fix(e2e): poll the register by reference, not a shared INGEDIEND cell (refs #78)

The verify stack is shared: earlier verify-projection/verify-domain checks leave
INGEDIEND rows in the register before the e2e submits. A status-only poll
short-circuited on a stale row, then the reference assertion ran against a
not-yet-reloaded page and timed out. Poll (with reload) on this submission's
reference cell instead — stronger, and it directly proves the #78 correlation.
Scope the INGEDIEND/INGESCHREVEN status checks to that reference row too.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/openbaar/src/app/register/register-page.html

@@ -43,7 +43,7 @@
         <tbody>
           @for (entry of entries(); track entry.id) {
             <tr>
-              <td>{{ entry.id }}</td>
+              <td>{{ entry.reference }}</td>
               <td>{{ entry.status }}</td>
             </tr>
           }

apps/openbaar/src/app/register/register-page.spec.ts

@@ -5,8 +5,8 @@ import { axe } from 'vitest-axe';
 import { RegisterPage } from './register-page';
 
 const sample: OpenbaarEntry[] = [
-  { id: 'zaak-abc', status: 'INGEDIEND' },
+  { id: 'zaak-abc', status: 'INGEDIEND', reference: 'REG-abc' },
-  { id: 'zaak-def', status: 'INGESCHREVEN' },
+  { id: 'zaak-def', status: 'INGESCHREVEN', reference: 'REG-def' },
 ];
 
 function providers(get = vi.fn().mockReturnValue(of(sample))) {
@@ -22,9 +22,11 @@ describe('RegisterPage', () => {
     await render(RegisterPage, { providers: providers(get).providers });
 
     expect(get).toHaveBeenCalled();
-    expect(await screen.findByText(/zaak-abc/)).toBeTruthy();
+    // The Referentie column shows the citizen's reference (matches the submit confirmation, #78),
+    // not the internal zaak id.
+    expect(await screen.findByText(/REG-abc/)).toBeTruthy();
     expect(screen.getByText(/INGEDIEND/)).toBeTruthy();
-    expect(screen.getByText(/zaak-def/)).toBeTruthy();
+    expect(screen.getByText(/REG-def/)).toBeTruthy();
   });
 
   it('searches by the entered term', async () => {

docs/architecture/adr-0011-approval-status-flow.md

@@ -0,0 +1,64 @@
+# ADR-0011: Approval sets the zaak eindstatus via the ACL and projects INGESCHREVEN from the notification alone
+
+- **Status:** Accepted
+- **Date:** 2026-07-13
+- **Deciders:** Respellion engineering
+- **Relates to:** S-09b (#75); split from S-09 (#10); builds on ADR-0001 (§8 loose coupling), ADR-0003 (ACL default-fill), ADR-0007 (OZ→NRC wiring), ADR-0008 (read projection), ADR-0009 (external-task worker)
+
+## Context
+
+The walking skeleton could submit a registration (INGEDIEND) and show it in the openbaar register,
+but nothing could **approve** it. S-09b adds a behandelaar approval that must make the entry publicly
+visible as a terminal status. There is no behandel-portal yet (S-12), so approval is triggered by a
+**temporary admin endpoint** on the Domain Service.
+
+Two decisions are non-obvious (§14) and cross service boundaries:
+
+1. **Who resolves the ZGW statustype?** Approval means "set the zaak to its final status", but the
+   domain must stay ZGW-ignorant (§8.1 — only the ACL talks to ZGW) and does not know statustype URLs.
+2. **How does the projection learn the new status?** The status is set in OpenZaak, which notifies over
+   NRC; the Event Subscriber projects it. But the subscriber **may not read OpenZaak** (§8.1), and an
+   NRC `status`/`create` notification's `resourceUrl` is the *status* resource, not the zaak, and does
+   not carry the statustype.
+
+## Decision
+
+**Approval flows Domain → ACL → OpenZaak → NRC → Event Subscriber → projection, using only the
+notification's own fields on the read side.**
+
+- **Domain.** `Registration.Approve()` advances INGEDIEND → INGESCHREVEN (requires an opened zaak; a
+  repeat is a no-op). The `ApproveRegistration` use case calls the ACL to set the zaak status, then
+  advances the aggregate. A temporary `POST /registrations/{id}/approve` endpoint drives it.
+- **ACL.** A new `POST /statussen` operation takes only the zaak URL. The ACL resolves the zaaktype's
+  **eindstatus** from the catalogus (`isEindstatus`, falling back to the highest `volgnummer`) and
+  POSTs a ZGW status against the zaak. The domain never names statustypen — the ACL owns the ZGW
+  translation (§8.1, ADR-0003).
+- **Event Subscriber.** It binds the NRC `hoofdObject` (always the zaak URL) and keys the projection on
+  it, so a `zaken`/`status`/`create` notification updates the **same** row the zaak-create created,
+  flipping it to INGESCHREVEN. It takes **any** status-create as the approval — in the walking skeleton
+  the only status ever set after creation is the approval — so it never has to read OpenZaak to learn
+  the statustype. The ZGW `resource` is retained in the notification log (new column) so a rebuild
+  reproduces the right status.
+
+## Consequences
+
+- The domain↔ACL boundary stays clean: the domain hands over a zaak URL and says "approve"; ZGW
+  statustype knowledge lives only in the ACL.
+- The projection remains rebuildable without OpenZaak (§8.1, ADR-0008): the log now records the ZGW
+  resource, which is all a rebuild needs to reproject the status.
+- The openbaar register shows real lifecycle: INGEDIEND on submit, INGESCHREVEN on approval.
+- **Walking-skeleton assumption:** "any status-create ⇒ INGESCHREVEN" holds only while approval is the
+  sole post-creation status transition. When more transitions arrive (beoordeling, afwijzing — S-12+),
+  the subscriber must distinguish statustypen. The honest options then are to carry the statustype
+  omschrijving in the notification `kenmerken`, or to have the ACL resolve it and re-notify — recorded
+  here so future-me revisits this rather than assuming it generalises.
+
+## Alternatives considered
+
+- **Inject the approved statustype URL into the ACL as config** (like the zaaktype URL). Rejected:
+  couples ACL config to seed output and adds compose/run-domain-check plumbing; runtime eindstatus
+  discovery keeps the ACL self-contained for one extra ZGW GET per approval.
+- **Have the Event Subscriber GET the status/statustype from OpenZaak** to map precisely. Rejected:
+  violates §8.1 (only the ACL talks to ZGW) and makes the projection depend on OpenZaak being up.
+- **Record the derived status in the notification log** instead of the ZGW resource. Rejected: the log
+  should retain notification *facts*, not projection semantics; the mapping stays in the projector.

docs/architecture/adr-0012-citizen-reference-correlation.md

@@ -0,0 +1,104 @@
+# ADR-0012: One citizen-facing reference across self-service and the openbaar register
+
+- **Status:** Accepted
+- **Date:** 2026-07-14
+- **Deciders:** Respellion engineering
+- **Relates to:** #78 (adr-proposal); builds on ADR-0008 (read projection), ADR-0001 (loose coupling), ADR-0009 (external-task worker / zaak creation)
+
+## Context
+
+A citizen submits through the self-service portal and is shown a confirmation with a
+**reference** so they can find their registration back in the public register. But the two
+sides showed **different identifiers**:
+
+- The self-service confirmation shows the **domain `registrationId`** — a GUID minted by the
+  domain aggregate (`RegistrationId.New()`) when the registration is created, before any zaak
+  exists.
+- The openbaar register showed the **zaak id** — the UUID from the NRC `hoofdObject` URL,
+  assigned by OpenZaak when the ACL opens the zaak.
+
+These never match, so the reference on the confirmation was useless for looking the entry up.
+The two identifiers live on opposite sides of the ACL boundary and are generated by different
+systems at different times, so there is no way to reconcile them after the fact without a
+correlating value carried across the boundary.
+
+The NRC notification the Event Subscriber consumes carries only the zaak URL plus the fixed
+`kenmerken` (`bronorganisatie`, `zaaktype`, `vertrouwelijkheidaanduiding`) — **not** the
+`registrationId`, the bsn, or the `identificatie`. ADR-0008 already recorded that filling any
+such field means reading the zaak **through the ACL** (§8.1) and deferred it as a follow-up.
+This is that follow-up, scoped to the one field the citizen actually needs.
+
+## Decision
+
+**Use the domain `registrationId` as the zaak's `identificatie`, and surface that single value
+as the citizen-facing `reference` on both portals. The Event Subscriber enriches the projection
+with the reference by reading the zaak through the ACL, and stores it in the replay log so
+rebuild stays log-only.**
+
+Concretely, following the request path:
+
+1. **Domain → ACL (write).** When the OpenZaak worker opens a zaak, it passes
+   `registration.Id` to the ACL (`IAclClient.OpenZaakAsync(bsn, reference, …)`). The ACL sets
+   it as the zaak's `identificatie` on `POST /zaken`. OpenZaak's `identificatie` is unique per
+   `bronorganisatie` and ≤ 40 chars — a GUID string fits. The ACL remains the only code that
+   constructs ZGW payloads (§8.1); the domain never sees a ZGW URL.
+2. **Event Subscriber → ACL (read).** On a notification, the subscriber asks the ACL for the
+   zaak's reference via a new `POST /zaken/reference` endpoint (`{ zaakUrl } → { reference }`),
+   which reads the zaak's `identificatie` through the ACL's OpenZaak gateway. The subscriber
+   still never talks to ZGW itself (§8.1) — it depends only on the ACL, over HTTP.
+3. **Projection + replay log.** The reference is written both to the `register_projection` row
+   **and** to the `processed_notifications` replay log (a new nullable `reference` column on
+   each). Storing it in the log is what keeps ADR-0008's "**rebuild replays the log, not
+   OpenZaak**" invariant true: `POST /admin/rebuild` reproduces the reference from the log
+   without re-reading the ACL.
+4. **BFF + openbaar.** The public view (`OpenbaarProjection.PublicView`) exposes
+   `id`, `status`, and `reference` (never bsn/naam), and the openbaar search matches on either
+   `id` or `reference`. The openbaar register's "Referentie" column now renders `reference`.
+
+The end-to-end guarantee is asserted in the Playwright walking-skeleton: the reference captured
+from the submit confirmation must appear as a cell in the public register.
+
+### Why HTTP to the ACL, not the ACL as a library
+
+ADR-0008 floated "extend the ACL with a zaak-read operation, consumed as a library." We instead
+call the ACL **over HTTP**, consistent with every other cross-service hop in this system
+(portals→BFF, domain→ACL). Sharing the ACL as a library would couple the subscriber to the
+ACL's infrastructure assembly and its ZGW client configuration, defeating the anti-corruption
+boundary. The HTTP endpoint keeps the ACL the single owner of ZGW access and its config.
+
+## Consequences
+
+**Positive**
+
+- One reference, end to end: the citizen's confirmation value is exactly what the public
+  register shows and searches by.
+- §8.1 stays intact — only the ACL reads or writes ZGW; the subscriber depends on the ACL, not
+  OpenZaak.
+- Rebuild stays log-only (ADR-0008): the reference is replayed from `processed_notifications`,
+  so `/admin/rebuild` needs no ACL/ZGW access.
+- The column additions are nullable and additive; older rows without a reference are tolerated.
+
+**Negative / costs**
+
+- A new coupling: the Event Subscriber now depends on the ACL being reachable
+  (`Acl__BaseUrl`, compose `depends_on: acl`). A registration whose reference read fails will
+  need the notification redelivered (NRC already redelivers; the projection upsert is
+  idempotent).
+- One extra HTTP hop per notification (subscriber→ACL→OpenZaak) on the projection path. Bounded:
+  one small GET per zaak, off the citizen's request path.
+- `identificatie` now carries semantic meaning (it equals the `registrationId`). If OpenZaak
+  were ever configured to auto-generate `identificatie`, the correlation would break; the ACL
+  setting it explicitly is now load-bearing.
+
+## Alternatives considered
+
+- **Carry the `registrationId` in the notification** — rejected: NRC `kenmerken` are fixed and
+  the notification content is not ours to extend; it would also couple the projection to a
+  bespoke notification shape.
+- **Show the zaak id on the confirmation instead** — rejected: the zaak does not exist yet when
+  the confirmation is returned (the worker opens it asynchronously, ADR-0009), so the domain has
+  no zaak id to show at submit time.
+- **Store only on the projection row, re-read the ACL on rebuild** — rejected: it would make
+  rebuild depend on the ACL/ZGW, breaking ADR-0008's log-only rebuild invariant.
+- **Reconcile the two ids in a lookup table** — rejected: adds write-only state and a second
+  source of truth for a value that can simply be the same on both sides.

docs/demo-script.md

@@ -195,5 +195,56 @@ curl -fsS http://localhost:8140/openbaar/register | jq   # same public-safe view
 # → [ { "id": "<zaak-uuid>", "status": "INGEDIEND" } ]
 ```
 
-> The register shows `INGEDIEND` entries today; the approval transition to a terminal status
+> The register shows `INGEDIEND` on submit; approval flips it to `INGESCHREVEN` — see S-09b below.
-> (e.g. `INGESCHREVEN`) lands with the approval flow (S-09b, #75).
+
+---
+
+## S-09b — Approval flow (public visibility flips to INGESCHREVEN)
+
+**Outcome:** a behandelaar approves a submitted registration via a temporary admin endpoint (no
+behandel-portal yet — S-12). The approval sets the zaak's final status through the ACL, which flows
+back to the projection over NRC, and the openbaar register then shows the entry as `INGESCHREVEN`.
+
+**The path:** `POST /registrations/{id}/approve` (domain) → ACL sets the zaak eindstatus (ZGW
+`/statussen`) → OpenZaak → NRC → Event Subscriber projects `INGESCHREVEN` → openbaar register.
+
+```bash
+# 1. Full stack up, then drive submit → public INGEDIEND → approve → public INGESCHREVEN:
+make up
+make verify-e2e
+
+# 2. Or by hand: submit (as in S-09), note the reference, then approve it.
+#    The zaak is opened off the request path, so approve once GET shows a zaakUrl.
