# ClusterClient → gRPC migration — live gate results

Rig: `docker/` (2 central + 3×2 site + traefik), rebuilt from the branch under test via
`bash docker/deploy.sh`. Recorded check-by-check in the family's live-gate format. Phase 5's
full eight-check gate is recorded further down as those phases land; this file starts with
Phase 0, whose DoD has its own smaller gate.

---

## Phase 0 — PSK auth + dead-code removal — **PASS** (2026-07-22)

Branch `feat/grpc-phase0-psk` @ `228ff8b4`. Image rebuilt, all 9 containers recreated.

### Baseline (pre-change build, same rig)

An unauthenticated call from the host to a site's audit-pull RPC was **accepted**:

```
$ grpcurl -plaintext -d '{"batch_size":1}' localhost:9023 sitestream.SiteStreamService/PullAuditEvents
{}
```

That is the gap Phase 0 closes, reproduced rather than assumed.

### Checks

| # | Check | Result |
|---|---|---|
| 1 | All 8 nodes boot with keys configured (new `StartupValidator` rule) | **PASS** — all recreated and reached ready |
| 2 | Unauthenticated `PullAuditEvents` ⇒ `PermissionDenied`, all 3 sites | **PASS** |
| 3 | Wrong key (site-b's key presented to site-a) ⇒ `PermissionDenied` | **PASS** — per-site scoping is real, not decorative |
| 4 | Correct key ⇒ success, all 3 sites | **PASS** |
| 5 | Central's own authenticated paths still work | **PASS** — 14 successful `PullAuditEvents` from central to site-a; **0** auth failures in either central's log |
| 6 | LocalDb sync unaffected by the new interceptor | **PASS** — **0** control-plane rejections and **0** sync auth failures on the passive peer; session connected after one boot-order retry |
| 7 | No interceptor-activation errors | **PASS** — 0 (see the defect below) |

Evidence for 2–4:

```
=== NO CREDENTIALS ===
  :9023 -> ERROR: Code: PermissionDenied  Message: Control plane authentication failed.
  :9033 -> ERROR: Code: PermissionDenied  Message: Control plane authentication failed.
  :9043 -> ERROR: Code: PermissionDenied  Message: Control plane authentication failed.

=== WRONG KEY (site-b's key against site-a) ===
  :9023 -> ERROR: Code: PermissionDenied  Message: Control plane authentication failed.

=== CORRECT KEY ===
  site-a :9023 -> {}
  site-b :9033 -> {}
  site-c :9043 -> {}
```

Site-a rejected exactly **2** calls — the two deliberate probes above — and nothing else.

### Defect the gate caught that the test suite did not

**First run of this gate FAILED**, and is worth recording because the failure mode is
deceptive.

`Grpc.AspNetCore` activates a type-registered interceptor through
`InterceptorRegistration.GetFactory()`, which throws when more than one public constructor is
applicable. `ControlPlaneAuthInterceptor` shipped with two — the DI one and a prefix-set
overload intended for later phases.

The throw happens **inside the pipeline, per call**, so:

- nothing failed at startup; the node booted, joined its pair and reported healthy;
- every gated call died with `Unknown / "Exception was thrown by handler"`, which reads as a
  handler bug rather than an auth bug;
- **correct key, wrong key and no key produced identical errors** — the tell. A gate that
  cannot distinguish those is not authenticating anything.

Site-a's log at the time: three `PullAuditEvents` calls, three identical
`System.InvalidOperationException: Multiple constructors accepting all given argument types
have been found in type 'ControlPlaneAuthInterceptor'`.

The full suite was green when this shipped — **29 suites, 6,872 tests, 0 failures**. The
in-process end-to-end test missed it because it registered the interceptor with
`AddSingleton` alongside `AddGrpc`, so DI returned the instance and gRPC's activation path
never ran.

Fixed in `228ff8b4`: the prefix-set constructor is `internal`; the end-to-end harness now
registers exactly as `Program.cs` does (by type, not in DI); and a reflection assertion pins
"exactly one public constructor", since that is the actual invariant.

**Lesson for phases 1A/1B, which both add services to this interceptor:** extend
`DefaultGatedPrefixes`; do not add a second public constructor. And any in-process harness for
a DI-activated component must mirror the production registration shape or it proves less than
it appears to.

### Not covered by this gate

- Streaming subscriptions were exercised in-process (TestServer), not over the rig. The
  interceptor is path-scoped, not method-scoped, so the rig's `PullAuditEvents` evidence covers
  the same code path — but a live `SubscribeInstance` under load is untested here.
- Key **rotation** on a live pair.
- `docker-env2` was updated with its own key but not redeployed or gated.