fix: recover durable route paths after restart

Dockerfile

@@ -11,8 +11,12 @@ CMD ["python", "-m", "unittest", "discover", "-s", "tests", "-v"]
 
 FROM python:3.11-slim
 ENV PYTHONDONTWRITEBYTECODE=1 PYTHONUNBUFFERED=1
-RUN groupadd --gid 1001 archive-control \
-    && useradd --uid 1001 --gid 1001 --no-create-home archive-control
+RUN if ! getent group 1001 >/dev/null; then \
+        groupadd --gid 1001 archive-control; \
+    fi \
+    && if ! getent passwd 1001 >/dev/null; then \
+        useradd --uid 1001 --gid 1001 --no-create-home archive-control; \
+    fi
 COPY --from=builder /wheels /wheels
 RUN pip install --no-cache-dir /wheels/*.whl && rm -rf /wheels
 USER 1001:1001

README.md

@@ -77,6 +77,13 @@ four eager-mesh routes, transfer/eviction/unarchive workflows, and the
 adversarial matrix without live infrastructure or Telegram. See
 `e2e/README.md`.
 
+## Deployment Preflight Tests
+
+Check deployment configuration immediately before bringing a new node online.
+The reusable read-only preflight validates the deployed image's filesystem and
+API view against its Docker bind mounts. See details in
+[docs/deployment-preflight.md](docs/deployment-preflight.md).
+
 The complete cross-project design, protocol, workflow, safety, deployment,
 Telegram UX, and testing documentation is published under [`docs/`](docs/).
 

deploy/production/README.md

@@ -1,30 +1,74 @@
 # Production deployment
 
 These files are the non-secret, host-specific deployment manifests for the
-initial x1/x2/lithium topology.
+initial x1/x2/lithium topology and the later helium archive node.
 
 - Install the x1 and x2 files as
   `~/compose/ArchiveControl-cache/{compose.yaml,client.toml}`.
 - Install the lithium files as
   `~/compose/ArchiveControl-archive/{compose.yaml,client.toml}`.
+- The helium directory contains three isolated compose-project manifests. Install
+  them under `~/Repositories/compose/{qbittorrent-helium,syncthing-helium,ArchiveControl-archive}`
+  as described in `helium/README.md`.
 - Create sibling `state`, `backups`, and `secrets` directories owned by the
   configured container UID/GID.
 - Secret files are never committed. Each `secrets` directory contains
   `archive_control_token`, `qb_password`, and `syncthing_api_key`, each a
   regular non-empty file with mode `0600`.
 
-The Syncthing mounts intentionally reproduce each instance's `/var/syncthing`
-layout, including nested data binds. This lets route discovery and route
-provisioning use one safe API-to-local path mapping without altering an
-existing Syncthing configuration.
+## Hardlink-safe bind-mount topology
 
-Before starting a stack, validate it with:
+For an archive source, the qB content path and every Syncthing route used for
+staging must resolve through the **same container mount**. Matching host
+filesystem device IDs alone is insufficient: two separate Docker bind mounts
+have different mount IDs and `link(2)` may return `EXDEV` across them. The
+client deliberately treats that case as copy-only and performs a full payload
+free-space check.
+
+Automatic routes always use the Syncthing API path `routes/<route-id>`. Bind
+that path from a dedicated directory beneath the qB data root, then map the
+same path through the qB client mount:
+
+```yaml
+# Syncthing compose project
+volumes:
+  - /srv/syncthing-config:/var/syncthing
+  - /srv/downloads/.archive-control-routes:/var/syncthing/routes
+
+# Archive Control client compose project
+volumes:
+  - /srv/downloads:/data/qb
+  - /srv/syncthing-config:/data/sync
+```
+
+```toml
+[syncthing]
+api_root = "/var/syncthing"
+local_root = "/data/sync"
+local_path_overrides = { "/var/syncthing/routes" = "/data/qb/.archive-control-routes" }
+```
+
+Do **not** mount the route directory separately into the client. The override
+is the authoritative mapping and keeps qB source files and automatic route
+folders in one mount namespace. Existing manually configured Syncthing folders
+below the qB tree may retain their own exact overrides. Use API-visible paths,
+not Syncthing folder IDs, as override keys.
+
+Before starting a stack, validate its config and then run the generic host
+preflight with that machine's own paths and container names:
 
 ```sh
 docker compose config
 docker compose run --rm archive-client --check-config
+python3 scripts/preflight-deployment.py --help
 ```
 
 The check is fail-fast and performs local permission, filesystem, sparse-file,
 hard-link, and reflink probes. Normal startup additionally probes the local
 qBittorrent and Syncthing APIs before registration.
+
+`scripts/preflight-deployment.py` is deliberately topology-agnostic: pass the
+host's `client.toml` and its client, qBittorrent, and Syncthing container names.
+It resolves Docker mounts rather than assuming project names or host paths. It
+also catches a common fatal error: a Syncthing `api_root` that names its config
+volume rather than the mounted shared-data tree.

deploy/production/helium/README.md

@@ -0,0 +1,34 @@
+# Helium archive-node deployment
+
+This directory contains the non-secret manifests for the dedicated helium
+archive node. Install the files into these separate compose projects:
+
+- `~/Repositories/compose/qbittorrent-helium/compose.yaml`
+- `~/Repositories/compose/syncthing-helium/compose.yaml`
+- `~/Repositories/compose/ArchiveControl-archive/{compose.yaml,client.toml}`
+
+The qBittorrent API and Syncthing GUI/API bind only to loopback. Syncthing
+transport/discovery ports are published normally. qBittorrent data and
+Syncthing route folders both live under `/media/Data2`; the Archive Control
+container therefore mounts `/media/Data2` once at `/data/storage` so archive
+placements can hardlink rather than make a full copy.
+
+`/media/Data2/Downloading` already contains unrelated files. The fresh qB
+instance must not import or manage them; only Archive Control-created torrents
+are managed.
+
+Before the first client start, run the repository preflight on the target host
+(replace container names if that host uses different compose project names):
+
+```sh
+python3 scripts/preflight-deployment.py \
+  --client-config ~/Repositories/compose/ArchiveControl-archive/client.toml \
+  --client-container archive-control-helium-archive-client-1 \
+  --syncthing-container helium-syncthing-syncthing-1 \
+  --qbittorrent-container helium-qbittorrent-qbittorrent-1
+```
+
+It is read-only: it checks the configured API roots resolve to the same host
+paths as the client roots, that both data roots share one client bind mount for
+hardlinks, secret-file permissions, filesystem capabilities, and the local qB
+and Syncthing APIs. It does not send the control token or modify any container.

deploy/production/helium/archive-control-compose.yaml

@@ -0,0 +1,19 @@
+name: archive-control-helium
+
+services:
+  archive-client:
+    image: sodium/archive-clients:v0.1.19
+    user: "1000:1000"
+    restart: unless-stopped
+    network_mode: host
+    command: ["--config", "/etc/archive-control/client.toml"]
+    environment:
+      QB_USER: admin
+    volumes:
+      - ./client.toml:/etc/archive-control/client.toml:ro
+      - ./secrets:/run/secrets:ro
+      - ./state:/var/lib/archive-control
+      - ./backups:/var/backups/archive-control
+      # Do not split this into separate qB and Sync bind mounts: hardlinks
+      # require both trees to resolve within this one mount namespace.
+      - /media/Data2:/data/storage

deploy/production/helium/client.toml

@@ -0,0 +1,42 @@
+client_id = "helium-archive"
+display_name = "helium archive"
+role = "archive"
+control_endpoint = "ws://bot.everdream.xyz:8766/archive_control"
+shared_token_file = "/run/secrets/archive_control_token"
+state_db = "/var/lib/archive-control/client.db"
+backup_dir = "/var/backups/archive-control"
+
+[connection]
+registration_timeout = "10s"
+heartbeat_interval = "15s"
+offline_timeout = "45s"
+reconnect_initial = "1s"
+reconnect_max = "60s"
+reconnect_reset_after = "60s"
+reconnect_jitter = true
+
+[jobs]
+stall_after = "30m"
+verification_timeout = "30m"
+poll_interval = "1s"
+free_space_reserve_bytes = 33554432
+
+[backup]
+interval = "6h"
+recent = 12
+daily = 14
+weekly = 8
+
+[qbittorrent]
+endpoint = "http://127.0.0.1:8081"
+username = "${QB_USER}"
+password_file = "/run/secrets/qb_password"
+api_root = "/downloads/Downloading"
+local_root = "/data/storage/Downloading"
+
+[syncthing]
+endpoint = "http://127.0.0.1:8384"
+api_key_file = "/run/secrets/syncthing_api_key"
+api_root = "/var/syncthing/Sync"
+local_root = "/data/storage/Sync"
+advertised_addresses = ["dynamic"]

