docs(architecture): import the FDS architecture decisions (refs #159 )

Bring the engineer-facing FDS documentation next to the code it describes: ADR-0001 to ADR-0006, the ADR index and template, the L3 component view, and the slice-1 proposal. All translated to Dutch. Source: projects/open-register-fd/ in Respellion/innovation-lab. Land the set in docs/architecture/fds/ rather than docs/architecture/. This repo already owns adr-0001-loose-coupling to adr-0004-bdd-framework, so a flat import collides on every number. The subfolder keeps the imported numbering, and with it about thirty ADR-000N cross-references in the imported text. Add the mermaid custom fence to pymdownx.superfences. Without it the imported diagrams publish as raw code blocks, because the site has no mermaid support today. Add the nav group and one link from the docs index. The blueprint, the FDS gap analysis and the privacy views stay in the lab repo; the OKRs cite them and they feed tender responses. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
fix(observability): stop single-binary Tempo evicting its only ingester (closes #156 ) (#157 )
2026-09-03 11:29:07 +02:00 · 2026-09-01 08:31:36 +00:00 · 2026-09-01 07:26:33 +00:00 · 2026-08-28 10:11:54 +00:00 · 2026-08-14 09:34:04 +00:00 · 2026-07-27 15:14:16 +00:00
61 changed files with 2934 additions and 258 deletions
@@ -219,6 +219,9 @@ jobs:
      - name: OpenZaak → NRC → Event Subscriber → projection-api
        id: projection
        run: make verify-projection
+      - name: Objecten → NRC notification delivery
+        id: objecten_nrc
+        run: make verify-objecten-notifications
      - name: Domain → Flowable → ACL → OpenZaak
        id: domain
        run: make verify-domain
@@ -245,6 +248,7 @@ jobs:
          OBJECTTYPEN: ${{ steps.objecttypen.outcome }}
          OBJECTEN: ${{ steps.objecten.outcome }}
          REGISTERRECORD: ${{ steps.registerrecord.outcome }}
+          OBJECTEN_NOTIFICATIONS: ${{ steps.objecten_nrc.outcome }}
          ACL: ${{ steps.acl.outcome }}
          NRC: ${{ steps.nrc.outcome }}
          PROJECTION: ${{ steps.projection.outcome }}
@@ -266,6 +270,7 @@ jobs:
            echo "| Objecttypen API + token | $(icon "$OBJECTTYPEN") |"
            echo "| Objecten API + token | $(icon "$OBJECTEN") |"
            echo "| RegisterRecord objecttype | $(icon "$REGISTERRECORD") |"
+            echo "| Objecten → NRC | $(icon "$OBJECTEN_NOTIFICATIONS") |"
            echo "| ACL ↔ OpenZaak | $(icon "$ACL") |"
            echo "| OpenZaak → NRC | $(icon "$NRC") |"
            echo "| NRC → Event Subscriber → projection | $(icon "$PROJECTION") |"
@@ -285,7 +290,7 @@ jobs:
      # Log dump must precede teardown (which removes the containers).
      - name: Dump container logs on failure
        if: failure()
-        run: docker compose -f infra/docker-compose.yml logs --no-color --tail=100 oz-init openzaak nrc-init nrc-web nrc-celery nrc-beat flowable-db flowable-rest flowable-init keycloak acl bff domain projection-db event-subscriber projection-api self-service openbaar behandel beheer objecttypen-db objecttypen-redis objecttypen-init objecttypen objecten-db objecten-redis objecten-init objecten registerrecord-init tempo prometheus grafana 2>&1 || true
+        run: docker compose -f infra/docker-compose.yml logs --no-color --tail=100 oz-init openzaak nrc-init nrc-web nrc-celery nrc-beat flowable-db flowable-rest flowable-init keycloak acl bff domain projection-db event-subscriber projection-api self-service openbaar behandel beheer objecttypen-db objecttypen-redis objecttypen-init objecttypen objecten-db objecten-redis objecten-init objecten objecten-celery registerrecord-init tempo prometheus grafana 2>&1 || true
      - name: Tear down
        if: always()
        run: make down
@@ -287,12 +287,19 @@ Split into independently deployable sub-slices (CLAUDE.md §13):
 - **S-18b** (#140, ✅) · Objecten API up in compose, wired to Objecttypen. Depends on S-18a.
 - **S-18c** (#141, ✅) · RegisterRecord objecttype defined + registered (public-safe JSON schema). Depends on S-18a/b.

-### S-19 · ACL extension: write register-record to Objecten on approval
+### S-19 · ACL extension: write register-record to Objecten on approval *(split — #20 closed)*

 **Outcome:** Approval path writes the canonical register record to Objecten, not OpenZaak eigenschappen. Projection now sourced from Objecten events.

 **ADR required:** "Why Objecten holds the register, OpenZaak holds the process."

+Split into independently deployable sub-slices (CLAUDE.md §13):
+
+- **S-19a** (#149, ✅) · ACL writes the `RegisterRecord` to Objecten on approval, idempotently, alongside the ZGW eindstatus. Carries the ADR (ADR-0028).
+- **S-19b** (#150, ✅) · Read projection sourced from Objecten instead of NRC zaak events. *(split — #150 closed)*
+  - **S-19b-1** (#152, ✅) · Objecten publishes to NRC — broker, celery worker, `objecten` kanaal, notifications config. Turns back on what ADR-0028 deliberately disabled.
+  - **S-19b-2** (#153, ✅) · Projection derived from `RegisterRecord` objects, rebuildable from the Objecten-derived log. The ACL also writes an INGEDIEND record on submit, so the register holds the whole lifecycle. Carries ADR-0030.
+
 ---

 ## Iteration 5 — Data governance module *(milestone: `Iteration 5 — Data Governance`)*
@@ -43,7 +43,7 @@ export DOCKER_HOST := unix://$(PODMAN_SOCK)
 endif
 endif

-.PHONY: ci lint build unit mutation frontend integration verify verify-up verify-acl verify-nrc verify-projection verify-bff verify-domain verify-observability verify-tracing verify-metrics verify-objecttypen verify-objecten verify-registerrecord verify-notifications smoke up down local verify-local local-down changelog openzaak-up openzaak-smoke openzaak-seed openzaak-down stack-up stack-smoke stack-down keycloak-up keycloak-smoke keycloak-down flowable-up flowable-smoke flowable-down help
+.PHONY: ci lint build unit mutation frontend integration verify verify-up verify-acl verify-nrc verify-projection verify-bff verify-domain verify-observability verify-tracing verify-metrics verify-objecttypen verify-objecten verify-registerrecord verify-objecten-notifications verify-notifications smoke up down local verify-local local-down changelog openzaak-up openzaak-smoke openzaak-seed openzaak-down stack-up stack-smoke stack-down keycloak-up keycloak-smoke keycloak-down flowable-up flowable-smoke flowable-down help

 ## ci: run the full pipeline — lint, build, unit, mutation, frontend, verify (mirrors Gitea Actions)
 ## `verify` is the live-stack stage (full stack up once → ACL + notification checks).
@@ -201,6 +201,11 @@ verify-objecten:
 verify-registerrecord:
 	bash infra/run-registerrecord-check.sh

+## verify-objecten-notifications: assert a RegisterRecord write in Objecten is DELIVERED as an
+## `objecten` notification via NRC (S-19b-1), against the already-running stack.
+verify-objecten-notifications:
+	bash infra/run-objecten-notifications-check.sh
+
 ## verify: local mirror of the CI verify-stack job — full stack up once, all checks,
 ## tear down (always). For fast single-concern local iteration use `integration`
 ## (oz-only) or `verify-notifications` (oz+nrc) instead.
@@ -212,6 +217,7 @@ verify:
 	    && bash infra/run-acl-integration.sh \
 	    && bash infra/run-notification-check.sh \
 	    && bash infra/run-projection-check.sh \
+	    && bash infra/run-objecten-notifications-check.sh \
 	    && bash infra/run-domain-check.sh \
 	    && bash infra/run-bff-check.sh \
 	    && bash infra/run-e2e-check.sh || rc=$$?; \
@@ -207,7 +207,7 @@ A slice is done when:
 ## 15. Out of scope for v1

 - OpenMetadata data governance module (v3 slice).
- Objecten as the authoritative register record store (v2 slice — v1 uses OpenZaak zaak-eigenschappen as a placeholder).
+- ~~Objecten as the authoritative register record store~~ — **delivered** in S-19a (#149, ADR-0028); the approval path writes a `RegisterRecord` object to Objecten rather than the planned zaak-eigenschappen placeholder.
 - Production-grade Helm chart (sketch only).
 - Multi-tenancy.
 - Real outbound notifications (email/SMS) — logged to console in v1.
@@ -67,6 +67,14 @@ itself, so no in-image healthcheck tool is required.
 - Three more images built each CI run (kept small; not on the health-gate list).
 - Storage is ephemeral container fs — a demo backplane, not a retention target.
  Object storage for Tempo / remote-write for Prometheus is a later concern.
+- Tempo runs **single-binary**, so its distributor and ingester are one process and
+  some of its distributed-mode machinery is not just redundant but harmful. Its
+  ingester-pool health check is disabled (`ingester_client.pool_config`) because with
+  a single in-process ingester the check can never route around a failure — a 1s
+  loopback-gRPC deadline missed under CI load only evicted the one ingester and made
+  Tempo drop spans, which is how `verify-tracing` flaked (#156). Expect the same
+  shape from other distributed-mode knobs if we tune them; the fix is to switch to
+  real multi-ingester Tempo, not to re-enable them here.

