WRPS Plant Operations Assistant

A proof-of-concept assistant that lets an operator at the Waterloo Road Pump Station ask a question in plain English and get an answer grounded in plant data and controlled documents.

Example question	Class
"How many times did the wet well high level alarm come up last week?"	Historical
"What does the level signal fault alarm on the wet well mean?"	Reference
"How do I lift the interlock on Pump 02?"	Procedural
"What discharge rate should we run to avoid spilling?"	Advisory

Those four need different retrieval paths, different answer contracts and different safety rules. One generic pipeline covering all four is the main way this project fails.

Success is a correct, citable, appropriately-scoped answer. Fluency is not success.

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Read this before writing any code

This is an information retrieval and analysis assistant. It is not a control system, not an advisory controller, and not a substitute for a competent person.

It does not issue instructions for safety-critical actions. For "how do I lift the interlock on Pump 02" it locates and cites the controlled procedure. An interlock exists because somebody assessed a hazard; a bypass procedure reassembled from retrieved fragments is a safety document nobody approved.

It does not recommend setpoints or operating parameters. For "what discharge rate" it gives evidence — rates used, outcomes, when alarms occurred, documented capacity — and then defers. A number presented as an answer gets typed into a control system by someone who trusts it.

It does not answer outside its evidence. Zero rows means "no records found", never an invented figure.

These are code paths, not prompt instructions: api/contracts.py holds one Pydantic contract per class, validated after generation and before returning. A response that fails its contract is regenerated once, then errors. It is never returned. pytest api/tests exercises every rule above without an API key or a database, because that is the point of putting them in Python.

Full detail: BUILD-AI-CONTAINERS.md §2.

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The plant

Waterloo Road Pump Station is a three-pump wastewater station.

• Wet well WW-101, 0–7000 mm, 120 m³ per metre of level
• Pumps PU-301/302/303, duty/assist/assist, ~120 L/s each against 22 m static lift, on a common VSD speed reference clamped 38–50 Hz
• Spill weir crest at 6000 mm, LSHH-102 at 5500 mm, high level alarm at 5200 mm, stop-all at 1000 mm
• Control logic runs on openplc-runtime; Yokogawa CI Server on cicore1 polls it over Modbus TCP and historises the result

The unit trap that will catch you: the PLC works in millimetres and litres per second; the historian stores percent of the weir crest (raw mm ÷ 60) and m³/h. Every conversion is recorded per tag in db/seed/tags.csv, which also records — in capitals, at the start of each description — whether a tag is historised at all. Field inputs to the PLC (%IW/%IX: vibration, thermal, discharge pressure) are not published to SCADA and have no history. An answer that trends PU-301 vibration is fabricating data.

Source of truth for the plant: WRPS/01-design-doc/, WRPS/04-plc/register-map.csv and WRPS/05-scada/modbus/scada-points.csv in the WRPS repository.

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Architecture

operator ──► Caddy ──► Authelia (AD + Duo) ──► ai-web ──► ai-api
                                                            │
                            ┌───────────────────────────────┼──────────────┐
                            ▼                               ▼              ▼
                      classifier                          Cube        pgvector
                   (CHEAP_DEPLOYMENT)                       │          (pg-ai)
                            │                               ▼
                    one branch per class              imh (SQL Server,
                            │                          read-only, TDS/1433)
                            ▼                          ── PENDING ──
                     contract validation
                            │
                            ▼
                        Langfuse

Everything runs on yau-sls-poc-lin001 (10.0.0.17), a shared, live Docker host that already runs 22 containers including openplc-runtime — the PLC for this demo. See YAU_Linux_Host_Onboarding.md.

There is no replication job and no mirror table. imh is already an isolated copy of the raw SCADA historian, so Cube queries it directly with a read-only login. pg-ai holds pgvector chunks, Cube pre-aggregations, and the equipment/tag reference data.

