From a1bf3e4315c8a04d62f7f8dc444fbfc5643dfcd7 Mon Sep 17 00:00:00 2001
From: Cabbagec <root@everdream.xyz>
Date: Fri, 14 Aug 2026 11:56:06 +0000
Subject: [PATCH] fix: resolve per-torrent qb save paths

---
 docs/deployment-and-usage.md       | 10 ++++
 docs/deployment-preflight.md       | 15 ++++-
 docs/storage-safety.md             |  8 ++-
 scripts/preflight-deployment.py    | 23 +++++++-
 src/archive_clients/cli.py         | 13 ++++-
 src/archive_clients/config.py      |  2 -
 src/archive_clients/daemon.py      |  8 ++-
 src/archive_clients/eviction.py    | 52 ++++++++++++-----
 src/archive_clients/jobs.py        | 94 +++++++++++++++++++++++++-----
 src/archive_clients/resources.py   | 22 ++++++-
 tests/test_cli.py                  | 59 +++++++++++++++++++
 tests/test_config.py               | 29 +++++++++
 tests/test_deployment_preflight.py | 20 +++++++
 tests/test_eviction.py             | 54 ++++++++++++++---
 tests/test_jobs.py                 | 67 ++++++++++++++++++++-
 tests/test_qbittorrent.py          |  9 ++-
 tests/test_resources.py            | 23 +++++++-
 17 files changed, 453 insertions(+), 55 deletions(-)
 create mode 100644 tests/test_cli.py

diff --git a/docs/deployment-and-usage.md b/docs/deployment-and-usage.md
index ae83a67..dd751d2 100644
--- a/docs/deployment-and-usage.md
+++ b/docs/deployment-and-usage.md
@@ -120,6 +120,8 @@ username = "${QB_USER}"
 password_file = "/run/secrets/qb_password"
 api_root = "/downloads"
 local_root = "/data/qb"
+# Optional only when a nested qB path uses a different client-visible mount.
+# local_path_overrides = { "/downloads/fast" = "/data/qb-fast" }
 
 [syncthing]
 endpoint = "http://syncthing:8384"
@@ -139,6 +141,14 @@ accounting. The override key is the normalized Syncthing folder path beneath
 `api_root`, not its folder ID. See the production deployment README for the
 required compose and override pattern.
 
+qBittorrent content is resolved differently: every existing torrent keeps its
+qB-reported `save_path`. The client maps that path beneath `qbittorrent.api_root`
+to its own mount before a source, existing-target, permission, or eviction
+operation. Thus `/downloads/Downloading` naturally maps below `/data/qb`;
+there is no migration or per-resource configuration. Add a qB
+`local_path_overrides` entry only when that nested API prefix is a separate
+client mount.
+
 The remaining node examples omit optional `[connection]`, `[jobs]`, and
 `[backup]` tables and therefore use these same defaults; deployments may
 override them per node.
diff --git a/docs/deployment-preflight.md b/docs/deployment-preflight.md
index 6a116b9..a954e91 100644
--- a/docs/deployment-preflight.md
+++ b/docs/deployment-preflight.md
@@ -86,6 +86,9 @@ python3 scripts/preflight-deployment.py ... \
 - That future route path and qBittorrent content root use one client bind
   mount, so hard-link staging remains possible rather than silently falling
   back to a space-consuming copy.
+- Every explicit `qbittorrent.local_path_overrides` entry maps the same host
+  path in the qBittorrent and client containers. This protects nested qB save
+  paths that use a dedicated bind mount.
 - A real `link(2)` operation between a unique zero-byte file in the qB root
   and one in the future automatic-route root. The probe verifies that both
   names refer to the same inode and removes them unconditionally.
@@ -96,7 +99,8 @@ python3 scripts/preflight-deployment.py ... \
 - The token, qB password, and Syncthing API-key files are non-empty regular
   files with no group/world permissions.
 - The client image can read its configuration and reports usable permissions,
-  sparse-file support, and filesystem capabilities for both roots.
+  sparse-file support, and filesystem capabilities for both primary roots and
+  every configured qBittorrent local-path override.
 - qBittorrent authentication/version compatibility and Syncthing
   authentication/device identity are healthy from the client container.
 
@@ -106,6 +110,15 @@ root and add a `local_path_overrides` mapping for that exact API path. This
 prevents automatic route folders being created on a small configuration
 filesystem while the client expects to hardlink from the qB data mount.
 
+qBittorrent resources may use any `save_path` below `qbittorrent.api_root`.
+At job preflight the client maps that qB API path to its local mount and uses
+it as the resource root; data is never moved to fit Archive Control. A resource
+outside the configured qB API root, or whose resolved directory is unavailable
+or not a real directory in the client container, fails that job before staging
+or eviction. Use `qbittorrent.local_path_overrides` only for a nested qB API
+prefix backed by a distinct client mount; this preflight verifies the Docker
+bind topology for each such override.
+
 When converting an existing node, stop its client and Syncthing containers,
 move each existing `routes/<route-id>` directory from the old Syncthing config
 tree into the new qB-backed route-root directory, then recreate Syncthing and
diff --git a/docs/storage-safety.md b/docs/storage-safety.md
index 8851a71..89ff268 100644
--- a/docs/storage-safety.md
+++ b/docs/storage-safety.md
@@ -14,6 +14,13 @@ client:
    a regular file or an explicitly created directory;
 5. verifies every operation remains beneath the local configured root.
 
