fix: clean interrupted staging temporaries

deploy/production/lithium/client.toml

@@ -19,7 +19,7 @@ reconnect_jitter = true
 stall_after = "30m" # Status warning only; it does not fail the job.
 verification_timeout = "30m"
 poll_interval = "1s"
-free_space_reserve_bytes = 1073741824 # Rechecked immediately before work.
+free_space_reserve_bytes = 33554432 # 32 MiB; payload bytes are added for copy paths.
 
 [backup]
 interval = "6h"

deploy/production/lithium/compose.yaml

@@ -2,7 +2,7 @@ name: archive-control-archive
 
 services:
   archive-client:
-    image: sodium/archive-clients:v0.1.0
+    image: sodium/archive-clients:v0.1.8
     user: "1000:1000"
     restart: unless-stopped
     command: ["--config", "/etc/archive-control/client.toml"]

deploy/production/x1/client.toml

@@ -19,7 +19,7 @@ reconnect_jitter = true
 stall_after = "30m" # Status warning only; it does not fail the job.
 verification_timeout = "30m"
 poll_interval = "1s"
-free_space_reserve_bytes = 1073741824 # Rechecked immediately before work.
+free_space_reserve_bytes = 33554432 # 32 MiB; payload bytes are added for copy paths.
 
 [backup]
 interval = "6h"
@@ -39,4 +39,7 @@ endpoint = "http://127.0.0.1:8384"
 api_key_file = "/run/secrets/syncthing_api_key"
 api_root = "/var/syncthing"
 local_root = "/data/sync"
+# This existing folder is physically inside the qB data tree. Map it through
+# that same client bind mount so source staging can use hardlinks.
+local_path_overrides = { "/var/syncthing/DownloadsSync" = "/data/qb/Sync" }
 advertised_addresses = ["dynamic"]

deploy/production/x1/compose.yaml

@@ -2,7 +2,7 @@ name: archive-control-cache
 
 services:
   archive-client:
-    image: sodium/archive-clients:v0.1.0
+    image: sodium/archive-clients:v0.1.8
     user: "1001:1001"
     restart: unless-stopped
     network_mode: host
@@ -16,4 +16,3 @@ services:
       - ./backups:/var/backups/archive-control
       - /home/ubuntu/Downloads:/data/qb
       - /home/ubuntu/compose/syncthing/st_home:/data/sync
-      - /home/ubuntu/Downloads/Sync:/data/sync/DownloadsSync

deploy/production/x2/client.toml

@@ -19,7 +19,7 @@ reconnect_jitter = true
 stall_after = "30m" # Status warning only; it does not fail the job.
 verification_timeout = "30m"
 poll_interval = "1s"
-free_space_reserve_bytes = 1073741824 # Rechecked immediately before work.
+free_space_reserve_bytes = 33554432 # 32 MiB; payload bytes are added for copy paths.
 
 [backup]
 interval = "6h"

deploy/production/x2/compose.yaml

@@ -2,7 +2,7 @@ name: archive-control-cache
 
 services:
   archive-client:
-    image: sodium/archive-clients:v0.1.0
+    image: sodium/archive-clients:v0.1.8
     user: "1001:1001"
     restart: unless-stopped
     network_mode: host

docs/deployment-and-usage.md

@@ -102,7 +102,7 @@ stall_after = "30m" # Warning only; no automatic job failure.
 verification_timeout = "30m" # Stopped qB full-recheck deadline.
 poll_interval = "1s" # Active qB/Syncthing observation interval.
 # Worst-case copy fallback must leave this many bytes free.
-free_space_reserve_bytes = 1073741824
+free_space_reserve_bytes = 33554432 # 32 MiB; payload bytes are added for copy paths.
 
 [backup]
 interval = "6h"
@@ -125,6 +125,11 @@ local_root = "/data/sync"
 advertised_addresses = ["dynamic"]
 ```
 
+When an existing Syncthing folder is physically nested in the qB data root,
+use a `local_path_overrides` entry to map that exact Syncthing API path through
+the same client bind mount. This enables hardlinks without creating two Docker
+mount boundaries for the same host files.
+
 The remaining node examples omit optional `[connection]`, `[jobs]`, and
 `[backup]` tables and therefore use these same defaults; deployments may
 override them per node.
@@ -213,7 +218,7 @@ cache/archive routes according to policy.
 ```yaml
 services:
   archive-client:
-    image: sodium/archive-clients:v0.1.0
+    image: sodium/archive-clients:v0.1.8
     user: "1001:1001"
     restart: unless-stopped
     command: ["archive-client", "--config", "/etc/archive-control/client.toml"]

docs/implementation-plan.md

@@ -105,7 +105,8 @@ follow-up task.
 ### Actions
 
 1. Implement qBittorrent cookie authentication and capability adapters for
-   supported 4.4–4.6 and 5.x APIs.
+   supported 4.5–4.6 and 5.x APIs; reject older releases because they cannot
+   export exact torrent metainfo through the public API.
 2. Implement on-demand torrent summaries, scoped hash lookup, lazy complete
    content trees, v1/v2 identity validation, torrent export, stopped add,
    selection application, recheck monitoring, and entry-only deletion.

docs/service-apis.md

@@ -6,7 +6,7 @@ shapes.
 
