# Milestone 20: declarative configuration for IaC

Goal: a config file an operator can keep in git and deploy with Ansible, where the file is the sole declarative source of truth, converged at every boot — without re-downloading every blocklist on every boot, and without the UI silently diverging from the file. Two authority modes, selected by the presence of one flag: bare `run` serves the DB; `run --config=<path>` makes the file authority.

Design finalized 2026-08-09 after three adversarial rounds (red team ops 1-16 and debt 1-14; Codex cross-validation F1-F12; a Codex round on the premise revision). All findings are folded in below or declined with written reasons; all file:line anchors were re-verified at the pre-implementation HEAD (7039a9f). A premise revision replaced the earlier `--config-source` mode enum with presence-of-`--config` and deleted the persisted authority marker; rulings 1, 6 and 8 record the reasons — do not reintroduce either.

## Implementation contract (read first)

- Read `AGENTS.md`, then this spec whole, before session work starts.
- Session order: R1 → R2 sequential; R3 and R4 parallel to both (Sessions, below). File ownership is write-exclusivity; the interfaces between sessions (`reconcile.Summary`, `WebState.authority` + `reconciled_at`, `RouteInfo.policy`) are fixed in this spec and are not renegotiable mid-build.
- Gates: `zig build test` and `zig build test -Dintegration` with 0 failed, plus the drift-guard regenerations the Tests section names. Skip counts are reported with their reasons (plain-suite skips are integration-gated; the 4 integration skips are the live-network TLS tests excluded by milestone-1 design). One `-Dlive` run covers the real download path (Tests).
- No `std.log.err` in new code. No secrets in logs — url redaction goes through `src/safe_url.zig` as everywhere else.
- Every fix or behaviour claim lands with a test the author watched fail against the reverted implementation (milestone-13 ruling F-f applies).
- Doc pages touched by R4 follow milestone-13 ruling 3: every command block in `tutorial/` and `how-to/` is executed on this host by the session that writes it, or marked in-page as unverified with the reason.
- The final commit is GPG-signed by the user (`git commit -S`, lowercase, single line); stage the work and hand the command over.

## Rulings (binding)

### 1. Authority is the invocation: `--config` present means the file governs

`nxdns run` — the DB is authority, today's appliance behaviour. `nxdns run --config=/etc/nxdns/config.zon` — the file is authority. The flag's presence selects the mode; there is no mode enum and no default path. `check` keeps its existing surface under the same rule: bare `check` grades the DB, `check --config <file>` grades the file. The DB-exists-wins heuristic in `checkImpl` (cli.zig:559-588) and `CheckArgs.config_explicit` are deleted.

Two principles, separated deliberately, because conflating them is what produced the rejected `--config-source` enum:

- **Authority must be explicit in the invocation.** An operator reads `ExecStart` and knows which authority is live. Probing `/etc/nxdns` for a file and switching behaviour on its existence is ambient magic — the same class of heuristic that made seed-once bootstrap a source of doc lies (the compose comment, the first-run tutorial) — and stays banned: a file on disk that no flag names changes nothing.
- **A mode enum is the wrong shape for a two-state choice a path already expresses.** `--config-source=db` names an implementation, not an operator intent, and a mode flag beside a path flag manufactures invalid combinations (path without mode, mode without path) that then need pairing rules and usage errors to defend. Presence-of-path has no invalid combinations and nothing to defend.

Breaking change, named: `run --config <file>` today means seed-once; the same syntax now means file authority — reconcile on every boot, UI config writes rejected. For an operator who seeded once and then configured through the UI, the first post-upgrade restart converges the DB to that old seed file, deleting the UI edits. The upgrade doc's breaking-changes section leads with this and gives the two exits (ruling 9): drop the flag, or re-export to the file path first. `check --config` keeps its meaning exactly. Greenfield rules apply — the seed-once interface does not survive for compatibility — but the break is loud in the docs, never silent-by-omission.

A rename (`--managed-config`) that would make the old invocation fail loudly was considered twice and declined: it trades a worse name and a permanent asymmetry with `check --config` against a one-time hazard whose exposed population is the pre-change install base of a project whose first release is days old. The hazard is real and the docs lead with it; the interface does not carry the scar. This is a judgment, recorded so it is revisited only with new facts (a real install base would be one).

### 2. File mode fails closed, and *declarative* failure is exit 2

File mode contract: the file is the sole declarative source; the DB stays the runtime substrate and the effective-config read path. Startup sequence, replacing the `seedFromFile` call at app.zig:196:

1. `DataDir.open` → open config DB → `migrate` (unchanged).
2. Read the file (existing 4 MiB cap), ZON parse (arena, never freed — keep the import.zig discipline), `validate.validate`.
3. Reconcile into the DB in one `BEGIN IMMEDIATE` transaction, `errdefer` rollback (ruling 3).
4. `config_export.readConfig` (app.zig:206) → serve, unchanged from there on.

A missing, unreadable, or invalid file fails startup. Never fall back to the DB: a fallback turns a deploy typo into a silently stale config.

Exit codes keep the 2am contract — exit 2 means "your config is wrong, run `nxdns check`"; exit 1 means "the box is wrong". `faults.isConfigFault` deliberately excludes `FileNotFound`/`AccessDenied` (faults.zig:107-108), and that stays true in general. The file-mode loader is the seam, and it maps **path-class open failures only**: `FileNotFound`, `AccessDenied`, `PermissionDenied`, `NotDir`, `IsDir`, `SymLinkLoop`, `NameTooLong`, `BadPathName` become `error.ManagedConfigUnreadable` (message includes the path), which joins the `ConfigFault` set beside `ParseZon`/`ConfigTooLarge`. Every other member of `ReadFileAllocError` — `SystemResources`, `ProcessFdQuotaExceeded`, `SystemFdQuotaExceeded`, I/O errors, `OutOfMemory` — propagates unmapped, exit 1: those are box faults a retry can clear, and once ruling 9 adds `RestartPreventExitStatus=2 64`, mapping them to exit 2 would stop the unit permanently on a transient fault. The mapping is an explicit named error set in the loader, switched exhaustively with `else => |other| return other`, so a std error added in a Zig bump defaults to exit 1 rather than silently to exit 2 — the same closed-set discipline faults.zig already documents. The mapping lives in **one shared helper** used by both `run` and `check`; two copies would let the two grade the same unreadable file differently, exactly the divergence faults.zig:1-8 exists to abolish.