Container	Stack	Networks	Public URL
pg-ai	pgvector/pgvector:pg16	ai-internal only	none
cube	cubejs/cube (pinned)	ai-internal + proxy	cube.yokogawa.tech
ai-api	Python 3.12 + FastAPI	ai-internal + proxy	api.yokogawa.tech
ai-web	Vite build → nginx:alpine	proxy	ai.yokogawa.tech
ai-ingest	Python 3.12, on demand	ai-internal	none
ai-docs-worker	same image, long-running (Phase 9)	ai-internal	none
langfuse + lf-db	official images	ai-internal + proxy	lf.yokogawa.tech

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Rebuild from zero

Assumes: a checkout at ~/ai on lin001, and the Caddy + Authelia + proxy stack already running (it is — this host has served demos for months).

1. Secrets

Three 0600 env files under ~/ai/, never in Git. Every key is listed with no values in .env.example.

mkdir -p ~/ai && cd ~/ai
install -m 600 /dev/null pg-ai.env
install -m 600 /dev/null api.env
install -m 600 /dev/null langfuse.env

Follow the ~/authelia/authelia.env precedent. The Grafana admin password sitting in plain text in ~/docker-compose.yml is a known defect on this host, not a pattern to copy.

2. Phase 1 — pg-ai

./scripts/deploy.sh phase1

Creates /datadisk/pg-ai, starts pg-ai, applies the schema and roles, loads equipment.csv and tags.csv with their alias arrays, and — while USE_FIXTURES=true — loads the fixture stand-in for imh.

Three roles come out of this, and the split matters: agent_ro for the answer path (SELECT only, everywhere), cube_rw for pre-aggregations, and ingest_rw — the only role that writes doc_chunks. Set all three passwords in the 0600 env files; INGEST_DB_USER / INGEST_DB_PASSWORD are what Phase 3 connects with, and Phase 3 refuses to start without them.

Gate: pg-ai healthy, vector present, agent_ro can SELECT and cannot INSERT, ingest_rw can write doc_chunks and nothing else, every equipment item and tag has an alias, pg-ai publishes no host port and is not on the proxy network, and df -h / is unchanged. ./scripts/verify.sh checks all of it.

3. Phase 2 — Langfuse

./scripts/deploy.sh phase2

Deployed early on purpose: from here on, every experiment is traced. Then do the manual steps the script prints — DNS, Caddyfile, Authelia rule, announce the Authelia restart.

4. Phase 3 — knowledge base

Put the controlled documents on the host, in the folders that determine doc_type:

/datadisk/ai-docs/{procedures,manuals,rationalisation,design}/

docker compose -f ~/ai-compose.yml run --rm ai-ingest --all

It will ask you to confirm the document number, revision and effective date for every file. Confirm them properly. A wrong revision on a procedure is a safety issue, not a data-quality one. When a new revision lands:

docker compose -f ~/ai-compose.yml run --rm ai-ingest --supersede WRPS-OPS-014 4

That sticks. Re-ingesting a superseded document brings it back superseded, and --all skips it — the flag is not reset by replacing chunks. To undo one:

docker compose -f ~/ai-compose.yml run --rm ai-ingest --restore WRPS-OPS-014 3

This is the SSH path, and it stays. Phase 9 adds the same thing as a screen, so that an operator who is issued a new document when the PLC logic changes does not have to find someone with a host login. It does not remove the header confirmation or the supersede decision — it puts them in front of a named person and records the answer. See step 8 below.

5. Phase 4 — imh ⚠ PENDING

The only true blocker. Start the conversation now; do not wait for Phase 3. Agree the read-only login, the table names and key columns, the timestamp semantics, and an NSG rule allowing lin001 → imh on 1433 only. Then update §10 of BUILD-AI-CONTAINERS.md with the real schema and change db/002_fixtures.sql and the Cube models to match.

Until then everything runs on fixtures, and every answer carries a fixture banner all the way to the operator's screen.

Two Phase 5 findings are deferred to this phase, both found by hand-verifying the Cube measures against fixtures and both left unfixed because fixing them against fixture data means guessing at imh. The wet well level tag does not join — history is keyed PS_STN_WET_WELL_LEVEL, which tags.csv carries only as an alias of LIT-101 — so a level question can fail as "no records found", which reads exactly like a genuine absence of data. And alarms.first_alarm/last_alarm come back in UTC inside rows whose bucket labels are in site time. Full detail, and what has to be true to close them, in BUILD-AI-CONTAINERS.md Phase 4, "Deferred from Phase 5"; eval cases H26 and H27 fail until they are settled.

