fix(acceptance): implement the resolve API in the in-memory ZGW gateway (refs #113)

The acceptance InMemoryZaakGateway now implements IZaakGateway's new
Resolve{Zaaktype,Informatieobjecttype}UrlAsync, and the "een zaak openen" step
configures the ACL by identificatie + points the fake's resolved zaaktype at the
scenario URL — the Release build (which compiles tests/acceptance) failed without
this. All 17 acceptance + 54 ACL unit tests green.

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

Makefile

@@ -43,7 +43,7 @@ export DOCKER_HOST := unix://$(PODMAN_SOCK)
 endif
 endif
 
-.PHONY: ci lint build unit mutation frontend integration verify verify-up verify-acl verify-nrc verify-projection verify-bff verify-domain verify-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 verify-local local-down changelog openzaak-up openzaak-smoke openzaak-seed openzaak-down stack-up stack-smoke stack-down keycloak-up keycloak-smoke keycloak-down flowable-up flowable-smoke flowable-down help
 
 ## ci: run the full pipeline — lint, build, unit, mutation, frontend, verify (mirrors Gitea Actions)
 ## `verify` is the live-stack stage (full stack up once → ACL + notification checks).
@@ -114,6 +114,11 @@ local:
 	docker compose -f $(LOCAL_COMPOSE) up -d --build
 	WAIT_TIMEOUT=420 bash infra/wait-healthy.sh $(WAIT_SVCS)
 
+## verify-local: acceptance check for the local stack (S-B04) — a fresh `make local` completes the
+## whole flow (zaaktype seeded + DMN deployed + NRC abonnement) with NO manual seeding.
+verify-local:
+	bash infra/run-local-flow-check.sh
+
 ## local-down: stop and remove the bind-mount stack
 local-down:
 	docker compose -f $(LOCAL_COMPOSE) down --volumes

docs/architecture/adr-0020-local-stack-self-seeds.md

@@ -0,0 +1,92 @@
+# ADR-0020: The local stack self-seeds the zaaktype, DMN, and NRC abonnement at bring-up
+
+- **Status:** Accepted
+- **Date:** 2026-07-22
+- **Deciders:** Respellion engineering
+- **Relates to:** S-B04 (#110). Local-stack twin of the seeding the verify-* scripts do for CI
+  (`infra/run-domain-check.sh`, `infra/verify-notification-driver.py`). Superseded in part by S-27
+  (#113), which would let the ACL resolve its zaaktype by identificatie and remove the URL injection.
+
+## Context
+
+`infra/docker-compose.local.yml` is the host-browser-friendly stack (`make local`) — the one a
+developer clicks through the portals with. It had drifted behind three slices, so a fresh bring-up
+could not complete the flow:
+
+1. The ACL pointed at a placeholder zaaktype (`…/00000000-…`), so zaak creation failed with OpenZaak
+   `400` and the registratie process stuck at `OpenZaakAanmaken` (S-05).
+2. `flowable-init` deployed only `registratie.bpmn`, not `diploma-eligibility.dmn`, so completing
+   `WachtOpDocumenten` 404'd on the missing decision and never reached `Beoordelen` (S-10a/S-13).
+3. No NRC abonnement was registered, so notifications reached NRC and went nowhere — the projection
+   and the openbaar register stayed empty (S-06).
+
+The CI stack (`infra/docker-compose.yml`) does not hit this because its `verify-*` scripts seed the
+zaaktype, deploy the DMN, and register the abonnement at *test* time. The local stack has no such
+harness — a developer just runs `make local` and browses. The non-obvious wrinkle is (1): the
+zaaktype **UUID is assigned by OpenZaak at creation**, so the ACL's zaaktype URL is not knowable when
+the compose file is written and cannot be a static value.
+
+## Decision
+
+**Make the local stack self-seed at bring-up via one-shot init containers, and hand the ACL its
+server-assigned zaaktype URL through a shared-volume env file it sources on startup.**
+
+- **DMN (gap 2).** `flowable-init` now deploys `diploma-eligibility.dmn` to the DMN engine
+  (`/flowable-rest/dmn-api/dmn-repository/deployments`) as a separate deployment alongside the BPMN —
+  identical to the CI `flowable-init`. Idempotent.
+- **Zaaktype + ACL wiring (gap 1).** A `local-seed` one-shot runs the existing
+  `infra/openzaak/seed_catalogus.py` (`OZ_PUBLISH=1`) against OpenZaak and writes the resulting
+  `Acl__Defaults__ZaaktypeUrl` / `…InformatieobjecttypeUrl` / `Acl__OpenZaak__BaseUrl` into
+  `seed-env:/out/acl.env`. The ACL mounts that volume read-only and overrides its entrypoint to
+  `sh -c 'set -a; . /seed/acl.env; set +a; exec dotnet Acl.Api.dll'`, so the real values override the
+  compose placeholders before the app reads config. The ACL `depends_on: local-seed
+  (service_completed_successfully)`.
+- **Abonnement (gap 3).** A `nrc-subscribe` one-shot registers an abonnement on the `zaken` kanaal
+  pointing at the event-subscriber's `/notifications` callback (`infra/local/register-abonnement.py`).
+  It is a leaf — nothing depends on it — so it can wait for the event-subscriber without forming a
+  cycle with the ACL bootstrap.
+- **Reach OpenZaak/NRC by container IP, not service name.** Both the seed's ZTC calls and the
+  abonnement's `callbackUrl` are validated by Django's URLValidator, which rejects a single-label host
+  like `openzaak` / `event-subscriber`. The scripts resolve the target's container IP at runtime (as
+  `infra/run-domain-check.sh` does), keeping the seeded URLs valid **and** host-consistent — the ACL's
+  base URL is set to the same OpenZaak IP that owns the zaaktype URL.
+- **Acceptance.** `make verify-local` (`infra/run-local-flow-check.sh`) submits against a fresh stack
+  and asserts the zaak opens, the case reaches the werkbak after documents, and the reference appears
+  in the openbaar register — the red-to-green test for all three gaps.
+
+## Consequences
+
+**Positive**
+
+- A fresh `make local` completes the full demo (submit → werkbak → openbaar) with no manual seeding —
+  the slice's stated outcome.
+- Reuses the proven CI mechanisms (`seed_catalogus.py`, the DMN deploy, the abonnement driver) rather
+  than inventing new ones; the only genuinely new piece is the entrypoint-sourced env file.
+- No service code changes — the fix is entirely in `infra/` (compose + two small scripts), so the ACL
+  image and the CI stack are untouched.
+
+**Negative / costs**
+
+- The two compose files diverge further: the CI stack seeds at test time, the local stack at bring-up.
+  Mitigated by reusing the same underlying scripts and cross-referencing them.
+- The ACL entrypoint override couples the local ACL to the seed-written file path (`/seed/acl.env`);
+  if the seed fails, the ACL fails to start (loud, healthcheck-visible — preferred over silently
+  running with a placeholder).
+- Container-IP-based URLs are re-derived on each bring-up; a keep-volumes restart with a changed
+  OpenZaak IP relies on OpenZaak rebuilding hyperlinked URLs from the request host (it does) so the
+  idempotent re-seed reports current-IP URLs.
+
+## Alternatives considered
+
+- **ACL resolves its zaaktype by identificatie (`BIG-REGISTRATIE`) at startup.** The cleaner,
+  less-brittle design — no server-assigned URL to capture — and it would help the CI stack too. But it
+  changes a service's runtime behaviour and its config contract, needs new ACL tests + mutation
+  coverage, and still needs a seed step to *create* the zaaktype. Deliberately split out as its own
+  slice with its own ADR (S-27 / #113) rather than folded into this infra-only fix.
+- **A documented `make local-seed` step run after `make local`.** Smallest change, but it fails the
+  slice's "no manual seeding" outcome — the local stack is exactly the one meant to just work in a
+  browser. Rejected.
+- **Fixed zaaktype UUID via OpenZaak `setup_configuration`/fixtures.** OpenZaak assigns UUIDs on POST;
+  declaratively creating a fully *published* zaaktype (statustypen + resultaattypen validated against
+  the Selectielijst + roltypen + iot relations) is not something `setup_configuration` supports
+  cleanly in 1.28.2. Rejected as more fragile than reusing `seed_catalogus.py`.