**Scope of the check/run agreement claim**: `check --config=<file>` grades exactly the declarative faults `run` would hit — read (path-class), parse, size, validate — through the same shared loader helper. Reconcile-time faults (FK violations, `SQLITE_BUSY` from a restart race, disk full) are runtime faults, exit 1, and structurally invisible to `check`, which needs no DB. The acceptance encodes the scoped claim, not "check passing guarantees run converges". The one *systematic* gap the red team found — a group removal tripping the un-cascaded `clients.group_id` FK against observed rows `check` cannot see — is eliminated in the engine itself (ruling 3's reassign rule), not papered over in `check`.

Reconcile-time diagnostics include the SQLite error (`SQLITE_FULL` by name when that is the cause) so a full SD card reads as "disk", not as a bare exit 1. Diagnostics render to `r.err` and flush immediately, keeping the current `seedFromFile` discipline (app.zig:137-178) — `serve` never returns, so a buffered error line is a lost error line.

Because every boot revalidates the file, a latent file error is no longer a first-boot-only hazard: a bad push that skips its restart handler detonates at the next power blip. Two mitigations, both in ruling 9: the shipped unit gains `RestartPreventExitStatus=2 64` (retrying a config fault every 2 s is pure loop; the journal holds the diagnostics), and the deployment docs mandate `nxdns check --config=<file>` as the pre-restart gate in any Ansible handler.

Db mode: steps 2-3 are skipped entirely; the DB is truth exactly as today. Bare `check` on a box with no `config.db` exits 2: `no config database at <path>` plus the ruling-6 hint line — the deleted heuristic's "nothing to check" branch (cli.zig:582-587) is replaced, not dropped.

### 3. Reconcile engine: replace declarative state, preserve runtime state by stable identity

New module `src/config/reconcile.zig`, replacing `applyToDb`'s wipe+reinsert. The defect it exists to fix: today's import deletes and reinserts `blocklist_sources` including runtime columns (checksum, `last_updated`, counters — config_schema.zig:46-56), and compiled blocklists are keyed by source row id (`<id>.list`/`<id>.wild`). A naive re-import every boot would force a full re-download and recompile of every blocklist on every restart.

Contract, per table: match rows by identity key ⇒ UPDATE declarative columns in place (row id survives); present in DB but absent from the file ⇒ DELETE; present in file but not DB ⇒ INSERT. Never wipe. One transaction. The `clients` table refines the match rule with promotion (below): an observed row whose IP the file declares is matched and updated, never deleted.

**Identity matching is on canonical forms.** Import already canonicalizes client IPs and prefixes before insert (import.zig:226-237; `FD00:0:0:0:0:0:0:1` stores as `fd00::1`) and the schema documents the columns as canonical text. The engine canonicalizes file values *before* matching; matching the raw file string against the canonical column would churn ids under an unchanged non-canonical file, violating ruling 5 in a way an exported-config test (export emits canonical forms) cannot catch. The idempotence test includes a non-canonical file.

**Writes only on difference.** A matched row whose declarative columns already equal the file's values gets no UPDATE. This is stronger than byte-stability: reconciling an unchanged file performs **zero writes**, so a no-op boot needs no WAL headroom and a querylog-full SD card cannot brick a file-mode restart that db mode would survive. Testable: the second reconcile returns an all-zero summary and `sqlite3_total_changes` does not move.

| Table | Identity key | Declarative columns | Runtime-owned (preserved on match) |
|---|---|---|---|
| `blocklist_sources` | `url` | `name`, `enabled`, `is_suggested` | **`id`**, `checksum`, `last_updated`, `domain_count`, `wildcard_count`, `skipped_regex_count` |
| `groups` | `name` (`default` pinned to id 1, existing assert kept) | `safe_search` | `id` |
| `clients` | canonical `ip` | `name`, `group_id`, `hand_edited=1` | `first_seen`, `last_seen`; observed rows (`hand_edited=0`) are kept wholesale; an observed row whose IP is now declared in the file is **promoted in place** (UPDATE `name`, `group_id`, `hand_edited` 0→1 — `first_seen`/`last_seen` untouched, row id survives, counts as `updated`); observed rows whose group is deleted are **reassigned to the default group** (below) |
| `rules` | the full tuple `(group_id, pattern, kind, action)` — no natural key exists; the identity is a **multiset**, exact duplicate tuples pair off by count | (the tuple) | `id`, `created_at` (unmatched inserts stamp `now`) |
| `upstreams` / `client_prefixes` / `forward_zones` / `local_records` | `url` / canonical `prefix` / `zone` / `(name, rtype, value)` | everything else | `id` — preserved as a consequence of the idempotence invariant (ruling 5), **not** for FK stability: nothing references these ids by FK and id-based REST mutations are rejected in file mode |
| `group_sources` | `(group_id, source_id)`, resolved via the name/url maps | whole row | — |
| `settings` | key | value via `settings_repo.putSetting` upsert, on difference only | delete keys not produced by `toSettings`, **except** `web.password_hash`, which the reconciler owns directly (ruling 4) |

**Pass order (binding).** `delete_order` alone under-specifies the engine: inserts need parents before children, and a group DELETE cascades through `rules`, `client_prefixes`, `group_sources` (config_schema.zig:35, :60, :67), which could silently undo child-table work and corrupt the diff counts if deletes ran first or interleaved. The order is:

- **Phase A — upserts, parents first**: `groups`, `blocklist_sources`, then the referrers (`clients`, `client_prefixes`, `rules`, `group_sources`, `upstreams`, `local_records`, `forward_zones`, `settings`), with the name→id / url→id maps built after the parent passes. Client promotion happens here, in the `clients` pass.
- **Phase B — delete-absent, child first**, in `delete_order` (config_schema.zig:99). Because every declarative child of a dying group is itself absent from the file (validate guarantees file rules/prefixes reference file groups), the child passes have already deleted and counted them by the time the parent DELETE runs; the FK cascades become a safety net, never the accountant.
- Immediately before the `groups` delete pass: observed clients (`hand_edited=0`) whose `group_id` belongs to a dying group are reassigned to the default group (id 1). `clients.group_id` has **no** ON DELETE clause (config_schema.zig:26) — without this step, removing or renaming a group that observed devices had been assigned to trips the FK mid-transaction: exit 1, restart loop, and a `check` that said the file was fine. The reassignment is the semantics we want anyway: the operator un-declared the group, not the devices.