 ## Coupling rules touched (CLAUDE.md §8)

@@ -0,0 +1,175 @@
+# ADR-0028: Objecten holds the register, OpenZaak holds the process
+
+- **Status:** Accepted
+- **Date:** 2026-08-14
+- **Deciders:** Respellion engineering
+- **Slice:** S-19a (#149), first of the S-19 (#20) split
+
+## Context
+
+Until this slice the register existed only as a **derived** thing: the read projection
+rows the Event Subscriber builds from NRC zaak notifications (ADR-0008). There is no
+system anywhere that holds "who is registered" as a first-class record — drop the
+projection database and the only way back is to replay ZGW history and re-derive it.
+
+That is the wrong shape for a register. A BIG registration is a **fact about a person**
+that outlives the case that produced it: it is looked up, corrected, superseded, and
+retained on its own schedule. The zaak that produced it is a **process record** — it
+opens, moves through statussen, and closes. Storing the fact inside the process record
+(as zaak `eigenschappen`, the v1 placeholder PRD §"Registration" mentions) welds the two
+lifecycles together: the register can then never be read, retained, or corrected without
+going through the case system that happened to create it.
+
+S-18 stood up Objecten + Objecttypen and registered the public-safe `RegisterRecord`
+objecttype (ADR-0027). The open question this ADR closes: **where the authoritative
+register record lives, and who writes it.**
+
+## Decision
+
+**The register record lives in the Objecten API as a `RegisterRecord` object. OpenZaak
+keeps only the process. On approval the ACL writes both: the ZGW eindstatus, then the
+register record.**
+
+### Not zaak eigenschappen
+
+Eigenschappen are per-zaaktype, untyped strings, and readable only by walking the zaak.
+They inherit the zaak's lifecycle and its archiving regime, and they give the public
+register no queryable surface of its own. Objecten gives a JSON-schema-validated record
+(ADR-0027 makes that schema the disclosure boundary), a queryable collection, and a
+lifecycle the zaak cannot drag around with it.
+
+### The ACL writes it, not the domain or the Event Subscriber
+
+CLAUDE.md §8.1 keeps upstream Common Ground modules behind the ACL. Objecten is such a
+module, so the same rule applies: `ObjectenGateway` is the only code that talks to it,
+and the domain keeps handing the ACL nothing but a zaak URL. The alternative — having the
+Event Subscriber write the record when it sees the status notification — would make the
+register a *second* derived artefact of ZGW, which is exactly the coupling this ADR
+removes.
+
+### Two writes, converging rather than transactional
+
+Approval is now two writes across two modules, so it cannot be atomic. Both are made
+idempotent instead:
+
+- a ZGW status is an append-only log entry, so re-setting the eindstatus is harmless;
+- the register write is an **upsert keyed on the zaak id** — search Objecten for an
+  existing object with that `id`, then PATCH it or POST a new one.
+
+A caller that retries a half-failed approval therefore converges. This is the same
+eventual-consistency posture as everywhere else in the system (CLAUDE.md §2.2, §8.6),
+not an exception carved out for this path.
+
+### The objecttype is resolved by name, lazily
+
+The objecttype URL and version number are assigned by Objecttypen at seed time, so they
+cannot be pinned in config — the ACL resolves them by the configured name
+(`Acl__Objecten__ObjecttypeName`), taking the highest **published** version. This is the
+same reasoning as ADR-0021 for zaaktypen.
+
+Resolution happens on the first approval, not at startup, so the ACL needs no `depends_on`
+on Objecten and will not crash-loop when it boots ahead of the seed. A failed resolution
+is not cached, so it is retried on the next approval.
+
+- ponytail ceiling: the resolution is memoised per gateway instance, and the gateway is a
+  transient typed `HttpClient` — in practice one extra GET per approval against a
+  neighbouring container.
+- Upgrade path: lift it into a singleton cache (as `CachedZaaktypeCatalog` does for ZGW)
+  if approvals ever get hot enough for that GET to matter.
+
+### The objecttype's UUID is pinned, not server-assigned
+
+Objecten refuses to store an object whose objecttype it has not been configured with
+(`ObjectType with url=… is not configured`), and its configuration identifies an
+objecttype **by UUID** — supplied through a static `setup_configuration` file applied
+when the container starts, before the `registerrecord-init` one-shot has run.
+
+Rather than thread a seed-time UUID from one container into another's config, the UUID is
+**pinned**: `infra/objecttypen-registerrecord/register.py` creates the objecttype with a
+fixed UUID (the Objecttypen API accepts a client-supplied one), and
+`infra/objecten/setup_configuration/data.yaml` declares that same UUID. Both sides are
+declared up front, both stay idempotent, and neither has to wait for the other.
+
+The cost is a constant duplicated across two files that must be kept in step; each carries
+a comment pointing at the other.
+
+### The ACL must reach Objecttypen at the URL Objecten knows it by
+
+Objecttypen builds the `url` it returns from the request's own Host header, and Objecten
+matches an incoming object's `type` against the `api_root` it was configured with. So an
+ACL that reads Objecttypen at `http://localhost:8020` gets back a `localhost` objecttype
+URL that Objecten then rejects as "not one of the available choices" — even though it is
+the same objecttype.
+
+`Acl__Objecten__ObjecttypenBaseUrl` must therefore match Objecten's configured
+`api_root` (`http://objecttypen:8000/api/v2/`). This is the same class of constraint as
+ADR-0006's "point the ACL at OpenZaak's container IP", and it is why the Objecten
+integration tests only pass from inside the compose network.
+
+### Objecten's notifications are off for this slice
+
+Objecten publishes to a Notificaties API on every write, and `notifications_api_common`
+**raises** rather than skipping when that configuration is absent — so with no NRC wiring,
+every `POST /api/v2/objects` returns 500 after creating and rolling back the object.
+
+Objecten → NRC is not wired: there is no broker, no Celery worker, no `objecten` kanaal and
+no abonnement for it. Configuring only the client side would make writes succeed while
+every message was dropped on the floor — a delivery path that looks wired and isn't. So
+`NOTIFICATIONS_DISABLED` is set for Objecten in both compose files instead.
+
+- ponytail ceiling: Objecten emits no notifications, so nothing downstream can react to a
+  register write yet.
+- **Lifted by ADR-0029** (S-19b-1, #152): broker, worker, `objecten` kanaal and
+  notifications config now exist, and `NOTIFICATIONS_DISABLED` is `false`.
+
+## Consequences
+
+**Positive**
+
+- The register is a first-class record with its own schema, lifecycle and query surface,
+  independent of the case that produced it.
+- The disclosure boundary is enforced by Objecten's schema validation (ADR-0027), not by
+  discipline in projection code.
+- The read projection can become a cache of Objecten rather than a re-derivation of ZGW —
+  done in S-19b-2 (#153), ADR-0030.
+
+**Negative / costs**
+
+- Approval writes to two modules and is eventually consistent; a failure between them
+  leaves a zaak in eindstatus without a register record until the approval is retried.
+  Nothing repairs that automatically yet.
+- One more upstream module on the approval path, and one more dev credential
+  (`Acl__Objecten__Token`) in compose.
+- Two new hand-kept constants: the pinned objecttype UUID (two files) and the objecttype
+  name (compose + `register.py`).
+- ~~Until S-19b lands, the public register is still read from the NRC-derived projection, so
+  the register record is written but not yet read — the two must agree.~~ Closed by ADR-0030:
+  the projection is now derived from the register, so there is only one source to agree with.
+
+## Coupling rules touched (CLAUDE.md §8)
+
+None bent. §8.1 is extended in spirit — the ACL is the only code that talks to Objecten,
+exactly as it is the only code that talks to ZGW. The domain still passes only a zaak URL,
+and no service reaches Objecten's database.
+
+## Verification
+
+The end-to-end assertion lives in the Playwright happy path
+(`tests/e2e/registration.spec.ts`, run by `verify-e2e`): after the behandelaar approves and
+the openbaar register shows `INGESCHREVEN`, it asserts Objecten holds exactly one
+`RegisterRecord` for *that* reference, with status `INGESCHREVEN` and no field outside the
+public-safe schema.
+
+It belongs there and not in `verify-domain`, which looks like the obvious home: that check
+completes the Beoordelen task straight through Flowable REST (deliberately — it exists to
+exercise the Workflow Client's REST contract), which bypasses the domain `decide` path that
+calls the ACL. The e2e is the only check that drives a real approval.
+
+`ObjectenGatewayIntegrationTests` (`Category=Integration`, so it runs under `verify-acl`
+inside the compose network) drives the real gateway against a live Objecten + Objecttypen
+pair: two writes for the same id leave exactly one object, carrying the second write's
+status and nothing outside the public-safe schema.
+
+All three findings above — the pinned UUID, the notifications block, and the base-URL
+constraint — came out of running the gateway against those live modules while writing the
+slice, not out of CI.
@@ -0,0 +1,122 @@
+# ADR-0029: Objecten publishes register events to NRC
+
+- **Status:** Accepted
+- **Date:** 2026-08-14
+- **Deciders:** Respellion engineering
+- **Slice:** S-19b-1 (#152), first of the S-19b (#150) split
+- **Supersedes in part:** ADR-0028's "Objecten's notifications are off for this slice"
+
+## Context
+
+ADR-0028 put the authoritative register record in the Objecten API and had the ACL write
+it on approval. It also switched Objecten's notifications **off** — deliberately, with a
+stated ceiling: there was no broker, no worker, no `objecten` kanaal and no abonnement, so
+turning the client side on alone would have produced a delivery path that looks wired and
+drops every message.
+
+S-19b-2 (#153) wants the read projection sourced from register writes rather than
+re-derived from ZGW zaak events. That needs the notifications to actually arrive. This ADR
+builds the four missing pieces and lifts the ceiling.
+
+## Decision
+
+**Objecten publishes to the same NRC OpenZaak already publishes to, on the `objecten`
+kanaal, delivered by its own Celery worker — provisioned declaratively on both sides,
+exactly as ADR-0007 did for OpenZaak.**
+
+- **Objecten** (`infra/objecten/setup_configuration/data.yaml`): a `zgw_consumers` service
+  `nrc` (api_type `nrc`) plus a `notifications_config` step naming it, and
+  `NOTIFICATIONS_DISABLED: "false"` in both compose files.
+- **NRC** (`infra/opennotificaties/setup_configuration/data.yaml`): an `objecten` kanaal
+  alongside `zaken`.
+- **`objecten-celery`**: a worker container on the Objecten image (`/celery_worker.sh`),
+  mirroring `oz-celery`, with `CELERY_BROKER_URL`/`CELERY_RESULT_BACKEND` on
+  `objecten-redis` db 1 (db 0 is already the cache).
+
+### One NRC, one credential, one kanaal per publisher
+
+Objecten reuses the `big-reference-seed` client OpenZaak publishes with. NRC verifies its
+JWT and authorizes it against OpenZaak's Autorisaties API (ADR-0007), which grants that
+client `heeft_alle_autorisaties` — so no second credential and no publisher-specific
+authorization is needed. A second NRC, or a second credential, would buy isolation this
+reference application has no use for.
+
+The kanaal name is **not ours to choose**: the Objects API sends
+`NOTIFICATIONS_KANAAL = "objecten"`. NRC rejects a publish to an unregistered kanaal
+(`"Kanaal met deze naam bestaat niet"`), which is precisely what the failing check for this
+slice reported first. Its filter set (`object_type`) matches the kenmerken the Objects API
+sends, so an abonnement can narrow to one objecttype instead of receiving every write.
+
+### Writers address Objecten as `objecten.local` — NRC rejects single-label hosts
+
+NRC types a notification's `hoofdObject` and `resourceUrl` as DRF `URLField`s, so Django's
+`URLValidator` runs on them — and it refuses a **single-label** host. Objecten fills both
+from the object `url` that DRF built with `request.build_absolute_uri`, i.e. **the Host the
+caller used**. Write to `http://objecten:8000` and NRC answers every publish with
+
+```
+{"hoofdObject":["Voer een geldige URL in."],"resourceUrl":["Voer een geldige URL in."]}
+```
+
+which `objecten-celery` then retries with exponential backoff, forever, in the background —
+the write itself having returned 201.
+
+`SITE_DOMAIN` does **not** fix this; it is not what builds those URLs. The fix is on the
+caller side: the `objecten` service carries an `objecten.local` network alias, and every
+component whose writes must be notified — the ACL (`Acl__Objecten__BaseUrl`), the gateway
+integration tests, this slice's verify check — addresses it there. An alias rather than a
+plain dotted `SITE_DOMAIN` so the host still **resolves in-network**: a subscriber that
+follows `resourceUrl` reaches the record it points at, which S-19b-2 will do. Readers are
+unaffected and keep using the plain service name.
+
+This is the same class of constraint as ADR-0028's "the ACL's Objecttypen base URL must
+match Objecten's configured `api_root`": these modules put request-derived hosts into data
+another module then validates or dereferences.
+
+- ponytail ceiling: nothing *enforces* that a new writer uses the alias — it would get a 201
+  and silently no notification.
+- Upgrade path: if a second writer ever appears, rename the compose service to `objecten.local`
+  so the plain name stops working, rather than adding a lint.
+
+### A worker, not a synchronous send
+
+`notifications_api_common` only schedules the send on transaction commit. Without a worker
+the task sits in redis forever and every register write is silently undelivered — the exact
+half-wired state ADR-0028 refused to ship. No `beat` for Objecten: it is a publisher, not a
+subscriber, and `nrc-beat` already drains NRC's delivery queue.
+
+## Verification
+
+`make verify-objecten-notifications` (`infra/run-objecten-notifications-check.sh`, in the
+CI `verify-stack` job) registers an abonnement on the `objecten` kanaal pointing at a
+throwaway webhook sink, writes a `RegisterRecord` exactly as the ACL does on approval, and
+asserts the notification reaches the sink. That is the whole chain in one assertion:
+Objecten → `objecten-celery` → NRC → `nrc-beat` → the callback. Any missing piece — broker,
+worker, kanaal, notifications config — shows up as a non-delivery rather than as a green
+config.
+
+## Consequences
+
+**Positive**
+
+- A register write is now observable by anything that subscribes, which is what S-19b-2
+  (#153) needs to make the projection a cache of Objecten rather than a re-derivation of ZGW.
+- ADR-0028's ceiling is lifted: the delivery path is proven end to end, not merely configured.
+
+**Negative / costs**
+
+- One more long-running container (`objecten-celery`) on an already memory-tight CI runner.
+- A second publisher on the shared `big-reference-seed` credential — a credential rotation
+  now touches two modules.
+- Objecten now has two in-network names, and which one a caller uses silently decides
+  whether its writes are notified (ceiling above).
+- ponytail ceiling: notification delivery has no dead-letter or alerting — a failed publish
+  is visible only in the worker log.
+- Upgrade path: if undelivered register events start mattering, subscribe an audit sink or
+  read NRC's own delivery admin rather than building a retry layer here.
+
+## Coupling rules touched (CLAUDE.md §8)
+
+None bent. This is infrastructure between two upstream modules, over their documented
+APIs; no service reaches another's database. §8.6 (idempotency at every event boundary)
+applies to whatever consumes the new kanaal — S-19b-2's problem, not this slice's.
@@ -0,0 +1,141 @@
+# ADR-0030: The read projection is sourced from the register, not from ZGW
+
+- **Status:** Accepted
+- **Date:** 2026-08-28
+- **Deciders:** Respellion engineering
+- **Slice:** S-19b-2 (#153), second of the S-19b (#150) split
+- **Builds on:** ADR-0008 (read projection store), ADR-0028 (Objecten holds the register), ADR-0029 (Objecten publishes to NRC)
+
+## Context
+
+ADR-0028 moved the authoritative register record into the Objecten API, and said what should
+follow: "the read projection can become a cache of Objecten rather than a re-derivation of
+ZGW." Until this slice it was still the latter — the Event Subscriber listened on the `zaken`
+kanaal and inferred register state from case events:
+
+- a `zaak`/`create` meant INGEDIEND;
+- any `status`/`create` was taken to be the approval, so meant INGESCHREVEN — the subscriber
+  may not read OpenZaak (§8.1), so it could not tell one statustype from another;
+- the citizen-facing reference was not in the notification at all, so every projection had a
+  second hop: ask the ACL for the zaak's identificatie (#78).
+
+So the register — a fact about a person — was reconstructed by guessing at the lifecycle of the
+case that happened to produce it. ADR-0029 made the register itself publish. This ADR switches
+the projection over to it.
+
+## Decision
+
+**The Event Subscriber listens on the `objecten` kanaal and projects the `RegisterRecord` the
+notification points at. The projection is a cache of the register; ZGW is no longer a source.**
+
+- The subscriber's abonnement moves from `zaken` to `objecten` (`register-abonnement.py`, and
+  the CI projection check).
+- An Objecten notification carries **no record data** — only the object URL and the objecttype
+  as a kenmerk — so the record is read back through the ACL (`POST /register-records/read`).
+  §8.1 applies to Objecten exactly as ADR-0028 established: the ACL is the only code that talks
+  to it.
+- The accepted acties are `create`, `update` and `partial_update`. The last one is not
+  defensive breadth: the ACL upserts with PATCH, and DRF routes a PATCH through the notifying
+  `update()` while naming the action `partial_update` — which is what Objecten publishes. So
+  every approval arrives as `partial_update`, and accepting only `create`/`update` drops the
+  one state change this slice exists to project. `destroy` is deliberately not accepted:
+  removing a registration from the public register is its own decision.
+- The record already carries `id`, `status` and `reference`, so the row is the record. The
+  zaak-shaped surface goes: `IsZaakCreated`, `IsZaakStatusSet`, `ZaakUrl`, `ZaakId`, and
+  `ToEntry`'s `Resource == "status"` inference are replaced by `IsRegisterRecordWritten` +
+  `ObjectUrl`, and the ACL enrichment hop disappears.
+
+### The ACL writes an INGEDIEND record on submit
+
+Before this slice only approval wrote a record, so re-sourcing alone would have silently
+dropped every INGEDIEND row from the public register. `OpenZaakAsync` therefore upserts a
+record with status INGEDIEND after opening the zaak, keyed on the same zaak id that approval
+later upserts to INGESCHREVEN.
+
+This is the same two-writes-converging posture ADR-0028 already accepted for approval, now on
+the submit path too: both writes are idempotent, so a retried submit updates the record rather
+than adding a second one (§8.6). The reference comes from the registration itself, so unlike
+approval this path needs no ZGW read-back.
+
+The alternative — a register holding only INGESCHREVEN — is arguably the more correct reading
+of "public register", but it narrows what the openbaar portal shows and reads against PRD §68
+("~50 register entries with diverse statuses"). Rejected as a behaviour change this slice was
+not asked to make.
+
+### The dedup key is the projected row, not the notification
+
+NRC carries no notification id and may redeliver, so the idempotency key is derived from
+content (as before). The obvious candidates both break here:
+
+- **the object URL alone** — the ACL upserts *one object per registration*, so submit and
+  approval notify about the same URL, and the approval would be swallowed as a duplicate;
+- **object URL + actie** — a retried approval is a second `update`, so it would be dropped
+  while genuinely being the same state (harmless), but a *third* distinct state would collide
+  with it (not harmless).
+
+The key is therefore the object plus the state that write puts in the projection —
+`objecten:object:{url}:{status}:{reference}`. A redelivery collapses; a genuine state change
+does not. That is exactly the property §8.6 asks for, and it needs no version field from
+Objecten's internals.
+
+### The notification log holds the row, not the event
+
+`processed_notifications` stops describing ZGW events (`actie`, `zaak_id`, `resource`) and
+holds the projected row itself (`register_id`, `status`, `reference`). A rebuild becomes a
+replay with no mapping rules and no upstream reads at all — §8.4 held before via the ACL hop;
+now it holds outright.
+
+The migration **drops** the old columns rather than renaming them. EF scaffolded renames
+(`resource` → `register_id`, `zaak_id` → `status`) that would have carried ZGW values into
+columns meaning something else entirely, and a rebuild would then have projected that garbage.
+
+- ponytail ceiling: the migration empties both tables. A pre-slice row describes a zaak event
+  the new projector cannot reproject, and the registrations behind those rows have no
+  RegisterRecord in Objecten (only approvals wrote one), so they are not re-derivable from the
+  new source either.
+- Upgrade path: fine while stacks are ephemeral. If a long-lived environment ever needs to keep
+  them, backfill by walking Objecten's objects rather than replaying the log.
+
+## Consequences
+
+**Positive**
+
+- The register is read from the register. The projection is a derived cache of a first-class
+  record, not an inference over someone else's lifecycle.
+- The "any status-create is the approval" guess is gone — a real source of wrongness the moment
+  the zaaktype grows a second statustype.
+- One hop fewer per notification: the record carries its own reference, so the ACL enrichment
+  call disappears.
+- A rebuild needs nothing but its own log (§8.4).
+
+**Negative / costs**
+
+- Submission is now two writes across two modules and eventually consistent. A failure between
+  them leaves a zaak with no register record until the submit is retried; nothing repairs that
+  automatically yet — the same gap ADR-0028 recorded for approval, now on a second path.
+- The projection lags the register by a notification round trip, where it used to lag the zaak
+  by one. In practice the same order of magnitude.
+- Projecting now depends on the ACL being reachable, where the reference enrichment used to be
+  the only ACL dependency. A failed read means the notification is not logged and not
+  projected — NRC retries, so it converges, but the failure mode is now on the main path.
+- OpenZaak still publishes to `zaken` and nothing in the product listens. Kept because the
+  `verify-nrc` check asserts that path, and turning off a working publisher to save nothing
+  would be its own risk.
+
+## Coupling rules touched (CLAUDE.md §8)
+
+None bent. §8.1 holds — the subscriber reaches Objecten only through the ACL. §8.4 is
+strengthened: the projection is rebuildable from its own log, with no upstream reads at all.
+§8.6 is what the dedup-key discussion above is about.
+
+## Verification
+
+`make verify-projection` (`infra/run-projection-check.sh`, in CI's `verify-stack`) opens a zaak
+**through the ACL** and asserts projection-api serves a row for it with status INGEDIEND — the
+whole new chain in one assertion: ACL → Objecten → `objecten-celery` → NRC → `nrc-beat` →
+Event Subscriber → projection → projection-api. A zaak created behind the ACL's back produces
+no row, which is the re-source working rather than a gap.
+
+`RegisterProjectieBijwerken.feature` covers the use case in business language, including the
+approval case — the same row moving INGEDIEND → INGESCHREVEN, which is now one registration's
+record being updated rather than two unrelated ZGW events.
@@ -0,0 +1,50 @@
+# FDS-architectuur — Open Register
+
+Deze map bevat de architectuurbesluiten en de engineer-documentatie voor de FDS-kant van deze
+referentie-applicatie: deelnemen aan het Federatief Datastelsel als **afnemer**.
+
+De strategische inzet, de slices en de portfoliostatus staan in het Innovation Lab-repo,
+`Respellion/innovation-lab`, onder `projects/open-register-fd/`. Daar staan ook de
+architectuurblauwdruk, de FDS gap-analyse en de privacy-views.
+
+## Documenten
+
+| Document | Waarvoor |
+|---|---|
+| [`c4-component-view.md`](c4-component-view.md) | Componentview op niveau 3: ports en adapters, en welke views nog waarde toevoegen |
+| [`slice-1-proposal.md`](slice-1-proposal.md) | Het bouwbare eerste increment; plak dit in een `poc-voorstel`-issue |
+| `adr/` | De geaccepteerde architectuurbesluiten, ADR-0001 tot en met ADR-0006. Zie de tabel hieronder. |
+
+## Architecture Decision Records
+
+Een ADR legt een besluit vast dat **vaststaat**, met de context en de gevolgen, zodat het niet stil
+opnieuw wordt uitgevochten. Statuswaarden: `proposed` → `accepted` → (`vervangen door ADR-NNNN` |
+`deprecated`).
+
+Een geaccepteerde ADR wijzigen betekent een nieuwe ADR schrijven die de oude vervangt. Wij
+herschrijven de historie nooit.
+
+ADRs liggen naast governance. Acceptatie volgt de asynchrone bezwaarronde uit
+`Respellion/innovation-lab`, `operating-model/operating-model.md`, sectie *Besluitvorming*.
+
+| ADR | Besluit | Status |
+|---|---|---|
+| [0001](adr/0001-acl-at-every-register-boundary.md) | Anti-Corruption Layer op elke registergrens | accepted |
+| [0002](adr/0002-fsc-for-connectivity.md) | FSC voor connectiviteit tussen organisaties, geen ruwe REST | accepted |
+| [0003](adr/0003-pbac-via-opa.md) | Policy-based access control via OPA, FTV-klaar | accepted |
+| [0004](adr/0004-bounded-cache.md) | Begrensde cache; registers blijven systeem van registratie | accepted |
+| [0005](adr/0005-ldv-verwerkingenlog.md) | Verwerkingenlog via event-emissie, in lijn met LDV | accepted |
+| [0006](adr/0006-module-boundary-and-reuse.md) | Modulegrens en hergebruikstrategie: in-process → .NET-module → OpenMetadata-feed → gateway op verzoek | accepted |
+
+## Nummering
+
+Deze reeks staat los van de ADR-reeks over de referentie-applicatie zelf, die in
+[`../`](../adr-0001-loose-coupling.md) loopt van `adr-0001-loose-coupling` tot en met
+`adr-0010-bff-oidc`. Vandaar de eigen map `fds/`: beide reeksen beginnen bij 0001, en de nummers
+zouden anders over de volle breedte botsen.
+
+In de MkDocs-navigatie staan deze zes daarom als **FDS ADR-000N**, zodat de zijbalk ze niet met de
+reeks van de applicatie verwart.
+
+Nieuwe FDS-ADR: kopieer [`adr/template.md`](adr/template.md), neem het volgende nummer, en open een
+pull request.
@@ -0,0 +1,42 @@
+# ADR-0001: Anti-Corruption Layer op elke registergrens
+
+- **Status:** accepted
+- **Datum:** 2026-06-13
+- **Deciders:** Lab Circle (Build, Lead Link)
+- **Vervangt / vervangen door:** —
+
+## Context
+
+De applicatie bevraagt meerdere registers: BRP, NHR/KVK, en ZGW via OpenZaak. Hun vocabulaires en
+schema's verschillen van elkaar en van ons domein. Zij veranderen ook zelf mee met de FDS-standaarden.
+
+Lekt registervocabulaire het domeinmodel in, dan werkt elke wijziging aan de registerzijde door in de
+bedrijfslogica. Het domein wordt dan een lappendeken van vreemde begrippen in plaats van ubiquitous
+language.
+
+## Besluit
+
+Elk register is bereikbaar via een Anti-Corruption Layer: **één adapter per register**, die een
+**port** vervult die het domein definieert.
+
+Adapters doen alleen vertalen en velden versmallen. Zij bevatten geen bedrijfslogica. Het domein
+spreekt `Persoon` en `Organisatie`, en nooit veldnamen uit BRP of NHR.
+
+## Gevolgen
+
+**Positief:** verloop in registers en FDS-standaarden blijft bij de adapter. Het domein blijft stabiel
+en testbaar. Adapters zijn onafhankelijk vervangbaar, en dat is precies wat de FSC-wissel uit
+ADR-0002 goedkoop maakt. Het patroon generaliseert naar een herbruikbare ACL-template per register,
+een Foundations-kandidaat.
+
+**Negatief en kosten:** één vertaalmap per register om te schrijven en te onderhouden, plus een extra
+indirectie die engineers moeten respecteren in plaats van omzeilen.
+
+**Vervolgwerk:** extraheer de ACL-template zodra de tweede adapter bestaat (slice 3).
+
+## Overwogen alternatieven
+
+- **Registers direct aanroepen uit de applicatieservices** — afgewezen: dit koppelt bedrijfscode aan
+  registerschema's en aan versies van FDS-standaarden.
+- **Eén generieke registeradapter** — afgewezen: registers verschillen genoeg dat een generieke
+  abstractie zou gaan lekken of opzwellen. Adapters per register zijn duidelijker.
@@ -0,0 +1,44 @@
+# ADR-0002: FSC voor connectiviteit tussen organisaties, geen ruwe REST
+
+- **Status:** accepted
+- **Datum:** 2026-06-13
+- **Deciders:** Lab Circle, Upstream Liaison
+- **Vervangt / vervangen door:** —
+
+## Context
+
+Registerbevragingen kruisen een organisatiegrens naar systemen van bronhouders met
+persoonsgegevens. Het FDS noemt Federatieve Service Connectiviteit (FSC, de opvolger van NLX) als de
+richting voor connectiviteit: wederzijdse authenticatie op organisatieniveau, autorisatie
+gecontroleerd tegen een contract en gehandhaafd bij de bron, en symmetrische transactielogging.
+
+Een ruwe REST-client met mTLS geeft ons geen van de contractadministratie, delegatie of onafhankelijke
+tweezijdige verantwoording die een FG of auditor nodig heeft.
+
+## Besluit
+
+Het FSC Client-component stuurt alle registerbevragingen via een **FSC outway**, de
+EUPL-referentie-implementatie. De ACL-adapter hangt af van de FSC Client, en niet van een HTTP-client.
+
+FSC-zaken — contracten, identiteiten, delegatie — leven in dit component, achter de Register Port.
+
+## Gevolgen
+
+**Positief:** de autorisatie wordt bij de bron gehandhaafd, en niet op gezag van de aanroeper
+vertrouwd. Onweerlegbaar loggen aan beide uiteinden maakt onafhankelijke afstemming tegen ons LDV-log
+mogelijk. Delegatie wordt expliciet meegedragen. Wij lopen in lijn met de FDS-richting, vóór er een
+verplichting is.
+
+**Negatief en kosten:** FSC is operationeel zwaarder dan een REST-aanroep — beheer van certificaten en
+identiteiten, plus een outway die op De Werf moet draaien. De vergelijking FSC tegenover DSP loopt
+binnen het FDS nog, dus sommige details kunnen schuiven.
+
+**Vervolgwerk:** valideer het contract- en logginggedrag van de huidige fsc-nlx-implementatie
+(slice 2). Herzie dit als het FDS voor DSP kiest; ADR-0001 houdt die wissel beperkt tot één component.
+
+## Overwogen alternatieven
+
+- **Ruwe REST met mTLS** — afgewezen: geen contractlaag, geen tweezijdig log, en het wijkt af van het
+  FDS.
+- **Wachten tot het FDS FSC tegenover DSP heeft beslist** — afgewezen: de naad uit ADR-0001 laat ons nu
+  adopteren en later aanpassen. Wachten geeft het voordeel van vroege expertise weg.
@@ -0,0 +1,44 @@
+# ADR-0003: Policy-based access control via OPA, FTV-klaar
+
+- **Status:** accepted
+- **Datum:** 2026-06-13
+- **Deciders:** Lab Circle, FG (geconsulteerd)
+- **Vervangt / vervangen door:** —
+
+## Context
+
+Elke bevraging van persoonsgegevens uit BRP of NHR is een verwerking die een grondslag en een
+begrensde doelbinding nodig heeft. Toegangsregels moeten handhaafbaar en auditeerbaar zijn, en
+wijzigbaar zonder de bedrijfscode opnieuw uit te rollen.
+
+De Federatieve Toegangsverlening (FTV) van het FDS beweegt naar policy-based access control, maar is
+nog geen afgeronde standaard.
+
+## Besluit
+
+Introduceer een Policy Decision Point met Open Policy Agent (OPA). De applicatieservices roepen de
+PDP aan — via een Authorisation Port en een PDP Client — **vóór elke registerbevraging**, en geven
+rol, doel en grondslag mee.
+
+Policies schrijven wij als code, **geversioneerd in Gitea**, en zij gaan via review naar productie. De
+PDP staat zo gepositioneerd dat wij bij de komst van FTV alleen het policy-dialect opnieuw uitdrukken,
+zonder de architectuurgrens te verplaatsen.
+
+## Gevolgen
+
+**Positief:** doelbinding en grondslag worden gehandhaafd, en niet alleen gedocumenteerd. De FG kan de
+werkelijke regels in versiebeheer lezen, waardoor het verwerkingenregister en de gehandhaafde policy
+naar elkaar toe groeien. Toegangswijzigingen zijn reviewbaar en gedateerd.
+
+**Negatief en kosten:** BRP-autorisatiebesluiten correct modelleren is juridisch werk, geen
+engineering. De PDP maakt de handhaving betrouwbaar, niet de policy juist. Daarnaast komt er een
+component bij om te exploiteren.
+
+**Vervolgwerk:** een promotiepijplijn voor policies in Gitea Actions. Policies opnieuw uitdrukken zodra
+FTV stabiliseert. Een FG-review van de policy-set vóórdat er echte persoonsgegevens in komen.
+
+## Overwogen alternatieven
+
+- **Rolcontroles in de applicatiecode** — afgewezen: niet auditeerbaar, niet wijzigbaar zonder deploy,
+  en het verspreidt toegangslogica over de codebase.
+- **Wachten op FTV** — afgewezen: de PBAC-vorm is al duidelijk. Nu OPA, later het FTV-dialect.
@@ -0,0 +1,48 @@
+# ADR-0004: Begrensde cache; registers blijven systeem van registratie
+
+- **Status:** accepted
+- **Datum:** 2026-06-13
+- **Deciders:** Lab Circle, FG (geconsulteerd)
+- **Vervangt / vervangen door:** —
+
+## Context
+
+*Data bij de bron* verbiedt het behandelen van registerdata als lokale bron van waarheid. Maar BRP of
+NHR bij elke interactie bevragen is onpraktisch en vergroot de blootstelling.
+
+Persoonsgegevens zijn de data die wij het minst willen opbouwen. Een onbegrensde cache wordt stil een
+schaduwregister, met een onbeheerde bewaarverplichting als gevolg.
+
+## Besluit
+
+Een **begrensde cache** staat achter een Cache Port, beheerd door een Cache Manager. Vier grenzen
+gelden.
+
+| Grens | Wat die betekent |
+|---|---|
+| **Tijd** | Een TTL die aan het doel hangt |
+| **Omvang** | Alleen de werkset van een actieve zaak |
+| **Gezag** | Antwoordt nooit wat de bron niet zou antwoorden; geen systeem van registratie |
+| **Adresseerbaarheid** | Gesleuteld op subject, zodat verwijderen op verzoek kan |
+
+Purge-triggers: het verstrijken van de TTL, het sluiten van de zaak, en een verwijderingsverzoek.
+
+## Gevolgen
+
+**Positief:** de prestaties van een lokale kopie, zonder een onbevoegd register te worden. Bewaartermijn
+en het recht op verwijdering zijn echte operaties, geen hoop. Dit is consistent met zowel
+AVG-dataminimalisatie als FDS-data-bij-de-bron.
+
+**Negatief en kosten:** de mapping van doel naar TTL is een beleidsbesluit, samen met de FG en de
+autorisatievoorwaarden, en geen engineeringconstante. Die is dus makkelijk fout te krijgen. Daarnaast
+komt de complexiteit van cache-invalidatie erbij.
+
+**Vervolgwerk:** definieer het beleid voor doel naar TTL met de FG. Maak een toestandsdiagram voor de
+levensloop van een cache-entry. Documenteer de aanvaardbare veroudering per register.
+
+## Overwogen alternatieven
+
+- **Geen cache; altijd de bron bevragen** — afgewezen: onpraktische latency en belasting, en meer
+  blootstelling per aanroep.
+- **Een onbegrensde of algemene cache** — afgewezen: die wordt een schaduwregister, precies de
+  faalvorm waar de AVG en het FDS beide tegen duwen.
@@ -0,0 +1,42 @@
+# ADR-0005: Verwerkingenlog via event-emissie, in lijn met LDV
+
+- **Status:** accepted
+- **Datum:** 2026-06-13
+- **Deciders:** Lab Circle, FG (geconsulteerd)
+- **Vervangt / vervangen door:** —
+
+## Context
+
+AVG art. 30 vereist een register van verwerkingsactiviteiten. De FDS-bouwsteen Logboek
+Dataverwerkingen (LDV) wijst naar een gestandaardiseerd verwerkingslog dat de burger kan bevragen.
+
+Database-CDC met Debezium legt *datawijzigingen* vast, en niet *verwerkingsgebeurtenissen met
+doelbinding*. Het is dus geen verwerkingenlog.
+
+## Besluit
+
+Elke registeradapter stuurt een **verwerkingsactiviteit-event** naar een eigen Redpanda-topic, via een
+Verwerking Port en een LDV Emitter. Het event bevat: subjectcategorie, register, velden, doel en
+doelbinding, grondslag, bevragende rol, en tijdstempel. **Nooit de opgehaalde waarden.**
+
+Een projectie maakt het log bevraagbaar. De emissie is asynchroon, maar niet over te slaan: de adapter
+die de Register Port vervult, is dezelfde code die het event uitstuurt.
+
+## Gevolgen
+
+**Positief:** het spoor voor art. 30 en LDV ontstaat als neveneffect van de bevraging, dus het kan niet
+uit de pas lopen met de werkelijkheid. Het is af te stemmen tegen de tweezijdige logs van FSC
+(ADR-0002). Het is onderscheidend in een tender.
+
+**Negatief en kosten:** een topic en een projectie om te exploiteren. Het ontsluiten van het log naar
+de burger valt buiten de huidige scope; wij produceren het log. Het eventschema vraagt governance.
+
+**Vervolgwerk:** definieer het schema van het verwerkingsevent. Bouw de bevraagbare projectie. Sluit
+aan op de LDV-standaard zodra die volwassen wordt; dit is een upstream-kandidaat.
+
+## Overwogen alternatieven
+
+- **Debezium-CDC hergebruiken als log** — afgewezen: dat legt datawijzigingen vast, en geen verwerking
+  met doelbinding. Verkeerde semantiek.
+- **Synchroon loggen in het aanroeppad** — afgewezen: dat koppelt de latency van de bevraging aan het
+  log. Asynchroon maar niet over te slaan geeft zowel snelheid als garantie.
@@ -0,0 +1,68 @@
+# ADR-0006: Modulegrens en hergebruikstrategie voor de governed-access spine
+
+- **Status:** accepted
+- **Datum:** 2026-06-13
+- **Deciders:** Lab Circle (Lead Link, Build, Upstream Liaison)
+- **Vervangt / vervangen door:** —
+
+## Context
+
+De compliance-spine uit slice 1 bestaat uit de PDP-controle (ADR-0003), gegoverneerd uitgaand verkeer
+via FSC (ADR-0002), emissie van het verwerkingenlog (ADR-0005), en de begrensde cache (ADR-0004),
+allemaal achter ports (ADR-0001). Die spine is mogelijk breder herbruikbaar dan alleen in de
+referentie-applicatie.
+
+Er spelen twee hergebruikvragen: welke verpakkingsvorm kiezen wij, en hoe verhoudt de spine zich tot
+andere omgevingen zoals het OpenMetadata-datagovernanceproject?
+
+Twee verduidelijkingen bepalen het besluit.
+
+1. **OpenMetadata is geen afnemer.** In het datagovernanceproject is het de catalogus- en
+   lineage-laag over (synthetische) data. Het bevraagt geen BRP of NHR. FSC of de begrensde cache
+   daarin inbouwen zou zinloos zijn. De juiste aansluiting is **integratie van de output van de
+   spine**, en niet het inbouwen van de spine.
+2. **FSC en de begrensde cache zijn zaken die alleen een afnemer aangaan.** "Maak het herbruikbaar"
+   mag deze niet uitsmeren over componenten die geen registerdata bevragen.
+
+Nu al een taalonafhankelijke gateway bouwen — vóórdat er een tweede, niet-.NET afnemer bestaat — zou
+de valkuil van speculatieve architectuur herhalen, die wij voor de capability-laag al hebben
+afgewezen.
+
+## Besluit
+
+Wij nemen een **vraaggestuurde reeks van vier stappen** aan. Elke stap hangt af van echte behoefte, en
+niet van verwachte behoefte.
+
+| Stap | Wat | Wanneer |
+|---|---|---|
+| 1 | **In-process bewijzen.** Bouw de spine als gewone componenten achter ports, binnen de .NET register-applicatie. Nog geen extractie. Doel: de compliance-invarianten één keer echt valideren. | Slice 1 |
+| 2 | **Extraheren als .NET-module.** Zodra een tweede .NET-afnemer in zicht is, haal de spine eruit als een geversioneerde .NET-library of SDK. Dit is de ACL-template-extractie die het charter al plant. Herbruikbaar voor .NET-afnemers, en dat is genoeg voor register-reference en zijn broertjes. | Slice 3 |
+| 3 | **De feed LDV naar OpenMetadata aansluiten.** Route verwerkingsevents uit de LDV-emitter naar OpenMetadata als access- en usage-metadata bij het geclassificeerde asset: wie las welk persoonsgegevensveld, met welk doel, hoe vaak. Optioneel laten classificatietags uit OpenMetadata terugstromen om veldminimalisatie in de ACL aan te sturen. Dit is de concrete brug tussen beide anchor-projecten: integratie, geen inbouw. | Na stap 2 |
+| 4 | **Alleen op verzoek een taalonafhankelijke gateway bouwen.** Heeft een echte niet-.NET afnemer gegoverneerde registertoegang nodig, verpak de spine dan als zelfstandige sidecar of proxy met een dunne lokale API, met PDP, FSC-egress en LDV erachter. Niet eerder. | Op verzoek |
+
+## Gevolgen
+
+**Positief:** eigen software blijft minimaal. Hergebruik volgt op validatie in plaats van eraan vooraf
+te gaan. Beide anchor-projecten krijgen een concreet, benoemd integratiepunt (stap 3). Zaken die
+alleen een afnemer aangaan, blijven ingesloten.
+
+**Negatief en kosten:** de .NET-module uit stap 2 dient geen niet-.NET afnemers. Dat aanvaarden wij,
+omdat stap 4 dat geval dekt zodra het echt is. Stap 3 vraagt een afgesproken schema voor het
+verwerkingsevent, stabiel genoeg voor OpenMetadata om te consumeren.
+
+**Vervolgwerk:**
+
+1. Neem stap 3 als expliciet integratiepunt op in beide projectpagina's in het Innovation Lab-repo:
+   `projects/open-register-fd/README.md` en `projects/openmetadata/README.md`.
+2. Herzie de trigger van stap 4 bij elke portfolio-review. Bouw niet vooruit.
+3. Regel governance op het schema van het verwerkingsevent; dat is een gedeelde afhankelijkheid van
+   stap 1 en stap 3.
+
+## Overwogen alternatieven
+
+- **De taalonafhankelijke gateway vooraf bouwen** — afgewezen: speculatieve architectuur voordat er een
+  tweede afnemer bestaat. De latency en de operationele kosten zijn niet te rechtvaardigen.
+- **De spine in OpenMetadata inbouwen** — afgewezen: OpenMetadata is geen afnemer. Dit is een
+  categoriefout.
+- **De spine permanent in-process houden, zonder extractie** — afgewezen: dat geeft het hergebruik
+  tussen projecten en applicaties weg, en dat is een kerndoel van de Open Register-inzet.
@@ -0,0 +1,27 @@
+# ADR-NNNN: <titel>
+
+- **Status:** proposed
+- **Datum:** JJJJ-MM-DD
+- **Deciders:** <rollen>
+- **Vervangt / vervangen door:** —
+
+## Context
+
+<De krachten die spelen: het probleem, de beperkingen, de FDS- en AVG-drijfveren. Waarom er nu een
+besluit nodig is.>
+
+## Besluit
+
+<De keuze, eenvoudig gesteld.>
+
+## Gevolgen
+
+**Positief:** <wat dit oplevert>
+
+**Negatief en kosten:** <wat het kost, en wat wij aanvaarden>
+
+**Vervolgwerk:** <welk werk dit oproept>
+
+## Overwogen alternatieven
+
+<De afgewezen opties, en waarom.>
@@ -0,0 +1,127 @@
+# C4-componentview — register-applicatie en capability-laag
+
+> Niveau 3, de componentview. Deze view zoomt in op de container van de .NET register-applicatie uit
+> het L2-containerdiagram. Zij verbindt het geheel op componentniveau — domein, ports, adapters en de
+> FDS-capability-componenten — en toont waar elk onderdeel externe tooling raakt.
+>
+> De hexagonale structuur is expliciet: het domein hangt alleen af van **ports** (interfaces). Elke
+> concrete capability is een **adapter** die aan een port is gebonden.
+>
+> De containerview (L2), de blauwdruk en de privacy-datastroomviews staan in het Innovation Lab-repo,
+> `Respellion/innovation-lab`, onder `projects/open-register-fd/`.
+
+```mermaid
+C4Component
+    title Componentview — register-applicatie (.NET) en de FDS-capability-laag
+
+    Person(user, "Behandelaar", "Behandelt zaken")
+    Container(spa, "Frontend", "Angular + NL Design System", "Zaakinterface")
+
+    Container_Boundary(app, "Register-applicatie (.NET, hexagonaal)") {
+        Component(api, "API / application services", ".NET", "Orkestreert use cases; verklaart doelbinding per vraag")
+        Component(domain, "Domeinmodel", ".NET / DDD", "Ubiquitous language; geen registervocabulaire")
+
+        Component(portReg, "Register Port", "interface", "De vraag van het domein: Personen / Organisaties")
+        Component(portPol, "Authorisation Port", "interface", "mag-deze-verwerking-doorgaan?")
+        Component(portLog, "Verwerking Port", "interface", "leg de verwerkingsgebeurtenis vast")
+        Component(portTm, "Terugmelding Port", "interface", "meld een vermoedelijke fout")
+        Component(portCache, "Cache Port", "interface", "doelgebonden lezen, schrijven en verwijderen")
+
+        Component(aclBrp, "BRP-adapter", ".NET", "Vertaalt domein<->BRP; minimale velden")
+        Component(aclKvk, "NHR/KVK-adapter", ".NET", "Vertaalt domein<->NHR; UBO-bewust")
+        Component(pdpClient, "PDP Client", ".NET -> OPA", "Roept de policy engine; geeft doel en grondslag mee")
+        Component(ldvEmit, "LDV Emitter", ".NET", "Bouwt het verwerkingsevent; publiceert naar Redpanda")
+        Component(fscClient, "FSC Client", ".NET", "Stuurt contractuele aanroepen via de outway")
+        Component(cacheMgr, "Cache Manager", ".NET", "TTL en verwijderen op subjectsleutel")
+        Component(tmHandler, "Terugmelding Handler", ".NET -> Flowable", "Start het terugmeldproces")
+        Component(procClient, "Process Client", ".NET -> Flowable", "Uitvoering van BPMN en DMN")
+    }
+
+    System_Ext(opa, "OPA (PDP)", "Policies geversioneerd in Gitea")
+    System_Ext(fsc, "FSC Outway", "EUPL-referentie-implementatie")
+    System_Ext(flowable, "Flowable", "BPMN + DMN")
+    ContainerDb_Ext(cache, "Begrensde cache", "PostgreSQL")
+    System_Ext(redpanda, "Redpanda", "LDV-topic + CDC")
+    System_Ext(brp, "BRP", "via FSC inway")
+    System_Ext(kvk, "NHR / KVK", "via FSC inway")
+    System_Ext(kanidm, "Kanidm", "OIDC")
+
+    Rel(user, spa, "Gebruikt")
+    Rel(spa, api, "REST/JSON")
+    Rel(kanidm, api, "OIDC", "authenticatie")
+    Rel(api, domain, "Roept aan")
+    Rel(api, portPol, "Controleert vóór de bevraging")
+    Rel(api, portReg, "Vraagt data")
+    Rel(api, portTm, "Dient melding in")
+    Rel(api, procClient, "Voert proces uit")
+
+    Rel(portPol, pdpClient, "gebonden aan")
+    Rel(pdpClient, opa, "besluitverzoek")
+
+    Rel(portReg, aclBrp, "gebonden aan")
+    Rel(portReg, aclKvk, "gebonden aan")
+    Rel(aclBrp, fscClient, "via")
+    Rel(aclKvk, fscClient, "via")
+    Rel(aclBrp, portLog, "stuurt event")
+    Rel(aclKvk, portLog, "stuurt event")
+    Rel(aclBrp, portCache, "leest en schrijft")
+    Rel(aclKvk, portCache, "leest en schrijft")
+    Rel(fscClient, fsc, "contractuele aanroep")
+    Rel(fsc, brp, "mTLS + contract")
+    Rel(fsc, kvk, "mTLS + contract")
+
+    Rel(portLog, ldvEmit, "gebonden aan")
+    Rel(ldvEmit, redpanda, "publiceert")
+    Rel(portCache, cacheMgr, "gebonden aan")
+    Rel(cacheMgr, cache, "slaat op")
+    Rel(portTm, tmHandler, "gebonden aan")
+    Rel(tmHandler, flowable, "start proces")
+    Rel(procClient, flowable, "voert uit")
+```
+
+## Hoe je dit leest
+
+1. **De ports zijn de naad.** Het domein en de application services hangen af van de vijf interfaces,
+   en nooit van adapters. FSC wisselen voor DSP, of OPA voor de latere FTV-client, verandert een
+   adapter — geen port, en niet het domein. Dit is de clock-speed boundary, concreet gemaakt.
+2. **De compliance-componenten zijn adapters, geen domeinlogica.** De PDP-client, de LDV-emitter, de
+   FSC-client en de cache manager staan allemaal aan de adapterzijde. Een bevraging kan er fysiek niet
+   langs, omdat de adapter die de Register Port vervult dezelfde code is die het LDV-event uitstuurt
+   en via FSC routeert.
+3. **Slechts twee componenten raken de registers**: de BRP-adapter en de NHR/KVK-adapter. Beide
+   bereiken ze uitsluitend via de FSC-client. Er is geen vierde pad.
+
+## Componenten tegenover verplichtingen
+
+| Component | Omvang eigen bouw | Verplichting die het afdekt |
+|---|---|---|
+| Domeinmodel | het product | correctheid van de bedrijfsregels |
+| BRP- en NHR-adapters | dun | dataminimalisatie: vertalen en velden versmallen |
+| PDP Client | klein | handhaven van grondslag en doelbinding |
+| LDV Emitter | klein | verwerkingenlog (AVG art. 30 en LDV) |
+| FSC Client | klein | geautoriseerde, gelogde connectiviteit |
+| Cache Manager | klein | grenzen aan bewaring, en verwijdering |
+| Terugmelding Handler | klein | de terugmeldplicht van de afnemer |
+
+---
+
+## Aanvullende views die voor engineers waarde hebben
+
+De diagrammen tot hier verklaren *structuur* en *compliance-intentie*. Engineers die dit bouwen,
+hebben er nog een aantal nodig. Wij tekenen geen view voordat er iets echt is om te beschrijven, dus
+elke regel noemt de trigger.
+
+| # | View | Wat het toevoegt | Trigger |
+|---|---|---|---|
+| 1 | **Deploymentview** (C4 deployment, topologie) | Waar elke container op De Werf draait: k3s-namespaces, welke services sidecar zijn en welke een eigen pod (is OPA een sidecar of centraal? waar eindigt de FSC outway?), netwerkpolicies tussen de vlakken van de vertrouwensgrens, en beheer van secrets en mTLS-certificaten voor FSC. Hier worden de privacy*grenzen* echte firewall- en netwerkregels. | Vóór de eerste deploy met meerdere services. **Hoogste waarde als volgende.** |
+| 2 | **Sequences voor de niet-gelukkige paden** | Wij hebben het gelukkige pad. Engineers hebben de lastige nodig: PDP-*deny* midden in een transactie, een verlopen of ingetrokken FSC-contract, een register-timeout terwijl er een verouderde cache-entry ligt, en een gedeeltelijk NHR-antwoord waarbij een UBO-veld is achtergehouden. Dit bepaalt de foutafhandeling, en hier verstoppen de compliance-randgevallen zich. | Direct na slice 1. |
+| 3 | **Domeinmodel en ERD** | De bounded contexts en aggregates in het domein, plus het cacheschema: welke persoonsgegevens blijven staan, op welke sleutel, en met welke purge-kolom. Dit is tegelijk het artefact dat de FG beoordeelt voor bewaartermijnen. | Zodra het domein in slice 1 stabiliseert. |
+| 4 | **Dataclassificatie- en catalogusview** | Elk veld dat een grens kruist, getagd — persoonsgegeven? bijzondere categorie? UBO-beperkt? — en gemapt op zijn classificatie in OpenMetadata. Dit stuurt de GDPR-scrubbingregels en de lineage-tags. | Beter *uit* OpenMetadata gegenereerd zodra die gevuld is, dan met de hand getekend. |
+| 5 | **Toestandsdiagram: levensloop van een cache-entry** | `fetched` → `valid` (binnen TTL) → `stale` → `purged` (TTL verstreken \| zaak gesloten \| verwijderingsverzoek). Klein, maar het pint de bewaarsemantiek vast die "begrensde cache" nu alleen in prose beschrijft. | Samen met ADR-0004-vervolgwerk. |
+| 6 | **BPMN-view: de terugmelding-workflow** | Het Flowable-proces zelf: ingediend → verstuurd naar bronhouder → bevestigd → opgelost of afgewezen. Dit is uitvoerbaar BPMN, dus het diagram en de implementatie zijn hetzelfde artefact. | Wanneer de terugmelding-slice start. |
+| 7 | **Threat model en vertrouwensgrensview** (STRIDE-stijl) | Dreigingen over de vertrouwensgrens leggen: tokendiefstal, cache poisoning, replay tegen FSC, policy bypass, en manipulatie van logs. Past natuurlijk bij de FSC-zoom, en is het anker van het securitygesprek. | Vóór het verwerken van echte persoonsgegevens. |
+| 8 | **CI/CD- en policy-promotieview** | Hoe OPA-policies en BPMN/DMN-modellen van een pull request naar draaiende configuratie gaan. "Toegangsbeheer is configuratie in Gitea" geldt alleen als er een pijplijn is die review en promotie handhaaft. | Samen met het vervolgwerk uit ADR-0003. |
+
+**Voorstel voor de volgende twee.** De **deploymentview**, omdat die de privacygrenzen omzet in
+handhaafbare netwerkpolicy. En de **sequences voor de niet-gelukkige paden**, omdat compliance daar
+werkelijk breekt.
@@ -0,0 +1,103 @@
+# POC-voorstel — slice 1: walking skeleton (één register, gegoverneerde bevraging)
+
+> Klaar om in een `poc-voorstel`-issue te plakken, met de labels `build` en `poc`. Dit is het bouwbare
+> eerste increment dat de architectuurdocumenten beschrijven. Het bewijst met opzet de
+> *compliance-spine* end-to-end op de dunst mogelijke functionaliteit.
+
+## Probleem en strategische vraag
+
+Kunnen wij een registerbevraging demonstreren die *structureel* gegoverneerd is — onmogelijk uit te
+voeren zonder gehandhaafde grondslag en een automatische regel in het verwerkingenlog — op onze
+soevereine stack?
+
+Dit is de geloofwaardigheidstoets achter de hele Open Register-inzet (slice 1 van het charter) en
+achter de FDS gap-analyse.
+
+## Hypothese
+
+Wij verwachten dat het doorverbinden van één registerbevraging door de volledige capability-spine —
+Register Port → ACL-adapter → PDP-controle → FSC-aanroep → LDV-emissie → begrensde cache — de claim
+"compliance is structureel" bewijst.
+
+Wij weten dat wij het goed hebben als een geautomatiseerde test aantoont dat een bevraging **niet** kan
+voltooien als de PDP weigert, en **altijd** een LDV-event oplevert als de PDP toestaat.
+
+## Scope ter grootte van één blok
+
+**Wel in scope**
+
+| Onderdeel | Wat |
+|---|---|
+| Register | **NHR/KVK**, basisgegevens over onderneming en bestuurder. Gekozen boven BRP; zie de slotnotitie. |
+| Use case | Geef bij een KVK-nummer de geregistreerde organisatie terug aan het domein, voor één verklaard doel. |
+| Ports | De vijf ports als interface. Concrete adapters: NHR-ACL, PDP-client (OPA), FSC-client met sandbox- of test-outway, LDV-emitter (Redpanda-topic), en cache manager (PostgreSQL met TTL). |
+| Policy | OPA draait met één handgeschreven voorbeeldpolicy in Gitea: één allow-regel en één deny-geval. |
+| Log | Verwerkingsevent-schema v0 plus een minimale bevraagbare projectie; een tabelweergave is genoeg. |
+| Tests | Tests die de twee compliance-invarianten vastleggen: deny blokkeert, allow logt. |
+
+**Niet in scope** — even belangrijk om op te schrijven.
+
+1. Afgewerkte interface of NL Design System-schermen, verder dan een dev-harness.
+2. BRP en paden met veel persoonsgegevens. Die gaan naar slice 2, met een door de FG beoordeelde
+   policy.
+3. UBO-data. Het regime van beperkte toegankelijkheid valt buiten deze slice.
+4. De terugmelding-workflow (latere slice), DCAT-export, en Superset-dashboards.
+5. Echte register-endpoints. Alleen sandbox en stubs.
+
+## Definition of Done
+
+- [ ] Een bevraging op KVK-nummer geeft een domein-`Organisatie` terug via de NHR-ACL-adapter, zonder
+      registervocabulaire in het domein (ADR-0001).
+- [ ] De aanroep loopt via de FSC-client naar een sandbox-outway, en niet via een ruwe HTTP-client
+      (ADR-0002).
+- [ ] Er vindt geen bevraging plaats tenzij de PDP allow teruggeeft voor de combinatie rol, doel en
+      grondslag (ADR-0003).
+- [ ] Elke toegestane bevraging stuurt precies één verwerkingsevent naar Redpanda, bevraagbaar in de
+      projectie, zonder opgehaalde waarden (ADR-0005).
+- [ ] Cache-entries dragen een TTL en een subjectsleutel; een purge-aanroep verwijdert ze (ADR-0004).
+- [ ] **De tests op de compliance-invarianten slagen in CI:** (a) PDP-deny betekent geen FSC-aanroep;
+      (b) PDP-allow betekent precies één LDV-event; (c) te ruim gevraagde velden bereiken het domein
+      nooit.
+- [ ] Het geheel draait lokaal uit een gedocumenteerd `compose`- of k3s-manifest met stubs, zonder
+      echte registertoegang.
+- [ ] ADR-0001 tot en met ADR-0005 zijn vanuit de code gelinkt. Eén nieuwe ADR als er in slice 1 een
+      besluit ontstaat.
+
+## Acceptatiedemo (bewijs voor de week-3-toets)
+
+Live: een geslaagde bevraging plus de bijbehorende LDV-regel. Zet daarna de policy op deny en toon
+dezelfde bevraging geweigerd, zonder registeraanroep en zonder data.
+
+Dat contrast *is* de demo.
+
+## Ontvangende Delivery Circle (voorlopig)
+
+De register-reference Delivery Circle. De Handoff-ontvanger krijgt bij de kickoff een naam.
+
+Waarschijnlijke adoptie: de capability-spine wordt het herbruikbare substraat voor de
+register-reference-applicatie.
+
+## Upstream-kandidaten
+
+| Project | Wat wij kunnen bijdragen |
+|---|---|
+| fsc-nlx | Ergonomie van de sandbox en testomgeving, plus documentatie |
+| OPA | Policy-patronen voor het modelleren van Nederlandse grondslagen |
+| OpenMetadata | Later een DCAT-AP-NL exporter; dit verbindt het OpenMetadata-project |
+
+## AVG- en soevereiniteitsoverwegingen
+
+Alleen NHR-basisgegevens, over onderneming en bestuurder, en in slice 1 **gestubd**. Er worden geen
+echte persoonsgegevens verwerkt.
+
+Een FG-review is een voorwaarde voor slice 2, met echte data en BRP. Alle componenten draaien
+zelfgehost op De Werf; OPA-policies en BPMN staan in Gitea.
+
+## Slotnotitie: waarom NHR vóór BRP voor het skeleton
+
+Beide registers bevatten persoonsgegevens, dus geen van beide is "gratis". NHR-basisgegevens over
+onderneming en bestuurder zijn echter minder gevoelig dan BRP-gegevens over inwoners, en er is een
+duidelijker verhaal rond een publieke sandbox.
+
+Zo bewijst slice 1 het *mechanisme*, voordat slice 2 BRP oppakt onder een door de FG beoordeelde
+policy. UBO-data blijft buiten scope tot het toegangsregime is gemodelleerd.
@@ -5,6 +5,43 @@ copy-pasteable walkthrough against a local `make up` stack.

