diff --git a/backend/src/module/database/user.py b/backend/src/module/database/user.py
index efba0618..f3a69069 100644
--- a/backend/src/module/database/user.py
+++ b/backend/src/module/database/user.py
@@ -73,10 +73,15 @@ class UserDatabase:
         try:
             result = self.session.exec(statement)
             users = list(result.all())
-        except Exception:
+        except Exception as e:
+            # Table may not exist yet during initial setup
+            logger.debug(
+                f"[Database] Could not query users table (may not exist yet): {e}"
+            )
             users = []
         if len(users) != 0:
             return
         user = User(username="admin", password=get_password_hash("adminadmin"))
         self.session.add(user)
         self.session.commit()
+        logger.info("[Database] Created default admin user")
diff --git a/backend/src/module/downloader/client/qb_downloader.py b/backend/src/module/downloader/client/qb_downloader.py
index b053c957..90efe007 100644
--- a/backend/src/module/downloader/client/qb_downloader.py
+++ b/backend/src/module/downloader/client/qb_downloader.py
@@ -26,9 +26,7 @@ class QbDownloader:
     async def auth(self, retry=3):
         times = 0
         timeout = httpx.Timeout(connect=3.1, read=10.0, write=10.0, pool=10.0)
-        self._client = httpx.AsyncClient(
-            timeout=timeout, verify=self.ssl
-        )
+        self._client = httpx.AsyncClient(timeout=timeout, verify=self.ssl)
         while times < retry:
             try:
                 resp = await self._client.post(
@@ -61,8 +59,12 @@ class QbDownloader:
         if self._client:
             try:
                 await self._client.post(self._url("auth/logout"))
-            except Exception:
-                pass
+            except (
+                httpx.ConnectError,
+                httpx.RequestError,
+                httpx.TimeoutException,
+            ) as e:
+                logger.debug(f"[Downloader] Logout request failed (non-critical): {e}")
             await self._client.aclose()
             self._client = None
 
@@ -114,7 +116,9 @@ class QbDownloader:
         )
         return resp.json()
 
-    async def add_torrents(self, torrent_urls, torrent_files, save_path, category, tags=None):
+    async def add_torrents(
+        self, torrent_urls, torrent_files, save_path, category, tags=None
+    ):
         data = {
             "savepath": save_path,
             "category": category,
@@ -133,9 +137,17 @@ class QbDownloader:
         if torrent_files:
             if isinstance(torrent_files, list):
                 for i, f in enumerate(torrent_files):
-                    files[f"torrents_{i}"] = (f"torrent_{i}.torrent", f, "application/x-bittorrent")
+                    files[f"torrents_{i}"] = (
+                        f"torrent_{i}.torrent",
+                        f,
+                        "application/x-bittorrent",
+                    )
             else:
-                files["torrents"] = ("torrent.torrent", torrent_files, "application/x-bittorrent")
+                files["torrents"] = (
+                    "torrent.torrent",
+                    torrent_files,
+                    "application/x-bittorrent",
+                )
 
         max_retries = 3
         for attempt in range(max_retries):
@@ -153,14 +165,14 @@ class QbDownloader:
                     )
                     await asyncio.sleep(2)
                 else:
-                    logger.error(f"[Downloader] Failed to add torrent after {max_retries} attempts: {e}")
+                    logger.error(
+                        f"[Downloader] Failed to add torrent after {max_retries} attempts: {e}"
+                    )
                     raise
 
     async def get_torrents_by_tag(self, tag: str) -> list[dict]:
         """Get all torrents with a specific tag."""
-        resp = await self._client.get(
-            self._url("torrents/info"), params={"tag": tag}
-        )
+        resp = await self._client.get(self._url("torrents/info"), params={"tag": tag})
         return resp.json()
 
     async def torrents_delete(self, hash, delete_files: bool = True):
@@ -191,7 +203,8 @@ class QbDownloader:
                 logger.debug(f"Conflict409Error: {old_path} >> {new_path}")
                 return False
             return resp.status_code == 200
-        except Exception:
+        except (httpx.ConnectError, httpx.RequestError, httpx.TimeoutException) as e:
+            logger.warning(f"[Downloader] Failed to rename file {old_path}: {e}")
             return False
 
     async def rss_add_feed(self, url, item_path):
@@ -216,6 +229,7 @@ class QbDownloader:
 
