docs(api-client): record the orval generator choice (refs #66)

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

.editorconfig

@@ -0,0 +1,17 @@
+# Editor configuration, see http://editorconfig.org
+root = true
+
+[*]
+indent_style = space
+indent_size = 2
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+# .NET sources use 4-space indent (dotnet format enforces this). The 2-space default
+# above is for the frontend (TS/HTML/CSS/JSON); C# keeps the .NET convention.
+[*.cs]
+indent_size = 4
+
+[*.md]
+max_line_length = off
+trim_trailing_whitespace = false

.gitea/workflows/ci.yaml

@@ -43,6 +43,20 @@ jobs:
           dotnet-version: '10.0.x'
       - run: make unit
 
+  # Frontend (Nx/Angular) lane: install with pnpm, then Nx lint + test + build.
+  frontend:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: https://github.com/actions/checkout@v4
+      - uses: https://github.com/pnpm/action-setup@v4
+        with:
+          version: 11
+      - uses: https://github.com/actions/setup-node@v4
+        with:
+          node-version: '24'
+          cache: 'pnpm'
+      - run: make frontend
+
   mutation:
     runs-on: ubuntu-latest
     steps:
@@ -51,23 +65,41 @@ jobs:
         with:
           dotnet-version: '10.0.x'
       - run: make mutation
-      # Publish the Stryker HTML report. `if: always()` uploads it even when the
+      # Publish the Stryker HTML reports. `if: always()` uploads them even when the
       # ratchet fails — that is exactly when you want to inspect the survivors.
-      # Glob handles Stryker's non-deterministic StrykerOutput/<timestamp>/ dir.
-      # Pinned to @v3 deliberately: @v4 refuses to run on Gitea (GHES guard) —
-      # see docs/runbooks/gitea-actions-gotchas.md §4.
+      # `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)
@@ -88,10 +120,14 @@ jobs:
         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=100 oz-init openzaak nrc-init nrc-web nrc-celery nrc-beat flowable-init keycloak acl bff projection-db event-subscriber projection-api 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

@@ -35,3 +35,20 @@ site/
 # OS
 .DS_Store
 Thumbs.db
+
+# ── Frontend (Nx / Angular / pnpm) ──
+node_modules/
+dist/
+tmp/
+out-tsc/
+/coverage
+.angular/
+.nx/cache
+.nx/workspace-data
+.nx/self-healing
+.nx/migrate-runs
+.nx/polygraph
+vite.config.*.timestamp*
+vitest.config.*.timestamp*
+
+.angular

.prettierignore

@@ -0,0 +1,8 @@
+# Add files here to ignore them from prettier formatting
+/dist
+/coverage
+/.nx/cache
+/.nx/workspace-data
+.angular
+
+.nx/self-healing

.prettierrc

@@ -0,0 +1,3 @@
+{
+  "singleQuote": true
+}

BACKLOG.md

@@ -151,17 +151,16 @@ The skeleton proves the spine end-to-end: a registration, a workflow, a zaak in
 
 ### S-08 · Self-Service portal (Angular, NL DS) — submit a registration
 
-**Outcome:** The self-service Angular app, in the Nx monorepo, lets a zorgprofessional log in via mock DigiD and submit a registration. NL Design System styling. Generated API client.
+> **S-08 was split** (CLAUDE.md §13; issue #9 closed) into the sub-slices below — it bundled the
+> Nx bootstrap, the generated client, the NL DS + DigiD form, and a full-stack Playwright e2e, well
+> past 1–2 days. Each sub-slice is independently demoable and CI-green.
 
-**Acceptance:**
+- **S-08a (#65)** · Nx monorepo + Angular tooling + CI Node lane. Placeholder `self-service` app; `nx lint/test/build` green in a new CI Node lane.
+- **S-08b (#66)** · Generated api-client lib from `services/bff/openapi.json` (never hand-written, §10) + a mocked-BFF unit test.
+- **S-08c (#67)** · Self-service submit form — NL Design System `libs/ui`, DigiD OIDC `libs/auth`, component tests (Angular Testing Library), axe WCAG 2.1 AA on the submit page.
+- **S-08d (#68)** · Playwright happy-path e2e (login → submit → success) against the full stack + compose serving + CI e2e lane.
 
-- E2E test (Playwright): full happy path, login → submit → success page.
-- Component tests (Testing Library) for the form.
-- Accessibility audit (axe-core) passes WCAG 2.1 AA on the submit page.
-
-**Touches:** `apps/self-service/`, `libs/ui/`, `libs/auth/`, `libs/api-client/`, tests.
-
-**Out of scope:** document upload, status tracking page.
+**Out of scope (whole of S-08):** document upload, status tracking page.
 
 ### S-09 · Openbaar Register portal — public lookup
 

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 event-subscriber projection-api
+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
@@ -43,11 +43,16 @@ export DOCKER_HOST := unix://$(PODMAN_SOCK)
 endif
 endif
 
-.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
+.PHONY: ci lint build unit mutation frontend integration verify verify-up verify-acl verify-nrc verify-projection verify-bff verify-domain 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, mutation, verify (mirrors Gitea Actions)
+## ci: run the full pipeline — lint, build, unit, mutation, frontend, verify (mirrors Gitea Actions)
 ## `verify` is the live-stack stage (full stack up once → ACL + notification checks).
-ci: lint build unit mutation verify
+ci: lint build unit mutation frontend verify
+
+## frontend: install deps and run the Nx lint/test/build for the portals (pnpm + Node required)
+frontend:
+	pnpm install --frozen-lockfile
+	pnpm nx run-many -t lint test build
 
 ## lint: verify formatting (no changes)
 lint:
@@ -64,12 +69,14 @@ unit:
 ## 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): services/acl/stryker-config.json and
-# services/event-subscriber/stryker-config.json. Scores never regress below baseline.
+# 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;
@@ -136,6 +143,16 @@ verify-nrc:
 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.
@@ -146,7 +163,9 @@ verify:
 	  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 || rc=$$?; \
+	    && bash infra/run-projection-check.sh \
+	    && bash infra/run-domain-check.sh \
+	    && bash infra/run-bff-check.sh || rc=$$?; \
 	  docker compose -f $(COMPOSE) down --volumes >/dev/null 2>&1; \
 	  docker volume rm -f $(CFG_VOLS) >/dev/null 2>&1; \
 	  exit $$rc'

apps/self-service/eslint.config.mjs

@@ -0,0 +1,34 @@
+import nx from '@nx/eslint-plugin';
+import baseConfig from '../../eslint.config.mjs';
+
+export default [
+  ...nx.configs['flat/angular'],
+  ...nx.configs['flat/angular-template'],
+  ...baseConfig,
+  {
+    files: ['**/*.ts'],
+    rules: {
+      '@angular-eslint/directive-selector': [
+        'error',
+        {
+          type: 'attribute',
+          prefix: 'app',
+          style: 'camelCase',
+        },
+      ],
+      '@angular-eslint/component-selector': [
+        'error',
+        {
+          type: 'element',
+          prefix: 'app',
+          style: 'kebab-case',
+        },
+      ],
+    },
+  },
+  {
+    files: ['**/*.html'],
+    // Override or add rules here
+    rules: {},
+  },
+];