+ref="<registration-reference-from-the-confirmation>"
+curl -fsS http://localhost:8130/registrations/$ref | jq       # domain (host port 8130): wait for .zaakUrl
+curl -fsS -X POST http://localhost:8130/registrations/$ref/approve -i   # → 204 No Content
+
+# 3. The public register now shows the entry as approved.
+curl -fsS http://localhost:8140/openbaar/register | jq
+# → [ { "id": "<zaak-uuid>", "status": "INGESCHREVEN" } ]
+```
+
+> **End of walking skeleton** (S-09 + S-09b): submit → process → projection → public visibility, from
+> INGEDIEND through approval to INGESCHREVEN. The subscriber takes any post-creation status-set as the
+> approval (ADR-0011) — a walking-skeleton assumption that tightens when more transitions arrive (S-12+).
+
+## #78 — One reference across both portals (ADR-0012)
+
+Before this change the self-service confirmation and the openbaar register showed **different**
+identifiers, so a citizen could not look their registration back up. Now both show the same
+**reference**: the domain `registrationId` is set as the zaak's `identificatie` by the ACL, and the
+Event Subscriber enriches the projection with it by reading the zaak through the ACL (§8.1) — storing
+it in the replay log so rebuild stays log-only (ADR-0008).
+
+**The path:** domain passes `registrationId` → ACL sets it as `zaak.identificatie` → NRC →
+Event Subscriber asks the ACL for the reference → projection row + replay log → openbaar register.
+
+```bash
+# Submit as in S-09 and note the reference on the confirmation, then find it in the public register:
+ref="<registration-reference-from-the-confirmation>"
+curl -fsS "http://localhost:8140/openbaar/register?q=$ref" | jq
+# → [ { "id": "<zaak-uuid>", "status": "INGEDIEND", "reference": "<same-ref-as-confirmation>" } ]
+```
+
+> The openbaar register's "Referentie" column and its search now use this reference — the exact value
+> the citizen saw on submit. Asserted end-to-end by the Playwright happy path.

infra/docker-compose.yml

@@ -396,6 +396,9 @@ services:
     image: register-referentie/event-subscriber:dev
     environment:
       ConnectionStrings__Projection: Host=projection-db;Database=projection;Username=projection;Password=projection
+      # The subscriber enriches the projection with each zaak's reference (identificatie) by asking
+      # the ACL — the only code allowed to read ZGW (§8.1, #78).
+      Acl__BaseUrl: http://acl:8080/
       # The bearer Open Notificaties must present on the abonnement callback. NRC's
       # registration probe expects a 401 without it (ADR-0007). Dev-only token.
       EventSubscriber__Webhook__AuthToken: ${NOTIFICATION_WEBHOOK_TOKEN:-Bearer big-reference-notifications}
@@ -410,6 +413,8 @@ services:
     depends_on:
       projection-db:
         condition: service_healthy
+      acl:
+        condition: service_healthy
     networks: [cg]
 
   # The read side of the projection. Shares Projection.ReadModel, so build context is root.

libs/api-client/src/lib/generated/bff-api.ts

@@ -27,6 +27,8 @@ import {
 export interface OpenbaarEntry {
   id: string;
   status: string;
+  /** @nullable */
+  reference: string | null;
 }
 
 export interface SubmitAccepted {

services/acl/Acl.Api/Program.cs

@@ -20,12 +20,32 @@ app.MapGet("/health", () => "Healthy");
 // The ACL's single operation, exposed as a service endpoint.
 app.MapPost("/zaken", async (OpenZaakRequest body, AclService acl, CancellationToken ct) =>
 {
-    var zaakUrl = await acl.OpenZaakAsync(new DomainRegistration(body.Bsn), ct);
+    var zaakUrl = await acl.OpenZaakAsync(new DomainRegistration(body.Bsn, body.Reference), ct);
     return Results.Ok(new { zaakUrl = zaakUrl.ToString() });
 });
 
+// Approve a zaak: set it to its zaaktype's eindstatus (S-09b). The domain hands over only the zaak
+// URL; the ACL owns the ZGW statustype resolution (§8.1).
+app.MapPost("/statussen", async (SetStatusRequest body, AclService acl, CancellationToken ct) =>
+{
+    await acl.ApproveZaakAsync(new Uri(body.ZaakUrl), ct);
+    return Results.NoContent();
+});
+
+// Read a zaak's public-safe reference (its identificatie). The Event Subscriber calls this to enrich
+// the read projection without reading ZGW itself (§8.1, #78).
+app.MapPost("/zaken/reference", async (ZaakReferenceRequest body, AclService acl, CancellationToken ct) =>
+{
+    var reference = await acl.GetZaakReferenceAsync(new Uri(body.ZaakUrl), ct);
+    return Results.Ok(new { reference });
+});
+
 app.Run();
 
-public sealed record OpenZaakRequest(string Bsn);
+public sealed record OpenZaakRequest(string Bsn, string Reference);
+
+public sealed record SetStatusRequest(string ZaakUrl);
+
+public sealed record ZaakReferenceRequest(string ZaakUrl);
 
 public partial class Program;

services/acl/Acl.Application/AclService.cs

@@ -13,8 +13,28 @@ public sealed class AclService(IZaakGateway gateway, AclDefaults defaults, ICloc
             defaults.VerantwoordelijkeOrganisatie,
             defaults.Vertrouwelijkheidaanduiding,
             defaults.ZaaktypeUrl,
-            clock.Today);
+            clock.Today,
+            registration.Reference);
 
         return gateway.OpenZaakAsync(request, ct);
     }
+
+    /// <summary>
+    /// Approve a zaak: set it to the eindstatus of the configured BIG zaaktype (ADR-0003 default). The
+    /// domain hands over only the zaak URL; the ACL owns which statustype means "approved" (§8.1).
+    /// </summary>
+    public Task ApproveZaakAsync(Uri zaakUrl, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(zaakUrl);
+
+        return gateway.SetZaakToEindstatusAsync(zaakUrl, defaults.ZaaktypeUrl, clock.Today, ct);
+    }
+
+    /// <summary>The zaak's reference (its ZGW identificatie), for the read projection (#78).</summary>
+    public Task<string> GetZaakReferenceAsync(Uri zaakUrl, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(zaakUrl);
+
+        return gateway.GetZaakIdentificatieAsync(zaakUrl, ct);
+    }
 }

services/acl/Acl.Application/DomainRegistration.cs

@@ -1,4 +1,5 @@
 namespace Acl.Application;
 
-/// <summary>Domain-language payload handed to the ACL. No ZGW concepts here.</summary>
+/// <summary>Domain-language payload handed to the ACL. No ZGW concepts here. <see cref="Reference"/>
-public sealed record DomainRegistration(string Bsn);
+/// is the registration's own id; the ACL records it as the zaak identificatie (adr-proposal #78).</summary>
+public sealed record DomainRegistration(string Bsn, string Reference);

services/acl/Acl.Application/IZaakGateway.cs

@@ -5,4 +5,15 @@ namespace Acl.Application;
 public interface IZaakGateway
 {
     Task<Uri> OpenZaakAsync(ZaakRequest request, CancellationToken ct = default);
+
+    /// <summary>
+    /// Set the given zaak to the <em>eindstatus</em> (final statustype) of the supplied zaaktype —
+    /// the ZGW translation of "approve". The gateway resolves which statustype is the eindstatus from
+    /// the catalogus and POSTs a status against the zaak, dated <paramref name="datumStatusGezet"/>.
+    /// </summary>
+    Task SetZaakToEindstatusAsync(Uri zaakUrl, Uri zaaktypeUrl, DateOnly datumStatusGezet, CancellationToken ct = default);
+
+    /// <summary>Read the zaak's <c>identificatie</c> — the public-safe reference the register shows.
+    /// The Event Subscriber calls this through the ACL rather than reading ZGW itself (§8.1, #78).</summary>
+    Task<string> GetZaakIdentificatieAsync(Uri zaakUrl, CancellationToken ct = default);
 }

services/acl/Acl.Application/ZaakRequest.cs

@@ -6,4 +6,5 @@ public sealed record ZaakRequest(
     string VerantwoordelijkeOrganisatie,
     string Vertrouwelijkheidaanduiding,
     Uri Zaaktype,
-    DateOnly Startdatum);
+    DateOnly Startdatum,
+    string Identificatie);

services/acl/Acl.Infrastructure/OpenZaakGateway.cs

@@ -20,7 +20,8 @@ public sealed class OpenZaakGateway(HttpClient http, OpenZaakOptions options) :
                 request.Zaaktype.ToString(),
                 request.VerantwoordelijkeOrganisatie,
                 request.Startdatum.ToString("yyyy-MM-dd"),
-                request.Vertrouwelijkheidaanduiding)),
+                request.Vertrouwelijkheidaanduiding,
+                request.Identificatie)),
         };
         message.Headers.Authorization =
             new AuthenticationHeaderValue("Bearer", ZgwToken.Mint(options.ClientId, options.Secret));
@@ -41,13 +42,144 @@ public sealed class OpenZaakGateway(HttpClient http, OpenZaakOptions options) :
         return new Uri(created.Url);
     }
 
+    public async Task SetZaakToEindstatusAsync(Uri zaakUrl, Uri zaaktypeUrl, DateOnly datumStatusGezet, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(zaakUrl);
+        ArgumentNullException.ThrowIfNull(zaaktypeUrl);
+
+        var eindstatus = await ResolveEindstatusAsync(zaaktypeUrl, ct);
+        var resultaattype = await ResolveResultaattypeAsync(zaaktypeUrl, ct);
+
+        // OpenZaak refuses to set a zaak's eindstatus unless the zaak has a resultaat
+        // ("resultaat-does-not-exist"), so record the resultaat first, then the status.
+        await PostAsync("/zaken/api/v1/resultaten",
+            new ResultaatDto(zaakUrl.ToString(), resultaattype.ToString()), "Setting the zaak resultaat", ct);
+
+        await PostAsync("/zaken/api/v1/statussen",
+            // datumStatusGezet is a ZGW date-time; set it at the start of the given day (UTC).
+            new StatusDto(zaakUrl.ToString(), eindstatus.ToString(),
+                datumStatusGezet.ToDateTime(TimeOnly.MinValue, DateTimeKind.Utc).ToString("yyyy-MM-ddTHH:mm:ssZ")),
+            "Setting the zaak status", ct);
+    }
+
+    public async Task<string> GetZaakIdentificatieAsync(Uri zaakUrl, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(zaakUrl);
+
+        using var message = new HttpRequestMessage(HttpMethod.Get, zaakUrl);
+        message.Headers.Authorization =
+            new AuthenticationHeaderValue("Bearer", ZgwToken.Mint(options.ClientId, options.Secret));
+        // The zaak is a geo resource; the Zaken API requires the CRS header even on GET.
+        message.Headers.Add("Accept-Crs", "EPSG:4326");
+
+        using var response = await http.SendAsync(message, ct);
+        await EnsureSuccessAsync(response, "Reading the zaak", ct);
+
+        var zaak = await response.Content.ReadFromJsonAsync<ZaakReadDto>(ct)
+            ?? throw new InvalidOperationException("OpenZaak returned an empty zaak response");
+        return zaak.Identificatie;
+    }
+
+    // POSTs a non-geo ZGW resource (resultaat/status — no CRS headers). Buffers the body so uwsgi gets
+    // a Content-Length instead of a chunked body (as with zaak-create).
+    private async Task PostAsync(string path, object dto, string action, CancellationToken ct)
+    {
+        using var message = new HttpRequestMessage(HttpMethod.Post, new Uri(options.BaseUrl, path))
+        {
+            Content = JsonContent.Create(dto),
+        };
+        message.Headers.Authorization =
+            new AuthenticationHeaderValue("Bearer", ZgwToken.Mint(options.ClientId, options.Secret));
+        await message.Content.LoadIntoBufferAsync(ct);
+
+        using var response = await http.SendAsync(message, ct);
+        await EnsureSuccessAsync(response, action, ct);
+    }
+
+    // EnsureSuccessStatusCode discards the response body; ZGW returns a JSON problem detail on 400 that
+    // is essential for diagnosing a rejected request, so surface it in the exception.
+    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($"{action} failed: {(int)response.StatusCode} {response.ReasonPhrase}. {body}");
+    }
+
+    /// <summary>Resolve the zaaktype's eindstatus (the terminal statustype) from the catalogus.</summary>
+    private async Task<Uri> ResolveEindstatusAsync(Uri zaaktypeUrl, CancellationToken ct)
+    {
+        var page = await GetCatalogusAsync<StatustypePage>("statustypen", zaaktypeUrl, "statustypen", ct);
+        var results = page.Results ?? [];
+
+        // OpenZaak flags the terminal statustype (highest volgnummer) as isEindstatus; fall back to the
+        // highest volgnummer if the flag is absent.
+        var eindstatus = results.FirstOrDefault(s => s.IsEindstatus)
+            ?? results.OrderByDescending(s => s.Volgnummer).FirstOrDefault()
+            ?? throw new InvalidOperationException($"No statustypen found for zaaktype {zaaktypeUrl}");
+        return new Uri(eindstatus.Url);
+    }
+
+    /// <summary>Resolve the zaaktype's resultaattype from the catalogus (the seed defines one).</summary>
+    private async Task<Uri> ResolveResultaattypeAsync(Uri zaaktypeUrl, CancellationToken ct)
+    {
+        var page = await GetCatalogusAsync<ResultaattypePage>("resultaattypen", zaaktypeUrl, "resultaattypen", ct);
+        var resultaattype = (page.Results ?? []).FirstOrDefault()
+            ?? throw new InvalidOperationException($"No resultaattypen found for zaaktype {zaaktypeUrl}");
+        return new Uri(resultaattype.Url);
+    }
+
+    // GETs a catalogus collection filtered by zaaktype (status=alles includes concept + published).