deploy/production/helium/qbittorrent-compose.yaml

@@ -0,0 +1,24 @@
+name: helium-qbittorrent
+
+services:
+  qbittorrent:
+    image: sodium/qbittorrent-nox:5.2.3-lt2-1-proxy-listen-amd64
+    environment:
+      PUID: "1000"
+      PGID: "1000"
+      TZ: Etc/UTC
+      WEBUI_PORT: "8081"
+      TORRENTING_PORT: "6881"
+    command: ["--webui-port=8081", "--confirm-legal-notice"]
+    volumes:
+      - ./config:/config
+      # This is deliberately one parent mount. Archive Control maps both the
+      # qB and Syncthing subtrees through the same mount namespace.
+      - /media/Data2:/downloads
+    ports:
+      # Keep the published and internal WebUI ports identical: qBittorrent
+      # rejects a forwarded request whose Host header carries a different port.
+      - "127.0.0.1:8081:8081"
+      - "6881:6881/tcp"
+      - "6881:6881/udp"
+    restart: unless-stopped

deploy/production/helium/start-syncthing.sh

@@ -0,0 +1,18 @@
+#!/bin/sh
+set -eu
+
+home=/var/syncthing
+api_key=$(cat /run/secrets/syncthing_api_key)
+
+if [ ! -f "$home/config.xml" ]; then
+    syncthing generate --home="$home" --no-port-probing
+fi
+
+exec syncthing serve \
+    --home="$home" \
+    --gui-address=http://0.0.0.0:8384 \
+    --gui-apikey="$api_key" \
+    --no-browser \
+    --no-port-probing \
+    --no-restart \
+    --no-upgrade

deploy/production/helium/syncthing-compose.yaml

@@ -0,0 +1,19 @@
+name: helium-syncthing
+
+services:
+  syncthing:
+    image: syncthing/syncthing:2.1.2@sha256:4464f4161dd0251e20d46bb3aec83363db75d80cef1abdd5d5fd4054b04a004d
+    user: "1000:1000"
+    hostname: helium
+    entrypoint: ["/bootstrap/start-syncthing.sh"]
+    volumes:
+      - ./start-syncthing.sh:/bootstrap/start-syncthing.sh:ro
+      - ./secrets:/run/secrets:ro
+      - ./config:/var/syncthing
+      - /media/Data2/Sync:/var/syncthing/Sync
+    ports:
+      - "127.0.0.1:8384:8384"
+      - "22000:22000/tcp"
+      - "22000:22000/udp"
+      - "21027:21027/udp"
+    restart: unless-stopped

deploy/production/lithium/client.toml

@@ -39,4 +39,5 @@ endpoint = "http://syncthing:8384"
 api_key_file = "/run/secrets/syncthing_api_key"
 api_root = "/var/syncthing"
 local_root = "/data/sync"
+local_path_overrides = { "/var/syncthing/routes" = "/data/qb/.archive-control-routes" }
 advertised_addresses = ["dynamic"]

deploy/production/lithium/compose.yaml

@@ -2,7 +2,7 @@ name: archive-control-archive
 
 services:
   archive-client:
-    image: sodium/archive-clients:v0.1.11
+    image: sodium/archive-clients:v0.1.14
     user: "1000:1000"
     restart: unless-stopped
     command: ["--config", "/etc/archive-control/client.toml"]

deploy/production/x1/client.toml

@@ -41,5 +41,5 @@ 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" }
+local_path_overrides = { "/var/syncthing/DownloadsSync" = "/data/qb/Sync", "/var/syncthing/routes" = "/data/qb/.archive-control-routes" }
 advertised_addresses = ["dynamic"]

deploy/production/x1/compose.yaml

@@ -2,7 +2,7 @@ name: archive-control-cache
 
 services:
   archive-client:
-    image: sodium/archive-clients:v0.1.11
+    image: sodium/archive-clients:v0.1.14
     user: "1001:1001"
     restart: unless-stopped
     network_mode: host

deploy/production/x2/client.toml

@@ -39,4 +39,8 @@ endpoint = "http://127.0.0.1:8384"
 api_key_file = "/run/secrets/syncthing_api_key"
 api_root = "/var/syncthing"
 local_root = "/data/sync"
+# `DownloadsSync-X2` is ~/Downloads/Sync on the host, nested below the qB
+# root. Resolve it through /data/qb rather than a second nested bind mount so
+# source staging can hardlink it.
+local_path_overrides = { "/var/syncthing/Downloads/Sync" = "/data/qb/Sync", "/var/syncthing/routes" = "/data/qb/.archive-control-routes" }
 advertised_addresses = ["dynamic"]

deploy/production/x2/compose.yaml

@@ -2,7 +2,7 @@ name: archive-control-cache
 
 services:
   archive-client:
-    image: sodium/archive-clients:v0.1.11
+    image: sodium/archive-clients:v0.1.14
     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/Downloads/Sync

docs/README.md

@@ -16,8 +16,9 @@ credentials and host-specific details.
 6. [Storage safety and recovery](storage-safety.md)
 7. [qBittorrent and Syncthing integration](service-apis.md)
 8. [Configuration, deployment, and usage](deployment-and-usage.md)
-9. [Telegram UX](telegram-ux.md)
-10. [Testing strategy](testing.md)
+9. [Deployment preflight tests](deployment-preflight.md)
+10. [Telegram UX](telegram-ux.md)
+11. [Testing strategy](testing.md)
 
 The independent protobuf source of truth lives in the
 `cabbage/archive-control-proto` repository. Generated bindings in this

docs/decisions.md

@@ -35,8 +35,11 @@ expand these rules but must not contradict them.
   manifests, and observed external state.
 - SQLite backups use the online backup API. Defaults are every six hours, 12
   recent, 14 daily, and eight weekly copies, plus pre/post-migration backups.
-- Default concurrency is one active data-moving job per client and per route.
-  Disjoint node pairs may run concurrently. Queueing is durable FIFO.
+- Default concurrency is unrestricted: every eligible queued job is admitted
+  in one scheduler pass and independent jobs execute concurrently on a client.
+  Physical qBittorrent, Syncthing, disk, and network capacity are therefore
+  the natural limit. `enforce_concurrency_limits=true` restores the optional
+  legacy per-client/per-route gates. Commands for one job remain serialized.
 - A queued job owns a per-resource reservation. Cancelling it removes only the
   queued record/reservation and never sends cleanup commands.
 - Connectivity or transfer stalls wait indefinitely. A configurable 30-minute

docs/deployment-and-usage.md

@@ -44,6 +44,9 @@ command_max_attempts = 3 # Total sends, including the initial attempt.
 stall_after = "30m" # Warning state only; jobs continue waiting.
 route_policy = "on_demand" # Alternative: eager_mesh.
 route_setup_timeout = "30m"
+# Default: allow all eligible jobs; disk/network/service capacity is the limit.
+enforce_concurrency_limits = false
+# Used only when enforce_concurrency_limits is true.
 max_active_per_client = 1
 max_active_per_route = 1
 max_envelope_bytes = 1048576
@@ -128,7 +131,12 @@ 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.
+mount boundaries for the same host files. Do not add a second bind mount for
+the nested folder: Linux treats it as a distinct mount even when it has the
+same `st_dev`, and the client correctly falls back to copy-only capacity
+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.
 