apps/self-service/project.json

@@ -0,0 +1,80 @@
+{
+  "name": "self-service",
+  "$schema": "../../node_modules/nx/schemas/project-schema.json",
+  "projectType": "application",
+  "prefix": "app",
+  "sourceRoot": "apps/self-service/src",
+  "tags": [],
+  "targets": {
+    "build": {
+      "executor": "@angular/build:application",
+      "outputs": ["{options.outputPath}"],
+      "defaultConfiguration": "production",
+      "options": {
+        "outputPath": "dist/apps/self-service",
+        "browser": "apps/self-service/src/main.ts",
+        "tsConfig": "apps/self-service/tsconfig.app.json",
+        "assets": [
+          {
+            "glob": "**/*",
+            "input": "apps/self-service/public"
+          }
+        ],
+        "styles": ["apps/self-service/src/styles.css"]
+      },
+      "configurations": {
+        "production": {
+          "budgets": [
+            {
+              "type": "initial",
+              "maximumWarning": "500kb",
+              "maximumError": "1mb"
+            },
+            {
+              "type": "anyComponentStyle",
+              "maximumWarning": "4kb",
+              "maximumError": "8kb"
+            }
+          ],
+          "outputHashing": "all"
+        },
+        "development": {
+          "optimization": false,
+          "extractLicenses": false,
+          "sourceMap": true
+        }
+      }
+    },
+    "serve": {
+      "continuous": true,
+      "executor": "@angular/build:dev-server",
+      "defaultConfiguration": "development",
+      "configurations": {
+        "production": {
+          "buildTarget": "self-service:build:production"
+        },
+        "development": {
+          "buildTarget": "self-service:build:development"
+        }
+      }
+    },
+    "lint": {
+      "executor": "@nx/eslint:lint"
+    },
+    "test": {
+      "executor": "@angular/build:unit-test",
+      "options": {
+        "watch": false
+      }
+    },
+    "serve-static": {
+      "continuous": true,
+      "executor": "@nx/web:file-server",
+      "options": {
+        "buildTarget": "self-service:build",
+        "staticFilePath": "dist/apps/self-service/browser",
+        "spa": true
+      }
+    }
+  }
+}

apps/self-service/src/app/app.config.ts

@@ -0,0 +1,10 @@
+import {
+  ApplicationConfig,
+  provideBrowserGlobalErrorListeners,
+} from '@angular/core';
+import { provideRouter } from '@angular/router';
+import { appRoutes } from './app.routes';
+
+export const appConfig: ApplicationConfig = {
+  providers: [provideBrowserGlobalErrorListeners(), provideRouter(appRoutes)],
+};

apps/self-service/src/app/app.html

@@ -0,0 +1,5 @@
+<main>
+  <h1>Zelfservice — BIG-registratie</h1>
+  <p>Portaal voor zorgprofessionals. Inloggen en indienen volgt in S-08c.</p>
+  <router-outlet></router-outlet>
+</main>

apps/self-service/src/app/app.routes.ts

@@ -0,0 +1,3 @@
+import { Route } from '@angular/router';
+
+export const appRoutes: Route[] = [];

apps/self-service/src/app/app.spec.ts

@@ -0,0 +1,17 @@
+import { TestBed } from '@angular/core/testing';
+import { App } from './app';
+
+describe('App', () => {
+  beforeEach(async () => {
+    await TestBed.configureTestingModule({
+      imports: [App],
+    }).compileComponents();
+  });
+
+  it('renders the self-service portal heading', async () => {
+    const fixture = TestBed.createComponent(App);
+    await fixture.whenStable();
+    const compiled = fixture.nativeElement as HTMLElement;
+    expect(compiled.querySelector('h1')?.textContent).toContain('Zelfservice');
+  });
+});

apps/self-service/src/app/app.ts

@@ -0,0 +1,12 @@
+import { Component } from '@angular/core';
+import { RouterModule } from '@angular/router';
+
+@Component({
+  imports: [RouterModule],
+  selector: 'app-root',
+  templateUrl: './app.html',
+  styleUrl: './app.css',
+})
+export class App {
+  protected title = 'self-service';
+}

apps/self-service/src/index.html

@@ -0,0 +1,13 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8" />
+    <title>self-service</title>
+    <base href="/" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <link rel="icon" type="image/x-icon" href="favicon.ico" />
+  </head>
+  <body>
+    <app-root></app-root>
+  </body>
+</html>

apps/self-service/src/main.ts

@@ -0,0 +1,5 @@
+import { bootstrapApplication } from '@angular/platform-browser';
+import { appConfig } from './app/app.config';
+import { App } from './app/app';
+
+bootstrapApplication(App, appConfig).catch((err) => console.error(err));

apps/self-service/src/styles.css

@@ -0,0 +1 @@
+/* You can add global styles to this file, and also import other style files */

apps/self-service/tsconfig.app.json

@@ -0,0 +1,9 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": "../../dist/out-tsc",
+    "types": []
+  },
+  "include": ["src/**/*.ts"],
+  "exclude": ["src/**/*.spec.ts", "src/**/*.test.ts"]
+}

apps/self-service/tsconfig.json

@@ -0,0 +1,31 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "strict": true,
+    "noImplicitOverride": true,
+    "noPropertyAccessFromIndexSignature": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
+    "isolatedModules": true,
+    "target": "es2022",
+    "moduleResolution": "bundler",
+    "emitDecoratorMetadata": false,
+    "module": "preserve"
+  },
+  "angularCompilerOptions": {
+    "enableI18nLegacyMessageIdFormat": false,
+    "strictInjectionParameters": true,
+    "strictInputAccessModifiers": true,
+    "strictTemplates": true
+  },
+  "files": [],
+  "include": [],
+  "references": [
+    {
+      "path": "./tsconfig.app.json"
+    },
+    {
+      "path": "./tsconfig.spec.json"
+    }
+  ]
+}

apps/self-service/tsconfig.spec.json

@@ -0,0 +1,8 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": "../../dist/out-tsc",
+    "types": ["vitest/globals"]
+  },
+  "include": ["src/**/*.ts", "src/**/*.d.ts"]
+}

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

@@ -5,6 +5,96 @@ copy-pasteable walkthrough against a local `make up` stack.
 
 ---
 
+## S-08a — Nx workspace + self-service portal skeleton
+
+**Outcome:** the frontend foundation — an Nx (pnpm) monorepo with the `self-service` Angular app
+(standalone + signals), lint/test/build green in a CI Node lane. The login + submit form follow in
+S-08c.
+
+```bash
+# From a fresh clone (Node 24 + pnpm 11):
+pnpm install                       # native builds are pre-approved in pnpm-workspace.yaml
+pnpm nx test self-service          # Vitest component test
+pnpm nx build self-service         # production build
+pnpm nx serve self-service         # → http://localhost:4200  (placeholder page)
+# Or the CI-equivalent one-shot:
+make frontend                      # install + nx lint/test/build
+```
+
+> Nx manages only `apps/`+`libs/`; the .NET services stay on `dotnet`/the Makefile. NL Design System
+> and the real form arrive in S-08c (#67); see `docs/frontend-decisions.md`.
+
+---
+
+## 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

