diff --git a/app/db/models/downloadhistory.py b/app/db/models/downloadhistory.py
index fc1ecad4e..af6f22173 100644
--- a/app/db/models/downloadhistory.py
+++ b/app/db/models/downloadhistory.py
@@ -1,16 +1,16 @@
 import time
-from typing import Any, List, Optional
+from typing import Any, List, Optional, Self
 
-from sqlalchemy import JSON, Index, Integer, String, delete, func, select, update
+from sqlalchemy import JSON, ColumnElement, Index, Integer, String, delete, func, select, update
 from sqlalchemy.ext.asyncio import AsyncSession
-from sqlalchemy.orm import Mapped, Session, mapped_column
+from sqlalchemy.orm import InstrumentedAttribute, Mapped, Session, mapped_column
 
 from app.db.base import Base, execute_dml, get_id_column
 from app.db.models._constraints import media_identity_constraint
 from app.schemas.types import MediaSource
 
 
-def _title_like(column, title: str):
+def _title_like(column: InstrumentedAttribute[str], title: str) -> ColumnElement[bool]:
     """构造跨数据库大小写不敏感的标题匹配条件。"""
     return column.ilike(f"%{title}%")
 
@@ -84,15 +84,17 @@ class DownloadHistory(Base):
     )
 
     @classmethod
-    def get_by_hash(cls, db: Session, download_hash: str):
-        return db.execute(
+    def get_by_hash(cls, db: Session, download_hash: str) -> Optional["DownloadHistory"]:
+        """按下载任务哈希读取登记时间最新的下载历史。"""
+        history: Optional[DownloadHistory] = db.execute(
             select(DownloadHistory)
             .where(DownloadHistory.download_hash == download_hash)
             .order_by(DownloadHistory.date.desc())
         ).scalars().first()
+        return history
 
     @classmethod
-    def get_by_hashes(cls, db: Session, download_hashes: List[str]):
+    def get_by_hashes(cls, db: Session, download_hashes: List[str]) -> list["DownloadHistory"]:
         """
         批量查询多个下载任务的最新历史记录，避免在上层形成 N+1 查询。
         """
@@ -127,7 +129,7 @@ class DownloadHistory(Base):
     def get_by_media_identity(
             cls, db: Session, media_source: MediaSource, media_id: str,
             music_type: Optional[str] = None,
-    ):
+    ) -> list["DownloadHistory"]:
         """按规范媒体身份查询下载历史。"""
         if not media_source or media_id is None or not str(media_id).strip():
             return []
@@ -142,7 +144,8 @@ class DownloadHistory(Base):
     @classmethod
     def list_by_page(
         cls, db: Session, page: int = 1, count: int = 30
-    ):
+    ) -> list["DownloadHistory"]:
+        """按时间和主键倒序分页读取下载历史。"""
         return list(db.execute(
             select(DownloadHistory)
             .order_by(DownloadHistory.date.desc(), DownloadHistory.id.desc())
@@ -153,7 +156,8 @@ class DownloadHistory(Base):
     @classmethod
     async def async_list_by_page(
         cls, db: AsyncSession, page: int = 1, count: int = 30
-    ):
+    ) -> list[Self]:
+        """异步按时间和主键倒序分页读取下载历史。"""
         result = await db.execute(
             select(cls)
             .order_by(cls.date.desc(), cls.id.desc())
@@ -169,7 +173,8 @@ class DownloadHistory(Base):
         title: str,
         page: int = 1,
         count: int = 30,
-    ):
+    ) -> list[Self]:
+        """异步按标题模糊匹配并分页读取下载历史。"""
         query = (
             select(cls).filter(_title_like(cls.title, title)).order_by(cls.date.desc())
         )
@@ -178,24 +183,29 @@ class DownloadHistory(Base):
         return list(result.scalars().all())
 
     @classmethod
-    async def async_count(cls, db: AsyncSession):
+    async def async_count(cls, db: AsyncSession) -> int:
+        """异步统计下载历史总数，空表返回零。"""
         result = await db.execute(select(func.count(cls.id)))
-        return result.scalar()
+        count: int = result.scalar()
+        return count
 
     @classmethod
-    async def async_count_by_title(cls, db: AsyncSession, title: str):
+    async def async_count_by_title(cls, db: AsyncSession, title: str) -> int:
+        """异步统计标题模糊匹配的下载历史数量。"""
         result = await db.execute(
             select(func.count(cls.id)).filter(_title_like(cls.title, title))
         )
-        return result.scalar()
+        count: int = result.scalar()
+        return count
 