 The remaining node examples omit optional `[connection]`, `[jobs]`, and
 `[backup]` tables and therefore use these same defaults; deployments may
@@ -218,7 +226,7 @@ cache/archive routes according to policy.
 ```yaml
 services:
   archive-client:
-    image: sodium/archive-clients:v0.1.11
+    image: sodium/archive-clients:v0.1.14
     user: "1001:1001"
     restart: unless-stopped
     command: ["archive-client", "--config", "/etc/archive-control/client.toml"]
@@ -251,6 +259,28 @@ Generated protobuf Python bindings are committed in each consumer with the
 exact `archive-control-proto` tag/commit recorded. Release order is proto,
 control consumer, client consumer, E2E, then image publication.
 
+### Reproducible multi-platform Buildx lifecycle
+
+The named Buildx builders are local acceleration/cache only; they are not a
+deployment dependency and can be removed after publication. To create a fresh
+builder, verify its platforms, publish a release, and remove it afterwards:
+
+```bash
+docker buildx create --name archive-control-release --driver docker-container --use
+docker buildx inspect --bootstrap
+docker buildx build --platform linux/amd64,linux/arm64 \
+  --tag sodium/archive-clients:vX.Y.Z --push .
+docker buildx rm archive-control-release
+```
+
+`docker buildx inspect` must list both `linux/amd64` and `linux/arm64` before
+publishing. If the host has no arm64 emulation, install/configure it according
+to the host Docker distribution before the build; do not publish a partial
+single-platform tag. Retain the pushed manifest digest in the release notes
+and deploy the immutable tag or digest. The optional `archive-control-qemu`
+builder follows the same lifecycle when it is used for an emulation smoke
+build.
+
 ## Operator usage
 
 1. Prepare local qB, sync, state, backup, config, and secret mounts with the

docs/deployment-preflight.md

@@ -0,0 +1,121 @@
+# Deployment preflight tests
+
+Run the deployment preflight on every new node after its qBittorrent and
+Syncthing stacks are running, but before starting the Archive Control daemon
+for normal operation or creating any routes/jobs. It does not contact the
+control daemon, alter Syncthing/qBittorrent state, or print secret contents.
+It does create and remove two unique, zero-byte probe files while proving that
+the live client mount topology permits hard-link staging; no resource data or
+configuration is modified.
+
+The script is [`scripts/preflight-deployment.py`](../scripts/preflight-deployment.py).
+It deliberately takes paths and container names as arguments rather than
+assuming hostnames, compose project names, mount paths, credentials, or roles.
+It can therefore be used unchanged on cache and archive nodes.
+
+## Requirements
+
+- Run it on the Docker host being checked.
+- Use Python 3.8 or newer. The script reads the mounted configuration through
+  the client image, so it does not depend on the host Python TOML library.
+- Have Docker CLI access to the daemon.
+- Have the checkout containing the script available on that host, or copy only
+  this script into the node's compose directory.
+- Bring up qBittorrent and Syncthing first. Do not start the normal Archive
+  Control daemon yet.
+
+The disposable client container below uses the exact `archive-client` service
+image, mounts, environment, and network specified by that node's compose file.
+Consequently its qB/Syncthing API probes validate the same runtime environment
+the daemon will use, not the host shell's network namespace.
+
+## New-node procedure
+
+The example uses generic names. Replace paths, compose project directories,
+service names, and real container names for the node being deployed.
+
+```sh
+# 1. Bring up only the local dependencies.
+cd /srv/compose/syncthing-node && docker compose up -d
+cd /srv/compose/qbittorrent-node && docker compose up -d
+
+# 2. Create a temporary client from the exact production image/config, without
+#    running the daemon or registering it with control.
+cd /srv/compose/ArchiveControl-archive
+docker compose run -d --no-deps --name archive-control-preflight \
+  --entrypoint sleep archive-client infinity
+
+# 3. Discover the real dependency container names if needed.
+docker ps --format '{{.Names}}'
+
+# 4. Run the deployment checks. They include a disposable hard-link probe.
+python3 /path/to/archive-clients/scripts/preflight-deployment.py \
+  --client-config /srv/compose/ArchiveControl-archive/client.toml \
+  --client-container archive-control-preflight \
+  --syncthing-container syncthing-node-syncthing-1 \
+  --qbittorrent-container qbittorrent-node-qbittorrent-1
+
+# 5. Remove the temporary container, then start the real daemon only after a
+#    successful result.
+docker rm -f archive-control-preflight
+docker compose up -d archive-client
+```
+
+If the real client configuration is mounted somewhere other than the standard
+`/etc/archive-control/client.toml`, pass that in-container location explicitly:
+
+```sh
+python3 scripts/preflight-deployment.py ... \
+  --container-config /custom/path/client.toml
+```
+
+## Required arguments
+
+| Argument | Meaning |
+| --- | --- |
+| `--client-config` | Host path to the exact `client.toml` that will be mounted into the daemon. |
+| `--client-container` | Running disposable or already-running client container to inspect and probe. |
+| `--syncthing-container` | Running Syncthing container for this node. |
+| `--qbittorrent-container` | Running qBittorrent container for this node. |
+| `--container-config` | Optional `client.toml` path inside the client container; defaults to `/etc/archive-control/client.toml`. |
+
+## What it checks
+
+- The future automatic `routes/<route-id>` path resolves through Docker mounts
+  to the same host path as its client-side mapping.
+- 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.
+- 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.
+- Every existing `archive-control:*` Syncthing folder beneath `routes/` still
+  has its local directory. This catches a route-root bind-mount migration that
+  would otherwise hide an already configured folder and later fail a job with
+  `No such file or directory`.
+- 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.
+- qBittorrent authentication/version compatibility and Syncthing
+  authentication/device identity are healthy from the client container.
+
+In particular, if `syncthing.api_root` is the Syncthing configuration root,
+bind its `routes` subdirectory from a dedicated directory beneath qB's data
+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.
+
+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
+run this preflight. Do not discard existing route directories: they can contain
+route handshake state or an in-progress transfer namespace.
+
+## Failure handling
+
+Treat a nonzero exit status as a deployment blocker. Correct the compose
+mounts, `client.toml`, secret permissions, service credentials, or service
+image/version that the message identifies, then rerun the same command. Do not
+work around a mapping failure by creating route folders manually: the route
+provisioner relies on those API/local path mappings being exact.

docs/service-apis.md

@@ -89,9 +89,11 @@ left unchanged.
 
 Syncthing may serialize a folder path relative to its home as `~/...`. The
 client normalizes that notation beneath the configured API-visible sync root
-before applying the API-to-local root mapping. Deployments must mirror
-Syncthing's nested bind mounts into the client so the normalized API path and
-the client filesystem path refer to the same bytes.
+before applying the API-to-local root mapping. When that folder is nested
+below qB's content root, an exact `local_path_overrides` entry must map it
+through the qB bind mount. Do not mirror it as a second nested client bind
+mount: it denotes the same host bytes but a distinct mount namespace boundary,
+which prevents hardlink staging.
 
 Provisioning uses idempotent device and folder configuration updates. Each
 client receives its peer device ID and optional advertised addresses

docs/system-design.md

@@ -133,10 +133,13 @@ a resource may be active or queued at a time. This prevents incompatible
 baselines even when jobs would use different nodes or observe different sides
 of a hybrid identity.
 
-Defaults allow one active data-moving job per client and one per route. A job
-must acquire its source client, target client, route, and resource reservation
-atomically. Disjoint node pairs may run concurrently. Route setup is a
-preflight activity and does not permit a data step to bypass these leases.
+By default every eligible queued job is claimed in the same scheduler pass and
+independent jobs run concurrently on each client; physical service and storage
+capacity are the limit. Set `enforce_concurrency_limits=true` on control to
+enable the optional one-per-client/one-per-route gates. A job always retains
+its resource reservation, and commands for the same job remain serialized.
+Route setup is a preflight activity and does not permit a data step to bypass
+the resource reservation.
 
 Offline nodes do not prevent unrelated jobs from being listed or run. A job
 requiring an offline node remains waiting indefinitely; it does not consume an
@@ -154,6 +157,12 @@ advances to the next step. On reconnect:
 4. Control observes relevant qBittorrent, Syncthing, staging, and manifest
    state before selecting retry, resume, compensation, cleanup, or manual
    intervention.
+
+If a connection disappears while a synchronous job operation is in progress,
+the client journals events locally, reconnects indefinitely, and serializes a
+replayed command behind the in-flight operation for that job. The replay reads
+the journal rather than repeating the data operation. This applies to every
+transfer step, including post-commit staging cleanup.
 5. A command is reissued with its original ID when the acceptance result is
    uncertain.
 

docs/telegram-ux.md

@@ -25,8 +25,10 @@ What do you want to do?
 [ Evict Cache ] [ Job Status ]
 ```
 
-All subsequent pages edit this message. `Cancel` closes the active selection
-flow. `Back` returns one level while retaining validated filters/selections.
+All subsequent pages edit this message. Leaving a resource/tree selection
+returns to the Archive Control operation menu without closing the shared
+conversation. Confirmation `Cancel` returns to its immediate prior selection;
+the main menu alone can close Archive Control.
 Callback payloads contain opaque session/action IDs, not resource names or
 paths, and are validated against persisted session revision and expiry.
 

docs/testing.md

@@ -225,7 +225,7 @@ Fixtures include small deterministic v1, v2, and hybrid torrents with:
 | Recovery | restart every step on source/target/control, lost DB with proof, ambiguous loss fails closed |
 | Messaging | duplicate command/event, lost ack, sequence gap, stale revision, duplicate client ID |
 | Safety | attempted download, corrupt same-size file, symlink/path escape, special file, partfile mismatch |
-| Operations | stall retains percent, offline wait, cancellation each phase, postcommit cleanup retry |
+| Operations | stall retains percent, offline wait, cancellation each phase, postcommit cleanup retry, disconnect/reconnect during every transfer step with exactly-once replay |
 | Database | online backup under load, pre/post migration, retention, corrupt backup rejection, offline restore |
 | UI | pagination/filter chain, stale/double callback, persisted session, clear vs evict separation |
 