docs/frontend-decisions.md

@@ -0,0 +1,50 @@
+# Frontend decisions
+
+A running log of frontend tooling and component decisions (CLAUDE.md §10). One entry per
+decision; record *why*, and note any deviation from NL Design System.
+
+---
+
+## Workspace & tooling (S-08a, #65)
+
+The portals live in an **Nx monorepo at the repository root**, alongside the .NET `services/`.
+
+- **Package manager: pnpm.** Native build scripts are approved explicitly in `pnpm-workspace.yaml`
+  under `allowBuilds` (pnpm 11 fails the install otherwise). Node 24, pnpm 11.
+- **Angular, standalone components + signals, no NgModules** (§10). Apps are generated with
+  `@nx/angular:application`.
+- **Unit tests: Vitest** via Angular's built-in `@angular/build:unit-test` (the `vitest-angular`
+  runner). **Angular Testing Library** is added for component tests when the first real components
+  land (S-08c); the S-08a placeholder uses a plain `TestBed` render assertion.
+- **Lint: ESLint** (flat config, `@nx/eslint`).
+- **Nx is scoped to `apps/` + `libs/` only.** The `@nx/docker` and `@nx/dotnet` plugins are **not**
+  installed — the .NET services are built by `dotnet`/the Makefile, and `@nx/docker` would otherwise
+  infer every `services/*/Dockerfile` as an unnamed Nx project and break the project graph.
+- **No Nx Cloud.** `nxCloudId` is stripped from `nx.json`; remote caching would depend on an
+  external service, and the repo is Gitea-only (§8.7). Nx's "configure-ai-agents" additions
+  (`.claude/settings.json`, a CLAUDE.md section referencing a GitHub marketplace) are **not**
+  committed for the same reason.
+- **CI:** a `frontend` job (`make frontend` → `pnpm install --frozen-lockfile` + `nx run-many -t
+  lint test build`) runs on pnpm + Node, with pinned action URLs (§15).
+
+**NL Design System:** not yet introduced — the S-08a app is a placeholder. NL DS components arrive
+with the submit form (S-08c, #67); any deviation from NL DS will be recorded here.
+
+---
+
+## API client generator (S-08b, #66)
+
+`libs/api-client` is **generated from `services/bff/openapi.json`** — never hand-written (§10).
+
+- **Generator: orval** (`client: 'angular'`), a **node-based** generator (no Java, unlike
+  `openapi-generator`), so it runs in the pnpm/Node CI lane. It emits an injectable
+  `BffApiV1Service` using Angular's `HttpClient` — which means the DigiD bearer token can be attached
+  by an **`HttpInterceptor`** (S-08c), the idiomatic Angular approach; a fetch-based SDK would bypass
+  the interceptor pipeline.
+- **Config:** `libs/api-client/orval.config.ts` (single-file output into `src/lib/generated/`,
+  `clean: true`, prettier). **Regenerate with `nx run api-client:generate`** after the BFF spec
+  changes; the output is deterministic (idempotent), and `src/lib/generated/` is never hand-edited.
+- **Tested** against a mocked BFF via `HttpClientTesting` (`libs/api-client/src/lib/bff-api.spec.ts`).
+- The BFF endpoints carry no `operationId`, so orval synthesises method names
+  (`postSelfServiceRegistrations`, `getOpenbaarRegister`); adding explicit operation ids to the BFF
+  is a possible later polish.

docs/runbooks/gitea-actions-gotchas.md

@@ -14,6 +14,7 @@ those containers share a filesystem — or a `localhost` — breaks.
 | `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) |
 
 ---
 
@@ -125,6 +126,22 @@ guard. Inputs are the same (`name`, `path`, `if-no-files-found`), so it is a dro
 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

eslint.config.mjs

@@ -0,0 +1,58 @@
+import nx from '@nx/eslint-plugin';
+
+export default [
+  ...nx.configs['flat/base'],
+  ...nx.configs['flat/typescript'],
+  ...nx.configs['flat/javascript'],
+  {
+    ignores: [
+      '**/dist',
+      '**/vite.config.*.timestamp*',
+      '**/vitest.config.*.timestamp*',
+    ],
+  },
+  {
+    files: ['**/*.ts', '**/*.tsx', '**/*.js', '**/*.jsx'],
+    rules: {
+      '@nx/enforce-module-boundaries': [
+        'error',
+        {
+          enforceBuildableLibDependency: true,
+          allow: ['^.*/eslint(\\.base)?\\.config\\.[cm]?[jt]s$'],
+          depConstraints: [
+            {
+              sourceTag: 'scope:shared',
+              onlyDependOnLibsWithTags: ['scope:shared'],
+            },
+            {
+              sourceTag: 'scope:shop',
+              onlyDependOnLibsWithTags: ['scope:shop', 'scope:shared'],
+            },
+            {
+              sourceTag: 'scope:api',
+              onlyDependOnLibsWithTags: ['scope:api', 'scope:shared'],
+            },
+            {
+              sourceTag: 'type:data',
+              onlyDependOnLibsWithTags: ['type:data'],
+            },
+          ],
+        },
+      ],
+    },
+  },
+  {
+    files: [
+      '**/*.ts',
+      '**/*.tsx',
+      '**/*.cts',
+      '**/*.mts',
+      '**/*.js',
+      '**/*.jsx',
+      '**/*.cjs',
+      '**/*.mjs',
+    ],
+    // Override or add rules here
+    rules: {},
+  },
+];

infra/docker-compose.yml

@@ -285,7 +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"
@@ -306,12 +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:
@@ -320,6 +359,13 @@ 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) ────────────────────────────────────────────────

infra/openzaak/seed_catalogus.py

@@ -210,6 +210,10 @@ def main():
     print(f"zaaktypen in BIG: {names}")
     assert "BIG-REGISTRATIE" in names, "BIG-REGISTRATIE not listed"
     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)")
 
 

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

libs/api-client/README.md

@@ -0,0 +1,7 @@
+# api-client
+
+This library was generated with [Nx](https://nx.dev).
+
+## Running unit tests
+
+Run `nx test api-client` to execute the unit tests.

libs/api-client/eslint.config.mjs

@@ -0,0 +1,34 @@
+import nx from '@nx/eslint-plugin';
+import baseConfig from '../../eslint.config.mjs';
+
+export default [
+  ...nx.configs['flat/angular'],
+  ...nx.configs['flat/angular-template'],
+  ...baseConfig,
+  {
+    files: ['**/*.ts'],
+    rules: {
+      '@angular-eslint/directive-selector': [
+        'error',
+        {
+          type: 'attribute',
+          prefix: 'lib',
+          style: 'camelCase',
+        },
+      ],
+      '@angular-eslint/component-selector': [
+        'error',
+        {
+          type: 'element',
+          prefix: 'lib',
+          style: 'kebab-case',
+        },
+      ],
+    },
+  },
+  {
+    files: ['**/*.html'],
+    // Override or add rules here
+    rules: {},
+  },
+];

libs/api-client/orval.config.ts

@@ -0,0 +1,17 @@
+import { defineConfig } from 'orval';
+
+// Generates the BFF client (Angular HttpClient service + models) from the committed
+// OpenAPI contract. Never hand-edit the generated output — re-run `nx run api-client:generate`
+// after the BFF spec changes (CLAUDE.md §10; docs/frontend-decisions.md).
+export default defineConfig({
+  bff: {
+    input: '../../services/bff/openapi.json',
+    output: {
+      target: './src/lib/generated/bff-api.ts',
+      client: 'angular',
+      mode: 'single',
+      clean: true,
+      prettier: true,
+    },
+  },
+});

libs/api-client/project.json

@@ -0,0 +1,20 @@
+{
+  "name": "api-client",
+  "$schema": "../../node_modules/nx/schemas/project-schema.json",
+  "sourceRoot": "libs/api-client/src",
+  "prefix": "lib",
+  "projectType": "library",
+  "tags": [],
+  "targets": {
+    "lint": {
+      "executor": "@nx/eslint:lint"
+    },
+    "generate": {
+      "executor": "nx:run-commands",
+      "options": {
+        "command": "orval --config orval.config.ts",
+        "cwd": "libs/api-client"
+      }
+    }
+  }
+}

libs/api-client/src/index.ts

@@ -0,0 +1,3 @@
+// The BFF API client is generated from services/bff/openapi.json (orval); never hand-edit
+// src/lib/generated. Re-run `nx run api-client:generate` after the BFF spec changes.
+export * from './lib/generated/bff-api';

