Merge pull request 'feat(bff): BFF with one endpoint per portal + OIDC validation (closes #8)' (#64) from feat/8-bff into main

Reviewed-on: #64

.config/dotnet-tools.json

@@ -0,0 +1,20 @@
+{
+  "version": 1,
+  "isRoot": true,
+  "tools": {
+    "dotnet-stryker": {
+      "version": "4.15.0",
+      "commands": [
+        "dotnet-stryker"
+      ],
+      "rollForward": false
+    },
+    "dotnet-ef": {
+      "version": "10.0.0",
+      "commands": [
+        "dotnet-ef"
+      ],
+      "rollForward": false
+    }
+  }
+}

.gitea/workflows/ci.yaml

@@ -43,14 +43,77 @@ jobs:
           dotnet-version: '10.0.x'
       - run: make unit
 
-  compose-smoke:
+  mutation:
     runs-on: ubuntu-latest
     steps:
       - uses: https://github.com/actions/checkout@v4
-      - run: make smoke
-      - name: dump container logs on failure
+      - uses: https://github.com/actions/setup-dotnet@v4
+        with:
+          dotnet-version: '10.0.x'
+      - run: make mutation
+      # Publish the Stryker HTML reports. `if: always()` uploads them even when the
+      # ratchet fails — that is exactly when you want to inspect the survivors.
+      # `continue-on-error` keeps the upload best-effort: the mutation *gate* is the
+      # ratchet (make mutation's exit code), not the report, so a Gitea artifact-backend
+      # 500 must not fail the job (gitea-actions-gotchas.md §4). Glob handles Stryker's
+      # non-deterministic StrykerOutput/<timestamp>/ dir. Pinned @v3: @v4's bundled
+      # @actions/artifact hard-aborts on non-github.com (GHES guard) — see the runbook.
+      - uses: https://github.com/actions/upload-artifact@v3
+        if: always()
+        continue-on-error: true
+        with:
+          name: acl-mutation-report
+          path: services/acl/StrykerOutput/**/reports/mutation-report.html
+          if-no-files-found: warn
+      - uses: https://github.com/actions/upload-artifact@v3
+        if: always()
+        continue-on-error: true
+        with:
+          name: event-subscriber-mutation-report
+          path: services/event-subscriber/StrykerOutput/**/reports/mutation-report.html
+          if-no-files-found: warn
+      - uses: https://github.com/actions/upload-artifact@v3
+        if: always()
+        continue-on-error: true
+        with:
+          name: domain-mutation-report
+          path: services/domain/StrykerOutput/**/reports/mutation-report.html
+          if-no-files-found: warn
+      - uses: https://github.com/actions/upload-artifact@v3
+        if: always()
+        continue-on-error: true
+        with:
+          name: bff-mutation-report
+          path: services/bff/StrykerOutput/**/reports/mutation-report.html
+          if-no-files-found: warn
+
+  # One stage for every check that needs the live stack. On the single self-hosted
+  # runner jobs run sequentially, so booting OpenZaak once (instead of once per job)
+  # is the cheapest layout (issue #58). No setup-dotnet: the ACL test runs in a built
+  # image and everything reaches services by container IP. Needs Docker + egress
+  # (base images, nuget, selectielijst.openzaak.nl).
+  verify-stack:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: https://github.com/actions/checkout@v4
+      # Bring the full stack up + wait for health — this also is the DoD "compose up
+      # reaches green health" smoke (it replaces the old compose-smoke job).
+      - name: Bring up the full stack & wait for health
+        run: make verify-up
+      - name: ACL ↔ OpenZaak integration tests
+        run: make verify-acl
+      - name: OpenZaak → NRC notification delivery
+        run: make verify-nrc
+      - name: OpenZaak → NRC → Event Subscriber → projection-api
+        run: make verify-projection
+      - name: Domain → Flowable → ACL → OpenZaak
+        run: make verify-domain
+      - name: BFF → Keycloak + domain + projection
+        run: make verify-bff
+      # Log dump must precede teardown (which removes the containers).
+      - name: Dump container logs on failure
         if: failure()
-        run: docker compose -f infra/docker-compose.yml logs --no-color --tail=80 oz-init openzaak nrc-init nrc-web flowable-init keycloak acl bff 2>&1 || true
-      - name: tear down on failure
-        if: failure()
-        run: docker compose -f infra/docker-compose.yml down --volumes 2>&1 || true
+        run: docker compose -f infra/docker-compose.yml logs --no-color --tail=100 oz-init openzaak nrc-init nrc-web nrc-celery nrc-beat flowable-db flowable-rest flowable-init keycloak acl bff domain projection-db event-subscriber projection-api 2>&1 || true
+      - name: Tear down
+        if: always()
+        run: make down

.gitignore

@@ -15,6 +15,9 @@ coverage*.json
 coverage*.xml
 *.coverage
 
+# Stryker.NET mutation-testing reports (regenerated by `make mutation`)
+StrykerOutput/
+
 # Rider / VS / VS Code
 .idea/
 .vs/

Makefile

@@ -10,7 +10,7 @@ COMPOSE    := infra/docker-compose.yml
 # Long-running services with a healthcheck — the smoke polls these for readiness
 # (infra/wait-healthy.sh). One-shot init jobs (oz-init, nrc-init, flowable-init)
 # are not polled; they only need to have run. See docs/runbooks/gitea-actions-gotchas.md.
-WAIT_SVCS  := openzaak nrc-web acl bff
+WAIT_SVCS  := openzaak nrc-web acl bff domain event-subscriber projection-api
 # Config files (OpenZaak data.yaml, Keycloak realms, Flowable BPMN) are streamed
 # into external named volumes via `docker cp` (infra/seed-config.sh) instead of
 # bind-mounted, because bind mounts don't reach sibling containers on the
@@ -18,7 +18,7 @@ WAIT_SVCS  := openzaak nrc-web acl bff
 # volumes are `external`, so compose won't remove them — CFG_VOLS lists them for
 # explicit teardown. See docs/runbooks/gitea-actions-gotchas.md.
 SEED       := bash infra/seed-config.sh
-CFG_VOLS   := rr-oz-config rr-kc-realms rr-fl-bpmn
+CFG_VOLS   := rr-oz-config rr-nrc-config rr-kc-realms rr-fl-bpmn
 # Local-only stack: same services but config is bind-mounted (no seed step), so a
 # plain `docker compose -f infra/docker-compose.local.yml up` works on any local
 # engine. This is the no-make / Windows-friendly path. See that file's header.
@@ -43,10 +43,11 @@ export DOCKER_HOST := unix://$(PODMAN_SOCK)
 endif
 endif
 
-.PHONY: ci lint build unit smoke up down local local-down changelog openzaak-up openzaak-smoke openzaak-seed openzaak-down stack-up stack-smoke stack-down keycloak-up keycloak-smoke keycloak-down flowable-up flowable-smoke flowable-down help
+.PHONY: ci lint build unit mutation integration verify verify-up verify-acl verify-nrc verify-projection verify-notifications smoke up down local local-down changelog openzaak-up openzaak-smoke openzaak-seed openzaak-down stack-up stack-smoke stack-down keycloak-up keycloak-smoke keycloak-down flowable-up flowable-smoke flowable-down help
 
-## ci: run the full pipeline — lint, build, unit, smoke (mirrors Gitea Actions)
-ci: lint build unit smoke
+## ci: run the full pipeline — lint, build, unit, mutation, verify (mirrors Gitea Actions)
+## `verify` is the live-stack stage (full stack up once → ACL + notification checks).
+ci: lint build unit mutation verify
 
 ## lint: verify formatting (no changes)
 lint:
@@ -56,9 +57,21 @@ lint:
 build:
 	dotnet build $(SLN) -c Release
 
-## unit: run unit tests
+## unit: run unit tests (excludes the container-backed Integration lane)
 unit:
-	dotnet test $(SLN) -c Release
+	dotnet test $(SLN) -c Release --filter "Category!=Integration"
+
+## mutation: run the Stryker.NET ratchet on each service with branching logic (fails below baseline)
+# Stryker is pinned as a local dotnet tool (.config/dotnet-tools.json); `tool restore`
+# makes `make mutation` work from a fresh clone. Each service owns its config + break
+# threshold (the ratchet, CLAUDE.md §5): each services/<svc>/stryker-config.json.
+# Scores never regress below baseline.
+mutation:
+	dotnet tool restore
+	cd services/acl && dotnet stryker
+	cd services/event-subscriber && dotnet stryker
+	cd services/domain && dotnet stryker
+	cd services/bff && dotnet stryker
 
 ## smoke: seed config, bring the whole stack up, wait for health-checked services, tear down
 # SEED populates the external config volumes first (upstream images used verbatim;
@@ -68,14 +81,14 @@ unit:
 # podman-compose, and needing no `--wait` flag or host port access. The one-shots
 # (oz-init, flowable-init) aren't polled; they just need to have run.
 smoke:
-	$(SEED) oz kc fl
+	$(SEED) oz nrc kc fl
 	docker compose -f $(COMPOSE) up -d --build
 	bash -c 'WAIT_TIMEOUT=420 bash infra/wait-healthy.sh $(WAIT_SVCS); rc=$$?; docker compose -f $(COMPOSE) down --volumes; docker volume rm -f $(CFG_VOLS) >/dev/null 2>&1; exit $$rc'
 
 ## up: seed config volumes and start the full stack (use instead of bare
 ## `docker compose up`, which can't self-seed the external config volumes)
 up:
-	$(SEED) oz kc fl
+	$(SEED) oz nrc kc fl
 	docker compose -f $(COMPOSE) up -d --build
 
 ## down: stop and remove the local stack (incl. the external config volumes)
@@ -97,6 +110,66 @@ local-down:
 changelog:
 	git-cliff --output CHANGELOG.md
 
+# ── ZGW verification ───────────────────────────────────────────────────────
+# On the single runner CI jobs run sequentially, so the OpenZaak-dependent checks
+# share ONE full-stack bring-up: the `verify-stack` CI job runs `verify-up` then
+# `verify-acl` + `verify-nrc` as steps against the same stack (issue #58). The
+# check logic lives in stack-agnostic runners that reach services by container IP
+# (gitea-actions-gotchas.md §5/§6); `integration` / `verify-notifications` are local
+# convenience wrappers that bring up a lighter stack and call the same runners.
+
+## verify-up: bring the FULL stack up and wait for health (CI verify-stack step 1;
+## subsumes the old compose-smoke health gate — the DoD "up reaches green" check).
+verify-up:
+	$(SEED) oz nrc kc fl
+	docker compose -f $(COMPOSE) up -d --build
+	WAIT_TIMEOUT=420 bash infra/wait-healthy.sh $(WAIT_SVCS)
+
+## verify-acl: ACL ↔ OpenZaak integration tests against the already-running stack.
+verify-acl:
+	bash infra/run-acl-integration.sh
+
+## verify-nrc: OpenZaak → NRC notification delivery against the already-running stack.
+verify-nrc:
+	bash infra/run-notification-check.sh
+
+## verify-projection: OpenZaak → NRC → Event Subscriber → projection-api end-to-end (S-06),
+## against the already-running stack.
+verify-projection:
+	bash infra/run-projection-check.sh
+
+## verify-domain: domain → Flowable → ACL → OpenZaak end-to-end (S-05), against the
+## already-running stack. Recreates the acl service to inject the seeded zaaktype URL.
+verify-domain:
+	bash infra/run-domain-check.sh
+
+## verify-bff: BFF end-to-end (S-07) against the up stack — token validation on self-service
+## + anonymous public-safe openbaar register (ADR-0010).
+verify-bff:
+	bash infra/run-bff-check.sh
+
+## verify: local mirror of the CI verify-stack job — full stack up once, all checks,
+## tear down (always). For fast single-concern local iteration use `integration`
+## (oz-only) or `verify-notifications` (oz+nrc) instead.
+verify:
+	$(SEED) oz nrc kc fl
+	docker compose -f $(COMPOSE) up -d --build
+	@bash -c 'set -e; rc=0; \
+	  WAIT_TIMEOUT=420 bash infra/wait-healthy.sh $(WAIT_SVCS) \
+	    && bash infra/run-acl-integration.sh \
+	    && bash infra/run-notification-check.sh \
+	    && bash infra/run-projection-check.sh \
+	    && bash infra/run-domain-check.sh \
+	    && bash infra/run-bff-check.sh || rc=$$?; \
+	  docker compose -f $(COMPOSE) down --volumes >/dev/null 2>&1; \
+	  docker volume rm -f $(CFG_VOLS) >/dev/null 2>&1; \
+	  exit $$rc'
+
+## integration: local convenience — ACL integration test against a throwaway
+## OpenZaak-only stack (fast iteration). CI uses verify-acl on the shared stack.
+integration:
+	bash infra/run-integration.sh
+
 ## openzaak-up: start the OpenZaak stack (migrations run on first start)
 openzaak-up:
 	$(SEED) oz
@@ -129,10 +202,16 @@ openzaak-down:
 	docker compose -f $(OZ_COMPOSE) down --volumes
 	-docker volume rm -f rr-oz-config
 
-## stack-up: start OpenZaak + Open Notificaties together (shared network)
+## verify-notifications: local convenience — OpenZaak → NRC notification delivery
+## against a throwaway oz+nrc stack (S-01-c). CI uses verify-nrc on the shared stack.
+verify-notifications:
+	bash infra/verify-notifications.sh
+
+## stack-up: start OpenZaak + Open Notificaties together (shared network), with
+## OpenZaak publishing notifications to NRC (S-01-c).
 stack-up:
-	$(SEED) oz
-	docker compose $(STACK_FILES) up -d
+	$(SEED) oz nrc
+	OZ_NOTIFICATIONS_DISABLED=false docker compose $(STACK_FILES) up -d
 
 ## stack-smoke: start both, assert OpenZaak (403/302/200) and NRC (302) are reachable
 stack-smoke: stack-up
@@ -151,7 +230,7 @@ stack-smoke: stack-up
 ## stack-down: stop and remove both stacks (wipes data)
 stack-down:
 	docker compose $(STACK_FILES) down --volumes
-	-docker volume rm -f rr-oz-config
+	-docker volume rm -f rr-oz-config rr-nrc-config
 
 ## keycloak-up: start Keycloak with the four imported realms
 keycloak-up:

docs/architecture/adr-0005-mutation-testing.md

@@ -0,0 +1,68 @@
+# ADR-0005: Stryker.NET for mutation testing, baseline on the ACL
+
+- **Status:** Accepted
+- **Date:** 2026-06-25
+- **Deciders:** Respellion engineering
+- **Relates to:** S-04b (#47); proposed in #51; supports CLAUDE.md §5 (mutation ratchet) and §3 (Definition of Done)
+
+## Context
+
+CLAUDE.md §5 mandates Stryker on every PR with a **ratchet**: CI fails on a regression
+below the established baseline, and the baseline only ever moves up. §3 lists "mutation
+(ratchet)" as a Definition-of-Done gate for **every** slice. Yet no baseline existed — so,
+strictly, no slice could satisfy that gate. S-04b establishes it.
+
+The ACL is the natural place to set the first baseline: it is the first service with real
+branching logic — `OpenZaakGateway` (HTTP contract, geo CRS headers, error handling),
+`ZgwToken` (HS256 JWT minting), and the `AclService` default-fill mapping. We need a tool
+that:
+
+- mutates C# and runs the existing xUnit suite per mutant,
+- is reproducible (same version locally and in CI, no global install),
+- understands this repo's `.slnx` solution format (used repo-wide),
+- emits a break threshold CI can gate on.
+
+## Decision
+
+**Use [Stryker.NET](https://stryker-mutator.io/docs/stryker-net/) (`dotnet-stryker`),
+pinned as a local dotnet tool**, configured in solution mode against `Acl.slnx`.
+
+- Pinned in `.config/dotnet-tools.json` (v4.15.0); `dotnet tool restore` makes
+  `make mutation` reproducible from a fresh clone, locally and in CI — no global install.
+- **Solution mode** (`stryker-config.json` → `solution: Acl.slnx`) mutates the two projects
+  under test (`Acl.Application`, `Acl.Infrastructure`); `Acl.Api` is untested and skipped.
+  Stryker 4.15 reads `.slnx` directly, so no throwaway `.sln` shim is needed.
+- A `mutation` make target runs it; it is wired into `make ci` and a parallel Gitea Actions
+  `mutation` job, keeping `make ci` an exact mirror of the pipeline.
+
+**Baseline:** writing S-04b's tests surfaced that the ACL suite was thin — the initial
+score was **35%** (survivors: unasserted CRS headers, null guards, error paths, and JWT
+claims). Those tests were strengthened (killing the mutants honestly rather than lowering
+the bar), raising the score to **95%**. The enforced `break` threshold is set to **90%** —
+one-mutant headroom over the ~20-mutant surface, since a single mutant is ≈5%.
+
+## Consequences
+
+- **Positive:** test *strength* is gated, not just coverage; the ratchet protects the ACL's
+  ZGW contract logic; the baseline is repo-wide and ratchets upward per §5.
+- **Cost:** a new dependency (`dotnet-stryker`) and a slower CI job than unit tests (~25 s on
+  the small ACL). Pinned + tool-restored, so reproducible.
+- **One accepted survivor:** a mutation of the empty-response *exception message string*.
+  Asserting exception message text is brittle and the behaviour (type + control flow) is
+  unchanged — treated as an equivalent mutant, not a test gap.
+- **Commitment:** later slices ratchet the threshold up deliberately, never down (§5). New
+  services add their own mutation run as they gain branching logic (BFF, Domain, …).
+- **Replaceable by:** no realistic .NET alternative — Stryker.NET is the tool §5 already
+  names; the fallback is no mutation testing, which §5 forbids.
+
+## Alternatives considered
+
+- **Global `dotnet tool install -g`** — rejected: not reproducible/pinned per clone; the
+  local manifest gives every checkout and the CI runner the same version.
+- **Mutate the whole `register-referentie.slnx`** — rejected for this slice: scopes the
+  baseline to services with no logic yet (BFF skeleton), diluting the signal. Each service
+  opts in as it gains logic.
+- **Application-only scope** — rejected: would leave `Acl.Infrastructure`'s HTTP/JWT logic —
+  the riskiest code — unguarded by the ratchet.
+- **Coverage gate instead of mutation** — rejected: line coverage does not measure whether
+  tests would *catch* a regression; that is the whole point of §5.

docs/architecture/adr-0006-integration-test-provisioning.md

@@ -0,0 +1,92 @@
+# ADR-0006: Provision the ACL integration test against the compose stack
+
+- **Status:** Accepted
+- **Date:** 2026-06-29
+- **Deciders:** Respellion engineering
+- **Relates to:** S-04a (#46); proposed in #53; builds on ADR-0001 (loose coupling), ADR-0002 (catalogus design), ADR-0003 (default-fill); supports CLAUDE.md §11 (integration tests via real containers)
+
+## Context
+
+S-04 delivered the ACL's one operation — `OpenZaakGateway.OpenZaakAsync` — with unit
+tests against a stubbed `HttpMessageHandler` and a Reqnroll scenario over an in-memory
+stand-in. The deferred S-04 acceptance criterion (S-04a) is the one a stub cannot meet:
+
+> Integration test using Testcontainers against real OpenZaak passes.
+
+The test must drive the gateway against a **real** OpenZaak — real ZGW JWT auth, the real
+`POST /zaken/api/v1/zaken` contract, real CRS handling — and assert a zaak comes back.
+
+Two ways to stand OpenZaak up were considered (the issue's open question): (a) a full
+**Testcontainers** graph started by the test, or (b) target the **running compose stack**
+the repo already defines (`infra/openzaak/docker-compose.yml`, `make openzaak-up`).
+
+Investigation reversed the initially-favoured Testcontainers option:
+
+1. **Testcontainers .NET has no docker-compose support.** OpenZaak needs PostGIS + Redis +
+   a `setup_configuration` one-shot (the JWT client) + the API. Honouring "full graph" would
+   mean re-implementing that five-service stack — init ordering, the config volume, health
+   gating — by hand in C#, duplicating the maintained compose file and rotting with it. That
+   rubs against CLAUDE.md §13 ("if a test is hard to write, the design is wrong").
+2. **The test cannot be hermetic anyway.** OpenZaak's Zaken API rejects a zaak against a
+   *concept* zaaktype (`not-published`), and a *published* zaaktype requires ≥1 resultaattype,
+   which OpenZaak validates by fetching the external **Selectielijst** reference API
+   (`selectielijst.openzaak.nl`). So a real zaak POST already depends on outbound internet
+   from the OpenZaak container — the self-containment that motivated Testcontainers is lost
+   regardless of how the containers are started.
+
+## Decision
+
+**The ACL integration test targets the running compose stack; it does not start containers
+itself. No new test dependency is added.**
+
+- A gated test project `Acl.IntegrationTests` (`[Trait("Category","Integration")]`) talks to
+  OpenZaak with a plain `HttpClient`, reusing the same endpoint + JWT-client config the seed
+  uses (`OZ_BASE` / `OZ_CLIENT_ID` / `OZ_SECRET`, defaulting to the local stack). It locates
+  the published `BIG-REGISTRATIE` zaaktype via the Catalogi API and exercises the real
+  `OpenZaakGateway` against it.
+- **The lane is kept out of the fast checks.** `make unit` runs with
+  `--filter "Category!=Integration"`; Stryker is pinned to `Acl.Tests` (`test-projects`), so
+  neither the unit nor the mutation lane needs a live stack. A `make integration` target
+  (`infra/run-integration.sh`) brings up a throwaway OpenZaak and runs the lane locally.
+  In CI the check runs as the `verify-acl` step of the consolidated `verify-stack` job
+  (issue #58) — one shared full-stack bring-up. This matches `make` being the single
+  source of truth (ADR-0005).
+- **Publishing is opt-in in the seed.** `infra/openzaak/seed_catalogus.py` gains an
+  `OZ_PUBLISH=1` path that adds the relations OpenZaak's publish requires — two statustypen
+  (begin/eind), a roltype, and a resultaattype whose Selectielijst procestype is matched onto
+  the zaaktype — then publishes. The default seed (S-01 / ADR-0002) still leaves the zaaktype
+  a concept; only `make integration` flips the switch.
+
+## Consequences
+
+- **Positive:** a small, honest test over the real ZGW contract with no bespoke orchestration
+  to maintain; the compose stack is exercised exactly as operators run it; no new dependency.
+- **It caught a real bug.** The gateway sent the zaak body via `JsonContent` without a
+  `Content-Length`, so .NET framed it as `Transfer-Encoding: chunked`, which OpenZaak's uwsgi
+  rejects with 400. A stubbed handler accepts either framing, so only a real OpenZaak surfaced
+  it. Fixed by buffering the body (`LoadIntoBufferAsync`); guarded in the fast lane by a unit
+  test asserting a `Content-Length` is set. This is the concrete justification for §11's
+  integration tier.
+- **External dependency:** the integration job needs the OpenZaak container to reach
+  `selectielijst.openzaak.nl`. It is a stable public reference API (the same one OpenZaak uses
+  in production) but it is a network touchpoint, and a CI environment without egress would need
+  a local Selectielijst service or a recorded fixture. `OZ_SELECTIELIJST` overrides the base URL.
+- **Cost:** the lane needs the stack up first, so it is separate from the fast lanes.
+- **Runs on the hosted runner.** A process *on* the runner can't reach the stack's published
+  ports (Compose starts sibling containers via the host daemon — gitea-actions-gotchas.md §5,
+  same split as §1), so `infra/run-integration.sh` runs both the seed and the test as containers
+  *joined to the OpenZaak network*, reaching it by **container IP** (a single-label host like
+  `openzaak` isn't URL-valid for OpenZaak's own `URLValidator`; an IPv4 literal is). Code is
+  delivered by image build / `docker cp`, never bind mounts. The CI job therefore needs only
+  Docker — no `setup-dotnet`. (This closed the follow-up that was originally split out as #55.)
+
+## Alternatives considered
+
+- **Full Testcontainers graph** — rejected: re-implements the compose stack in C# (brittle,
+  duplicative) for no hermeticity gain, since the Selectielijst dependency remains.
+- **Single OpenZaak container (sqlite/locmem)** — rejected: diverges from the real
+  PostGIS-backed, Redis-cached deployment; the Zaken API is a geo API and the divergence would
+  undermine the contract the test exists to verify.
+- **Mock OpenZaak / record-replay** — rejected: that is what the existing stubbed-handler unit
+  tests already do; it cannot exercise the real contract, and would not have caught the chunked
+  body bug.

docs/architecture/adr-0007-notification-wiring.md

@@ -0,0 +1,77 @@
+# ADR-0007: Wiring OpenZaak → Open Notificaties (NRC) for notifications
+
+- **Status:** Accepted
+- **Date:** 2026-06-29
+- **Deciders:** Respellion engineering
+- **Relates to:** S-01-c (#56); completes S-01 (#2); unblocks the Event Subscriber (#7); builds on ADR-0002 (catalogus/seed) and ADR-0006 (runner-safe container harnesses)
+
+## Context
+
+S-01 brought OpenZaak + Open Notificaties (NRC) up in compose but **deferred the
+notification wiring**: OpenZaak ran with `NOTIFICATIONS_DISABLED=true` and NRC's
+`setup_configuration` was empty. The walking skeleton (PRD §12) needs the upstream
+event path — a zaak created in OpenZaak must publish a notification NRC fans out to
+subscribers — before the Event Subscriber (#7) can consume it.
+
+The OpenZaak↔NRC handshake is intricate and several details are non-obvious; they
+were nailed down by iterating `setup_configuration` against the running stack.
+
+## Decision
+
+**Provision both sides declaratively via `setup_configuration`, authenticate with the
+existing `big-reference-seed` client, and run NRC's celery-beat so deliveries happen.**
+
+- **OpenZaak** (`infra/openzaak/setup_configuration/data.yaml`): a `zgw_consumers`
+  service `nrc` (api_type `nrc`, the NRC API root) plus `notifications_config` naming
+  it. `NOTIFICATIONS_DISABLED` is flipped to `false` **only when NRC is present** —
+  the full stack and the local twin set it; OpenZaak-only bring-ups (`openzaak-up`,
+  the ACL integration test) default it back to `true` via `OZ_NOTIFICATIONS_DISABLED`
+  so they don't 500 publishing to an absent NRC.
+- **NRC** (`infra/opennotificaties/setup_configuration/data.yaml`): the
+  `big-reference-seed` JWT credential (to verify OpenZaak's token), a `zgw_consumers`
+  `ac` service pointing at **OpenZaak's Autorisaties API**, the `autorisaties_api`
+  step delegating authorization to that AC, and the `zaken` kanaal. NRC's init
+  container switches from `migrate` to `/setup_configuration.sh`; its data.yaml is
+  delivered through the `rr-nrc-config` external volume by `infra/seed-config.sh`
+  (the same `docker cp` pattern as OpenZaak — bind mounts don't reach the CI runner's
+  daemon).
+- **celery-beat is required.** NRC accepts a notification and writes a
+  `ScheduledNotification`; a periodic `execute_notifications` task (celery-beat,
+  every `NOTIFICATION_SEC_INTERVAL`s) drains it to the worker for delivery. The lean
+  S-01 stack dropped beat — so notifications were accepted but never delivered. An
+  `nrc-beat` service is added to every compose; the interval is lowered to 5s.
+
+Verification is a runner-safe smoke (`infra/run-notification-check.sh`): it seeds a
+published BIG zaaktype, registers an abonnement to a webhook sink, creates a zaak, and
+asserts the sink receives the `zaken`/`create` notification — all from containers
+**inside** the compose network (ADR-0006). Locally it runs via `make verify-notifications`
+(a throwaway oz+nrc stack); in CI it runs as the `verify-nrc` step of the consolidated
+`verify-stack` job (one shared full-stack bring-up — issue #58).
+
+## Consequences
+
+- **Positive:** the walking-skeleton event path works end to end; #7 can consume real
+  notifications; the wiring is declarative and reproducible from a fresh `make`.
+- **Gotchas captured (see gitea-actions-gotchas.md):**
+  - **Single-label hosts aren't URL-valid.** OpenZaak/NRC reject `http://openzaak…`
+    /`http://nrc-web…` in URLs they validate (Django `URLValidator`); the verify
+    harness reaches services and registers the sink callback **by container IP**.
+  - **Abonnement callbacks must enforce auth.** NRC probes the callback during
+    registration and refuses it (`no-auth-on-callback-url`) unless it returns 401
+    without the configured `Authorization`; the sink enforces a bearer token.
+- **Cost:** an extra long-running service (`nrc-beat`) per stack, and the verify job
+  needs egress (base images + `selectielijst.openzaak.nl`, since the published
+  zaaktype the check creates a zaak against depends on it — ADR-0006).
+- **Dev-only credentials** reused (`big-reference-seed` / its secret) across publish,
+  AC lookup, and seeding — acceptable for the reference app, not production.
+
+## Alternatives considered
+
+- **NRC with its own (non-AC) authorization** — rejected: delegating to OpenZaak's
+  Autorisaties API is the upstream-intended model and reuses the applicatie that
+  already grants `heeft_alle_autorisaties`.
+- **Keep beat out, deliver synchronously** — not an option: Open Notificaties 1.16
+  delivers via scheduled notifications drained by beat; there is no sync path.
+- **A persistent abonnement in `setup_configuration`** instead of registering one in
+  the verify harness — deferred: the real subscriber is #7; the harness's sink
+  abonnement is throwaway and IP-specific.