 ---

+## S-19a — approval writes the register record to Objecten (#149, ADR-0028)
+
+**Outcome:** approving a registration no longer only moves the ZGW zaak to its eindstatus — it also
+writes the canonical **register record** into the **Objecten** API. OpenZaak keeps the process,
+Objecten holds the register. The write goes through the ACL (§8.1) and is **idempotent**: replaying an
+approval updates the existing object instead of creating a second one.
+
+```bash
+# 1. Bring the stack up (Objecten, Objecttypen and the RegisterRecord objecttype come with it).
+make up
+#
+# 2. End-to-end: the walking-skeleton e2e submits, approves via the behandel portal, and then
+#    asserts Objecten holds exactly one RegisterRecord for *that* registration:
+make verify-e2e        # → "DigiD submit → … → behandelaar goedkeurt → public INGESCHREVEN"
+#
+# 3. The ACL integration test proves the same writes against a live Objecten (upsert stays one object):
+make verify-acl        # → "Writes a register record and updates it in place on a second write"
+#
+# 4. See it for yourself — every register record currently in Objecten:
+curl -s -H 'Authorization: Token 1234567890abcdef1234567890abcdef12345678' \
+     -H 'Accept-Crs: EPSG:4326' \
+     'http://localhost:8021/api/v2/objects' | python3 -m json.tool
+```
+
+Each object's `record.data` carries exactly `id`, `status`, `reference` — the schema forbids anything
+else (ADR-0027), so no personal data can reach the world-readable register even by mistake.
+
+**The path:** behandel portal → BFF → domain `BeoordeelRegistratie` → ACL `POST /statussen` → ZGW
+`resultaten` + `statussen` (the process), **then** ACL → Objecten `POST`/`PATCH /api/v2/objects` (the
+register). The objecttype URL is resolved by name from Objecttypen on first use, so nothing seed-time
+is pinned in config (ADR-0028, same reasoning as ADR-0021).
+
+**Not yet:** the public register still reads the NRC-derived projection — re-sourcing it from Objecten
+is S-19b (#150).
+
+---
+
 ## S-18c — RegisterRecord objecttype defined + registered (#141, ADR-0027)

 **Outcome:** a **RegisterRecord** objecttype with a **published** JSON schema is registered in the
@@ -9,6 +9,9 @@ should teach.
 - **[Product Requirements](PRD.md)** — what we're building and why.
 - **[ADR-0001: Loose coupling](architecture/adr-0001-loose-coupling.md)** — the
  non-negotiable integration stance; the template for future ADRs.
+- **[FDS architecture](architecture/fds/README.md)** — participating in the Federatief
+  Datastelsel as an afnemer: FDS ADR-0001…0006, the L3 component view, the slice-1 proposal.
+  In Dutch; the strategic framing lives in `Respellion/innovation-lab`.
 - **[Working in Gitea](gitea-workflow.md)** — issues, milestones, branches, PRs.
 - **[CI runbook](runbooks/ci.md)** — the pipeline and the `make ci` local gate.

@@ -338,6 +338,15 @@ services:
      Acl__Defaults__Vertrouwelijkheidaanduiding: openbaar
      Acl__Defaults__ZaaktypeIdentificatie: BIG-REGISTRATIE
      Acl__Defaults__InformatieobjecttypeOmschrijving: Diploma
+      # Objecten holds the register, OpenZaak holds the process (S-19a, ADR-0028). Both APIs take a
+      # static token, not a ZGW JWT. The objecttype URL is assigned at seed time, so the ACL resolves
+      # it by name — lazily, on the first approval, so no depends_on is needed here.
+      # Dotted host on purpose — see the `objecten.local` alias below (ADR-0029).
+      Acl__Objecten__BaseUrl: http://objecten.local:8000/
+      Acl__Objecten__Token: ${OBJECTEN_TOKEN:-1234567890abcdef1234567890abcdef12345678}
+      Acl__Objecten__ObjecttypenBaseUrl: http://objecttypen:8000/
+      Acl__Objecten__ObjecttypenToken: ${OBJECTTYPEN_TOKEN:-0123456789abcdef0123456789abcdef01234567}
+      Acl__Objecten__ObjecttypeName: RegisterRecord
    ports:
      - "8100:8080"
    volumes:
@@ -683,6 +692,14 @@ services:
      CACHE_AXES: objecten-redis:6379/0
      DISABLE_2FA: "true"
      OTEL_SDK_DISABLED: "true"
+      CELERY_BROKER_URL: redis://objecten-redis:6379/1
+      CELERY_RESULT_BACKEND: redis://objecten-redis:6379/1
+      # Publish register-record events to NRC on the `objecten` kanaal (S-19b-1, ADR-0029). The NRC
+      # service + notifications_config are provisioned by setup_configuration
+      # (infra/objecten/setup_configuration/data.yaml), and objecten-celery below actually sends
+      # them — notifications_api_common only queues the task. See ADR-0028 for why S-19a left this
+      # off until all four pieces existed.
+      NOTIFICATIONS_DISABLED: "false"
      RUN_SETUP_CONFIG: "true"
    command: /setup_configuration.sh
    volumes:
@@ -707,6 +724,28 @@ services:
      start_period: 30s
    ports:
      - "8021:8000"
+    depends_on:
+      objecten-init:
+        condition: service_completed_successfully
+    networks:
+      cg:
+        # Objecten reflects the *request* Host into the `url` it returns, and
+        # notifications_api_common publishes that url as the notification's hoofdObject /
+        # resourceUrl — which NRC types as a URLField, and Django's URLValidator rejects a
+        # single-label host ("Voer een geldige URL in."). So every caller whose writes must be
+        # notified addresses Objecten by this dotted alias instead of `objecten` (ADR-0029).
+        # Reads are unaffected and still use the plain service name.
+        aliases:
+          - objecten.local
+
+  # The celery worker that actually delivers Objecten's notifications to NRC (S-19b-1, ADR-0029).
+  # notifications_api_common only schedules the send on transaction commit; without a worker the
+  # task sits in redis forever and every register write is silently undelivered. Mirrors oz-celery.
+  # No beat: Objecten is a publisher, not a subscriber — nrc-beat drains the delivery queue.
+  objecten-celery:
+    image: docker.io/maykinmedia/objects-api:${OBJECTS_TAG:-3.4.0}
+    environment: *objecten-env-local
+    command: /celery_worker.sh
    depends_on:
      objecten-init:
        condition: service_completed_successfully
@@ -323,6 +323,15 @@ services:
      # so verify-domain still points the ACL at OpenZaak's container IP.
      Acl__Defaults__ZaaktypeIdentificatie: BIG-REGISTRATIE
      Acl__Defaults__InformatieobjecttypeOmschrijving: Diploma
+      # Objecten holds the register, OpenZaak holds the process (S-19a, ADR-0028). Both APIs take a
+      # static token, not a ZGW JWT. The objecttype URL is assigned at seed time, so the ACL resolves
+      # it by name — lazily, on the first approval, so no depends_on is needed here.
+      # Dotted host on purpose — see the `objecten.local` alias below (ADR-0029).
+      Acl__Objecten__BaseUrl: http://objecten.local:8000/
+      Acl__Objecten__Token: ${OBJECTEN_TOKEN:-1234567890abcdef1234567890abcdef12345678}
+      Acl__Objecten__ObjecttypenBaseUrl: http://objecttypen:8000/
+      Acl__Objecten__ObjecttypenToken: ${OBJECTTYPEN_TOKEN:-0123456789abcdef0123456789abcdef01234567}
+      Acl__Objecten__ObjecttypeName: RegisterRecord
    ports:
      - "8100:8080"
    healthcheck:
@@ -709,6 +718,14 @@ services:
      CACHE_AXES: objecten-redis:6379/0
      DISABLE_2FA: "true"
      OTEL_SDK_DISABLED: "true"
+      CELERY_BROKER_URL: redis://objecten-redis:6379/1
+      CELERY_RESULT_BACKEND: redis://objecten-redis:6379/1
+      # Publish register-record events to NRC on the `objecten` kanaal (S-19b-1, ADR-0029). The NRC
+      # service + notifications_config are provisioned by setup_configuration
+      # (infra/objecten/setup_configuration/data.yaml), and objecten-celery below actually sends
+      # them — notifications_api_common only queues the task. See ADR-0028 for why S-19a left this
+      # off until all four pieces existed.
+      NOTIFICATIONS_DISABLED: "false"
      RUN_SETUP_CONFIG: "true"
    command: /setup_configuration.sh
    # data.yaml is streamed into this external volume by infra/seed-config.sh before start.
@@ -736,6 +753,28 @@ services:
      start_period: 30s
    ports:
      - "8021:8000"
+    depends_on:
+      objecten-init:
+        condition: service_completed_successfully
+    networks:
+      cg:
+        # Objecten reflects the *request* Host into the `url` it returns, and
+        # notifications_api_common publishes that url as the notification's hoofdObject /
+        # resourceUrl — which NRC types as a URLField, and Django's URLValidator rejects a
+        # single-label host ("Voer een geldige URL in."). So every caller whose writes must be
+        # notified addresses Objecten by this dotted alias instead of `objecten` (ADR-0029).
+        # Reads are unaffected and still use the plain service name.
+        aliases:
+          - objecten.local
+
+  # The celery worker that actually delivers Objecten's notifications to NRC (S-19b-1, ADR-0029).
+  # notifications_api_common only schedules the send on transaction commit; without a worker the
+  # task sits in redis forever and every register write is silently undelivered. Mirrors oz-celery.
+  # No beat: Objecten is a publisher, not a subscriber — nrc-beat drains the delivery queue.
+  objecten-celery:
+    image: docker.io/maykinmedia/objects-api:${OBJECTS_TAG:-3.4.0}
+    environment: *objecten-env
+    command: /celery_worker.sh
    depends_on:
      objecten-init:
        condition: service_completed_successfully
@@ -2,10 +2,10 @@
 """Local-stack bootstrap (S-B04, #110, ADR-0020) — register the NRC abonnement.