docs/architecture/adr-0021-acl-resolves-zaaktype-by-identificatie.md

@@ -0,0 +1,67 @@
+# ADR-0021: The ACL resolves its zaaktype by identificatie, not a pinned URL
+
+- **Status:** Accepted
+- **Date:** 2026-07-22
+- **Deciders:** Respellion engineering
+- **Relates to:** S-27 (#113), proposed in #117. The cleaner design deliberately split out of S-B04
+  (#110, ADR-0020), which fixed the local stack with an infra-only bootstrap.
+
+## Context
+
+The ACL was handed a **pinned zaaktype URL** (`Acl__Defaults__ZaaktypeUrl`) and diploma
+informatieobjecttype URL. OpenZaak assigns those UUIDs at creation, so the URL is not knowable when
+the compose file is written — every stack had to seed the catalogus and then capture + inject the
+resulting URLs out of band: `run-domain-check.sh` for CI, and the `local-seed` → `acl.env` bootstrap
+(ADR-0020) for `make local`. Brittle, and a stale/placeholder URL failed opaquely (OpenZaak 400).
+
+## Decision
+
+**The ACL resolves its zaaktype (by `identificatie`) and diploma informatieobjecttype (by
+`omschrijving`) from OpenZaak's Catalogi API, instead of being handed the URLs.**
+
+- **Config:** `AclDefaults.ZaaktypeUrl`/`InformatieobjecttypeUrl` → `ZaaktypeIdentificatie`
+  (`BIG-REGISTRATIE`) / `InformatieobjecttypeOmschrijving` (`Diploma`).
+- **Lookup (gateway, §8.1):** `GET /catalogi/api/v1/zaaktypen?status=definitief&identificatie=…` →
+  the published zaaktype URL; `GET /catalogi/api/v1/informatieobjecttypen?status=definitief` matched
+  on `omschrijving`. Reuses the gateway's existing catalogus-query machinery.
+- **Timing = lazy + cached (`CachedZaaktypeCatalog`).** Resolve on first use (first zaak open /
+  document store) and cache for the process lifetime. Lazy avoids a startup ordering coupling — the
+  ACL never crash-loops when it boots before the catalogus is published. A **failed** resolution is
+  not cached, so it is retried on the next call (e.g. once the zaaktype is published); a restart
+  re-resolves.
+- **Failure mode:** no published match → a clear "No published zaaktype with identificatie '…' found
+  in OpenZaak — is the BIG catalogus seeded and published?" error, replacing the opaque placeholder
+  400.
+
+## Consequences
+
+**Positive**
+
+- No stack captures or injects a server-assigned URL any more: `run-domain-check.sh` drops the
+  `ACL_ZAAKTYPE_URL`/`ACL_INFORMATIEOBJECTTYPE_URL` capture+inject, `docker-compose.yml`/`.local.yml`
+  drop the placeholder URL env, and `local-seed`/`acl.env` shrink to a single line. The ACL
+  self-configures from the catalogus it already talks to.
+- The failure mode is legible (a named error instead of a 400 on a zeros-UUID).
+
+**Negative / costs**
+
+- The ACL still needs its OpenZaak **BaseUrl** pointed at a **URL-valid host (a container IP)**, so
+  the base-URL injection from ADR-0020 stays (the local `acl.env` now carries only that; CI keeps
+  `ACL_OPENZAAK_BASEURL`). This is **not** something S-27 can remove: OpenZaak validates the
+  `zaaktype` field on zaak-create with Django's URLValidator and **rejects a single-label host**
+  (`http://openzaak:8000/…` → `zaaktype: bad-url, "Voer een geldige URL in."`, confirmed empirically).
+  So ADR-0020's `seed-env` volume + ACL entrypoint shim are **simplified, not deleted**.
+- New branching in the gateway/resolver → unit + integration test surface; the mutation ratchet
+  covers it (§5).
+- A seed step still **creates + publishes** the zaaktype (this ADR changes only discovery). Reaching
+  OpenZaak's Catalogi API to *seed* likewise needs the IP host (its query params hit the same
+  URLValidator) — unchanged from before.
+
+## Alternatives considered
+
+- **Resolve at startup** (eager). Simpler cache, but reintroduces the ordering coupling (crash-loop
+  if the catalogus isn't published yet). Rejected in favour of lazy.
+- **Per-request resolution** (no cache). No stale-cache risk, but a Catalogi lookup on every ACL
+  operation. Rejected; a process-lifetime cache with restart-to-refresh is enough here.
+- **Keep the pinned URL** (status quo / ADR-0020 only). Rejected — the brittleness this ADR removes is
+  exactly what S-27 was carved out to fix.

docs/demo-script.md

@@ -5,6 +5,55 @@ copy-pasteable walkthrough against a local `make up` stack.
 
 ---
 
+## S-B04 — `make local` completes the whole flow with no manual seeding (#110, ADR-0020)
+
+**Outcome:** the host-browser stack (`make local`) now self-seeds at bring-up — it publishes the BIG
+zaaktype and wires the ACL to it, deploys the `diploma-eligibility` DMN, and registers the NRC
+abonnement — so a fresh bring-up runs submit → werkbak → openbaar without the manual seeding the
+`verify-*` scripts do for CI. (Previously the process stuck at `OpenZaakAanmaken`, the werkbak stayed
+empty, and the openbaar register showed nothing.)
+
+```bash
+# 1. Fresh bring-up (self-seeding init containers: local-seed, nrc-subscribe; DMN in flowable-init).
+make local
+
+# 2. Assert the whole flow works with no manual seeding — submit opens a zaak, documents route it to
+#    the werkbak, and the reference appears in the openbaar register:
+make verify-local     # → "OK — a fresh local stack completed the flow with no manual seeding ..."
+
+# 3. Or by hand in the browser: log in at http://localhost:8140 (jan-burger / test123), submit +
+#    upload a PDF, then approve it in the werkbak at http://localhost:8142 (merel-behandelaar /
+#    test123); it shows as INGESCHREVEN in the openbaar register at http://localhost:8141.
+```
+
+> The zaaktype is discovered by the ACL itself since S-27 (below); `local-seed`'s `acl.env` now
+> carries only OpenZaak's IP base URL, which the ACL still needs because OpenZaak rejects a
+> single-label host on zaak-create (ADR-0020 + ADR-0021).
+
+---
+
+## S-27 — ACL resolves its zaaktype by identificatie, not a pinned URL (#113, ADR-0021)
+
+**Outcome:** the ACL discovers its BIG zaaktype (by `identificatie`) and diploma informatieobjecttype
+(by `omschrijving`) from OpenZaak's Catalogi API, instead of being handed the server-assigned URLs.
+No user-visible behaviour change — the flow runs exactly as before — but no stack captures/injects a
+zaaktype URL any more, and a missing catalogus now fails with a clear message instead of an opaque 400.
+
+```bash
+# The live ACL↔OpenZaak integration test proves resolution against a real seeded OpenZaak:
+make verify-acl     # → "resolves the published BIG-REGISTRATIE zaaktype + Diploma informatieobjecttype by business key"
+
+# End-to-end unchanged (the ACL self-discovers the zaaktype during the flow):
+make verify-local   # local stack — still green, now with no zaaktype-URL injection
+make verify-domain  # CI stack — recreates the ACL pointed only at OpenZaak's IP (no URL to inject)
+```
+
+> The ACL still needs its OpenZaak base URL at a URL-valid host (a container IP): OpenZaak's
+> URLValidator rejects a single-label host like `openzaak:8000` on zaak-create. So ADR-0020's base-URL
+> injection stays; only the zaaktype/informatieobjecttype **URL** injection is gone (ADR-0021).
+
+---
+
 ## S-08d — Walking skeleton complete: browser → submit, end-to-end
 
 **Outcome:** the self-service portal is served in the stack and the full front-of-house happy path

infra/docker-compose.local.yml

@@ -1,7 +1,12 @@
 # LOCAL development stack — runs with a plain `docker compose up`, no make / no
-# seed step / no bash. Use this on a local engine (Docker Desktop on Windows or
+# external seed step / no bash. Use this on a local engine (Docker Desktop on Windows or
 # macOS, or rootless Podman on Linux).
 #
+# Self-seeding (S-B04, #110, ADR-0020): unlike the CI stack — where the verify-* scripts seed the
+# zaaktype and register the NRC abonnement at test time — this stack does that itself, via one-shot
+# init containers (local-seed, nrc-subscribe) + a DMN deploy in flowable-init, so a fresh bring-up
+# completes the whole flow with no manual steps. `make verify-local` asserts it.
+#
 #   docker compose -f infra/docker-compose.local.yml up -d --build         # podman
 #   docker compose -f infra/docker-compose.local.yml up -d --build --wait  # Docker Desktop
 #   docker compose -f infra/docker-compose.local.yml down --volumes
@@ -257,38 +262,79 @@ services:
     restart: "no"
     volumes:
       - ../workflows/registratie.bpmn:/work/registratie.bpmn:ro,z
+      - ../workflows/diploma-eligibility.dmn:/work/diploma-eligibility.dmn:ro,z
     command:
       - sh
       - -c
       - |
-        base=http://flowable-rest:8080/flowable-rest/service/repository/deployments
-        until curl -sf -u rest-admin:test "$$base" >/dev/null 2>&1; do echo "waiting for flowable-rest..."; sleep 3; done
-        if curl -s -u rest-admin:test "$$base?name=registratie" | grep -q '"name":"registratie"'; then
-          echo "registratie already deployed; skip"
+        svc=http://flowable-rest:8080/flowable-rest/service/repository/deployments
+        dmn=http://flowable-rest:8080/flowable-rest/dmn-api/dmn-repository/deployments
+        until curl -sf -u rest-admin:test "$$svc" >/dev/null 2>&1; do echo "waiting for flowable-rest..."; sleep 3; done
+        # Deploy the DMN to the DMN engine and the BPMN to the process engine as SEPARATE deployments:
+        # flowable-rest does NOT cascade a .dmn bundled in a process .bar into the DMN engine, so the DMN
+        # must go via dmn-api. The registratie process's DMN service task then resolves the decision across
+        # deployments by key (S-13, ADR-0016). Without this the WachtOpDocumenten completion 404s on the
+        # missing decision and the case never reaches Beoordelen (S-B04). Both steps are idempotent.
+        if curl -s -u rest-admin:test "$$dmn" | grep -q '"name":"diploma-eligibility.dmn"'; then
+          echo "diploma-eligibility DMN already deployed; skip"
         else
-          curl -sf -u rest-admin:test -F 'file=@/work/registratie.bpmn;filename=registratie.bpmn' "$$base" >/dev/null && echo "deployed registratie"
+          curl -sf -u rest-admin:test -F 'file=@/work/diploma-eligibility.dmn;filename=diploma-eligibility.dmn' "$$dmn" >/dev/null && echo "deployed diploma-eligibility DMN"
+        fi
+        if curl -s -u rest-admin:test "$$svc?name=registratie" | grep -q '"name":"registratie"'; then
+          echo "registratie BPMN already deployed; skip"
+        else
+          curl -sf -u rest-admin:test -F 'file=@/work/registratie.bpmn;filename=registratie.bpmn' "$$svc" >/dev/null && echo "deployed registratie BPMN"
         fi
     depends_on:
       flowable-rest:
         condition: service_started
     networks: [cg]
 