docs/architecture/adr-0008-read-projection-store.md

@@ -0,0 +1,89 @@
+# ADR-0008: The read projection — a shared, rebuildable store with a writer and a reader
+
+- **Status:** Accepted
+- **Date:** 2026-06-30
+- **Deciders:** Respellion engineering
+- **Relates to:** S-06 (#7); builds on ADR-0001 (loose coupling), ADR-0007 (#56, OZ→NRC wiring); first EF Core usage in the repo
+
+## Context
+
+S-06 (#7) adds the upstream event path's destination: an **Event Subscriber** that consumes
+NRC notifications and a **read projection** the openbaar register reads. The walking-skeleton
+projection (PRD §8.4) holds one row per zaak — `id`, `bsn`, `naam_placeholder`, `status` —
+and must be **idempotent** (NRC redelivers and reorders, CLAUDE.md §8.6) and **rebuildable**
+(a derived artefact, never a write-only source of truth).
+
+Two design questions had no obvious answer:
+
+1. **Where does `bsn` come from?** The NRC `zaken`/`zaak`/`create` notification carries only the
+   zaak URL plus the fixed `kenmerken` (`bronorganisatie`, `zaaktype`, `vertrouwelijkheidaanduiding`).
+   It does **not** carry the bsn. Reading it means calling a ZGW API — which **only the ACL** may
+   do (CLAUDE.md §8.1). The issue's "Touches" lists only `event-subscriber` + `projection-api`,
+   not the ACL.
+2. **Who owns the projection schema?** The subscriber writes the projection; the projection-api
+   reads it. CLAUDE.md §8.5 says "no direct DB access across services; each service owns its
+   schema." Two deployables on one table looks like a violation.
+
+## Decision
+
+**One Postgres database is the read projection. The Event Subscriber writes it (projector) and
+the projection-api reads it (query); both are processes of the single "Read Projection" bounded
+context and share one schema, defined in a shared `Projection.ReadModel` library. `bsn` is
+deferred.**
+
+- **Schema ownership.** The read model — `register_projection` plus the subscriber's
+  `processed_notifications` log — lives in `services/projection-api/Projection.ReadModel`
+  (EF Core + Npgsql). Both services reference it. This is the textbook CQRS read-model split
+  (one writer, one reader over one derived store), **not** the cross-*domain* DB reach §8.5
+  forbids: no domain owns write-state here; the projection is rebuildable (§8.4). §8.5 still
+  holds for every domain database.
+- **Idempotency** is the primary key on `processed_notifications.key` (a deterministic key
+  derived from the immutable notification content). A duplicate insert raises a unique violation,
+  caught and reported as "already recorded", so the duplicate never reaches the projection. The
+  projection upsert is itself idempotent on the zaak id, a second line of defence.
+- **Rebuild replays the log, not OpenZaak.** `POST /admin/rebuild` clears `register_projection`
+  and reprojects every row in `processed_notifications`. So "rebuildable" needs **no** ZGW access
+  (§8.1) and no ACL dependency — keeping S-06 within its stated scope.
+- **`bsn` and `naam_placeholder` are deferred.** They are columns (nullable) but the minimal slice
+  populates only `id` + `status` (`INGEDIEND`) from the notification. Populating personal data
+  requires reading the zaak **through the ACL** (§8.1) and is its own follow-up; the column shape
+  is in place so that change is additive.
+- **New dependency: EF Core 10 + `Npgsql.EntityFrameworkCore.PostgreSQL`.** What it gives us: a
+  migrated relational schema, LINQ queries, and a clean port implementation. What we'd write
+  instead: hand-rolled SQL + a migration runner. Risk: ORM complexity and an extra dependency
+  graph — bounded here to a tiny two-table read model. `dotnet-ef` is pinned as a local tool for
+  migrations; `NuGetAuditMode=direct` keeps EF's design-time-only tooling transitive out of the
+  audited, shipped graph.
+
+The end-to-end path is verified by a runner-safe live-stack smoke (`infra/run-projection-check.sh`,
+the `verify-projection` step of the `verify-stack` job, #58): register an abonnement at the real
+Event Subscriber's callback, create a zaak, assert projection-api serves an `INGEDIEND` row — all
+in-network, reaching services by container IP (ADR-0006/0007).
+
+## Consequences
+
+- **Positive:** the upstream event path reaches a queryable projection; idempotent and rebuildable
+  without OpenZaak; S-06 stays inside its stated touch-set (no ACL change); the projection-api is
+  ready for S-09 to tighten public-safe field filtering.
+- **Negative / deferred:**
+  - `bsn`/`naam_placeholder` stay empty until a follow-up wires zaak reads via the ACL.
+  - The abonnement is registered by the verify harness (by container IP), not provisioned
+    persistently — ADR-0007 already deferred a persistent abonnement, and a single-label service
+    host is not URL-valid for NRC, so persistent registration needs a dotted network alias. Tracked
+    as a follow-up; a plain `make up` therefore needs the abonnement registered before the event
+    path flows.
+  - Two services share one database. Acceptable for a derived read model; revisit if the read and
+    write sides ever need independent scaling or storage.
+
+## Alternatives considered
+
+- **Subscriber reads OpenZaak directly to fill `bsn`** — rejected: breaks §8.1 (only the ACL talks
+  to ZGW) and would need its own ADR to bend the rule.
+- **Extend the ACL with a zaak-read operation, consumed as a library** — viable and §8.1-clean, but
+  it grows S-06 beyond its stated scope (touches the ACL) and pulls personal-data handling forward;
+  deferred to a follow-up.
+- **projection-api owns the DB and exposes an internal write endpoint the subscriber calls** —
+  rejected for the walking skeleton: adds an HTTP hop and a write surface on a read service for no
+  current benefit over a shared, rebuildable read model.
+- **Separate databases for the log and the projection** — rejected as premature: both are the read
+  side's private, rebuildable state; one DB is simpler and still honours §8.5's intent.

docs/architecture/adr-0009-external-task-job-worker.md

@@ -0,0 +1,88 @@
+# ADR-0009: The Domain Service drives Flowable as an external-task job worker
+
+- **Status:** Accepted
+- **Date:** 2026-06-30
+- **Deciders:** Respellion engineering
+- **Relates to:** S-05 (#6); proposal #60; builds on ADR-0001 (loose coupling, §8.1/§8.2), S-03 (#4, the `registratie` BPMN), S-04 (#5, the ACL `OpenZaak` operation)
+
+## Context
+
+S-05 (#6) adds the **BIG Domain Service**. Submitting a registration must: create a
+`Registration` aggregate, **start the Flowable `registratie` process** (S-03), have the
+`OpenZaakAanmaken` task **open a zaak via the ACL** (S-04), and store the resulting zaak URL
+back on the aggregate.
+
+`OpenZaakAanmaken` is a Flowable **external-worker** service task (`flowable:type="external-worker"`,
+topic `OpenZaakAanmaken`). Flowable does not push it anywhere — it parks the job and waits for a
+worker to **acquire and lock** it, do the work, and **complete** it. Two coupling rules constrain
+who may do what:
+
+- **§8.2 — the Workflow Client is the only code that talks to Flowable.** BPMN models never embed
+  OpenZaak knowledge; they ask the Workflow Client to execute external tasks.
+- **§8.1 — the ACL is the only code that talks to ZGW.** The worker opens the zaak *through the ACL*,
+  never by constructing ZGW URLs itself.
+
+This is an ADR-worthy moment (§14): a service boundary is defined and both coupling rules are
+exercised. The open question is *how* the external task is driven.
+
+## Decision
+
+**The Domain Service drives the `OpenZaakAanmaken` task as a hosted external-task job worker
+(PRD §36). Orchestration is eventually consistent, not request-synchronous.**
+
+- **`POST /registrations` is fast and side-effecting only on the domain side.** It creates the
+  `Registration` aggregate in state `INGEDIEND`, persists it, and asks the Workflow Client to start
+  one `registratie` process instance, recording the process-instance id on the aggregate. It returns
+  immediately; it does **not** wait for the zaak to be opened.
+- **A hosted worker polls Flowable for `OpenZaakAanmaken` jobs.** It acquires and locks a job, calls
+  the ACL `OpenZaak` operation (§8.1), attaches the returned zaak URL to the matching aggregate
+  (`Registration.AttachZaak`), and completes the job in Flowable. The process then runs to its end
+  event.
+- **The Workflow Client is the only Flowable client (§8.2).** It lives in the Domain Service's
+  `Infrastructure` layer and speaks Flowable's REST API (start process-instance; acquire/lock/complete
+  external-worker jobs). No other code — not the Application layer, not the BPMN — knows Flowable
+  exists.
+- **The worker *logic* is an Application service over ports**, not Flowable-aware code. `OpenZaakWorker`
+  takes an acquired job (topic + the registration id it carries), calls `IAclClient` and
+  `IRegistrationStore`, and returns the zaak URL to complete with. The **polling loop** is a thin
+  `BackgroundService` in `Infrastructure` that fetches jobs via the Workflow Client and feeds them to
+  the worker. So the orchestration is covered by fast unit tests against fakes; only the REST framing
+  needs a container integration test.
+
+## Scope decisions for the minimal slice
+
+- **Registration persistence is in-memory.** The walking skeleton's *read* path is fed by
+  NRC → Event Subscriber → projection (S-06, #7), not by the domain database. An EF-backed domain
+  store buys nothing the demo needs yet, so it is a documented follow-up; the `IRegistrationStore`
+  port keeps that change additive. (PRD §88 envisions EF Core for the domain DB eventually.)
+- **The aggregate's state machine is minimal:** `INGEDIEND` on submission. Later flows (withdrawal,
+  beoordeling, herregistratie) add states in their own slices — they are out of scope here.
+- **No bsn flows to ZGW yet.** The ACL `OpenZaak` operation already default-fills the ZGW-mandatory
+  fields (ADR-0003) and takes the bsn as its domain payload; the domain hands it through unchanged.
+
+## Consequences
+
+- **Positive:** the submit request is decoupled from ACL/OpenZaak latency; the documented Common
+  Ground pattern (external-task worker) is realised; both coupling rules (§8.1, §8.2) hold with the
+  Flowable knowledge isolated to one Infrastructure class; the orchestration is unit-testable.
+- **Negative / deferred:**
+  - Eventual consistency: immediately after `POST /registrations` the aggregate has no zaak URL yet.
+    Acceptable — the read side is the projection, not the domain store.
+  - In-memory registration state is lost on restart; fine for the skeleton, replaced by an EF store
+    in a follow-up.
+  - The worker polls (no push); poll interval is a tuning knob, not a correctness concern, since
+    Flowable holds the job until completed.
+
+## Alternatives considered
+
+- **Synchronous acquire+complete inside the `POST /registrations` request** — rejected: simpler and
+  deterministic, but couples the submit request to ACL/OpenZaak latency and failure, and is not the
+  external-task worker pattern PRD §36 mandates. It would also make the request fail if OpenZaak is
+  briefly down, instead of the job simply staying parked for the worker to retry.
+- **A standalone Workflow Client service, separate from the Domain Service** — rejected for this
+  slice: the worker needs the domain's aggregate store and the ACL client anyway, and PRD §9 places
+  the Workflow Client inside the Domain Service deployment. A separate process adds a hop and a
+  shared store for no current benefit.
+- **Flowable pushes to a webhook instead of being polled** — rejected: Flowable's external-worker
+  model is pull-based (acquire/lock/complete); a push shim would re-implement it with weaker
+  delivery guarantees.

docs/architecture/adr-0010-bff-oidc.md

@@ -0,0 +1,74 @@
+# ADR-0010: The BFF validates Keycloak tokens and is the portals' only backend
+
+- **Status:** Accepted
+- **Date:** 2026-07-01
+- **Deciders:** Respellion engineering
+- **Relates to:** S-07 (#8); proposal #63; builds on ADR-0001 (loose coupling, §8.3), S-02 (#3, Keycloak realms), S-05 (#6, Domain Service), S-06 (#7, read projection)
+
+## Context
+
+S-07 (#8) adds the **BFF (Backend-for-Frontend)** — the single backend the Angular portals talk
+to (CLAUDE.md §8.3). For the walking skeleton it exposes two endpoints and fans out to services
+already built:
+
+- `POST /self-service/registrations` → Domain Service `POST /registrations` (S-05).
+- `GET /openbaar/register?q=…` → projection-api `GET /register` (S-06).
+
+It must validate tokens issued by Keycloak (S-02). This is an ADR-worthy moment (§14): a new
+dependency (JWT bearer authentication) and two new service boundaries (BFF→domain, BFF→projection).
+
+## Decision
+
+**The BFF is the portals' only backend; it validates Keycloak `digid`-realm JWTs on the
+self-service endpoint, leaves the openbaar lookup anonymous, and fans out to the domain and
+projection over typed HTTP clients.**
+
+- **Auth model.** `POST /self-service/registrations` requires a valid `digid`-realm bearer token;
+  the BFF reads the `bsn` claim and forwards it to the domain. Missing / invalid / expired token →
+  **401**. `GET /openbaar/register` is **anonymous** — the openbaar register is a public lookup
+  (S-09), so no token is required.
+- **Portals talk only to the BFF (§8.3).** They never call the Domain Service, ACL, projection, or
+  OpenZaak directly. The BFF orchestrates via typed `HttpClient`s whose base URLs come from config.
+  Downstream calls are unauthenticated on the internal network for the walking skeleton; a
+  service-to-service auth story (e.g. client-credentials) is a later slice, not this one.
+- **Validation is `Microsoft.AspNetCore.Authentication.JwtBearer`** pointed at the Keycloak `digid`
+  realm authority. **New dependency justification:** it gives us standards-based OIDC/JWT validation
+  (signature, issuer, expiry, audience) maintained by the framework; rolling our own JWT validation
+  would be error-prone security code; the risk is a first-party ASP.NET Core package — minimal.
+- **Tests mint their own tokens.** `WebApplicationFactory` tests override the bearer options with a
+  **test signing key**, so valid / invalid / expired tokens are minted in-process without a live
+  Keycloak. Real Keycloak validation is exercised by a live-stack `verify-bff` check.
+- **OpenAPI is generated and committed** (`services/bff/openapi.json`) from .NET's built-in OpenAPI,
+  so S-08's Angular client is generated from the spec, never hand-written (§10).
+
+## Known wrinkle — container OIDC issuer mismatch
+
+Keycloak stamps tokens with an `iss` equal to its **browser-facing** URL (what the portal used to
+log in), which differs from the BFF's **in-container** authority (`http://keycloak:8080/realms/digid`).
+Strict issuer validation then rejects otherwise-valid tokens. Unit tests avoid this (test key).
+`verify-bff` handles it by aligning the configured authority/issuer with the token's `iss` (and, if
+needed, disabling metadata address rewriting). Recorded so it is not rediscovered each time.
+
+## Consequences
+
+- **Positive:** the walking skeleton gains its front door; §8.3 holds with all portal traffic going
+  through one backend; token validation is standard and testable without infra; the committed
+  OpenAPI unblocks S-08.
+- **Negative / deferred:**
+  - Downstream service-to-service auth is deferred (internal-network trust for now).
+  - The openbaar endpoint is anonymous; when public-safe field filtering tightens (S-09) it stays
+    anonymous but the projection query narrows.
+  - The issuer-mismatch handling is dev-oriented; a production reverse-proxy setup would align the
+    browser and internal issuer URLs instead.
+
+## Alternatives considered
+
+- **Token-gate the openbaar endpoint too** — rejected: the openbaar register is public by design
+  (S-09); requiring a login would contradict the slice's intent.
+- **Validate tokens by calling Keycloak's introspection endpoint per request** — rejected: adds a
+  network hop per call and a Keycloak dependency on the hot path; local JWT signature validation via
+  the realm's JWKS is the standard, faster choice.
+- **Hand-written JWT parsing** — rejected: security-sensitive code we shouldn't own when a
+  first-party validator exists.
+- **Generate the OpenAPI client by hand / keep the spec uncommitted** — rejected: §10 requires a
+  generated client from a committed spec.

docs/demo-script.md

@@ -0,0 +1,104 @@
+# Demo script
+
+A running log of demoable outcomes, one section per slice. Each entry is a short,
+copy-pasteable walkthrough against a local `make up` stack.
+
+---
+
+## S-07 — BFF: the portals' single backend
+
+**Outcome:** the BFF validates Keycloak `digid` tokens on the self-service submit (forwarding the
+bsn to the domain) and serves the openbaar register anonymously with only public-safe fields — the
+front door the portals (S-08/S-09) will talk to.
+
+**The path:** portal → BFF `POST /self-service/registrations` (token-gated) → domain; and
+BFF `GET /openbaar/register` (anonymous) → projection-api. See ADR-0010.
+
+```bash
+# 1. Bring the full stack up.
+make up
+
+# 2. Drive the BFF end-to-end (401 without a token, 202 with a real digid token, anonymous openbaar).
+make verify-bff        # → "OK — BFF: 401 without token, 202 with a digid token, anonymous ..."
+
+# 3. Try it by hand (BFF on host port 8080).
+#    a) A digid access token for the mock user jan-burger (bsn 123456782):
+tok=$(curl -s -X POST http://localhost:8180/realms/digid/protocol/openid-connect/token \
+  -d grant_type=password -d client_id=big-portal -d username=jan-burger -d password=test123 \
+  | python3 -c "import sys,json;print(json.load(sys.stdin)['access_token'])")
+
+#    b) Submit — without the token it is 401; with it, 202:
+curl -s -o /dev/null -w "no token  -> %{http_code}\n" -X POST http://localhost:8080/self-service/registrations
+curl -s -o /dev/null -w "with token-> %{http_code}\n" -X POST http://localhost:8080/self-service/registrations \
+  -H "Authorization: Bearer $tok"
+
+#    c) The openbaar register is anonymous and exposes only id + status (never the bsn):
+curl -fsS http://localhost:8080/openbaar/register | jq
+```
+
+> The self-service token is validated against Keycloak's `digid` realm; the openbaar lookup needs no
+> token (S-09). The generated contract lives at `services/bff/openapi.json` — S-08's client is built
+> from it.
+
+---
+
+## S-05 — BIG Domain Service: submit a registration
+
+**Outcome:** submitting a registration starts a Flowable process; the external-task worker
+opens a zaak via the ACL and records it on the aggregate — the upstream half of the skeleton
+that produces the zaak S-06 then projects.
+
+**The path:** domain `POST /registrations` → Flowable `registratie` process → `OpenZaakAanmaken`
+worker → ACL → OpenZaak; `GET /registrations/{id}` shows the opened zaak (ADR-0009).
+
+```bash
+# 1. Bring the full stack up (seeds config, builds our services, waits for health).
+make up
+
+# 2. Drive the full path end-to-end. This also seeds a published BIG zaaktype and points the
+#    ACL at it (the zaak's zaaktype URL is server-assigned, so it isn't known at bring-up).
+make verify-domain      # → "OK — the domain opened a zaak and recorded it on the registration"
+
+# 3. Submit one yourself (domain on host port 8130). Returns 202 + a Location to read back.
+loc=$(curl -fsS -D - -o /dev/null -X POST http://localhost:8130/registrations \
+  -H 'Content-Type: application/json' -d '{"bsn":"123456782"}' | sed -n 's/\r$//; s/^[Ll]ocation: //p')
+
+# 4. The worker opens the zaak off the request path (eventual consistency, ADR-0009); poll
+#    until zaakUrl is filled. (Step 2 must have run first, so the ACL knows the zaaktype.)
+curl -fsS "http://localhost:8130$loc" | jq
+# → { "registrationId": "...", "status": "Ingediend", "zaakUrl": "http://.../zaken/api/v1/zaken/<uuid>" }
+```
+
+> Registration state is in-memory for this slice (ADR-0009); the rebuildable read model is the
+> projection (S-06), fed by the very zaak this flow opens.
+
+---
+
+## S-06 — Event Subscriber + read projection
+
+**Outcome:** a zaak created in OpenZaak flows through NRC to the Event Subscriber, which
+projects it into a rebuildable read projection the projection-api serves.
+
+**The path:** OpenZaak → (notification) NRC → (abonnement callback) Event Subscriber →
+`register_projection` → projection-api `GET /register`.
+
+```bash
+# 1. Bring the full stack up (seeds config, builds our services, waits for health).
+make up
+
+# 2. Register the Event Subscriber's abonnement and create a zaak, then read it back.
+#    (The verify-projection check does exactly this end-to-end and asserts the result.)
+make verify-projection            # → "OK — projection-api serves zaak <uuid> with status INGEDIEND"
+
+# 3. Observe the projection directly via the read API (host port 8120).
+curl -fsS http://localhost:8120/register | jq
+# → [ { "id": "<zaak-uuid>", "status": "INGEDIEND", "bsn": null, "naamPlaceholder": null } ]
+
+# 4. Idempotency + rebuild: replays don't duplicate; a rebuild repopulates from the
+#    notification log (no OpenZaak access needed — ADR-0008).
+curl -fsS -X POST http://localhost:8110/admin/rebuild   # Event Subscriber, host port 8110
+curl -fsS http://localhost:8120/register | jq 'length'  # → unchanged
+```
+
+> `bsn` / `naam_placeholder` are deferred (ADR-0008) — the notification doesn't carry them and
+> the subscriber may not read OpenZaak directly (§8.1). They surface in a later slice.

docs/runbooks/ci.md

@@ -15,14 +15,23 @@ and CI cannot drift:
 |---|---|---|
 | `lint` | `make lint` → `dotnet format … --verify-no-changes` | .NET 10 SDK |
 | `build` | `make build` → `dotnet build … -c Release` | .NET 10 SDK |
-| `unit` | `make unit` → `dotnet test … -c Release` | .NET 10 SDK |
-| `compose-smoke` | `make smoke` → seed config volumes → `up -d` (full stack) → `up --wait` durable services → `down` | container engine + compose v2 |
+| `unit` | `make unit` → `dotnet test … -c Release --filter "Category!=Integration"` | .NET 10 SDK |
+| `mutation` | `make mutation` → `dotnet tool restore` → `dotnet stryker` (ACL); uploads the HTML report as an artifact | .NET 10 SDK |
+| `verify-stack` | the single live-stack stage — steps: `make verify-up` (full stack up + health, the DoD smoke) → `make verify-acl` (ACL ↔ OpenZaak) → `make verify-nrc` (OpenZaak → NRC delivery) → `make down` | container engine + egress (base images, nuget, `selectielijst.openzaak.nl`) |
+
+> **Why one `verify-stack` job, not three.** The single self-hosted runner runs jobs
+> **sequentially**, so booting OpenZaak once (instead of once per check) is the
+> cheapest layout (issue #58). It subsumes the old `integration`, `notifications`, and
+> `compose-smoke` jobs — the bring-up step *is* the "compose up reaches green health"
+> gate. No `setup-dotnet`: the ACL test runs in a built image and every check reaches
+> services by **container IP** (the runner can't reach published ports — see
+> [gitea-actions-gotchas.md §5/§6](gitea-actions-gotchas.md)).
 
 All `uses:` references are absolute, tag-pinned URLs (`https://github.com/actions/checkout@v4`,
 `https://github.com/actions/setup-dotnet@v4`) per CLAUDE.md §8.7 and §15 — Gitea
 Actions resolves them from GitHub.
 
-> **`compose-smoke` runs on a containerized runner.** Workspace bind mounts do
+> **`verify-stack` runs on a containerized runner.** Workspace bind mounts do
 > **not** reach the sibling containers Compose starts, so config/assets are
 > streamed into external named volumes via `docker cp` (`infra/seed-config.sh`),
 > and the upstream images are used verbatim (no build). If you add a service that
@@ -30,6 +39,38 @@ Actions resolves them from GitHub.
 > bare `docker compose up` no longer self-seeds; use `make up`. See
 > [gitea-actions-gotchas.md](gitea-actions-gotchas.md).
 
+## Mutation testing (the ratchet)
+
+The `mutation` job enforces test *strength*, not just coverage (CLAUDE.md §5).
+[Stryker.NET](https://stryker-mutator.io/docs/stryker-net/) is pinned as a local
+dotnet tool (`.config/dotnet-tools.json`), so it runs identically locally and in CI:
+
+```bash
+make mutation     # dotnet tool restore + dotnet stryker on the ACL
+```
+
+Config lives in [`services/acl/stryker-config.json`](../../services/acl/stryker-config.json).
+It runs in **solution mode** against `Acl.slnx`, mutating the two projects under test
+(`Acl.Application`, `Acl.Infrastructure`); `Acl.Api` has no tests and is skipped.
+
+**Baseline (the ratchet):** the ACL is the first service with branching logic, so it
+sets the repo-wide baseline. Observed score **95%**; enforced `break` threshold **90%**
+(one-mutant headroom over the ~20-mutant surface). Stryker exits non-zero — failing the
+job — when the score drops below `break`. Per §5 the baseline only moves **up**, and only
+as a slice's stated outcome; never lower it. New services add their own mutation run as
+they gain logic.
+
+The HTML report is written to `services/acl/StrykerOutput/<timestamp>/reports/` (git-ignored);
+open it to see survived vs. killed mutants.
+
+In CI the `mutation` job publishes that report as the **`acl-mutation-report`** artifact
+(download it from the run's summary page). The upload step uses `if: always()`, so the
+report is available even when the ratchet *fails* — which is exactly when you want to inspect
+the survivors. It is the repo's first use of `actions/upload-artifact`, pinned to **`@v3`**:
+`@v4` refuses to run on Gitea (its `@actions/artifact` v2 library blocks any non-github.com
+server as "GHES"), while `@v3` speaks the artifact protocol Gitea implements. See
+[gitea-actions-gotchas.md §4](gitea-actions-gotchas.md) (§15).
+
 ## Running the stack locally without `make` (Windows / Docker Desktop)
 
 `make` and the bash helpers assume a Unix shell. To bring the whole stack up on a
@@ -52,14 +93,24 @@ the containerized CI runner). Keep the two files in sync.
 
 ## Running CI locally (`make ci`)
 
-Until the runner exists, run the full pipeline yourself before pushing:
+`make ci` runs the exact same checks as the pipeline — handy to run before pushing:
 
 ```bash
-make ci          # lint + build + unit + smoke — what the pipeline runs
+make ci          # lint + build + unit + mutation + verify — mirrors the pipeline
 make lint        # or a single stage
-make smoke       # compose up --wait, curl /health, tear down
+make mutation    # Stryker.NET ratchet on the ACL
+make verify      # the live-stack stage: full stack up once → ACL + NRC checks → down
 ```
 
+> **`make verify`** mirrors the CI `verify-stack` job: it boots the full stack once and
+> runs both the ACL ↔ OpenZaak and OpenZaak → NRC checks against it. For fast,
+> single-concern local iteration use a lighter throwaway stack instead:
+>
+> ```bash
+> make integration          # ACL ↔ OpenZaak only (no NRC)
+> make verify-notifications # OpenZaak → NRC delivery only
+> ```
+
 **Prerequisites:** .NET 10 SDK, a container engine with Compose v2, and `curl`.
 