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "archive-clients"
-version = "0.1.11"
+version = "0.1.19"
 requires-python = ">=3.11"
 dependencies = ["protobuf==7.35.1", "websockets==16.0"]
 

scripts/preflight-deployment.py

@@ -0,0 +1,327 @@
+#!/usr/bin/env python3
+"""Validate a host's Archive Control Docker deployment before it is used.
+
+This intentionally relies only on the config file and the named containers on
+the host where it runs. It never reads secret contents or calls a remote
+control daemon. The hard-link probe creates uniquely named, empty files in
+the configured qB and automatic-route directories and removes them afterward.
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import os
+import stat
+import subprocess
+import sys
+from dataclasses import dataclass
+from pathlib import Path, PurePosixPath
+from typing import Any
+
+
+class CheckFailure(RuntimeError):
+    pass
+
+
+@dataclass(frozen=True)
+class Mapping:
+    source: Path
+    destination: PurePosixPath
+
+
+def docker_inspect(container: str) -> dict[str, Any]:
+    result = subprocess.run(
+        ["docker", "inspect", container], check=False, text=True,
+        capture_output=True,
+    )
+    if result.returncode:
+        raise CheckFailure(f"cannot inspect container {container!r}")
+    try:
+        value = json.loads(result.stdout)
+        return value[0]
+    except (json.JSONDecodeError, IndexError, TypeError) as exc:
+        raise CheckFailure(f"invalid Docker inspection for {container!r}") from exc
+
+
+def map_path(container: dict[str, Any], path: str) -> Mapping:
+    candidate = PurePosixPath(path)
+    matches: list[tuple[int, Mapping]] = []
+    for mount in container.get("Mounts", []):
+        if mount.get("Type") not in {"bind", "volume"}:
+            continue
+        source, destination = mount.get("Source"), mount.get("Destination")
+        if not isinstance(source, str) or not isinstance(destination, str):
+            continue
+        destination_path = PurePosixPath(destination)
+        try:
+            relative = candidate.relative_to(destination_path)
+        except ValueError:
+            continue
+        matches.append((len(destination_path.parts), Mapping(
+            Path(source).joinpath(*relative.parts), destination_path
+        )))
+    if not matches:
+        raise CheckFailure(f"{path} is not backed by a Docker bind/volume mount")
+    return max(matches, key=lambda item: item[0])[1]
+
+
+def container_user(container: dict[str, Any]) -> str | None:
+    value = container.get("Config", {}).get("User")
+    return value if isinstance(value, str) and value else None
+
+
+def require_same_path(label: str, left: Mapping, right: Mapping) -> None:
+    if left.source.resolve(strict=False) != right.source.resolve(strict=False):
+        raise CheckFailure(
+            f"{label} host paths differ: {left.source} != {right.source}"
+        )
+
+
+def require_regular_secret(path: Path) -> None:
+    try:
+        mode = path.stat().st_mode
+    except OSError as exc:
+        raise CheckFailure(f"secret is unavailable: {path}") from exc
+    if not stat.S_ISREG(mode) or stat.S_IMODE(mode) & 0o077 or path.stat().st_size == 0:
+        raise CheckFailure(f"secret must be a non-empty mode-0600 regular file: {path}")
+
+
+def route_local_path(syncthing: dict[str, Any]) -> str:
+    """Resolve the fixed, future automatic ``routes/`` path in the client."""
+
+    api_root = PurePosixPath(syncthing["api_root"])
+    candidate = api_root / "routes"
+    overrides = syncthing.get("local_path_overrides", {})
+    if not isinstance(overrides, dict):
+        raise CheckFailure("syncthing.local_path_overrides must be a table")
+    matches: list[tuple[int, PurePosixPath, str]] = []
+    for raw_api, raw_local in overrides.items():
+        if not isinstance(raw_api, str) or not isinstance(raw_local, str):
+            raise CheckFailure("syncthing.local_path_overrides entries are invalid")
+        root = PurePosixPath(raw_api)
+        try:
+            relative = candidate.relative_to(root)
+        except ValueError:
+            continue
+        matches.append((len(root.parts), relative, raw_local))
+    if matches:
+        _, relative, local_root = max(matches, key=lambda item: item[0])
+        return str(Path(local_root).joinpath(*relative.parts))
+    try:
+        relative = candidate.relative_to(api_root)
+    except ValueError as exc:
+        raise CheckFailure("future route path is outside syncthing.api_root") from exc
+    return str(Path(syncthing["local_root"]).joinpath(*relative.parts))
+
+
+def run_client_check(container: str, config: str, flag: str) -> None:
+    result = subprocess.run(
+        ["docker", "exec", container, "archive-client", "--config", config, flag],
+        check=False, text=True, capture_output=True,
+    )
+    if result.returncode:
+        detail = result.stderr.strip() or result.stdout.strip() or "failed"
+        raise CheckFailure(f"client {flag} failed: {detail}")
+    print(result.stdout.strip())
+
+
+def mounted_config(container: str, config: str) -> dict[str, Any]:
+    """Read normalized non-secret config through the client image itself."""
+
+    program = '''import json,sys
+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["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(
+        ["docker", "exec", container, "python", "-c", program, config],
+        check=False, text=True, capture_output=True,
+    )
+    if result.returncode:
+        detail = result.stderr.strip() or result.stdout.strip() or "failed"
+        raise CheckFailure(f"cannot load mounted client config: {detail}")
+    try:
+        value = json.loads(result.stdout)
+    except json.JSONDecodeError as exc:
+        raise CheckFailure("mounted client config output is invalid") from exc
+    if not isinstance(value, dict):
+        raise CheckFailure("mounted client config is invalid")
+    return value
+
+
+def run_service_check(container: str, config: str) -> None:
+    program = '''import json,sys
+from pathlib import Path
+from archive_clients.config import ClientConfig
+from archive_clients.probes import probe_root
+from archive_clients.services import probe_qbittorrent,probe_syncthing
+config=ClientConfig.load(Path(sys.argv[1]))
+sync_probe=probe_root(config.syncthing.local_root)
+probes=[probe_qbittorrent(config.qbittorrent),probe_syncthing(config.syncthing,sparse_supported=sync_probe.sparse_files)]
+print(json.dumps({"services":[{"service":p.service,"state":p.state,"detail":p.detail,"version":p.version,"device_id":p.device_id} for p in probes]},sort_keys=True))
+raise SystemExit(0 if all(p.state == 1 for p in probes) else 1)'''
+    result = subprocess.run(
+        ["docker", "exec", container, "python", "-c", program, config],
+        check=False, text=True, capture_output=True,
+    )
+    if result.returncode:
+        detail = result.stderr.strip() or result.stdout.strip() or "failed"
+        raise CheckFailure(f"client local-service probe failed: {detail}")
+    print(result.stdout.strip())
+
+
+def run_hardlink_probe(
+    container: str, qb_root: str, route_root: str, user: str | None = None,
+) -> None:
+    """Prove that the daemon can hard-link from qB data into automatic routes."""
+
+    program = r'''import os,sys,tempfile
+source_root,route_root=sys.argv[1:]
+source_path=None
+destination_path=None
+try:
+    source_fd,source_path=tempfile.mkstemp(prefix=".archive-control-preflight-",dir=source_root)
+    os.close(source_fd)
+    destination_fd,destination_path=tempfile.mkstemp(prefix=".archive-control-preflight-",dir=route_root)
+    os.close(destination_fd)
+    os.unlink(destination_path)
+    os.link(source_path,destination_path)
+    source_stat=os.stat(source_path)
+    destination_stat=os.stat(destination_path)
+    if source_stat.st_dev != destination_stat.st_dev or source_stat.st_ino != destination_stat.st_ino:
+        raise RuntimeError("link(2) did not produce the same filesystem inode")
+    print("hard-link staging probe passed")
+finally:
+    for path in (destination_path,source_path):
+        if path:
+            try:
+                os.unlink(path)
+            except FileNotFoundError:
+                pass
+'''
+    command = ["docker", "exec"]
+    if user:
+        command.extend(["--user", user])
+    command.extend([container, "python", "-c", program, qb_root, route_root])
+    result = subprocess.run(
+        command,
+        check=False, text=True, capture_output=True,
+    )
+    if result.returncode:
+        detail = result.stderr.strip() or result.stdout.strip() or "failed"
+        raise CheckFailure(f"hard-link staging probe failed: {detail}")
+    print(result.stdout.strip())
+
+
+def run_existing_route_directory_check(container: str, config: str) -> None:
+    """Reject a mount migration that hides an already configured route folder."""
+
+    program = r'''import json,os,sys
+from pathlib import Path,PurePosixPath
+from archive_clients.config import ClientConfig
+from archive_clients.syncthing import SyncthingHttp
+config=ClientConfig.load(Path(sys.argv[1]))
+transport=SyncthingHttp(config.syncthing)
+route_root=config.syncthing.api_root / "routes"
+missing=[]
+checked=[]
+for folder in transport.get_json("/rest/config").get("folders",[]):
+    if not isinstance(folder,dict) or not str(folder.get("label","")).startswith("archive-control:"):
+        continue
+    raw=folder.get("path")
+    if not isinstance(raw,str) or not raw:
+        continue
+    api=PurePosixPath(raw)
+    if api.parts and api.parts[0] == "~":
+        api=config.syncthing.api_root.joinpath(*api.parts[1:])
+    try:
+        api.relative_to(route_root)
+    except ValueError:
+        continue
+    local=config.syncthing.roots.api_to_local(api.as_posix())
+    checked.append(str(local))
+    if not local.is_dir():
+        missing.append({"folder_id":folder.get("id",""),"path":str(local)})
+print(json.dumps({"checked":checked,"missing":missing},sort_keys=True))
+raise SystemExit(1 if missing else 0)
+'''
+    result = subprocess.run(
+        ["docker", "exec", container, "python", "-c", program, config],
+        check=False, text=True, capture_output=True,
+    )
+    if result.returncode:
+        detail = result.stderr.strip() or result.stdout.strip() or "failed"
+        raise CheckFailure(
+            "an existing Archive Control Syncthing route directory is missing; "
+            f"complete the route-directory migration before starting jobs: {detail}"
+        )
+    print(result.stdout.strip())
+
+
+def main(argv: list[str] | None = None) -> int:
+    parser = argparse.ArgumentParser(
+        description="Read-only Archive Control Docker deployment preflight"
+    )
+    parser.add_argument("--client-config", type=Path, required=True,
+                        help="host path to client.toml")
+    parser.add_argument("--client-container", required=True)
+    parser.add_argument("--syncthing-container", required=True)
+    parser.add_argument("--qbittorrent-container", required=True)
+    parser.add_argument("--container-config", default="/etc/archive-control/client.toml",
+                        help="client.toml path inside the client container")
+    args = parser.parse_args(argv)
+    try:
+        client = docker_inspect(args.client_container)
+        syncthing = docker_inspect(args.syncthing_container)
+        qbittorrent = docker_inspect(args.qbittorrent_container)
+        configured_host_path = map_path(client, args.container_config).source
+        if configured_host_path.resolve(strict=False) != args.client_config.resolve(strict=False):
+            raise CheckFailure(
+                "--client-config does not match the file mounted into the client"
+            )
+        config = mounted_config(args.client_container, args.container_config)
+        qb = config["qbittorrent"]
+        sync = config["syncthing"]
+
+        client_qb = map_path(client, qb["local_root"])
+        client_route = map_path(client, route_local_path(sync))
+        syncthing_route = map_path(
+            syncthing, str(PurePosixPath(sync["api_root"]) / "routes")
+        )
+        qb_api = map_path(qbittorrent, qb["api_root"])
+        require_same_path(
+            "future Syncthing routes/local route mapping",
+            syncthing_route, client_route,
+        )
+        require_same_path("qBittorrent api_root/local_root", qb_api, client_qb)
+        if client_qb.destination != client_route.destination:
+            raise CheckFailure(
+                "qBittorrent and future route roots use separate client bind "
+                "mounts; hard-link staging would be unavailable"
+            )
+        run_hardlink_probe(
+            args.client_container, qb["local_root"], route_local_path(sync),
+            container_user(client),
+        )
+        run_existing_route_directory_check(
+            args.client_container, args.container_config
+        )
+        for key in ("shared_token_file",):
+            require_regular_secret(map_path(client, config[key]).source)
+        for service, key in ((qb, "password_file"), (sync, "api_key_file")):
+            require_regular_secret(map_path(client, service[key]).source)
+        run_client_check(args.client_container, args.container_config, "--check-config")
+        run_service_check(args.client_container, args.container_config)
+    except (CheckFailure, KeyError, OSError) as exc:
+        print(f"preflight failed: {exc}", file=sys.stderr)
+        return 1
+    print("preflight passed: bind mappings, hard-link staging, secrets, filesystem capabilities, and local APIs are healthy")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())