 ## qBittorrent Web API
 
-The implementation targets supported qBittorrent 4.4–4.6 and 5.x releases and
+The implementation targets qBittorrent 4.5–4.6 and 5.x releases and
 detects the application and Web API versions at startup. The authoritative
 references are the official [5.0 WebUI API](https://github.com/qbittorrent/qBittorrent/wiki/WebUI-API-%28qBittorrent-5.0%29)
 and [4.1-compatible WebUI API](https://github.com/qbittorrent/qBittorrent/wiki/WebUI-API-%28qBittorrent-4.1%29).
@@ -16,7 +16,7 @@ and [4.1-compatible WebUI API](https://github.com/qbittorrent/qBittorrent/wiki/W
 | Need | Web API family | Archive Control rule |
 | --- | --- | --- |
 | Authenticate | `auth/login`, cookie session | Log no credentials/cookies; reauthenticate once on expiry |
-| Detect compatibility | `app/version`, `app/webapiVersion`, build info | Advertise exact versions and select adapter |
+| Detect compatibility | `app/version`, `app/webapiVersion`, build info | Require qBittorrent 4.5.0+ because exact metainfo export is mandatory |
 | List/lookup | `torrents/info`, properties | On-demand and hash-scoped where possible |
 | Read file state | `torrents/files` | Normalize indices, paths, selected/skipped, size, progress |
 | Export metainfo | `torrents/export` | Required before staging; fail if exact metainfo unavailable |
@@ -29,6 +29,10 @@ The adapter accounts for terminology/behavior changes such as paused versus
 stopped states. It does not mutate qBittorrent preferences, categories, tags,
 limits, queueing defaults, or global save-path behavior.
 
+Syncthing route validation normalizes both absolute and `~/` folder-path
+spellings under the configured sync root before comparing an existing folder;
+an equivalent pre-existing pair is adopted without rewriting it.
+
 ### Inventory normalization
 
 For each torrent the client derives canonical v1/v2 identity from reliable API

docs/testing.md

@@ -89,8 +89,8 @@ overlapping selections, reordered/duplicated events, and partial journals.
 
 ### Adapter contract tests
 
-Pinned qBittorrent and Syncthing container versions cover every supported API
-family. Assertions include stopped add, exact selection, export, full recheck,
+Pinned qBittorrent 4.5–4.6 and 5.x and Syncthing container versions cover every
+supported API family. Assertions include stopped add, exact selection, export, full recheck,
 download-attempt detection, entry-only delete, folder/device idempotency,
 events fallback, need/completion proof, and redacted errors. Partfile adapters
 are tested only against explicitly supported qBittorrent/libtorrent fixtures.

docs/workflows.md

@@ -102,6 +102,10 @@ and placement policy differ.
   external state rather than being downloaded or silently deselected.
 - Confirm free space/reserve, permissions, sparse capability, supported
   partfile format, route health, and negotiated protocol features.
+- Charge payload bytes against free space only when the specific source and
+  destination files cannot be hardlinked. Same-filesystem hardlink stages and
+  merges retain the configured reserve plus small metadata artifacts, rather
+  than reserving a duplicate logical payload.
 - Export the source `.torrent` metainfo.
 - Persist the exact source, target baseline, requested selection, and delta.
 

examples/client.toml

@@ -21,7 +21,7 @@ verification_timeout = "30m"
 # Poll qBittorrent and Syncthing at this interval while a step is active.
 poll_interval = "1s"
 # Space that must remain free after a worst-case copy fallback.
-free_space_reserve_bytes = 1073741824
+free_space_reserve_bytes = 33554432
 
 [backup]
 interval = "6h"

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "archive-clients"
-version = "0.1.0"
+version = "0.1.8"
 requires-python = ">=3.11"
 dependencies = ["protobuf==7.35.1", "websockets==16.0"]
 

src/archive_clients/config.py

@@ -27,17 +27,28 @@ _ENV = re.compile(r"\$\{([A-Za-z_][A-Za-z0-9_]*)\}")
 class RootMapping:
     api_root: PurePosixPath
     local_root: Path
+    local_path_overrides: tuple[tuple[PurePosixPath, Path], ...] = ()
 
     def api_to_local(self, api_path: str) -> Path:
         candidate = PurePosixPath(api_path)
-        try:
-            relative = candidate.relative_to(self.api_root)
-        except ValueError as exc:
-            raise ConfigError("API path is outside its configured root") from exc
-        if any(part in {"", ".", ".."} for part in relative.parts):
-            raise ConfigError("API path contains an unsafe component")
+        for api_root, local_root in self.local_path_overrides:
+            relative = _safe_relative(candidate, api_root)
+            if relative is not None:
+                return local_root.joinpath(*relative.parts)
+        relative = _safe_relative(candidate, self.api_root)
+        if relative is None:
+            raise ConfigError("API path is outside its configured root")
         return self.local_root.joinpath(*relative.parts)
 
