gunnar_server/

control_plane.rs

//! `gunnar-grpc`'s [`ControlPlane`] seam, over `gunnar-core` and
//! `gunnar-store`: the adapter its module docs asked for.
//!
//! `gunnar-grpc` was written before `gunnar-core` existed and defined a local
//! trait describing what the seven services need. Its own docs say the trait
//! must become *"a thin adapter, one impl in this crate"* and must never be a
//! second source of truth for what a `Repo` is. This is that adapter, living
//! one level up because it is the binary that knows both halves.
//!
//! # What is real here, and what is not
//!
//! | surface | status |
//! |---|---|
//! | namespaces, repos | real, [`RepoCatalog`] |
//! | principals, keys, grants | real, [`AuthTable`] |
//! | `Refs.List` / `Get` / `ReadObject` / `Log` | real, the repository's own stores |
//! | `Admin.Stats` / `StorageInfo` | real, measured off the `fs` backend |
//! | `Refs.Diff` | **`Unimplemented`**: no diff engine on the server side |
//! | `Policy.*` | **`Unimplemented`**: `gunnar-core` has no protection store |
//! | `Mirror.*` | **`Unimplemented`**: mirroring needs `gunnar-client`, which an `S` crate must never link |
//!
//! Every one of those is an explicit [`ControlError::Unimplemented`] and never
//! an empty success. An empty ref list is indistinguishable from a working
//! server with no refs (measured, not asserted), and the same is true of "0 mirrors synced".
//!
//! # Three model mismatches, recorded rather than papered over
//!
//! 1. **`RepoPath` cannot express a nested namespace.** `gunnar-proto`'s
//!    `RepoPath::validate` rejects a `/` inside `namespace`, but nesting makes
//!    `team/sub/repo.git` legal over SSH. Such a repository is reachable by git
//!    and invisible to gRPC. That is a `gunnar-proto` change, not one to make
//!    here.
//! 2. **`Scope::Server` has no `RepoPath`.** A server-wide grant is carried as
//!    an empty namespace and an empty repo, which `MemoryControlPlane` refuses
//!    on the way in. The test double is the one that is wrong: without a
//!    server-scoped grant the bootstrap admin cannot create the first namespace
//!    (the secret-store seam).
//! 3. **`Namespace` in `gunnar-core` carries only a name** — no description, no
//!    creation time — so those two proto fields come back empty rather than
//!    invented.

use std::sync::Arc;

use gunnar_core::{Grant, HashKind, Level, PrincipalKind, RepoRef, Scope, UnixMillis, Visibility};
use gunnar_grpc::seam::ControlCounts;
use gunnar_grpc::MergedRef;
use gunnar_grpc::{ControlError, ControlPlane, ControlResult, NewRepo as ProtoNewRepo};
use gunnar_proto::{
    BranchProtection, Commit, FileChange, GrantLevel, MirrorConfig, Namespace, Principal,
    PublicKey, PullRequest, PullRequestState, ReadLfsObjectResponse, ReadObjectResponse,
    RefNamePolicy, RefTarget, Repo, RepoPath, RepoStorage, Signature, StorageInfoResponse,
};
use gunnar_store::git_storage_trait::{GitServe, ObjType, RefRow};
use gunnar_store::object;
use gunnar_wire::RefSnapshot;

use crate::storage::OpenRepo;
use crate::stores::ServerStores;

/// **How long abdication waits for the standby's queues to drain**, seconds.
///
/// A ceiling, not a promise: a standby that is down must not wedge the
/// hand-off, so after this the roster is cleared anyway (a recovered standby
/// replays from this box when it is re-added the other way round). Long enough
/// that a reachable standby with a normal backlog finishes first.
///
/// The wait itself is already a POLL (drained-or-deadline, below) — it returns
/// the instant every queue is empty and never sleeps a fixed span. The one
/// thing a fixed default cannot know is the box's LOAD: on a heavily loaded rig
/// a healthy standby's normal backlog can take longer than 30 s to drain, and
/// clearing the roster early truncates the flush. So the ceiling is TUNABLE —
/// `GUNNAR_ABDICATE_FLUSH_SECS` raises it for a loaded deployment without
/// changing the poll's shape (still drained-or-deadline, still short-circuits).
#[cfg(feature = "replication")]
const ABDICATE_FLUSH_SECS: u64 = 30;

/// The abdication flush ceiling in effect: `GUNNAR_ABDICATE_FLUSH_SECS` if it
/// parses to a positive value, else the [`ABDICATE_FLUSH_SECS`] default. A zero
/// or unparseable value is ignored (a 0 s ceiling would clear the roster before
/// a single job could drain — never what an operator means).
#[cfg(feature = "replication")]
fn abdicate_flush_secs() -> u64 {
    // The raw string is HANDED IN to the pure resolver so the parse is unit
    // tested without `set_var` — which is process-global and flakes the whole
    // suite across threads (see `wg.rs`'s note on the same hazard).
    resolve_flush_secs(std::env::var("GUNNAR_ABDICATE_FLUSH_SECS").ok().as_deref())
}

/// Pure ceiling resolver: a positive parsed override wins; anything else
/// (absent, blank, non-numeric, zero) falls back to [`ABDICATE_FLUSH_SECS`].
#[cfg(feature = "replication")]
fn resolve_flush_secs(raw: Option<&str>) -> u64 {
    raw.and_then(|v| v.trim().parse::<u64>().ok())
        .filter(|&s| s > 0)
        .unwrap_or(ABDICATE_FLUSH_SECS)
}

/// Company SSO's storage on the identity table (`gunnar_grpc::sso::plane::SsoPlane`).
mod sso_plane;

/// **The refusal a read of the transaction log answers** — one spelling for `Mirror.LogFetch`
/// gathered and streamed: a released log is the named, retryable [`gunnar_grpc::PRIMARY_GROWING`],
/// a range retention dropped is `FailedPrecondition` (a snapshot is needed), a sequence above the
/// head is `InvalidArgument`.
fn log_read_refusal(e: gunnar_core::txlog::Error) -> ControlError {
    match e {
        gunnar_core::txlog::Error::Released(_) => ControlError::Unavailable(format!(
            "{} this box's data set is being grown (unmounted): its transaction log is back after the remount — ask again",
            gunnar_grpc::PRIMARY_GROWING
        )),
        gunnar_core::txlog::Error::NotRetained { seq, first } => ControlError::FailedPrecondition(format!(
            "seq {seq} is no longer retained; the oldest is {first} — a snapshot is needed, not a range"
        )),
        gunnar_core::txlog::Error::BeyondHead { seq, head } => ControlError::InvalidArgument(format!("seq {seq} is beyond the head {head}")),
        other => ControlError::Internal(format!("transaction log: {other}")),
    }
}

/// **A streamed range onto the wire as `LogChunk` pieces** (twin-streaming, 2026-10-06): `meta`
/// on an entry's first piece, `last` on the piece that completes its declared length — which
/// [`crate::twin::stream_range`] hands over only after the entry's payload crc checked — and an
/// entry with no blob as one empty last piece at its end.
///
/// Since restore-large-entry (2026-10-07) every piece says the byte of the blob it starts at
/// (`offset`), an entry may begin part-way ([`crate::twin::stream_range_at`], the resumed
/// restore's `from_offset`), and the last piece carries the entry's checked payload crc
/// (`entry_crc`), so a box that put the entry together across several streams applies it only
/// if it IS the entry.
#[allow(clippy::type_complexity)] // the seam's sink, spelled as the seam spells it
struct ChunkOut<'s> {
    sink: &'s mut dyn FnMut(gunnar_proto::LogChunk) -> ControlResult<()>,
    open: Option<OutEntry>,
}

/// The entry [`ChunkOut`] is sending.
struct OutEntry {
    seq: u64,
    kind: u32,
    /// Not yet sent: it goes on the first piece.
    meta: Option<Vec<u8>>,
    blob_len: u64,
    /// The byte of the blob the next piece starts at.
    at: u64,
    /// The checked payload crc, once the source said it (before the last piece).
    crc: Option<u32>,
    /// The `last` piece went out.
    ended: bool,
}

impl ChunkOut<'_> {
    fn send(&mut self, blob: &[u8]) -> anyhow::Result<()> {
        let Some(o) = self.open.as_mut() else {
            anyhow::bail!("a piece outside an entry");
        };
        let offset = o.at;
        o.at += blob.len() as u64;
        anyhow::ensure!(
            o.at <= o.blob_len,
            "seq {}: more than its {} blob bytes",
            o.seq,
            o.blob_len
        );
        let last = o.at == o.blob_len;
        o.ended |= last;
        let chunk = gunnar_proto::LogChunk {
            seq: o.seq,
            kind: o.kind,
            meta: o.meta.take().unwrap_or_default(),
            blob_len: o.blob_len,
            blob: blob.to_vec(),
            last,
            restore_head: 0,
            restore_bytes: 0,
            log_id: String::new(),
            offset: Some(offset),
            entry_crc: if last { o.crc } else { None },
            snapshot_item: None,
            snapshot_id: String::new(),
        };
        (self.sink)(chunk).map_err(anyhow::Error::from)
    }
}

impl crate::twin::FrameSink for ChunkOut<'_> {
    fn begin(&mut self, seq: u64, kind: u16, meta: &[u8], blob_len: u64) -> anyhow::Result<()> {
        self.begin_at(seq, kind, meta, blob_len, 0)
    }
    fn begin_at(
        &mut self,
        seq: u64,
        kind: u16,
        meta: &[u8],
        blob_len: u64,
        offset: u64,
    ) -> anyhow::Result<()> {
        anyhow::ensure!(self.open.is_none(), "seq {seq} began inside another entry");
        anyhow::ensure!(
            offset <= blob_len,
            "seq {seq}: from byte {offset} of a {blob_len}-byte blob"
        );
        self.open = Some(OutEntry {
            seq,
            kind: u32::from(kind),
            meta: Some(meta.to_vec()),
            blob_len,
            at: offset,
            crc: None,
            ended: false,
        });
        Ok(())
    }
    fn checked(&mut self, payload_crc: u32) -> anyhow::Result<()> {
        if let Some(o) = self.open.as_mut() {
            o.crc = Some(payload_crc);
        }
        Ok(())
    }
    fn piece(&mut self, bytes: &[u8]) -> anyhow::Result<()> {
        self.send(bytes)
    }
    fn end(&mut self) -> anyhow::Result<()> {
        // An empty blob, or one resumed AT its end: one empty last piece carries the end (and
        // the crc).
        if matches!(&self.open, Some(o) if !o.ended) {
            self.send(&[])?;
        }
        let Some(o) = self.open.take() else {
            anyhow::bail!("an entry ended that never began");
        };
        anyhow::ensure!(
            o.at == o.blob_len && o.ended,
            "seq {}: {} of {} blob bytes went out",
            o.seq,
            o.at,
            o.blob_len
        );
        Ok(())
    }
}

impl CoreControlPlane {
    /// **The log `Mirror.LogFetch` reads**, or the named refusal while it cannot be read: a set
    /// held for its own growth (the guard over an unmounted set; MEASURED release-3 mock
    /// 2026-09-29: `txlog: No such file or directory` mid twin-grow), or a PRIMARY whose log is
    /// released for its own growth's remount (M1, release-3 test2 mock 2026-09-29) — both named
    /// and retryable, never `Internal: txlog: No such file or directory`.
    fn readable_log(&self) -> ControlResult<&gunnar_core::txlog::Log> {
        if crate::twin::maintenance::is_held(self.stores.root()) {
            return Err(ControlError::Unavailable(
                "this box's data set is held for its own growth (unmounted): its transaction log is not readable until the growth mounts it back".into(),
            ));
        }
        if !self.stores.is_twin() {
            if let Some(why) = crate::twin::fenced_why(self.stores.root()) {
                return Err(ControlError::FailedPrecondition(format!(
                    "{why}. Nothing is read from it"
                )));
            }
        }
        let log: &gunnar_core::txlog::Log = self.stores.txlog();
        if log.is_released() {
            return Err(log_read_refusal(gunnar_core::txlog::Error::Released(
                log.dir().to_path_buf(),
            )));
        }
        // ★ twin-resync-space (2026-10-06): a twin that gave its stale copy up for a resync, or
        // is mid-install, holds no state at any one sequence — its log is not half a recharge.
        if self.stores.is_twin() {
            if let Some(why) = crate::twin::snapshot::not_whole(self.stores.root()) {
                return Err(ControlError::FailedPrecondition(format!(
                    "{why}. Nothing is read from it"
                )));
            }
        }
        Ok(log)
    }
}

/// The control plane, backed by the real catalog and identity table.
pub struct CoreControlPlane {
    stores: Arc<ServerStores>,
    /// **The runtime data-set growth** (`crate::grow`), when `serve` wired
    /// one. `None` on a bare plane (tests, `--dry-run`): `GrowStatus` then
    /// answers the seam's honest default and `GrowStart` is refused by name.
    grow: Option<Arc<crate::grow::GrowMachine>>,
    /// Started `--role twin` ([`CoreControlPlane::with_twin_role`]).
    twin_role: bool,
    /// **The git listener this server actually bound**, when `serve` handed it
    /// in ([`CoreControlPlane::with_git_listener`]) — the fact
    /// `Bootstrap.Status.serving_git` reports. `None` on a bare plane, and the
    /// status door then falls back to the boot window alone, exactly as it
    /// always answered. See [`crate::readiness::GitListener`].
    git_listener: Option<crate::readiness::GitListener>,
    /// **The ONE admission gate** the three git fronts share, when `serve`
    /// handed it in — read by `Mirror.FlushReplication` for the in-flight
    /// count the watermark needs (T11). `None` on a bare plane.
    admission: Option<Arc<gunnar_ssh::Admission>>,
    /// **What replication is doing**, for `Admin.Stats`.
    ///
    /// A [`ReplicationView`](crate::replication_view::ReplicationView) and not
    /// a replicator: this plane is built before the replicator is started
    /// (replication is started last on purpose, so nothing above it can be
    /// slowed by it), and the view is the slot `serve` drops it into
    /// afterwards. It also keeps `feature = "replication"` and every replication type
    /// out of this file, which is what lets the two lanes working on that
    /// module and on this one stay out of each other's way.
    ///
    /// Unfilled it reads `configured: false` — what a box with no standby *is*,
    /// and a fact rather than an absence.
    replication: crate::replication_view::ReplicationView,
    /// **What replication is CONFIGURED to do**, for `Mirror.SetReplication` /
    /// `RemoveReplication` / `ReplicationStatus`.
    ///
    /// The write half beside the read half above, and the two are not twins: the
    /// view answers *what has happened*, the slot decides *what runs*. It is
    /// `Option` and behind the feature's own name only through
    /// [`with_replication`](Self::with_replication), so a build without
    /// `replication` — and a `CoreControlPlane` built by a test that has no
    /// server around it — refuses the three verbs by name instead of failing to
    /// compile.
    ///
    /// **This is the whole reason the appliance can be told about a standby.**
    /// the reference appliance is an OS-less image running as PID 1: no shell, no
    /// editor, no `scp`. Before this, `replication.json` could only be written
    /// by something with a filesystem to write it from, which on that box is
    /// nothing at all.
    #[cfg(feature = "replication")]
    replication_slot: Option<Arc<crate::mirror::ReplicationSlot>>,
    /// **The live webhook slot**, so an operator can name an outbound endpoint
    /// over the control plane — the appliance has no shell, exactly as with the
    /// replication slot above.
    #[cfg(feature = "webhooks")]
    webhook_slot: Option<Arc<crate::webhook::WebhookSlot>>,
    /// **The live entitlement slot** (`metered` only): what `Entitlement.Set`
    /// writes and the front doors read. `None` on a metered build started
    /// without `--monetize-pubkey`: every namespace Free, and `Set` refuses by
    /// name rather than accepting a fact it could not verify.
    #[cfg(feature = "metered")]
    entitlement: Option<Arc<crate::entitlement::EntitlementSlot>>,
    /// **The disk-headroom gate** `Repos.Create` asks — the SAME object the
    /// front doors' chain holds, so "the disk is full" is one line on both
    /// doors (one implementation). `None` on a bare plane (a test not about the disk).
    headroom: Option<Arc<gunnar_ssh::DiskHeadroomGate>>,
    /// The largest object `Refs.ReadObject` will inflate. See
    /// [`DEFAULT_MAX_OBJECT_BYTES`] for the arithmetic and
    /// [`with_max_object_bytes`](Self::with_max_object_bytes) for changing it.
    max_object_bytes: u64,
    /// **The one gc at a time this box runs**, behind `Repos.Gc` and
    /// `Repos.GcStatus`.
    ///
    /// It belongs to the plane and not to a caller for the reason
    /// [`crate::gc_queue`] opens with: a console can serialise itself, and
    /// nothing else. Built here so every door onto this plane — the console, the
    /// CLI over gRPC, anything else holding a credential — queues behind the
    /// same worker. No thread is started until something is actually enqueued.
    gc: crate::gc_queue::GcQueue,
    /// **The one account purge at a time this box runs**, behind
    /// `Accounts.Purge` and `Accounts.PurgeStatus`.
    ///
    /// Its own queue and not the gc one — see [`crate::purge_queue`]: a gc
    /// waits holding nothing, a purge waits holding a total lockout on a
    /// customer's account, and putting them in one line would keep a user shut
    /// out through somebody else's repository maintenance.
    purge: crate::purge_queue::PurgeQueue,
    /// **The one mirror sync at a time this box runs**, behind `Mirror.Sync`
    /// and `Mirror.Status`.
    ///
    /// Its own queue and not the gc one — see [`crate::mirror_queue`]: a gc
    /// waits holding nothing, a mirror waits holding a repository that is not
    /// yet usable, and making a first sync queue behind somebody else's hour of
    /// compaction is the mistake `job_queue`'s module doc names in advance.
    mirror: crate::mirror_queue::MirrorQueue,
    /// **The directory import, one per account at a time** (`Sso.ImportUsers`
    /// and `Sso.ImportStatus`, A34-17): its own lane, see
    /// [`crate::sso_import_queue`].
    sso_import: crate::sso_import_queue::SsoImportQueue,
    /// **Where the event bus arrives, if this plane is ever given one.**
    ///
    /// The mirror runner is built in [`CoreControlPlane::new`] and the bus is
    /// handed over later by [`CoreControlPlane::with_bus`] (`serve.rs` builds
    /// the bus first and the plane after, but `new` is also what every test
    /// calls). A slot the closure captures is what lets the runner publish
    /// `MirrorSynced` **when the sync finishes** rather than when it was asked
    /// for — an event announcing a fetch that has not happened is worse than no
    /// event.
    ///
    /// `OnceLock`, so it is written once and read without a lock on every
    /// completed sync. A plane that never gets one simply publishes nothing,
    /// which is what every test plane wants.
    bus: Arc<std::sync::OnceLock<Arc<gunnar_grpc::EventBus>>>,
    /// **The keys `Bootstrap.Restore` is taken from, as the medium named them**
    /// (`--restore-pubkey`, [`CoreControlPlane::with_restore_keys`]). The installer's fed
    /// keys are added at each ask ([`gunnar_grpc::ControlPlane::restore_keys`]). Empty on a
    /// bare plane, which with no feed is a box that refuses every restore by name.
    restore_keys: Vec<String>,
}

impl CoreControlPlane {
    /// Serve out of `stores`, with the default object ceiling.
    pub fn new(stores: Arc<ServerStores>) -> Self {
        let for_gc = Arc::clone(&stores);
        let bus: Arc<std::sync::OnceLock<Arc<gunnar_grpc::EventBus>>> = Arc::default();
        CoreControlPlane {
            stores,
            grow: None,
            twin_role: false,
            git_listener: None,
            admission: None,
            replication: crate::replication_view::ReplicationView::new(),
            #[cfg(feature = "replication")]
            replication_slot: None,
            #[cfg(feature = "webhooks")]
            webhook_slot: None,
            #[cfg(feature = "metered")]
            entitlement: None,
            headroom: None,
            max_object_bytes: DEFAULT_MAX_OBJECT_BYTES,
            gc: Self::gc_queue(Arc::clone(&for_gc)),
            purge: Self::purge_queue(Arc::clone(&for_gc)),
            mirror: Self::mirror_queue(Arc::clone(&for_gc), Arc::clone(&bus)),
            sso_import: crate::sso_import_queue::SsoImportQueue::new(
                crate::sso_import_queue::SsoImport,
            ),
            bus,
            restore_keys: Vec::new(),
        }
    }

    /// **Keys this box takes a `Bootstrap.Restore` from** (h-v1-6a, 2026-09-28): OpenSSH
    /// public key lines, from `--restore-pubkey`. For a box that no installer feeds — the
    /// kit, a drill — this is the only way a restore can be taken at all.
    pub fn with_restore_keys(mut self, keys: Vec<String>) -> Self {
        self.restore_keys = keys;
        self
    }

    /// **Publish this plane's event-stream events onto `bus`.**
    ///
    /// Today that is one event and one producer: `MirrorSynced`, from the
    /// mirror queue's worker, when a sync actually completes. It is a slot
    /// rather than a constructor argument because `CoreControlPlane::new` is
    /// what every test calls and a bus is not something a test of the disk
    /// should have to build.
    pub fn with_bus(self, bus: Arc<gunnar_grpc::EventBus>) -> Self {
        // A second `with_bus` is the caller's mistake and is ignored rather
        // than panicking a running server; the first bus wins, which is the
        // one the listener is serving from.
        let _ = self.bus.set(bus);
        self
    }

    /// **This box was started `--role twin`** (`serve.rs`). `Bootstrap.Status`
    /// then answers `role twin` before the join, when `twin.json` does not
    /// exist yet and [`ServerStores::is_twin`] still says no — the moment an
    /// installer door and a re-image verify ask.
    pub fn with_twin_role(mut self, twin_role: bool) -> Self {
        self.twin_role = twin_role;
        self
    }

    /// **The address the git listener took**, handed in by `serve::start` from
    /// `local_addr()` beside the address that was asked for.
    ///
    /// This is what makes `Bootstrap.Status.serving_git` a reading of a SOCKET
    /// rather than of a boot latch. Per-plane and not a static: two servers in
    /// one test process are two listeners, and a process-wide slot would let
    /// the second answer for the first.
    pub fn with_git_listener(mut self, listener: crate::readiness::GitListener) -> Self {
        self.git_listener = Some(listener);
        self
    }

    /// **Release every purge lease this box is still holding.**
    ///
    /// Called once at start-up, and it is the fast half of the crash-recovery
    /// story. A purge that was interrupted by a SIGKILL or a power cut left its
    /// lease in the identity table; nothing is running any more, so every one
    /// of them is stale by construction — this process has just started and has
    /// enqueued nothing.
    ///
    /// Without it those accounts stay shut until their leases expire, which is
    /// up to [`gunnar_core::PURGE_LEASE_MS`] of a paying customer being told
    /// their account is locked by a purge that is not happening. The lease is
    /// still there as the backstop for the case this cannot cover — a box that
    /// never comes back up.
    ///
    /// **Administrative gates are left alone.** They carry no deadline and were
    /// set by a person; a restart must not un-suspend an account.
    ///
    /// Returns how many were released. Failures are logged and not fatal: a
    /// server that refused to start because it could not tidy a lease would
    /// turn a recoverable state into an outage.
    pub fn release_stale_purge_leases(stores: &ServerStores) -> u64 {
        let gates = match stores.auth().gates() {
            Ok(gates) => gates,
            Err(err) => {
                tracing::error!(
                    target: "gunnar::audit",
                    error = %err,
                    "the account gates could not be read at start-up; any purge lease left by a \
                     crash will stay in force until it expires"
                );
                return 0;
            }
        };
        let mut released = 0;
        for gate in gates {
            if gate.reason != gunnar_core::GateReason::Purge {
                continue;
            }
            match stores.auth().lift_gate_held_by(&gate.account, &gate.holder) {
                Ok(Some(_)) => {
                    released += 1;
                    tracing::warn!(
                        target: "gunnar::audit",
                        event = "account.stale_lease_released",
                        account = %gate.account,
                        job = %gate.holder,
                        "an account was still locked by a purge that did not finish; the lockout \
                         has been lifted and the account may still hold bytes the purge did not \
                         reclaim — `repo list-orphans` shows them"
                    );
                }
                Ok(None) => {}
                Err(err) => tracing::error!(
                    target: "gunnar::audit",
                    account = %gate.account,
                    error = %err,
                    "a stale purge lease could not be lifted at start-up"
                ),
            }
        }
        released
    }

    /// The purge queue's two closures: the walk, and the unlock.
    ///
    /// The walk is [`crate::account_purge::purge_account`] — the same function
    /// the CLI verb calls, so there is one definition of what emptying an
    /// account means (one implementation). The unlock is
    /// `AuthTable::lift_gate_held_by`, **held_by** and not the unconditional
    /// lift, so a purge finishing cannot clear a suspension an operator put on
    /// while it ran.
    ///
    /// The lease is re-stamped on every store reclaimed. A purge of a large
    /// account outlives [`gunnar_core::PURGE_LEASE_MS`] easily, and a lease
    /// that ran out mid-walk would unlock the account the walk is still
    /// emptying — a reader could then start re-exploding a read cache into a
    /// directory the purge has not reached yet. A renewal that FAILS is logged
    /// and not fatal: it means the row is somebody else's now, the account is
    /// still shut, and stopping the purge over it would leave more behind.
    fn purge_queue(stores: Arc<ServerStores>) -> crate::purge_queue::PurgeQueue {
        let for_release = Arc::clone(&stores);
        crate::purge_queue::PurgeQueue::new(
            Arc::new(
                move |order: &crate::purge_queue::PurgeOrder,
                      progress: &crate::purge_queue::Progress| {
                    let request = crate::account_purge::PurgeRequest {
                        account: order.account.clone(),
                        principal_id: order.principal_id.clone(),
                        reason: order.reason.clone(),
                        remove_principal: order.remove_principal,
                        expect_empty: order.expect_empty,
                    };
                    let auth = stores.auth();
                    let account = order.account.clone();
                    let job_id = order.job_id.clone();
                    let mut step = |step: crate::account_purge::Step| match step {
                        crate::account_purge::Step::Found(stores_found) => {
                            progress.found(stores_found)
                        }
                        crate::account_purge::Step::Reclaimed { bytes, .. } => {
                            progress.reclaimed(bytes);
                            // **The heartbeat.** Pushed out after every store,
                            // so a purge that takes an hour never runs out of
                            // lease — and a purge that dies still hands the
                            // account back within PURGE_LEASE_MS.
                            let until = gunnar_core::now_ms() + gunnar_core::PURGE_LEASE_MS;
                            if let Err(err) = auth.renew_gate(&account, &job_id, until) {
                                tracing::warn!(
                                    target: "gunnar::audit",
                                    account = %account,
                                    job = %job_id,
                                    error = %err,
                                    "a purge could not renew its lockout lease; the account is \
                                     still shut and the walk continues"
                                );
                            }
                        }
                        crate::account_purge::Step::Failed(note) => progress.failed(note),
                        crate::account_purge::Step::PrincipalRemoved => {
                            progress.principal_removed()
                        }
                    };
                    let report = crate::account_purge::purge_account(&stores, request, &mut step)
                        .map_err(|err| format!("{err:#}"))?;
                    // A walk that ran and left stores behind is a FAILURE, and
                    // the queue is told so here rather than left to infer it
                    // from a report it cannot see. The names are already on the
                    // job through `Step::Failed`; this is the sentence.
                    if report.failures.is_empty() {
                        Ok(())
                    } else {
                        Err(format!(
                            "{} of {} stores could not be reclaimed and are still on the disk; \
                             `repo list-orphans` shows them",
                            report.failures.len(),
                            report.stores_found
                        ))
                    }
                },
            ),
            Arc::new(move |account: &str, job_id: &str| {
                for_release
                    .auth()
                    .lift_gate_held_by(account, job_id)
                    .map(|lifted| lifted.is_some())
                    .map_err(|err| format!("{err}"))
            }),
        )
    }

    /// The queue's runner: resolve the catalog row, then **call the same
    /// `admin::gc_one` the CLI verb calls** (one implementation).
    ///
    /// Errors come back as strings because they are going onto a job a console
    /// will read, not up a call stack. The resolution happens *inside* the
    /// runner rather than at enqueue time on purpose: a repository can be
    /// deleted while its job waits, and discovering that when the work starts
    /// is a FAILED job saying so, which is the truth. Resolving early would
    /// have queued a row that no longer describes anything.
    fn gc_queue(stores: Arc<ServerStores>) -> crate::gc_queue::GcQueue {
        crate::gc_queue::GcQueue::new(Arc::new(move |path: &str| {
            let repo_ref = gunnar_core::resolve_repo_path(path)
                .map_err(|err| format!("`{path}` is not a valid <namespace>/<name>: {err:#}"))?;
            let repo = stores
                .catalog()
                .get(&repo_ref)
                .map_err(|err| format!("reading the catalog row for {path}: {err:#}"))?
                .ok_or_else(|| format!("{path} is no longer a live repository"))?;
            let report = crate::admin::gc_one(&stores, &repo)
                .map_err(|err| format!("maintaining {path}: {err:#}"))?;
            Ok(crate::admin::reclaimed_bytes(&report))
        }))
    }

    /// **The mirror queue's runner: read the sealed credential, then run the
    /// one fetch (one implementation).**
    ///
    /// The credential is read **here, on the worker**, and not carried on the
    /// order. Two reasons, and both are about where a secret is allowed to be:
    /// an order is `Debug` and lives on a job a status RPC renders, so a key on
    /// it would be one `{:?}` away from a log line; and a credential rotated
    /// while a sync waited should be the one the sync uses, not the one that
    /// was current when somebody clicked.
    ///
    /// Errors come back as strings because they are going onto a job a console
    /// will read, not up a call stack — the same reason `gc_queue`'s runner
    /// returns one. None of them can contain the credential: the only paths out
    /// of `mirror_fetch` that mention the remote scrub its userinfo first.
    fn mirror_queue(
        stores: Arc<ServerStores>,
        bus: Arc<std::sync::OnceLock<Arc<gunnar_grpc::EventBus>>>,
    ) -> crate::mirror_queue::MirrorQueue {
        crate::mirror_queue::MirrorQueue::new(Arc::new(
            move |order: &crate::mirror_queue::MirrorOrder,
                  report: &crate::job_queue::Reporter<crate::mirror_queue::Mirror>| {
                let repo_ref = gunnar_core::resolve_repo_path(&order.path).map_err(|err| {
                    format!(
                        "`{}` is not a valid <namespace>/<name>: {err:#}",
                        order.path
                    )
                })?;
                // **In flight, durably**, before anything is dialled: a restart
                // during the sync leaves this mark, and the next start settles
                // the sync as interrupted and resumes it
                // (`resume_interrupted_mirrors`) instead of leaving a
                // repository with nothing in it and a registration that says
                // nothing went wrong.
                let first = first_sync_of(
                    stores
                        .mirrors()
                        .mark_started(&repo_ref, gunnar_grpc::bus::now_unix_ms()),
                    &order.path,
                )?;
                let outcome = read_credential(&stores, &repo_ref).and_then(|credential| {
                    crate::mirror_fetch::sync_once(&stores, order, &credential, report)
                });
                audit_mirror_outcome(
                    &stores,
                    &repo_ref,
                    order,
                    first,
                    outcome.as_ref().err().map(String::as_str),
                    report,
                );

                // **The registration records every attempt, good or bad.**
                // `record_sync` moves `last_sync_at_unix_ms` only on success —
                // that field means "when this mirror was last correct", and
                // moving it on a failure would make a mirror that has been
                // broken for a week look fresh.
                let error = outcome.as_ref().err().map(String::as_str);
                if let Err(err) =
                    stores
                        .mirrors()
                        .record_sync(&repo_ref, gunnar_grpc::bus::now_unix_ms(), error)
                {
                    tracing::warn!(
                        target: "gunnar::git",
                        repo = %order.path,
                        %err,
                        "a mirror sync finished and its registration could not be updated; the \
                         fetch itself is unaffected"
                    );
                }

                // The event stream, **after** the work and only on success. An event that
                // announced a fetch which had not happened would be worse than
                // no event, which is why `Mirror.Sync` no longer publishes one.
                if outcome.is_ok() {
                    if let Some(bus) = bus.get() {
                        let job = report.snapshot();
                        let updates = job
                            .map(|job| job.report.updates)
                            .unwrap_or_default()
                            .into_iter()
                            .map(|(ref_name, old_oid, new_oid)| gunnar_proto::RefUpdate {
                                ref_name,
                                old_oid,
                                new_oid,
                            })
                            .collect::<Vec<_>>();
                        bus.publish(gunnar_proto::event::Payload::MirrorSynced(
                            gunnar_proto::MirrorSynced {
                                repo: Some(RepoPath::new(repo_ref.namespace(), repo_ref.name())),
                                remote_url: order.upstream.clone(),
                                refs_changed: updates.len() as u32,
                                updates,
                            },
                        ));
                    }
                }
                outcome
            },
        ))
    }

    /// **Settle every sync a stopped process left in flight, and resume it**
    /// (import-big, 2026-10-26).
    ///
    /// The job queue is memory: a restart in the middle of an import (an
    /// out-of-memory kill, an update, a power cut) forgot the job, and what was
    /// left was a repository with nothing in it and a registration with no
    /// error — a console that showed no failure for an import that never
    /// landed. The registration now carries an in-flight mark
    /// (`MirrorRecord::sync_started_at_unix_ms`); here, once at start, each
    /// marked sync is settled as interrupted (its `last_error` says so, and the
    /// account's audit log has a line) and enqueued again, up to
    /// [`gunnar_core::MAX_RESUMES`] times in a row. Past that it stays FAILED
    /// with the reason, for a person to press Sync. Returns how many were
    /// resumed.
    pub fn resume_interrupted_mirrors(&self) -> usize {
        let settled = match self
            .stores
            .mirrors()
            .settle_interrupted(gunnar_grpc::bus::now_unix_ms())
        {
            Ok(settled) => settled,
            Err(err) => {
                tracing::warn!(target: "gunnar::git", %err, "the mirror registrations could not be read to resume interrupted syncs");
                return 0;
            }
        };
        let mut resumed = 0;
        for record in settled {
            let Ok(repo_ref) = gunnar_core::resolve_repo_path(&record.repo) else {
                continue;
            };
            let again = record.interrupted <= gunnar_core::MAX_RESUMES;
            audit_line(
                &self.stores,
                &repo_ref,
                if again {
                    "mirror.sync.interrupted"
                } else {
                    "mirror.sync.failed"
                },
                &record.last_error,
                true,
            );
            tracing::warn!(
                target: "gunnar::git",
                event = "mirror.sync.interrupted",
                repo = %record.repo,
                interrupted = record.interrupted,
                resumed = again,
                "a mirror sync was in flight when the server stopped"
            );
            if again {
                self.mirror.enqueue(crate::mirror_queue::MirrorOrder {
                    path: repo_ref.key(),
                    upstream: record.remote_url.clone(),
                    prune: record.prune,
                    ca: mirror_ca_of(&record),
                });
                resumed += 1;
            }
        }
        resumed
    }

    /// **Take the lockout a purge runs under, without downgrading one that is
    /// already there.**
    ///
    /// A lease is written only when the account is *not* already gated. If it
    /// is — an operator suspending a customer, monetize locking a non-payer —
    /// that gate stands, and the purge runs under it. Two consequences, both
    /// deliberate:
    ///
    /// * the account does not quietly acquire a **deadline** it did not have.
    ///   Overwriting an administrative gate with a lease would mean a
    ///   suspension expiring ten minutes after a purge finished with it, which
    ///   is a suspended account silently coming back.
    /// * the job will report `gate_released: false` and the account stays shut,
    ///   because `lift_gate_held_by` will find a holder that is not this job.
    ///   That is the correct outcome: the purge did not take that lockout and
    ///   has no standing to lift it.
    fn gate_for_purge(
        &self,
        account: &str,
        job_id: &str,
        options: &gunnar_grpc::seam::PurgeAccountOptions,
    ) -> ControlResult<()> {
        if self
            .stores
            .auth()
            .gate_covering(account)
            .map_err(internal)?
            .is_some()
        {
            return Ok(());
        }
        let lease = gunnar_core::AccountGate::purge_lease(
            account,
            job_id,
            gunnar_core::now_ms() + gunnar_core::PURGE_LEASE_MS,
        )
        .by(&options.principal_id)
        .noted(format!(
            "this account is being permanently deleted: {}",
            options.reason
        ));
        self.stores.auth().gate(lease).map_err(gate_error)?;
        Ok(())
    }

    /// **Hand the disk-headroom gate in.** From here on `Repos.Create` refuses
    /// under the floor with `RESOURCE_EXHAUSTED` and the gate's own line —
    /// the one a refused `git push` prints, because it is the same function.
    #[must_use]
    pub fn with_headroom(mut self, gate: Arc<gunnar_ssh::DiskHeadroomGate>) -> Self {
        self.headroom = Some(gate);
        self
    }

    /// **Hand this plane the runtime growth** (`crate::grow`). Called by
    /// `serve` once the admission gate and the stores exist.
    pub fn with_grow(mut self, grow: Arc<crate::grow::GrowMachine>) -> Self {
        self.grow = Some(grow);
        self
    }

    /// **Hand this plane the admission gate** the git fronts share, for the
    /// in-flight count `Mirror.FlushReplication` reports.
    pub fn with_admission(mut self, admission: Arc<gunnar_ssh::Admission>) -> Self {
        self.admission = Some(admission);
        self
    }

    /// The growth, or the seam's refusal by name.
    fn grow_machine(&self) -> ControlResult<&Arc<crate::grow::GrowMachine>> {
        self.grow.as_ref().ok_or(ControlError::Unimplemented(
            "this control plane was built with no runtime growth wired in, so it cannot grow the data set",
        ))
    }

    /// Verify a signed membership event before it changes anything.
    ///
    /// The same shape as `forge_append`'s check and for the same reason (one
    /// implementation): a membership log that took an event it could not verify would be a
    /// log of claims, and the point of the design is that it is a log of
    /// evidence. The key must be in the ACL table (or no later reader could
    /// check it), it must be the claimed actor's own, and the event must
    /// describe the change the caller named — re-checked here at the seam
    /// because this door can also be reached without a connection.
    fn verify_membership_event(
        &self,
        signed: gunnar_proto::SignedMembershipEvent,
        group_id: &str,
        member_id: &str,
        action: gunnar_core::MembershipAction,
    ) -> ControlResult<gunnar_core::SignedMembershipEvent> {
        let signed = from_proto_membership(signed)?;
        if signed.event.group != group_id || signed.event.member != member_id {
            return Err(ControlError::InvalidArgument(format!(
                "the signed event is about {:?}/{:?} but the change is {:?}/{:?}",
                signed.event.group, signed.event.member, group_id, member_id
            )));
        }
        if signed.event.action != action {
            return Err(ControlError::InvalidArgument(
                "the signed event's action does not match the change (add vs remove)".to_owned(),
            ));
        }
        let key = self
            .stores
            .auth()
            .signing_keys()
            .map_err(|err| ControlError::Unavailable(format!("{err:#}")))?
            .into_iter()
            .find(|row| row.fingerprint_sha256 == signed.key_fingerprint)
            .ok_or_else(|| {
                ControlError::InvalidArgument(format!(
                    "{} is not registered on this server, so nobody reading this event later \
                     could check its signature",
                    signed.key_fingerprint
                ))
            })?;
        if key.principal_id != signed.event.actor {
            return Err(ControlError::InvalidArgument(format!(
                "this membership change is attributed to {:?} and is signed by {}, which is \
                 {:?}'s key; a membership change is the actor's own word, so it must carry the \
                 actor's own signature",
                signed.event.actor, signed.key_fingerprint, key.principal_id
            )));
        }
        let public = gunnar_core::ssh_key::PublicKey::from_openssh(&key.openssh)
            .map_err(|err| ControlError::Internal(format!("stored key is unreadable: {err}")))?;
        gunnar_core::membership::verify_event(&signed, &public)
            .map_err(|problem| ControlError::InvalidArgument(format!("{problem}")))?;
        Ok(signed)
    }

    /// Append a verified membership event to the signed membership log, and
    /// return the index it landed at — the index an inclusion proof is taken
    /// at. Append-only and never rewritten, so a removal followed by a re-add
    /// leaves two standing events, which is what makes the history evidence.
    fn append_membership_event(
        &self,
        signed: &gunnar_core::SignedMembershipEvent,
    ) -> ControlResult<u64> {
        let log = self.stores.membership_log();
        let mut line = serde_json::to_string(signed)
            .map_err(|err| ControlError::Internal(format!("encoding the event: {err}")))?;
        line.push('\n');
        let _framed =
            gunnar_core::txlog::sink::append_line(log.records_path(), line.trim_end_matches('\n'))
                .map_err(|err| {
                    ControlError::Unavailable(format!(
                        "framing the line in the transaction log: {err}"
                    ))
                })?;
        use std::io::Write as _;
        let mut file = std::fs::OpenOptions::new()
            .create(true)
            .append(true)
            .open(log.records_path())
            .map_err(|err| {
                ControlError::Unavailable(format!("opening the membership log: {err}"))
            })?;
        file.write_all(line.as_bytes()).map_err(|err| {
            ControlError::Unavailable(format!("appending to the membership log: {err}"))
        })?;
        let count = log
            .lines_of()
            .map_err(|err| ControlError::Unavailable(format!("{err:#}")))?
            .len() as u64;
        Ok(count.saturating_sub(1))
    }

    /// Every membership event on the server, decoded, in append order.
    fn membership_log_events(&self) -> ControlResult<Vec<gunnar_core::SignedMembershipEvent>> {
        self.stores
            .membership_log()
            .lines_of()
            .map_err(|err| ControlError::Unavailable(format!("{err:#}")))?
            .iter()
            .map(|line| {
                serde_json::from_str(line).map_err(|err| {
                    ControlError::Internal(format!("decoding a membership event: {err}"))
                })
            })
            .collect()
    }

    /// **Hand this plane the live replication slot**, so an operator can name a
    /// standby over the control plane.
    ///
    /// Called by `Server::start` before the plane is wrapped in an `Arc`, and
    /// before anything is running in the slot — which is the point: a target has
    /// to be settable on a box that has never had one and holds no repositories
    /// yet, and that is every box on its first boot.
    #[cfg(feature = "replication")]
    pub fn with_replication(mut self, slot: Arc<crate::mirror::ReplicationSlot>) -> Self {
        self.replication_slot = Some(slot);
        self
    }

    /// The slot, or a refusal that names WHY there is none.
    ///
    /// `Unimplemented` and not `Internal`: a plane built without a slot is a
    /// plane with no server around it (a unit test), and telling a caller "this
    /// server cannot do that" is true, actionable and not an incident.
    #[cfg(feature = "replication")]
    fn replication_slot(&self) -> ControlResult<&Arc<crate::mirror::ReplicationSlot>> {
        self.replication_slot.as_ref().ok_or(ControlError::Unimplemented(
            "this control plane was built with no replication slot, so it cannot configure                  a standby",
        ))
    }

    /// **Hand this plane the live webhook slot**, so an operator can name an
    /// outbound endpoint over the control plane. Called by `Server::start`
    /// before the plane is wrapped in an `Arc`.
    #[cfg(feature = "webhooks")]
    pub fn with_webhooks(mut self, slot: Arc<crate::webhook::WebhookSlot>) -> Self {
        self.webhook_slot = Some(slot);
        self
    }

    /// Hand the entitlement slot in (`metered` only).
    #[cfg(feature = "metered")]
    pub fn with_entitlement(mut self, slot: Arc<crate::entitlement::EntitlementSlot>) -> Self {
        self.entitlement = Some(slot);
        self
    }

    /// The entitlement slot, or a refusal that names WHY there is none.
    #[cfg(feature = "metered")]
    fn entitlement(&self) -> ControlResult<&Arc<crate::entitlement::EntitlementSlot>> {
        self.entitlement.as_ref().ok_or_else(|| {
            ControlError::FailedPrecondition(
                "this metered server was started without `--monetize-pubkey`, so it holds no \
                 key to verify an entitlement fact against and refuses every one; every \
                 namespace is Free"
                    .into(),
            )
        })
    }

    /// The webhook slot, or a refusal that names WHY there is none.
    #[cfg(feature = "webhooks")]
    fn webhook_slot(&self) -> ControlResult<&Arc<crate::webhook::WebhookSlot>> {
        self.webhook_slot.as_ref().ok_or(ControlError::Unimplemented(
            "this control plane was built with no webhook slot, so it cannot configure                  an outbound endpoint",
        ))
    }