Consequences that make the fix complete: an unchanged URL keeps id **and** checksum + counters + `last_updated` together, so `loadSource` never sees `.never_fetched`, `needsRefresh` does not fire spuriously (preserving `last_updated` matters — checksum alone is not enough), `sweepOrphans` never orphans `<id>.list`/`<id>.wild`, and a restart costs zero downloads. A changed URL is a new identity: new row, new id, fresh download — consistent with artifacts keyed by id. **Accepted trade, stated**: the old row's compiled `<old-id>.list`/`<old-id>.wild` are orphaned at commit and swept before the new source's first fetch succeeds, so a URL edit whose new host is down leaves that list unenforced until a fetch lands. Deferring the sweep until a successor fetch would need a cross-artifact lifecycle for an event that is rare, operator-initiated, and bounded by the scheduler's retry — not worth the machinery on a household box. The REST `updateSource` keeps runtime columns across a URL edit; in file mode that route is rejected (ruling 7), so the divergence is unreachable; in db mode the reconciler only runs via explicit `import`.

Related clock fix, same subsystem: `needsRefresh` is wall-clock arithmetic (`now - last >= interval`, manager.zig:1201-1202) and the Pi has no RTC. A fetch stamped while the clock was ahead (pre-NTP boot, restored image) suspends refresh until real time catches the future timestamp — and this design's idempotence would faithfully preserve the poison forever, having deleted the wipe that used to be the accidental reset lever. The engine's sibling fix: `needsRefresh` treats `last_updated > now` as refresh-due. One comparison, with a test.

Client promotion in place makes the `saved_clients` lift/merge/restore scaffolding (import.zig:268-361, including `merge_observed_timestamps_sql`) unnecessary: that machinery exists only because the wipe destroyed `first_seen`/`last_seen` and had to smuggle them across. With no wipe, the semantics it encodes — observed history survives declaration — are a plain UPDATE that never touches the timestamp columns. The scaffolding dies with the wipe (Deletions); its tests' semantics move to the promotion tests.

**Ordering invariant**: reconcile commits before `manager.reload` (app.zig:400) runs and before the scheduler's `sweepOrphans` can fire, so preserved ids and checksums are visible to the filter layer before any pruning. This holds by construction — reconcile completes inside `serve()` before the manager exists — and is enforced *behaviorally*, not by a statement-order unit test with nothing to grip: the restart-no-redownload integration test (Tests, below) fails if anything between reconcile and reload re-orders or wipes. No `serve()` restructuring is chartered for this.

The engine returns a summary (ruling 8's input and the cross-session contract):

```zig
pub const TableCounts = struct { inserted: u32, updated: u32, deleted: u32 };
pub const Summary = struct {
    groups: TableCounts, sources: TableCounts, clients: TableCounts,
    client_prefixes: TableCounts, rules: TableCounts, group_sources: TableCounts,
    upstreams: TableCounts, local_records: TableCounts, forward_zones: TableCounts,
    settings: TableCounts,
    auth_transition: enum { none, enabled, disabled, rotated },
};
```

`updated` counts only rows actually written (writes-on-difference); observed-client preservation counts nothing; promotion and reassignment count as `updated` on `clients`. `deleted` on `clients` means exactly one thing: a formerly declared (`hand_edited=1`) row absent from the file. An unchanged file yields an all-zero summary.

New repo verbs carry the engine (`sources_repo.upsertByUrl`, per-table `deleteWhereNotIn`-style helpers), not new call ordering. `applyToDb` and its wipe loop are deleted; import.zig keeps its parse/validate/diagnostics plumbing.

### 4. Password: the file overrides when it speaks, and only then

`model.Web` changes to `password: ?[]const u8 = null` and `password_hash: ?[]const u8 = null`. The settings bridge splits its skip policy by direction — `isSkipped` becomes two functions, because encode and decode need different sets:

- `isEncodeSkipped` = {`web.password`, `web.password_hash`}: `toSettings` stops emitting `web.password_hash` (the reconciler owns that settings row directly) and continues to never emit `web.password`.
- `isDecodeSkipped` = {`web.password`} only: `fromSettings` **still loads** `web.password_hash` from the settings table — the reconciler owning the write does not mean the read path stops seeing it. Skipping it on decode would leave `cfg.web.password_hash` null on every read path (`config_export.readConfig` at export.zig:52, `mutations.loadConfig`), turn `authEnabled` false, and silently disable auth in both modes.
- `decodeValue` gains an `.optional => try decodeValue(child, text)` arm (model.zig:408-421 has none today; an unskipped optional field is currently a `@compileError`). Absent key ⇒ default `null`; present ⇒ non-null.

`auth.authEnabled` becomes `(web.password_hash orelse "").len != 0` (auth.zig:62-63); app.zig:475's `.live_hash = .init(...)` unwraps with `orelse ""`. The cases:

- **Both set**: existing error (`PasswordAndHashBothSet`, import.zig:250, validate.zig:395 — the check ports to `!= null` on both fields).
- **`password` present and empty**: rejected by `validate` with a new diagnostic naming the remedy — `password_hash = ""` is how auth is disabled declaratively. Without this rejection, `.password = ""` would hash the empty string into a non-empty PHC (`authEnabled` true) while auth.zig:90 refuses every empty-password login: auth on, unreachable. A declarative fault, exit 2, so ruling 2's check/run agreement holds.
- **`password` set (non-empty plaintext)**: verify against the stored `web.password_hash` with argon2; on match keep the stored hash, on mismatch or absent stored hash, hash fresh. The justification is ruling 5 alone: hashing unconditionally generates a fresh salt per apply and breaks byte-stability. It is **not** a cost saving — argon2 verification recomputes the full function (same t=2, m=19 MiB) with the stored salt, so verify-and-keep costs exactly what hashing costs. Do not "optimize" the verify away with any cached-plaintext scheme; that would be a security bug.
- **`password_hash` set**: written verbatim. An explicit `password_hash = ""` is the declarative way to disable auth (auth.zig's documented empty-hash state).
- **Neither set**: the stored hash is untouched. This is the deliberate carve-out from file-as-sole-truth, because the naive alternative is a trap the red team walked straight into: `toSettings` today always emits `web.password_hash` with default `""` (model.zig:534, :93), so an operator who hand-trims the ugly PHC string out of an exported file — meaning "keep the current password" — would silently reconcile `""` over the stored hash and open the admin UI to the LAN (`authEnabled` is `len != 0`, auth.zig:63). Silence must mean "keep", and disabling auth must require the explicit empty string.

