.public_url.return_value = "http://tos/a.png"
+
+        res = self.client.post("/api/assets/free-assets/quick-upload/", {"file": self._image("new.png")}, format="multipart")
+
+        self.assertEqual(res.status_code, 201)
+        self.assertFalse(FreeAsset.objects.filter(group=old_group).exists())
+        new_group = FreeAssetGroup.objects.exclude(id=old_group.id).get(team=self.team)
+        self.assertEqual(new_group.remote_group_id, "Group-2")
+        self.assertEqual(new_group.assets.count(), 1)
+        get_group.assert_called_once_with("Old-Group")
+        create_group.assert_called_once()
+        create_asset.assert_called_once_with("Group-2", "http://tos/a.png", name="new.png", asset_type=FreeAsset.Type.IMAGE)
+
     @patch("apps.assets.free_library.assets_client.is_enabled", return_value=True)
     @patch("apps.assets.free_library.assets_client.create_asset_group", return_value="Group-1")
     @patch("apps.assets.free_library.TosStorage")
@@ -219,6 +279,143 @@ class FreeAssetQuickUploadTests(TestCase):
         create_group.assert_called_once()
 
 
+class FreeAssetGroupUploadTests(TestCase):
+    def setUp(self):
+        self.user, self.team = _mk_team("fgu", "TeamFGU")
+        self.client = APIClient()
+        self.client.force_authenticate(self.user)
+        self.group = FreeAssetGroup.objects.create(
+            team=self.team,
+            created_by=self.user,
+            name="旧素材组",
+            description="",
+            remote_group_id="Old-Group",
+        )
+        self.stored = SimpleNamespace(object_key="teams/x/free-create/library/a.png", bucket="b", content_type="image/png", size_bytes=10)
+
+    def _image(self, name="a.png"):
+        return SimpleUploadedFile(name, b"img", content_type="image/png")
+
+    @patch("apps.assets.free_library.assets_client.is_enabled", return_value=True)
+    @patch(
+        "apps.assets.free_library.assets_client.create_asset",
+        side_effect=assets_client.AssetsAPIError("NotFound.group_id", "old group not visible"),
+    )
+    @patch("apps.assets.free_library.TosStorage")
+    def test_upload_to_old_remote_group_returns_clear_message(self, storage_cls, create_asset, _enabled):
+        storage = storage_cls.return_value
+        storage.upload_fileobj.return_value = self.stored
+        storage.public_url.return_value = "http://tos/a.png"
+
+        res = self.client.post(f"/api/assets/free-groups/{self.group.id}/assets/", {"file": self._image()}, format="multipart")
+
+        self.assertEqual(res.status_code, 400)
+        self.assertEqual(res.json()["detail"], "该素材组属于其他火山账号，请新建素材组后重新上传")
+        self.assertFalse(FreeAsset.objects.filter(group=self.group).exists())
+        create_asset.assert_called_once_with("Old-Group", "http://tos/a.png", name="a.png", asset_type=FreeAsset.Type.IMAGE)
+
+
+class FreeAssetDeleteCompatibilityTests(TestCase):
+    def setUp(self):
+        self.user, self.team = _mk_team("fdel", "TeamFDEL")
+        self.client = APIClient()
+        self.client.force_authenticate(self.user)
+        self.group = FreeAssetGroup.objects.create(
+            team=self.team,
+            created_by=self.user,
+            name="旧素材组",
+            description="",
+            remote_group_id="Old-Group",
+        )
+        self.asset = FreeAsset.objects.create(
+            group=self.group,
+            remote_asset_id="Old-Asset",
+            name="旧素材.png",
+            url="http://tos/a.png",
+            asset_type=FreeAsset.Type.IMAGE,
+            thumbnail_url="http://tos/a.png",
+            status=FreeAsset.Status.ACTIVE,
+        )
+
+    @patch(
+        "apps.assets.free_library.assets_client.delete_asset",
+        side_effect=assets_client.AssetsAPIError("NotFound.asset_id", "old asset not visible"),
+    )
+    def test_delete_old_remote_asset_clears_local_asset(self, delete_asset):
+        res = self.client.delete(f"/api/assets/free-assets/{self.asset.id}/")
+
+        self.assertEqual(res.status_code, 204)
+        self.assertFalse(FreeAsset.objects.filter(id=self.asset.id).exists())
+        delete_asset.assert_called_once_with("Old-Asset")
+
+    @patch(
+        "apps.assets.free_library.assets_client.delete_asset_group",
+        side_effect=assets_client.AssetsAPIError("NotFound.group_id", "old group not visible"),
+    )
+    def test_delete_old_remote_group_marks_local_group_deleted(self, delete_group):
+        res = self.client.delete(f"/api/assets/free-groups/{self.group.id}/")
+
+        self.assertEqual(res.status_code, 204)
+        self.group.refresh_from_db()
+        self.assertTrue(self.group.is_deleted)
+        self.assertTrue(FreeAsset.objects.filter(id=self.asset.id).exists())
+        delete_group.assert_called_once_with("Old-Group")
+
+
+class FreeAssetRenameCompatibilityTests(TestCase):
+    def setUp(self):
+        self.user, self.team = _mk_team("fren", "TeamFREN")
+        self.client = APIClient()
+        self.client.force_authenticate(self.user)
+        self.group = FreeAssetGroup.objects.create(
+            team=self.team,
+            created_by=self.user,
+            name="旧素材组",
+            description="old description",
+            remote_group_id="Old-Group",
+        )
+        self.asset = FreeAsset.objects.create(
+            group=self.group,
+            remote_asset_id="Old-Asset",
+            name="旧素材.png",
+            url="http://tos/a.png",
+            asset_type=FreeAsset.Type.IMAGE,
+            thumbnail_url="http://tos/a.png",
+            status=FreeAsset.Status.ACTIVE,
+        )
+
+    @patch(
+        "apps.assets.free_library.assets_client.update_asset",
+        side_effect=assets_client.AssetsAPIError("NotFound.asset_id", "old asset not visible"),
+    )
+    def test_rename_old_remote_asset_returns_clear_message_without_saving(self, update_asset):
+        res = self.client.patch(f"/api/assets/free-assets/{self.asset.id}/", {"name": "新名字.png"}, format="json")
+
+        self.assertEqual(res.status_code, 400)
+        self.assertEqual(res.json()["detail"], "该素材属于其他火山账号，请重新上传后再编辑")
+        self.asset.refresh_from_db()
+        self.assertEqual(self.asset.name, "旧素材.png")
+        update_asset.assert_called_once_with("Old-Asset", name="新名字.png")
+
+    @patch(
+        "apps.assets.free_library.assets_client.update_asset_group",
+        side_effect=assets_client.AssetsAPIError("NotFound.group_id", "old group not visible"),
+    )
+    def test_rename_old_remote_group_returns_clear_message_without_saving(self, update_group):
+        res = self.client.patch(
+            f"/api/assets/free-groups/{self.group.id}/",
+            {"name": "新素材组", "description": "new description"},
+            format="json",
+        )
+
+        self.assertEqual(res.status_code, 400)
+        self.assertEqual(res.json()["detail"], "该素材组属于其他火山账号，请新建素材组后重新上传")
+        self.group.refresh_from_db()
+        self.assertEqual(self.group.name, "旧素材组")
+        self.assertEqual(self.group.description, "old description")
+        update_group.assert_called_once_with("Old-Group", name="新素材组", description="new description")
+
+
 class VideoPacksTests(TestCase):
     """视频成品按项目素材包分组(与导出同源:取 VideoSegment.adopted_version 的真实视频资产)。"""
 
