diff --git a/backend/internal/store/store.go b/backend/internal/store/store.go
index eb0effc..70e5121 100644
--- a/backend/internal/store/store.go
+++ b/backend/internal/store/store.go
@@ -147,8 +147,6 @@ func scanUser(row pgx.Row) (User, error) {
 	return u, err
 }
 
-
-
 // ---------- libraries ----------
 
 func (s *Store) CreateLibrary(ctx context.Context, name, root string) (int64, error) {
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index dff0d81..55a6e63 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -8,6 +8,35 @@ The format loosely follows Keep a Changelog and can be adapted to the team's hab
 
 ## [Unreleased]
 
+### Fixed / 修复
+
+- Rate limiter `IncrWindow` uses atomic Lua script for INCR+EXPIRE, preventing permanent IP lockout on EXPIRE failure (B1).
+- 限流器 `IncrWindow` 改用 Lua 脚本原子执行 INCR+EXPIRE，防止 EXPIRE 失败导致 IP 永久锁定（B1）。
+- Distributed lock `Lock` handles `rand.Read` failure by degrading to no-lock instead of using a zero token (B2).
+- 分布式锁 `Lock` 在 `rand.Read` 失败时降级为无锁模式，而非使用全零 token（B2）。
+- Lock unlock uses `context.WithoutCancel` to survive caller cancellation (B3).
+- 锁的解锁改用 `context.WithoutCancel`，在调用方上下文取消后仍能正常释放（B3）。
+- Upload part writes to `.tmp` then renames, preventing truncated parts from being reported as received (B4).
+- 分片上传先写 `.tmp` 再 rename，防止崩溃截断的分片被误报为已接收（B4）。
+- `DeleteUser` last-admin check is now transactional, eliminating TOCTOU race (B5).
+- `DeleteUser` 的最后管理员检查改为事务内执行，消除 TOCTOU 竞态（B5）。
+- Single-file upload `io.Copy` errors other than `MaxBytesError` return 500 instead of 413 (B6).
+- 单文件上传中非 `MaxBytesError` 的 `io.Copy` 错误返回 500 而非 413（B6）。
+- `/auth/me` distinguishes `no rows` (401) from database errors (503) (B7).
+- `/auth/me` 区分无记录（401）和数据库错误（503）（B7）。
+- Library creation rejects reserved names (`cache`, `.uploads`) with `400 reserved_name` (B8).
+- 创建书库时拒绝保留名（`cache`、`.uploads`），返回 `400 reserved_name`（B8）。
+- Scanner lock auto-renews every TTL/2 during long scans; per-library single-flight prevents concurrent scans (B9).
+- 扫描锁每 TTL/2 自动续期；库级 single-flight 防止并发扫描（B9）。
+- Scanner `SetBookState` errors are now logged instead of silently discarded (B10).
+- 扫描器 `SetBookState` 的错误现在会记录日志而非静默丢弃（B10）。
+- Cover write errors fully checked; orphan `.tmp` files cleaned only on failure (B11).
+- 封面写入错误全部检查；孤儿 `.tmp` 文件仅在失败路径清理（B11）。
+- Upload handler retries on `O_EXCL` collision for concurrent same-name uploads (B12).
+- 上传处理器在 `O_EXCL` 冲突时重试，处理并发同名上传（B12）。
+- Bookmark methods check `err` before `RowsAffected` to avoid invalid reads on query failure (B13).
+- 书签方法先检查 `err` 再读 `RowsAffected`，避免查询失败时的无效读取（B13）。
+
 ### Changed / 变更
 
 - Add ordered migration system with `schema_migrations` tracking and pg advisory lock for safe multi-replica schema evolution. Existing databases are auto-baselined. To change the schema, add a new `NNNN_description.sql` file under `backend/internal/db/migrations/`; never modify an already-applied file. No down migrations — rollback via backup, fix-forward.