fancy-dns/STATUS.md

# fancy-dns — development status and continuation plan

Last updated after the round that finished the test coverage of every package
that has logic worth covering, fixed two live bugs and pinned the open
questions. `AGENTS.md` holds the decisions, invariants and working rules; this
file holds state and the plan.

## Goal

A lightweight, high-performance recursive DNS server with:

- **Go backend** — sharded LRU cache backed by bbolt, blocklist replication from
  multiple formats, per-client ACLs, query logging, Prometheus metrics.
- **Secure DNS** — DNS-over-TLS (RFC 7858) and DNS-over-HTTPS (RFC 8484).
  DNSSEC validation was explicitly scoped **out**; AD/CD/extended-RCODE are
  passed through only.
- **React + Tailwind admin console** embedded in the binary.
- **Config as zone files + YAML**, hot-reloadable, with **Valkey/Redis** for
  cross-instance sync (chosen over AMQP).

## Architecture decisions (settled with the user)

| Decision | Choice | Why |
|---|---|---|
| Scope | Full production | clustering, metrics, ACLs, query logs, hot reload, Docker, k8s, CI |
| Config store | YAML + DNS master files | reviewable/diffable in git |
| Cluster sync | Valkey (Redis protocol) | simple, mature Go client, easy local dev |
| Secure DNS | DoT + DoH, no DNSSEC validation | avoids signer/anchor machinery; pass-through only |
| Hot cache | Sharded LRU in memory, bbolt for snapshots | no I/O on the hot path; warm restart |
| k8s networking | No hostNetwork, LoadBalancer Service | the server never sets SO_REUSEPORT, so two host-network pods cannot share :53 |
| Memory | Soft GOMEMLIMIT, cache byte budget | a cgroup kill is an outage; a cache miss is not |
| Scale-out | StatefulSet, no HPA | an HPA cannot drive a StatefulSet |
| Unknown YAML keys | Ignore, loudly documented | `KnownFields(true)` was considered and rejected as a behaviour change for anyone carrying extra keys. Pinned by `TestLoadIgnoresUnknownKeys`. |

## Package layout

```
cmd/fancy-dns/main.go          entrypoint: flags, signals, SIGHUP reload
internal/
  config/       Config struct, Duration, Size, Validate, atomic Store + hooks,
                ${VAR} environment expansion in Load
  zonefile/     RFC 1035 master-file parser ($TTL/$ORIGIN, parens, serial math)
  blocklist/    Set (exact/sub/root maps), 4 parsers, Manager (fetch+compile+swap)
  cache/        Key, Entry, sharded LRU, TTL policy, serve-stale, bbolt Store
  resolver/     Upstream pool: health, circuit breakers, parallel/failover/random
  acl/          compiled groups, CIDR/PTR/tag matching, per-group domain policy
  localzone/    authoritative data from master files, wildcards, delegations
  engine/       THE QUERY PIPELINE (see below), reverse-PTR cache
  server/       UDP, TCP, DoT, DoH listeners; all funnel into one handler
  qlog/         bbolt query-log ring + live in-memory ring + SSE fanout
  metrics/      Prometheus collectors + rolling time-series rings
  cluster/      Valkey pub/sub, leader lease, divergence detection
  api/          admin REST + SSE, auth, CORS, rate limiting
  app/          wiring, lifecycle, API hook implementations, memory envelope,
                and the response contract the console is written against
  web/          go:embed of the built console
web/            Vite + React + TS + Tailwind console
deploy/         example config, example zones, k8s manifests
```

### Query pipeline order (engine.Handle)

```
validate → ACL deny → per-client concurrency → global concurrency → rate limit
  → group allow/deny domains → local zone → blocklist → cache → upstream
  → cache put → finalize (EDNS0, UDP truncation) → metrics + qlog
```

Cache is a single shard-local lookup; only a miss touches the network.