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

@@ -0,0 +1,50 @@
+import { provideHttpClient } from '@angular/common/http';
+import {
+  HttpTestingController,
+  provideHttpClientTesting,
+} from '@angular/common/http/testing';
+import { TestBed } from '@angular/core/testing';
+import {
+  BffApiV1Service,
+  type OpenbaarEntry,
+  type SubmitAccepted,
+} from '../index';
+
+describe('BffApiV1Service (generated from services/bff/openapi.json)', () => {
+  let service: BffApiV1Service;
+  let http: HttpTestingController;
+
+  beforeEach(() => {
+    TestBed.configureTestingModule({
+      providers: [provideHttpClient(), provideHttpClientTesting()],
+    });
+    service = TestBed.inject(BffApiV1Service);
+    http = TestBed.inject(HttpTestingController);
+  });
+
+  afterEach(() => http.verify());
+
+  it('submits a registration via POST /self-service/registrations', () => {
+    let result: SubmitAccepted | undefined;
+    service.postSelfServiceRegistrations().subscribe((r) => (result = r));
+
+    const req = http.expectOne('/self-service/registrations');
+    expect(req.request.method).toBe('POST');
+    req.flush({ registrationId: 'reg-1', status: 'Ingediend' });
+
+    expect(result?.registrationId).toBe('reg-1');
+    expect(result?.status).toBe('Ingediend');
+  });
+
+  it('reads the openbaar register via GET /openbaar/register with the query', () => {
+    let rows: OpenbaarEntry[] | undefined;
+    service.getOpenbaarRegister({ q: 'abc' }).subscribe((r) => (rows = r));
+
+    const req = http.expectOne((r) => r.url === '/openbaar/register');
+    expect(req.request.method).toBe('GET');
+    expect(req.request.params.get('q')).toBe('abc');
+    req.flush([{ id: 'abc-111', status: 'INGEDIEND' }]);
+
+    expect(rows?.[0].id).toBe('abc-111');
+  });
+});

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

@@ -0,0 +1,216 @@
+/**
+ * Generated by orval v8.19.0 🍺
+ * Do not edit manually.
+ * Bff.Api | v1
+ * OpenAPI spec version: 1.0.0
+ */
+import {
+  HttpClient,
+  HttpHeaders,
+  HttpResponse as AngularHttpResponse
+} from '@angular/common/http';
+import type {
+  HttpContext,
+  HttpEvent,
+  HttpParams
+} from '@angular/common/http';
+
+import {
+  Injectable,
+  inject
+} from '@angular/core';
+
+import {
+  Observable
+} from 'rxjs';
+
+export interface OpenbaarEntry {
+  id: string;
+  status: string;
+}
+
+export interface SubmitAccepted {
+  registrationId: string;
+  status: string;
+}
+
+export type GetOpenbaarRegisterParams = {
+q?: string;
+};
+
+interface HttpClientOptions {
+  readonly headers?: HttpHeaders | Record<string, string | string[]>;
+  readonly context?: HttpContext;
+  readonly params?:
+        | HttpParams
+      | Record<string, string | number | boolean | Array<string | number | boolean>>;
+  readonly reportProgress?: boolean;
+  readonly withCredentials?: boolean;
+  readonly credentials?: RequestCredentials;
+  readonly keepalive?: boolean;
+  readonly priority?: RequestPriority;
+  readonly cache?: RequestCache;
+  readonly mode?: RequestMode;
+  readonly redirect?: RequestRedirect;
+  readonly referrer?: string;
+  readonly integrity?: string;
+  readonly referrerPolicy?: ReferrerPolicy;
+  readonly transferCache?: {includeHeaders?: string[]} | boolean;
+  readonly timeout?: number;
+}
+
+type HttpClientBodyOptions = HttpClientOptions & {
+  readonly observe?: 'body';
+};
+
+type HttpClientEventOptions = HttpClientOptions & {
+  readonly observe: 'events';
+};
+
+type HttpClientResponseOptions = HttpClientOptions & {
+  readonly observe: 'response';
+};
+
+type HttpClientObserveOptions = HttpClientOptions & {
+  readonly observe?: 'body' | 'events' | 'response';
+};
+
+type AngularHttpParamValue = string | number | boolean | Array<string | number | boolean>;
+type AngularHttpParamValueWithNullable = AngularHttpParamValue | null;
+
+function filterParams(
+  params: Record<string, unknown>,
+  requiredNullableKeys?: ReadonlySet<string>,
+  preserveRequiredNullables?: false,
+  passthroughKeys?: undefined,
+): Record<string, AngularHttpParamValue>;
+function filterParams(
+  params: Record<string, unknown>,
+  requiredNullableKeys: ReadonlySet<string> | undefined,
+  preserveRequiredNullables: true,
+  passthroughKeys?: undefined,
+): Record<string, AngularHttpParamValueWithNullable>;
+function filterParams(
+  params: Record<string, unknown>,
+  requiredNullableKeys: ReadonlySet<string> | undefined,
+  preserveRequiredNullables: boolean | undefined,
+  passthroughKeys: ReadonlySet<string>,
+): Record<string, unknown>;
+function filterParams(
+  params: Record<string, unknown>,
+  requiredNullableKeys: ReadonlySet<string> = new Set(),
+  preserveRequiredNullables = false,
+  passthroughKeys: ReadonlySet<string> = new Set(),
+): Record<string, unknown> {
+  const filteredParams: Record<string, unknown> = {};
+  for (const [key, value] of Object.entries(params)) {
+    if (passthroughKeys.has(key)) {
+      if (value !== undefined) {
+        filteredParams[key] = value;
+      }
+      continue;
+    }
+    if (Array.isArray(value)) {
+      const filtered = value.filter(
+        (item) =>
+          item != null &&
+          (typeof item === 'string' ||
+            typeof item === 'number' ||
+            typeof item === 'boolean'),
+      ) as Array<string | number | boolean>;
+      if (filtered.length) {
+        filteredParams[key] = filtered;
+      }
+    } else if (
+      preserveRequiredNullables &&
+      value === null &&
+      requiredNullableKeys.has(key)
+    ) {
+      filteredParams[key] = null;
+    } else if (
+      value != null &&
+      (typeof value === 'string' ||
+        typeof value === 'number' ||
+        typeof value === 'boolean')
+    ) {
+      filteredParams[key] = value;
+    }
+  }
+  return filteredParams;
+}
+
+
+
+
+
+@Injectable({ providedIn: 'root' })
+export class BffApiV1Service {
+  private readonly http = inject(HttpClient);
+ postSelfServiceRegistrations<TData = SubmitAccepted>( options?: HttpClientBodyOptions): Observable<TData>;
+ postSelfServiceRegistrations<TData = SubmitAccepted>( options?: HttpClientEventOptions): Observable<HttpEvent<TData>>;
+ postSelfServiceRegistrations<TData = SubmitAccepted>( options?: HttpClientResponseOptions): Observable<AngularHttpResponse<TData>>;
+  postSelfServiceRegistrations<TData = SubmitAccepted>(
+     options?: HttpClientObserveOptions): Observable<TData | HttpEvent<TData> | AngularHttpResponse<TData>> {
+    if (options?.observe === 'events') {
+      return this.http.post<TData>(
+      `/self-service/registrations`,
+      undefined,{
+        ...(options as Omit<NonNullable<typeof options>, 'observe'>),
+        observe: 'events',
+      }
+    );
+    }
+
+    if (options?.observe === 'response') {
+      return this.http.post<TData>(
+      `/self-service/registrations`,
+      undefined,{
+        ...(options as Omit<NonNullable<typeof options>, 'observe'>),
+        observe: 'response',
+      }
+    );
+    }
+
+    return this.http.post<TData>(
+      `/self-service/registrations`,
+      undefined,{
+        ...(options as Omit<NonNullable<typeof options>, 'observe'>),
+        observe: 'body',
+      }
+    );
+  }
+
+ getOpenbaarRegister<TData = OpenbaarEntry[]>(params?: GetOpenbaarRegisterParams, options?: HttpClientBodyOptions): Observable<TData>;
+ getOpenbaarRegister<TData = OpenbaarEntry[]>(params?: GetOpenbaarRegisterParams, options?: HttpClientEventOptions): Observable<HttpEvent<TData>>;
+ getOpenbaarRegister<TData = OpenbaarEntry[]>(params?: GetOpenbaarRegisterParams, options?: HttpClientResponseOptions): Observable<AngularHttpResponse<TData>>;
+  getOpenbaarRegister<TData = OpenbaarEntry[]>(
+    params?: GetOpenbaarRegisterParams, options?: HttpClientObserveOptions): Observable<TData | HttpEvent<TData> | AngularHttpResponse<TData>> {
+    const filteredParams = filterParams({...params, ...options?.params}, new Set<string>([]));
+
+    if (options?.observe === 'events') {
+      return this.http.get<TData>(
+      `/openbaar/register`,{
+    ...(options as Omit<NonNullable<typeof options>, 'observe'>),
+        observe: 'events',
+        params: filteredParams,}
+    );
+    }
+
+    if (options?.observe === 'response') {
+      return this.http.get<TData>(
+      `/openbaar/register`,{
+    ...(options as Omit<NonNullable<typeof options>, 'observe'>),
+        observe: 'response',
+        params: filteredParams,}
+    );
+    }
+
+    return this.http.get<TData>(
+      `/openbaar/register`,{
+    ...(options as Omit<NonNullable<typeof options>, 'observe'>),
+        observe: 'body',
+        params: filteredParams,}
+    );
+  }
+
+};