+  # ── Local bootstrap: seed the zaaktype + wire the ACL (S-B04, #110, ADR-0020) ─────────────────
+  # The zaaktype UUID is assigned by OpenZaak at creation, so it can't be a static value in this
+  # file. This one-shot seeds + publishes the BIG zaaktype (and the Diploma informatieobjecttype)
+  # and writes their server-assigned URLs into a shared volume as acl.env, which the ACL sources on
+  # startup (below). It is the local-stack equivalent of what infra/run-domain-check.sh does for CI.
+  # Reaches OpenZaak by its container IP because a single-label host fails OpenZaak's URLValidator.
+  local-seed:
+    image: docker.io/library/python:3-slim
+    restart: "no"
+    volumes:
+      - ./openzaak/seed_catalogus.py:/work/seed_catalogus.py:ro,z
+      - ./local/seed-zaaktype.sh:/work/seed-zaaktype.sh:ro,z
+      - seed-env:/out
+    command: ["sh", "/work/seed-zaaktype.sh"]
+    depends_on:
+      openzaak:
+        condition: service_healthy
+    networks: [cg]
+
   # ── ACL ──────────────────────────────────────────────────────────────────
   acl:
     build:
       context: ../services/acl
       dockerfile: Dockerfile
     image: register-referentie/acl:dev
+    # The ACL discovers its zaaktype + informatieobjecttype URLs from the Catalogi API by the business
+    # keys below (S-27, ADR-0021), so no URL is injected. It still needs its OpenZaak BaseUrl pointed at
+    # a URL-valid host (OpenZaak rejects a single-label host like `openzaak` on zaak-create), so the
+    # local-seed one-shot writes that IP base into seed-env:/seed/acl.env, which the entrypoint sources
+    # (set -a) before the app starts. A runtime-generated env file is why we override the entrypoint here
+    # rather than use `env_file:` (which compose reads at parse time, before the seed has run).
+    entrypoint: ["/bin/sh", "-c", "set -a; . /seed/acl.env; set +a; exec dotnet Acl.Api.dll"]
     environment:
-      Acl__OpenZaak__BaseUrl: http://openzaak:8000/
+      Acl__OpenZaak__BaseUrl: http://openzaak:8000/   # placeholder; seed-env/acl.env supplies the IP base
       Acl__OpenZaak__ClientId: big-reference-seed
       Acl__OpenZaak__Secret: insecure-dev-secret-change-me
       Acl__Defaults__Bronorganisatie: "517439943"
       Acl__Defaults__VerantwoordelijkeOrganisatie: "517439943"
       Acl__Defaults__Vertrouwelijkheidaanduiding: openbaar
-      Acl__Defaults__ZaaktypeUrl: ${ACL_ZAAKTYPE_URL:-http://openzaak:8000/catalogi/api/v1/zaaktypen/00000000-0000-0000-0000-000000000000}
+      Acl__Defaults__ZaaktypeIdentificatie: BIG-REGISTRATIE
+      Acl__Defaults__InformatieobjecttypeOmschrijving: Diploma
     ports:
       - "8100:8080"
+    volumes:
+      - seed-env:/seed:ro
     healthcheck:
       test: ["CMD", "curl", "-fsS", "http://localhost:8080/health"]
       interval: 5s
@@ -298,6 +344,8 @@ services:
     depends_on:
       openzaak:
         condition: service_healthy
+      local-seed:
+        condition: service_completed_successfully
     networks: [cg]
 
   # ── BFF ──────────────────────────────────────────────────────────────────
@@ -400,6 +448,31 @@ services:
         condition: service_healthy
     networks: [cg]
 
+  # ── Local bootstrap: register the NRC abonnement (S-B04, #110, ADR-0020) ──────────────────────
+  # Without a subscription, OpenZaak's notifications reach NRC and are delivered nowhere, so the
+  # projection (and the openbaar register) stay empty. This one-shot registers an abonnement on the
+  # `zaken` kanaal pointing at the event-subscriber's /notifications callback — the CI equivalent is
+  # infra/verify-notification-driver.py. The callback uses the event-subscriber's container IP (a
+  # single-label host fails NRC's URLValidator). It is a leaf (nothing depends on it), so it can wait
+  # for the event-subscriber without creating a cycle with the ACL bootstrap.
+  nrc-subscribe:
+    image: docker.io/library/python:3-slim
+    restart: "no"
+    volumes:
+      - ./local/register-abonnement.py:/work/register-abonnement.py:ro,z
+    environment:
+      NRC_BASE: http://nrc-web:8000
+      SINK_HOST: event-subscriber
+      SINK_PORT: "8080"
+      SINK_AUTH: ${NOTIFICATION_WEBHOOK_TOKEN:-Bearer big-reference-notifications}
+    command: ["python", "/work/register-abonnement.py"]
+    depends_on:
+      nrc-web:
+        condition: service_healthy
+      event-subscriber:
+        condition: service_started
+    networks: [cg]
+
   projection-api:
     build:
       context: ..
@@ -492,6 +565,8 @@ volumes:
   nrc-db:
   flowable-db:
   projection-db:
+  # Carries the seed-generated acl.env (server-assigned zaaktype URLs) from local-seed to the ACL.
+  seed-env:
 
 networks:
   cg:

infra/docker-compose.yml

@@ -15,12 +15,12 @@
 #
 #   docker compose -f infra/docker-compose.yml up -d --build --wait
 #
-# After first boot, seed the BIG catalogus and note the zaaktype URL:
-#   python infra/openzaak/seed_catalogus.py
-# Then set ACL_ZAAKTYPE_URL in a .env file or your shell and re-up the acl
-# service:
-#   export ACL_ZAAKTYPE_URL=http://openzaak:8000/catalogi/api/v1/zaaktypen/<uuid>
-#   docker compose -f infra/docker-compose.yml up -d acl
+# After first boot, seed + publish the BIG catalogus:
+#   OZ_PUBLISH=1 python infra/openzaak/seed_catalogus.py
+# The ACL discovers the zaaktype by identificatie (S-27, ADR-0021), so there is no URL to inject —
+# just point its BaseUrl at an OpenZaak host OpenZaak accepts on zaak-create (a container IP; a
+# single-label host is rejected):
+#   ACL_OPENZAAK_BASEURL=http://<openzaak-ip>:8000/ docker compose -f infra/docker-compose.yml up -d acl
 
 services:
 
@@ -304,11 +304,12 @@ services:
       Acl__Defaults__Bronorganisatie: "517439943"
       Acl__Defaults__VerantwoordelijkeOrganisatie: "517439943"
       Acl__Defaults__Vertrouwelijkheidaanduiding: openbaar
-      # Override with the real zaaktype URL after running seed_catalogus.py.
-      Acl__Defaults__ZaaktypeUrl: ${ACL_ZAAKTYPE_URL:-http://openzaak:8000/catalogi/api/v1/zaaktypen/00000000-0000-0000-0000-000000000000}
-      # The informatieobjecttype a diploma is filed under (S-10b). Placeholder until seed_catalogus.py
-      # (OZ_PUBLISH=1) reports the real URL, which verify-domain injects like the zaaktype URL.
-      Acl__Defaults__InformatieobjecttypeUrl: ${ACL_INFORMATIEOBJECTTYPE_URL:-http://openzaak:8000/catalogi/api/v1/informatieobjecttypen/00000000-0000-0000-0000-000000000000}
+      # The ACL resolves the (server-assigned) zaaktype + diploma informatieobjecttype URLs from the
+      # Catalogi API by these stable business keys (S-27, ADR-0021) — no URL to capture and inject.
+      # BaseUrl above stays overridable because OpenZaak rejects a single-label host on zaak creation,
+      # so verify-domain still points the ACL at OpenZaak's container IP.
+      Acl__Defaults__ZaaktypeIdentificatie: BIG-REGISTRATIE
+      Acl__Defaults__InformatieobjecttypeOmschrijving: Diploma
     ports:
       - "8100:8080"
     healthcheck:

infra/local/register-abonnement.py

@@ -0,0 +1,78 @@
+#!/usr/bin/env python3
+"""Local-stack bootstrap (S-B04, #110, ADR-0020) — register the NRC abonnement.
+
+Runs as the `nrc-subscribe` init container of infra/docker-compose.local.yml. Registers an
+abonnement on the `zaken` kanaal pointing at the event-subscriber's /notifications callback, so
+OpenZaak's notifications (zaak create + status set) reach the projection — without this the openbaar
+(public) register stays empty. This is what infra/verify-notification-driver.py does for CI (minus
+the test zaak it also creates).
+
+The callback host is the event-subscriber's resolved **container IP**, not `event-subscriber`, because
+NRC validates callbackUrl with Django's URLValidator (a single-label host is rejected — same reason the
+zaaktype seed uses OpenZaak's IP). Idempotent + restart-safe: it removes any stale /notifications
+abonnement first, then registers one for the current IP. Stdlib only.
+
+Env: NRC_BASE, SINK_HOST, SINK_PORT, SINK_AUTH, OZ_CLIENT_ID, OZ_SECRET.
+"""
+import base64, hashlib, hmac, json, os, socket, sys, time, urllib.error, urllib.request
+
+NRC = os.environ.get("NRC_BASE", "http://nrc-web:8000").rstrip("/")
+SINK_HOST = os.environ.get("SINK_HOST", "event-subscriber")
+SINK_PORT = os.environ.get("SINK_PORT", "8080")
+SINK_AUTH = os.environ.get("SINK_AUTH", "Bearer big-reference-notifications")
+CID = os.environ.get("OZ_CLIENT_ID", "big-reference-seed")
+SECRET = os.environ.get("OZ_SECRET", "insecure-dev-secret-change-me")
+
+
+def token():
+    b64 = lambda b: base64.urlsafe_b64encode(b).rstrip(b"=")
+    seg = (
+        b64(json.dumps({"alg": "HS256", "typ": "JWT"}, separators=(",", ":")).encode())
+        + b"."
+        + b64(json.dumps(
+            {"iss": CID, "iat": int(time.time()), "client_id": CID,
+             "user_id": "local-seed", "user_representation": "local-seed"},
+            separators=(",", ":")).encode())
+    )
+    return (seg + b"." + b64(hmac.new(SECRET.encode(), seg, hashlib.sha256).digest())).decode()
+
+
+def call(method, url, body=None):
+    data = json.dumps(body).encode() if body is not None else None
+    req = urllib.request.Request(url, data=data, method=method, headers={
+        "Authorization": "Bearer " + token(),
+        "Content-Type": "application/json", "Accept": "application/json"})
+    try:
+        with urllib.request.urlopen(req, timeout=30) as r:
+            raw = r.read()
+            return r.status, (json.loads(raw) if raw else None)
+    except urllib.error.HTTPError as e:
+        raw = e.read()
+        return e.code, (json.loads(raw) if raw else None)
+
+
+def main():
+    ip = socket.gethostbyname(SINK_HOST)
+    callback = f"http://{ip}:{SINK_PORT}/notifications"
+
+    # Restart-safe: drop any prior /notifications abonnement (its IP may be stale) before creating a
+    # fresh one for the current event-subscriber IP.
+    status, body = call("GET", f"{NRC}/api/v1/abonnement")
+    for ab in (body or []) if status == 200 else []:
+        if str(ab.get("callbackUrl", "")).endswith("/notifications"):
+            if ab.get("callbackUrl") == callback:
+                print(f"abonnement already current: {ab['url']}")
+                return
+            call("DELETE", ab["url"])
+            print(f"removed stale abonnement {ab['url']}")
+
+    status, ab = call("POST", f"{NRC}/api/v1/abonnement", {
+        "callbackUrl": callback, "auth": SINK_AUTH,
+        "kanalen": [{"naam": "zaken", "filters": {}}]})
+    if status != 201:
+        sys.exit(f"create abonnement -> {status}: {json.dumps(ab)}")
+    print(f"abonnement registered: {ab['url']} -> {callback}")
+
+
+if __name__ == "__main__":
+    main()