## Status

### Green, end to end

`gofmt` clean, `go build ./...` clean, `go vet ./...` clean, and
`go test -race -count=1 -timeout 300s ./...` green across every package.

| Package | top-level tests | notes |
|---|---|---|
| `internal/acl` | 26 | group compilation, matching, first-group-wins |
| `internal/api` | 55 (156 cases) | the whole route table, three auth modes, CORS, rate limiting, SSE, settings, error branches, pinned limitations |
| `internal/app` | 25 | wiring, hooks, the API response contract, integration |
| `internal/blocklist` | 28 | four parsers, the set, the manager, the shipped example zone |
| `internal/cache` | 27 | LRU, TTL policy, serve-stale, bbolt round-trip |
| `internal/cluster` | in progress | Valkey lease, pub/sub, divergence |
| `internal/config` | 22 | Duration/Size, `${VAR}`, unknown keys, the shipped example configs |
| `internal/engine` | 26 | the pipeline end to end, plus the pins |
| `internal/localzone` | 18 | wildcards, delegation, CNAME following |
| `internal/metrics` | 10 | the metric names, which are the contract with the dashboards |
| `internal/qlog` | 18 | ring, bbolt, top domains, sampling |
| `internal/resolver` | 10 | pool, breakers, health, policies |
| `internal/server` | 36 | four listeners, UDP deadline reset, truncation, DoH limits, identity, shutdown, stats |
| `internal/zonefile` | 29 | the master-file parser and the shipped example zone |
| `web` | 0 | typecheck and `oxlint` clean (0 errors), no test runner |
| `cmd/fancy-dns` | 0 | exercised by `make smoke` and the CI smoke job instead |

### The commands that matter

- `make check-go` — the inner loop (~1.3 s): gofmt check, vet, compile. Uses
  `go-build`, not `build`, because `build` depends on `web` and shells out to npm.
- `make check` — `check-go` + the suite. What CI runs.
- `make smoke` — **new.** Boots the real binary with the console embedded on
  unprivileged ports (the same `sed` rewrite CI uses), then checks `-check`,
  `/api/healthz`, the embedded console, the unauthenticated 401, an
  authenticated `whoami` and `/api/metrics`. Catches a broken embed, a bad
  default and an auth regression in one command.
- `make web-check` — console typecheck and production build.
- `make bench` — cache and blocklist benchmarks.

### Test coverage is no longer the interesting gap

The API **response contract** is. The console's types are hand-written and
`apiFetch` ends in `JSON.parse(text) as T`, so nothing in the toolchain compared
them with the Go structs; a field that lost its `json` tag, or a response a
struct never had, showed up as an empty table in a browser and nowhere else.
`internal/app` now has contract tests that assert the exact JSON key set of
every admin endpoint — see the fix list.

