docs(arch): ADR-0035 and the runbook section for publishing the stack (refs #177)

The ADR records why the edge is in the cluster rather than on the Fedora host —
routing and certificates should be state a `helm upgrade` can see — and the
three costs that buys: the host forward nobody in the cluster can repair, the
Let's Encrypt rate limit that makes `persistence.storageClass` non-optional, and
publishing behandel and beheer to the internet behind synthetic accounts.

Runbook §10 is the operational half: the five DNS records, the two firewalld
rules (including the masquerade that makes the return path work), and the
symptoms each missing piece produces.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/architecture/adr-0035-public-tls-edge-in-cluster.md

@@ -0,0 +1,102 @@
+# ADR-0035: The public TLS edge is a Caddy deployment in the cluster
+
+- **Status:** Accepted
+- **Date:** 2026-09-18
+- **Deciders:** Respellion engineering
+- **Slice:** [#177](https://git.labs.respellion.tech/eho/register-referentie/issues/177)
+
+## Context
+
+The stack deploys to a Talos VM on the lab server (ADR-0033, issue #175). Until now it was
+only usable through five SSH port-forwards: the portals' OIDC flow uses PKCE, PKCE needs
+`crypto.subtle`, and browsers expose that only in a **secure context** — HTTPS or an origin
+on `localhost`. A NodePort on the VM's address is neither, so the deployment was pinned to
+`host: localhost` and every viewer had to forward all five browser-facing ports (a portal
+without Keycloak on the same `localhost:30180` fails on the discovery document).
+
+That is not a demo anyone can be sent a link to. We want public hostnames with real
+certificates — and we want the routing and the certificates to be cluster state, not
+host-side configuration that no `helm upgrade` can see.
+
+The public IP is on the Fedora host (`46.224.220.37`); the cluster is a libvirt guest
+behind it.
+
+## Decision
+
+**Terminate TLS in the cluster, with a Caddy deployment rendered by the chart
+(`templates/edge.yaml`), and give the Fedora host nothing but a layer-4 forward.**
+
+- `public.domain` is the single switch. Empty — the default, and what compose and CI use —
+  renders nothing: the stack is reached on its NodePorts and `host` pins the OIDC origin
+  exactly as before. Set it, and the edge appears.
+- `public.routes` maps a subdomain to an in-cluster `service:port`. Caddy proxies to the
+  **ClusterIP** services, so a public deployment does not use the browser-facing NodePorts
+  at all.
+- Caddy obtains and renews certificates itself (ACME HTTP-01). There is no cert-manager.
+- The host forwards `:80`/`:443` to two NodePorts with two `firewall-cmd
+  --add-forward-port` rules. No TLS, no routing, no per-service knowledge there — adding a
+  portal is a chart change, not a host change.
+- `KC_HOSTNAME` and the portals' `config.json` stop being `host` + NodePort. Both now come
+  from one helper, `big.keycloakUrl`, so the issuer Keycloak pins and the authority the
+  portals are configured with cannot drift apart (ADR-0010).
+
+### Alternatives considered
+
+- **Caddy on the Fedora host.** Fewest moving parts — but the routing table and the
+  certificates would live outside the cluster, in a file no deployment touches, and adding
+  a portal would mean editing a host we deploy to over SSH. Rejected on exactly the ground
+  this ADR exists to record.
+- **Traefik or ingress-nginx, plus cert-manager.** The conventional answer, and the right
+  one for a cluster with many teams and changing hostnames. Here it buys a controller, a
+  set of CRDs and Ingress objects to describe five hostnames that never change — and
+  cert-manager to do what Caddy already does unprompted.
+- **A `LoadBalancer` service (MetalLB).** Solves address allocation, which is not the
+  problem; the node has exactly one address and it still is not the public one.
+- **Keep the SSH forwards.** Free, and genuinely fine for one developer. It is not a demo
+  you can send to someone.
+
+## Consequences
+
+**Positive**
+
+- No new dependency: the four portals already run `caddy:2-alpine` (ADR-0034), whose
+  ceiling note called this out — *"a real hostname makes TLS a one-line `Caddyfile`
+  change"*. This is that change.
+- Routing is cluster state: `kubectl -n big get cm caddy-edge-config -o yaml` is the whole
+  truth about what is published, and `helm upgrade` is how it changes.
+- The secure context is real, so `TALOS_HOST=localhost` and the five forwards disappear —
+  and with them the class of failure where a mismatched issuer logs the user out silently.
+- Nothing changes for compose, CI or a laptop cluster: with `public.domain` empty the
+  rendered manifests are byte-identical to before.
+
+**Negative / costs**
+
+- The host forward is irreducible. Two firewalld rules, applied by hand once, with `sudo`
+  on a machine our pipeline reaches only over SSH. If someone rebuilds that host, the stack
+  is unreachable until they are re-applied, and nothing in the cluster can tell them so.
+- **Certificates need a volume.** On the default `emptyDir` every pod restart asks Let's
+  Encrypt again, and its duplicate-certificate limit is five per week — a handful of
+  restarts and the edge serves an untrusted certificate for a week. `persistence.storageClass`
+  stops being optional for anything public (runbook §6).
+- **All five hostnames are published, including `behandel` and `beheer`**, which approve
+  registrations and administer the register. They are protected by synthetic accounts with
+  well-known passwords, and by MFA on the medewerker realm (ADR-0031). That is a deliberate
+  choice for a demonstration environment holding synthetic data only, and it is the reason
+  this bullet is in the ADR rather than in a comment: if this stack ever holds anything
+  real, this decision is the first one to revisit.
+- One more workload in the chart with no counterpart in compose — compose has no edge
+  because it has no hostname. The drift check (`make k8s-drift`) renders the defaults, so
+  it does not see it.
+- `auth` is load-bearing: `big.keycloakUrl` builds the issuer from that subdomain, so
+  renaming the key in `public.routes` without the helper breaks every login. Both carry a
+  comment saying so.
+
+- ponytail ceiling: one replica, no HSTS, no security headers beyond Caddy's defaults, no
+  rate limiting, and HTTP-01 rather than DNS-01 (so a wildcard certificate is not
+  available). Upgrade path in that order; DNS-01 first if the subdomain list ever grows.
+
+## Coupling rules touched (CLAUDE.md §8)
+
+None. §8.3 holds — the browser reaches a portal, the portal reverse-proxies its own BFF
+group, and the edge is in front of all of it. The edge terminates TLS and routes by
+hostname; it does not know what any service does.