libs/api-client/src/test-setup.ts

@@ -0,0 +1,5 @@
+import '@angular/compiler';
+import '@analogjs/vitest-angular/setup-snapshots';
+import { setupTestBed } from '@analogjs/vitest-angular/setup-testbed';
+
+setupTestBed({ zoneless: false });

libs/api-client/tsconfig.json

@@ -0,0 +1,31 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "isolatedModules": true,
+    "target": "es2022",
+    "moduleResolution": "bundler",
+    "strict": true,
+    "noImplicitOverride": true,
+    "noPropertyAccessFromIndexSignature": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
+    "emitDecoratorMetadata": false,
+    "module": "preserve"
+  },
+  "angularCompilerOptions": {
+    "enableI18nLegacyMessageIdFormat": false,
+    "strictInjectionParameters": true,
+    "strictInputAccessModifiers": true,
+    "strictTemplates": true
+  },
+  "files": [],
+  "include": [],
+  "references": [
+    {
+      "path": "./tsconfig.lib.json"
+    },
+    {
+      "path": "./tsconfig.spec.json"
+    }
+  ]
+}

libs/api-client/tsconfig.lib.json

@@ -0,0 +1,26 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": "../../dist/out-tsc",
+    "declaration": true,
+    "declarationMap": true,
+    "inlineSources": true,
+    "types": []
+  },
+  "include": ["src/**/*.ts"],
+  "exclude": [
+    "src/**/*.spec.ts",
+    "src/**/*.test.ts",
+    "vite.config.ts",
+    "vite.config.mts",
+    "vitest.config.ts",
+    "vitest.config.mts",
+    "src/**/*.test.tsx",
+    "src/**/*.spec.tsx",
+    "src/**/*.test.js",
+    "src/**/*.spec.js",
+    "src/**/*.test.jsx",
+    "src/**/*.spec.jsx",
+    "src/test-setup.ts"
+  ]
+}

libs/api-client/tsconfig.spec.json

@@ -0,0 +1,29 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": "../../dist/out-tsc",
+    "types": [
+      "vitest/globals",
+      "vitest/importMeta",
+      "vite/client",
+      "node",
+      "vitest"
+    ]
+  },
+  "include": [
+    "vite.config.ts",
+    "vite.config.mts",
+    "vitest.config.ts",
+    "vitest.config.mts",
+    "src/**/*.test.ts",
+    "src/**/*.spec.ts",
+    "src/**/*.test.tsx",
+    "src/**/*.spec.tsx",
+    "src/**/*.test.js",
+    "src/**/*.spec.js",
+    "src/**/*.test.jsx",
+    "src/**/*.spec.jsx",
+    "src/**/*.d.ts"
+  ],
+  "files": ["src/test-setup.ts"]
+}

libs/api-client/vite.config.mts

@@ -0,0 +1,28 @@
+/// <reference types='vitest' />
+import { defineConfig } from 'vite';
+import angular from '@analogjs/vite-plugin-angular';
+import { nxViteTsPaths } from '@nx/vite/plugins/nx-tsconfig-paths.plugin';
+import { nxCopyAssetsPlugin } from '@nx/vite/plugins/nx-copy-assets.plugin';
+
+export default defineConfig(() => ({
+  root: __dirname,
+  cacheDir: '../../node_modules/.vite/libs/api-client',
+  plugins: [angular(), nxViteTsPaths(), nxCopyAssetsPlugin(['*.md'])],
+  // Uncomment this if you are using workers.
+  // worker: {
+  //   plugins: () => [ nxViteTsPaths() ],
+  // },
+  test: {
+    name: 'api-client',
+    watch: false,
+    globals: true,
+    environment: 'jsdom',
+    include: ['{src,tests}/**/*.{test,spec}.{js,mjs,cjs,ts,mts,cts,jsx,tsx}'],
+    setupFiles: ['src/test-setup.ts'],
+    reporters: ['default'],
+    coverage: {
+      reportsDirectory: '../../coverage/libs/api-client',
+      provider: 'v8' as const,
+    },
+  },
+}));