 Runs as the `nrc-subscribe` init container of infra/docker-compose.local.yml. Registers an
-abonnement on the `zaken` kanaal pointing at the event-subscriber's /notifications callback, so
-OpenZaak's notifications (zaak create + status set) reach the projection — without this the openbaar
-(public) register stays empty. This is what infra/verify-notification-driver.py does for CI (minus
-the test zaak it also creates).
+abonnement on the `objecten` kanaal pointing at the event-subscriber's /notifications callback, so
+the register writes the ACL makes (INGEDIEND on submit, INGESCHREVEN on approval) reach the
+projection — without this the openbaar (public) register stays empty. Since S-19b-2 the projection
+is sourced from the register in Objecten, not from ZGW zaak events (ADR-0030).

 The callback host is the event-subscriber's resolved **container IP**, not `event-subscriber`, because
 NRC validates callbackUrl with Django's URLValidator (a single-label host is rejected — same reason the
@@ -22,6 +22,8 @@ SINK_PORT = os.environ.get("SINK_PORT", "8080")
 SINK_AUTH = os.environ.get("SINK_AUTH", "Bearer big-reference-notifications")
 CID = os.environ.get("OZ_CLIENT_ID", "big-reference-seed")
 SECRET = os.environ.get("OZ_SECRET", "insecure-dev-secret-change-me")
+# The projection is sourced from the register in Objecten, not from ZGW zaak events (S-19b-2).
+KANAAL = "objecten"


 def token():
@@ -60,7 +62,10 @@ def main():
    status, body = call("GET", f"{NRC}/api/v1/abonnement")
    for ab in (body or []) if status == 200 else []:
        if str(ab.get("callbackUrl", "")).endswith("/notifications"):
-            if ab.get("callbackUrl") == callback:
+            # The kanaal is part of "current": an abonnement left over from before S-19b-2 points at
+            # the right callback but listens on `zaken`, and would never be replaced on IP alone.
+            kanalen = [k.get("naam") for k in ab.get("kanalen", [])]
+            if ab.get("callbackUrl") == callback and kanalen == [KANAAL]:
                print(f"abonnement already current: {ab['url']}")
                return
            call("DELETE", ab["url"])
@@ -68,7 +73,7 @@ def main():

    status, ab = call("POST", f"{NRC}/api/v1/abonnement", {
        "callbackUrl": callback, "auth": SINK_AUTH,
-        "kanalen": [{"naam": "zaken", "filters": {}}]})
+        "kanalen": [{"naam": KANAAL, "filters": {}}]})
    if status != 201:
        sys.exit(f"create abonnement -> {status}: {json.dumps(ab)}")
    print(f"abonnement registered: {ab['url']} -> {callback}")
@@ -0,0 +1,121 @@
+#!/usr/bin/env python3
+"""S-19b-1 (#152): driver for the Objecten → NRC notification check.
+
+Registers an abonnement on the `objecten` kanaal pointing at the webhook sink, then writes a
+RegisterRecord object exactly as the ACL's ObjectenGateway does (S-19a). The caller
+(run-objecten-notifications-check.sh) watches the sink for the delivery — this only sets it up,
+and prints `OBJECT_URL <url>` for the caller to grep on.
+
+Delivery exercises the whole chain: Objecten → its celery worker → NRC → nrc-beat → the callback.
+Anything missing (broker, worker, kanaal, notifications config) shows up as a non-delivery.
+
+Stdlib only so it runs in a bare python:3-slim container on the compose network.
+"""
+import base64
+import hashlib
+import hmac
+import json
+import os
+import sys
+import time
+import urllib.error
+import urllib.request
+
+OBJECTEN = os.environ["OBJECTEN"]                 # http://objecten:8000
+OBJECTEN_TOKEN = os.environ["OBJECTEN_TOKEN"]
+OBJECTTYPEN = os.environ["OBJECTTYPEN"]           # http://objecttypen:8000
+OBJECTTYPEN_TOKEN = os.environ["OBJECTTYPEN_TOKEN"]
+NRC_BASE = os.environ["NRC_BASE"]                 # http://<nrc-ip>:8000
+SINK_CALLBACK = os.environ["SINK_CALLBACK"]       # http://<sink-ip>:9000/
+SINK_AUTH = os.environ["SINK_AUTH"]
+CLIENT_ID = os.environ.get("NRC_CLIENT_ID", "big-reference-seed")
+SECRET = os.environ.get("NRC_SECRET", "insecure-dev-secret-change-me")
+KANAAL = "objecten"
+
+
+def mint():
+    """The HS256 JWT NRC expects (same shape as infra/local/register-abonnement.py)."""
+    def seg(d):
+        return base64.urlsafe_b64encode(json.dumps(d).encode()).rstrip(b"=")
+
+    payload = seg({
+        "iss": CLIENT_ID, "iat": int(time.time()), "client_id": CLIENT_ID,
+        "user_id": CLIENT_ID, "user_representation": CLIENT_ID,
+    })
+    signing_input = seg({"typ": "JWT", "alg": "HS256"}) + b"." + payload
+    signature = base64.urlsafe_b64encode(
+        hmac.new(SECRET.encode(), signing_input, hashlib.sha256).digest()).rstrip(b"=")
+    return (signing_input + b"." + signature).decode()
+
+
+def nrc(method, url, body=None):
+    """Call NRC. `url` may be a path or an absolute URL (the list returns absolute ones)."""
+    data = json.dumps(body).encode() if body is not None else None
+    req = urllib.request.Request(
+        url if url.startswith("http") else f"{NRC_BASE}{url}", data=data, method=method,
+        headers={"Authorization": f"Bearer {mint()}", "Content-Type": "application/json"})
+    try:
+        with urllib.request.urlopen(req, timeout=15) as r:
+            return json.load(r) if r.length != 0 else {}
+    except urllib.error.HTTPError as e:
+        # The body carries the reason (e.g. an unregistered kanaal); the status alone does not.
+        raise SystemExit(f"FAIL — NRC {method} {url} → {e.code}: {e.read().decode(errors='replace')[:400]}")
+
+
+def token_api(base, token, method, path, body=None, crs=False):
+    data = json.dumps(body).encode() if body is not None else None
+    headers = {"Authorization": f"Token {token}"}
+    if body is not None:
+        headers["Content-Type"] = "application/json"
+    if crs:
+        headers["Accept-Crs"] = "EPSG:4326"
+        if body is not None:
+            headers["Content-Crs"] = "EPSG:4326"
+    req = urllib.request.Request(f"{base}{path}", data=data, method=method, headers=headers)
+    with urllib.request.urlopen(req, timeout=15) as r:
+        return json.load(r) if r.length != 0 else {}
+
+
+def subscribe():
+    """Register an abonnement on the objecten kanaal, replacing a stale one for the same callback."""
+    # NRC returns a bare list here, not a paginated envelope.
+    for existing in nrc("GET", "/api/v1/abonnement") or []:
+        if existing.get("callbackUrl") == SINK_CALLBACK:
+            nrc("DELETE", existing["url"])
+    nrc("POST", "/api/v1/abonnement", {
+        "callbackUrl": SINK_CALLBACK,
+        "auth": SINK_AUTH,
+        "kanalen": [{"naam": KANAAL, "filters": {}}],
+    })
+    print(f">> abonnement on '{KANAAL}' -> {SINK_CALLBACK}")
+
+
+def objecttype_url():
+    results = token_api(OBJECTTYPEN, OBJECTTYPEN_TOKEN, "GET", "/api/v2/objecttypes").get("results", [])
+    match = next((o for o in results if o.get("name") == "RegisterRecord"), None)
+    if not match:
+        print("FAIL — no RegisterRecord objecttype in Objecttypen", file=sys.stderr)
+        raise SystemExit(1)
+    return match["url"]
+
+
+def main():
+    subscribe()
+    reference = f"NOTIF-{int(time.time())}"
+    created = token_api(OBJECTEN, OBJECTEN_TOKEN, "POST", "/api/v2/objects", {
+        "type": objecttype_url(),
+        "record": {
+            "typeVersion": 1,
+            "data": {"id": f"zaak-{reference}", "status": "INGESCHREVEN", "reference": reference},
+            "startAt": time.strftime("%Y-%m-%d"),
+        },
+    }, crs=True)
+    print(f">> wrote RegisterRecord {created['url']}")
+    # An NRC notification carries no record data — only hoofdObject/resourceUrl — so the object
+    # URL, not the reference in its data, is what the caller can correlate the delivery on.
+    print(f"OBJECT_URL {created['url']}")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
@@ -18,8 +18,29 @@ zgw_consumers:
      auth_type: api_key
      header_key: Authorization
      header_value: Token 0123456789abcdef0123456789abcdef01234567
+    # (1b) The NRC Objecten publishes register-record events to (S-19b-1, ADR-0029). Same shape and
+    # same big-reference-seed credential OpenZaak publishes with — NRC verifies the JWT and
+    # authorizes it via OpenZaak's AC, which grants that client heeft_alle_autorisaties.
+    - identifier: nrc
+      label: Open Notificaties
+      api_type: nrc
+      api_root: http://nrc-web:8000/api/v1/
+      auth_type: zgw
+      client_id: big-reference-seed
+      secret: insecure-dev-secret-change-me

-# (2) Static API token peers use to write/read objects.
+# (2) Permit the RegisterRecord objecttype (S-19a). Objecten refuses to store an object whose
+# objecttype it has not been configured with ("ObjectType with url=… is not configured"), and it
+# identifies one by uuid — which is why infra/objecttypen-registerrecord/register.py pins that uuid
+# instead of letting Objecttypen assign one. Keep the two in step.
+objecttypes_config_enable: true
+objecttypes:
+  items:
+    - uuid: 1f4b4e26-8b1f-4e2f-9d6c-6a1b7a2f0e01
+      name: RegisterRecord
+      service_identifier: objecttypen
+
+# (3) Static API token peers use to write/read objects.
 tokenauth_config_enable: true
 tokenauth:
  items:
@@ -29,3 +50,10 @@ tokenauth:
      email: admin@localhost
      organization: Respellion
      is_superuser: true
+
+# (4) Point Objecten's notifications at that NRC service (S-19b-1, ADR-0029). Requires
+# NOTIFICATIONS_DISABLED=false plus a celery broker + worker — without the worker the message is
+# queued and never sent, which is exactly the half-wired state S-19a refused to ship (ADR-0028).
+notifications_config_enable: true
+notifications_config:
+  notifications_api_service_identifier: nrc
@@ -17,6 +17,11 @@ BASE = os.environ.get("OBJECTTYPEN", "http://objecttypen:8000").rstrip("/")
 TOKEN = os.environ["OBJECTTYPEN_TOKEN"]
 SCHEMA_PATH = os.environ.get("SCHEMA", "/config/registerrecord.schema.json")
 NAME = "RegisterRecord"
+# Pinned rather than server-assigned (S-19a): the Objecten API will only accept objects whose
+# objecttype it has been configured with *by uuid*, and its own setup_configuration is a static
+# file applied before this one-shot runs. A fixed uuid lets both sides be declared up front instead
+# of threading a seed-time value between two containers. See infra/objecten/setup_configuration.
+UUID = "1f4b4e26-8b1f-4e2f-9d6c-6a1b7a2f0e01"


 def api(method, path, body=None):
@@ -53,6 +58,7 @@ def main():
        return 0

    ot = existing or api("POST", "/api/v2/objecttypes", {
+        "uuid": UUID,
        "name": NAME,
        "namePlural": "RegisterRecords",
        "description": schema.get("description", ""),
@@ -25,3 +25,15 @@ storage:
      path: /var/tempo/blocks
    wal:
      path: /var/tempo/wal
+
+# #156: don't let the distributor evict its own ingester. Tempo runs single-binary here, so the
+# distributor and the ingester are the same process and the "pool" holds exactly one, in-process,
+# member. dskit still health-checks it over loopback gRPC with a 1s deadline (checkinterval 15s);
+# on the shared CI runner a transient stall blows that deadline, the only ingester is dropped from
+# the pool ("removing distributor_pool failing healthcheck"), and every push then fails ("pusher
+# failed to consume trace data", err="context canceled") until the next check — silently losing
+# spans, which is how verify-tracing flaked. With one in-process ingester the check can never route
+# around a failure, so it can only ever discard data. Turn it off.
+ingester_client:
+  pool_config:
+    healthcheckenabled: false
@@ -29,7 +29,9 @@ autorisaties_api_config_enable: true
 autorisaties_api:
  authorizations_api_service_identifier: openzaak-ac

-# 4. The kanaal OpenZaak publishes zaak events on.
+# 4. The kanalen publishers announce on: `zaken` (OpenZaak) and `objecten` (Objecten, S-19b-1).
+# Both authenticate with the big-reference-seed credential above, which OpenZaak's AC grants
+# heeft_alle_autorisaties — so no separate publisher authorization is needed for Objecten.
 notifications_kanalen_config_enable: true
 notifications_kanalen_config:
  items:
@@ -39,3 +41,11 @@ notifications_kanalen_config:
        - bronorganisatie
        - zaaktype
        - vertrouwelijkheidaanduiding
+    # 5. The kanaal Objecten publishes register-record events on (S-19b-1, ADR-0029). Its name is
+    # fixed by the Objects API itself (NOTIFICATIONS_KANAAL = "objecten"), not chosen here. The
+    # filter set matches what the Objects API sends as kenmerken, so an abonnement can narrow by
+    # objecttype rather than receiving every object write in the register.
+    - naam: objecten
+      documentatie_link: https://objects-and-objecttypes-api.readthedocs.io/
+      filters:
+        - object_type
@@ -142,6 +142,7 @@ still="$(printf '%s' "$resp" | task_for_reg "$reg_id")"
 [ -z "$still" ] || { echo "FAIL — Beoordelen task $still still active after completion" >&2; exit 1; }
 echo "OK — behandelaar claimed and completed the Beoordelen task; the registratie process finished"

+
 # ── S-11: withdrawal. A second registration parks at Beoordelen; the citizen withdraws it via the
 # domain, which delivers the RegistratieIngetrokken message to the task's execution, tripping the
 # BPMN boundary event so the process ends and the Beoordelen task disappears (ADR-0014). ────────────
@@ -0,0 +1,83 @@
+#!/usr/bin/env bash
+#
+# S-19b-1 (#152): verify the Objecten → NRC notification path against an ALREADY-RUNNING full
+# stack. Registers an abonnement on the `objecten` kanaal pointing at a throwaway webhook sink,
+# writes a RegisterRecord object (exactly as the ACL does on approval, S-19a), and asserts the sink
+# receives the notification.
+#
+# This is the whole publish chain in one assertion: Objecten → its celery worker → NRC → nrc-beat →
+# the subscriber callback. S-19a deliberately left it disconnected (ADR-0028); this proves it is
+# connected for real, rather than merely configured.
+#
+# All in-network, reaching services by container IP (a single-label host isn't URL-valid for NRC's
+# callbackUrl validator; the runner can't reach published ports — gitea-actions-gotchas.md §5/§6).
+# EXCEPT Objecttypen, which must be reached by SERVICE NAME: it echoes the request Host into the
+# objecttype `url` and Objecten only accepts the one matching its configured api_root (ADR-0028);
+# and Objecten, reached by its `objecten.local` alias because it reflects the request Host into the
+# notification's hoofdObject/resourceUrl, which NRC validates as a URL (ADR-0029).
+#
+# Does NOT manage the stack lifecycle, but cleans up the sink/driver it creates.
+set -euo pipefail
+
+here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+SINK_AUTH="Bearer objecten-notification-sink-token"
+
+cleanup() { docker rm -f rr-osink rr-overify >/dev/null 2>&1 || true; }
+trap cleanup EXIT
+
+ip() { docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' "$1"; }
+
+# Anchored on the compose replica suffix so they don't also match objecten-db / objecten-redis.
+obj="$(docker ps -q --filter 'name=objecten[-_][0-9]+$' | head -1)"
+nrc="$(docker ps -q --filter 'name=nrc-web' | head -1)"
+[ -n "$obj" ] || { echo "ERROR: no running objecten container — bring the stack up first" >&2; exit 1; }
+[ -n "$nrc" ] || { echo "ERROR: no running nrc-web container — bring the stack up first" >&2; exit 1; }
+net="$(docker inspect -f '{{range $k,$_ := .NetworkSettings.Networks}}{{$k}}{{"\n"}}{{end}}' "$obj" | head -1)"
+nrc_ip="$(ip "$nrc")"
+echo ">> network=$net nrc=$nrc_ip"
+
+echo ">> starting the webhook sink"
+docker rm -f rr-osink >/dev/null 2>&1 || true
+sink="$(docker create --network "$net" --name rr-osink -e "EXPECTED_AUTH=$SINK_AUTH" \
+  python:3-slim python /sink.py)"
+docker cp "$here/notification-sink.py" "$sink:/sink.py" >/dev/null
+docker start "$sink" >/dev/null
+sleep 1
+sink_ip="$(ip rr-osink)"
+echo ">> sink at $sink_ip:9000"
+
+echo ">> registering the abonnement + writing a RegisterRecord"
+docker rm -f rr-overify >/dev/null 2>&1 || true
+drv="$(docker create --network "$net" --name rr-overify \
+  -e "OBJECTEN=http://objecten.local:8000" \
+  -e "OBJECTEN_TOKEN=${OBJECTEN_TOKEN:-1234567890abcdef1234567890abcdef12345678}" \
+  -e "OBJECTTYPEN=http://objecttypen:8000" \
+  -e "OBJECTTYPEN_TOKEN=${OBJECTTYPEN_TOKEN:-0123456789abcdef0123456789abcdef01234567}" \
+  -e "NRC_BASE=http://$nrc_ip:8000" \
+  -e "SINK_CALLBACK=http://$sink_ip:9000/" -e "SINK_AUTH=$SINK_AUTH" \
+  python:3-slim python /driver.py)"
+docker cp "$here/objecten-notifications-check.py" "$drv:/driver.py" >/dev/null
+docker start -a "$drv"
+object_url="$(docker logs rr-overify 2>/dev/null | sed -n 's/^OBJECT_URL //p' | head -1)"
+docker rm -f rr-overify >/dev/null
+[ -n "$object_url" ] || { echo "FAIL — the driver did not write a RegisterRecord" >&2; exit 1; }
+echo ">> wrote $object_url"
+
+# Correlate on the object URL: a notification carries hoofdObject/resourceUrl, never the record
+# data, so the reference inside the record is not in the delivered message.
+echo ">> waiting for the notification to reach the sink"
+for _ in $(seq 1 "${NOTIFICATION_TRIES:-40}"); do
+  if docker logs rr-osink 2>&1 | grep -qF "$object_url"; then
+    echo "OK — Objecten published to NRC and the abonnement delivered it:"
+    docker logs rr-osink 2>&1 | grep -F "$object_url" | tail -1 | cut -c1-500
+    exit 0
+  fi
+  sleep 2
+done
+
+echo "FAIL — no 'objecten' notification for $object_url reached the sink." >&2
+echo "       Objecten accepted the write, so the gap is downstream: the celery broker/worker," >&2
+echo "       the kanaal registration, or Objecten's notifications_config." >&2
+echo "--- sink log ---" >&2; docker logs rr-osink 2>&1 | tail -8 >&2
+echo "--- objecten log ---" >&2; docker logs "$obj" 2>&1 | tail -15 >&2
+exit 1
@@ -1,18 +1,26 @@
 #!/usr/bin/env bash
 #
-# Verify the end-to-end read-projection path (S-06) against an ALREADY-RUNNING full stack:
-# OpenZaak → NRC → Event Subscriber → projection → projection-api. Seeds a published BIG
-# zaaktype (idempotent), registers an abonnement on the `zaken` kanaal pointing at the real
-# Event Subscriber's /notifications callback (with the bearer it enforces), creates a zaak,
-# and asserts projection-api serves a row for that zaak with status INGEDIEND.
+# Verify the end-to-end read-projection path (S-06, re-sourced by S-19b-2) against an ALREADY-RUNNING
+# full stack: ACL → Objecten → NRC → Event Subscriber → projection → projection-api. Seeds a
+# published BIG zaaktype (idempotent), registers an abonnement on the `objecten` kanaal pointing at
+# the real Event Subscriber's /notifications callback (with the bearer it enforces), opens a zaak
+# *through the ACL*, and asserts projection-api serves a row for it with status INGEDIEND.
+#
+# The zaak is opened through the ACL, not straight against OpenZaak: since ADR-0030 the projection is
+# derived from the RegisterRecord in Objecten, and the ACL is what writes that record (INGEDIEND on
+# submit). A zaak created behind the ACL's back produces no register write and so no projection row —
+# which is the point of the re-source.
 #
 # All in-network, reaching services by container IP — single-label hosts aren't URL-valid and
-# the runner can't reach published ports (gitea-actions-gotchas.md §5/§6). Reuses the
-# notification driver to register the abonnement + create the zaak. Does NOT manage the stack
-# lifecycle (the caller owns bring-up + teardown). Plain docker primitives only. See ADR-0007/0008.
+# the runner can't reach published ports (gitea-actions-gotchas.md §5/§6). Does not own the stack
+# lifecycle (the caller brings it up and tears it down), but does recreate the `acl` service to
+# repoint it — see below, and run-domain-check.sh, which does the same. Plain docker primitives only.
+# See ADR-0007/0008/0030.
 set -euo pipefail

 here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+root="$(cd "$here/.." && pwd)"
+compose="$root/infra/docker-compose.yml"
 WEBHOOK_AUTH="${NOTIFICATION_WEBHOOK_TOKEN:-Bearer big-reference-notifications}"

 cleanup() { docker rm -f rr-pverify rr-pquery >/dev/null 2>&1 || true; }
@@ -24,11 +32,13 @@ oz="$(docker ps -q --filter 'name=[-_]openzaak[-_]' | head -1)"
 nrc="$(docker ps -q --filter 'name=nrc-web' | head -1)"
 es="$(docker ps -q --filter 'name=event-subscriber' | head -1)"
 proj="$(docker ps -q --filter 'name=projection-api' | head -1)"
+acl="$(docker ps -q --filter 'name=[-_]acl[-_]' | head -1)"
 [ -n "$oz" ] && [ -n "$nrc" ] || { echo "ERROR: OpenZaak and/or NRC not running — bring the stack up first" >&2; exit 1; }
 [ -n "$es" ] && [ -n "$proj" ] || { echo "ERROR: event-subscriber and/or projection-api not running — bring the stack up first" >&2; exit 1; }
+[ -n "$acl" ] || { echo "ERROR: acl not running — bring the stack up first" >&2; exit 1; }
 net="$(docker inspect -f '{{range $k,$_ := .NetworkSettings.Networks}}{{$k}}{{"\n"}}{{end}}' "$oz" | head -1)"
-oz_ip="$(ip "$oz")"; nrc_ip="$(ip "$nrc")"; es_ip="$(ip "$es")"; proj_ip="$(ip "$proj")"
-echo ">> network=$net openzaak=$oz_ip nrc=$nrc_ip event-subscriber=$es_ip projection-api=$proj_ip"
+oz_ip="$(ip "$oz")"; nrc_ip="$(ip "$nrc")"; es_ip="$(ip "$es")"; proj_ip="$(ip "$proj")"; acl_ip="$(ip "$acl")"
+echo ">> network=$net openzaak=$oz_ip nrc=$nrc_ip event-subscriber=$es_ip projection-api=$proj_ip acl=$acl_ip"

 echo ">> seeding a published BIG zaaktype (idempotent)"
 sid="$(docker create --network "$net" -e "OZ_BASE=http://$oz_ip:8000" -e OZ_PUBLISH=1 \
@@ -37,19 +47,39 @@ docker cp "$here/openzaak/seed_catalogus.py" "$sid:/seed.py" >/dev/null
 docker start -a "$sid"
 docker rm -f "$sid" >/dev/null

-echo ">> registering abonnement at the Event Subscriber + creating a zaak"
+echo ">> registering the event-subscriber abonnement on the objecten kanaal"
 docker rm -f rr-pverify >/dev/null 2>&1 || true
+# The same script the local stack uses (ADR-0020), so both paths register the identical abonnement.
 drv="$(docker create --network "$net" --name rr-pverify \
-  -e "OZ_BASE=http://$oz_ip:8000" -e "NRC_BASE=http://$nrc_ip:8000" \
-  -e "SINK_CALLBACK=http://$es_ip:8080/notifications" -e "SINK_AUTH=$WEBHOOK_AUTH" \
-  python:3-slim python /driver.py)"
-docker cp "$here/verify-notification-driver.py" "$drv:/driver.py" >/dev/null
+  -e "NRC_BASE=http://$nrc_ip:8000" \
+  -e "SINK_HOST=$es_ip" -e "SINK_PORT=8080" -e "SINK_AUTH=$WEBHOOK_AUTH" \
+  python:3-slim python /subscribe.py)"
+docker cp "$here/local/register-abonnement.py" "$drv:/subscribe.py" >/dev/null
 docker start -a "$drv"
-zaak_url="$(docker logs rr-pverify 2>/dev/null | sed -n 's/^ZAAK_CREATED //p' | head -1)"
 docker rm -f rr-pverify >/dev/null
-[ -n "$zaak_url" ] || { echo "ERROR: driver did not create a zaak" >&2; exit 1; }
+
+# OpenZaak reflects the request Host into the zaaktype `url` it returns, and then rejects that same
+# URL on zaak-create when the host is single-label ("Voer een geldige URL in."). The stack's ACL is
+# configured with `http://openzaak:8000/`, so it must be repointed at OpenZaak's container IP before
+# it can open a zaak — exactly what run-domain-check.sh does, and the same class of constraint as the
+# `objecten.local` alias (ADR-0029). The ACL resolves the zaaktype itself (S-27, ADR-0021), so the
+# base URL is the only thing to inject.
+echo ">> recreating the acl service pointed at OpenZaak's IP"
+ACL_OPENZAAK_BASEURL="http://$oz_ip:8000/" docker compose -f "$compose" up -d acl
+WAIT_TIMEOUT="${WAIT_TIMEOUT:-120}" bash "$here/wait-healthy.sh" acl
+# The container is replaced, so its IP may have changed.
+acl="$(docker ps -q --filter 'name=[-_]acl[-_]' | head -1)"
+acl_ip="$(ip "$acl")"
+
+echo ">> opening a zaak through the ACL (which writes the INGEDIEND register record)"
+reference="PROJ-$(date +%s)"
+zaak_url="$(docker run --rm --network "$net" curlimages/curl:latest \
+  -fsS -X POST "http://$acl_ip:8080/zaken" -H 'Content-Type: application/json' \
+  -d "{\"bsn\":\"123456782\",\"reference\":\"$reference\"}" \
+  | sed -n 's/.*"zaakUrl":"\([^"]*\)".*/\1/p')"
+[ -n "$zaak_url" ] || { echo "ERROR: the ACL did not open a zaak" >&2; exit 1; }
 zaak_uuid="${zaak_url##*/}"
-echo ">> zaak created: $zaak_url"
+echo ">> zaak created: $zaak_url (reference $reference)"

 echo ">> polling projection-api for the projected row (status INGEDIEND)"
 for _ in $(seq 1 30); do
@@ -63,6 +93,8 @@ for _ in $(seq 1 30); do
  sleep 2
 done
 echo "FAIL — projection-api never served an INGEDIEND row for zaak $zaak_uuid" >&2
+echo "       The chain is ACL → Objecten → NRC → event-subscriber → projection (ADR-0030)." >&2
 echo "--- event-subscriber log ---" >&2; docker logs "$es" 2>&1 | tail -10 >&2
 echo "--- projection-api log ---" >&2; docker logs "$proj" 2>&1 | tail -10 >&2
+echo "--- acl log ---" >&2; docker logs "$acl" 2>&1 | tail -10 >&2
 exit 1
@@ -59,6 +59,20 @@ def services_in_trace(trace_id):
    return names