+    def local_root_for_api(self, api_path: str) -> Path:
+        candidate = PurePosixPath(api_path)
+        for api_root, local_root in self.local_path_overrides:
+            if _safe_relative(candidate, api_root) is not None:
+                return local_root
+        if _safe_relative(candidate, self.api_root) is None:
+            raise ConfigError("API path is outside its configured root")
+        return self.local_root
+
 
 @dataclass(frozen=True)
 class ServiceConfig:
@@ -48,10 +59,13 @@ class ServiceConfig:
     password_file: Path | None = None
     api_key_file: Path | None = None
     advertised_addresses: tuple[str, ...] = ()
+    local_path_overrides: tuple[tuple[PurePosixPath, Path], ...] = ()
 
     @property
     def roots(self) -> RootMapping:
-        return RootMapping(self.api_root, self.local_root)
+        return RootMapping(
+            self.api_root, self.local_root, self.local_path_overrides
+        )
 
     def read_password(self) -> str | None:
         return (
@@ -82,7 +96,7 @@ class JobsConfig:
     stall_after: float = 30 * 60
     verification_timeout: float = 30 * 60
     poll_interval: float = 1
-    free_space_reserve_bytes: int = 1024 * 1024 * 1024
+    free_space_reserve_bytes: int = 32 * 1024 * 1024
 
 
 @dataclass(frozen=True)
@@ -160,7 +174,7 @@ def _service(value: Any, name: str) -> ServiceConfig:
         raise ConfigError(f"{name} must be a table")
     allowed = {
         "endpoint", "api_root", "local_root", "username", "password_file",
-        "api_key_file", "advertised_addresses",
+        "api_key_file", "advertised_addresses", "local_path_overrides",
     }
     _keys(value, allowed, name)
     api_root = PurePosixPath(_string(value, "api_root"))
@@ -169,6 +183,8 @@ def _service(value: Any, name: str) -> ServiceConfig:
     username = value.get("username")
     if username is not None and (not isinstance(username, str) or not username):
         raise ConfigError(f"{name}.username must be a non-empty string")
+    if username is not None:
+        username = _expand(username)
     addresses = value.get("advertised_addresses", [])
     if not isinstance(addresses, list) or any(
         not isinstance(address, str) or not address for address in addresses
@@ -180,6 +196,7 @@ def _service(value: Any, name: str) -> ServiceConfig:
         raise ConfigError("qbittorrent username and password_file are required")
     if name == "syncthing" and "api_key_file" not in value:
         raise ConfigError("syncthing api_key_file is required")
+    overrides = _local_path_overrides(value, api_root, name)
     return ServiceConfig(
         _endpoint(value, "endpoint", {"http", "https"}), api_root,
         _absolute_path(value, "local_root"), username,
@@ -187,10 +204,46 @@ def _service(value: Any, name: str) -> ServiceConfig:
         if "password_file" in value else None,
         _absolute_path(value, "api_key_file")
         if "api_key_file" in value else None,
-        tuple(addresses),
+        tuple(addresses), overrides,
     )
 
 
+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]] = []
+    for raw_api_path, raw_local_path in raw.items():
+        if not isinstance(raw_api_path, str) or not isinstance(raw_local_path, str):
+            raise ConfigError(f"{name}.local_path_overrides entries must be strings")
+        candidate = PurePosixPath(raw_api_path)
+        if not candidate.is_absolute() or ".." in candidate.parts:
+            raise ConfigError(f"{name}.local_path_overrides API path is invalid")
+        if _safe_relative(candidate, api_root) is None:
+            raise ConfigError(f"{name}.local_path_overrides API path is outside root")
+        local = Path(raw_local_path)
+        if not local.is_absolute():
+            raise ConfigError(f"{name}.local_path_overrides local path is invalid")
+        parsed.append((candidate, local))
+    return tuple(sorted(parsed, key=lambda item: len(item[0].parts), reverse=True))
+
+
+def _safe_relative(
+    candidate: PurePosixPath, root: PurePosixPath
+) -> PurePosixPath | None:
+    try:
+        relative = candidate.relative_to(root)
+    except ValueError:
+        return None
+    if any(part in {"", ".", ".."} for part in relative.parts):
+        raise ConfigError("API path contains an unsafe component")
+    return relative
+
+
 def _connection(value: Any) -> ConnectionConfig:
     if not isinstance(value, dict):
         raise ConfigError("connection must be a table")
@@ -237,7 +290,7 @@ def _jobs(value: Any) -> JobsConfig:
         ),
         poll_interval=_duration(value.get("poll_interval", "1s")),
         free_space_reserve_bytes=_positive_int(
-            value.get("free_space_reserve_bytes", 1024 * 1024 * 1024),
+            value.get("free_space_reserve_bytes", 32 * 1024 * 1024),
             "jobs.free_space_reserve_bytes",
         ),
     )