docs/runbooks/kubernetes-talos.md

@@ -222,6 +222,9 @@ string, so the port the browser uses has to match the one baked into `config.jso
 This is the same mechanism `infra/host-browser.yml` uses for the compose stack (which pins
 `localhost:8180`); only the addresses differ.
 
+All of this is what §10 removes: with a public domain the portals have real certificates,
+so the browser gets its secure context and no forwarding is involved.
+
 ### The admin UIs work straight off the NodePorts
 
 These are server-rendered and need no secure context, so they are reachable at the VM's
@@ -360,6 +363,68 @@ immutable, so `helm upgrade` is rejected with `cannot patch "…" with kind Job`
 | Pods `Evicted` / `OOMKilled` | the VM is too small (§0) |
 | A Job shows `BackoffLimitExceeded` | read it: `kubectl -n big logs job/<name>` |
 
+## 10. Publishing it on a public domain
+
+By default the stack has no hostname: it is reached on NodePorts, and §5's secure-context
+problem forces `TALOS_HOST=localhost` plus five SSH forwards. Setting `public.domain` puts a
+Caddy deployment in front of it that terminates TLS for real hostnames (ADR-0035), and the
+forwards go away.
+
+### Once, outside the cluster
+
+**DNS** — five A records to the *host's* public address (the cluster is behind it):
+
+```
+register.<domain>  mijn.<domain>  behandel.<domain>  beheer.<domain>  auth.<domain>  →  46.224.220.37
+```
+
+**The host's forward** — the public IP is on the Fedora host, so it has to hand 80/443 to
+the node. This is the only host-side configuration, and it is dumb layer 4:
+
+```bash
+sudo firewall-cmd --permanent --zone=public --add-forward-port=port=80:proto=tcp:toaddr=<TALOS_VM_IP>:toport=32080
+sudo firewall-cmd --permanent --zone=public --add-forward-port=port=443:proto=tcp:toaddr=<TALOS_VM_IP>:toport=32443
+sudo firewall-cmd --permanent --zone=public --add-masquerade
+sudo firewall-cmd --reload
+```
+
+`--add-masquerade` is what makes the return path work: without it the node answers the
+client's address directly and the reply never goes back through the host.
+
+**A StorageClass.** Caddy's certificates live in `/data`, which is an `emptyDir` unless
+`persistence.storageClass` is set (§6). Let's Encrypt allows five duplicate certificates per
+week, so on an `emptyDir` a handful of pod restarts leaves the edge serving an untrusted
+certificate until the limit resets. Install local-path first (§6).
+
+### Deploy
+
+```bash
+make k8s-up TALOS_HOST=<domain-facing name> K8S_REGISTRY=<TALOS_VM_IP>:30500 \
+  K8S_SET='--set public.domain=<domain> --set public.email=<ops address> --set persistence.storageClass=local-path'
+```
+
+`public.domain` is the only switch: with it empty nothing in `templates/edge.yaml` renders
+and the stack behaves exactly as §4 describes. With it set, `KC_HOSTNAME` and the portals'
+`config.json` both become `https://auth.<domain>` — one helper builds both, so the issuer
+and the authority cannot drift (ADR-0010).
+
+Watch the first certificate being issued:
+
+```bash
+kubectl -n big logs deploy/caddy-edge -f        # "certificate obtained successfully"
+curl -sSI https://register.<domain>/openbaar/register | head -1
+```
+
+### When it doesn't work
+
+| Symptom | Cause |
+|---|---|
+| ACME fails with `connection refused` or a timeout on the HTTP-01 challenge | the host's 80 → 32080 forward is missing, or `--add-masquerade` is |
+| ACME fails with `NXDOMAIN` / `no such host` | the A record isn't there yet. Caddy retries with backoff; fix DNS and it recovers |
+| An untrusted certificate after several restarts | the Let's Encrypt duplicate limit, from certificates on an `emptyDir` — see above |
+| The portal loads but login bounces back logged out | `public.domain` changed without the portals rolling. The chart hashes the issuer into their pod template, so `helm upgrade` should do it — check `kubectl -n big describe deploy/self-service` |
+| `404` from the edge on a name that should work | the name isn't in `public.routes`; Caddy answers 404 for a Host it has no site block for |
+
 ## What is not ported
 
 - **Observability** (Tempo, Prometheus, Grafana) is defined but disabled — those are built

mkdocs.yml

@@ -56,6 +56,7 @@ nav:
       - "ADR-0032: Werkbak live refresh": architecture/adr-0032-werkbak-live-refresh.md
       - "ADR-0033: Kubernetes via one Helm chart": architecture/adr-0033-kubernetes-via-one-helm-chart.md
       - "ADR-0034: Caddy serves the portals": architecture/adr-0034-caddy-serves-the-portals.md
+      - "ADR-0035: Public TLS edge in the cluster": architecture/adr-0035-public-tls-edge-in-cluster.md
   - FDS-architectuur:
       - Overzicht: architecture/fds/README.md
       - Componentview (L3): architecture/fds/c4-component-view.md