mkdocs.yml

@@ -31,7 +31,9 @@ nav:
       - "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
+  - Frontend decisions: frontend-decisions.md
   - Demo script: demo-script.md
   - Runbooks:
       - CI: runbooks/ci.md

nx.json

@@ -0,0 +1,120 @@
+{
+  "$schema": "./node_modules/nx/schemas/nx-schema.json",
+  "namedInputs": {
+    "default": [
+      "{projectRoot}/**/*",
+      "sharedGlobals"
+    ],
+    "production": [
+      "default",
+      "!{projectRoot}/.eslintrc.json",
+      "!{projectRoot}/eslint.config.mjs",
+      "!{projectRoot}/**/?(*.)+(spec|test).[jt]s?(x)?(.snap)",
+      "!{projectRoot}/tsconfig.spec.json",
+      "!{projectRoot}/src/test-setup.[jt]s",
+      "!{projectRoot}/jest.config.[jt]s",
+      "!{projectRoot}/test-setup.[jt]s"
+    ],
+    "sharedGlobals": []
+  },
+  "targetDefaults": {
+    "@angular/build:application": {
+      "cache": true,
+      "dependsOn": [
+        "^build"
+      ],
+      "inputs": [
+        "production",
+        "^production"
+      ]
+    },
+    "@nx/eslint:lint": {
+      "cache": true,
+      "inputs": [
+        "default",
+        "^default",
+        "{workspaceRoot}/.eslintrc.json",
+        "{workspaceRoot}/.eslintignore",
+        "{workspaceRoot}/eslint.config.mjs",
+        "{workspaceRoot}/tools/eslint-rules/**/*"
+      ]
+    },
+    "@nx/esbuild:esbuild": {
+      "cache": true,
+      "dependsOn": [
+        "^build"
+      ],
+      "inputs": [
+        "production",
+        "^production"
+      ]
+    },
+    "@nx/js:tsc": {
+      "cache": true,
+      "dependsOn": [
+        "^build"
+      ],
+      "inputs": [
+        "production",
+        "^production"
+      ]
+    },
+    "@nx/vitest:test": {
+      "cache": true,
+      "inputs": [
+        "default",
+        "^production"
+      ]
+    },
+    "@angular/build:unit-test": {
+      "cache": true,
+      "inputs": [
+        "default",
+        "^production"
+      ]
+    }
+  },
+  "plugins": [
+    {
+      "plugin": "@nx/eslint/plugin",
+      "options": {
+        "targetName": "lint"
+      }
+    },
+    {
+      "plugin": "@nx/vite/plugin",
+      "options": {
+        "buildTargetName": "build",
+        "serveTargetName": "serve",
+        "devTargetName": "dev",
+        "previewTargetName": "preview",
+        "serveStaticTargetName": "serve-static",
+        "typecheckTargetName": "typecheck",
+        "buildDepsTargetName": "build-deps",
+        "watchDepsTargetName": "watch-deps"
+      }
+    },
+    {
+      "plugin": "@nx/vitest",
+      "options": {
+        "testTargetName": "test"
+      }
+    }
+  ],
+  "generators": {
+    "@nx/angular:application": {
+      "e2eTestRunner": "playwright",
+      "linter": "eslint",
+      "style": "css",
+      "unitTestRunner": "vitest-analog"
+    },
+    "@nx/angular:library": {
+      "linter": "eslint",
+      "unitTestRunner": "vitest-analog"
+    },
+    "@nx/angular:component": {
+      "style": "css"
+    }
+  },
+  "analytics": false
+}

package.json

@@ -0,0 +1,65 @@
+{
+  "name": "register-referentie",
+  "version": "0.0.0",
+  "license": "MIT",
+  "scripts": {},
+  "private": true,
+  "dependencies": {
+    "@angular-devkit/build-angular": "21.2.7",
+    "@angular/common": "21.2.9",
+    "@angular/compiler": "21.2.9",
+    "@angular/core": "21.2.9",
+    "@angular/forms": "21.2.9",
+    "@angular/platform-browser": "21.2.9",
+    "@angular/router": "21.2.9",
+    "rxjs": "~7.8.0",
+    "zone.js": "0.16.0"
+  },
+  "devDependencies": {
+    "@analogjs/vite-plugin-angular": "2.2.0",
+    "@analogjs/vitest-angular": "2.2.0",
+    "@angular-devkit/core": "21.2.7",
+    "@angular-devkit/schematics": "21.2.7",
+    "@angular/build": "21.2.7",
+    "@angular/cli": "21.2.7",
+    "@angular/compiler-cli": "21.2.9",
+    "@angular/language-service": "21.2.9",
+    "@eslint/js": "^9.8.0",
+    "@nx/angular": "23.0.1",
+    "@nx/devkit": "23.0.1",
+    "@nx/esbuild": "23.0.1",
+    "@nx/eslint": "23.0.1",
+    "@nx/eslint-plugin": "23.0.1",
+    "@nx/js": "23.0.1",
+    "@nx/vite": "23.0.1",
+    "@nx/vitest": "23.0.1",
+    "@nx/web": "23.0.1",
+    "@nx/workspace": "23.0.1",
+    "@oxc-project/runtime": "^0.115.0",
+    "@schematics/angular": "21.2.7",
+    "@swc-node/register": "1.11.1",
+    "@swc/core": "1.15.8",
+    "@swc/helpers": "0.5.18",
+    "@types/node": "20.19.9",
+    "@typescript-eslint/utils": "^8.40.0",
+    "@vitest/coverage-v8": "~4.1.0",
+    "@vitest/ui": "~4.1.0",
+    "angular-eslint": "21.3.1",
+    "esbuild": "^0.27.0",
+    "eslint": "^9.8.0",
+    "eslint-config-prettier": "^10.0.0",
+    "jiti": "2.4.2",
+    "jsdom": "~22.1.0",
+    "jsonc-eslint-parser": "^2.1.0",
+    "nx": "23.0.1",
+    "orval": "^8.19.0",
+    "prettier": "^3.8.1",
+    "ts-node": "10.9.1",
+    "tslib": "^2.3.0",
+    "typescript": "~5.9.2",
+    "typescript-eslint": "^8.40.0",
+    "vite": "8.0.9",
+    "vite-tsconfig-paths": "^5.1.4",
+    "vitest": "~4.1.0"
+  }
+}

pnpm-workspace.yaml

@@ -0,0 +1,10 @@
+packages: []
+allowBuilds:
+  '@parcel/watcher': true
+  less: true
+  esbuild: true
+  '@swc/core': true
+  nx: true
+  unrs-resolver: true
+  lmdb: true
+  msgpackr-extract: true

register-referentie.slnx

@@ -9,6 +9,9 @@
   </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/">

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/Registration.cs

@@ -7,8 +7,6 @@ namespace Big.Domain;
 /// </summary>
 public sealed class Registration
 {
-    // STUB (red): mutators are no-ops and Submit leaves the bsn empty so the behaviour tests
-    // compile and fail on their assertions. The green commit implements the invariants.
     private Registration(RegistrationId id, string bsn)
     {
         Id = id;
@@ -31,17 +29,39 @@ public sealed class Registration
     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) => new(RegistrationId.New(), string.Empty);
+    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)
     {
-        // STUB (red).
+        ArgumentException.ThrowIfNullOrWhiteSpace(processInstanceId);
+        ProcessInstanceId = processInstanceId;
     }
 