+For qBittorrent content, the root is resolved per resource: qB's authoritative
+API-visible `save_path` is mapped beneath `qbittorrent.api_root` (or a more
+specific configured local override) into the client namespace. This permits
+existing nested save paths without moving data, but does not permit paths
+outside the configured boundary. The resolved path remains local client state
+and is never sent to the control daemon.
+
 Sockets, devices, FIFOs, symlinks, and other special entries fail preflight.
 Permission or ownership mismatch is fail-fast. Archive Control never changes
 source ownership or mode to make a job pass.
@@ -150,4 +157,3 @@ Offline tooling provides list, verify, and restore. Restore requires stopped
 daemon access, verifies the chosen backup, preserves the suspect database under
 a timestamped name, installs the replacement atomically, and runs integrity and
 schema checks before normal startup. Backups contain no configured secrets.
-
diff --git a/scripts/preflight-deployment.py b/scripts/preflight-deployment.py
index c1f5bf4..e8ccc41 100755
--- a/scripts/preflight-deployment.py
+++ b/scripts/preflight-deployment.py
@@ -134,7 +134,7 @@ from pathlib import Path
 from archive_clients.config import ClientConfig
 config=ClientConfig.load(Path(sys.argv[1]))
 value={"shared_token_file":str(config.shared_token_file)}
-value["qbittorrent"]={"api_root":str(config.qbittorrent.api_root),"local_root":str(config.qbittorrent.local_root),"password_file":str(config.qbittorrent.password_file)}
+value["qbittorrent"]={"api_root":str(config.qbittorrent.api_root),"local_root":str(config.qbittorrent.local_root),"password_file":str(config.qbittorrent.password_file),"local_path_overrides":{str(api):str(local) for api,local in config.qbittorrent.local_path_overrides}}
 value["syncthing"]={"api_root":str(config.syncthing.api_root),"local_root":str(config.syncthing.local_root),"api_key_file":str(config.syncthing.api_key_file),"local_path_overrides":{str(api):str(local) for api,local in config.syncthing.local_path_overrides}}
 print(json.dumps(value,sort_keys=True))'''
     result = subprocess.run(
@@ -174,6 +174,26 @@ raise SystemExit(0 if all(p.state == 1 for p in probes) else 1)'''
     print(result.stdout.strip())
 
 
+def require_qb_override_mappings(
+    client: dict[str, Any], qbittorrent: dict[str, Any], qb: dict[str, Any],
+) -> None:
+    """Prove every explicit qB API/local override sees the same host bytes."""
+
+    overrides = qb.get("local_path_overrides", {})
+    if not isinstance(overrides, dict):
+        raise CheckFailure("qbittorrent.local_path_overrides must be a table")
+    for api_path, local_path in overrides.items():
+        if not isinstance(api_path, str) or not isinstance(local_path, str):
+            raise CheckFailure(
+                "qbittorrent.local_path_overrides entries are invalid"
+            )
+        require_same_path(
+            f"qBittorrent override {api_path}/local mapping",
+            map_path(qbittorrent, api_path),
+            map_path(client, local_path),
+        )
+
+
 def run_hardlink_probe(
     container: str, qb_root: str, route_root: str, user: str | None = None,
 ) -> None:
@@ -298,6 +318,7 @@ def main(argv: list[str] | None = None) -> int:
             syncthing_route, client_route,
         )
         require_same_path("qBittorrent api_root/local_root", qb_api, client_qb)
+        require_qb_override_mappings(client, qbittorrent, qb)
         if client_qb.destination != client_route.destination:
             raise CheckFailure(
                 "qBittorrent and future route roots use separate client bind "
diff --git a/src/archive_clients/cli.py b/src/archive_clients/cli.py
index 12cec10..5496bda 100644
--- a/src/archive_clients/cli.py
+++ b/src/archive_clients/cli.py
@@ -27,10 +27,16 @@ def main(argv: Sequence[str] | None = None) -> int:
     parser.add_argument("--check-config", action="store_true")
     arguments = parser.parse_args(argv)
     config = ClientConfig.load(arguments.config, arguments.mode)
+    qb_extra_roots = tuple(sorted({
+        root
+        for _, root in config.qbittorrent.local_path_overrides
+        if root != config.qbittorrent.local_root
+    }))
     probes = [
         probe_root(config.qbittorrent.local_root),
         probe_root(config.syncthing.local_root),
     ]
+    qb_extra_probes = tuple(probe_root(root) for root in qb_extra_roots)
     probe_writable_directory(config.state_db.parent)
     probe_writable_directory(config.backup_dir)
     shared_token = config.read_shared_token()
@@ -40,7 +46,10 @@ def main(argv: Sequence[str] | None = None) -> int:
         print(json.dumps({
             "client_id": config.client_id,
             "role": config.role,
-            "filesystems": [probe.__dict__ | {"root": str(probe.root)} for probe in probes],
+            "filesystems": [
+                probe.__dict__ | {"root": str(probe.root)}
+                for probe in (*probes[:1], *qb_extra_probes, *probes[1:])
+            ],
         }, sort_keys=True))
         return 0
     configure_logging(
@@ -68,7 +77,7 @@ def main(argv: Sequence[str] | None = None) -> int:
                 },
             )
         asyncio.run(ArchiveClientDaemon(
-            config, probes, service_probes,
+            config, probes, service_probes, qb_extra_probes=qb_extra_probes,
             resource_reader=QBittorrentReader(config.qbittorrent),
         ).run())
     except KeyboardInterrupt:
diff --git a/src/archive_clients/config.py b/src/archive_clients/config.py
index b748707..cc7c5a6 100644
--- a/src/archive_clients/config.py
+++ b/src/archive_clients/config.py
@@ -213,8 +213,6 @@ def _local_path_overrides(
     value: dict[str, Any], api_root: PurePosixPath, name: str
 ) -> tuple[tuple[PurePosixPath, Path], ...]:
     raw = value.get("local_path_overrides", {})
-    if name != "syncthing" and raw:
-        raise ConfigError(f"{name}.local_path_overrides is unsupported")
     if not isinstance(raw, dict):
         raise ConfigError(f"{name}.local_path_overrides must be a table")
     parsed: list[tuple[PurePosixPath, Path]] = []
diff --git a/src/archive_clients/daemon.py b/src/archive_clients/daemon.py
index d561994..af45deb 100644
--- a/src/archive_clients/daemon.py
+++ b/src/archive_clients/daemon.py
@@ -64,6 +64,7 @@ class ArchiveClientDaemon:
         service_probes: list[ServiceProbe],
         resource_reader: QBittorrentReader | None = None,
         route_manager: SyncthingRouteManager | None = None,
+        qb_extra_probes: tuple[FilesystemProbe, ...] = (),
     ):
         if len(probes) != 2:
             raise ValueError(
@@ -71,6 +72,7 @@ class ArchiveClientDaemon:
             )
         self.config = config
         self.probes = probes
+        self.qb_probes = (probes[0], *qb_extra_probes)
         self.service_probes = service_probes
         self.inventory = (
             InventoryService(resource_reader, config.client_id)
@@ -119,9 +121,13 @@ class ArchiveClientDaemon:
                 store=self.store,
                 qb_root=config.qbittorrent.local_root,
                 qb_api_root=config.qbittorrent.api_root,
+                qb_roots=config.qbittorrent.roots,
                 route_path=self._route_path,
                 syncthing_transport=self.routes.transport,
-                sparse_supported=all(probe.sparse_files for probe in probes),
+                sparse_supported=all(
+                    probe.sparse_files
+                    for probe in (*self.qb_probes, probes[1])
+                ),
                 poll_interval=config.jobs.poll_interval,
                 verification_timeout=config.jobs.verification_timeout,
                 free_space_reserve_bytes=(
diff --git a/src/archive_clients/eviction.py b/src/archive_clients/eviction.py
index e9ca22e..e89098f 100644
--- a/src/archive_clients/eviction.py
+++ b/src/archive_clients/eviction.py
@@ -7,7 +7,7 @@ import hashlib
 import os
 import stat
 from pathlib import Path, PurePosixPath
-from typing import Iterable
+from typing import Callable, Iterable
 