     @classmethod
-    def get_by_path(cls, db: Session, path: str):
+    def get_by_path(cls, db: Session, path: str) -> Optional["DownloadHistory"]:
         """保存目录被多次下载复用时，按登记顺序返回最新历史。"""
-        return db.execute(
+        history: Optional[DownloadHistory] = db.execute(
             select(DownloadHistory).where(DownloadHistory.path == path)
             .order_by(DownloadHistory.id.desc()).limit(1)
         ).scalars().first()
+        return history
 
     @classmethod
     def get_last_by(
@@ -208,7 +218,7 @@ class DownloadHistory(Base):
         episode: Optional[str] = None,
         media_source: Optional[MediaSource] = None,
         media_id: Optional[str] = None,
-    ):
+    ) -> list["DownloadHistory"]:
         """
         按媒体身份、季集或标题年份查询下载记录。
         """
@@ -235,7 +245,7 @@ class DownloadHistory(Base):
         ).scalars().all())
 
     @classmethod
-    def list_by_user_date(cls, db: Session, date: str, username: Optional[str] = None):
+    def list_by_user_date(cls, db: Session, date: str, username: Optional[str] = None) -> list["DownloadHistory"]:
         """
         查询某用户某时间之前的下载历史。
 
@@ -261,7 +271,7 @@ class DownloadHistory(Base):
         media_source: MediaSource,
         media_id: str,
         seasons: Optional[str] = None,
-    ):
+    ) -> list["DownloadHistory"]:
         """
         查询某时间之后的下载历史
         """
@@ -278,7 +288,8 @@ class DownloadHistory(Base):
         ).scalars().all())
 
     @classmethod
-    def list_by_type(cls, db: Session, mtype: str, days: int):
+    def list_by_type(cls, db: Session, mtype: str, days: int) -> list["DownloadHistory"]:
+        """读取指定媒体类型在最近若干天内的下载历史。"""
         return list(db.execute(
             select(DownloadHistory).where(
                 DownloadHistory.type == mtype,
@@ -340,25 +351,30 @@ class DownloadFiles(Base):
     )
 
     @classmethod
-    def get_by_hash(cls, db: Session, download_hash: str, state: Optional[int] = None):
+    def get_by_hash(cls, db: Session, download_hash: str, state: Optional[int] = None) -> list[Self]:
+        """按下载任务哈希读取文件列表，可选限定文件状态。"""
         statement = select(cls).where(cls.download_hash == download_hash)
         if state is not None:
             statement = statement.where(cls.state == state)
         return list(db.execute(statement).scalars().all())
 
     @classmethod
-    def get_by_fullpath(cls, db: Session, fullpath: str, all_files: bool = False):
+    def get_by_fullpath(cls, db: Session, fullpath: str, all_files: bool = False) -> list[Self] | Self | None:
+        """按完整路径返回最新记录，或在 all_files 为真时返回全部记录。"""
         result = db.execute(
             select(cls).where(cls.fullpath == fullpath).order_by(cls.id.desc())
         ).scalars()
-        return list(result.all()) if all_files else result.first()
+        files: list[Self] | Self | None = list(result.all()) if all_files else result.first()
+        return files
 
     @classmethod
-    def get_by_savepath(cls, db: Session, savepath: str):
+    def get_by_savepath(cls, db: Session, savepath: str) -> list[Self]:
+        """读取同一保存目录下的全部下载文件记录。"""
         return list(db.execute(select(cls).where(cls.savepath == savepath)).scalars().all())
 
     @classmethod
-    def delete_by_fullpath(cls, db: Session, fullpath: str):
+    def delete_by_fullpath(cls, db: Session, fullpath: str) -> None:
+        """把完整路径匹配的正常文件标记为删除，保留历史记录。"""
         db.execute(
             update(cls).where(cls.fullpath == fullpath, cls.state == 1).values(state=0)
         )
diff --git a/docs/code-quality.md b/docs/code-quality.md
index 519d6cda8..bf5ff3276 100644
--- a/docs/code-quality.md
+++ b/docs/code-quality.md
@@ -75,7 +75,7 @@ uv run --locked --no-sync python scripts/architecture/complexity.py
 回调和返回值类型；全仓错误计数为零并不保证单独纳入 strict frontier 后也为零。
 