src/archive_clients/bencode.py

@@ -168,7 +168,7 @@ def _v1_files(info: dict[bytes, Any]) -> list[MetaFile]:
         components = [name] + [_component(part) for part in raw_path]
         result.append(MetaFile(
             "/".join(components), _length(item.get(b"length")),
-            _padding(item),
+            _padding(item) or _bitcomet_padding_name(components[-1]),
         ))
     return result
 
@@ -223,3 +223,13 @@ def _length(value: Any) -> int:
 def _padding(value: dict[bytes, Any]) -> bool:
     attributes = value.get(b"attr", b"")
     return isinstance(attributes, bytes) and b"p" in attributes
+
+
+def _bitcomet_padding_name(component: str) -> bool:
+    """Recognize BitComet's legacy padding-file convention.
+
+    Such v1 torrents often omit the standard ``attr=p`` flag, but
+    qBittorrent/libtorrent still hides these synthetic entries from its file
+    API.  The exact reserved prefix is the interoperable marker.
+    """
+    return component.startswith("_____padding_file_")

src/archive_clients/daemon.py

@@ -11,6 +11,7 @@ from pathlib import Path, PurePosixPath
 from typing import Any
 
 from websockets.asyncio.client import connect
+from websockets.exceptions import ConnectionClosedOK
 
 from archive_clients.backup import SQLiteBackupManager
 from archive_clients.config import ClientConfig
@@ -42,6 +43,19 @@ from archive_control.v1 import (
 logger = logging.getLogger(__name__)
 
 
+def _job_id_for_command(command: control_pb2.Command) -> str:
+    """Return the durable job key for commands whose execution is serialized."""
+
+    payload = command.WhichOneof("payload")
+    if payload == "assign_job":
+        return command.assign_job.job.job_id
+    if payload == "execute_step":
+        return command.execute_step.job_id
+    if payload == "cancel_job":
+        return command.cancel_job.job_id
+    raise ValueError(f"command {command.command_id} does not execute a job")
+
+
 class ArchiveClientDaemon:
     def __init__(
         self,
@@ -94,7 +108,10 @@ class ArchiveClientDaemon:
         self._lease = DatabaseLease(config.state_db)
         self._active_route_commands: set[str] = set()
         self._active_job_commands: set[str] = set()
-        self._job_execution_lock = asyncio.Lock()
+        # Commands for one job remain ordered locally, while unrelated jobs
+        # may use the node's available qB/Syncthing/filesystem capacity in
+        # parallel. The control daemon owns admission policy.
+        self._job_execution_locks: dict[str, asyncio.Lock] = {}
         self.jobs = (
             ClientJobExecutor(
                 client_id=config.client_id,
@@ -205,7 +222,23 @@ class ArchiveClientDaemon:
             command_tasks: set[asyncio.Task[None]] = set()
             try:
                 await self._resume_commands(outbound, command_tasks)
-                async for frame in websocket:
+                # A proxy can leave the TCP/WebSocket socket apparently open
+                # after the control server has discarded its session.  The
+                # server then cannot deliver durable commands and its pending
+                # outbox remains stranded unless the client independently
+                # detects the missing application heartbeats and reconnects.
+                while True:
+                    try:
+                        frame = await asyncio.wait_for(
+                            websocket.recv(),
+                            self.config.connection.offline_timeout,
+                        )
+                    except ConnectionClosedOK:
+                        return
+                    except asyncio.TimeoutError as exc:
+                        raise RuntimeError(
+                            "control heartbeat timed out"
+                        ) from exc
                     await self._handle(decode(frame), outbound, command_tasks)
             finally:
                 writer.cancel()
@@ -543,7 +576,9 @@ class ArchiveClientDaemon:
         correlation_id: str,
         outbound: asyncio.Queue[str],
     ) -> None:
-        async with self._job_execution_lock:
+        job_id = _job_id_for_command(command)
+        lock = self._job_execution_locks.setdefault(job_id, asyncio.Lock())
+        async with lock:
             await self._execute_job_command_locked(
                 command, correlation_id, outbound
             )
@@ -662,7 +697,22 @@ class ArchiveClientDaemon:
                 decode_message(str(row["update_json"]), control_pb2.RouteUpdate())
             )
             await outbound.put(encode(response))
-        if attempt["state"] in {"ready", "failed"}:
+        if attempt["state"] == "ready":
+            # Route readiness is durable, but this process-local lookup is
+            # not. Reconfigure (which validates the existing Syncthing folder
+            # and recreates its local directory if necessary) before replaying
+            # the stored READY updates. This is essential after a daemon or
+            # mount restart: a previously ready route may otherwise point at a
+            # path that is no longer present, and a later source-stage command
+            # would fail with a bare ENOENT.
+            configured = await asyncio.to_thread(
+                self.routes.configure,
+                spec,
+                time.monotonic() + spec.setup_timeout_seconds,
+            )
+            self._known_route_paths[spec.route_id] = configured.local_path
+            return
+        if attempt["state"] == "failed":
             return
 