diff --git a/core/frontend/src/components/app-shell.tsx b/core/frontend/src/components/app-shell.tsx
index 1b87a1c..17f8fc7 100644
--- a/core/frontend/src/components/app-shell.tsx
+++ b/core/frontend/src/components/app-shell.tsx
@@ -431,11 +431,12 @@ export function ToastLike({ notice }: { notice: NonNullable<Notice> }) {
     return () => cancelAnimationFrame(raf);
   }, []);
   const Icon = notice.type === "error" ? AlertCircle : notice.type === "info" ? Info : Check;
-  return (
+  return createPortal(
     <div className={`toast${show ? " show" : ""}`} role="status" aria-live="polite">
       <div className="ic-t"><Icon size={13} /></div>
       <div className="txt">{notice.text}<span className="mono">[ {notice.type.toUpperCase()} ]</span></div>
-    </div>
+    </div>,
+    document.body,
   );
 }
 
diff --git a/core/frontend/src/design-restraint.css b/core/frontend/src/design-restraint.css
index f8b6a89..edc57cc 100644
--- a/core/frontend/src/design-restraint.css
+++ b/core/frontend/src/design-restraint.css
@@ -1728,7 +1728,7 @@ table.t tbody tr:hover { background: var(--black-alpha-4); }
   box-shadow: var(--shadow-floating);
   transform: translateX(420px);
   transition: transform var(--t-slow);
-  z-index: 1000;
+  z-index: 10000;
   min-width: 260px;
 }
 .toast.show { transform: translateX(0); }