    /// Configuration **and** running state, in one answer.
    ///
    /// Both halves, always, because they can disagree and the disagreement is
    /// the interesting part: `targets` non-empty with `standbys` empty is a
    /// server that has the configuration and is not running it.
    #[cfg(feature = "replication")]
    ///
    /// **`include_refs` is the operator's, and it is false for everything but a
    /// `replication list --refs`.** The mutating verbs print a snapshot back to
    /// confirm the roster, and the ref-coverage walk they used to trigger opens
    /// every repository's reference database for a number nobody asked
    /// for — so they pass `false`, and only the explicit status verb forwards
    /// the flag the operator set.
    fn replication_snapshot(
        &self,
        include_refs: bool,
    ) -> ControlResult<gunnar_proto::ReplicationStatusResponse> {
        let slot = self.replication_slot()?;
        let config = slot
            .config()
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        let mut out = gunnar_proto::ReplicationStatusResponse {
            targets: config
                .targets
                .iter()
                .map(crate::replication_wire::target_to_proto)
                .collect(),
            role: config.role.to_proto() as i32,
            ..Default::default()
        };
        if let Some(replicator) = slot.replicator() {
            crate::replication_wire::running_to_proto(&replicator, include_refs, &mut out);
        }
        Ok(out)
    }

    /// **The slot `serve` drops the replicator's counters into**, so
    /// `Admin.Stats` can report them.
    ///
    /// Without it the counters exist and nothing reads them, which is exactly
    /// the state that let every configured standby receive NOTHING from
    /// `e31ab8f4` to 2026-08-30 while five log lines out of five said so into a
    /// file nobody was tailing.
    pub fn replication_view(&self) -> crate::replication_view::ReplicationView {
        self.replication.clone()
    }

    /// Every forge event, as it was written.
    ///
    /// Verifying nothing: the fold is over what is in the log, and whether an
    /// event is evidence is a separate question with its own answer, asked
    /// per approval in [`CoreControlPlane::thread_state`].
    fn forge_events(&self) -> ControlResult<Vec<gunnar_core::SignedEvent>> {
        self.stores
            .forge_log()
            .lines_of()
            .map_err(|err| ControlError::Unavailable(format!("reading the forge log: {err:#}")))?
            .iter()
            .map(|line| {
                serde_json::from_str(line).map_err(|err| {
                    ControlError::Internal(format!("a forge event will not decode: {err}"))
                })
            })
            .collect()
    }

    /// **The subject of a forge event must exist and be open** — the one check
    /// for an event its actor signed and one gunnar attested (GHUNT-19).
    fn forge_subject_open(&self, signed: &gunnar_core::SignedEvent) -> ControlResult<()> {
        // **The subject must exist and be open**, and which subject that is
        // depends on the kind. A review event names a pull request the record
        // owns; an issue event names an issue THIS log owns. Both refuse an
        // event on something merged, closed or never opened — evidence about
        // nothing — but they ask different authorities, so they branch here.
        let (namespace, name) = signed.event.repo.split_once('/').ok_or_else(|| {
            ControlError::InvalidArgument(format!(
                "`repo` must be `<namespace>/<repo>`, got {:?}",
                signed.event.repo
            ))
        })?;
        let path = RepoPath::new(namespace, name);
        match &signed.event.event {
            // An opening creates the issue and so has no precondition: there is
            // nothing yet to be open. Its number is the fold's to assign.
            gunnar_core::Event::IssueOpened { .. } => {}
            // A comment or close names an issue by number. The issue is folded
            // from this same log — there is no record behind it — so the check
            // is against the fold rather than `get_pull`.
            gunnar_core::Event::IssueCommented { .. } | gunnar_core::Event::IssueClosed { .. } => {
                let repo_events: Vec<gunnar_core::ForgeEvent> = self
                    .forge_events()?
                    .into_iter()
                    .filter(|e| e.event.repo == signed.event.repo)
                    .map(|e| e.event)
                    .collect();
                match gunnar_core::forge::fold_issue(signed.event.pull, &repo_events) {
                    None => {
                        return Err(ControlError::FailedPrecondition(format!(
                            "no issue #{} in {}: nobody has opened one, so an event on it is \
                             evidence about nothing",
                            signed.event.pull, signed.event.repo
                        )));
                    }
                    Some(issue) if !issue.open => {
                        return Err(ControlError::FailedPrecondition(format!(
                            "issue #{} in {} is closed; an event on it cannot change what has \
                             already happened",
                            signed.event.pull, signed.event.repo
                        )));
                    }
                    Some(_) => {}
                }
            }
            // A review event names a pull request, whose record is the authority
            // for whether it exists and is open.
            gunnar_core::Event::Commented { .. }
            | gunnar_core::Event::Approved { .. }
            | gunnar_core::Event::Rejected { .. } => {
                let record = self.get_pull(&path, signed.event.pull)?;
                if record.state != gunnar_proto::PullRequestState::Open as i32 {
                    return Err(ControlError::FailedPrecondition(format!(
                        "pull request #{} in {} is not open; a review event cannot change what \
                         has already happened",
                        signed.event.pull, signed.event.repo
                    )));
                }
            }
        }
        Ok(())
    }

    /// Append a checked forge event to the log, and say where it landed.
    fn forge_write(&self, signed: &gunnar_core::SignedEvent) -> ControlResult<u64> {
        let log = self.stores.forge_log();
        let mut line = serde_json::to_string(signed)
            .map_err(|err| ControlError::Internal(format!("encoding the event: {err}")))?;
        line.push('\n');
        let _framed =
            gunnar_core::txlog::sink::append_line(log.records_path(), line.trim_end_matches('\n'))
                .map_err(|err| {
                    ControlError::Unavailable(format!(
                        "framing the line in the transaction log: {err}"
                    ))
                })?;
        use std::io::Write as _;
        let mut file = std::fs::OpenOptions::new()
            .create(true)
            .append(true)
            .open(log.records_path())
            .map_err(|err| ControlError::Unavailable(format!("opening the forge log: {err}")))?;
        file.write_all(line.as_bytes()).map_err(|err| {
            ControlError::Unavailable(format!("appending to the forge log: {err}"))
        })?;
        // The index it landed at, counted after the write so it names this
        // event and not the one before it.
        let count = self
            .stores
            .forge_log()
            .lines_of()
            .map_err(|err| ControlError::Unavailable(format!("{err:#}")))?
            .len() as u64;
        Ok(count.saturating_sub(1))
    }

    /// A folded review, with **every approval re-checked against the ACL key
    /// table right now** — not trusted because it is in the file.
    ///
    /// That re-check is the difference the whole design is about, and it is why
    /// the wire carries a verdict per approval rather than a count: an approval
    /// whose key was since removed has not failed and has not passed, and a
    /// number cannot say so.
    ///
    /// **The key must be the claimed actor's own.** A signature proves which
    /// KEY spoke; only the key table's `principal_id` says whose voice that
    /// is. Until 2026-08-31 the fingerprint was looked up across the whole
    /// table, so an approval claiming `actor: alice` signed by any other
    /// registered principal's key verified — and merged. The verdict for that
    /// case names the key's real owner, because "your signature failed" and
    /// "that is somebody else's key" send an operator down different roads.
    fn review_state(
        &self,
        repo: &str,
        state: &gunnar_core::forge::Review,
        all: &[gunnar_core::SignedEvent],
    ) -> ControlResult<gunnar_proto::ReviewState> {
        let keys: Vec<(String, String, gunnar_core::ssh_key::PublicKey)> = self
            .stores
            .auth()
            .signing_keys()
            .map_err(|err| ControlError::Unavailable(format!("{err:#}")))?
            .iter()
            .filter_map(|row| {
                gunnar_core::ssh_key::PublicKey::from_openssh(&row.openssh)
                    .ok()
                    .map(|key| {
                        (
                            row.fingerprint_sha256.clone(),
                            row.principal_id.clone(),
                            key,
                        )
                    })
            })
            .collect();
        // Gunnar's own forge-attestation key, read without minting: an
        // attested approval verifies against it and nothing else (GHUNT-19).
        let attest_key = self
            .stores
            .forge_attest_public()
            .map_err(|err| ControlError::Unavailable(format!("{err:#}")))?;

        let approvals = state
            .approvals
            .iter()
            .map(|(actor, commit)| {
                let signed = all.iter().rev().find(|e| {
                    e.event.repo == repo
                        && e.event.pull == state.pull
                        && e.event.actor == *actor
                        && matches!(&e.event.event, gunnar_core::Event::Approved { commit: c } if c == commit)
                });
                let (verified, verdict) = match signed {
                    None => (false, "NO EVENT".to_owned()),
                    // **Gunnar's attestation for a person's stepped-up
                    // session**: signed by gunnar's own key, the actor named,
                    // the step-up inside the signature. Checked against that
                    // key alone — never against a principal's.
                    Some(signed) if signed.attested.is_some() => match &attest_key {
                        None => (false, "UNKNOWN KEY".to_owned()),
                        Some(key) => match gunnar_core::forge::verify_event(signed, key) {
                            Ok(()) => (
                                true,
                                signed.attested.as_ref().map(|a| a.words()).unwrap_or_default(),
                            ),
                            Err(problem) => (false, format!("BAD ({problem})")),
                        },
                    },
                    Some(signed) => match keys
                        .iter()
                        .find(|(fingerprint, _, _)| *fingerprint == signed.key_fingerprint)
                    {
                        None => (false, "UNKNOWN KEY".to_owned()),
                        // The key is registered — to somebody else. The
                        // signature may be perfectly good; it is still not
                        // this actor's word, and saying whose it is lets the
                        // operator see a filed-in-another's-name attempt for
                        // what it is.
                        Some((_, owner, _)) if *owner != *actor => {
                            (false, format!("KEY OF {owner}, NOT {actor}"))
                        }
                        Some((_, _, key)) => match gunnar_core::forge::verify_event(signed, key) {
                            Ok(()) => (true, "verified".to_owned()),
                            Err(problem) => (false, format!("BAD ({problem})")),
                        },
                    },
                };
                gunnar_proto::Approval {
                    actor: actor.clone(),
                    commit: commit.clone(),
                    verified,
                    verdict,
                }
            })
            .collect();

        Ok(gunnar_proto::ReviewState {
            repo: repo.to_owned(),
            pull: state.pull,
            approvals,
            comments: state.comments as u64,
        })
    }

    /// **Set the deployment's object ceiling** for `Refs.ReadObject`.
    ///
    /// `0` disables the ceiling, which restores the unbounded behaviour: the
    /// server will inflate an object of any size to answer a request. That is a
    /// real choice for a single-tenant box with a trusted control port and a
    /// repository full of large blobs, and it is spelled explicitly rather than
    /// being what you get by forgetting to configure anything.
    ///
    /// This exists as much for the tests as for the operator: a ceiling that can
    /// only be a compile-time constant can only be exercised by writing an object
    /// bigger than it, which for the real default means a 64 MiB fixture. Being
    /// able to set it small is what lets the refusal be seen red cheaply — and it
    /// proves the configuration is *wired*, which a test against the constant
    /// could never show.
    pub fn with_max_object_bytes(mut self, bytes: u64) -> Self {
        self.max_object_bytes = bytes;
        self
    }

    /// The pull-request table, opened against the same control store the
    /// catalog and the identity table live in. A fresh handle per call: the
    /// document cache rides the handle, and a pull-request operation is rare
    /// enough that re-parsing beats holding one more long-lived Arc chain.
    fn pulls(&self) -> ControlResult<gunnar_core::Pulls> {
        gunnar_core::Pulls::new(Arc::clone(self.stores.control_store()))
            .map_err(|err| ControlError::Internal(format!("opening the pulls table: {err:#}")))
    }

    fn repo_ref(path: &RepoPath) -> ControlResult<RepoRef> {
        path.validate()
            .map_err(|err| ControlError::InvalidArgument(err.to_string()))?;
        RepoRef::new(&path.namespace, &path.repo)
            .map_err(|err| ControlError::InvalidArgument(err.to_string()))
    }

    /// Resolve a tree-ish — a ref name, a hex oid, or `HEAD` — to the **tree**
    /// it names.
    ///
    /// The resolution half is the one `log` already does: a hex oid is taken as
    /// one, anything else is validated as a reference name and looked up in the
    /// snapshot, and an oid of the wrong hash kind is refused with a sentence
    /// that says which kind the repository is. What is added here is the last
    /// hop — a commit is followed to its tree, a tag is peeled first, and a tree
    /// is already the answer — so `from`/`to` accept everything `git diff`
    /// accepts in the same position.
    fn tree_of(
        &self,
        git: &dyn GitServe,
        hash: gix_hash::Kind,
        path: &RepoPath,
        spec: &str,
    ) -> ControlResult<gix_hash::ObjectId> {
        let id = match gix_hash::ObjectId::from_hex(spec.as_bytes()) {
            Ok(id) => {
                if id.kind() != hash {
                    return Err(ControlError::InvalidArgument(format!(
                        "{spec} is a {} oid; this repository is {hash}",
                        id.kind()
                    )));
                }
                id
            }
            Err(_) => {
                gunnar_store::refname::validate(spec)
                    .map_err(|err| ControlError::InvalidArgument(err.to_string()))?;
                let snapshot = RefSnapshot::read(git).map_err(wire_error)?;
                let resolved = if spec == gunnar_store::HEAD {
                    snapshot.head(git).map_err(wire_error)?
                } else {
                    snapshot.resolve(spec).map_err(wire_error)?
                };
                resolved.ok_or_else(|| ControlError::NotFound(format!("{spec} in {path}")))?
            }
        };
        let id = peel(git, hash, id)?;
        let (kind, bytes) = git
            .read(id.as_bytes())
            .map_err(store_error)?
            .ok_or_else(|| ControlError::NotFound(format!("object {id} in {path}")))?;
        match kind {
            ObjType::Tree => Ok(id),
            ObjType::Commit => object::commit(&bytes, hash)
                .map(|commit| commit.tree)
                .map_err(|err| ControlError::Internal(format!("decoding commit {id}: {err}"))),
            // A blob is a legal object and not a legal side of a tree diff.
            // Saying so beats walking it and reporting that nothing changed.
            other => Err(ControlError::InvalidArgument(format!(
                "{spec} names a {other:?}; a diff needs a commit, a tag or a tree"
            ))),
        }
    }

    /// The repository's policy as `gunnar-policy` understands it.
    ///
    /// A repository with no stored policy reads as
    /// [`PolicyConfig::default`](gunnar_policy::PolicyConfig) — no gates —
    /// which is the same thing the push path concludes and is stated in one
    /// place rather than two. A stored document that does **not parse** is an
    /// error here and not an empty policy: this path is a caller asking what
    /// the rules are, and answering "there are none" about a document that
    /// exists and is broken is the worst available answer.
    fn policy_of(&self, repo: &gunnar_core::Repo) -> ControlResult<gunnar_policy::PolicyConfig> {
        let stored = self.stores.policies().get(&repo.path()).map_err(internal)?;
        match stored {
            None => Ok(gunnar_policy::PolicyConfig::default()),
            Some(document) => gunnar_policy::PolicyConfig::from_json(&document).map_err(|err| {
                ControlError::Internal(format!(
                    "the stored policy for {} does not parse: {err}",
                    repo.key()
                ))
            }),
        }
    }

    /// Write `config` back, or delete the document when it configures nothing.
    ///
    /// Deleting rather than storing an empty document is what keeps "nobody has
    /// configured this repository" and "somebody configured nothing" the same
    /// state. Two states that behave identically and read differently are a
    /// question an operator cannot answer.
    fn store_policy(
        &self,
        repo: &gunnar_core::Repo,
        config: &gunnar_policy::PolicyConfig,
    ) -> ControlResult<()> {
        let policies = self.stores.policies();
        if *config == gunnar_policy::PolicyConfig::default() {
            policies.remove(&repo.path()).map_err(internal)?;
            return Ok(());
        }
        let json = config
            .to_json()
            .map_err(|err| ControlError::Internal(format!("rendering the policy: {err}")))?;
        policies.set(&repo.path(), &json).map_err(internal)
    }

    fn open(&self, path: &RepoPath) -> ControlResult<(gunnar_core::Repo, Arc<OpenRepo>)> {
        let repo_ref = Self::repo_ref(path)?;
        let repo = self
            .stores
            .catalog()
            .get(&repo_ref)
            .map_err(internal)?
            .ok_or_else(|| ControlError::NotFound(format!("repository {path}")))?;
        let store = self.stores.repo_store(&repo).map_err(|err| {
            ControlError::Internal(format!("opening the repository's stores: {err:#}"))
        })?;
        Ok((repo, store))
    }

    /// **A mirror's registration, with its repository opened when it has
    /// one.** A registration whose repository is still to come (an import's
    /// first sync has not landed: `MirrorRecord::creates_repo`) has none to
    /// open, and that is not an error; every other registration's repository
    /// must open, as it always had to.
    fn mirror_record(&self, path: &RepoPath) -> ControlResult<gunnar_core::MirrorRecord> {
        let repo_ref = Self::repo_ref(path)?;
        let record = self.stores.mirrors().get(&repo_ref).map_err(internal)?;
        match record {
            Some(record)
                if record.creates_repo
                    && self
                        .stores
                        .catalog()
                        .get(&repo_ref)
                        .map_err(internal)?
                        .is_none() =>
            {
                Ok(record)
            }
            record => {
                self.open(path)?;
                record.ok_or_else(|| {
                    ControlError::NotFound(format!("no mirror registered for {path}"))
                })
            }
        }
    }
}

/// **The one place a [`crate::gc_queue::GcJob`] becomes a seam job.**
///
/// The queue keys on `<namespace>/<name>` because that is what its runner
/// needs; the seam speaks [`RepoPath`] because that is what the wire does.
/// `path` is threaded in rather than re-parsed out of the job's own string: it
/// is the request's own path, already validated, and re-parsing it here would
/// be a second resolver that could disagree with the first (one implementation).
fn gc_job_out(path: &RepoPath, job: crate::gc_queue::GcJob) -> gunnar_grpc::seam::GcJob {
    gunnar_grpc::seam::GcJob {
        job_id: job.job_id,
        path: path.clone(),
        state: match job.state {
            crate::gc_queue::GcState::Queued => gunnar_grpc::seam::GcState::Queued,
            crate::gc_queue::GcState::Running => gunnar_grpc::seam::GcState::Running,
            crate::gc_queue::GcState::Done => gunnar_grpc::seam::GcState::Done,
            crate::gc_queue::GcState::Failed => gunnar_grpc::seam::GcState::Failed,
        },
        queue_position: job.queue_position,
        // Named through `report` rather than through the job's `Deref`: the
        // job is being taken apart field by field here, and a deref borrow in
        // the middle of that would be reading a value that is half moved.
        bytes_reclaimed: job.report.bytes_reclaimed,
        error: job.error,
        enqueued_at_unix_ms: job.enqueued_at_unix_ms,
        finished_at_unix_ms: job.finished_at_unix_ms,
    }
}

/// `gunnar_core`'s gate onto the seam's.
fn gate_out(gate: gunnar_core::AccountGate) -> gunnar_grpc::seam::AccountGate {
    gunnar_grpc::seam::AccountGate {
        account: gate.account,
        reason: match gate.reason {
            gunnar_core::GateReason::Administrative => {
                gunnar_grpc::seam::GateReason::Administrative
            }
            gunnar_core::GateReason::Purge => gunnar_grpc::seam::GateReason::Purge,
        },
        holder: gate.holder,
        actor: gate.actor,
        note: gate.note,
        at_unix_ms: gate.at,
        // **0 on the seam means "no deadline"**, which is what `None` means
        // here. Flattened at this boundary rather than on the wire so the proto
        // stays a plain `int64` and every reader of it applies the same rule.
        expires_unix_ms: gate.expires.unwrap_or(0),
    }
}

/// The queue's job onto the seam's.
fn purge_job_out(job: crate::purge_queue::PurgeJob) -> gunnar_grpc::seam::PurgeJob {
    // The purge's own half, taken out whole before the queue's half is: the
    // failure list is owned and has to be MOVED onto the seam, and a job's
    // `Deref` only ever lends its report.
    let report = job.report;
    gunnar_grpc::seam::PurgeJob {
        job_id: job.job_id,
        // The queue keys on the account, so the account IS the job's key.
        account: job.key,
        state: match job.state {
            crate::purge_queue::PurgeState::Queued => gunnar_grpc::seam::PurgeState::Queued,
            crate::purge_queue::PurgeState::Running => gunnar_grpc::seam::PurgeState::Running,
            crate::purge_queue::PurgeState::Done => gunnar_grpc::seam::PurgeState::Done,
            crate::purge_queue::PurgeState::Failed => gunnar_grpc::seam::PurgeState::Failed,
        },
        queue_position: job.queue_position,
        stores_found: report.stores_found,
        stores_purged: report.stores_purged,
        bytes_reclaimed: report.bytes_reclaimed,
        principal_removed: report.principal_removed,
        gate_released: report.gate_released,
        error: job.error,
        failures: report.failures,
        enqueued_at_unix_ms: job.enqueued_at_unix_ms,
        started_at_unix_ms: job.started_at_unix_ms,
        finished_at_unix_ms: job.finished_at_unix_ms,
    }
}

/// A gate write that was refused, as the error the caller wants.
///
/// A reserved or malformed account name is the caller's mistake and comes back
/// as `INVALID_ARGUMENT`; anything else is the table failing to be written and
/// is not the caller's fault. Folding the first into `Internal` would send an
/// operator looking at the disk over a typo.
fn gate_error(err: gunnar_core::Error) -> ControlError {
    match err {
        gunnar_core::Error::ReservedPrincipalId(_) | gunnar_core::Error::InvalidPath { .. } => {
            ControlError::InvalidArgument(format!("{err}"))
        }
        other => internal(other),
    }
}

/// **One stored flow row → one `DayActivity`.** The single writer of that
/// mapping, so the wire and the ledger cannot drift by a field.
///
/// `refused_by_reason` carries only the reasons that HAPPENED. A reason with no
/// refusals that day is absent rather than 0, because the map is a breakdown of
/// a number the caller already has (`refused`) and a zero entry in it adds a
/// row to a console's list that says nothing.
fn day_activity(day: i64, row: &gunnar_core::FlowDay) -> gunnar_proto::DayActivity {
    gunnar_proto::DayActivity {
        day_unix_ms: gunnar_core::midnight_of(day),
        bytes_in: row.bytes_in,
        bytes_out: row.bytes_out,
        pushes: row.pushes,
        fetches: row.fetches,
        lfs_bytes_in: row.lfs_bytes_in,
        lfs_bytes_out: row.lfs_bytes_out,
        refused: row.refused(),
        refused_by_reason: gunnar_core::Refusal::ALL
            .into_iter()
            .filter(|reason| row.refused_for(*reason) > 0)
            .map(|reason| (reason.name().to_owned(), row.refused_for(reason)))
            .collect(),
        auth_failures: row.auth_failures,
        last_push_unix_ms: row.last_push_unix_ms,
        last_fetch_unix_ms: row.last_fetch_unix_ms,
        distinct_principals: row.distinct_principals(),
        distinct_principals_capped: row.principals_capped,
    }
}

/// **A create's refusal, classified** — the repository or namespace named, a box being
/// restored (or off the stripe) as UNAVAILABLE (RUN A 2026-10-08: a create on a main being
/// restored answered INTERNAL, and the console showed "transaction log" and "twin" to a
/// customer), any other core error INTERNAL, anything else (the disk's own refusal) as is.
pub(crate) fn create_error(err: &anyhow::Error, path: &RepoPath) -> ControlError {
    match err.downcast_ref::<gunnar_core::Error>() {
        Some(gunnar_core::Error::RepoExists(_)) => {
            ControlError::AlreadyExists(format!("repository {path}"))
        }
        Some(gunnar_core::Error::NoSuchNamespace(ns)) => {
            ControlError::NotFound(format!("namespace {ns}"))
        }
        Some(e @ (gunnar_core::Error::LogFollows | gunnar_core::Error::OffStripe { .. })) => {
            ControlError::Unavailable(e.to_string())
        }
        Some(_) => ControlError::Internal(format!("{err:#}")),
        None => ControlError::FailedPrecondition(format!("{err:#}")),
    }
}

/// **Is this the mirror's first sync, from its in-flight mark?** (`mark_started`, IMPORT-BIG).
/// The mark is what lets a restart resume the import and what makes its outcome audited.
pub(crate) fn first_sync_of<E: std::fmt::Display>(
    mark: Result<Option<gunnar_core::MirrorRecord>, E>,
    path: &str,
) -> Result<bool, String> {
    match mark {
        Ok(record) => {
            Ok(record.is_some_and(|record| record.creates_repo || record.sync_count == 0))
        }
        Err(err) => {
            // RA4-10: unwritten, a restart could not resume this import and its outcome would go
            // unaudited, so the sync does not start.
            tracing::error!(target: "gunnar::git", "ALERT mirror.mark-unwritten {path}: the in-flight mark was not written ({err}); the sync is not started");
            Err(format!("{path}: the mirror's in-flight mark was not written ({err}); nothing was fetched, ask again"))
        }
    }
}

#[cfg(test)]
mod mirror_mark_tests {
    use super::*;

    /// ★ RA4-10 RED: **an in-flight mark that is not written fails the sync by name** — a
    /// dropped write meant a restart could not resume the import and its outcome went
    /// unaudited.
    #[test]
    fn a_mark_that_is_not_written_fails_the_sync_by_name() {
        let why = first_sync_of::<String>(Err("the mirrors store is full".into()), "acme/linux")
            .expect_err("refused");
        assert!(
            why.contains("acme/linux")
                && why.contains("the mirrors store is full")
                && why.contains("in-flight mark"),
            "{why}"
        );
        assert_eq!(first_sync_of::<String>(Ok(None), "acme/linux"), Ok(false));
    }
}

#[cfg(test)]
mod create_error_tests {
    use super::*;

    /// ★ **A create on a box being restored is UNAVAILABLE, never INTERNAL** (RUN A R8,
    /// 2026-10-08): the console turns UNAVAILABLE + this sentence into its own word.
    #[test]
    fn a_create_on_a_restoring_box_is_unavailable() {
        let path = RepoPath::new("acme", "site");
        let restoring = anyhow::Error::new(gunnar_core::Error::LogFollows);
        assert!(
            matches!(create_error(&restoring, &path), ControlError::Unavailable(m) if m.contains("being restored"))
        );
        let exists = anyhow::Error::new(gunnar_core::Error::RepoExists(
            gunnar_core::RepoRef::new("acme", "site").unwrap(),
        ));
        assert!(matches!(
            create_error(&exists, &path),
            ControlError::AlreadyExists(_)
        ));
        assert!(matches!(
            create_error(&anyhow::anyhow!("a store already stands there"), &path),
            ControlError::FailedPrecondition(_)
        ));
    }
}

/// A catalog error, mapped to the status code that says **whose fault it is**.
///
/// This used to be `ControlError::Internal(err.to_string())` for every one of
/// its thirty-four call sites, so `gunnar control repo set-default-branch
/// team/project trunk` came back as
///
/// ```text
/// gunnar: Internal error: internal error: not a legal default branch name: "trunk"
/// ```
///
/// An `INTERNAL` says *the server is broken*. What actually happened is that
/// the caller typed a short branch name where a full ref was required, and
/// nothing in that sentence tells them to fix their argument rather than read
/// the server's logs. Every "this repository does not exist", "that name is
/// taken" and "you are not allowed to" arrived the same way.
///
/// `enrolment_error` already classified its own errors for exactly this
/// reason; this is the same job for the rest of the surface, in one function
/// rather than at thirty-four call sites (one implementation). The mapping follows gRPC's
/// own definitions:
///
/// * **INVALID_ARGUMENT** — the request is malformed however the server feels.
/// * **NOT_FOUND** / **ALREADY_EXISTS** — the named thing is or is not there.
/// * **FAILED_PRECONDITION** — well formed, and the server's *state* refuses.
/// * **PERMISSION_DENIED** — authenticated, not allowed.
/// * **UNAVAILABLE** — storage did not answer; retrying may work.
/// * **INTERNAL** — only what is genuinely a bug here, which is the point:
///   an `INTERNAL` an operator sees now means something.
fn internal(err: gunnar_core::Error) -> ControlError {
    use gunnar_core::Error as E;
    match err {
        // The caller's argument.
        e @ (E::InvalidPath { .. }
        | E::PathEscape { .. }
        | E::ReservedPrincipalId(_)
        | E::BadBranchName(_)
        | E::BadFingerprint(_)
        | E::Key(_)
        | E::InvalidInput { .. }) => ControlError::InvalidArgument(e.to_string()),
        // What is not there.
        e @ (E::NoSuchRepo(_)
        | E::NoSuchNamespace(_)
        | E::NoSuchPrincipal(_)
        | E::NoSuchCredential(_)) => ControlError::NotFound(e.to_string()),
        // …and what already is.
        e @ (E::RepoExists(_)
        | E::NamespaceExists(_)
        | E::PrincipalExists(_)
        | E::NameExists { .. }
        | E::KeyExists { .. }
        | E::CredentialExists { .. }
        | E::InviteExists(_)
        | E::TokenExists { .. }
        | E::AlreadyBootstrapped { .. }
        | E::AlreadyProvisioned { .. }) => ControlError::AlreadyExists(e.to_string()),
        // Well formed; the server's state says no. A namespace that still holds
        // repositories is the case an operator meets, and `--delete-repos` is
        // the answer — which is a precondition, not a bad request.
        e @ (E::NamespaceNotEmpty { .. }
        | E::Contended { .. }
        | E::NotAPerson { .. }
        | E::NotAMachine { .. }) => ControlError::FailedPrecondition(e.to_string()),
        e @ (E::Denied { .. } | E::CounterRollback { .. } | E::InviteInvalid) => {
            ControlError::PermissionDenied(e.to_string())
        }
        // Storage did not answer. NOT `Internal`: the request may well succeed
        // on a retry, and telling a caller their request was wrong when the
        // disk was busy sends them to fix the wrong thing.
        e @ (E::Store(_) | E::Json(_)) => ControlError::Unavailable(e.to_string()),
        // The control store is OFF THE STRIPE while the data set grows: the
        // write is refused by name and the caller retries after the growth —
        // D7's "refuse", and UNAVAILABLE says exactly that to a generated
        // client where INTERNAL would say "look at this server".
        e @ E::OffStripe { .. } => ControlError::Unavailable(e.to_string()),
        // A box being restored takes no write until the restore is whole: "try again".
        e @ E::LogFollows => ControlError::Unavailable(e.to_string()),
        // A document that will not parse, and anything unclassified. These are
        // what genuinely mean "look at this server". `gunnar_core::Error` is
        // `#[non_exhaustive]`, so a variant added later lands here — `INTERNAL`
        // is the right default for "gunnar does not know what this is", and it
        // errs toward the server's fault rather than toward blaming the caller
        // for something nobody has classified.
        e => ControlError::Internal(e.to_string()),
    }
}

/// **An archive cut's error, classified by whose fault it is** — the same job
/// [`internal`] does for `gunnar_core::Error`, for the one path that reports an
/// `anyhow` chain instead.
///
/// Two classes, and they are told apart by what is *in* the chain rather than
/// by matching on a message:
///
/// * an `io::Error` anywhere in it means the disk or the socket did not answer
///   — `UNAVAILABLE`, because a retry may well work, and a `BrokenPipe` is the
///   *client* having hung up rather than this server being broken;
/// * anything else is a refusal the cut made on purpose — the watermark above a
///   pack a GC has rewritten, a directory with no `objects.pack`, a repository
///   directory holding two stores. Those are `FAILED_PRECONDITION`: the request
///   is well formed and the server's state says no. A full archive
///   (`--from-generation 0`) is the answer to the first, and the message says so
///   in the plugin's own words.
#[cfg(feature = "engine-znippy")]
fn archive_error(err: anyhow::Error) -> ControlError {
    let io = err
        .chain()
        .any(|cause| cause.downcast_ref::<std::io::Error>().is_some());
    let message = format!("{err:#}");
    if io {
        ControlError::Unavailable(message)
    } else {
        ControlError::FailedPrecondition(message)
    }
}

/// **The one storage-fault conversion in this file** (one implementation).
///
/// `GitOps` and `GitServe` answer in `anyhow`, so every read of a repository
/// arrives here. `{:#}` and not `to_string()`: the cause chain is the whole of
/// what an operator has to go on, and `to_string()` prints only the outermost
/// context — *"reading the ref namespace"* with the errno dropped.
///
/// **The status code is unchanged, deliberately.** `Internal` is what this
/// answered before, and `internal_or_denied` twenty lines above classifies
/// `gunnar_core::Error::Store` as `Unavailable` for a reason that applies here
/// too — a storage fault may well succeed on a retry. Changing it is a change
/// to what every gRPC client of `Refs.*` retries on, so it is **recorded here
/// and not taken as a drive-by** of a compile fix.
///
/// ⚠ **A lost compare-and-swap and a broken disk arrive as the same string** on
/// this path. `git-storage-trait` carries [`RefRejection`] for exactly that
/// distinction and `RefRejection::of(&err)` is how it is recovered; nothing in
/// this file needs it yet. Whatever does must use that, and **never** match on
/// the message text.
///
/// [`RefRejection`]: gunnar_store::git_storage_trait::RefRejection
fn store_error(err: anyhow::Error) -> ControlError {
    ControlError::Internal(format!("{err:#}"))
}

/// The same, for the one authority on following a symbolic reference.
///
/// [`gunnar_wire::refs`] returns `gunnar_wire::Error` rather than
/// `anyhow::Error`; a symref walk that refuses is a fault in what the store
/// holds, which is the same `Internal` this control plane already reports for
/// [`store_error`], so the two funnel to one variant rather than inventing a
/// second grade of failure for the same event.
fn wire_error(err: gunnar_wire::Error) -> ControlError {
    ControlError::Internal(format!("{err:#}"))
}

// ── model translation ───────────────────────────────────────────────────────

/// The one translation of a hash kind into the proto enum. `transport.rs`
/// reuses it for the push attestation rather than writing a second `match`
/// that could drift from this one (one implementation).
pub(crate) fn hash_kind(kind: HashKind) -> gunnar_proto::HashKind {
    match kind {
        HashKind::Sha1 => gunnar_proto::HashKind::Sha1,
        HashKind::Sha256 => gunnar_proto::HashKind::Sha256,
    }
}

/// gunnar has **two** visibilities, not three.
///
/// The proto still carries `VISIBILITY_INTERNAL`, and it used to alias
/// `PUBLIC` here — honestly, at the time: with no anonymous path at all,
/// "readable by any authenticated principal" and "public" named the same set.
/// Anonymous read (2026-08-03) broke that equivalence — `Public` now means readable by
/// ANYONE, with no key — and the alias survived the redefinition. What that
/// cost, MEASURED 2026-08-19 through the console: an operator chose
/// "internal" and the repository came out anonymous-readable. Silently
/// WIDENING an access request is the one direction a coercion must never
/// fail, so `INTERNAL` is now refused by name instead of mapped. The day a
/// real internal tier exists in [`Visibility`], this arm becomes its
/// translation; until then the wire value is a claim with no implementation.
fn visibility_in(v: gunnar_proto::Visibility) -> ControlResult<Visibility> {
    match v {
        gunnar_proto::Visibility::Public => Ok(Visibility::Public),
        gunnar_proto::Visibility::Internal => Err(ControlError::InvalidArgument(
            "visibility \"internal\" has no implementation: since 2026-08-03, \"public\" means \
             readable with no key at all, so \"internal\" (any authenticated principal) \
             no longer aliases it and gunnar refuses to guess which you meant. Choose \
             \"private\" or \"public\""
                .into(),
        )),
        gunnar_proto::Visibility::Private | gunnar_proto::Visibility::Unspecified => {
            Ok(Visibility::Private)
        }
    }
}

/// The one translation of a stored pull request into the proto shape (one implementation).
fn pull_out(path: &RepoPath, record: gunnar_core::PullRecord) -> PullRequest {
    PullRequest {
        repo: Some(path.clone()),
        number: record.number,
        title: record.title,
        description: record.description,
        source_ref: record.source_ref,
        target_ref: record.target_ref,
        state: match record.state {
            gunnar_core::PullState::Open => PullRequestState::Open,
            gunnar_core::PullState::Merged => PullRequestState::Merged,
            gunnar_core::PullState::Closed => PullRequestState::Closed,
        } as i32,
        author: record.author,
        created_at_unix_ms: record.created_ms,
        updated_at_unix_ms: record.updated_ms,
        source_oid: record.source_oid,
        merge_oid: record.merge_oid.unwrap_or_default(),
    }
}

fn visibility_out(v: Visibility) -> gunnar_proto::Visibility {
    match v {
        Visibility::Private => gunnar_proto::Visibility::Private,
        Visibility::Public => gunnar_proto::Visibility::Public,
    }
}

fn principal_kind_in(kind: gunnar_proto::PrincipalKind) -> PrincipalKind {
    match kind {
        gunnar_proto::PrincipalKind::Machine => PrincipalKind::Machine,
        gunnar_proto::PrincipalKind::Deploy => PrincipalKind::Deploy,
        gunnar_proto::PrincipalKind::Group => PrincipalKind::Group,
        gunnar_proto::PrincipalKind::User | gunnar_proto::PrincipalKind::Unspecified => {
            PrincipalKind::User
        }
    }
}

impl CoreControlPlane {
    /// **Whose account the namespace `name` is** (`Namespace.owner_kind`): the
    /// kind of the principal whose id it is, else UNSPECIFIED — so a reader
    /// that bills per namespace can leave out the estate's own machines by
    /// what they ARE, not by a list of their names. A store that cannot be
    /// read says UNSPECIFIED (the namespace is still listed).
    ///
    /// A GROUP whose every direct member is a machine is the estate's own too
    /// (the `twin` group, the twin's log readers — MEASURED on the mock
    /// 2026-09-29, listed as a tenant) and answers MACHINE; a group with anyone
    /// else in it, or with nobody, stays a group.
    fn owner_kind(&self, name: &str) -> i32 {
        let auth = self.stores.auth();
        match auth.principal(name) {
            Ok(Some(p)) if p.kind == PrincipalKind::Group => {
                let members = auth.members_of(name).unwrap_or_default();
                let machines = !members.is_empty() && members.iter().all(|m| matches!(auth.principal(m), Ok(Some(q)) if q.kind == PrincipalKind::Machine));
                if machines {
                    gunnar_proto::PrincipalKind::Machine as i32
                } else {
                    principal_kind_out(p.kind) as i32
                }
            }
            Ok(Some(p)) => principal_kind_out(p.kind) as i32,
            _ => gunnar_proto::PrincipalKind::Unspecified as i32,
        }
    }

    /// The catalog's namespace onto the wire — one mapping for create, list
    /// and the single lookup, so the account's settings and its employee count
    /// cannot be on one and missing from another. `employees` is derived (an
    /// account with any is an enterprise account; nothing is set).
    fn namespace_out(&self, namespace: gunnar_core::Namespace, employees: u32) -> Namespace {
        Namespace {
            owner_kind: self.owner_kind(&namespace.name),
            // A store that cannot be read says SELLER: a customer left out for one tick is given
            // its fact on the next, while a fact given to the operator's own namespace stays.
            owner_server_grant: self
                .stores
                .auth()
                .holds_server_grant(&namespace.name)
                .unwrap_or(true),
            name: namespace.name,
            description: String::new(),
            created_at_unix_ms: 0,
            public: namespace.public,
            events_public: namespace.events_public,
            employees,
        }
    }

    /// How many employees `account` has enrolled.
    fn employee_count(&self, account: &str) -> ControlResult<u32> {
        Ok(self
            .stores
            .auth()
            .employees_of(account)
            .map_err(internal)?
            .len() as u32)
    }
}

fn principal_kind_out(kind: PrincipalKind) -> gunnar_proto::PrincipalKind {
    match kind {
        PrincipalKind::User => gunnar_proto::PrincipalKind::User,
        PrincipalKind::Machine => gunnar_proto::PrincipalKind::Machine,
        PrincipalKind::Deploy => gunnar_proto::PrincipalKind::Deploy,
        PrincipalKind::Group => gunnar_proto::PrincipalKind::Group,
        // **Unreachable, and mapped honestly rather than plausibly.**
        // Every principal that reaches this function came out of the identity
        // table, and `AuthTable::add_principal` refuses the anonymous id, so
        // there is no anonymous row to list. `gunnar-proto` has no `ANONYMOUS`
        // value, and picking `USER` would put a fabricated human in an operator's
        // principal list; `UNSPECIFIED` is the value that means "gunnar cannot
        // name this", which is the truth. Adding the enum value is a
        // `gunnar-proto` change and is recorded there, not invented here.
        PrincipalKind::Anonymous => gunnar_proto::PrincipalKind::Unspecified,
    }
}

fn level_in(level: GrantLevel) -> ControlResult<Level> {
    match level {
        GrantLevel::Read => Ok(Level::Read),
        GrantLevel::Write => Ok(Level::Write),
        GrantLevel::Admin => Ok(Level::Admin),
        GrantLevel::Unspecified => Err(ControlError::InvalidArgument(
            "grant level unspecified".into(),
        )),
    }
}

fn level_out(level: Level) -> GrantLevel {
    match level {
        Level::Read => GrantLevel::Read,
        Level::Write => GrantLevel::Write,
        Level::Admin => GrantLevel::Admin,
    }
}

fn repo_out(repo: &gunnar_core::Repo) -> Repo {
    Repo {
        path: Some(RepoPath::new(&repo.namespace, &repo.name)),
        hash_kind: hash_kind(repo.hash_kind) as i32,
        default_branch: repo.default_branch.clone(),
        visibility: visibility_out(repo.visibility) as i32,
        created_at_unix_ms: repo.created,
        description: repo.description.clone(),
        encrypted: repo.encrypted,
    }
}

/// A stored web credential, as the wire carries it (no key material).
fn web_credential_out(
    row: &gunnar_core::WebCredential,
) -> ControlResult<gunnar_proto::WebCredential> {
    let credential_id = gunnar_grpc::webauthn::from_b64url(&row.id).ok_or_else(|| {
        ControlError::Internal(format!(
            "a stored web credential has an id that is not base64url: {}",
            row.id
        ))
    })?;
    Ok(gunnar_proto::WebCredential {
        credential_id,
        principal_id: row.principal_id.clone(),
        label: row.label.clone(),
        created_at_unix_ms: row.created,
        last_used_unix_ms: row.last_used,
        sign_count: row.sign_count,
    })
}

fn principal_out(principal: &gunnar_core::Principal) -> Principal {
    Principal {
        id: principal.id.clone(),
        name: principal.name.clone(),
        kind: principal_kind_out(principal.kind) as i32,
        // The table's stamp. `0` for a row from before the field existed,
        // which is exactly what this reported for every row until then.
        created_at_unix_ms: principal.created,
    }
}

/// Clans on the identity table (`gunnar_grpc::clans::ClanPlane`, 2026-10-05).
mod clan_plane;

fn key_out(key: &gunnar_core::PublicKey) -> PublicKey {
    PublicKey {
        fingerprint: key.fingerprint_sha256.clone(),
        algo: key.algo.clone(),
        principal_id: key.principal_id.clone(),
        // The OpenSSH comment field is part of the stored line; gunnar-core
        // normalises the line and does not split it out.
        comment: String::new(),
        added_at_unix_ms: key.added,
        last_used_unix_ms: key.last_used,
        expires_at_unix_ms: key.expires,
    }
}

/// A grant, as `<namespace, repo>` strings.
///
/// A [`Scope::Server`] grant has neither, and is carried as two empty strings.
/// See the module docs: that is a proto gap, not an invention here.
fn grant_out(grant: &Grant) -> gunnar_proto::Grant {
    let (namespace, repo) = match &grant.scope {
        Scope::Server => (String::new(), String::new()),
        Scope::Namespace(name) => (name.clone(), String::new()),
        Scope::Repo(path) => (path.namespace().to_owned(), path.name().to_owned()),
    };
    gunnar_proto::Grant {
        principal_id: grant.principal.clone(),
        namespace,
        repo,
        level: level_out(grant.level) as i32,
        granted_at_unix_ms: 0,
    }
}

fn scope_in(namespace: &str, repo: &str) -> ControlResult<Scope> {
    match (namespace.is_empty(), repo.is_empty()) {
        (true, true) => Ok(Scope::Server),
        (false, true) => Ok(Scope::Namespace(namespace.to_owned())),
        (false, false) => RepoRef::new(namespace, repo)
            .map(Scope::Repo)
            .map_err(|err| ControlError::InvalidArgument(err.to_string())),
        (true, false) => Err(ControlError::InvalidArgument(
            "a repository-scoped grant must name a namespace (multi-tenancy has \
             no ungrouped repos)"
                .into(),
        )),
    }
}