 On a **rootless Podman** box (the default dev setup here), the `smoke` target needs

docs/runbooks/gitea-actions-gotchas.md

@@ -13,6 +13,8 @@ those containers share a filesystem — or a `localhost` — breaks.
 | Bind-mounted config arrives empty | `docker cp` config into external volumes | `infra/seed-config.sh` |
 | `docker compose up --wait` is unsupported / flaky | poll health with `docker inspect` | `infra/wait-healthy.sh` |
 | `pg_isready` passes before PostGIS is ready | add a `PostGIS_Version()` probe | the db healthchecks |
+| `upload-artifact@v4` fails ("not supported on GHES") | pin `@v3` | `.gitea/workflows/ci.yaml` (`mutation` job) |
+| `upload-artifact@v3` fails with "Artifact service responded with 500" | mark the upload `continue-on-error: true` (server-side; issue #62) | `.gitea/workflows/ci.yaml` (`mutation` job) |
 
 ---
 
@@ -98,3 +100,99 @@ plus app start.
 container that starts migrating in that window can fail on a missing PostGIS. So
 the db healthchecks add a `SELECT PostGIS_Version()` probe, making dependents wait
 for the extension, not just the port.
+
+---
+
+## 4. `actions/upload-artifact@v4` refuses to run on Gitea
+
+**Symptom** — the `mutation` job's `make mutation` step passes (95% score), but the
+upload step right after it fails the job:
+
+```
+::error::@actions/artifact v2.0.0+, upload-artifact@v4+ and download-artifact@v4+
+are not currently supported on GHES.
+❌  Failure - Main https://github.com/actions/upload-artifact@v4
+```
+
+**Why** — `upload-artifact@v4` bundles `@actions/artifact` v2, which inspects the
+server URL and **hard-aborts on anything that isn't `github.com`**, treating Gitea
+as an unsupported GitHub Enterprise Server. The check fires regardless of whether
+the Gitea server can actually store artifacts (1.24+ can). It is the *action*, not
+the server, that refuses.
+
+**Fix** — pin **`actions/upload-artifact@v3`** (and `download-artifact@v3` if ever
+needed). v3 uses the older artifact protocol that Gitea implements, and has no GHES
+guard. Inputs are the same (`name`, `path`, `if-no-files-found`), so it is a drop-in
+swap. Do **not** bump to `@v4` until act_runner advertises github.com-compatible
+artifact support.
+
+**Second failure mode — the server's artifact backend returns 500.** Even on the
+correctly-pinned `@v3`, uploads can fail with:
+
+```
+Create Artifact Container - Attempt 5 of 5 failed with error: Artifact service responded with 500
+::error::Create Artifact Container failed: Artifact service responded with 500
+```
+
+This is the **Gitea server's** artifact storage failing (not the action's GHES guard),
+so it is outside the repo's control. Because the `mutation` job's upload steps run with
+`if: always()`, that 500 would fail the job even though the ratchet passed. **Fix:** mark
+the uploads `continue-on-error: true` (issue #62). The mutation *gate* is the Stryker
+ratchet — `make mutation`'s exit code fails the job on a real regression — so the report
+upload is best-effort: when the server's artifact storage is restored, reports publish
+again with no workflow change.
+
+---
+
+## 5. A runner process can't reach a service container's published port
+
+**Symptom** — green locally, but a CI step that runs *on the runner* and talks to a
+compose service over `localhost` fails. The ACL integration test's seed died with:
+
+```
+OpenZaak ready (000)
+urllib.error.URLError: <urlopen error [Errno 111] Connection refused>
+make: *** [Makefile:114: integration] Error 1
+```
+
+OpenZaak was demonstrably up — uwsgi had been serving for ~2 minutes — yet
+`curl`/`urllib` to `localhost:8000` from the runner were refused the whole time.
+
+**Why** — the same sibling-container split as §1. Compose starts the stack via the
+host daemon, so `ports: ["8000:8000"]` publishes to the *daemon host*, not to the job
+container. From the runner, `localhost:8000` has nothing listening. (`make smoke`
+sidesteps this by polling readiness via `docker inspect` (§2), never a service port.)
+
+**Fix** — don't talk to service ports from the runner. Either check state via `docker
+inspect` (health), or run the client **inside the compose network** so it reaches the
+service by name (`http://openzaak:8000`). For a test/seed that needs the repo's own
+code, deliver it via a **built image** (not a bind mount — §1), then
+`docker run --network <stack>_cg …`.
+
+**Applied** — `make integration` (ADR-0006) and `make verify-notifications` (ADR-0007)
+do exactly this: they run the seed/test/driver as containers on the stack network and
+reach services by **container IP** (see §6).
+
+---
+
+## 6. OpenZaak / NRC reject single-label hosts in URLs
+
+**Symptom** — talking to OpenZaak or NRC by compose **service name** fails where a URL
+is validated: catalogus/zaaktype filters, the zaak `zaaktype` URL, and abonnement
+`callbackUrl` come back `400 "Voer een geldige URL in."` — even though the host
+resolves and is reachable.
+
+**Why** — these apps validate URLs with Django's `URLValidator`, which rejects a
+**single-label** host like `openzaak` or `nrc-web` (no dot, and not `localhost`).
+`localhost` passes (so it's invisible in host-port-based local runs); in-network the
+reality is a service name or an IPv4 literal — and only the IP passes.
+
+**Fix** — in-network tooling reaches OpenZaak/NRC by **container IP**
+(`docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}'`), not
+service name; the notif verify harness also registers the sink callback by IP.
+(`infra/run-acl-integration.sh`, `infra/run-notification-check.sh`.)
+
+**Related — abonnement callbacks must enforce auth.** NRC probes a callback when an
+abonnement is registered and refuses it (`no-auth-on-callback-url`) unless it returns
+**401** without the configured `Authorization`. The verify sink
+(`infra/notification-sink.py`) enforces a bearer token for exactly this reason.

infra/docker-compose.local.yml

@@ -59,7 +59,8 @@ services:
       CELERY_BROKER_URL: redis://oz-redis:6379/1
       CELERY_RESULT_BACKEND: redis://oz-redis:6379/1
       DISABLE_2FA: "true"
-      NOTIFICATIONS_DISABLED: "true"
+      # Publish notifications to NRC (always present in this twin). See ADR-0007.
+      NOTIFICATIONS_DISABLED: "false"
       OPENZAAK_SUPERUSER_USERNAME: admin
       DJANGO_SUPERUSER_PASSWORD: admin
       OPENZAAK_SUPERUSER_EMAIL: admin@localhost
@@ -122,7 +123,9 @@ services:
     networks: [cg]
 
   nrc-init:
-    # Migrations only (see the canonical compose / ADR-0002); no config needed.
+    # Migrations + setup_configuration (S-01-c): the JWT credential, Autorisaties-API
+    # delegation, and the `zaken` kanaal that let OpenZaak publish. Config is
+    # bind-mounted here (this twin is the local/no-make path). See ADR-0007.
     image: docker.io/openzaak/open-notificaties:${OPENNOTIFICATIES_TAG:-1.16.1}
     environment: &nrc-env
       DJANGO_SETTINGS_MODULE: nrc.conf.docker
@@ -141,7 +144,11 @@ services:
       OPENNOTIFICATIES_SUPERUSER_USERNAME: admin
       DJANGO_SUPERUSER_PASSWORD: admin
       OPENNOTIFICATIES_SUPERUSER_EMAIL: admin@localhost
-    command: ["sh", "-c", "/wait_for_db.sh && OTEL_SDK_DISABLED=True python src/manage.py migrate"]
+      RUN_SETUP_CONFIG: "true"
+      NOTIFICATION_SEC_INTERVAL: "5"
+    command: /setup_configuration.sh
+    volumes:
+      - ./opennotificaties/setup_configuration:/app/setup_configuration:ro,z
     depends_on:
       nrc-db:
         condition: service_healthy
@@ -176,6 +183,17 @@ services:
         condition: service_completed_successfully
     networks: [cg]
 
+  # Celery beat drains scheduled notifications to subscribers — required for
+  # delivery, not optional. See ADR-0007.
+  nrc-beat:
+    image: docker.io/openzaak/open-notificaties:${OPENNOTIFICATIES_TAG:-1.16.1}
+    environment: *nrc-env
+    command: /celery_beat.sh
+    depends_on:
+      nrc-init:
+        condition: service_completed_successfully
+    networks: [cg]
+
   # ── Keycloak (S-02) ──────────────────────────────────────────────────────
   keycloak:
     image: quay.io/keycloak/keycloak:26.1
@@ -287,10 +305,68 @@ services:
       start_period: 10s
     networks: [cg]
 
+  # ── Read projection (S-06) ────────────────────────────────────────────────
+  projection-db:
+    image: docker.io/library/postgres:16
+    environment:
+      POSTGRES_USER: projection
+      POSTGRES_PASSWORD: projection
+      POSTGRES_DB: projection
+    volumes:
+      - projection-db:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U projection -d projection"]
+      interval: 5s
+      timeout: 3s
+      retries: 10
+    networks: [cg]
+
+  event-subscriber:
+    build:
+      context: ..
+      dockerfile: services/event-subscriber/Dockerfile
+    image: register-referentie/event-subscriber:dev
+    environment:
+      ConnectionStrings__Projection: Host=projection-db;Database=projection;Username=projection;Password=projection
+      EventSubscriber__Webhook__AuthToken: ${NOTIFICATION_WEBHOOK_TOKEN:-Bearer big-reference-notifications}
+    ports:
+      - "8110:8080"
+    healthcheck:
+      test: ["CMD", "curl", "-fsS", "http://localhost:8080/health"]
+      interval: 5s
+      timeout: 3s
+      retries: 5
+      start_period: 15s
+    depends_on:
+      projection-db:
+        condition: service_healthy
+    networks: [cg]
+
+  projection-api:
+    build:
+      context: ..
+      dockerfile: services/projection-api/Dockerfile
+    image: register-referentie/projection-api:dev
+    environment:
+      ConnectionStrings__Projection: Host=projection-db;Database=projection;Username=projection;Password=projection
+    ports:
+      - "8120:8080"
+    healthcheck:
+      test: ["CMD", "curl", "-fsS", "http://localhost:8080/health"]
+      interval: 5s
+      timeout: 3s
+      retries: 5
+      start_period: 15s
+    depends_on:
+      projection-db:
+        condition: service_healthy
+    networks: [cg]
+
 volumes:
   oz-db:
   nrc-db:
   flowable-db:
+  projection-db:
 
 networks:
   cg:

infra/docker-compose.yml

@@ -9,6 +9,8 @@
 #   8080  BFF               GET /health → Healthy
 #   8090  Flowable REST     http://localhost:8090/flowable-rest/service/
 #   8100  ACL               GET /health → Healthy  POST /zaken
+#   8110  Event Subscriber  GET /health → Healthy  POST /notifications
+#   8120  projection-api    GET /health → Healthy  GET /register
 #   8180  Keycloak          (admin: admin / admin)
 #
 #   docker compose -f infra/docker-compose.yml up -d --build --wait
@@ -62,7 +64,10 @@ services:
       CELERY_BROKER_URL: redis://oz-redis:6379/1
       CELERY_RESULT_BACKEND: redis://oz-redis:6379/1
       DISABLE_2FA: "true"
-      NOTIFICATIONS_DISABLED: "true"
+      # Publish notifications to NRC (always present in this full stack). The NRC
+      # service + notifications_config are provisioned by setup_configuration
+      # (infra/openzaak/setup_configuration/data.yaml). See ADR-0007 / S-01-c.
+      NOTIFICATIONS_DISABLED: "false"
       OPENZAAK_SUPERUSER_USERNAME: admin
       DJANGO_SUPERUSER_PASSWORD: admin
       OPENZAAK_SUPERUSER_EMAIL: admin@localhost
@@ -146,11 +151,17 @@ services:
       OPENNOTIFICATIES_SUPERUSER_USERNAME: admin
       DJANGO_SUPERUSER_PASSWORD: admin
       OPENNOTIFICATIES_SUPERUSER_EMAIL: admin@localhost
-    # Migrations only for now. No setup_configuration steps are enabled yet (the
-    # OZ<->NRC notification wiring lands in S-06), and NRC's `setup_configuration`
-    # aborts with "No steps enabled" on the empty data.yaml — so we run `migrate`
-    # directly instead of /setup_configuration.sh. See data.yaml and ADR-0002.
-    command: ["sh", "-c", "/wait_for_db.sh && OTEL_SDK_DISABLED=True python src/manage.py migrate"]
+      RUN_SETUP_CONFIG: "true"
+      # nrc-beat fires `execute_notifications` this often to drain scheduled
+      # notifications to subscribers (upstream default 20s). See ADR-0007.
+      NOTIFICATION_SEC_INTERVAL: "5"
+    # Runs migrations + setup_configuration (S-01-c): the JWT credential, the
+    # Autorisaties-API delegation, and the `zaken` kanaal that let OpenZaak publish.
+    # data.yaml is streamed into rr-nrc-config by infra/seed-config.sh (bind mounts
+    # don't reach sibling containers on the CI runner). See data.yaml + ADR-0007.
+    command: /setup_configuration.sh
+    volumes:
+      - nrc-config:/app/setup_configuration:ro
     depends_on:
       nrc-db:
         condition: service_healthy
@@ -185,6 +196,18 @@ services:
         condition: service_completed_successfully
     networks: [cg]
 
+  # Celery beat drains the ScheduledNotification rows the API creates on publish
+  # and hands them to the worker. Without it, notifications are accepted but never
+  # delivered to subscribers — required, not optional. See ADR-0007.
+  nrc-beat:
+    image: docker.io/openzaak/open-notificaties:${OPENNOTIFICATIES_TAG:-1.16.1}
+    environment: *nrc-env
+    command: /celery_beat.sh
+    depends_on:
+      nrc-init:
+        condition: service_completed_successfully
+    networks: [cg]
+
   # ── Keycloak (S-02) ──────────────────────────────────────────────────────
   keycloak:
     image: quay.io/keycloak/keycloak:26.1
@@ -262,7 +285,9 @@ services:
       dockerfile: Dockerfile
     image: register-referentie/acl:dev
     environment:
-      Acl__OpenZaak__BaseUrl: http://openzaak:8000/
+      # Overridable so verify-domain can point the ACL at the same OpenZaak host that
+      # owns the seeded zaaktype URL (host-consistent zaak creation, ADR-0009).
+      Acl__OpenZaak__BaseUrl: ${ACL_OPENZAAK_BASEURL:-http://openzaak:8000/}
       Acl__OpenZaak__ClientId: big-reference-seed
       Acl__OpenZaak__Secret: insecure-dev-secret-change-me
       Acl__Defaults__Bronorganisatie: "517439943"
@@ -283,12 +308,49 @@ services:
         condition: service_healthy
     networks: [cg]
 
+  # ── BIG Domain Service (S-05) ──────────────────────────────────────────────
+  # Orchestrates a registration: POST /registrations creates the aggregate and
+  # starts the registratie Flowable process; a hosted worker acquires the
+  # OpenZaakAanmaken job, opens a zaak via the ACL and completes it (ADR-0009).
+  # Talks only to Flowable (Workflow Client, §8.2) and the ACL (§8.1).
+  domain:
+    build:
+      context: ../services/domain
+      dockerfile: Dockerfile
+    image: register-referentie/domain:dev
+    environment:
+      Flowable__BaseUrl: http://flowable-rest:8080/flowable-rest/
+      Flowable__Username: rest-admin
+      Flowable__Password: test
+      Acl__BaseUrl: http://acl:8080/
+    ports:
+      - "8130:8080"
+    healthcheck:
+      test: ["CMD", "curl", "-fsS", "http://localhost:8080/health"]
+      interval: 5s
+      timeout: 3s
+      retries: 5
+      start_period: 10s
+    depends_on:
+      acl:
+        condition: service_healthy
+      flowable-init:
+        condition: service_completed_successfully
+    networks: [cg]
+
   # ── BFF ──────────────────────────────────────────────────────────────────
   bff:
     build:
       context: ../services/bff
       dockerfile: Dockerfile
     image: register-referentie/bff:dev
+    environment:
+      # The BFF is the portals' only backend; it validates digid tokens and fans out (ADR-0010).
+      # Keycloak (start-dev) derives the issuer from the request host, so the BFF authority and the
+      # verify token request both use keycloak:8080 to keep the issuer consistent.
+      Keycloak__Authority: http://keycloak:8080/realms/digid
+      Downstream__Domain__BaseUrl: http://domain:8080/
+      Downstream__Projection__BaseUrl: http://projection-api:8080/
     ports:
       - "8080:8080"
     healthcheck:
@@ -297,18 +359,94 @@ services:
       timeout: 3s
       retries: 5
       start_period: 10s
+    depends_on:
+      domain:
+        condition: service_healthy
+      projection-api:
+        condition: service_healthy
+      keycloak:
+        condition: service_started
+    networks: [cg]
+
+  # ── Read projection (S-06) ────────────────────────────────────────────────
+  # One Postgres DB backing the rebuildable read projection (PRD §8.4): the Event
+  # Subscriber writes it, projection-api reads it. See ADR-0008.
+  projection-db:
+    image: docker.io/library/postgres:16
+    environment:
+      POSTGRES_USER: projection
+      POSTGRES_PASSWORD: projection
+      POSTGRES_DB: projection
+    volumes:
+      - projection-db:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U projection -d projection"]
+      interval: 5s
+      timeout: 3s
+      retries: 10
+    networks: [cg]
+
+  # Consumes NRC notifications (abonnement callback) and projects zaak-created events
+  # into register_projection. Build context is the repo root: it shares the read model
+  # in services/projection-api/Projection.ReadModel.
+  event-subscriber:
+    build:
+      context: ..
+      dockerfile: services/event-subscriber/Dockerfile
+    image: register-referentie/event-subscriber:dev
+    environment:
+      ConnectionStrings__Projection: Host=projection-db;Database=projection;Username=projection;Password=projection
+      # 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}
+    ports:
+      - "8110:8080"
+    healthcheck:
+      test: ["CMD", "curl", "-fsS", "http://localhost:8080/health"]
+      interval: 5s
+      timeout: 3s
+      retries: 5
+      start_period: 15s
+    depends_on:
+      projection-db:
+        condition: service_healthy
+    networks: [cg]
+
+  # The read side of the projection. Shares Projection.ReadModel, so build context is root.
+  projection-api:
+    build:
+      context: ..
+      dockerfile: services/projection-api/Dockerfile
+    image: register-referentie/projection-api:dev
+    environment:
+      ConnectionStrings__Projection: Host=projection-db;Database=projection;Username=projection;Password=projection
+    ports:
+      - "8120:8080"
+    healthcheck:
+      test: ["CMD", "curl", "-fsS", "http://localhost:8080/health"]
+      interval: 5s
+      timeout: 3s
+      retries: 5
+      start_period: 15s
+    depends_on:
+      projection-db:
+        condition: service_healthy
     networks: [cg]
 
 volumes:
   oz-db:
   nrc-db:
   flowable-db:
+  projection-db:
   # Config volumes — created and populated out-of-band by infra/seed-config.sh
   # (docker cp), because bind mounts don't reach sibling containers on the CI
   # runner. `external` keeps the names deterministic; the seed step manages them.
   oz-config:
     external: true
     name: rr-oz-config
+  nrc-config:
+    external: true
+    name: rr-nrc-config
   kc-realms:
     external: true
     name: rr-kc-realms

infra/notification-sink.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+"""A throwaway webhook sink for verifying the OpenZaak → NRC notification path.
+
+NRC delivers abonnement callbacks here as POSTs; each body is printed to stdout
+(prefixed `NOTIFICATION `) so the verify harness can assert on `docker logs`.
+
+NRC refuses to register an abonnement whose callback is unauthenticated
+(`no-auth-on-callback`): when validating it sends a probe and expects the callback
+to reject a request without the configured `Authorization` value. So this sink
+enforces that header (EXPECTED_AUTH env) — 401 without it, 204 with it.
+
+Stdlib only. Listens on :9000. See infra/verify-notifications.sh / S-01-c (#56).
+"""
+import http.server
+import os
+import sys
+
+EXPECTED_AUTH = os.environ.get("EXPECTED_AUTH", "Bearer notification-sink-token")
+
+
+class Handler(http.server.BaseHTTPRequestHandler):
+    def do_POST(self):
+        length = int(self.headers.get("content-length", 0))
+        body = self.rfile.read(length).decode("utf-8", "replace")
+        if self.headers.get("Authorization") != EXPECTED_AUTH:
+            self.send_response(401)
+            self.end_headers()
+            return
+        print("NOTIFICATION " + body, flush=True)
+        self.send_response(204)
+        self.end_headers()
+
+    def log_message(self, *args):  # silence default request logging
+        pass
+
+
+if __name__ == "__main__":
+    http.server.HTTPServer(("0.0.0.0", 9000), Handler).serve_forever()
+    sys.exit(0)

infra/opennotificaties/docker-compose.yml

@@ -52,11 +52,18 @@ services:
       OPENNOTIFICATIES_SUPERUSER_USERNAME: admin
       DJANGO_SUPERUSER_PASSWORD: admin
       OPENNOTIFICATIES_SUPERUSER_EMAIL: admin@localhost
-    # Migrations only for now. No setup_configuration steps are enabled yet (the
-    # OZ<->NRC notification wiring lands in S-06), and NRC's `setup_configuration`
-    # aborts with "No steps enabled" on the empty data.yaml — so we run `migrate`
-    # directly instead of /setup_configuration.sh. See data.yaml and ADR-0002.
-    command: ["sh", "-c", "/wait_for_db.sh && OTEL_SDK_DISABLED=True python src/manage.py migrate"]
+      RUN_SETUP_CONFIG: "true"
+      # Delivery cadence: nrc-beat fires `execute_notifications` this often to drain
+      # scheduled notifications to subscribers. Upstream default is 20s; 5s keeps the
+      # walking-skeleton + the verify smoke responsive.
+      NOTIFICATION_SEC_INTERVAL: "5"
+    # Runs migrations + setup_configuration (S-01-c): the JWT credential, the
+    # Autorisaties-API delegation, and the `zaken` kanaal that let OpenZaak publish
+    # notifications. data.yaml is streamed into this external volume by
+    # infra/seed-config.sh (same pattern as oz-init). See data.yaml + ADR-0006.
+    command: /setup_configuration.sh
+    volumes:
+      - nrc-config:/app/setup_configuration:ro
     depends_on:
       nrc-db:
         condition: service_healthy
@@ -89,8 +96,25 @@ services:
         condition: service_completed_successfully
     networks: [cg]
 
+  # Celery beat: periodically fires `execute_notifications`, which drains the
+  # ScheduledNotification rows the API creates on publish and hands them to the
+  # worker for delivery. Without beat, notifications are accepted but never
+  # delivered to subscribers — so it is required, not optional. See ADR-0007.
+  nrc-beat:
+    image: docker.io/openzaak/open-notificaties:${OPENNOTIFICATIES_TAG:-1.16.1}
+    environment: *nrc-env
+    command: /celery_beat.sh
+    depends_on:
+      nrc-init:
+        condition: service_completed_successfully
+    networks: [cg]
+
 volumes:
   nrc-db:
+  # populated out-of-band by infra/seed-config.sh (docker cp) — see that script.
+  nrc-config:
+    external: true
+    name: rr-nrc-config
 
 networks:
   cg:

infra/opennotificaties/setup_configuration/data.yaml

@@ -1,5 +1,41 @@
-# Open Notificaties setup_configuration.
-# Stage 1 (this commit): intentionally minimal — the init container runs
-# migrations; no steps enabled yet. The OpenZaak<->NRC notification wiring
-# (Services, Authorization, JWT, Kanalen) is added next. See ADR-0002 / S-01-c.
-{}
+# Open Notificaties (NRC) setup_configuration (S-01-c, #56).
+# Wires NRC so OpenZaak can publish notifications:
+#  - the JWT credential OpenZaak authenticates with,
+#  - delegation of authorization checks to OpenZaak's Autorisaties API (AC),
+#  - the `zaken` kanaal OpenZaak publishes zaak events on.
+# Dev-only credentials — not for production. Steps from nrc.setup_configuration.
+
+# 1. JWT credential NRC uses to verify the token OpenZaak presents.
+vng_api_common_credentials_config_enable: true
+vng_api_common_credentials:
+  items:
+    - identifier: big-reference-seed
+      secret: insecure-dev-secret-change-me
+
+# 2. The Autorisaties API (OpenZaak's AC) NRC consults to authorize publishers.
+zgw_consumers_config_enable: true
+zgw_consumers:
+  services:
+    - identifier: openzaak-ac
+      label: OpenZaak Autorisaties API
+      api_type: ac
+      api_root: http://openzaak:8000/autorisaties/api/v1/
+      auth_type: zgw
+      client_id: big-reference-seed
+      secret: insecure-dev-secret-change-me
+
+# 3. Delegate authorization to that AC.
+autorisaties_api_config_enable: true
+autorisaties_api:
+  authorizations_api_service_identifier: openzaak-ac
+
+# 4. The kanaal OpenZaak publishes zaak events on.
+notifications_kanalen_config_enable: true
+notifications_kanalen_config:
+  items:
+    - naam: zaken
+      documentatie_link: https://github.com/VNG-Realisatie/gemma-zaken
+      filters:
+        - bronorganisatie
+        - zaaktype
+        - vertrouwelijkheidaanduiding

infra/openzaak/docker-compose.yml

@@ -47,9 +47,12 @@ services:
       CELERY_BROKER_URL: redis://oz-redis:6379/1
       CELERY_RESULT_BACKEND: redis://oz-redis:6379/1
       DISABLE_2FA: "true"
-      # Notifications go to Open Notificaties (NRC), which arrives in S-01-c.
-      # Until then, disable outbound notifications so writes don't 500.
-      NOTIFICATIONS_DISABLED: "true"
+      # Notifications are OFF by default so OpenZaak-only bring-ups (openzaak-up,
+      # the ACL integration test) don't 500 trying to reach an absent NRC. When
+      # OpenZaak runs together with the NRC stack, set OZ_NOTIFICATIONS_DISABLED=false
+      # (make stack-up does) to publish; the NRC service + notifications_config that
+      # name it are provisioned by setup_configuration (data.yaml, S-01-c).
+      NOTIFICATIONS_DISABLED: "${OZ_NOTIFICATIONS_DISABLED:-true}"
       OPENZAAK_SUPERUSER_USERNAME: admin
       DJANGO_SUPERUSER_PASSWORD: admin
       OPENZAAK_SUPERUSER_EMAIL: admin@localhost

infra/openzaak/seed_catalogus.py

@@ -18,6 +18,16 @@ SECRET = os.environ.get("OZ_SECRET", "insecure-dev-secret-change-me")
 ZTC = f"{BASE}/catalogi/api/v1"
 RSIN = "517439943"  # elfproef-valid test RSIN
 
+# Opt-in: also publish the zaaktype so OpenZaak's Zaken API accepts a zaak against
+# it (a concept zaaktype is rejected with `not-published`). Off by default — the
+# S-01 compose seed keeps it a concept (ADR-0002). The ACL integration test
+# (S-04a, #46) sets OZ_PUBLISH=1. Publishing requires ≥2 statustypen, ≥1 roltype
+# and ≥1 resultaattype; the resultaattype is validated against the external
+# Selectielijst reference API, so this path needs outbound access to it. See ADR-0006.
+PUBLISH = os.environ.get("OZ_PUBLISH", "").lower() in ("1", "true", "yes")
+SELECTIELIJST = os.environ.get(
+    "OZ_SELECTIELIJST", "https://selectielijst.openzaak.nl/api/v1").rstrip("/")
+
 
 def token():
     b64 = lambda b: base64.urlsafe_b64encode(b).rstrip(b"=")
@@ -52,6 +62,68 @@ def find(path):
     return body.get("results", [])
 
 
+def selectielijst(path):
+    """GET the external Selectielijst reference API (no auth). Used only when publishing."""
+    req = urllib.request.Request(f"{SELECTIELIJST}{path}", headers={"Accept": "application/json"})
+    with urllib.request.urlopen(req, timeout=30) as r:
+        return json.loads(r.read())
+
+
+def publish_zaaktype(zt):
+    """Add the relations OpenZaak requires to publish, then publish (idempotent).
+
+    Publish validation (verified against OpenZaak 1.28.2) demands: ≥2 statustypen
+    (begin + eind), ≥1 roltype, ≥1 resultaattype. A resultaattype needs a
+    Selectielijst `selectielijstklasse` whose procestype matches the zaaktype's
+    `selectielijstProcestype`, plus a `resultaattypeomschrijving`.
+    """
+    have_st = {s.get("volgnummer") for s in find(f"/statustypen?zaaktype={zt['url']}&status=alles")}
+    for volgnummer, omschrijving in [(1, "Ontvangen"), (2, "Afgehandeld")]:
+        if volgnummer not in have_st:
+            st, body = api("POST", "/statustypen", {
+                "omschrijving": omschrijving, "zaaktype": zt["url"], "volgnummer": volgnummer})
+            if st != 201:
+                sys.exit(f"create statustype {volgnummer} -> {st}: {json.dumps(body, indent=2)}")
+            print(f"create statustype {volgnummer} ({omschrijving})")
+
+    if find(f"/roltypen?zaaktype={zt['url']}&status=alles"):
+        print("skip   roltype Aanvrager")
+    else:
+        st, body = api("POST", "/roltypen", {
+            "zaaktype": zt["url"], "omschrijving": "Aanvrager", "omschrijvingGeneriek": "initiator"})
+        if st != 201:
+            sys.exit(f"create roltype -> {st}: {json.dumps(body, indent=2)}")
+        print("create roltype Aanvrager")
+
+    if find(f"/resultaattypen?zaaktype={zt['url']}&status=alles"):
+        print("skip   resultaattype Geregistreerd")
+    else:
+        resultaat = selectielijst("/resultaten?pageSize=1")["results"][0]
+        omschrijvingen = selectielijst("/resultaattypeomschrijvingen")
+        oms = (omschrijvingen if isinstance(omschrijvingen, list) else omschrijvingen["results"])[0]["url"]
+        # The selectielijstklasse and the zaaktype must share a procestype.
+        st, body = api("PATCH", zt["url"], {"selectielijstProcestype": resultaat["procesType"]})
+        if st != 200:
+            sys.exit(f"set procestype -> {st}: {json.dumps(body, indent=2)}")
+        st, body = api("POST", "/resultaattypen", {
+            "zaaktype": zt["url"], "omschrijving": "Geregistreerd",
+            "resultaattypeomschrijving": oms, "selectielijstklasse": resultaat["url"],
+            "archiefnominatie": "blijvend_bewaren",
+            "brondatumArchiefprocedure": {"afleidingswijze": "afgehandeld"},
+        })
+        if st != 201:
+            sys.exit(f"create resultaattype -> {st}: {json.dumps(body, indent=2)}")
+        print("create resultaattype Geregistreerd")
+
+    if zt.get("concept", True):
+        st, body = api("POST", f"{zt['url']}/publish")
+        if st != 200:
+            sys.exit(f"publish zaaktype -> {st}: {json.dumps(body, indent=2)}")
+        print(f"publish zaaktype BIG-REGISTRATIE ({zt['url']})")
+    else:
+        print("skip   publish (already published)")
+
+
 def main():
     # 1. Catalogus
     existing = [c for c in find(f"/catalogussen?domein=BIG") if c.get("domein") == "BIG"]
@@ -121,16 +193,28 @@ def main():
     else:
         print("warn   zaaktype already published; cannot add bsn eigenschap")
 
