diff --git a/apps/api/app/api/routes/assets.py b/apps/api/app/api/routes/assets.py
index 3a407e81b..80a199aff 100755
--- a/apps/api/app/api/routes/assets.py
+++ b/apps/api/app/api/routes/assets.py
@@ -576,9 +576,7 @@ def smart_match_assets(
             request.library_id, request.kind, status=["ready"], limit=10000
         )
     else:
-        filtered_assets = asset_repository.find_by_library(
-            request.library_id, status=["ready"], limit=10000
-        )
+        filtered_assets = asset_repository.find_by_library(request.library_id, status=["ready"], limit=10000)
     total_candidates = len(filtered_assets)
 
     # 调用统一智能选素材算法（kind 已在 DB 层过滤，无需重复过滤）
@@ -610,9 +608,11 @@ def smart_match_assets(
             continue
         filtered_results.append(r)
 
+    # 扁平结构：SmartMatchItem 继承 AssetResponse，素材字段直接在条目顶层，
+    # 前端无需解析 item.asset 包装层，item.id / item.usable / 余量字段直接可读
     items = [
         SmartMatchItem(
-            asset=_to_asset_response(r.asset),
+            **_to_asset_response(r.asset).model_dump(),
             score=r.score,
             breakdown=r.breakdown,
         )
diff --git a/apps/api/app/api/routes/templates_editor/clips.py b/apps/api/app/api/routes/templates_editor/clips.py
index 8f25ddcb0..08d4bc307 100755
--- a/apps/api/app/api/routes/templates_editor/clips.py
+++ b/apps/api/app/api/routes/templates_editor/clips.py
@@ -367,7 +367,6 @@ def batch_delete_editor_clips(
     return ClipBatchDeleteResponse(deleted_count=deleted, plan_id=plan_id)
 
 
-
 def _safe_segment_duration(value, default: float) -> float:
     """安全地将数据库中的时长值转换为正浮点数.
 
@@ -403,9 +402,7 @@ def _get_template_segments(
         if clip_configs:
             result = []
             for cc in clip_configs:
-                dur_min = _safe_segment_duration(
-                    cc.min_duration, _DEFAULT_EDITOR_CLIP_DURATION
-                )
+                dur_min = _safe_segment_duration(cc.min_duration, _DEFAULT_EDITOR_CLIP_DURATION)
                 dur_max = _safe_segment_duration(
                     cc.max_duration or cc.min_duration,
                     _DEFAULT_EDITOR_CLIP_DURATION,
@@ -492,7 +489,7 @@ def _get_mediakit_recommendations(
         prompt = (
             "请分析每段视频，找出最精彩的5秒片段应该从哪个时间点开始。"
             "考虑因素：画面清晰度、主体是否明确、是否有明显的动作或场景变化。"
-            '请严格以JSON数组格式返回，不要包含其他文字：'
+            "请严格以JSON数组格式返回，不要包含其他文字："
             '[{"asset_id": "素材ID", "recommended_start_time": 12.5, "reason": "原因"}]'
         )
 
@@ -545,9 +542,7 @@ def _get_mediakit_recommendations(
 
             # 尝试正则提取
             if not parsed:
-                time_match = re.search(
-                    r'recommended_start_time["\s:]+([\d.]+)', content_text
-                )
+                time_match = re.search(r'recommended_start_time["\s:]+([\d.]+)', content_text)
                 if time_match:
                     try:
                         recommendations[asset_id] = float(time_match.group(1))
@@ -598,14 +593,17 @@ def create_clips_from_assets_editor(
             detail="模板没有片段配置，无法创建片段",
         )
 
-    if not body.asset_ids:
+    # 防御：schema validator 已过滤 null/空串，这里再归一化一次，
+    # 避免异常入参（undefined → null）导致后续 /assets/{id} 404 / 422
+    asset_ids = [str(aid).strip() for aid in (body.asset_ids or []) if isinstance(aid, str) and aid.strip()]
+    if not asset_ids:
         raise HTTPException(
             status_code=status.HTTP_400_BAD_REQUEST,
             detail="素材列表为空，无法创建片段",
         )
 