/// The contract's object kind, in the proto's vocabulary.
///
/// [`ObjType`] also has `OfsDelta` and `RefDelta`, and neither can appear here:
/// [`GitServe::read`] and [`GitServe::header`] answer with the **resolved**
/// type by contract — that is the difference between them and
/// `GitOps::get`, which hands back the pack entry delta and all. A delta
/// reaching this function is a backend that broke its own promise, so it is
/// named as one rather than folded into `Unspecified`, which a client would
/// read as "an object of a kind this server is too old to name".
fn object_kind_out(kind: ObjType) -> ControlResult<gunnar_proto::ObjectKind> {
    match kind {
        ObjType::Blob => Ok(gunnar_proto::ObjectKind::Blob),
        ObjType::Tree => Ok(gunnar_proto::ObjectKind::Tree),
        ObjType::Commit => Ok(gunnar_proto::ObjectKind::Commit),
        ObjType::Tag => Ok(gunnar_proto::ObjectKind::Tag),
        other => Err(ControlError::Internal(format!(
            "the store answered a read with `{}`, which is a delta; GitServe::read is \
             documented to return the resolved type",
            other.as_str()
        ))),
    }
}

/// Follow an annotated tag down to the object it names.
///
/// A bounded loop, not a recursion: a tag chain is legal git and a cycle is
/// not, but a cycle is also cheap to write and would otherwise hang a control
/// plane that has no timeout.
///
/// What object id `segments` names under `tree` — a blob's id, a subtree's id,
/// or `None` when the path names nothing there.
///
/// The log's path filter rests on this: a commit changed a path exactly when
/// this answer differs from its first parent's. A path that continues THROUGH
/// a non-directory names nothing, the same rule the wire's tree walk applies.
fn oid_at_path(
    git: &dyn GitServe,
    hash_kind: gix_hash::Kind,
    tree: gix_hash::ObjectId,
    segments: &[&[u8]],
) -> ControlResult<Option<gix_hash::ObjectId>> {
    let mut current = tree;
    let last = segments.len().saturating_sub(1);
    for (index, segment) in segments.iter().enumerate() {
        let Some((kind, bytes)) = git.read(current.as_bytes()).map_err(store_error)? else {
            return Ok(None);
        };
        if kind != ObjType::Tree {
            return Ok(None);
        }
        let Some(entry) = object::tree_entry_named(&bytes, hash_kind, segment)
            .map_err(|err| ControlError::Internal(format!("decoding tree {current}: {err}")))?
        else {
            return Ok(None);
        };
        if index == last {
            return Ok(Some(entry.oid));
        }
        if entry.kind != object::EntryKind::Tree {
            return Ok(None);
        }
        current = entry.oid;
    }
    Ok(Some(current))
}

/// `hash_kind` is a parameter and never a default: it comes from
/// [`OpenRepo::hash_kind`], which comes from the catalog entry, and answering
/// `sha1` for a sha256 repository does not error — it decodes garbage.
/// Where a `Refs.Log` walk begins: one start (a ref name, an oid, or empty
/// for `HEAD`), or every branch and tag tip plus `HEAD`.
#[derive(Clone, Copy)]
enum LogStart<'a> {
    One(&'a str),
    AllRefs,
}

/// One `Refs.Log` start resolved to an oid: an oid as given, otherwise a ref
/// name (empty means `HEAD`) resolved against one snapshot.
fn resolve_log_start(
    git: &dyn GitServe,
    hash: gix_hash::Kind,
    path: &RepoPath,
    start: &str,
) -> ControlResult<gix_hash::ObjectId> {
    let start = if start.is_empty() {
        gunnar_store::HEAD
    } else {
        start
    };
    let head = match gix_hash::ObjectId::from_hex(start.as_bytes()) {
        Ok(id) => id,
        Err(_) => {
            gunnar_store::refname::validate(start)
                .map_err(|err| ControlError::InvalidArgument(err.to_string()))?;
            let snapshot = RefSnapshot::read(git).map_err(wire_error)?;
            // `HEAD` is not in the snapshot (the `GitServe` HEAD ruling) and it is this verb's
            // own default, so it is asked through the accessor pair. Both
            // branches resolve against the same snapshot.
            let resolved = if start == gunnar_store::HEAD {
                snapshot.head(git).map_err(wire_error)?
            } else {
                snapshot.resolve(start).map_err(wire_error)?
            };
            resolved.ok_or_else(|| ControlError::NotFound(format!("{start} in {path}")))?
        }
    };
    if head.kind() != hash {
        return Err(ControlError::InvalidArgument(format!(
            "{start} is a {} oid; this repository is {hash}",
            head.kind()
        )));
    }
    Ok(head)
}

impl CoreControlPlane {
    fn log_walk(
        &self,
        path: &RepoPath,
        start: LogStart<'_>,
        limit: u32,
        touching: &str,
    ) -> ControlResult<Vec<Commit>> {
        use std::collections::{BinaryHeap, HashMap, HashSet};

        let (_, store) = self.open(path)?;
        let git = store.serve();
        let hash = store.hash_kind();

        // The path filter, refused loudly rather than normalised: a filter
        // that silently ate `..` would answer for a different path than the
        // caller named.
        let filter: Option<Vec<&[u8]>> = if touching.is_empty() {
            None
        } else {
            let mut segments = Vec::new();
            for segment in touching.split('/').filter(|s| !s.is_empty()) {
                if segment == "." || segment == ".." {
                    return Err(ControlError::InvalidArgument(format!(
                        "the log path filter cannot contain {segment:?}"
                    )));
                }
                segments.push(segment.as_bytes());
            }
            (!segments.is_empty()).then_some(segments)
        };

        let heads: Vec<gix_hash::ObjectId> = match start {
            LogStart::One(start) => vec![resolve_log_start(git, hash, path, start)?],
            LogStart::AllRefs => {
                let snapshot = RefSnapshot::read(git).map_err(wire_error)?;
                let mut heads = Vec::new();
                if let Some(head) = snapshot.head(git).map_err(wire_error)? {
                    heads.push(head);
                }
                for row in snapshot.rows().iter().filter(|r| {
                    r.name.starts_with("refs/heads/") || r.name.starts_with("refs/tags/")
                }) {
                    if let Some(id) = snapshot.resolve_row(row).map_err(wire_error)? {
                        heads.push(id);
                    }
                }
                heads
            }
        };

        // Newest first, by EACH COMMIT'S OWN committer time — so tips of
        // several branches interleave the way `git log --date-order --all`
        // does, and a page cut by `limit` is the newest `limit` commits.
        // Each commit is decoded once, when it is queued, and kept until it
        // is popped.
        let limit = if limit == 0 { 50 } else { limit } as usize;
        let mut heap: BinaryHeap<(i64, gix_hash::ObjectId)> = BinaryHeap::new();
        let mut seen: HashSet<gix_hash::ObjectId> = HashSet::new();
        let mut queued: HashMap<gix_hash::ObjectId, object::Commit> = HashMap::new();
        let mut enqueue = |id: gix_hash::ObjectId,
                           heap: &mut BinaryHeap<(i64, gix_hash::ObjectId)>,
                           queued: &mut HashMap<gix_hash::ObjectId, object::Commit>|
         -> ControlResult<()> {
            if !seen.insert(id) {
                return Ok(());
            }
            // A shallow edge (not in this store) or a tip that peels to a
            // non-commit ends that line quietly, as it always did.
            let Some((kind, bytes)) = git.read(id.as_bytes()).map_err(store_error)? else {
                return Ok(());
            };
            if kind != ObjType::Commit {
                return Ok(());
            }
            let commit = object::commit(&bytes, hash)
                .map_err(|err| ControlError::Internal(format!("decoding commit {id}: {err}")))?;
            heap.push((commit.committer.seconds, id));
            queued.insert(id, commit);
            Ok(())
        };
        for head in heads {
            let head = peel(git, hash, head)?;
            enqueue(head, &mut heap, &mut queued)?;
        }
        let mut out = Vec::new();

        // What a FILTERED walk may visit before giving up. A path nothing ever
        // touched must not cost a full traversal of a quarter-million commits
        // per page; a page that comes back short because of this bound is a
        // short page, not the end of history — the proto says so.
        const MAX_FILTERED_SCAN: usize = 20_000;
        let mut scanned = 0usize;
        // commit → its tree, remembered so a parent decoded for the filter is
        // not decoded again when the walk reaches it — and vice versa.
        let mut tree_of: HashMap<gix_hash::ObjectId, gix_hash::ObjectId> = HashMap::new();

        while let Some((_, id)) = heap.pop() {
            if out.len() >= limit {
                break;
            }
            let Some(commit) = queued.remove(&id) else {
                continue;
            };
            let object::Commit {
                tree,
                parents,
                author,
                committer,
                message,
            } = commit;

            // ── the path filter: did THIS commit change what the path names? ─
            //
            // Judged against the FIRST parent, which is what `git log -- path`
            // shows for ordinary history: "what did landing this commit change
            // here". Identical ids mean identical content all the way down, so
            // the question costs two short descents, never a blob.
            if let Some(segments) = &filter {
                scanned += 1;
                if scanned > MAX_FILTERED_SCAN {
                    break;
                }
                tree_of.insert(id, tree);
                let current = oid_at_path(git, hash, tree, segments)?;
                let previous = match parents.first() {
                    None => None,
                    Some(parent) => {
                        let parent_tree = match tree_of.get(parent) {
                            Some(known) => Some(*known),
                            None => match git.read(parent.as_bytes()).map_err(store_error)? {
                                Some((ObjType::Commit, parent_bytes)) => {
                                    let decoded =
                                        object::commit(&parent_bytes, hash).map_err(|err| {
                                            ControlError::Internal(format!(
                                                "decoding commit {parent}: {err}"
                                            ))
                                        })?;
                                    tree_of.insert(*parent, decoded.tree);
                                    Some(decoded.tree)
                                }
                                // A shallow edge: the parent is not in this
                                // store. Comparing against nothing keeps the
                                // commit visible rather than silently dropped.
                                _ => None,
                            },
                        };
                        match parent_tree {
                            Some(parent_tree) => oid_at_path(git, hash, parent_tree, segments)?,
                            None => None,
                        }
                    }
                };
                if current == previous {
                    // Untouched here — keep walking, show nothing.
                    for parent in parents {
                        enqueue(parent, &mut heap, &mut queued)?;
                    }
                    continue;
                }
            }

            out.push(Commit {
                oid: id.to_string(),
                parent_oids: parents.iter().map(|p| p.to_string()).collect(),
                tree_oid: tree.to_string(),
                author: Some(signature_out(
                    &author.name,
                    &author.email,
                    author.seconds,
                    author.offset_seconds,
                )),
                committer: Some(signature_out(
                    &committer.name,
                    &committer.email,
                    committer.seconds,
                    committer.offset_seconds,
                )),
                message: String::from_utf8_lossy(&message).into_owned(),
            });
            for parent in parents {
                enqueue(parent, &mut heap, &mut queued)?;
            }
        }
        Ok(out)
    }
}

fn peel(
    git: &dyn GitServe,
    hash_kind: gix_hash::Kind,
    mut id: gix_hash::ObjectId,
) -> ControlResult<gix_hash::ObjectId> {
    for _ in 0..16 {
        let Some((kind, bytes)) = git.read(id.as_bytes()).map_err(store_error)? else {
            return Ok(id);
        };
        if kind != ObjType::Tag {
            return Ok(id);
        }
        id = object::tag_target(&bytes, hash_kind)
            .map_err(|err| ControlError::Internal(format!("decoding tag {id}: {err}")))?;
    }
    Err(ControlError::FailedPrecondition(format!(
        "the tag chain at {id} is longer than 16 links, or cyclic"
    )))
}

/// One [`RefRow`] as the proto's `RefTarget`, resolved against `snapshot` — the
/// **same** snapshot the row came out of, so an answer cannot name an oid for a
/// reference that had already moved. See [`gunnar_wire::refs`].
fn ref_target_out(
    git: &dyn GitServe,
    hash_kind: gix_hash::Kind,
    snapshot: &RefSnapshot,
    row: &RefRow,
    want_peeled: bool,
) -> ControlResult<RefTarget> {
    let (oid, symbolic) = match (&row.oid, &row.symref_target) {
        // A symbolic reference is resolved through the snapshot, whatever else
        // it carries: the row's own `oid` on a symref is the store's cache of
        // the same walk, and one authority is enough.
        (_, Some(inner)) => (snapshot.resolve(inner).map_err(wire_error)?, inner.clone()),
        (Some(raw), None) => (
            Some(gunnar_wire::refs::oid(raw).map_err(wire_error)?),
            String::new(),
        ),
        (None, None) => (None, String::new()),
    };
    let peeled = match (want_peeled, oid) {
        // `row.peeled` is not used even when the store filled it in: `peel`
        // follows the whole chain and a stored peel is one hop, so taking the
        // cheaper answer where one exists would make two references with the
        // same tag chain answer differently.
        (true, Some(id)) => {
            let peeled = peel(git, hash_kind, id)?;
            if peeled == id {
                String::new()
            } else {
                peeled.to_string()
            }
        }
        _ => String::new(),
    };
    Ok(RefTarget {
        ref_name: row.name.clone(),
        oid: oid.map(|id| id.to_string()).unwrap_or_default(),
        symbolic_target: symbolic,
        peeled_oid: peeled,
    })
}

/// A commit's author or committer line, as the gRPC message spells it.
///
/// **Bytes and numbers, not `gix_actor::SignatureRef`.** That was the parameter
/// type until 2026-08-10, and it was the whole reason `gix-actor` was a direct
/// dependency of this crate: one private four-line function, in the manifest
/// beside `gix-pack`, where the next reader had to work out whether the server
/// was *using* an actor parser or merely naming one. It was merely naming one.
/// `gix-object` still arrives here — it is what decodes the commit these fields
/// come out of — and it brings `gix-actor` with it; what is gone is gunnar
/// asserting a need it does not have.
///
/// `from_utf8_lossy` matches what `BStr`'s own `Display` did before: a name in
/// a commit header is whatever the committing client wrote, a gRPC string field
/// is UTF-8, and this is a *report* about history rather than anything looked
/// up by name.
fn signature_out(name: &[u8], email: &[u8], seconds: i64, tz_offset_seconds: i32) -> Signature {
    Signature {
        name: String::from_utf8_lossy(name).into_owned(),
        email: String::from_utf8_lossy(email).into_owned(),
        time_unix_seconds: seconds,
        tz_offset_minutes: tz_offset_seconds / 60,
    }
}

// ───────────────────────────────────────────────────────────────────────────

/// **First boot, delegated straight to `gunnar_core::AuthTable`.**
///
/// Nothing is decided here. `bootstrap_state` reads the one predicate the
/// writer also reads, and `enroll_first_identity` is a call into the one
/// compare-and-swap that can produce a `BootstrapRecord`. A second opinion in
/// this adapter — "the table looks empty, so the window is open" — would be a
/// status that could disagree with the gate, and the permissive one would win
/// silently (one implementation).
impl gunnar_grpc::FirstBoot for CoreControlPlane {
    fn bootstrap_state(&self) -> ControlResult<gunnar_grpc::BootstrapState> {
        let auth = self.stores.auth();
        // Every one of these is a `Result`. A read fault becomes UNAVAILABLE
        // and never a window that is reported as open or as shut on a guess.
        let window_open = auth.bootstrap_window_open().map_err(unavailable)?;
        let record = auth.bootstrap_record().map_err(unavailable)?;
        let (principals, keys, _grants) = auth.counts().map_err(unavailable)?;
        Ok(gunnar_grpc::BootstrapState {
            window_open,
            bootstrapped: record.is_some(),
            bootstrapped_at_unix_ms: record.as_ref().map(|r| r.at).unwrap_or_default(),
            bootstrapped_principal: record
                .as_ref()
                .map(|r| r.principal_id.clone())
                .unwrap_or_default(),
            bootstrapped_fingerprint: record
                .as_ref()
                .map(|r| r.fingerprint.clone())
                .unwrap_or_default(),
            principals: principals as u64,
            keys: keys as u64,
            // The boot window (`crate::readiness`). Answered here rather than
            // on `Admin.Health` because this is the one call a server nobody
            // holds a key for can answer, and a boot script is exactly that
            // caller.
            // TWO facts, and the second one is new. The boot window is this
            // process's start-up; the listener is a socket. A twin closes no
            // window and binds no reachable git port, so before the listener
            // was consulted this field answered `true` for a box whose :2222
            // was answering ECONNREFUSED — measured on 10.13.8.101, 2026-09-20.
            serving_git: crate::readiness::is_serving_git(self.git_listener),
            readiness: crate::readiness::detail_with(self.git_listener),
            build: gunnar_common::BUILD_REF.to_owned(),
            role: if self.twin_role || self.stores.is_twin() {
                "twin"
            } else {
                "primary"
            }
            .to_owned(),
            // A RECHARGED main (the installer's re-admit) or a HELD one (the boot
            // check, R-7b) says what it awaits (the restore lane reads it).
            recharge_from: awaited_twin(&self.stores),
            restoring: crate::twin::is_restoring(self.stores.root()),
            log_head_seq: self.stores.txlog().head_seq(),
            // What a restoring box holds of its next entry: where the next stream resumes it.
            restore_partial: if crate::twin::is_restoring(self.stores.root()) {
                crate::twin::intake::partial(self.stores.root())
            } else {
                None
            },
            // restore-after-snapshot: this box stages a twin's base across streams, and says how
            // much of one it holds while it is restoring.
            restore_snapshot_resumable: true,
            restore_snapshot: if crate::twin::is_restoring(self.stores.root()) {
                crate::twin::snapshot::held_snapshot(self.stores.root())
                    .map(|h| (h.id, h.items, h.bytes, h.whole))
            } else {
                None
            },
        })
    }

    fn enroll_first_identity(
        &self,
        name: &str,
        openssh_public_key: &str,
    ) -> ControlResult<gunnar_grpc::Enrolled> {
        // R-7b: a box the boot check found with its data lost (a twin can give it
        // back) takes no first admin while it is held.
        #[cfg(feature = "replication")]
        if let Some(twin) = crate::repair::held(&self.stores) {
            return Err(ControlError::FailedPrecondition(
                crate::repair::held_refusal(&twin),
            ));
        }
        let enrolled = self
            .stores
            .auth()
            .enroll_first_user(name, openssh_public_key)
            .map_err(enrolment_error)?;
        // The account namespace, after the door is shut. Deliberately NOT
        // inside the identity CAS: it lives in the catalog, a different
        // document, and one write cannot span both. The ordering is what makes
        // that safe — the security boundary (the record) has already landed, so
        // the worst a failure here can do is leave a gunnar-admin whose account
        // namespace has to be created by hand, never a second open window.
        //
        // Idempotent: `AlreadyExists` on a namespace this principal already
        // intrinsically owns is not a failure of enrolment.
        if let Err(err) = self
            .stores
            .catalog()
            .create_namespace(&enrolled.record.account)
        {
            tracing::warn!(
                account = %enrolled.record.account,
                %err,
                "the first user was enrolled and the enrolment window is closed, but its account \
                 namespace could not be created. The user is admin of it by rule and can create \
                 it themselves with Repos.CreateNamespace."
            );
        }
        // ── the bootstrap admin's client certificate ────────────────────────
        //
        // Minted AFTER the CAS, so the security boundary is already shut when
        // this runs and a failure here cannot reopen it — the same ordering
        // argument as the namespace above. Server-generated key, deliberately:
        // there is no authenticated channel yet to carry a CSR, and this is the
        // one exchange in the server's life where handing a private key over
        // the wire is the honest trade. The server retains no copy of the key.
        let (client_cert_pem, client_key_pem, issuer_cert_pem) = match self.stores.pki() {
            Ok(pki) => match pki.issuer() {
                Ok(Some(issuer)) => {
                    match pki.issue_with_server_key(
                        &enrolled.principal.id,
                        gunnar_core::DEFAULT_LEAF_DAYS,
                    ) {
                        Ok(issued) => {
                            if let Err(err) = self.stores.auth().register_certificate(
                                &enrolled.principal.id,
                                &issued.cert_der,
                                None,
                            ) {
                                tracing::warn!(
                                    principal = %enrolled.principal.id,
                                    %err,
                                    "the bootstrap certificate was minted but could not be \
                                     registered; it is returned anyway and gunnar-admin can \
                                     register it with `gunnar key add`"
                                );
                            }
                            (
                                issued.cert_pem,
                                issued.key_pem.unwrap_or_default(),
                                issuer.cert_pem,
                            )
                        }
                        Err(err) => {
                            tracing::warn!(
                                principal = %enrolled.principal.id,
                                %err,
                                "no bootstrap certificate: the issuer refused to mint"
                            );
                            (String::new(), String::new(), String::new())
                        }
                    }
                }
                Ok(None) => (String::new(), String::new(), String::new()),
                Err(err) => {
                    tracing::warn!(%err, "no bootstrap certificate: the PKI document could not \
                                          be read");
                    (String::new(), String::new(), String::new())
                }
            },
            Err(_) => (String::new(), String::new(), String::new()),
        };
        Ok(gunnar_grpc::Enrolled {
            principal: principal_out(&enrolled.principal),
            key: key_out(&enrolled.key),
            account: enrolled.record.account,
            bootstrapped_at_unix_ms: enrolled.record.at,
            client_cert_pem,
            client_key_pem,
            issuer_cert_pem,
        })
    }
}

/// A read fault on the identity table. **Never a denial and never a state.**
fn unavailable(err: gunnar_core::Error) -> ControlError {
    ControlError::Unavailable(format!("the identity table could not be read: {err}"))
}

/// The refusals of the enrolment window, mapped so a caller can tell them apart
/// from a malformed request.
/// **The twin this box awaits** (`Bootstrap.Status.recharge_from`): the installer's
/// re-admit ([`crate::pairing::recharge_awaited`]), else the boot check's hold
/// ([`crate::repair::held`]); empty on every other box.
fn awaited_twin(stores: &ServerStores) -> String {
    #[cfg(feature = "wg-client")]
    if let Some(twin) = crate::pairing::recharge_awaited(stores) {
        return twin;
    }
    #[cfg(feature = "replication")]
    if let Some(twin) = crate::repair::held(stores) {
        return twin;
    }
    let _ = stores;
    String::new()
}

fn enrolment_error(err: gunnar_core::Error) -> ControlError {
    match err {
        // The door is shut. FAILED_PRECONDITION, because the request was well
        // formed and the *server's state* is what refuses it.
        e @ (gunnar_core::Error::AlreadyBootstrapped { .. }
        | gunnar_core::Error::AlreadyProvisioned { .. }) => {
            ControlError::FailedPrecondition(e.to_string())
        }
        // A bad name or a key that is not an authorized_keys line.
        e @ (gunnar_core::Error::InvalidPath { .. }
        | gunnar_core::Error::ReservedPrincipalId(_)
        | gunnar_core::Error::Key(_)) => ControlError::InvalidArgument(e.to_string()),
        // Storage. Not "the door is shut", which is what a caller would read a
        // FAILED_PRECONDITION as, and not OK, which would be the disaster.
        other => ControlError::Unavailable(other.to_string()),
    }
}

impl CoreControlPlane {
    /// ★ **The estate's operator, made on its first claim** — the one writer
    /// behind `Accounts.ClaimOperator` and behind the primary's own claim when
    /// the installer feeds `operator_name` ([`crate::fed_principals::install`]).
    ///
    /// `fed` is the installer's name for the operator and wins; `asked` is the
    /// caller's, used only when nothing was fed (`gunnar_grpc::seam::operator_name`).
    ///
    /// * A PERSON already under that id or name is the answer, unchanged but
    ///   for two upserts that make it what an operator is: its account
    ///   namespace exists, and it is gunnar-admin.
    /// * Anything else under it — a machine, a group — is refused by name: an
    ///   estate's parts are never its operator.
    /// * Otherwise the principal is created, KEYLESS (the console's credential
    ///   for the person is its first key, which owes nobody an attestation; the
    ///   person's own SSH keys come after and are vouched for by it), with its
    ///   account namespace — and **a namespace of that name that already exists
    ///   with no owner is ADOPTED** rather than refused. MEASURED on test2
    ///   2026-10-04: a first push with the installer's admin key
    ///   (`rickard/t2-scratch`) conjured `rickard`, and `AddPrincipal` refused
    ///   the operator's own account from then on — the first admin's passkey
    ///   bound to nothing. Adoption is safe exactly here: the namespace has no
    ///   principal of its id (this call is creating it), only a server Admin can
    ///   ask, and that Admin could already delete the namespace or grant it.
    pub fn claim_operator_named(
        &self,
        fed: Option<&str>,
        asked: &str,
    ) -> ControlResult<gunnar_grpc::OperatorClaim> {
        let (name, named_by) = gunnar_grpc::seam::operator_name(fed, asked)?;
        let auth = self.stores.auth();
        let held = match auth.principal(name).map_err(internal)? {
            Some(p) => Some(p),
            None => auth.principal_by_name(name).map_err(internal)?,
        };
        if let Some(p) = held {
            if p.kind != PrincipalKind::User {
                return Err(ControlError::FailedPrecondition(format!(
                    "the operator's name {name:?} is held by principal {:?}, which is not a person \
                     ({:?}); an estate's machines are never its operator",
                    p.id, p.kind
                )));
            }
            let adopted_namespace = false;
            if self
                .stores
                .catalog()
                .namespace(&p.id)
                .map_err(internal)?
                .is_none()
            {
                self.stores
                    .catalog()
                    .create_namespace(&p.id)
                    .map_err(internal)?;
            }
            self.grant(&p.id, "", "", GrantLevel::Admin)?;
            return Ok(gunnar_grpc::OperatorClaim {
                principal: principal_out(&p),
                created: false,
                adopted_namespace,
                named_by,
            });
        }
        let principal =
            gunnar_core::Principal::new(name, name, PrincipalKind::User).map_err(internal)?;
        let created = auth.add_principal(principal).map_err(internal)?;
        let adopted_namespace = match self.stores.catalog().create_namespace(&created.id) {
            Ok(_) => false,
            Err(gunnar_core::Error::NamespaceExists(_)) => true,
            Err(err) => {
                let _ = auth.remove_principal(&created.id);
                return Err(internal(err));
            }
        };
        if let Err(err) = self.grant(&created.id, "", "", GrantLevel::Admin) {
            // Not left half-made: an operator that is not the estate's admin is
            // not the one that was asked for, and the next claim makes it whole.
            let _ = auth.remove_principal(&created.id);
            return Err(err);
        }
        self.stores.mirror_identity();
        tracing::warn!(
            target: "gunnar::audit",
            event = "operator.claimed",
            operator = %created.id,
            adopted_namespace,
            named_by,
            "the estate's operator was created: a person, keyless, gunnar-admin, with its account \
             namespace{}",
            if adopted_namespace {
                " — the namespace already existed with no owner (a first push conjured it) and is \
                 now the operator's account"
            } else {
                ""
            }
        );
        Ok(gunnar_grpc::OperatorClaim {
            principal: principal_out(&created),
            created: true,
            adopted_namespace,
            named_by,
        })
    }
}

/// The owner's enterprise list on the real stores (`gunnar_grpc::enterprise::EnterprisePlane`).
mod enterprise_plane;

impl ControlPlane for CoreControlPlane {
    fn enterprise(&self) -> Option<&dyn gunnar_grpc::enterprise::EnterprisePlane> {
        Some(self)
    }

    // ── namespaces ─────────────────────────────────────────────────────────

    fn create_namespace(&self, name: &str, _description: &str) -> ControlResult<Namespace> {
        // An EMPLOYEE's id is never a namespace: a namespace named after a
        // principal makes that principal its admin (`owns_account`), and an
        // employee is admin of nothing (`AuthTable::enroll_employee`).
        if self
            .stores
            .auth()
            .employer_of(name)
            .map_err(internal)?
            .is_some()
        {
            return Err(ControlError::AlreadyExists(format!(
                "{name} is an employee's id, and an employee holds no account of its own"
            )));
        }
        let namespace = self
            .stores
            .catalog()
            .create_namespace(name)
            .map_err(internal)?;
        Ok(self.namespace_out(namespace, 0))
    }

    fn list_namespaces(&self) -> ControlResult<Vec<Namespace>> {
        let mut employees: std::collections::BTreeMap<String, u32> = Default::default();
        for principal in self.stores.auth().principals().map_err(internal)? {
            if let Some(account) = self
                .stores
                .auth()
                .employer_of(&principal.id)
                .map_err(internal)?
            {
                *employees.entry(account).or_default() += 1;
            }
        }
        Ok(self
            .stores
            .catalog()
            .namespaces()
            .map_err(internal)?
            .into_iter()
            .map(|ns| {
                let count = employees.get(&ns.name).copied().unwrap_or(0);
                self.namespace_out(ns, count)
            })
            .collect())
    }

    /// One catalog probe, not the listing the trait's default walks: this is
    /// asked by the account settings and the outsider's view of a namespace.
    fn namespace(&self, name: &str) -> ControlResult<Option<Namespace>> {
        let Some(ns) = self.stores.catalog().namespace(name).map_err(internal)? else {
            return Ok(None);
        };
        let count = self.employee_count(name)?;
        Ok(Some(self.namespace_out(ns, count)))
    }

    fn namespace_for_outsider(
        &self,
        principal_id: &str,
        name: &str,
    ) -> ControlResult<Option<Namespace>> {
        // The gate, both directions, before the setting — the same walk
        // `AuthTable::may` makes (an ancestor's gate closes a nested account).
        let auth = self.stores.auth();
        if auth
            .gate_covering(principal_id)
            .map_err(internal)?
            .is_some()
            || auth.gate_covering(name).map_err(internal)?.is_some()
        {
            return Ok(None);
        }
        self.namespace(name)
    }

    fn set_namespace_settings(
        &self,
        name: &str,
        public: Option<bool>,
        events_public: Option<bool>,
    ) -> ControlResult<Namespace> {
        let catalog = self.stores.catalog();
        let mut ns = catalog
            .namespace(name)
            .map_err(internal)?
            .ok_or_else(|| ControlError::NotFound(format!("namespace {name}")))?;
        if let Some(public) = public {
            ns = catalog
                .set_namespace_public(name, public)
                .map_err(internal)?;
        }
        if let Some(events_public) = events_public {
            ns = catalog
                .set_namespace_events_public(name, events_public)
                .map_err(internal)?;
        }
        let count = self.employee_count(name)?;
        Ok(self.namespace_out(ns, count))
    }

    fn delete_namespace(&self, name: &str, delete_repos: bool) -> ControlResult<u32> {
        // A CLAN's namespace goes with the clan (`Clans.Dissolve`), never on
        // its own: a clan left without its namespace would be a name nobody
        // could make anything in, and the namespace's repositories are the
        // clan's to dissolve, not one admin grant's to delete.
        if self.stores.auth().is_clan(name).map_err(internal)? {
            return Err(ControlError::FailedPrecondition(format!(
                "namespace {name} is clan {name}'s: it goes when the clan's admin dissolves the clan"
            )));
        }
        let gone = self
            .stores
            .catalog()
            .delete_namespace(name, delete_repos)
            .map_err(internal)?;
        // **The flow half of deleting a tenant.** The activity ledger keeps
        // four hundred days per namespace INCLUDING which key fingerprints
        // pushed, and a tenant that is gone must not leave a record of who
        // worked on it. Deliberately after the catalog delete: if that refused
        // — a non-empty namespace without `delete_repos` — nothing has been
        // deleted and the series must stay.
        //
        // A failure here is logged and not returned: the namespace IS gone, and
        // reporting the delete as failed would send an operator to re-run it
        // against a name that no longer exists.
        if let Err(err) = self.stores.flow().forget(name) {
            tracing::warn!(
                target: "gunnar::store",
                event = "flow.forget_failed",
                namespace = %name,
                %err,
                "the namespace was deleted but its activity series could not be removed"
            );
        }
        Ok(gone.len() as u32)
    }

    // ── repositories ───────────────────────────────────────────────────────

    fn create_repo(&self, spec: ProtoNewRepo) -> ControlResult<Repo> {
        let path = Self::repo_ref(&spec.path)?;
        // **The disk, before the row.** A repository created on a full disk is
        // a catalog row whose store cannot be materialised, which is the
        // "listed but git says it does not exist" shape `ServerStores::create_repo`
        // exists to prevent — refused here, by the gate the front doors share,
        // with the line a refused push prints.
        if let Some(line) = self.headroom.as_ref().and_then(|gate| gate.refusal()) {
            return Err(ControlError::ResourceExhausted(line));
        }
        let mut new = gunnar_core::NewRepo::new(path).visibility(visibility_in(spec.visibility)?);
        if spec.hash_kind != gunnar_proto::HashKind::Unspecified {
            new = new.hash_kind(match spec.hash_kind {
                gunnar_proto::HashKind::Sha1 => HashKind::Sha1,
                _ => HashKind::Sha256,
            });
        }
        if !spec.default_branch.is_empty() {
            new = new.default_branch(spec.default_branch.clone());
        }
        // The catalog entry and the on-disk repository are created together
        // and transactionally — `ServerStores::create_repo` looks at the disk
        // first (a store already standing at the name is refused BY NAME
        // unless `adopt`), writes the row, makes the store, and rolls the row
        // back if the store fails. Creating one without the other is the
        // shape that produces "it is listed but git says it does not exist";
        // adopting a stranger's directory is the shape that resurrected a
        // deleted repository on 2026-08-30.
        let repo = self
            .stores
            .create_repo(new, spec.adopt)
            .map_err(|err| create_error(&err, &spec.path))?;
        Ok(repo_out(&repo))
    }

    fn write_first_commit(&self, path: &RepoPath, readme: &str) -> ControlResult<String> {
        let (repo, store) = self.open(path)?;
        let kind = match repo.hash_kind {
            HashKind::Sha1 => gix_hash::Kind::Sha1,
            _ => gix_hash::Kind::Sha256,
        };
        let when = std::time::SystemTime::now()
            .duration_since(std::time::UNIX_EPOCH)
            .map(|d| d.as_secs() as i64)
            .unwrap_or(0);
        let (pack, commit) = crate::first_commit::first_commit_pack(
            kind,
            "README.md",
            readme.as_bytes(),
            "Welcome",
            when,
        )
        .map_err(ControlError::InvalidArgument)?;
        store
            .serve()
            .put(
                &pack,
                &[gunnar_store::git_storage_trait::RefUpdate::set(
                    repo.default_branch.clone(),
                    commit.clone(),
                )],
            )
            .map_err(|err| {
                ControlError::Internal(format!("writing the first commit of {path}: {err:#}"))
            })?;
        Ok(commit)
    }

    /// The front doors' plan chain (`ServerStores::plan_gates`), asked as a
    /// push-to-create asks it: the verdict on a write (a suspended or retained
    /// plan: `FailedPrecondition`), then the cap (`ResourceExhausted`). A gate
    /// that does not bind machines is not asked for one.
    fn create_room(&self, namespace: &str, machine: bool) -> ControlResult<()> {
        use gunnar_ssh::{PlanAction, PlanVerdict};
        for gate in self
            .stores
            .plan_gates()
            .iter()
            .filter(|gate| !machine || gate.applies_to_machine())
        {
            if let PlanVerdict::Refuse(line) = gate.verdict(namespace, PlanAction::Write) {
                return Err(ControlError::FailedPrecondition(line));
            }
            if let PlanVerdict::Refuse(line) = gate.pack_quota(namespace) {
                return Err(ControlError::ResourceExhausted(line));
            }
        }
        Ok(())
    }

    fn get_repo(&self, path: &RepoPath) -> ControlResult<Repo> {
        let repo_ref = Self::repo_ref(path)?;
        self.stores
            .catalog()
            .get(&repo_ref)
            .map_err(internal)?
            .as_ref()
            .map(repo_out)
            .ok_or_else(|| ControlError::NotFound(format!("repository {path}")))
    }

    fn list_repos(&self, namespace: Option<&str>) -> ControlResult<Vec<Repo>> {
        Ok(self
            .stores
            .catalog()
            .list(namespace)
            .map_err(internal)?
            .iter()
            .map(repo_out)
            .collect())
    }

    /// **Delete: a dated tombstone by default, a reclaim when asked.**
    ///
    /// Two facts had to be held at once here, and they pull in opposite
    /// directions:
    ///
    /// * **The reclaim**: `repo delete` must reclaim the disk. Before it, the
    ///   catalog row went and the objects stayed — 25 GB of a kernel push left
    ///   on the appliance with its indexer still running, invisible because
    ///   nothing listed it.
    /// * **Measured**: the bytes are gone in ~2 seconds (181 GiB to 33 MiB
    ///   measured) and a mirror does not help, because the delete replicates.
    ///   The failure a paying customer is most likely to cause is deleting
    ///   their own repository.
    ///
    /// A tombstone answers both, and only because it is **dated and listed**:
    /// the bytes are held on purpose with a deadline written at the instant of
    /// the delete, [`ServerStores::sweep_expired_tombstones`] reclaims them
    /// when it passes, and `Repos.ListDeleted` / `Admin.StorageInfo` report
    /// them so they are never the invisible 25 GB again. **They still count
    /// against the account** — see [`Self::storage_info`].
    fn delete_repo(
        &self,
        path: &RepoPath,
        options: gunnar_grpc::seam::DeleteOptions,
    ) -> ControlResult<gunnar_grpc::seam::DeleteOutcome> {
        let repo_ref = Self::repo_ref(path)?;
        // The row is read BEFORE it is removed: the tombstone records what the
        // repository was, and an undelete that guessed the hash kind would
        // reopen the resurrection the reclaim rules closed from the other side.
        let was = self.stores.catalog().get(&repo_ref).map_err(internal)?;
        // **An ORPHAN is a delete to finish, not a not-found** (2026-08-30). A
        // store on disk with no row and no tombstone is what an old
        // catalog-only delete left, and on the appliance 2026-08-30 it was ~25-39
        // GB at `alice/linux` that `delete` answered with `NoSuchRepo` after
        // the access check had already refused everybody. `--purge` is
        // honoured — the bytes are what the operator asked for and the row is
        // already gone — and a SOFT delete is refused by name, because a
        // tombstone with no row promises an undelete the server cannot honour.
        let orphan = was.is_none() && self.stores.is_orphan(&repo_ref).unwrap_or(false);
        if orphan && !options.purge {
            return Err(ControlError::FailedPrecondition(
                crate::stores::ServerStores::orphan_soft_delete_refusal(&repo_ref),
            ));
        }
        // A name that is not in the catalog but is TOMBSTONED (a previous
        // delete could not reclaim its store) is a delete to retry, not a
        // not-found: the row is already gone, the reclaim is what is owed.
        match self.stores.catalog().delete(&repo_ref) {
            Ok(_) => {}
            Err(gunnar_core::Error::NoSuchRepo(_))
                if orphan || self.stores.is_tombstoned(&repo_ref).unwrap_or(false) => {}
            Err(err) => return Err(internal(err)),
        }
        if options.purge {
            let (before, after) = self.stores.purge_repo(&repo_ref).map_err(|err| {
                ControlError::Internal(format!("removing the repository's directory: {err:#}"))
            })?;
            return Ok(gunnar_grpc::seam::DeleteOutcome::Purged {
                bytes_reclaimed: before.saturating_sub(after),
            });
        }
        let retention = std::time::Duration::from_secs(
            u64::from(
                options
                    .retention_days
                    .unwrap_or(crate::stores::DEFAULT_DELETE_RETENTION_DAYS),
            ) * 86_400,
        );
        let record = self
            .stores
            .soft_delete(&repo_ref, was.as_ref(), &options.principal_id, retention)
            .map_err(|err| ControlError::FailedPrecondition(format!("{err:#}")))?;
        let bytes_kept = self
            .stores
            .repo_dir(&repo_ref)
            .map(|dir| crate::stores::dir_bytes(&dir))
            .unwrap_or(0);
        Ok(gunnar_grpc::seam::DeleteOutcome::Tombstoned {
            purge_after_unix_ms: record.purge_after_unix_ms.unwrap_or_default(),
            bytes_kept,
        })
    }

    /// **Undelete: the row back first, the tombstone off second.**
    ///
    /// That order is not tidiness. A crash between the two leaves a repository
    /// that is catalogued *and* still fenced off, which an operator can fix
    /// with a second `undelete`; the other order leaves a name with no
    /// tombstone and no row, which the next `repo create` would adopt — and
    /// adopting a store a create did not make is exactly the 2026-08-30
    /// resurrection.
    fn undelete_repo(&self, path: &RepoPath) -> ControlResult<Repo> {
        let repo_ref = Self::repo_ref(path)?;
        if self
            .stores
            .catalog()
            .get(&repo_ref)
            .map_err(internal)?
            .is_some()
        {
            return Err(ControlError::AlreadyExists(format!(
                "{path} is in the catalog already; it is not deleted"
            )));
        }
        let spec = self
            .stores
            .undelete_spec(&repo_ref)
            .map_err(|err| ControlError::FailedPrecondition(format!("{err:#}")))?;
        // `adopt`: the store on disk is the one this repository always had.
        // This is the second of the two cases where adopting is right rather
        // than a resurrection (the first is `archive-in`), and it is right
        // because the tombstone says so and carries the hash kind the adopt
        // path checks the store's marker against.
        let repo = self
            .stores
            .create_repo(spec, true)
            .map_err(|err| ControlError::Internal(format!("restoring {path}: {err:#}")))?;
        self.stores
            .clear_tombstone(&repo_ref)
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        Ok(repo_out(&repo))
    }

    fn purge_repo(&self, path: &RepoPath) -> ControlResult<u64> {
        let repo_ref = Self::repo_ref(path)?;
        if self
            .stores
            .catalog()
            .get(&repo_ref)
            .map_err(internal)?
            .is_some()
        {
            return Err(ControlError::FailedPrecondition(format!(
                "{path} is a LIVE repository, not a deleted one. `repo delete {path} --purge` \
                 deletes and reclaims it in one step; purge alone only ends a retention window."
            )));
        }
        let tombstone = self
            .stores
            .tombstone_of(&repo_ref)
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        if tombstone.is_none() {
            return Err(ControlError::NotFound(format!(
                "{path} is neither catalogued nor tombstoned; there is nothing to purge"
            )));
        }
        let (before, after) = self
            .stores
            .purge_repo(&repo_ref)
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        Ok(before.saturating_sub(after))
    }

    /// **`Repos.Gc` — the console's door onto the maintenance the CLI has
    /// always had.**
    ///
    /// The whole body is a resolve and a call: the maintenance itself is
    /// [`crate::admin::gc_one`], the same function `gunnar gc` runs, so there
    /// is one writer and not a second implementation to drift (one implementation).
    ///
    /// Unlike [`Self::purge_repo`] this one demands the repository be **live**.
    /// A tombstoned store is on its way out and sealing it would spend the I/O
    /// of a compaction on bytes a sweep is about to unlink; that is `Purge`'s
    /// job, and saying so by name is better than maintaining a corpse.
    fn gc_repo(&self, path: &RepoPath) -> ControlResult<gunnar_grpc::seam::GcJob> {
        let repo_ref = Self::repo_ref(path)?;
        // **The existence check is here and the resolve is in the runner**, and
        // that is not a duplicate. This one refuses a name that was never a
        // repository *now*, so a typo comes back as NOT_FOUND on the request
        // that made it rather than as a FAILED job somebody has to go and read;
        // the runner's is what happens when a repository that WAS live is gone
        // by the time its turn comes, minutes later.
        if self
            .stores
            .catalog()
            .get(&repo_ref)
            .map_err(internal)?
            .is_none()
        {
            return Err(ControlError::NotFound(format!(
                "{path} is not a live repository; nothing to gc"
            )));
        }
        Ok(gc_job_out(path, self.gc.enqueue(&repo_ref.to_string())))
    }

    fn gc_status(&self, path: &RepoPath) -> ControlResult<Option<gunnar_grpc::seam::GcJob>> {
        let repo_ref = Self::repo_ref(path)?;
        Ok(self
            .gc
            .status(&repo_ref.to_string())
            .map(|job| gc_job_out(path, job)))
    }