 from archive_clients.qbittorrent import QBittorrentReader
 from archive_clients.resources import NormalizedResource
@@ -23,7 +23,7 @@ def verify_and_snapshot(
     job_id: str,
     resource: NormalizedResource,
     selected_indices: Iterable[int],
-    qb_root: Path,
+    content_root: Path,
     store: ClientStore,
 ) -> dict[str, object]:
     selected = set(selected_indices)
@@ -38,7 +38,7 @@ def verify_and_snapshot(
                 f"cache file {index} is not selected and complete"
             )
         relative = _relative(item.canonical_path)
-        path = qb_root.joinpath(*relative.parts)
+        path = content_root.joinpath(*relative.parts)
         try:
             metadata = path.lstat()
         except FileNotFoundError as exc:
@@ -65,7 +65,7 @@ def verify_and_snapshot(
                 "sha256": _sha256(path),
             }
         )
-    snapshot = {"files": files}
+    snapshot = {"content_root": str(content_root), "files": files}
     return store.put_job_artifact(job_id, "eviction-snapshot", snapshot)["value"]
 
 
@@ -90,9 +90,9 @@ def remove_qb_entry(
 def safe_unlink(
     *,
     job_id: str,
-    qb_root: Path,
     qbittorrent: QBittorrentReader,
     store: ClientStore,
+    resource_root: Callable[[NormalizedResource], Path],
 ) -> dict[str, object]:
     completed = store.get_job_artifact(job_id, "eviction-unlinked")
     if completed is not None:
@@ -101,11 +101,19 @@ def safe_unlink(
     if snapshot_row is None:
         raise EvictionError("eviction snapshot is missing")
     snapshot = snapshot_row["value"]
+    if not isinstance(snapshot, dict):
+        raise EvictionError("eviction snapshot is invalid")
+    content_root_value = snapshot.get("content_root")
+    if not isinstance(content_root_value, str):
+        raise EvictionError("eviction snapshot content root is missing")
+    content_root = Path(content_root_value)
+    if not content_root.is_absolute() or content_root.is_symlink():
+        raise EvictionError("eviction snapshot content root is unsafe")
     files = snapshot.get("files")
     if not isinstance(files, list):
         raise EvictionError("eviction snapshot is invalid")
 
-    referenced = _remaining_paths(qbittorrent.list_resources())
+    referenced = _remaining_paths(qbittorrent.list_resources(), resource_root)
     removed: list[str] = []
     retained: list[dict[str, str]] = []
     directories: set[Path] = set()
@@ -113,10 +121,10 @@ def safe_unlink(
         if not isinstance(record, dict) or not isinstance(record.get("path"), str):
             raise EvictionError("eviction file record is invalid")
         relative = _relative(record["path"])
-        if relative.as_posix() in referenced:
+        path = content_root.joinpath(*relative.parts)
+        if path in referenced:
             retained.append({"path": relative.as_posix(), "reason": "shared"})
             continue
-        path = qb_root.joinpath(*relative.parts)
         try:
             metadata = path.lstat()
         except FileNotFoundError:
@@ -142,7 +150,7 @@ def safe_unlink(
         path.unlink()
         removed.append(relative.as_posix())
         parent = path.parent
-        while parent != qb_root:
+        while parent != content_root:
             directories.add(parent)
             parent = parent.parent
 
@@ -153,7 +161,7 @@ def safe_unlink(
         try:
             directory.rmdir()
             removed_directories.append(
-                directory.relative_to(qb_root).as_posix()
+                directory.relative_to(content_root).as_posix()
             )
         except OSError as exc:
             if exc.errno not in {errno.ENOTEMPTY, errno.ENOENT}:
@@ -214,12 +222,24 @@ def compensate_materialized_files(
     return removed
 