     # 2. 获取素材实际时长（去重查询）
-    unique_asset_ids = list(dict.fromkeys(body.asset_ids))
+    unique_asset_ids = list(dict.fromkeys(asset_ids))
     asset_durations: dict[str, float] = {}
     for asset_id in unique_asset_ids:
         asset = asset_repo.get(asset_id)
@@ -615,9 +613,7 @@ def create_clips_from_assets_editor(
     # 3. 在内存中计算所有片段数据（使用随机起始时间，不调用MediaKit）
     # 读取素材 metadata 中持久化的历史已用区间（跨任务/跨调用去重），
     # 格式与 _calc_random_start_time 的 used_segments 参数一致
-    used_segments: dict[str, list[tuple[float, float]]] = get_used_segments(
-        db, unique_asset_ids
-    )
+    used_segments: dict[str, list[tuple[float, float]]] = get_used_segments(db, unique_asset_ids)
     # 受控复用回调：可用区间耗尽时复用最久未用且未达复用上限（3次）的历史区间，
     # 复用片段时长累加到 reused_durations 供 15% 占比控制
     reused_durations: dict[str, float] = {}
@@ -655,9 +651,9 @@ def create_clips_from_assets_editor(
         asset_id = ""
         clip_duration = 0.0
         start_time: float | None = None
-        n_assets = len(body.asset_ids)
+        n_assets = len(asset_ids)
         for offset in range(n_assets):
-            candidate = body.asset_ids[(i + offset) % n_assets]
+            candidate = asset_ids[(i + offset) % n_assets]
             candidate_total = asset_durations.get(candidate, 0.0)
             if candidate_total <= 0:
                 continue
@@ -701,18 +697,12 @@ def create_clips_from_assets_editor(
             )
 
         # 记录已使用时间段（内存，供本次后续片段避开）
-        used_segments.setdefault(asset_id, []).append(
-            (start_time, start_time + clip_duration)
-        )
-        asset_assigned_durations[asset_id] = (
-            asset_assigned_durations.get(asset_id, 0.0) + clip_duration
-        )
+        used_segments.setdefault(asset_id, []).append((start_time, start_time + clip_duration))
+        asset_assigned_durations[asset_id] = asset_assigned_durations.get(asset_id, 0.0) + clip_duration
         # 同步写入素材 metadata（不 commit，与下方 replace_all_clips_transactional
         # 处于同一事务，任一步失败整体回滚，不留脏数据）；
         # 复用区间与历史记录高度重叠时 record 内部自动累加 use_count
-        record_used_segments(
-            db, asset_id, start_time, start_time + clip_duration, plan_id
-        )
+        record_used_segments(db, asset_id, start_time, start_time + clip_duration, plan_id)
 
         clips_data.append(
             {
@@ -803,18 +793,14 @@ def _update_mediakit_recommendations_async(  # pragma: no cover
 
         # 批量预加载所有涉及的素材（消除 N+1 查询）
         unique_asset_ids = list({getattr(c, "asset_id", "") or "" for c in clips} - {""})
-        assets_map: dict[str, object] = {
-            a.id: a for a in asset_repo.find_by_ids(unique_asset_ids)
-        }
+        assets_map: dict[str, object] = {a.id: a for a in asset_repo.find_by_ids(unique_asset_ids)}
 
         # 按 asset_id 预分组片段时间段（消除 O(N^2) 嵌套循环）
         clips_by_asset: dict[str, list[tuple[str, float, float]]] = defaultdict(list)
         for clip in clips:
             aid = getattr(clip, "asset_id", "") or ""
             if aid and clip.start_time is not None:
-                clips_by_asset[aid].append(
-                    (clip.id, clip.start_time, clip.start_time + clip.duration)
-                )
+                clips_by_asset[aid].append((clip.id, clip.start_time, clip.start_time + clip.duration))
 
         # 读取素材全部历史已用区间（跨任务/跨 plan 持久化记录）：
         # MediaKit 挪点必须与随机选片一样避让历史区间，否则会把片段挪回已用过的画面
@@ -861,6 +847,7 @@ def _update_mediakit_recommendations_async(  # pragma: no cover
                 if cid != clip.id and cid not in updated_clip_ids
             ]
             other_segments.extend(updated_segments.get(asset_id, []))
+
             # 并入该素材全部历史已用区间（含其他 plan/其他任务），set 去重：
             # 本 plan 片段创建时已写入历史记录
             # 并入该素材全部历史已用区间（含其他 plan/其他任务）。
@@ -869,9 +856,7 @@ def _update_mediakit_recommendations_async(  # pragma: no cover
             def _norm(segs):
                 return {(round(float(a), 3), round(float(b), 3)) for a, b in segs}
 
-            other_segments = list(
-                _norm(other_segments) | _norm(historical_segments.get(asset_id, []))
-            )
+            other_segments = list(_norm(other_segments) | _norm(historical_segments.get(asset_id, [])))
 