    // ── accounts: the gate, and the per-user hard purge ────────────────────

    fn gate_account(
        &self,
        account: &str,
        actor: &str,
        note: &str,
    ) -> ControlResult<(gunnar_grpc::seam::AccountGate, bool)> {
        // Read before write, so `was_already_gated` reports what was there
        // rather than what this call put there. Not atomic with the write, and
        // it does not need to be: the field is a courtesy to a console, and the
        // worst a lost race costs is a console saying "you locked this" about a
        // lockout that arrived a millisecond earlier. The *lockout* is atomic,
        // because `AuthTable::gate` is one compare-and-swap.
        let before = self
            .stores
            .auth()
            .gate_covering(account)
            .map_err(internal)?
            .is_some();
        let gate = self
            .stores
            .auth()
            .gate(gunnar_core::AccountGate::administrative(
                account, actor, note,
            ))
            .map_err(gate_error)?;
        tracing::warn!(
            target: "gunnar::audit",
            event = "account.gated",
            account = %account,
            actor = %actor,
            note = %note,
            already = before,
            "an account was locked out: every level, both doors, until it is ungated"
        );
        Ok((gate_out(gate), before))
    }

    fn ungate_account(
        &self,
        account: &str,
    ) -> ControlResult<Option<gunnar_grpc::seam::AccountGate>> {
        let lifted = self
            .stores
            .auth()
            .lift_gate(account)
            .map_err(internal)?
            .map(gate_out);
        if let Some(gate) = &lifted {
            tracing::warn!(
                target: "gunnar::audit",
                event = "account.ungated",
                account = %account,
                held_by = %gate.holder,
                "an account lockout was lifted"
            );
        }
        Ok(lifted)
    }

    fn account_gates(&self) -> ControlResult<Vec<gunnar_grpc::seam::AccountGate>> {
        Ok(self
            .stores
            .auth()
            .gates()
            .map_err(internal)?
            .into_iter()
            .map(gate_out)
            .collect())
    }

    /// **Gate first, enqueue second — and read the gate BACK.**
    ///
    /// The order is the whole guarantee: by the time this returns the account
    /// is shut, so there is no window in which a purge has been accepted and
    /// the user can still push into the account it is about to walk.
    ///
    /// The gate is then read back out of the table rather than the one just
    /// written being returned, and that is not belt-and-braces — it is the only
    /// correct answer in two cases this call cannot distinguish up front:
    ///
    /// * the account was **already** under an administrative gate. The lease is
    ///   not written over it (`gate_for_purge` refuses to downgrade), so the
    ///   gate in force is somebody else's and the job will not lift it.
    /// * the account already had a purge **queued or running**. The queue
    ///   returns that job instead of this one, so the lease that will be
    ///   released is the *other* job's, and returning this call's freshly
    ///   minted id would name a lockout nothing is going to lift.
    fn purge_account(
        &self,
        account: &str,
        options: gunnar_grpc::seam::PurgeAccountOptions,
    ) -> ControlResult<(gunnar_grpc::seam::PurgeJob, gunnar_grpc::seam::AccountGate)> {
        let account = account.trim();
        if account.is_empty() {
            return Err(ControlError::InvalidArgument(
                "an account purge needs an account name".into(),
            ));
        }
        // **A machine's account is never purged** (owner ruling g-nonpay 2026-09-29:
        // "machine principals ... are never touched"). Only a person's account holds a
        // customer's data; a machine, a deploy key or a group is the estate itself —
        // the twin, the billing principal, a CI bot — and emptying it is never the
        // answer to a question about money. Refused before the lockout: nothing is
        // locked and nothing is queued.
        if let Some(p) = self.stores.auth().principal(account).map_err(internal)? {
            if p.kind != gunnar_core::PrincipalKind::User {
                return Err(ControlError::FailedPrecondition(format!(
                    "{account} is a machine principal ({:?}), not a person: a machine's account is never \
                     purged. Remove the principal itself if it is really to go.",
                    p.kind
                )));
            }
        }
        let job_id = self.purge.next_job_id();
        // **The lockout, before anything else.** A failure here is a refusal
        // and nothing is enqueued: a purge that could not lock the account is
        // a purge that would race every reader in it, and running it anyway
        // would be worse than not running it.
        self.gate_for_purge(account, &job_id, &options)?;

        let order = crate::purge_queue::PurgeOrder::new(account, &job_id, &options.reason)
            .by(&options.principal_id)
            .removing_principal(options.remove_principal)
            .expecting_empty(options.expect_empty);
        let job = self.purge.enqueue(order);

        let gate = self
            .stores
            .auth()
            .gate_covering(account)
            .map_err(internal)?
            .map(gate_out)
            // The account is gated — this call just gated it — so an absence
            // here means the row went between the write and the read, which is
            // an operator ungating an account mid-request. Reported as the
            // fact it is rather than as a gate that is not there.
            .unwrap_or_else(|| gunnar_grpc::seam::AccountGate {
                account: account.to_owned(),
                reason: gunnar_grpc::seam::GateReason::Purge,
                holder: job_id.clone(),
                actor: options.principal_id.clone(),
                note: "the lockout was lifted between being taken and being read back".into(),
                at_unix_ms: gunnar_core::now_ms(),
                expires_unix_ms: 0,
            });
        Ok((purge_job_out(job), gate))
    }

    fn purge_account_status(
        &self,
        account: &str,
    ) -> ControlResult<(
        Option<gunnar_grpc::seam::PurgeJob>,
        Option<gunnar_grpc::seam::AccountGate>,
    )> {
        let job = self.purge.status(account).map(purge_job_out);
        let gate = self
            .stores
            .auth()
            .gate_covering(account)
            .map_err(internal)?
            .map(gate_out);
        Ok((job, gate))
    }

    fn default_delete_retention_days(&self) -> u32 {
        crate::stores::DEFAULT_DELETE_RETENTION_DAYS
    }

    fn list_deleted(
        &self,
        namespace: Option<&str>,
    ) -> ControlResult<Vec<gunnar_grpc::seam::DeletedRepoRow>> {
        Ok(self
            .stores
            .tombstones()
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?
            .into_iter()
            .filter(|row| namespace.is_none_or(|want| row.path.namespace() == want))
            .map(|row| gunnar_grpc::seam::DeletedRepoRow {
                path: RepoPath {
                    namespace: row.path.namespace().to_owned(),
                    repo: row.path.name().to_owned(),
                },
                deleted_at_unix_ms: row.tombstone.deleted_at_unix_ms,
                purge_after_unix_ms: row.tombstone.purge_after_unix_ms.unwrap_or_default(),
                principal_id: row.tombstone.principal_id,
                bytes: row.bytes,
            })
            .collect())
    }

    /// **The store directories with no catalog row and no tombstone.**
    ///
    /// It walks the disk rather than asking the catalog — the same reason
    /// [`Self::list_deleted`] does, one step further: a tombstone at least
    /// exists as a file, and an orphan is defined by the absence of *every*
    /// record. On the appliance 2026-08-30 that absence made ~25-39 GB at
    /// `alice/linux` unreachable by `delete`, `purge`, `undelete`, the sweep
    /// AND `list-deleted`, while `create` refused the name because the bytes
    /// were there.
    fn list_orphans(
        &self,
        namespace: Option<&str>,
    ) -> ControlResult<Vec<gunnar_grpc::seam::OrphanRow>> {
        Ok(self
            .stores
            .orphans()
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?
            .into_iter()
            .filter(|row| namespace.is_none_or(|want| row.path.namespace() == want))
            .map(|row| gunnar_grpc::seam::OrphanRow {
                path: RepoPath {
                    namespace: row.path.namespace().to_owned(),
                    repo: row.path.name().to_owned(),
                },
                dir: row.dir.display().to_string(),
                bytes: row.bytes,
                hash_marker: row.hash_marker.unwrap_or_default(),
                modified_unix_ms: row.modified_unix_ms,
                failed_reclaim: row.failed_reclaim.unwrap_or_default(),
            })
            .collect())
    }

    /// **Reclaim an orphan.** `FailedPrecondition` when it is not one, because
    /// "this is a live repository" is a fact the caller can act on and not an
    /// internal fault.
    fn reclaim_orphan(&self, path: &RepoPath) -> ControlResult<u64> {
        let repo_ref = Self::repo_ref(path)?;
        self.stores
            .reclaim_orphan(&repo_ref)
            .map_err(|err| ControlError::FailedPrecondition(format!("{err:#}")))
    }

    fn index_progress(&self) -> ControlResult<Vec<gunnar_grpc::seam::IndexProgressRow>> {
        Ok(self
            .stores
            .engine()
            .index_progress()
            .into_iter()
            .filter_map(|(dir, s)| {
                let (namespace, name) = self.stores.repo_of_dir(&dir)?;
                Some(gunnar_grpc::seam::IndexProgressRow {
                    namespace,
                    name,
                    pack_id: s.pack_id,
                    objects_done: s.objects_done,
                    objects_total: s.objects_total,
                    bytes_done: s.bytes_done,
                    bytes_total: s.bytes_total,
                    phase: if s.active {
                        s.phase.to_string()
                    } else {
                        "idle".to_string()
                    },
                    started_at_unix_ms: s.started_at_ms as i64,
                    resumed: s.resumed,
                    reinflations: s.reinflations,
                    pauses: s.pauses,
                })
            })
            .filter(|r| r.phase != "idle")
            .collect())
    }

    fn set_default_branch(&self, path: &RepoPath, default_branch: &str) -> ControlResult<Repo> {
        let repo_ref = Self::repo_ref(path)?;
        let repo = self
            .stores
            .catalog()
            .set_default_branch(&repo_ref, default_branch)
            .map_err(internal)?;
        // The catalog is the authority; the repository's `HEAD` is a projection
        // of it and does not move on its own. Without this line the call
        // answers with the new branch and `repo get` reads it back, while the
        // reference advertisement — which reads `HEAD`, not the catalog — keeps
        // naming the old one. That was the whole of the 2026-08-06 defect: a
        // `master` donor pushed cleanly into a repository nobody could clone,
        // and `set-default-branch` looked like it had fixed it.
        self.stores.repoint_head(&repo).map_err(|err| {
            ControlError::Internal(format!("pointing HEAD at the new default branch: {err:#}"))
        })?;
        Ok(repo_out(&repo))
    }

    fn set_visibility(
        &self,
        path: &RepoPath,
        visibility: gunnar_proto::Visibility,
    ) -> ControlResult<Repo> {
        if visibility == gunnar_proto::Visibility::Unspecified {
            return Err(ControlError::InvalidArgument(
                "visibility unspecified".into(),
            ));
        }
        let repo_ref = Self::repo_ref(path)?;
        self.stores
            .catalog()
            .set_visibility(&repo_ref, visibility_in(visibility)?)
            .map(|repo| repo_out(&repo))
            .map_err(internal)
    }

    /// **A member's ONE encryption key** (CRYPT-YUBI 2026-10-26): a repository's ring is
    /// wrapped to the person's encryption public key, never to an SSH key. Empty when they
    /// have none yet.
    fn recipient_keys(&self, principal_id: &str) -> ControlResult<Vec<gunnar_proto::RecipientKey>> {
        let public = self
            .stores
            .encryption_keys()
            .public_of(principal_id)
            .map_err(key_refusal)?;
        Ok(public
            .into_iter()
            .map(|public| gunnar_proto::RecipientKey {
                fingerprint: gunnar_core::auth::fingerprint_of_blob(public.as_bytes()).to_string(),
                algo: if public.starts_with("age1pq1") {
                    gunnar_core::auth::PQ_RECIPIENT_ALGO.to_owned()
                } else {
                    "X25519".to_owned()
                },
                openssh: public,
            })
            .collect())
    }

    fn encryption_key(
        &self,
        principal_id: &str,
    ) -> ControlResult<gunnar_proto::GetEncryptionKeyResponse> {
        Ok(encryption_key_out(
            self.stores
                .encryption_keys()
                .get(principal_id)
                .map_err(key_refusal)?,
        ))
    }

    fn create_encryption_key(
        &self,
        principal_id: &str,
        public_key: &str,
        first: gunnar_proto::UnlockMethod,
    ) -> ControlResult<gunnar_proto::GetEncryptionKeyResponse> {
        let first = method_in(first)?;
        let key = self
            .stores
            .encryption_keys()
            .create(
                principal_id,
                public_key,
                first,
                gunnar_core::now_ms().max(0) as u64,
            )
            .map_err(key_refusal)?;
        Ok(encryption_key_out(Some(key)))
    }

    fn add_unlock_method(
        &self,
        principal_id: &str,
        method: gunnar_proto::UnlockMethod,
    ) -> ControlResult<gunnar_proto::GetEncryptionKeyResponse> {
        let method = method_in(method)?;
        let key = self
            .stores
            .encryption_keys()
            .add_method(principal_id, method, gunnar_core::now_ms().max(0) as u64)
            .map_err(key_refusal)?;
        Ok(encryption_key_out(Some(key)))
    }

    fn remove_unlock_method(
        &self,
        principal_id: &str,
        id: &str,
    ) -> ControlResult<gunnar_proto::GetEncryptionKeyResponse> {
        let key = self
            .stores
            .encryption_keys()
            .remove_method(principal_id, id)
            .map_err(key_refusal)?;
        Ok(encryption_key_out(Some(key)))
    }

    fn set_encrypted(&self, path: &RepoPath, encrypted: bool) -> ControlResult<Repo> {
        let repo_ref = Self::repo_ref(path)?;
        self.stores
            .catalog()
            .set_encrypted(&repo_ref, encrypted)
            .map(|repo| repo_out(&repo))
            .map_err(internal)
    }

    /// **`Repos.ArchiveOut`: the same bytes `gunnar repo archive-out` writes,
    /// into a sink the control plane owns** — so a cron on another machine can
    /// pull a backup off a box that has no shell.
    ///
    /// It does **not** go through [`Self::open`]. An archive is three files
    /// read out of a directory; taking the handle cache and the store's lock
    /// for it would make a backup contend with serving, and the whole reason
    /// there is no `freeze` verb is that it does not have to. The pack is
    /// append-only and fsynced below the cut, so what is read is durable and
    /// what arrives after the cut belongs to the next one.
    #[cfg(feature = "engine-znippy")]
    fn archive_out(
        &self,
        path: &RepoPath,
        from_generation: u64,
        sink: &mut dyn std::io::Write,
    ) -> ControlResult<gunnar_grpc::seam::ArchiveCut> {
        let repo_ref = Self::repo_ref(path)?;
        let dir = self
            .stores
            .repo_dir(&repo_ref)
            .map_err(|err| ControlError::Internal(format!("resolving {path}: {err:#}")))?;
        if !dir.is_dir() {
            return Err(ControlError::NotFound(format!(
                "{path} has nothing on disk at {}",
                dir.display()
            )));
        }
        let receipt =
            crate::storage::znippy_engine::archive_out_to(&dir, &mut { sink }, from_generation)
                .map_err(archive_error)?;
        // **The second bytes-out counting point, and the only one outside the
        // git transport.** `Repos.ArchiveOut` streams a repository's archive
        // over gRPC and never touches `transport::serve_blocking`, so its bytes
        // are in neither `ServerMetrics::bytes_out` nor — before this line —
        // any tenant's meter. A replica pulling a hundred gigabytes would have
        // read as a silent namespace.
        //
        // It counts as a FETCH: a caller asked for objects and objects were
        // served, which is what `fetches` means. The principal is not in scope
        // at this seam — the gRPC caller's identity stops at the service layer —
        // so this transfer moves bytes in nobody's name, which is a smaller
        // untruth than attributing it to whoever pushed last.
        self.stores.flow().record(
            &path.namespace,
            gunnar_core::now_ms(),
            &gunnar_core::Transfer {
                bytes_out: receipt.bytes_out,
                fetched: true,
                ..gunnar_core::Transfer::default()
            },
        );
        Ok(gunnar_grpc::seam::ArchiveCut {
            from_generation: receipt.from_generation,
            to_generation: receipt.to_generation,
            bytes_out: receipt.bytes_out,
            file_sha256: receipt.file_sha256,
        })
    }

    // ── refs and objects ───────────────────────────────────────────────────

    fn list_refs(
        &self,
        path: &RepoPath,
        prefix: &str,
        peel_them: bool,
    ) -> ControlResult<Vec<RefTarget>> {
        let (_, store) = self.open(path)?;
        let git = store.serve();
        // **One `refs()` call is one snapshot.** The prefix is filtered here
        // rather than pushed into the store because `GitOps::refs` takes no
        // filter — it hands back the ref namespace, and narrowing it is the
        // caller's. See `gunnar_wire::refs`.
        let snapshot = RefSnapshot::read(git).map_err(wire_error)?;
        let mut out = Vec::new();
        for row in snapshot.with_prefix(Some(prefix)) {
            out.push(ref_target_out(
                git,
                store.hash_kind(),
                &snapshot,
                row,
                peel_them,
            )?);
        }
        Ok(out)
    }

    fn get_ref(
        &self,
        path: &RepoPath,
        ref_name: &str,
        peel_them: bool,
    ) -> ControlResult<RefTarget> {
        let (_, store) = self.open(path)?;
        let git = store.serve();
        // `FullName::new` was the validator and it died with `RefStore`; the
        // rules live in `gunnar_store::refname` now, one authority for the
        // whole tree. It is still checked here rather than trusted: this is a
        // caller's string, and `refname::validate` is a path-traversal boundary
        // wherever a name can become a lookup.
        gunnar_store::refname::validate(ref_name)
            .map_err(|err| ControlError::InvalidArgument(err.to_string()))?;
        let snapshot = RefSnapshot::read(git).map_err(wire_error)?;
        // `refname::validate` admits exactly `HEAD` and `refs/…`, and `HEAD` is
        // **not** one of the rows (the `GitServe` HEAD ruling) — so asking for it in the snapshot
        // would answer `NotFound` for a reference every repository has. The
        // accessor pair is where it comes from; its target still resolves
        // against the snapshot, so both branches answer out of one snapshot.
        let head_row;
        let row = if ref_name == gunnar_store::HEAD {
            head_row = git
                .head()
                .map_err(store_error)?
                .ok_or_else(|| ControlError::NotFound(format!("{ref_name} in {path}")))?;
            &head_row
        } else {
            snapshot
                .get(ref_name)
                .ok_or_else(|| ControlError::NotFound(format!("{ref_name} in {path}")))?
        };
        ref_target_out(git, store.hash_kind(), &snapshot, row, peel_them)
    }

    fn log(
        &self,
        path: &RepoPath,
        start: &str,
        limit: u32,
        touching: &str,
    ) -> ControlResult<Vec<Commit>> {
        self.log_walk(path, LogStart::One(start), limit, touching)
    }

    /// Every branch and tag tip, and `HEAD`, walked as one history: the
    /// History page's "all branches" view (owner order 2026-10-18), so a
    /// commit that lives only on a side branch is drawn too.
    fn log_all_refs(
        &self,
        path: &RepoPath,
        limit: u32,
        touching: &str,
    ) -> ControlResult<Vec<Commit>> {
        self.log_walk(path, LogStart::AllRefs, limit, touching)
    }

    fn create_pull(
        &self,
        path: &RepoPath,
        author: &str,
        title: &str,
        description: &str,
        source_ref: &str,
        target_ref: &str,
    ) -> ControlResult<PullRequest> {
        for (what, name) in [("source_ref", source_ref), ("target_ref", target_ref)] {
            if !name.starts_with("refs/heads/") {
                return Err(ControlError::InvalidArgument(format!(
                    "{what} must be a full branch name under refs/heads/, got {name:?}: a pull \
                     request merges branches, and a short name stored today is an ambiguity \
                     resolved differently tomorrow"
                )));
            }
        }
        if source_ref == target_ref {
            return Err(ControlError::InvalidArgument(
                "a branch cannot be merged into itself".to_owned(),
            ));
        }
        if title.trim().is_empty() {
            return Err(ControlError::InvalidArgument(
                "a title is required".to_owned(),
            ));
        }
        let repo_ref = Self::repo_ref(path)?;
        let (_, store) = self.open(path)?;
        let git = store.serve();
        let snapshot = RefSnapshot::read(git).map_err(wire_error)?;
        let source = snapshot
            .resolve(source_ref)
            .map_err(wire_error)?
            .ok_or_else(|| ControlError::NotFound(format!("{source_ref} in {path}")))?;
        snapshot
            .resolve(target_ref)
            .map_err(wire_error)?
            .ok_or_else(|| ControlError::NotFound(format!("{target_ref} in {path}")))?;
        let record = self
            .pulls()?
            .create(
                &repo_ref.to_string(),
                author,
                title,
                description,
                source_ref,
                target_ref,
                &source.to_string(),
            )
            .map_err(internal)?;
        Ok(pull_out(path, record))
    }

    fn list_pulls(&self, path: &RepoPath, state: i32) -> ControlResult<Vec<PullRequest>> {
        let repo_ref = Self::repo_ref(path)?;
        // Existence check: a list for a repository that is not there is
        // NotFound, never an empty success.
        self.get_repo(path)?;
        let filter = match PullRequestState::try_from(state) {
            Ok(PullRequestState::Unspecified) | Err(_) => None,
            Ok(PullRequestState::Open) => Some(gunnar_core::PullState::Open),
            Ok(PullRequestState::Merged) => Some(gunnar_core::PullState::Merged),
            Ok(PullRequestState::Closed) => Some(gunnar_core::PullState::Closed),
        };
        Ok(self
            .pulls()?
            .list(&repo_ref.to_string(), filter)
            .map_err(internal)?
            .into_iter()
            .map(|record| pull_out(path, record))
            .collect())
    }

    fn get_pull(&self, path: &RepoPath, number: u64) -> ControlResult<PullRequest> {
        let repo_ref = Self::repo_ref(path)?;
        self.get_repo(path)?;
        self.pulls()?
            .get(&repo_ref.to_string(), number)
            .map_err(internal)?
            .map(|record| pull_out(path, record))
            .ok_or_else(|| ControlError::NotFound(format!("pull request #{number} in {path}")))
    }

    fn close_pull(&self, path: &RepoPath, number: u64) -> ControlResult<PullRequest> {
        let repo_ref = Self::repo_ref(path)?;
        self.get_repo(path)?;
        match self
            .pulls()?
            .close(&repo_ref.to_string(), number)
            .map_err(internal)?
        {
            gunnar_core::PullTransition::Done(record) => Ok(pull_out(path, record)),
            gunnar_core::PullTransition::NotFound => Err(ControlError::NotFound(format!(
                "pull request #{number} in {path}"
            ))),
            gunnar_core::PullTransition::NotOpen(state) => Err(ControlError::FailedPrecondition(
                format!("pull request #{number} is already {state:?}, not open"),
            )),
        }
    }

    /// A fast-forward, a merge commit or a squash (GUN-MERGE-ENGINE, 2026-11-01), and
    /// every step is ordered so a failure leaves the truth on disk: the ancestry is
    /// decided by the same [`gunnar_policy::ancestry::is_descendant_of`] branch
    /// protection trusts (fail-closed: inconclusive is a refusal, never an allow), a
    /// merge commit is made by [`crate::merge_engine`] and judged by every gate before
    /// it is stored, the ref moves through the store's own compare-and-swap — the
    /// primitive receive-pack uses, so this is not a second ref-write path — and the
    /// record is marked merged only AFTER the ref has moved.
    fn merge_pull(
        &self,
        path: &RepoPath,
        number: u64,
        principal_id: &str,
        options: &gunnar_grpc::MergeOptions,
    ) -> ControlResult<(PullRequest, MergedRef)> {
        self.merge_or_check(path, number, principal_id, options, false)
    }

    /// Every check of [`Self::merge_pull`], and no write (GUN-FIELD-TEST, 2026-11-01).
    fn merge_signing_key(&self) -> ControlResult<(String, String)> {
        // Read first: a box that takes no write (a twin, a browse replica) never mints.
        let public = match self
            .stores
            .merge_signing_public()
            .map_err(|err| ControlError::Unavailable(format!("{err:#}")))?
        {
            Some(public) => public,
            None => {
                if let Some(why) = self.frozen() {
                    return Err(ControlError::Unavailable(format!(
                        "{why}: no merge-signing key here yet; ask the primary"
                    )));
                }
                self.stores
                    .merge_signing_key()
                    .map_err(|err| ControlError::Unavailable(format!("{err:#}")))?
                    .public_key()
                    .clone()
            }
        };
        let mut public = public;
        public.set_comment("gunnar-merge-signing");
        let openssh = public
            .to_openssh()
            .map_err(|err| ControlError::Internal(format!("the merge-signing key: {err}")))?;
        Ok((openssh, gunnar_core::sshsig::fingerprint(&public)))
    }

    fn check_merge(
        &self,
        path: &RepoPath,
        number: u64,
        principal_id: &str,
        options: &gunnar_grpc::MergeOptions,
    ) -> ControlResult<(PullRequest, MergedRef)> {
        self.merge_or_check(path, number, principal_id, options, true)
    }

    fn read_object(
        &self,
        path: &RepoPath,
        oid: &str,
        max_bytes: u64,
    ) -> ControlResult<ReadObjectResponse> {
        let (_, store) = self.open(path)?;
        let git = store.serve();
        let id = gix_hash::ObjectId::from_hex(oid.as_bytes())
            .map_err(|err| ControlError::InvalidArgument(format!("{oid}: {err}")))?;

        // ── the object ceiling, contract half, now complete ────────────────
        //
        // `header()` costs no inflate — `gix-odb` answers kind and size out of
        // the index — so the size is known before any allocation, and both
        // refusals happen HERE rather than after the object is materialised.
        //
        // Two ceilings, and they are different in kind. See their constants.
        if let Some((_, object_bytes)) = git.header(id.as_bytes()).map_err(store_error)? {
            // The OBJECT ceiling first, and the order is deliberate: an object
            // over it cannot be served at any `max_bytes`, so saying so
            // immediately is better than sending the caller off to retry with a
            // prefix that will be refused for a second reason.
            if self.max_object_bytes != 0 && object_bytes > self.max_object_bytes {
                return Err(ControlError::ResourceExhausted(format!(
                    "object {oid} is {object_bytes} bytes, over this server's {}-byte ceiling \
                     for reading an object. Reading any part of it costs the whole object in \
                     memory, because a prefix of a delta-encoded object needs its entire base \
                     chain, so no max_bytes makes this request cheaper.",
                    self.max_object_bytes
                )));
            }
            // The RESPONSE ceiling second: this one costs nobody anything, and
            // `max_bytes` is the way past it.
            let response_bytes = if max_bytes == 0 {
                object_bytes
            } else {
                object_bytes.min(max_bytes)
            };
            if response_bytes > MAX_RESPONSE_BYTES {
                return Err(ControlError::ResourceExhausted(format!(
                    "object {oid} is {object_bytes} bytes and the response would be \
                     {response_bytes}, over the {MAX_RESPONSE_BYTES}-byte limit a gRPC client \
                     can receive by default. Ask for a prefix with max_bytes."
                )));
            }
        }

        // The half with no contract change: the object is inflated once
        // and then **moved** into the response, where it used to be copied out
        // of `buf` a second time by `to_vec()`. On a one-gigabyte blob that
        // second copy was another gigabyte, for nothing.
        //
        // `GitServe::read` returns the inflated bytes owned, so the move is the
        // signature now rather than a borrow that had to be ended first — the
        // `{ … }` block this replaced existed only to drop a `Data<'a>` tied to
        // the caller's buffer.
        let Some((kind, mut buf)) = git.read(id.as_bytes()).map_err(store_error)? else {
            return Err(ControlError::NotFound(format!("object {oid} in {path}")));
        };
        let size = buf.len() as u64;

        // The first inflation is still whole-object — `GitServe` has no bounded
        // read and for a delta-encoded object cannot honestly grow one — but it
        // is now BOUNDED, by `max_object_bytes` above. A caller asking for one
        // byte of a one-gigabyte blob is refused rather than served at the cost
        // of a gigabyte.
        let truncated = max_bytes != 0 && size > max_bytes;
        if truncated {
            buf.truncate(max_bytes as usize);
        }
        Ok(ReadObjectResponse {
            oid: id.to_string(),
            kind: object_kind_out(kind)? as i32,
            size,
            data: buf,
            truncated,
        })
    }

    /// **`Refs.ReadLfsObject`, served out of the repository's own LFS store.**
    ///
    /// The same store the SSH adapter and the HTTP batch API serve
    /// (`gunnar_lfs::FsLfsStore` under `<git_dir>/lfs`), opened the same way
    /// `transport::open_lfs_store` opens it, so there is one place an object
    /// lives and one answer to where it is.
    ///
    /// # Whole object or nothing, and the ceiling that decides
    ///
    /// `read_object` truncates a git blob past `max_bytes`, because a prefix of
    /// a file is still a file's beginning. This does not: the caller asked for
    /// a PDF, and half a PDF is not a smaller PDF. So the SIZE decides before
    /// a byte is read — `size_of` costs a `stat`, not an open — and an object
    /// over the ceiling is refused with its size in the message, which is what
    /// lets the caller go to `git lfs` instead.
    ///
    /// The ceiling is the caller's `max_bytes`, lowered to
    /// [`MAX_RESPONSE_BYTES`] because that is what a gRPC client can receive by
    /// default. Nothing here allocates from a number the client sent: the
    /// allocation is the object's own size, after that size has been refused
    /// or accepted.
    ///
    /// # A ranged read (2026-10-15)
    ///
    /// With `range`, the same ceiling bounds a RANGE instead of the object, so
    /// a caller with no `git lfs` — a console handing a browser a 6 MB README
    /// picture — reads any object a range at a time, and one that needs only
    /// a picture's header reads only that. The store seeks (`open_at`), so a
    /// range deep into a large object does not read what lies before it. Still
    /// never a silent prefix: a range ends early only at the object's end,
    /// which `offset` + the length against `size` says.
    fn read_lfs_object(
        &self,
        path: &RepoPath,
        oid: &str,
        max_bytes: u64,
        range: Option<(u64, u64)>,
    ) -> ControlResult<ReadLfsObjectResponse> {
        let (_, store) = self.open(path)?;
        let id = gunnar_lfs::Oid::parse(oid)
            .map_err(|err| ControlError::InvalidArgument(format!("{oid}: {err}")))?;
        // The trait the store's two readers live on; `gunnar-lfs` keeps the
        // wire adapters and the backend apart, and this is the backend half.
        use gunnar_lfs::LfsStore as _;

        let lfs = gunnar_lfs::FsLfsStore::open_or_init(store.git_dir()).map_err(|err| {
            ControlError::Internal(format!("opening the repository's LFS store: {err}"))
        })?;

        let ceiling = match max_bytes {
            0 => MAX_RESPONSE_BYTES,
            n => n.min(MAX_RESPONSE_BYTES),
        };
        let size = lfs
            .size_of(&id)
            .map_err(|err| ControlError::Internal(format!("reading the LFS store: {err}")))?
            .ok_or_else(|| ControlError::NotFound(format!("LFS object {oid} in {path}")))?;

        // **A ranged read** (`offset`/`length` not both 0): the ceiling bounds
        // the RANGE, so an object of any size is read a range at a time. An
        // offset at or past the end is refused by name rather than answered
        // empty, and a length over the ceiling is refused rather than cut — a
        // caller never gets fewer bytes than it asked for unless the object's
        // end is the reason.
        if let Some((offset, length)) = range {
            if offset > size || (offset == size && size > 0) {
                return Err(ControlError::InvalidArgument(format!(
                    "offset {offset} is past the end of LFS object {oid}, which is {size} bytes"
                )));
            }
            if length > ceiling {
                return Err(ControlError::ResourceExhausted(format!(
                    "a range of {length} bytes of LFS object {oid} is over the {ceiling}-byte ceiling \
                     for this request; ask for {ceiling} bytes or fewer at a time"
                )));
            }
            let want = if length == 0 { ceiling } else { length }.min(size - offset);
            let object = lfs
                .open_at(&id, offset)
                .map_err(|err| ControlError::Internal(format!("opening LFS object {oid}: {err}")))?
                .ok_or_else(|| ControlError::NotFound(format!("LFS object {oid} in {path}")))?;
            let mut data = Vec::with_capacity(want as usize);
            let mut reader = std::io::Read::take(object.reader, want);
            std::io::Read::read_to_end(&mut reader, &mut data).map_err(|err| {
                ControlError::Internal(format!("reading LFS object {oid}: {err}"))
            })?;
            if (data.len() as u64) < want {
                return Err(ControlError::Internal(format!(
                    "LFS object {oid} ended {} bytes into a {want}-byte range at {offset}",
                    data.len()
                )));
            }
            return Ok(ReadLfsObjectResponse {
                oid: oid.to_owned(),
                size: object.size,
                data,
                offset,
            });
        }

        if size > ceiling {
            return Err(ControlError::ResourceExhausted(format!(
                "LFS object {oid} is {size} bytes, over the {ceiling}-byte ceiling for this \
                 request. An LFS object is served whole or not at all — a prefix of one is not a \
                 smaller file — so no max_bytes makes this request smaller. `git lfs` streams it, \
                 and a ranged read (offset/length) reads it a range at a time."
            )));
        }

        let object = lfs
            .open(&id)
            .map_err(|err| ControlError::Internal(format!("opening LFS object {oid}: {err}")))?
            .ok_or_else(|| ControlError::NotFound(format!("LFS object {oid} in {path}")))?;
        // `size_of` and `open` are two calls on a store an upload can commit
        // to in between, so the length is taken from the object that was
        // actually opened and the read is bounded by it rather than by the
        // earlier answer.
        if object.size > ceiling {
            return Err(ControlError::ResourceExhausted(format!(
                "LFS object {oid} is {} bytes, over the {ceiling}-byte ceiling for this request",
                object.size
            )));
        }
        let mut data = Vec::with_capacity(object.size as usize);
        let mut reader = std::io::Read::take(object.reader, object.size);
        std::io::Read::read_to_end(&mut reader, &mut data)
            .map_err(|err| ControlError::Internal(format!("reading LFS object {oid}: {err}")))?;

        Ok(ReadLfsObjectResponse {
            oid: oid.to_owned(),
            size: data.len() as u64,
            data,
            offset: 0,
        })
    }

    /// **`Refs.Diff`, served** (`crate::diff`).
    ///
    /// It used to answer `Unimplemented` — *"the server has no tree-diff
    /// engine; gix's blob-diff is client-side porcelain and an S crate must not
    /// link it"*. The constraint was right and the conclusion was not: a tree
    /// diff needs `GitServe::read` and nothing else, so it costs no crate and
    /// the appliance can serve one. `crate::diff` says what it computes exactly
    /// and what it deliberately does not (rename detection).
    fn diff(
        &self,
        path: &RepoPath,
        from: &str,
        to: &str,
        path_prefixes: &[String],
    ) -> ControlResult<Vec<FileChange>> {
        // The repository is opened first so a bad path is still a NotFound
        // rather than an argument error, which would hide a typo.
        let (_repo, store) = self.open(path)?;
        let git = store.serve();
        let hash = store.hash_kind();

        // An empty side is the empty tree, which is what makes "everything this
        // commit added" expressible without a magic oid: `from: ""` diffs
        // against nothing.
        let resolve = |spec: &str| -> ControlResult<Option<gix_hash::ObjectId>> {
            if spec.is_empty() {
                return Ok(None);
            }
            Ok(Some(self.tree_of(git, hash, path, spec)?))
        };
        let old = resolve(from)?;
        let new = resolve(to)?;

        crate::diff::compare(git, hash, old, new, path_prefixes).map_err(|err| match err {
            // A tree-ish that names an object this repository does not hold is
            // the caller's mistake, not a fault: `NotFound`, with the id.
            crate::diff::DiffError::Missing(oid) => {
                ControlError::NotFound(format!("object {oid} in {path}"))
            }
            crate::diff::DiffError::WrongKind { .. } => {
                ControlError::InvalidArgument(err.to_string())
            }
            crate::diff::DiffError::Corrupt { .. } | crate::diff::DiffError::Backend(_) => {
                ControlError::Internal(err.to_string())
            }
        })
    }

    // ── identity and access ────────────────────────────────────────────────

    fn add_principal(
        &self,
        id: &str,
        name: &str,
        kind: gunnar_proto::PrincipalKind,
    ) -> ControlResult<Principal> {
        // gunnar-core's principals carry an id chosen by the caller, not a
        // minted one: grants name it, so a generated id would make every grant
        // in a config file unwritable until after the principal existed.
        //
        // The id and the name are two arguments on purpose (2026-09-12). Until
        // then this line read `Principal::new(name, name, …)`, which twinned
        // the account slug with the display name; every rename was a
        // re-identification and every console had to pin "the name I saw".
        // The service hands the name as the id when the caller set none, so
        // every caller from before keeps exactly what it had.
        let principal =
            gunnar_core::Principal::new(id, name, principal_kind_in(kind)).map_err(internal)?;
        let created = self
            .stores
            .auth()
            .add_principal(principal)
            .map(|p| principal_out(&p))
            .map_err(internal)?;
        // ── the account, created WITH the user ─────────────────────────────
        //
        // A principal is intrinsically admin of the namespace named after its
        // ID (`gunnar_core::AuthTable::owns_account`), which is the `<account>`
        // in `<host>/<account>/<repo>`. That rule reads no table, so it can
        // only be sound if the two names cannot be claimed independently — and
        // this is the half that makes them one claim: creating the principal
        // creates the namespace, and a namespace that already exists makes the
        // whole call fail, principal and all.
        //
        // Rolled back on failure rather than left half-made. A principal with
        // somebody else's namespace as its account is exactly the state the
        // intrinsic rule must never be able to reach.
        if let Err(err) = self.stores.catalog().create_namespace(id) {
            let _ = self.stores.auth().remove_principal(id);
            return Err(ControlError::AlreadyExists(format!(
                "cannot create the account namespace \"{id}\" for this user: {err}. A user's \
                 account is the namespace named after their id and cannot be somebody else's; \
                 the principal was not created."
            )));
        }
        // The metadata mirror's identity half, off the stripe. After the write,
        // best effort, never the reason a verb fails: see
        // `ServerStores::mirror_identity`.
        self.stores.mirror_identity();
        Ok(created)
    }

    fn enroll_employee(
        &self,
        account: &str,
        ask: &gunnar_grpc::EmployeeAsk,
    ) -> ControlResult<gunnar_grpc::EmployeeAnswer> {
        if self
            .stores
            .catalog()
            .namespace(account)
            .map_err(internal)?
            .is_none()
        {
            return Err(ControlError::NotFound(format!("account {account}")));
        }
        // A clan is no account: employees are a person's account's (clans,
        // 2026-10-05), and a clan's members are accounts of their own.
        if self.stores.auth().is_clan(account).map_err(internal)? {
            return Err(ControlError::FailedPrecondition(format!(
                "{account} is a clan, not an account: employees are enrolled by an account's admin, \
                 and a clan's members are accounts that join it"
            )));
        }
        let principal = if ask.seats == 0 {
            // An id that names a namespace would make the employee that
            // namespace's admin by name (`owns_account`). Refused, as the
            // account a principal is born with would refuse it.
            if self
                .stores
                .catalog()
                .namespace(&ask.id)
                .map_err(internal)?
                .is_some()
            {
                return Err(ControlError::AlreadyExists(format!(
                    "namespace {} exists, so an employee may not be called that",
                    ask.id
                )));
            }
            Some(
                gunnar_core::Principal::new(&ask.id, &ask.name, gunnar_core::PrincipalKind::User)
                    .map_err(internal)?,
            )
        } else {
            None
        };
        let room = gunnar_core::RoomAsk {
            room_bytes: ask.room_bytes,
            seats: ask.seats,
            from_seat: ask.from_seat,
            cap: ask.cap,
            stored: ask.stored,
            order: ask.order.clone(),
            dry_run: ask.dry_run,
        };
        let answer = match self
            .stores
            .auth()
            .enroll_with_room(account, principal, &room)
        {
            Ok(answer) => answer,
            // Short is an ANSWER at the seam (nothing was written); the
            // service says it in the one sentence every plane shares.
            Err(gunnar_core::Error::RoomShort {
                need,
                unused,
                short,
                ..
            }) => {
                let (seats, seats_open) = self.stores.auth().seats_of(account).map_err(internal)?;
                return Ok(gunnar_grpc::EmployeeAnswer {
                    principal: None,
                    room_bytes: ask.room_bytes,
                    seats,
                    seats_open,
                    need_bytes: need,
                    unused_bytes: Some(unused),
                    shortfall_bytes: short,
                    unchanged: true,
                });
            }
            Err(gunnar_core::Error::PrincipalExists(id)) => {
                return Err(ControlError::AlreadyExists(format!(
                    "principal {id} already exists, and an existing principal can never become an \
                     employee"
                )))
            }
            Err(err @ gunnar_core::Error::NoOpenSeat(_)) => {
                return Err(ControlError::FailedPrecondition(err.to_string()))
            }
            Err(err @ gunnar_core::Error::NameExists { .. }) => {
                return Err(ControlError::AlreadyExists(err.to_string()))
            }
            Err(err @ gunnar_core::Error::InvalidInput { .. }) => {
                return Err(ControlError::InvalidArgument(err.to_string()))
            }
            Err(other) => return Err(internal(other)),
        };
        if !answer.unchanged {
            self.stores.mirror_identity();
        }
        Ok(gunnar_grpc::EmployeeAnswer {
            principal: answer.principal.as_ref().map(principal_out),
            room_bytes: answer.room_bytes,
            seats: answer.seats,
            seats_open: answer.seats_open,
            need_bytes: answer.need_bytes,
            unused_bytes: answer.unused_bytes,
            shortfall_bytes: answer.shortfall_bytes,
            unchanged: answer.unchanged,
        })
    }

    fn seats(&self, account: &str) -> ControlResult<(u32, u32)> {
        self.stores.auth().seats_of(account).map_err(internal)
    }

    fn clans(&self) -> Option<&dyn gunnar_grpc::clans::ClanPlane> {
        Some(self)
    }

    fn has_employees(&self, account: &str) -> ControlResult<bool> {
        self.stores.auth().is_enterprise(account).map_err(internal)
    }

    fn employees(&self, account: &str) -> ControlResult<Vec<Principal>> {
        Ok(self
            .stores
            .auth()
            .employees_of(account)
            .map_err(internal)?
            .iter()
            .map(principal_out)
            .collect())
    }

    fn principal_by_name(&self, name: &str) -> ControlResult<Option<Principal>> {
        Ok(self
            .stores
            .auth()
            .principal_by_name(name)
            .map_err(internal)?
            .as_ref()
            .map(principal_out))
    }