+    private async Task<T> GetCatalogusAsync<T>(string resource, Uri zaaktypeUrl, string label, CancellationToken ct)
+    {
+        var query = new Uri(options.BaseUrl,
+            $"/catalogi/api/v1/{resource}?status=alles&zaaktype=" + Uri.EscapeDataString(zaaktypeUrl.ToString()));
+        using var message = new HttpRequestMessage(HttpMethod.Get, query);
+        message.Headers.Authorization =
+            new AuthenticationHeaderValue("Bearer", ZgwToken.Mint(options.ClientId, options.Secret));
+
+        using var response = await http.SendAsync(message, ct);
+        await EnsureSuccessAsync(response, $"Querying {label}", ct);
+
+        return await response.Content.ReadFromJsonAsync<T>(ct)
+            ?? throw new InvalidOperationException($"OpenZaak returned an empty {label} response");
+    }
+
     private sealed record ZaakDto(
         [property: JsonPropertyName("bronorganisatie")] string Bronorganisatie,
         [property: JsonPropertyName("zaaktype")] string Zaaktype,
         [property: JsonPropertyName("verantwoordelijkeOrganisatie")] string VerantwoordelijkeOrganisatie,
         [property: JsonPropertyName("startdatum")] string Startdatum,
-        [property: JsonPropertyName("vertrouwelijkheidaanduiding")] string Vertrouwelijkheidaanduiding);
+        [property: JsonPropertyName("vertrouwelijkheidaanduiding")] string Vertrouwelijkheidaanduiding,
+        [property: JsonPropertyName("identificatie")] string Identificatie);
 
     private sealed record ZaakCreatedDto(
         [property: JsonPropertyName("url")] string Url);
+
+    private sealed record ZaakReadDto(
+        [property: JsonPropertyName("identificatie")] string Identificatie);
+
+    private sealed record StatusDto(
+        [property: JsonPropertyName("zaak")] string Zaak,
+        [property: JsonPropertyName("statustype")] string Statustype,
+        [property: JsonPropertyName("datumStatusGezet")] string DatumStatusGezet);
+
+    private sealed record StatustypePage(
+        [property: JsonPropertyName("results")] IReadOnlyList<StatustypeDto>? Results);
+
+    private sealed record StatustypeDto(
+        [property: JsonPropertyName("url")] string Url,
+        [property: JsonPropertyName("volgnummer")] int Volgnummer,
+        [property: JsonPropertyName("isEindstatus")] bool IsEindstatus);
+
+    private sealed record ResultaatDto(
+        [property: JsonPropertyName("zaak")] string Zaak,
+        [property: JsonPropertyName("resultaattype")] string Resultaattype);
+
+    private sealed record ResultaattypePage(
+        [property: JsonPropertyName("results")] IReadOnlyList<ResultaattypeDto>? Results);
+
+    private sealed record ResultaattypeDto(
+        [property: JsonPropertyName("url")] string Url);
 }

services/acl/Acl.IntegrationTests/OpenZaakFixture.cs

@@ -65,6 +65,43 @@ public sealed class OpenZaakFixture : IDisposable
         return JsonDocument.Parse(json).RootElement.Clone();
     }
 
+    /// <summary>GETs a non-geo ZGW resource (e.g. a status) by URL — no CRS headers.</summary>
+    public async Task<JsonElement> GetJsonAsync(Uri url, CancellationToken ct = default)
+    {
+        using var message = new HttpRequestMessage(HttpMethod.Get, url);
+        message.Headers.Authorization = new AuthenticationHeaderValue("Bearer", MintToken());
+
+        using var response = await Http.SendAsync(message, ct);
+        response.EnsureSuccessStatusCode();
+        var json = await response.Content.ReadAsStringAsync(ct);
+        return JsonDocument.Parse(json).RootElement.Clone();
+    }
+
+    /// <summary>The zaaktype's eindstatus (terminal statustype) URL — the one an approval sets.</summary>
+    public async Task<Uri> FindEindstatustypeAsync(Uri zaaktypeUrl, CancellationToken ct = default)
+    {
+        var query = new Uri(BaseUrl,
+            "/catalogi/api/v1/statustypen?status=alles&zaaktype=" + Uri.EscapeDataString(zaaktypeUrl.ToString()));
+        var page = await GetJsonAsync(query, ct);
+        var results = page.GetProperty("results");
+
+        Uri? fallback = null;
+        var highest = int.MinValue;
+        foreach (var st in results.EnumerateArray())
+        {
+            if (st.TryGetProperty("isEindstatus", out var eind) && eind.GetBoolean())
+                return new Uri(st.GetProperty("url").GetString()!);
+            var volgnummer = st.GetProperty("volgnummer").GetInt32();
+            if (volgnummer > highest)
+            {
+                highest = volgnummer;
+                fallback = new Uri(st.GetProperty("url").GetString()!);
+            }
+        }
+
+        return fallback ?? throw new InvalidOperationException($"No statustypen for zaaktype {zaaktypeUrl}");
+    }
+
     // A ZGW (vng-api-common) HS256 JWT, mirroring the seed's client. Minted here
     // rather than reusing Acl.Infrastructure's internal minter to keep that internal.
     private string MintToken()

services/acl/Acl.IntegrationTests/OpenZaakGatewayIntegrationTests.cs

@@ -22,12 +22,14 @@ public sealed class OpenZaakGatewayIntegrationTests(OpenZaakFixture stack)
             "seed it with OZ_PUBLISH=1 (`make integration` does this).");
 
         var gateway = new OpenZaakGateway(stack.Http, stack.Options);
+        var reference = Guid.NewGuid().ToString(); // zaak identificatie must be unique per bronorganisatie
         var request = new ZaakRequest(
             Bronorganisatie: "517439943",
             VerantwoordelijkeOrganisatie: "517439943",
             Vertrouwelijkheidaanduiding: "openbaar",
             Zaaktype: zaaktype!,
-            Startdatum: DateOnly.FromDateTime(DateTime.UtcNow));
+            Startdatum: DateOnly.FromDateTime(DateTime.UtcNow),
+            Identificatie: reference);
 
         var zaakUrl = await gateway.OpenZaakAsync(request);
 
@@ -36,10 +38,40 @@ public sealed class OpenZaakGatewayIntegrationTests(OpenZaakFixture stack)
             new Uri(stack.BaseUrl, "/zaken/api/v1/zaken/").ToString(),
             zaakUrl.ToString());
 
-        // ...and that zaak is really persisted with the default-filled fields.
+        // ...and that zaak is really persisted with the default-filled fields + the reference identificatie.
         var zaak = await stack.GetZaakAsync(zaakUrl);
         Assert.Equal(zaaktype.ToString(), zaak.GetProperty("zaaktype").GetString());
         Assert.Equal("517439943", zaak.GetProperty("bronorganisatie").GetString());
         Assert.Equal("openbaar", zaak.GetProperty("vertrouwelijkheidaanduiding").GetString());
+        Assert.Equal(reference, zaak.GetProperty("identificatie").GetString());
+    }
+
+    [Fact]
+    public async Task Setting_a_zaak_to_its_eindstatus_records_the_terminal_statustype()
+    {
+        var zaaktype = await stack.FindPublishedBigZaaktypeAsync();
+        Assert.True(zaaktype is not null,
+            "No published BIG-REGISTRATIE zaaktype found in OpenZaak — bring the stack up and " +
+            "seed it with OZ_PUBLISH=1 (`make integration` does this).");
+
+        var gateway = new OpenZaakGateway(stack.Http, stack.Options);
+        var zaakUrl = await gateway.OpenZaakAsync(new ZaakRequest(
+            Bronorganisatie: "517439943",
+            VerantwoordelijkeOrganisatie: "517439943",
+            Vertrouwelijkheidaanduiding: "openbaar",
+            Zaaktype: zaaktype!,
+            Startdatum: DateOnly.FromDateTime(DateTime.UtcNow),
+            Identificatie: Guid.NewGuid().ToString()));
+
+        await gateway.SetZaakToEindstatusAsync(zaakUrl, zaaktype!, DateOnly.FromDateTime(DateTime.UtcNow));
+
+        // The zaak now carries a current status, and it is the zaaktype's eindstatus.
+        var zaak = await stack.GetZaakAsync(zaakUrl);
+        var statusUrl = zaak.GetProperty("status").GetString();
+        Assert.False(string.IsNullOrEmpty(statusUrl), "the approved zaak has no current status");
+
+        var status = await stack.GetJsonAsync(new Uri(statusUrl!));
+        var eindstatustype = await stack.FindEindstatustypeAsync(zaaktype!);
+        Assert.Equal(eindstatustype.ToString(), status.GetProperty("statustype").GetString());
     }
 }

services/acl/Acl.Tests/AclServiceTests.cs

@@ -9,13 +9,37 @@ public class AclServiceTests
         public ZaakRequest? Captured;
         public Uri Result { get; } = new("http://openzaak/zaken/api/v1/zaken/abc");
 
+        public (Uri Zaak, Uri Zaaktype, DateOnly Datum)? Approved;
+
         public Task<Uri> OpenZaakAsync(ZaakRequest request, CancellationToken ct = default)
         {
             Captured = request;
             return Task.FromResult(Result);
         }
+
+        public Task SetZaakToEindstatusAsync(Uri zaakUrl, Uri zaaktypeUrl, DateOnly datumStatusGezet, CancellationToken ct = default)
+        {
+            Approved = (zaakUrl, zaaktypeUrl, datumStatusGezet);
+            return Task.CompletedTask;
+        }
+
+        public Uri? ReadReferenceFor;
+
+        public Task<string> GetZaakIdentificatieAsync(Uri zaakUrl, CancellationToken ct = default)
+        {
+            ReadReferenceFor = zaakUrl;
+            return Task.FromResult("REG-FROM-ZAAK");
+        }
     }
 
+    private static AclDefaults Defaults() => new()
+    {
+        Bronorganisatie = "517439943",
+        VerantwoordelijkeOrganisatie = "517439943",
+        Vertrouwelijkheidaanduiding = "openbaar",
+        ZaaktypeUrl = new("http://openzaak/catalogi/api/v1/zaaktypen/big"),
+    };
+
     private sealed class FixedClock(DateOnly today) : IClock
     {
         public DateOnly Today { get; } = today;
@@ -34,7 +58,7 @@ public class AclServiceTests
         };
         var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
 
-        var url = await service.OpenZaakAsync(new DomainRegistration("123456782"));
+        var url = await service.OpenZaakAsync(new DomainRegistration("123456782", "reg-77"));
 
         Assert.Equal(gateway.Result, url);
         var req = Assert.IsType<ZaakRequest>(gateway.Captured);
@@ -43,6 +67,8 @@ public class AclServiceTests
         Assert.Equal("openbaar", req.Vertrouwelijkheidaanduiding);
         Assert.Equal(defaults.ZaaktypeUrl, req.Zaaktype);
         Assert.Equal(new DateOnly(2026, 6, 4), req.Startdatum);
+        // The registration reference becomes the zaak identificatie (#78).
+        Assert.Equal("reg-77", req.Identificatie);
     }
 
     [Fact]
@@ -61,4 +87,53 @@ public class AclServiceTests
         await Assert.ThrowsAsync<ArgumentNullException>(() => service.OpenZaakAsync(null!));
         Assert.Null(gateway.Captured);
     }
+
+    [Fact]
+    public async Task Approving_a_zaak_sets_it_to_its_zaaktypes_eindstatus_dated_today()
+    {
+        var gateway = new FakeGateway();
+        var defaults = Defaults();
+        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+        var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");
+
+        await service.ApproveZaakAsync(zaak);
+
+        Assert.NotNull(gateway.Approved);
+        Assert.Equal(zaak, gateway.Approved!.Value.Zaak);
+        Assert.Equal(defaults.ZaaktypeUrl, gateway.Approved.Value.Zaaktype);
+        Assert.Equal(new DateOnly(2026, 6, 4), gateway.Approved.Value.Datum);
+    }
+
+    [Fact]
+    public async Task Approving_a_null_zaak_is_rejected_without_touching_the_gateway()
+    {
+        var gateway = new FakeGateway();
+        var service = new AclService(gateway, Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => service.ApproveZaakAsync(null!));
+        Assert.Null(gateway.Approved);
+    }
+
+    [Fact]
+    public async Task Reading_a_zaak_reference_returns_the_zaaks_identificatie()
+    {
+        var gateway = new FakeGateway();
+        var service = new AclService(gateway, Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+        var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");
+
+        var reference = await service.GetZaakReferenceAsync(zaak);
+
+        Assert.Equal("REG-FROM-ZAAK", reference);
+        Assert.Equal(zaak, gateway.ReadReferenceFor);
+    }
+
+    [Fact]
+    public async Task Reading_a_null_zaak_reference_is_rejected()
+    {
+        var gateway = new FakeGateway();
+        var service = new AclService(gateway, Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => service.GetZaakReferenceAsync(null!));
+        Assert.Null(gateway.ReadReferenceFor);
+    }
 }

services/acl/Acl.Tests/OpenZaakGatewayTests.cs

@@ -22,7 +22,7 @@ public class OpenZaakGatewayTests
 
     private static ZaakRequest SampleRequest() => new(
         "517439943", "517439943", "openbaar",
-        new("http://openzaak/catalogi/api/v1/zaaktypen/big"), new DateOnly(2026, 6, 4));
+        new("http://openzaak/catalogi/api/v1/zaaktypen/big"), new DateOnly(2026, 6, 4), "REG-REF-1");
 
     private static StubHandler Created(out RequestCapture capture)
     {
@@ -67,6 +67,8 @@ public class OpenZaakGatewayTests
         Assert.Contains("\"vertrouwelijkheidaanduiding\":\"openbaar\"", capture.Body);
         Assert.Contains("\"startdatum\":\"2026-06-04\"", capture.Body);
         Assert.Contains("\"zaaktype\":\"http://openzaak/catalogi/api/v1/zaaktypen/big\"", capture.Body);
+        // The registration reference is set as the zaak identificatie (#78).