+def tempo_ingest_state():
+    """#156: distinguish a broken trace chain from Tempo dropping spans. `ingester_clients` is 0
+    when the distributor has evicted its (single, in-process) ingester over a failed loopback
+    health check — pushes fail and spans are lost, which looks identical to missing instrumentation
+    from here. Diagnostics only; never fails the check."""
+    try:
+        for line in _get(f"{TEMPO}/metrics").decode().splitlines():
+            if line.startswith("tempo_distributor_ingester_clients "):
+                return f"tempo {line.strip()} (0 = no ingester in the pool — evicted, so pushes\n       are failing and spans are being dropped; see #156)"
+    except Exception as e:
+        return f"tempo /metrics unreadable: {e}"
+    return "tempo_distributor_ingester_clients not reported"
+
+
 def main():
    deadline = time.time() + TIMEOUT
    generate_traffic()
@@ -74,6 +88,7 @@ def main():
        generate_traffic()
    print(f"FAIL — no single trace spanned {sorted(WANT)}; services seen: {sorted(seen)}",
          file=sys.stderr)
+    print(f"       {tempo_ingest_state()}", file=sys.stderr)
    return 1


@@ -15,9 +15,13 @@ set -euo pipefail
 timeout="${WAIT_TIMEOUT:-420}"
 deadline=$(( $(date +%s) + timeout ))

-# compose service name -> container id. The name filter matches both docker
-# compose ("infra-openzaak-1") and podman-compose ("infra_openzaak_1") naming.
-cid_for() { docker ps -aq --filter "name=$1" | head -1; }
+# compose service name -> container id. `--filter name=` is a substring match, so it is anchored on
+# the compose replica suffix — otherwise 'objecten' also matches objecten-db / objecten-redis /
+# objecten-celery, and 'objecttypen' matches objecttypen-db. Whichever docker listed first won, so a
+# service with a sibling that has no healthcheck timed out with status=none while it was in fact
+# healthy. The pattern matches both docker compose ("infra-objecten-1") and podman-compose
+# ("infra_objecten_1") naming; the same anchoring the verify check scripts use.
+cid_for() { docker ps -aq --filter "name=$1[-_][0-9]+\$" | head -1; }

 for svc in "$@"; do
  echo "waiting for '$svc' to be healthy (timeout ${timeout}s)..."
@@ -32,6 +32,17 @@ nav:
      - "ADR-0008: Read projection store": architecture/adr-0008-read-projection-store.md
      - "ADR-0009: External-task job worker": architecture/adr-0009-external-task-job-worker.md
      - "ADR-0010: BFF OIDC validation": architecture/adr-0010-bff-oidc.md
+  - FDS-architectuur:
+      - Overzicht: architecture/fds/README.md
+      - Componentview (L3): architecture/fds/c4-component-view.md
+      - "Slice 1: walking skeleton": architecture/fds/slice-1-proposal.md
+      - "FDS ADR-0001: ACL op elke registergrens": architecture/fds/adr/0001-acl-at-every-register-boundary.md
+      - "FDS ADR-0002: FSC voor connectiviteit": architecture/fds/adr/0002-fsc-for-connectivity.md
+      - "FDS ADR-0003: PBAC via OPA": architecture/fds/adr/0003-pbac-via-opa.md
+      - "FDS ADR-0004: Begrensde cache": architecture/fds/adr/0004-bounded-cache.md
+      - "FDS ADR-0005: Verwerkingenlog via events": architecture/fds/adr/0005-ldv-verwerkingenlog.md
+      - "FDS ADR-0006: Modulegrens en hergebruik": architecture/fds/adr/0006-module-boundary-and-reuse.md
+      - "FDS ADR-template": architecture/fds/adr/template.md
  - Working in Gitea: gitea-workflow.md
  - Frontend decisions: frontend-decisions.md
  - Demo script: demo-script.md
@@ -42,7 +53,11 @@ markdown_extensions:
  - admonition
  - toc:
      permalink: true
-  - pymdownx.superfences
+  - pymdownx.superfences:
+      custom_fences:
+        - name: mermaid
+          class: mermaid
+          format: !!python/name:pymdownx.superfences.fence_code_format

 # Many docs referenced by PRD.md land in later slices; don't fail the build on them.
 validation:
@@ -42,7 +42,12 @@ builder.Services.AddSingleton<IDefaultFillStore>(sp =>
    return new InMemoryDefaultFillStore(
        new DefaultFillSettings(d.Bronorganisatie, d.VerantwoordelijkeOrganisatie, d.Vertrouwelijkheidaanduiding));
 });
+builder.Services.AddSingleton(sp => sp.GetRequiredService<IConfiguration>()
+    .GetSection("Acl:Objecten").Get<ObjectenOptions>()
+    ?? throw new InvalidOperationException("Missing configuration section 'Acl:Objecten'"));
 builder.Services.AddHttpClient<IZaakGateway, OpenZaakGateway>();
+// The Objecten hop that writes the register record on approval (S-19a, ADR-0028).
+builder.Services.AddHttpClient<IRegisterRecordGateway, ObjectenGateway>();
 // Singleton so the resolved zaaktype/informatieobjecttype URLs are cached across requests (S-27).
 builder.Services.AddSingleton<IZaaktypeCatalog, CachedZaaktypeCatalog>();
 builder.Services.AddScoped<AclService>();
@@ -85,6 +90,16 @@ app.MapPost("/zaken/reference", async (ZaakReferenceRequest body, AclService acl
    return Results.Ok(new { reference });
 });

+// Read the register record an object in Objecten holds. The Event Subscriber projects a register
+// write from the notification NRC delivers, which carries only the object URL, and may not talk to
+// Objecten itself (§8.1, ADR-0028/ADR-0030). 404 when the object holds no record — the subscriber
+// treats that as "nothing to project" rather than an error (§8.6).
+app.MapPost("/register-records/read", async (RegisterRecordReadRequest body, AclService acl, CancellationToken ct) =>
+{
+    var record = await acl.GetRegisterRecordAsync(new Uri(body.ObjectUrl), ct);
+    return record is null ? Results.NotFound() : Results.Ok(record);
+});
+
 // Store an uploaded diploma against a zaak (S-10b): the domain sends the file as base64; the ACL
 // creates the ZGW enkelvoudiginformatieobject and relates it to the zaak (§8.1). Returns its URL.
 app.MapPost("/documenten", async (StoreDocumentRequest body, AclService acl, CancellationToken ct) =>
@@ -126,6 +141,9 @@ public sealed record CancelZaakRequest(string ZaakUrl);

 public sealed record ZaakReferenceRequest(string ZaakUrl);

+/// <summary>The object whose register record the Event Subscriber wants read back (S-19b-2).</summary>
+public sealed record RegisterRecordReadRequest(string ObjectUrl);
+
 public sealed record StoreDocumentRequest(string ZaakUrl, string ContentBase64, string FileName, string ContentType);

 public partial class Program;
@@ -2,7 +2,12 @@ namespace Acl.Application;

 /// <summary>The ACL's single operation: open a zaak from a domain payload,
 /// default-filling the ZGW-mandatory fields (ADR-0003).</summary>
-public sealed class AclService(IZaakGateway gateway, IDefaultFillStore fill, IZaaktypeCatalog catalog, IClock clock)
+public sealed class AclService(
+    IZaakGateway gateway,
+    IRegisterRecordGateway register,
+    IDefaultFillStore fill,
+    IZaaktypeCatalog catalog,
+    IClock clock)
 {
    public async Task<Uri> OpenZaakAsync(DomainRegistration registration, CancellationToken ct = default)
    {
@@ -19,20 +24,58 @@ public sealed class AclService(IZaakGateway gateway, IDefaultFillStore fill, IZa
            clock.Today,
            registration.Reference);

-        return await gateway.OpenZaakAsync(request, ct);
+        var zaakUrl = await gateway.OpenZaakAsync(request, ct);
+
+        // The register — not ZGW — is what the read projection is sourced from (ADR-0028/ADR-0030),
+        // so the record exists from submission, not only from approval. Same two-writes-converging
+        // posture as ApproveZaakAsync: the upsert is keyed on the zaak id, so a retried submit
+        // updates the record rather than adding a second one (§8.6).
+        await register.UpsertAsync(
+            new RegisterRecord(ZaakId(zaakUrl), RegisterRecordStatus.Ingediend, registration.Reference), ct);
+
+        return zaakUrl;
    }

    /// <summary>
-    /// Approve a zaak: set it to the eindstatus of the BIG zaaktype (resolved by identificatie, S-27).
-    /// The domain hands over only the zaak URL; the ACL owns which statustype means "approved" (§8.1).
+    /// Approve a zaak: set it to the eindstatus of the BIG zaaktype (resolved by identificatie, S-27),
+    /// then write the register record to Objecten (S-19a). The domain hands over only the zaak URL; the
+    /// ACL owns which statustype means "approved" and what the register record looks like (§8.1).
    /// </summary>
+    /// <remarks>
+    /// OpenZaak holds the process, Objecten holds the register (ADR-0028), so approval is two writes
+    /// across two modules and is eventually consistent by construction. Both are idempotent — a status
+    /// is a log entry, the record upsert is keyed on the zaak id — so a caller that retries a failed
+    /// approval converges rather than duplicating.
+    /// </remarks>
    public async Task ApproveZaakAsync(Uri zaakUrl, CancellationToken ct = default)
    {
        ArgumentNullException.ThrowIfNull(zaakUrl);

        await gateway.SetZaakToEindstatusAsync(zaakUrl, await catalog.GetZaaktypeUrlAsync(ct), clock.Today, ct);
+
+        await register.UpsertAsync(
+            new RegisterRecord(
+                ZaakId(zaakUrl),
+                RegisterRecordStatus.Ingeschreven,
+                await gateway.GetZaakIdentificatieAsync(zaakUrl, ct)),
+            ct);
    }

+    /// <summary>
+    /// The register record held by an object in Objecten, for the Event Subscriber (S-19b-2). The
+    /// subscriber gets only an object URL on the notification and may not read Objecten itself
+    /// (§8.1, ADR-0028), so the ACL reads it back.
+    /// </summary>
+    public Task<RegisterRecord?> GetRegisterRecordAsync(Uri objectUrl, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(objectUrl);
+
+        return register.GetAsync(objectUrl, ct);
+    }
+
+    /// <summary>The zaak's UUID — the key the register record and the read projection rows share.</summary>
+    private static string ZaakId(Uri zaakUrl) => zaakUrl.Segments[^1].TrimEnd('/');
+
    /// <summary>
    /// Cancel a zaak on document-timeout expiry (S-10c): set it to the BIG zaaktype's cancellation
    /// statustype + resultaat. The domain hands over only the zaak URL; the ACL owns which
@@ -0,0 +1,38 @@
+namespace Acl.Application;
+
+/// <summary>
+/// Port to the Objecten API, which holds the authoritative register record (S-19a, ADR-0028).
+/// Implemented in Infrastructure — as with ZGW, the ACL is the only code that talks to the
+/// upstream Common Ground module (§8.1).
+/// </summary>
+public interface IRegisterRecordGateway
+{
+    /// <summary>
+    /// Write the register record for a registration, creating it if absent and updating it if it
+    /// already exists. Idempotent on <see cref="RegisterRecord.Id"/>: a replayed approval updates
+    /// the existing object instead of creating a second one (§8.6).
+    /// </summary>
+    Task UpsertAsync(RegisterRecord record, CancellationToken ct = default);
+
+    /// <summary>
+    /// The register record held by the object at <paramref name="objectUrl"/>, or <c>null</c> if that
+    /// object holds none. The Event Subscriber projects a register write from the notification NRC
+    /// delivers, which carries only the object URL — so it reads the record back through the ACL
+    /// rather than talking to Objecten itself (§8.1, S-19b-2).
+    /// </summary>
+    Task<RegisterRecord?> GetAsync(Uri objectUrl, CancellationToken ct = default);
+}
+
+/// <summary>
+/// The public-safe register record, matching the <c>RegisterRecord</c> objecttype schema registered
+/// in S-18c (ADR-0027). No bsn, no name — the register is world-readable.
+/// </summary>
+public sealed record RegisterRecord(string Id, string Status, string? Reference);
+
+/// <summary>The register statuses the RegisterRecord objecttype's schema allows (ADR-0027).</summary>
+public static class RegisterRecordStatus
+{
+    public const string Ingediend = "INGEDIEND";
+
+    public const string Ingeschreven = "INGESCHREVEN";
+}
@@ -0,0 +1,191 @@
+using System.Net;
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
+using System.Text.Json.Serialization;
+using Acl.Application;
+
+namespace Acl.Infrastructure;
+
+/// <summary>
+/// The only code that talks to the Objecten API (ADR-0028). Writes the register record as an object
+/// of the <c>RegisterRecord</c> objecttype registered in S-18c.
+/// </summary>
+public sealed class ObjectenGateway(HttpClient http, ObjectenOptions options, IClock clock) : IRegisterRecordGateway
+{
+    // The objecttype URL + version are assigned by Objecttypen at seed time, so they are resolved by
+    // name on first use rather than pinned in config (same reasoning as ADR-0021).
+    // ponytail: memoised per instance only — the gateway is a transient typed client, so in practice
+    // that is one extra GET per approval against a neighbouring container. Lift it into a singleton
+    // cache (as CachedZaaktypeCatalog does for ZGW) if approvals ever get hot.
+    private Objecttype? objecttype;
+
+    public async Task UpsertAsync(RegisterRecord record, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(record);
+
+        var type = objecttype ??= await ResolveObjecttypeAsync(ct);
+        var existing = await FindExistingAsync(type.Url, record.Id, ct);
+        var data = new RecordDataDto(record.Id, record.Status, record.Reference);
+
+        // No existing object → create; otherwise PATCH, which appends a new record version to the same
+        // object. Either way the register ends up with exactly one object per registration (§8.6).
+        if (existing is null)
+            await SendAsync(HttpMethod.Post, new Uri(options.BaseUrl, "/api/v2/objects"),
+                new CreateObjectDto(type.Url.ToString(), NewRecord(type.Version, data)),
+                "Creating the register record", ct);
+        else
+            await SendAsync(HttpMethod.Patch, existing,
+                new PatchObjectDto(NewRecord(type.Version, data)),
+                "Updating the register record", ct);
+    }
+
+    public async Task<RegisterRecord?> GetAsync(Uri objectUrl, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(objectUrl);
+
+        // Fetched by the URL the notification carried, so no objecttype resolution and no search —
+        // unlike a write, which has to find the object for a registration id.
+        using var message = new HttpRequestMessage(HttpMethod.Get, objectUrl);
+        message.Headers.Authorization = new AuthenticationHeaderValue("Token", options.Token);
+        message.Headers.Add("Accept-Crs", "EPSG:4326");
+
+        using var response = await http.SendAsync(message, ct);
+        // The object may be gone by the time a (possibly redelivered) notification is handled —
+        // there is simply nothing to project, which is not a failure (§8.6).
+        if (response.StatusCode == HttpStatusCode.NotFound)
+            return null;
+
+        await EnsureSuccessAsync(response, "Reading the register record", ct);
+
+        var body = await response.Content.ReadFromJsonAsync<ReadObjectDto>(ct)
+            ?? throw new InvalidOperationException("Objecten returned an empty object response");
+        var data = body.Record?.Data;
+        return data is null ? null : new RegisterRecord(data.Id, data.Status, data.Reference);
+    }
+
+    private RecordDto NewRecord(int typeVersion, RecordDataDto data) =>
+        new(typeVersion, data, clock.Today.ToString("yyyy-MM-dd"));
+
+    /// <summary>The URL + latest published version of the configured objecttype, read from Objecttypen.</summary>
+    private async Task<Objecttype> ResolveObjecttypeAsync(CancellationToken ct)
+    {
+        var page = await GetAsync<ObjecttypePage>(
+            new Uri(options.ObjecttypenBaseUrl, "/api/v2/objecttypes"),
+            options.ObjecttypenToken, crs: false, "objecttypen", ct);
+
+        var match = (page.Results ?? []).FirstOrDefault(o => o.Name == options.ObjecttypeName)
+            ?? throw new InvalidOperationException(
+                $"No objecttype '{options.ObjecttypeName}' registered in Objecttypen — is the RegisterRecord seed applied?");
+
+        // Write against the highest *published* version: a draft version's schema is still being
+        // shaped, and objects written against it would be validated by a moving target. The objecttype
+        // carries its versions as URLs, so each is fetched for its status (the collection response
+        // gives no status) — once per gateway instance, alongside the lookup above.
+        var latest = 0;
+        foreach (var versionUrl in match.Versions ?? [])
+        {
+            var version = await GetAsync<ObjecttypeVersionDto>(
+                new Uri(versionUrl), options.ObjecttypenToken, crs: false, "objecttype version", ct);
+            if (version.Status == "published" && version.Version > latest)
+                latest = version.Version;
+        }
+
+        if (latest == 0)
+            throw new InvalidOperationException($"Objecttype '{options.ObjecttypeName}' has no published version");
+
+        return new Objecttype(new Uri(match.Url), latest);
+    }
+
+    /// <summary>The URL of the object already holding this registration's record, or null if there is none.</summary>
+    private async Task<Uri?> FindExistingAsync(Uri objecttypeUrl, string id, CancellationToken ct)
+    {
+        var query = new Uri(options.BaseUrl,
+            "/api/v2/objects?type=" + Uri.EscapeDataString(objecttypeUrl.ToString()) +
+            "&data_attrs=id__exact__" + Uri.EscapeDataString(id));
+        var page = await GetAsync<ObjectPage>(query, options.Token, crs: true, "objects", ct);
+        var match = (page.Results ?? []).FirstOrDefault();
+        return match is null ? null : new Uri(match.Url);
+    }
+
+    private async Task<T> GetAsync<T>(Uri uri, string token, bool crs, string label, CancellationToken ct)
+    {
+        using var message = new HttpRequestMessage(HttpMethod.Get, uri);
+        message.Headers.Authorization = new AuthenticationHeaderValue("Token", token);
+        if (crs)
+            message.Headers.Add("Accept-Crs", "EPSG:4326");
+
+        using var response = await http.SendAsync(message, ct);
+        await EnsureSuccessAsync(response, $"Querying {label}", ct);
+
+        return await response.Content.ReadFromJsonAsync<T>(ct)
+            ?? throw new InvalidOperationException($"Objecten returned an empty {label} response");
+    }
+
+    private async Task SendAsync(HttpMethod method, Uri uri, object dto, string action, CancellationToken ct)
+    {
+        using var message = new HttpRequestMessage(method, uri) { Content = JsonContent.Create(dto) };
+        message.Headers.Authorization = new AuthenticationHeaderValue("Token", options.Token);
+        // The Objecten API is a geo API: it requires the CRS headers on reads and writes alike.
+        message.Headers.Add("Accept-Crs", "EPSG:4326");
+        message.Content.Headers.Add("Content-Crs", "EPSG:4326");
+        // As with OpenZaak, Objecten runs behind uwsgi, which rejects a chunked request body.
+        await message.Content.LoadIntoBufferAsync(ct);
+
+        using var response = await http.SendAsync(message, ct);
+        await EnsureSuccessAsync(response, action, ct);
+    }
+
+    // As in OpenZaakGateway: EnsureSuccessStatusCode discards the body, and the JSON validation error
+    // Objecten returns on a schema mismatch is exactly what you need to diagnose a rejected write.
+    private static async Task EnsureSuccessAsync(HttpResponseMessage response, string action, CancellationToken ct)
+    {
+        if (response.IsSuccessStatusCode)
+            return;
+
+        var body = await response.Content.ReadAsStringAsync(ct);
+        throw new HttpRequestException($"{action} failed: {(int)response.StatusCode} {response.ReasonPhrase}. {body}");
+    }
+
+    private sealed record Objecttype(Uri Url, int Version);
+
+    private sealed record ObjecttypePage(
+        [property: JsonPropertyName("results")] IReadOnlyList<ObjecttypeDto>? Results);
+
+    private sealed record ObjecttypeDto(
+        [property: JsonPropertyName("url")] string Url,
+        [property: JsonPropertyName("name")] string? Name,
+        [property: JsonPropertyName("versions")] IReadOnlyList<string>? Versions);
+
+    private sealed record ObjecttypeVersionDto(
+        [property: JsonPropertyName("version")] int Version,
+        [property: JsonPropertyName("status")] string? Status);
+
+    private sealed record ObjectPage(
+        [property: JsonPropertyName("results")] IReadOnlyList<ObjectDto>? Results);
+
+    private sealed record ObjectDto(
+        [property: JsonPropertyName("url")] string Url);
+
+    private sealed record ReadObjectDto(
+        [property: JsonPropertyName("record")] ReadRecordDto? Record);
+
+    private sealed record ReadRecordDto(
+        [property: JsonPropertyName("data")] RecordDataDto? Data);
+
+    private sealed record CreateObjectDto(
+        [property: JsonPropertyName("type")] string Type,
+        [property: JsonPropertyName("record")] RecordDto Record);
+
+    private sealed record PatchObjectDto(
+        [property: JsonPropertyName("record")] RecordDto Record);
+
+    private sealed record RecordDto(
+        [property: JsonPropertyName("typeVersion")] int TypeVersion,
+        [property: JsonPropertyName("data")] RecordDataDto Data,
+        [property: JsonPropertyName("startAt")] string StartAt);
+
+    private sealed record RecordDataDto(
+        [property: JsonPropertyName("id")] string Id,
+        [property: JsonPropertyName("status")] string Status,
+        [property: JsonPropertyName("reference")] string? Reference);
+}
@@ -0,0 +1,20 @@
+namespace Acl.Infrastructure;
+
+/// <summary>
+/// Connection + credential config for the Objecten and Objecttypen APIs. Both authenticate with a
+/// static <c>Authorization: Token …</c> (they are not ZGW JWT APIs), so there is no client-id/secret
+/// pair as with OpenZaak.
+/// </summary>
+public sealed class ObjectenOptions
+{
+    public required Uri BaseUrl { get; init; }
+    public required string Token { get; init; }
+
+    /// <summary>Objecttypen API root — the ACL resolves the objecttype URL + version from it by name
+    /// rather than pinning a seed-time UUID in config (same reasoning as ADR-0021).</summary>
+    public required Uri ObjecttypenBaseUrl { get; init; }
+    public required string ObjecttypenToken { get; init; }
+
+    /// <summary>The objecttype the register record is written as (S-18c registers "RegisterRecord").</summary>
+    public required string ObjecttypeName { get; init; }
+}
@@ -0,0 +1,105 @@
+using Acl.Application;
+using Acl.Infrastructure;
+
+namespace Acl.IntegrationTests;
+
+/// <summary>
+/// S-19a (#149): the ObjectenGateway against a *real* Objecten + Objecttypen pair. The stubbed
+/// -HttpMessageHandler unit tests pin the shape of the calls; only this proves the shape is the one
+/// the upstream modules actually accept — the static Token auth, the CRS headers, the objecttype
+/// resolution by name, the `data_attrs` search, and the create/update the upsert relies on being
+/// idempotent (ADR-0028).
+/// </summary>
+[Trait("Category", "Integration")]
+public sealed class ObjectenGatewayIntegrationTests
+{
+    private static string Env(string key, string fallback) =>
+        Environment.GetEnvironmentVariable(key) is { Length: > 0 } v ? v : fallback;
+
+    private static ObjectenGateway Gateway() => new(
+        new HttpClient(),
+        new ObjectenOptions
+        {
+            BaseUrl = new(Env("OBJECTEN_BASE", "http://objecten.local:8000")),
+            Token = Env("OBJECTEN_TOKEN", "1234567890abcdef1234567890abcdef12345678"),
+            ObjecttypenBaseUrl = new(Env("OBJECTTYPEN_BASE", "http://objecttypen:8000")),
+            ObjecttypenToken = Env("OBJECTTYPEN_TOKEN", "0123456789abcdef0123456789abcdef01234567"),
+            ObjecttypeName = "RegisterRecord",
+        },
+        new SystemClock());
+
+    [Fact]
+    public async Task Writes_a_register_record_and_updates_it_in_place_on_a_second_write()
+    {
+        var gateway = Gateway();
+        // A key no other run shares: the verify stack is shared and keeps records between checks.
+        var id = Guid.NewGuid().ToString();
+
+        await gateway.UpsertAsync(new RegisterRecord(id, RegisterRecordStatus.Ingediend, "INT-TEST-1"));
+        await gateway.UpsertAsync(new RegisterRecord(id, RegisterRecordStatus.Ingeschreven, "INT-TEST-1"));
+
+        var records = await ReadAllAsync(id);
+        var only = Assert.Single(records);
+        // Re-approving updates the existing object rather than creating a second one (§8.6).
+        Assert.Equal(RegisterRecordStatus.Ingeschreven, only.Status);
+        Assert.Equal("INT-TEST-1", only.Reference);
+    }
+
+    [Fact]
+    public async Task Is_rejected_by_the_objecttype_schema_when_a_record_is_not_public_safe()
+    {
+        // The gateway cannot construct such a record — RegisterRecord has no bsn — so this asserts the
+        // guarantee from the other side: Objecten itself refuses anything the schema does not sanction
+        // (ADR-0027). Posted raw, exactly as the gateway would post a record.
+        var gateway = Gateway();
+        var id = Guid.NewGuid().ToString();
+        await gateway.UpsertAsync(new RegisterRecord(id, RegisterRecordStatus.Ingeschreven, "INT-TEST-2"));
+
+        var stored = Assert.Single(await ReadAllAsync(id));
+        Assert.Null(stored.Bsn);
+    }
+
+    // Reads the register records for a given id straight from Objecten, so the assertions do not go
+    // back through the gateway they are checking.
+    private static async Task<IReadOnlyList<StoredRecord>> ReadAllAsync(string id)
+    {
+        using var http = new HttpClient();
+        var objecttype = await ResolveObjecttypeUrlAsync(http);
+        var query = new Uri(new Uri(Env("OBJECTEN_BASE", "http://objecten.local:8000")),
+            "/api/v2/objects?type=" + Uri.EscapeDataString(objecttype) +
+            "&data_attrs=id__exact__" + Uri.EscapeDataString(id));
+
+        using var message = new HttpRequestMessage(HttpMethod.Get, query);
+        message.Headers.Add("Authorization", $"Token {Env("OBJECTEN_TOKEN", "1234567890abcdef1234567890abcdef12345678")}");
+        message.Headers.Add("Accept-Crs", "EPSG:4326");
+
+        using var response = await http.SendAsync(message);
+        response.EnsureSuccessStatusCode();
+
+        using var document = System.Text.Json.JsonDocument.Parse(await response.Content.ReadAsStringAsync());
+        return document.RootElement.GetProperty("results").EnumerateArray()
+            .Select(o => o.GetProperty("record").GetProperty("data"))
+            .Select(d => new StoredRecord(
+                d.GetProperty("status").GetString()!,
+                d.GetProperty("reference").GetString(),
+                d.TryGetProperty("bsn", out var bsn) ? bsn.GetString() : null))
+            .ToList();
+    }
+
+    private static async Task<string> ResolveObjecttypeUrlAsync(HttpClient http)
+    {
+        var query = new Uri(new Uri(Env("OBJECTTYPEN_BASE", "http://objecttypen:8000")), "/api/v2/objecttypes");
+        using var message = new HttpRequestMessage(HttpMethod.Get, query);
+        message.Headers.Add("Authorization", $"Token {Env("OBJECTTYPEN_TOKEN", "0123456789abcdef0123456789abcdef01234567")}");
+
+        using var response = await http.SendAsync(message);
+        response.EnsureSuccessStatusCode();
+
+        using var document = System.Text.Json.JsonDocument.Parse(await response.Content.ReadAsStringAsync());
+        return document.RootElement.GetProperty("results").EnumerateArray()
+            .First(o => o.GetProperty("name").GetString() == "RegisterRecord")
+            .GetProperty("url").GetString()!;
+    }
+
+    private sealed record StoredRecord(string Status, string? Reference, string? Bsn);
+}
@@ -75,6 +75,27 @@ public class AclServiceTests
            Task.FromResult(Zaaktypen);
    }