     async def rss_set_rule(self, rule_name, rule_def):
         import json
+
         await self._client.post(
             self._url("rss/setRule"),
             data={"ruleName": rule_name, "ruleDef": json.dumps(rule_def)},
diff --git a/backend/src/module/downloader/download_client.py b/backend/src/module/downloader/download_client.py
index 77261c87..8b2a8e9a 100644
--- a/backend/src/module/downloader/download_client.py
+++ b/backend/src/module/downloader/download_client.py
@@ -70,10 +70,13 @@ class DownloadClient(TorrentPath):
             "rss_refresh_interval": 30,
         }
         await self.client.prefs_init(prefs=prefs)
+        # Category creation may fail if it already exists (HTTP 409) or network issues
         try:
             await self.client.add_category("BangumiCollection")
-        except Exception:
-            logger.debug("[Downloader] Cannot add new category, maybe already exists.")
+        except Exception as e:
+            logger.debug(
+                f"[Downloader] Could not add category (may already exist): {e}"
+            )
         if settings.downloader.path == "":
             prefs = await self.client.get_app_prefs()
             settings.downloader.path = self._join_path(prefs["save_path"], "Bangumi")
@@ -107,7 +110,9 @@ class DownloadClient(TorrentPath):
         await asyncio.gather(*[self.set_rule(info) for info in bangumi_info])
         logger.debug("[Downloader] Finished.")
 
-    async def get_torrent_info(self, category="Bangumi", status_filter="completed", tag=None):
+    async def get_torrent_info(
+        self, category="Bangumi", status_filter="completed", tag=None
+    ):
         return await self.client.torrents_info(
             status_filter=status_filter, category=category, tag=tag
         )
@@ -137,7 +142,9 @@ class DownloadClient(TorrentPath):
         async with RequestContent() as req:
             if isinstance(torrent, list):
                 if len(torrent) == 0:
-                    logger.debug(f"[Downloader] No torrent found: {bangumi.official_title}")
+                    logger.debug(
+                        f"[Downloader] No torrent found: {bangumi.official_title}"
+                    )
                     return False
                 if "magnet" in torrent[0].url:
                     torrent_url = [t.url for t in torrent]
@@ -149,7 +156,9 @@ class DownloadClient(TorrentPath):
                     # Filter out None values (failed fetches)
                     torrent_file = [f for f in torrent_file if f is not None]
                     if not torrent_file:
-                        logger.warning(f"[Downloader] Failed to fetch torrent files for: {bangumi.official_title}")
+                        logger.warning(
+                            f"[Downloader] Failed to fetch torrent files for: {bangumi.official_title}"
+                        )
                         return False
                     torrent_url = None
             else:
@@ -159,7 +168,9 @@ class DownloadClient(TorrentPath):
                 else:
                     torrent_file = await req.get_content(torrent.url)
                     if torrent_file is None:
-                        logger.warning(f"[Downloader] Failed to fetch torrent file for: {bangumi.official_title}")
+                        logger.warning(
+                            f"[Downloader] Failed to fetch torrent file for: {bangumi.official_title}"
+                        )
                         return False
                     torrent_url = None
         # Create tag with bangumi_id for offset lookup during rename
@@ -175,10 +186,14 @@ class DownloadClient(TorrentPath):
                 logger.debug(f"[Downloader] Add torrent: {bangumi.official_title}")
                 return True
             else:
-                logger.debug(f"[Downloader] Torrent added before: {bangumi.official_title}")
+                logger.debug(
+                    f"[Downloader] Torrent added before: {bangumi.official_title}"
+                )
                 return False
         except Exception as e:
-            logger.error(f"[Downloader] Failed to add torrent for {bangumi.official_title}: {e}")
+            logger.error(
+                f"[Downloader] Failed to add torrent for {bangumi.official_title}: {e}"
+            )
             return False
 
     async def move_torrent(self, hashes, location):
diff --git a/backend/src/module/parser/title_parser.py b/backend/src/module/parser/title_parser.py
index 96f757ef..78a84271 100644
--- a/backend/src/module/parser/title_parser.py
+++ b/backend/src/module/parser/title_parser.py
@@ -44,7 +44,9 @@ class TitleParser:
 
     @staticmethod
     async def tmdb_poster_parser(bangumi: Bangumi):
-        tmdb_info = await tmdb_parser(bangumi.official_title, settings.rss_parser.language)
+        tmdb_info = await tmdb_parser(
+            bangumi.official_title, settings.rss_parser.language
+        )
         if tmdb_info:
             logger.debug(f"TMDB Matched, official title is {tmdb_info.title}")
             bangumi.poster_link = tmdb_info.poster_link
@@ -98,9 +100,8 @@ class TitleParser:
                 offset=0,
                 filter=",".join(settings.rss_parser.filter),
             )
-        except Exception as e:
-            logger.debug(e)
-            logger.warning(f"Cannot parse {raw}.")
+        except (ValueError, AttributeError, TypeError) as e:
+            logger.warning(f"Cannot parse '{raw}': {type(e).__name__}: {e}")
             return None
 
     @staticmethod