## Fixed this round

- **Every query from a client that asks for EDNS0 NSID got SERVFAIL.**
  `dns.EDNS0_NSID.Nsid` is a *hex string* in miekg/dns v1.1.73 — `pack`
  hex-decodes it, `unpack` hex-encodes it — and the engine put the literal
  `"fancy-dns"` in it. `hex.DecodeString("fancy-dns")` fails, so the forwarded
  upstream query could not be built, the exchange failed, and the client got
  SERVFAIL. A one-line bug with total blast radius on a documented feature.
  Fixed with `hex.EncodeToString`, and pinned from both sides:
  `TestClientNSIDIsAnswered` (a client asking for NSID gets a real answer, the
  option we forward upstream decodes to our own name, and `dns.hide_identity`
  drops it) and `TestPinnedEDNS0NSIDIsHex` (the library contract, so a future
  bump that changes `Nsid` to raw bytes fails here with an explanation instead
  of silently breaking the feature).
- **The login rate limiter was applied to every route except the one it exists
  for.** `allowRequest` is the only reader of `limitState.lockedTill` and it ran
  behind `authed`, while the login route was registered through `public`. So N
  bad API keys gave N × 401 and never a 429, and the lockout instead locked the
  caller out of the *rest* of the API — brute-force protection is the one thing
  the auth surface most needs, and it was the one thing that did not work. There
  is now a `limited()` wrapper (the limiter only, no auth) on the login route;
  `allowRequest` stays the single reader of the lockout state. Pinned by
  `TestLoginBruteForceEventuallyHitsTheRateLimiter`,
  `TestLoginLockoutExpiresWithTheClock`, `TestLoginLockoutIsPerIP`,
  `TestLoginLockoutDisabledWithoutFailures` and the `TestAuthedRouteRateLimit*`
  family, so both routes stay honest.
- **A successful login reset the attacker's request budget.**
  `clearLoginFailures` deleted the whole per-IP `limitState`, which also reset
  the per-minute window, so one valid key in the middle of a brute-force burst
  handed back a fresh budget. It now clears only `failures` and `lockedTill`,
  and `TestSuccessfulLoginDoesNotResetTheRequestWindow` /
  `TestSuccessfulLoginClearsTheFailureCounter` pin both halves.
- **DoH GET had no size cap.** The POST path is capped by `readCapped` at
  `dns.MaxMsgSize`; the GET path handed `?dns=` straight to a base64 decode and an
  `Unpack`, so the only limit was net/http's `MaxHeaderBytes` — roughly a
  megabyte of attacker-chosen base64 decoded per request, unauthenticated,
  against a 64 KiB cap on the neighbouring path. A DNS message cannot exceed
  65535 bytes, so the cap is `base64.RawURLEncoding.EncodedLen(dns.MaxMsgSize)`
  and cannot refuse a conforming client. Pinned by
  `TestDoHGETQueryStringOverTheCapIsRefused` (413) and
  `TestDoHServesALargeButLegalQuery` (a message just under the wire limit is
  still served, so the cap cannot be tightened carelessly).
- **A clean `Stop` sometimes returned "use of closed network connection".** The
  DoH listener has two owners: `Stop`'s close list, and `http.Server.Shutdown`,
  which tracks the same `net.Listener` because `serveDoH` hands it to
  `srv.Serve`. Whichever lost that race made an orderly shutdown look like a
  failed one. Closing an already-closed listener is not a failure, so `Stop` now
  ignores `net.ErrClosed` and only reports a real close error. It reproduced 3
  times in 3 runs with DoH enabled and never with it disabled, which is what
  made it findable; `TestStopIsIdempotent` is the pin.