+        Assert.Contains("\"identificatie\":\"REG-REF-1\"", capture.Body);
     }
 
     [Fact]
@@ -131,8 +133,9 @@ public class OpenZaakGatewayTests
                 Content = new StringContent("null", Encoding.UTF8, "application/json"),
             }));
 
-        await Assert.ThrowsAsync<InvalidOperationException>(
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
             () => Gateway(handler).OpenZaakAsync(SampleRequest()));
+        Assert.Contains("empty zaak response", ex.Message);
     }
 
     [Fact]
@@ -144,6 +147,284 @@ public class OpenZaakGatewayTests
             () => Gateway(handler).OpenZaakAsync(null!));
     }
 
+    // --- SetZaakToEindstatusAsync (approval / S-09b) ---
+
+    private const string ZaakUrl = "http://openzaak/zaken/api/v1/zaken/xyz";
+    private static readonly Uri Zaaktype = new("http://openzaak/catalogi/api/v1/zaaktypen/big");
+
+    private sealed class Recorder
+    {
+        public List<HttpRequestMessage> Requests { get; } = [];
+        public List<string?> Bodies { get; } = [];
+        public List<long?> ContentLengths { get; } = [];
+
+        public int IndexOf(string pathContains) =>
+            Requests.FindIndex(r => r.RequestUri!.ToString().Contains(pathContains));
+
+        // The (body, content-length, request) of the single request whose URL contains the segment.
+        public (string? Body, long? Length, HttpRequestMessage Request) Sent(string pathContains)
+        {
+            var i = IndexOf(pathContains);
+            return (Bodies[i], ContentLengths[i], Requests[i]);
+        }
+    }
+
+    // Per-route response config for the four calls the approval makes.
+    private sealed class OzRoutes
+    {
+        public string StatustypenJson { get; init; } = StatustypenPage(withEindstatusFlag: true);
+        public string ResultaattypenJson { get; init; } = """{"results":[{"url":"http://openzaak/catalogi/api/v1/resultaattypen/1"}]}""";
+        public HttpStatusCode StatustypenStatus { get; init; } = HttpStatusCode.OK;
+        public HttpStatusCode ResultaattypenStatus { get; init; } = HttpStatusCode.OK;
+        public HttpStatusCode ResultaatPostStatus { get; init; } = HttpStatusCode.Created;
+        public HttpStatusCode StatusPostStatus { get; init; } = HttpStatusCode.Created;
+    }
+
+    // Routes the approval's four calls by URL: GET /statustypen, GET /resultaattypen (catalogus),
+    // then POST /resultaten and POST /statussen (zaken).
+    private static StubHandler ApprovalStub(Recorder rec, OzRoutes routes) => new(async req =>
+    {
+        rec.Requests.Add(req);
+        // Capture the length BEFORE reading the body (ReadAsStringAsync buffers as a side effect).
+        rec.ContentLengths.Add(req.Content?.Headers.ContentLength);
+        rec.Bodies.Add(req.Content is null ? null : await req.Content.ReadAsStringAsync());
+
+        var url = req.RequestUri!.ToString();
+        if (req.Method == HttpMethod.Get && url.Contains("/statustypen"))
+            return Json(routes.StatustypenStatus, routes.StatustypenJson);
+        if (req.Method == HttpMethod.Get && url.Contains("/resultaattypen"))
+            return Json(routes.ResultaattypenStatus, routes.ResultaattypenJson);
+        if (url.Contains("/resultaten"))
+            return Json(routes.ResultaatPostStatus, """{"url":"http://openzaak/zaken/api/v1/resultaten/new"}""");
+        return Json(routes.StatusPostStatus, """{"url":"http://openzaak/zaken/api/v1/statussen/new"}""");
+    });
+
+    private static HttpResponseMessage Json(HttpStatusCode status, string body) =>
+        new(status) { Content = new StringContent(body, Encoding.UTF8, "application/json") };
+
+    // Two statustypen; the eindstatus is flagged on the *lower* volgnummer so the tests prove the
+    // isEindstatus flag is preferred over "highest volgnummer", not coincidentally equal to it.
+    private static string StatustypenPage(bool withEindstatusFlag) => JsonSerializer.Serialize(new
+    {
+        results = new object[]
+        {
+            new { url = "http://openzaak/catalogi/api/v1/statustypen/1", volgnummer = 1, isEindstatus = withEindstatusFlag },
+            new { url = "http://openzaak/catalogi/api/v1/statustypen/2", volgnummer = 2, isEindstatus = false },
+        },
+    });
+
+    [Fact]
+    public async Task Approving_sets_a_resultaat_then_posts_the_flagged_eindstatus_against_the_zaak()
+    {
+        var rec = new Recorder();
+
+        await Gateway(ApprovalStub(rec, new OzRoutes()))
+            .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4));
+
+        Assert.Equal(4, rec.Requests.Count);
+
+        // Both catalogus queries filter by the zaaktype and carry the bearer.
+        var statustypenGet = rec.Sent("/statustypen").Request;
+        Assert.Equal(HttpMethod.Get, statustypenGet.Method);
+        Assert.Contains(Uri.EscapeDataString(Zaaktype.ToString()), statustypenGet.RequestUri!.ToString());
+        Assert.Equal("Bearer", statustypenGet.Headers.Authorization!.Scheme);
+        Assert.Contains(Uri.EscapeDataString(Zaaktype.ToString()), rec.Sent("/resultaattypen").Request.RequestUri!.ToString());
+
+        // OpenZaak requires a resultaat before the eindstatus, so /resultaten precedes /statussen.
+        Assert.True(rec.IndexOf("/resultaten") < rec.IndexOf("/statussen"));
+
+        var resultaat = rec.Sent("/resultaten");
+        Assert.Equal("http://openzaak/zaken/api/v1/resultaten", resultaat.Request.RequestUri!.ToString());
+        Assert.Equal("Bearer", resultaat.Request.Headers.Authorization!.Scheme);
+        Assert.Contains("\"zaak\":\"" + ZaakUrl + "\"", resultaat.Body);
+        Assert.Contains("\"resultaattype\":\"http://openzaak/catalogi/api/v1/resultaattypen/1\"", resultaat.Body);
+        Assert.True(resultaat.Length > 0);
+
+        var status = rec.Sent("/statussen");
+        Assert.Equal("http://openzaak/zaken/api/v1/statussen", status.Request.RequestUri!.ToString());
+        Assert.Equal("Bearer", status.Request.Headers.Authorization!.Scheme);
+        Assert.Contains("\"zaak\":\"" + ZaakUrl + "\"", status.Body);
+        // The isEindstatus-flagged statustype (/1) is chosen — even though /2 has a higher volgnummer.
+        Assert.Contains("\"statustype\":\"http://openzaak/catalogi/api/v1/statustypen/1\"", status.Body);
+        Assert.Contains("\"datumStatusGezet\":\"2026-06-04T00:00:00Z\"", status.Body);
+        // Bodies are buffered (Content-Length set), so uwsgi doesn't get a chunked body.
+        Assert.True(status.Length > 0);
+    }
+
+    [Fact]
+    public async Task Approving_falls_back_to_the_highest_volgnummer_when_no_eindstatus_is_flagged()
+    {
+        var rec = new Recorder();
+
+        await Gateway(ApprovalStub(rec, new OzRoutes { StatustypenJson = StatustypenPage(withEindstatusFlag: false) }))
+            .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4));
+
+        // No isEindstatus flag → the highest volgnummer (/2) is chosen.
+        Assert.Contains("\"statustype\":\"http://openzaak/catalogi/api/v1/statustypen/2\"", rec.Sent("/statussen").Body);
+    }
+
+    [Fact]
+    public async Task Approving_throws_when_the_zaaktype_has_no_statustypen()
+    {
+        var rec = new Recorder();
+
+        // A page with no `results` property (Results is null) — the eindstatus cannot be resolved.
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() =>
+            Gateway(ApprovalStub(rec, new OzRoutes { StatustypenJson = "{}" }))
+                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));
+
+        Assert.Contains("No statustypen found", ex.Message);
+        // It never posts anything when it cannot resolve the eindstatus.
+        Assert.Single(rec.Requests);
+    }
+
+    [Fact]
+    public async Task Approving_throws_when_the_statustypen_response_is_empty()
+    {
+        var rec = new Recorder();
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() =>
+            Gateway(ApprovalStub(rec, new OzRoutes { StatustypenJson = "null" }))
+                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));
+
+        Assert.Contains("empty statustypen", ex.Message);
+        Assert.Single(rec.Requests);
+    }
+
+    [Fact]
+    public async Task Approving_throws_when_the_statustypen_query_fails()
+    {
+        var rec = new Recorder();
+
+        var ex = await Assert.ThrowsAsync<HttpRequestException>(() =>
+            Gateway(ApprovalStub(rec, new OzRoutes { StatustypenStatus = HttpStatusCode.InternalServerError }))
+                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));
+
+        Assert.Contains("Querying statustypen", ex.Message);
+    }
+
+    [Fact]
+    public async Task Approving_throws_when_the_resultaattypen_query_fails()
+    {
+        var rec = new Recorder();
+
+        var ex = await Assert.ThrowsAsync<HttpRequestException>(() =>
+            Gateway(ApprovalStub(rec, new OzRoutes { ResultaattypenStatus = HttpStatusCode.InternalServerError }))
+                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));
+
+        Assert.Contains("Querying resultaattypen", ex.Message);
+        Assert.Equal(-1, rec.IndexOf("/resultaten"));
+    }
+
+    [Fact]
+    public async Task Approving_throws_when_the_zaaktype_has_no_resultaattype()
+    {
+        var rec = new Recorder();
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() =>
+            Gateway(ApprovalStub(rec, new OzRoutes { ResultaattypenJson = "{}" }))
+                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));
+
+        Assert.Contains("No resultaattypen found", ex.Message);
+        // Resolved the eindstatus + queried resultaattypen, but posted nothing.
+        Assert.Equal(-1, rec.IndexOf("/resultaten"));
+        Assert.Equal(-1, rec.IndexOf("/statussen"));
+    }
+
+    [Fact]
+    public async Task Approving_throws_when_posting_the_resultaat_fails()
+    {
+        var rec = new Recorder();
+
+        var ex = await Assert.ThrowsAsync<HttpRequestException>(() =>
+            Gateway(ApprovalStub(rec, new OzRoutes { ResultaatPostStatus = HttpStatusCode.BadRequest }))
+                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));
+
+        Assert.Contains("Setting the zaak resultaat", ex.Message);
+        // The status is never posted if the resultaat could not be recorded.
+        Assert.Equal(-1, rec.IndexOf("/statussen"));
+    }
+
+    [Fact]
+    public async Task Approving_throws_when_posting_the_status_fails()
+    {
+        var rec = new Recorder();
+
+        var ex = await Assert.ThrowsAsync<HttpRequestException>(() =>
+            Gateway(ApprovalStub(rec, new OzRoutes { StatusPostStatus = HttpStatusCode.BadRequest }))
+                .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));
+
+        Assert.Contains("Setting the zaak status", ex.Message);
+        // It got as far as the resultaat + the status POST (4 calls) before failing.
+        Assert.Equal(4, rec.Requests.Count);
+    }
+
+    [Fact]
+    public async Task Reading_a_zaak_returns_its_identificatie_with_bearer_and_crs()
+    {
+        RequestCapture? capture = null;
+        var handler = new StubHandler(req =>
+        {
+            capture = new RequestCapture { Seen = req };
+            return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+            {
+                Content = JsonContent.Create(new { identificatie = "REG-XYZ", url = ZaakUrl }),
+            });
+        });
+
+        var reference = await Gateway(handler).GetZaakIdentificatieAsync(new Uri(ZaakUrl));
+
+        Assert.Equal("REG-XYZ", reference);
+        Assert.Equal(HttpMethod.Get, capture!.Seen!.Method);
+        Assert.Equal(ZaakUrl, capture.Seen.RequestUri!.ToString());
+        Assert.Equal("Bearer", capture.Seen.Headers.Authorization!.Scheme);
+        Assert.Equal("EPSG:4326", Assert.Single(capture.Seen.Headers.GetValues("Accept-Crs")));
+    }
+
+    [Fact]
+    public async Task Reading_a_zaak_throws_when_openzaak_rejects_it()
+    {
+        var handler = new StubHandler(_ =>
+            Task.FromResult(new HttpResponseMessage(HttpStatusCode.NotFound) { Content = new StringContent("nope") }));
+
+        var ex = await Assert.ThrowsAsync<HttpRequestException>(
+            () => Gateway(handler).GetZaakIdentificatieAsync(new Uri(ZaakUrl)));
+        Assert.Contains("Reading the zaak", ex.Message);
+    }
+
+    [Fact]
+    public async Task Reading_a_zaak_throws_when_openzaak_returns_an_empty_body()
+    {
+        var handler = new StubHandler(_ =>
+            Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+            {
+                Content = new StringContent("null", System.Text.Encoding.UTF8, "application/json"),
+            }));
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => Gateway(handler).GetZaakIdentificatieAsync(new Uri(ZaakUrl)));
+        Assert.Contains("empty zaak response", ex.Message);
+    }
+
+    [Fact]
+    public async Task Reading_a_null_zaak_is_rejected()
+    {
+        var handler = new StubHandler(_ => throw new InvalidOperationException("should not be sent"));
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => Gateway(handler).GetZaakIdentificatieAsync(null!));
+    }
+
+    [Fact]
+    public async Task Approving_rejects_a_null_zaak_or_zaaktype()
+    {
+        var handler = new StubHandler(_ => throw new InvalidOperationException("should not be sent"));
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() =>
+            Gateway(handler).SetZaakToEindstatusAsync(null!, Zaaktype, new DateOnly(2026, 6, 4)));
+        await Assert.ThrowsAsync<ArgumentNullException>(() =>
+            Gateway(handler).SetZaakToEindstatusAsync(new Uri(ZaakUrl), null!, new DateOnly(2026, 6, 4)));
+    }
+
     // ZGW tokens are base64url with padding stripped (ZgwToken.B64Url); restore it to decode.
     private static string DecodeSegment(string segment)
     {

services/bff/Bff.Api/DownstreamClients.cs

@@ -6,11 +6,12 @@ namespace Bff.Api;
 public sealed record SubmitAccepted(string RegistrationId, string Status);
 
 /// <summary>A projection row as the projection-api serves it. <c>Bsn</c>/<c>NaamPlaceholder</c> are
-/// read but never surfaced by the openbaar endpoint (public-safe filtering, ADR-0010/S-09).</summary>
+/// read but never surfaced by the openbaar endpoint (public-safe filtering, ADR-0010/S-09).