-    # Intentionally NOT published. Publishing requires roltypen, resultaattypen
-    # and statustypen, which go beyond the "lean / schema-mandatory" zaaktype this
-    # slice asks for; they arrive with the workflow/zaak slices. See ADR-0002.
+    # 4. Optionally publish. By default the zaaktype stays a concept: publishing
+    # requires roltypen, resultaattypen and statustypen, beyond the "lean /
+    # schema-mandatory" zaaktype S-01 asks for (ADR-0002). Set OZ_PUBLISH=1 to add
+    # those relations and publish — needed so a real zaak POST is accepted, which
+    # the ACL integration test (S-04a, #46) exercises. See ADR-0006.
+    if PUBLISH:
+        # Re-fetch: the bsn-eigenschap branch above may hold a stale concept flag.
+        zt = next(z for z in find(f"/zaaktypen?catalogus={cat['url']}&status=alles")
+                  if z.get("identificatie") == "BIG-REGISTRATIE")
+        publish_zaaktype(zt)
 
-    # 4. Verify the JWT client can list the zaaktype (concepts included).
+    # 5. Verify the JWT client can list the zaaktype (concepts included).
     zaaktypen = find(f"/zaaktypen?catalogus={cat['url']}&status=alles")
     names = [z.get("identificatie") for z in zaaktypen]
     print(f"zaaktypen in BIG: {names}")
     assert "BIG-REGISTRATIE" in names, "BIG-REGISTRATIE not listed"
-    print("OK — BIG catalogus seeded (BIG-REGISTRATIE concept + bsn eigenschap)")
+    state = "published" if PUBLISH else "concept"
+    # Machine-readable line so callers (e.g. infra/run-domain-check.sh) can capture the
+    # zaaktype URL to configure the ACL's default-fill (ADR-0003/0009).
+    zt_url = next(z["url"] for z in zaaktypen if z.get("identificatie") == "BIG-REGISTRATIE")
+    print(f"ZAAKTYPE_URL {zt_url}")
+    print(f"OK — BIG catalogus seeded (BIG-REGISTRATIE {state} + bsn eigenschap)")
 
 
 if __name__ == "__main__":

infra/openzaak/setup_configuration/data.yaml

@@ -20,3 +20,22 @@ vng_api_common_applicaties:
         - big-reference-seed
       label: BIG reference seed client
       heeft_alle_autorisaties: true
+
+# ── OpenZaak → Open Notificaties (NRC) publishing (S-01-c, #56) ─────────────
+# The NRC service OpenZaak posts notifications to, authenticating with the same
+# big-reference-seed client (NRC verifies the JWT and authorizes it via the AC).
+zgw_consumers_config_enable: true
+zgw_consumers:
+  services:
+    - identifier: nrc
+      label: Open Notificaties
+      api_type: nrc
+      api_root: http://nrc-web:8000/api/v1/
+      auth_type: zgw
+      client_id: big-reference-seed
+      secret: insecure-dev-secret-change-me
+
+# Point OpenZaak's notifications at that service. Requires NOTIFICATIONS_DISABLED=false.
+notifications_config_enable: true
+notifications_config:
+  notifications_api_service_identifier: nrc

infra/run-acl-integration.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+#
+# Run the ACL integration tests (Category=Integration) against the OpenZaak that is
+# ALREADY running — works for any stack: oz-only (`make integration`), the standalone
+# oz+nrc stack, or the full compose stack (the CI `verify-stack` job). Seeds a
+# published BIG zaaktype (idempotent), then builds + runs the test image on the stack
+# network, reaching OpenZaak by container IP (a single-label host isn't URL-valid;
+# the runner can't reach published ports — see gitea-actions-gotchas.md §5/§6).
+#
+# Does NOT manage the stack lifecycle: the caller owns bring-up + teardown. Plain
+# docker primitives only (docker/podman-portable). See ADR-0006.
+set -euo pipefail
+
+here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+root="$(cd "$here/.." && pwd)"
+
+# The OpenZaak API container, matched across compose projects + docker/podman naming
+# (`<project>[-_]openzaak[-_]<n>`); the delimiters exclude oz-db / oz-redis / oz-init.
+oz="$(docker ps -q --filter 'name=[-_]openzaak[-_]' | head -1)"
+[ -n "$oz" ] || { echo "ERROR: no running OpenZaak container found — bring the stack up first" >&2; exit 1; }
+net="$(docker inspect -f '{{range $k,$_ := .NetworkSettings.Networks}}{{$k}}{{"\n"}}{{end}}' "$oz" | head -1)"
+oz_ip="$(docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' "$oz")"
+oz_base="http://$oz_ip:8000"
+echo ">> OpenZaak at $oz_base on network $net"
+
+echo ">> seeding a published BIG zaaktype (idempotent)"
+sid="$(docker create --network "$net" -e "OZ_BASE=$oz_base" -e OZ_PUBLISH=1 \
+  python:3-slim python /seed.py)"
+docker cp "$here/openzaak/seed_catalogus.py" "$sid:/seed.py" >/dev/null
+docker start -a "$sid"
+docker rm -f "$sid" >/dev/null
+
+echo ">> building the integration test image"
+docker build -f "$root/services/acl/Dockerfile.integration" -t rr-acl-integration "$root/services/acl"
+
+echo ">> running the ACL integration tests (inside the network)"
+docker run --rm --network "$net" -e "OZ_BASE=$oz_base" rr-acl-integration

infra/run-bff-check.sh

@@ -0,0 +1,58 @@
+#!/usr/bin/env bash
+#
+# Verify the BFF end-to-end (S-07) against an ALREADY-RUNNING full stack. The BFF is the portals'
+# only backend (§8.3): it validates Keycloak digid tokens on the self-service submit and serves the
+# openbaar register anonymously with only public-safe fields (ADR-0010).
+#
+# Checks, in-network (services reached by container IP; Keycloak by its service name so the token's
+# host-derived issuer matches the BFF's authority — see the compose bff env and ADR-0010):
+#   1. POST /self-service/registrations without a token            -> 401
+#   2. mint a real digid access token (direct grant) and POST it   -> 202 (forwarded to the domain)
+#   3. GET /openbaar/register (anonymous)                          -> 200 JSON array, never a bsn
+#
+# Does NOT manage the stack lifecycle (the caller owns bring-up + teardown). Plain docker primitives.
+set -euo pipefail
+
+ip() { docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' "$1"; }
+
+bff="$(docker ps -q --filter 'name=[-_]bff[-_]' | head -1)"
+kc="$(docker ps -q --filter 'name=keycloak' | head -1)"
+[ -n "$bff" ] || { echo "ERROR: no running bff container — bring the stack up first" >&2; exit 1; }
+[ -n "$kc" ] || { echo "ERROR: no running keycloak container — bring the stack up first" >&2; exit 1; }
+net="$(docker inspect -f '{{range $k,$_ := .NetworkSettings.Networks}}{{$k}}{{"\n"}}{{end}}' "$bff" | head -1)"
+bff_ip="$(ip "$bff")"
+echo ">> bff=$bff_ip network=$net"
+
+# Helper: run curl inside a throwaway container on the stack network (reaches services by name/IP).
+net_curl() { docker run --rm --network "$net" curlimages/curl:latest "$@"; }
+
+echo ">> 1. self-service submit without a token must be 401"
+code="$(net_curl -s -o /dev/null -w '%{http_code}' -X POST "http://$bff_ip:8080/self-service/registrations" \
+  -H 'Content-Type: application/json' -d '{}')"
+echo "   -> $code"; [ "$code" = "401" ] || { echo "FAIL: expected 401, got $code" >&2; exit 1; }
+
+echo ">> 2. minting a digid token (direct grant) via keycloak:8080 (host-consistent issuer)"
+token=""
+for _ in $(seq 1 20); do
+  token="$(net_curl -s -X POST "http://keycloak:8080/realms/digid/protocol/openid-connect/token" \
+    -H 'Content-Type: application/x-www-form-urlencoded' \
+    --data-urlencode 'grant_type=password' --data-urlencode 'client_id=big-portal' \
+    --data-urlencode 'username=jan-burger' --data-urlencode 'password=test123' \
+    | sed -n 's/.*"access_token":"\([^"]*\)".*/\1/p')"
+  [ -n "$token" ] && break
+  sleep 3
+done
+[ -n "$token" ] || { echo "FAIL: could not obtain a digid access token" >&2; exit 1; }
+echo "   -> got a token"
+
+echo ">> 2b. self-service submit with the token must be 202"
+code="$(net_curl -s -o /dev/null -w '%{http_code}' -X POST "http://$bff_ip:8080/self-service/registrations" \
+  -H "Authorization: Bearer $token" -H 'Content-Type: application/json' -d '{}')"
+echo "   -> $code"; [ "$code" = "202" ] || { echo "FAIL: expected 202, got $code" >&2; docker logs "$bff" 2>&1 | tail -15 >&2; exit 1; }
+
+echo ">> 3. openbaar register (anonymous) must be 200 JSON, never a bsn"
+body="$(net_curl -s "http://$bff_ip:8080/openbaar/register")"
+echo "$body" | grep -q '^\[' || { echo "FAIL: openbaar did not return a JSON array: $body" >&2; exit 1; }
+if echo "$body" | grep -q '"bsn"'; then echo "FAIL: openbaar leaked a bsn field" >&2; exit 1; fi
+
+echo "OK — BFF: 401 without token, 202 with a digid token, anonymous public-safe openbaar register"

infra/run-domain-check.sh

@@ -0,0 +1,68 @@
+#!/usr/bin/env bash
+#
+# Verify the BIG Domain Service end-to-end (S-05) against an ALREADY-RUNNING full stack:
+# domain → Flowable (start the registratie process + external-task worker) → ACL → OpenZaak.
+# Submits a registration to the domain and asserts the worker opens a zaak in OpenZaak and
+# records its URL on the aggregate (ADR-0009).
+#
+# The seeded zaaktype URL is server-assigned, so it isn't knowable at initial bring-up. This
+# script therefore seeds a published BIG zaaktype and recreates the `acl` service configured to
+# default-fill it — pointing the ACL at the SAME OpenZaak host that owns the URL, so zaak creation
+# is host-consistent (exactly the configuration the ACL integration test proves, ADR-0006). That
+# one recreate aside, the caller owns stack bring-up + teardown.
+#
+# All in-network, reaching services by container IP (a single-label host isn't URL-valid; the
+# runner can't reach published ports — gitea-actions-gotchas.md §5/§6). Plain docker primitives.
+set -euo pipefail
+
+here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+root="$(cd "$here/.." && pwd)"
+compose="$root/infra/docker-compose.yml"
+
+ip() { docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' "$1"; }
+
+oz="$(docker ps -q --filter 'name=[-_]openzaak[-_]' | head -1)"
+dom="$(docker ps -q --filter 'name=domain' | head -1)"
+[ -n "$oz" ] || { echo "ERROR: no running OpenZaak container — bring the stack up first" >&2; exit 1; }
+[ -n "$dom" ] || { echo "ERROR: no running domain container — bring the stack up first" >&2; exit 1; }
+net="$(docker inspect -f '{{range $k,$_ := .NetworkSettings.Networks}}{{$k}}{{"\n"}}{{end}}' "$oz" | head -1)"
+oz_ip="$(ip "$oz")"; dom_ip="$(ip "$dom")"
+oz_base="http://$oz_ip:8000"
+echo ">> openzaak=$oz_ip domain=$dom_ip network=$net"
+
+echo ">> seeding a published BIG zaaktype (idempotent) and capturing its URL"
+sid="$(docker create --network "$net" -e "OZ_BASE=$oz_base" -e OZ_PUBLISH=1 python:3-slim python /seed.py)"
+docker cp "$here/openzaak/seed_catalogus.py" "$sid:/seed.py" >/dev/null
+zt_url="$(docker start -a "$sid" | sed -n 's/^ZAAKTYPE_URL //p' | head -1)"
+docker rm -f "$sid" >/dev/null
+[ -n "$zt_url" ] || { echo "ERROR: seed did not report a ZAAKTYPE_URL" >&2; exit 1; }
+echo ">> zaaktype: $zt_url"
+
+echo ">> recreating the acl service pointed at the seeded zaaktype (host-consistent)"
+ACL_ZAAKTYPE_URL="$zt_url" ACL_OPENZAAK_BASEURL="$oz_base/" docker compose -f "$compose" up -d acl
+WAIT_TIMEOUT="${WAIT_TIMEOUT:-120}" bash "$here/wait-healthy.sh" acl
+
+echo ">> submitting a registration to the domain"
+loc="$(docker run --rm --network "$net" curlimages/curl:latest \
+  -fsS -D - -o /dev/null -X POST "http://$dom_ip:8080/registrations" \
+  -H 'Content-Type: application/json' -d '{"bsn":"123456782"}' \
+  | sed -n 's/\r$//; s/^[Ll]ocation: //p' | head -1)"
+[ -n "$loc" ] || { echo "ERROR: POST /registrations returned no Location" >&2; exit 1; }
+echo ">> registration accepted at $loc"
+
+echo ">> polling the domain until the worker records the opened zaak"
+for _ in $(seq 1 30); do
+  body="$(docker run --rm --network "$net" curlimages/curl:latest \
+    -fsS "http://$dom_ip:8080$loc" 2>/dev/null || true)"
+  if echo "$body" | grep -q '/zaken/api/v1/zaken/'; then
+    echo "OK — the domain opened a zaak and recorded it on the registration:"
+    echo "$body" | cut -c1-300
+    exit 0
+  fi
+  sleep 2
+done
+echo "FAIL — the registration never received a zaak URL" >&2
+echo "--- domain log ---" >&2; docker logs "$dom" 2>&1 | tail -15 >&2
+acl="$(docker ps -q --filter 'name=[-_]acl[-_]' | head -1)"
+[ -n "$acl" ] && { echo "--- acl log ---" >&2; docker logs "$acl" 2>&1 | tail -15 >&2; }
+exit 1

infra/run-integration.sh

@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+#
+# Local convenience: run the ACL integration test against a throwaway OpenZaak-only
+# stack (fast iteration on the ACL gateway). Brings OpenZaak up, runs the shared
+# stack-agnostic check (infra/run-acl-integration.sh), then always tears down.
+#
+# CI does not use this — there the full stack is brought up once and the same runner
+# is invoked as a step (see the `verify-stack` job / Makefile `verify-*`). See ADR-0006.
+set -euo pipefail
+
+here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+OZ_COMPOSE="$here/openzaak/docker-compose.yml"
+
+cleanup() {
+  docker compose -f "$OZ_COMPOSE" down --volumes >/dev/null 2>&1 || true
+  docker volume rm -f rr-oz-config >/dev/null 2>&1 || true
+}
+trap cleanup EXIT
+
+echo ">> bringing OpenZaak up"
+bash "$here/seed-config.sh" oz
+docker compose -f "$OZ_COMPOSE" up -d
+
+echo ">> waiting for the OpenZaak API container to be healthy"
+for _ in $(seq 1 140); do
+  oz="$(docker ps -q --filter 'name=[-_]openzaak[-_]' | head -1)"
+  if [ -n "$oz" ] && [ "$(docker inspect -f '{{if .State.Health}}{{.State.Health.Status}}{{end}}' "$oz" 2>/dev/null || true)" = healthy ]; then
+    break
+  fi
+  sleep 3
+done
+[ -n "${oz:-}" ] || { echo "ERROR: OpenZaak never came up" >&2; exit 1; }
+
+bash "$here/run-acl-integration.sh"

infra/run-notification-check.sh

@@ -0,0 +1,72 @@
+#!/usr/bin/env bash
+#
+# Verify the OpenZaak → NRC notification path against an ALREADY-RUNNING oz+nrc stack
+# (the standalone stack via `make verify-notifications`, or the full compose stack in
+# the CI `verify-stack` job). Seeds a published BIG zaaktype (idempotent), registers
+# an abonnement to a webhook sink, creates a zaak, and asserts the sink receives the
+# `zaken`/`create` notification. All in-network, reaching services by container IP
+# (single-label hosts aren't URL-valid; the runner can't reach published ports).
+#
+# Does NOT manage the stack lifecycle (the caller owns bring-up + teardown), but it
+# cleans up the throwaway sink/driver it creates. Plain docker primitives only.
+# See ADR-0007.
+set -euo pipefail
+
+here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+SINK_AUTH="Bearer notification-sink-token"
+
+cleanup() { docker rm -f rr-nsink rr-nverify >/dev/null 2>&1 || true; }
+trap cleanup EXIT
+
+ip() { docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' "$1"; }
+
+oz="$(docker ps -q --filter 'name=[-_]openzaak[-_]' | head -1)"
+nrc="$(docker ps -q --filter 'name=nrc-web' | head -1)"
+[ -n "$oz" ] && [ -n "$nrc" ] || { echo "ERROR: OpenZaak and/or NRC not running — bring the stack up first" >&2; exit 1; }
+net="$(docker inspect -f '{{range $k,$_ := .NetworkSettings.Networks}}{{$k}}{{"\n"}}{{end}}' "$oz" | head -1)"
+oz_ip="$(ip "$oz")"; nrc_ip="$(ip "$nrc")"
+echo ">> network=$net openzaak=$oz_ip nrc=$nrc_ip"
+
+echo ">> seeding a published BIG zaaktype (idempotent)"
+sid="$(docker create --network "$net" -e "OZ_BASE=http://$oz_ip:8000" -e OZ_PUBLISH=1 \
+  python:3-slim python /seed.py)"
+docker cp "$here/openzaak/seed_catalogus.py" "$sid:/seed.py" >/dev/null
+docker start -a "$sid"
+docker rm -f "$sid" >/dev/null
+
+echo ">> starting the webhook sink"
+docker rm -f rr-nsink >/dev/null 2>&1 || true
+sink="$(docker create --network "$net" --name rr-nsink -e "EXPECTED_AUTH=$SINK_AUTH" \
+  python:3-slim python /sink.py)"
+docker cp "$here/notification-sink.py" "$sink:/sink.py" >/dev/null
+docker start "$sink" >/dev/null
+sleep 1
+sink_ip="$(ip rr-nsink)"
+echo ">> sink at $sink_ip:9000"
+
+echo ">> registering abonnement + creating a zaak"
+docker rm -f rr-nverify >/dev/null 2>&1 || true
+drv="$(docker create --network "$net" --name rr-nverify \
+  -e "OZ_BASE=http://$oz_ip:8000" -e "NRC_BASE=http://$nrc_ip:8000" \
+  -e "SINK_CALLBACK=http://$sink_ip:9000/" -e "SINK_AUTH=$SINK_AUTH" \
+  python:3-slim python /driver.py)"
+docker cp "$here/verify-notification-driver.py" "$drv:/driver.py" >/dev/null
+docker start -a "$drv"
+zaak_url="$(docker logs rr-nverify 2>/dev/null | sed -n 's/^ZAAK_CREATED //p' | head -1)"
+docker rm -f rr-nverify >/dev/null
+[ -n "$zaak_url" ] || { echo "ERROR: driver did not create a zaak" >&2; exit 1; }
+zaak_uuid="${zaak_url##*/}"
+echo ">> zaak created: $zaak_url"
+
+echo ">> waiting for the notification to reach the sink"
+for _ in $(seq 1 30); do
+  if docker logs rr-nsink 2>&1 | grep -q "$zaak_uuid"; then
+    echo "OK — NRC delivered the zaken notification for zaak $zaak_uuid to the sink"
+    docker logs rr-nsink 2>&1 | grep "$zaak_uuid" | tail -1 | cut -c1-300
+    exit 0
+  fi
+  sleep 2
+done
+echo "FAIL — the sink never received a notification for zaak $zaak_uuid" >&2
+echo "--- sink log ---" >&2; docker logs rr-nsink 2>&1 | tail -8 >&2
+exit 1

infra/run-projection-check.sh

@@ -0,0 +1,68 @@
+#!/usr/bin/env bash
+#
+# Verify the end-to-end read-projection path (S-06) against an ALREADY-RUNNING full stack:
+# OpenZaak → NRC → Event Subscriber → projection → projection-api. Seeds a published BIG
+# zaaktype (idempotent), registers an abonnement on the `zaken` kanaal pointing at the real
+# Event Subscriber's /notifications callback (with the bearer it enforces), creates a zaak,
+# and asserts projection-api serves a row for that zaak with status INGEDIEND.
+#
+# All in-network, reaching services by container IP — single-label hosts aren't URL-valid and
+# the runner can't reach published ports (gitea-actions-gotchas.md §5/§6). Reuses the
+# notification driver to register the abonnement + create the zaak. Does NOT manage the stack
+# lifecycle (the caller owns bring-up + teardown). Plain docker primitives only. See ADR-0007/0008.
+set -euo pipefail
+
+here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+WEBHOOK_AUTH="${NOTIFICATION_WEBHOOK_TOKEN:-Bearer big-reference-notifications}"
+
+cleanup() { docker rm -f rr-pverify rr-pquery >/dev/null 2>&1 || true; }
+trap cleanup EXIT
+
+ip() { docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' "$1"; }
+
+oz="$(docker ps -q --filter 'name=[-_]openzaak[-_]' | head -1)"
+nrc="$(docker ps -q --filter 'name=nrc-web' | head -1)"
+es="$(docker ps -q --filter 'name=event-subscriber' | head -1)"
+proj="$(docker ps -q --filter 'name=projection-api' | head -1)"
+[ -n "$oz" ] && [ -n "$nrc" ] || { echo "ERROR: OpenZaak and/or NRC not running — bring the stack up first" >&2; exit 1; }
+[ -n "$es" ] && [ -n "$proj" ] || { echo "ERROR: event-subscriber and/or projection-api not running — bring the stack up first" >&2; exit 1; }
+net="$(docker inspect -f '{{range $k,$_ := .NetworkSettings.Networks}}{{$k}}{{"\n"}}{{end}}' "$oz" | head -1)"
+oz_ip="$(ip "$oz")"; nrc_ip="$(ip "$nrc")"; es_ip="$(ip "$es")"; proj_ip="$(ip "$proj")"
+echo ">> network=$net openzaak=$oz_ip nrc=$nrc_ip event-subscriber=$es_ip projection-api=$proj_ip"
+
+echo ">> seeding a published BIG zaaktype (idempotent)"
+sid="$(docker create --network "$net" -e "OZ_BASE=http://$oz_ip:8000" -e OZ_PUBLISH=1 \
+  python:3-slim python /seed.py)"
+docker cp "$here/openzaak/seed_catalogus.py" "$sid:/seed.py" >/dev/null
+docker start -a "$sid"
+docker rm -f "$sid" >/dev/null
+
+echo ">> registering abonnement at the Event Subscriber + creating a zaak"
+docker rm -f rr-pverify >/dev/null 2>&1 || true
+drv="$(docker create --network "$net" --name rr-pverify \
+  -e "OZ_BASE=http://$oz_ip:8000" -e "NRC_BASE=http://$nrc_ip:8000" \
+  -e "SINK_CALLBACK=http://$es_ip:8080/notifications" -e "SINK_AUTH=$WEBHOOK_AUTH" \
+  python:3-slim python /driver.py)"
+docker cp "$here/verify-notification-driver.py" "$drv:/driver.py" >/dev/null
+docker start -a "$drv"
+zaak_url="$(docker logs rr-pverify 2>/dev/null | sed -n 's/^ZAAK_CREATED //p' | head -1)"
+docker rm -f rr-pverify >/dev/null
+[ -n "$zaak_url" ] || { echo "ERROR: driver did not create a zaak" >&2; exit 1; }
+zaak_uuid="${zaak_url##*/}"
+echo ">> zaak created: $zaak_url"
+
+echo ">> polling projection-api for the projected row (status INGEDIEND)"
+for _ in $(seq 1 30); do
+  body="$(docker run --rm --network "$net" curlimages/curl:latest \
+    -fsS "http://$proj_ip:8080/register/$zaak_uuid" 2>/dev/null || true)"
+  if echo "$body" | grep -q '"INGEDIEND"'; then
+    echo "OK — projection-api serves zaak $zaak_uuid with status INGEDIEND"
+    echo "$body" | cut -c1-300
+    exit 0
+  fi
+  sleep 2
+done
+echo "FAIL — projection-api never served an INGEDIEND row for zaak $zaak_uuid" >&2
+echo "--- event-subscriber log ---" >&2; docker logs "$es" 2>&1 | tail -10 >&2
+echo "--- projection-api log ---" >&2; docker logs "$proj" 2>&1 | tail -10 >&2
+exit 1

infra/seed-config.sh

@@ -33,11 +33,12 @@ populate() {  # volume  source(file or dir/.)
   echo "  seeded $vol"
 }
 