         deadline = time.monotonic() + spec.setup_timeout_seconds

src/archive_clients/jobs.py

@@ -86,6 +86,8 @@ class ClientJobExecutor:
         self.verification_timeout = verification_timeout
         self.free_space_reserve_bytes = free_space_reserve_bytes
         self._cancel_events: dict[str, threading.Event] = {}
+        self._execution_locks: dict[str, threading.Lock] = {}
+        self._execution_locks_guard = threading.Lock()
 
     def request_cancel(self, job_id: str) -> None:
         self._cancel_events.setdefault(job_id, threading.Event()).set()
@@ -115,6 +117,22 @@ class ClientJobExecutor:
         self,
         command: control_pb2.ExecuteStepCommand,
         event_callback: Callable[[control_pb2.JobEvent], None] | None = None,
+    ) -> list[control_pb2.JobEvent]:
+        # asyncio cancellation of a connection-bound task cannot stop the
+        # synchronous filesystem/qB operation already running in its worker
+        # thread. A replay after reconnect therefore waits for that operation
+        # and then reads its durable event journal instead of executing twice.
+        with self._execution_lock(command.job_id):
+            return self._execute_locked(command, event_callback)
+
+    def _execution_lock(self, job_id: str) -> threading.Lock:
+        with self._execution_locks_guard:
+            return self._execution_locks.setdefault(job_id, threading.Lock())
+
+    def _execute_locked(
+        self,
+        command: control_pb2.ExecuteStepCommand,
+        event_callback: Callable[[control_pb2.JobEvent], None] | None = None,
     ) -> list[control_pb2.JobEvent]:
         definition = self._definition(command.job_id)
         replay = self._replay(
@@ -653,6 +671,15 @@ class ClientJobExecutor:
                 # Syncthing can expose the per-job directory before the
                 # ready marker and manifest have arrived atomically as a set.
                 pass
+            except RouteSetupError as exc:
+                # A network interruption can temporarily make the local
+                # Syncthing REST API unavailable.  The staged payload is
+                # durable and the job must remain recoverable; keep polling
+                # instead of turning a transient outage into a failed job.
+                logger.warning("syncthing_status_deferred", extra={
+                    "job_id": definition.job_id,
+                    "error_type": type(exc).__name__,
+                })
             time.sleep(self.poll_interval)
 
     def _target_materialize(

src/archive_clients/qbittorrent.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import json
+import logging
 import threading
 import time
 import uuid
@@ -16,6 +17,8 @@ from urllib import error, parse, request
 from archive_clients.config import ServiceConfig
 from archive_clients.resources import NormalizedResource, normalize_resource
 
+logger = logging.getLogger(__name__)
+
 
 class QBittorrentError(RuntimeError):
     pass
@@ -72,7 +75,17 @@ class QBittorrentReader:
             torrent_hash = torrent.get("hash")
             if not isinstance(torrent_hash, str):
                 raise QBittorrentError("qBittorrent torrent hash is invalid")
-            result.append(self._normalize(torrent, torrent_hash))
+            try:
+                result.append(self._normalize(torrent, torrent_hash))
+            except ValueError as exc:
+                # A stale or malformed qBittorrent entry must not hide every
+                # otherwise valid resource from Archive/Evict inventory.
+                # Keep it ineligible and leave an operator-visible diagnosis.
+                logger.warning(
+                    "Skipping qBittorrent resource with inconsistent "
+                    "metadata: hash=%s name=%r reason=%s",
+                    torrent_hash, torrent.get("name"), exc,
+                )
         return result
 
     def get_resource(self, torrent_hash: str) -> NormalizedResource | None:

src/archive_clients/resources.py

@@ -91,12 +91,21 @@ def normalize_resource(
     observed_at: datetime | None = None,
 ) -> NormalizedResource:
     metainfo = decode_metainfo(metainfo_bytes)
-    if len(raw_files) != len(metainfo.files):
+    # qBittorrent/libtorrent may omit torrent padding files from
+    # /torrents/files while keeping them in the exported metainfo.
+    visible_metainfo_files = tuple(
+        item for item in metainfo.files if not item.padding
+    )
+    if len(raw_files) == len(metainfo.files):
+        matched_metainfo_files = metainfo.files
+    elif len(raw_files) == len(visible_metainfo_files):
+        matched_metainfo_files = visible_metainfo_files
+    else:
         raise ResourceError("qBittorrent and metainfo file counts differ")
     files = []
     canonical = True
     for expected_index, (raw, meta_file) in enumerate(
-        zip(raw_files, metainfo.files, strict=True)
+        zip(raw_files, matched_metainfo_files, strict=True)
     ):
         index = _integer(raw.get("index"), "file index")
         if index != expected_index:

src/archive_clients/state.py

@@ -7,6 +7,8 @@ import json
 import os
 import sqlite3
 import stat
+import threading
+from contextlib import contextmanager
 from dataclasses import dataclass
 from pathlib import Path
 
@@ -14,6 +16,12 @@ from pathlib import Path
 SCHEMA_VERSION = 3
 
 
+# A client daemon executes unrelated jobs concurrently.  SQLite still permits
+# only one writer, so serialize this process's short state transactions rather
+# than allowing an otherwise healthy job to fail after its busy timeout.
+_DATABASE_LOCK = threading.RLock()
+
+
 class CommandConflict(RuntimeError):
     pass
 
@@ -557,14 +565,30 @@ class ClientStore:
             ).fetchall()
         return [dict(row) for row in rows]
 
-    def _connect(self) -> sqlite3.Connection:
-        connection = sqlite3.connect(self.database, isolation_level=None, timeout=5)
-        connection.row_factory = sqlite3.Row
-        connection.execute("PRAGMA foreign_keys = ON")
-        connection.execute("PRAGMA journal_mode = WAL")
-        connection.execute("PRAGMA synchronous = FULL")
-        connection.execute("PRAGMA busy_timeout = 5000")
-        return connection
+    @contextmanager
+    def _connect(self):
+        """Yield one connection while serializing local SQLite writers.
+
+        The longer SQLite timeout also covers a short lock held by a separate
+        maintenance process such as a backup.  The lock is deliberately held
+        for the full transaction, including ``BEGIN IMMEDIATE``.
+        """
+        with _DATABASE_LOCK:
+            connection = sqlite3.connect(
+                self.database, isolation_level=None, timeout=30
+            )
+            try:
+                connection.row_factory = sqlite3.Row
+                connection.execute("PRAGMA foreign_keys = ON")
+                connection.execute("PRAGMA journal_mode = WAL")
+                connection.execute("PRAGMA synchronous = FULL")
+                connection.execute("PRAGMA busy_timeout = 30000")
+                # Preserve the original ``with connection`` commit/rollback
+                # behavior used by every store operation.
+                with connection:
+                    yield connection
+            finally:
+                connection.close()
 
 
 def _canonical(value: object) -> str:

src/archive_clients/syncthing.py

@@ -192,11 +192,19 @@ class SyncthingTransferObserver:
                 for relative_path, expected_bytes in declared_files
             )
             observed_fraction = observed_bytes / total if total else 1.0
-            # Folder completion remains useful when Syncthing has already
-            # atomically published a file but still reports it in its need
-            # queue; the allocated-byte estimate is needed for sparse temp
-            # files that are pre-sized before their blocks arrive.
-            fraction = min(observed_fraction, float(raw_fraction) / 100)
+            # ``/db/completion`` is folder-wide.  It can be near zero when a
+            # route contains a freshly-created item even though the tracked
+            # job's temporary payload has already received many blocks.  For
+            # an incomplete temporary file, its allocated blocks are the only
+            # job-specific signal, so do not cap them with that unrelated
+            # folder aggregate.  Once every declared file is atomically
+            # present, retain the completion value as a conservative guard
+            # until the need queue has caught up.
+            fraction = (
+                observed_fraction
+                if observed_fraction < 1.0
+                else min(1.0, float(raw_fraction) / 100)
+            )
             completed_bytes = int(total * fraction)
         if complete:
             fraction = 1.0