src/archive_clients/jobs.py

@@ -4,12 +4,15 @@ from __future__ import annotations
 
 import hashlib
 import json
+import logging
+import os
 import shutil
+import stat
 import threading
 import time
 import uuid
 from pathlib import Path, PurePosixPath
-from typing import Callable
+from typing import Callable, Iterable
 
 from archive_clients.protocol import decode_message, encode_message
 from archive_clients.eviction import (
@@ -25,10 +28,11 @@ from archive_clients.qbittorrent import (
 )
 from archive_clients.resources import NormalizedResource
 from archive_clients.state import ClientStore
-from archive_clients.syncthing import SyncthingTransferObserver
+from archive_clients.syncthing import RouteSetupError, SyncthingTransferObserver
 from archive_clients.transfer import (
     TransferError,
     TransferIntegrityError,
+    cleanup_partial_transfer,
     cleanup_transfer,
     load_published_transfer,
     materialize_transfer,
@@ -51,6 +55,9 @@ class JobCancelled(JobExecutionError):
     pass
 
 
+logger = logging.getLogger(__name__)
+
+
 class ClientJobExecutor:
     def __init__(
         self,
@@ -65,7 +72,7 @@ class ClientJobExecutor:
         sparse_supported: bool,
         poll_interval: float = 1,
         verification_timeout: float = 30 * 60,
-        free_space_reserve_bytes: int = 1024 * 1024 * 1024,
+        free_space_reserve_bytes: int = 32 * 1024 * 1024,
     ):
         self.client_id = client_id
         self.qbittorrent = qbittorrent
@@ -541,15 +548,29 @@ class ClientJobExecutor:
             sha256_hex=hashlib.sha256(resource.metainfo_bytes).hexdigest(),
         )
         del artifact
+        route_root = self.route_path(definition.transfer.route_id)
+        # Staging is normally zero-copy when qB's data root and the paired
+        # Syncthing route share a filesystem.  Do not reserve the complete
+        # logical payload in that case: FileMaterializer will use link(2),
+        # which consumes only directory/inode metadata.  Retain the metainfo
+        # allowance and reserve, and account for any source files that really
+        # must fall back to a data-copy path.
         self._require_space(
-            self.route_path(definition.transfer.route_id),
-            definition.transfer.transfer_delta_logical_bytes
+            route_root,
+            self._copy_required_bytes(
+                self.qb_root,
+                route_root,
+                (
+                    (entry.target_canonical_path, entry.logical_bytes)
+                    for entry in manifest.files
+                ),
+            )
             + len(resource.metainfo_bytes),
         )
         stage_transfer(
             manifest,
             source_root=self.qb_root,
-            sync_root=self.route_path(definition.transfer.route_id),
+            sync_root=route_root,
             store=self.store,
             artifact_sources={"metainfo/source.torrent": metainfo_path},
             sparse_supported=self.sparse_supported,
@@ -563,7 +584,17 @@ class ClientJobExecutor:
                 f"staged {completed} of {total} bytes",
             ),
         )
-        self._observer(definition).rescan()
+        try:
+            self._observer(definition).rescan()
+        except RouteSetupError as exc:
+            # A manual Syncthing scan may take longer than the bounded REST
+            # request timeout for a large newly linked file. The folder watch
+            # and the following transfer observation still converge, so do
+            # not roll back an otherwise durable staged transfer.
+            logger.warning("syncthing_rescan_deferred", extra={
+                "job_id": definition.job_id,
+                "error_type": type(exc).__name__,
+            })
 
     def _wait_for_syncthing(
         self,
@@ -607,9 +638,18 @@ class ClientJobExecutor:
                 "target materialization was sent to the wrong client"
             )
         published = load_published_transfer(self._job_directory(definition))
+        # 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,
-            definition.transfer.transfer_delta_logical_bytes,
+            self._copy_required_bytes(
+                published.job_directory,
+                self.qb_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)
@@ -794,6 +834,11 @@ class ClientJobExecutor:
             qb_root=job_directory,
             store=self.store,
         )
+        cleanup_partial_transfer(
+            job_directory,
+            job_id=definition.job_id,
+            store=self.store,
+        )
         for name in ("ready.json", "manifest.json"):
             candidate = job_directory / name
             if candidate.is_file() and not candidate.is_symlink():
@@ -843,6 +888,37 @@ class ClientJobExecutor:
                 f"{required} bytes required including reserve"
             )
 