- **A per-transport `dropped` counter did not exist.** The DoH drop fix above
  was invisible in the UI: `HandlerStats.Dropped` is an aggregate that cannot
  say which transport dropped, and `TransportStats` had no `Dropped` field at
  all, even though all four transports bump the counter. Added, with the
  reasoning in the field's comment.
- **A DoH drop was not counted as a drop.**
  `dropped` when `res.Drop`; the DoH path only reached `classify`, which maps
  `drop` to `errors`, so `HandlerStats.Dropped` under-counted DoH. One line, in
  the same position as the other two.
- **Both shipped zone files matched nothing.** `blocklist.local_zones` and the
  `rpz`-format list source are read with the origin taken from the file's base
  name (`zonefile.OriginFromPath`: `local.example.zone` → `local.`), so the
  relative owner names in the examples were being qualified with that — a
  `*.doubleclick.net` rule blocked `*.doubleclick.net.local.`, and the local
  zone mixed relative owners with absolute ones. An operator copying either file
  got a server that answered nothing and blocked nothing. Both examples now
  spell every name out in full, and
  `TestExampleLocalZoneIsOriginIndependent` (zonefile) plus
  `TestExampleRPZZoneBlocksWhatItSays` (blocklist, through the real
  `parseRPZFiles` path) fail if they are "tidied up" back to relative names.
- **The shipped configs were never loaded by anything.**
  `deploy/config.example.yaml` and the ConfigMap in `deploy/k8s/00-config.yaml`
  are now loaded through `config.Load` (which ends in `Validate`) and
  spot-checked, including that the k8s `${FANCYDNS_API_KEY}` still expands and
  still *fails* when the Secret is missing, and that the memory envelope matches
  the StatefulSet's 1Gi limit.
- **The admin API's response shapes had drifted from the console's types** —
  verified against a running binary, not inferred. `blocklist.Source` has no
  `json` tags at all, so the Sources table rendered blank rows and its
  per-row toggle posted `name: undefined`; `acl.GroupSummary` is flat where the
  console expects a nested `match`, so every group card read "matches nothing";
  and **both write endpoints answered 400 to the payload the console actually
  sends** (`json: unknown field "ptr_suffixes"` on `PUT /api/clients`,
  `unknown field "health"` on `PUT /api/upstreams`). The Go side is being fixed
  with contract tests that assert the exact key set of every endpoint; the
  console side is the next piece of work.
- **The GitHub Actions image job could never tag an image.** It used
  `${{ gitea.sha }}` in a workflow under `.github/`, and the `gitea` context
  only exists on Gitea; the image is also published by
  `.gitea/workflows/build.yaml`, which is the pipeline with registry access. It
  now tags with `github.sha` and only logs in and pushes when this repository
  actually has a registry token, so a GitHub runner builds and stops instead of
  failing.
- **`api.constantTimeEqual` had no callers**, and the `authenticator` doc
  comment described a constant-time "API key scan" that does not exist. The real
  design is better than the comment (API keys are compared as SHA-256 digests
  through a hash-keyed map, so the plaintext is never stored) — the dead
  function is gone and the comment now describes the code.
- **`maxGETResponse` was dead code** whose comment claimed a guarantee the
  handler did not provide. Deleted; the DoH response is written as packed.