infra/local/seed-zaaktype.sh

@@ -0,0 +1,33 @@
+#!/bin/sh
+# Local-stack bootstrap (S-B04, #110, ADR-0020) — the "seed zaaktype + wire the ACL" step.
+#
+# Runs as the `local-seed` init container of infra/docker-compose.local.yml. It seeds + publishes
+# the BIG zaaktype (and the Diploma informatieobjecttype) into OpenZaak, then writes the resulting
+# **server-assigned** URLs into /out/acl.env, which the ACL entrypoint sources before starting. This
+# is the local-stack equivalent of what infra/run-domain-check.sh does for CI: the zaaktype UUID is
+# assigned by OpenZaak at creation, so it can't be a static value in the compose file.
+#
+# Why the container IP and not the `openzaak` service name: OpenZaak validates URL query params
+# (e.g. ?catalogus=) with Django's URLValidator, which rejects a single-label host like `openzaak`.
+# Seeding against the resolved IP keeps the seeded URLs valid AND host-consistent with the ACL, which
+# we point at the same IP below. See docs/runbooks/gitea-actions-gotchas.md and ADR-0020.
+set -eu
+
+oz_ip="$(python3 -c "import socket;print(socket.gethostbyname('openzaak'))")"
+OZ_BASE="http://${oz_ip}:8000"
+export OZ_BASE OZ_PUBLISH=1
+
+echo ">> seeding + publishing the BIG zaaktype at ${OZ_BASE} (idempotent)"
+out="$(python3 /work/seed_catalogus.py)"
+echo "$out"
+
+# Sanity-check that the zaaktype was actually published (the ACL discovers it by identificatie, S-27).
+printf '%s\n' "$out" | grep -q '^ZAAKTYPE_URL ' || { echo "ERROR: seed did not publish the zaaktype" >&2; exit 1; }
+
+# The ACL resolves the zaaktype/informatieobjecttype URLs itself (S-27, ADR-0021); the only value it
+# still needs injected is the OpenZaak base URL at a URL-valid host (the container IP), because OpenZaak
+# rejects a single-label host on zaak-create. The ACL entrypoint sources this.
+cat > /out/acl.env <<EOF
+Acl__OpenZaak__BaseUrl=${OZ_BASE}/
+EOF
+echo ">> wrote /out/acl.env (base=${OZ_BASE}/)"

infra/run-domain-check.sh

@@ -30,21 +30,18 @@ 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"
+echo ">> seeding + publishing a BIG zaaktype (idempotent)"
 sid="$(docker create --network "$net" -e "OZ_BASE=$oz_base" -e OZ_PUBLISH=1 python:3-slim python /seed.py)"
 docker cp "$here/openzaak/seed_catalogus.py" "$sid:/seed.py" >/dev/null
 seed_out="$(docker start -a "$sid")"
-zt_url="$(printf '%s\n' "$seed_out" | sed -n 's/^ZAAKTYPE_URL //p' | head -1)"
-iot_url="$(printf '%s\n' "$seed_out" | sed -n 's/^INFORMATIEOBJECTTYPE_URL //p' | head -1)"
 docker rm -f "$sid" >/dev/null
-[ -n "$zt_url" ] || { echo "ERROR: seed did not report a ZAAKTYPE_URL" >&2; exit 1; }
-[ -n "$iot_url" ] || { echo "ERROR: seed did not report an INFORMATIEOBJECTTYPE_URL" >&2; exit 1; }
-echo ">> zaaktype: $zt_url"
-echo ">> informatieobjecttype: $iot_url"
+printf '%s\n' "$seed_out" | grep -q '^ZAAKTYPE_URL ' || { echo "ERROR: seed did not publish the zaaktype" >&2; exit 1; }
 
-echo ">> recreating the acl service pointed at the seeded zaaktype + informatieobjecttype (host-consistent)"
-ACL_ZAAKTYPE_URL="$zt_url" ACL_INFORMATIEOBJECTTYPE_URL="$iot_url" ACL_OPENZAAK_BASEURL="$oz_base/" \
-  docker compose -f "$compose" up -d acl
+# The ACL resolves the zaaktype + informatieobjecttype by identificatie/omschrijving (S-27, ADR-0021),
+# so there is no URL to inject — only the OpenZaak base URL, pointed at the same host's container IP
+# (OpenZaak rejects a single-label host on zaak-create).
+echo ">> recreating the acl service pointed at OpenZaak's IP (it resolves the zaaktype itself, S-27)"
+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"

infra/run-local-flow-check.sh

@@ -0,0 +1,67 @@
+#!/usr/bin/env bash
+#
+# Acceptance check for the local stack (S-B04, #110): a fresh `make local` must complete the whole
+# flow with NO manual seeding. Run against an already-up local stack (infra/docker-compose.local.yml)
+# via the host-published ports. It exercises, and thereby covers, the three bring-up gaps the slice
+# fixes:
+#
+#   1. zaaktype seeded + ACL wired  -> a submitted registration opens a zaak (zaakUrl gets filled).
+#   2. diploma-eligibility DMN deployed -> providing documents completes WachtOpDocumenten, routes
+#      through the DMN, and the case lands on Beoordelen (visible in the behandel werkbak).
+#   3. NRC abonnement registered    -> the zaak shows up in the openbaar (public) register.
+#
+# Before the fix this fails at step 1 (ACL points at a placeholder zaaktype -> OpenZaak 400).
+set -euo pipefail
+
+DOM=${DOM:-http://localhost:8130}     # domain
+BFF=${BFF:-http://localhost:8080}     # bff (openbaar register)
+BSN=${BSN:-123456782}
+# A minimal, valid PDF, base64-encoded (the diploma upload).
+PDF_B64="$(printf '%%PDF-1.4\n1 0 obj<</Type/Catalog>>endobj\ntrailer<</Root 1 0 R>>\n%%%%EOF\n' | base64 | tr -d '\n')"
+
+echo ">> 1. submit a registration (no manual seeding expected)"
+loc="$(curl -fsS -D - -o /dev/null -X POST "$DOM/registrations" \
+  -H 'Content-Type: application/json' -d "{\"bsn\":\"$BSN\"}" \
+  | sed -n 's/\r$//; s/^[Ll]ocation: //p' | head -1)"
+[ -n "$loc" ] || { echo "FAIL: POST /registrations returned no Location" >&2; exit 1; }
+id="${loc##*/}"
+echo "   accepted: $id"
+
+echo ">> 2. poll until the ACL opens the zaak (proves the zaaktype is seeded + wired)"
+zaak=""
+for _ in $(seq 1 30); do
+  zaak="$(curl -fsS "$DOM$loc" | python3 -c 'import sys,json;print(json.load(sys.stdin).get("zaakUrl") or "")' 2>/dev/null || true)"
+  [ -n "$zaak" ] && break
+  sleep 3
+done
+[ -n "$zaak" ] || { echo "FAIL: zaak never opened — ACL zaaktype not wired (gap 1)" >&2; exit 1; }
+echo "   zaak opened: $zaak"
+
+echo ">> 3. provide documents (proves the diploma-eligibility DMN is deployed)"
+code="$(curl -s -o /dev/null -w '%{http_code}' -X POST "$DOM/registrations/$id/documents" \
+  -H 'Content-Type: application/json' \
+  -d "{\"bsn\":\"$BSN\",\"contentBase64\":\"$PDF_B64\",\"fileName\":\"diploma.pdf\",\"contentType\":\"application/pdf\"}")"
+[ "$code" = "204" ] || { echo "FAIL: provide documents -> $code (DMN missing routes WachtOpDocumenten to a 404 — gap 2)" >&2; exit 1; }
+echo "   documents accepted (204)"
+
+echo ">> 4. poll the werkbak until the registration awaits beoordeling (reached Beoordelen)"
+in_werkbak=""
+for _ in $(seq 1 20); do
+  in_werkbak="$(curl -fsS "$DOM/behandel/werkbak" | python3 -c "import sys,json;print(any(r.get('registrationId')=='$id' for r in json.load(sys.stdin)))" 2>/dev/null || true)"
+  [ "$in_werkbak" = "True" ] && break
+  sleep 3
+done
+[ "$in_werkbak" = "True" ] || { echo "FAIL: registration never reached the werkbak (gap 2)" >&2; exit 1; }
+echo "   in the werkbak"
+
+echo ">> 5. poll the openbaar register until the reference is publicly visible (proves NRC abonnement)"
+public=""
+for _ in $(seq 1 30); do
+  public="$(curl -fsS "$BFF/openbaar/register" | python3 -c "import sys,json;print(any(r.get('reference')=='$id' for r in json.load(sys.stdin)))" 2>/dev/null || true)"
+  [ "$public" = "True" ] && break
+  sleep 3
+done
+[ "$public" = "True" ] || { echo "FAIL: reference never appeared in the openbaar register — NRC abonnement not registered (gap 3)" >&2; exit 1; }
+echo "   visible in the openbaar register"
+
+echo "OK — a fresh local stack completed the flow with no manual seeding (zaaktype + DMN + abonnement)"

services/acl/Acl.Api/Program.cs

@@ -11,6 +11,8 @@ builder.Services.AddSingleton(sp => sp.GetRequiredService<IConfiguration>()
     .GetSection("Acl:OpenZaak").Get<OpenZaakOptions>()
     ?? throw new InvalidOperationException("Missing configuration section 'Acl:OpenZaak'"));
 builder.Services.AddHttpClient<IZaakGateway, OpenZaakGateway>();
+// Singleton so the resolved zaaktype/informatieobjecttype URLs are cached across requests (S-27).
+builder.Services.AddSingleton<IZaaktypeCatalog, CachedZaaktypeCatalog>();
 builder.Services.AddScoped<AclService>();
 
 var app = builder.Build();

services/acl/Acl.Application/AclDefaults.cs

@@ -6,9 +6,12 @@ public sealed class AclDefaults
     public required string Bronorganisatie { get; init; }
     public required string VerantwoordelijkeOrganisatie { get; init; }
     public required string Vertrouwelijkheidaanduiding { get; init; }
-    public required Uri ZaaktypeUrl { get; init; }
 