**Export's canonical form**: `password = null`, `password_hash = <stored value, including "">`. A non-null `password` is never emitted — the current `cfg.web.password = "";` at export.zig:71 ported literally would make every export carry a present-empty password beside a stored hash, tripping `PasswordAndHashBothSet` on re-import: export's own output failing its own rule, breaking ruling 9's adoption walkthrough and ruling 5's round trip. The comment at export.zig:67-70 and the header sample change with it. With `password = null`, the empty-plaintext rejection above does not fire and the "hash written verbatim" branch keeps idempotence.

Any auth transition (enabled/disabled/rotated) is reported in the summary and printed by ruling 8 — an auth change is never a silent line item in a count.

### 5. Idempotence is the invariant

Reconciling the same file twice produces a byte-identical database — ids, checksums, timestamps, `created_at`, password hash, the whole settings table — **and** the second pass performs zero writes (all-zero summary, `total_changes` unmoved). The unit test asserts byte-stability via the `dump()` helper (import.zig:469), which is rewritten to iterate an explicit all-tables list (`config_schema.table_names`, all ten content-bearing tables) because its current driver, `content_tables`, is deleted (ruling 6). Anything that churns under an unchanged file — including a *non-canonical but equivalent* file — is a bug in the engine, by definition. (This invariant is what forces ruling 3's rules-multiset, canonical matching, and writes-on-difference, and ruling 4's password handling — the places a naive design silently violates it. It is also half of why ruling 8 persists no authority state at all.)

### 6. `import` becomes a thin wrapper over reconcile; the guard becomes diff-gated

`nxdns import` is db mode's one-shot apply and the restore tool, reimplemented on the reconcile engine. Reconcile is non-destructive of *runtime* state, but deletion of declarative rows absent from the file is still a first-class outcome (ruling 3) — a mistaken `nxdns import ./wrong.zon` against a configured DB would still remove every group, rule, upstream, and source not in that file. So the guard is **retargeted, not deleted**: emptiness-gating (`isEmpty`) becomes diff-gating.

- After the reconcile passes, still inside the same `BEGIN IMMEDIATE` — preserving import.zig:199-203's deliberate check-inside-the-write-lock property, no TOCTOU — if any table's `deleted != 0` and no override flag, roll back and fail exit 2 with the per-table delete counts in the message. Observed-client reassignment is not declarative data and never trips the gate (and under ruling 3's promotion rule, observed rows are never deleted by reconcile at all).
- The flag is `--allow-delete` (`Options.allow_delete`), the renamed `--force`; the error is `error.DestructiveImport`, the renamed `DatabaseNotEmpty`, exit-2-mapped where cli.zig:533 maps today. This is strictly better than the emptiness guard: additive and edit-only re-imports stop needing a flag at all, and the flag now names what it permits. "Edit-only" means edits to declarative columns on a matched identity; an edit that *changes an identity column* — a group name, a source or upstream url, a prefix, a zone, a rule tuple, a local-record identity — is a delete plus an insert to the engine (ruling 3) and needs the flag. cli.md states the distinction.
- `import.isEmpty` and `content_tables` still die — the diff-gate needs no table list.

`import` does not detect a file-managed DB, because nothing records one: authority lives in the invocation (ruling 1) and the DB carries no marker (ruling 8). On a box whose unit runs file mode, `import` behaves like any other import — the diff-gate guards deletion, and the next boot's reconcile converges the DB back to the file, its summary reporting what it corrected. The docs own this story plainly: `import` is a **stop-first operation**, on a file-mode box doubly so — against a running instance its effect is partial (the runtime divergence below) and lasts only until the next restart. The file-authority contract is stated with the same precision everywhere: the file is the sole declarative source, **converged at every boot** — not a lock on the database between boots. A detect-and-warn variant was designed and deleted (ruling 8) — a per-invocation warning cannot *prevent* db-side writes anyway, the CLI user is root on their own box, and the asymmetry with the web layer's 403 is intentional: the web UI has anonymous-ish LAN users, the CLI has the operator.

What a mid-run import against a *running* file-mode instance actually does — documented, because the divergence is partial, not merely deferred: `Manager.reload` re-reads `blocklist_sources`, `groups`, `group_sources`, `rules`, `clients`, `client_prefixes` from the DB at runtime (manager.zig:405-489) and the scheduler runs `sweepOrphans` before every pass (manager.zig:1095, :1115), so filtering follows the imported rows on the next reload and can unlink the compiled `<id>.list`/`<id>.wild` of sources the import deleted — while upstreams, listeners, and settings stay at boot values, and the web UI shows the imported state under the file-authority banner. The next restart's reconcile re-inserts deleted sources from the file with new ids: a full re-download, the exact cost this design exists to prevent. That is why the docs name the restart requirement and the re-download cost. The settings envelope's `reconciled_at` cannot see a CLI import — ruling 7's weakened claim covers exactly this.

The startup-vs-import race needs no code: both paths take `BEGIN IMMEDIATE` under the 5 s busy timeout (db.zig:252), so the outcome is ordering, not corruption — an import racing a restart may be reverted by the reconcile that wins the lock second. Documented, not engineered around.

First-run story in db mode, after bootstrap dies: a fresh empty DB fails validation naturally (`NoUsableUpstreams`, exit 2). The remediation hint — one fixed line naming `nxdns import` and `run --config` — is owned by **cli.zig's db-source fault renderer** (one arm, beside the exit-code mapping; Zig errors carry no text and validate.zig must stay mode-blind), and the same line serves bare `check` with no DB (ruling 2). One location, R2's charter.

`export` is unchanged in role: the diagnostic/capture tool in both modes, and the file-mode adoption tool (its canonical password form changes per ruling 4).

### 7. Web layer: policy as data, rejected after auth, plain 403

`WebState` gains `authority: union(enum) { database, managed_file: []const u8 }` and `reconciled_at: ?i64`, built where `WebState` is assembled (app.zig:468). The `managed_file` path slice is owned by `serve`'s arena, which outlives `WebState` — R2 provides it, R3 consumes it, neither copies. `reconciled_at` is stamped by `serve` immediately after the reconcile commits — same process, same frame, a local — and is `null` in db mode, which never reconciles.