 2026-10-16 开始逐文件清理类型债务，`app/domain/title.py` 通过局部可空类型声明保留
-既有搜索解析行为，并纳入严格清单；当前清单共 131 个文件（130 个生产文件和 1 个脚本）。
+既有搜索解析行为，并纳入严格清单；当前清单共 132 个文件（131 个生产文件和 1 个脚本）。
 每个治理提交聚焦一个生产文件及其必要测试、门禁配置、真实下降基线和指标文档。
 验收同时检查完整严格清单与全宿主 Linux 分析，避免 `follow_imports = skip` 隐藏依赖
 签名冲突；不通过忽略诊断或放宽类型合同接受回退。最新文件清单以 `mypy.ini` 为准，
diff --git a/docs/refactor/optimization-checklist.md b/docs/refactor/optimization-checklist.md
index 688524c26..b168faab1 100644
--- a/docs/refactor/optimization-checklist.md
+++ b/docs/refactor/optimization-checklist.md
@@ -106,9 +106,9 @@ ARCH-201 至 ARCH-204 均达到实现、验证、提交、推送和远端门禁
 | Model/Oper 事务债务 | 0 | 自建 Session、自动事务装饰器、直接 commit/rollback 等基线均为零 |
 | Module Contract | 215 specs / 211 methods / 263 calls | 动态方法名为 0；分类事实富化通过显式合同进入插件调度，旧 YAML 分类方法已移除；download 新增 custom_words 可选参数，旧 provider 签名通过显式合同兼容 |
 | Event Contract | 53 | 均已有 payload model，但当前全部是 diagnostic enforcement |
-| Python 源码量 | 372,622 行 | 本次重新扫描物理行数，排除 `app/plugins/**`；74 个文件超过 1,000 行，12 个超过 2,000 行；源码尺寸仅作观察 |
+| Python 源码量 | 372,638 行 | 本次重新扫描物理行数，排除 `app/plugins/**`；74 个文件超过 1,000 行，12 个超过 2,000 行；源码尺寸仅作观察 |
 | 长方法 | 309 个超过 80 行 | 本次 AST 扫描排除 `app/plugins/**`；61 个超过 150 行，17 个超过 250 行；新增函数仍受 C901/嵌套深度门禁约束 |
-| 全量 mypy 历史债务 | 8,648 / 424 文件 | 通知排版补齐 Slack 消息块类型，历史债务减少 2 项；工作流资源过滤改用领域对象调用过滤链，恢复的节点输出在消费前归一化，并收紧可空资源列表的类型低水位；消息媒体交互类型债务已清零，canonical Facade 与 endpoint 类型边界已补齐，低水位只允许继续下降；微信 ClawBot 入站 item_list 媒体解析改为按子项键名分派后，类型错误减少 4 项；站点解析器分享率改用浮点初值，类型错误减少 20 项；本次下载与文件安全修复再减少 3 项；Transmission 进度回退值归一化再减少 2 项，逐文件逐错误码无增长 |
+| 全量 mypy 历史债务 | 8,627 / 423 文件 | 通知排版补齐 Slack 消息块类型，历史债务减少 2 项；工作流资源过滤改用领域对象调用过滤链，恢复的节点输出在消费前归一化，并收紧可空资源列表的类型低水位；消息媒体交互类型债务已清零，canonical Facade 与 endpoint 类型边界已补齐，低水位只允许继续下降；微信 ClawBot 入站 item_list 媒体解析改为按子项键名分派后，类型错误减少 4 项；站点解析器分享率改用浮点初值，类型错误减少 20 项；本次下载与文件安全修复再减少 3 项；Transmission 进度回退值归一化再减少 2 项，逐文件逐错误码无增长 |
 | Ruff 历史诊断 | 98 | 低水位门禁通过，但规则集只覆盖 `E4/E7/E9/F/I` |
 | 覆盖率固定基线 | Application 80.00%，Domain 80.00% | Chain、Runtime、Agent、Adapter、Startup 未进入包级覆盖率门禁 |
 
diff --git a/mypy.ini b/mypy.ini
index 3332aa8e5..4d8af5fc9 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -110,6 +110,7 @@ files =
     app/db/models/agenttask.py,
     app/db/models/agenttaskrun.py,
     app/db/models/downloadfailure.py,
+    app/db/models/downloadhistory.py,
     app/db/models/mediaserver.py,
     app/db/models/message.py,
     app/db/models/passkey.py,
diff --git a/tests/fixtures/architecture/mypy-baseline.json b/tests/fixtures/architecture/mypy-baseline.json
index 0216b9a8f..3cda9505d 100644
--- a/tests/fixtures/architecture/mypy-baseline.json
+++ b/tests/fixtures/architecture/mypy-baseline.json
@@ -977,9 +977,6 @@
     "no-any-return": 1,
     "redundant-cast": 2
   },
-  "app/db/models/downloadhistory.py": {
-    "no-untyped-def": 19
-  },
   "app/db/models/subscribe.py": {
     "arg-type": 8,
     "no-untyped-def": 18
@@ -990,7 +987,7 @@
     "type-arg": 1
   },
   "app/db/oper/downloadhistory.py": {
-    "no-any-return": 3,
+    "no-any-return": 1,
     "no-untyped-def": 9,
     "type-arg": 3,
     "union-attr": 2