-    /// <summary>The informatieobjecttype an uploaded diploma is filed under (S-10b). Seeded in the
-    /// catalogus and injected like <see cref="ZaaktypeUrl"/>.</summary>
-    public required Uri InformatieobjecttypeUrl { get; init; }
+    /// <summary>The BIG zaaktype's stable business key. The ACL resolves the (server-assigned) zaaktype
+    /// URL from this via the Catalogi API instead of being handed a pinned URL (S-27, ADR-0021).</summary>
+    public required string ZaaktypeIdentificatie { get; init; }
+
+    /// <summary>The omschrijving of the informatieobjecttype an uploaded diploma is filed under (S-10b);
+    /// resolved to a URL by the Catalogi API, like <see cref="ZaaktypeIdentificatie"/>.</summary>
+    public required string InformatieobjecttypeOmschrijving { get; init; }
 }

services/acl/Acl.Application/AclService.cs

@@ -2,9 +2,9 @@ namespace Acl.Application;
 
 /// <summary>The ACL's single operation: open a zaak from a domain payload,
 /// default-filling the ZGW-mandatory fields (ADR-0003).</summary>
-public sealed class AclService(IZaakGateway gateway, AclDefaults defaults, IClock clock)
+public sealed class AclService(IZaakGateway gateway, AclDefaults defaults, IZaaktypeCatalog catalog, IClock clock)
 {
-    public Task<Uri> OpenZaakAsync(DomainRegistration registration, CancellationToken ct = default)
+    public async Task<Uri> OpenZaakAsync(DomainRegistration registration, CancellationToken ct = default)
     {
         ArgumentNullException.ThrowIfNull(registration);
 
@@ -12,34 +12,34 @@ public sealed class AclService(IZaakGateway gateway, AclDefaults defaults, ICloc
             defaults.Bronorganisatie,
             defaults.VerantwoordelijkeOrganisatie,
             defaults.Vertrouwelijkheidaanduiding,
-            defaults.ZaaktypeUrl,
+            await catalog.GetZaaktypeUrlAsync(ct),
             clock.Today,
             registration.Reference);
 
-        return gateway.OpenZaakAsync(request, ct);
+        return await gateway.OpenZaakAsync(request, ct);
     }
 
     /// <summary>
-    /// Approve a zaak: set it to the eindstatus of the configured BIG zaaktype (ADR-0003 default). The
-    /// domain hands over only the zaak URL; the ACL owns which statustype means "approved" (§8.1).
+    /// Approve a zaak: set it to the eindstatus of the BIG zaaktype (resolved by identificatie, S-27).
+    /// The domain hands over only the zaak URL; the ACL owns which statustype means "approved" (§8.1).
     /// </summary>
-    public Task ApproveZaakAsync(Uri zaakUrl, CancellationToken ct = default)
+    public async Task ApproveZaakAsync(Uri zaakUrl, CancellationToken ct = default)
     {
         ArgumentNullException.ThrowIfNull(zaakUrl);
 
-        return gateway.SetZaakToEindstatusAsync(zaakUrl, defaults.ZaaktypeUrl, clock.Today, ct);
+        await gateway.SetZaakToEindstatusAsync(zaakUrl, await catalog.GetZaaktypeUrlAsync(ct), clock.Today, ct);
     }
 
     /// <summary>
-    /// Cancel a zaak on document-timeout expiry (S-10c): set it to the configured BIG zaaktype's
-    /// cancellation statustype + resultaat. The domain hands over only the zaak URL; the ACL owns which
+    /// Cancel a zaak on document-timeout expiry (S-10c): set it to the BIG zaaktype's cancellation
+    /// statustype + resultaat. The domain hands over only the zaak URL; the ACL owns which
     /// statustype/resultaat means "cancelled" (§8.1).
     /// </summary>
-    public Task CancelZaakAsync(Uri zaakUrl, CancellationToken ct = default)
+    public async Task CancelZaakAsync(Uri zaakUrl, CancellationToken ct = default)
     {
         ArgumentNullException.ThrowIfNull(zaakUrl);
 
-        return gateway.SetZaakToCancellationStatusAsync(zaakUrl, defaults.ZaaktypeUrl, clock.Today, ct);
+        await gateway.SetZaakToCancellationStatusAsync(zaakUrl, await catalog.GetZaaktypeUrlAsync(ct), clock.Today, ct);
     }
 
     /// <summary>The zaak's reference (its ZGW identificatie), for the read projection (#78).</summary>
@@ -56,7 +56,7 @@ public sealed class AclService(IZaakGateway gateway, AclDefaults defaults, ICloc
     /// and hand the file to the gateway, which creates the informatieobject and relates it to the zaak.
     /// The domain supplies only the zaak, the bytes, and the file's name/type (§8.1).
     /// </summary>
-    public Task<Uri> StoreDiplomaAsync(Uri zaakUrl, byte[] content, string fileName, string contentType, CancellationToken ct = default)
+    public async Task<Uri> StoreDiplomaAsync(Uri zaakUrl, byte[] content, string fileName, string contentType, CancellationToken ct = default)
     {
         ArgumentNullException.ThrowIfNull(zaakUrl);
         ArgumentNullException.ThrowIfNull(content);
@@ -65,7 +65,7 @@ public sealed class AclService(IZaakGateway gateway, AclDefaults defaults, ICloc
 
         var request = new DocumentRequest(
             defaults.Bronorganisatie,
-            defaults.InformatieobjecttypeUrl,
+            await catalog.GetInformatieobjecttypeUrlAsync(ct),
             defaults.Vertrouwelijkheidaanduiding,
             zaakUrl,
             clock.Today,
@@ -76,6 +76,6 @@ public sealed class AclService(IZaakGateway gateway, AclDefaults defaults, ICloc
             Formaat: contentType,
             Inhoud: content);
 
-        return gateway.StoreDocumentAsync(request, ct);
+        return await gateway.StoreDocumentAsync(request, ct);
     }
 }

services/acl/Acl.Application/CachedZaaktypeCatalog.cs

@@ -0,0 +1,46 @@
+namespace Acl.Application;
+
+/// <summary>Resolves the zaaktype + diploma-informatieobjecttype URLs from the Catalogi API on first
+/// use and caches them for the process lifetime (S-27, ADR-0021). Lazy (not at startup) so the ACL
+/// never crash-loops when it boots before the catalogus is seeded/published; a <em>failed</em>
+/// resolution is not cached, so it is retried on the next call (e.g. once the zaaktype is published).
+/// A process restart re-resolves.</summary>
+public sealed class CachedZaaktypeCatalog(IZaakGateway gateway, AclDefaults defaults) : IZaaktypeCatalog
+{
+    private readonly SemaphoreSlim gate = new(1, 1);
+    private Uri? zaaktype;
+    private Uri? informatieobjecttype;
+
+    public Task<Uri> GetZaaktypeUrlAsync(CancellationToken ct = default) =>
+        ResolveOnceAsync(
+            () => zaaktype, value => zaaktype = value,
+            () => gateway.ResolveZaaktypeUrlAsync(defaults.ZaaktypeIdentificatie, ct), ct);
+
+    public Task<Uri> GetInformatieobjecttypeUrlAsync(CancellationToken ct = default) =>
+        ResolveOnceAsync(
+            () => informatieobjecttype, value => informatieobjecttype = value,
+            () => gateway.ResolveInformatieobjecttypeUrlAsync(defaults.InformatieobjecttypeOmschrijving, ct), ct);
+
+    // Double-checked, single-flight resolution: return the cache if set; otherwise resolve under the
+    // gate and cache only on success (a throw leaves the cache empty so the next call retries).
+    private async Task<Uri> ResolveOnceAsync(Func<Uri?> read, Action<Uri> store, Func<Task<Uri>> resolve, CancellationToken ct)
+    {
+        if (read() is { } cached)
+            return cached;
+
+        await gate.WaitAsync(ct);
+        try
+        {
+            if (read() is { } existing)
+                return existing;
+
+            var resolved = await resolve();
+            store(resolved);
+            return resolved;
+        }
+        finally
+        {
+            gate.Release();
+        }
+    }
+}

services/acl/Acl.Application/IZaakGateway.cs

@@ -32,4 +32,12 @@ public interface IZaakGateway
     /// the created informatieobject.
     /// </summary>
     Task<Uri> StoreDocumentAsync(DocumentRequest request, CancellationToken ct = default);
+
+    /// <summary>Resolve the URL of the published zaaktype with the given <paramref name="identificatie"/>
+    /// from the Catalogi API (S-27). Throws if no published zaaktype matches.</summary>
+    Task<Uri> ResolveZaaktypeUrlAsync(string identificatie, CancellationToken ct = default);
+
+    /// <summary>Resolve the URL of the published informatieobjecttype with the given
+    /// <paramref name="omschrijving"/> from the Catalogi API (S-27). Throws if none matches.</summary>
+    Task<Uri> ResolveInformatieobjecttypeUrlAsync(string omschrijving, CancellationToken ct = default);
 }

services/acl/Acl.Application/IZaaktypeCatalog.cs

@@ -0,0 +1,12 @@
+namespace Acl.Application;
+
+/// <summary>Supplies the ACL's zaaktype + diploma-informatieobjecttype URLs, resolved from OpenZaak's
+/// Catalogi API by their stable business keys (<see cref="AclDefaults.ZaaktypeIdentificatie"/> /
+/// <see cref="AclDefaults.InformatieobjecttypeOmschrijving"/>) rather than pinned in config (S-27,
+/// ADR-0021). Implementations resolve lazily on first use and cache the result.</summary>
+public interface IZaaktypeCatalog
+{
+    Task<Uri> GetZaaktypeUrlAsync(CancellationToken ct = default);
+
+    Task<Uri> GetInformatieobjecttypeUrlAsync(CancellationToken ct = default);
+}

services/acl/Acl.Infrastructure/OpenZaakGateway.cs

@@ -142,6 +142,48 @@ public sealed class OpenZaakGateway(HttpClient http, OpenZaakOptions options) :
         return created;
     }
 