`RouteInfo` gains `policy: enum { read, config_write, runtime_action }` beside `auth` and `rate_limit` — policy-as-data, matching the table's existing style. No default value: all 56 route entries state their class explicitly, and router.zig's `test_table` (:198) gains the field too. Classification is per-route, not per-prefix: `POST /api/blocklists/update` is a `runtime_action`; its CRUD siblings are `config_write`.

- Config writes, rejected in file mode: all group / blocklist / rule / local-record / forward-zone / upstream / client-prefix mutations, `PUT /api/settings` (password changes go through the file; its `live_hash.installAndRevoke` side effect never fires in file mode), and client PUT — naming or regrouping an observed client is declarative drift (open question 1).
- Client DELETE is a **runtime action**: deleting an observed (`hand_edited=0`) row discards runtime state the file never declared — without this, a mis-identified or departed device's row is immortal in file mode, since the file can only promote IPs, never remove them. Deleting a *declared* client contradicts the file: the handler answers the same 403 envelope. This is the one policy decision that needs a row read; it lives in the client handler, not the router. (After ruling 3's promotion, a declared IP's row *is* declared — DELETE answers 403, the intended reading.)
- Runtime actions, always live: pause, blocklist refresh, cert reload, login/logout.

Enforcement lives in `router.dispatch` **after** `check_auth`, before the handler — match → rate limit → auth → policy. Pre-auth rejection would leak route existence; the codebase answers 401 first and this design keeps that.

Rejection is **403**, body the existing single-field envelope: `{"error":"configuration is managed by /etc/nxdns/config.zon; edit the file and restart"}`. Not 409 — that status already means constraint conflict four ways in openapi.yaml — and **no `code` field**: 403 is unused today, so the status alone is machine-readable; the UI learns authority declaratively from `GET /api/settings`, not by probing errors; and the single-property `Error` schema, golden contract samples, and `api.ts` stay untouched. An optional field with no consumer is machinery, not a contract.

The envelope must survive its own path: `respondError` today builds into a fixed 512-byte buffer and **silently downgrades to `text/plain`** on overflow (http_util.zig:315-327) — a long managed-file path (nested bind mounts) would demote the documented JSON envelope. Fix at the root: `respondError` gets the arena treatment `respondJson` already uses (`Writer.Allocating` over `request.arena`, :337-339) and the `respondPlain` silent-downgrade path is deleted — which fixes every long error message, not just this one. `src/web/http_util.zig` joins R3's ownership.

Authority discovery: the `GET /api/settings` envelope gains `authority: {mode, path, reconciled_at}` — an authenticated route, so the filesystem path never leaks through open `/api/version`/`/api/health`. All three come from `WebState` (live truth); `path` is present in file mode only and `reconciled_at` is nullable — `null` in db mode. Its meaning is exactly "**this process loaded the file at T**" — restart-pending detection: an mtime newer than `reconciled_at` means the running process has not loaded the current file. The comparison is one-directional and non-authoritative — a stepped clock (pre-NTP boot stamping the future, ruling 3's clock fix territory) or a preserved mtime (`git checkout`, `rsync -a`) can make a newer file look older, and the DB can move without either timestamp moving (ruling 6's `import`, this ruling's `runtime_action` routes). It does not answer "is the file what the server uses"; answering that would take content hashing, which the anti-requirements refuse. The UI renders a read-only banner (RestartBanner slot precedent) and disables mutation controls, with the 403 as backstop.

### 8. The operator can see what happened

- `logStartup` (after `logging.install`) logs the authority: `authority: database` / `authority: file (/etc/nxdns/config.zon)`.
- In file mode, the reconcile summary (ruling 3's `Summary`) prints through the Runner at startup, matching `seedFromFile`'s existing output discipline: per-table inserted/updated/deleted counts, the changed settings **keys** (never values), and the auth transition when there is one. It is the answer to "what did that restart change" without opening sqlite.
- **Authority is never persisted.** The DB carries no record of which mode wrote it: authority lives in the invocation (ruling 1), per-process state (`WebState.authority`, `reconciled_at`) serves the API (ruling 7), and the journal holds the history. A persisted marker was designed twice and deleted twice. A per-boot `reconciled_at` settings row breaks ruling 5 outright — `dump()` iterates the settings table, so any row rewritten per reconcile forfeits byte-identity, and `putSetting` moves `total_changes`, forfeiting zero-writes. The write-on-difference `authority.mode`/`path` variant survived idempotence but cost a reserved key namespace, a `fromSettings` decode filter, and a reconciler sweep exemption — three mechanisms whose only consumer was one `import` warning (ruling 6). State that exists to power a courtesy message is not worth a namespace. The settings sweep's exemption list is therefore exactly one key: `web.password_hash` (ruling 4).

No `std.log.err` in any new code, per the standing spec rule for new code (the pre-existing calls in db.zig/tls_server.zig are out of scope).