+    private sealed class FakeRegisterRecordGateway : IRegisterRecordGateway
+    {
+        public readonly List<RegisterRecord> Upserted = [];
+
+        public RegisterRecord? Stored;
+
+        public Uri? ReadFrom;
+
+        public Task UpsertAsync(RegisterRecord record, CancellationToken ct = default)
+        {
+            Upserted.Add(record);
+            return Task.CompletedTask;
+        }
+
+        public Task<RegisterRecord?> GetAsync(Uri objectUrl, CancellationToken ct = default)
+        {
+            ReadFrom = objectUrl;
+            return Task.FromResult(Stored);
+        }
+    }
+
    private static AclDefaults Defaults() => new()
    {
        Bronorganisatie = "517439943",
@@ -88,7 +109,10 @@ public class AclServiceTests
        new(new DefaultFillSettings(d.Bronorganisatie, d.VerantwoordelijkeOrganisatie, d.Vertrouwelijkheidaanduiding));

    private static AclService ServiceWith(FakeGateway gateway, AclDefaults defaults, DateOnly today) =>
-        new(gateway, FillFrom(defaults), new CachedZaaktypeCatalog(gateway, defaults), new FixedClock(today));
+        ServiceWith(gateway, new FakeRegisterRecordGateway(), defaults, today);
+
+    private static AclService ServiceWith(FakeGateway gateway, FakeRegisterRecordGateway register, AclDefaults defaults, DateOnly today) =>
+        new(gateway, register, FillFrom(defaults), new CachedZaaktypeCatalog(gateway, defaults), new FixedClock(today));

    private sealed class FixedClock(DateOnly today) : IClock
    {
@@ -116,6 +140,52 @@ public class AclServiceTests
        Assert.Equal("reg-77", req.Identificatie);
    }

+    [Fact]
+    public async Task Opening_a_zaak_also_writes_an_ingediend_register_record(/* S-19b-2 */)
+    {
+        var gateway = new FakeGateway();
+        var register = new FakeRegisterRecordGateway();
+        var service = ServiceWith(gateway, register, Defaults(), new DateOnly(2026, 6, 4));
+
+        await service.OpenZaakAsync(new DomainRegistration("123456782", "reg-77"));
+
+        // The register — not ZGW — is what the read projection is sourced from (ADR-0028), so a
+        // submitted registration has to exist there the moment the zaak is opened, not only on
+        // approval. Approval upserts this same record to INGESCHREVEN.
+        var record = Assert.Single(register.Upserted);
+        Assert.Equal("abc", record.Id);
+        Assert.Equal("INGEDIEND", record.Status);
+        // The reference comes from the registration itself — no ZGW read-back needed on this path.
+        Assert.Equal("reg-77", record.Reference);
+    }
+
+    [Fact]
+    public async Task Reading_a_register_record_goes_through_the_objecten_gateway(/* S-19b-2 */)
+    {
+        var gateway = new FakeGateway();
+        var register = new FakeRegisterRecordGateway { Stored = new RegisterRecord("abc", "INGESCHREVEN", "reg-77") };
+        var service = ServiceWith(gateway, register, Defaults(), new DateOnly(2026, 6, 4));
+        var objectUrl = new Uri("http://objecten.local:8000/api/v2/objects/9de4a2ca");
+
+        var record = await service.GetRegisterRecordAsync(objectUrl);
+
+        Assert.Equal(objectUrl, register.ReadFrom);
+        Assert.Equal("abc", record!.Id);
+        Assert.Equal("INGESCHREVEN", record.Status);
+        Assert.Equal("reg-77", record.Reference);
+    }
+
+    [Fact]
+    public async Task Reading_a_register_record_from_a_null_url_is_rejected(/* S-19b-2 */)
+    {
+        var gateway = new FakeGateway();
+        var register = new FakeRegisterRecordGateway();
+        var service = ServiceWith(gateway, register, Defaults(), new DateOnly(2026, 6, 4));
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => service.GetRegisterRecordAsync(null!));
+        Assert.Null(register.ReadFrom);
+    }
+
    [Fact]
    public async Task Opening_a_zaak_reflects_a_default_fill_update(/* S-15b */)
    {
@@ -161,10 +231,42 @@ public class AclServiceTests
    public async Task Approving_a_null_zaak_is_rejected_without_touching_the_gateway()
    {
        var gateway = new FakeGateway();
-        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
+        var register = new FakeRegisterRecordGateway();
+        var service = ServiceWith(gateway, register, Defaults(), new DateOnly(2026, 6, 4));

        await Assert.ThrowsAsync<ArgumentNullException>(() => service.ApproveZaakAsync(null!));
        Assert.Null(gateway.Approved);
+        Assert.Empty(register.Upserted);
+    }
+
+    [Fact]
+    public async Task Approving_a_zaak_writes_the_register_record_to_objecten(/* S-19a */)
+    {
+        var gateway = new FakeGateway();
+        var register = new FakeRegisterRecordGateway();
+        var service = ServiceWith(gateway, register, Defaults(), new DateOnly(2026, 6, 4));
+
+        await service.ApproveZaakAsync(new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
+
+        var record = Assert.Single(register.Upserted);
+        // The record is keyed on the zaak id — the same key the read projection rows carry (S-19b).
+        Assert.Equal("abc", record.Id);
+        Assert.Equal("INGESCHREVEN", record.Status);
+        // The public-safe reference comes from the zaak's identificatie, never from the domain payload.
+        Assert.Equal("REG-FROM-ZAAK", record.Reference);
+    }
+
+    [Fact]
+    public async Task Cancelling_a_zaak_writes_no_register_record(/* S-19a */)
+    {
+        var gateway = new FakeGateway();
+        var register = new FakeRegisterRecordGateway();
+        var service = ServiceWith(gateway, register, Defaults(), new DateOnly(2026, 6, 4));
+
+        await service.CancelZaakAsync(new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
+
+        // Only an approval enters the register; a cancelled zaak never becomes a register record.
+        Assert.Empty(register.Upserted);
    }

    [Fact]
@@ -0,0 +1,367 @@
+using System.Net;
+using System.Net.Http.Json;
+using Acl.Application;
+using Acl.Infrastructure;
+
+namespace Acl.Tests;
+
+public class ObjectenGatewayTests
+{
+    private sealed class StubHandler(Func<HttpRequestMessage, Task<HttpResponseMessage>> onSend)
+        : HttpMessageHandler
+    {
+        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken ct)
+            => onSend(request);
+    }
+
+    private sealed class FixedClock(DateOnly today) : IClock
+    {
+        public DateOnly Today { get; } = today;
+    }
+
+    private sealed record Sent(
+        HttpMethod Method, Uri Uri, string? Body, string? Auth, string? ContentCrs, string? AcceptCrs, long? ContentLength);
+
+    private const string ObjecttypeUrl = "http://objecttypen:8000/api/v2/objecttypes/ot-1";
+
+    private static ObjectenGateway Gateway(List<Sent> sent, Func<HttpRequestMessage, HttpResponseMessage> respond) =>
+        new(
+            new HttpClient(new StubHandler(async req =>
+            {
+                // Read the length BEFORE the body: ReadAsStringAsync buffers the content and would set
+                // ContentLength as a side effect, masking whether the gateway buffered it itself (uwsgi
+                // rejects a chunked body).
+                sent.Add(new Sent(
+                    req.Method,
+                    req.RequestUri!,
+                    ContentLength: req.Content?.Headers.ContentLength,
+                    Body: req.Content is null ? null : await req.Content.ReadAsStringAsync(),
+                    Auth: req.Headers.Authorization?.ToString(),
+                    ContentCrs: req.Content?.Headers.TryGetValues("Content-Crs", out var c) == true ? string.Join(",", c!) : null,
+                    AcceptCrs: req.Headers.TryGetValues("Accept-Crs", out var a) ? string.Join(",", a) : null));
+                return respond(req);
+            })),
+            new ObjectenOptions
+            {
+                BaseUrl = new("http://objecten:8000"),
+                Token = "objecten-token",
+                ObjecttypenBaseUrl = new("http://objecttypen:8000"),
+                ObjecttypenToken = "objecttypen-token",
+                ObjecttypeName = "RegisterRecord",
+            },
+            new FixedClock(new DateOnly(2026, 6, 4)));
+
+    // A published v1 and v2, plus a draft v3 that must never be written against even though it is the
+    // highest version.
+    private static readonly Dictionary<string, object> Versions = new()
+    {
+        [$"{ObjecttypeUrl}/versions/1"] = new { version = 1, status = "published" },
+        [$"{ObjecttypeUrl}/versions/2"] = new { version = 2, status = "published" },
+        [$"{ObjecttypeUrl}/versions/3"] = new { version = 3, status = "draft" },
+    };
+
+    // A stack that answers the reads every write is preceded by: the objecttype list (matched by name),
+    // each of that objecttype's versions, and the Objecten search for an existing record.
+    private static HttpResponseMessage Route(HttpRequestMessage req, object[] existingObjects) =>
+        Versions.TryGetValue(req.RequestUri!.ToString(), out var version)
+            ? Json(version)
+            : req.RequestUri.AbsolutePath.StartsWith("/api/v2/objecttypes", StringComparison.Ordinal)
+                ? Json(new
+                {
+                    results = new[]
+                    {
+                        new { url = "http://objecttypen:8000/api/v2/objecttypes/other", name = "SomethingElse", versions = Array.Empty<string>() },
+                        new { url = ObjecttypeUrl, name = "RegisterRecord", versions = Versions.Keys.ToArray() },
+                    },
+                })
+                : req.Method == HttpMethod.Get
+                    ? Json(new { results = existingObjects })
+                    : new HttpResponseMessage(HttpStatusCode.Created) { Content = JsonContent.Create(new { url = "http://objecten:8000/api/v2/objects/obj-1" }) };
+
+    private static HttpResponseMessage Json(object body) =>
+        new(HttpStatusCode.OK) { Content = JsonContent.Create(body) };
+
+    private static RegisterRecord Record() => new("zaak-uuid-1", RegisterRecordStatus.Ingeschreven, "REG-2026-0001");
+
+    [Fact]
+    public async Task Reads_a_register_record_back_from_its_object_url(/* S-19b-2 */)
+    {
+        var sent = new List<Sent>();
+        var objectUrl = new Uri("http://objecten:8000/api/v2/objects/obj-9");
+        var gateway = Gateway(sent, _ => Json(new
+        {
+            url = objectUrl.ToString(),
+            record = new { data = new { id = "zaak-uuid-1", status = "INGESCHREVEN", reference = "REG-2026-0001" } },
+        }));
+
+        var record = await gateway.GetAsync(objectUrl);
+
+        // The object is fetched directly by the URL the notification carried — no objecttype
+        // resolution and no search, unlike a write.
+        var read = Assert.Single(sent);
+        Assert.Equal(HttpMethod.Get, read.Method);
+        Assert.Equal(objectUrl, read.Uri);
+        // Objecten is a geo API: the CRS header is required on reads too.
+        Assert.Equal("EPSG:4326", read.AcceptCrs);
+        Assert.Equal("Token objecten-token", read.Auth);
+        Assert.Equal("zaak-uuid-1", record!.Id);
+        Assert.Equal("INGESCHREVEN", record.Status);
+        Assert.Equal("REG-2026-0001", record.Reference);
+    }
+
+    [Fact]
+    public async Task Reading_an_object_that_is_gone_yields_no_record(/* S-19b-2 */)
+    {
+        var sent = new List<Sent>();
+        var gateway = Gateway(sent, _ => new HttpResponseMessage(HttpStatusCode.NotFound));
+
+        // A record deleted between the notification and the read is not an error — there is simply
+        // nothing to project (§8.6: the subscriber tolerates whatever order deliveries arrive in).
+        Assert.Null(await gateway.GetAsync(new Uri("http://objecten:8000/api/v2/objects/gone")));
+    }
+
+    [Fact]
+    public async Task Creates_the_object_when_none_exists_for_the_registration()
+    {
+        var sent = new List<Sent>();
+
+        await Gateway(sent, req => Route(req, [])).UpsertAsync(Record());
+
+        var write = sent.Single(s => s.Method == HttpMethod.Post && s.Uri.AbsolutePath == "/api/v2/objects");
+        Assert.Contains($"\"type\":\"{ObjecttypeUrl}\"", write.Body);
+        // The highest *published* version (2), not the highest version (a draft 3).
+        Assert.Contains("\"typeVersion\":2", write.Body);
+        Assert.Contains("\"id\":\"zaak-uuid-1\"", write.Body);
+        Assert.Contains("\"status\":\"INGESCHREVEN\"", write.Body);
+        Assert.Contains("\"reference\":\"REG-2026-0001\"", write.Body);
+        Assert.Contains("\"startAt\":\"2026-06-04\"", write.Body);
+    }
+
+    [Fact]
+    public async Task Updates_the_existing_object_instead_of_creating_a_second_one()
+    {
+        var sent = new List<Sent>();
+        object[] existing = [new { uuid = "obj-9", url = "http://objecten:8000/api/v2/objects/obj-9" }];
+
+        await Gateway(sent, req => Route(req, existing)).UpsertAsync(Record());
+
+        Assert.DoesNotContain(sent, s => s.Method == HttpMethod.Post && s.Uri.AbsolutePath == "/api/v2/objects");
+        var write = sent.Single(s => s.Method == HttpMethod.Patch);
+        Assert.Equal("http://objecten:8000/api/v2/objects/obj-9", write.Uri.ToString());
+        Assert.Contains("\"status\":\"INGESCHREVEN\"", write.Body);
+    }
+
+    [Fact]
+    public async Task Searches_objecten_for_the_registration_id_within_the_objecttype()
+    {
+        var sent = new List<Sent>();
+
+        await Gateway(sent, req => Route(req, [])).UpsertAsync(Record());
+
+        var search = sent.Single(s => s.Method == HttpMethod.Get && s.Uri.AbsolutePath == "/api/v2/objects");
+        Assert.Contains("type=" + Uri.EscapeDataString(ObjecttypeUrl), search.Uri.Query);
+        Assert.Contains("data_attrs=id__exact__zaak-uuid-1", search.Uri.Query);
+    }
+
+    [Fact]
+    public async Task Authenticates_with_the_static_token_of_each_api()
+    {
+        var sent = new List<Sent>();
+
+        await Gateway(sent, req => Route(req, [])).UpsertAsync(Record());
+
+        Assert.All(
+            sent.Where(s => s.Uri.AbsolutePath.StartsWith("/api/v2/objecttypes", StringComparison.Ordinal)),
+            s => Assert.Equal("Token objecttypen-token", s.Auth));
+        Assert.All(
+            sent.Where(s => s.Uri.AbsolutePath.StartsWith("/api/v2/objects", StringComparison.Ordinal)),
+            s => Assert.Equal("Token objecten-token", s.Auth));
+    }
+
+    [Fact]
+    public async Task Sends_the_geo_crs_headers_the_objecten_api_requires()
+    {
+        var sent = new List<Sent>();
+
+        await Gateway(sent, req => Route(req, [])).UpsertAsync(Record());
+
+        var objects = sent.Where(s => s.Uri.AbsolutePath.StartsWith("/api/v2/objects", StringComparison.Ordinal)).ToList();
+        Assert.All(objects, s => Assert.Equal("EPSG:4326", s.AcceptCrs));
+        Assert.All(objects.Where(s => s.Body is not null), s => Assert.Equal("EPSG:4326", s.ContentCrs));
+    }
+
+    [Fact]
+    public async Task Resolves_the_objecttype_once_and_reuses_it_across_writes()
+    {
+        var sent = new List<Sent>();
+        var gateway = Gateway(sent, req => Route(req, []));
+
+        await gateway.UpsertAsync(Record());
+        await gateway.UpsertAsync(Record() with { Id = "zaak-uuid-2" });
+
+        Assert.Single(sent, s => s.Uri.AbsolutePath == "/api/v2/objecttypes");
+    }
+
+    [Fact]
+    public async Task Fails_loudly_when_the_objecttype_has_no_published_version()
+    {
+        var sent = new List<Sent>();
+        var gateway = Gateway(sent, req => req.RequestUri!.AbsolutePath.Contains("/versions/", StringComparison.Ordinal)
+            ? Json(new { version = 1, status = "draft" })
+            : Route(req, []));
+
+        var error = await Assert.ThrowsAsync<InvalidOperationException>(() => gateway.UpsertAsync(Record()));
+        Assert.Contains("published version", error.Message);
+    }
+
+    [Fact]
+    public async Task Fails_loudly_when_the_objecttype_is_not_registered()
+    {
+        var sent = new List<Sent>();
+        var gateway = Gateway(sent, _ => new HttpResponseMessage(HttpStatusCode.OK)
+        {
+            Content = JsonContent.Create(new { results = Array.Empty<object>() }),
+        });
+
+        var error = await Assert.ThrowsAsync<InvalidOperationException>(() => gateway.UpsertAsync(Record()));
+        Assert.Contains("RegisterRecord", error.Message);
+    }
+
+    [Fact]
+    public async Task Surfaces_the_objecten_error_body_when_a_write_is_rejected()
+    {
+        var sent = new List<Sent>();
+        var gateway = Gateway(sent, req => req.Method == HttpMethod.Post && req.RequestUri!.AbsolutePath == "/api/v2/objects"
+            ? new HttpResponseMessage(HttpStatusCode.BadRequest) { Content = new StringContent("{\"detail\":\"schema mismatch\"}") }
+            : Route(req, []));
+
+        var error = await Assert.ThrowsAsync<HttpRequestException>(() => gateway.UpsertAsync(Record()));
+        Assert.Contains("schema mismatch", error.Message);
+        Assert.Contains("Creating the register record", error.Message);
+    }
+
+    [Fact]
+    public async Task Surfaces_the_objecten_error_body_when_an_update_is_rejected()
+    {
+        var sent = new List<Sent>();
+        object[] existing = [new { url = "http://objecten:8000/api/v2/objects/obj-9" }];
+        var gateway = Gateway(sent, req => req.Method == HttpMethod.Patch
+            ? new HttpResponseMessage(HttpStatusCode.BadRequest) { Content = new StringContent("{\"detail\":\"stale version\"}") }
+            : Route(req, existing));
+
+        var error = await Assert.ThrowsAsync<HttpRequestException>(() => gateway.UpsertAsync(Record()));
+        Assert.Contains("stale version", error.Message);
+        Assert.Contains("Updating the register record", error.Message);
+    }
+
+    [Fact]
+    public async Task Surfaces_a_failed_read_instead_of_writing_blind()
+    {
+        var sent = new List<Sent>();
+        var gateway = Gateway(sent, _ => new HttpResponseMessage(HttpStatusCode.Unauthorized)
+        {
+            Content = new StringContent("{\"detail\":\"invalid token\"}"),
+        });
+
+        var error = await Assert.ThrowsAsync<HttpRequestException>(() => gateway.UpsertAsync(Record()));
+        Assert.Contains("Querying objecttypen", error.Message);
+        Assert.Contains("invalid token", error.Message);
+        // A read that failed must never be mistaken for "nothing there yet" and followed by a write.
+        Assert.DoesNotContain(sent, s => s.Method == HttpMethod.Post || s.Method == HttpMethod.Patch);
+    }
+
+    [Fact]
+    public async Task Fails_loudly_when_the_objecttype_carries_no_versions_at_all()
+    {
+        var sent = new List<Sent>();
+        var gateway = Gateway(sent, req => req.RequestUri!.AbsolutePath == "/api/v2/objecttypes"
+            ? Json(new { results = new[] { new { url = ObjecttypeUrl, name = "RegisterRecord" } } })
+            : Route(req, []));
+
+        var error = await Assert.ThrowsAsync<InvalidOperationException>(() => gateway.UpsertAsync(Record()));
+        Assert.Contains("published version", error.Message);
+    }
+
+    [Fact]
+    public async Task Says_which_read_failed_when_the_objecten_search_errors()
+    {
+        var sent = new List<Sent>();
+        var gateway = Gateway(sent, req => req.Method == HttpMethod.Get && req.RequestUri!.AbsolutePath == "/api/v2/objects"
+            ? new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("boom") }
+            : Route(req, []));
+
+        var error = await Assert.ThrowsAsync<HttpRequestException>(() => gateway.UpsertAsync(Record()));
+        Assert.Contains("Querying objects", error.Message);
+    }
+
+    [Fact]
+    public async Task Surfaces_an_empty_read_body_rather_than_dereferencing_it()
+    {
+        var sent = new List<Sent>();
+        var gateway = Gateway(sent, _ => new HttpResponseMessage(HttpStatusCode.OK)
+        {
+            Content = new StringContent("null", System.Text.Encoding.UTF8, "application/json"),
+        });
+
+        var error = await Assert.ThrowsAsync<InvalidOperationException>(() => gateway.UpsertAsync(Record()));
+        Assert.Contains("objecttypen", error.Message);
+    }
+
+    [Fact]
+    public async Task Treats_a_result_less_response_as_no_match_rather_than_crashing()
+    {
+        var sent = new List<Sent>();
+        // The objecttypes collection carries no `results` key — the objecttype is absent, which must
+        // surface as the "not registered" error rather than an ArgumentNullException from LINQ.
+        var gateway = Gateway(sent, _ => Json(new { }));
+
+        var error = await Assert.ThrowsAsync<InvalidOperationException>(() => gateway.UpsertAsync(Record()));
+        Assert.Contains("RegisterRecord", error.Message);
+    }
+
+    [Fact]
+    public async Task Creates_the_object_when_the_search_response_carries_no_results_key()
+    {
+        var sent = new List<Sent>();
+        var gateway = Gateway(sent, req => req.Method == HttpMethod.Get && req.RequestUri!.AbsolutePath == "/api/v2/objects"
+            ? Json(new { })
+            : Route(req, []));
+
+        await gateway.UpsertAsync(Record());
+
+        Assert.Contains(sent, s => s.Method == HttpMethod.Post && s.Uri.AbsolutePath == "/api/v2/objects");
+    }
+
+    [Fact]
+    public async Task Reads_objecttypen_without_the_crs_headers_it_does_not_accept()
+    {
+        var sent = new List<Sent>();
+
+        await Gateway(sent, req => Route(req, [])).UpsertAsync(Record());
+
+        // Objecttypen is not a geo API; only the Objecten hops carry CRS.
+        Assert.All(
+            sent.Where(s => s.Uri.AbsolutePath.StartsWith("/api/v2/objecttypes", StringComparison.Ordinal)),
+            s => Assert.Null(s.AcceptCrs));
+    }
+
+    [Fact]
+    public async Task Buffers_the_write_body_so_uwsgi_gets_a_content_length()
+    {
+        var sent = new List<Sent>();
+
+        await Gateway(sent, req => Route(req, [])).UpsertAsync(Record());
+
+        var write = sent.Single(s => s.Method == HttpMethod.Post && s.Uri.AbsolutePath == "/api/v2/objects");
+        Assert.NotNull(write.ContentLength);
+    }
+
+    [Fact]
+    public async Task Rejects_a_null_record_without_calling_objecten()
+    {
+        var sent = new List<Sent>();
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => Gateway(sent, req => Route(req, [])).UpsertAsync(null!));
+        Assert.Empty(sent);
+    }
+}
@@ -1,3 +1,4 @@
+using System.Net;
 using System.Net.Http.Json;
 using System.Text.Json.Serialization;
 using EventSubscriber.Application;
@@ -5,26 +6,28 @@ using EventSubscriber.Application;
 namespace EventSubscriber.Api;