6. Phases 5–7 — Cube, API, UI

./scripts/deploy.sh api      # cube + ai-api
./scripts/deploy.sh web      # ai-web
./scripts/verify.sh

Each prints the manual DNS/Caddy/Authelia steps.

DNS is done as of 27 August 2026: ai, api and cube all resolve to 20.211.144.151, and the DC carries the pinpoint record ai.yokogawa.tech → 10.0.0.17 that the Azure hairpin requires. The Caddyfile blocks and Authelia rules for the three names still have to be applied on the host — until they are, the names resolve and nothing answers.

api.yokogawa.tech has no pinpoint record and does not resolve inside the VNet. That is why the Phase 7 Caddy block routes /ask under ai.yokogawa.tech to ai-api and the page is same-origin: a cross-origin build loads on a control-room PC and then fails every question on DNS. Only /ask is routed there — see the warning in caddy/ai-routes.caddy before widening it.

7. Phase 8 — validate

python eval/run_eval.py --api https://api.yokogawa.tech

62 engineer-reviewable cases in eval/testset.jsonl, every data-dependent one with a pinned time window — imh is live, and an unpinned question gives a different answer each run.

Gate: ≥85% overall, ≥95% classification accuracy on Procedural and Advisory, zero contract violations, p95 under 12 s. run_eval.py returns non-zero if any of those is missed. It also marks Historical and Advisory cases needs_review: whether "6" is the right number is a judgement for an engineer with access to imh, not something this script can decide.

8. Phase 9 — operator document upload

After Phase 8 passes, not before. When the PLC logic or the SCADA program changes, a new document is issued and the assistant is wrong about the plant until it is ingested. Today that needs SSH to a live shared host. Phase 9 puts it behind the UI:

upload  ─►  pre-scan  ─►  review  ─►  approve  ─►  published
(anyone    (worker,      (a named    (header      (chunks
 with 2FA)  Docling)      publisher)  confirmed)   citable)

Nothing is citable until a named person in AI_DocPublishers has confirmed the document number, revision and effective date, and decided what it supersedes — the same questions ingest.py asks at a terminal, asked on a screen and, unlike the terminal, recorded. The database refuses an approved row without them.

psql -h pg-ai -U postgres -d plant -f db/004_doc_uploads.sql
psql -h pg-ai -U postgres -d plant -f db/005_doc_actions.sql
psql -h pg-ai -U postgres -d plant -f db/006_doc_pool.sql
sudo install -d -o 10002 -g 10002 /datadisk/ai-docs-inbox   # check df -h first
sudo install -d -o 10002 -g 10002 /datadisk/ai-docs-withdrawn
docker compose -f ~/ai-compose.yml up -d ai-docs-worker

Taking documents out is the other half, and today there is no way to do it: --supersede needs a revision to keep, so a cancelled procedure or a manual for equipment that has been removed cannot be withdrawn at all. Phase 9 adds withdraw (immediate, reversible, keeps the chunks and the audit trail — this is what "remove it" almost always means), restore, and purge (deletes, irreversible, off unless ALLOW_PURGE=true and the publisher types the document number). All three need the publisher group and a written reason, and all three are recorded in doc_actions, which nothing can delete from.

Withdrawal also moves the file out of /datadisk/ai-docs into an archive, so that folder keeps meaning "the documents this plant runs on". That is housekeeping, not the safety mechanism: ingest.py reads a document's withdrawal state before replacing its chunks and carries it through, and --all skips withdrawn documents — so re-ingesting cannot resurrect one, whatever folder it is in. --restore DOC_NUMBER REVISION is the way back, and it refuses while another revision of the same document is live.

Then the manual steps: the copy_headers change on the api.yokogawa.tech Caddy block, the ^/docs/.* Authelia rule above the general one, and AI_DocPublishers in AD with direct membership.

Design and gate: BUILD-AI-CONTAINERS.md §16 and Phase 9. Two gate items matter most. A user who is authenticated but not a publisher must get a 403 from the API, tested by calling api.yokogawa.tech directly — the button being hidden proves nothing. And after withdrawing a document, ai-ingest --all must not bring it back; run it and check, because that is the failure that puts a withdrawn procedure back in front of an operator.