-[ "$#" -gt 0 ] || { echo "usage: seed-config.sh <oz|kc|fl> ..." >&2; exit 2; }
+[ "$#" -gt 0 ] || { echo "usage: seed-config.sh <oz|nrc|kc|fl> ..." >&2; exit 2; }
 
 for key in "$@"; do
   case "$key" in
     oz) populate rr-oz-config "$here/openzaak/setup_configuration/." ;;
+    nrc) populate rr-nrc-config "$here/opennotificaties/setup_configuration/." ;;
     kc) populate rr-kc-realms "$here/keycloak/realms/." ;;
     fl) populate rr-fl-bpmn  "$here/../workflows/registratie.bpmn" ;;
     *)  echo "unknown seed key: $key" >&2; exit 2 ;;

infra/verify-notification-driver.py

@@ -0,0 +1,90 @@
+#!/usr/bin/env python3
+"""Drive the OpenZaak → NRC notification check from *inside* the compose network.
+
+Registers an abonnement on the `zaken` kanaal pointing at a webhook sink, then
+creates a zaak against the published BIG zaaktype. OpenZaak publishes a
+`zaken`/`create` notification; NRC delivers it to the sink. The host harness
+(infra/verify-notifications.sh) then asserts the sink received it.
+
+Reached by container IP, not service name: OpenZaak/NRC validate URLs with Django's
+URLValidator, which rejects a single-label host like `openzaak`. Stdlib only.
+Env: OZ_BASE, NRC_BASE, SINK_CALLBACK, SINK_AUTH, OZ_CLIENT_ID, OZ_SECRET.
+"""
+import base64
+import hashlib
+import hmac
+import json
+import os
+import sys
+import time
+import urllib.error
+import urllib.request
+
+OZ = os.environ["OZ_BASE"].rstrip("/")
+NRC = os.environ["NRC_BASE"].rstrip("/")
+SINK_CALLBACK = os.environ["SINK_CALLBACK"]
+SINK_AUTH = os.environ.get("SINK_AUTH", "Bearer notification-sink-token")
+CID = os.environ.get("OZ_CLIENT_ID", "big-reference-seed")
+SECRET = os.environ.get("OZ_SECRET", "insecure-dev-secret-change-me")
+RSIN = "517439943"
+
+
+def token():
+    b64 = lambda b: base64.urlsafe_b64encode(b).rstrip(b"=")
+    seg = (
+        b64(json.dumps({"alg": "HS256", "typ": "JWT"}, separators=(",", ":")).encode())
+        + b"."
+        + b64(json.dumps(
+            {"iss": CID, "iat": int(time.time()), "client_id": CID,
+             "user_id": "verify", "user_representation": "verify"},
+            separators=(",", ":")).encode())
+    )
+    return (seg + b"." + b64(hmac.new(SECRET.encode(), seg, hashlib.sha256).digest())).decode()
+
+
+def call(method, url, body=None, crs=False):
+    headers = {"Authorization": "Bearer " + token(),
+               "Content-Type": "application/json", "Accept": "application/json"}
+    if crs:
+        headers["Accept-Crs"] = "EPSG:4326"
+        headers["Content-Crs"] = "EPSG:4326"
+    data = json.dumps(body).encode() if body is not None else None
+    try:
+        with urllib.request.urlopen(
+            urllib.request.Request(url, data=data, method=method, headers=headers), timeout=30
+        ) as r:
+            return r.status, json.loads(r.read() or "null")
+    except urllib.error.HTTPError as e:
+        return e.code, json.loads(e.read() or "null")
+
+
+def main():
+    status, ab = call("POST", f"{NRC}/api/v1/abonnement", {
+        "callbackUrl": SINK_CALLBACK,
+        "auth": SINK_AUTH,
+        "kanalen": [{"naam": "zaken", "filters": {}}],
+    })
+    if status != 201:
+        sys.exit(f"create abonnement -> {status}: {json.dumps(ab)}")
+    print(f"abonnement: {ab['url']}")
+
+    status, body = call(
+        "GET", f"{OZ}/catalogi/api/v1/zaaktypen?identificatie=BIG-REGISTRATIE&status=definitief")
+    results = body.get("results", []) if status == 200 else []
+    if not results:
+        sys.exit("no published BIG-REGISTRATIE zaaktype — seed with OZ_PUBLISH=1 first")
+    zaaktype = results[0]["url"]
+
+    status, zaak = call("POST", f"{OZ}/zaken/api/v1/zaken", {
+        "bronorganisatie": RSIN, "verantwoordelijkeOrganisatie": RSIN,
+        "zaaktype": zaaktype, "startdatum": time.strftime("%Y-%m-%d"),
+        "vertrouwelijkheidaanduiding": "openbaar",
+    }, crs=True)
+    if status != 201:
+        sys.exit(f"create zaak -> {status}: {json.dumps(zaak)}")
+    # The harness greps the sink for this exact URL.
+    print(f"ZAAK_CREATED {zaak['url']}")
+
+
+if __name__ == "__main__":
+    main()

infra/verify-notifications.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+#
+# Local convenience: verify the OpenZaak → NRC notification path against a throwaway
+# oz+nrc stack. Brings both up (notifications enabled), runs the shared stack-agnostic
+# check (infra/run-notification-check.sh), then always tears down.
+#
+# CI does not use this — there the full stack is brought up once and the same runner
+# is invoked as a step (see the `verify-stack` job / Makefile `verify-*`). See ADR-0007.
+set -euo pipefail
+
+here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+OZ_COMPOSE="$here/openzaak/docker-compose.yml"
+NRC_COMPOSE="$here/opennotificaties/docker-compose.yml"
+
+cleanup() {
+  docker compose -f "$OZ_COMPOSE" -f "$NRC_COMPOSE" down --volumes >/dev/null 2>&1 || true
+  docker volume rm -f rr-oz-config rr-nrc-config >/dev/null 2>&1 || true
+}
+trap cleanup EXIT
+
+wait_healthy() {  # name-regex
+  local re="$1" cid
+  for _ in $(seq 1 140); do
+    cid="$(docker ps -q --filter "name=$re" | head -1)"
+    if [ -n "$cid" ] && [ "$(docker inspect -f '{{if .State.Health}}{{.State.Health.Status}}{{end}}' "$cid" 2>/dev/null || true)" = healthy ]; then
+      return 0
+    fi
+    sleep 3
+  done
+  return 1
+}
+
+echo ">> bringing up OpenZaak + Open Notificaties (notifications enabled)"
+bash "$here/seed-config.sh" oz nrc
+OZ_NOTIFICATIONS_DISABLED=false docker compose -f "$OZ_COMPOSE" -f "$NRC_COMPOSE" up -d
+
+echo ">> waiting for OpenZaak + NRC to be healthy"
+wait_healthy '[-_]openzaak[-_]' || { echo "ERROR: OpenZaak not healthy" >&2; exit 1; }
+wait_healthy 'nrc-web' || { echo "ERROR: NRC not healthy" >&2; exit 1; }
+
+bash "$here/run-notification-check.sh"

mkdocs.yml

@@ -26,7 +26,14 @@ nav:
       - "ADR-0002: Catalogus design": architecture/adr-0002-catalogus-design.md
       - "ADR-0003: ACL default-fill": architecture/adr-0003-default-fill.md
       - "ADR-0004: BDD framework": architecture/adr-0004-bdd-framework.md
+      - "ADR-0005: Mutation testing": architecture/adr-0005-mutation-testing.md
+      - "ADR-0006: ACL integration test provisioning": architecture/adr-0006-integration-test-provisioning.md
+      - "ADR-0007: OpenZaak → NRC notification wiring": architecture/adr-0007-notification-wiring.md
+      - "ADR-0008: Read projection store": architecture/adr-0008-read-projection-store.md
+      - "ADR-0009: External-task job worker": architecture/adr-0009-external-task-job-worker.md
+      - "ADR-0010: BFF OIDC validation": architecture/adr-0010-bff-oidc.md
   - Working in Gitea: gitea-workflow.md
+  - Demo script: demo-script.md
   - Runbooks:
       - CI: runbooks/ci.md
 

register-referentie.slnx

@@ -4,12 +4,29 @@
     <Project Path="services/acl/Acl.Api/Acl.Api.csproj" />
     <Project Path="services/acl/Acl.Application/Acl.Application.csproj" />
     <Project Path="services/acl/Acl.Infrastructure/Acl.Infrastructure.csproj" />
+    <Project Path="services/acl/Acl.IntegrationTests/Acl.IntegrationTests.csproj" />
     <Project Path="services/acl/Acl.Tests/Acl.Tests.csproj" />
   </Folder>
+  <Folder Name="/services/domain/">
+    <Project Path="services/domain/Big.Domain/Big.Domain.csproj" />
+    <Project Path="services/domain/Big.Application/Big.Application.csproj" />
+    <Project Path="services/domain/Big.Infrastructure/Big.Infrastructure.csproj" />
+    <Project Path="services/domain/Big.Api/Big.Api.csproj" />
+    <Project Path="services/domain/Big.Tests/Big.Tests.csproj" />
+  </Folder>
   <Folder Name="/services/bff/">
     <Project Path="services/bff/Bff.Api/Bff.Api.csproj" />
     <Project Path="services/bff/Bff.Tests/Bff.Tests.csproj" />
   </Folder>
+  <Folder Name="/services/event-subscriber/">
+    <Project Path="services/event-subscriber/EventSubscriber.Api/EventSubscriber.Api.csproj" />
+    <Project Path="services/event-subscriber/EventSubscriber.Application/EventSubscriber.Application.csproj" />
+    <Project Path="services/event-subscriber/EventSubscriber.Tests/EventSubscriber.Tests.csproj" />
+  </Folder>
+  <Folder Name="/services/projection-api/">
+    <Project Path="services/projection-api/Projection.ReadModel/Projection.ReadModel.csproj" />
+    <Project Path="services/projection-api/ProjectionApi.Api/ProjectionApi.Api.csproj" />
+  </Folder>
   <Folder Name="/tests/">
     <Project Path="tests/acceptance/Acceptance.csproj" />
   </Folder>

services/acl/Acl.Infrastructure/OpenZaakGateway.cs

@@ -27,6 +27,11 @@ public sealed class OpenZaakGateway(HttpClient http, OpenZaakOptions options) :
         // ZRC is a geo API; it requires the CRS headers.
         message.Headers.Add("Accept-Crs", "EPSG:4326");
         message.Content.Headers.Add("Content-Crs", "EPSG:4326");
+        // OpenZaak runs behind uwsgi, which rejects a chunked request body with 400.
+        // JsonContent streams without a known length (→ Transfer-Encoding: chunked),
+        // so buffer it first to send a Content-Length instead. Only a real OpenZaak
+        // surfaces this — a stubbed HttpMessageHandler accepts either framing.
+        await message.Content.LoadIntoBufferAsync(ct);
 
         using var response = await http.SendAsync(message, ct);
         response.EnsureSuccessStatusCode();

services/acl/Acl.IntegrationTests/Acl.IntegrationTests.csproj

@@ -0,0 +1,30 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <!-- Integration tests: they talk to a real OpenZaak (the compose stack), so they
+       are gated behind [Trait("Category","Integration")] and excluded from the fast
+       `make unit` / mutation lanes. `make integration` brings the stack up, seeds a
+       published BIG zaaktype (OZ_PUBLISH=1) and runs this project. See ADR-0006. -->
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Acl.Application\Acl.Application.csproj" />
+    <ProjectReference Include="..\Acl.Infrastructure\Acl.Infrastructure.csproj" />
+  </ItemGroup>
+
+</Project>

services/acl/Acl.IntegrationTests/OpenZaakFixture.cs

@@ -0,0 +1,97 @@
+using System.Net.Http.Headers;
+using System.Security.Cryptography;
+using System.Text;
+using System.Text.Json;
+using Acl.Infrastructure;
+
+namespace Acl.IntegrationTests;
+
+/// <summary>
+/// Shared connection to the running OpenZaak compose stack (ADR-0006). Reads the
+/// same endpoint + JWT-client config the seed uses, and locates the published
+/// BIG-REGISTRATIE zaaktype the ACL opens zaken against. Defaults match
+/// `infra/openzaak/seed_catalogus.py`; override via OZ_BASE / OZ_CLIENT_ID / OZ_SECRET.
+/// </summary>
+public sealed class OpenZaakFixture : IDisposable
+{
+    private static string Env(string key, string fallback) =>
+        Environment.GetEnvironmentVariable(key) is { Length: > 0 } v ? v : fallback;
+
+    public Uri BaseUrl { get; } = new(Env("OZ_BASE", "http://localhost:8000"));
+    public string ClientId { get; } = Env("OZ_CLIENT_ID", "big-reference-seed");
+    public string Secret { get; } = Env("OZ_SECRET", "insecure-dev-secret-change-me");
+
+    public HttpClient Http { get; } = new();
+
+    public OpenZaakOptions Options => new()
+    {
+        BaseUrl = BaseUrl,
+        ClientId = ClientId,
+        Secret = Secret,
+    };
+
+    /// <summary>
+    /// The URL of the published BIG-REGISTRATIE zaaktype, or null when none is
+    /// published yet (a concept-only stack). `status=definitief` returns published
+    /// zaaktypen only — a concept zaaktype is deliberately excluded.
+    /// </summary>
+    public async Task<Uri?> FindPublishedBigZaaktypeAsync(CancellationToken ct = default)
+    {
+        var query = new Uri(BaseUrl,
+            "/catalogi/api/v1/zaaktypen?identificatie=BIG-REGISTRATIE&status=definitief");
+        using var message = new HttpRequestMessage(HttpMethod.Get, query);
+        message.Headers.Authorization = new AuthenticationHeaderValue("Bearer", MintToken());
+
+        using var response = await Http.SendAsync(message, ct);
+        response.EnsureSuccessStatusCode();
+
+        using var document = JsonDocument.Parse(await response.Content.ReadAsStringAsync(ct));
+        var results = document.RootElement.GetProperty("results");
+        return results.GetArrayLength() == 0
+            ? null
+            : new Uri(results[0].GetProperty("url").GetString()!);
+    }
+
+    /// <summary>GETs a previously-created zaak to prove it was really persisted.</summary>
+    public async Task<JsonElement> GetZaakAsync(Uri zaakUrl, CancellationToken ct = default)
+    {
+        using var message = new HttpRequestMessage(HttpMethod.Get, zaakUrl);
+        message.Headers.Authorization = new AuthenticationHeaderValue("Bearer", MintToken());
+        message.Headers.Add("Accept-Crs", "EPSG:4326");
+
+        using var response = await Http.SendAsync(message, ct);
+        response.EnsureSuccessStatusCode();
+        var json = await response.Content.ReadAsStringAsync(ct);
+        return JsonDocument.Parse(json).RootElement.Clone();
+    }
+
+    // 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()
+    {
+        static string B64(byte[] b) =>
+            Convert.ToBase64String(b).TrimEnd('=').Replace('+', '-').Replace('/', '_');
+
+        var header = B64(JsonSerializer.SerializeToUtf8Bytes(new { alg = "HS256", typ = "JWT" }));
+        var payload = B64(JsonSerializer.SerializeToUtf8Bytes(new
+        {
+            iss = ClientId,
+            iat = DateTimeOffset.UtcNow.ToUnixTimeSeconds(),
+            client_id = ClientId,
+            user_id = "acl-integration-test",
+            user_representation = "acl-integration-test",
+        }));
+        var signingInput = $"{header}.{payload}";
+        using var hmac = new HMACSHA256(Encoding.UTF8.GetBytes(Secret));
+        var signature = B64(hmac.ComputeHash(Encoding.UTF8.GetBytes(signingInput)));
+        return $"{signingInput}.{signature}";
+    }
+
+    public void Dispose() => Http.Dispose();
+}
+
+[CollectionDefinition(Name)]
+public sealed class OpenZaakCollection : ICollectionFixture<OpenZaakFixture>
+{
+    public const string Name = "OpenZaak";
+}

services/acl/Acl.IntegrationTests/OpenZaakGatewayIntegrationTests.cs

@@ -0,0 +1,45 @@
+using Acl.Application;
+using Acl.Infrastructure;
+
+namespace Acl.IntegrationTests;
+
+/// <summary>
+/// S-04a (#46): the deferred S-04 acceptance criterion — the ACL's OpenZaakGateway
+/// opening a zaak against a *real* OpenZaak, exercising real ZGW JWT auth and the
+/// real POST /zaken/api/v1/zaken contract (CRS headers, default-fill, the created
+/// zaak URL) that the stubbed-HttpMessageHandler unit tests cannot. See ADR-0006.
+/// </summary>
+[Trait("Category", "Integration")]
+[Collection(OpenZaakCollection.Name)]
+public sealed class OpenZaakGatewayIntegrationTests(OpenZaakFixture stack)
+{
+    [Fact]
+    public async Task Opens_a_real_zaak_against_the_published_big_zaaktype_and_returns_its_url()
+    {
+        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 request = new ZaakRequest(
+            Bronorganisatie: "517439943",
+            VerantwoordelijkeOrganisatie: "517439943",
+            Vertrouwelijkheidaanduiding: "openbaar",
+            Zaaktype: zaaktype!,
+            Startdatum: DateOnly.FromDateTime(DateTime.UtcNow));
+
+        var zaakUrl = await gateway.OpenZaakAsync(request);
+
+        // The gateway returns the canonical zaak URL on OpenZaak's Zaken API...
+        Assert.StartsWith(
+            new Uri(stack.BaseUrl, "/zaken/api/v1/zaken/").ToString(),
+            zaakUrl.ToString());
+
+        // ...and that zaak is really persisted with the default-filled fields.
+        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());
+    }
+}

services/acl/Acl.Tests/AclServiceTests.cs

@@ -44,4 +44,21 @@ public class AclServiceTests
         Assert.Equal(defaults.ZaaktypeUrl, req.Zaaktype);
         Assert.Equal(new DateOnly(2026, 6, 4), req.Startdatum);
     }
+
+    [Fact]
+    public async Task Rejects_a_null_registration_without_calling_the_gateway()
+    {
+        var gateway = new FakeGateway();
+        var defaults = new AclDefaults
+        {
+            Bronorganisatie = "517439943",
+            VerantwoordelijkeOrganisatie = "517439943",
+            Vertrouwelijkheidaanduiding = "openbaar",
+            ZaaktypeUrl = new("http://openzaak/catalogi/api/v1/zaaktypen/big"),
+        };
+        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => service.OpenZaakAsync(null!));
+        Assert.Null(gateway.Captured);
+    }
 }

services/acl/Acl.Tests/OpenZaakGatewayTests.cs

@@ -1,5 +1,7 @@
 using System.Net;
 using System.Net.Http.Json;
+using System.Text;
+using System.Text.Json;
 using Acl.Application;
 using Acl.Infrastructure;
 
@@ -14,38 +16,139 @@ public class OpenZaakGatewayTests
             => onSend(request);
     }
 
-    [Fact]
-    public async Task Posts_zaak_to_openzaak_with_bearer_and_default_fields_and_returns_url()
+    private static OpenZaakGateway Gateway(StubHandler handler) => new(
+        new HttpClient(handler),
+        new OpenZaakOptions { BaseUrl = new("http://openzaak"), ClientId = "cid", Secret = "sec" });
+
+    private static ZaakRequest SampleRequest() => new(
+        "517439943", "517439943", "openbaar",
+        new("http://openzaak/catalogi/api/v1/zaaktypen/big"), new DateOnly(2026, 6, 4));
+
+    private static StubHandler Created(out RequestCapture capture)
     {
-        HttpRequestMessage? seen = null;
-        string? body = null;
-        var handler = new StubHandler(async req =>
+        var c = new RequestCapture();
+        capture = c;
+        return new StubHandler(async req =>
         {
-            seen = req;
-            body = await req.Content!.ReadAsStringAsync();
+            c.Seen = req;
+            // Capture the length BEFORE reading the body: ReadAsStringAsync buffers the
+            // content and would set ContentLength as a side effect, masking the gateway's
+            // own buffering. Read here to assert the gateway sent a length (not chunked).
+            c.ContentLength = req.Content?.Headers.ContentLength;
+            c.Body = req.Content is null ? null : await req.Content.ReadAsStringAsync();
             return new HttpResponseMessage(HttpStatusCode.Created)
             {
                 Content = JsonContent.Create(new { url = "http://openzaak/zaken/api/v1/zaken/xyz" }),
             };
         });
-        var gateway = new OpenZaakGateway(
-            new HttpClient(handler),
-            new OpenZaakOptions { BaseUrl = new("http://openzaak"), ClientId = "cid", Secret = "sec" });
-        var request = new ZaakRequest(
-            "517439943", "517439943", "openbaar",
-            new("http://openzaak/catalogi/api/v1/zaaktypen/big"), new DateOnly(2026, 6, 4));
+    }
 
-        var url = await gateway.OpenZaakAsync(request);
+    private sealed class RequestCapture
+    {
+        public HttpRequestMessage? Seen;
+        public string? Body;
+        public long? ContentLength;
+    }
+
+    [Fact]
+    public async Task Posts_zaak_to_openzaak_with_bearer_and_default_fields_and_returns_url()
+    {
+        var handler = Created(out var capture);
+
+        var url = await Gateway(handler).OpenZaakAsync(SampleRequest());
 
         Assert.Equal("http://openzaak/zaken/api/v1/zaken/xyz", url.ToString());
-        Assert.Equal(HttpMethod.Post, seen!.Method);
-        Assert.Equal("http://openzaak/zaken/api/v1/zaken", seen.RequestUri!.ToString());
-        Assert.Equal("Bearer", seen.Headers.Authorization!.Scheme);
-        Assert.False(string.IsNullOrWhiteSpace(seen.Headers.Authorization.Parameter));
-        Assert.Contains("\"bronorganisatie\":\"517439943\"", body);
-        Assert.Contains("\"verantwoordelijkeOrganisatie\":\"517439943\"", body);
-        Assert.Contains("\"vertrouwelijkheidaanduiding\":\"openbaar\"", body);
-        Assert.Contains("\"startdatum\":\"2026-06-04\"", body);
-        Assert.Contains("\"zaaktype\":\"http://openzaak/catalogi/api/v1/zaaktypen/big\"", body);
+        Assert.Equal(HttpMethod.Post, capture.Seen!.Method);
+        Assert.Equal("http://openzaak/zaken/api/v1/zaken", capture.Seen.RequestUri!.ToString());
+        Assert.Equal("Bearer", capture.Seen.Headers.Authorization!.Scheme);
+        Assert.False(string.IsNullOrWhiteSpace(capture.Seen.Headers.Authorization.Parameter));
+        Assert.Contains("\"bronorganisatie\":\"517439943\"", capture.Body);
+        Assert.Contains("\"verantwoordelijkeOrganisatie\":\"517439943\"", capture.Body);
+        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);
+    }
+
+    [Fact]
+    public async Task Sends_the_geo_crs_headers_required_by_the_zaken_api()
+    {
+        var handler = Created(out var capture);
+
+        await Gateway(handler).OpenZaakAsync(SampleRequest());
+
+        Assert.Equal("EPSG:4326", Assert.Single(capture.Seen!.Headers.GetValues("Accept-Crs")));
+        Assert.Equal("EPSG:4326", Assert.Single(capture.Seen.Content!.Headers.GetValues("Content-Crs")));
+    }
+
+    [Fact]
+    public async Task Sends_the_body_with_a_content_length_so_it_is_not_chunked()
+    {
+        // OpenZaak's uwsgi rejects a chunked request body (400). The gateway buffers
+        // the body so a Content-Length is sent. JsonContent has no length until
+        // buffered, so this guards the fix the real-OpenZaak integration test found.
+        var handler = Created(out var capture);
+
+        await Gateway(handler).OpenZaakAsync(SampleRequest());
+
+        Assert.NotNull(capture.ContentLength);
+        Assert.True(capture.ContentLength > 0);
+    }
+
+    [Fact]
+    public async Task Mints_a_hs256_jwt_carrying_the_acl_identity_claims()
+    {
+        var handler = Created(out var capture);
+
+        await Gateway(handler).OpenZaakAsync(SampleRequest());
+
+        var parts = capture.Seen!.Headers.Authorization!.Parameter!.Split('.');
+        Assert.Equal(3, parts.Length);
+        using var header = JsonDocument.Parse(DecodeSegment(parts[0]));
+        Assert.Equal("HS256", header.RootElement.GetProperty("alg").GetString());
+        Assert.Equal("JWT", header.RootElement.GetProperty("typ").GetString());
+        using var payload = JsonDocument.Parse(DecodeSegment(parts[1]));
+        Assert.Equal("cid", payload.RootElement.GetProperty("client_id").GetString());
+        Assert.Equal("acl", payload.RootElement.GetProperty("user_id").GetString());
+        Assert.Equal("acl", payload.RootElement.GetProperty("user_representation").GetString());
+    }
+
+    [Fact]
+    public async Task Throws_when_openzaak_rejects_the_request()
+    {
+        var handler = new StubHandler(_ =>
+            Task.FromResult(new HttpResponseMessage(HttpStatusCode.BadRequest)));
+
+        await Assert.ThrowsAsync<HttpRequestException>(
+            () => Gateway(handler).OpenZaakAsync(SampleRequest()));
+    }
+
+    [Fact]
+    public async Task Throws_when_openzaak_returns_an_empty_body()
+    {
+        var handler = new StubHandler(_ =>
+            Task.FromResult(new HttpResponseMessage(HttpStatusCode.Created)
+            {
+                Content = new StringContent("null", Encoding.UTF8, "application/json"),
+            }));
+
+        await Assert.ThrowsAsync<InvalidOperationException>(
+            () => Gateway(handler).OpenZaakAsync(SampleRequest()));
+    }
+
+    [Fact]
+    public async Task Rejects_a_null_request()
+    {
+        var handler = new StubHandler(_ => throw new InvalidOperationException("should not be sent"));
+
+        await Assert.ThrowsAsync<ArgumentNullException>(
+            () => Gateway(handler).OpenZaakAsync(null!));
+    }
+
+    // ZGW tokens are base64url with padding stripped (ZgwToken.B64Url); restore it to decode.
+    private static string DecodeSegment(string segment)
+    {
+        var b64 = segment.Replace('-', '+').Replace('_', '/');
+        b64 = (b64.Length % 4) switch { 2 => b64 + "==", 3 => b64 + "=", _ => b64 };
+        return Encoding.UTF8.GetString(Convert.FromBase64String(b64));
     }
 }

services/acl/Acl.slnx

@@ -2,5 +2,6 @@
   <Project Path="Acl.Api/Acl.Api.csproj" />
   <Project Path="Acl.Application/Acl.Application.csproj" />
   <Project Path="Acl.Infrastructure/Acl.Infrastructure.csproj" />
+  <Project Path="Acl.IntegrationTests/Acl.IntegrationTests.csproj" />
   <Project Path="Acl.Tests/Acl.Tests.csproj" />
 </Solution>

services/acl/Dockerfile.integration

@@ -0,0 +1,26 @@
+# Runs the ACL integration tests (Category=Integration) from *inside* the compose
+# network, so they reach OpenZaak at http://openzaak:8000 by service name. On the
+# hosted CI runner a process on the runner can't reach the stack's published ports
+# (sibling containers — gitea-actions-gotchas.md §5), so the test runs as a
+# container joined to that network instead. See ADR-0006 / #55.
+#
+# Build context is services/acl (like the service Dockerfile). dotnet lives in this
+# image, so the CI `integration` job needs only Docker — no setup-dotnet step.
+FROM mcr.microsoft.com/dotnet/sdk:10.0
+WORKDIR /src
+
+# Restore first (cached unless the .csproj files change). The integration test
+# project pulls in Acl.Application + Acl.Infrastructure via its ProjectReferences.
+COPY Acl.Application/Acl.Application.csproj Acl.Application/
+COPY Acl.Infrastructure/Acl.Infrastructure.csproj Acl.Infrastructure/
+COPY Acl.IntegrationTests/Acl.IntegrationTests.csproj Acl.IntegrationTests/
+RUN dotnet restore Acl.IntegrationTests/Acl.IntegrationTests.csproj
+
+COPY Acl.Application/ Acl.Application/
+COPY Acl.Infrastructure/ Acl.Infrastructure/
+COPY Acl.IntegrationTests/ Acl.IntegrationTests/
+
+# OZ_BASE is supplied at run time (the OpenZaak container IP — see run-integration.sh,
+# which passes `-e OZ_BASE=http://<ip>:8000`; a single-label host is not URL-valid).
+ENTRYPOINT ["dotnet", "test", "Acl.IntegrationTests/Acl.IntegrationTests.csproj", \
+            "-c", "Release", "--filter", "Category=Integration"]

services/acl/stryker-config.json

@@ -0,0 +1,12 @@
+{
+  "stryker-config": {
+    "solution": "Acl.slnx",
+    "test-projects": ["Acl.Tests/Acl.Tests.csproj"],
+    "reporters": ["progress", "html"],
+    "thresholds": {
+      "high": 95,
+      "low": 90,
+      "break": 90
+    }
+  }
+}

services/bff/Bff.Api/Bff.Api.csproj

@@ -6,4 +6,10 @@
     <ImplicitUsings>enable</ImplicitUsings>
   </PropertyGroup>
 
+  <ItemGroup>
+    <!-- OIDC/JWT validation of Keycloak-issued tokens (ADR-0010) and OpenAPI generation. -->
+    <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="10.0.8" />
+    <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="10.0.8" />
+  </ItemGroup>
+
 </Project>

services/bff/Bff.Api/DownstreamClients.cs

@@ -0,0 +1,47 @@
+using System.Net.Http.Json;
+
+namespace Bff.Api;
+
+/// <summary>What the self-service submit returns to the portal (the domain's registration id + status).</summary>
+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>
+public sealed record ProjectionEntry(string Id, string Status, 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);
+
+/// <summary>Port to the Domain Service (§8.3: the BFF is the portals' only backend; it fans out).</summary>
+public interface IDomainClient
+{
+    Task<SubmitAccepted> SubmitRegistrationAsync(string bsn, CancellationToken ct = default);
+}
+
+/// <summary>Port to the read projection.</summary>
+public interface IProjectionClient
+{
+    Task<IReadOnlyList<ProjectionEntry>> GetRegisterAsync(CancellationToken ct = default);
+}
+
+/// <summary>Calls the Domain Service's <c>POST /registrations</c>.</summary>
+public sealed class DomainClient(HttpClient http) : IDomainClient
+{
+    public async Task<SubmitAccepted> SubmitRegistrationAsync(string bsn, CancellationToken ct = default)
+    {
+        using var response = await http.PostAsJsonAsync("registrations", new { bsn }, ct);
+        response.EnsureSuccessStatusCode();
+        var dto = await response.Content.ReadFromJsonAsync<DomainResponse>(ct)
+            ?? throw new InvalidOperationException("The Domain Service returned an empty registration response.");
+        return new SubmitAccepted(dto.RegistrationId, dto.Status);
+    }
+
+    private sealed record DomainResponse(string RegistrationId, string Status, string? ZaakUrl);
+}
+
+/// <summary>Calls the projection-api's <c>GET /register</c>.</summary>
+public sealed class ProjectionClient(HttpClient http) : IProjectionClient
+{
+    public async Task<IReadOnlyList<ProjectionEntry>> GetRegisterAsync(CancellationToken ct = default)
+        => await http.GetFromJsonAsync<List<ProjectionEntry>>("register", ct) ?? [];
+}

services/bff/Bff.Api/OpenbaarProjection.cs

@@ -0,0 +1,18 @@
+namespace Bff.Api;
+
+/// <summary>
+/// The public view of the read projection: filters rows by the openbaar search term and maps each to
+/// a public-safe <see cref="OpenbaarEntry"/> (only <c>id</c> + <c>status</c> — bsn/naam never leave the
+/// BFF). Pure so it is unit- and mutation-tested directly (ADR-0010).
+/// </summary>
+public static class OpenbaarProjection
+{
+    public static IReadOnlyList<OpenbaarEntry> PublicView(IReadOnlyList<ProjectionEntry> entries, string? q)
+    {
+        var filtered = string.IsNullOrWhiteSpace(q)
+            ? entries
+            : entries.Where(e => e.Id.Contains(q, StringComparison.OrdinalIgnoreCase));
+
+        return [.. filtered.Select(e => new OpenbaarEntry(e.Id, e.Status))];
+    }
+}

services/bff/Bff.Api/Program.cs

@@ -1,10 +1,72 @@
+using System.Security.Claims;
+using Bff.Api;
+using Microsoft.AspNetCore.Authentication.JwtBearer;
+
 var builder = WebApplication.CreateBuilder(args);
+
+var keycloakAuthority = builder.Configuration["Keycloak:Authority"]
+    ?? throw new InvalidOperationException("Missing configuration 'Keycloak:Authority'");
+var domainBaseUrl = builder.Configuration["Downstream:Domain:BaseUrl"]
+    ?? throw new InvalidOperationException("Missing configuration 'Downstream:Domain:BaseUrl'");
+var projectionBaseUrl = builder.Configuration["Downstream:Projection:BaseUrl"]
+    ?? throw new InvalidOperationException("Missing configuration 'Downstream:Projection:BaseUrl'");
+
+// Validate Keycloak-issued tokens (ADR-0010). Audience validation is off for the walking skeleton —
+// Keycloak's audience mapping is a later hardening; signature/issuer/expiry are validated.
+builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
+    .AddJwtBearer(options =>
+    {
+        options.Authority = keycloakAuthority;
+        options.RequireHttpsMetadata = false;
+        options.TokenValidationParameters.ValidateAudience = false;
+    });
+builder.Services.AddAuthorization();
+
+// The BFF is the portals' only backend; it fans out to the domain and projection (§8.3).
+builder.Services.AddHttpClient<IDomainClient, DomainClient>(c => c.BaseAddress = new Uri(domainBaseUrl));
+builder.Services.AddHttpClient<IProjectionClient, ProjectionClient>(c => c.BaseAddress = new Uri(projectionBaseUrl));
+
 builder.Services.AddHealthChecks();
+// Clear the auto-populated `servers` block so the committed spec is stable regardless of the host
+// the doc was generated from (the client sets its own base URL). Keeps the drift guard deterministic.
+builder.Services.AddOpenApi(options =>
+    options.AddDocumentTransformer((document, _, _) =>
+    {
+        document.Servers?.Clear();
+        return Task.CompletedTask;
+    }));
 
 var app = builder.Build();
 
