diff --git a/tests/unit/test_prepare_dedup_1714.py b/tests/unit/test_prepare_dedup_1714.py
index acc96df97..cb0ad9ff8 100644
--- a/tests/unit/test_prepare_dedup_1714.py
+++ b/tests/unit/test_prepare_dedup_1714.py
@@ -369,3 +369,103 @@ def test_create_pending_asset_creates_when_no_match():
     assert result.file_hash == "newhash"
     assert result.client_upload_id == "newcuid"
     assert repo.saved == 1
+
+
+# ---------------------------------------------------------------------------
+# 兜底去重：PROCESSING 占位 hash 不同时跳过
+# ---------------------------------------------------------------------------
+
+
+def test_filename_fallback_skips_processing_with_different_hash():
+    """PROCESSING/UPLOADING 占位记录仅当 hash 一致（或占位无 hash）才命中；hash 不同跳过。"""
+    repo = _FakeAssetRepo()
+    repo.create(_make_pending(id="p1", file_hash="oldhash"))
+    repo.find_recent_active_by_library_and_name = lambda **kw: repo.assets["p1"]
+    result = upload_route._find_duplicate_asset(
+        repo,
+        library_id="lib-1",
+        file_hash="differenthash",  # 新上传内容不同
+        client_upload_id="",
+        filename="test.mp4",
+        file_size=1024,
+    )
+    assert result is None
+
+
+def test_filename_fallback_matches_processing_with_same_hash():
+    """PROCESSING 占位 hash 与请求一致时命中（重试场景）。"""
+    repo = _FakeAssetRepo()
+    repo.create(_make_pending(id="p1", file_hash="samehash"))
+    repo.find_recent_active_by_library_and_name = lambda **kw: repo.assets["p1"]
+    result = upload_route._find_duplicate_asset(
+        repo,
+        library_id="lib-1",
+        file_hash="samehash",
+        client_upload_id="",
+        filename="test.mp4",
+        file_size=1024,
+    )
+    assert result is not None
+    assert result.id == "p1"
+
+
+# ---------------------------------------------------------------------------
+# prepare 预建失败降级：不阻塞签名
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.asyncio
+async def test_prepare_pending_asset_create_failure_degrades_gracefully():
+    """预建 asset 抛异常时，prepare 仍正常返回签名（duplicated=False, asset_id 空）。"""
+
+    class _BrokenRepo(_FakeAssetRepo):
+        def create(self, asset):
+            raise RuntimeError("db down")
+
+    repo = _BrokenRepo()
+    req = SimpleNamespace(
+        project_id="p-1",
+        library_id="lib-1",
+        filename="test.mp4",
+        content_type="video/mp4",
+        file_size=1024,
+        file_hash="abc123",
+        client_upload_id="cuid-1",
+    )
+    resp = await upload_route.prepare_direct_upload(
+        request=req,
+        authenticated_user=_user(),
+        project_repository=_StubProjectRepo(_FIXTURE_PROJECT),
+        asset_library_repository=_StubLibraryRepo(_FIXTURE_LIBRARY),
+        asset_repository=repo,
+        storage_service=_storage(),
+    )
+    assert resp.duplicated is False
+    assert resp.skip_transfer is False
+    assert resp.asset_id == ""  # 预建失败，降级无 asset_id
+    assert resp.upload_url != ""  # 签名仍正常返回
+
+
+def test_create_pending_asset_update_failure_swallowed():
+    """复用占位记录时字段补齐 update 抛异常被吞掉，不阻塞返回。"""
+
+    class _UpdateBrokenRepo(_FakeAssetRepo):
+        def update(self, asset):
+            raise RuntimeError("db down")
+
+    repo = _UpdateBrokenRepo()
+    repo.create(_make_pending(file_hash="abc123", client_upload_id="", id="p1"))
+    result = upload_route._create_pending_asset(
+        asset_repository=repo,
+        project_id="p-1",
+        library_id="lib-1",
+        storage_key="uploads/new/test.mp4",
+        filename="test.mp4",
+        mime_type="video/mp4",
+        user_id="user-1",
+        file_hash="abc123",
+        client_upload_id="cuid-new",
+        file_size=1024,
+    )
+    assert result.id == "p1"  # 仍复用，不抛异常
+    assert repo.saved == 1