tests/test_daemon.py

@@ -22,6 +22,94 @@ from archive_control.v1 import (
 
 
 class DaemonTransportTests(unittest.IsolatedAsyncioTestCase):
+    async def test_unrelated_job_commands_execute_concurrently(self):
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            token = root / "token"
+            token.write_text("shared-secret", encoding="utf-8")
+            os.chmod(token, 0o600)
+            service = ServiceConfig("http://local", PurePosixPath("/api"), root)
+            config = ClientConfig(
+                "cache-1", "Cache 1", "cache", "ws://control", token,
+                root / "state.db", root / "backups", service, service,
+            )
+            probe = FilesystemProbe(root, True, True, True, True, True)
+            daemon = ArchiveClientDaemon(config, [probe, probe], [])
+            started: set[str] = set()
+            release = asyncio.Event()
+
+            async def execute(command, correlation_id, outbound):
+                started.add(command.assign_job.job.job_id)
+                await release.wait()
+
+            daemon._execute_job_command_locked = execute
+            commands = []
+            for _ in range(2):
+                command = control_pb2.Command(command_id=str(uuid4()))
+                command.assign_job.job.job_id = str(uuid4())
+                commands.append(command)
+            outbound = asyncio.Queue()
+            tasks = [
+                asyncio.create_task(
+                    daemon._execute_job_command(command, "", outbound)
+                )
+                for command in commands
+            ]
+            for _ in range(100):
+                if len(started) == 2:
+                    break
+                await asyncio.sleep(0.01)
+            self.assertEqual(len(started), 2)
+            release.set()
+            await asyncio.gather(*tasks)
+
+    async def test_silent_control_connection_ends_for_reconnect(self):
+        """A lost server heartbeat must not leave durable commands stranded."""
+
+        async def control(websocket):
+            registration = decode(await websocket.recv())
+            self.assertEqual(registration.WhichOneof("payload"), "register_request")
+            response = new_envelope()
+            response.correlation_id = registration.message_id
+            response.register_response.status = (
+                client_pb2.REGISTRATION_STATUS_ACCEPTED
+            )
+            response.register_response.negotiated_version.major = 1
+            await websocket.send(encode(response))
+            # Deliberately keep TCP/WebSocket open but send no application
+            # heartbeats. This models a stale proxy/server-side session.
+            await websocket.wait_closed()
+
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            token = root / "token"
+            token.write_text("shared-secret", encoding="utf-8")
+            os.chmod(token, 0o600)
+            async with serve(control, "127.0.0.1", 0, ping_interval=None) as server:
+                port = server.sockets[0].getsockname()[1]
+                service = ServiceConfig(
+                    "http://local", PurePosixPath("/api"), root,
+                )
+                config = ClientConfig(
+                    "cache-1", "Cache 1", "cache",
+                    f"ws://127.0.0.1:{port}", token,
+                    root / "state.db", root / "backups", service, service,
+                    ConnectionConfig(
+                        registration_timeout=1,
+                        offline_timeout=0.05,
+                        reconnect_initial=0.01,
+                        reconnect_max=0.01,
+                        reconnect_jitter=False,
+                    ),
+                )
+                probe = FilesystemProbe(root, True, True, True, True, True)
+                daemon = ArchiveClientDaemon(config, [probe, probe], [])
+                await asyncio.to_thread(daemon.store.initialize)
+                with self.assertRaisesRegex(
+                    RuntimeError, "control heartbeat timed out"
+                ):
+                    await asyncio.wait_for(daemon._connection(), 1)
+
     async def test_eviction_assignment_and_steps_are_admitted(self):
         with tempfile.TemporaryDirectory() as directory:
             root = Path(directory)
@@ -192,6 +280,10 @@ class DaemonTransportTests(unittest.IsolatedAsyncioTestCase):
                 for _ in range(3)
             ]
             self.assertEqual([item.sequence for item in resumed], [1, 2, 3])
+            self.assertEqual(manager.configure.call_count, 2)
+            self.assertEqual(
+                restarted._route_path("route-1"), root / "routes/route-1"
+            )
 
     async def test_slow_inventory_does_not_block_heartbeat(self):
         with tempfile.TemporaryDirectory() as directory:

tests/test_deployment_preflight.py

@@ -0,0 +1,83 @@
+import importlib.util
+import sys
+import unittest
+from unittest import mock
+from pathlib import Path
+
+
+_SCRIPT = Path(__file__).parents[1] / "scripts" / "preflight-deployment.py"
+_SPEC = importlib.util.spec_from_file_location("deployment_preflight", _SCRIPT)
+assert _SPEC is not None and _SPEC.loader is not None
+preflight = importlib.util.module_from_spec(_SPEC)
+sys.modules[_SPEC.name] = preflight
+_SPEC.loader.exec_module(preflight)
+
+
+class DeploymentPreflightTests(unittest.TestCase):
+    def test_maps_nested_container_path_to_host_source(self):
+        container = {
+            "Mounts": [
+                {"Type": "bind", "Source": "/srv/data", "Destination": "/data"},
+                {"Type": "bind", "Source": "/srv/sync", "Destination": "/data/Sync"},
+            ]
+        }
+        mapping = preflight.map_path(container, "/data/Sync/routes/route-1")
+        self.assertEqual(mapping.source, Path("/srv/sync/routes/route-1"))
+        self.assertEqual(str(mapping.destination), "/data/Sync")
+
+    def test_rejects_api_and_client_roots_from_different_host_paths(self):
+        with self.assertRaisesRegex(preflight.CheckFailure, "host paths differ"):
+            preflight.require_same_path(
+                "Syncthing api_root/local_root",
+                preflight.Mapping(Path("/srv/syncthing-config/routes"), Path("/var/syncthing")),
+                preflight.Mapping(Path("/srv/sync/routes"), Path("/data/storage")),
+            )
+
+    def test_rejects_unmounted_container_path(self):
+        with self.assertRaisesRegex(preflight.CheckFailure, "not backed"):
+            preflight.map_path({"Mounts": []}, "/missing")
+
+    def test_maps_future_route_through_syncthing_override(self):
+        config = {
+            "api_root": "/var/syncthing",
+            "local_root": "/data/sync",
+            "local_path_overrides": {
+                "/var/syncthing/routes": "/data/qb/.archive-control-routes",
+            },
+        }
+        self.assertEqual(
+            preflight.route_local_path(config),
+            "/data/qb/.archive-control-routes",
+        )
+
+    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=""
+        )
+        with mock.patch.object(preflight.subprocess, "run", return_value=completed) as run:
+            preflight.run_hardlink_probe(
+                "client", "/data/qb", "/data/qb/routes", "1001:1001"
+            )
+        args = run.call_args.args[0]
+        self.assertEqual(args[:6], ["docker", "exec", "--user", "1001:1001", "client", "python"])
+        self.assertEqual(args[-2:], ["/data/qb", "/data/qb/routes"])
+
+    def test_hardlink_probe_failure_is_actionable(self):
+        completed = __import__("subprocess").CompletedProcess(
+            args=[], returncode=1, stdout="", stderr="[Errno 18] Invalid cross-device link"
+        )
+        with mock.patch.object(preflight.subprocess, "run", return_value=completed):
+            with self.assertRaisesRegex(preflight.CheckFailure, "hard-link staging probe failed"):
+                preflight.run_hardlink_probe("client", "/data/qb", "/data/qb/routes")
+
+    def test_existing_route_directory_failure_is_actionable(self):
+        completed = __import__("subprocess").CompletedProcess(
+            args=[], returncode=1, stdout='{"missing":[{"folder_id":"route-1"}]}', stderr=""
+        )
+        with mock.patch.object(preflight.subprocess, "run", return_value=completed):
+            with self.assertRaisesRegex(preflight.CheckFailure, "route directory is missing"):
+                preflight.run_existing_route_directory_check("client", "/config.toml")
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/test_jobs.py

@@ -1,5 +1,6 @@
 import hashlib
 import tempfile
+import threading
 import unittest
 from pathlib import Path
 from unittest.mock import Mock, patch
@@ -11,7 +12,7 @@ from archive_clients.jobs import (
     JobExecutionError,
     _resource_fingerprint,
 )
-from archive_clients.syncthing import RouteSetupError
+from archive_clients.syncthing import RouteSetupError, SyncthingTransferStatus
 from archive_clients.resources import normalize_resource
 from archive_clients.state import ClientStore
 from archive_control.v1 import control_pb2, job_pb2
@@ -38,6 +39,120 @@ class SlowRescanSyncthing(CompleteSyncthing):
 