 
-def _remaining_paths(resources: Iterable[NormalizedResource]) -> set[str]:
-    return {
-        item.canonical_path
-        for resource in resources
-        for item in resource.files
-    }
+def _remaining_paths(
+    resources: Iterable[NormalizedResource],
+    resource_root: Callable[[NormalizedResource], Path],
+) -> set[Path]:
+    result: set[Path] = set()
+    for resource in resources:
+        try:
+            root = resource_root(resource)
+        except (OSError, RuntimeError, ValueError):
+            # A malformed unrelated qB entry must not stop an otherwise
+            # safe eviction.  Its unresolvable path cannot be considered a
+            # shared path under the verified eviction root.
+            continue
+        result.update(
+            root.joinpath(*_relative(item.canonical_path).parts)
+            for item in resource.files
+        )
+    return result
 
 
 def _relative(value: str) -> PurePosixPath:
diff --git a/src/archive_clients/jobs.py b/src/archive_clients/jobs.py
index 91e5764..645350f 100644
--- a/src/archive_clients/jobs.py
+++ b/src/archive_clients/jobs.py
@@ -14,6 +14,7 @@ import uuid
 from pathlib import Path, PurePosixPath
 from typing import Callable, Iterable
 
+from archive_clients.config import ConfigError, RootMapping
 from archive_clients.protocol import decode_message, encode_message
 from archive_clients.eviction import (
     EvictionError,
@@ -67,6 +68,7 @@ class ClientJobExecutor:
         store: ClientStore,
         qb_root: Path,
         qb_api_root: PurePosixPath,
+        qb_roots: RootMapping | None = None,
         route_path: Callable[[str], Path],
         syncthing_transport: object,
         sparse_supported: bool,
@@ -78,7 +80,10 @@ class ClientJobExecutor:
         self.qbittorrent = qbittorrent
         self.store = store
         self.qb_root = qb_root
-        self.qb_api_root = qb_api_root
+        self.qb_api_root = PurePosixPath(qb_api_root)
+        self.qb_roots = qb_roots or RootMapping(
+            self.qb_api_root, self.qb_root
+        )
         self.route_path = route_path
         self.syncthing_transport = syncthing_transport
         self.sparse_supported = sparse_supported
@@ -479,6 +484,7 @@ class ClientJobExecutor:
                     "archive coverage no longer covers the cache selection"
                 )
             resource = self._resource(definition)
+            resource_root = self._resource_root(resource)
             current = _resource_fingerprint(resource, self.client_id)
             if not _fingerprint_matches(
                 current, definition.eviction.cache_fingerprint
@@ -490,7 +496,7 @@ class ClientJobExecutor:
                 job_id=definition.job_id,
                 resource=resource,
                 selected_indices=requested,
-                qb_root=self.qb_root,
+                content_root=resource_root,
                 store=self.store,
             )
             return None
@@ -505,9 +511,9 @@ class ClientJobExecutor:
         if step == job_pb2.JOB_STEP_KIND_SAFE_FILE_UNLINK:
             safe_unlink(
                 job_id=definition.job_id,
-                qb_root=self.qb_root,
                 qbittorrent=self.qbittorrent,
                 store=self.store,
+                resource_root=self._resource_root,
             )
             placement = resource_pb2.Placement(
                 client_id=self.client_id,
@@ -538,7 +544,8 @@ class ClientJobExecutor:
             raise JobExecutionError(
                 "source resource changed after job confirmation"
             )
-        self._reject_unsafe_partfile(definition, resource)
+        source_root = self._resource_root(resource)
+        self._reject_unsafe_partfile(definition, resource, source_root)
         indices = _selection_indices(definition.transfer.transfer_delta_files)
         by_index = {item.file_index: item for item in resource.files}
         if not indices or any(index not in by_index for index in indices):
@@ -602,7 +609,7 @@ class ClientJobExecutor:
         self._require_space(
             route_root,
             self._copy_required_bytes(
-                self.qb_root,
+                source_root,
                 route_root,
                 (
                     (entry.target_canonical_path, entry.logical_bytes)
@@ -613,7 +620,7 @@ class ClientJobExecutor:
         )
         stage_transfer(
             manifest,
-            source_root=self.qb_root,
+            source_root=source_root,
             sync_root=route_root,
             store=self.store,
             artifact_sources={"metainfo/source.torrent": metainfo_path},
@@ -691,23 +698,27 @@ class ClientJobExecutor:
                 "target materialization was sent to the wrong client"
             )
         published = load_published_transfer(self._job_directory(definition))
+        info_hash = _info_hash(definition)
+        resource = self.qbittorrent.get_resource(info_hash)
+        target_root = (
+            self._resource_root(resource)
+            if resource is not None else self.qb_root
+        )
         # The target can likewise hardlink an arrived Syncthing payload into
         # qB's content root when those directories share a filesystem.
         self._require_space(
-            self.qb_root,
+            target_root,
             self._copy_required_bytes(
                 published.job_directory,
-                self.qb_root,
+                target_root,
                 (
                     (entry.payload_relative_path, entry.logical_bytes)
                     for entry in published.manifest.files
                 ),
             ),
         )
-        info_hash = _info_hash(definition)
-        resource = self.qbittorrent.get_resource(info_hash)
         if resource is not None:
-            self._reject_unsafe_partfile(definition, resource)
+            self._reject_unsafe_partfile(definition, resource, target_root)
         if definition.transfer.HasField("target_baseline_fingerprint"):
             if resource is None or not _fingerprint_matches(
                 _resource_fingerprint(resource, self.client_id),
@@ -732,13 +743,14 @@ class ClientJobExecutor:
                 == resource_pb2.TORRENT_RUNTIME_STATE_STOPPED
             ),
             "total_file_count": len(published.manifest.files),
+            "content_root": str(target_root),
         }
         self.store.put_job_artifact(
             definition.job_id, "target-baseline", baseline
         )
         materialize_transfer(
             published,
-            target_root=self.qb_root,
+            target_root=target_root,
             store=self.store,
             sparse_supported=self.sparse_supported,
             cancel_check=lambda: self._raise_if_cancelled(
@@ -813,7 +825,9 @@ class ClientJobExecutor:
             raise JobExecutionError(
                 "verified qBittorrent resource disappeared"
             )
-        _normalize_verified_resource_permissions(self.qb_root, verified)
+        _normalize_verified_resource_permissions(
+            self._resource_root(verified), verified
+        )
         if should_start:
             self.qbittorrent.start(qb_torrent_id)
         placement = resource_pb2.Placement(
@@ -852,6 +866,7 @@ class ClientJobExecutor:
             )
             return
         baseline = baseline_row["value"]
+        content_root = self._artifact_content_root(baseline)
         info_hash = _info_hash(definition)
         present = self.qbittorrent.get_resource(info_hash)
         if present is not None:
@@ -870,7 +885,7 @@ class ClientJobExecutor:
                 self.qbittorrent.delete_entry(qb_torrent_id)
         compensate_materialized_files(
             job_id=definition.job_id,
-            qb_root=self.qb_root,
+            qb_root=content_root,
             store=self.store,
         )
 