-    /// <summary>Attach the zaak the ACL opened. Idempotent on the same URL; a conflicting URL is rejected.</summary>
+    /// <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)
     {
-        // STUB (red).
+        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.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

@@ -20,6 +20,8 @@
 
   <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

@@ -21,7 +21,7 @@ public class RegistrationTests
     [InlineData("   ")]
     [InlineData(null)]
     public void Submitting_without_a_bsn_is_rejected(string? bsn)
-        => Assert.Throws<ArgumentException>(() => Registration.Submit(bsn!));
+        => Assert.ThrowsAny<ArgumentException>(() => Registration.Submit(bsn!));
 
     [Fact]
     public void Recording_the_started_process_keeps_its_instance_id()
@@ -33,6 +33,17 @@ public class RegistrationTests
         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()
     {
@@ -71,7 +82,9 @@ public class RegistrationTests
         var registration = Registration.Submit("123456782");
         registration.AttachZaak(new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
 
-        Assert.Throws<InvalidOperationException>(
+        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

@@ -1,4 +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
+    }
+  }
+}

tests/acceptance/Acceptance.csproj

@@ -9,6 +9,8 @@
 
   <ItemGroup>
     <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <!-- The BFF acceptance scenario drives the real HTTP endpoints in-process (ADR-0010). -->
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="10.0.8" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
     <PackageReference Include="Reqnroll.xUnit" Version="3.3.4" />
     <PackageReference Include="xunit" Version="2.9.3" />
@@ -19,6 +21,8 @@
     <ProjectReference Include="..\..\services\acl\Acl.Application\Acl.Application.csproj" />
     <ProjectReference Include="..\..\services\acl\Acl.Infrastructure\Acl.Infrastructure.csproj" />
     <ProjectReference Include="..\..\services\event-subscriber\EventSubscriber.Application\EventSubscriber.Application.csproj" />
+    <ProjectReference Include="..\..\services\domain\Big.Application\Big.Application.csproj" />
+    <ProjectReference Include="..\..\services\bff\Bff.Api\Bff.Api.csproj" />
   </ItemGroup>
 
 </Project>

tests/acceptance/Features/BffToegang.feature

@@ -0,0 +1,22 @@
+# language: en
+# Drives S-07 (#8). 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). Tokens are minted with a local test key; real Keycloak validation is verify-bff.
+Feature: Toegang via de BFF
+  Als portaal wil ik uitsluitend via de BFF met de backend praten
+  zodat tokenvalidatie en veilige velden centraal geregeld zijn.
+
+  Scenario: Indienen met een geldig token wordt doorgezet naar het domein
+    Given a zorgprofessional with a valid DigiD token for BSN "123456782"
+    When they submit a registration via the BFF
+    Then the BFF accepts it and forwards BSN "123456782" to the domain
+
+  Scenario: Indienen zonder token wordt geweigerd
+    Given a caller without a token
+    When they submit a registration via the BFF
+    Then the BFF rejects it as unauthorized
+
+  Scenario: Het openbaar register is anoniem en toont geen BSN
+    Given the projection contains a zaak "abc-111" for BSN "123456782"
+    When the openbaar register is queried anonymously
+    Then the response lists "abc-111" without exposing the BSN

tests/acceptance/Features/RegistratieIndienen.feature

@@ -0,0 +1,18 @@
+# language: en
+# Drives S-05 (#6). A zorgprofessional submits a registration; the Domain Service starts the
+# registratie process and, via the external-task worker, opens a zaak through the ACL and records
+# it on the aggregate (ADR-0009). This scenario exercises the use cases against in-memory stand-ins
+# for the Workflow Client and the ACL; real Flowable + ACL + OpenZaak delivery is verified by the
+# live-stack check (verify-domain).
+Feature: Een registratie indienen
+  Als zorgprofessional wil ik mijn registratie indienen
+  zodat er een registratieproces start en een zaak wordt geopend.
+
+  Scenario: Indienen start het registratieproces en opent een zaak
+    Given a zorgprofessional submits a registration for BSN "123456782"
+    When the domain service handles the submission
+    Then a registratie process is started for the registration
+    And the registration has status "INGEDIEND"
+    When the OpenZaakAanmaken external task is handled for the registration
+    Then a zaak is opened via the ACL for BSN "123456782"
+    And the zaak is recorded on the registration

tests/acceptance/Steps/BffToegangSteps.cs

@@ -0,0 +1,83 @@
+using System.Net;
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
+using Acceptance.Support;
+using Bff.Api;
+using Reqnroll;
+using Xunit;
+
+namespace Acceptance.Steps;
+
+/// <summary>Bindings for <c>BffToegang.feature</c> (S-07). Drives the real BFF over HTTP with a
+/// fake domain + projection and locally-minted tokens (ADR-0010). One host per scenario.</summary>
+[Binding]
+public sealed class BffToegangSteps : IDisposable
+{
+    private readonly BffAcceptanceHost _host = new();
+    private HttpClient _client = null!;
+    private string? _token;
+    private HttpResponseMessage? _response;
+
+    [Given("a zorgprofessional with a valid DigiD token for BSN \"(.*)\"")]
+    public void GivenAValidToken(string bsn)
+    {
+        _token = BffAcceptanceHost.MintToken(bsn);
+        _client = _host.CreateClient();
+    }
+
+    [Given("a caller without a token")]
+    public void GivenNoToken() => _client = _host.CreateClient();
+
+    [Given("the projection contains a zaak \"(.*)\" for BSN \"(.*)\"")]
+    public void GivenTheProjectionContains(string zaakId, string bsn)
+    {
+        _host.Projection.Entries.Add(new ProjectionEntry(zaakId, "INGEDIEND", bsn, null));
+        _client = _host.CreateClient();
+    }
+
+    [When("they submit a registration via the BFF")]
+    public async Task WhenTheySubmit()
+    {
+        var request = new HttpRequestMessage(HttpMethod.Post, "/self-service/registrations")
+        {
+            Content = JsonContent.Create(new { }),
+        };
+        if (_token is not null)
+            request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", _token);
+        _response = await _client.SendAsync(request);
+    }
+
+    [When("the openbaar register is queried anonymously")]
+    public async Task WhenTheOpenbaarRegisterIsQueried()
+        => _response = await _client.GetAsync("/openbaar/register");
+
+    [Then("the BFF accepts it and forwards BSN \"(.*)\" to the domain")]
+    public void ThenAcceptedAndForwarded(string bsn)
+    {
+        Assert.Equal(HttpStatusCode.Accepted, _response!.StatusCode);
+        Assert.Equal(bsn, _host.Domain.SubmittedBsn);
+    }
+
+    [Then("the BFF rejects it as unauthorized")]
+    public void ThenUnauthorized()
+    {
+        Assert.Equal(HttpStatusCode.Unauthorized, _response!.StatusCode);
+        Assert.Null(_host.Domain.SubmittedBsn);
+    }
+
+    [Then("the response lists \"(.*)\" without exposing the BSN")]
+    public async Task ThenListsWithoutBsn(string zaakId)
+    {
+        Assert.Equal(HttpStatusCode.OK, _response!.StatusCode);
+        var body = await _response.Content.ReadAsStringAsync();
+        Assert.Contains(zaakId, body);
+        Assert.DoesNotContain("123456782", body);
+    }
+
+    public void Dispose()
+    {
+        _response?.Dispose();
+        _client?.Dispose();
+        _host.Dispose();
+    }
+}