### 9. Deployment and migration

- **systemd**: the shipped unit stays flagless (db default) and gains two lines. `RestartPreventExitStatus=2 64` — a config fault or usage error must not restart-loop every 2 s until StartLimitBurst; the journal holds the diagnostics and the fix is a file edit, not a retry. (Correct in db mode too: exit 2 means the config is wrong in either mode. And it is why ruling 2 keeps exit 2 to *declarative* faults only — a transient box fault mapped to exit 2 would stop the unit permanently.) And `ReadOnlyPaths=/etc/nxdns` — `ConfigurationDirectory=nxdns` makes systemd create the directory owned by the service user, so without this line the source-of-truth file is writable by the very process whose mutation routes file mode exists to disable; nxdns never writes `/etc/nxdns` in either mode, so the base unit ships the enforcement rather than recommending it. Docs show a drop-in for file mode: `ExecStart=` reset plus `--config=/etc/nxdns/config.zon`.
- **Ansible / config-management**: the docs' deployment guidance mandates `nxdns check --config=<file>` as the handler precondition — validate the pushed file *before* restarting, so a typo is a failed deploy at noon, not a dead resolver at the next 3am power blip.
- **docker**: compose ships file mode as its example — `command: ["run", "--config=/etc/nxdns/config.zon"]` (resolving old open question 4; the `:ro` mount at compose.yaml:15 already suggests it). This keeps the fresh-install and volume-loss stories working after bootstrap dies: a recreated `nxdns-data` volume reconciles from the mounted file on next start, which is *better* than the old seed-once self-heal. The binary's default stays db. The seed-once comment (compose.yaml:9-12) is rewritten. For db-mode-in-docker, the docs show the recovery one-liner (`docker compose run --rm nxdns import /etc/nxdns/config.zon` — the file is positional, `ImportArgs.file` at cli.zig:61, plus `--allow-delete` when the diff deletes) — without it, `restart: unless-stopped` plus exit 2 is an infinite crash loop (docker has no start limit) with no documented way out.
- **Adopt file mode** on a UI-configured box: **stop the service first**, then `nxdns export --out /etc/nxdns/config.zon` → `nxdns check --config=/etc/nxdns/config.zon` → add the flag → start. Stop-first is load-bearing twice: any UI edit landing between a live export and the restart would be silently reverted by the first reconcile, and `check` refuses to grade a live database (immutable open, `WalPending` against the steady-state WAL, db.zig:222-226) so the pre-flight gate only works stopped. (Sync note, found in R4: the spec originally claimed `export` itself refuses against a live instance — it does not; `export` opens read/write and succeeds. The claim was corrected to name `check`.) Stopped, the first reconcile's summary is all-zero and writes nothing — blocklist state, compiled files, and client history all survive. Every unchanged boot after it writes nothing either.
- **Leave file mode**: drop the flag (remove the drop-in), restart. The DB already holds the last reconciled state; nothing else needed.
- **Binary downgrade from file mode**: no unit edit is needed — the old binary accepts `run --config` with seed-once semantics, and against the already-configured DB it ignores the file and serves the last-reconciled state. The rollback note states the consequence: file edits stop applying until the binary is upgraded again.
- **Restore from backup**: db mode is stop → restore `config.db` → start, with the WAL caveat db.zig itself documents: take backups only from a stopped instance (or use `export`), and on restore delete any stale `config.db-wal`/`config.db-shm` beside the target — a mismatched WAL is silently discarded by SQLite, which turns "restore" into "lose the tail". Restoring an *exported file* into a populated DB via `import` is exactly the deleting case: back-up-and-restore.md documents `--allow-delete` there (ruling 6) — the flag choreography is rewritten, not removed. In file mode `config.db` is not the config backup — the file is; restore = redeploy the file. The query-log DB restores independently in both modes.

Migration honesty, replacing the earlier blanket claim: a db-mode install that never passed `--config` needs nothing. Anyone whose unit, wrapper, or compose `command` carries `run --config` (the documented seed-once invocation in first-run.md and three how-to labs) gets file authority at the first post-upgrade start — the seed file becomes the config, and UI edits made since seeding are deleted by the first reconcile. The upgrade doc's breaking-changes section leads with this and gives the two exits: drop the flag to keep the DB, or re-export to the file path first to adopt file mode cleanly (the walkthrough above). `check --config` keeps its meaning. Docker db-mode fresh installs must use the new compose or run `import` once. No schema migration.

### 10. Documentation is part of the change

`explanation/configuration-model.md` is rewritten around the two-mode model (its "why the database wins" argument becomes mode-scoped, not superseded). Seed-once claims are corrected in: the first-run tutorial, install-with-systemd, install-with-docker, upgrade (breaking-changes + rollback sections, ruling 9), back-up-and-restore (new restore semantics, WAL sidecars, `--allow-delete`), set-up-admin-authentication (the ruling 4 absence/empty-string rule), troubleshoot, cli.md (`run`/`check`/`import`/`export`, `--allow-delete`), configuration.md (optional password fields), files-and-directories.md, api.md (settings envelope, 403, per-route rejectability), the compose.yaml comment, README/INSTALL.

## Deletions (complete list)

`config/bootstrap.zig` (+2 tests, S7 cases 15-18, + app.zig import/call sites
:35/:142/:146 and tests :1124/:1237) · `import.isEmpty` (+6 tests, + the
storage_integration_test.zig call sites :763/:795/:894, + the clients_repo.zig doc comments :6/:129) · `config_schema.content_tables` (+its test; `dump()` re-pointed to the new `table_names` list) · `app.seedFromFile` (+its app.zig tests) · `CheckArgs.config_explicit` · the `checkImpl` source heuristic · `applyToDb`'s wipe loop, including the `saved_clients` lift/merge/restore scaffolding (import.zig:268-361 — superseded by ruling 3's promotion-in-place) · `toSettings`'s `web.password_hash` emission (+its key-list test row; the model.zig:665-670 "skipped in both directions" test is rewritten for the encode/decode split) · `http_util.respondPlain`'s silent-downgrade path (`respondError` rebuilt on the request arena).

Renamed, not deleted (ruling 6): `Options.force` → `Options.allow_delete` (`--force` → `--allow-delete`), `error.DatabaseNotEmpty` → `error.DestructiveImport` (cli.zig:533 arm retargeted, faults.zig exclusion and tests follow the name).

## Sessions

R1 lands first and R2 rewires onto it and carries every deletion — they are ordered, not parallel (the old plan had R1 deleting `bootstrap.zig` out from under R2-owned app.zig call sites). R1 is **additive engine plus one coordinated model change**, not purely additive: the `model.Web` optional fields force same-session edits at every site that reads them, or the tree stops building. R3 and R4 run parallel to both; their interfaces (`reconcile.Summary`, `WebState.authority` + `reconciled_at`, `RouteInfo.policy`) are fixed here.

### Session R1: reconcile engine + the coordinated model change

Owns `src/config/reconcile.zig` (engine + `Summary` as specified), the new repo verbs in `src/storage/repositories/`, the `needsRefresh` clock clamp in `src/filter/manager.zig`, registration in `src/tests.zig`. Rulings 3, 4, 5.

Owns `src/config/model.zig` whole: the optional `Web.password`/`password_hash` fields, the `isEncodeSkipped`/`isDecodeSkipped` split, `decodeValue`'s `.optional` arm, and the bridge tests. And the sites the optional fields break, which no session previously owned: `validate.zig` (:395 both-set port, the new empty-password rejection, test :1966-1968), `auth.zig` (`authEnabled` orelse), `export.zig` (canonical `password = null`, comment and header sample), `src/web/handlers/settings.zig` (`newPassword`'s `orelse` chain at :184-186, and `FieldType` collapsing `?T` so `Partial`'s `?FieldType(...)` at :114 does not generate a double optional — landing this in R1 keeps R3's `web/` work unblocked). R1 also makes the one-line `orelse ""` edit at app.zig:475 so the tree builds; app.zig otherwise stays R2's, and R2 absorbs that line into its startup rewire.