@@ -906,10 +921,11 @@ class ClientJobExecutor:
         self,
         definition: job_pb2.JobDefinition,
         resource: NormalizedResource,
+        content_root: Path,
     ) -> None:
-        roots = {self.qb_root}
+        roots = {content_root}
         for item in resource.files:
-            candidate = self.qb_root / PurePosixPath(item.canonical_path).parts[0]
+            candidate = content_root / PurePosixPath(item.canonical_path).parts[0]
             roots.add(candidate if candidate.is_dir() else candidate.parent)
         hashes = {
             value.lower() for value in (
@@ -928,6 +944,52 @@ class ClientJobExecutor:
                         "safely transferred by this client"
                     )
 
+    def _resource_root(self, resource: NormalizedResource) -> Path:
+        """Resolve a qB resource's save path within this client's mounts.
+
+        qB returns paths in its own API/container namespace.  The configured
+        root mapping translates those paths into the client namespace and
+        supports nested save paths and explicit prefix overrides.  A missing
+        save path is retained only for older in-process test fixtures; every
+        normalized qB API resource has one.
+        """
+
+        if resource.save_path is None:
+            return self.qb_root
+        try:
+            root = self.qb_roots.api_to_local(resource.save_path.as_posix())
+        except ConfigError as exc:
+            raise JobExecutionError(
+                "qBittorrent resource save path is outside the configured "
+                "API root or has no local path mapping"
+            ) from exc
+        try:
+            metadata = root.lstat()
+        except FileNotFoundError as exc:
+            raise JobExecutionError(
+                "qBittorrent resource save path is not visible in the "
+                "client container"
+            ) from exc
+        if not stat.S_ISDIR(metadata.st_mode):
+            raise JobExecutionError(
+                "qBittorrent resource save path is not a real directory in "
+                "the client container"
+            )
+        return root
+
+    def _artifact_content_root(self, baseline: object) -> Path:
+        if not isinstance(baseline, dict):
+            raise JobExecutionError("target baseline is invalid")
+        value = baseline.get("content_root")
+        if not isinstance(value, str):
+            # A pre-existing durable baseline predates per-resource roots.
+            # It can only have materialized to the configured target root.
+            return self.qb_root
+        root = Path(value)
+        if not root.is_absolute() or root.is_symlink():
+            raise JobExecutionError("target baseline content root is unsafe")
+        return root
+
     def _raise_if_cancelled(self, job_id: str) -> None:
         event = self._cancel_events.get(job_id)
         if event is not None and event.is_set():
diff --git a/src/archive_clients/resources.py b/src/archive_clients/resources.py
index 9e6131f..f15f54b 100644
--- a/src/archive_clients/resources.py
+++ b/src/archive_clients/resources.py
@@ -23,6 +23,9 @@ class NormalizedResource:
     files: tuple[resource_pb2.TorrentFile, ...]
     metainfo: Metainfo
     metainfo_bytes: bytes = b""
+    # qBittorrent's API-visible save path is intentionally local-only.  It
+    # must never become part of inventory or placement protocol messages.
+    save_path: PurePosixPath | None = None
 
 
 def build_content_tree(
@@ -137,6 +140,7 @@ def normalize_resource(
         character not in "0123456789abcdef" for character in qb_torrent_id
     ):
         raise ResourceError("torrent hash is invalid")
+    save_path = _save_path(torrent.get("save_path"))
     summary = resource_pb2.ResourceSummary(
         qb_torrent_id=qb_torrent_id,
         display_name=_string(torrent.get("name"), "torrent name"),
@@ -172,7 +176,9 @@ def normalize_resource(
         revision_data, sort_keys=True, separators=(",", ":"),
     ).encode("utf-8")).hexdigest()
     summary.observed_at.FromDatetime(observed_at)
-    return NormalizedResource(summary, tuple(files), metainfo, metainfo_bytes)
+    return NormalizedResource(
+        summary, tuple(files), metainfo, metainfo_bytes, save_path
+    )
 
 
 def _set_selection(target: Any, indices: list[int]) -> None:
@@ -217,6 +223,20 @@ def _path(value: Any) -> str:
     return candidate.as_posix()
 