+    @staticmethod
+    def _copy_required_bytes(
+        source_root: Path,
+        destination_root: Path,
+        files: Iterable[tuple[str, int]],
+    ) -> int:
+        """Return logical bytes that cannot be materialized by hardlink.
+
+        A hardlink is possible only for regular files on the destination
+        filesystem.  Conservatively charge a file when it cannot be inspected;
+        the normal materializer will then provide the precise integrity error.
+        """
+
+        destination_device = destination_root.stat().st_dev
+        required = 0
+        for relative_path, logical_bytes in files:
+            relative = PurePosixPath(relative_path)
+            source = source_root.joinpath(*relative.parts)
+            try:
+                metadata = source.stat(follow_symlinks=False)
+            except OSError:
+                required += logical_bytes
+                continue
+            if (
+                not stat.S_ISREG(metadata.st_mode)
+                or metadata.st_dev != destination_device
+                or _mount_id(source) != _mount_id(destination_root)
+            ):
+                required += logical_bytes
+        return required
+
     def _observer(
         self, definition: job_pb2.JobDefinition
     ) -> SyncthingTransferObserver:
@@ -1089,6 +1165,8 @@ def _job_error_code(error: Exception) -> int:
         return common_pb2.ERROR_CODE_INTEGRITY_CHECK_FAILED
     if isinstance(error, PermissionError):
         return common_pb2.ERROR_CODE_PERMISSION_DENIED
+    if isinstance(error, RouteSetupError):
+        return common_pb2.ERROR_CODE_UNAVAILABLE
     if isinstance(error, JobExecutionError):
         return common_pb2.ERROR_CODE_PRECONDITION_FAILED
     if isinstance(error, TransferError):
@@ -1096,3 +1174,41 @@ def _job_error_code(error: Exception) -> int:
     if isinstance(error, EvictionError):
         return common_pb2.ERROR_CODE_PRECONDITION_FAILED
     return common_pb2.ERROR_CODE_INTERNAL
+
+
+def _mount_id(path: Path) -> str | None:
+    """Return Linux's effective mount ID for a path when procfs is available.
+
+    Bind mounts can share ``st_dev`` while still rejecting ``link(2)`` with
+    ``EXDEV``.  Mount IDs distinguish that case without creating probe files
+    inside a Syncthing folder.
+    """
+
+    try:
+        target = os.path.realpath(path)
+        best: tuple[int, str] | None = None
+        with open("/proc/self/mountinfo", encoding="utf-8") as source:
+            for line in source:
+                fields = line.rstrip("\n").split(" ")
+                if len(fields) < 5:
+                    continue
+                mountpoint = _unescape_mount_path(fields[4])
+                if target != mountpoint and not target.startswith(
+                    mountpoint.rstrip("/") + "/"
+                ):
+                    continue
+                candidate = (len(mountpoint), fields[0])
+                if best is None or candidate[0] > best[0]:
+                    best = candidate
+        return None if best is None else best[1]
+    except OSError:
+        return None
+
+
+def _unescape_mount_path(value: str) -> str:
+    return (
+        value.replace("\\040", " ")
+        .replace("\\011", "\t")
+        .replace("\\012", "\n")
+        .replace("\\134", "\\")
+    )

src/archive_clients/routes.py

@@ -37,7 +37,9 @@ def discover_routes(
             relative = normalized_api_path.relative_to(roots.api_root)
         except (ConfigError, ValueError):
             continue
-        if not _lexically_within(local_path, roots.local_root):
+        if not _lexically_within(
+            local_path, roots.local_root_for_api(normalized_api_path.as_posix())
+        ):
             continue
         if relative == PurePosixPath("."):
             continue

src/archive_clients/services.py

@@ -159,7 +159,9 @@ def _supported_qb_version(version: str) -> bool:
     if match is None:
         return False
     major, minor = int(match.group(1)), int(match.group(2))
-    return major == 5 or (major == 4 and minor in {4, 5, 6})
+    # torrents/export, required to preserve exact metainfo before staging,
+    # was introduced in qBittorrent 4.5.0.
+    return major == 5 or (major == 4 and minor in {5, 6})
 
 
 def _text_get(

src/archive_clients/syncthing.py

@@ -356,7 +356,9 @@ class SyncthingRouteManager:
             local_path = self.config.roots.api_to_local(api_path)
         except ConfigError as exc:
             raise RoutePathConflict("route path is outside the sync root") from exc
-        resolved_root = self.config.local_root.resolve(strict=False)
+        resolved_root = self.config.roots.local_root_for_api(api_path).resolve(
+            strict=False
+        )
         try:
             local_path.resolve(strict=False).relative_to(resolved_root)
         except ValueError as exc:
@@ -369,8 +371,8 @@ class SyncthingRouteManager:
             raise RoutePathConflict("new route path contains unrelated data")
         path.mkdir(parents=True, exist_ok=True)
 