    /// The fed name is read where the installer left it — the last join reply,
    /// `<data>/pairing/joined.toml` — so it holds across restarts and needs no
    /// second record. A build without the pairing loop was fed nothing.
    /// ★ **The operator's first invite**, kept in the identity table (the
    /// twin replicates it): the break-glass token's hash as
    /// `operator-bootstrap` for the operator's first passkey, no server grant.
    /// The identity core reads it as a fed invite of its own and spends it
    /// there (IDENTITY-HOST). Spent — and a leftover one withdrawn — once the
    /// operator holds a passkey; otherwise recorded, or renewed for another
    /// `OPERATOR_INVITE_TTL_MS` when the same hash is pending: one update.
    fn operator_bootstrap_invite(
        &self,
        operator: &str,
        secret_sha256: &str,
        now_unix_ms: i64,
        ttl_ms: i64,
    ) -> ControlResult<gunnar_grpc::BootstrapInvite> {
        use gunnar_grpc::seam::OPERATOR_INVITE_ID;
        let hash = gunnar_grpc::seam::bootstrap_hash(secret_sha256)?;
        let ttl_ms = gunnar_grpc::seam::bootstrap_ttl(ttl_ms)?;
        let auth = self.stores.auth();
        if !auth
            .web_credentials(Some(operator))
            .map_err(internal)?
            .is_empty()
        {
            if auth
                .drop_first_invite(OPERATOR_INVITE_ID)
                .map_err(internal)?
                .is_some()
            {
                self.stores.mirror_identity();
            }
            return Ok(gunnar_grpc::BootstrapInvite::Spent);
        }
        let renewed = auth
            .first_invite(OPERATOR_INVITE_ID)
            .map_err(internal)?
            .is_some_and(|row| row.secret_hash == hash && row.principal_id == operator);
        auth.put_first_invite(gunnar_core::FirstInviteRow {
            id: OPERATOR_INVITE_ID.to_owned(),
            principal_id: operator.to_owned(),
            secret_hash: hash,
            created_by: "installer".to_owned(),
            created: now_unix_ms,
            expires: now_unix_ms + ttl_ms,
            note: "the operator's first passkey: the installer's first invite".to_owned(),
            server_level: None,
        })
        .map_err(internal)?;
        self.stores.mirror_identity();
        if !renewed {
            tracing::warn!(
                target: "gunnar::audit",
                event = "operator.bootstrap_invite",
                operator,
                ttl_days = ttl_ms / 86_400_000,
                "the installer's first invite (its hash) is recorded for the operator: his first passkey registers on his account, by gunnar's word"
            );
        }
        Ok(if renewed {
            gunnar_grpc::BootstrapInvite::Renewed
        } else {
            gunnar_grpc::BootstrapInvite::Recorded
        })
    }

    fn claim_operator(&self, asked: &str) -> ControlResult<gunnar_grpc::OperatorClaim> {
        #[cfg(feature = "wg-client")]
        let fed = crate::fed_principals::fed_operator(self.stores.root());
        #[cfg(not(feature = "wg-client"))]
        let fed: Option<String> = None;
        self.claim_operator_named(fed.as_deref(), asked)
    }

    fn rename_principal(&self, principal_id: &str, name: &str) -> ControlResult<Principal> {
        // The label alone. The namespace is the id's and does not move; nothing
        // keyed on the id is touched, and `AuthTable::rename_principal` says so
        // in its tests.
        let renamed = self
            .stores
            .auth()
            .rename_principal(principal_id, name)
            .map(|p| principal_out(&p))
            .map_err(internal)?;
        self.stores.mirror_identity();
        Ok(renamed)
    }

    fn list_principals(&self) -> ControlResult<Vec<Principal>> {
        Ok(self
            .stores
            .auth()
            .principals()
            .map_err(internal)?
            .iter()
            .map(principal_out)
            .collect())
    }

    fn principal_activity(
        &self,
    ) -> ControlResult<std::collections::BTreeMap<String, gunnar_grpc::PrincipalSeen>> {
        Ok(self
            .stores
            .activity()
            .all()
            .into_iter()
            .map(|(id, seen)| {
                (
                    id,
                    gunnar_grpc::PrincipalSeen {
                        last_sign_in_unix_ms: seen.signed_in,
                        last_operation_unix_ms: seen.operated,
                    },
                )
            })
            .collect())
    }

    fn holds_server_grant(&self, principal_id: &str) -> ControlResult<bool> {
        self.stores
            .auth()
            .holds_server_grant(principal_id)
            .map_err(internal)
    }

    fn add_credential(
        &self,
        principal_id: &str,
        credential_id: &[u8],
        public_key: &[u8],
        label: &str,
        sign_count: u32,
    ) -> ControlResult<gunnar_proto::WebCredential> {
        let stored = self
            .stores
            .auth()
            .add_web_credential(gunnar_core::WebCredential {
                id: gunnar_grpc::webauthn::b64url(credential_id),
                principal_id: principal_id.to_owned(),
                label: label.to_owned(),
                public_key_hex: hex::encode(public_key),
                sign_count,
                created: gunnar_core::now_ms(),
                last_used: None,
                sessions: Vec::new(),
            })
            .map_err(internal)?;
        web_credential_out(&stored)
    }

    fn credentials(
        &self,
        principal_id: Option<&str>,
    ) -> ControlResult<Vec<gunnar_proto::WebCredential>> {
        self.stores
            .auth()
            .web_credentials(principal_id)
            .map_err(internal)?
            .iter()
            .map(web_credential_out)
            .collect()
    }

    fn credential(
        &self,
        credential_id: &[u8],
    ) -> ControlResult<Option<gunnar_grpc::StoredCredential>> {
        let Some(row) = self
            .stores
            .auth()
            .web_credential(&gunnar_grpc::webauthn::b64url(credential_id))
            .map_err(internal)?
        else {
            return Ok(None);
        };
        let public_key = hex::decode(&row.public_key_hex).map_err(|err| {
            ControlError::Internal(format!(
                "web credential {} holds a key that is not hex: {err}",
                row.id
            ))
        })?;
        Ok(Some(gunnar_grpc::StoredCredential {
            credential: web_credential_out(&row)?,
            public_key,
        }))
    }

    fn record_passkey_use(
        &self,
        credential_id: &[u8],
        sign_count: u32,
        now_unix_ms: i64,
    ) -> ControlResult<gunnar_proto::WebCredential> {
        let row = self
            .stores
            .auth()
            .touch_web_credential(
                &gunnar_grpc::webauthn::b64url(credential_id),
                sign_count,
                now_unix_ms,
            )
            .map_err(internal)?;
        self.stores.mirror_identity();
        // A session was issued: the person's last sign-in (2026-10-21).
        self.stores
            .activity()
            .signed_in(&row.principal_id, now_unix_ms);
        web_credential_out(&row)
    }

    fn revoke_credential(
        &self,
        credential_id: &[u8],
    ) -> ControlResult<Option<gunnar_proto::WebCredential>> {
        let removed = self
            .stores
            .auth()
            .revoke_web_credential(&gunnar_grpc::webauthn::b64url(credential_id))
            .map_err(internal)?;
        // Its session keys went with it.
        self.stores.mirror_identity();
        removed.as_ref().map(web_credential_out).transpose()
    }

    fn rename_credential(
        &self,
        credential_id: &[u8],
        label: &str,
    ) -> ControlResult<Option<gunnar_proto::WebCredential>> {
        self.stores
            .auth()
            .rename_web_credential(&gunnar_grpc::webauthn::b64url(credential_id), label)
            .map_err(internal)?
            .as_ref()
            .map(web_credential_out)
            .transpose()
    }

    fn first_invite(&self) -> ControlResult<Option<gunnar_grpc::FirstInvite>> {
        Ok(self
            .stores
            .auth()
            .first_invite(gunnar_grpc::seam::OPERATOR_INVITE_ID)
            .map_err(internal)?
            .map(|row| gunnar_grpc::FirstInvite {
                principal_id: row.principal_id,
                secret_hash: row.secret_hash,
                created_at_unix_ms: row.created,
                expires_at_unix_ms: row.expires,
            }))
    }

    fn drop_first_invite(&self) -> ControlResult<()> {
        if self
            .stores
            .auth()
            .drop_first_invite(gunnar_grpc::seam::OPERATOR_INVITE_ID)
            .map_err(internal)?
            .is_some()
        {
            self.stores.mirror_identity();
        }
        Ok(())
    }

    fn employer_of(&self, principal_id: &str) -> ControlResult<Option<String>> {
        self.stores
            .auth()
            .employer_of(principal_id)
            .map_err(internal)
    }

    fn sso(&self) -> Option<&dyn gunnar_grpc::sso::plane::SsoPlane> {
        Some(self)
    }

    fn sso_import(
        &self,
        order: gunnar_grpc::sso::scim::ImportOrder,
    ) -> ControlResult<gunnar_grpc::sso::scim::ImportJob> {
        // RA5-39: enqueued under an id of its own, and the queue's answer is the judge (never a
        // status read before it, which a second import at the same moment also passed): a job
        // that is not this order's is the live import of the account, and this file is refused.
        let account = order.account.clone();
        let id = self.sso_import.next_job_id();
        let job = self.sso_import.enqueue_as(order, id.clone());
        if job.job_id != id {
            return Err(ControlError::FailedPrecondition(format!(
                "an import for account {account} is already {} (job {}): wait for it to finish",
                if job.state == crate::job_queue::JobState::Queued {
                    "queued"
                } else {
                    "running"
                },
                job.job_id
            )));
        }
        Ok(crate::sso_import_queue::job_out(job))
    }

    fn sso_import_status(
        &self,
        account: &str,
    ) -> ControlResult<Option<gunnar_grpc::sso::scim::ImportJob>> {
        Ok(self
            .sso_import
            .status(account)
            .map(crate::sso_import_queue::job_out))
    }

    fn approve_machine_enrolment(
        &self,
        approval: gunnar_grpc::MachineApproval,
    ) -> ControlResult<gunnar_grpc::MachineApproved> {
        let step_up = approval
            .step_up
            .as_ref()
            .map(|(id, count)| (gunnar_grpc::webauthn::b64url(id), *count));
        let (principal, credential, created) = self
            .stores
            .auth()
            .approve_machine_credential(
                &approval.machine,
                level_in(approval.server_level)?,
                gunnar_core::WebCredential {
                    id: gunnar_grpc::webauthn::b64url(&approval.credential_id),
                    principal_id: String::new(),
                    label: approval.label,
                    public_key_hex: hex::encode(&approval.public_key),
                    sign_count: approval.sign_count,
                    created: approval.now_unix_ms,
                    last_used: None,
                    sessions: Vec::new(),
                },
                step_up.as_ref().map(|(id, count)| (id.as_str(), *count)),
                approval.now_unix_ms,
            )
            .map_err(internal)?;
        self.stores.mirror_identity();
        Ok(gunnar_grpc::MachineApproved {
            principal: principal_out(&principal),
            credential: web_credential_out(&credential)?,
            created,
        })
    }

    fn remove_principal(&self, principal_id: &str) -> ControlResult<(u32, u32)> {
        let before_keys = self.stores.auth().keys().map_err(internal)?.len();
        let before_grants = self.stores.auth().grants(None).map_err(internal)?.len();
        self.stores
            .auth()
            .remove_principal(principal_id)
            .map_err(internal)?;
        let after_keys = self.stores.auth().keys().map_err(internal)?.len();
        let after_grants = self.stores.auth().grants(None).map_err(internal)?.len();
        self.stores.mirror_identity();
        Ok((
            before_keys.saturating_sub(after_keys) as u32,
            before_grants.saturating_sub(after_grants) as u32,
        ))
    }

    fn add_key(
        &self,
        principal_id: &str,
        openssh_public_key: &str,
        _comment: &str,
        expires_at_unix_ms: Option<i64>,
        caller: &str,
        attestation: Option<gunnar_proto::SignedKeyAttestation>,
    ) -> ControlResult<PublicKey> {
        // The fingerprint the attestation must name is derived HERE from the
        // key line, never taken from the client: an attestation over a
        // fingerprint the client chose would attest to nothing the SSH listener
        // will ever match. Parsed once more inside `register_key`; that is one
        // parse of one line on a verb that runs when a person gets a machine.
        // An `age1…` line is an encryption key, never an SSH key (CRYPT-PQ-LEGACY).
        if openssh_public_key.trim().starts_with("age1") {
            return Err(ControlError::InvalidArgument(
                gunnar_core::auth::AGE_LINE_IS_NO_SSH_KEY.to_owned(),
            ));
        }
        let adding = gunnar_core::Fingerprint::of_key(
            &gunnar_core::auth::parse_public_key(openssh_public_key).map_err(internal)?,
        );
        let holders = self
            .stores
            .auth()
            .attesting_keys_of(principal_id)
            .map_err(internal)?;
        // **The key it already holds is already there** (L1, release-3 recharge): a restored
        // main holds the twin's key from the log, and the pairing door enrols it again. That
        // is no new key, so no attestation is owed — ALREADY_EXISTS, which callers tolerate.
        if holders.iter().any(|k| k.fingerprint == adding.as_str()) {
            return Err(ControlError::AlreadyExists(format!(
                "principal {principal_id} already holds key {}",
                adding.as_str()
            )));
        }
        let requirement =
            gunnar_core::key_attestation::Requirement::of(principal_id, caller, holders);
        let attestation = attestation.map(from_proto_attestation).transpose()?;
        gunnar_core::key_attestation::check(
            &requirement,
            principal_id,
            adding.as_str(),
            attestation.as_ref(),
        )
        .map_err(|problem| match problem {
            // Required and absent: the request is well formed and the table
            // says "not without their word" — a precondition, with the
            // command that satisfies it in the message.
            gunnar_core::AttestationProblem::Missing { .. } => {
                ControlError::FailedPrecondition(problem.to_string())
            }
            // Present and wrong: the caller's argument.
            _ => ControlError::InvalidArgument(problem.to_string()),
        })?;
        let registered = self
            .stores
            .auth()
            .register_key(
                principal_id,
                openssh_public_key,
                expires_at_unix_ms.map(|ms| ms as UnixMillis),
            )
            .map(|key| key_out(&key))
            .map_err(internal)?;
        self.stores.mirror_identity();
        Ok(registered)
    }

    fn revoke_key(&self, fingerprint: &str) -> ControlResult<()> {
        let parsed = gunnar_core::Fingerprint::parse(fingerprint)
            .map_err(|err| ControlError::InvalidArgument(err.to_string()))?;
        let revoked = self.stores.auth().revoke_key(&parsed).map_err(internal)?;
        self.stores.mirror_identity();
        match revoked {
            Some(_) => Ok(()),
            None => Err(ControlError::NotFound(format!("key {fingerprint}"))),
        }
    }

    fn list_keys(&self, principal_id: Option<&str>) -> ControlResult<Vec<PublicKey>> {
        let keys = match principal_id {
            Some(id) => self.stores.auth().keys_of(id).map_err(internal)?,
            None => self.stores.auth().keys().map_err(internal)?,
        };
        Ok(keys.iter().map(key_out).collect())
    }

    fn grant(
        &self,
        principal_id: &str,
        namespace: &str,
        repo: &str,
        level: GrantLevel,
    ) -> ControlResult<gunnar_proto::Grant> {
        let scope = scope_in(namespace, repo)?;
        let grant = Grant {
            principal: principal_id.to_owned(),
            scope,
            level: level_in(level)?,
        };
        self.stores
            .auth()
            .grant(grant)
            .map(|g| grant_out(&g))
            .map_err(internal)
    }

    fn revoke(&self, principal_id: &str, namespace: &str, repo: &str) -> ControlResult<()> {
        let scope = scope_in(namespace, repo)?;
        match self
            .stores
            .auth()
            .revoke_grant(principal_id, &scope)
            .map_err(internal)?
        {
            true => Ok(()),
            false => Err(ControlError::NotFound(format!(
                "grant for {principal_id} on {scope}"
            ))),
        }
    }

    fn list_grants(
        &self,
        principal_id: Option<&str>,
        namespace: Option<&str>,
        repo: Option<&str>,
    ) -> ControlResult<Vec<gunnar_proto::Grant>> {
        Ok(self
            .stores
            .auth()
            .grants(principal_id)
            .map_err(internal)?
            .iter()
            .map(grant_out)
            .filter(|g| namespace.is_none_or(|want| want == g.namespace))
            .filter(|g| repo.is_none_or(|want| want == g.repo))
            .collect())
    }

    // ── groups (punkt 9) ───────────────────────────────────────────────────

    fn add_group_member(
        &self,
        group_id: &str,
        member_id: &str,
        signed: gunnar_proto::SignedMembershipEvent,
    ) -> ControlResult<u64> {
        let signed = self.verify_membership_event(
            signed,
            group_id,
            member_id,
            gunnar_core::MembershipAction::Add,
        )?;
        // Apply to the live table first: if the typecheck (group exists and is
        // a group, member exists) fails, nothing is signed into the log. A
        // membership event in the log names a change that was actually made.
        self.stores
            .auth()
            .add_to_group(group_id, member_id)
            .map_err(internal)?;
        self.append_membership_event(&signed)
    }

    fn remove_group_member(
        &self,
        group_id: &str,
        member_id: &str,
        signed: gunnar_proto::SignedMembershipEvent,
    ) -> ControlResult<(bool, u64)> {
        let signed = self.verify_membership_event(
            signed,
            group_id,
            member_id,
            gunnar_core::MembershipAction::Remove,
        )?;
        let was_member = self
            .stores
            .auth()
            .remove_from_group(group_id, member_id)
            .map_err(internal)?;
        // Recorded even when it was a no-op: the attempt to remove is evidence
        // too, and a reader folding the log sees a remove of a non-member leave
        // the set unchanged, exactly as `remove_from_group` did.
        let index = self.append_membership_event(&signed)?;
        Ok((was_member, index))
    }

    fn membership_events(
        &self,
        group_id: Option<&str>,
    ) -> ControlResult<Vec<gunnar_proto::SignedMembershipEvent>> {
        Ok(self
            .membership_log_events()?
            .into_iter()
            .filter(|signed| group_id.is_none_or(|g| signed.event.group == g))
            .map(to_proto_membership)
            .collect())
    }

    fn list_group_members(&self, group_id: &str) -> ControlResult<Vec<Principal>> {
        // The group must exist and be a group, so "no members" and "no such
        // group" cannot be confused into the same empty list.
        let auth = self.stores.auth();
        match auth.principal(group_id).map_err(internal)? {
            Some(p) if p.kind == PrincipalKind::Group => {}
            Some(_) => {
                return Err(ControlError::InvalidArgument(format!(
                    "principal \"{group_id}\" is not a group"
                )))
            }
            None => return Err(ControlError::NotFound(format!("group {group_id}"))),
        }
        // Membership is stored by member id; resolve each to a full principal so
        // a UI can show names and kinds, not bare ids.
        let mut members = Vec::new();
        for id in auth.members_of(group_id).map_err(internal)? {
            if let Some(p) = auth.principal(&id).map_err(internal)? {
                members.push(principal_out(&p));
            }
        }
        Ok(members)
    }

    // ── policy ─────────────────────────────────────────────────────────────

    fn get_protection(
        &self,
        path: &RepoPath,
        ref_pattern: Option<&str>,
    ) -> ControlResult<Vec<BranchProtection>> {
        let (repo, _) = self.open(path)?;
        let config = self.policy_of(&repo)?;
        Ok(config
            .protection
            .iter()
            .filter(|rule| ref_pattern.is_none_or(|want| rule.pattern.as_str() == want))
            .map(protection_out)
            .collect())
    }

    /// **Write one protection rule**, replacing any rule with the same pattern.
    ///
    /// Two things this deliberately does not do, both of them places where the
    /// proto and `gunnar_policy::ProtectionRule` do not line up. Getting either
    /// wrong silently is how an operator ends up with a policy they did not
    /// write:
    ///
    /// * **The per-pattern byte and object limits are refused, not dropped.**
    ///   `BranchProtection` carries `max_object_bytes` and
    ///   `max_objects_per_push` per rule; `gunnar-policy`'s `LimitPolicy` is
    ///   **repository-wide**. Storing a per-rule number into a repository-wide
    ///   limit would apply it to references the caller never named, and
    ///   ignoring it would report success for a limit that is not enforced.
    ///   Both are worse than saying so.
    /// * **`allow_create` and `ancestry_budget` survive a round trip.** They
    ///   have no proto field, so a rule written over gRPC would otherwise reset
    ///   whatever a `gunnar-policy.json` had set — an edit through the console
    ///   quietly widening a rule it did not display. The existing rule is read
    ///   first and only the fields the proto carries are overwritten.
    fn set_protection(
        &self,
        path: &RepoPath,
        protection: BranchProtection,
    ) -> ControlResult<BranchProtection> {
        let (repo, _) = self.open(path)?;
        if protection.max_object_bytes != 0 || protection.max_objects_per_push != 0 {
            return Err(ControlError::InvalidArgument(
                "max_object_bytes and max_objects_per_push are per-rule in the protocol and \
                 repository-wide in this server's policy engine, so a value here would apply to \
                 references this rule does not name. Leave them 0 and set the repository's \
                 limits in its policy document."
                    .to_owned(),
            ));
        }
        let pattern = gunnar_policy::RefPattern::new(protection.ref_pattern.clone())
            .map_err(|err| ControlError::InvalidArgument(err.to_string()))?;

        let mut config = self.policy_of(&repo)?;
        // Start from the rule that is there, so the two fields the proto cannot
        // express keep their values.
        let mut rule = config
            .protection
            .iter()
            .find(|rule| rule.pattern == pattern)
            .cloned()
            .unwrap_or_else(|| {
                gunnar_policy::ProtectionRule::protect(pattern.as_str())
                    .expect("the pattern was compiled one line above")
            });
        rule.pattern = pattern;
        rule.allow_force_push = protection.allow_force_push;
        rule.allow_delete = protection.allow_delete;
        rule.require_signature = protection.require_signature;
        // Empty in the proto means "anybody"; `None` means the same in the
        // policy. A `Some(vec![])` would mean **nobody may push**, which is a
        // very different rule to arrive at by accident.
        rule.allowed_principals = if protection.allowed_principal_ids.is_empty() {
            None
        } else {
            Some(protection.allowed_principal_ids.clone())
        };
        rule.forbid_self_approval = protection.forbid_self_approval;
        rule.required_approvals = protection.required_approvals;

        config
            .protection
            .retain(|other| other.pattern != rule.pattern);
        config.protection.push(rule.clone());
        self.store_policy(&repo, &config)?;
        Ok(protection_out(&rule))
    }

    fn delete_protection(&self, path: &RepoPath, ref_pattern: &str) -> ControlResult<()> {
        let (repo, _) = self.open(path)?;
        let mut config = self.policy_of(&repo)?;
        let before = config.protection.len();
        config
            .protection
            .retain(|rule| rule.pattern.as_str() != ref_pattern);
        if config.protection.len() == before {
            return Err(ControlError::NotFound(format!(
                "no protection rule for {ref_pattern} in {path}"
            )));
        }
        self.store_policy(&repo, &config)
    }

    fn get_ref_name_policy(&self, path: &RepoPath) -> ControlResult<RefNamePolicy> {
        let (repo, _) = self.open(path)?;
        let config = self.policy_of(&repo)?;
        Ok(ref_name_policy_out(&config.ref_names))
    }

    /// The gates a push to `path` meets: the stored policy's own (`PolicyConfig::gates`, the
    /// list the push path's `PolicyGate::open` starts from), plus the plaintext check an
    /// ENCRYPTED repository adds, exactly as the push path adds it.
    fn live_gates(&self, path: &RepoPath) -> ControlResult<Option<Vec<String>>> {
        use gunnar_policy::Gate as _;
        let (repo, _) = self.open(path)?;
        let config = self.policy_of(&repo)?;
        let mut names: Vec<String> = config.gates().iter().map(|g| g.name().to_owned()).collect();
        if repo.encrypted {
            names.push("encrypted".to_owned());
        }
        Ok(Some(names))
    }

    fn set_ref_name_policy(
        &self,
        path: &RepoPath,
        policy: RefNamePolicy,
    ) -> ControlResult<RefNamePolicy> {
        let (repo, _) = self.open(path)?;
        let compiled = gunnar_policy::RefNamePolicy::new(
            policy.allow_patterns.clone(),
            policy.deny_patterns.clone(),
        )
        .map_err(|err| ControlError::InvalidArgument(err.to_string()))?;
        let mut config = self.policy_of(&repo)?;
        config.ref_names = compiled.clone();
        self.store_policy(&repo, &config)?;
        Ok(ref_name_policy_out(&compiled))
    }

    // ── forge (roadmap phase 1) ────────────────────────────────────────────
    //
    // **Real**, over the same append-only log `gunnar forge` writes. There is
    // one forge log per server and the events carry their repository, so the
    // gRPC surface and the CLI are two doors onto one file rather than two
    // stores that can disagree (one implementation).

    fn forge_append(&self, event: gunnar_proto::SignedForgeEvent) -> ControlResult<u64> {
        if event.attested.is_some() {
            return Err(ControlError::InvalidArgument(
                "this event carries an attestation, and an attestation is gunnar's own word: \
                 only gunnar makes one, for a person's session that stepped up"
                    .to_owned(),
            ));
        }
        let signed = from_proto_event(event)?;

        // **The signature is checked before anything is written.** A review log
        // that took an event it could not verify would be a log of claims, and
        // the point of the whole design is that it is a log of evidence. The
        // key must already be in the ACL table for the same reason: a signature
        // by a key gunnar does not know is not something a later reader could
        // check at all.
        let key = self
            .stores
            .auth()
            .signing_keys()
            .map_err(|err| ControlError::Unavailable(format!("{err:#}")))?
            .into_iter()
            .find(|row| row.fingerprint_sha256 == signed.key_fingerprint)
            .ok_or_else(|| {
                ControlError::InvalidArgument(format!(
                    "{} is not registered on this server, so nobody reading this event later \
                     could check its signature",
                    signed.key_fingerprint
                ))
            })?;
        // **The key must be the claimed actor's own.** The signature proves
        // which key spoke; the table's `principal_id` says whose voice that
        // is, and an event attributed to one principal signed by another's
        // key is a claim filed in somebody else's name — exactly what the
        // service layer's actor==caller check refuses, re-checked here at the
        // seam because this door can also be reached without a connection.
        if key.principal_id != signed.event.actor {
            return Err(ControlError::InvalidArgument(format!(
                "this event is attributed to {:?} and is signed by {}, which is {:?}'s key; \
                 an approval is the actor's own word, so it must carry the actor's own \
                 signature",
                signed.event.actor, signed.key_fingerprint, key.principal_id
            )));
        }
        let public = gunnar_core::ssh_key::PublicKey::from_openssh(&key.openssh)
            .map_err(|err| ControlError::Internal(format!("stored key is unreadable: {err}")))?;
        gunnar_core::forge::verify_event(&signed, &public)
            .map_err(|problem| ControlError::InvalidArgument(format!("{problem}")))?;

        self.forge_subject_open(&signed)?;
        self.forge_write(&signed)
    }

    fn forge_append_attested(
        &self,
        event: gunnar_proto::SignedForgeEvent,
        session_stepped_up_at_unix_ms: i64,
    ) -> ControlResult<(u64, String)> {
        // **The caller's own signature is not what this takes.** A session
        // holds no key of the person's; what it holds is a fresh touch of their
        // passkey, which the service checked. A signature on the wire here is
        // somebody's key speaking, and that is `forge_append`'s door.
        if !event.key_fingerprint.is_empty()
            || !event.signature.is_empty()
            || event.attested.is_some()
        {
            return Err(ControlError::InvalidArgument(
                "an event gunnar attests arrives unsigned: a signed one is checked against its \
                 signer's key instead, and an attestation is gunnar's own to make"
                    .to_owned(),
            ));
        }
        let event = from_proto_event(event)?.event;
        if event.actor.is_empty() {
            return Err(ControlError::InvalidArgument(
                "an attested event must name the person it is attested for".to_owned(),
            ));
        }
        let key = self
            .stores
            .forge_attest_key()
            .map_err(|err| ControlError::Unavailable(format!("{err:#}")))?;
        let signed = gunnar_core::forge::attest_event(
            &key,
            event,
            gunnar_core::Attested {
                session_stepped_up_at_unix_ms,
            },
        )
        .map_err(|err| ControlError::Internal(format!("signing the attested event: {err}")))?;
        self.forge_subject_open(&signed)?;
        let words = signed
            .attested
            .as_ref()
            .map(|a| a.words())
            .unwrap_or_default();
        Ok((self.forge_write(&signed)?, words))
    }

    fn forge_review(
        &self,
        repo: &str,
        pull: u64,
    ) -> ControlResult<(
        gunnar_proto::ReviewState,
        Vec<gunnar_proto::SignedForgeEvent>,
    )> {
        let all = self.forge_events()?;
        let mine: Vec<gunnar_core::ForgeEvent> = all
            .iter()
            .filter(|signed| signed.event.repo == repo)
            .map(|signed| signed.event.clone())
            .collect();
        let state = gunnar_core::forge::fold(pull, &mine);
        let events = all
            .iter()
            .filter(|signed| signed.event.repo == repo && signed.event.pull == pull)
            .cloned()
            .map(to_proto_event)
            .collect();
        Ok((self.review_state(repo, &state, &all)?, events))
    }

    fn forge_reviews(&self, repo: &str) -> ControlResult<Vec<gunnar_proto::ReviewState>> {
        let all = self.forge_events()?;
        let mine: Vec<gunnar_core::ForgeEvent> = all
            .iter()
            .filter(|signed| signed.event.repo == repo)
            .map(|signed| signed.event.clone())
            .collect();
        let mut numbers: Vec<u64> = mine.iter().map(|event| event.pull).collect();
        numbers.sort_unstable();
        numbers.dedup();
        let mut out = Vec::new();
        for pull in numbers {
            let state = gunnar_core::forge::fold(pull, &mine);
            out.push(self.review_state(repo, &state, &all)?);
        }
        Ok(out)
    }

    fn forge_issue(
        &self,
        repo: &str,
        number: u64,
    ) -> ControlResult<
        Option<(
            gunnar_proto::IssueState,
            Vec<gunnar_proto::SignedForgeEvent>,
        )>,
    > {
        let all = self.forge_events()?;
        let mine: Vec<gunnar_core::ForgeEvent> = all
            .iter()
            .filter(|signed| signed.event.repo == repo)
            .map(|signed| signed.event.clone())
            .collect();
        let Some(issue) = gunnar_core::forge::fold_issue(number, &mine) else {
            return Ok(None);
        };
        // The whole thread, in log order: the opening, every comment, and the
        // close. An `IssueOpened` carries `pull == 0`, so it is matched by
        // position — the Nth opening is issue N — while comments and closes name
        // their number directly, exactly as the fold reads them.
        let mut opened_seen = 0u64;
        let events = all
            .iter()
            .filter(|signed| {
                if signed.event.repo != repo {
                    return false;
                }
                match &signed.event.event {
                    gunnar_core::Event::IssueOpened { .. } => {
                        opened_seen += 1;
                        opened_seen == number
                    }
                    gunnar_core::Event::IssueCommented { .. }
                    | gunnar_core::Event::IssueClosed { .. } => signed.event.pull == number,
                    _ => false,
                }
            })
            .cloned()
            .map(to_proto_event)
            .collect();
        Ok(Some((issue_state(repo, &issue), events)))
    }

    fn forge_issues(&self, repo: &str) -> ControlResult<Vec<gunnar_proto::IssueState>> {
        let mine: Vec<gunnar_core::ForgeEvent> = self
            .forge_events()?
            .into_iter()
            .filter(|signed| signed.event.repo == repo)
            .map(|signed| signed.event)
            .collect();
        Ok(gunnar_core::forge::fold_issues(&mine)
            .iter()
            .map(|issue| issue_state(repo, issue))
            .collect())
    }

    // ── admin ──────────────────────────────────────────────────────────────

    /// **The two numbers an operator is surprised by if nobody reports them.**
    ///
    /// Tombstoned bytes, because a customer who deletes a repository and sees
    /// no change in their usage will call the bill wrong; and replication,
    /// because every configured standby on this project received NOTHING from
    /// `e31ab8f4` until 2026-08-30 and the only thing that said so was a log
    /// line nobody was tailing.
    fn stats_extras(&self) -> ControlResult<gunnar_grpc::seam::StatsExtras> {
        let tombstones = self.stores.tombstones().unwrap_or_default();
        let report = self.replication.report();
        // The tenants row, off the same slot the band reads (one implementation). A build
        // without `metered`, or a metered one with no slot, counts nothing.
        #[allow(unused_mut)]
        let mut tenants = crate::dashboard::TenantCounts::default();
        #[cfg(feature = "metered")]
        if let Some(slot) = &self.entitlement {
            tenants = slot.counts();
        }
        Ok(gunnar_grpc::seam::StatsExtras {
            tombstoned_repos: tombstones.len() as u64,
            tombstoned_bytes: tombstones.iter().map(|row| row.bytes).sum(),
            replication_configured: report.configured,
            replication_enqueued: report.enqueued,
            replication_synced: report.synced,
            replication_failed: report.failed,
            replication_bus_gaps: report.bus_gaps,
            replication_refs_total: report.refs.total,
            replication_refs_unmirrored: report.refs.unmirrored,
            standbys: report
                .standbys
                .into_iter()
                .map(|row| gunnar_proto::StandbyStatus {
                    // The word the console badge prints, decided once here
                    // (one implementation) rather than re-derived from the booleans by
                    // every surface that draws a standby.
                    verdict: row.verdict().word().to_owned(),
                    name: row.name,
                    remote: row.remote,
                    pending: row.pending,
                    consecutive_failures: row.consecutive_failures,
                    last_error: row.last_error,
                    last_success_unix_ms: row.last_success_unix_ms,
                    needs_full_resync: row.needs_full_resync,
                    stale: row.stale,
                })
                .collect(),
            tenants_paid: tenants.paid,
            tenants_grace: tenants.grace,
            tenants_suspended: tenants.suspended,
        })
    }

    fn counts(&self) -> ControlResult<ControlCounts> {
        let (namespaces, repos) = self.stores.catalog().counts().map_err(internal)?;
        let (principals, keys, grants) = self.stores.auth().counts().map_err(internal)?;
        Ok(ControlCounts {
            namespaces: namespaces as u64,
            repos: repos as u64,
            principals: principals as u64,
            keys: keys as u64,
            grants: grants as u64,
        })
    }

    fn verify_chain(
        &self,
        request: &gunnar_proto::VerifyChainRequest,
    ) -> ControlResult<gunnar_proto::VerifyChainResponse> {
        // The SAME walk `gunnar verify` runs (one implementation): `crate::verify` is the
        // one implementation, and this method is a projection of its `Chain`
        // onto the wire. No verdict is computed here.
        let target = match request.target.as_str() {
            "" => None,
            spec => Some(spec),
        };
        let Some(repo) = &request.repo else {
            return Err(ControlError::InvalidArgument(
                "name a repository".to_owned(),
            ));
        };
        let rev = match request.rev.as_str() {
            "" => "HEAD",
            rev => rev,
        };
        let chain = crate::verify::verify(&self.stores, self, repo, rev, target)
            // A walk that cannot START is a refusal with the reason — a missing
            // repository, a rev that names nothing, a malformed target. It is
            // never an empty chain: four grey rows would render as "merely
            // incomplete", which is a pass a console reader would believe.
            .map_err(|err| ControlError::FailedPrecondition(format!("{err:#}")))?;
        Ok(chain.to_proto())
    }

    fn blame(
        &self,
        path: &RepoPath,
        rev: &str,
        file: &str,
    ) -> ControlResult<gunnar_proto::BlameResponse> {
        // The SAME walk `gunnar blame` runs (one implementation): `crate::blame::blame` is
        // the one implementation, routed here through the store handle the
        // running server already holds (`&self.stores`) — never a fresh
        // `ServerStores::open`, which would fight the server's exclusive lock.
        // That is the whole of it: down the verb takes the lock and cannot
        // run while a `serve` holds it; here it runs against the open store.
        let rev = if rev.is_empty() { "HEAD" } else { rev };
        let rows = crate::blame::blame(&self.stores, self, path, rev, file)
            .map_err(|err| ControlError::FailedPrecondition(format!("{err:#}")))?;
        Ok(gunnar_proto::BlameResponse {
            lines: rows
                .into_iter()
                .map(|row| gunnar_proto::BlameLine {
                    commit: row.commit.to_hex().to_string(),
                    author: row.author,
                    line: row.line,
                })
                .collect(),
        })
    }

    fn search(
        &self,
        path: &RepoPath,
        rev: &str,
        pattern: &str,
        max_file_bytes: u64,
        max_matches: u32,
    ) -> ControlResult<gunnar_proto::SearchResponse> {
        // As `blame` above: one implementation (`crate::search::search`),
        // walked live against the running server's open store. A zero ceiling
        // means the module's default rather than "no files" / "no matches".
        let rev = if rev.is_empty() { "HEAD" } else { rev };
        let defaults = crate::search::Limits::default();
        let limits = crate::search::Limits {
            max_file_bytes: if max_file_bytes == 0 {
                defaults.max_file_bytes
            } else {
                max_file_bytes
            },
            max_matches: if max_matches == 0 {
                defaults.max_matches
            } else {
                max_matches as usize
            },
        };
        let hits = crate::search::search(&self.stores, self, path, rev, pattern, limits)
            .map_err(|err| ControlError::FailedPrecondition(format!("{err:#}")))?;
        Ok(gunnar_proto::SearchResponse {
            matches: hits
                .into_iter()
                .map(|hit| gunnar_proto::SearchMatch {
                    path: hit.path,
                    line_number: hit.line_number as u32,
                    line: hit.line,
                })
                .collect(),
        })
    }

    /// **The PKI document, read** (`Admin.IssuerInfo`) — the ONE
    /// implementation, and the same document `gunnar issuer show` prints.
    ///
    /// Through [`ServerStores::pki_readonly`] and never `pki()`: the handle
    /// this opens installs a secret store that refuses every call, so the
    /// capability to sign is absent from the value rather than absent from
    /// whoever remembered not to call `create` on it. A future edit of this
    /// body cannot mint with it.
    ///
    /// An unreadable document is [`ControlError::Unavailable`] and not an
    /// empty answer, for the reason that error exists: "this box has no
    /// issuer" and "I could not find out" are different facts, and the first
    /// one invites an operator to mint over a CA their whole fleet pins.
    fn issuer_info(&self) -> ControlResult<gunnar_proto::IssuerInfoResponse> {
        let pki = self.stores.pki_readonly().map_err(|err| {
            ControlError::Unavailable(format!("the PKI document could not be opened: {err:#}"))
        })?;
        // The SAME reader `gunnar issuer show` prints from (one
        // implementation): there is no second assembly of this answer, so the
        // wire and the disk cannot describe one document differently.
        crate::admin::issuer_document(&pki).map_err(|err| {
            ControlError::Unavailable(format!("the PKI document could not be read: {err:#}"))
        })
    }

    fn setting(&self, name: &str) -> ControlResult<Option<Vec<u8>>> {
        self.stores.settings().get(name).map_err(internal)
    }

    fn set_setting(&self, name: &str, value: &[u8]) -> ControlResult<Option<Vec<u8>>> {
        self.stores.settings().set(name, value).map_err(internal)
    }

    /// **The audit chain, read as a shape** (`Admin.AuditTrail`, lane T11).
    ///
    /// Opened fresh from [`ServerStores::audit_path`] rather than reaching for
    /// the live `AuditChain` the gate holds: the gate's copy carries an
    /// in-memory tip and would answer from it, and the question being asked is
    /// about the FILE — whether it still holds what gunnar wrote. So this
    /// re-reads and re-verifies, which is also what makes `verified: false`
    /// mean something.
    ///
    /// A chain that will not open is **not** an error: it is `present: false`
    /// with `why`, because "this box has no durable trail" is exactly the
    /// answer an operator needs from a box whose disk filled or whose trail
    /// somebody has edited, and turning it into a failed RPC would hide it.
    /// The one thing never done here is to answer an empty chain, which would
    /// read as "nothing has happened" instead of "I hold no record".
    fn audit_trail(&self, at_seq: u64) -> ControlResult<gunnar_proto::AuditTrailResponse> {
        let path = self.stores.audit_path();
        // Whether the trail is replicated is a property of this BOX, not of
        // the open: a twin and a box mid-restore originate nothing and keep a
        // per-box trail, and on a primary this is false only when the server
        // already shouted about it at start-up.
        let replicated = !self.stores.is_twin()
            && !crate::twin::is_restoring(self.stores.root())
            && gunnar_core::txlog::sink::log_for(&path)
                .is_some_and(|(_, rel)| rel == gunnar_core::txlog::AUDIT_REL);
        let mut out = gunnar_proto::AuditTrailResponse {
            present: false,
            entries: 0,
            tip: String::new(),
            verified: false,
            replicated,
            hash_at_seq: String::new(),
            why: String::new(),
            tip_seq: 0,
        };
        let chain = match gunnar_core::AuditChain::open(&path) {
            Ok(chain) => chain,
            Err(err) => {
                out.why = format!("{err}");
                return Ok(out);
            }
        };
        let entries = match chain.entries() {
            Ok(entries) => entries,
            Err(err) => {
                out.why = format!("{err}");
                return Ok(out);
            }
        };
        out.present = true;
        out.entries = entries.len() as u64;
        if let Some(last) = entries.last() {
            out.tip.clone_from(&last.hash);
            // Reported, not computed from the count: see the proto comment.
            out.tip_seq = last.seq;
        }
        match chain.verify() {
            Ok(_) => out.verified = true,
            Err(err) => out.why = format!("{err}"),
        }
        if at_seq != 0 {
            // `seq` is dense from 0, so the entry with this seq is at this
            // index — but it is LOOKED UP by `seq` rather than indexed, because
            // a chain that has been cut is exactly the case this is asked in
            // and an index would answer confidently with the wrong entry.
            match entries.iter().find(|e| e.seq == at_seq) {
                Some(e) => out.hash_at_seq = e.hash.clone(),
                None => {
                    let sep = if out.why.is_empty() { "" } else { "; " };
                    out.why = format!(
                        "{}{sep}this trail holds no entry at seq {at_seq} (it holds {} entries)",
                        out.why,
                        entries.len()
                    );
                }
            }
        }
        Ok(out)
    }

    fn storage_info(&self, path: Option<&RepoPath>) -> ControlResult<StorageInfoResponse> {
        let repos = match path {
            Some(path) => vec![self.open(path)?.0],
            None => self.stores.catalog().list(None).map_err(internal)?,
        };
        let mut total_hot = 0u64;
        let mut total_explode = 0u64;
        let mut total_budget = 0u64;
        // One registry walk for every open store, rather than one per
        // repository: `Admin.StorageInfo` over a server with a thousand
        // repositories is already an unbounded recursive `stat` walk
        // (`control_plane_starvation`), and adding a per-repository lookup
        // inside that loop would make it two.
        let bands: std::collections::HashMap<std::path::PathBuf, crate::storage::ExplodeBand> =
            self.stores.engine().explode_use().into_iter().collect();
        let mut out = Vec::new();
        for repo in repos {
            let store = self.stores.repo_store(&repo).map_err(|err| {
                ControlError::Internal(format!("opening the repository's stores: {err:#}"))
            })?;
            let (loose, _objects_dir) = object_dir_stats(store.git_dir());
            // `hot_bytes` was `object_dir_stats`'s byte count until 2026-09-04
            // — a walk of `<git_dir>/objects`, which the znippy engine does not
            // have (its store is `<git_dir>/gunnar-git.znippy/`), so every
            // appliance repository reported 0 hot bytes. It is now the same
            // per-file walk `Usage.Read` bills from (`repo_bytes`, one implementation):
            // the whole directory minus LFS, which is what the proto comment
            // on `RepoStorage.hot_bytes` always said it was.
            let bytes = repo_bytes(store.git_dir()).hot();
            let refs = store.serve().refs().map_err(store_error)?.len() as u64;
            total_hot += bytes;
            // A repository nobody has opened has no band to report, and zero is
            // the truth of that: the cache is per open store and an unopened
            // one is holding nothing this process can name.
            let band = bands.get(store.git_dir()).copied().unwrap_or_default();
            total_explode += band.used();
            total_budget += band.budget;
            out.push(RepoStorage {
                repo: Some(RepoPath::new(&repo.namespace, &repo.name)),
                hash_kind: hash_kind(repo.hash_kind) as i32,
                loose_object_count: loose,
                hot_bytes: bytes,
                // **Not a measurement.** The znippy engine keeps ONE archive
                // per repository (counted in `hot_bytes` with the rest of the
                // directory) and has no cold tier; the two fields stay 0 and
                // `cold_measured: false` says the 0 is not a reading, so a
                // console shows N/A rather than "0 B" (owner, 2026-09-28).
                cold_bytes: 0,
                cold_object_count: 0,
                cold_measured: false,
                last_repack_at_unix_ms: 0,
                ref_count: refs,
                explode_bytes: band.used(),
                explode_budget_bytes: band.budget,
                explode_evicted_bytes: band.evicted_bytes,
            });
        }
        // The backend strings report what THIS process is running, not a plan
        // and not what it could have been built with. There is no "none" arm
        // any more: `gunnar-server` refuses to compile without an engine, so
        // the engine-free binary that used to answer here cannot be built.
        //
        // Both strings come off the same `Engine`, because one engine answers
        // for objects *and* refs — they were two strings when they were two
        // backends, and reporting two different ones now would be a shape the
        // storage contract no longer has.
        let engine = self.stores.engine();
        let (object_backend, ref_backend) = (engine.describe(), engine.describe());
        // **Tombstoned bytes are reported here or nowhere.** They are in
        // none of the `repos` rows above, because a tombstoned repository has
        // no catalog row — which is exactly how the measured 25 GB stayed
        // invisible. They are still on the disk and still on the account.
        let tombstones = self.stores.tombstones().unwrap_or_default();
        let total_tombstoned_bytes = tombstones.iter().map(|row| row.bytes).sum();
        let tombstoned = tombstones
            .into_iter()
            .map(|row| gunnar_proto::TombstonedRepo {
                repo: Some(RepoPath {
                    namespace: row.path.namespace().to_owned(),
                    repo: row.path.name().to_owned(),
                }),
                bytes: row.bytes,
                deleted_at_unix_ms: row.tombstone.deleted_at_unix_ms,
                purge_after_unix_ms: row.tombstone.purge_after_unix_ms.unwrap_or_default(),
            })
            .collect();
        Ok(StorageInfoResponse {
            object_backend,
            ref_backend,
            // The same engine, in parts (name, description, source repository).
            engine: Some(engine.report()),
            total_hot_bytes: total_hot,
            // Not a measurement; see `cold_measured` on each row.
            total_cold_bytes: 0,
            cold_measured: false,
            repos: out,
            total_explode_bytes: total_explode,
            total_explode_budget_bytes: total_budget,
            total_tombstoned_bytes,
            tombstoned,
            // **The storage reality of the machine.** The appliance has no
            // shell, so this call is the only way anyone ever sees which disks
            // became `/data`, what was rejected and why, or whether the
            // metadata mirror is genuinely on another spindle.
            reality: Some(self.stores.storage_reality()),
        })
    }