 
+def _save_path(value: Any) -> PurePosixPath:
+    """Validate qBittorrent's API-visible per-torrent content root."""
+
+    path = _string(value, "torrent save path")
+    candidate = PurePosixPath(path)
+    if (
+        not candidate.is_absolute()
+        or ".." in candidate.parts
+        or "." in candidate.parts
+    ):
+        raise ResourceError("qBittorrent torrent save path is unsafe")
+    return candidate
+
+
 def _integer(value: Any, name: str) -> int:
     if isinstance(value, bool) or not isinstance(value, int) or value < 0:
         raise ResourceError(f"{name} is invalid")
diff --git a/tests/test_cli.py b/tests/test_cli.py
new file mode 100644
index 0000000..8537afd
--- /dev/null
+++ b/tests/test_cli.py
@@ -0,0 +1,59 @@
+import io
+import json
+import os
+import tempfile
+import unittest
+from contextlib import redirect_stdout
+from pathlib import Path
+
+from archive_clients.cli import main
+
+
+class ClientCliTests(unittest.TestCase):
+    def test_check_config_probes_every_qb_override_root(self):
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            for name in ("token", "qb-password", "syncthing-key"):
+                path = root / name
+                path.write_text(name, encoding="utf-8")
+                os.chmod(path, 0o600)
+            for name in ("qb", "qb-fast", "sync", "backups"):
+                (root / name).mkdir()
+            config = root / "client.toml"
+            config.write_text(
+                f'''client_id = "cache-1"
+display_name = "Cache 1"
+role = "cache"
+control_endpoint = "ws://control/archive_control"
+shared_token_file = "{root / "token"}"
+state_db = "{root / "state.db"}"
+backup_dir = "{root / "backups"}"
+
+[qbittorrent]
+endpoint = "http://qb"
+username = "admin"
+password_file = "{root / "qb-password"}"
+api_root = "/downloads"
+local_root = "{root / "qb"}"
+local_path_overrides = {{ "/downloads/fast" = "{root / "qb-fast"}" }}
+
+[syncthing]
+endpoint = "http://syncthing"
+api_key_file = "{root / "syncthing-key"}"
+api_root = "/sync"
+local_root = "{root / "sync"}"
+''',
+                encoding="utf-8",
+            )
+            output = io.StringIO()
+            with redirect_stdout(output):
+                self.assertEqual(main(["--config", str(config), "--check-config"]), 0)
+            reported = json.loads(output.getvalue())
+            self.assertEqual(
+                [item["root"] for item in reported["filesystems"]],
+                [str(root / "qb"), str(root / "qb-fast"), str(root / "sync")],
+            )
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/tests/test_config.py b/tests/test_config.py
index a806b7b..da88144 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -78,6 +78,35 @@ class ConfigTests(unittest.TestCase):
             Path("/local/qb/Sync"),
         )
 
+    def test_qbittorrent_can_override_a_nested_save_path(self):
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            for name in ("token", "qb-password", "syncthing-key"):
+                path = root / name
+                path.write_text(name, encoding="utf-8")
+                os.chmod(path, 0o600)
+            (root / "qb").mkdir()
+            (root / "fast").mkdir()
+            (root / "sync").mkdir()
+            config_path = root / "client.toml"
+            config_path.write_text(
+                _config(root).replace(
+                    f'local_root = "{root / "qb"}"',
+                    f'local_root = "{root / "qb"}"\n'
+                    "local_path_overrides = { \"/downloads/fast\" = "
+                    f'"{root / "fast"}" }}',
+                    1,
+                ),
+                encoding="utf-8",
+            )
+            config = ClientConfig.load(config_path)
+            self.assertEqual(
+                config.qbittorrent.roots.api_to_local(
+                    "/downloads/fast/resource/file.bin"
+                ),
+                root / "fast/resource/file.bin",
+            )
+
     def test_endpoint_scheme_and_job_keys_are_strict(self):
         with tempfile.TemporaryDirectory() as directory:
             root = Path(directory)
diff --git a/tests/test_deployment_preflight.py b/tests/test_deployment_preflight.py
index 55d3698..33fa6dc 100644
--- a/tests/test_deployment_preflight.py
+++ b/tests/test_deployment_preflight.py
@@ -50,6 +50,26 @@ class DeploymentPreflightTests(unittest.TestCase):
             "/data/qb/.archive-control-routes",
         )
 
+    def test_qb_override_must_map_to_the_same_host_path(self):
+        client = {"Mounts": [
+            {"Type": "bind", "Source": "/srv/fast", "Destination": "/data/fast"},
+        ]}
+        qbittorrent = {"Mounts": [
+            {"Type": "bind", "Source": "/srv/fast", "Destination": "/downloads/fast"},
+        ]}
+        preflight.require_qb_override_mappings(
+            client, qbittorrent,
+            {"local_path_overrides": {"/downloads/fast": "/data/fast"}},
+        )
+        with self.assertRaisesRegex(preflight.CheckFailure, "host paths differ"):
+            preflight.require_qb_override_mappings(
+                client,
+                {"Mounts": [{
+                    "Type": "bind", "Source": "/other", "Destination": "/downloads/fast",
+                }]},
+                {"local_path_overrides": {"/downloads/fast": "/data/fast"}},
+            )
+
     def test_runs_hardlink_probe_with_qb_and_route_roots(self):
         completed = __import__("subprocess").CompletedProcess(
             args=[], returncode=0, stdout="hard-link staging probe passed\n", stderr=""
diff --git a/tests/test_eviction.py b/tests/test_eviction.py
index 138d5f1..92ce62c 100644
--- a/tests/test_eviction.py
+++ b/tests/test_eviction.py
@@ -1,5 +1,7 @@
 import tempfile
 import unittest
+from dataclasses import replace
+from pathlib import PurePosixPath
 from pathlib import Path
 
 from archive_clients.eviction import (
@@ -86,7 +88,7 @@ class EvictionTests(unittest.TestCase):
             job_id="job-1",
             resource=evicted,
             selected_indices=[0, 1],
-            qb_root=self.root,
+            content_root=self.root,
             store=self.store,
         )
         remove_qb_entry(
@@ -97,9 +99,9 @@ class EvictionTests(unittest.TestCase):
         )
         result = safe_unlink(
             job_id="job-1",
-            qb_root=self.root,
             qbittorrent=qb,
             store=self.store,
+            resource_root=lambda _: self.root,
         )
         self.assertTrue((self.root / "tree/shared.bin").exists())
         self.assertFalse((self.root / "tree/owned.bin").exists())
@@ -121,7 +123,7 @@ class EvictionTests(unittest.TestCase):
             job_id="job-1",
             resource=evicted,
             selected_indices=[0],
-            qb_root=self.root,
+            content_root=self.root,
             store=self.store,
         )
         path.unlink()
@@ -134,9 +136,9 @@ class EvictionTests(unittest.TestCase):
         )
         result = safe_unlink(
             job_id="job-1",
-            qb_root=self.root,
             qbittorrent=qb,
             store=self.store,
+            resource_root=lambda _: self.root,
         )
         self.assertTrue(path.exists())
         self.assertEqual(
@@ -152,7 +154,7 @@ class EvictionTests(unittest.TestCase):
             job_id="job-1",
             resource=evicted,
             selected_indices=[0],
-            qb_root=self.root,
+            content_root=self.root,
             store=self.store,
         )
         remove_qb_entry(
@@ -163,19 +165,57 @@ class EvictionTests(unittest.TestCase):
         )
         first = safe_unlink(
             job_id="job-1",
-            qb_root=self.root,
             qbittorrent=qb,
             store=self.store,
+            resource_root=lambda _: self.root,
         )
         second = safe_unlink(
             job_id="job-1",
-            qb_root=self.root,
             qbittorrent=qb,
             store=self.store,
+            resource_root=lambda _: self.root,
         )
         self.assertEqual(first, second)
         self.assertEqual(qb.deleted, ["a" * 40])
 