+    public async Task<Uri> ResolveZaaktypeUrlAsync(string identificatie, CancellationToken ct = default)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(identificatie);
+
+        // The published zaaktype with this identificatie; status=definitief excludes concepts.
+        var page = await GetAsync<ZaaktypePage>(
+            "/catalogi/api/v1/zaaktypen?status=definitief&identificatie=" + Uri.EscapeDataString(identificatie),
+            "zaaktypen", ct);
+        var match = (page.Results ?? []).FirstOrDefault()
+            ?? throw new InvalidOperationException(
+                $"No published zaaktype with identificatie '{identificatie}' found in OpenZaak — is the BIG catalogus seeded and published?");
+        return new Uri(match.Url);
+    }
+
+    public async Task<Uri> ResolveInformatieobjecttypeUrlAsync(string omschrijving, CancellationToken ct = default)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(omschrijving);
+
+        // The informatieobjecttypen collection has no omschrijving filter, so match client-side over the
+        // published ones.
+        var page = await GetAsync<InformatieobjecttypePage>(
+            "/catalogi/api/v1/informatieobjecttypen?status=definitief", "informatieobjecttypen", ct);
+        var match = (page.Results ?? []).FirstOrDefault(i => i.Omschrijving == omschrijving)
+            ?? throw new InvalidOperationException(
+                $"No published informatieobjecttype '{omschrijving}' found in OpenZaak — is the BIG catalogus seeded and published?");
+        return new Uri(match.Url);
+    }
+
+    // GETs an absolute-by-path ZGW resource with auth (no CRS — catalogi is not a geo API).
+    private async Task<T> GetAsync<T>(string pathAndQuery, string label, CancellationToken ct)
+    {
+        using var message = new HttpRequestMessage(HttpMethod.Get, new Uri(options.BaseUrl, pathAndQuery));
+        message.Headers.Authorization =
+            new AuthenticationHeaderValue("Bearer", ZgwToken.Mint(options.ClientId, options.Secret));
+
+        using var response = await http.SendAsync(message, ct);
+        await EnsureSuccessAsync(response, $"Querying {label}", ct);
+
+        return await response.Content.ReadFromJsonAsync<T>(ct)
+            ?? throw new InvalidOperationException($"OpenZaak returned an empty {label} response");
+    }
+
     // POSTs a non-geo ZGW resource (resultaat/status — no CRS headers). Buffers the body so uwsgi gets
     // a Content-Length instead of a chunked body (as with zaak-create).
     private async Task PostAsync(string path, object dto, string action, CancellationToken ct)
@@ -298,4 +340,18 @@ public sealed class OpenZaakGateway(HttpClient http, OpenZaakOptions options) :
     private sealed record ZaakInformatieobjectDto(
         [property: JsonPropertyName("zaak")] string Zaak,
         [property: JsonPropertyName("informatieobject")] string Informatieobject);
+
+    private sealed record ZaaktypePage(
+        [property: JsonPropertyName("results")] IReadOnlyList<ZaaktypeDto>? Results);
+
+    private sealed record ZaaktypeDto(
+        [property: JsonPropertyName("url")] string Url,
+        [property: JsonPropertyName("identificatie")] string? Identificatie);
+
+    private sealed record InformatieobjecttypePage(
+        [property: JsonPropertyName("results")] IReadOnlyList<InformatieobjecttypeDto>? Results);
+
+    private sealed record InformatieobjecttypeDto(
+        [property: JsonPropertyName("url")] string Url,
+        [property: JsonPropertyName("omschrijving")] string? Omschrijving);
 }

services/acl/Acl.IntegrationTests/OpenZaakGatewayIntegrationTests.cs

@@ -161,4 +161,32 @@ public sealed class OpenZaakGatewayIntegrationTests(OpenZaakFixture stack)
         Assert.Contains(relations.EnumerateArray(),
             r => r.GetProperty("zaak").GetString() == zaakUrl.ToString());
     }
+
+    [Fact]
+    public async Task Resolves_the_published_zaaktype_and_diploma_informatieobjecttype_by_business_key()
+    {
+        var expectedZaaktype = await stack.FindPublishedBigZaaktypeAsync();
+        Assert.True(expectedZaaktype is not null,
+            "No published BIG-REGISTRATIE zaaktype found — seed the stack with OZ_PUBLISH=1.");
+        var expectedInformatieobjecttype = await stack.FindPublishedDiplomaInformatieobjecttypeAsync();
+        Assert.True(expectedInformatieobjecttype is not null,
+            "No published Diploma informatieobjecttype found — seed the stack with OZ_PUBLISH=1.");
+
+        var gateway = new OpenZaakGateway(stack.Http, stack.Options);
+
+        // The ACL discovers both URLs from the live Catalogi API by their stable business keys (S-27),
+        // matching what the fixture found independently — no pinned URL needed.
+        Assert.Equal(expectedZaaktype, await gateway.ResolveZaaktypeUrlAsync("BIG-REGISTRATIE"));
+        Assert.Equal(expectedInformatieobjecttype, await gateway.ResolveInformatieobjecttypeUrlAsync("Diploma"));
+    }
+
+    [Fact]
+    public async Task Resolving_an_unknown_zaaktype_identificatie_throws_a_clear_error()
+    {
+        var gateway = new OpenZaakGateway(stack.Http, stack.Options);
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => gateway.ResolveZaaktypeUrlAsync("NO-SUCH-ZAAKTYPE"));
+        Assert.Contains("NO-SUCH-ZAAKTYPE", ex.Message);
+    }
 }

services/acl/Acl.Tests/AclServiceTests.cs

@@ -6,6 +6,12 @@ public class AclServiceTests
 {
     private sealed class FakeGateway : IZaakGateway
     {
+        // The URLs the catalogus resolves the configured identificatie/omschrijving to (S-27).
+        public Uri ResolvedZaaktype { get; } = new("http://openzaak/catalogi/api/v1/zaaktypen/big");
+        public Uri ResolvedInformatieobjecttype { get; } = new("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip");
+        public string? ResolvedByIdentificatie;
+        public string? ResolvedByOmschrijving;
+
         public ZaakRequest? Captured;
         public Uri Result { get; } = new("http://openzaak/zaken/api/v1/zaken/abc");
 
@@ -47,6 +53,18 @@ public class AclServiceTests
             StoredDocument = request;
             return Task.FromResult(DocumentResult);
         }
+
+        public Task<Uri> ResolveZaaktypeUrlAsync(string identificatie, CancellationToken ct = default)
+        {
+            ResolvedByIdentificatie = identificatie;
+            return Task.FromResult(ResolvedZaaktype);
+        }
+
+        public Task<Uri> ResolveInformatieobjecttypeUrlAsync(string omschrijving, CancellationToken ct = default)
+        {
+            ResolvedByOmschrijving = omschrijving;
+            return Task.FromResult(ResolvedInformatieobjecttype);
+        }
     }
 
     private static AclDefaults Defaults() => new()
@@ -54,28 +72,23 @@ public class AclServiceTests
         Bronorganisatie = "517439943",
         VerantwoordelijkeOrganisatie = "517439943",
         Vertrouwelijkheidaanduiding = "openbaar",
-        ZaaktypeUrl = new("http://openzaak/catalogi/api/v1/zaaktypen/big"),
-        InformatieobjecttypeUrl = new("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip"),
+        ZaaktypeIdentificatie = "BIG-REGISTRATIE",
+        InformatieobjecttypeOmschrijving = "Diploma",
     };
 
+    private static AclService ServiceWith(FakeGateway gateway, AclDefaults defaults, DateOnly today) =>
+        new(gateway, defaults, new CachedZaaktypeCatalog(gateway, defaults), new FixedClock(today));
+
     private sealed class FixedClock(DateOnly today) : IClock
     {
         public DateOnly Today { get; } = today;
     }
 
     [Fact]
-    public async Task Opening_a_zaak_default_fills_zgw_fields_and_returns_the_zaak_url()
+    public async Task Opening_a_zaak_default_fills_zgw_fields_and_uses_the_resolved_zaaktype()
     {
         var gateway = new FakeGateway();
-        var defaults = new AclDefaults
-        {
-            Bronorganisatie = "517439943",
-            VerantwoordelijkeOrganisatie = "517439943",
-            Vertrouwelijkheidaanduiding = "openbaar",
-            ZaaktypeUrl = new("http://openzaak/catalogi/api/v1/zaaktypen/big"),
-            InformatieobjecttypeUrl = new("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip"),
-        };
-        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
 
         var url = await service.OpenZaakAsync(new DomainRegistration("123456782", "reg-77"));
 