 
 class ClientJobHappyPathTests(unittest.TestCase):
+    def test_syncthing_api_outage_during_transfer_is_retried(self):
+        """A transient local REST outage must not terminally fail the job."""
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            store = ClientStore(root / "client.db")
+            store.initialize()
+            definition = job_pb2.JobDefinition(
+                job_id=str(uuid4()),
+                transfer={
+                    "source_client_id": "cache-1",
+                    "target_client_id": "archive-1",
+                    "route_id": "route-1",
+                },
+            )
+            observer = Mock()
+            observer.status.side_effect = [
+                RouteSetupError("Syncthing API is unavailable"),
+                SyncthingTransferStatus(1, 42, 42, True, 0),
+            ]
+            executor = ClientJobExecutor(
+                client_id="archive-1",
+                qbittorrent=Mock(),
+                store=store,
+                qb_root=root,
+                qb_api_root=Path("/downloads"),
+                route_path=lambda _: root,
+                syncthing_transport=Mock(),
+                sparse_supported=True,
+                poll_interval=0,
+            )
+            executor._observer = Mock(return_value=observer)
+            progress = Mock()
+
+            executor._wait_for_syncthing(definition, progress)
+
+            self.assertEqual(observer.status.call_count, 2)
+            progress.assert_called_once_with(1, 42, 42, "0 Syncthing items still needed")
+
+    def test_reconnect_replay_never_duplicates_any_transfer_step(self):
+        for step in (
+            job_pb2.JOB_STEP_KIND_SOURCE_STAGE,
+            job_pb2.JOB_STEP_KIND_SYNCTHING_TRANSFER,
+            job_pb2.JOB_STEP_KIND_TARGET_MATERIALIZE,
+            job_pb2.JOB_STEP_KIND_QB_VERIFY,
+            job_pb2.JOB_STEP_KIND_STAGING_CLEANUP,
+        ):
+            with self.subTest(step=step), tempfile.TemporaryDirectory() as directory:
+                root = Path(directory)
+                store = ClientStore(root / "client.db")
+                store.initialize()
+                definition = job_pb2.JobDefinition(
+                    job_id=str(uuid4()),
+                    idempotency_key=str(uuid4()),
+                    operation=job_pb2.JOB_OPERATION_ARCHIVE,
+                    resource_display_name="reconnect fixture",
+                    transfer={
+                        "source_client_id": "cache-1",
+                        "target_client_id": "archive-1",
+                        "route_id": "route-1",
+                    },
+                )
+                definition.resource_id.info_hash_v1_hex = "a" * 40
+                definition.created_at.GetCurrentTime()
+                executor = ClientJobExecutor(
+                    client_id="cache-1",
+                    qbittorrent=Mock(),
+                    store=store,
+                    qb_root=root,
+                    qb_api_root=Path("/downloads"),
+                    route_path=lambda _: root,
+                    syncthing_transport=Mock(),
+                    sparse_supported=True,
+                )
+                executor.assign(control_pb2.AssignJobCommand(
+                    job=definition,
+                    expected_job_revision=1,
+                    expected_last_event_sequence=0,
+                ))
+                entered = threading.Event()
+                release = threading.Event()
+
+                def execute_step(*_args):
+                    entered.set()
+                    release.wait(1)
+                    return None
+
+                executor._execute_step = Mock(side_effect=execute_step)
+                command = control_pb2.ExecuteStepCommand(
+                    job_id=definition.job_id,
+                    expected_job_revision=1,
+                    expected_last_event_sequence=1,
+                    step=step,
+                    attempt=1,
+                )
+                results: list[list[control_pb2.JobEvent]] = []
+                first = threading.Thread(
+                    target=lambda: results.append(executor.execute(command))
+                )
+                second = threading.Thread(
+                    target=lambda: results.append(executor.execute(command))
+                )
+                first.start()
+                self.assertTrue(entered.wait(1))
+                second.start()
+                release.set()
+                first.join(1)
+                second.join(1)
+
+                self.assertFalse(first.is_alive())
+                self.assertFalse(second.is_alive())
+                self.assertEqual(executor._execute_step.call_count, 1)
+                self.assertEqual(len(results), 2)
+                self.assertEqual(results[0][-1].event_id, results[1][-1].event_id)
+
     def test_capacity_guard_fails_before_data_movement(self):
         with tempfile.TemporaryDirectory() as directory:
             root = Path(directory)

tests/test_qbittorrent.py

@@ -205,6 +205,54 @@ class QBittorrentReaderTests(unittest.TestCase):
         self.assertEqual(resources, [])
         self.assertEqual(len(opener.calls), 2)
 
+    def test_listing_skips_malformed_torrent_and_keeps_valid_resources(self):
+        def torrent(name, content):
+            info = {
+                b"length": len(content), b"name": name.encode(),
+                b"piece length": 16384, b"pieces": b"x" * 20,
+            }
+            return encode({b"info": info}), hashlib.sha1(encode(info)).hexdigest()
+
+        first_bytes, first_hash = torrent("first.txt", b"one")
+        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"},
+        ]
+        responses = [
+            b"Ok.", json.dumps(torrents).encode(),
+            b'[{"index":0,"name":"first.txt","size":3,"progress":1,"priority":1}]',
+            first_bytes,
+            b'[{"index":0,"name":"broken.txt","size":3,"progress":1,"priority":1},'
+            b'{"index":1,"name":"unexpected.txt","size":1,"progress":1,"priority":1}]',
+            malformed_bytes,
+            b'[{"index":0,"name":"second.txt","size":3,"progress":1,"priority":1}]',
+            second_bytes,
+        ]
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            password = root / "password"
+            password.write_text("secret", encoding="utf-8")
+            os.chmod(password, 0o600)
+            config = ServiceConfig(
+                "http://qb", PurePosixPath("/downloads"), root,
+                username="admin", password_file=password,
+            )
+            opener = _Opener(responses)
+            with patch(
+                "archive_clients.qbittorrent.request.build_opener",
+                return_value=opener,
+            ), self.assertLogs("archive_clients.qbittorrent", "WARNING") as logs:
+                resources = QBittorrentReader(config).list_resources()
+
+        self.assertEqual(
+            [resource.summary.display_name for resource in resources],
+            ["first.txt", "second.txt"],
+        )
+        self.assertIn(malformed_hash, "\n".join(logs.output))
+
     def test_stopped_add_selection_recheck_and_entry_only_delete(self):
         torrent_hash = "a" * 40
         responses = [

tests/test_resources.py

@@ -118,6 +118,47 @@ class ResourceTests(unittest.TestCase):
         self.assertEqual(root.available_file_count, 1)
         self.assertEqual(root.available_logical_bytes, 3)
 
+    def test_qbittorrent_hidden_padding_files_are_normalized(self):
+        info = {
+            b"files": [
+                {b"length": 3, b"path": [b"first.bin"]},
+                {
+                    b"length": 5,
+                    b"path": [b"_____padding_file_5"],
+                },
+                {b"length": 7, b"path": [b"last.bin"]},
+            ],
+            b"name": b"with-padding",
+            b"piece length": 16384,
+            b"pieces": b"x" * 20,
+        }
+        metainfo = encode({b"info": info})
+        torrent_hash = hashlib.sha1(encode(info)).hexdigest()
+        normalized = normalize_resource(
+            {
+                "hash": torrent_hash,
+                "name": "with-padding",
+                "state": "stalledUP",
+            },
+            [
+                {
+                    "index": 0, "name": "with-padding/first.bin",
+                    "size": 3, "completed": 3, "priority": 1,
+                },
+                {
+                    "index": 1, "name": "with-padding/last.bin",
+                    "size": 7, "completed": 7, "priority": 1,
+                },
+            ],
+            metainfo,
+        )
+        self.assertEqual(
+            [item.canonical_path for item in normalized.files],
+            ["with-padding/first.bin", "with-padding/last.bin"],
+        )
+        self.assertEqual(normalized.summary.total_file_count, 2)
+        self.assertEqual(normalized.summary.selected_complete_bytes, 10)
+
     def test_noncanonical_and_unsafe_paths_are_distinct(self):
         info = {
             b"length": 3,

tests/test_state.py

@@ -1,6 +1,7 @@
 import tempfile
 import unittest
 import os
+import threading
 from pathlib import Path
 from uuid import uuid4
 
@@ -13,6 +14,40 @@ from archive_clients.state import (
 
 
 class ClientStoreTests(unittest.TestCase):
+    def test_database_connections_serialize_local_writers(self):
+        """Concurrent jobs share one daemon DB without SQLite lock failures."""
+        with tempfile.TemporaryDirectory() as directory:
+            database = Path(directory) / "state.db"
+            first = ClientStore(database)
+            second = ClientStore(database)
+            first.initialize()
+            barrier = threading.Barrier(2)
+            failures: list[Exception] = []
+
+            def write(store, command_id):
+                try:
+                    barrier.wait()
+                    store.accept_command(command_id, '{"kind":"job"}', '{"ok":true}')
+                except Exception as exc:  # pragma: no cover - assertion below
+                    failures.append(exc)
+
+            left = threading.Thread(target=write, args=(first, "command-1"))
+            right = threading.Thread(target=write, args=(second, "command-2"))
+            left.start()
+            right.start()
+            left.join(1)
+            right.join(1)
+
+            self.assertFalse(left.is_alive())
+            self.assertFalse(right.is_alive())
+            self.assertEqual(failures, [])
+            self.assertEqual(len(first.list_accepted_commands()), 2)
+            with first._connect() as connection:
+                self.assertEqual(
+                    connection.execute("PRAGMA busy_timeout").fetchone()[0],
+                    30000,
+                )
+
     def test_command_acceptance_is_durable_and_content_addressed(self):
         with tempfile.TemporaryDirectory() as directory:
             database = Path(directory) / "state.db"