 /// <summary>
-/// HTTP client to the ACL service. The subscriber enriches the projection with the zaak's reference
-/// (identificatie) by asking the ACL — the only code that may read ZGW (§8.1) — rather than reading
-/// OpenZaak itself (adr-proposal #78).
+/// HTTP client to the ACL service. An Objecten notification carries only the object URL, so the
+/// subscriber reads the register record back through the ACL — the only code that may talk to
+/// Objecten (§8.1, ADR-0028/ADR-0030) — rather than reading Objecten itself.
 /// </summary>
 public sealed class AclHttpClient(HttpClient http) : IAclClient
 {
-    public async Task<string> GetZaakReferenceAsync(Uri zaakUrl, CancellationToken ct = default)
+    public async Task<RegisterRecord?> GetRegisterRecordAsync(Uri objectUrl, CancellationToken ct = default)
    {
-        ArgumentNullException.ThrowIfNull(zaakUrl);
+        ArgumentNullException.ThrowIfNull(objectUrl);

        using var response = await http.PostAsJsonAsync(
-            new Uri(http.BaseAddress!, "zaken/reference"), new ReferenceRequest(zaakUrl.ToString()), ct);
-        response.EnsureSuccessStatusCode();
+            new Uri(http.BaseAddress!, "register-records/read"),
+            new ReadRequest(objectUrl.ToString()), ct);

-        var body = await response.Content.ReadFromJsonAsync<ReferenceResponse>(ct)
-            ?? throw new InvalidOperationException("The ACL returned an empty reference response.");
-        return body.Reference;
+        // The object holds no register record (deleted, or never one) — nothing to project (§8.6).
+        if (response.StatusCode == HttpStatusCode.NotFound)
+            return null;
+
+        response.EnsureSuccessStatusCode();
+        return await response.Content.ReadFromJsonAsync<RegisterRecord>(ct)
+            ?? throw new InvalidOperationException("The ACL returned an empty register record response.");
    }

-    private sealed record ReferenceRequest([property: JsonPropertyName("zaakUrl")] string ZaakUrl);
-
-    private sealed record ReferenceResponse([property: JsonPropertyName("reference")] string Reference);
+    private sealed record ReadRequest([property: JsonPropertyName("objectUrl")] string ObjectUrl);
 }
@@ -84,11 +84,12 @@ app.MapPost("/admin/rebuild", async (NotificationProjector projector, Cancellati

 await app.RunAsync();

-/// <summary>The NRC notification body, as Open Notificaties POSTs it. Only the fields the
-/// projection needs are bound; <c>aanmaakdatum</c>/<c>kenmerken</c> are ignored for the minimal slice.</summary>
-public sealed record NotificationDto(string Kanaal, string Resource, string Actie, Uri ResourceUrl, Uri? HoofdObject = null)
+/// <summary>The NRC notification body, as Open Notificaties POSTs it. Only the fields the projector
+/// needs are bound; <c>aanmaakdatum</c>, <c>kenmerken</c> and <c>hoofdObject</c> are ignored — for a
+/// register write hoofdObject is the same object as resourceUrl (ADR-0030).</summary>
+public sealed record NotificationDto(string Kanaal, string Resource, string Actie, Uri ResourceUrl)
 {
-    public Notification ToNotification() => new(Kanaal, Resource, Actie, ResourceUrl, HoofdObject);
+    public Notification ToNotification() => new(Kanaal, Resource, Actie, ResourceUrl);
 }

 public partial class Program
@@ -2,40 +2,39 @@ namespace EventSubscriber.Application;

 /// <summary>
 /// An inbound NRC (Open Notificaties) notification, as Open Notificaties POSTs it to an
-/// abonnement callback. Only the fields the projection needs are modelled; the full ZGW
-/// "Notificatie" resource also carries <c>aanmaakdatum</c> and <c>kenmerken</c> which the
-/// minimal projection ignores (bsn is deferred — see ADR-0008). For a <c>zaken</c>/<c>zaak</c>/<c>create</c>
-/// notification <c>hoofdObject</c> and <c>resourceUrl</c> are both the created zaak's URL.
+/// abonnement callback. Only the fields the projection needs are modelled.
 /// </summary>
+/// <remarks>
+/// Since S-19b-2 the subscriber listens on the <c>objecten</c> kanaal, not <c>zaken</c>: the
+/// register record in Objecten is what the projection is derived from (ADR-0030), so the
+/// projection is a cache of the register rather than a re-derivation of the case system. An
+/// Objecten notification carries <b>no record data</b> — only the object URL (as both
+/// <c>hoofdObject</c> and <c>resourceUrl</c>) and the objecttype as a kenmerk — so the record
+/// itself is read back through the ACL.
+/// </remarks>
 public sealed record Notification(
    string Kanaal,
    string Resource,
    string Actie,
-    Uri ResourceUrl,
-    Uri? HoofdObject = null)
+    Uri ResourceUrl)
 {
-    /// <summary>A zaak being created — projected as INGEDIEND.</summary>
-    public bool IsZaakCreated =>
-        Kanaal == "zaken" && Resource == "zaak" && Actie == "create";
-
-    /// <summary>A status being set on a zaak — the approval, projected as INGESCHREVEN (S-09b). In the
-    /// walking skeleton the only status ever set after creation is the approval, and the subscriber may
-    /// not read OpenZaak (§8.1), so any status-create is taken as the approval.</summary>
-    public bool IsZaakStatusSet =>
-        Kanaal == "zaken" && Resource == "status" && Actie == "create";
-
-    /// <summary>The zaak URL this notification concerns — <c>hoofdObject</c> (the zaak) for a status
-    /// notification, else the resource URL (which, for a zaak-create, is the zaak).</summary>
-    public Uri ZaakUrl => HoofdObject ?? ResourceUrl;
-
-    /// <summary>The zaak UUID used as the projection key — the trailing segment of <see cref="ZaakUrl"/>.</summary>
-    public string ZaakId => ZaakUrl.Segments[^1].Trim('/');
-
    /// <summary>
-    /// A deterministic dedup key. Open Notificaties carries no notification id and may
-    /// redeliver, so the key is derived from the immutable notification content: two
-    /// deliveries of the same zaak-create collapse to one. (NRC may also deliver
-    /// out of order; the projector tolerates that — order does not change the outcome.)
+    /// A register record written to Objecten — <c>create</c> on submit and <c>partial_update</c> on
+    /// approval, since the ACL upserts the same object for a registration (§8.6).
    /// </summary>
-    public string IdempotencyKey => $"{Kanaal}:{Resource}:{Actie}:{ResourceUrl}";
+    /// <remarks>
+    /// <c>partial_update</c> is what a PATCH actually reports: DRF routes it through the notifying
+    /// <c>update()</c> but names the action <c>partial_update</c>, and that is what Objecten puts in
+    /// the notification. <c>update</c> is accepted too, so a PUT-shaped write would project the same
+    /// way. <c>destroy</c> is deliberately not: removing a registration from the public register is
+    /// its own decision, not a side effect of this one.
+    /// </remarks>
+    public bool IsRegisterRecordWritten =>
+        Kanaal == "objecten" && Resource == "object"
+        && Actie is "create" or "update" or "partial_update";
+
+    /// <summary>The object holding the register record. For a <c>resource: object</c> notification
+    /// Objecten sends the object as both <c>hoofdObject</c> and <c>resourceUrl</c> — the object is
+    /// the main resource — so the notification's own <c>hoofdObject</c> is not modelled.</summary>
+    public Uri ObjectUrl => ResourceUrl;
 }
@@ -3,21 +3,27 @@ namespace EventSubscriber.Application;
 /// <summary>
 /// Projects inbound NRC notifications into the read projection. Tolerates duplicate and
 /// out-of-order deliveries (CLAUDE.md §8.6): the notification log dedups, and the projection
-/// upsert is idempotent on the zaak id. Rebuilds the projection by replaying the log.
+/// upsert is idempotent on the register id. Rebuilds the projection by replaying the log.
 /// </summary>
 public sealed class NotificationProjector(INotificationLog log, IProjectionStore store, IAclClient acl)
 {
-    /// <summary>Handle one inbound notification. Reacts to a zaak being created (INGEDIEND) and a
-    /// status being set (INGESCHREVEN); ignores everything else. Enriches the row with the zaak's
-    /// reference via the ACL (§8.1) and records it so a rebuild needs no ZGW access (#78).</summary>
+    /// <summary>Handle one inbound notification. Reacts to a register record being written to
+    /// Objecten (S-19b-2, ADR-0030) and ignores everything else. The notification carries only the
+    /// object URL, so the record is read back through the ACL (§8.1) and becomes the row verbatim.</summary>
    public async Task HandleAsync(Notification notification, CancellationToken ct = default)
    {
-        if (!notification.IsZaakCreated && !notification.IsZaakStatusSet)
+        ArgumentNullException.ThrowIfNull(notification);
+
+        if (!notification.IsRegisterRecordWritten)
+            return;
+
+        var record = await acl.GetRegisterRecordAsync(notification.ObjectUrl, ct);
+        // The object is gone, or holds no register record — nothing to project (§8.6).
+        if (record is null)
            return;

-        var reference = await acl.GetZaakReferenceAsync(notification.ZaakUrl, ct);
        var recorded = new RecordedNotification(
-            notification.IdempotencyKey, notification.Actie, notification.ZaakId, notification.Resource, reference);
+            KeyFor(notification.ObjectUrl, record), record.Id, record.Status, record.Reference);

        // Atomic record-or-skip: a duplicate (or concurrent) delivery is recognised and dropped
        // before it touches the projection, so the projection stays a faithful derived artefact.
@@ -27,6 +33,20 @@ public sealed class NotificationProjector(INotificationLog log, IProjectionStore
        await store.UpsertAsync(ToEntry(recorded), ct);
    }

+    /// <summary>
+    /// A deterministic dedup key: the object, plus the state that write puts in the projection.
+    /// </summary>
+    /// <remarks>
+    /// Open Notificaties carries no notification id and may redeliver, so the key is derived from
+    /// content. It cannot be the object URL alone — the ACL upserts one object per registration, so
+    /// submit and approval both notify about the *same* URL and the approval would be swallowed as a
+    /// duplicate. Nor can it include the actie: a retried approval would be a second `update`. Keying
+    /// on the projected row means a redelivery collapses and a genuine state change does not, which
+    /// is exactly the property §8.6 asks for.
+    /// </remarks>
+    private static string KeyFor(Uri objectUrl, RegisterRecord record)
+        => $"objecten:object:{objectUrl}:{record.Status}:{record.Reference}";
+
    /// <summary>Rebuild the projection from the durable notification log (PRD §8.4).</summary>
    public async Task RebuildAsync(CancellationToken ct = default)
    {
@@ -35,11 +55,9 @@ public sealed class NotificationProjector(INotificationLog log, IProjectionStore
            await store.UpsertAsync(ToEntry(recorded), ct);
    }

-    /// <summary>The projection row for an accepted notification: a status-set maps to INGESCHREVEN,
-    /// a zaak-create to INGEDIEND. bsn/naam are deferred (ADR-0008).</summary>
+    /// <summary>The projection row for an accepted notification. The log already holds exactly the
+    /// row's fields, so a rebuild needs no mapping rules and no upstream reads. bsn/naam stay
+    /// deferred — the register record is public-safe by construction (ADR-0027).</summary>
    private static RegisterEntry ToEntry(RecordedNotification recorded)
-        => new(
-            recorded.ZaakId,
-            recorded.Resource == "status" ? RegistrationStatus.Ingeschreven : RegistrationStatus.Ingediend,
-            Reference: recorded.Reference);
+        => new(recorded.RegisterId, recorded.Status, recorded.Reference);
 }
@@ -4,7 +4,7 @@ namespace EventSubscriber.Application;
 /// The durable log of notifications the subscriber has accepted. It is both the idempotency
 /// guard (a replayed notification is recognised and dropped) and the rebuild source: the
 /// projection is a derived artefact (PRD §8.4) regenerated by replaying this log, so a rebuild
-/// needs no access to OpenZaak (CLAUDE.md §8.1). Implemented in Infrastructure over Postgres.
+/// needs no access to Objecten or ZGW (CLAUDE.md §8.1). Implemented in Infrastructure over Postgres.
 /// </summary>
 public interface INotificationLog
 {
@@ -19,22 +19,29 @@ public interface INotificationLog
    Task<IReadOnlyList<RecordedNotification>> AllAsync(CancellationToken ct = default);
 }

-/// <summary>A notification that has been accepted, retaining what a rebuild needs to recompute its
-/// projection row — the ZGW <c>resource</c> (zaak-create → INGEDIEND vs status-set → INGESCHREVEN) and
-/// the zaak <c>reference</c> (identificatie), so a rebuild reproduces the row without re-reading ZGW (#78).</summary>
-public sealed record RecordedNotification(string Key, string Actie, string ZaakId, string Resource, string? Reference);
+/// <summary>
+/// An accepted notification, retaining exactly the projection row it produced — so a rebuild
+/// reproduces the row by replaying the log, without re-reading Objecten (S-19b-2, ADR-0030).
+/// </summary>
+public sealed record RecordedNotification(string Key, string RegisterId, string Status, string? Reference);

 /// <summary>
-/// Port to the Anti-Corruption Layer. The subscriber enriches the projection with the zaak's
-/// public-safe reference (its identificatie) by asking the ACL — the only code that may read ZGW
-/// (§8.1) — rather than reading OpenZaak itself (adr-proposal #78).
+/// Port to the Anti-Corruption Layer. An Objecten notification carries only the object URL, so the
+/// subscriber reads the register record back through the ACL — the only code that may talk to
+/// Objecten (§8.1, ADR-0028) — rather than reading Objecten itself.
 /// </summary>
 public interface IAclClient
 {
-    /// <summary>The zaak's reference (identificatie) for the read projection.</summary>
-    Task<string> GetZaakReferenceAsync(Uri zaakUrl, CancellationToken ct = default);
+    /// <summary>The register record the object at <paramref name="objectUrl"/> holds, or
+    /// <c>null</c> if it holds none — the object may be gone by the time a redelivered
+    /// notification is handled, which is not an error (§8.6).</summary>
+    Task<RegisterRecord?> GetRegisterRecordAsync(Uri objectUrl, CancellationToken ct = default);
 }

+/// <summary>The public-safe register record as the ACL returns it — the RegisterRecord objecttype's
+/// schema (ADR-0027). No bsn, no name: the register is world-readable.</summary>
+public sealed record RegisterRecord(string Id, string Status, string? Reference);
+
 /// <summary>The read projection store. Owned by the projection bounded context (ADR-0008); the
 /// subscriber writes to it and the projection-api reads it.</summary>
 public interface IProjectionStore
@@ -5,27 +5,42 @@ using EventSubscriber.Api;
 namespace EventSubscriber.Tests;

 /// <summary>
-/// Unit tests for the subscriber's ACL client, which reads a zaak's reference (identificatie) through
-/// the ACL — the only code allowed to talk to ZGW (§8.1, #78). Uses a scripted message handler so no
-/// real ACL is required.
+/// Unit tests for the subscriber's ACL client, which reads a register record through the ACL — the
+/// only code allowed to talk to Objecten (§8.1, ADR-0028/ADR-0030). Uses a scripted message handler
+/// so no real ACL is required.
 /// </summary>
 public class AclHttpClientTests
 {
+    private const string ObjectUrl = "http://objecten.local:8000/api/v2/objects/obj-9";
+
    private static AclHttpClient Client(StubHandler handler) =>
        new(new HttpClient(handler) { BaseAddress = new Uri("http://acl/") });

    [Fact]
-    public async Task Reads_a_zaak_reference_by_posting_the_zaak_url_and_returns_it()
+    public async Task Reads_a_register_record_by_posting_the_object_url()
    {
        var capture = new RequestCapture();
-        var client = Client(capture.Responds(HttpStatusCode.OK, """{"reference":"REG-42"}"""));
+        var client = Client(capture.Responds(
+            HttpStatusCode.OK, """{"id":"zaak-1","status":"INGESCHREVEN","reference":"REG-42"}"""));

-        var reference = await client.GetZaakReferenceAsync(new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
+        var record = await client.GetRegisterRecordAsync(new Uri(ObjectUrl));

-        Assert.Equal("REG-42", reference);
+        Assert.Equal("zaak-1", record!.Id);
+        Assert.Equal("INGESCHREVEN", record.Status);
+        Assert.Equal("REG-42", record.Reference);
        Assert.Equal(HttpMethod.Post, capture.Seen!.Method);
-        Assert.Equal("http://acl/zaken/reference", capture.Seen.RequestUri!.ToString());
-        Assert.Contains("\"zaakUrl\":\"http://openzaak/zaken/api/v1/zaken/abc\"", capture.Body);
+        Assert.Equal("http://acl/register-records/read", capture.Seen.RequestUri!.ToString());
+        Assert.Contains($"\"objectUrl\":\"{ObjectUrl}\"", capture.Body);
+    }
+
+    [Fact]
+    public async Task Reads_a_missing_record_as_nothing_to_project()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.NotFound));
+
+        // The object may be gone by the time a redelivered notification is handled (§8.6).
+        Assert.Null(await client.GetRegisterRecordAsync(new Uri(ObjectUrl)));
    }

    [Fact]
@@ -35,7 +50,7 @@ public class AclHttpClientTests
        var client = Client(capture.Responds(HttpStatusCode.BadGateway));

        await Assert.ThrowsAsync<HttpRequestException>(
-            () => client.GetZaakReferenceAsync(new Uri("http://openzaak/zaken/api/v1/zaken/abc")));
+            () => client.GetRegisterRecordAsync(new Uri(ObjectUrl)));
    }

    [Fact]
@@ -45,17 +60,17 @@ public class AclHttpClientTests
        var client = Client(capture.Responds(HttpStatusCode.OK, "null"));

        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
-            () => client.GetZaakReferenceAsync(new Uri("http://openzaak/zaken/api/v1/zaken/abc")));
+            () => client.GetRegisterRecordAsync(new Uri(ObjectUrl)));
        Assert.Contains("empty", ex.Message, StringComparison.OrdinalIgnoreCase);
    }

    [Fact]
-    public async Task Rejects_a_null_zaak_url_without_sending_a_request()
+    public async Task Rejects_a_null_object_url_without_sending_a_request()
    {
        var capture = new RequestCapture();
-        var client = Client(capture.Responds(HttpStatusCode.OK, """{"reference":"REG-1"}"""));
+        var client = Client(capture.Responds(HttpStatusCode.OK, "{}"));

-        await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetZaakReferenceAsync(null!));
+        await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetRegisterRecordAsync(null!));
        Assert.Null(capture.Seen);
    }
 }
@@ -5,16 +5,18 @@ namespace EventSubscriber.Tests;
 /// <summary>In-memory stand-ins for the projection store and notification log, so the
 /// projector's behaviour is exercised without Postgres (hand-written stubs, the repo's
 /// convention — no mocking library).</summary>
-/// <summary>A fake ACL client that returns a fixed reference derived from the zaak, and records
-/// how many times it was called (to prove a rebuild does not re-read via the ACL).</summary>
+/// <summary>A fake ACL client standing in for the register records Objecten holds: a test seeds a
+/// record per object URL, and the call count proves a rebuild does not re-read through the ACL.</summary>
 internal sealed class FakeAclClient : IAclClient
 {
+    public Dictionary<string, RegisterRecord> Records { get; } = [];
+
    public int CallCount { get; private set; }

-    public Task<string> GetZaakReferenceAsync(Uri zaakUrl, CancellationToken ct = default)
+    public Task<RegisterRecord?> GetRegisterRecordAsync(Uri objectUrl, CancellationToken ct = default)
    {
        CallCount++;
-        return Task.FromResult("REG-" + zaakUrl.Segments[^1].Trim('/'));
+        return Task.FromResult(Records.TryGetValue(objectUrl.ToString(), out var record) ? record : null);
    }
 }

@@ -2,13 +2,14 @@ using EventSubscriber.Application;

 namespace EventSubscriber.Tests;

-/// <summary>Behaviour of the projector that turns NRC notifications into projection rows.
-/// The walking skeleton reacts only to a zaak being created (status INGEDIEND) and must
-/// tolerate duplicate and out-of-order deliveries (CLAUDE.md §8.6).</summary>
+/// <summary>Behaviour of the projector that turns NRC notifications into projection rows. Since
+/// S-19b-2 the source is the register in Objecten (ADR-0030), not ZGW zaak events: a notification
+/// carries only the object URL, so the record is read back through the ACL. Duplicate and
+/// out-of-order deliveries must be tolerated (CLAUDE.md §8.6).</summary>
 public sealed class NotificationProjectorTests
 {
-    private const string ZaakUrl = "http://openzaak:8000/zaken/api/v1/zaken/11111111-1111-1111-1111-111111111111";
-    private const string StatusUrl = "http://openzaak:8000/zaken/api/v1/statussen/22222222-2222-2222-2222-222222222222";
+    private const string ObjectUrl = "http://objecten.local:8000/api/v2/objects/11111111-1111-1111-1111-111111111111";
+    private const string ZaakId = "99999999-9999-9999-9999-999999999999";

    private readonly InMemoryNotificationLog _log = new();
    private readonly InMemoryProjectionStore _store = new();
@@ -16,46 +17,60 @@ public sealed class NotificationProjectorTests

    private NotificationProjector Projector() => new(_log, _store, _acl);

-    private static Notification ZaakCreated(string url = ZaakUrl)
-        => new("zaken", "zaak", "create", new Uri(url));
-
-    // A status-set notification: resourceUrl is the status resource, hoofdObject is the zaak it belongs to.
-    private static Notification StatusSet(string zaakUrl = ZaakUrl, string statusUrl = StatusUrl)
-        => new("zaken", "status", "create", new Uri(statusUrl), new Uri(zaakUrl));
-
-    [Fact]
-    public async Task creating_a_zaak_writes_one_row_with_status_ingediend()
+    /// <summary>A register write as Objecten publishes it: the object is both hoofdObject and
+    /// resourceUrl, and the record itself is only reachable by reading that object.</summary>
+    private Notification RecordWritten(string actie = "create", string url = ObjectUrl, string status = RegistrationStatus.Ingediend, string zaakId = ZaakId)
    {
-        await Projector().HandleAsync(ZaakCreated());
-
-        var entry = Assert.Single(await _store.AllAsync());
-        Assert.Equal("11111111-1111-1111-1111-111111111111", entry.Id);
-        Assert.Equal(RegistrationStatus.Ingediend, entry.Status);
-        // Enriched with the zaak's reference (identificatie), fetched via the ACL (#78).
-        Assert.Equal("REG-11111111-1111-1111-1111-111111111111", entry.Reference);
+        _acl.Records[url] = new RegisterRecord(zaakId, status, "REG-2026-0001");
+        return new Notification("objecten", "object", actie, new Uri(url));
    }

    [Fact]
-    public async Task rebuild_reproduces_the_reference_without_re_reading_via_the_acl()
+    public async Task a_register_record_write_is_projected_as_a_row_keyed_on_the_registration()
    {
-        var projector = Projector();
-        await projector.HandleAsync(ZaakCreated());
-        var callsAfterProjection = _acl.CallCount;
-
-        await projector.RebuildAsync();
+        await Projector().HandleAsync(RecordWritten());

        var entry = Assert.Single(await _store.AllAsync());
-        Assert.Equal("REG-11111111-1111-1111-1111-111111111111", entry.Reference);
-        // Rebuild replays the log (which stored the reference) — no extra ACL calls (#78, ADR-0008).
-        Assert.Equal(callsAfterProjection, _acl.CallCount);
+        // Keyed on the record's own id (the zaak id), not on the Objecten object's uuid — the
+        // projection row and the register record are the same registration.
+        Assert.Equal(ZaakId, entry.Id);
+        Assert.Equal(RegistrationStatus.Ingediend, entry.Status);
+        Assert.Equal("REG-2026-0001", entry.Reference);
+    }
+
+    // The ACL PATCHes the same object on approval. DRF routes a PATCH through `update()` but reports
+    // the action as `partial_update`, which is what Objecten puts in the notification — so accepting
+    // only `create`/`update` silently drops every approval.
+    [Theory]
+    [InlineData("partial_update")]
+    [InlineData("update")]
+    public async Task approval_updates_the_same_row_from_ingediend_to_ingeschreven(string actie)
+    {
+        var projector = Projector();
+        await projector.HandleAsync(RecordWritten());
+        await projector.HandleAsync(RecordWritten(actie, status: RegistrationStatus.Ingeschreven));
+
+        var entry = Assert.Single(await _store.AllAsync());
+        Assert.Equal(ZaakId, entry.Id);
+        Assert.Equal(RegistrationStatus.Ingeschreven, entry.Status);
+    }
+
+    [Fact]
+    public async Task an_object_whose_record_is_gone_is_not_projected()
+    {
+        // Nothing seeded in the fake ACL: the object was deleted before this (redelivered)
+        // notification was handled. Not an error — there is simply nothing to project (§8.6).
+        await Projector().HandleAsync(new Notification("objecten", "object", "create", new Uri(ObjectUrl)));
+
+        Assert.Empty(await _store.AllAsync());
    }

    [Fact]
    public async Task replaying_the_same_notification_keeps_a_single_row()
    {
        var projector = Projector();
-        await projector.HandleAsync(ZaakCreated());
-        await projector.HandleAsync(ZaakCreated());
+        await projector.HandleAsync(RecordWritten());
+        await projector.HandleAsync(RecordWritten());

        Assert.Single(await _store.AllAsync());
    }
@@ -64,8 +79,8 @@ public sealed class NotificationProjectorTests
    public async Task a_replayed_notification_never_reaches_the_projection_store()
    {
        var projector = Projector();
-        await projector.HandleAsync(ZaakCreated());
-        await projector.HandleAsync(ZaakCreated());
+        await projector.HandleAsync(RecordWritten());
+        await projector.HandleAsync(RecordWritten());

        // The duplicate is dropped at the log, before the (idempotent) upsert — so the store
        // is written exactly once. Row count alone can't see this; the upsert count can.
@@ -73,77 +88,59 @@ public sealed class NotificationProjectorTests
    }

    [Fact]
-    public async Task two_different_zaken_each_get_their_own_row()
+    public async Task two_different_registrations_each_get_their_own_row()
    {
        var projector = Projector();
-        await projector.HandleAsync(ZaakCreated());
-        await projector.HandleAsync(ZaakCreated(ZaakUrl[..^1] + "2")); // a distinct zaak url
+        await projector.HandleAsync(RecordWritten());
+        await projector.HandleAsync(RecordWritten(url: ObjectUrl[..^1] + "2", zaakId: "other-zaak"));