## Pinned, not fixed (each one has a test that says so out loud)

The standing decision for this round was: **pin, do not change**. Every item
below is behaviour someone may want to change deliberately; each has a test
that fails when it changes, and says what to do when it does.

- **Unknown config keys are silently ignored** (a settled decision, see the
  table above). `TestLoadIgnoresUnknownKeys` in `internal/config` also pins the
  asymmetry that makes this surprising: a typo is invisible, while a known key
  with a bad *type* is a startup failure.
- **`metrics.OutcomeLocal` has no producer.** The engine reports a local-zone
  answer as `qlog.ActionAllow`, which `outcomeFor` maps to `OutcomeUpstream`, so
  every locally answered query is counted as an upstream one and the
  `outcome="local"` series is never published — the dashboard's local column is
  permanently empty. `TestPinnedLocalAnswersAreCountedAsUpstream` asserts the
  upstream counter moves by one and the local series stays absent. Fixing it
  moves published counters, so it wants a decision and a dashboard note.
- **An RPZ record does not cover the name it names.** `rpzRule` gives a bare
  owner name the subdomain form (`*.name`), and a subdomain-form rule matches
  the name's children but not the name itself, so `analytics.example.org.` in a
  policy zone blocks `cdn.analytics.example.org.` and leaves
  `analytics.example.org.` resolving normally. RPZ semantics say the record
  applies to the domain and everything under it, so `**.name` is what belongs
  here — a one-character change in `rpzRule` that alters which queries get
  blocked. Verified end to end against a running binary: the subdomain is
  NXDOMAIN, the apex is not. Pinned by `TestExampleRPZZoneApexIsNotCovered`,
  which also shows the same gap on the allow side (an `rpz-passthru.` record
  for a domain does not allowlist the domain itself).
- **Auth configuration is frozen at `New`.** `api.base_path`,
  `api.trusted_proxies` and the authenticator (`auth.mode`, `api_keys`) are
  captured once; a reload re-reads CORS only. Writing a new API key through
  `PUT /api/settings` answers `ok` while the running server keeps the old key.
  `TestPinnedWrittenAuthConfigIsNotAppliedUntilRestart` and
  `TestCORSOriginsAreReadAtHandlerBuild` hold this in place until someone decides
  whether a reload should re-apply it.
- **DoH clients behind an Ingress all present as the proxy.** `httpRemoteAddr`
  uses the raw `RemoteAddr` and never consults `trusted_proxies`, so every DoH
  client lands in the Ingress's ACL group: fail-closed if that group is
  restrictive, fail-open if it is permissive.
  `TestDoHClientIdentityIsTheProxyNotTheForwardedForHeader` pins it, with the
  reason honouring `X-Forwarded-For` without `trusted_proxies` would break the
  ACL and rate-limit invariants.
- **`api.cors_origins: ["*"]` echoes the request's `Origin` and sets
  `Access-Control-Allow-Credentials: true`.** Deliberate (a literal `*` is
  ignored by browsers when credentials are involved), but it does mean any
  website can drive the admin API with whatever the browser has cached for that
  host. The preflight also answers 204 for any origin and any path.
  `TestCORSWildcardEchoesTheOrigin` and `TestCORSPreflight` pin all of it.
- **A partial bind failure is invisible.** `serveDoT`/`serveDoH` record a failed
  bind in an error list only, so `ListenerInfo.Err` is never set and the admin
  API cannot show which address failed.
  `TestStartReportsAPartialFailureButServes` pins that `Start` returns nil
  whenever any listener came up.
- **A question-less message is answered on UDP and kills the connection on
  TCP/DoT.** `TestUDPQuestionlessMessageReachesTheEngine` pins the UDP half (the
  engine turns it into a FORMERR); the stream path returns instead. Probably
  right for both, but it is an asymmetry worth knowing about.
- **A UDP query in flight at `Stop` can be lost.** The stream paths register
  with `s.wait`, so `Stop` waits for them; `servePacket` does not, so a UDP
  query already inside the pipeline when the listener closes may never be
  answered. That is arguable — UDP has no connection to hang up on and the
  client will retry — but the asymmetry with TCP/DoT is not pinned anywhere, and
  it should be a decision rather than an accident.
- **`doh.sent` is never bumped.** The DoH handler writes its answer through
  `net/http`, so the `sent` counter is only meaningful on UDP/TCP/DoT, and the
  console's transport table shows `sent: 0` for DoH. Pinned as current
  behaviour by `TestCountersFollowTheEngineOutcome` with a comment saying why.
- **`api.metrics.path` is ignored**
  always `${base_path}/metrics`); `POST /api/blocklists/refresh` returned
  `{"names": null}`; an empty `config_yaml` in the settings form is not valid (it
  decodes onto `Default()`, which enables a blocklist with no sources); `"1Gi"`
  is not a valid size — only `GiB`, `G`, `GB` — even though that is how k8s
  spells it.

## Continuation plan, in order

1. **`internal/cluster` suite** — in progress. The rolling heartbeat, the Valkey
   lease and leader handoff, pub/sub config sync, divergence detection and
   reconnect, against `miniredis`.
2. **The API response contract** — in progress on the Go side
   (`internal/app` contract tests + the fixes listed above).
3. **The console side of that contract** — the next piece of work, and it should
   be done against the canonical key list from step 2: the `qtype` fields that
   are numbers on the wire but strings in TypeScript (the server also sends
   `qtype_name`), `blocked_pct` arriving as 0..100 from the dashboard and 0..1
   over SSE, the `whoami.can_write` / `read_only` flags that are fetched and
   never used (a read-only key still shows every Save control), a `latency`
   block the dashboard never receives, the cache "Lookups"/"Last seen" columns
   reading `count`/`last_seen` where the API sends `hits`, and the refresh toast
   that says "0 sources queued" because the API returned null.
4. **The remaining server tests** — in progress: shutdown ordering (in-flight
   queries, idempotent `Stop`, a cancelled context, the port actually being
   released), the stats counters, and a table for the pure helpers.
5. **Decide the open questions** in the pinned list above, one at a time, each
   with a changelog note: the RPZ apex, `OutcomeLocal`, the frozen auth config,
   the DoH client identity, CORS wildcards.
6. **Stop hand-writing the console's types.** The contract tests make the Go
   side authoritative; the cheapest durable answer is generating
   `web/src/lib/types.ts` from the Go structs (or an OpenAPI document emitted by
   the server) so `apiFetch` is typed against something real instead of
   `JSON.parse(text) as T`.