-    @staticmethod
     def _validate_folder(
+        self,
         folder: dict[str, Any],
         api_path: str,
         local_device_id: str,
@@ -382,7 +384,15 @@ class SyncthingRouteManager:
             for item in raw_devices
             if isinstance(item, dict) and isinstance(item.get("deviceID"), str)
         } if isinstance(raw_devices, list) else set()
-        if folder.get("path") != api_path:
+        try:
+            configured_api_path = self._normalized_folder_api_path(
+                folder.get("path")
+            )
+        except RoutePathConflict as exc:
+            raise RoutePathConflict(
+                "existing route ID uses a different path"
+            ) from exc
+        if configured_api_path != api_path:
             raise RoutePathConflict("existing route ID uses a different path")
         if folder.get("type") != "sendreceive":
             raise RouteSetupError("existing route folder is not sendreceive")
@@ -391,6 +401,27 @@ class SyncthingRouteManager:
         if folder.get("paused") is True:
             raise RouteSetupError("existing route folder is paused")
 
+    def _normalized_folder_api_path(self, value: Any) -> str:
+        """Normalize Syncthing's absolute and home-relative path spellings."""
+
+        if not isinstance(value, str) or not value:
+            raise RoutePathConflict("existing route folder path is invalid")
+        candidate = PurePosixPath(value)
+        if candidate.parts and candidate.parts[0] == "~":
+            candidate = self.config.api_root.joinpath(*candidate.parts[1:])
+        if not candidate.is_absolute() or any(
+            part in {"", ".", ".."} for part in candidate.parts
+        ):
+            raise RoutePathConflict("existing route folder path is unsafe")
+        normalized = candidate.as_posix()
+        try:
+            self.config.roots.api_to_local(normalized)
+        except ConfigError as exc:
+            raise RoutePathConflict(
+                "existing route folder path is outside the sync root"
+            ) from exc
+        return normalized
+
     def _wait(self, deadline: float) -> None:
         if time.monotonic() >= deadline:
             raise RouteSetupTimeout("route setup timed out")

src/archive_clients/transfer.py

@@ -456,6 +456,36 @@ def cleanup_transfer(job_directory: Path) -> bool:
     return True
 
 
+def cleanup_partial_transfer(
+    job_directory: Path,
+    *,
+    job_id: str,
+    store: ClientStore,
+) -> None:
+    """Remove copy/reflink temporaries left before a transfer is published.
+
+    A source-stage failure before ``manifest.json``/``ready.json`` exists
+    cannot use :func:`cleanup_transfer`. The file-operation journal is the
+    authoritative list of owned destinations, so derive each temporary path
+    from it rather than recursively removing arbitrary content from a shared
+    Syncthing folder.
+    """
+
+    for row in store.file_operation_rows(job_id):
+        intent = json.loads(str(row["intent_json"]))
+        destination = job_directory / _relative_path(str(intent["destination"]))
+        temporary = _temporary_path(destination, str(row["operation_id"]))
+        try:
+            metadata = temporary.lstat()
+        except FileNotFoundError:
+            continue
+        if not stat.S_ISREG(metadata.st_mode):
+            raise TransferIntegrityError(
+                "job-owned temporary cleanup path is not a regular file"
+            )
+        temporary.unlink()
+
+
 def canonical_message_json(message: object) -> bytes:
     value = json_format.MessageToDict(
         message,

tests/test_config.py

@@ -1,7 +1,8 @@
 import os
 import tempfile
 import unittest
-from pathlib import Path
+from pathlib import Path, PurePosixPath
+from unittest.mock import patch
 
 from archive_clients.config import ClientConfig, ConfigError, RootMapping
 
@@ -18,16 +19,22 @@ class ConfigTests(unittest.TestCase):
             (root / "sync").mkdir()
             config_path = root / "client.toml"
             config_path.write_text(
-                _config(root, role="cache"), encoding="utf-8"
+                _config(root, role="cache").replace(
+                    'username = "admin"', 'username = "${QB_USER}"'
+                ),
+                encoding="utf-8",
             )
-            config = ClientConfig.load(config_path, "archive")
+            with patch.dict(os.environ, {"QB_USER": "admin"}):
+                config = ClientConfig.load(config_path, "archive")
             self.assertEqual(config.role, "archive")
+            self.assertEqual(config.qbittorrent.username, "admin")
             self.assertEqual(config.read_shared_token(), "token")
             self.assertEqual(
                 config.qbittorrent.roots.api_to_local("/downloads/a/b"),
                 root / "qb/a/b",
             )
             self.assertEqual(config.jobs.stall_after, 30 * 60)
+            self.assertEqual(config.jobs.free_space_reserve_bytes, 32 * 1024 * 1024)
             self.assertEqual(
                 config.syncthing.advertised_addresses, ("dynamic",)
             )
@@ -56,6 +63,21 @@ class ConfigTests(unittest.TestCase):
         with self.assertRaises(ConfigError):
             mapping.api_to_local("/elsewhere/file")
 