### Session R2: CLI + startup + deletions

Owns `src/cli.zig`, `src/app.zig`, `src/config/faults.zig`, `src/config/import.zig` (thin-wrapper rewrite, diff-gate, `--allow-delete`), the shared loader-fault mapping helper (ruling 2, used by `run` and `check`), and the entire Deletions list plus the renames. Rulings 1, 2, 6, 8. Threads authority and `reconciled_at` into `WebState` (arena-owned path) but does not touch the router. Owns the cli.zig hint-line renderer arm.

### Session R3: web enforcement + UI

Owns `src/web/router.zig` (dispatch policy step, `test_table` gains the policy column), `src/web/routes.zig` (all 56 entries state `policy` explicitly — no default), `src/web/http_util.zig` (`respondError` arena rewrite, `respondPlain` downgrade deletion), `src/web/openapi.yaml`, the client-DELETE observed/declared branch in the clients handler, `web/` frontend (banner, disabled controls, settings envelope with nullable `reconciled_at`). Ruling 7. Consumes `WebState.authority`/`reconciled_at` as fixed above.

### Session R4: deployment + docs

Owns `deploy/**`, `docs/**`, `README.md`, `INSTALL`, compose file + comment, the systemd unit's two new lines. Rulings 9, 10.

### Orchestrator

This spec, R1→R2 sequencing, cross-session integration, the drift-guard regenerations that span sessions (contract samples, openapi route counts, api.md/cli.md rows), and the `-Dlive` acceptance run.

## Tests

- **Reconcile unit tests** (R1, `:memory:` + migrate): idempotence via the rewritten `dump()` byte-stability across all tables after applying the same file twice — including a file carrying a plaintext password **and a non-canonical but equivalent file** (`FD00::1`-style) — plus the zero-writes assertion (all-zero `Summary`, `total_changes` unmoved) on the second pass; per-table preservation via `sources_repo.SourceRow` after seeding stats with `updateSourceStats`; URL change ⇒ new id; source removal; observed-client survival, **promote-on-declare (asserting `first_seen`/`last_seen` survive the promotion and the row id is stable)**, and **reassign-to-default when their group is removed or renamed** (the un-cascaded FK case); `safe_search` edit on an existing group converges; rules `created_at` stability including duplicate tuples; password verify-keeps-hash, mismatch-rehashes, absent-keeps-stored, explicit-empty-disables; rollback on mid-tx failure; default-group id 1 pin; `needsRefresh` future-`last_updated` clamp.
- **Model/bridge tests** (R1, model.zig test neighbourhood at :659): `decodeValue` on an optional field (absent ⇒ null, present ⇒ value); `web.password_hash` decodes from settings but is not encoded (the encode/decode split); `validate` rejects present-and-empty `password` with the `password_hash = ""` remedy in the diagnostic; export ⇒ import round trip with the canonical `password = null` form.
- **Import gate tests** (R2): a file whose diff deletes rows, without `--allow-delete` ⇒ rollback, exit 2, per-table delete counts in the message; with the flag ⇒ applied; additive/edit-only import needs no flag.
- **Loader-fault mapping** (R2, on the shared helper directly): each path-class open error ⇒ `ManagedConfigUnreadable`; a non-path member of the set propagates unmapped.
- **Restart-no-redownload** in filter_integration_test.zig: reconcile, then a `Manager` restart reuses `<id>.list`/`<id>.wild` with no refetch (fixtures already assert reuse by id) — this is also the behavioral enforcement of ruling 3's ordering invariant. Plus **one `-Dlive` run of the real download path** — hermetic suites have hidden a process-killing bug on the real network path before (MEMORY), so the acceptance includes the real path once.
- **Router**: policy classification unit tests via `test_table`/`matchPath`, no sockets; the contract table in web_integration_test.zig gains a `policy` column and the existing 1:1 coverage assertion widens so classification cannot drift; one socketed test per class in file mode (config write → 403, runtime action → 2xx, read → 200) plus observed-vs-declared client DELETE, via `EnvOptions` authority; `respondError` with a message longer than the old 512-byte buffer stays `application/json`. Route count stays 56 — no new routes.
- **CLI**: `parseArgs` tests: `run` without `--config` selects db authority; `run --config=<path>` selects file authority and the path lands in the run args; `--allow-delete` parsing; `usage_text` test; exit-2 for a missing managed file and for bare `check` with no DB (hint line present) — via the `Captured` runner (in-process; remember the buffered-writer caveat — flush through a real `File.Writer` where the test asserts delivery).
- **Drift guards knowingly tripped and regenerated**: openapi.yaml (settings envelope, 403 responses), golden contract samples (`-Dcontract-samples-out`), api.md rows, cli.md sections, docs_drift_test, `toSettings` key-list test.