## Design notes worth preserving

- **Cache stores packed wire bytes, not `*dns.Msg`.** A hit costs one `Unpack`
  and yields a private copy, so serving never mutates shared state and TTL
  ageing is free. Same trade dnsmasq makes.
- **Everything the query path reads is behind an `atomic.Pointer` holder** — ACL,
  blocklist, localzone, and now the upstream pool. Readers load the pointer once
  and work against a value that cannot change under them. Prefer a new immutable
  snapshot over a lock.
- **Cache invalidation on rule changes flushes the cache** rather than guessing
  which subtrees are affected (`invalidateBlocklistCache` in
  `internal/app/hooks.go`).
- **API responses share the field names in `internal/app/hooks.go`.** If you
  rename one, grep the frontend too — and now also expect `internal/app`'s
  contract test to fail, which is the point of it.
- **API keys are compared by SHA-256 hash, constant-time**, and
  `X-Forwarded-For` is honoured *only* from `trusted_proxies`.
- **The UDP listener resets its read deadline every iteration.** A deadline set
  once expires for good and turns the loop into a spin that never reads another
  packet (caught by `TestBlocklistToggle`).
- **Only the Valkey lease holder fetches lists**, so N instances do not hit a
  mirror N times.
- **Serve-stale** answers get TTL 1; an expired upstream answer is never cached;
  a truncated answer is never cached (it would be served truncated forever).
- **`PatternKind.Pattern` is the display form; `WireName` is the wildcard form.**
  The internal `*.` / `**.` prefixes must not leak into the UI, but the API
  needs them to re-add a rule unchanged (the domains list ships `rule` for
  exactly this).
- **pprof is loopback-only by construction**, not by policy, so no config flag
  can turn it into a network-reachable unauthenticated endpoint.
- **A master file's origin is its base name**, so a relative owner name in a
  zone is qualified with the file's name, not with the zone you meant. Absolute
  names are the only spelling that survives a rename.

## Test-hygiene traps

- `dns.NewRR` needs a TTL column: `dns.NewRR("host.example.com")` does not
  parse. That is a fixture bug, not a product bug.
- A test that closes a stop channel *after* `wg.Wait()` deadlocks the whole
  package and looks like "the suite hangs". Close first, then wait.
- Assert on invariants, not on what a concurrent goroutine happened to observe.
  "A reader must have seen address X" is a flake; "every list a reader sees is
  one of the published ones" is a real property and cannot flake.
- `tsc -b` replays **cached diagnostics** from `node_modules/.tmp/*.tsbuildinfo`.
  After a large edit, `rm node_modules/.tmp/*.tsbuildinfo`.
- `vite build` empties `outDir` and **deletes `internal/web/dist/.gitkeep`**.
  Restore it or the directory disappears from git. `//go:embed all:dist` still
  builds while the directory is empty, so a console rebuild in the middle of
  someone else's `go build` is not fatal.
- **A `TXT` string over 255 bytes does not pack** in miekg/dns v1.1.73 — the
  error is `dns: string exceeded 255 bytes in txt`, and 255 is the exact
  boundary. On a fake upstream's write path the failure is silent and presents
  as a client timeout, so build a multi-kilobyte answer out of many short
  strings and assert the fake's write error before blaming the client.
- **`dns.EDNS0_NSID.Nsid` is a hex string, not the bytes on the wire.** A plain
  value such as `"fancy-dns"` fails with `dns: overflow packing opt`, and a long
  NSID packs fine (unlike `TXT`). Always hex-encode on the way in.
- `gofmt -l internal/` is the fastest way to see that a file does not parse.
- The console has **no test runner at all** — only `tsc -b --noEmit` and
  `oxlint`. A field-name drift between the API and the console is invisible to
  both, which is why the Go side now has contract tests.