-app.MapGet("/", () => "BFF placeholder");
+app.UseAuthentication();
+app.UseAuthorization();
+
 app.MapHealthChecks("/health");
+app.MapOpenApi();
+
+// Self-service submit: requires a valid digid token; the bsn comes from the token, not the body,
+// and is forwarded to the domain (ADR-0010). Returns 202 — the zaak is opened asynchronously (S-05).
+app.MapPost("/self-service/registrations", async (ClaimsPrincipal user, IDomainClient domain, CancellationToken ct) =>
+{
+    var bsn = user.FindFirstValue("bsn");
+    if (string.IsNullOrWhiteSpace(bsn))
+        return Results.BadRequest("The token carries no bsn claim.");
+
+    var accepted = await domain.SubmitRegistrationAsync(bsn, ct);
+    return Results.Accepted($"/self-service/registrations/{accepted.RegistrationId}", accepted);
+})
+    .RequireAuthorization()
+    .Produces<SubmitAccepted>(StatusCodes.Status202Accepted)
+    .Produces(StatusCodes.Status400BadRequest)
+    .Produces(StatusCodes.Status401Unauthorized);
+
+// Openbaar register: an anonymous public lookup that exposes only public-safe fields (S-09).
+app.MapGet("/openbaar/register", async (string? q, IProjectionClient projection, CancellationToken ct) =>
+{
+    var entries = await projection.GetRegisterAsync(ct);
+    return Results.Ok(OpenbaarProjection.PublicView(entries, q));
+})
+    .Produces<IReadOnlyList<OpenbaarEntry>>(StatusCodes.Status200OK);
 
 app.Run();
 

services/bff/Bff.Api/appsettings.json

@@ -5,5 +5,12 @@
       "Microsoft.AspNetCore": "Warning"
     }
   },
-  "AllowedHosts": "*"
+  "AllowedHosts": "*",
+  "Keycloak": {
+    "Authority": "http://localhost:8180/realms/digid"
+  },
+  "Downstream": {
+    "Domain": { "BaseUrl": "http://localhost:8130/" },
+    "Projection": { "BaseUrl": "http://localhost:8120/" }
+  }
 }

services/bff/Bff.Tests/BffFactory.cs

@@ -0,0 +1,78 @@
+using System.Text;
+using Bff.Api;
+using Microsoft.AspNetCore.Authentication.JwtBearer;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Mvc.Testing;
+using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.IdentityModel.Protocols.OpenIdConnect;
+using Microsoft.IdentityModel.Tokens;
+
+namespace Bff.Tests;
+
+/// <summary>
+/// Test host for the BFF. It swaps the downstream clients for in-memory fakes and reconfigures the
+/// JWT bearer to validate against a local test key (no live Keycloak) — so token validation is
+/// exercised in-process with tokens the tests mint (ADR-0010).
+/// </summary>
+internal sealed class BffFactory : WebApplicationFactory<Program>
+{
+    public static readonly SymmetricSecurityKey TestSigningKey =
+        new(Encoding.UTF8.GetBytes("bff-test-signing-key-that-is-at-least-256-bits-long!"));
+
+    public FakeDomainClient Domain { get; } = new();
+    public FakeProjectionClient Projection { get; } = new();
+
+    protected override void ConfigureWebHost(IWebHostBuilder builder)
+    {
+        builder.UseSetting("Keycloak:Authority", "https://keycloak.invalid/realms/digid");
+        builder.UseSetting("Downstream:Domain:BaseUrl", "http://domain.invalid/");
+        builder.UseSetting("Downstream:Projection:BaseUrl", "http://projection.invalid/");
+
+        builder.ConfigureTestServices(services =>
+        {
+            services.AddSingleton<IDomainClient>(Domain);
+            services.AddSingleton<IProjectionClient>(Projection);
+
+            services.Configure<JwtBearerOptions>(JwtBearerDefaults.AuthenticationScheme, options =>
+            {
+                // Validate locally against the test key; never reach out for OIDC metadata.
+                options.Authority = null;
+                options.MetadataAddress = null!;
+                options.RequireHttpsMetadata = false;
+                options.Configuration = new OpenIdConnectConfiguration();
+                options.TokenValidationParameters = new TokenValidationParameters
+                {
+                    ValidateIssuer = false,
+                    ValidateAudience = false,
+                    ValidateLifetime = true,
+                    ValidateIssuerSigningKey = true,
+                    IssuerSigningKey = TestSigningKey,
+                    ClockSkew = TimeSpan.Zero,
+                };
+            });
+        });
+    }
+}
+
+/// <summary>Captures the bsn the BFF forwarded and returns a canned acceptance.</summary>
+internal sealed class FakeDomainClient : IDomainClient
+{
+    public string? SubmittedBsn { get; private set; }
+    public SubmitAccepted Result { get; set; } = new("reg-123", "Ingediend");
+
+    public Task<SubmitAccepted> SubmitRegistrationAsync(string bsn, CancellationToken ct = default)
+    {
+        SubmittedBsn = bsn;
+        return Task.FromResult(Result);
+    }
+}
+
+/// <summary>Serves a configurable set of projection rows.</summary>
+internal sealed class FakeProjectionClient : IProjectionClient
+{
+    public List<ProjectionEntry> Entries { get; } = [];
+
+    public Task<IReadOnlyList<ProjectionEntry>> GetRegisterAsync(CancellationToken ct = default)
+        => Task.FromResult<IReadOnlyList<ProjectionEntry>>(Entries);
+}

services/bff/Bff.Tests/OpenApiSpecTests.cs

@@ -0,0 +1,34 @@
+using System.Runtime.CompilerServices;
+using System.Text.Json;
+
+namespace Bff.Tests;
+
+/// <summary>
+/// Guards the committed OpenAPI contract (<c>services/bff/openapi.json</c>) against drift: it must
+/// equal the document the running BFF serves. S-08's Angular client is generated from this file, so a
+/// stale spec is a bug. To regenerate: run the BFF and save <c>/openapi/v1.json</c> over the file.
+/// </summary>
+public class OpenApiSpecTests
+{
+    [Fact]
+    public async Task Committed_openapi_spec_matches_the_served_document()
+    {
+        using var factory = new BffFactory();
+
+        var served = await factory.CreateClient().GetStringAsync("/openapi/v1.json");
+        var committed = await File.ReadAllTextAsync(SpecPath());
+
+        Assert.Equal(Canonical(committed), Canonical(served));
+    }
+
+    // Reformat both sides identically so the comparison is about content, not whitespace.
+    private static string Canonical(string json)
+    {
+        using var doc = JsonDocument.Parse(json);
+        return JsonSerializer.Serialize(doc.RootElement, new JsonSerializerOptions { WriteIndented = true });
+    }
+
+    // The committed spec sits at services/bff/openapi.json — one level up from this test file.
+    private static string SpecPath([CallerFilePath] string thisFile = "")
+        => Path.Combine(Path.GetDirectoryName(thisFile)!, "..", "openapi.json");
+}

services/bff/Bff.Tests/OpenbaarEndpointTests.cs

@@ -0,0 +1,38 @@
+using System.Net;
+using System.Net.Http.Json;
+using Bff.Api;
+
+namespace Bff.Tests;
+
+public class OpenbaarEndpointTests
+{
+    [Fact]
+    public async Task Serves_public_safe_rows_anonymously()
+    {
+        using var factory = new BffFactory();
+        factory.Projection.Entries.Add(new ProjectionEntry("abc-111", "INGEDIEND", "123456782", "Jan"));
+
+        // No Authorization header — the openbaar register is a public lookup (ADR-0010/S-09).
+        var response = await factory.CreateClient().GetAsync("/openbaar/register");
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var body = await response.Content.ReadAsStringAsync();
+        Assert.Contains("abc-111", body);
+        Assert.Contains("INGEDIEND", body);
+        // The bsn must never appear in a public response.
+        Assert.DoesNotContain("123456782", body);
+    }
+
+    [Fact]
+    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("def-222", "INGEDIEND", null, null));
+
+        var rows = await factory.CreateClient()
+            .GetFromJsonAsync<List<OpenbaarEntry>>("/openbaar/register?q=abc");
+
+        Assert.Equal("abc-111", Assert.Single(rows!).Id);
+    }
+}

services/bff/Bff.Tests/OpenbaarProjectionTests.cs

@@ -0,0 +1,48 @@
+using Bff.Api;
+
+namespace Bff.Tests;
+
+public class OpenbaarProjectionTests
+{
+    private static readonly ProjectionEntry[] Sample =
+    [
+        new("abc-111", "INGEDIEND", "123456782", "Jan"),
+        new("def-222", "INGEDIEND", "987654321", "Piet"),
+    ];
+
+    [Fact]
+    public void Maps_every_row_to_public_safe_fields_when_no_query()
+    {
+        var view = OpenbaarProjection.PublicView(Sample, null);
+
+        Assert.Equal(2, view.Count);
+        Assert.Equal("abc-111", view[0].Id);
+        Assert.Equal("INGEDIEND", view[0].Status);
+    }
+
+    [Fact]
+    public void Public_view_exposes_only_id_and_status()
+    {
+        // OpenbaarEntry structurally carries only Id + Status — bsn/naam can never leak.
+        var props = typeof(OpenbaarEntry).GetProperties().Select(p => p.Name).ToArray();
+        Assert.Equal(["Id", "Status"], props);
+    }
+
+    [Theory]
+    [InlineData("abc", 1)]
+    [InlineData("ABC", 1)]
+    [InlineData("2", 1)]
+    [InlineData("zzz", 0)]
+    public void Filters_by_id_containing_the_query_case_insensitively(string q, int expected)
+    {
+        var view = OpenbaarProjection.PublicView(Sample, q);
+
+        Assert.Equal(expected, view.Count);
+    }
+
+    [Fact]
+    public void Blank_query_is_treated_as_no_filter()
+    {
+        Assert.Equal(2, OpenbaarProjection.PublicView(Sample, "   ").Count);
+    }
+}

services/bff/Bff.Tests/SelfServiceEndpointTests.cs

@@ -0,0 +1,75 @@
+using System.Net;
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
+
+namespace Bff.Tests;
+
+public class SelfServiceEndpointTests
+{
+    private static HttpRequestMessage Submit(string? bearer)
+    {
+        var request = new HttpRequestMessage(HttpMethod.Post, "/self-service/registrations")
+        {
+            Content = JsonContent.Create(new { }),
+        };
+        if (bearer is not null)
+            request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", bearer);
+        return request;
+    }
+
+    [Fact]
+    public async Task Rejects_a_request_without_a_token()
+    {
+        using var factory = new BffFactory();
+        var client = factory.CreateClient();
+
+        var response = await client.SendAsync(Submit(bearer: null));
+
+        Assert.Equal(HttpStatusCode.Unauthorized, response.StatusCode);
+        Assert.Null(factory.Domain.SubmittedBsn);
+    }
+
+    [Theory]
+    [InlineData("not-a-jwt")]
+    public async Task Rejects_a_malformed_token(string bearer)
+    {
+        using var factory = new BffFactory();
+        var response = await factory.CreateClient().SendAsync(Submit(bearer));
+
+        Assert.Equal(HttpStatusCode.Unauthorized, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task Rejects_a_token_signed_with_the_wrong_key()
+    {
+        using var factory = new BffFactory();
+        var response = await factory.CreateClient().SendAsync(Submit(TestTokens.WrongKey("123456782")));
+
+        Assert.Equal(HttpStatusCode.Unauthorized, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task Rejects_an_expired_token()
+    {
+        using var factory = new BffFactory();
+        var response = await factory.CreateClient().SendAsync(Submit(TestTokens.Expired("123456782")));
+
+        Assert.Equal(HttpStatusCode.Unauthorized, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task Accepts_a_valid_token_and_forwards_the_bsn_to_the_domain()
+    {
+        using var factory = new BffFactory();
+        var client = factory.CreateClient();
+
+        var response = await client.SendAsync(Submit(TestTokens.Valid("123456782")));
+
+        Assert.Equal(HttpStatusCode.Accepted, response.StatusCode);
+        Assert.Equal("123456782", factory.Domain.SubmittedBsn);
+        var body = await response.Content.ReadFromJsonAsync<SubmitAcceptedDto>();
+        Assert.Equal("reg-123", body!.RegistrationId);
+    }
+
+    private sealed record SubmitAcceptedDto(string RegistrationId, string Status);
+}

services/bff/Bff.Tests/TestTokens.cs

@@ -0,0 +1,30 @@
+using System.Text;
+using Microsoft.IdentityModel.JsonWebTokens;
+using Microsoft.IdentityModel.Tokens;
+
+namespace Bff.Tests;
+
+/// <summary>Mints JWTs for the BFF tests — signed with the factory's test key (valid) or otherwise
+/// (a wrong key / expired) to exercise the bearer validation the BFF configures.</summary>
+internal static class TestTokens
+{
+    public static string Valid(string bsn) => Create(bsn, BffFactory.TestSigningKey, expired: false);
+
+    public static string Expired(string bsn) => Create(bsn, BffFactory.TestSigningKey, expired: true);
+
+    public static string WrongKey(string bsn) => Create(
+        bsn,
+        new SymmetricSecurityKey(Encoding.UTF8.GetBytes("a-different-signing-key-256-bits-long-indeed-yes!")),
+        expired: false);
+
+    private static string Create(string bsn, SymmetricSecurityKey key, bool expired)
+    {
+        var handler = new JsonWebTokenHandler();
+        return handler.CreateToken(new SecurityTokenDescriptor
+        {
+            Claims = new Dictionary<string, object> { ["bsn"] = bsn },
+            Expires = DateTime.UtcNow.AddMinutes(expired ? -5 : 30),
+            SigningCredentials = new SigningCredentials(key, SecurityAlgorithms.HmacSha256),
+        });
+    }
+}

services/bff/openapi.json

@@ -0,0 +1,104 @@
+{
+  "openapi": "3.1.1",
+  "info": {
+    "title": "Bff.Api | v1",
+    "version": "1.0.0"
+  },
+  "paths": {
+    "/self-service/registrations": {
+      "post": {
+        "tags": [
+          "Bff.Api"
+        ],
+        "responses": {
+          "202": {
+            "description": "Accepted",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/SubmitAccepted"
+                }
+              }
+            }
+          },
+          "400": {
+            "description": "Bad Request"
+          },
+          "401": {
+            "description": "Unauthorized"
+          }
+        }
+      }
+    },
+    "/openbaar/register": {
+      "get": {
+        "tags": [
+          "Bff.Api"
+        ],
+        "parameters": [
+          {
+            "name": "q",
+            "in": "query",
+            "schema": {
+              "type": "string"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "OK",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "type": "array",
+                  "items": {
+                    "$ref": "#/components/schemas/OpenbaarEntry"
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  },
+  "components": {
+    "schemas": {
+      "OpenbaarEntry": {
+        "required": [
+          "id",
+          "status"
+        ],
+        "type": "object",
+        "properties": {
+          "id": {
+            "type": "string"
+          },
+          "status": {
+            "type": "string"
+          }
+        }
+      },
+      "SubmitAccepted": {
+        "required": [
+          "registrationId",
+          "status"
+        ],
+        "type": "object",
+        "properties": {
+          "registrationId": {
+            "type": "string"
+          },
+          "status": {
+            "type": "string"
+          }
+        }
+      }
+    }
+  },
+  "tags": [
+    {
+      "name": "Bff.Api"
+    }
+  ]
+}

services/bff/stryker-config.json

@@ -0,0 +1,16 @@
+{
+  "stryker-config": {
+    "solution": "Bff.slnx",
+    "test-projects": ["Bff.Tests/Bff.Tests.csproj"],
+    "reporters": ["progress", "html"],
+    "mutate": [
+      "!**/Program.cs",
+      "!**/DownstreamClients.cs"
+    ],
+    "thresholds": {
+      "high": 95,
+      "low": 90,
+      "break": 90
+    }
+  }
+}

services/domain/.dockerignore

@@ -0,0 +1,4 @@
+**/bin
+**/obj
+**/*.user
+StrykerOutput

services/domain/Big.Api/Big.Api.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <ItemGroup>
+    <ProjectReference Include="..\Big.Application\Big.Application.csproj" />
+    <ProjectReference Include="..\Big.Infrastructure\Big.Infrastructure.csproj" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+</Project>

services/domain/Big.Api/Program.cs

@@ -0,0 +1,64 @@
+using Big.Application;
+using Big.Domain;
+using Big.Infrastructure;
+
+var builder = WebApplication.CreateBuilder(args);
+
+// Options bound from configuration (compose sets Flowable__* and Acl__* env vars).
+builder.Services.AddSingleton(sp => sp.GetRequiredService<IConfiguration>()
+    .GetSection("Flowable").Get<FlowableOptions>()
+    ?? throw new InvalidOperationException("Missing configuration section 'Flowable'"));
+builder.Services.AddSingleton(sp => sp.GetRequiredService<IConfiguration>()
+    .GetSection("Acl").Get<AclOptions>()
+    ?? throw new InvalidOperationException("Missing configuration section 'Acl'"));
+
+// The in-memory registration store is shared between the submit endpoint and the worker (ADR-0009).
+builder.Services.AddSingleton<IRegistrationStore, InMemoryRegistrationStore>();
+
+// The Workflow Client is one type behind two ports (start side + worker side); both resolve to the
+// same HttpClient-backed implementation — the only code that talks to Flowable (§8.2).
+builder.Services.AddHttpClient<FlowableWorkflowClient>();
+builder.Services.AddTransient<IWorkflowClient>(sp => sp.GetRequiredService<FlowableWorkflowClient>());
+builder.Services.AddTransient<IExternalWorkerClient>(sp => sp.GetRequiredService<FlowableWorkflowClient>());
+builder.Services.AddHttpClient<IAclClient, AclHttpClient>();
+
+builder.Services.AddScoped<SubmitRegistration>();
+builder.Services.AddScoped<OpenZaakWorker>();
+builder.Services.AddScoped<OpenZaakJobProcessor>();
+
+// The hosted external-task job worker polls Flowable and drives OpenZaakAanmaken to completion.
+builder.Services.AddHostedService<OpenZaakJobPump>();
+
+var app = builder.Build();
+
+app.MapGet("/health", () => "Healthy");
+
+// Submit a registration. The aggregate is created (INGEDIEND) and the registratie process started;
+// the zaak is opened later, off the request path, by the worker — so this returns 202 Accepted with
+// a location to read the registration's progress (ADR-0009, eventual consistency).
+app.MapPost("/registrations", async (SubmitRegistrationRequest body, SubmitRegistration submit, CancellationToken ct) =>
+{
+    var id = await submit.HandleAsync(new SubmitRegistrationCommand(body.Bsn), ct);
+    return Results.Accepted($"/registrations/{id}", new RegistrationResponse(id.ToString(), RegistrationStatus.Ingediend.ToString(), null));
+});
+
+// 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) =>
+{
+    if (!Guid.TryParse(id, out var guid))
+        return Results.NotFound();
+
+    var registration = await store.GetAsync(new RegistrationId(guid), ct);
+    return registration is null
+        ? Results.NotFound()
+        : Results.Ok(new RegistrationResponse(
+            registration.Id.ToString(), registration.Status.ToString(), registration.ZaakUrl?.ToString()));
+});
+
+await app.RunAsync();
+
+public sealed record SubmitRegistrationRequest(string Bsn);
+
+public sealed record RegistrationResponse(string RegistrationId, string Status, string? ZaakUrl);
+
+public partial class Program;

services/domain/Big.Api/appsettings.json

@@ -0,0 +1,9 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*"
+}

services/domain/Big.Application/Big.Application.csproj

@@ -0,0 +1,15 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <!-- The application layer (CLAUDE.md §9): use cases over ports. Depends on Domain only;
+       Infrastructure implements the ports. -->
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Big.Domain\Big.Domain.csproj" />
+  </ItemGroup>
+
+</Project>

services/domain/Big.Application/OpenZaakWorker.cs

@@ -0,0 +1,36 @@
+using Big.Domain;
+
+namespace Big.Application;
+
+/// <summary>
+/// Handles one acquired <c>OpenZaakAanmaken</c> external-worker job (ADR-0009): load the registration
+/// the job correlates to, open a zaak for it via the ACL (§8.1), attach the zaak to the aggregate, and
+/// return the zaak URL so the caller can complete the Flowable job. Pure application logic over ports —
+/// it knows nothing of Flowable; the polling loop that feeds it jobs lives in Infrastructure.
+/// </summary>
+public sealed class OpenZaakWorker(IRegistrationStore store, IAclClient acl)
+{
+    /// <summary>
+    /// Process the job and return the URL of the (existing or newly opened) zaak. Idempotent: if the
+    /// registration already has a zaak — a job redelivered after its completion was lost — it returns
+    /// that zaak without opening a second one (§8.6, at-least-once delivery). An unknown registration
+    /// is an error: it throws, leaving the job un-completed for Flowable to redeliver.
+    /// </summary>
+    public async Task<Uri> HandleAsync(OpenZaakJob job, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(job);
+
+        var registration = await store.GetAsync(job.RegistrationId, ct)
+            ?? throw new InvalidOperationException(
+                $"No registration {job.RegistrationId} for OpenZaakAanmaken job {job.JobId}.");
+
+        // A redelivered job whose zaak was already opened completes without opening a second one.
+        if (registration.ZaakUrl is not null)
+            return registration.ZaakUrl;
+
+        var zaakUrl = await acl.OpenZaakAsync(registration.Bsn, ct);
+        registration.AttachZaak(zaakUrl);
+        await store.SaveAsync(registration, ct);
+        return zaakUrl;
+    }
+}

services/domain/Big.Application/Ports.cs

@@ -0,0 +1,47 @@
+using Big.Domain;
+
+namespace Big.Application;
+
+/// <summary>
+/// The port to the workflow engine. Implemented by the Workflow Client in Infrastructure — the
+/// <em>only</em> code that talks to Flowable (CLAUDE.md §8.2). The application asks it to start the
+/// registratie process; it never knows Flowable exists.
+/// </summary>
+public interface IWorkflowClient
+{
+    /// <summary>
+    /// Start one <c>registratie</c> process instance for the given registration, carrying the
+    /// registration id so the <c>OpenZaakAanmaken</c> external task can be correlated back to its
+    /// aggregate. Returns the process instance id.
+    /// </summary>
+    Task<string> StartRegistrationProcessAsync(RegistrationId registrationId, CancellationToken ct = default);
+}
+
+/// <summary>
+/// The port to the Anti-Corruption Layer. Implemented in Infrastructure by an HTTP client to the
+/// ACL service — the <em>only</em> code that talks to ZGW (CLAUDE.md §8.1). The domain hands over a
+/// bsn; the ACL default-fills the ZGW-mandatory fields (ADR-0003) and returns the created zaak URL.
+/// </summary>
+public interface IAclClient
+{
+    Task<Uri> OpenZaakAsync(string bsn, CancellationToken ct = default);
+}
+
+/// <summary>
+/// Persistence port for the <see cref="Registration"/> aggregate. In-memory for the minimal slice
+/// (ADR-0009); an EF-backed store is a documented follow-up, and this port keeps that change additive.
+/// </summary>
+public interface IRegistrationStore
+{
+    /// <summary>Insert or update the registration, keyed on its id.</summary>
+    Task SaveAsync(Registration registration, CancellationToken ct = default);
+
+    /// <summary>Load a registration by id, or <c>null</c> if none exists.</summary>
+    Task<Registration?> GetAsync(RegistrationId id, CancellationToken ct = default);
+}
+
+/// <summary>
+/// An acquired <c>OpenZaakAanmaken</c> external-worker job: the Flowable job id (needed to complete
+/// it) and the registration id it carries as a process variable.
+/// </summary>
+public sealed record OpenZaakJob(string JobId, RegistrationId RegistrationId);

services/domain/Big.Application/SubmitRegistration.cs

@@ -0,0 +1,33 @@
+using Big.Domain;
+
+namespace Big.Application;
+
+/// <summary>A zorgprofessional's request to register, in domain language. No ZGW concepts.</summary>
+public sealed record SubmitRegistrationCommand(string Bsn);
+
+/// <summary>
+/// The submit use case: create the <see cref="Registration"/> aggregate (INGEDIEND), persist it,
+/// then start the registratie workflow process and record its instance id. It returns as soon as
+/// the process is started — opening the zaak happens later, off the request path, in the external-task
+/// worker (ADR-0009). Persisting <em>before</em> starting the process closes the race where the worker
+/// acquires the OpenZaakAanmaken job before the aggregate it correlates to exists.
+/// </summary>
+public sealed class SubmitRegistration(IRegistrationStore store, IWorkflowClient workflow)
+{
+    public async Task<RegistrationId> HandleAsync(SubmitRegistrationCommand command, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(command);
+
+        var registration = Registration.Submit(command.Bsn);
+
+        // Persist before starting the process so the worker can correlate the OpenZaakAanmaken
+        // job back to an aggregate that already exists (ADR-0009).
+        await store.SaveAsync(registration, ct);
+
+        var processInstanceId = await workflow.StartRegistrationProcessAsync(registration.Id, ct);
+        registration.RecordProcessStarted(processInstanceId);
+        await store.SaveAsync(registration, ct);
+
+        return registration.Id;
+    }
+}

services/domain/Big.Domain/Big.Domain.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <!-- The domain layer (CLAUDE.md §9): aggregates, value objects, invariants.
+       Pure C# — no external dependencies, no infrastructure concerns. -->
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

services/domain/Big.Domain/Registration.cs

@@ -0,0 +1,67 @@
+namespace Big.Domain;
+
+/// <summary>
+/// The Registration aggregate root (CLAUDE.md §2.2): a zorgprofessional's submission to the BIG
+/// register. It owns its lifecycle invariants — it starts <see cref="RegistrationStatus.Ingediend"/>
+/// on submission, remembers the Flowable process that drives it, and records the zaak the ACL opens.
+/// </summary>
+public sealed class Registration
+{
+    private Registration(RegistrationId id, string bsn)
+    {
+        Id = id;
+        Bsn = bsn;
+        Status = RegistrationStatus.Ingediend;
+    }
+
+    public RegistrationId Id { get; }
+
+    /// <summary>The citizen-service number of the submitting zorgprofessional. Handed to the ACL
+    /// as the domain payload; the domain never constructs ZGW concepts from it (§8.1).</summary>
+    public string Bsn { get; }
+
+    public RegistrationStatus Status { get; private set; }
+
+    /// <summary>The Flowable process instance driving this registration, once started.</summary>
+    public string? ProcessInstanceId { get; private set; }
+
+    /// <summary>The zaak the ACL opened for this registration, once the external task has run.</summary>
+    public Uri? ZaakUrl { get; private set; }
+
+    /// <summary>Submit a new registration. It begins in <see cref="RegistrationStatus.Ingediend"/>.</summary>
+    public static Registration Submit(string bsn)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(bsn);
+        return new Registration(RegistrationId.New(), bsn);
+    }
+
+    /// <summary>Record that the registratie workflow process has been started for this registration.</summary>
+    public void RecordProcessStarted(string processInstanceId)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(processInstanceId);
+        ProcessInstanceId = processInstanceId;
+    }
+
+    /// <summary>
+    /// Attach the zaak the ACL opened. The external-task worker may deliver the same job more than
+    /// once (at-least-once), so re-attaching the identical URL is a no-op; a different URL signals a
+    /// genuine conflict and is rejected. The status stays <see cref="RegistrationStatus.Ingediend"/>:
+    /// opening the zaak does not advance the registration's lifecycle in this slice.
+    /// </summary>
+    public void AttachZaak(Uri zaakUrl)
+    {
+        ArgumentNullException.ThrowIfNull(zaakUrl);
+
+        if (ZaakUrl is not null)
+        {
+            if (ZaakUrl != zaakUrl)
+                throw new InvalidOperationException(
+                    $"Registration {Id} already has zaak {ZaakUrl}; cannot attach a different zaak {zaakUrl}.");
+            // Stryker disable once Statement : equivalent — re-assigning the identical URL below is a
+            // no-op, so removing this early return is behaviourally indistinguishable.
+            return;
+        }
+
+        ZaakUrl = zaakUrl;
+    }
+}