+    def test_nested_save_path_uses_its_own_root_and_not_a_same_named_peer(self):
+        nested = self.root / "Downloading"
+        nested.mkdir()
+        evicted = replace(
+            normalized("a" * 40, ["resource/file.bin"]),
+            save_path=PurePosixPath("/downloads/Downloading"),
+        )
+        peer = replace(
+            normalized("b" * 40, ["resource/file.bin"]),
+            save_path=PurePosixPath("/downloads"),
+        )
+        nested_file = nested / "resource/file.bin"
+        nested_file.parent.mkdir()
+        nested_file.write_bytes(b"x" * evicted.files[0].logical_bytes)
+        root_file = self.root / "resource/file.bin"
+        root_file.parent.mkdir()
+        root_file.write_bytes(b"x" * peer.files[0].logical_bytes)
+        qb = FakeQB(evicted, [peer])
+
+        verify_and_snapshot(
+            job_id="job-1", resource=evicted, selected_indices=[0],
+            content_root=nested, store=self.store,
+        )
+        remove_qb_entry(
+            job_id="job-1", torrent_hash="a" * 40,
+            qbittorrent=qb, store=self.store,
+        )
+        safe_unlink(
+            job_id="job-1", qbittorrent=qb, store=self.store,
+            resource_root=lambda item: (
+                nested
+                if item.save_path == PurePosixPath("/downloads/Downloading")
+                else self.root
+            ),
+        )
+        self.assertFalse(nested_file.exists())
+        self.assertTrue(root_file.exists())
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/tests/test_jobs.py b/tests/test_jobs.py
index dfa1f53..6fc315b 100644
--- a/tests/test_jobs.py
+++ b/tests/test_jobs.py
@@ -4,11 +4,13 @@ import stat
 import tempfile
 import threading
 import unittest
-from pathlib import Path
+from dataclasses import replace
+from pathlib import Path, PurePosixPath
 from unittest.mock import Mock, patch
 from uuid import uuid4
 
 from archive_clients.bencode import encode
+from archive_clients.config import RootMapping
 from archive_clients.jobs import (
     ClientJobExecutor,
     JobExecutionError,
@@ -246,6 +248,55 @@ class ClientJobHappyPathTests(unittest.TestCase):
                 content=b"x" * 4096,
             )
 