@@ -84,7 +97,9 @@ public class AclServiceTests
         Assert.Equal("517439943", req.Bronorganisatie);
         Assert.Equal("517439943", req.VerantwoordelijkeOrganisatie);
         Assert.Equal("openbaar", req.Vertrouwelijkheidaanduiding);
-        Assert.Equal(defaults.ZaaktypeUrl, req.Zaaktype);
+        // The zaaktype is resolved from the configured identificatie, not a pinned URL (S-27).
+        Assert.Equal("BIG-REGISTRATIE", gateway.ResolvedByIdentificatie);
+        Assert.Equal(gateway.ResolvedZaaktype, req.Zaaktype);
         Assert.Equal(new DateOnly(2026, 6, 4), req.Startdatum);
         // The registration reference becomes the zaak identificatie (#78).
         Assert.Equal("reg-77", req.Identificatie);
@@ -94,33 +109,24 @@ public class AclServiceTests
     public async Task Rejects_a_null_registration_without_calling_the_gateway()
     {
         var gateway = new FakeGateway();
-        var defaults = new AclDefaults
-        {
-            Bronorganisatie = "517439943",
-            VerantwoordelijkeOrganisatie = "517439943",
-            Vertrouwelijkheidaanduiding = "openbaar",
-            ZaaktypeUrl = new("http://openzaak/catalogi/api/v1/zaaktypen/big"),
-            InformatieobjecttypeUrl = new("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip"),
-        };
-        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
 
         await Assert.ThrowsAsync<ArgumentNullException>(() => service.OpenZaakAsync(null!));
         Assert.Null(gateway.Captured);
     }
 
     [Fact]
-    public async Task Approving_a_zaak_sets_it_to_its_zaaktypes_eindstatus_dated_today()
+    public async Task Approving_a_zaak_sets_it_to_its_resolved_zaaktypes_eindstatus_dated_today()
     {
         var gateway = new FakeGateway();
-        var defaults = Defaults();
-        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
         var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");
 
         await service.ApproveZaakAsync(zaak);
 
         Assert.NotNull(gateway.Approved);
         Assert.Equal(zaak, gateway.Approved!.Value.Zaak);
-        Assert.Equal(defaults.ZaaktypeUrl, gateway.Approved.Value.Zaaktype);
+        Assert.Equal(gateway.ResolvedZaaktype, gateway.Approved.Value.Zaaktype);
         Assert.Equal(new DateOnly(2026, 6, 4), gateway.Approved.Value.Datum);
     }
 
@@ -128,7 +134,7 @@ public class AclServiceTests
     public async Task Approving_a_null_zaak_is_rejected_without_touching_the_gateway()
     {
         var gateway = new FakeGateway();
-        var service = new AclService(gateway, Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
 
         await Assert.ThrowsAsync<ArgumentNullException>(() => service.ApproveZaakAsync(null!));
         Assert.Null(gateway.Approved);
@@ -138,15 +144,14 @@ public class AclServiceTests
     public async Task Cancelling_a_zaak_sets_it_to_the_cancellation_status_dated_today()
     {
         var gateway = new FakeGateway();
-        var defaults = Defaults();
-        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
         var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");
 
         await service.CancelZaakAsync(zaak);
 
         Assert.NotNull(gateway.Cancelled);
         Assert.Equal(zaak, gateway.Cancelled!.Value.Zaak);
-        Assert.Equal(defaults.ZaaktypeUrl, gateway.Cancelled.Value.Zaaktype);
+        Assert.Equal(gateway.ResolvedZaaktype, gateway.Cancelled.Value.Zaaktype);
         Assert.Equal(new DateOnly(2026, 6, 4), gateway.Cancelled.Value.Datum);
         // Cancellation must not touch the approval path.
         Assert.Null(gateway.Approved);
@@ -156,18 +161,17 @@ public class AclServiceTests
     public async Task Cancelling_a_null_zaak_is_rejected_without_touching_the_gateway()
     {
         var gateway = new FakeGateway();
-        var service = new AclService(gateway, Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
 
         await Assert.ThrowsAsync<ArgumentNullException>(() => service.CancelZaakAsync(null!));
         Assert.Null(gateway.Cancelled);
     }
 
     [Fact]
-    public async Task Storing_a_diploma_default_fills_the_document_fields_and_returns_its_url()
+    public async Task Storing_a_diploma_default_fills_the_document_fields_and_uses_the_resolved_informatieobjecttype()
     {
         var gateway = new FakeGateway();
-        var defaults = Defaults();
-        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
         var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");
 
         var url = await service.StoreDiplomaAsync(zaak, [1, 2, 3], "diploma.pdf", "application/pdf");
@@ -175,7 +179,9 @@ public class AclServiceTests
         Assert.Equal(gateway.DocumentResult, url);
         var req = gateway.StoredDocument!;
         Assert.Equal(zaak, req.Zaak);
-        Assert.Equal(defaults.InformatieobjecttypeUrl, req.Informatieobjecttype);
+        // The informatieobjecttype is resolved from the configured omschrijving (S-27).
+        Assert.Equal("Diploma", gateway.ResolvedByOmschrijving);
+        Assert.Equal(gateway.ResolvedInformatieobjecttype, req.Informatieobjecttype);
         Assert.Equal("517439943", req.Bronorganisatie);
         Assert.Equal("openbaar", req.Vertrouwelijkheidaanduiding);
         Assert.Equal(new DateOnly(2026, 6, 4), req.Creatiedatum);
@@ -188,7 +194,7 @@ public class AclServiceTests
     [Fact]
     public async Task Storing_a_diploma_rejects_null_or_blank_arguments()
     {
-        var service = new AclService(new FakeGateway(), Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(new FakeGateway(), Defaults(), new DateOnly(2026, 6, 4));
         var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");
 
         await Assert.ThrowsAsync<ArgumentNullException>(() => service.StoreDiplomaAsync(null!, [1], "d.pdf", "application/pdf"));
@@ -201,7 +207,7 @@ public class AclServiceTests
     public async Task Reading_a_zaak_reference_returns_the_zaaks_identificatie()
     {
         var gateway = new FakeGateway();
-        var service = new AclService(gateway, Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
         var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");
 
         var reference = await service.GetZaakReferenceAsync(zaak);
@@ -214,7 +220,7 @@ public class AclServiceTests
     public async Task Reading_a_null_zaak_reference_is_rejected()
     {
         var gateway = new FakeGateway();
-        var service = new AclService(gateway, Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
 
         await Assert.ThrowsAsync<ArgumentNullException>(() => service.GetZaakReferenceAsync(null!));
         Assert.Null(gateway.ReadReferenceFor);

services/acl/Acl.Tests/OpenZaakGatewayTests.cs

@@ -675,4 +675,153 @@ public class OpenZaakGatewayTests
 
         await Assert.ThrowsAsync<ArgumentNullException>(() => Gateway(handler).StoreDocumentAsync(null!));
     }
+
+    // ── Catalogi resolution by business key (S-27) ────────────────────────────────────────────────
+
+    [Fact]
+    public async Task Resolves_the_published_zaaktype_url_by_identificatie()
+    {
+        HttpRequestMessage? seen = null;
+        var handler = new StubHandler(req =>
+        {
+            seen = req;
+            return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+            {
+                Content = JsonContent.Create(new
+                {
+                    results = new[] { new { url = "http://openzaak/catalogi/api/v1/zaaktypen/big", identificatie = "BIG-REGISTRATIE" } },
+                }),
+            });
+        });
+
+        var url = await Gateway(handler).ResolveZaaktypeUrlAsync("BIG-REGISTRATIE");
+
+        Assert.Equal("http://openzaak/catalogi/api/v1/zaaktypen/big", url.ToString());
+        Assert.Equal(HttpMethod.Get, seen!.Method);
+        // Filters to the published zaaktype with that identificatie, and authenticates.
+        Assert.Contains("/catalogi/api/v1/zaaktypen", seen.RequestUri!.ToString());
+        Assert.Contains("status=definitief", seen.RequestUri!.Query);
+        Assert.Contains("identificatie=BIG-REGISTRATIE", seen.RequestUri!.Query);
+        Assert.Equal("Bearer", seen.Headers.Authorization!.Scheme);
+    }
+
+    [Fact]
+    public async Task Resolving_a_zaaktype_throws_a_clear_error_when_none_is_published()
+    {
+        var handler = new StubHandler(_ => Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+        {
+            Content = JsonContent.Create(new { results = Array.Empty<object>() }),
+        }));
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => Gateway(handler).ResolveZaaktypeUrlAsync("BIG-REGISTRATIE"));
+        Assert.Contains("BIG-REGISTRATIE", ex.Message);
+    }
+
+    [Fact]
+    public async Task Resolves_the_informatieobjecttype_url_by_omschrijving()
+    {
+        HttpRequestMessage? seen = null;
+        var handler = new StubHandler(req =>
+        {
+            seen = req;
+            return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+            {
+                Content = JsonContent.Create(new
+                {
+                    results = new[]
+                    {
+                        new { url = "http://openzaak/catalogi/api/v1/informatieobjecttypen/other", omschrijving = "Overig" },
+                        new { url = "http://openzaak/catalogi/api/v1/informatieobjecttypen/dip", omschrijving = "Diploma" },
+                    },
+                }),
+            });
+        });
+
+        var url = await Gateway(handler).ResolveInformatieobjecttypeUrlAsync("Diploma");
+
+        // Queries the published informatieobjecttypen collection, and matches on omschrijving (not position).
+        Assert.Contains("/catalogi/api/v1/informatieobjecttypen", seen!.RequestUri!.ToString());
+        Assert.Contains("status=definitief", seen.RequestUri!.Query);
+        Assert.Equal("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip", url.ToString());
+    }
+
+    [Fact]
+    public async Task Resolving_a_zaaktype_throws_when_the_response_carries_no_results()
+    {
+        // No "results" property → the page's Results is null; the gateway must treat that as "none
+        // found" (not dereference null).
+        var handler = new StubHandler(_ => Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+        {
+            Content = JsonContent.Create(new { count = 0 }),
+        }));
+
+        await Assert.ThrowsAsync<InvalidOperationException>(
+            () => Gateway(handler).ResolveZaaktypeUrlAsync("BIG-REGISTRATIE"));
+    }
+
+    [Fact]
+    public async Task Resolving_an_informatieobjecttype_throws_when_the_response_carries_no_results()
+    {
+        var handler = new StubHandler(_ => Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+        {
+            Content = JsonContent.Create(new { count = 0 }),
+        }));
+
+        await Assert.ThrowsAsync<InvalidOperationException>(
+            () => Gateway(handler).ResolveInformatieobjecttypeUrlAsync("Diploma"));
+    }
+
+    [Fact]
+    public async Task Resolving_a_zaaktype_surfaces_a_non_success_catalogi_response()
+    {
+        var handler = new StubHandler(_ => Task.FromResult(new HttpResponseMessage(HttpStatusCode.InternalServerError)
+        {
+            Content = new StringContent("boom"),
+        }));
+
+        var ex = await Assert.ThrowsAsync<HttpRequestException>(
+            () => Gateway(handler).ResolveZaaktypeUrlAsync("BIG-REGISTRATIE"));
+        // The error names the resource being queried and includes OpenZaak's body.
+        Assert.Contains("zaaktypen", ex.Message);
+        Assert.Contains("boom", ex.Message);
+    }
+
+    [Fact]
+    public async Task Resolving_an_informatieobjecttype_surfaces_a_non_success_catalogi_response()
+    {
+        var handler = new StubHandler(_ => Task.FromResult(new HttpResponseMessage(HttpStatusCode.InternalServerError)
+        {
+            Content = new StringContent("boom"),
+        }));
+
+        var ex = await Assert.ThrowsAsync<HttpRequestException>(
+            () => Gateway(handler).ResolveInformatieobjecttypeUrlAsync("Diploma"));
+        Assert.Contains("informatieobjecttypen", ex.Message);
+    }
+
+    [Fact]
+    public async Task Resolving_an_informatieobjecttype_throws_when_no_omschrijving_matches()
+    {
+        var handler = new StubHandler(_ => Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+        {
+            Content = JsonContent.Create(new
+            {
+                results = new[] { new { url = "http://openzaak/catalogi/api/v1/informatieobjecttypen/other", omschrijving = "Overig" } },
+            }),
+        }));
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => Gateway(handler).ResolveInformatieobjecttypeUrlAsync("Diploma"));
+        Assert.Contains("Diploma", ex.Message);
+    }
+
+    [Fact]
+    public async Task Resolving_rejects_a_blank_business_key_without_calling_openzaak()
+    {
+        var handler = new StubHandler(_ => throw new InvalidOperationException("should not be sent"));
+
+        await Assert.ThrowsAnyAsync<ArgumentException>(() => Gateway(handler).ResolveZaaktypeUrlAsync(" "));
+        await Assert.ThrowsAnyAsync<ArgumentException>(() => Gateway(handler).ResolveInformatieobjecttypeUrlAsync(" "));
+    }
 }