services/domain/Big.Domain/RegistrationId.cs

@@ -0,0 +1,15 @@
+namespace Big.Domain;
+
+/// <summary>The identity of a <see cref="Registration"/> aggregate — opaque, server-assigned,
+/// and distinct from the OpenZaak zaak id (which the projection keys on). A value object so the
+/// id can travel as a Flowable process variable and back without ever being a bare string.</summary>
+public readonly record struct RegistrationId(Guid Value)
+{
+    /// <summary>Mint a fresh identity for a newly submitted registration.</summary>
+    public static RegistrationId New() => new(Guid.NewGuid());
+
+    /// <summary>Rehydrate an id carried as a string (e.g. a Flowable process variable).</summary>
+    public static RegistrationId Parse(string value) => new(Guid.Parse(value));
+
+    public override string ToString() => Value.ToString();
+}

services/domain/Big.Domain/RegistrationStatus.cs

@@ -0,0 +1,10 @@
+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
+/// 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,
+}

services/domain/Big.Infrastructure/AclHttpClient.cs

@@ -0,0 +1,28 @@
+using System.Net.Http.Json;
+using System.Text.Json.Serialization;
+using Big.Application;
+
+namespace Big.Infrastructure;
+
+/// <summary>
+/// HTTP client to the ACL service — the boundary the domain crosses to open a zaak (§8.1). It POSTs
+/// the bsn to the ACL's <c>/zaken</c> endpoint and returns the created zaak URL; it never constructs
+/// ZGW URLs or talks to OpenZaak itself.
+/// </summary>
+public sealed class AclHttpClient(HttpClient http, AclOptions options) : IAclClient
+{
+    public async Task<Uri> OpenZaakAsync(string bsn, CancellationToken ct = default)
+    {
+        using var response = await http.PostAsJsonAsync(
+            new Uri(options.BaseUrl, "zaken"), new OpenZaakRequest(bsn), ct);
+        response.EnsureSuccessStatusCode();
+
+        var opened = await response.Content.ReadFromJsonAsync<OpenZaakResponse>(ct)
+            ?? throw new InvalidOperationException("The ACL returned an empty zaak response.");
+        return new Uri(opened.ZaakUrl);
+    }
+
+    private sealed record OpenZaakRequest([property: JsonPropertyName("bsn")] string Bsn);
+
+    private sealed record OpenZaakResponse([property: JsonPropertyName("zaakUrl")] string ZaakUrl);
+}

services/domain/Big.Infrastructure/Big.Infrastructure.csproj

@@ -0,0 +1,24 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <!-- The infrastructure layer (CLAUDE.md §9): adapters implementing the Application ports.
+       The Workflow Client (Flowable REST) and the ACL HTTP client live here — the only code
+       that talks to Flowable (§8.2) and to the ACL respectively. -->
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Big.Application\Big.Application.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <!-- The external-task job worker is a hosted BackgroundService (ADR-0009); it logs and
+         resolves a per-tick scope. Abstractions only — the host (Api) brings the implementations. -->
+    <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="10.0.0" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="10.0.0" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.0" />
+  </ItemGroup>
+
+</Project>

services/domain/Big.Infrastructure/FlowableWorkflowClient.cs

@@ -0,0 +1,110 @@
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
+using System.Text;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Big.Application;
+using Big.Domain;
+
+namespace Big.Infrastructure;
+
+/// <summary>
+/// The Workflow Client — the only code that talks to Flowable (§8.2). It starts registratie process
+/// instances and drives the <c>OpenZaakAanmaken</c> external-worker jobs over Flowable's REST API
+/// (start: <c>service/runtime/process-instances</c>; acquire/complete: <c>external-job-api/…</c>).
+/// The REST contract here is the one verified against a live flowable-rest engine (ADR-0009).
+/// </summary>
+public sealed class FlowableWorkflowClient(HttpClient http, FlowableOptions options)
+    : IWorkflowClient, IExternalWorkerClient
+{
+    private const string Topic = "OpenZaakAanmaken";
+    private const string ProcessDefinitionKey = "registratie";
+    private const string RegistrationIdVariable = "registrationId";
+    private const string ZaakUrlVariable = "zaakUrl";
+
+    public async Task<string> StartRegistrationProcessAsync(RegistrationId registrationId, CancellationToken ct = default)
+    {
+        var request = new StartProcessRequest(
+            ProcessDefinitionKey,
+            [new Variable(RegistrationIdVariable, "string", registrationId.ToString())]);
+
+        var created = await PostAsync<StartProcessRequest, ProcessInstance>(
+            "service/runtime/process-instances", request, ct)
+            ?? throw new InvalidOperationException("Flowable returned an empty process-instance response.");
+        return created.Id;
+    }
+
+    public async Task<IReadOnlyList<OpenZaakJob>> AcquireOpenZaakJobsAsync(int maxJobs, CancellationToken ct = default)
+    {
+        var request = new AcquireJobsRequest(Topic, options.LockDuration, maxJobs, options.WorkerId);
+
+        var jobs = await PostAsync<AcquireJobsRequest, List<AcquiredJob>>(
+            "external-job-api/acquire/jobs", request, ct) ?? [];
+
+        return [.. jobs.Select(job => new OpenZaakJob(job.Id, RegistrationId.Parse(job.RegistrationId())))];
+    }
+
+    public async Task CompleteOpenZaakJobAsync(string jobId, Uri zaakUrl, CancellationToken ct = default)
+    {
+        var request = new CompleteJobRequest(
+            options.WorkerId,
+            [new Variable(ZaakUrlVariable, "string", zaakUrl.ToString())]);
+
+        using var response = await SendAsync(
+            $"external-job-api/acquire/jobs/{jobId}/complete", request, ct);
+        response.EnsureSuccessStatusCode();
+    }
+
+    private async Task<TResponse?> PostAsync<TRequest, TResponse>(string path, TRequest body, CancellationToken ct)
+    {
+        using var response = await SendAsync(path, body, ct);
+        response.EnsureSuccessStatusCode();
+        return await response.Content.ReadFromJsonAsync<TResponse>(ct);
+    }
+
+    private Task<HttpResponseMessage> SendAsync<TRequest>(string path, TRequest body, CancellationToken ct)
+    {
+        var message = new HttpRequestMessage(HttpMethod.Post, new Uri(options.BaseUrl, path))
+        {
+            Content = JsonContent.Create(body),
+        };
+        message.Headers.Authorization = new AuthenticationHeaderValue("Basic", BasicCredentials());
+        return http.SendAsync(message, ct);
+    }
+
+    private string BasicCredentials()
+        => Convert.ToBase64String(Encoding.ASCII.GetBytes($"{options.Username}:{options.Password}"));
+
+    private sealed record StartProcessRequest(
+        [property: JsonPropertyName("processDefinitionKey")] string ProcessDefinitionKey,
+        [property: JsonPropertyName("variables")] IReadOnlyList<Variable> Variables);
+
+    private sealed record AcquireJobsRequest(
+        [property: JsonPropertyName("topic")] string Topic,
+        [property: JsonPropertyName("lockDuration")] string LockDuration,
+        [property: JsonPropertyName("numberOfTasks")] int NumberOfTasks,
+        [property: JsonPropertyName("workerId")] string WorkerId);
+
+    private sealed record CompleteJobRequest(
+        [property: JsonPropertyName("workerId")] string WorkerId,
+        [property: JsonPropertyName("variables")] IReadOnlyList<Variable> Variables);
+
+    private sealed record Variable(
+        [property: JsonPropertyName("name")] string Name,
+        [property: JsonPropertyName("type")] string Type,
+        [property: JsonPropertyName("value")] string Value);
+
+    private sealed record ProcessInstance([property: JsonPropertyName("id")] string Id);
+
+    private sealed record AcquiredJob(
+        [property: JsonPropertyName("id")] string Id,
+        [property: JsonPropertyName("variables")] IReadOnlyList<Variable> Variables)
+    {
+        /// <summary>The registration id this job carries as a process variable.</summary>
+        public string RegistrationId() =>
+            // Stryker disable once Linq : equivalent — Single and SingleOrDefault both throw on a job
+            // with no registrationId variable (the only untested branch), so the mutant is indistinguishable.
+            Variables.SingleOrDefault(v => v.Name == "registrationId")?.Value
+            ?? throw new InvalidOperationException($"OpenZaakAanmaken job {Id} carries no registrationId variable.");
+    }
+}

services/domain/Big.Infrastructure/IExternalWorkerClient.cs

@@ -0,0 +1,18 @@
+using Big.Application;
+
+namespace Big.Infrastructure;
+
+/// <summary>
+/// The worker-facing side of the Workflow Client: acquiring and completing Flowable external-worker
+/// jobs (ADR-0009). Kept separate from the Application's <see cref="IWorkflowClient"/> because job
+/// acquisition is a Flowable-specific polling mechanic the application never needs to know about.
+/// Implemented by <see cref="FlowableWorkflowClient"/> — the only code that talks to Flowable (§8.2).
+/// </summary>
+public interface IExternalWorkerClient
+{
+    /// <summary>Acquire and lock up to <paramref name="maxJobs"/> <c>OpenZaakAanmaken</c> jobs.</summary>
+    Task<IReadOnlyList<OpenZaakJob>> AcquireOpenZaakJobsAsync(int maxJobs, CancellationToken ct = default);
+
+    /// <summary>Complete an acquired job, passing the opened zaak URL back into the process.</summary>
+    Task CompleteOpenZaakJobAsync(string jobId, Uri zaakUrl, CancellationToken ct = default);
+}

services/domain/Big.Infrastructure/InMemoryRegistrationStore.cs

@@ -0,0 +1,25 @@
+using System.Collections.Concurrent;
+using Big.Application;
+using Big.Domain;
+
+namespace Big.Infrastructure;
+
+/// <summary>
+/// In-memory <see cref="IRegistrationStore"/> for the minimal slice (ADR-0009). The walking
+/// skeleton's read path is the projection (S-06), not this store, so durable domain persistence is a
+/// documented follow-up. Registered as a singleton so the submit endpoint and the worker share it.
+/// </summary>
+public sealed class InMemoryRegistrationStore : IRegistrationStore
+{
+    private readonly ConcurrentDictionary<RegistrationId, Registration> _byId = new();
+
+    public Task SaveAsync(Registration registration, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(registration);
+        _byId[registration.Id] = registration;
+        return Task.CompletedTask;
+    }
+
+    public Task<Registration?> GetAsync(RegistrationId id, CancellationToken ct = default)
+        => Task.FromResult(_byId.GetValueOrDefault(id));
+}

services/domain/Big.Infrastructure/OpenZaakJobProcessor.cs

@@ -0,0 +1,39 @@
+using Big.Application;
+using Microsoft.Extensions.Logging;
+
+namespace Big.Infrastructure;
+
+/// <summary>
+/// One poll tick of the external-task worker (ADR-0009): acquire the parked <c>OpenZaakAanmaken</c>
+/// jobs, hand each to the <see cref="OpenZaakWorker"/> to open a zaak via the ACL, and complete the
+/// Flowable job with the resulting zaak URL. A job that fails is logged and left un-completed so
+/// Flowable redelivers it (§8.6). Split out from the hosted <see cref="OpenZaakJobPump"/> so the
+/// acquire→process→complete logic is unit-testable without a running host.
+/// </summary>
+public sealed class OpenZaakJobProcessor(
+    IExternalWorkerClient client,
+    OpenZaakWorker worker,
+    ILogger<OpenZaakJobProcessor> logger)
+{
+    /// <summary>Acquire and process up to <paramref name="maxJobs"/> jobs. Returns the number acquired.</summary>
+    public async Task<int> PumpOnceAsync(int maxJobs, CancellationToken ct = default)
+    {
+        var jobs = await client.AcquireOpenZaakJobsAsync(maxJobs, ct);
+
+        foreach (var job in jobs)
+        {
+            try
+            {
+                var zaakUrl = await worker.HandleAsync(job, ct);
+                await client.CompleteOpenZaakJobAsync(job.JobId, zaakUrl, ct);
+            }
+            catch (Exception ex)
+            {
+                // Leave the job un-completed: its lock expires and Flowable redelivers it (§8.6).
+                logger.LogError(ex, "OpenZaakAanmaken job {JobId} failed; leaving it for redelivery.", job.JobId);
+            }
+        }
+
+        return jobs.Count;
+    }
+}

services/domain/Big.Infrastructure/OpenZaakJobPump.cs

@@ -0,0 +1,48 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+
+namespace Big.Infrastructure;
+
+/// <summary>
+/// The hosted polling loop of the external-task job worker (ADR-0009): on an interval it resolves a
+/// scoped <see cref="OpenZaakJobProcessor"/> and asks it to drain the parked <c>OpenZaakAanmaken</c>
+/// jobs. A deliberately thin shell — all acquire/process/complete logic lives in the processor, which
+/// is unit-tested; this class only owns the timer, the per-tick scope, and loop resilience.
+/// </summary>
+public sealed class OpenZaakJobPump(
+    IServiceScopeFactory scopeFactory,
+    FlowableOptions options,
+    ILogger<OpenZaakJobPump> logger) : BackgroundService
+{
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        while (!stoppingToken.IsCancellationRequested)
+        {
+            try
+            {
+                using var scope = scopeFactory.CreateScope();
+                var processor = scope.ServiceProvider.GetRequiredService<OpenZaakJobProcessor>();
+                await processor.PumpOnceAsync(options.MaxJobsPerPoll, stoppingToken);
+            }
+            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
+            {
+                break;
+            }
+            catch (Exception ex)
+            {
+                // A transient fault (e.g. Flowable briefly unreachable) must not kill the loop.
+                logger.LogError(ex, "OpenZaakAanmaken job poll failed; retrying after the poll interval.");
+            }
+
+            try
+            {
+                await Task.Delay(options.PollInterval, stoppingToken);
+            }
+            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
+            {
+                break;
+            }
+        }
+    }
+}

services/domain/Big.Infrastructure/Options.cs

@@ -0,0 +1,29 @@
+namespace Big.Infrastructure;
+
+/// <summary>Configuration for the Flowable Workflow Client. <see cref="BaseUrl"/> is the flowable-rest
+/// root and must end with a slash (e.g. <c>http://flowable-rest:8080/flowable-rest/</c>) so the
+/// <c>service/…</c> and <c>external-job-api/…</c> sub-paths resolve correctly.</summary>
+public sealed class FlowableOptions
+{
+    public Uri BaseUrl { get; set; } = null!;
+    public string Username { get; set; } = "";
+    public string Password { get; set; } = "";
+
+    /// <summary>The id this worker locks jobs under, so two workers don't process the same job.</summary>
+    public string WorkerId { get; set; } = "big-domain-worker";
+
+    /// <summary>How long an acquired job stays locked to this worker (ISO-8601 duration).</summary>
+    public string LockDuration { get; set; } = "PT5M";
+
+    /// <summary>How many OpenZaakAanmaken jobs to acquire per poll.</summary>
+    public int MaxJobsPerPoll { get; set; } = 5;
+
+    /// <summary>How often the worker polls Flowable for new jobs.</summary>
+    public TimeSpan PollInterval { get; set; } = TimeSpan.FromSeconds(2);
+}
+
+/// <summary>Configuration for the ACL HTTP client. <see cref="BaseUrl"/> is the ACL service root.</summary>
+public sealed class AclOptions
+{
+    public Uri BaseUrl { get; set; } = null!;
+}

services/domain/Big.Tests/AclHttpClientTests.cs

@@ -0,0 +1,44 @@
+using System.Net;
+using Big.Infrastructure;
+
+namespace Big.Tests;
+
+public class AclHttpClientTests
+{
+    private static AclHttpClient Client(StubHandler handler) => new(
+        new HttpClient(handler), new AclOptions { BaseUrl = new("http://acl/") });
+
+    [Fact]
+    public async Task Opens_a_zaak_by_posting_the_bsn_and_returns_the_zaak_url()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.OK,
+            """{"zaakUrl":"http://openzaak/zaken/api/v1/zaken/abc"}"""));
+
+        var url = await client.OpenZaakAsync("123456782");
+
+        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);
+    }
+
+    [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.OpenZaakAsync("123456782"));
+    }
+
+    [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.OpenZaakAsync("123456782"));
+        Assert.Contains("empty", ex.Message, StringComparison.OrdinalIgnoreCase);
+    }
+}

services/domain/Big.Tests/Big.Tests.csproj

@@ -0,0 +1,27 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Big.Domain\Big.Domain.csproj" />
+    <ProjectReference Include="..\Big.Application\Big.Application.csproj" />
+    <ProjectReference Include="..\Big.Infrastructure\Big.Infrastructure.csproj" />
+  </ItemGroup>
+
+</Project>

services/domain/Big.Tests/CapturingLogger.cs

@@ -0,0 +1,24 @@
+using Microsoft.Extensions.Logging;
+
+namespace Big.Tests;
+
+/// <summary>A minimal <see cref="ILogger{T}"/> that records the level and rendered message of each
+/// entry, so tests can assert that (for example) a failing job was logged.</summary>
+internal sealed class CapturingLogger<T> : ILogger<T>
+{
+    public List<(LogLevel Level, string Message)> Entries { get; } = [];
+
+    public IDisposable BeginScope<TState>(TState state) where TState : notnull => NullScope.Instance;
+
+    public bool IsEnabled(LogLevel logLevel) => true;
+
+    public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception,
+        Func<TState, Exception?, string> formatter)
+        => Entries.Add((logLevel, formatter(state, exception)));
+
+    private sealed class NullScope : IDisposable
+    {
+        public static readonly NullScope Instance = new();
+        public void Dispose() { }
+    }
+}

services/domain/Big.Tests/Fakes.cs

@@ -0,0 +1,61 @@
+using Big.Application;
+using Big.Domain;
+
+namespace Big.Tests;
+
+/// <summary>An in-memory <see cref="IRegistrationStore"/> for the application-layer tests. Upserts
+/// keyed on the registration id, mirroring the production store (kept distinct from the production
+/// <c>InMemoryRegistrationStore</c> so tests can seed and inspect save counts).</summary>
+internal sealed class FakeRegistrationStore : IRegistrationStore
+{
+    private readonly Dictionary<RegistrationId, Registration> _byId = [];
+
+    public int SaveCount { get; private set; }
+
+    public Task SaveAsync(Registration registration, CancellationToken ct = default)
+    {
+        SaveCount++;
+        _byId[registration.Id] = registration;
+        return Task.CompletedTask;
+    }
+
+    public Task<Registration?> GetAsync(RegistrationId id, CancellationToken ct = default)
+        => Task.FromResult(_byId.GetValueOrDefault(id));
+
+    public void Seed(Registration registration) => _byId[registration.Id] = registration;
+}
+
+/// <summary>A fake Workflow Client that records the registration it was asked to start a process for
+/// and returns a fixed process-instance id. An optional callback runs at start time, letting a test
+/// assert ordering (e.g. that the registration was persisted before the process started).</summary>
+internal sealed class FakeWorkflowClient(string processInstanceId = "proc-1", Action<RegistrationId>? onStart = null)
+    : IWorkflowClient
+{
+    public RegistrationId? StartedFor { get; private set; }
+
+    public Task<string> StartRegistrationProcessAsync(RegistrationId registrationId, CancellationToken ct = default)
+    {
+        onStart?.Invoke(registrationId);
+        StartedFor = registrationId;
+        return Task.FromResult(processInstanceId);
+    }
+}
+
+/// <summary>A fake ACL client that records the bsn it was asked to open a zaak for and returns a
+/// fixed zaak URL.</summary>
+internal sealed class FakeAclClient(Uri? zaakUrl = null) : IAclClient
+{
+    public static readonly Uri DefaultZaakUrl = new("http://openzaak/zaken/api/v1/zaken/abc");
+
+    private readonly Uri _zaakUrl = zaakUrl ?? DefaultZaakUrl;
+
+    public string? OpenedForBsn { get; private set; }
+    public int CallCount { get; private set; }
+
+    public Task<Uri> OpenZaakAsync(string bsn, CancellationToken ct = default)
+    {
+        CallCount++;
+        OpenedForBsn = bsn;
+        return Task.FromResult(_zaakUrl);
+    }
+}

services/domain/Big.Tests/FlowableWorkflowClientTests.cs

@@ -0,0 +1,139 @@
+using System.Net;
+using System.Text;
+using Big.Domain;
+using Big.Infrastructure;
+
+namespace Big.Tests;
+
+public class FlowableWorkflowClientTests
+{
+    private static readonly Uri Base = new("http://flowable/flowable-rest/");
+
+    private static FlowableWorkflowClient Client(StubHandler handler) => new(
+        new HttpClient(handler),
+        new FlowableOptions { BaseUrl = Base, Username = "rest-admin", Password = "test", WorkerId = "worker-x" });
+
+    private static string DecodeBasic(HttpRequestMessage request)
+        => Encoding.ASCII.GetString(Convert.FromBase64String(request.Headers.Authorization!.Parameter!));
+
+    [Fact]
+    public async Task Start_posts_the_registration_id_variable_and_returns_the_instance_id()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.Created, """{"id":"pi-1"}"""));
+        var rid = RegistrationId.New();
+
+        var pid = await client.StartRegistrationProcessAsync(rid);
+
+        Assert.Equal("pi-1", pid);
+        Assert.Equal(HttpMethod.Post, capture.Seen!.Method);
+        Assert.Equal("http://flowable/flowable-rest/service/runtime/process-instances",
+            capture.Seen.RequestUri!.ToString());
+        Assert.Equal("Basic", capture.Seen.Headers.Authorization!.Scheme);
+        Assert.Equal("rest-admin:test", DecodeBasic(capture.Seen));
+        Assert.Contains("\"processDefinitionKey\":\"registratie\"", capture.Body);
+        Assert.Contains("\"name\":\"registrationId\"", capture.Body);
+        Assert.Contains("\"type\":\"string\"", capture.Body);
+        Assert.Contains($"\"value\":\"{rid}\"", capture.Body);
+    }
+
+    [Fact]
+    public async Task Start_uses_the_configured_worker_credentials_and_defaults()
+    {
+        var capture = new RequestCapture();
+        // Only BaseUrl set — the worker id and (empty) credentials must come from the defaults.
+        var client = new FlowableWorkflowClient(
+            new HttpClient(capture.Responds(HttpStatusCode.OK, "[]")),
+            new FlowableOptions { BaseUrl = Base });
+
+        await client.AcquireOpenZaakJobsAsync(1);
+
+        Assert.Equal(":", DecodeBasic(capture.Seen!));
+        Assert.Contains("\"workerId\":\"big-domain-worker\"", capture.Body);
+        Assert.Contains("\"lockDuration\":\"PT5M\"", capture.Body);
+    }
+
+    [Fact]
+    public async Task Acquire_posts_the_topic_and_parses_jobs_with_their_registration_id()
+    {
+        var rid = RegistrationId.New();
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.OK,
+            $$"""[{"id":"job-1","variables":[{"name":"registrationId","type":"string","value":"{{rid}}"}]}]"""));
+
+        var jobs = await client.AcquireOpenZaakJobsAsync(3);
+
+        var job = Assert.Single(jobs);
+        Assert.Equal("job-1", job.JobId);
+        Assert.Equal(rid, job.RegistrationId);
+        Assert.Equal("http://flowable/flowable-rest/external-job-api/acquire/jobs",
+            capture.Seen!.RequestUri!.ToString());
+        Assert.Contains("\"topic\":\"OpenZaakAanmaken\"", capture.Body);
+        Assert.Contains("\"numberOfTasks\":3", capture.Body);
+        Assert.Contains("\"workerId\":\"worker-x\"", capture.Body);
+        Assert.Contains("\"lockDuration\":\"PT5M\"", capture.Body);
+    }
+
+    [Theory]
+    [InlineData("[]")]
+    [InlineData("null")]
+    public async Task Acquire_returns_empty_when_flowable_has_no_parked_jobs(string body)
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.OK, body));
+
+        var jobs = await client.AcquireOpenZaakJobsAsync(1);
+
+        Assert.NotNull(capture.Seen);
+        Assert.Empty(jobs);
+    }
+
+    [Fact]
+    public async Task Acquire_throws_when_a_job_carries_no_registration_id()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.OK, """[{"id":"job-1","variables":[]}]"""));
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => client.AcquireOpenZaakJobsAsync(1));
+        Assert.Contains("job-1", ex.Message);
+        Assert.Contains("registrationId", ex.Message);
+    }
+
+    [Fact]
+    public async Task Complete_posts_the_zaak_url_variable_to_the_job_complete_endpoint()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.NoContent));
+
+        await client.CompleteOpenZaakJobAsync("job-1", new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
+
+        Assert.NotNull(capture.Seen);
+        Assert.Equal(HttpMethod.Post, capture.Seen!.Method);
+        Assert.Equal("http://flowable/flowable-rest/external-job-api/acquire/jobs/job-1/complete",
+            capture.Seen.RequestUri!.ToString());
+        Assert.Contains("\"workerId\":\"worker-x\"", capture.Body);
+        Assert.Contains("\"name\":\"zaakUrl\"", capture.Body);
+        Assert.Contains("\"type\":\"string\"", capture.Body);
+        Assert.Contains("\"value\":\"http://openzaak/zaken/api/v1/zaken/abc\"", capture.Body);
+    }
+
+    [Fact]
+    public async Task Start_throws_when_flowable_rejects_the_request()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.InternalServerError));
+
+        await Assert.ThrowsAsync<HttpRequestException>(
+            () => client.StartRegistrationProcessAsync(RegistrationId.New()));
+    }
+
+    [Fact]
+    public async Task Complete_throws_when_flowable_rejects_the_request()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.InternalServerError));
+
+        await Assert.ThrowsAsync<HttpRequestException>(
+            () => client.CompleteOpenZaakJobAsync("job-1", new Uri("http://openzaak/zaken/api/v1/zaken/abc")));
+    }
+}

services/domain/Big.Tests/HttpStubs.cs

@@ -0,0 +1,30 @@
+using System.Net;
+
+namespace Big.Tests;
+
+/// <summary>A test double for <see cref="HttpMessageHandler"/> that records the last request and
+/// returns a scripted response — the same approach the ACL gateway tests use.</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; }
+
+    /// <summary>A handler that records the request, then replies with <paramref name="status"/> and
+    /// <paramref name="json"/>.</summary>
+    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, System.Text.Encoding.UTF8, "application/json");
+        return response;
+    });
+}

services/domain/Big.Tests/InMemoryRegistrationStoreTests.cs

@@ -0,0 +1,44 @@
+using Big.Domain;
+using Big.Infrastructure;
+
+namespace Big.Tests;
+
+public class InMemoryRegistrationStoreTests
+{
+    [Fact]
+    public async Task Saves_and_reads_back_a_registration_by_id()
+    {
+        var store = new InMemoryRegistrationStore();
+        var registration = Registration.Submit("123456782");
+
+        await store.SaveAsync(registration);
+
+        var loaded = await store.GetAsync(registration.Id);
+        Assert.NotNull(loaded);
+        Assert.Equal(registration.Id, loaded.Id);
+        Assert.Null(await store.GetAsync(RegistrationId.New()));
+    }
+
+    [Fact]
+    public async Task Saving_the_same_id_upserts()
+    {
+        var store = new InMemoryRegistrationStore();
+        var registration = Registration.Submit("123456782");
+        await store.SaveAsync(registration);
+
+        registration.AttachZaak(new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
+        await store.SaveAsync(registration);
+
+        var loaded = await store.GetAsync(registration.Id);
+        Assert.NotNull(loaded);
+        Assert.Equal("http://openzaak/zaken/api/v1/zaken/abc", loaded.ZaakUrl!.ToString());
+    }
+
+    [Fact]
+    public async Task Saving_a_null_registration_is_rejected()
+    {
+        var store = new InMemoryRegistrationStore();
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => store.SaveAsync(null!));
+    }
+}