    /// **"If a tenant's cap rose to N bytes, could you serve it?"** —
    /// `Admin.Capacity`, the question monetize must ask before it buys a disk.
    ///
    /// Three measurements, none of them new (one implementation):
    ///
    /// * the bytes are the disk gate's own `statvfs` — the SAME one a push is
    ///   refused under, so the capacity a seller is quoted and the floor a
    ///   push dies at cannot disagree;
    /// * what the tenant already holds is [`Self::usage`]'s `pack_bytes` —
    ///   the meter `caps["pack_bytes"]` caps, so the delta is computed against
    ///   the number the quota is actually about;
    /// * whether the set can grow is the header band's `/proc/mounts` + md
    ///   sysfs read;
    /// * the box's cores and RAM — product scope, the ceilings a seller may
    ///   sell up to — are [`crate::capacity::MachineFacts::measure`]: the
    ///   `available_parallelism` the budgets use and the band's
    ///   `/proc/meminfo`, absent (never 0) when unreadable.
    ///
    /// [`crate::capacity::answer`] decides over them, and is pure so that the
    /// SEALED arm can be driven on a developer box where gunnar is never PID 1.
    ///
    /// **No gate wired is `Unimplemented`, not a default floor.** A plane
    /// built without [`Self::with_headroom`] does not know the `--disk-floor`
    /// in force, and quoting a seller against a floor this server is not
    /// enforcing is worse than declining to answer.
    fn capacity(
        &self,
        request: &gunnar_proto::CapacityRequest,
    ) -> ControlResult<gunnar_proto::CapacityResponse> {
        let Some(gate) = self.headroom.as_ref() else {
            return Err(ControlError::Unimplemented(
                "Admin.Capacity (no disk-headroom gate is wired on this control plane, so the \
                 --disk-floor in force is unknown and no quote can be made against it)",
            ));
        };
        // A named namespace must EXIST. `usage` is NotFound for one the
        // catalog does not hold, and that error is propagated rather than
        // swallowed into "it holds nothing": quoting a raise against the wrong
        // tenant's zero is how a seller oversells.
        let held_bytes = if request.namespace.is_empty() {
            0
        } else {
            self.usage(Some(&request.namespace))?
                .first()
                .map(|row| row.pack_bytes)
                .unwrap_or(0)
        };
        let root = gate.root().to_path_buf();
        let mut answer = crate::capacity::answer(&crate::capacity::Question {
            room: gate.headroom().map_err(|err| err.to_string()),
            floor_spec: gate.floor().to_string(),
            requested_bytes: request.requested_bytes,
            held_bytes,
            namespace: request.namespace.clone(),
            growth: crate::capacity::GrowthFacts::measure(&root),
            machine: crate::capacity::MachineFacts::measure(),
            root: root.clone(),
        });
        // Every disk, only when asked: a seller's quote never pays for the
        // mount-table walk (`CapacityRequest.disks`).
        if request.disks {
            let slow = self.stores.slow();
            let serialdat = std::path::PathBuf::from(slow.serialdat());
            let mut disks = crate::capacity::measure_disks(&root, Some(&serialdat), gate.floor());
            // What is on /serialdat, thing by thing — only the paths that
            // actually live under it (a directory configured elsewhere is not
            // this mount's).
            let log = slow.path_of(crate::slow::LOG_DIR);
            let known: Vec<(&str, std::path::PathBuf)> = [
                ("metadata copy", slow.path_of(crate::slow::META_DIR)),
                ("crash record", slow.path_of(crate::slow::CRASH_DIR)),
                ("audit trail", log.join("audit-chain.jsonl")),
                ("logs", log),
                ("grow journal", serialdat.join("grow-journal")),
                ("repository mirror", serialdat.join(crate::slow::REPOS_DIR)),
            ]
            .into_iter()
            .filter(|(_, path)| path.starts_with(&serialdat))
            .collect();
            let used = disks
                .mounts
                .iter()
                .find(|m| m.labels.iter().any(|l| l == "serialdat") && m.measured)
                .map(|m| m.used_bytes);
            if disks
                .mounts
                .iter()
                .any(|m| m.labels.iter().any(|l| l == "serialdat"))
            {
                disks.serialdat = crate::capacity::serialdat_breakdown(&known, used);
            }
            answer.disks = Some(disks);
        }
        Ok(answer)
    }

    // ── the runtime data-set growth (`crate::grow`) ─────────────────────

    fn grow_start(
        &self,
        request: &gunnar_proto::GrowStartRequest,
    ) -> ControlResult<gunnar_proto::GrowStatusResponse> {
        self.grow_machine()?
            .start(request)
            .map_err(ControlError::FailedPrecondition)
    }

    fn grow_status(&self) -> ControlResult<gunnar_proto::GrowStatusResponse> {
        match &self.grow {
            Some(grow) => Ok(grow.status()),
            // No machine wired: the seam's honest default, never Unimplemented
            // — see the trait's note on why the credential-free status must
            // always answer.
            None => Ok(gunnar_proto::GrowStatusResponse {
                phase: "idle".to_owned(),
                engine_present: false,
                serving: true,
                server_unix_ms: gunnar_grpc::bus::now_unix_ms(),
                detail: "this control plane has no runtime growth wired in".to_owned(),
                hotplug: crate::dashboard::probe::pci_hotplug().present,
                journal: gunnar_grpc::grow_journal::Summary::measure().map(|s| s.to_wire()),
                ..Default::default()
            }),
        }
    }

    fn grow_resume(&self, give_up: bool) -> ControlResult<gunnar_proto::GrowStatusResponse> {
        self.grow_machine()?
            .resume(give_up)
            .map_err(ControlError::FailedPrecondition)
    }

    /// **The meters, per namespace.** See `usage.proto` for what each counts
    /// and [`repo_bytes`] for the one walk that attributes a directory.
    ///
    /// Reads the DISK, not the open handles: `Admin.StorageInfo` opens every
    /// repository it reports (`repo_store`) to ask for its ref count, which
    /// on a server with a thousand repositories is a thousand store opens for
    /// one bill. A bill needs bytes, and bytes are on the disk whether or not
    /// the store is open — so this walks `repo_dir` and opens nothing. The one
    /// meter that IS about open handles (`objects`) reads the engine's live
    /// registry, which is a few `len()` calls and no disk.
    ///
    /// Tombstones are charged to the namespace the tombstone names, off the
    /// same walk `Admin.StorageInfo` and `Admin.Stats` use — a deleted
    /// repository's bytes are on the account until the purge, and a bill that
    /// forgot them would be the one an operator cannot explain.
    fn usage(&self, namespace: Option<&str>) -> ControlResult<Vec<gunnar_proto::NamespaceUsage>> {
        // A box growing its own data set has /data unmounted for the remount: its repositories'
        // sizes are not readable until it is back — a named, retryable refusal the caller waits
        // on, never `Internal: … the repository root does not resolve` (round 4 fresh UpCloud
        // mockup: a 502 at the console mid-growth). As `log_fetch` says it.
        self.usage_readable()?;
        // **One namespace: its own repositories and its own tombstones, walked
        // now** (2026-10-06). This used to list the WHOLE catalog and walk the
        // WHOLE repository root for tombstones on every call, so a poller
        // reading N tenants one by one did O(N²) work (load test: ~25–30 s of
        // 1.4 cores on main per 300 s at 1,000 tenants). The usage ledger's
        // index answers which repositories are the namespace's; the walk is
        // the same `repo_bytes`, so the answer is the same exact reading.
        if let Some(name) = namespace {
            let measured_at_unix_ms = gunnar_core::now_ms();
            let Some((held, _)) = self
                .stores
                .usage_ledger()
                .exact(&self.stores, name)
                .map_err(internal)?
            else {
                return Err(ControlError::NotFound(format!(
                    "namespace {name} is not in the catalog"
                )));
            };
            let objects = self.open_objects_of(name);
            return Ok(vec![self.usage_row(
                name,
                &held,
                objects,
                measured_at_unix_ms,
            )]);
        }
        self.usage_all()
    }

    /// **One namespace's repositories with what each stores** — the same
    /// per-repository walk [`Self::usage`] sums, row by row (see the seam).
    fn repo_usage(&self, namespace: &str) -> ControlResult<Vec<gunnar_proto::RepoStored>> {
        let Some((_, repos)) = self
            .stores
            .usage_ledger()
            .exact(&self.stores, namespace)
            .map_err(internal)?
        else {
            return Err(ControlError::NotFound(format!(
                "namespace {namespace} is not in the catalog"
            )));
        };
        let open_objects: std::collections::HashMap<std::path::PathBuf, u64> = self
            .stores
            .engine()
            .open_object_counts()
            .into_iter()
            .collect();
        // Sorted by repository name: the ledger keeps them in a BTreeMap.
        Ok(repos
            .into_iter()
            .map(|(name, bytes, dir)| gunnar_proto::RepoStored {
                repo: Some(gunnar_proto::RepoPath::new(namespace, &name)),
                stored_bytes: bytes.pack,
                cache_bytes: bytes.cache,
                lfs_bytes: bytes.lfs,
                objects: dir.and_then(|d| open_objects.get(&d).copied()).unwrap_or(0),
            })
            .collect())
    }

    /// **One page of every namespace's meters, out of the usage ledger**
    /// (`UsageBatch.ReadMany`, 2026-10-06) — re-measuring only what changed
    /// since the ledger last looked, and with a cursor answering only the
    /// namespaces whose row moved. See `crate::usage_ledger`.
    fn usage_page(
        &self,
        page_token: &str,
        page_size: usize,
        changed_since: &str,
    ) -> ControlResult<gunnar_proto::ReadManyUsageResponse> {
        self.usage_readable()?;
        let now = gunnar_core::now_ms();
        let ledger = self.stores.usage_ledger();
        let (cursor, after) = gunnar_grpc::seam::usage_page_token::decode(page_token);
        // The cursor is taken BEFORE the settle, on the first page, and carried
        // in the token by every later one: a change during the read is answered
        // again next time rather than lost.
        let cursor = if cursor.is_empty() {
            ledger.cursor_now(now)
        } else {
            cursor
        };
        let (rows, more, changed_only) = ledger
            .page(&self.stores, &after, page_size, changed_since, now)
            .map_err(internal)?;
        let next_page_token = match (more, rows.last()) {
            (true, Some((last, _))) => gunnar_grpc::seam::usage_page_token::encode(&cursor, last),
            _ => String::new(),
        };
        let usages = rows
            .iter()
            .map(|(name, held)| self.usage_row(name, held, held.objects, now))
            .collect();
        Ok(gunnar_proto::ReadManyUsageResponse {
            usages,
            next_page_token,
            cursor,
            changed_only,
            as_of_unix_ms: now,
        })
    }

    /// **The flow series** (`Usage.Activity`) — see the seam for the contract.
    ///
    /// The window is resolved HERE and not in the handler, because this is the
    /// half that knows what this server keeps: `0` for `since` means the whole
    /// kept window, `0` for `until` means now, and both ends are clamped to
    /// whole UTC days. A window that runs backwards returns nothing rather than
    /// an error — it is an empty question, and an empty answer is what it
    /// deserves.
    ///
    /// A named namespace must EXIST, for [`ControlPlane::usage`]'s reason:
    /// answering "no activity" for a namespace that is not in the catalog would
    /// let a typo read as a silent tenant, which is the one conclusion this
    /// whole ledger exists to make reliable.
    ///
    /// **Today is flushed before it is read.** The live slot holds today, the
    /// store holds a copy taken at the last tick, and a series that read only
    /// the store would end a minute in the past. Rather than fold the live slot
    /// into the answer — a second arithmetic on top of the flush's — the flush
    /// is simply run, which is a copy and cannot double a count.
    fn activity(
        &self,
        namespace: &str,
        since_unix_ms: i64,
        until_unix_ms: i64,
    ) -> ControlResult<(Vec<gunnar_proto::DayActivity>, i64)> {
        if self
            .stores
            .catalog()
            .namespace(namespace)
            .map_err(internal)?
            .is_none()
        {
            return Err(ControlError::NotFound(format!(
                "namespace {namespace} is not in the catalog"
            )));
        }
        let now = gunnar_core::now_ms();
        let flow = self.stores.flow();
        if let Err(err) = flow.flush(now) {
            // Not fatal: the store still holds everything up to the last tick,
            // and a read that refused because a write failed would be worse
            // than a read that is a minute stale and says nothing about it.
            tracing::warn!(
                target: "gunnar::store",
                event = "flow.flush_failed",
                %err,
                "could not flush the flow ledger before an Activity read; the series is as of \
                 the last successful flush"
            );
        }
        let today = gunnar_core::day_of(now);
        let from = if since_unix_ms == 0 {
            today - gunnar_core::RETENTION_DAYS
        } else {
            gunnar_core::day_of(since_unix_ms)
        }
        .max(today - gunnar_core::RETENTION_DAYS);
        let to = if until_unix_ms == 0 {
            today
        } else {
            gunnar_core::day_of(until_unix_ms)
        }
        .min(today);
        if from > to {
            return Ok((Vec::new(), gunnar_core::RETENTION_DAYS));
        }
        let days = flow
            .store()
            .series(namespace, from, to)
            .map_err(internal)?
            .into_iter()
            .map(|(day, row)| day_activity(day, &row))
            .collect();
        Ok((days, gunnar_core::RETENTION_DAYS))
    }

    /// **The admission plan** (`Usage.AdmitPlan`) — see the seam for the
    /// contract. A read for the admin view and the tenant, never on the
    /// admission path: the policy is asked exactly as the gate asks it, with
    /// the usage the gate would plan with, once per kind of work this server
    /// admits (`request` stands for ls-remote and gc).
    fn admit_plan(&self, namespace: &str) -> ControlResult<gunnar_proto::AdmitPlanResponse> {
        use gunnar_ssh::edda_admit::{Consumer, Work};
        use gunnar_ssh::governor::OpClass;
        if self
            .stores
            .catalog()
            .namespace(namespace)
            .map_err(internal)?
            .is_none()
        {
            return Err(ControlError::NotFound(format!(
                "namespace {namespace} is not in the catalog"
            )));
        }
        let Some(gate) = &self.admission else {
            return Err(ControlError::Unimplemented("Usage.AdmitPlan"));
        };
        let policy = gate.admit_policy();
        let usage = gate.admit_usage(&*policy, namespace);
        let limit = policy.limit();
        let who = Consumer::Namespace(namespace.to_owned());
        let estimates = policy.estimates();
        let kinds = [
            OpClass::Clone,
            OpClass::Fetch,
            OpClass::Push,
            OpClass::LsRemote,
        ]
        .into_iter()
        .map(|class| {
            let kind = gunnar_ssh::admission::work_kind(class);
            let plan = policy.plan(&Work::new(kind, None), &who, &usage);
            gunnar_proto::AdmitPlanKind {
                kind: kind.name().to_owned(),
                admit_class: plan.class.name().to_owned(),
                why: plan.why,
                estimate_bytes: plan.estimate.usage_bytes(),
                estimate_cpu_ms: plan.estimate.cpu_ms,
                samples: estimates
                    .iter()
                    .find(|row| row.kind == kind)
                    .map_or(0, |row| row.samples),
            }
        })
        .collect();
        Ok(gunnar_proto::AdmitPlanResponse {
            policy: policy.policy().to_owned(),
            window_days: usage.window_days,
            used_bytes: usage.bytes,
            limit_bytes: limit.map(|l| l.bytes),
            budget_left_bytes: limit.map(|l| l.bytes.saturating_sub(usage.bytes)),
            kinds,
        })
    }

    // ── the metered appliance: `Entitlement` ────────────────────────────────

    #[cfg(feature = "metered")]
    fn entitlement_get(
        &self,
        namespace: &str,
    ) -> ControlResult<Option<gunnar_proto::EntitlementFact>> {
        self.entitlement()?
            .get(namespace)
            .map_err(|err| ControlError::Internal(format!("{err:#}")))
    }

    #[cfg(feature = "metered")]
    fn entitlement_list(&self) -> ControlResult<Vec<gunnar_proto::EntitlementFact>> {
        self.entitlement()?
            .list()
            .map_err(|err| ControlError::Internal(format!("{err:#}")))
    }

    #[cfg(feature = "metered")]
    fn entitlement_refused_at_boot(&self) -> ControlResult<Option<gunnar_proto::RefusedAtBoot>> {
        Ok(self.entitlement()?.refusal())
    }

    /// The refusals, by kind: a forged fact is `PermissionDenied` (the caller
    /// held the admin grant and still may not move a plan without monetize's
    /// signature), a malformed one `InvalidArgument`, and one this box could
    /// not record `FailedPrecondition` — verified, and still not enforced,
    /// because a plan the log does not show is not a plan.
    #[cfg(feature = "metered")]
    fn entitlement_set(
        &self,
        fact: gunnar_proto::EntitlementFact,
    ) -> ControlResult<(gunnar_proto::EntitlementState, u64)> {
        use crate::entitlement::SetRefused;
        let (state, seq) = self.entitlement()?.set(fact).map_err(|err| match err {
            SetRefused::Forged { .. } => ControlError::PermissionDenied(err.to_string()),
            // **`PermissionDenied` and not `FailedPrecondition`, deliberately.**
            // monetize's poller treats a refusal as final and stops retrying
            // that fact, and that is the right answer here: a fact this box has
            // moved past will never become acceptable, so retrying it for ever
            // would be a hot loop against a decision that is not going to
            // change. It is the same code as a forged fact because it is the
            // same sentence — this caller may not move this plan with this
            // fact — and the words say which of the two it was.
            SetRefused::Replayed { .. }
            | SetRefused::Unstamped { .. }
            | SetRefused::Behind { .. } => ControlError::PermissionDenied(err.to_string()),
            SetRefused::Malformed(_) => ControlError::InvalidArgument(err.to_string()),
            SetRefused::NotRecorded { .. } => ControlError::FailedPrecondition(err.to_string()),
            SetRefused::NoKey { .. } => ControlError::FailedPrecondition(err.to_string()),
        })?;
        Ok((crate::entitlement::state_to_proto(state), seq))
    }

    // ── the metered appliance: `Billing` ────────────────────────────────────
    //
    // The key is read out of the sealed secret store on every call rather than
    // cached on this struct. Both verbs are human-paced — one is an operator
    // reading a string to paste into a configuration, the other is a customer
    // clicking renew — so a redb read and an OpenSSH parse are free at this
    // rate, and a cached key is a copy that has to be invalidated the day the
    // key is rolled. `ServerStores::actor_ticket_key` mints on first use, so
    // the FIRST of these calls on a fresh appliance is what brings the key into
    // existence; nothing has to run at boot for this to work.

    #[cfg(feature = "metered")]
    fn actor_ticket_public_key_hex(&self) -> ControlResult<String> {
        Ok(self
            .stores
            .actor_ticket_key()
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?
            .public_key_hex()
            .to_owned())
    }

    #[cfg(feature = "metered")]
    fn actor_ticket_sign(&self, message: &[u8]) -> ControlResult<[u8; 64]> {
        Ok(self
            .stores
            .actor_ticket_key()
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?
            .sign(message))
    }

    // The named sealed slot (2026-10-09): stored through the sealed, logged
    // secret store; a twin or a box being restored refuses the write as every
    // logged write is refused there.
    #[cfg(feature = "metered")]
    fn sealed_get(&self, name: &str) -> ControlResult<Option<(String, Vec<u8>)>> {
        self.stores
            .sealed_slot_get(name)
            .map_err(|err| ControlError::Internal(format!("{err:#}")))
    }

    #[cfg(feature = "metered")]
    fn sealed_put(&self, name: &str, owner: &str, value: &[u8]) -> ControlResult<bool> {
        self.stores
            .sealed_slot_put(name, owner, value)
            .map_err(|err| ControlError::Unavailable(format!("{err:#}")))
    }

    // ── mirror ─────────────────────────────────────────────────────────────

    /// **Register an upstream.** Bookkeeping only — no fetch happens here.
    ///
    /// `create_repo` is honoured before the registration, because a mirror of a
    /// repository that does not exist is a registration nothing can ever act
    /// on. Without the flag the repository must already be there, and a missing
    /// one is `NotFound` rather than a silently created empty one.
    fn mirror_add(
        &self,
        path: &RepoPath,
        remote_url: &str,
        prune: bool,
        create_repo: bool,
    ) -> ControlResult<MirrorConfig> {
        if remote_url.trim().is_empty() {
            return Err(ControlError::InvalidArgument(
                "a mirror needs a remote URL".to_owned(),
            ));
        }
        // **The destination, before it is written down.** `Mirror.Add` reaches
        // every enrolled principal — `owns_account` makes a caller intrinsically
        // Admin in its own namespace — so without this the verb is an
        // arbitrary outbound request from the server's network position,
        // authorised by having a key. See `mirror_fetch::check_destination`.
        // Refused at REGISTRATION rather than only on the first sync, so the
        // operator's mistake and the attacker's are both answered on the call
        // that made them.
        crate::mirror_fetch::classify(remote_url).map_err(ControlError::InvalidArgument)?;
        crate::mirror_fetch::check_destination(remote_url, self.stores.root())
            .map_err(ControlError::InvalidArgument)?;
        let repo_ref = Self::repo_ref(path)?;
        // **The repository is NOT created here** (owner order 2026-10-18).
        // Its object format and its default branch are the upstream's, and
        // only the upstream can say them: an ssh upstream is never asked here,
        // and a private one answers nothing before its credential is set — so
        // creating it now meant a guess (sha256, `main`) that a sha1 upstream
        // could never be fetched into, and an empty private repository left
        // behind by every import that failed. The registration says the
        // repository is to come, and the first sync that reaches the upstream
        // creates it (`mirror_fetch::sync_once`).
        let creates = create_repo && self.get_repo(path).is_err();
        if creates {
            // The disk, refused now by the gate `Repos.Create` asks, rather
            // than on a job minutes later.
            if let Some(line) = self.headroom.as_ref().and_then(|gate| gate.refusal()) {
                return Err(ControlError::ResourceExhausted(line));
            }
            if self
                .stores
                .catalog()
                .namespace(path.namespace.as_str())
                .map_err(internal)?
                .is_none()
            {
                return Err(ControlError::NotFound(format!(
                    "namespace {}",
                    path.namespace
                )));
            }
        } else {
            // Opened rather than merely catalogued: a registration against a
            // repository whose store cannot be opened would look fine and fail
            // on the first sync.
            self.open(path)?;
        }
        let mut record = gunnar_core::MirrorRecord::new(
            &repo_ref,
            remote_url,
            prune,
            gunnar_grpc::bus::now_unix_ms(),
        );
        record.creates_repo = creates;
        let stored = self
            .stores
            .mirrors()
            .set(&repo_ref, record)
            .map_err(internal)?;
        Ok(mirror_out(&stored))
    }

    /// **The one verb that genuinely needs the client half**, and the only one
    /// still refused.
    ///
    /// The original refusal covered all four: *"mirroring runs over
    /// gunnar-client (nornir-git ls-remote + fetch), which an S crate must
    /// never link (the dependency budget)"*. That is true of a sync and of nothing else — adding,
    /// listing and removing a registration are a document write, a document
    /// read and a document delete. Narrowing the gap to the verb that has it is
    /// the difference between "mirroring is unimplemented" and "this build
    /// cannot fetch".
    /// **Enqueue one sync, and return without syncing.**
    ///
    /// The refusal this replaced covered all four verbs and then just this
    /// one: *"mirroring runs over gunnar-client (nornir-git ls-remote + fetch),
    /// which an S crate must never link (the dependency budget)"*. That was true while the only
    /// fetch client in the constellation needed `gix`, a `.git` directory and a
    /// worktree — none of which exist on an appliance running as PID 1 over
    /// znippy. `gunnar_wire::fetch_pack` is a fetch client with none of those
    /// requirements, over the same `BufRead`/`Write` pair `upload_pack`
    /// already answers on, so the gap is closed rather than narrowed again.
    ///
    /// **Registration first**, so an unregistered repository is `NotFound` by
    /// name and not a job that fails four minutes later — two very different
    /// things to tell an operator, and only one of them is their mistake.
    ///
    /// The upstream and `prune` are read HERE and carried on the order, because
    /// they are what the caller asked about; the credential is read on the
    /// worker (see [`CoreControlPlane::mirror_queue`]) because it is a secret
    /// and an order is `Debug`.
    fn mirror_sync(&self, path: &RepoPath) -> ControlResult<MirrorConfig> {
        let record = self.mirror_record(path)?;
        let repo_ref = Self::repo_ref(path)?;
        // Refused at the DOOR rather than on the queue: a remote gunnar cannot
        // dial is the caller's mistake and it is knowable now, and a job that
        // sat QUEUED and then failed on the shape of a URL is a console button
        // that went down for nothing.
        crate::mirror_fetch::classify(&record.remote_url).map_err(ControlError::InvalidArgument)?;
        // Same door, same reason: a registration that predates the destination
        // rule must not become a dial by being clicked.
        crate::mirror_fetch::check_destination(&record.remote_url, self.stores.root())
            .map_err(ControlError::InvalidArgument)?;
        let job = self.mirror.enqueue(crate::mirror_queue::MirrorOrder {
            path: repo_ref.key(),
            upstream: record.remote_url.clone(),
            prune: record.prune,
            ca: mirror_ca_of(&record),
        });
        let mut out = mirror_out(&record);
        out.job = Some(mirror_job_out(path, job));
        Ok(out)
    }

    /// **Seal the credential first, then record its kind.**
    ///
    /// That order is the correctness argument. A document that claims a
    /// credential the secret store does not hold makes every later sync fail
    /// with "no credential stored" against an operator who can see one listed;
    /// a sealed value with no document pointing at it is unreachable and
    /// harmless. So the value is written before the fact, and forgotten after
    /// it.
    ///
    /// The value never comes back out of this function. `mirror_out` has no
    /// field for it, `MirrorConfig` has no field for it, and the two error
    /// paths below quote the repository and the kind and nothing else.
    fn mirror_set_credential(
        &self,
        path: &RepoPath,
        kind: gunnar_proto::MirrorCredentialKind,
        secret: &str,
        username: &str,
    ) -> ControlResult<MirrorConfig> {
        gunnar_grpc::seam::credential_arguments(kind, secret)?;
        self.mirror_record(path)?;
        let repo_ref = Self::repo_ref(path)?;

        let kind = credential_kind_in(kind);
        let secrets = self.stores.secrets().map_err(|err| {
            ControlError::Internal(format!("the sealed secret store is not available: {err:#}"))
        })?;
        let key = gunnar_core::credential_secret_key(&repo_ref);
        let stored = if kind.is_set() {
            gunnar_store::SecretStore::put(&secrets, &key, secret.as_bytes())
        } else {
            gunnar_store::SecretStore::delete(&secrets, &key)
        };
        stored.map_err(|err| {
            // `{err}` and not the value: this string reaches a client.
            ControlError::Internal(format!(
                "the mirror credential for {path} could not be sealed: {err}"
            ))
        })?;

        let record = self
            .stores
            .mirrors()
            .set_credential(&repo_ref, kind, username)
            .map_err(internal)?
            .ok_or_else(|| ControlError::NotFound(format!("no mirror registered for {path}")))?;
        Ok(mirror_out(&record))
    }

    fn mirror_set_ca(&self, path: &RepoPath, ca_pem: &str) -> ControlResult<MirrorConfig> {
        self.mirror_record(path)?;
        let repo_ref = Self::repo_ref(path)?;
        let ca = if ca_pem.trim().is_empty() {
            None
        } else {
            // Judged by the IdP CA's rules (one implementation): PEM, CERTIFICATE blocks
            // only, every one a CA valid now; a key or a server's own certificate is
            // refused by name and never kept.
            let ders = gunnar_grpc::sso::idp_ca::parse_ca(
                ca_pem,
                gunnar_grpc::bus::now_unix_ms(),
                "the mirror's CA",
                "the upstream",
            )
            .map_err(ControlError::InvalidArgument)?;
            let (subject, fingerprint) = gunnar_grpc::sso::idp_ca::ca_shown(&ders[0]);
            Some((
                gunnar_grpc::sso::idp_ca::idp_ca_pem(&ders),
                subject,
                fingerprint,
            ))
        };
        let record = self
            .stores
            .mirrors()
            .set_ca(&repo_ref, ca)
            .map_err(internal)?
            .ok_or_else(|| ControlError::NotFound(format!("no mirror registered for {path}")))?;
        Ok(mirror_out(&record))
    }

    fn mirror_status(
        &self,
        namespace: Option<&str>,
        path: Option<&RepoPath>,
    ) -> ControlResult<Vec<MirrorConfig>> {
        let all = self.stores.mirrors().all().map_err(internal)?;
        Ok(all
            .iter()
            .filter(|record| match path {
                Some(want) => record.repo == format!("{}/{}", want.namespace, want.repo),
                None => true,
            })
            .filter(|record| match namespace {
                Some(want) => record
                    .repo
                    .split_once('/')
                    .is_some_and(|(ns, _)| ns == want),
                None => true,
            })
            .map(|record| {
                let mut out = mirror_out(record);
                // **The job belongs on the listing**, which is what makes
                // `Mirror.Status` the poll a console uses: state, queue
                // position, progress, error and report, in the `GcStatus`
                // shape. A separate `MirrorSyncStatus` verb would have been a
                // second door onto one fact.
                out.job = out
                    .repo
                    .as_ref()
                    .zip(self.mirror.status(&record.repo))
                    .map(|(path, job)| mirror_job_out(path, job));
                // **A failure outlives its job** (import-big, 2026-10-26). The
                // queue forgets a job at a restart and after its retention, and
                // the registration's `last_error` does not: when the queue holds
                // nothing, the last failure is shown as the FAILED job it was,
                // so the repository page and the mirrors list say why an import
                // is empty instead of "idle".
                if out.job.is_none() && !record.last_error.is_empty() {
                    out.job = out.repo.clone().map(|path| gunnar_proto::MirrorJob {
                        job_id: String::new(),
                        path: Some(path),
                        state: gunnar_proto::MirrorJobState::Failed as i32,
                        error: record.last_error.clone(),
                        ..Default::default()
                    });
                }
                out
            })
            .collect())
    }

    /// **Un-register an upstream, and forget its credential with it.**
    ///
    /// The registration goes first and the sealed value second, and the order
    /// is the correctness argument — the mirror image of
    /// [`Self::mirror_set_credential`]'s. That function writes the value before
    /// the document so a document can never claim a credential the store does
    /// not hold; this one removes the document before the value for the same
    /// reason read backwards. A sealed secret with no document pointing at it
    /// is unreachable and harmless; a document with no secret makes every later
    /// sync fail with "no credential stored" against an operator who can see
    /// one listed. So the failure mode of a crash between the two lines is the
    /// harmless one, and the `NotFound` path deletes nothing.
    ///
    /// Before 2026-09-11 the value was simply left behind: `Mirror.Remove` took
    /// the document away and the ssh private key or forge token stayed in the
    /// sealed store for the life of the box, with nothing on the control plane
    /// naming it or able to name it — un-listable, un-rotatable, and still
    /// decryptable by anything that reaches the KEK. An operator who removes a
    /// mirror because its credential leaked has been told the credential is
    /// gone.
    fn mirror_remove(&self, path: &RepoPath) -> ControlResult<()> {
        self.mirror_record(path)?;
        let repo_ref = Self::repo_ref(path)?;
        if !self.stores.mirrors().remove(&repo_ref).map_err(internal)? {
            return Err(ControlError::NotFound(format!(
                "no mirror registered for {path}"
            )));
        }
        let secrets = self.stores.secrets().map_err(|err| {
            ControlError::Internal(format!("the sealed secret store is not available: {err:#}"))
        })?;
        gunnar_store::SecretStore::delete(&secrets, &gunnar_core::credential_secret_key(&repo_ref))
            .map_err(|err| {
                // `{err}` and not the value: this string reaches a client. The
                // registration IS gone by now, so this says exactly that rather
                // than reading as "nothing happened".
                ControlError::Internal(format!(
                    "the registration for {path} was removed and its sealed credential could \
                     not be deleted: {err}. The secret is still on this box; remove it before \
                     trusting that it is gone."
                ))
            })?;
        Ok(())
    }

    // ── replication: the three verbs the appliance is configured with ──────

    #[cfg(feature = "replication")]
    fn replication_set(
        &self,
        target: gunnar_proto::ReplicationTarget,
    ) -> ControlResult<gunnar_proto::ReplicationStatusResponse> {
        let slot = self.replication_slot()?;
        let mut target = crate::replication_wire::target_from_proto(target)?;
        // **The key the appliance pushes with, minted ON THE BOX.**
        //
        // An operator who names no identity is not asking for the client key
        // ladder — on an image with no home directory that ladder finds nothing
        // and every push fails on authentication forever. They are asking for
        // "use this box's own key", and there was no way to put one there. So
        // the server mints one, keeps the private half, and hands back the
        // public line for them to authorise on the standby. See
        // `replication_wire::REPLICATION_KEY`.
        let minted_public = if target.identity.is_none() {
            let (path, public) = crate::replication_wire::ensure_identity(self.stores.root())?;
            target.identity = Some(path);
            Some(public)
        } else {
            None
        };
        // The public-only requirements that depend on the key, now that there
        // IS one. Checked here rather than in `target_from_proto` because that
        // runs before the mint — and refusing a target for the absence of a key
        // this function is about to create is how the browse replica's own
        // documented one-liner became unrunnable on an appliance.
        crate::replication_wire::require_public_only_identity(&target)?;
        let mut config = slot
            .config()
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        // `set_target` REPLACES by name. That is what makes the verb
        // idempotent, and idempotent is what an operator on a flaky link needs:
        // a retried `SetReplication` must not leave two standbys behind.
        config.set_target(target);
        slot.apply(config)
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        let mut out = self.replication_snapshot(false)?;
        out.identity_public_key = minted_public.unwrap_or_default();
        Ok(out)
    }

    #[cfg(feature = "replication")]
    fn replication_remove(
        &self,
        name: &str,
    ) -> ControlResult<gunnar_proto::ReplicationStatusResponse> {
        let slot = self.replication_slot()?;
        let mut config = slot
            .config()
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        if !config.remove_target(name) {
            // NotFound and not a silent success. "I removed the standby" about a
            // standby that was never there reads identically to "I removed the
            // standby" about the one you meant, and the difference is whether
            // your data is still going somewhere.
            return Err(ControlError::NotFound(format!(
                "no replication target named {name:?}"
            )));
        }
        slot.apply(config)
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        self.replication_snapshot(false)
    }

    // ── The transaction log: what the twin fetches ──────────────────────────

    fn is_group_member(&self, principal_id: &str, group: &str) -> ControlResult<bool> {
        self.stores
            .auth()
            .groups_of(principal_id)
            .map(|groups| groups.iter().any(|g| g == group))
            .map_err(|err| ControlError::Unavailable(format!("reading group membership: {err}")))
    }

    fn become_twin(&self, primary: &str) -> ControlResult<String> {
        let key = crate::twin::become_twin(&self.stores, primary)
            .map_err(|err| ControlError::FailedPrecondition(format!("{err:#}")))?;
        // Following starts now, not at the next boot: the key is enrolled on
        // the primary next, and the loop retries until it is.
        crate::twin::start_follower(Arc::clone(&self.stores));
        Ok(key)
    }

    #[cfg(feature = "wg-client")]
    fn assign_tunnel_address(
        &self,
        address: &str,
    ) -> ControlResult<gunnar_proto::AssignTunnelAddressResponse> {
        let window_open = self.stores.auth().bootstrap_window_open().map_err(|err| {
            ControlError::Unavailable(format!("reading the bootstrap window: {err}"))
        })?;
        crate::appliance::tunnel_address_answer(self.stores.root(), address, window_open)
    }

    #[cfg(feature = "wg-client")]
    fn set_tunnel_address(
        &self,
        address: &str,
    ) -> ControlResult<gunnar_proto::AssignTunnelAddressResponse> {
        // `Admin.SetTunnelAddress`: the service already held the caller to
        // server-wide Admin, which is what the open window stands in for on
        // the unauthenticated door.
        crate::appliance::tunnel_address_answer(self.stores.root(), address, true)
    }

    fn twin_csr(&self) -> ControlResult<String> {
        crate::twin_tls::request(self.stores.root())
            .map_err(|err| ControlError::FailedPrecondition(format!("{err:#}")))
    }

    fn install_twin_certificate(
        &self,
        cert_pem: &str,
        ca_pem: &str,
        replication_port: u16,
        replication_host: &str,
    ) -> ControlResult<i64> {
        let host = (!replication_host.is_empty()).then_some(replication_host);
        crate::twin_tls::install_at(self.stores.root(), cert_pem, ca_pem, replication_port, host)
            .map(|expiry| expiry.days_left)
            .map_err(|err| ControlError::FailedPrecondition(format!("{err:#}")))
    }

    fn issue_twin_certificate(
        &self,
        principal: &str,
        csr_pem: &str,
    ) -> ControlResult<(String, String, u16, String)> {
        crate::twin_tls::issue_for_twin(&self.stores, principal, csr_pem)
            .map(|(cert, ca, port)| {
                (
                    cert,
                    ca,
                    port,
                    crate::twin_tls::replication_host(self.stores.root()).unwrap_or_default(),
                )
            })
            .map_err(|err| ControlError::FailedPrecondition(format!("{err:#}")))
    }

    fn twin_git_listener_needs_restart(&self) -> bool {
        crate::twin::git_listener_needs_restart(&self.stores)
    }

    fn restore_begin(&self, owner: &str) -> ControlResult<u64> {
        crate::twin::restore_begin_by(&self.stores, owner).map_err(|err| {
            // Somebody else's restore is a NO to a known caller, not a box in the wrong state.
            if err.downcast_ref::<crate::twin::RestoreNotYours>().is_some() {
                ControlError::PermissionDenied(format!("{err:#}"))
            } else {
                ControlError::FailedPrecondition(format!("{err:#}"))
            }
        })
    }

    /// The keys handed in by `serve` (`--restore-pubkey`), then the admin-grade keys the
    /// installer's door fed this box ([`crate::fed_principals::restore_keys_at`]). Read on
    /// every call: a feed that arrives while the box runs counts from the next stream on.
    fn restore_keys(&self) -> ControlResult<Vec<String>> {
        #[allow(unused_mut)]
        let mut keys = self.restore_keys.clone();
        #[cfg(feature = "wg-client")]
        keys.extend(
            crate::fed_principals::restore_keys_at(self.stores.root())
                .map_err(ControlError::Unavailable)?,
        );
        keys.sort();
        keys.dedup();
        Ok(keys)
    }

    fn restore_room(&self, announced_bytes: u64) -> ControlResult<()> {
        crate::twin::room_for_restore(self.stores.root(), announced_bytes)
            .map_err(|err| ControlError::FailedPrecondition(format!("{err:#}")))
    }

    /// **The server's intake** (restore-large-entry, 2026-10-07): an entry larger than one piece
    /// is staged on this box's disk as it arrives and survives the stream ending inside it
    /// ([`crate::twin::intake`]).
    fn restore_intake<'a>(
        &'a self,
        owner: &str,
    ) -> ControlResult<Option<Box<dyn gunnar_grpc::RestoreIntake + 'a>>> {
        match crate::twin::intake::Intake::open(&self.stores, owner) {
            Ok(Some(intake)) => Ok(Some(Box::new(intake))),
            Ok(None) => Ok(None),
            // Somebody else's restore is a NO to a known caller, not a box in the wrong state.
            Err(err) if err.downcast_ref::<crate::twin::RestoreNotYours>().is_some() => {
                Err(ControlError::PermissionDenied(format!("{err:#}")))
            }
            Err(err) => Err(ControlError::FailedPrecondition(format!("{err:#}"))),
        }
    }

    fn restore_apply(&self, entry: gunnar_proto::LogEntry) -> ControlResult<bool> {
        let e = gunnar_core::txlog::Entry {
            seq: entry.seq,
            kind: entry.kind as u16,
            meta: entry.meta,
            blob: entry.blob,
        };
        match crate::twin::restore_apply(&self.stores, &e) {
            Ok(crate::twin::Applied::Lost(_)) => Ok(true),
            Ok(_) => Ok(false),
            Err(err) => Err(ControlError::Internal(format!(
                "restoring seq {}: {err:#}",
                e.seq
            ))),
        }
    }

    fn restore_finish(&self, announced_head: u64, log_id_of_source: &str) -> ControlResult<u64> {
        let head =
            crate::twin::restore_finish_streamed(&self.stores, announced_head, log_id_of_source)
                .map_err(|err| ControlError::FailedPrecondition(format!("{err:#}")))?;
        // c-no-restart: the restored box restarts ITSELF (the appliance's PID 1).
        crate::twin::restart_after_restore();
        Ok(head)
    }

    fn snapshot_stream(
        &self,
        sink: &mut dyn FnMut(gunnar_proto::LogChunk) -> ControlResult<()>,
    ) -> ControlResult<u64> {
        self.snapshot_stream_from(0, 0, "", sink)
    }