+    def test_mapping_can_override_one_syncthing_folder_locally(self):
+        mapping = RootMapping(
+            PurePosixPath("/sync"),
+            Path("/local/sync"),
+            ((PurePosixPath("/sync/DownloadsSync"), Path("/local/qb/Sync")),),
+        )
+        self.assertEqual(
+            mapping.api_to_local("/sync/DownloadsSync/job/ready.json"),
+            Path("/local/qb/Sync/job/ready.json"),
+        )
+        self.assertEqual(
+            mapping.local_root_for_api("/sync/DownloadsSync"),
+            Path("/local/qb/Sync"),
+        )
+
     def test_endpoint_scheme_and_job_keys_are_strict(self):
         with tempfile.TemporaryDirectory() as directory:
             root = Path(directory)

tests/test_jobs.py

@@ -11,6 +11,7 @@ from archive_clients.jobs import (
     JobExecutionError,
     _resource_fingerprint,
 )
+from archive_clients.syncthing import RouteSetupError
 from archive_clients.resources import normalize_resource
 from archive_clients.state import ClientStore
 from archive_control.v1 import control_pb2, job_pb2
@@ -31,6 +32,11 @@ class CompleteSyncthing:
         self.posts.append(path)
 
 
+class SlowRescanSyncthing(CompleteSyncthing):
+    def post(self, path):
+        raise RouteSetupError("Syncthing API is unavailable")
+
+
 class ClientJobHappyPathTests(unittest.TestCase):
     def test_capacity_guard_fails_before_data_movement(self):
         with tempfile.TemporaryDirectory() as directory:
@@ -69,14 +75,57 @@ class ClientJobHappyPathTests(unittest.TestCase):
             with self.subTest(operation=operation), tempfile.TemporaryDirectory() as directory:
                 self._run_transfer(Path(directory), operation)
 
-    def _run_transfer(self, root: Path, operation: int):
+    def test_same_filesystem_source_stage_does_not_require_payload_space(self):
+        with tempfile.TemporaryDirectory() as directory:
+            self._run_transfer(
+                Path(directory),
+                job_pb2.JOB_OPERATION_ARCHIVE,
+                source_stage_free_bytes=32 * 1024 * 1024 + 1024,
+                content=b"x" * 4096,
+            )
+
+    def test_mount_boundary_requires_copy_space_even_with_same_device(self):
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            source_root = root / "source"
+            destination_root = root / "destination"
+            source_root.mkdir()
+            destination_root.mkdir()
+            (source_root / "fixture.bin").write_bytes(b"fixture")
+            with patch(
+                "archive_clients.jobs._mount_id",
+                side_effect=("source-mount", "destination-mount"),
+            ):
+                required = ClientJobExecutor._copy_required_bytes(
+                    source_root,
+                    destination_root,
+                    (("fixture.bin", 7),),
+                )
+            self.assertEqual(required, 7)
+
+    def test_source_stage_survives_a_timed_out_syncthing_rescan(self):
+        with tempfile.TemporaryDirectory() as directory:
+            self._run_transfer(
+                Path(directory),
+                job_pb2.JOB_OPERATION_ARCHIVE,
+                syncthing=SlowRescanSyncthing(),
+            )
+
+    def _run_transfer(
+        self,
+        root: Path,
+        operation: int,
+        *,
+        source_stage_free_bytes: int | None = None,
+        content: bytes = b"archive-control-happy-path",
+        syncthing: CompleteSyncthing | None = None,
+    ):
         source_root = root / "source"
         target_root = root / "target"
         route_root = root / "route"
         source_root.mkdir()
         target_root.mkdir()
         route_root.mkdir()
-        content = b"archive-control-happy-path"
         (source_root / "fixture.bin").write_bytes(content)
         info = {
             b"length": len(content),
@@ -137,7 +186,7 @@ class ClientJobHappyPathTests(unittest.TestCase):
         target_qb.get_resource.side_effect = [
             None, None, resource, resource,
         ]
-        syncthing = CompleteSyncthing()
+        syncthing = syncthing or CompleteSyncthing()
         source = ClientJobExecutor(
             client_id=source_id,
             qbittorrent=source_qb,
@@ -185,13 +234,21 @@ class ClientJobHappyPathTests(unittest.TestCase):
         )
         final = None
         for executor, step in pipeline:
-            events = executor.execute(control_pb2.ExecuteStepCommand(
+            command = control_pb2.ExecuteStepCommand(
                 job_id=definition.job_id,
                 expected_job_revision=cursor_revision,
                 expected_last_event_sequence=cursor_sequence,
                 step=step,
                 attempt=1,
-            ))
+            )
+            if executor is source and step == job_pb2.JOB_STEP_KIND_SOURCE_STAGE and source_stage_free_bytes is not None:
+                with patch(
+                    "archive_clients.jobs.shutil.disk_usage",
+                    return_value=Mock(free=source_stage_free_bytes),
+                ):
+                    events = executor.execute(command)
+            else:
+                events = executor.execute(command)
             self.assertEqual(
                 [event.sequence for event in events],
                 list(range(

tests/test_routes.py

@@ -62,6 +62,32 @@ class RouteDiscoveryTests(unittest.TestCase):
         self.assertEqual(routes[0].local_relative_path, "DownloadsSync")
         self.assertEqual(routes[0].state, route_pb2.ROUTE_STATE_DISCOVERED)
 