+    def test_nested_qb_save_path_stages_from_mapped_subdirectory(self):
+        with tempfile.TemporaryDirectory() as directory:
+            self._run_transfer(
+                Path(directory),
+                job_pb2.JOB_OPERATION_UNARCHIVE,
+                source_save_path="/downloads/Downloading",
+            )
+
+    def test_qb_save_path_preflight_rejects_unmapped_path(self):
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            executor = ClientJobExecutor(
+                client_id="cache-1", qbittorrent=Mock(),
+                store=ClientStore(root / "state.db"), qb_root=root,
+                qb_api_root=PurePosixPath("/downloads"),
+                route_path=lambda _: root, syncthing_transport=Mock(),
+                sparse_supported=True,
+            )
+            resource = NormalizedResource(
+                resource_pb2.ResourceSummary(), (), Mock(),
+                save_path=PurePosixPath("/outside"),
+            )
+            with self.assertRaisesRegex(JobExecutionError, "outside"):
+                executor._resource_root(resource)
+
+    def test_qb_save_path_override_uses_its_dedicated_local_mount(self):
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            primary = root / "primary"
+            override = root / "override"
+            primary.mkdir()
+            override.mkdir()
+            executor = ClientJobExecutor(
+                client_id="cache-1", qbittorrent=Mock(),
+                store=ClientStore(root / "state.db"), qb_root=primary,
+                qb_api_root=PurePosixPath("/downloads"),
+                qb_roots=RootMapping(
+                    PurePosixPath("/downloads"), primary,
+                    ((PurePosixPath("/downloads/slow"), override),),
+                ),
+                route_path=lambda _: root, syncthing_transport=Mock(),
+                sparse_supported=True,
+            )
+            resource = NormalizedResource(
+                resource_pb2.ResourceSummary(), (), Mock(),
+                save_path=PurePosixPath("/downloads/slow"),
+            )
+            self.assertEqual(executor._resource_root(resource), override)
+
     def test_mount_boundary_requires_copy_space_even_with_same_device(self):
         with tempfile.TemporaryDirectory() as directory:
             root = Path(directory)
@@ -390,6 +441,7 @@ class ClientJobHappyPathTests(unittest.TestCase):
         source_stage_free_bytes: int | None = None,
         content: bytes = b"archive-control-happy-path",
         syncthing: CompleteSyncthing | None = None,
+        source_save_path: str = "/downloads",
     ):
         source_root = root / "source"
         target_root = root / "target"
@@ -397,7 +449,12 @@ class ClientJobHappyPathTests(unittest.TestCase):
         source_root.mkdir()
         target_root.mkdir()
         route_root.mkdir()
-        (source_root / "fixture.bin").write_bytes(content)
+        save_relative = PurePosixPath(source_save_path).relative_to(
+            PurePosixPath("/downloads")
+        )
+        source_content_root = source_root.joinpath(*save_relative.parts)
+        source_content_root.mkdir(parents=True, exist_ok=True)
+        (source_content_root / "fixture.bin").write_bytes(content)
         info = {
             b"length": len(content),
             b"name": b"fixture.bin",
@@ -411,6 +468,7 @@ class ClientJobHappyPathTests(unittest.TestCase):
                 "hash": torrent_hash,
                 "name": "fixture.bin",
                 "state": "uploading",
+                "save_path": source_save_path,
             },
             [{
                 "index": 0,
@@ -454,8 +512,11 @@ class ClientJobHappyPathTests(unittest.TestCase):
         source_qb = Mock()
         source_qb.get_resource.return_value = resource
         target_qb = Mock()
+        target_resource = replace(
+            resource, save_path=PurePosixPath("/downloads")
+        )
         target_qb.get_resource.side_effect = [
-            None, None, resource, resource,
+            None, None, target_resource, target_resource,
         ]
         syncthing = syncthing or CompleteSyncthing()
         source = ClientJobExecutor(
diff --git a/tests/test_qbittorrent.py b/tests/test_qbittorrent.py
index 0744479..87c72ea 100644
--- a/tests/test_qbittorrent.py
+++ b/tests/test_qbittorrent.py
@@ -55,6 +55,7 @@ class QBittorrentReaderTests(unittest.TestCase):
             b"Ok.",
             json.dumps([{
                 "hash": torrent_hash, "name": "a.txt", "state": "uploading",
+                "save_path": "/downloads",
             }]).encode(),
             b'[{"index":0,"name":"a.txt","size":3,"progress":1,"priority":1}]',
             torrent_bytes,
@@ -102,6 +103,7 @@ class QBittorrentReaderTests(unittest.TestCase):
             b"Ok.",
             json.dumps([{
                 "hash": qb_hash, "name": "a.txt", "state": "uploading",
+                "save_path": "/downloads",
             }]).encode(),
             b'[{"index":0,"name":"a.txt","size":3,"progress":1,"priority":1}]',
             torrent_bytes,
@@ -157,6 +159,7 @@ class QBittorrentReaderTests(unittest.TestCase):
                 "infohash_v2": v2_hash,
                 "name": "a.txt",
                 "state": "uploading",
+                "save_path": "/downloads",
             }]).encode(),
             b'[{"index":0,"name":"a.txt","size":3,"progress":1,"priority":1}]',
             torrent_bytes,
@@ -217,9 +220,9 @@ class QBittorrentReaderTests(unittest.TestCase):
         malformed_bytes, malformed_hash = torrent("broken.txt", b"bad")
         second_bytes, second_hash = torrent("second.txt", b"two")
         torrents = [
-            {"hash": first_hash, "name": "first.txt", "state": "uploading"},
-            {"hash": malformed_hash, "name": "broken.txt", "state": "stalledUP"},
-            {"hash": second_hash, "name": "second.txt", "state": "uploading"},
+            {"hash": first_hash, "name": "first.txt", "state": "uploading", "save_path": "/downloads"},
+            {"hash": malformed_hash, "name": "broken.txt", "state": "stalledUP", "save_path": "/downloads"},
+            {"hash": second_hash, "name": "second.txt", "state": "uploading", "save_path": "/downloads"},
         ]
         responses = [
             b"Ok.", json.dumps(torrents).encode(),
diff --git a/tests/test_resources.py b/tests/test_resources.py
index f0fd3f3..07c9c07 100644
--- a/tests/test_resources.py
+++ b/tests/test_resources.py
@@ -40,6 +40,7 @@ class ResourceTests(unittest.TestCase):
                 "hash": decoded.info_hash_v2_hex,
                 "name": "v2.bin",
                 "state": "stoppedUP",
+                "save_path": "/downloads",
             },
             [{
                 "index": 0,
@@ -91,6 +92,7 @@ class ResourceTests(unittest.TestCase):
                 "hash": decoded.info_hash_v1_hex,
                 "name": "resource",
                 "state": "stoppedUP",
+                "save_path": "/downloads/nested",
             },
             [
                 {
@@ -106,6 +108,7 @@ class ResourceTests(unittest.TestCase):
             observed,
         )
         summary = normalized.summary
+        self.assertEqual(normalized.save_path.as_posix(), "/downloads/nested")
         self.assertEqual(
             summary.runtime_state, resource_pb2.TORRENT_RUNTIME_STATE_STOPPED
         )
@@ -139,6 +142,7 @@ class ResourceTests(unittest.TestCase):
                 "hash": torrent_hash,
                 "name": "with-padding",
                 "state": "stalledUP",
+                "save_path": "/downloads",
             },
             [
                 {
@@ -169,7 +173,7 @@ class ResourceTests(unittest.TestCase):
         metainfo = encode({b"info": info})
         torrent = {
             "hash": hashlib.sha1(encode(info)).hexdigest(),
-            "name": "renamed", "state": "uploading",
+            "name": "renamed", "state": "uploading", "save_path": "/downloads",
         }
         renamed = normalize_resource(torrent, [{
             "index": 0, "name": "renamed.txt", "size": 3,
@@ -182,6 +186,23 @@ class ResourceTests(unittest.TestCase):
                 "progress": 1.0, "priority": 1,
             }], metainfo)
 
+    def test_missing_or_out_of_shape_save_path_is_rejected(self):
+        info = {
+            b"length": 3, b"name": b"a.txt", b"piece length": 16384,
+            b"pieces": b"x" * 20,
+        }
+        metainfo = encode({b"info": info})
+        torrent = {
+            "hash": hashlib.sha1(encode(info)).hexdigest(),
+            "name": "a.txt", "state": "uploading", "save_path": "relative",
+        }
+        with self.assertRaisesRegex(ResourceError, "save path is unsafe"):
+            normalize_resource(torrent, [{
+                "index": 0, "name": "a.txt", "size": 3,
+                "completed": 3, "priority": 1,
+            }], metainfo)
+
+
     def test_noncanonical_bencode_is_rejected(self):
         with self.assertRaisesRegex(BencodeError, "unsorted"):
             decode_metainfo(b"d4:infod1:b1:x1:a1:yee")