             # 检查推荐时间是否与同 plan 片段或历史已用区间冲突（含 0.3s 边缘间隙）：
             # 冲突时放弃该推荐、保留原随机起点（不硬挪到已用过的画面）
@@ -893,9 +878,7 @@ def _update_mediakit_recommendations_async(  # pragma: no cover
                 # 保证 clip.start_time 与 metadata.used_time_ranges 不出现不一致。
                 plan_svc.update_clip(clip.id, start_time=recommended_start)
                 try:
-                    if remove_used_segment(
-                        db, asset_id, old_start, old_end, plan_id=plan_id
-                    ):
+                    if remove_used_segment(db, asset_id, old_start, old_end, plan_id=plan_id):
                         record_used_segments(
                             db,
                             asset_id,
@@ -915,18 +898,14 @@ def _update_mediakit_recommendations_async(  # pragma: no cover
                 updated_count += 1
                 updated_clip_ids.add(clip.id)
             except Exception as ue:
-                logger.warning(
-                    "后台任务: 单个片段更新失败: clip_id=%s error=%s", clip.id, ue
-                )
+                logger.warning("后台任务: 单个片段更新失败: clip_id=%s error=%s", clip.id, ue)
                 try:
                     db.rollback()
                 except Exception:
                     pass
                 continue
 
-            updated_segments.setdefault(asset_id, []).append(
-                (recommended_start, recommended_start + clip_duration)
-            )
+            updated_segments.setdefault(asset_id, []).append((recommended_start, recommended_start + clip_duration))
             logger.info(
                 "后台任务: 更新片段起始时间: clip_id=%s asset_id=%s start_time=%.2f",
                 clip.id,
@@ -950,4 +929,3 @@ def _update_mediakit_recommendations_async(  # pragma: no cover
                 db.close()
             except Exception:
                 pass
-
diff --git a/apps/api/app/api/routes/templates_editor/schemas.py b/apps/api/app/api/routes/templates_editor/schemas.py
index 2403d22b5..8d4f036b9 100755
--- a/apps/api/app/api/routes/templates_editor/schemas.py
+++ b/apps/api/app/api/routes/templates_editor/schemas.py
@@ -167,7 +167,18 @@ class ClipsFromAssetsRequest(BaseModel):
 
     asset_ids: List[str] = Field(..., min_length=1, max_length=200, description="素材 ID 列表，按顺序追加到时间线末尾")
     clip_type: str = Field(default="main", description="片段类型，默认 main")
-    required_clips_count: Optional[int] = Field(default=None, ge=1, le=200, description="要求创建的片段数量；不传则等于素材数量")
+    required_clips_count: Optional[int] = Field(
+        default=None, ge=1, le=200, description="要求创建的片段数量；不传则等于素材数量"
+    )
+
+    @validator("asset_ids", pre=True)
+    def _drop_invalid_asset_ids(cls, v):  # noqa: N805
+        """容错过滤：前端异常情况下可能把 undefined 序列化成 null 或空串混入
+        asset_ids（会直接 422 或导致后续 /assets/{id} 404），这里统一剔除。
+        过滤后为空时由 Field(min_length=1) / 路由层 400 兜底。"""
+        if not isinstance(v, list):
+            return v
+        return [x for x in v if isinstance(x, str) and x.strip()]
 
 
 class ClipsFromAssetsResponse(BaseModel):
diff --git a/apps/api/app/schemas/asset.py b/apps/api/app/schemas/asset.py
index 1f9d2927c..39480135a 100755
--- a/apps/api/app/schemas/asset.py
+++ b/apps/api/app/schemas/asset.py
@@ -129,10 +129,13 @@ class SmartMatchRequest(BaseModel):
     )
 
 
-class SmartMatchItem(BaseModel):
-    """智能选素材结果条目。"""
+class SmartMatchItem(AssetResponse):
+    """智能选素材结果条目（扁平结构）。
+
+    素材字段（id/usable/余量等）直接挂在条目顶层，前端拿到 item 即可读 item.id，
+    与 AssetResponse 字段完全一致；score/breakdown 为智能匹配附加的评分字段。
+    """
 