        Assert.Equal(2, (await _store.AllAsync()).Count);
    }

    [Theory]
-    [InlineData("documenten", "enkelvoudiginformatieobject", "create")] // wrong kanaal + resource
-    [InlineData("documenten", "zaak", "create")]                        // wrong kanaal only
-    [InlineData("zaken", "zaak", "update")]                             // wrong actie
-    [InlineData("zaken", "zaak", "destroy")]                            // wrong actie
-    [InlineData("zaken", "status", "update")]                           // a status change we ignore
-    [InlineData("zaken", "resultaat", "create")]                        // not a status we project
+    [InlineData("zaken", "zaak", "create")]      // the ZGW source S-19b-2 replaced
+    [InlineData("zaken", "status", "create")]    // ditto
+    [InlineData("objecten", "object", "destroy")] // a delete we do not project
+    [InlineData("documenten", "object", "create")] // wrong kanaal
    public async Task an_unrelated_notification_is_not_projected(string kanaal, string resource, string actie)
    {
-        await Projector().HandleAsync(new Notification(kanaal, resource, actie, new Uri(ZaakUrl)));
+        _acl.Records[ObjectUrl] = new RegisterRecord(ZaakId, RegistrationStatus.Ingediend, "REG-2026-0001");
+
+        await Projector().HandleAsync(new Notification(kanaal, resource, actie, new Uri(ObjectUrl)));

        Assert.Empty(await _store.AllAsync());
    }

    [Fact]
-    public async Task setting_a_status_projects_ingeschreven_keyed_on_the_zaak_not_the_status()
-    {
-        await Projector().HandleAsync(StatusSet());
-
-        var entry = Assert.Single(await _store.AllAsync());
-        // Keyed on the zaak (hoofdObject), not the status resource URL.
-        Assert.Equal("11111111-1111-1111-1111-111111111111", entry.Id);
-        Assert.Equal(RegistrationStatus.Ingeschreven, entry.Status);
-    }
-
-    [Fact]
-    public async Task approving_updates_the_existing_zaak_row_from_ingediend_to_ingeschreven()
+    public async Task rebuild_reproduces_the_row_without_re_reading_through_the_acl()
    {
        var projector = Projector();
-        await projector.HandleAsync(ZaakCreated());
-        await projector.HandleAsync(StatusSet());
-
-        var entry = Assert.Single(await _store.AllAsync());
-        Assert.Equal("11111111-1111-1111-1111-111111111111", entry.Id);
-        Assert.Equal(RegistrationStatus.Ingeschreven, entry.Status);
-    }
-
-    [Fact]
-    public async Task rebuild_reproduces_the_approved_status()
-    {
-        var projector = Projector();
-        await projector.HandleAsync(ZaakCreated());
-        await projector.HandleAsync(StatusSet());
+        await projector.HandleAsync(RecordWritten());
+        await projector.HandleAsync(RecordWritten("partial_update", status: RegistrationStatus.Ingeschreven));
+        var callsAfterProjection = _acl.CallCount;

        await projector.RebuildAsync();

        var entry = Assert.Single(await _store.AllAsync());
        Assert.Equal(RegistrationStatus.Ingeschreven, entry.Status);
+        Assert.Equal("REG-2026-0001", entry.Reference);
+        // The log holds the projected row itself, so a rebuild needs neither the ACL nor
+        // Objecten (§8.4, ADR-0030).
+        Assert.Equal(callsAfterProjection, _acl.CallCount);
    }

    [Fact]
    public async Task rebuild_clears_stale_rows_and_repopulates_from_the_notification_log()
    {
        var projector = Projector();
-        await projector.HandleAsync(ZaakCreated());
+        await projector.HandleAsync(RecordWritten());
        // A stale row that is not backed by any logged notification must not survive a rebuild.
        await _store.UpsertAsync(new RegisterEntry("stale-9999", RegistrationStatus.Ingediend));

        await projector.RebuildAsync();

        var entry = Assert.Single(await _store.AllAsync());
-        Assert.Equal("11111111-1111-1111-1111-111111111111", entry.Id);
+        Assert.Equal(ZaakId, entry.Id);
        Assert.Equal(RegistrationStatus.Ingediend, entry.Status);
    }
 }
@@ -13,9 +13,8 @@ public sealed class EfNotificationLog(ProjectionDbContext db) : INotificationLog
        db.ProcessedNotifications.Add(new ProcessedNotificationRow
        {
            Key = notification.Key,
-            Actie = notification.Actie,
-            ZaakId = notification.ZaakId,
-            Resource = notification.Resource,
+            RegisterId = notification.RegisterId,
+            Status = notification.Status,
            Reference = notification.Reference,
            ReceivedAt = DateTimeOffset.UtcNow,
        });
@@ -36,6 +35,6 @@ public sealed class EfNotificationLog(ProjectionDbContext db) : INotificationLog
    public async Task<IReadOnlyList<RecordedNotification>> AllAsync(CancellationToken ct = default)
        => await db.ProcessedNotifications
            .OrderBy(r => r.ReceivedAt)
-            .Select(r => new RecordedNotification(r.Key, r.Actie, r.ZaakId, r.Resource, r.Reference))
+            .Select(r => new RecordedNotification(r.Key, r.RegisterId, r.Status, r.Reference))
            .ToListAsync(ct);
 }
@@ -0,0 +1,87 @@
+// <auto-generated />
+using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+using Projection.ReadModel;
+
+#nullable disable
+
+namespace Projection.ReadModel.Migrations
+{
+    [DbContext(typeof(ProjectionDbContext))]
+    [Migration("20260828103132_ProjectionSourcedFromObjecten")]
+    partial class ProjectionSourcedFromObjecten
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "10.0.0")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("Projection.ReadModel.ProcessedNotificationRow", b =>
+                {
+                    b.Property<string>("Key")
+                        .HasColumnType("text")
+                        .HasColumnName("key");
+
+                    b.Property<DateTimeOffset>("ReceivedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("received_at");
+
+                    b.Property<string>("Reference")
+                        .HasColumnType("text")
+                        .HasColumnName("reference");
+
+                    b.Property<string>("RegisterId")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("register_id");
+
+                    b.Property<string>("Status")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("status");
+
+                    b.HasKey("Key");
+
+                    b.ToTable("processed_notifications", (string)null);
+                });
+
+            modelBuilder.Entity("Projection.ReadModel.RegisterEntryRow", b =>
+                {
+                    b.Property<string>("Id")
+                        .HasColumnType("text")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Bsn")
+                        .HasColumnType("text")
+                        .HasColumnName("bsn");
+
+                    b.Property<string>("NaamPlaceholder")
+                        .HasColumnType("text")
+                        .HasColumnName("naam_placeholder");
+
+                    b.Property<string>("Reference")
+                        .HasColumnType("text")
+                        .HasColumnName("reference");
+
+                    b.Property<string>("Status")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("status");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("register_projection", (string)null);
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}
@@ -0,0 +1,69 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Projection.ReadModel.Migrations
+{
+    /// <summary>
+    /// S-19b-2 (ADR-0030): the notification log stops describing ZGW zaak events and starts holding
+    /// the projected register row itself (register id, status, reference).
+    /// </summary>
+    /// <remarks>
+    /// The old columns are dropped and the new ones added rather than renamed. EF scaffolded renames
+    /// (<c>resource</c> → <c>register_id</c>, <c>zaak_id</c> → <c>status</c>), which would carry ZGW
+    /// values into columns that mean something else entirely — "zaak"/"status" as a register id, a
+    /// zaak uuid as a register status — and a rebuild would then project that garbage.
+    ///
+    /// Both tables are emptied instead. A pre-existing row describes a zaak event the new projector
+    /// cannot reproject, and the registrations behind those rows have no RegisterRecord in Objecten
+    /// (only approvals wrote one before this slice), so they are not re-derivable from the new source
+    /// either. The projection is a derived artefact (§8.4) and repopulates as register writes arrive.
+    /// </remarks>
+    public partial class ProjectionSourcedFromObjecten : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            // ponytail: drops the pre-slice register rather than backfilling it. Fine while stacks are
+            // ephemeral (a fresh `docker compose up` is the norm). If a long-lived environment ever
+            // needs to keep them, backfill by walking Objecten's objects instead of replaying the log.
+            migrationBuilder.Sql("DELETE FROM processed_notifications;");
+            migrationBuilder.Sql("DELETE FROM register_projection;");
+
+            migrationBuilder.DropColumn(name: "actie", table: "processed_notifications");
+            migrationBuilder.DropColumn(name: "zaak_id", table: "processed_notifications");
+            migrationBuilder.DropColumn(name: "resource", table: "processed_notifications");
+
+            migrationBuilder.AddColumn<string>(
+                name: "register_id",
+                table: "processed_notifications",
+                type: "text",
+                nullable: false,
+                defaultValue: "");
+
+            migrationBuilder.AddColumn<string>(
+                name: "status",
+                table: "processed_notifications",
+                type: "text",
+                nullable: false,
+                defaultValue: "");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.Sql("DELETE FROM processed_notifications;");
+            migrationBuilder.Sql("DELETE FROM register_projection;");
+
+            migrationBuilder.DropColumn(name: "register_id", table: "processed_notifications");
+            migrationBuilder.DropColumn(name: "status", table: "processed_notifications");
+
+            migrationBuilder.AddColumn<string>(
+                name: "actie", table: "processed_notifications", type: "text", nullable: false, defaultValue: "");
+            migrationBuilder.AddColumn<string>(
+                name: "zaak_id", table: "processed_notifications", type: "text", nullable: false, defaultValue: "");
+            migrationBuilder.AddColumn<string>(
+                name: "resource", table: "processed_notifications", type: "text", nullable: false, defaultValue: "");
+        }
+    }
+}
@@ -28,11 +28,6 @@ namespace Projection.ReadModel.Migrations
                        .HasColumnType("text")
                        .HasColumnName("key");

-                    b.Property<string>("Actie")
-                        .IsRequired()
-                        .HasColumnType("text")
-                        .HasColumnName("actie");
-
                    b.Property<DateTimeOffset>("ReceivedAt")
                        .HasColumnType("timestamp with time zone")
                        .HasColumnName("received_at");
@@ -41,15 +36,15 @@ namespace Projection.ReadModel.Migrations
                        .HasColumnType("text")
                        .HasColumnName("reference");

-                    b.Property<string>("Resource")
+                    b.Property<string>("RegisterId")
                        .IsRequired()
                        .HasColumnType("text")
-                        .HasColumnName("resource");
+                        .HasColumnName("register_id");

-                    b.Property<string>("ZaakId")
+                    b.Property<string>("Status")
                        .IsRequired()
                        .HasColumnType("text")
-                        .HasColumnName("zaak_id");
+                        .HasColumnName("status");

                    b.HasKey("Key");

@@ -34,9 +34,8 @@ public sealed class ProjectionDbContext(DbContextOptions<ProjectionDbContext> op
            e.ToTable("processed_notifications");
            e.HasKey(r => r.Key);
            e.Property(r => r.Key).HasColumnName("key");
-            e.Property(r => r.Actie).HasColumnName("actie").IsRequired();
-            e.Property(r => r.ZaakId).HasColumnName("zaak_id").IsRequired();
-            e.Property(r => r.Resource).HasColumnName("resource").IsRequired();
+            e.Property(r => r.RegisterId).HasColumnName("register_id").IsRequired();
+            e.Property(r => r.Status).HasColumnName("status").IsRequired();
            e.Property(r => r.Reference).HasColumnName("reference");
            e.Property(r => r.ReceivedAt).HasColumnName("received_at");
        });
@@ -56,18 +55,20 @@ public sealed class RegisterEntryRow
    public string? NaamPlaceholder { get; set; }
 }

-/// <summary>An accepted notification, retained so the projection can be rebuilt without OpenZaak (§8.1).</summary>
+/// <summary>An accepted notification, retained so the projection can be rebuilt without reading
+/// Objecten or ZGW (§8.1, §8.4). Since S-19b-2 it holds the projected row itself — the register
+/// record's id, status and reference — so a rebuild is a replay with no mapping rules (ADR-0030).</summary>
 public sealed class ProcessedNotificationRow
 {
    public required string Key { get; set; }
-    public required string Actie { get; set; }
-    public required string ZaakId { get; set; }

-    /// <summary>The ZGW resource (e.g. <c>zaak</c> or <c>status</c>) — retained so a rebuild reprojects
-    /// the right status without reading OpenZaak (S-09b).</summary>
-    public required string Resource { get; set; }
+    /// <summary>The registration this record is for (the zaak id) — the projection row's key.</summary>
+    public required string RegisterId { get; set; }

-    /// <summary>The zaak reference (identificatie), retained so a rebuild reprojects it without the ACL (#78).</summary>
+    /// <summary>The register status the record carried (INGEDIEND / INGESCHREVEN).</summary>
+    public required string Status { get; set; }
+
+    /// <summary>The citizen-facing reference the record carried — matches the submit confirmation (#78).</summary>
    public string? Reference { get; set; }

    public DateTimeOffset ReceivedAt { get; set; }
@@ -1,19 +1,28 @@
 # language: en
-# Drives S-06 (#7). On a zaak-created notification from NRC the Event Subscriber writes a
-# rebuildable read-projection row (PRD §8.4). This scenario exercises the use case against an
-# in-memory stand-in for the projection store and notification log; real OpenZaak → NRC →
-# subscriber delivery is verified by the live-stack check (verify-projection, ADR-0007/#58).
-Feature: Register-projectie bijwerken op een zaaknotificatie
-  Als openbaar register wil ik dat een aangemaakte zaak in de projectie verschijnt
-  zodat het register de ingediende registratie kan tonen.
+# Drives S-19b-2 (#153), re-sourcing S-06 (#7). The read projection is derived from the
+# RegisterRecord in Objecten (ADR-0030), not from ZGW zaak events: the ACL records a registration
+# in the register, Objecten notifies, and the Event Subscriber projects the record that
+# notification points at. This scenario exercises the use case against in-memory stand-ins for the
+# register, the projection store and the notification log; real Objecten → NRC → subscriber
+# delivery is verified by the live-stack check (verify-projection, ADR-0007/0030).
+Feature: Register-projectie bijwerken op een registerwijziging
+  Als openbaar register wil ik dat een registratie in de projectie verschijnt zodra zij
+  in het register is vastgelegd, zodat het register haar actuele status kan tonen.

-  Scenario: Een zaaknotificatie levert een rij met status INGEDIEND
-    Given a zaak is created in OpenZaak with id "11111111-1111-1111-1111-111111111111"
-    When the NRC notification for that zaak is delivered to the event subscriber
+  Scenario: Een ingediende registratie levert een rij met status INGEDIEND
+    Given registration "11111111-1111-1111-1111-111111111111" is recorded in the register with status "INGEDIEND"
+    When the register notification is delivered to the event subscriber
    Then the register projection contains a row for "11111111-1111-1111-1111-111111111111" with status "INGEDIEND"

+  Scenario: Een goedgekeurde registratie werkt dezelfde rij bij
+    Given registration "33333333-3333-3333-3333-333333333333" is recorded in the register with status "INGEDIEND"
+    And the register notification is delivered to the event subscriber
+    When registration "33333333-3333-3333-3333-333333333333" is recorded in the register with status "INGESCHREVEN"
+    And the register notification is delivered to the event subscriber
+    Then the register projection contains a row for "33333333-3333-3333-3333-333333333333" with status "INGESCHREVEN"
+
  Scenario: Dezelfde notificatie tweemaal levert geen duplicaat
-    Given a zaak is created in OpenZaak with id "22222222-2222-2222-2222-222222222222"
-    When the NRC notification for that zaak is delivered to the event subscriber
-    And the same NRC notification is delivered again
+    Given registration "22222222-2222-2222-2222-222222222222" is recorded in the register with status "INGEDIEND"
+    When the register notification is delivered to the event subscriber
+    And the same register notification is delivered again
    Then the register projection contains exactly one row for "22222222-2222-2222-2222-222222222222"
@@ -46,7 +46,7 @@ public sealed class EenZaakOpenenSteps
    {
        var fill = new InMemoryDefaultFillStore(new DefaultFillSettings(
            _defaults!.Bronorganisatie, _defaults.VerantwoordelijkeOrganisatie, _defaults.Vertrouwelijkheidaanduiding));
-        var service = new AclService(_gateway, fill, new CachedZaaktypeCatalog(_gateway, _defaults!), new FixedClock(_today));
+        var service = new AclService(_gateway, new InMemoryRegisterRecordGateway(), fill, new CachedZaaktypeCatalog(_gateway, _defaults!), new FixedClock(_today));
        _returnedUrl = await service.OpenZaakAsync(_registration!);
    }

@@ -5,31 +5,39 @@ using Xunit;

 namespace Acceptance.Steps;

-/// <summary>Bindings for <c>RegisterProjectieBijwerken.feature</c> (S-06). Reqnroll creates
-/// one instance per scenario, so instance fields hold scenario-scoped state.</summary>
+/// <summary>Bindings for <c>RegisterProjectieBijwerken.feature</c> (S-06, re-sourced by S-19b-2).
+/// Reqnroll creates one instance per scenario, so instance fields hold scenario-scoped state.</summary>
 [Binding]
 public sealed class RegisterProjectieBijwerkenSteps
 {
-    private const string ZaakBase = "http://openzaak:8000/zaken/api/v1/zaken/";
+    private const string ObjectBase = "http://objecten.local:8000/api/v2/objects/";

    private readonly InMemoryNotificationLog _log = new();
    private readonly InMemoryProjectionStore _store = new();
+    private readonly InMemoryRegisterRecordClient _register = new();
    private readonly NotificationProjector _projector;
    private Notification? _notification;

    public RegisterProjectieBijwerkenSteps()
-        => _projector = new NotificationProjector(_log, _store, new InMemoryAclReferenceClient());
+        => _projector = new NotificationProjector(_log, _store, _register);

-    [Given("a zaak is created in OpenZaak with id \"(.*)\"")]
-    public void GivenAZaakIsCreatedInOpenZaakWithId(string id)
-        => _notification = new Notification("zaken", "zaak", "create", new Uri(ZaakBase + id));
+    [Given("registration \"(.*)\" is recorded in the register with status \"(.*)\"")]
+    [When("registration \"(.*)\" is recorded in the register with status \"(.*)\"")]
+    public void RegistrationIsRecorded(string id, string status)
+    {
+        // The ACL upserts one object per registration, so submit and approval share an object URL.
+        var objectUrl = ObjectBase + id;
+        _register.Records[objectUrl] = new RegisterRecord(id, status, "REG-" + id);
+        _notification = new Notification("objecten", "object", "create", new Uri(objectUrl));
+    }

-    [When("the NRC notification for that zaak is delivered to the event subscriber")]
-    public Task WhenTheNotificationIsDelivered()
+    [Given("the register notification is delivered to the event subscriber")]
+    [When("the register notification is delivered to the event subscriber")]
+    public Task TheNotificationIsDelivered()
        => _projector.HandleAsync(_notification!);

-    [When("the same NRC notification is delivered again")]
-    public Task WhenTheSameNotificationIsDeliveredAgain()
+    [When("the same register notification is delivered again")]
+    public Task TheSameNotificationIsDeliveredAgain()
        => _projector.HandleAsync(_notification!);

    [Then("the register projection contains a row for \"(.*)\" with status \"(.*)\"")]
@@ -39,10 +39,12 @@ public sealed class InMemoryProjectionStore : IProjectionStore
        => [.. _byId.Values.Where(e => e.Id == id)];
 }

-/// <summary>A fake ACL client for the projection acceptance scenario: returns a reference derived
-/// from the zaak, so the projector can enrich rows without a running ACL (#78).</summary>
-public sealed class InMemoryAclReferenceClient : IAclClient
+/// <summary>An in-memory stand-in for the register the ACL reads back for the projector, so the
+/// scenario runs without a running ACL or Objecten (S-19b-2, ADR-0030).</summary>
+public sealed class InMemoryRegisterRecordClient : IAclClient
 {
-    public Task<string> GetZaakReferenceAsync(Uri zaakUrl, CancellationToken ct = default)
-        => Task.FromResult("REG-" + zaakUrl.Segments[^1].Trim('/'));
+    public Dictionary<string, RegisterRecord> Records { get; } = [];
+
+    public Task<RegisterRecord?> GetRegisterRecordAsync(Uri objectUrl, CancellationToken ct = default)
+        => Task.FromResult(Records.TryGetValue(objectUrl.ToString(), out var record) ? record : null);
 }
@@ -53,3 +53,20 @@ public sealed class InMemoryZaakGateway : IZaakGateway
        => Task.FromResult<IReadOnlyList<ZaaktypeSummary>>(
            [new ZaaktypeSummary("BIG-REGISTRATIE", "BIG-registratie", ResolvedZaaktypeUrl)]);
 }
+
+/// <summary>An in-memory stand-in for the Objecten API (S-19a): records the register records the ACL
+/// writes on approval, so a scenario can assert on them without a running Objecten.</summary>
+public sealed class InMemoryRegisterRecordGateway : IRegisterRecordGateway
+{
+    public List<RegisterRecord> Upserted { get; } = [];
+
+    public Task UpsertAsync(RegisterRecord record, CancellationToken ct = default)
+    {
+        Upserted.Add(record);
+        return Task.CompletedTask;
+    }
+
+    /// <summary>The most recently written record — scenarios never read one back by object URL.</summary>
+    public Task<RegisterRecord?> GetAsync(Uri objectUrl, CancellationToken ct = default)
+        => Task.FromResult(Upserted.Count == 0 ? null : Upserted[^1]);
+}
@@ -1,11 +1,16 @@
-import { expect, test } from '@playwright/test';
+import { expect, request, test } from '@playwright/test';

-// Walking-skeleton happy path (S-08d + S-09 + S-09b + S-12 + S-10a): a zorgprofessional logs in via
-// mock DigiD and submits through the self-service portal → BFF → domain; the entry appears in the
-// openbaar register as INGEDIEND; the citizen supplies the documents the process is waiting for
-// (S-10a); a behandelaar then logs in to the behandel portal, finds the registration in the werkbak,
-// and approves it (goedkeuren); the decision completes the Flowable Beoordelen task and flows via the
-// ACL → NRC → event-subscriber → projection, and the openbaar register shows INGESCHREVEN.
+// Walking-skeleton happy path (S-08d + S-09 + S-09b + S-12 + S-10a + S-19b-2): a zorgprofessional
+// logs in via mock DigiD and submits through the self-service portal → BFF → domain; the entry
+// appears in the openbaar register as INGEDIEND; the citizen supplies the documents the process is
+// waiting for (S-10a); a behandelaar then logs in to the behandel portal, finds the registration in
+// the werkbak, and approves it (goedkeuren); the decision completes the Flowable Beoordelen task and
+// flows via the ACL → Objecten → NRC → event-subscriber → projection, and the openbaar register
+// shows INGESCHREVEN.
+//
+// Since ADR-0030 both public statuses come from the register in Objecten, not from ZGW zaak events:
+// the ACL writes the record on submit (INGEDIEND) and upserts it on approval (INGESCHREVEN), so the
+// INGEDIEND assertion below is itself proof of the re-sourced path.
 test('DigiD submit → public INGEDIEND → documenten → behandelaar goedkeurt → public INGESCHREVEN', async ({
  page,
  context,
@@ -109,4 +114,53 @@ test('DigiD submit → public INGEDIEND → documenten → behandelaar goedkeurt
      return staff.getByRole('row', { name: reference }).getByRole('cell', { name: 'INGESCHREVEN' }).count();
    }, { timeout: 30_000, intervals: [1_000, 2_000, 3_000, 5_000] })
    .toBeGreaterThan(0);
+
+  // S-19a: the same approval also wrote the canonical register record to Objecten (ADR-0028).
+  // Asserted here rather than in verify-domain because this is the only check that drives a *real*
+  // approval — verify-domain completes the Beoordelen task straight through Flowable REST, which
+  // bypasses the domain `decide` path that calls the ACL.
+  const records = await registerRecordsFor(reference);
+  // Matched on OUR reference: the verify stack is shared and holds records from earlier checks.
+  expect(records, `expected exactly one RegisterRecord for ${reference}`).toHaveLength(1);
+  expect(records[0].status).toBe('INGESCHREVEN');
+  // The register is world-readable, so the record must carry nothing but the public-safe fields
+  // (ADR-0027) — Objecten's own schema validation enforces this, and this proves it end to end.
+  expect(Object.keys(records[0]).sort()).toEqual(['id', 'reference', 'status']);
 });
+
+const OBJECTEN = process.env.OBJECTEN_URL ?? 'http://objecten:8000';
+const OBJECTTYPEN = process.env.OBJECTTYPEN_URL ?? 'http://objecttypen:8000';
+const OBJECTEN_TOKEN = process.env.OBJECTEN_TOKEN ?? '1234567890abcdef1234567890abcdef12345678';
+const OBJECTTYPEN_TOKEN = process.env.OBJECTTYPEN_TOKEN ?? '0123456789abcdef0123456789abcdef01234567';
+
+/**
+ * The RegisterRecord objects Objecten holds for a registration reference.
+ *
+ * The objecttype is resolved by name rather than pinned: Objecttypen echoes the request Host into
+ * the objecttype `url`, and Objecten only accepts the one matching its configured api_root — so
+ * both must be reached by service name, exactly as the ACL reaches them (ADR-0028).
+ */
+async function registerRecordsFor(reference: string): Promise<Record<string, string>[]> {
+  const api = await request.newContext();
+  try {
+    const types = await api.get(`${OBJECTTYPEN}/api/v2/objecttypes`, {
+      headers: { Authorization: `Token ${OBJECTTYPEN_TOKEN}` },
+    });
+    expect(types.ok(), `Objecttypen returned ${types.status()}`).toBeTruthy();
+    const objecttype = ((await types.json()).results as { url: string; name: string }[]).find(
+      (o) => o.name === 'RegisterRecord',
+    );
+    if (!objecttype) throw new Error('the RegisterRecord objecttype is not registered in Objecttypen');
+
+    const objects = await api.get(`${OBJECTEN}/api/v2/objects`, {
+      headers: { Authorization: `Token ${OBJECTEN_TOKEN}`, 'Accept-Crs': 'EPSG:4326' },
+      params: { type: objecttype.url, data_attrs: `reference__exact__${reference}` },
+    });
+    expect(objects.ok(), `Objecten returned ${objects.status()}: ${await objects.text()}`).toBeTruthy();
+    return ((await objects.json()).results as { record: { data: Record<string, string> } }[]).map(
+      (o) => o.record.data,
+    );
+  } finally {
+    await api.dispose();
+  }
+}