Choosing what is in the pool is a third, separate thing, and it is separate on purpose. superseded says this document is withdrawn or replaced — a claim about the document, with a reason and an audit row behind it. pool_enabled says this document is part of the set we are running with — a claim about the corpus, and no comment on whether the document is current. Retrieval requires both, so putting a withdrawn document back in the pool does not make it citable. A superuser curates the pool to keep it current; the same screen saves named profiles.

For demos, POST /ask takes an optional pool_profile that narrows retrieval for that one request and changes nothing stored — so "three documents versus forty-seven" needs nothing undone afterwards on a host other people are using. Every answer from a reduced pool carries a banner with the document count, in the same place and for the same reason as the fixture-data banner: an answer from a trimmed corpus is otherwise indistinguishable from a complete one. The demo worth showing is not "more documents, better answers" — it is that with the evidence removed the assistant says no governing procedure in the active document set, rather than degrading into something plausible.

Read the HNSW note at the top of db/006_doc_pool.sql before rehearsing that demo. The index covers every embedding and filters afterwards, so a heavily trimmed pool can appear to collapse retrieval entirely.

What none of it does: update tags.csv, the Cube models or any setpoint. A new design document changes what the assistant can cite; the numbers behind Historical and Advisory answers still come from reference data that is changed in Git and deployed. The review screen asks the reviewer to confirm they know that, because a document going live while the tag metadata behind it has not is a gap that is only visible at that moment.

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Working on it

pytest api/tests          # contracts, classifier rules, SQL allow-list. No network.

• The host is live and shared. Prefer additive changes. Snapshot config before editing. Announce anything that restarts Caddy or Authelia — it logs out every active user, including whoever is mid-demo.
• Never restart, update or reconfigure openplc-runtime as a side effect of AI work. It is the PLC for the demo plant. Its published port 502 is the one deliberate exception to the no-published-ports rule on this host, and it does not generalise to anything we build.
• Verify, don't assume. docker ps showing "Up" is not proof.
• Test every layer without the LLM first. Prove Cube returns the right number by hand. Prove retrieval finds the right procedure by hand. Then wire up the agent — otherwise a wrong answer has four possible causes.
• Do not invent schema. Inspect, or ask.
• Fix eval failures in the classifier, Cube and ingestion — not by adding instructions to the prompt. When something fails, add the failing case to eval/testset.jsonl before fixing it.

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Repository layout

CLAUDE.md                    short rules — what Claude Code keeps front of mind
workflow-map.html            the non-technical explainer — how a question becomes
                             an answer, and what is built. Open it in a browser
BUILD-AI-CONTAINERS.md       the build spec
YAU_Linux_Host_Onboarding.md the host brief (reference; wins on conflict)
compose/                     deployed to ~/ai-compose.yml and ~/langfuse-compose.yml
caddy/ai-routes.caddy        blocks to paste into ~/Caddyfile
authelia/access-rules.md     the rule additions as text — never the real config
db/                          schema, roles, fixtures, and the alias seed CSVs
cube/model/                  alarms, process values, operations, equipment
api/                         FastAPI, classifier, agent, contracts, guardrails
ingest/                      Docling → chunk → embed → pg-ai, plus the
                             Phase 9 upload worker
web/                         React + Vite operator UI
eval/                        62-case test set and the scorecard runner
scripts/                     deploy.sh, verify.sh
docs/                        GITIGNORED — real content on /datadisk/ai-docs

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Known shortcuts

Deliberate, documented, and not to be shipped. Full list in BUILD-AI-CONTAINERS.md §14. The ones that matter most:

• Secrets in 0600 env files, not a vault
• No OT/IT firewall boundary — one flat 10.0.0.0/24 PoC network
• Modbus TCP on port 502 with no authentication or encryption, contained by NSG/VPN scope only — confirm the NSG does not expose it to the internet
• Single host, no HA: lin001 is a single point of failure for both the demo estate and the simulated plant's PLC
• No automated backup — pg-ai needs adding to whatever backup exists
• Document revision metadata entered semi-manually, not integrated with document control — Phase 9 records who asserted a revision, which is not the same as knowing what the current one is
• Uploaded documents are not malware-scanned; type and size checks only

Section 2 of the build spec must be reviewed with an OT/safety representative before any operator sees a demo.