    /// **A snapshot from item `from_item`, byte `from_offset` on** (restore-after-snapshot,
    /// 2026-10-07): a twin's kept base, every piece with its item, offset, the item's crc on its
    /// last and the base's id ([`crate::twin::snapshot::serve_from`]); a primary's own snapshot,
    /// a new cut each time, with none. A base that changed is `[snapshot-changed]`.
    fn snapshot_stream_from(
        &self,
        from_item: u64,
        from_offset: u64,
        expect_id: &str,
        sink: &mut dyn FnMut(gunnar_proto::LogChunk) -> ControlResult<()>,
    ) -> ControlResult<u64> {
        // The one copy a piece takes: out of the producer's buffer into the wire message.
        let mut pieces = |p: crate::twin::snapshot::Piece<'_>,
                          pos: Option<crate::twin::snapshot::PiecePos<'_>>|
         -> anyhow::Result<()> {
            sink(gunnar_proto::LogChunk {
                seq: 0,
                kind: u32::from(p.kind),
                meta: p.meta.to_vec(),
                blob_len: p.blob_len,
                blob: p.blob.to_vec(),
                last: p.last,
                restore_head: 0,
                restore_bytes: 0,
                log_id: String::new(),
                offset: pos.map(|q| q.offset),
                entry_crc: pos.and_then(|q| q.crc),
                snapshot_item: pos.map(|q| q.item),
                snapshot_id: pos.map(|q| q.id.to_owned()).unwrap_or_default(),
            })
            .map_err(|err| anyhow::anyhow!("{err}"))
        };
        crate::twin::snapshot::serve_from(
            &self.stores,
            from_item,
            from_offset,
            expect_id,
            &mut pieces,
        )
        .map_err(|err| {
            match err.downcast_ref::<crate::twin::snapshot::SnapshotChanged>() {
                Some(changed) => ControlError::FailedPrecondition(changed.to_string()),
                None => ControlError::Internal(format!("producing a snapshot: {err:#}")),
            }
        })
    }

    fn log_retain(&self, from: u64) -> ControlResult<gunnar_proto::LogHeadResponse> {
        let log = self.stores.txlog();
        if log.is_follower() {
            return Err(ControlError::FailedPrecondition(
                "retention: a twin's log is the primary's numbers; retain on the primary".into(),
            ));
        }
        let from = if from == 0 { log.head_seq() + 1 } else { from };
        let first = log.retain_from(from).map_err(|err| {
            ControlError::Unavailable(format!("retaining the transaction log from {from}: {err}"))
        })?;
        tracing::warn!(target: gunnar_core::observe::TARGET_TWIN, from, first, head = log.head_seq(), "the transaction log now retains from {first}; a twin behind it takes a snapshot");
        self.log_head()
    }

    fn log_layout(&self) -> ControlResult<Vec<(u64, u64, u64)>> {
        let log = self.stores.txlog();
        if log.is_follower() {
            return Err(ControlError::FailedPrecondition(
                "retention: a twin's log is the primary's numbers; retain on the primary".into(),
            ));
        }
        Ok(log.layout())
    }

    fn data_volume(&self) -> Option<(u64, u64)> {
        // While the set is released for a growth, statvfs of the data root reads the box's
        // root filesystem: no number is better than that one.
        if self.stores.txlog().is_released() {
            return None;
        }
        let vfs = rustix::fs::statvfs(self.stores.root()).ok()?;
        let total = vfs.f_blocks.saturating_mul(vfs.f_frsize);
        let free = vfs.f_bfree.saturating_mul(vfs.f_frsize);
        (total > 0).then(|| (total, total.saturating_sub(free)))
    }

    fn twin_owed_read(&self) -> ControlResult<Vec<u8>> {
        match std::fs::read(self.stores.root().join(crate::twin::TWIN_OWED_FILE)) {
            Ok(b) => Ok(b),
            Err(e) if e.kind() == std::io::ErrorKind::NotFound => Ok(Vec::new()),
            Err(e) => Err(ControlError::Unavailable(format!(
                "reading {}: {e}",
                crate::twin::TWIN_OWED_FILE
            ))),
        }
    }

    fn twin_owed_write(&self, bytes: &[u8]) -> ControlResult<()> {
        if self.stores.txlog().is_released() {
            return Err(ControlError::Unavailable("the data set is released for a growth; twin-owed.json is written after the remount".into()));
        }
        // Per box, never a transaction: what a primary owes its twins is not the twins' to hold.
        crate::durable::write_atomic_unframed(
            self.stores.root(),
            crate::twin::TWIN_OWED_FILE,
            bytes,
        )
        .map_err(|e| {
            ControlError::Unavailable(format!("writing {}: {e:#}", crate::twin::TWIN_OWED_FILE))
        })
    }

    fn restore_snapshot_chunk(&self, chunk: &gunnar_proto::LogChunk) -> ControlResult<Option<u64>> {
        let kind = u16::try_from(chunk.kind).map_err(|_| {
            ControlError::InvalidArgument(format!("snapshot piece of kind {}", chunk.kind))
        })?;
        let piece = crate::twin::snapshot::Piece {
            kind,
            meta: &chunk.meta,
            blob_len: chunk.blob_len,
            blob: &chunk.blob,
            last: chunk.last,
        };
        crate::twin::snapshot::restore_piece(&self.stores, piece)
            .map_err(|err| ControlError::Internal(format!("installing the snapshot: {err:#}")))
    }

    fn health_alarms(&self) -> Vec<gunnar_proto::HealthAlarm> {
        #[allow(unused_mut)]
        let mut alarms = Vec::new();
        // A box stuck mid-restore serves reads and refuses every write: say so on the wire.
        if !self.stores.is_twin() && crate::twin::is_restoring(self.stores.root()) {
            alarms.push(gunnar_proto::HealthAlarm {
                event: "twin.restoring_at_open".into(),
                count: 1,
                since_unix_ms: 0,
                detail: "this box is MID-RESTORE: it originates no transactions and refuses every \
                         control-plane write until a restore finishes — resend the twin's log"
                    .into(),
            });
        }
        // An old main fenced off by a newer generation of its log (stinky row 18): it serves
        // reads and refuses every write, and must say so rather than look like a broken box.
        if !self.stores.is_twin() {
            if let Some(why) = crate::twin::fenced_why(self.stores.root()) {
                alarms.push(gunnar_proto::HealthAlarm {
                    event: "twin.fenced_by_generation".into(),
                    count: 1,
                    since_unix_ms: 0,
                    detail: why,
                });
            }
        }
        // ★ twin-resync-space (2026-10-06): a twin that gave its stale copy up to make room for
        // a full resync holds NO copy until it lands — main is the only one meanwhile.
        if self.stores.is_twin() {
            if let Some(d) = crate::twin::snapshot::dropped(self.stores.root()) {
                let too_small = crate::twin::snapshot::too_small_total(self.stores.root())
                    .map(|t| format!(" The resync did not fit even then: this twin's volume ({t} bytes) must be grown to at least main's data set before it is tried again ({}).", gunnar_grpc::TWIN_TOO_SMALL))
                    .unwrap_or_default();
                alarms.push(gunnar_proto::HealthAlarm {
                    event: "twin.resync_without_copy".into(),
                    count: 1,
                    since_unix_ms: d.at_unix_ms,
                    detail: format!("{}.{too_small}", d.sentence()),
                });
            }
        }
        // The log's size over its cap (2026-09-22): a warning, never a deletion. A twin's log is
        // its primary's numbers and is trimmed there, so only a box that originates one is told.
        if !self.stores.is_twin() {
            let (total, _) = crate::twin::volume_bytes(self.stores.root());
            match crate::twin::txlog_alarm_cap(
                std::env::var(crate::twin::TXLOG_ALARM_ENV).ok().as_deref(),
                total,
            ) {
                Ok(Some((cap, how))) => alarms.extend(crate::twin::txlog_size_alarm(
                    self.stores.txlog().bytes(),
                    cap,
                    &how,
                )),
                Ok(None) => {}
                Err(why) => alarms.push(gunnar_proto::HealthAlarm {
                    event: crate::twin::TXLOG_SIZE_ALARM.into(),
                    count: 1,
                    since_unix_ms: 0,
                    detail: why,
                }),
            }
        }
        #[cfg(feature = "metered")]
        if let Some(a) = self.entitlement.as_ref().and_then(|slot| slot.alarm()) {
            alarms.push(a);
        }
        // The growth's own alarm (DEFECT D, 2026-09-29): /data kept unmounted past the growth's
        // bound (`grow.unmounted_too_long`), or a set that could not be mounted back (`grow.fatal`).
        if let Some(a) = self.grow.as_ref().and_then(|g| g.alarm()) {
            alarms.push(a);
        }
        // The installer's feed (`crate::feed`): a medium value the door contradicted, or a
        // fed monetize key that waits for a restart.
        alarms.extend(crate::feed::alarms());
        alarms
    }

    fn is_twin(&self) -> bool {
        self.stores.is_twin()
    }

    fn frozen(&self) -> Option<String> {
        if self.stores.is_twin() {
            Some("this box is a twin".to_owned())
        } else if self
            .stores
            .browse()
            .load(std::sync::atomic::Ordering::SeqCst)
        {
            Some("this box is a browse replica".to_owned())
        } else {
            None
        }
    }

    fn log_follows(&self) -> bool {
        self.stores.is_twin() || self.stores.txlog().is_follower()
    }

    fn topology_facts(&self) -> gunnar_grpc::topology::Facts {
        crate::topology::facts(self.stores.root())
    }

    fn maintenance_reasons(&self) -> Vec<String> {
        #[allow(unused_mut)]
        let mut why = Vec::new();
        #[cfg(feature = "metered")]
        if self
            .entitlement
            .as_ref()
            .is_some_and(|slot| slot.maintenance())
        {
            why.push(crate::entitlement::KEY_MISMATCH_ALARM.to_string());
        }
        why
    }

    fn primary_heartbeat(&self, silent_after_ms: u64) -> Option<gunnar_proto::PrimaryHeartbeat> {
        let cfg = crate::twin::TwinConfig::load(self.stores.root())
            .ok()
            .flatten()?;
        // The follower's OWN word and reason travel with the numbers (X2): a
        // twin that cannot start, or whose every poll fails, records both, and
        // this is the only door that reads them out to anybody.
        let st = crate::twin::status(self.stores.root());
        let (last, primary_head, applied) = match &st {
            Some(s) => (s.last_answer_unix_ms, s.primary_head_seq, s.applied_seq),
            None => (0, 0, self.stores.txlog().head_seq()),
        };
        let own = st.as_ref().map(|s| (s.state.to_string(), s.why.clone()));
        Some(gunnar_grpc::heartbeat::primary_view(
            &cfg.primary,
            last,
            primary_head,
            applied,
            crate::twin::now_ms(),
            silent_after_ms,
            own.as_ref().map(|(a, b)| (a.as_str(), b.as_str())),
        ))
    }

    fn log_head(&self) -> ControlResult<gunnar_proto::LogHeadResponse> {
        self.log_head_signed("")
    }

    fn log_head_signed(&self, nonce: &str) -> ControlResult<gunnar_proto::LogHeadResponse> {
        // **A twin's poll in the restore window is refused by name** (T17, 2026-09-21; T15's
        // TD8). Mid-replay (`txlog-restoring`) or finished and owed its restart
        // (`txlog-reseal`), this process holds the fresh box's KEK while the replayed host key
        // is sealed under the dead primary's; the re-seal that reconciles them runs on the next
        // open. Answering would mean an UNSIGNED answer a pinned twin refuses, and a
        // `cannot read its host key … wrong key-encrypting key` WARN that reads like a broken
        // box (MEASURED under KVM, 0.4 s after "Restore finished"). The box is not yet the
        // primary it will be, and says exactly that; the twin records it as its `why` and polls
        // again. Only a nonce asks for proof of identity — an unnonced LogHead (an operator,
        // `twin replay`) still gets the numbers.
        if !nonce.trim().is_empty() {
            let root = self.stores.root();
            if crate::twin::is_restoring(root) {
                return Err(ControlError::Unavailable(
                    "this box is being restored from a twin and is not a primary yet: it answers a twin's poll \
                     once the replay has finished and the box has restarted"
                        .to_owned(),
                ));
            }
            if crate::twin::reseal_pending(root) {
                return Err(ControlError::Unavailable(
                    "this box finished a restore and must restart before it answers a twin: its host key is \
                     sealed under the key-encrypting key the restart re-seals, so until then it cannot prove \
                     which box it is"
                        .to_owned(),
                ));
            }
        }
        let mut head = crate::twin::own_head(&self.stores);
        // **Prove which box answered** (2026-09-21, lane T4). Signed last, over
        // the nonce the caller just minted plus the identity and the numbers
        // above, so a recorded answer cannot be replayed at the next poll and
        // the numbers cannot be edited in flight. No nonce = not a twin's poll,
        // and then there is nothing to be fresh about and nothing is signed.
        //
        // The generation (stinky row 18, 2026-10-10) is signed with them: a
        // primary names which restore of its log it is, a twin the highest its
        // primary has been. A fence that cannot be read is refused by name, never
        // answered as 0 — a twin would take that for an old main.
        let root = self.stores.root();
        let generation = if crate::twin::is_twin_root(root) {
            crate::twin::pinned_generation(root)
        } else {
            crate::twin::log_generation(root)
        };
        head.generation = generation
            .map_err(|err| ControlError::Internal(format!("this box's log generation: {err:#}")))?;
        let (key, sig) = crate::twin::sign_head_answer(
            &self.stores,
            nonce,
            &head.log_id,
            head.first_seq,
            head.head_seq,
            head.generation,
        );
        head.answer_key = key;
        head.answer_sig = sig;
        Ok(head)
    }

    fn fence_by_generation(&self, proof: &gunnar_proto::GenerationProof) -> ControlResult<()> {
        crate::twin::fence_by_proof(&self.stores, proof)
            .map(drop)
            .map_err(|err| {
                ControlError::Internal(format!(
                    "fencing this box off as an old generation of its log: {err:#}"
                ))
            })
    }

    fn log_fetch(
        &self,
        from: u64,
        to: u64,
        max_bytes: u64,
    ) -> ControlResult<Vec<gunnar_proto::LogEntry>> {
        let log = self.readable_log()?;
        let entries =
            crate::twin::fetch_range(log, from, to, max_bytes).map_err(log_read_refusal)?;
        Ok(entries
            .into_iter()
            .map(|e| gunnar_proto::LogEntry {
                seq: e.seq,
                kind: e.kind as u32,
                meta: e.meta,
                blob: e.blob,
            })
            .collect())
    }

    /// **`Mirror.LogFetch` off the segments, a piece at a time** (twin-streaming, 2026-10-06):
    /// the refusals now, as the call's status; then [`crate::twin::stream_range`] — the payload
    /// crc of every entry checked before its last piece leaves — through [`ChunkOut`] onto the
    /// wire. What this box holds of an entry is one piece, whatever its size.
    fn log_fetch_stream(
        &self,
        from: u64,
        to: u64,
        max_bytes: u64,
    ) -> ControlResult<gunnar_grpc::seam::LogFetchProducer> {
        self.log_fetch_stream_at(from, 0, to, max_bytes)
    }

    /// [`Self::log_fetch_stream`] with the first entry from byte `from_offset` on
    /// (restore-large-entry, 2026-10-07): [`crate::twin::stream_range_at`].
    fn log_fetch_stream_at(
        &self,
        from: u64,
        from_offset: u64,
        to: u64,
        max_bytes: u64,
    ) -> ControlResult<gunnar_grpc::seam::LogFetchProducer> {
        let log = self.readable_log()?;
        crate::twin::check_range(log, from, to).map_err(log_read_refusal)?;
        let stores = Arc::clone(&self.stores);
        Ok(Box::new(move |sink| {
            let mut out = ChunkOut { sink, open: None };
            crate::twin::stream_range_at(stores.txlog(), from, from_offset, to, max_bytes, &mut out)
                .map(drop)
                .map_err(|err| {
                    let err = match err.downcast::<ControlError>() {
                        Ok(said) => return said,
                        Err(other) => other,
                    };
                    match err.downcast::<gunnar_core::txlog::Error>() {
                        Ok(e) => log_read_refusal(e),
                        Err(other) => ControlError::Internal(format!("transaction log: {other:#}")),
                    }
                })
        }))
    }

    #[cfg(feature = "replication")]
    fn replication_status(
        &self,
        include_refs: bool,
    ) -> ControlResult<gunnar_proto::ReplicationStatusResponse> {
        self.replication_slot()?;
        self.replication_snapshot(include_refs)
    }

    /// **The replication watermark** (`Mirror.FlushReplication`,
    /// `DATA-SET-GROWTH-FLOW.md` §2.2, G2, T11): step 0 of the runtime
    /// growth, and the proof — as far as replication can give one — that the
    /// twin is caught up before `/data` is unmounted.
    ///
    /// The flush half of `replication_abdicate`, alone: optionally enqueue
    /// every repository (`resync`, the only way a repository nobody pushed
    /// since the twin existed reaches it), then wait — bounded — for every
    /// standby's queue to drain. No freeze, no demote. The tuple it answers
    /// is §2.2's conjunction, measured at the end of the wait, and `verdict`
    /// says in words what it proves and what §2.1 says it cannot.
    #[cfg(feature = "replication")]
    fn replication_flush(
        &self,
        request: &gunnar_proto::FlushReplicationRequest,
    ) -> ControlResult<gunnar_proto::FlushReplicationResponse> {
        let slot = self.replication_slot()?;
        let began = gunnar_grpc::bus::now_unix_ms();
        let started = std::time::Instant::now();
        let ceiling = if request.timeout_secs == 0 {
            abdicate_flush_secs()
        } else {
            u64::from(request.timeout_secs)
        };
        let Some(replicator) = slot.replicator() else {
            return Err(ControlError::FailedPrecondition(
                "no replicator is running on this box (no standby configured, or this box is not a primary); there is nothing to flush and nothing to prove".to_owned(),
            ));
        };
        if request.resync {
            replicator
                .resync_scoped(None, None, &[])
                .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        }
        let deadline = started + std::time::Duration::from_secs(ceiling);
        loop {
            let drained = replicator.status().iter().all(|s| s.pending == 0);
            if drained || std::time::Instant::now() >= deadline {
                break;
            }
            std::thread::sleep(std::time::Duration::from_millis(100));
        }
        let status = replicator.status();
        let counters = replicator.counters();
        let pending: u64 = status.iter().map(|s| s.pending as u64).sum();
        let needs_full_resync = status.iter().any(|s| s.needs_full_resync);
        let last_success = status
            .iter()
            .map(|s| s.last_success_unix_ms.unwrap_or(0))
            .min()
            .unwrap_or(0);
        let in_flight = self.admission.as_ref().map(|a| a.in_flight()).unwrap_or(0);
        let catalog_repos = self
            .stores
            .catalog()
            .counts()
            .map(|(_, repos)| repos as u64)
            .unwrap_or(0);
        let standbys = self.replication_snapshot(false)?.standbys;
        let caught_up = in_flight == 0
            && !status.is_empty()
            && pending == 0
            && !needs_full_resync
            && status.iter().all(|s| {
                s.last_success_unix_ms.is_some_and(|t| t >= began)
                    || s.pending == 0 && s.last_success_unix_ms.is_some()
            });
        let verdict = if status.is_empty() {
            "no standby is configured: nothing was flushed and nothing is proven".to_owned()
        } else if caught_up {
            format!(
                "CAUGHT UP as far as replication can prove: {} standby(s), nothing pending, no full-resync hole, {} transfer(s) in flight, {} bus gap(s) since boot{}. What this does NOT prove (DATA-SET-GROWTH-FLOW.md §2.1): refs outside heads/tags, LFS objects, the control database, visibility, tombstones, and — unless `resync` ran once since the twin existed — repositories nobody pushed since",
                status.len(),
                in_flight,
                counters.bus_gaps,
                if request.resync { " (every catalog repository was enqueued)" } else { "" }
            )
        } else {
            let names: Vec<String> = status
                .iter()
                .filter(|s| s.pending > 0 || s.needs_full_resync)
                .map(|s| {
                    format!(
                        "{} (pending {}{})",
                        s.name,
                        s.pending,
                        if s.needs_full_resync {
                            ", needs full resync"
                        } else {
                            ""
                        }
                    )
                })
                .collect();
            format!(
                "NOT caught up after {} s: {} transfer(s) in flight, {} repository(ies) pending [{}]{}; the growth must not unmount the set on this",
                started.elapsed().as_secs(),
                in_flight,
                pending,
                names.join(", "),
                if needs_full_resync { " — a standby has a hole retrying will not close: run `replication resync`" } else { "" }
            )
        };
        tracing::info!(
            target: "gunnar::replication",
            event = "replication.flush",
            caught_up,
            in_flight,
            pending,
            bus_gaps = counters.bus_gaps,
            needs_full_resync,
            waited_ms = started.elapsed().as_millis() as u64,
            "{verdict}"
        );
        Ok(gunnar_proto::FlushReplicationResponse {
            caught_up,
            in_flight,
            pending,
            bus_gaps: counters.bus_gaps,
            needs_full_resync,
            last_success_unix_ms: last_success,
            flushed_at_unix_ms: began,
            waited_ms: started.elapsed().as_millis() as u64,
            standbys,
            catalog_repos,
            verdict,
        })
    }

    /// **Demote: clear EVERY replication target in one write.** The failover
    /// primitive — see the `Mirror.DemoteReplication` proto comment for the
    /// split-brain it closes. A recovered old-primary still lists the box that
    /// is now the new primary, and its replicator force-clobbers the new
    /// primary's post-failover writes; demoting it drops that whole roster so it
    /// can be re-added as the new primary's standby instead.
    ///
    /// Idempotent, and never `NotFound`: unlike `replication_remove`, which
    /// names one standby and must distinguish "removed the one you meant" from
    /// "removed one that was never there", demote clears the lot — a box with no
    /// targets is a perfectly good thing to demote and comes back `Ok` with zero
    /// cleared, because "make sure I am not a primary" must not fail on a box
    /// that already is not one.
    #[cfg(feature = "replication")]
    fn replication_demote(&self) -> ControlResult<gunnar_proto::ReplicationStatusResponse> {
        let slot = self.replication_slot()?;
        let mut config = slot
            .config()
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        config.clear_targets();
        slot.apply(config)
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        self.replication_snapshot(false)
    }

    /// **Set this box's role**: a writable `Primary`, or a read-only `Standby`.
    ///
    /// The one writer. It persists the role into `replication.json` (so it
    /// survives the reboot after a power cut) AND flips the shared
    /// write-gate the SSH/HTTP front doors read — both from
    /// [`ReplicationSlot::apply`], which is the single place the two are kept in
    /// step (one implementation). `PRIMARY` is the **takeover flip** a promoted standby runs;
    /// `STANDBY` is how a box is deliberately made read-only. Idempotent: setting
    /// the role a box already holds writes the same file and the same flag.
    #[cfg(feature = "replication")]
    fn replication_set_role(
        &self,
        role: gunnar_proto::ReplicationRole,
    ) -> ControlResult<gunnar_proto::ReplicationStatusResponse> {
        let slot = self.replication_slot()?;
        let mut config = slot
            .config()
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        let wanted = crate::mirror::Role::from_proto(role);
        // **A browse replica cannot be promoted** (the browse replica). Not by an
        // operator's `SetRole PRIMARY`, not by `abdicate --promote`, not by the
        // passive heartbeat: the box holds only public repositories and serves
        // strangers; as a primary it would be a git host with half the data
        // and an open door. The only way out is `STANDBY`, which narrows what
        // the box serves and keeps it frozen — from there an operator may
        // promote, and by then they have said so twice.
        if config.role.is_browse() && wanted == crate::mirror::Role::Primary {
            return Err(ControlError::FailedPrecondition(
                "this box is a browse replica; it cannot be promoted to primary. It holds only \
                 public repositories and serves anonymous reads — first `gunnar control \
                 replication demote` it to a plain standby, then promote that"
                    .into(),
            ));
        }
        config.role = wanted;
        slot.apply(config)
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        self.replication_snapshot(false)
    }

    /// **Abdicate: the master steps down cleanly, in order.** The voluntary
    /// counterpart to the crash [`Self::replication_demote`] covers, and the
    /// order is the whole difference between a hand-off and a crash:
    ///
    /// 1. **FREEZE** — role → `Standby`, so this box stops taking client writes
    ///    before the flush begins. This closes the residual race `demote` alone
    ///    left open (a client pushing to the box in the window before it is
    ///    demoted): once frozen, there is no such write to lose.
    /// 2. **FLUSH** — resync every standby and wait, with a ceiling, for the
    ///    queues to drain, so the standby has everything that was pending. The
    ///    wait is best-effort: a standby that is down must not wedge the
    ///    abdication forever — the roster still clears below, and a recovered
    ///    standby replays from this box's history when it is re-added the other
    ///    way round.
    /// 3. **DEMOTE** — clear the roster (reusing the same `clear_targets`
    ///    primitive), so the abdicated box can never later clobber the new
    ///    primary.
    ///
    /// It does NOT promote the standby: naming a new primary is the operator's
    /// decision, run as abdication's last act (`SetRole(PRIMARY)` on the
    /// standby — the CLI's `--promote`), never a default this box picks.
    #[cfg(feature = "replication")]
    fn replication_abdicate(&self) -> ControlResult<gunnar_proto::ReplicationStatusResponse> {
        let slot = self.replication_slot()?;

        // 1. FREEZE. role -> Standby, targets untouched (the replicator stays up
        //    for the flush below).
        let mut config = slot
            .config()
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        config.role = crate::mirror::Role::Standby;
        slot.apply(config)
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;

        // 2. FLUSH. Enqueue every repository for every standby, then wait for
        //    the queues to empty, bounded so a dead standby cannot hang the
        //    hand-off. The workers run on the git runtime, so they make progress
        //    while this admin thread sleeps.
        if let Some(replicator) = slot.replicator() {
            replicator
                .resync_scoped(None, None, &[])
                .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
            let deadline =
                std::time::Instant::now() + std::time::Duration::from_secs(abdicate_flush_secs());
            loop {
                let drained = replicator.status().iter().all(|s| s.pending == 0);
                if drained || std::time::Instant::now() >= deadline {
                    break;
                }
                std::thread::sleep(std::time::Duration::from_millis(100));
            }
        }

        // 3. DEMOTE. Clear the roster so this box can never clobber the new
        //    primary. Re-read: the flush did not change the config, but reading
        //    it back keeps this the same load-modify-apply the other verbs use.
        let mut config = slot
            .config()
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        config.clear_targets();
        slot.apply(config)
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
        self.replication_snapshot(false)
    }

    /// **The backfill verb.** See `mirror::Replicator::resync_scoped` for the
    /// gap it closes and why enqueueing is the whole of it.
    ///
    /// Three refusals, each of which would otherwise be a silent nothing:
    ///
    /// * a server with a **configuration but no running replicator** — a target
    ///   is on disk and nothing is draining its queue — is `Unavailable` and not
    ///   an `Ok` with zero queued, because the two read identically and only one
    ///   of them makes a second copy;
    /// * a **standby name that is not configured** is `NotFound`, the same rule
    ///   `replication_remove` already applies;
    /// * a **repository this server does not have** is `NotFound` rather than a
    ///   resync of nothing, because the ordinary way to get there is a typo.
    #[cfg(feature = "replication")]
    fn replication_resync(
        &self,
        name: &str,
        repo: Option<&gunnar_proto::RepoPath>,
        except: &[gunnar_proto::RepoPath],
    ) -> ControlResult<gunnar_proto::ResyncReplicationResponse> {
        let slot = self.replication_slot()?;
        let Some(replicator) = slot.replicator() else {
            return Err(ControlError::Unavailable(format!(
                "no replicator is running, so nothing would drain a backfill queue. \
                 `replication.json` holds {} target(s); the server has not started them.",
                slot.config().map(|c| c.targets.len()).unwrap_or(0)
            )));
        };
        let only = match repo {
            None => None,
            Some(path) => Some(Self::repo_ref(path)?),
        };
        let except = except
            .iter()
            .map(Self::repo_ref)
            .collect::<ControlResult<Vec<_>>>()?;
        let reports = replicator
            .resync_scoped(Some(name), only.as_ref(), &except)
            .map_err(|err| ControlError::NotFound(format!("{err:#}")))?;
        Ok(gunnar_proto::ResyncReplicationResponse {
            standbys: reports
                .into_iter()
                .map(|r| gunnar_proto::ResyncStandby {
                    standby: r.standby,
                    in_scope: r.in_scope,
                    queued: r.queued,
                    already_pending: r.already_pending,
                    refused: r.refused,
                    sha1_repos: r.sha1_repos,
                    excluded: r.excluded,
                })
                .collect(),
            status: Some(self.replication_snapshot(false)?),
        })
    }

    // ── outbound webhooks ──────────────────────────────────────────────────

    #[cfg(feature = "webhooks")]
    fn webhook_add(
        &self,
        request: gunnar_proto::AddWebhookRequest,
    ) -> ControlResult<gunnar_proto::WebhookListResponse> {
        let slot = self.webhook_slot()?;
        let endpoint = crate::webhook::Endpoint {
            name: request.name,
            url: request.url,
            kinds: request.kinds,
            namespace: request.namespace,
            repo: request.repo,
            // An empty secret is "no HMAC", not a secret that is the empty
            // string — so it maps to None and `has_secret` reads false.
            secret: Some(request.secret).filter(|s| !s.is_empty()),
            added_at_unix_ms: gunnar_grpc::bus::now_unix_ms(),
        };
        // `add` validates the URL and the kind names, so a typo is refused here
        // (InvalidArgument) rather than silently delivering nowhere.
        slot.add(endpoint)
            .map_err(|err| ControlError::InvalidArgument(format!("{err:#}")))
    }

    #[cfg(feature = "webhooks")]
    fn webhook_list(&self) -> ControlResult<gunnar_proto::WebhookListResponse> {
        self.webhook_slot()?
            .list_response()
            .map_err(|err| ControlError::Internal(format!("{err:#}")))
    }

    #[cfg(feature = "webhooks")]
    fn webhook_remove(&self, name: &str) -> ControlResult<gunnar_proto::WebhookListResponse> {
        let slot = self.webhook_slot()?;
        slot.remove(name)
            .map_err(|err| ControlError::Internal(format!("{err:#}")))?
            // NotFound and not a silent success: "removed the endpoint" about
            // one that was never there reads identically to removing the one you
            // meant, and the difference is whether events are still being sent.
            .ok_or_else(|| ControlError::NotFound(format!("no webhook endpoint named {name:?}")))
    }
}

/// The largest `Refs.ReadObject` response, and it is **not** a number somebody
/// picked.
///
/// # Measured off the transport, not chosen
///
/// `tonic 0.13.1`'s `DEFAULT_MAX_RECV_MESSAGE_SIZE` is `4 * 1024 * 1024`
/// (`tonic/src/codec/mod.rs:100`; the send default beside it is `usize::MAX`).
/// gunnar overrides neither. So a response larger than this **cannot be
/// received by a client using the generated stub's defaults** — it fails on the
/// client with a length error after the server has already paid for it. Refusing
/// it before inflating turns an expensive failure into a cheap one; it does not
/// turn a working request into a refusal, which is the objection that kept this
/// entry open.
///
/// The refusal is on the size of the **response**, not of the object, so
/// `max_bytes` still works: asking for a 1 KiB prefix of a 1 GiB blob is
/// answered exactly as before.
///
/// # What this alone does NOT fix
///
/// The server still inflates the whole object to produce that prefix, because
/// `ObjectStore` has no bounded read and cannot honestly grow one — a prefix of
/// a delta-encoded object needs its whole base chain (the investigation is in
/// the object-ceiling record, checked against `gix-odb 0.83.0`). Bounding *that* needs a
/// ceiling on the **object**, which is [`DEFAULT_MAX_OBJECT_BYTES`] below.
const MAX_RESPONSE_BYTES: u64 = 4 * 1024 * 1024;

/// The memory this deployment is willing to spend on `Refs.ReadObject`
/// inflations, in total, across every control-plane worker at once.
///
/// 512 MiB. The control plane is an administrative surface — a handful of
/// operators and a UI — sharing a box with the thing that actually matters, the
/// git serving path. Half a gigabyte is a rounding error against a forge host's
/// memory and is far more than object *inspection* has any business using; the
/// number that would need defending is a larger one, not this.
const READ_OBJECT_MEMORY_BUDGET: u64 = 512 * 1024 * 1024;

/// The most control-plane workers that can be inflating at once.
///
/// `read_object` runs **synchronously** on a control-plane worker (the split gave
/// the control plane its own runtime and deliberately did not add
/// `spawn_blocking`), so the number of concurrent inflations is the number of
/// those workers, and further callers queue rather than allocate.
/// [`control_plane_workers`](crate::serve::control_plane_workers) is
/// `cores / 4` clamped to `4..=8` (the handler workers, R5.1-G), so **8** is its ceiling on any machine.
///
/// The clamp's upper bound is used rather than the live count on purpose: a
/// default derived from `available_parallelism()` would make this RPC refuse
/// different requests on a laptop and on the forge host, which is precisely the
/// class of difference that is not found until production.
///
/// **This bound moves** if these methods are ever wrapped in `spawn_blocking` —
/// which `gunnar-grpc/src/seam.rs` still asks for, and the admission record says
/// the gRPC router still has no `ConcurrencyLimitLayer`. On that day the
/// denominator becomes unbounded and this constant is where to start.
const MAX_CONCURRENT_INFLATES: u64 = 8;

/// **The object ceiling** `Refs.ReadObject` refuses above — 64 MiB.
///
/// ```text
///   ceiling  =  memory budget for this RPC  ÷  concurrent inflates
///            =  512 MiB                     ÷  8
///            =  64 MiB          (a 512 MiB worst case, which is the budget)
/// ```
///
/// # This one really does refuse a request that works today
///
/// [`MAX_RESPONSE_BYTES`] costs nobody anything — it declines to build a response
/// no client could receive. This is different: asking for a 1 KiB prefix of a
/// 100 MiB blob is a request the server can answer today and will now refuse,
/// because answering it means materialising 100 MiB to hand back a kilobyte, and
/// eight of those concurrently is 800 MiB out of the git path's memory on an
/// unauthenticated RPC.
///
/// 64 MiB is chosen against what git itself does rather than out of the air: a
/// blob that large is already outside what belongs in a pack — it is what
/// `gunnar-lfs` exists for — and this is an *inspection* surface, not the clone
/// path, which is untouched by this and streams. The refusal names the object's
/// size, so a caller learns the fact rather than a limit.
///
/// A deployment that disagrees sets its own with
/// [`CoreControlPlane::with_max_object_bytes`], including `0` for no ceiling.
const DEFAULT_MAX_OBJECT_BYTES: u64 = READ_OBJECT_MEMORY_BUDGET / MAX_CONCURRENT_INFLATES;

// `PROTECTION_GAP` stood here, and it read:
//
//   > Policy.*: gunnar-core has no store for branch protection or ref-name
//   > policy … Serving this over gRPC needs a policy document in the catalog
//
// There is one — `gunnar_core::PolicyStore`, at `refs/gunnar/policy` — and
// every `Policy.*` verb below is served from it. The constant outlived the
// refusal it explained: `cargo check` called it `never used` while
// `gunnar-ui/docs/coverage.md` was still quoting it to render six console
// panels as disabled. A dead string that a doc still believes is worse than no
// string, so it is gone rather than left as a comment with a name.

// `MIRROR_GAP` stood here too, and it read:
//
//   > Mirror.*: mirroring runs over gunnar-client (nornir-git ls-remote +
//   > fetch), which an S crate must never link (the dependency budget). Use `gunnar mirror` on a
//   > normal-OS host instead
//
// It had already been narrowed from all four verbs to the one that genuinely
// needed a fetch client. That client exists in-tree now —
// `gunnar_wire::fetch_pack`, no gix, no `.git` directory, no worktree, over the
// same `BufRead`/`Write` pair `upload_pack` answers on — so `Mirror.Sync` is
// served rather than refused and the string is gone for the reason
// `PROTECTION_GAP`'s is: a dead refusal a doc still quotes is worse than no
// refusal. `gunnar-cli/tests/policy_mirror.rs` mentions it by name; that is
// prose about the history, and this paragraph is what it now describes.

impl CoreControlPlane {
    /// `Usage.*` is not readable while the data set is unmounted for a growth.
    fn usage_readable(&self) -> ControlResult<()> {
        if self.stores.txlog().is_released()
            || crate::twin::maintenance::is_held(self.stores.root())
        {
            return Err(ControlError::Unavailable(format!(
                "{} this box's data set is being grown (unmounted): its usage is read again after the remount — ask again",
                gunnar_grpc::PRIMARY_GROWING
            )));
        }
        Ok(())
    }

    /// The indexed objects of `namespace`'s OPEN stores, now.
    fn open_objects_of(&self, namespace: &str) -> u64 {
        let prefix = self
            .stores
            .repos_root()
            .canonicalize()
            .unwrap_or_else(|_| self.stores.repos_root().to_path_buf())
            .join(namespace);
        self.stores
            .engine()
            .open_object_counts()
            .into_iter()
            .filter(|(dir, _)| dir.parent() == Some(prefix.as_path()))
            .map(|(_, n)| n)
            .sum()
    }

    /// **One `NamespaceUsage` row**: what the ledger holds, the open objects,
    /// and the FLOW half off the flow ledger's live atomics.
    fn usage_row(
        &self,
        name: &str,
        held: &crate::usage_ledger::Held,
        objects: u64,
        measured_at_unix_ms: i64,
    ) -> gunnar_proto::NamespaceUsage {
        let mut row = gunnar_proto::NamespaceUsage {
            namespace: name.to_owned(),
            measured_at_unix_ms,
            pack_bytes: held.bytes.pack,
            cache_bytes: held.bytes.cache,
            lfs_bytes: held.bytes.lfs,
            tombstoned_bytes: held.tombstoned_bytes,
            repos: held.repos,
            objects,
            ..Default::default()
        };
        fill_flow(&mut row, self.stores.flow(), name, measured_at_unix_ms);
        row
    }

    /// **Every namespace, walked now** (`Usage.ReadAll`): the full recount —
    /// one catalog list, one tombstone walk, every repository's directory. The
    /// reading the usage ledger must always agree with.
    fn usage_all(&self) -> ControlResult<Vec<gunnar_proto::NamespaceUsage>> {
        let catalog = self.stores.catalog();
        let namespaces: Vec<String> = catalog
            .namespaces()
            .map_err(internal)?
            .into_iter()
            .map(|ns| ns.name)
            .collect();
        let repos = catalog.list(None).map_err(internal)?;
        let tombstones = self.stores.tombstones().unwrap_or_default();
        let open_objects: std::collections::HashMap<std::path::PathBuf, u64> = self
            .stores
            .engine()
            .open_object_counts()
            .into_iter()
            .collect();
        let flow = self.stores.flow();
        let measured_at_unix_ms = gunnar_core::now_ms();
        let mut by_ns: std::collections::HashMap<&str, Vec<&gunnar_core::Repo>> =
            std::collections::HashMap::new();
        for repo in &repos {
            by_ns.entry(repo.namespace.as_str()).or_default().push(repo);
        }
        let mut out = Vec::with_capacity(namespaces.len());
        for name in namespaces {
            let mut row = gunnar_proto::NamespaceUsage {
                namespace: name.clone(),
                measured_at_unix_ms,
                ..Default::default()
            };
            for repo in by_ns.get(name.as_str()).map(Vec::as_slice).unwrap_or(&[]) {
                let path = RepoRef::new(&repo.namespace, &repo.name).map_err(|err| {
                    ControlError::Internal(format!(
                        "a catalogued repository has an illegal path: {err}"
                    ))
                })?;
                let dir = self
                    .stores
                    .repo_dir(&path)
                    .map_err(|err| ControlError::Internal(format!("{err:#}")))?;
                let bytes = repo_bytes(&dir);
                row.repos += 1;
                row.pack_bytes += bytes.pack;
                row.cache_bytes += bytes.cache;
                row.lfs_bytes += bytes.lfs;
                row.objects += open_objects.get(&dir).copied().unwrap_or(0);
            }
            row.tombstoned_bytes = tombstones
                .iter()
                .filter(|t| t.path.namespace() == name)
                .map(|t| t.bytes)
                .sum();
            fill_flow(&mut row, flow, &name, measured_at_unix_ms);
            out.push(row);
        }
        Ok(out)
    }
}

/// ── the FLOW half of a usage row ────────────────────────────────────────────
///
/// Everything else in a row is what the namespace HOLDS, and it reads the same
/// for a tenant who pushed this morning and a tenant who last touched this box
/// in March. These seven are what MOVED, read off the flow ledger's live
/// atomics — no walk, no disk, one hash lookup — so that a console showing a
/// usage row can tell a working customer from a silent one without a second
/// call.
///
/// A namespace nothing has moved through today has zeroes here, and for a flow
/// meter a zero is a fact: a transfer either occurred or it did not.
/// `last_push_unix_ms` and `last_fetch_unix_ms` are the exception and look back
/// over the WHOLE kept window, because "how long has this tenant been quiet" is
/// the question they exist for.
fn fill_flow(
    row: &mut gunnar_proto::NamespaceUsage,
    flow: &gunnar_core::FlowLedger,
    name: &str,
    now_unix_ms: i64,
) {
    let glance = flow.glance(name, now_unix_ms);
    row.bytes_in_today = glance.today.bytes_in;
    row.bytes_out_today = glance.today.bytes_out;
    row.pushes_today = glance.today.pushes;
    row.fetches_today = glance.today.fetches;
    row.refused_today = glance.today.refused();
    row.last_push_unix_ms = glance.last_push_unix_ms;
    row.last_fetch_unix_ms = glance.last_fetch_unix_ms;
}

/// Loose object count and total bytes under `objects/`.
///
/// Walked rather than estimated: `Admin.StorageInfo` exists so an operator can
/// see what is actually on the disk, and a number that came from a guess would
/// be worse than no number.
fn object_dir_stats(git_dir: &std::path::Path) -> (u64, u64) {
    fn walk(dir: &std::path::Path, loose: &mut u64, bytes: &mut u64, in_loose_shard: bool) {
        let Ok(entries) = std::fs::read_dir(dir) else {
            return;
        };
        for entry in entries.flatten() {
            let Ok(kind) = entry.file_type() else {
                continue;
            };
            let name = entry.file_name();
            let name = name.to_string_lossy();
            if kind.is_dir() {
                // A loose-object shard is two hex characters.
                let shard = name.len() == 2 && name.chars().all(|c| c.is_ascii_hexdigit());
                walk(&entry.path(), loose, bytes, shard);
            } else if kind.is_file() {
                if in_loose_shard {
                    *loose += 1;
                }
                if let Ok(meta) = entry.metadata() {
                    *bytes += meta.len();
                }
            }
        }
    }
    let mut loose = 0;
    let mut bytes = 0;
    walk(&git_dir.join("objects"), &mut loose, &mut bytes, false);
    (loose, bytes)
}

/// **One repository's bytes, attributed per file.** The one walk both
/// `Admin.StorageInfo` and `Usage.Read` are summed from (one implementation), so the two
/// cannot disagree about what a directory weighs.
///
/// The classification is by file name and is engine-neutral on purpose:
///
/// | file | meter |
/// |---|---|
/// | `<git_dir>/lfs/**` | `lfs` |
/// | `…/objects.exploded*` (znippy's eager and lazy pools) | `cache` |
/// | everything else — `objects.pack` + journal, `objects.index` (the persisted oid index, 2026-09-04), `objects.tail`, `objects.graph`, `refs.log`, `OBJECT_FORMAT`; gix's `objects/**` and refs (`objects.ordinal` is gone as of 2026-09-04 — the index's oid column is the ordinal space; a stale one is deleted at open) | `pack` |
///
/// `pack` is therefore "the hot tier minus the exploded cache" exactly as
/// `usage.proto` promises — it includes the derived index files, which are
/// re-derivable, because that is the contract monetize's own client-side sum
/// reaches and two definitions of one bill is the thing to avoid. The file
/// list is written in `usage.proto`'s header; a new file the engine grows lands
/// in `pack` until somebody names it, which errs on the side of the operator
/// seeing it rather than not.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct RepoBytes {
    /// The truth and its indexes: everything that is neither cache nor LFS.
    pub pack: u64,
    /// znippy's exploded read cache, as it is on the disk right now.
    pub cache: u64,
    /// LFS objects, committed and in flight.
    pub lfs: u64,
}

impl RepoBytes {
    /// The whole directory minus LFS: what `RepoStorage.hot_bytes` reports.
    pub fn hot(&self) -> u64 {
        self.pack + self.cache
    }
}

/// See [`RepoBytes`].
pub fn repo_bytes(git_dir: &std::path::Path) -> RepoBytes {
    fn walk(dir: &std::path::Path, acc: &mut RepoBytes) {
        let Ok(entries) = std::fs::read_dir(dir) else {
            return;
        };
        for entry in entries.flatten() {
            let Ok(meta) = entry.metadata() else {
                continue;
            };
            if meta.is_dir() {
                walk(&entry.path(), acc);
            } else if entry
                .file_name()
                .to_string_lossy()
                .starts_with("objects.exploded")
            {
                acc.cache += meta.len();
            } else {
                acc.pack += meta.len();
            }
        }
    }
    let mut acc = RepoBytes::default();
    let Ok(entries) = std::fs::read_dir(git_dir) else {
        return acc;
    };
    for entry in entries.flatten() {
        let Ok(meta) = entry.metadata() else {
            continue;
        };
        if meta.is_dir() && entry.file_name() == gunnar_lfs::fs_store::LFS_DIR {
            acc.lfs += crate::stores::dir_bytes(&entry.path());
        } else if meta.is_dir() {
            walk(&entry.path(), &mut acc);
        } else {
            acc.pack += meta.len();
        }
    }
    acc
}

// ───────────────────────────────────────────────────────────────────────────
// ACL identity: the gRPC gate's two questions, answered by `AuthTable`
// ───────────────────────────────────────────────────────────────────────────

/// **The one place gRPC identity is decided, and it decides nothing itself.**
///
/// `gunnar-grpc` closed the allow-all authentication hole with SSH-key-derived
/// identity: a caller signs a single-use challenge with a key that is already
/// in the ACL key table, and the gate asks the control plane two questions:
/// *whose key is this*, and *may they*. Both are delegated here, and both land
/// on [`AuthTable`]:
///
/// | question | answered by |
/// |---|---|
/// | whose key is this | [`AuthTable::principal_by_fingerprint`] (expiry included) |
/// | may they | [`AuthTable::may_server`] / [`AuthTable::may_namespace`] / [`AuthTable::may`] |
///
/// So gRPC and SSH share one identity table and **one** ACL. Revoking a key
/// over gRPC revokes it for git in the same instant, and there is no second
/// grant decision that could drift from the first — one implementation,
/// because two disagreeing security checks have cost this design once already.
impl gunnar_grpc::Identity for CoreControlPlane {
    /// The installer's feed, as `crate::fed_principals::note_fed` left it: the
    /// keys this primary will enrol and has not yet.
    fn awaiting_enrolment(&self, fingerprint: &str) -> Option<String> {
        self.stores.awaiting_enrolment(fingerprint)
    }

    fn registered_key(
        &self,
        fingerprint: &str,
    ) -> ControlResult<Option<gunnar_grpc::RegisteredKey>> {
        // A malformed fingerprint is "no such key", not an error: the string
        // came off a public port and refusing to parse it loudly would make
        // this an oracle for what a well-formed fingerprint looks like.
        let Ok(parsed) = gunnar_core::Fingerprint::parse(fingerprint) else {
            return Ok(None);
        };
        // `principal_by_fingerprint` is the SSH listener's own lookup; it
        // already refuses an expired key and a key whose principal is gone.
        let Some(principal) = self
            .stores
            .auth()
            .principal_by_fingerprint(&parsed)
            .map_err(internal)?
        else {
            return Ok(None);
        };
        let key = self
            .stores
            .auth()
            .keys_of(&principal.id)
            .map_err(internal)?
            .into_iter()
            .find(|key| key.fingerprint_sha256 == fingerprint);
        let machine = principal.kind == gunnar_core::PrincipalKind::Machine;
        Ok(key.map(|key| gunnar_grpc::RegisteredKey {
            principal_id: principal.id,
            machine,
            // The `authorized_keys` line the key was registered from. The gate
            // verifies the sshsig against it and re-derives the fingerprint
            // from it, so a wrong row here cannot become a wrong identity.
            openssh: key.openssh,
        }))
    }