-public sealed record ProjectionEntry(string Id, string Status, string? Bsn, string? NaamPlaceholder);
+/// <c>Reference</c> is the public-safe citizen reference (the zaak identificatie, #78).</summary>
+public sealed record ProjectionEntry(string Id, string Status, string? Reference, string? Bsn, string? NaamPlaceholder);
 
 /// <summary>A public-safe openbaar register row — only non-sensitive fields leave the BFF.</summary>
-public sealed record OpenbaarEntry(string Id, string Status);
+public sealed record OpenbaarEntry(string Id, string Status, string? Reference);
 
 /// <summary>Port to the Domain Service (§8.3: the BFF is the portals' only backend; it fans out).</summary>
 public interface IDomainClient

services/bff/Bff.Api/OpenbaarProjection.cs

@@ -11,8 +11,10 @@ public static class OpenbaarProjection
     {
         var filtered = string.IsNullOrWhiteSpace(q)
             ? entries
-            : entries.Where(e => e.Id.Contains(q, StringComparison.OrdinalIgnoreCase));
+            : entries.Where(e =>
+                e.Id.Contains(q, StringComparison.OrdinalIgnoreCase) ||
+                (e.Reference?.Contains(q, StringComparison.OrdinalIgnoreCase) ?? false));
 
-        return [.. filtered.Select(e => new OpenbaarEntry(e.Id, e.Status))];
+        return [.. filtered.Select(e => new OpenbaarEntry(e.Id, e.Status, e.Reference))];
     }
 }

services/bff/Bff.Tests/OpenbaarEndpointTests.cs

@@ -10,7 +10,7 @@ public class OpenbaarEndpointTests
     public async Task Serves_public_safe_rows_anonymously()
     {
         using var factory = new BffFactory();
-        factory.Projection.Entries.Add(new ProjectionEntry("abc-111", "INGEDIEND", "123456782", "Jan"));
+        factory.Projection.Entries.Add(new ProjectionEntry("abc-111", "INGEDIEND", "REG-abc", "123456782", "Jan"));
 
         // No Authorization header — the openbaar register is a public lookup (ADR-0010/S-09).
         var response = await factory.CreateClient().GetAsync("/openbaar/register");
@@ -19,7 +19,9 @@ public class OpenbaarEndpointTests
         var body = await response.Content.ReadAsStringAsync();
         Assert.Contains("abc-111", body);
         Assert.Contains("INGEDIEND", body);
-        // The bsn must never appear in a public response.
+        // The public reference is surfaced (matches the submit confirmation, #78)...
+        Assert.Contains("REG-abc", body);
+        // ...but the bsn must never appear in a public response.
         Assert.DoesNotContain("123456782", body);
     }
 
@@ -27,8 +29,8 @@ public class OpenbaarEndpointTests
     public async Task Filters_by_the_query_parameter()
     {
         using var factory = new BffFactory();
-        factory.Projection.Entries.Add(new ProjectionEntry("abc-111", "INGEDIEND", null, null));
+        factory.Projection.Entries.Add(new ProjectionEntry("abc-111", "INGEDIEND", "REG-abc", null, null));
-        factory.Projection.Entries.Add(new ProjectionEntry("def-222", "INGEDIEND", null, null));
+        factory.Projection.Entries.Add(new ProjectionEntry("def-222", "INGEDIEND", "REG-def", null, null));
 
         var rows = await factory.CreateClient()
             .GetFromJsonAsync<List<OpenbaarEntry>>("/openbaar/register?q=abc");

services/bff/Bff.Tests/OpenbaarProjectionTests.cs

@@ -6,8 +6,8 @@ public class OpenbaarProjectionTests
 {
     private static readonly ProjectionEntry[] Sample =
     [
-        new("abc-111", "INGEDIEND", "123456782", "Jan"),
+        new("abc-111", "INGEDIEND", Reference: "REG-A", Bsn: "123456782", NaamPlaceholder: "Jan"),
-        new("def-222", "INGEDIEND", "987654321", "Piet"),
+        new("def-222", "INGESCHREVEN", Reference: "REG-B", Bsn: "987654321", NaamPlaceholder: "Piet"),
     ];
 
     [Fact]
@@ -18,31 +18,47 @@ public class OpenbaarProjectionTests
         Assert.Equal(2, view.Count);
         Assert.Equal("abc-111", view[0].Id);
         Assert.Equal("INGEDIEND", view[0].Status);
+        // The public reference (zaak identificatie) is surfaced so it matches the submit confirmation (#78).
+        Assert.Equal("REG-A", view[0].Reference);
     }
 
     [Fact]
-    public void Public_view_exposes_only_id_and_status()
+    public void Public_view_exposes_only_id_status_and_reference()
     {
-        // OpenbaarEntry structurally carries only Id + Status — bsn/naam can never leak.
+        // OpenbaarEntry structurally carries only public-safe fields — bsn/naam can never leak.
         var props = typeof(OpenbaarEntry).GetProperties().Select(p => p.Name).ToArray();
-        Assert.Equal(["Id", "Status"], props);
+        Assert.Equal(["Id", "Status", "Reference"], props);
     }
 
     [Theory]
-    [InlineData("abc", 1)]
+    [InlineData("abc", 1)]   // by id
-    [InlineData("ABC", 1)]
+    [InlineData("ABC", 1)]   // by id, case-insensitive
-    [InlineData("2", 1)]
+    [InlineData("def", 1)]   // by id
-    [InlineData("zzz", 0)]
+    [InlineData("zzz", 0)]   // no match
     public void Filters_by_id_containing_the_query_case_insensitively(string q, int expected)
-    {
+        => Assert.Equal(expected, OpenbaarProjection.PublicView(Sample, q).Count);
-        var view = OpenbaarProjection.PublicView(Sample, q);
 
-        Assert.Equal(expected, view.Count);
+    [Theory]
-    }
+    [InlineData("REG-A", 1)] // by reference — the citizen's confirmation reference
+    [InlineData("reg-a", 1)] // by reference, case-insensitive
+    [InlineData("REG", 2)]   // both share the prefix
+    public void Filters_by_reference_containing_the_query_case_insensitively(string q, int expected)
+        => Assert.Equal(expected, OpenbaarProjection.PublicView(Sample, q).Count);
 
     [Fact]
     public void Blank_query_is_treated_as_no_filter()
     {
         Assert.Equal(2, OpenbaarProjection.PublicView(Sample, "   ").Count);
     }
+
+    [Fact]
+    public void A_row_without_a_reference_never_matches_a_query()
+    {
+        // Older rows can have a null reference (the column is additive, #78/ADR-0012). A search must
+        // simply not match them — it must not throw and must not treat "no reference" as a match.
+        var entries = new[] { new ProjectionEntry("xyz-999", "INGEDIEND", Reference: null, Bsn: null, NaamPlaceholder: null) };
+
+        Assert.Empty(OpenbaarProjection.PublicView(entries, "REG"));
+        Assert.Equal("xyz-999", Assert.Single(OpenbaarProjection.PublicView(entries, "xyz")).Id);
+    }
 }

services/bff/openapi.json

@@ -67,7 +67,8 @@
       "OpenbaarEntry": {
         "required": [
           "id",
-          "status"
+          "status",
+          "reference"
         ],
         "type": "object",
         "properties": {
@@ -76,6 +77,12 @@
           },
           "status": {
             "type": "string"
+          },
+          "reference": {
+            "type": [
+              "null",
+              "string"
+            ]
           }
         }
       },

services/domain/Big.Api/Program.cs

@@ -23,6 +23,7 @@ builder.Services.AddTransient<IExternalWorkerClient>(sp => sp.GetRequiredService
 builder.Services.AddHttpClient<IAclClient, AclHttpClient>();
 
 builder.Services.AddScoped<SubmitRegistration>();
+builder.Services.AddScoped<ApproveRegistration>();
 builder.Services.AddScoped<OpenZaakWorker>();
 builder.Services.AddScoped<OpenZaakJobProcessor>();
 
@@ -42,6 +43,18 @@ app.MapPost("/registrations", async (SubmitRegistrationRequest body, SubmitRegis
     return Results.Accepted($"/registrations/{id}", new RegistrationResponse(id.ToString(), RegistrationStatus.Ingediend.ToString(), null));
 });
 
+// Temporary admin endpoint (S-09b): approve a registration — the behandelaar's decision, until the
+// behandel-portal exists (S-12). The zaak's final status is set via the ACL, which flows back over
+// NRC to the projection, making the entry publicly visible as INGESCHREVEN. Idempotent.
+app.MapPost("/registrations/{id}/approve", async (string id, ApproveRegistration approve, CancellationToken ct) =>
+{
+    if (!Guid.TryParse(id, out var guid))
+        return Results.NotFound();
+
+    await approve.HandleAsync(new ApproveRegistrationCommand(new RegistrationId(guid)), ct);
+    return Results.NoContent();
+});
+
 // Read a registration. Its zaak URL appears once the worker has opened the zaak (eventually).
 app.MapGet("/registrations/{id}", async (string id, IRegistrationStore store, CancellationToken ct) =>
 {

services/domain/Big.Application/ApproveRegistration.cs

@@ -0,0 +1,36 @@
+using Big.Domain;
+
+namespace Big.Application;
+
+/// <summary>A behandelaar's decision to approve a registration, in domain language.</summary>
+public sealed record ApproveRegistrationCommand(RegistrationId RegistrationId);
+
+/// <summary>
+/// The approve use case (S-09b): set the registration's zaak to its final status via the ACL (§8.1),
+/// then advance the aggregate to INGESCHREVEN. Idempotent — a redelivered or repeated approval of an
+/// already-approved registration is a no-op, so the ACL is not asked to set the status twice. The
+/// zaak status is the projection's source of truth (it flows back over NRC); the aggregate transition
+/// keeps the domain's own view consistent.
+/// </summary>
+public sealed class ApproveRegistration(IRegistrationStore store, IAclClient acl)
+{
+    public async Task HandleAsync(ApproveRegistrationCommand command, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(command);
+
+        var registration = await store.GetAsync(command.RegistrationId, ct)
+            ?? throw new InvalidOperationException($"No registration {command.RegistrationId} to approve.");
+
+        // A repeated approval is a no-op: don't set the zaak status a second time.
+        if (registration.Status == RegistrationStatus.Ingeschreven)
+            return;
+
+        if (registration.ZaakUrl is null)
+            throw new InvalidOperationException(
+                $"Registration {command.RegistrationId} has no zaak yet; it cannot be approved.");
+
+        await acl.ApproveZaakAsync(registration.ZaakUrl, ct);
+        registration.Approve();
+        await store.SaveAsync(registration, ct);
+    }
+}

services/domain/Big.Application/OpenZaakWorker.cs

@@ -28,7 +28,7 @@ public sealed class OpenZaakWorker(IRegistrationStore store, IAclClient acl)
         if (registration.ZaakUrl is not null)
             return registration.ZaakUrl;
 
-        var zaakUrl = await acl.OpenZaakAsync(registration.Bsn, ct);
+        var zaakUrl = await acl.OpenZaakAsync(registration.Bsn, registration.Id.ToString(), ct);
         registration.AttachZaak(zaakUrl);
         await store.SaveAsync(registration, ct);
         return zaakUrl;

services/domain/Big.Application/Ports.cs

@@ -24,7 +24,16 @@ public interface IWorkflowClient
 /// </summary>
 public interface IAclClient
 {
-    Task<Uri> OpenZaakAsync(string bsn, CancellationToken ct = default);
+    /// <summary>Open a zaak for the registration. <paramref name="reference"/> is the registration's
+    /// own reference (its id); the ACL records it as the zaak's identificatie so the openbaar register
+    /// can show the same reference the zorgprofessional was given (S-09b follow-up, adr-proposal #78).</summary>
+    Task<Uri> OpenZaakAsync(string bsn, string reference, CancellationToken ct = default);
+
+    /// <summary>
+    /// Record the approval on the given zaak. The ACL translates this to the ZGW concept — setting
+    /// the zaak's final status — which OpenZaak notifies over NRC; the domain never names statustypen.
+    /// </summary>
+    Task ApproveZaakAsync(Uri zaakUrl, CancellationToken ct = default);
 }
 
 /// <summary>

services/domain/Big.Domain/Registration.cs

@@ -64,4 +64,23 @@ public sealed class Registration
 
         ZaakUrl = zaakUrl;
     }
+
+    /// <summary>
+    /// Approve the registration — the behandelaar's decision to enter it in the register. Advances
+    /// <see cref="RegistrationStatus.Ingediend"/> → <see cref="RegistrationStatus.Ingeschreven"/>.
+    /// Requires an opened zaak (the approval sets that zaak's status via the ACL), and only a
+    /// submitted registration can be approved: re-approving is rejected as an invalid transition.
