TEST ONLY: sqlalchemy<2.1 (No module named psycopg with sientia_do 1.12.2) - dev test, do not merge

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CLAUDE.md

@@ -60,7 +60,7 @@ Any change to slot/lease counts should be traced through `manage_leases`/`manage
 
 **ServerReader** (SIENTIAPDE-1974, default `READ_ENGINE=v2`; the legacy `OpcManager` stays as plan B with `READ_ENGINE=legacy` — slot v1 only, certificate files from the Gitea clone — until it is unused and the tests pass the same without it) reads one OPC server through a `SubscriptionEngine`: the connection comes from the shared `OpcConnectionPool` (also used by NATS writes and gRPC), which fetches the platform certificate from MinIO via `CertProvider` and uses `SecurityPolicyBasic256Sha256` — no certificate files in the repo/image. Slots are parsed by `io/slots.py` (`parse_slot`), which accepts slot v2 (`names[]`) and converts the legacy v1 (`topics`). `datachange_notification` fans each value out to every `names` entry via `DataSink`. Subscribed connections are pinned in the pool so the idle sweep never drops them. Tracks `non_receive_count` to detect silently-dead subscriptions (`check_cycles` / `check_opc_listenning`); a lost server is shut down (pool connection evicted) and re-initialized on the next loop.
 
-**Writes** (SIENTIAPDE-1975): `NatsWriteConsumer` → `WriteEngine` → pool, then `DataSink.update_write_status`. Commands (C2) carry only `server_id`; `ServerConfigResolver` (`connection/servers.py`) resolves the connection (command override → live pooled connection → `connectors` → `opc-servers`). `write_status` keeps the worst outcome (`ok` < `error` < `session_bad`; same rule as the Laborious' `laborious/utils/write_status.py` — keep both in sync). The NATS first connect is bounded (it runs on the main loop); reconnection after it is unbounded.
+**Writes** (SIENTIAPDE-1975): `NatsWriteConsumer` → `WriteEngine` → pool, then `DataSink.update_write_status`. Commands (C2) carry only `server_id`; `ServerConfigResolver` (`connection/servers.py`) resolves the connection (command override → live pooled connection → `connectors` → `opc-servers`). `write_status` keeps the worst outcome (`ok` < `error` < `session_bad`); the gateway is the only one that updates it (the Laborious inserts the row as `pending` and never records OPC outcomes). The NATS first connect is bounded (it runs on the main loop); reconnection after it is unbounded.
 
 **Metrics** (`ingestor/metrics.py`): all Prometheus metrics defined here, always labeled by `pod_id`. Emitted via `SientiaMonitoring.emit_metric(...)` (from `sientia_do`), not the prometheus client directly — new metrics should follow that pattern for consistency with logging/notifications.
 

README.md

@@ -91,8 +91,9 @@ The Laborious publishes one command per tag (SIENTIAPDE-1975):
   Lookups are cached for 60 s. An unknown server is a failed write (`server_not_found`).
 - **Outcome**: `UPDATE ... SET write_status` on the prediction row (by `timestamp` +
   `model_id`), keeping the worst outcome: `ok` < `error` < `session_bad`, and
-  `pending`/NULL are replaced by any answer. The Laborious applies the same rule to
-  the outcomes it records itself, so the order of the answers does not matter.
+  `pending`/NULL are replaced by any answer, so the order of the answers does not
+  matter. The gateway is the only one that updates the column: the Laborious inserts the
+  row as `pending` (merged with its PI Web API outcome) and never records OPC outcomes.
   The UPDATE never raises; its outcome (`updated`, `kept`, `row_not_found`,
   `invalid`, `error`) is logged and counted in `opc_write_status_update_total`.
   The reason of a failed write is logged by `WriteEngine`.

ingestor/io/data_sink.py

@@ -10,8 +10,8 @@ import ingestor.metrics as metrics
 _IDENTIFIER_RE = re.compile(r'\w+', re.ASCII)
 
 # Worst-wins precedence of predictions.write_status (SIENTIAPDE-1975), from best to worst;
-# NULL, 'pending' and unknown values rank 0. Same rule as the Laborious
-# (laborious/utils/write_status.py): keep both in sync.
+# NULL, 'pending' and unknown values rank 0. The gateway is the only writer that updates the
+# column: the Laborious only sets the value of the rows it inserts ('pending', PI outcome).
 STATUS_RANK = {'ok': 1, 'error': 2, 'session_bad': 3}
 
 
@@ -78,8 +78,9 @@ class DataSink:
         The row is found by timestamp + model_id. A prediction is written to several
         tags, each answered by its own command, so a better outcome never replaces a
         worse one: ``ok`` < ``error`` < ``session_bad``, and ``pending``/NULL are
-        replaced by any answer. The Laborious runs the same statement for the outcomes it
-        records itself (SIENTIAPDE-1975), so the order of the answers does not matter.
+        replaced by any answer, so the order of the answers does not matter. Only the
+        gateway updates the column (SIENTIAPDE-1975): the Laborious publishes the commands
+        and sets ``pending`` (merged with its PI Web API outcome) on the row it inserts.
 
         Never raises: a failure here must not reach the NATS callback nor hide the OPC
         write itself, which already happened. The outcome is logged and counted instead.

requirements.txt

@@ -4,6 +4,9 @@ redis
 # (generic Mongo find_one/distinct/aggregate methods) — not in 1.12.2 yet.
 # Local dev uses an editable install of the local checkout (feature/SIENTIAPDE-1590).
 sientia_do==1.12.2
+# TEST ONLY (SIENTIAPDE-1975 dev test): SQLAlchemy 2.1 makes psycopg (v3) the default driver for
+# postgresql:// URLs; sientia_do 1.12.2 builds that URL and ships only psycopg2-binary.
+sqlalchemy<2.1
 prometheus_client
 pymongo
 nats-py>=2.6