## Fixed earlier and worth not re-breaking

A running list, kept because each of these was invisible until it was found:

- `config.ParseSize` ignored the unit multiplier entirely (`512MiB` parsed as
  512 bytes), so every memory budget in the tree was off by a factor of the
  unit. `size_test.go` pins the units, the shadowing cases, the range and the
  truncating rounding.
- A cache miss and a stale hit moved only the Prometheus counter and not the
  atomics the console's `Totals` reads, so the Cache page read zero for the
  life of the process.
- `finalize` — the EDNS0/UDP-size step that turns an oversized answer into a
  question-only TC reply — ran only on the cache-hit path, so a multi-kilobyte
  answer from upstream, from the local zone or from a sinkhole was left as a
  datagram a 512-byte UDP client silently dropped.
- The serve-stale prefetch gate was a 64-slot channel, so a burst of stale hits
  on one hot name launched up to 64 duplicate upstream exchanges instead of the
  one its own comment promised. It is a per-key latch now.
- The upstream UDP client read buffer was hard-coded to 1232 while the engine
  advertises `dns.max_udp_size`, so an operator who raised it got SERVFAIL for
  every answer over 1232 bytes.
- Every relative RDATA name in a master file pointed at the DNS root: the
  qualification pass ran *after* `dns.NewRR`, so `www CNAME host` became
  `CNAME host.`. It is now a token-level pass driven by a table of which RDATA
  positions hold a name.
- The cache snapshot never round-tripped: `Load` decoded the record header out of
  the *key's* remainder instead of the value, so every restart was a cold cache.
  There is now an `encodeRecord`/`decodeRecord` pair with a version byte and a
  CRC-32C trailer, and `Load` drops expired entries and rewrites the TTL to the
  time actually left.
- `${VAR}` expansion never worked inside quotes — the only form anyone writes —
  because the reference check sat below the quote branches in the same switch.
  The admin API key was the literal string `"${FANCYDNS_API_KEY}"`.
- ACL PTR suffix matching crossed label boundaries, so a group scoped to
  `example.com.` also swallowed `ample.com.`; the ACL `*` catch-all was dropped
  from the rendered domain patterns; `Upstream.Success` never closed an open
  breaker; `Exchange` fanned out in parallel even under `policy: failover`; the
  cache byte budget was never fed to the LRU.
- **`TestRebindUnderConcurrentQueries` was a flake** (2 runs in 10) because it
  asserted a reader had to observe two specific addresses. It now pins the
  copy-on-write invariant itself.
- CI could not have passed (`go.mod` requires Go 1.27.1, CI and the Dockerfile
  pinned 1.23), the Dockerfile clobbered the console by copying the source tree
  after the bundle, and the k8s set could not have worked (`hostNetwork: true`
  with `replicas: 2` and no SO_REUSEPORT).
- `$TTL` was ignored by the zone parser; every record got the SOA minimum.
- Blocklist: leading BOM stripped, `!allow` works, `SourceMeta` exists for a
  rule-only source, `Pattern()` reports the bare name while `WireName()` gives
  the wildcard form, RPZ inherits the zone default TTL, hosts files complain
  about a missing address, adblock handles CRLF and over-long lines.
- `serveUDP` called `net.ResolveUDPAddr` per packet; the peer already is a
  `*net.UDPAddr`.