+    /// </summary>
+    public void Approve()
+    {
+        if (ZaakUrl is null)
+            throw new InvalidOperationException(
+                $"Registration {Id} has no zaak yet; it cannot be approved before its zaak is opened.");
+
+        if (Status != RegistrationStatus.Ingediend)
+            throw new InvalidOperationException(
+                $"Registration {Id} is {Status}; only an INGEDIEND registration can be approved.");
+
+        Status = RegistrationStatus.Ingeschreven;
+    }
 }

services/domain/Big.Domain/RegistrationStatus.cs

@@ -1,10 +1,13 @@
 namespace Big.Domain;
 
 /// <summary>The lifecycle states a <see cref="Registration"/> moves through. The walking
-/// skeleton knows only <see cref="Ingediend"/>; withdrawal, beoordeling and herregistratie
+/// skeleton knows <see cref="Ingediend"/> and the terminal <see cref="Ingeschreven"/>; withdrawal,
-/// states arrive in their own slices (Iteration 2+).</summary>
+/// beoordeling and herregistratie states arrive in their own slices (Iteration 2+).</summary>
 public enum RegistrationStatus
 {
     /// <summary>Submitted by the zorgprofessional; the registratie process has been started.</summary>
     Ingediend,
+
+    /// <summary>Approved: entered in the register. Terminal in the walking skeleton (S-09b).</summary>
+    Ingeschreven,
 }

services/domain/Big.Infrastructure/AclHttpClient.cs

@@ -11,10 +11,10 @@ namespace Big.Infrastructure;
 /// </summary>
 public sealed class AclHttpClient(HttpClient http, AclOptions options) : IAclClient
 {
-    public async Task<Uri> OpenZaakAsync(string bsn, CancellationToken ct = default)
+    public async Task<Uri> OpenZaakAsync(string bsn, string reference, CancellationToken ct = default)
     {
         using var response = await http.PostAsJsonAsync(
-            new Uri(options.BaseUrl, "zaken"), new OpenZaakRequest(bsn), ct);
+            new Uri(options.BaseUrl, "zaken"), new OpenZaakRequest(bsn, reference), ct);
         response.EnsureSuccessStatusCode();
 
         var opened = await response.Content.ReadFromJsonAsync<OpenZaakResponse>(ct)
@@ -22,7 +22,20 @@ public sealed class AclHttpClient(HttpClient http, AclOptions options) : IAclCli
         return new Uri(opened.ZaakUrl);
     }
 
-    private sealed record OpenZaakRequest([property: JsonPropertyName("bsn")] string Bsn);
+    public async Task ApproveZaakAsync(Uri zaakUrl, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(zaakUrl);
+
+        using var response = await http.PostAsJsonAsync(
+            new Uri(options.BaseUrl, "statussen"), new SetStatusRequest(zaakUrl.ToString()), ct);
+        response.EnsureSuccessStatusCode();
+    }
+
+    private sealed record OpenZaakRequest(
+        [property: JsonPropertyName("bsn")] string Bsn,
+        [property: JsonPropertyName("reference")] string Reference);
 
     private sealed record OpenZaakResponse([property: JsonPropertyName("zaakUrl")] string ZaakUrl);
+
+    private sealed record SetStatusRequest([property: JsonPropertyName("zaakUrl")] string ZaakUrl);
 }

services/domain/Big.Tests/AclHttpClientTests.cs

@@ -15,12 +15,13 @@ public class AclHttpClientTests
         var client = Client(capture.Responds(HttpStatusCode.OK,
             """{"zaakUrl":"http://openzaak/zaken/api/v1/zaken/abc"}"""));
 
-        var url = await client.OpenZaakAsync("123456782");
+        var url = await client.OpenZaakAsync("123456782", "reg-42");
 
         Assert.Equal("http://openzaak/zaken/api/v1/zaken/abc", url.ToString());
         Assert.Equal(HttpMethod.Post, capture.Seen!.Method);
         Assert.Equal("http://acl/zaken", capture.Seen.RequestUri!.ToString());
         Assert.Contains("\"bsn\":\"123456782\"", capture.Body);
+        Assert.Contains("\"reference\":\"reg-42\"", capture.Body);
     }
 
     [Fact]
@@ -29,7 +30,7 @@ public class AclHttpClientTests
         var capture = new RequestCapture();
         var client = Client(capture.Responds(HttpStatusCode.BadGateway));
 
-        await Assert.ThrowsAsync<HttpRequestException>(() => client.OpenZaakAsync("123456782"));
+        await Assert.ThrowsAsync<HttpRequestException>(() => client.OpenZaakAsync("123456782", "reg-1"));
     }
 
     [Fact]
@@ -38,7 +39,40 @@ public class AclHttpClientTests
         var capture = new RequestCapture();
         var client = Client(capture.Responds(HttpStatusCode.OK, "null"));
 
-        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => client.OpenZaakAsync("123456782"));
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => client.OpenZaakAsync("123456782", "reg-1"));
         Assert.Contains("empty", ex.Message, StringComparison.OrdinalIgnoreCase);
     }
+
+    [Fact]
+    public async Task Approves_a_zaak_by_posting_its_url_to_statussen()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.NoContent));
+
+        await client.ApproveZaakAsync(new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
+
+        Assert.Equal(HttpMethod.Post, capture.Seen!.Method);
+        Assert.Equal("http://acl/statussen", capture.Seen.RequestUri!.ToString());
+        Assert.Contains("\"zaakUrl\":\"http://openzaak/zaken/api/v1/zaken/abc\"", capture.Body);
+    }
+
+    [Fact]
+    public async Task Approve_throws_when_the_acl_rejects_the_request()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.BadGateway));
+
+        await Assert.ThrowsAsync<HttpRequestException>(
+            () => client.ApproveZaakAsync(new Uri("http://openzaak/zaken/api/v1/zaken/abc")));
+    }
+
+    [Fact]
+    public async Task Approve_rejects_a_null_zaak_url_without_sending_a_request()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.NoContent));
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => client.ApproveZaakAsync(null!));
+        Assert.Null(capture.Seen);
+    }
 }

services/domain/Big.Tests/ApproveRegistrationTests.cs

@@ -0,0 +1,89 @@
+using Big.Application;
+using Big.Domain;
+
+namespace Big.Tests;
+
+public class ApproveRegistrationTests
+{
+    private static Registration WithZaak(string bsn = "123456782")
+    {
+        var registration = Registration.Submit(bsn);
+        registration.AttachZaak(FakeAclClient.DefaultZaakUrl);
+        return registration;
+    }
+
+    [Fact]
+    public async Task Approving_sets_the_zaak_status_via_the_acl_and_marks_the_registration_ingeschreven()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var registration = WithZaak();
+        store.Seed(registration);
+        var handler = new ApproveRegistration(store, acl);
+
+        await handler.HandleAsync(new ApproveRegistrationCommand(registration.Id));
+
+        var saved = await store.GetAsync(registration.Id);
+        Assert.Equal(RegistrationStatus.Ingeschreven, saved!.Status);
+        Assert.Equal(FakeAclClient.DefaultZaakUrl, acl.ApprovedZaakUrl);
+        Assert.Equal(1, acl.ApproveCallCount);
+        // The approved aggregate is persisted (not just mutated in memory).
+        Assert.Equal(1, store.SaveCount);
+    }
+
+    [Fact]
+    public async Task Rejects_a_null_command_without_touching_the_store_or_acl()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var handler = new ApproveRegistration(store, acl);
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => handler.HandleAsync(null!));
+        Assert.Equal(0, acl.ApproveCallCount);
+    }
+
+    [Fact]
+    public async Task Approving_an_unknown_registration_throws_and_does_not_call_the_acl()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var handler = new ApproveRegistration(store, acl);
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => handler.HandleAsync(new ApproveRegistrationCommand(RegistrationId.New())));
+        Assert.Contains("No registration", ex.Message);
+        Assert.Equal(0, acl.ApproveCallCount);
+    }
+
+    [Fact]
+    public async Task Approving_before_the_zaak_is_opened_throws_without_calling_the_acl()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var registration = Registration.Submit("123456782"); // no zaak yet
+        store.Seed(registration);
+        var handler = new ApproveRegistration(store, acl);
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => handler.HandleAsync(new ApproveRegistrationCommand(registration.Id)));
+        Assert.Contains("no zaak", ex.Message);
+        Assert.Equal(0, acl.ApproveCallCount);
+    }
+
+    [Fact]
+    public async Task Re_approving_an_already_ingeschreven_registration_is_idempotent()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var registration = WithZaak();
+        store.Seed(registration);
+        var handler = new ApproveRegistration(store, acl);
+
+        await handler.HandleAsync(new ApproveRegistrationCommand(registration.Id));
+        await handler.HandleAsync(new ApproveRegistrationCommand(registration.Id));
+
+        // The second approval is a no-op: the ACL is not asked to set the status again.
+        Assert.Equal(1, acl.ApproveCallCount);
+        Assert.Equal(RegistrationStatus.Ingeschreven, (await store.GetAsync(registration.Id))!.Status);
+    }
+}

services/domain/Big.Tests/Fakes.cs

@@ -50,12 +50,24 @@ internal sealed class FakeAclClient(Uri? zaakUrl = null) : IAclClient
     private readonly Uri _zaakUrl = zaakUrl ?? DefaultZaakUrl;
 
     public string? OpenedForBsn { get; private set; }
+    public string? OpenedWithReference { get; private set; }
     public int CallCount { get; private set; }
 
-    public Task<Uri> OpenZaakAsync(string bsn, CancellationToken ct = default)
+    public Uri? ApprovedZaakUrl { get; private set; }
+    public int ApproveCallCount { get; private set; }
+
+    public Task<Uri> OpenZaakAsync(string bsn, string reference, CancellationToken ct = default)
     {
         CallCount++;
         OpenedForBsn = bsn;
+        OpenedWithReference = reference;
         return Task.FromResult(_zaakUrl);
     }
+
+    public Task ApproveZaakAsync(Uri zaakUrl, CancellationToken ct = default)
+    {
+        ApproveCallCount++;
+        ApprovedZaakUrl = zaakUrl;
+        return Task.CompletedTask;
+    }
 }

services/domain/Big.Tests/OpenZaakWorkerTests.cs

@@ -25,6 +25,9 @@ public class OpenZaakWorkerTests
 
         Assert.Equal(FakeAclClient.DefaultZaakUrl, zaakUrl);
         Assert.Equal("123456782", acl.OpenedForBsn);
+        // The registration's own id is handed to the ACL as the zaak reference (identificatie),
+        // so the openbaar register can show the reference the zorgprofessional received (#78).
+        Assert.Equal(registration.Id.ToString(), acl.OpenedWithReference);
         var saved = await store.GetAsync(registration.Id);
         Assert.Equal(FakeAclClient.DefaultZaakUrl, saved!.ZaakUrl);
         Assert.Equal(1, store.SaveCount);

services/domain/Big.Tests/RegistrationTests.cs

@@ -87,4 +87,38 @@ public class RegistrationTests
         Assert.Contains("/zaken/abc", ex.Message);
         Assert.Contains("/zaken/other", ex.Message);
     }
+
+    [Fact]
+    public void Approving_a_registration_with_a_zaak_sets_it_ingeschreven()
+    {
+        var registration = Registration.Submit("123456782");
+        registration.AttachZaak(new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
+
+        registration.Approve();
+
+        Assert.Equal(RegistrationStatus.Ingeschreven, registration.Status);
+    }
+
+    [Fact]
+    public void Approving_before_the_zaak_is_opened_is_rejected()
+    {
+        var registration = Registration.Submit("123456782");
+
+        var ex = Assert.Throws<InvalidOperationException>(() => registration.Approve());
+
+        Assert.Contains("no zaak", ex.Message, StringComparison.OrdinalIgnoreCase);
+        Assert.Equal(RegistrationStatus.Ingediend, registration.Status);
+    }
+
+    [Fact]
+    public void Approving_an_already_ingeschreven_registration_is_rejected()
+    {
+        var registration = Registration.Submit("123456782");
+        registration.AttachZaak(new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
+        registration.Approve();
+
+        var ex = Assert.Throws<InvalidOperationException>(() => registration.Approve());
+        Assert.Contains("only an INGEDIEND", ex.Message);
+        Assert.Equal(RegistrationStatus.Ingeschreven, registration.Status);
+    }
 }

services/event-subscriber/EventSubscriber.Api/AclHttpClient.cs

@@ -0,0 +1,30 @@
+using System.Net.Http.Json;
+using System.Text.Json.Serialization;
+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).
+/// </summary>
+public sealed class AclHttpClient(HttpClient http) : IAclClient
+{
+    public async Task<string> GetZaakReferenceAsync(Uri zaakUrl, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(zaakUrl);
+
+        using var response = await http.PostAsJsonAsync(
+            new Uri(http.BaseAddress!, "zaken/reference"), new ReferenceRequest(zaakUrl.ToString()), ct);
+        response.EnsureSuccessStatusCode();
+
+        var body = await response.Content.ReadFromJsonAsync<ReferenceResponse>(ct)
+            ?? throw new InvalidOperationException("The ACL returned an empty reference response.");
+        return body.Reference;
+    }
+
+    private sealed record ReferenceRequest([property: JsonPropertyName("zaakUrl")] string ZaakUrl);
+
+    private sealed record ReferenceResponse([property: JsonPropertyName("reference")] string Reference);
+}

services/event-subscriber/EventSubscriber.Api/Program.cs

@@ -11,9 +11,15 @@ var connectionString = builder.Configuration.GetConnectionString("Projection")
 // this value (ADR-0007), so the webhook enforces it.
 var webhookToken = builder.Configuration["EventSubscriber:Webhook:AuthToken"]
     ?? throw new InvalidOperationException("Missing configuration 'EventSubscriber:Webhook:AuthToken'");
+// The ACL is the only code that may read ZGW (§8.1); the subscriber enriches the projection with the
+// zaak reference through it (adr-proposal #78).
+var aclBaseUrl = builder.Configuration["Acl:BaseUrl"]
+    ?? throw new InvalidOperationException("Missing configuration 'Acl:BaseUrl'");
 
 builder.Services.AddProjectionReadModel(connectionString);
 builder.Services.AddProjectionWriteSide();
+builder.Services.AddHttpClient<EventSubscriber.Application.IAclClient, EventSubscriber.Api.AclHttpClient>(
+    c => c.BaseAddress = new Uri(aclBaseUrl));
 
 var app = builder.Build();
 
@@ -54,9 +60,9 @@ 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)
+public sealed record NotificationDto(string Kanaal, string Resource, string Actie, Uri ResourceUrl, Uri? HoofdObject = null)
 {
-    public Notification ToNotification() => new(Kanaal, Resource, Actie, ResourceUrl);
+    public Notification ToNotification() => new(Kanaal, Resource, Actie, ResourceUrl, HoofdObject);
 }
 
 public partial class Program

services/event-subscriber/EventSubscriber.Application/Notification.cs

@@ -11,14 +11,25 @@ public sealed record Notification(
     string Kanaal,
     string Resource,
     string Actie,
-    Uri ResourceUrl)
+    Uri ResourceUrl,
+    Uri? HoofdObject = null)
 {
-    /// <summary>The only event the walking-skeleton projection reacts to: a zaak being created.</summary>
+    /// <summary>A zaak being created — projected as INGEDIEND.</summary>
     public bool IsZaakCreated =>
         Kanaal == "zaken" && Resource == "zaak" && Actie == "create";
 
-    /// <summary>The zaak UUID — the trailing path segment of the resource URL — used as the projection key.</summary>
+    /// <summary>A status being set on a zaak — the approval, projected as INGESCHREVEN (S-09b). In the
-    public string ZaakId => ResourceUrl.Segments[^1].Trim('/');
+    /// 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

services/event-subscriber/EventSubscriber.Application/NotificationProjector.cs

@@ -5,15 +5,19 @@ namespace EventSubscriber.Application;
 /// 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.
