fix: avoid duplicate capacity reservation for hardlinks

deploy/production/lithium/compose.yaml

@@ -2,7 +2,7 @@ name: archive-control-archive
 
 services:
   archive-client:
-    image: sodium/archive-clients:v0.1.2
+    image: sodium/archive-clients:v0.1.4
     user: "1000:1000"
     restart: unless-stopped
     command: ["--config", "/etc/archive-control/client.toml"]

deploy/production/x1/compose.yaml

@@ -2,7 +2,7 @@ name: archive-control-cache
 
 services:
   archive-client:
-    image: sodium/archive-clients:v0.1.2
+    image: sodium/archive-clients:v0.1.4
     user: "1001:1001"
     restart: unless-stopped
     network_mode: host

deploy/production/x2/compose.yaml

@@ -2,7 +2,7 @@ name: archive-control-cache
 
 services:
   archive-client:
-    image: sodium/archive-clients:v0.1.2
+    image: sodium/archive-clients:v0.1.4
     user: "1001:1001"
     restart: unless-stopped
     network_mode: host

docs/deployment-and-usage.md

@@ -213,7 +213,7 @@ cache/archive routes according to policy.
 ```yaml
 services:
   archive-client:
-    image: sodium/archive-clients:v0.1.2
+    image: sodium/archive-clients:v0.1.4
     user: "1001:1001"
     restart: unless-stopped
     command: ["archive-client", "--config", "/etc/archive-control/client.toml"]

docs/service-apis.md

@@ -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/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.
 

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "archive-clients"
-version = "0.1.2"
+version = "0.1.4"
 requires-python = ">=3.11"
 dependencies = ["protobuf==7.35.1", "websockets==16.0"]
 

src/archive_clients/jobs.py

@@ -5,11 +5,12 @@ from __future__ import annotations
 import hashlib
 import json
 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 (
@@ -541,15 +542,29 @@ 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),
+            route_root,
-            definition.transfer.transfer_delta_logical_bytes
+            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,
@@ -607,9 +622,18 @@ 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)
@@ -843,6 +867,36 @@ 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
+            ):
+                required += logical_bytes
+        return required
+
     def _observer(
         self, definition: job_pb2.JobDefinition
     ) -> SyncthingTransferObserver:

src/archive_clients/syncthing.py

@@ -369,8 +369,8 @@ 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 +382,15 @@ 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 +399,27 @@ 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")

tests/test_jobs.py

@@ -69,14 +69,29 @@ 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=1024 * 1024 * 1024 + 1024,
+                content=b"x" * 4096,
+            )
+
+    def _run_transfer(
+        self,
+        root: Path,
+        operation: int,
+        *,
+        source_stage_free_bytes: int | None = None,
+        content: bytes = b"archive-control-happy-path",
+    ):
         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),
@@ -185,13 +200,21 @@ 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_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 / (