services/acl/Acl.Tests/ZaaktypeCatalogTests.cs

@@ -0,0 +1,92 @@
+using Acl.Application;
+
+namespace Acl.Tests;
+
+public class ZaaktypeCatalogTests
+{
+    // A gateway that only supports resolution; the other members are unused here.
+    private sealed class ResolvingGateway : IZaakGateway
+    {
+        public int ZaaktypeCalls;
+        public int InformatieobjecttypeCalls;
+        public string? LastIdentificatie;
+        public string? LastOmschrijving;
+        public int ThrowZaaktypeTimes;
+        public Uri ZaaktypeUrl { get; } = new("http://openzaak/catalogi/api/v1/zaaktypen/big");
+        public Uri InformatieobjecttypeUrl { get; } = new("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip");
+
+        public Task<Uri> ResolveZaaktypeUrlAsync(string identificatie, CancellationToken ct = default)
+        {
+            ZaaktypeCalls++;
+            LastIdentificatie = identificatie;
+            if (ZaaktypeCalls <= ThrowZaaktypeTimes)
+                throw new InvalidOperationException("no published zaaktype yet");
+            return Task.FromResult(ZaaktypeUrl);
+        }
+
+        public Task<Uri> ResolveInformatieobjecttypeUrlAsync(string omschrijving, CancellationToken ct = default)
+        {
+            InformatieobjecttypeCalls++;
+            LastOmschrijving = omschrijving;
+            return Task.FromResult(InformatieobjecttypeUrl);
+        }
+
+        public Task<Uri> OpenZaakAsync(ZaakRequest request, CancellationToken ct = default) => throw new NotSupportedException();
+        public Task SetZaakToEindstatusAsync(Uri z, Uri zt, DateOnly d, CancellationToken ct = default) => throw new NotSupportedException();
+        public Task SetZaakToCancellationStatusAsync(Uri z, Uri zt, DateOnly d, CancellationToken ct = default) => throw new NotSupportedException();
+        public Task<string> GetZaakIdentificatieAsync(Uri z, CancellationToken ct = default) => throw new NotSupportedException();
+        public Task<Uri> StoreDocumentAsync(DocumentRequest r, CancellationToken ct = default) => throw new NotSupportedException();
+    }
+
+    private static AclDefaults Defaults() => new()
+    {
+        Bronorganisatie = "517439943",
+        VerantwoordelijkeOrganisatie = "517439943",
+        Vertrouwelijkheidaanduiding = "openbaar",
+        ZaaktypeIdentificatie = "BIG-REGISTRATIE",
+        InformatieobjecttypeOmschrijving = "Diploma",
+    };
+
+    [Fact]
+    public async Task Resolves_the_zaaktype_and_informatieobjecttype_by_their_configured_business_keys()
+    {
+        var gateway = new ResolvingGateway();
+        var catalog = new CachedZaaktypeCatalog(gateway, Defaults());
+
+        Assert.Equal(gateway.ZaaktypeUrl, await catalog.GetZaaktypeUrlAsync());
+        Assert.Equal(gateway.InformatieobjecttypeUrl, await catalog.GetInformatieobjecttypeUrlAsync());
+        Assert.Equal("BIG-REGISTRATIE", gateway.LastIdentificatie);
+        Assert.Equal("Diploma", gateway.LastOmschrijving);
+    }
+
+    [Fact]
+    public async Task Caches_the_resolved_urls_so_the_gateway_is_hit_once()
+    {
+        var gateway = new ResolvingGateway();
+        var catalog = new CachedZaaktypeCatalog(gateway, Defaults());
+
+        for (var i = 0; i < 3; i++)
+        {
+            await catalog.GetZaaktypeUrlAsync();
+            await catalog.GetInformatieobjecttypeUrlAsync();
+        }
+
+        Assert.Equal(1, gateway.ZaaktypeCalls);
+        Assert.Equal(1, gateway.InformatieobjecttypeCalls);
+    }
+
+    [Fact]
+    public async Task Does_not_cache_a_failed_resolution_so_it_is_retried()
+    {
+        // The zaaktype is not published yet on the first call; the catalog must retry (not cache the
+        // failure) so a later call succeeds once it is published.
+        var gateway = new ResolvingGateway { ThrowZaaktypeTimes = 1 };
+        var catalog = new CachedZaaktypeCatalog(gateway, Defaults());
+
+        await Assert.ThrowsAsync<InvalidOperationException>(() => catalog.GetZaaktypeUrlAsync());
+        var url = await catalog.GetZaaktypeUrlAsync();
+
+        Assert.Equal(gateway.ZaaktypeUrl, url);
+        Assert.Equal(2, gateway.ZaaktypeCalls);
+    }
+}

tests/acceptance/Steps/EenZaakOpenenSteps.cs

@@ -29,9 +29,12 @@ public sealed class EenZaakOpenenSteps
             Bronorganisatie = values["bronorganisatie"],
             VerantwoordelijkeOrganisatie = values["verantwoordelijkeOrganisatie"],
             Vertrouwelijkheidaanduiding = values["vertrouwelijkheidaanduiding"],
-            ZaaktypeUrl = new Uri(values["zaaktype"]),
-            InformatieobjecttypeUrl = new Uri("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip"),
+            ZaaktypeIdentificatie = "BIG-REGISTRATIE",
+            InformatieobjecttypeOmschrijving = "Diploma",
         };
+        // The ACL resolves the zaaktype by identificatie (S-27); the scenario's zaaktype URL is what
+        // the catalogus resolves it to, so the created zaak still carries that URL.
+        _gateway.ResolvedZaaktypeUrl = new Uri(values["zaaktype"]);
     }
 
     [Given("today is \"(.*)\"")]
@@ -41,7 +44,7 @@ public sealed class EenZaakOpenenSteps
     [When("the domain asks the ACL to open a zaak")]
     public async Task WhenTheDomainAsksTheAclToOpenAZaak()
     {
-        var service = new AclService(_gateway, _defaults!, new FixedClock(_today));
+        var service = new AclService(_gateway, _defaults!, new CachedZaaktypeCatalog(_gateway, _defaults!), new FixedClock(_today));
         _returnedUrl = await service.OpenZaakAsync(_registration!);
     }
 

tests/acceptance/Support/InMemoryZaakGateway.cs

@@ -14,6 +14,11 @@ public sealed class InMemoryZaakGateway : IZaakGateway
     public (Uri Zaak, Uri Zaaktype, DateOnly Datum)? Approved { get; private set; }
     public (Uri Zaak, Uri Zaaktype, DateOnly Datum)? Cancelled { get; private set; }
 
+    // The URLs the catalogus resolves the configured identificatie/omschrijving to (S-27); settable so
+    // a scenario can pin the zaaktype the ACL should default-fill.
+    public Uri ResolvedZaaktypeUrl { get; set; } = new("http://openzaak/catalogi/api/v1/zaaktypen/big");
+    public Uri ResolvedInformatieobjecttypeUrl { get; set; } = new("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip");
+
     public Task<Uri> OpenZaakAsync(ZaakRequest request, CancellationToken ct = default)
     {
         Captured = request;
@@ -37,4 +42,10 @@ public sealed class InMemoryZaakGateway : IZaakGateway
 
     public Task<Uri> StoreDocumentAsync(DocumentRequest request, CancellationToken ct = default)
         => Task.FromResult(new Uri("http://openzaak/documenten/api/v1/enkelvoudiginformatieobjecten/acc-doc"));
+
+    public Task<Uri> ResolveZaaktypeUrlAsync(string identificatie, CancellationToken ct = default)
+        => Task.FromResult(ResolvedZaaktypeUrl);
+
+    public Task<Uri> ResolveInformatieobjecttypeUrlAsync(string omschrijving, CancellationToken ct = default)
+        => Task.FromResult(ResolvedInformatieobjecttypeUrl);
 }