 /// </summary>
-public sealed class NotificationProjector(INotificationLog log, IProjectionStore store)
+public sealed class NotificationProjector(INotificationLog log, IProjectionStore store, IAclClient acl)
 {
-    /// <summary>Handle one inbound notification. Ignores anything that is not a zaak-created event.</summary>
+    /// <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>
     public async Task HandleAsync(Notification notification, CancellationToken ct = default)
     {
-        if (!notification.IsZaakCreated)
+        if (!notification.IsZaakCreated && !notification.IsZaakStatusSet)
             return;
 
-        var recorded = new RecordedNotification(notification.IdempotencyKey, notification.Actie, notification.ZaakId);
+        var reference = await acl.GetZaakReferenceAsync(notification.ZaakUrl, ct);
+        var recorded = new RecordedNotification(
+            notification.IdempotencyKey, notification.Actie, notification.ZaakId, notification.Resource, 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.
@@ -31,8 +35,11 @@ public sealed class NotificationProjector(INotificationLog log, IProjectionStore
             await store.UpsertAsync(ToEntry(recorded), ct);
     }
 
-    /// <summary>The minimal projection row for an accepted notification. A zaak-create maps to
+    /// <summary>The projection row for an accepted notification: a status-set maps to INGESCHREVEN,
-    /// INGEDIEND; bsn/naam are deferred (ADR-0008).</summary>
+    /// a zaak-create to INGEDIEND. bsn/naam are deferred (ADR-0008).</summary>
     private static RegisterEntry ToEntry(RecordedNotification recorded)
-        => new(recorded.ZaakId, RegistrationStatus.Ingediend);
+        => new(
+            recorded.ZaakId,
+            recorded.Resource == "status" ? RegistrationStatus.Ingeschreven : RegistrationStatus.Ingediend,
+            Reference: recorded.Reference);
 }

services/event-subscriber/EventSubscriber.Application/Ports.cs

@@ -19,8 +19,21 @@ 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.</summary>
+/// <summary>A notification that has been accepted, retaining what a rebuild needs to recompute its
-public sealed record RecordedNotification(string Key, string Actie, string ZaakId);
+/// 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>
+/// 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).
+/// </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 read projection store. Owned by the projection bounded context (ADR-0008); the
 /// subscriber writes to it and the projection-api reads it.</summary>

services/event-subscriber/EventSubscriber.Application/RegisterEntry.cs

@@ -9,6 +9,7 @@ namespace EventSubscriber.Application;
 public sealed record RegisterEntry(
     string Id,
     string Status,
+    string? Reference = null,
     string? Bsn = null,
     string? NaamPlaceholder = null);
 
@@ -17,4 +18,7 @@ public static class RegistrationStatus
 {
     /// <summary>A zaak has been created; the registration is submitted.</summary>
     public const string Ingediend = "INGEDIEND";
+
+    /// <summary>The registration has been approved and entered in the register (S-09b).</summary>
+    public const string Ingeschreven = "INGESCHREVEN";
 }

services/event-subscriber/EventSubscriber.Tests/AclHttpClientTests.cs

@@ -0,0 +1,86 @@
+using System.Net;
+using System.Text;
+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.
+/// </summary>
+public class AclHttpClientTests
+{
+    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()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.OK, """{"reference":"REG-42"}"""));
+
+        var reference = await client.GetZaakReferenceAsync(new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
+
+        Assert.Equal("REG-42", 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);
+    }
+
+    [Fact]
+    public async Task Throws_when_the_acl_rejects_the_request()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.BadGateway));
+
+        await Assert.ThrowsAsync<HttpRequestException>(
+            () => client.GetZaakReferenceAsync(new Uri("http://openzaak/zaken/api/v1/zaken/abc")));
+    }
+
+    [Fact]
+    public async Task Throws_when_the_acl_returns_an_empty_body()
+    {
+        var capture = new RequestCapture();
+        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")));
+        Assert.Contains("empty", ex.Message, StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public async Task Rejects_a_null_zaak_url_without_sending_a_request()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.OK, """{"reference":"REG-1"}"""));
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetZaakReferenceAsync(null!));
+        Assert.Null(capture.Seen);
+    }
+}
+
+/// <summary>A test double for <see cref="HttpMessageHandler"/> that records the last request and
+/// returns a scripted response — mirrors the ACL/domain gateway tests.</summary>
+internal sealed class StubHandler(Func<HttpRequestMessage, Task<HttpResponseMessage>> onSend) : HttpMessageHandler
+{
+    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken ct)
+        => onSend(request);
+}
+
+/// <summary>Captures the request a client sent, including the (buffered) body.</summary>
+internal sealed class RequestCapture
+{
+    public HttpRequestMessage? Seen { get; private set; }
+    public string? Body { get; private set; }
+
+    public StubHandler Responds(HttpStatusCode status, string? json = null) => new(async req =>
+    {
+        Seen = req;
+        Body = req.Content is null ? null : await req.Content.ReadAsStringAsync();
+        var response = new HttpResponseMessage(status);
+        if (json is not null)
+            response.Content = new StringContent(json, Encoding.UTF8, "application/json");
+        return response;
+    });
+}

services/event-subscriber/EventSubscriber.Tests/EventSubscriber.Tests.csproj

@@ -19,6 +19,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <ProjectReference Include="..\EventSubscriber.Api\EventSubscriber.Api.csproj" />
     <ProjectReference Include="..\EventSubscriber.Application\EventSubscriber.Application.csproj" />
   </ItemGroup>
 

services/event-subscriber/EventSubscriber.Tests/InMemoryStores.cs

@@ -5,6 +5,19 @@ 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>
+internal sealed class FakeAclClient : IAclClient
+{
+    public int CallCount { get; private set; }
+
+    public Task<string> GetZaakReferenceAsync(Uri zaakUrl, CancellationToken ct = default)
+    {
+        CallCount++;
+        return Task.FromResult("REG-" + zaakUrl.Segments[^1].Trim('/'));
+    }
+}
+
 internal sealed class InMemoryNotificationLog : INotificationLog
 {
     private readonly Dictionary<string, RecordedNotification> _byKey = [];

services/event-subscriber/EventSubscriber.Tests/NotificationProjectorTests.cs

@@ -8,15 +8,21 @@ namespace EventSubscriber.Tests;
 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 readonly InMemoryNotificationLog _log = new();
     private readonly InMemoryProjectionStore _store = new();
+    private readonly FakeAclClient _acl = new();
 
-    private NotificationProjector Projector() => new(_log, _store);
+    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()
     {
@@ -25,6 +31,23 @@ public sealed class NotificationProjectorTests
         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);
+    }
+
+    [Fact]
+    public async Task rebuild_reproduces_the_reference_without_re_reading_via_the_acl()
+    {
+        var projector = Projector();
+        await projector.HandleAsync(ZaakCreated());
+        var callsAfterProjection = _acl.CallCount;
+
+        await projector.RebuildAsync();
+
+        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);
     }
 
     [Fact]
@@ -62,16 +85,53 @@ public sealed class NotificationProjectorTests
     [Theory]
     [InlineData("documenten", "enkelvoudiginformatieobject", "create")] // wrong kanaal + resource
     [InlineData("documenten", "zaak", "create")]                        // wrong kanaal only
-    [InlineData("zaken", "status", "create")]                           // wrong resource only
     [InlineData("zaken", "zaak", "update")]                             // wrong actie
     [InlineData("zaken", "zaak", "destroy")]                            // wrong actie
-    public async Task only_a_zaken_zaak_create_notification_is_projected(string kanaal, string resource, string actie)
+    [InlineData("zaken", "status", "update")]                           // a status change we ignore
+    [InlineData("zaken", "resultaat", "create")]                        // not a status we project
+    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)));
 
         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()
+    {
+        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.RebuildAsync();
+
+        var entry = Assert.Single(await _store.AllAsync());
+        Assert.Equal(RegistrationStatus.Ingeschreven, entry.Status);
+    }
+
     [Fact]
     public async Task rebuild_clears_stale_rows_and_repopulates_from_the_notification_log()
     {

services/projection-api/Projection.ReadModel/EfNotificationLog.cs

@@ -15,6 +15,8 @@ public sealed class EfNotificationLog(ProjectionDbContext db) : INotificationLog
             Key = notification.Key,
             Actie = notification.Actie,
             ZaakId = notification.ZaakId,
+            Resource = notification.Resource,
+            Reference = notification.Reference,
             ReceivedAt = DateTimeOffset.UtcNow,
         });
 
@@ -34,6 +36,6 @@ 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))
+            .Select(r => new RecordedNotification(r.Key, r.Actie, r.ZaakId, r.Resource, r.Reference))
             .ToListAsync(ct);
 }

services/projection-api/Projection.ReadModel/EfProjectionStore.cs

@@ -15,6 +15,7 @@ public sealed class EfProjectionStore(ProjectionDbContext db) : IProjectionStore
             {
                 Id = entry.Id,
                 Status = entry.Status,
+                Reference = entry.Reference,
                 Bsn = entry.Bsn,
                 NaamPlaceholder = entry.NaamPlaceholder,
             });
@@ -22,6 +23,7 @@ public sealed class EfProjectionStore(ProjectionDbContext db) : IProjectionStore
         else
         {
             row.Status = entry.Status;
+            row.Reference = entry.Reference;
             row.Bsn = entry.Bsn;
             row.NaamPlaceholder = entry.NaamPlaceholder;
         }
@@ -35,6 +37,6 @@ public sealed class EfProjectionStore(ProjectionDbContext db) : IProjectionStore
     public async Task<IReadOnlyList<RegisterEntry>> AllAsync(CancellationToken ct = default)
         => await db.RegisterEntries
             .OrderBy(r => r.Id)
-            .Select(r => new RegisterEntry(r.Id, r.Status, r.Bsn, r.NaamPlaceholder))
+            .Select(r => new RegisterEntry(r.Id, r.Status, Reference: r.Reference, Bsn: r.Bsn, NaamPlaceholder: r.NaamPlaceholder))
             .ToListAsync(ct);
 }

services/projection-api/Projection.ReadModel/Migrations/20260713145944_AddNotificationResource.Designer.cs

@@ -0,0 +1,84 @@
+// <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("20260713145944_AddNotificationResource")]
+    partial class AddNotificationResource
+    {
+        /// <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<string>("Actie")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("actie");
+
+                    b.Property<DateTimeOffset>("ReceivedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("received_at");
+
+                    b.Property<string>("Resource")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("resource");
+
+                    b.Property<string>("ZaakId")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("zaak_id");
+
+                    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>("Status")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("status");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("register_projection", (string)null);
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

services/projection-api/Projection.ReadModel/Migrations/20260713145944_AddNotificationResource.cs

@@ -0,0 +1,31 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Projection.ReadModel.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddNotificationResource : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            // Pre-existing rows are all zaak-creates (the only notification the projector recorded
+            // before S-09b), so default the backfill to "zaak" rather than "".
+            migrationBuilder.AddColumn<string>(
+                name: "resource",
+                table: "processed_notifications",
+                type: "text",
+                nullable: false,
+                defaultValue: "zaak");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "resource",
+                table: "processed_notifications");
+        }
+    }
+}

services/projection-api/Projection.ReadModel/Migrations/20260714101642_AddReferenceColumns.Designer.cs

@@ -0,0 +1,92 @@
+// <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("20260714101642_AddReferenceColumns")]
+    partial class AddReferenceColumns
+    {
+        /// <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<string>("Actie")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("actie");
+
+                    b.Property<DateTimeOffset>("ReceivedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("received_at");
+
+                    b.Property<string>("Reference")
+                        .HasColumnType("text")
+                        .HasColumnName("reference");
+
+                    b.Property<string>("Resource")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("resource");
+
+                    b.Property<string>("ZaakId")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("zaak_id");
+
+                    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
+        }
+    }
+}

services/projection-api/Projection.ReadModel/Migrations/20260714101642_AddReferenceColumns.cs

@@ -0,0 +1,38 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Projection.ReadModel.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddReferenceColumns : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "reference",
+                table: "register_projection",
+                type: "text",
+                nullable: true);
+
+            migrationBuilder.AddColumn<string>(
+                name: "reference",
+                table: "processed_notifications",
+                type: "text",
+                nullable: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "reference",
+                table: "register_projection");
+
+            migrationBuilder.DropColumn(
+                name: "reference",
+                table: "processed_notifications");
+        }
+    }
+}

services/projection-api/Projection.ReadModel/Migrations/ProjectionDbContextModelSnapshot.cs

@@ -37,6 +37,15 @@ namespace Projection.ReadModel.Migrations
                         .HasColumnType("timestamp with time zone")
                         .HasColumnName("received_at");
 
+                    b.Property<string>("Reference")
+                        .HasColumnType("text")
+                        .HasColumnName("reference");
+
+                    b.Property<string>("Resource")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("resource");
+
                     b.Property<string>("ZaakId")
                         .IsRequired()
                         .HasColumnType("text")
@@ -61,6 +70,10 @@ namespace Projection.ReadModel.Migrations
                         .HasColumnType("text")
                         .HasColumnName("naam_placeholder");
 
+                    b.Property<string>("Reference")
+                        .HasColumnType("text")
+                        .HasColumnName("reference");
+
                     b.Property<string>("Status")
                         .IsRequired()
                         .HasColumnType("text")

services/projection-api/Projection.ReadModel/ProjectionDbContext.cs

@@ -24,6 +24,7 @@ public sealed class ProjectionDbContext(DbContextOptions<ProjectionDbContext> op
             e.HasKey(r => r.Id);
             e.Property(r => r.Id).HasColumnName("id");
             e.Property(r => r.Status).HasColumnName("status").IsRequired();
+            e.Property(r => r.Reference).HasColumnName("reference");
             e.Property(r => r.Bsn).HasColumnName("bsn");
             e.Property(r => r.NaamPlaceholder).HasColumnName("naam_placeholder");
         });
@@ -35,6 +36,8 @@ public sealed class ProjectionDbContext(DbContextOptions<ProjectionDbContext> op
             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.Reference).HasColumnName("reference");
             e.Property(r => r.ReceivedAt).HasColumnName("received_at");
         });
     }
@@ -45,6 +48,10 @@ public sealed class RegisterEntryRow
 {
     public required string Id { get; set; }
     public required string Status { get; set; }
+
+    /// <summary>The citizen-facing reference (the zaak's identificatie) — matches the submit confirmation (#78).</summary>
+    public string? Reference { get; set; }
+
     public string? Bsn { get; set; }
     public string? NaamPlaceholder { get; set; }
 }
@@ -55,5 +62,13 @@ 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 zaak reference (identificatie), retained so a rebuild reprojects it without the ACL (#78).</summary>
+    public string? Reference { get; set; }
+
     public DateTimeOffset ReceivedAt { get; set; }
 }

services/projection-api/Projection.ReadModel/ServiceCollectionExtensions.cs

@@ -19,12 +19,46 @@ public static class ServiceCollectionExtensions
         return services;
     }
 
+    // A fixed application-scoped key for the migration advisory lock (any stable 64-bit constant).