-    asset: AssetResponse
     score: float = Field(..., ge=0, le=100, description="综合得分 0-100")
     breakdown: dict[str, float] = Field(default_factory=dict, description="各维度得分明细")
 
diff --git a/tests/unit/test_asset_availability.py b/tests/unit/test_asset_availability.py
index e12d6da18..8e9cda6e2 100755
--- a/tests/unit/test_asset_availability.py
+++ b/tests/unit/test_asset_availability.py
@@ -386,14 +386,14 @@ class TestSmartMatchFiltersExhausted:
             _fresh_asset("a-fresh-1"),
         ]
         resp = self._call(assets)
-        returned_ids = {item.asset.id for item in resp.items}
+        returned_ids = {item.id for item in resp.items}
         assert "a-fresh-1" in returned_ids
         assert "a-exhausted-1" not in returned_ids
         assert "a-exhausted-2" not in returned_ids
         # total_candidates 是过滤前的候选总数
         assert resp.total_candidates == 3
         # 返回的素材全部 usable=True
-        assert all(item.asset.usable for item in resp.items)
+        assert all(item.usable for item in resp.items)
 
     def test_all_exhausted_returns_empty(self):
         """全部素材已用尽时返回空列表（不报错，前端显示空结果）。"""
@@ -406,4 +406,49 @@ class TestSmartMatchFiltersExhausted:
         assets = [_fresh_asset("a-1"), _fresh_asset("a-2")]
         resp = self._call(assets)
         assert len(resp.items) == 2
-        assert all(item.asset.usable for item in resp.items)
+        assert all(item.usable for item in resp.items)
+
+
+class TestSmartMatchFlatStructure:
+    """P0 回归：smart-match 响应必须扁平——item 顶层直接可读素材字段，
+    前端 items.map(a => a.id) 不能再拿到 undefined（此前 item.asset 嵌套包装
+    导致 GET /assets/undefined 404 + from-assets 422，自动模式全链路断裂）。"""
+
+    def test_item_id_at_top_level(self):
+        """item.id 直接在顶层可读，不存在 item.asset 包装层。"""
+        assets = [_fresh_asset("a-flat-1"), _fresh_asset("a-flat-2")]
+        resp = TestSmartMatchFiltersExhausted()._call(assets)
+        ids = [item.id for item in resp.items]
+        assert ids == ["a-flat-1", "a-flat-2"]
+        # 嵌套 asset 字段已移除
+        assert all(not hasattr(item, "asset") for item in resp.items)
+
+    def test_item_is_asset_response_superset(self):
+        """条目携带 AssetResponse 全部关键字段 + usable/余量，前端可直接渲染卡片。"""
+        assets = [_fresh_asset("a-fields-1")]
+        resp = TestSmartMatchFiltersExhausted()._call(assets)
+        item = resp.items[0]
+        assert item.id == "a-fields-1"
+        assert item.name == "fresh-a-fields-1"
+        assert item.storage_key == "key/test-asset.mp4"
+        assert item.mime_type == "video/mp4"
+        assert item.duration == 60.0
+        assert item.status == "ready"
+        assert item.thumbnail_url is None or item.thumbnail_url.startswith("http")
+        # 余量/可用性字段顶层可读（isAssetUsable 依赖）
+        assert item.usable is True
+        assert item.used_duration == 0.0
+        assert item.available_duration == 60.0
+        assert item.used_ratio == 0.0
+        # 评分字段保留
+        assert 0.0 <= item.score <= 100.0
+        assert isinstance(item.breakdown, dict)
+
+    def test_score_and_breakdown_preserved(self):
+        """扁平化后评分字段不丢失。"""
+        assets = [_fresh_asset("a-score-1")]
+        resp = TestSmartMatchFiltersExhausted()._call(assets)
+        item = resp.items[0]
+        assert isinstance(item.score, float)
+        assert item.score > 0
+        assert isinstance(item.breakdown, dict) and item.breakdown
diff --git a/tests/unit/test_editor_clips_random_start.py b/tests/unit/test_editor_clips_random_start.py
index 6501a6fa7..bba35e223 100644
--- a/tests/unit/test_editor_clips_random_start.py
+++ b/tests/unit/test_editor_clips_random_start.py
@@ -747,3 +747,83 @@ class TestReuseRatioGate:
         assert len(clips_data) == 2
         # 耗尽素材被跳过，两个片段都分配给新鲜素材
         assert all(c["asset_id"] == "fresh" for c in clips_data)
+
+
+# ── P0 回归：from-assets 对 undefined/null/空串 asset_ids 容错 ──────────────
+# 线上事故：前端 smart-match 拿到 {asset: {...}} 包装层后 items.map(a=>a.id)
+# 全为 undefined，POST /clips/from-assets 携带 null → 422，自动模式预览断裂。
+
+
+class TestClipsFromAssetsInvalidIds:
+    def test_schema_filters_null_and_empty_ids(self):
+        """请求 schema 在 pre 阶段剔除 null/空串/空白 id，不触发 422。"""
+        from app.api.routes.templates_editor.schemas import ClipsFromAssetsRequest