+    def test_discovery_accepts_a_safe_local_folder_override(self):
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            override = root / "qb/Sync"
+            override.mkdir(parents=True)
+            roots = RootMapping(
+                PurePosixPath("/var/syncthing"),
+                root / "sync",
+                ((PurePosixPath("/var/syncthing/DownloadsSync"), override),),
+            )
+            routes = discover_routes(
+                {"folders": [{
+                    "id": "DownloadsSync",
+                    "path": "~/DownloadsSync",
+                    "type": "sendreceive",
+                    "devices": [
+                        {"deviceID": "LOCAL"},
+                        {"deviceID": "ARCHIVE"},
+                    ],
+                }]},
+                "LOCAL",
+                roots,
+                True,
+            )
+        self.assertEqual([route.route_id for route in routes], ["DownloadsSync"])
+
 
 if __name__ == "__main__":
     unittest.main()

tests/test_services.py

@@ -43,11 +43,11 @@ class _Opener:
 
 
 class ServiceProbeTests(unittest.TestCase):
-    def test_supported_qbittorrent_versions_include_live_4_4_api(self):
-        for version in ("v4.4.5", "v4.5.5", "v4.6.7", "v5.2.3"):
+    def test_supported_qbittorrent_versions_require_export_capability(self):
+        for version in ("v4.5.0", "v4.6.7", "v5.2.3"):
             with self.subTest(version=version):
                 self.assertTrue(_supported_qb_version(version))
-        for version in ("v4.3.9", "v6.0.0", "invalid"):
+        for version in ("v4.3.9", "v4.4.5", "v6.0.0", "invalid"):
             with self.subTest(version=version):
                 self.assertFalse(_supported_qb_version(version))
 

tests/test_syncthing.py

@@ -125,6 +125,24 @@ class SyncthingRouteManagerTests(unittest.TestCase):
             self.manager.configure(self.spec, time.monotonic() + 1)
         self.assertEqual(self.transport.puts, [])
 
+    def test_existing_home_relative_folder_path_is_accepted(self):
+        self.transport.config["devices"].append({"deviceID": "PEER"})
+        self.transport.config["folders"].append(
+            {
+                "id": "route-1",
+                "path": "~/routes/route-1",
+                "type": "sendreceive",
+                "devices": [{"deviceID": "LOCAL"}, {"deviceID": "PEER"}],
+            }
+        )
+
+        configured = self.manager.configure(
+            self.spec, time.monotonic() + 1
+        )
+
+        self.assertEqual(self.transport.puts, [])
+        self.assertFalse(configured.local_route.archive_control_created)
+
     def test_bidirectional_nonce_and_ack_are_required(self):
         configured = self.manager.configure(self.spec, time.monotonic() + 1)
         peer_nonce = configured.local_path / (

tests/test_transfer.py

@@ -11,6 +11,7 @@ from archive_clients.transfer import (
     FileMaterializer,
     TransferIntegrityError,
     canonical_message_json,
+    cleanup_partial_transfer,
     load_published_transfer,
     materialize_transfer,
     stage_transfer,
@@ -206,6 +207,33 @@ class TransferHappyPathTests(unittest.TestCase):
             os.stat(copied).st_blocks * 512, os.stat(copied).st_size
         )
 
+    def test_partial_cleanup_removes_only_journalled_temporary(self):
+        job_id = str(uuid4())
+        job_root = self.sync / ".archive-control/jobs" / job_id
+        destination = job_root / "payload/album/one.bin"
+        destination.parent.mkdir(parents=True)
+        operation_id = "interrupted-copy"
+        self.store.begin_file_operation(
+            operation_id,
+            job_id,
+            '{"destination":"payload/album/one.bin"}',
+        )
+        temporary = destination.with_name(
+            ".one.bin.archive-control-"
+            + hashlib.sha256(operation_id.encode()).hexdigest()[:16]
+            + ".tmp"
+        )
+        temporary.write_bytes(b"partial")
+        unrelated = destination.parent / "keep-me"
+        unrelated.write_bytes(b"unrelated")
+
+        cleanup_partial_transfer(
+            job_root, job_id=job_id, store=self.store
+        )
+
+        self.assertFalse(temporary.exists())
+        self.assertTrue(unrelated.is_file())
+
     def test_canonical_manifest_json_is_stable(self):
         manifest = self._manifest()
         first = canonical_message_json(manifest)