## Acceptance (design complete when implemented)

- [x] `nxdns run --config=<file>` on a DB with fetched blocklists (any boot
      after adoption): restart performs zero downloads **and zero DB writes**;
      source ids, checksums, `last_updated`, and compiled
      `<id>.list`/`<id>.wild` files are identical before and after. Proven
      once with `-Dlive` against a real source. *(Closed by
      filter_integration test 10e: a hermetic HTTP fixture counts accepted
      connections across a full Manager restart — 1 download total; inode,
      mtime and source ids identical. The `-Dlive` gate passed 1559/1559
      with 0 skips, which includes this test against the fixture and the
      live-network suites against real upstreams.)*
- [x] Reconciling an unchanged exported config twice yields a byte-identical
      `dump()` and an all-zero summary — including with a plaintext
      `password` in the file, and with non-canonical addresses.
- [x] Removing (and renaming) a group that observed clients were assigned to
      converges: clients land in the default group, no FK error, counts
      reported. Declaring an observed client's IP promotes the row in place:
      `first_seen`/`last_seen` and row id survive, counted as `updated`.
- [x] A file with neither `password` nor `password_hash` leaves the stored
      hash — and auth — intact; `password_hash = ""` disables auth and the
      startup summary says so; a present-but-empty `password` is refused at
      validate with a diagnostic naming `password_hash = ""` as the disable
      path.
- [x] `run --config=<file>` with a missing file exits 2 with the path in
      the message; with an invalid file exits 2 with diagnostics; never serves
      from the DB. An open failure outside the path class (fd exhaustion, I/O
      error) exits 1, not 2. `check --config=<file>` agrees with `run`
      on every parse/validate/path fault via the shared helper (the scoped
      claim of ruling 2).
- [ ] A config file present at `/etc/nxdns/config.zon` with no `--config`
      flag changes nothing: bare `run` serves the DB and never reads the
      file. *(Design claim, verified structurally: no code path opens
      `/etc/nxdns` — the deletion gate below proves the seed-by-presence
      path is gone, and tests cover bare `run` with a config file present
      in a lab directory. Not executed against the literal path
      `/etc/nxdns/config.zon` on a host that has one; this machine does
      not run nxdns from /etc.)*
- [x] `nxdns import` whose diff would delete rows fails exit 2 without
      `--allow-delete`, printing per-table delete counts, and rolls back;
      with the flag it applies; an additive import needs no flag.
- [ ] Fresh empty DB in db mode exits 2 (`NoUsableUpstreams`) with the hint
      line; bare `check` with no `config.db` exits 2 with the
      same hint; neither restart-loops under the shipped unit
      (`RestartPreventExitStatus=2 64`).
      *(Exit codes and hint lines are test-covered and closed. The
      no-restart-loop half is a design claim: the unit line parses under
      `systemd-analyze verify`, but no root systemd host was available to
      observe systemd actually holding the unit down. Close it on the Pi 5
      deployment.)*
- [x] The shipped compose file boots a fresh container (empty volume, mounted
      config.zon) into file mode successfully; the db-mode import recovery
      one-liner is documented and works. *(Run against a locally built
      image: first boot reconciled `upstreams +1 ~0 -0; settings +45` with
      auth enabled; second boot logged no changes.)*
- [x] In file mode: every `config_write` route answers 403 with the
      single-field error envelope — `application/json` even when the managed
      path is long; every `runtime_action` and `read` route behaves as in db
      mode; DELETE of an observed client succeeds, of a declared client
      answers 403; unauthenticated requests to protected routes still answer
      401, not 403.
- [x] `GET /api/settings` reports `authority` with `reconciled_at` (null in
      db mode); the UI shows the read-only banner and disables mutation
      controls in file mode.
- [x] `rg -n 'import\.isEmpty|content_tables|config/bootstrap|seedFromFile|config_explicit' src/`
      returns nothing (historical specs exempt; pattern chosen so
      fetcher.zig's `host.isEmpty()` and validate.zig's "bootstrap problem"
      prose cannot false-positive).
- [x] Adopt-file-mode walkthrough (stop → `export` → `check --config` → add
      the flag → start) run end to end on a UI-configured instance: the first
      reconcile summary is all-zero and writes nothing, as does every
      unchanged boot after it; leave-file-mode (drop the flag, restart)
      serves identically; `check` against the *running* instance's database
      refuses with the uncheckpointed-WAL message, as documented (corrected
      from `export`, which opens read/write and succeeds live — see ruling 9's
      sync note).
- [x] All existing gates pass; tripped drift guards are regenerated, not
      suppressed. *(Final numbers: `zig build test` 1429/1559 pass, 130
      skipped, 0 failed; `-Dintegration` 1555/1559, 4 skipped, 0 failed;
      `-Dintegration -Dlive` 1559/1559, 0 skipped, 0 failed. The live gate
      also caught and fixed storage S7 case 22, whose expectation had been
      stale since milestone 13 because nothing ran `-Dlive` in between.)*

## Anti-requirements

- No file watcher, no inotify, no SIGHUP reload — restart is the reload.
- No UI write-back to the file, no partial/merge authority, no per-table hybrid modes, no multi-file config.
- No persisted authority state, no config hashing, no content-based change detection — authority lives in the invocation; last-load time is per-process state in the settings envelope, honest about what it can and cannot answer (ruling 7).
- No deferred deletion of a replaced source's compiled artifacts — the URL-edit gap is an accepted trade (ruling 3), bounded by the scheduler retry.
- No etag/conditional GET for blocklist fetches.
- No `code` field or richer error envelope — the status is the machine contract.
- No rule-identity schema change (no synthetic rule key column).
- No preservation of rule `created_at` across pattern edits — an edited rule is a new rule.
- No CLI-side blocking or detection of `import` against a file-mode box's DB — the diff-gate guards deletion; the next boot converges and its summary reports what it corrected.
- No fallback from file mode to db mode under any failure.

## Resolved defaults (were open questions; the user may overrule before R3/R4)

1. **UI naming and regrouping of observed (`hand_edited=0`) clients in file mode: rejected as declarative drift** (client PUT stays `config_write`, ruling 7). The household user adds the client to the file instead. The alternative — carving naming/grouping out as a runtime action — reintroduces two-way merge for one table, which the anti-requirements refuse. Affects R3.
2. **`export` output is byte-identical in both modes** — no file-mode annotation. An annotation would make export → file → adopt produce a different file than the one checked, for a label the operator already has in the unit file. Affects R4's round-trip docs.
3. **File mode ships as a documented systemd drop-in**, not a second commented `ExecStart` in the packaged unit. The packaged unit stays flagless and correct by itself; a commented alternative line in a unit file is a doc pretending to be config. Affects R4.

## Cross-validation findings rejected

Round 1: none — all twelve findings (F1-F12) were confirmed against the repo and are folded into the rulings above. The F1 remedy has since been superseded: the premise revision deleted the persisted marker entirely (ruling 8) instead of keeping it write-on-difference.

Round 2 (on the premise revision) returned three important findings and one minor. Folded: the docker recovery one-liner used a `--config` flag `import` does not have (fixed in ruling 9, file is positional); `import` is now stated everywhere as a stop-first operation and the file-authority contract as "converged at every boot" (ruling 6); identity-column edits are named as delete-plus-insert needing `--allow-delete` (ruling 6). Declined: renaming `run --config` to `--managed-config` — reasons recorded in ruling 1.

## Red-team findings rejected

None rejected outright — every finding checked out against the repo. Two proposed remedies were declined while their findings were accepted:

- **ops 10's mitigation** (keep the old compiled artifact until the successor URL's first successful fetch): declined — a cross-artifact lifecycle for a rare, operator-initiated event on a household box; the trade is now stated in ruling 3 and the anti-requirements instead.
- **ops 14's db-mode warning** ("a config file exists but authority is database"): declined — db mode is given no file path, so warning would mean probing a well-known location, which is precisely the ambient inference ruling 1 bans; the accepted half (drift visibility) is served by the settings envelope's `authority` block and per-process `reconciled_at`.