+
+        body = ClipsFromAssetsRequest(asset_ids=["a1", None, "", "  ", "a2"])  # type: ignore[list-item]
+        assert body.asset_ids == ["a1", "a2"]
+
+    def test_schema_all_invalid_raises(self):
+        """全部为非法 id 时 min_length=1 兜底报校验错误（前端得到 422 而非脏数据）。"""
+        from app.api.routes.templates_editor.schemas import ClipsFromAssetsRequest
+        from pydantic import ValidationError
+
+        with pytest.raises(ValidationError):
+            ClipsFromAssetsRequest(asset_ids=[None, "", "  "])  # type: ignore[list-item]
+
+    @patch("app.api.routes.templates_editor.clips.get_storage_service")
+    def test_route_filters_invalid_ids_and_uses_valid(self, mock_storage):
+        """路由层二次兜底：混有 null/空串时只用合法 id 正常创建片段。"""
+        from app.api.routes.templates_editor.clips import (
+            create_clips_from_assets_editor,
+        )
+        from app.api.routes.templates_editor.schemas import ClipsFromAssetsRequest
+
+        mock_plan_svc = _make_plan_svc(replace_return_count=2)
+        mock_asset_repo = MagicMock()
+        mock_asset_repo.get = MagicMock(side_effect=lambda aid: _make_mock_asset(aid, 30.0))
+
+        body = ClipsFromAssetsRequest(asset_ids=["a1", None, "", "a2"])  # type: ignore[list-item]
+
+        with _patch_segments(_segments(2, dur_min=3.0, dur_max=5.0)):
+            result = create_clips_from_assets_editor(
+                template_id="tpl-001",
+                body=body,
+                background_tasks=MagicMock(),
+                plan_id=TEST_PLAN_ID,
+                services=(MagicMock(), mock_plan_svc),
+                asset_repo=mock_asset_repo,
+                db=MagicMock(),
+                current_user=_make_auth_user(),
+            )
+
+        assert result.created_count == 2
+        clips_data = _get_clips_data_from_call(mock_plan_svc)
+        assert {c["asset_id"] for c in clips_data} == {"a1", "a2"}
+
+    @patch("app.api.routes.templates_editor.clips.get_storage_service")
+    def test_route_all_empty_ids_raises_400(self, mock_storage):
+        """schema 被绕过直接调路由、且 id 全非法时，路由 400 而非 500/422。"""
+        from app.api.routes.templates_editor.clips import (
+            create_clips_from_assets_editor,
+        )
+
+        mock_plan_svc = _make_plan_svc()
+        mock_asset_repo = MagicMock()
+
+        body = MagicMock()
+        body.asset_ids = [None, "", "  "]
+
+        with _patch_segments(DEFAULT_SEGMENTS):
+            with pytest.raises(HTTPException) as exc_info:
+                create_clips_from_assets_editor(
+                    template_id="tpl-001",
+                    body=body,
+                    background_tasks=MagicMock(),
+                    plan_id=TEST_PLAN_ID,
+                    services=(MagicMock(), mock_plan_svc),
+                    asset_repo=mock_asset_repo,
+                    db=MagicMock(),
+                    current_user=_make_auth_user(),
+                )
+        assert exc_info.value.status_code == 400
+        mock_plan_svc.replace_all_clips_transactional.assert_not_called()
diff --git a/tests/unit/test_smart_match.py b/tests/unit/test_smart_match.py
index 3a7b12266..0a31b4c34 100755
--- a/tests/unit/test_smart_match.py
+++ b/tests/unit/test_smart_match.py
@@ -425,6 +425,12 @@ class TestSmartMatchEndpoint:
         for item in data["items"]:
             assert "quality" in item["breakdown"]
             assert "duration" in item["breakdown"]
+        # P0 回归：扁平结构——素材字段在 item 顶层，无 asset 包装层
+        for item in data["items"]:
+            assert item["id"]
+            assert "asset" not in item
+            assert item["mime_type"].startswith("video/")
+            assert "usable" in item
 
     def test_limit_parameter(self):
         project, library, assets = _make_test_data()
@@ -463,7 +469,7 @@ class TestSmartMatchEndpoint:
         assert resp.status_code == 200
         data = resp.json()
         assert len(data["items"]) == 1
-        assert data["items"][0]["asset"]["mime_type"] == "image/png"
+        assert data["items"][0]["mime_type"] == "image/png"
         # total_candidates should only count filtered-by-kind assets (1 image, not 3 videos)
         assert data["total_candidates"] == 1