fix(qbittorrent): preserve torrent metadata in incremental updates

backend/src/media_library_viewer_api/clients/qbittorrent.py

@@ -220,7 +220,12 @@ class QbittorrentClient:
                 if fields is None:
                     snap["torrents"].pop(hash_, None)
                 else:
-                    snap["torrents"][hash_] = fields
+                    previous = snap["torrents"].get(hash_)
+                    snap["torrents"][hash_] = (
+                        {**previous, **fields}
+                        if isinstance(previous, dict) and isinstance(fields, dict)
+                        else fields
+                    )
         for hash_ in update.get("torrents_removed") or []:
             snap["torrents"].pop(hash_, None)
         categories = update.get("categories")

backend/tests/test_qbittorrent_client.py

@@ -125,13 +125,21 @@ class QbittorrentClientTests(unittest.TestCase):
             "rid": 10,
             "full_update": True,
             "server_state": {"dl_info_speed": 100},
-            "torrents": {"a": {"name": "A", "state": "downloading"}},
+            "torrents": {
+                "a": {
+                    "name": "A",
+                    "state": "downloading",
+                    "size": 1_024,
+                    "progress": 0.5,
+                    "dlspeed": 100,
+                }
+            },
         }
         partial = {
             "rid": 11,
             "full_update": False,
             "server_state": {"dl_info_speed": 200},
-            "torrents": {"a": {"name": "A", "state": "pausedDL"}},
+            "torrents": {"a": {"dlspeed": 200}},
         }
         self.session.get.side_effect = [self._get_response(full), self._get_response(partial)]
 
@@ -143,7 +151,11 @@ class QbittorrentClientTests(unittest.TestCase):
         r2 = self.client.maindata()
         self.assertEqual(self.session.get.call_args_list[1].kwargs["params"].get("rid"), 10)
         self.assertEqual(r2["server_state"]["dl_info_speed"], 200)  # merged
-        self.assertEqual(r2["torrents"]["a"]["state"], "pausedDL")  # merged
+        self.assertEqual(r2["torrents"]["a"]["dlspeed"], 200)
+        self.assertEqual(r2["torrents"]["a"]["name"], "A")
+        self.assertEqual(r2["torrents"]["a"]["state"], "downloading")
+        self.assertEqual(r2["torrents"]["a"]["size"], 1_024)
+        self.assertEqual(r2["torrents"]["a"]["progress"], 0.5)
 
     def test_maindata_caches_concurrent_calls_within_ttl(self) -> None:
         """Two calls within the TTL collapse to a single HTTP fetch."""
@@ -227,8 +239,8 @@ class QbittorrentClientTests(unittest.TestCase):
         self.session.post.return_value = self._login_response()
         self.client._login()
         call_kwargs = self.session.post.call_args.kwargs
-        assert call_kwargs["timeout"] == (5.0, 5.0)
+        self.assertEqual(call_kwargs["timeout"], (5.0, 5.0))
-        assert not isinstance(call_kwargs["timeout"], int)
+        self.assertNotIsInstance(call_kwargs["timeout"], int)
 
     def test_login_fails_message_names_bad_credentials(self) -> None:
         """'Fails.' body yields a clear 'invalid username or password' error."""

docs/REQUIREMENTS.md

@@ -321,6 +321,9 @@ These do not reference a service.
 - The scheduler should run immediately after startup with per-service staggering, use fixed-delay execution, prevent overlap/backlog, and reconcile configuration changes without a backend restart.
 - Poll failures should remain enabled, be persisted, and retry with bounded exponential backoff. A successful scheduled or manual run should clear backoff.
 - The qBittorrent widget-data endpoint must become read-only; only the scheduler may contact qBittorrent and append samples.
+- The qBittorrent client must merge incremental torrent patches with the prior
+  snapshot so active-transfer rows retain their name, size, progress, and state
+  when only throughput changes.
 - The service UI should expose polling settings, current status, stale-data state, a manual `Run now` action, the shared selectable chart windows, an **All values** option that fetches every retained speed sample, and paginated scheduled-action history.
 - Scheduled-action runs should use dedicated generic records, retain at most 30 days or 1,000 runs per service/action, and never store secrets or raw credentials.
 - Disabling a qBittorrent service pauses polling while retaining history; deleting the service purges its samples and scheduler history through the existing cascade-delete behavior.