+    private const long MigrationAdvisoryLockKey = 727501;
+
     /// <summary>Apply any pending EF migrations. Called once on service start so a fresh stack
-    /// reaches a usable schema without a manual migration step (DoD: compose up reaches green).</summary>
+    /// reaches a usable schema without a manual migration step (DoD: compose up reaches green).
+    ///
+    /// The Event Subscriber and the projection-api share this DB and both migrate on start. EF's
+    /// migrations-history lock is released between individual migrations, so with more than one pending
+    /// migration two migrators can interleave and one re-applies a migration the other just did
+    /// ("column already exists"). Hold a Postgres session <c>pg_advisory_lock</c> across the whole
+    /// sequence so it runs exactly once; the second migrator then finds nothing pending.</summary>
     public static async Task MigrateProjectionAsync(this IServiceProvider services, CancellationToken ct = default)
     {
         await using var scope = services.CreateAsyncScope();
         var db = scope.ServiceProvider.GetRequiredService<ProjectionDbContext>();
-        await db.Database.MigrateAsync(ct);
+        var connection = db.Database.GetDbConnection();
+
+        await connection.OpenAsync(ct);
+        try
+        {
+            await ExecuteAsync(connection, $"SELECT pg_advisory_lock({MigrationAdvisoryLockKey})", ct);
+            try
+            {
+                await db.Database.MigrateAsync(ct);
+            }
+            finally
+            {
+                await ExecuteAsync(connection, $"SELECT pg_advisory_unlock({MigrationAdvisoryLockKey})", ct);
+            }
+        }
+        finally
+        {
+            await connection.CloseAsync();
+        }
+    }
+
+    private static async Task ExecuteAsync(System.Data.Common.DbConnection connection, string sql, CancellationToken ct)
+    {
+        await using var command = connection.CreateCommand();
+        command.CommandText = sql;
+        await command.ExecuteNonQueryAsync(ct);
     }
 }

services/projection-api/ProjectionApi.Api/Program.cs

@@ -10,8 +10,9 @@ builder.Services.AddProjectionReadModel(connectionString);
 
 var app = builder.Build();
 
-// Ensure the schema exists before serving reads. EF serialises concurrent migrators via the
+// Ensure the schema exists before serving reads. The Event Subscriber migrates this shared DB too;
-// migrations-history lock, so it is safe that the Event Subscriber migrates too.
+// MigrateProjectionAsync serialises concurrent migrators with a session advisory lock so the whole
+// migration sequence runs exactly once (see ServiceCollectionExtensions).
 await app.Services.MigrateProjectionAsync();
 
 app.MapGet("/health", () => "Healthy");
@@ -22,7 +23,7 @@ app.MapGet("/register", async (ProjectionDbContext db, CancellationToken ct) =>
 {
     var rows = await db.RegisterEntries
         .OrderBy(r => r.Id)
-        .Select(r => new RegisterEntryDto(r.Id, r.Status, r.Bsn, r.NaamPlaceholder))
+        .Select(r => new RegisterEntryDto(r.Id, r.Status, r.Reference, r.Bsn, r.NaamPlaceholder))
         .ToListAsync(ct);
     return Results.Ok(rows);
 });
@@ -31,13 +32,13 @@ app.MapGet("/register/{id}", async (string id, ProjectionDbContext db, Cancellat
 {
     var row = await db.RegisterEntries
         .Where(r => r.Id == id)
-        .Select(r => new RegisterEntryDto(r.Id, r.Status, r.Bsn, r.NaamPlaceholder))
+        .Select(r => new RegisterEntryDto(r.Id, r.Status, r.Reference, r.Bsn, r.NaamPlaceholder))
         .SingleOrDefaultAsync(ct);
     return row is null ? Results.NotFound() : Results.Ok(row);
 });
 
 await app.RunAsync();
 
-public sealed record RegisterEntryDto(string Id, string Status, string? Bsn, string? NaamPlaceholder);
+public sealed record RegisterEntryDto(string Id, string Status, string? Reference, string? Bsn, string? NaamPlaceholder);
 
 public partial class Program;

tests/acceptance/Steps/BffToegangSteps.cs

@@ -31,7 +31,7 @@ public sealed class BffToegangSteps : IDisposable
     [Given("the projection contains a zaak \"(.*)\" for BSN \"(.*)\"")]
     public void GivenTheProjectionContains(string zaakId, string bsn)
     {
-        _host.Projection.Entries.Add(new ProjectionEntry(zaakId, "INGEDIEND", bsn, null));
+        _host.Projection.Entries.Add(new ProjectionEntry(zaakId, "INGEDIEND", "REG-" + zaakId, bsn, null));
         _client = _host.CreateClient();
     }
 

tests/acceptance/Steps/EenZaakOpenenSteps.cs

@@ -18,7 +18,7 @@ public sealed class EenZaakOpenenSteps
 
     [Given("a domain registration for BSN \"(.*)\"")]
     public void GivenADomainRegistrationForBsn(string bsn)
-        => _registration = new DomainRegistration(bsn);
+        => _registration = new DomainRegistration(bsn, "ACC-REF-1");
 
     [Given("the ACL is configured with these defaults:")]
     public void GivenTheAclIsConfiguredWithTheseDefaults(DataTable defaults)

tests/acceptance/Steps/RegisterProjectieBijwerkenSteps.cs

@@ -17,7 +17,8 @@ public sealed class RegisterProjectieBijwerkenSteps
     private readonly NotificationProjector _projector;
     private Notification? _notification;
 
-    public RegisterProjectieBijwerkenSteps() => _projector = new NotificationProjector(_log, _store);
+    public RegisterProjectieBijwerkenSteps()
+        => _projector = new NotificationProjector(_log, _store, new InMemoryAclReferenceClient());
 
     [Given("a zaak is created in OpenZaak with id \"(.*)\"")]
     public void GivenAZaakIsCreatedInOpenZaakWithId(string id)

tests/acceptance/Support/InMemoryDomainPorts.cs

@@ -26,12 +26,21 @@ public sealed class InMemoryAclClient : IAclClient
     public static readonly Uri OpenedZaakUrl = new("http://openzaak/zaken/api/v1/zaken/acc-zaak");
 
     public string? OpenedForBsn { get; private set; }
+    public string? OpenedWithReference { get; private set; }
+    public Uri? ApprovedZaakUrl { get; private set; }
 
-    public Task<Uri> OpenZaakAsync(string bsn, CancellationToken ct = default)
+    public Task<Uri> OpenZaakAsync(string bsn, string reference, CancellationToken ct = default)
     {
         OpenedForBsn = bsn;
+        OpenedWithReference = reference;
         return Task.FromResult(OpenedZaakUrl);
     }
+
+    public Task ApproveZaakAsync(Uri zaakUrl, CancellationToken ct = default)
+    {
+        ApprovedZaakUrl = zaakUrl;
+        return Task.CompletedTask;
+    }
 }
 
 /// <summary>An in-memory registration store for the domain acceptance scenario.</summary>

tests/acceptance/Support/InMemoryProjectionStores.cs

@@ -38,3 +38,11 @@ public sealed class InMemoryProjectionStore : IProjectionStore
     public IReadOnlyList<RegisterEntry> RowsFor(string id)
         => [.. _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
+{
+    public Task<string> GetZaakReferenceAsync(Uri zaakUrl, CancellationToken ct = default)
+        => Task.FromResult("REG-" + zaakUrl.Segments[^1].Trim('/'));
+}

tests/acceptance/Support/InMemoryZaakGateway.cs

@@ -11,10 +11,20 @@ public sealed class InMemoryZaakGateway : IZaakGateway
     public static readonly Uri CreatedZaakUrl = new("http://openzaak/zaken/api/v1/zaken/created-123");
 
     public ZaakRequest? Captured { get; private set; }
+    public (Uri Zaak, Uri Zaaktype, DateOnly Datum)? Approved { get; private set; }
 
     public Task<Uri> OpenZaakAsync(ZaakRequest request, CancellationToken ct = default)
     {
         Captured = request;
         return Task.FromResult(CreatedZaakUrl);
     }
+
+    public Task SetZaakToEindstatusAsync(Uri zaakUrl, Uri zaaktypeUrl, DateOnly datumStatusGezet, CancellationToken ct = default)
+    {
+        Approved = (zaakUrl, zaaktypeUrl, datumStatusGezet);
+        return Task.CompletedTask;
+    }
+
+    public Task<string> GetZaakIdentificatieAsync(Uri zaakUrl, CancellationToken ct = default)
+        => Task.FromResult("ACC-REF-1");
 }

tests/e2e/registration.spec.ts

@@ -1,9 +1,10 @@
 import { expect, test } from '@playwright/test';
 
-// Walking-skeleton happy path (S-08d + S-09): a zorgprofessional logs in via mock DigiD and submits a
+// Walking-skeleton happy path (S-08d + S-09 + S-09b): a zorgprofessional logs in via mock DigiD and
-// registration through the self-service portal → BFF → domain; the projection is updated via NRC → the
+// submits through the self-service portal → BFF → domain; the entry appears in the openbaar register
-// event-subscriber, and the entry becomes publicly visible in the openbaar register portal.
+// as INGEDIEND; a behandelaar approves it via the temporary admin endpoint; the approval flows via the
-test('DigiD login → submit → confirmation → public visibility', async ({ page }) => {
+// ACL → NRC → event-subscriber → projection, and the openbaar register then shows it as INGESCHREVEN.
+test('DigiD login → submit → public INGEDIEND → approve → public INGESCHREVEN', async ({ page, request }) => {
   // Visiting the guarded page redirects to the Keycloak (mock DigiD) login.
   await page.goto('/');
 
@@ -17,18 +18,50 @@ test('DigiD login → submit → confirmation → public visibility', async ({ p
 
   await page.getByRole('button', { name: /indienen/i }).click();
 
-  // The BFF accepted it and the page shows the confirmation.
+  // The BFF accepted it and the page shows the confirmation with the reference.
-  await expect(page.getByText(/ontvangen/i)).toBeVisible();
+  const confirmation = page.getByText(/ontvangen/i);
+  await expect(confirmation).toBeVisible();
+  const reference = (await confirmation.textContent())?.match(/Referentie:\s*([0-9a-fA-F-]+)/)?.[1];
+  expect(reference, 'the confirmation shows a registration reference').toBeTruthy();
 
   // The openbaar register (anonymous, its own origin) shows the submitted entry once the projection
   // catches up. The projection updates asynchronously (NRC → event-subscriber), and the register loads
-  // on open, so reload until a submitted (INGEDIEND) row appears.
+  // on open, so reload until *this* submission's row appears. We poll on the reference cell (not a
+  // generic INGEDIEND cell): the shared verify stack already holds INGEDIEND rows from earlier checks,
+  // so a status-only poll would short-circuit on a stale row before our row is projected.
   await page.goto('http://openbaar/');
   await expect(page.getByRole('heading', { name: /Openbaar BIG-register/i })).toBeVisible();
+
+  // #78: the reference shown in the public register must be the exact one the citizen saw on the
+  // submit confirmation — no mismatch between the two portals.
   await expect
     .poll(async () => {
       await page.reload();
-      return page.getByRole('cell', { name: 'INGEDIEND' }).count();
+      return page.getByRole('cell', { name: reference }).count();
+    }, { timeout: 30_000, intervals: [1_000, 2_000, 3_000, 5_000] })
+    .toBeGreaterThan(0);
+  await expect(page.getByRole('row', { name: reference }).getByRole('cell', { name: 'INGEDIEND' }))
+    .toBeVisible();
+
+  // Approve via the temporary admin endpoint (reached directly on the compose network, as a
+  // behandelaar would until the behandel-portal exists — S-12). The zaak is opened off the request
+  // path by the worker, so wait for it before approving.
+  await expect
+    .poll(async () => {
+      const res = await request.get(`http://domain:8080/registrations/${reference}`);
+      return res.ok() ? (await res.json()).zaakUrl : null;
+    }, { timeout: 30_000, intervals: [1_000, 2_000, 3_000, 5_000] })
+    .toBeTruthy();
+
+  const approve = await request.post(`http://domain:8080/registrations/${reference}/approve`);
+  expect(approve.status()).toBe(204);
+
+  // The approval flows back to the projection; the openbaar register now shows *our* row (matched by
+  // its reference) as INGESCHREVEN.
+  await expect
+    .poll(async () => {
+      await page.reload();
+      return page.getByRole('row', { name: reference }).getByRole('cell', { name: 'INGESCHREVEN' }).count();
     }, { timeout: 30_000, intervals: [1_000, 2_000, 3_000, 5_000] })
     .toBeGreaterThan(0);
 });