tests/acceptance/Steps/RegistratieIndienenSteps.cs

@@ -0,0 +1,54 @@
+using Acceptance.Support;
+using Big.Application;
+using Big.Domain;
+using Reqnroll;
+using Xunit;
+
+namespace Acceptance.Steps;
+
+/// <summary>Bindings for <c>RegistratieIndienen.feature</c> (S-05). Drives the SubmitRegistration
+/// and OpenZaakWorker use cases against in-memory ports; one instance per scenario.</summary>
+[Binding]
+public sealed class RegistratieIndienenSteps
+{
+    private readonly InMemoryWorkflowClient _workflow = new();
+    private readonly InMemoryAclClient _acl = new();
+    private readonly InMemoryRegistrationStore _store = new();
+    private string _bsn = "";
+    private RegistrationId _id;
+
+    [Given("a zorgprofessional submits a registration for BSN \"(.*)\"")]
+    public void GivenAZorgprofessionalSubmitsARegistration(string bsn) => _bsn = bsn;
+
+    [When("the domain service handles the submission")]
+    public async Task WhenTheDomainServiceHandlesTheSubmission()
+        => _id = await new SubmitRegistration(_store, _workflow).HandleAsync(new SubmitRegistrationCommand(_bsn));
+
+    [Then("a registratie process is started for the registration")]
+    public void ThenARegistratieProcessIsStarted()
+        => Assert.Equal(_id, _workflow.StartedFor);
+
+    [Then("the registration has status \"(.*)\"")]
+    public async Task ThenTheRegistrationHasStatus(string expected)
+    {
+        var registration = await _store.GetAsync(_id);
+        Assert.NotNull(registration);
+        Assert.Equal(expected, registration.Status.ToString().ToUpperInvariant());
+        Assert.Equal(InMemoryWorkflowClient.StartedProcessInstanceId, registration.ProcessInstanceId);
+    }
+
+    [When("the OpenZaakAanmaken external task is handled for the registration")]
+    public async Task WhenTheExternalTaskIsHandled()
+        => await new OpenZaakWorker(_store, _acl).HandleAsync(new OpenZaakJob("job-acc-1", _id));
+
+    [Then("a zaak is opened via the ACL for BSN \"(.*)\"")]
+    public void ThenAZaakIsOpenedViaTheAcl(string bsn)
+        => Assert.Equal(bsn, _acl.OpenedForBsn);
+
+    [Then("the zaak is recorded on the registration")]
+    public async Task ThenTheZaakIsRecordedOnTheRegistration()
+    {
+        var registration = await _store.GetAsync(_id);
+        Assert.Equal(InMemoryAclClient.OpenedZaakUrl, registration!.ZaakUrl);
+    }
+}

tests/acceptance/Support/BffAcceptanceHost.cs

@@ -0,0 +1,80 @@
+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.JsonWebTokens;
+using Microsoft.IdentityModel.Protocols.OpenIdConnect;
+using Microsoft.IdentityModel.Tokens;
+
+namespace Acceptance.Support;
+
+/// <summary>Hosts the real BFF in-process for the acceptance scenario, with fake downstreams and a
+/// local test signing key so tokens can be minted without a live Keycloak (ADR-0010).</summary>
+public sealed class BffAcceptanceHost : WebApplicationFactory<Program>
+{
+    private static readonly SymmetricSecurityKey TestKey =
+        new(Encoding.UTF8.GetBytes("acceptance-bff-signing-key-at-least-256-bits-long!!"));
+
+    public CapturingDomainClient Domain { get; } = new();
+    public StubProjectionClient Projection { get; } = new();
+
+    public static string MintToken(string bsn) => new JsonWebTokenHandler().CreateToken(new SecurityTokenDescriptor
+    {
+        Claims = new Dictionary<string, object> { ["bsn"] = bsn },
+        Expires = DateTime.UtcNow.AddMinutes(30),
+        SigningCredentials = new SigningCredentials(TestKey, SecurityAlgorithms.HmacSha256),
+    });
+
+    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 =>
+            {
+                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 = TestKey,
+                    ClockSkew = TimeSpan.Zero,
+                };
+            });
+        });
+    }
+}
+
+/// <summary>Records the bsn the BFF forwarded.</summary>
+public sealed class CapturingDomainClient : IDomainClient
+{
+    public string? SubmittedBsn { get; private set; }
+
+    public Task<SubmitAccepted> SubmitRegistrationAsync(string bsn, CancellationToken ct = default)
+    {
+        SubmittedBsn = bsn;
+        return Task.FromResult(new SubmitAccepted("reg-acc-1", "Ingediend"));
+    }
+}
+
+/// <summary>Serves configurable projection rows.</summary>
+public sealed class StubProjectionClient : IProjectionClient
+{
+    public List<ProjectionEntry> Entries { get; } = [];
+
+    public Task<IReadOnlyList<ProjectionEntry>> GetRegisterAsync(CancellationToken ct = default)
+        => Task.FromResult<IReadOnlyList<ProjectionEntry>>(Entries);
+}

tests/acceptance/Support/InMemoryDomainPorts.cs

@@ -0,0 +1,50 @@
+using Big.Application;
+using Big.Domain;
+
+namespace Acceptance.Support;
+
+/// <summary>An in-memory Workflow Client for the domain acceptance scenario: it records which
+/// registration a process was started for and returns a fixed instance id. The acceptance test
+/// drives the use case without a running Flowable (live verification is the verify-domain check).</summary>
+public sealed class InMemoryWorkflowClient : IWorkflowClient
+{
+    public const string StartedProcessInstanceId = "proc-acc-1";
+
+    public RegistrationId? StartedFor { get; private set; }
+
+    public Task<string> StartRegistrationProcessAsync(RegistrationId registrationId, CancellationToken ct = default)
+    {
+        StartedFor = registrationId;
+        return Task.FromResult(StartedProcessInstanceId);
+    }
+}
+
+/// <summary>An in-memory ACL stand-in: records the bsn it opened a zaak for and returns a fixed URL,
+/// so the scenario verifies the domain crosses the ACL boundary (§8.1) without a running OpenZaak.</summary>
+public sealed class InMemoryAclClient : IAclClient
+{
+    public static readonly Uri OpenedZaakUrl = new("http://openzaak/zaken/api/v1/zaken/acc-zaak");
+
+    public string? OpenedForBsn { get; private set; }
+
+    public Task<Uri> OpenZaakAsync(string bsn, CancellationToken ct = default)
+    {
+        OpenedForBsn = bsn;
+        return Task.FromResult(OpenedZaakUrl);
+    }
+}
+
+/// <summary>An in-memory registration store for the domain acceptance scenario.</summary>
+public sealed class InMemoryRegistrationStore : IRegistrationStore
+{
+    private readonly Dictionary<RegistrationId, Registration> _byId = [];
+
+    public Task SaveAsync(Registration registration, CancellationToken ct = default)
+    {
+        _byId[registration.Id] = registration;
+        return Task.CompletedTask;
+    }
+
+    public Task<Registration?> GetAsync(RegistrationId id, CancellationToken ct = default)
+        => Task.FromResult(_byId.GetValueOrDefault(id));
+}