services/domain/Big.Tests/OpenZaakJobProcessorTests.cs

@@ -0,0 +1,83 @@
+using Big.Application;
+using Big.Domain;
+using Big.Infrastructure;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+
+namespace Big.Tests;
+
+public class OpenZaakJobProcessorTests
+{
+    /// <summary>A fake external-worker client: scripts the jobs to acquire and records completions.</summary>
+    private sealed class FakeExternalWorkerClient(params OpenZaakJob[] jobs) : IExternalWorkerClient
+    {
+        public int AcquireCount { get; private set; }
+        public List<(string JobId, Uri ZaakUrl)> Completed { get; } = [];
+
+        public Task<IReadOnlyList<OpenZaakJob>> AcquireOpenZaakJobsAsync(int maxJobs, CancellationToken ct = default)
+        {
+            AcquireCount++;
+            return Task.FromResult<IReadOnlyList<OpenZaakJob>>(jobs.Take(maxJobs).ToList());
+        }
+
+        public Task CompleteOpenZaakJobAsync(string jobId, Uri zaakUrl, CancellationToken ct = default)
+        {
+            Completed.Add((jobId, zaakUrl));
+            return Task.CompletedTask;
+        }
+    }
+
+    private static OpenZaakJobProcessor Processor(IExternalWorkerClient client, IRegistrationStore store, FakeAclClient acl)
+        => new(client, new OpenZaakWorker(store, acl), NullLogger<OpenZaakJobProcessor>.Instance);
+
+    [Fact]
+    public async Task Acquires_a_job_opens_the_zaak_and_completes_it()
+    {
+        var registration = Registration.Submit("123456782");
+        var store = new FakeRegistrationStore();
+        store.Seed(registration);
+        var client = new FakeExternalWorkerClient(new OpenZaakJob("job-1", registration.Id));
+        var acl = new FakeAclClient();
+
+        var acquired = await Processor(client, store, acl).PumpOnceAsync(5);
+
+        Assert.Equal(1, acquired);
+        var completed = Assert.Single(client.Completed);
+        Assert.Equal("job-1", completed.JobId);
+        Assert.Equal(FakeAclClient.DefaultZaakUrl, completed.ZaakUrl);
+        Assert.Equal(FakeAclClient.DefaultZaakUrl, (await store.GetAsync(registration.Id))!.ZaakUrl);
+    }
+
+    [Fact]
+    public async Task A_failing_job_is_left_uncompleted_for_flowable_to_redeliver()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        // The job correlates to a registration that is not in the store, so the worker throws.
+        var client = new FakeExternalWorkerClient(new OpenZaakJob("job-1", RegistrationId.New()));
+        var logger = new CapturingLogger<OpenZaakJobProcessor>();
+        var processor = new OpenZaakJobProcessor(client, new OpenZaakWorker(store, acl), logger);
+
+        var acquired = await processor.PumpOnceAsync(5);
+
+        Assert.Equal(1, acquired);
+        Assert.Empty(client.Completed);
+        // The failure is logged (and the job left for redelivery), not swallowed silently.
+        var error = Assert.Single(logger.Entries, e => e.Level == LogLevel.Error);
+        Assert.Contains("job-1", error.Message);
+    }
+
+    [Fact]
+    public async Task Does_nothing_but_poll_when_there_are_no_jobs()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var client = new FakeExternalWorkerClient();
+
+        var acquired = await Processor(client, store, acl).PumpOnceAsync(5);
+
+        Assert.Equal(0, acquired);
+        Assert.Equal(1, client.AcquireCount);
+        Assert.Empty(client.Completed);
+    }
+}

services/domain/Big.Tests/OpenZaakWorkerTests.cs

@@ -0,0 +1,70 @@
+using Big.Application;
+using Big.Domain;
+
+namespace Big.Tests;
+
+public class OpenZaakWorkerTests
+{
+    private static Registration Submitted(string bsn = "123456782")
+    {
+        var registration = Registration.Submit(bsn);
+        registration.RecordProcessStarted("proc-1");
+        return registration;
+    }
+
+    [Fact]
+    public async Task Handling_a_job_opens_a_zaak_via_the_acl_and_attaches_it()
+    {
+        var registration = Submitted();
+        var store = new FakeRegistrationStore();
+        store.Seed(registration);
+        var acl = new FakeAclClient();
+        var worker = new OpenZaakWorker(store, acl);
+
+        var zaakUrl = await worker.HandleAsync(new OpenZaakJob("job-1", registration.Id));
+
+        Assert.Equal(FakeAclClient.DefaultZaakUrl, zaakUrl);
+        Assert.Equal("123456782", acl.OpenedForBsn);
+        var saved = await store.GetAsync(registration.Id);
+        Assert.Equal(FakeAclClient.DefaultZaakUrl, saved!.ZaakUrl);
+        Assert.Equal(1, store.SaveCount);
+    }
+
+    [Fact]
+    public async Task Handling_a_null_job_is_rejected()
+    {
+        var worker = new OpenZaakWorker(new FakeRegistrationStore(), new FakeAclClient());
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => worker.HandleAsync(null!));
+    }
+
+    [Fact]
+    public async Task Handling_a_job_for_an_unknown_registration_throws_and_opens_no_zaak()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var worker = new OpenZaakWorker(store, acl);
+
+        var job = new OpenZaakJob("job-1", RegistrationId.New());
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => worker.HandleAsync(job));
+        Assert.Contains(job.RegistrationId.ToString(), ex.Message);
+        Assert.Equal(0, acl.CallCount);
+    }
+
+    [Fact]
+    public async Task Handling_a_redelivered_job_is_idempotent_and_does_not_open_a_second_zaak()
+    {
+        var registration = Submitted();
+        var store = new FakeRegistrationStore();
+        store.Seed(registration);
+        var acl = new FakeAclClient();
+        var worker = new OpenZaakWorker(store, acl);
+        var job = new OpenZaakJob("job-1", registration.Id);
+
+        var first = await worker.HandleAsync(job);
+        var second = await worker.HandleAsync(job);
+
+        Assert.Equal(first, second);
+        Assert.Equal(1, acl.CallCount);
+    }
+}

services/domain/Big.Tests/RegistrationTests.cs

@@ -0,0 +1,90 @@
+using Big.Domain;
+
+namespace Big.Tests;
+
+public class RegistrationTests
+{
+    [Fact]
+    public void Submitting_a_registration_starts_in_ingediend()
+    {
+        var registration = Registration.Submit("123456782");
+
+        Assert.Equal(RegistrationStatus.Ingediend, registration.Status);
+        Assert.Equal("123456782", registration.Bsn);
+        Assert.NotEqual(Guid.Empty, registration.Id.Value);
+        Assert.Null(registration.ZaakUrl);
+        Assert.Null(registration.ProcessInstanceId);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("   ")]
+    [InlineData(null)]
+    public void Submitting_without_a_bsn_is_rejected(string? bsn)
+        => Assert.ThrowsAny<ArgumentException>(() => Registration.Submit(bsn!));
+
+    [Fact]
+    public void Recording_the_started_process_keeps_its_instance_id()
+    {
+        var registration = Registration.Submit("123456782");
+
+        registration.RecordProcessStarted("proc-42");
+
+        Assert.Equal("proc-42", registration.ProcessInstanceId);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("   ")]
+    [InlineData(null)]
+    public void Recording_an_empty_process_instance_id_is_rejected(string? processInstanceId)
+    {
+        var registration = Registration.Submit("123456782");
+
+        Assert.ThrowsAny<ArgumentException>(() => registration.RecordProcessStarted(processInstanceId!));
+    }
+
+    [Fact]
+    public void Attaching_a_zaak_records_its_url_and_keeps_the_status_ingediend()
+    {
+        var registration = Registration.Submit("123456782");
+        var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");
+
+        registration.AttachZaak(zaak);
+
+        Assert.Equal(zaak, registration.ZaakUrl);
+        Assert.Equal(RegistrationStatus.Ingediend, registration.Status);
+    }
+
+    [Fact]
+    public void Attaching_a_null_zaak_is_rejected()
+    {
+        var registration = Registration.Submit("123456782");
+
+        Assert.Throws<ArgumentNullException>(() => registration.AttachZaak(null!));
+    }
+
+    [Fact]
+    public void Re_attaching_the_same_zaak_is_idempotent()
+    {
+        var registration = Registration.Submit("123456782");
+        var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");
+
+        registration.AttachZaak(zaak);
+        registration.AttachZaak(zaak);
+
+        Assert.Equal(zaak, registration.ZaakUrl);
+    }
+
+    [Fact]
+    public void Attaching_a_conflicting_zaak_is_rejected()
+    {
+        var registration = Registration.Submit("123456782");
+        registration.AttachZaak(new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
+
+        var ex = Assert.Throws<InvalidOperationException>(
+            () => registration.AttachZaak(new Uri("http://openzaak/zaken/api/v1/zaken/other")));
+        Assert.Contains("/zaken/abc", ex.Message);
+        Assert.Contains("/zaken/other", ex.Message);
+    }
+}

services/domain/Big.Tests/SubmitRegistrationTests.cs

@@ -0,0 +1,66 @@
+using Big.Application;
+using Big.Domain;
+
+namespace Big.Tests;
+
+public class SubmitRegistrationTests
+{
+    [Fact]
+    public async Task Submitting_persists_an_ingediend_registration_and_starts_the_process()
+    {
+        var store = new FakeRegistrationStore();
+        var workflow = new FakeWorkflowClient(processInstanceId: "proc-42");
+        var handler = new SubmitRegistration(store, workflow);
+
+        var id = await handler.HandleAsync(new SubmitRegistrationCommand("123456782"));
+
+        var saved = await store.GetAsync(id);
+        Assert.NotNull(saved);
+        Assert.Equal("123456782", saved.Bsn);
+        Assert.Equal(RegistrationStatus.Ingediend, saved.Status);
+        Assert.Equal("proc-42", saved.ProcessInstanceId);
+        Assert.Equal(id, workflow.StartedFor);
+        Assert.Null(saved.ZaakUrl);
+        // Persisted twice: once before starting the process, once after recording the instance id.
+        Assert.Equal(2, store.SaveCount);
+    }
+
+    [Fact]
+    public async Task Rejects_a_null_command_without_touching_the_store_or_workflow()
+    {
+        var store = new FakeRegistrationStore();
+        var workflow = new FakeWorkflowClient();
+        var handler = new SubmitRegistration(store, workflow);
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => handler.HandleAsync(null!));
+        Assert.Equal(0, store.SaveCount);
+        Assert.Null(workflow.StartedFor);
+    }
+
+    [Fact]
+    public async Task Submitting_persists_the_registration_before_starting_the_process()
+    {
+        // The worker correlates the OpenZaakAanmaken job back to the aggregate by id, so the
+        // aggregate must already be persisted when the process starts (ADR-0009).
+        var store = new FakeRegistrationStore();
+        Registration? visibleAtStart = null;
+        var workflow = new FakeWorkflowClient(onStart: id => visibleAtStart = store.GetAsync(id).Result);
+        var handler = new SubmitRegistration(store, workflow);
+
+        await handler.HandleAsync(new SubmitRegistrationCommand("123456782"));
+
+        Assert.NotNull(visibleAtStart);
+    }
+
+    [Fact]
+    public async Task Submitting_without_a_bsn_is_rejected_and_starts_no_process()
+    {
+        var store = new FakeRegistrationStore();
+        var workflow = new FakeWorkflowClient();
+        var handler = new SubmitRegistration(store, workflow);
+
+        await Assert.ThrowsAnyAsync<ArgumentException>(
+            () => handler.HandleAsync(new SubmitRegistrationCommand("")));
+        Assert.Null(workflow.StartedFor);
+    }
+}

services/domain/Big.slnx

@@ -0,0 +1,7 @@
+<Solution>
+  <Project Path="Big.Domain/Big.Domain.csproj" />
+  <Project Path="Big.Application/Big.Application.csproj" />
+  <Project Path="Big.Infrastructure/Big.Infrastructure.csproj" />
+  <Project Path="Big.Api/Big.Api.csproj" />
+  <Project Path="Big.Tests/Big.Tests.csproj" />
+</Solution>

services/domain/Dockerfile

@@ -0,0 +1,34 @@
+# Multi-stage build for the BIG Domain Service (.NET 10).
+# Build context is services/domain (see infra/docker-compose.yml).
+FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
+WORKDIR /src
+
+# Restore first (cached unless .csproj files change).
+COPY Big.Api/Big.Api.csproj Big.Api/
+COPY Big.Application/Big.Application.csproj Big.Application/
+COPY Big.Infrastructure/Big.Infrastructure.csproj Big.Infrastructure/
+COPY Big.Domain/Big.Domain.csproj Big.Domain/
+RUN dotnet restore Big.Api/Big.Api.csproj
+
+COPY Big.Api/ Big.Api/
+COPY Big.Application/ Big.Application/
+COPY Big.Infrastructure/ Big.Infrastructure/
+COPY Big.Domain/ Big.Domain/
+RUN dotnet publish Big.Api/Big.Api.csproj -c Release -o /app/publish /p:UseAppHost=false
+
+FROM mcr.microsoft.com/dotnet/aspnet:10.0 AS runtime
+WORKDIR /app
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends curl \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY --from=build /app/publish .
+
+ENV ASPNETCORE_URLS=http://+:8080
+EXPOSE 8080
+
+HEALTHCHECK --interval=5s --timeout=3s --start-period=10s --retries=5 \
+    CMD curl -fsS http://localhost:8080/health || exit 1
+
+ENTRYPOINT ["dotnet", "Big.Api.dll"]

services/domain/stryker-config.json

@@ -0,0 +1,15 @@
+{
+  "stryker-config": {
+    "solution": "Big.slnx",
+    "test-projects": ["Big.Tests/Big.Tests.csproj"],
+    "reporters": ["progress", "html"],
+    "mutate": [
+      "!**/OpenZaakJobPump.cs"
+    ],
+    "thresholds": {
+      "high": 95,
+      "low": 90,
+      "break": 90
+    }
+  }
+}

services/event-subscriber/Dockerfile

@@ -0,0 +1,32 @@
+# Multi-stage build for the Event Subscriber service (.NET 10).
+# Build context is services/event-subscriber, but it references the shared read model in
+# services/projection-api, so the context is the repo root (see infra/docker-compose.yml).
+FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
+WORKDIR /src
+
+# Restore first (cached unless .csproj files change).
+COPY services/event-subscriber/EventSubscriber.Api/EventSubscriber.Api.csproj services/event-subscriber/EventSubscriber.Api/
+COPY services/event-subscriber/EventSubscriber.Application/EventSubscriber.Application.csproj services/event-subscriber/EventSubscriber.Application/
+COPY services/projection-api/Projection.ReadModel/Projection.ReadModel.csproj services/projection-api/Projection.ReadModel/
+RUN dotnet restore services/event-subscriber/EventSubscriber.Api/EventSubscriber.Api.csproj
+
+COPY services/event-subscriber/ services/event-subscriber/
+COPY services/projection-api/Projection.ReadModel/ services/projection-api/Projection.ReadModel/
+RUN dotnet publish services/event-subscriber/EventSubscriber.Api/EventSubscriber.Api.csproj -c Release -o /app/publish /p:UseAppHost=false
+
+FROM mcr.microsoft.com/dotnet/aspnet:10.0 AS runtime
+WORKDIR /app
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends curl \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY --from=build /app/publish .
+
+ENV ASPNETCORE_URLS=http://+:8080
+EXPOSE 8080
+
+HEALTHCHECK --interval=5s --timeout=3s --start-period=15s --retries=5 \
+    CMD curl -fsS http://localhost:8080/health || exit 1
+
+ENTRYPOINT ["dotnet", "EventSubscriber.Api.dll"]

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

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <ItemGroup>
+    <ProjectReference Include="..\EventSubscriber.Application\EventSubscriber.Application.csproj" />
+    <ProjectReference Include="..\..\projection-api\Projection.ReadModel\Projection.ReadModel.csproj" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+</Project>

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

@@ -0,0 +1,66 @@
+using System.Text.Json;
+using EventSubscriber.Application;
+using Projection.ReadModel;
+
+var builder = WebApplication.CreateBuilder(args);
+
+var connectionString = builder.Configuration.GetConnectionString("Projection")
+    ?? throw new InvalidOperationException("Missing connection string 'ConnectionStrings:Projection'");
+// The exact Authorization header value Open Notificaties sends on each abonnement callback.
+// NRC probes the callback during registration and refuses it unless it returns 401 without
+// this value (ADR-0007), so the webhook enforces it.
+var webhookToken = builder.Configuration["EventSubscriber:Webhook:AuthToken"]
+    ?? throw new InvalidOperationException("Missing configuration 'EventSubscriber:Webhook:AuthToken'");
+
+builder.Services.AddProjectionReadModel(connectionString);
+builder.Services.AddProjectionWriteSide();
+
+var app = builder.Build();
+
+// Apply migrations on start so a fresh stack reaches a usable schema unattended.
+await app.Services.MigrateProjectionAsync();
+
+app.MapGet("/health", () => "Healthy");
+
+// The NRC abonnement callback. Open Notificaties POSTs a notification here; we project it.
+// Auth-on-callback is mandatory: the auth check runs *before* the body is read, so NRC's
+// registration probe (a POST without the configured Authorization, and without a valid
+// notification body) gets the 401 it requires rather than a 400 (ADR-0007).
+app.MapPost("/notifications", async (
+    HttpRequest request,
+    NotificationProjector projector,
+    CancellationToken ct) =>
+{
+    if (request.Headers.Authorization != webhookToken)
+        return Results.Unauthorized();
+
+    var dto = await JsonSerializer.DeserializeAsync<NotificationDto>(
+        request.Body, SerializerOptions, ct);
+    if (dto is null)
+        return Results.BadRequest();
+
+    await projector.HandleAsync(dto.ToNotification(), ct);
+    return Results.NoContent();
+});
+
+// Admin: rebuild the projection from the durable notification log (PRD §8.4 — rebuildable).
+app.MapPost("/admin/rebuild", async (NotificationProjector projector, CancellationToken ct) =>
+{
+    await projector.RebuildAsync(ct);
+    return Results.NoContent();
+});
+
+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 Notification ToNotification() => new(Kanaal, Resource, Actie, ResourceUrl);
+}
+
+public partial class Program
+{
+    // NRC sends camelCase JSON; match it case-insensitively.
+    private static readonly JsonSerializerOptions SerializerOptions = new(JsonSerializerDefaults.Web);
+}

services/event-subscriber/EventSubscriber.Api/appsettings.json

@@ -0,0 +1,8 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  }
+}

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

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+</Project>

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

@@ -0,0 +1,30 @@
+namespace EventSubscriber.Application;
+
+/// <summary>
+/// An inbound NRC (Open Notificaties) notification, as Open Notificaties POSTs it to an
+/// abonnement callback. Only the fields the projection needs are modelled; the full ZGW
+/// "Notificatie" resource also carries <c>aanmaakdatum</c> and <c>kenmerken</c> which the
+/// minimal projection ignores (bsn is deferred — see ADR-0008). For a <c>zaken</c>/<c>zaak</c>/<c>create</c>
+/// notification <c>hoofdObject</c> and <c>resourceUrl</c> are both the created zaak's URL.
+/// </summary>
+public sealed record Notification(
+    string Kanaal,
+    string Resource,
+    string Actie,
+    Uri ResourceUrl)
+{
+    /// <summary>The only event the walking-skeleton projection reacts to: a zaak being created.</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>
+    public string ZaakId => ResourceUrl.Segments[^1].Trim('/');
+
+    /// <summary>
+    /// A deterministic dedup key. Open Notificaties carries no notification id and may
+    /// redeliver, so the key is derived from the immutable notification content: two
+    /// deliveries of the same zaak-create collapse to one. (NRC may also deliver
+    /// out of order; the projector tolerates that — order does not change the outcome.)
+    /// </summary>
+    public string IdempotencyKey => $"{Kanaal}:{Resource}:{Actie}:{ResourceUrl}";
+}

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

@@ -0,0 +1,38 @@
+namespace EventSubscriber.Application;
+
+/// <summary>
+/// Projects inbound NRC notifications into the read projection. Tolerates duplicate and
+/// out-of-order deliveries (CLAUDE.md §8.6): the notification log dedups, and the projection
+/// upsert is idempotent on the zaak id. Rebuilds the projection by replaying the log.
+/// </summary>
+public sealed class NotificationProjector(INotificationLog log, IProjectionStore store)
+{
+    /// <summary>Handle one inbound notification. Ignores anything that is not a zaak-created event.</summary>
+    public async Task HandleAsync(Notification notification, CancellationToken ct = default)
+    {
+        if (!notification.IsZaakCreated)
+            return;
+
+        var recorded = new RecordedNotification(notification.IdempotencyKey, notification.Actie, notification.ZaakId);
+
+        // 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.
+        if (!await log.TryRecordAsync(recorded, ct))
+            return;
+
+        await store.UpsertAsync(ToEntry(recorded), ct);
+    }
+
+    /// <summary>Rebuild the projection from the durable notification log (PRD §8.4).</summary>
+    public async Task RebuildAsync(CancellationToken ct = default)
+    {
+        await store.ClearAsync(ct);
+        foreach (var recorded in await log.AllAsync(ct))
+            await store.UpsertAsync(ToEntry(recorded), ct);
+    }
+
+    /// <summary>The minimal projection row for an accepted notification. A zaak-create maps to
+    /// INGEDIEND; bsn/naam are deferred (ADR-0008).</summary>
+    private static RegisterEntry ToEntry(RecordedNotification recorded)
+        => new(recorded.ZaakId, RegistrationStatus.Ingediend);
+}

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

@@ -0,0 +1,37 @@
+namespace EventSubscriber.Application;
+
+/// <summary>
+/// The durable log of notifications the subscriber has accepted. It is both the idempotency
+/// guard (a replayed notification is recognised and dropped) and the rebuild source: the
+/// projection is a derived artefact (PRD §8.4) regenerated by replaying this log, so a rebuild
+/// needs no access to OpenZaak (CLAUDE.md §8.1). Implemented in Infrastructure over Postgres.
+/// </summary>
+public interface INotificationLog
+{
+    /// <summary>
+    /// Record a notification. Returns <c>true</c> if it was newly recorded, <c>false</c> if an
+    /// entry with the same key already existed (a duplicate delivery). Must be atomic so that
+    /// concurrent duplicate deliveries cannot both observe <c>true</c>.
+    /// </summary>
+    Task<bool> TryRecordAsync(RecordedNotification notification, CancellationToken ct = default);
+
+    /// <summary>Every accepted notification, for rebuilding the projection.</summary>
+    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>
+public sealed record RecordedNotification(string Key, string Actie, string ZaakId);
+
+/// <summary>The read projection store. Owned by the projection bounded context (ADR-0008); the
+/// subscriber writes to it and the projection-api reads it.</summary>
+public interface IProjectionStore
+{
+    /// <summary>Insert or update the row for <see cref="RegisterEntry.Id"/>. Idempotent on the id.</summary>
+    Task UpsertAsync(RegisterEntry entry, CancellationToken ct = default);
+
+    /// <summary>Remove every row — the first step of a rebuild.</summary>
+    Task ClearAsync(CancellationToken ct = default);
+
+    /// <summary>Every projection row (used by tests and the rebuild verification).</summary>
+    Task<IReadOnlyList<RegisterEntry>> AllAsync(CancellationToken ct = default);
+}

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

@@ -0,0 +1,20 @@
+namespace EventSubscriber.Application;
+
+/// <summary>
+/// A row of the rebuildable read projection (PRD §8.4). For the minimal slice it carries
+/// the zaak id and a status; <c>Bsn</c> and <c>NaamPlaceholder</c> are part of the schema but
+/// are deferred — the NRC notification does not carry them and the subscriber may not read
+/// OpenZaak directly (CLAUDE.md §8.1). Populating them is a follow-up (ADR-0008).
+/// </summary>
+public sealed record RegisterEntry(
+    string Id,
+    string Status,
+    string? Bsn = null,
+    string? NaamPlaceholder = null);
+
+/// <summary>The projection statuses the walking skeleton knows about.</summary>
+public static class RegistrationStatus
+{
+    /// <summary>A zaak has been created; the registration is submitted.</summary>
+    public const string Ingediend = "INGEDIEND";
+}

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

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\EventSubscriber.Application\EventSubscriber.Application.csproj" />
+  </ItemGroup>
+
+</Project>

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

@@ -0,0 +1,42 @@
+using EventSubscriber.Application;
+
+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>
+internal sealed class InMemoryNotificationLog : INotificationLog
+{
+    private readonly Dictionary<string, RecordedNotification> _byKey = [];
+
+    public Task<bool> TryRecordAsync(RecordedNotification notification, CancellationToken ct = default)
+        => Task.FromResult(_byKey.TryAdd(notification.Key, notification));
+
+    public Task<IReadOnlyList<RecordedNotification>> AllAsync(CancellationToken ct = default)
+        => Task.FromResult<IReadOnlyList<RecordedNotification>>([.. _byKey.Values]);
+}
+
+internal sealed class InMemoryProjectionStore : IProjectionStore
+{
+    private readonly Dictionary<string, RegisterEntry> _byId = [];
+
+    /// <summary>How many times a write was attempted — lets a test prove a deduped delivery
+    /// never reaches the store (an idempotent upsert hides the difference in row count alone).</summary>
+    public int UpsertCount { get; private set; }
+
+    public Task UpsertAsync(RegisterEntry entry, CancellationToken ct = default)
+    {
+        UpsertCount++;
+        _byId[entry.Id] = entry;
+        return Task.CompletedTask;
+    }
+
+    public Task ClearAsync(CancellationToken ct = default)
+    {
+        _byId.Clear();
+        return Task.CompletedTask;
+    }
+
+    public Task<IReadOnlyList<RegisterEntry>> AllAsync(CancellationToken ct = default)
+        => Task.FromResult<IReadOnlyList<RegisterEntry>>([.. _byId.Values]);
+}

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

@@ -0,0 +1,89 @@
+using EventSubscriber.Application;
+
+namespace EventSubscriber.Tests;
+
+/// <summary>Behaviour of the projector that turns NRC notifications into projection rows.
+/// The walking skeleton reacts only to a zaak being created (status INGEDIEND) and must
+/// tolerate duplicate and out-of-order deliveries (CLAUDE.md §8.6).</summary>
+public sealed class NotificationProjectorTests
+{
+    private const string ZaakUrl = "http://openzaak:8000/zaken/api/v1/zaken/11111111-1111-1111-1111-111111111111";
+
+    private readonly InMemoryNotificationLog _log = new();
+    private readonly InMemoryProjectionStore _store = new();
+
+    private NotificationProjector Projector() => new(_log, _store);
+
+    private static Notification ZaakCreated(string url = ZaakUrl)
+        => new("zaken", "zaak", "create", new Uri(url));
+
+    [Fact]
+    public async Task creating_a_zaak_writes_one_row_with_status_ingediend()
+    {
+        await Projector().HandleAsync(ZaakCreated());
+
+        var entry = Assert.Single(await _store.AllAsync());
+        Assert.Equal("11111111-1111-1111-1111-111111111111", entry.Id);
+        Assert.Equal(RegistrationStatus.Ingediend, entry.Status);
+    }
+
+    [Fact]
+    public async Task replaying_the_same_notification_keeps_a_single_row()
+    {
+        var projector = Projector();
+        await projector.HandleAsync(ZaakCreated());
+        await projector.HandleAsync(ZaakCreated());
+
+        Assert.Single(await _store.AllAsync());
+    }
+
+    [Fact]
+    public async Task a_replayed_notification_never_reaches_the_projection_store()
+    {
+        var projector = Projector();
+        await projector.HandleAsync(ZaakCreated());
+        await projector.HandleAsync(ZaakCreated());
+
+        // The duplicate is dropped at the log, before the (idempotent) upsert — so the store
+        // is written exactly once. Row count alone can't see this; the upsert count can.
+        Assert.Equal(1, _store.UpsertCount);
+    }
+
+    [Fact]
+    public async Task two_different_zaken_each_get_their_own_row()
+    {
+        var projector = Projector();
+        await projector.HandleAsync(ZaakCreated());
+        await projector.HandleAsync(ZaakCreated(ZaakUrl[..^1] + "2")); // a distinct zaak url
+
+        Assert.Equal(2, (await _store.AllAsync()).Count);
+    }
+
+    [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)
+    {
+        await Projector().HandleAsync(new Notification(kanaal, resource, actie, new Uri(ZaakUrl)));
+
+        Assert.Empty(await _store.AllAsync());
+    }
+
+    [Fact]
+    public async Task rebuild_clears_stale_rows_and_repopulates_from_the_notification_log()
+    {
+        var projector = Projector();
+        await projector.HandleAsync(ZaakCreated());
+        // A stale row that is not backed by any logged notification must not survive a rebuild.
+        await _store.UpsertAsync(new RegisterEntry("stale-9999", RegistrationStatus.Ingediend));
+
+        await projector.RebuildAsync();
+
+        var entry = Assert.Single(await _store.AllAsync());
+        Assert.Equal("11111111-1111-1111-1111-111111111111", entry.Id);
+        Assert.Equal(RegistrationStatus.Ingediend, entry.Status);
+    }
+}