    /// The X.509 half of the **same** table `registered_key` reads.
    ///
    /// `gunnar control bootstrap` has minted client certificates and registered
    /// them under `algo: "x509"` since the certificate-identity plan's first-boot
    /// half landed; until the listener grew mTLS there was nothing that could
    /// look one up, so those registrations were inert. This is the lookup, and it
    /// is deliberately the
    /// same three steps `registered_key` takes — hash, principal, key row — so
    /// that revoking a certificate over gRPC revokes it for the handshake in
    /// the same instant, out of one table (one implementation).
    ///
    /// No `openssh` line comes back and none is wanted: the handshake already
    /// proved possession, so there is no second signature to check. See
    /// [`gunnar_grpc::CertificateIdentity`].
    fn registered_certificate(
        &self,
        der: &[u8],
    ) -> ControlResult<Option<gunnar_grpc::CertificateIdentity>> {
        // The one place that decides what bytes a certificate credential is.
        // `gunnar-grpc` hands the DER across the seam rather than a
        // fingerprint precisely so this stays the only spelling of it.
        let fingerprint = gunnar_core::auth::fingerprint_of_certificate(der);
        let Some(principal) = self
            .stores
            .auth()
            .principal_by_fingerprint(&fingerprint)
            .map_err(internal)?
        else {
            return Ok(None);
        };
        // `principal_by_fingerprint` already refuses an expired key and a key
        // whose principal is gone. The row is re-read so that a fingerprint
        // that resolves to a principal but has no key row — a state only a
        // corrupted table can be in — is "no identity" rather than an
        // identity with no credential behind it.
        let registered = self
            .stores
            .auth()
            .keys_of(&principal.id)
            .map_err(internal)?
            .into_iter()
            .any(|key| key.fingerprint_sha256 == fingerprint.to_string());
        if !registered {
            return Ok(None);
        }
        Ok(Some(gunnar_grpc::CertificateIdentity {
            principal_id: principal.id,
            fingerprint: fingerprint.to_string(),
        }))
    }

    /// f-principal-reach: what `fed_principals::install` narrowed a `billing`
    /// principal to, from the data root.
    fn narrowed_methods(&self, principal_id: &str) -> ControlResult<Option<Vec<String>>> {
        // ★ The estate's repair principal is narrowed by its NAME, on every box and in every
        // build (main rebuild, owner 2026-10-12): never admin, whatever it was granted.
        if principal_id == gunnar_grpc::REPAIR_PRINCIPAL {
            return Ok(Some(
                gunnar_grpc::REPAIR_METHODS
                    .iter()
                    .map(|m| m.to_string())
                    .collect(),
            ));
        }
        // The narrowing is written by the fed principals (the `wg-client` build,
        // the appliance's); a build without them narrows nobody.
        #[cfg(feature = "wg-client")]
        return crate::fed_principals::narrowed_of(self.stores.root(), principal_id)
            .map_err(ControlError::Internal);
        #[cfg(not(feature = "wg-client"))]
        {
            let _ = principal_id;
            Ok(None)
        }
    }

    fn may(
        &self,
        principal_id: &str,
        access: &gunnar_grpc::Access,
        level: gunnar_proto::GrantLevel,
    ) -> ControlResult<bool> {
        let level = level_in(level)?;
        let auth = self.stores.auth();
        match access {
            gunnar_grpc::Access::Server => auth.may_server(principal_id, level).map_err(internal),
            gunnar_grpc::Access::Namespace(namespace) => auth
                .may_namespace(principal_id, namespace, level)
                .map_err(internal),
            gunnar_grpc::Access::Repo(path) => {
                let repo_ref = Self::repo_ref(path)?;
                // A grant on a repository that does not exist means nothing.
                // Answering `true` here would let a caller probe the ACL for
                // repositories it cannot see.
                let Some(repo) = self.stores.catalog().get(&repo_ref).map_err(internal)? else {
                    return Ok(false);
                };
                auth.may(principal_id, &repo, level).map_err(internal)
            }
        }
    }

    /// One read of the catalog and one of the identity table for the whole
    /// listing (round 5.3.1); a row that does not exist is `false`, as `may`.
    fn may_each_repo(
        &self,
        principal_id: &str,
        paths: &[RepoPath],
        level: gunnar_proto::GrantLevel,
    ) -> ControlResult<Vec<bool>> {
        let level = level_in(level)?;
        let refs = paths
            .iter()
            .map(Self::repo_ref)
            .collect::<ControlResult<Vec<_>>>()?;
        let rows = self.stores.catalog().get_many(&refs).map_err(internal)?;
        let known: Vec<gunnar_core::model::Repo> = rows.iter().flatten().cloned().collect();
        let mut answers = self
            .stores
            .auth()
            .may_each(principal_id, &known, level)
            .map_err(internal)?
            .into_iter();
        Ok(rows
            .iter()
            .map(|row| row.is_some() && answers.next().unwrap_or(false))
            .collect())
    }
}

// ───────────────────────────────────────────────────────────────────────────
// Policy: the proto shape and the engine shape
// ───────────────────────────────────────────────────────────────────────────

/// One `gunnar_policy::ProtectionRule`, as the protocol spells it.
///
/// The two limit fields come back **0**, which the proto documents as "no
/// limit", and that is the truth about a *per-rule* limit: this engine has
/// none. The repository-wide ceilings live in the policy document's `limits`
/// and are reported by nothing on this service — see `set_protection` for why
/// writing them here is refused rather than approximated.
fn protection_out(rule: &gunnar_policy::ProtectionRule) -> BranchProtection {
    BranchProtection {
        ref_pattern: rule.pattern.as_str().to_owned(),
        allow_force_push: rule.allow_force_push,
        allow_delete: rule.allow_delete,
        require_signature: rule.require_signature,
        // `None` — "anybody" — is the empty list, which is what the proto
        // means by empty. The round trip is stable in both directions.
        allowed_principal_ids: rule.allowed_principals.clone().unwrap_or_default(),
        max_object_bytes: 0,
        max_objects_per_push: 0,
        forbid_self_approval: rule.forbid_self_approval,
        required_approvals: rule.required_approvals,
    }
}

fn ref_name_policy_out(policy: &gunnar_policy::RefNamePolicy) -> RefNamePolicy {
    RefNamePolicy {
        allow_patterns: policy.allow.iter().map(|p| p.as_str().to_owned()).collect(),
        deny_patterns: policy.deny.iter().map(|p| p.as_str().to_owned()).collect(),
    }
}

/// One `gunnar_core::MirrorRecord`, as the protocol spells it.
///
/// The state is **derived from the record's own facts**, not stored beside
/// them: `SYNCING` is a live condition and nothing here runs a sync, so a
/// stored `SYNCING` could only ever be a lie left behind by a crash. What the
/// record can honestly report is `FAILED` when the last attempt left an error
/// and `IDLE` otherwise — and a registration nobody has synced is `IDLE`, which
/// is what it is.
fn mirror_out(record: &gunnar_core::MirrorRecord) -> MirrorConfig {
    let (namespace, repo) = record
        .repo
        .split_once('/')
        .unwrap_or((record.repo.as_str(), ""));
    MirrorConfig {
        repo: Some(RepoPath::new(namespace, repo)),
        remote_url: record.remote_url.clone(),
        prune: record.prune,
        state: if record.last_error.is_empty() {
            gunnar_proto::MirrorState::Idle as i32
        } else {
            gunnar_proto::MirrorState::Failed as i32
        },
        added_at_unix_ms: record.added_at_unix_ms,
        last_sync_at_unix_ms: record.last_sync_at_unix_ms,
        last_error: record.last_error.clone(),
        sync_count: record.sync_count,
        // **The kind, and never the value.** `WebhookEndpoint.has_secret`'s
        // rule, one step wider because there are two kinds here and picking the
        // wrong one is a refusal an operator has to be able to see coming.
        credential: credential_kind_out(record.credential) as i32,
        credential_username: record.credential_username.clone(),
        // Filled in by the caller that holds the queue; a bare record does not
        // know whether a job exists for it.
        job: None,
        repo_pending: record.creates_repo,
        lfs_not_copied: record.lfs_detected,
        ca_subject: record.ca_subject.clone(),
        ca_fingerprint_sha256: record.ca_fingerprint_sha256.clone(),
    }
}

/// **A mirror's private CA, DER** (GUN-MIRROR-CA): what its order trusts beside the
/// public roots, for its own calls alone. Empty when none is set.
fn mirror_ca_of(record: &gunnar_core::MirrorRecord) -> Vec<Vec<u8>> {
    record
        .ca_pem
        .as_deref()
        .map(gunnar_grpc::sso::idp_ca::idp_ca_blocks)
        .unwrap_or_default()
}

/// The proto's credential kind onto the store's.
fn credential_kind_in(
    kind: gunnar_proto::MirrorCredentialKind,
) -> gunnar_core::MirrorCredentialKind {
    match kind {
        gunnar_proto::MirrorCredentialKind::Unspecified => gunnar_core::MirrorCredentialKind::None,
        gunnar_proto::MirrorCredentialKind::SshKey => gunnar_core::MirrorCredentialKind::SshKey,
        gunnar_proto::MirrorCredentialKind::Token => gunnar_core::MirrorCredentialKind::Token,
    }
}

/// The store's credential kind onto the proto's.
fn credential_kind_out(
    kind: gunnar_core::MirrorCredentialKind,
) -> gunnar_proto::MirrorCredentialKind {
    match kind {
        gunnar_core::MirrorCredentialKind::None => gunnar_proto::MirrorCredentialKind::Unspecified,
        gunnar_core::MirrorCredentialKind::SshKey => gunnar_proto::MirrorCredentialKind::SshKey,
        gunnar_core::MirrorCredentialKind::Token => gunnar_proto::MirrorCredentialKind::Token,
    }
}

/// **Unseal the credential a sync dials with, or say there is none.**
///
/// The document is the authority on WHETHER there is one and the secret store
/// on WHAT it is, and a disagreement between them is reported rather than
/// smoothed over: a record that claims a credential whose sealed value is gone
/// would otherwise dial anonymously and be refused by the upstream, which sends
/// an operator to rotate a key that is not the problem.
///
/// The returned [`crate::mirror_fetch::Credential`] is deliberately not
/// `Debug`, so nothing downstream can format it by accident.
fn read_credential(
    stores: &Arc<ServerStores>,
    repo: &gunnar_core::RepoRef,
) -> Result<crate::mirror_fetch::Credential, String> {
    let record = stores
        .mirrors()
        .get(repo)
        .map_err(|err| {
            format!(
                "reading the mirror registration for {}: {err:#}",
                repo.key()
            )
        })?
        .ok_or_else(|| format!("no mirror is registered for {} any more", repo.key()))?;
    if !record.credential.is_set() {
        return Ok(crate::mirror_fetch::Credential::None);
    }
    let secrets = stores
        .secrets()
        .map_err(|err| format!("the sealed secret store is not available: {err:#}"))?;
    let key = gunnar_core::credential_secret_key(repo);
    let sealed = gunnar_store::SecretStore::get(&secrets, &key)
        // `{err}` and not `{err:#}`: this string lands on a job a console
        // renders, and a chain from the secret store is where a value could
        // ride out.
        .map_err(|err| {
            format!(
                "the mirror credential for {} could not be read: {err}",
                repo.key()
            )
        })?
        .ok_or_else(|| {
            format!(
                "{} is registered as having {}, and the sealed value is not in the secret \
                 store. Set it again with `Mirror.SetCredential`; dialling anonymously \
                 instead would be refused by the upstream and read as a bad key.",
                repo.key(),
                record.credential.name()
            )
        })?;
    Ok(match record.credential {
        gunnar_core::MirrorCredentialKind::SshKey => {
            crate::mirror_fetch::Credential::SshKey(sealed)
        }
        gunnar_core::MirrorCredentialKind::Token => crate::mirror_fetch::Credential::Token {
            username: record.credential_username.clone(),
            secret: String::from_utf8(sealed).map_err(|_| {
                format!(
                    "the token stored for {} is not utf-8, so it cannot be an HTTP header value",
                    repo.key()
                )
            })?,
        },
        gunnar_core::MirrorCredentialKind::None => crate::mirror_fetch::Credential::None,
    })
}

/// **One line in the namespace's account audit log** about a mirror sync, and
/// the same on the `gunnar::audit` target (a namespace with no account, a
/// community box, has the target only).
fn audit_line(
    stores: &ServerStores,
    repo: &gunnar_core::RepoRef,
    kind: &str,
    detail: &str,
    refused: bool,
) {
    tracing::info!(
        target: gunnar_grpc::AUDIT_TARGET,
        event = kind,
        repo = %repo.key(),
        detail,
        "mirror"
    );
    let Ok(Some(account)) = stores.auth().account_of_namespace(repo.namespace()) else {
        return;
    };
    let event = gunnar_core::account_audit::AccountEvent {
        kind,
        actor: "",
        actor_role: "system",
        target: &repo.key(),
        detail,
        outcome: if refused {
            gunnar_core::account_audit::Outcome::Refused
        } else {
            gunnar_core::account_audit::Outcome::Ok
        },
    };
    if let Err(err) = stores
        .account_audit()
        .append(&account, event, gunnar_core::now_ms())
    {
        tracing::warn!(target: "gunnar::git", repo = %repo.key(), %err, "a mirror sync's audit line was not written");
    }
}

/// **How a sync ended, audited**: an import's (a first sync's) outcome always,
/// a later sync's only when it failed — a mirror polled every few minutes
/// would otherwise fill the log with "nothing new".
fn audit_mirror_outcome(
    stores: &ServerStores,
    repo: &gunnar_core::RepoRef,
    order: &crate::mirror_queue::MirrorOrder,
    first: bool,
    error: Option<&str>,
    report: &crate::job_queue::Reporter<crate::mirror_queue::Mirror>,
) {
    let upstream = crate::mirror_fetch::scrub(&order.upstream);
    match (first, error) {
        (true, None) => {
            let refs = report
                .snapshot()
                .map(|job| job.report.updates.len())
                .unwrap_or_default();
            audit_line(
                stores,
                repo,
                "mirror.import.done",
                &format!("imported {refs} reference(s) from {upstream}"),
                false,
            );
        }
        (true, Some(why)) => audit_line(
            stores,
            repo,
            "mirror.import.failed",
            &format!("from {upstream}: {why}"),
            true,
        ),
        (false, Some(why)) => audit_line(
            stores,
            repo,
            "mirror.sync.failed",
            &format!("from {upstream}: {why}"),
            true,
        ),
        (false, None) => {}
    }
}

/// **The one place a [`crate::mirror_queue::MirrorJob`] becomes a wire job.**
///
/// `gc_job_out`'s twin, and shaped after it deliberately: three status RPCs
/// render the same queue fields, so a console reads a gc, a purge and a mirror
/// with one renderer.
///
/// `path` is threaded in rather than re-parsed out of the job's own key — it is
/// the request's own path, already validated, and re-parsing it here would be a
/// second resolver that could disagree with the first (one implementation).
fn mirror_job_out(path: &RepoPath, job: crate::mirror_queue::MirrorJob) -> gunnar_proto::MirrorJob {
    // The mirror's own half, taken out whole before the queue's half is: the
    // update list is owned and has to be MOVED onto the wire, and a job's
    // `Deref` only ever lends its report.
    let report = job.report;
    let report_refused = report.refused;
    let (progress_done, progress_total) = job.progress.unwrap_or((0, 0));
    gunnar_proto::MirrorJob {
        job_id: job.job_id,
        path: Some(path.clone()),
        state: match job.state {
            crate::mirror_queue::MirrorState::Queued => gunnar_proto::MirrorJobState::Queued as i32,
            crate::mirror_queue::MirrorState::Running => {
                gunnar_proto::MirrorJobState::Running as i32
            }
            crate::mirror_queue::MirrorState::Done => gunnar_proto::MirrorJobState::Done as i32,
            crate::mirror_queue::MirrorState::Failed => gunnar_proto::MirrorJobState::Failed as i32,
        },
        queue_position: job.queue_position,
        // **`has_progress` first.** A job that has not reached the packfile
        // header has no denominator, and `0/0` would be a progress bar
        // claiming zero per cent instead of admitting it does not know yet.
        has_progress: job.progress.is_some(),
        progress_done,
        progress_total,
        objects: report.objects,
        bytes: report.bytes,
        updates: report
            .updates
            .into_iter()
            .map(|(ref_name, old_oid, new_oid)| gunnar_proto::RefUpdate {
                ref_name,
                old_oid,
                new_oid,
            })
            .collect(),
        error: job.error.unwrap_or_default(),
        enqueued_at_unix_ms: job.enqueued_at_unix_ms,
        started_at_unix_ms: job.started_at_unix_ms,
        finished_at_unix_ms: job.finished_at_unix_ms,
        // Only a FAILED job carries the plan's refusal; a later success of
        // the same registration starts a new job with a fresh report.
        refused_reason: match (job.state, report_refused) {
            (crate::mirror_queue::MirrorState::Failed, crate::mirror_queue::Refusal::Plan) => {
                gunnar_proto::MirrorRefusal::Plan as i32
            }
            (crate::mirror_queue::MirrorState::Failed, crate::mirror_queue::Refusal::PackCap) => {
                gunnar_proto::MirrorRefusal::PackCap as i32
            }
            _ => gunnar_proto::MirrorRefusal::Unspecified as i32,
        },
    }
}

// ── the forge event, across the wire ───────────────────────────────────────
//
// Two functions and no derive, because the wire shape and the signed shape are
// deliberately different things: the signed shape is what `sshsig` covers and
// may never change to suit a transport, and the wire shape is a `oneof` because
// protobuf has no sum type otherwise. Keeping the conversion explicit is what
// makes a change to either one a compile error rather than a silent re-encoding
// that breaks every stored signature.

/// The wire form of a signed membership event.
fn to_proto_membership(
    signed: gunnar_core::SignedMembershipEvent,
) -> gunnar_proto::SignedMembershipEvent {
    gunnar_proto::SignedMembershipEvent {
        event: Some(gunnar_proto::MembershipEvent {
            group: signed.event.group,
            member: signed.event.member,
            action: proto_action(signed.event.action) as i32,
            actor: signed.event.actor,
            at_unix_ms: signed.event.at_unix_ms,
        }),
        key_fingerprint: signed.key_fingerprint,
        signature: signed.signature,
    }
}

/// The signed core form of a wire key attestation. An absent `attestation` is
/// refused rather than defaulted, for the reason `from_proto_membership` gives.
fn from_proto_attestation(
    wire: gunnar_proto::SignedKeyAttestation,
) -> ControlResult<gunnar_core::SignedKeyAttestation> {
    let attestation = wire.attestation.ok_or_else(|| {
        ControlError::InvalidArgument("`attestation.attestation` is required".to_owned())
    })?;
    Ok(gunnar_core::SignedKeyAttestation {
        attestation: gunnar_core::KeyAttestation {
            principal_id: attestation.principal_id,
            fingerprint: attestation.fingerprint,
            at_unix_ms: attestation.at_unix_ms,
        },
        key_fingerprint: wire.key_fingerprint,
        signature: wire.signature,
    })
}

/// The signed core form of a wire membership event.
///
/// An absent `event` or an `UNSPECIFIED` action is refused rather than
/// defaulted: proto3 makes every field optional, and a membership change with
/// no action is not a thing that happened.
fn from_proto_membership(
    wire: gunnar_proto::SignedMembershipEvent,
) -> ControlResult<gunnar_core::SignedMembershipEvent> {
    let event = wire
        .event
        .ok_or_else(|| ControlError::InvalidArgument("`event` is required".to_owned()))?;
    let action = match gunnar_proto::MembershipAction::try_from(event.action) {
        Ok(gunnar_proto::MembershipAction::Add) => gunnar_core::MembershipAction::Add,
        Ok(gunnar_proto::MembershipAction::Remove) => gunnar_core::MembershipAction::Remove,
        _ => {
            return Err(ControlError::InvalidArgument(
                "`event.action` must be ADD or REMOVE".to_owned(),
            ))
        }
    };
    Ok(gunnar_core::SignedMembershipEvent {
        event: gunnar_core::MembershipEvent {
            group: event.group,
            member: event.member,
            action,
            actor: event.actor,
            at_unix_ms: event.at_unix_ms,
        },
        key_fingerprint: wire.key_fingerprint,
        signature: wire.signature,
    })
}

/// The wire enum for a core [`gunnar_core::MembershipAction`].
fn proto_action(action: gunnar_core::MembershipAction) -> gunnar_proto::MembershipAction {
    match action {
        gunnar_core::MembershipAction::Add => gunnar_proto::MembershipAction::Add,
        gunnar_core::MembershipAction::Remove => gunnar_proto::MembershipAction::Remove,
    }
}

/// The wire form of a signed event.
fn to_proto_event(signed: gunnar_core::SignedEvent) -> gunnar_proto::SignedForgeEvent {
    use gunnar_proto::forge_event::Kind;

    let kind = match signed.event.event {
        gunnar_core::Event::Commented {
            body,
            path,
            line,
            blob_oid,
        } => Kind::Commented(gunnar_proto::Commented {
            body,
            path,
            line,
            blob_oid,
        }),
        gunnar_core::Event::Approved { commit } => {
            Kind::Approved(gunnar_proto::Approved { commit })
        }
        gunnar_core::Event::Rejected { commit, reason } => {
            Kind::Rejected(gunnar_proto::Rejected { commit, reason })
        }
        gunnar_core::Event::IssueOpened { title, body } => {
            Kind::IssueOpened(gunnar_proto::IssueOpened { title, body })
        }
        gunnar_core::Event::IssueCommented { body } => {
            Kind::IssueCommented(gunnar_proto::IssueCommented { body })
        }
        gunnar_core::Event::IssueClosed { reason } => {
            Kind::IssueClosed(gunnar_proto::IssueClosed { reason })
        }
    };
    gunnar_proto::SignedForgeEvent {
        event: Some(gunnar_proto::ForgeEvent {
            repo: signed.event.repo,
            pull: signed.event.pull,
            actor: signed.event.actor,
            at_unix_ms: signed.event.at_unix_ms,
            kind: Some(kind),
        }),
        key_fingerprint: signed.key_fingerprint,
        signature: signed.signature,
        attested: signed.attested.map(|a| gunnar_proto::ForgeAttestation {
            session_stepped_up_at_unix_ms: a.session_stepped_up_at_unix_ms,
        }),
    }
}

/// A folded [`gunnar_core::forge::Issue`], as the wire carries it.
///
/// Unlike a review, this IS the whole state — title, body, open — because there
/// is no record behind an issue for a reader to ask instead. The signatures on
/// the events are what make it evidence; the fold is what makes it a state.
fn issue_state(repo: &str, issue: &gunnar_core::forge::Issue) -> gunnar_proto::IssueState {
    gunnar_proto::IssueState {
        repo: repo.to_owned(),
        number: issue.number,
        title: issue.title.clone(),
        body: issue.body.clone(),
        author: issue.author.clone(),
        open: issue.open,
        comments: issue.comments as u64,
        opened_at_unix_ms: issue.opened_at_unix_ms,
    }
}

/// The signed form of a wire event.
///
/// An absent `kind` is refused rather than defaulted: proto3 makes every field
/// optional, and a `ForgeEvent` with no kind is not a thing that happened.
fn from_proto_event(
    wire: gunnar_proto::SignedForgeEvent,
) -> ControlResult<gunnar_core::SignedEvent> {
    use gunnar_proto::forge_event::Kind;

    let event = wire
        .event
        .ok_or_else(|| ControlError::InvalidArgument("`event` is required".to_owned()))?;
    let kind = event
        .kind
        .ok_or_else(|| ControlError::InvalidArgument("`event.kind` is required".to_owned()))?;
    let inner = match kind {
        Kind::Commented(it) => gunnar_core::Event::Commented {
            body: it.body,
            path: it.path,
            line: it.line,
            blob_oid: it.blob_oid,
        },
        Kind::Approved(it) => gunnar_core::Event::Approved { commit: it.commit },
        Kind::Rejected(it) => gunnar_core::Event::Rejected {
            commit: it.commit,
            reason: it.reason,
        },
        Kind::IssueOpened(it) => gunnar_core::Event::IssueOpened {
            title: it.title,
            body: it.body,
        },
        Kind::IssueCommented(it) => gunnar_core::Event::IssueCommented { body: it.body },
        Kind::IssueClosed(it) => gunnar_core::Event::IssueClosed { reason: it.reason },
    };
    Ok(gunnar_core::SignedEvent {
        event: gunnar_core::ForgeEvent {
            repo: event.repo,
            pull: event.pull,
            actor: event.actor,
            at_unix_ms: event.at_unix_ms,
            event: inner,
        },
        key_fingerprint: wire.key_fingerprint,
        signature: wire.signature,
        // A client's word never becomes gunnar's attestation: `forge_append`
        // refuses a wire event that carries one, and only
        // `forge_append_attested` makes one.
        attested: None,
    })
}
#[cfg(test)]
mod tests {
    use super::*;

    /// ★ **A box being RESTORED answers a write UNAVAILABLE, never INTERNAL** (r5.1, integration
    /// dev run 3: the front certifying the twin against a main being restored read "the primary
    /// would not enrol gunnar-twin: the membership: Internal: internal error" for minutes — a bug
    /// to anyone reading the log, and to the guest). Its log follows the twin's until the restore
    /// is whole, so every write is refused: said as "try again", which a generated client retries.
    #[test]
    fn a_write_on_a_restoring_box_is_unavailable_not_internal() {
        let td = tempfile::tempdir().unwrap();
        let stores = crate::stores::ServerStores::open(td.path()).unwrap();
        stores.txlog().set_follower(true);
        let p = gunnar_core::Principal::new("alice", "alice", gunnar_core::PrincipalKind::User)
            .unwrap();
        let err = stores
            .auth()
            .add_principal(p)
            .map_err(internal)
            .expect_err("a follower log takes no write");
        assert!(matches!(err, ControlError::Unavailable(_)), "{err:?}");
        assert!(err.to_string().contains("restor"), "{err}");
    }

    /// **`INTERNAL` must be refused by name, never widened.**
    ///
    /// The regression this locks down was real: `visibility_in` aliased
    /// `INTERNAL` onto `Public` from before 2026-08-03, when public still meant
    /// "any authenticated principal". After that the alias silently PUBLISHED
    /// repositories whose creator asked for the narrower thing, and the
    /// console's visibility picker walked straight into it (2026-08-19).
    /// The green arms are the identity-value guard: without them a
    /// `visibility_in` that refuses everything would pass the red arm too.
    #[test]
    fn internal_is_refused_by_name_and_the_two_real_visibilities_pass() {
        let err = visibility_in(gunnar_proto::Visibility::Internal)
            .expect_err("INTERNAL has no implementation and must be refused");
        let text = err.to_string();
        assert!(
            text.contains("internal") && text.contains("private"),
            "the refusal must name the value and the real choices: {text}"
        );
        assert_eq!(
            visibility_in(gunnar_proto::Visibility::Public).expect("public is real"),
            Visibility::Public
        );
        assert_eq!(
            visibility_in(gunnar_proto::Visibility::Private).expect("private is real"),
            Visibility::Private
        );
        // Unspecified still lands on the only safe default.
        assert_eq!(
            visibility_in(gunnar_proto::Visibility::Unspecified).expect("unspecified defaults"),
            Visibility::Private
        );
    }

    /// **The abdication flush ceiling is env-tunable, but only UPWARD-sane.**
    ///
    /// The flush is a poll (drained-or-deadline); the ceiling only bounds how
    /// long a slow standby is given before the roster clears. A loaded rig may
    /// need more than the 30 s default, so `GUNNAR_ABDICATE_FLUSH_SECS` raises
    /// it — but a garbage or zero value must NOT collapse it to something that
    /// truncates the flush before a single job drains. The identity-value guard
    /// here is the default-path assert: without it a resolver that ignored the
    /// override entirely (always returning 30) would still pass the "bad input
    /// falls back" arms, so the `120 -> 120` arm is what proves the override is
    /// actually read.
    #[cfg(feature = "replication")]
    #[test]
    fn abdicate_flush_ceiling_honours_a_sane_override_and_rejects_the_rest() {
        // A real, larger ceiling for a loaded box is taken verbatim.
        assert_eq!(
            resolve_flush_secs(Some("120")),
            120,
            "a positive override must win"
        );
        assert_eq!(
            resolve_flush_secs(Some("  90 ")),
            90,
            "surrounding whitespace is trimmed"
        );
        // The default when nothing is set — and it must NOT equal the override
        // above, or the test could not tell a read override from a dead one.
        assert_eq!(resolve_flush_secs(None), ABDICATE_FLUSH_SECS);
        assert_ne!(
            ABDICATE_FLUSH_SECS, 120,
            "default must differ from the override arm"
        );
        // Every wrong shape falls back to the safe default, never to 0.
        assert_eq!(
            resolve_flush_secs(Some("")),
            ABDICATE_FLUSH_SECS,
            "blank falls back"
        );
        assert_eq!(
            resolve_flush_secs(Some("nope")),
            ABDICATE_FLUSH_SECS,
            "non-numeric falls back"
        );
        assert_eq!(
            resolve_flush_secs(Some("0")),
            ABDICATE_FLUSH_SECS,
            "zero would truncate — refused"
        );
        assert_eq!(
            resolve_flush_secs(Some("-5")),
            ABDICATE_FLUSH_SECS,
            "negative does not parse as u64"
        );
    }
}

/// An encryption-key refusal as the control plane says it (CRYPT-YUBI).
fn key_refusal(r: gunnar_core::encryption_key::KeyRefusal) -> ControlError {
    use gunnar_core::encryption_key::KeyRefusal as R;
    match r {
        R::AlreadyHasKey(s) | R::MethodHeld(s) => ControlError::AlreadyExists(s),
        R::NoSuchMethod(s) => ControlError::NotFound(s),
        R::NoKey(s) => ControlError::FailedPrecondition(s),
        R::LastMethod(s) => ControlError::FailedPrecondition(s),
        R::Invalid(s) => ControlError::InvalidArgument(s),
        R::Store(e) => internal(e),
    }
}

fn method_in(
    m: gunnar_proto::UnlockMethod,
) -> ControlResult<gunnar_core::encryption_key::UnlockMethod> {
    Ok(gunnar_core::encryption_key::UnlockMethod {
        id: String::new(),
        kind: gunnar_core::encryption_key::MethodKind::parse(&m.kind).map_err(key_refusal)?,
        label: m.label.trim().to_owned(),
        method_ref: m.method_ref.trim().to_owned(),
        rp_id: m.rp_id.trim().to_owned(),
        wrap: m.wrap,
        added_ms: 0,
    })
}

fn encryption_key_out(
    key: Option<gunnar_core::encryption_key::EncryptionKey>,
) -> gunnar_proto::GetEncryptionKeyResponse {
    match key {
        None => gunnar_proto::GetEncryptionKeyResponse::default(),
        Some(k) => gunnar_proto::GetEncryptionKeyResponse {
            exists: true,
            public_key: k.public_key,
            methods: k
                .methods
                .into_iter()
                .map(|m| gunnar_proto::UnlockMethod {
                    id: m.id,
                    kind: m.kind.word().to_owned(),
                    label: m.label,
                    method_ref: m.method_ref,
                    rp_id: m.rp_id,
                    wrap: m.wrap,
                    added_ms: m.added_ms,
                })
                .collect(),
        },
    }
}

/// How many times a merge checks again against a target that moved under it before it
/// gives up (GUN-MERGE-ENGINE, 2026-11-01).
const MERGE_RECHECKS: usize = 3;

/// The identity gunnar commits a merge as: the committer, never the author.
fn gunnar_ident() -> crate::merge_engine::Ident {
    crate::merge_engine::Ident {
        name: "Gunnar".to_owned(),
        email: "noreply@gunnar.invalid".to_owned(),
    }
}

/// A principal as a commit names it: the display name, and an address under `.invalid`
/// built from the id. gunnar keeps no e-mail address for a principal and never invents a
/// deliverable one.
fn principal_ident(principal: &gunnar_core::Principal) -> crate::merge_engine::Ident {
    crate::merge_engine::Ident {
        name: principal.name.clone(),
        email: format!("{}@gunnar.invalid", principal.id),
    }
}

/// The short form of a ref for a commit message: `refs/heads/topic` is `topic`.
fn short_ref(name: &str) -> &str {
    name.strip_prefix("refs/heads/").unwrap_or(name)
}

/// One attempt at a merge: done, or the target moved under the compare-and-swap.
enum MergeAttempt {
    Done(Box<(PullRequest, MergedRef)>),
    TargetMoved,
}

/// **Which strategy the merge uses** — the caller's ask against what the repository's
/// policy allows and whether the head descends from the target.
fn choose_strategy(
    asked: gunnar_proto::MergeStrategy,
    fast_forward: bool,
    allowed: &gunnar_policy::MergePolicy,
    record: &gunnar_core::PullRecord,
) -> ControlResult<gunnar_proto::MergeStrategy> {
    use gunnar_proto::MergeStrategy as S;
    let behind = || {
        format!(
            "not a fast-forward: {} does not descend from {}",
            record.source_ref, record.target_ref
        )
    };
    let refuse = |line: String| Err(ControlError::FailedPrecondition(line));
    match asked {
        S::FastForward if !allowed.allow_fast_forward => refuse(
            "fast-forward merges are turned off for this repository (policy              merge.allow_fast_forward); merge without asking for one"
                .to_owned(),
        ),
        S::FastForward if !fast_forward => refuse(format!(
            "{}. Merge without asking for a fast-forward (gunnar writes a merge commit), or              rebase or merge locally, push the result, and merge again",
            behind()
        )),
        S::FastForward => Ok(S::FastForward),
        S::MergeCommit if !allowed.allow_merge_commit => refuse(
            "merge commits are turned off for this repository (policy              merge.allow_merge_commit)"
                .to_owned(),
        ),
        S::MergeCommit => Ok(S::MergeCommit),
        S::Squash if !allowed.allow_squash => refuse(
            "squash merges are not turned on for this repository (policy merge.allow_squash)"
                .to_owned(),
        ),
        S::Squash => Ok(S::Squash),
        S::Unspecified => {
            if fast_forward && allowed.allow_fast_forward {
                Ok(S::FastForward)
            } else if allowed.allow_merge_commit {
                Ok(S::MergeCommit)
            } else if allowed.allow_squash {
                Ok(S::Squash)
            } else if fast_forward {
                refuse(
                    "this repository's policy allows no merge strategy (merge.allow_fast_forward,                      merge.allow_merge_commit and merge.allow_squash are all off)"
                        .to_owned(),
                )
            } else {
                refuse(format!(
                    "{}, and this repository allows only fast-forward merges (policy                      merge.allow_merge_commit is off): rebase or merge locally, push the result,                      and merge again",
                    behind()
                ))
            }
        }
    }
}

impl CoreControlPlane {
    /// The merge, or with `dry_run` only its checks: one body, so the check can never
    /// say yes where the merge would say no (GUN-FIELD-TEST, 2026-11-01). A target that
    /// moves under the compare-and-swap is checked again from the top — every gate, the
    /// merge, the conflicts — against the new tip (GUN-MERGE-ENGINE).
    fn merge_or_check(
        &self,
        path: &RepoPath,
        number: u64,
        principal_id: &str,
        options: &gunnar_grpc::MergeOptions,
        dry_run: bool,
    ) -> ControlResult<(PullRequest, MergedRef)> {
        let mut rechecked = false;
        for _ in 0..=MERGE_RECHECKS {
            match self.merge_attempt(path, number, principal_id, options, dry_run, rechecked)? {
                MergeAttempt::Done(out) => return Ok(*out),
                MergeAttempt::TargetMoved => rechecked = true,
            }
        }
        Err(ControlError::FailedPrecondition(format!(
            "the target of pull request #{number} kept moving while gunnar merged it ({}              checks against {} tips); no ref moved — merge again",
            MERGE_RECHECKS + 1,
            MERGE_RECHECKS + 1
        )))
    }

    /// One attempt: every check against the tips as they are now, the merge, the gates
    /// over the merge result, and (not `dry_run`) the write.
    #[allow(clippy::too_many_lines)]
    fn merge_attempt(
        &self,
        path: &RepoPath,
        number: u64,
        principal_id: &str,
        options: &gunnar_grpc::MergeOptions,
        dry_run: bool,
        mut rechecked: bool,
    ) -> ControlResult<MergeAttempt> {
        use gunnar_proto::MergeStrategy as S;
        let repo_ref = Self::repo_ref(path)?;
        let key = repo_ref.to_string();
        let pulls = self.pulls()?;
        let record = pulls
            .get(&key, number)
            .map_err(internal)?
            .ok_or_else(|| ControlError::NotFound(format!("pull request #{number} in {path}")))?;
        if record.state != gunnar_core::PullState::Open {
            return Err(ControlError::FailedPrecondition(format!(
                "pull request #{number} is already {:?}, not open",
                record.state
            )));
        }

        let (repo_record, store) = self.open(path)?;
        let git = store.serve();
        let snapshot = RefSnapshot::read(git).map_err(wire_error)?;
        let source = snapshot
            .resolve(&record.source_ref)
            .map_err(wire_error)?
            .ok_or_else(|| {
                ControlError::FailedPrecondition(format!(
                    "the source branch {} is gone; nothing to merge",
                    record.source_ref
                ))
            })?;
        let target = snapshot
            .resolve(&record.target_ref)
            .map_err(wire_error)?
            .ok_or_else(|| {
                ControlError::FailedPrecondition(format!(
                    "the target branch {} is gone",
                    record.target_ref
                ))
            })?;
        // The caller's check answered another target tip: everything below runs
        // against this one, and the answer says it was checked again.
        if let Some(expected) = &options.expected_target_oid {
            if !expected.eq_ignore_ascii_case(&target.to_string()) {
                rechecked = true;
            }
        }

        // ── MERGED OUTSIDE GUNNAR: the target already holds the head ───────
        //
        // GUN-PR-FIELD-2026-11-01 item 3. source == target is "already up to
        // date", and a target that descends from the head was merged another way
        // (somebody pushed the branch to it). Nothing is left to merge and no ref
        // moves. The answer names the commit on the target that contains the head.
        //
        // ★ SEC-G1 (sec review 2026-11-01): "merged" is an approval claim — webhooks
        // and changelogs believe it — and this branch runs before the review gate. A
        // Write user who resets the branch onto the target's tip (or an ancestor)
        // must not get a rejected pull request recorded merged. So the record is
        // marked merged only when the head carries the approvals the target's review
        // policy asks of a merge (the gate's and the policy's rules, below); else it
        // is CLOSED with "closed: content already on target", and no approval is
        // claimed.
        let budget = gunnar_policy::ancestry::DEFAULT_ANCESTRY_BUDGET;
        let contained = source == target
            || gunnar_policy::ancestry::is_descendant_of(git, &target, &source, budget).map_err(
                |err| {
                    ControlError::FailedPrecondition(format!(
                        "the ancestry walk could not be completed ({err}); refusing rather than \
                         guessing"
                    ))
                },
            )?;
        if contained {
            let approvers =
                self.approvals_enough(&key, number, &record, &repo_record, &source.to_string())?;
            let done = MergedRef {
                ref_name: record.target_ref.clone(),
                old_oid: target.to_string(),
                new_oid: target.to_string(),
                head_oid: source.to_string(),
                rechecked,
                contained_in: target.to_string(),
                approvers: approvers.clone().unwrap_or_default(),
                closed: if approvers.is_some() {
                    String::new()
                } else {
                    gunnar_grpc::CONTENT_ALREADY_ON_TARGET.to_owned()
                },
                ..MergedRef::default()
            };
            if dry_run {
                return Ok(MergeAttempt::Done(Box::new((
                    pull_out(path, record.clone()),
                    done,
                ))));
            }
            if approvers.is_none() {
                let closed = match pulls
                    .close_because(&key, number, gunnar_grpc::CONTENT_ALREADY_ON_TARGET)
                    .map_err(internal)?
                {
                    gunnar_core::PullTransition::Done(record) => record,
                    gunnar_core::PullTransition::NotFound => {
                        return Err(ControlError::NotFound(format!(
                            "pull request #{number} in {path}"
                        )))
                    }
                    gunnar_core::PullTransition::NotOpen(state) => {
                        return Err(ControlError::FailedPrecondition(format!(
                            "pull request #{number} is already {state:?}, not open"
                        )))
                    }
                };
                return Ok(MergeAttempt::Done(Box::new((pull_out(path, closed), done))));
            }
            let merged = self.mark_merged(&pulls, &key, number, &target.to_string())?;
            return Ok(MergeAttempt::Done(Box::new((pull_out(path, merged), done))));
        }

        // ── THE REVIEW GATE ────────────────────────────────────────────────
        //
        // A verified approval must name the commit this is about to move to.
        //
        // `source` and not `record.source_oid`: the record's oid is the tip at
        // CREATION and the branch may have advanced since. The approval names
        // what was reviewed, so if the branch moved after the review, no
        // approval names the new tip and this refuses — which is the whole
        // point. A force-push after a review does not inherit the review, and
        // the refusal says which commit was actually approved so the reviewer
        // can be asked again.
        //
        // Verified, not merely present: `review_state` re-checks every approval
        // against the ACL key table right now, so an approval by a key that has
        // since been revoked stops counting the moment the key does.
        let head = source.to_string();
        // Read once: `review_state` needs the SIGNED events to re-check each
        // approval, and the fold needs the unsigned halves of the same list.
        let signed = self.forge_events()?;
        let events: Vec<gunnar_core::ForgeEvent> = signed
            .iter()
            .filter(|s| s.event.repo == key)
            .map(|s| s.event.clone())
            .collect();
        let review = gunnar_core::forge::fold(number, &events);
        let approved = self.review_state(&key, &review, &signed)?;
        let ok = approved
            .approvals
            .iter()
            .any(|a| a.verified && a.commit == head);
        if !ok {
            let named: Vec<String> = approved
                .approvals
                .iter()
                .map(|a| {
                    format!(
                        "{} → {} [{}]",
                        a.actor,
                        &a.commit[..12.min(a.commit.len())],
                        a.verdict
                    )
                })
                .collect();
            return Err(ControlError::FailedPrecondition(format!(
                "no verified approval names {}, the commit {} is at. gunnar does not merge on \
                 an approval of something else: an approval names the commit it approved, so a \
                 branch that moved after the review has not been reviewed.{}",
                &head[..12.min(head.len())],
                record.source_ref,
                if named.is_empty() {
                    " Nobody has approved this pull request.".to_owned()
                } else {
                    format!(" What is approved: {}", named.join(", "))
                }
            )));
        }

        // ── THE REVIEW POLICY ──────────────────────────────────────────────
        //
        // Who may count, and how many — from the SAME policy document branch
        // protection lives in, on the rules covering the TARGET ref. The gate
        // above asked "is there a verified approval of this tip"; these two
        // fields ask "whose, and how many", and they are policy rather than
        // fact, which is why they live in a `ProtectionRule` an administrator
        // wrote and not in this function's opinion.
        //
        // Distinct by construction: the fold keys approvals by actor, so a
        // principal who approves twice holds ONE entry, and this count can
        // never be inflated by pressing the button again.
        let policy = self.policy_of(&repo_record)?;
        let rules: Vec<&gunnar_policy::ProtectionRule> = policy
            .protection
            .iter()
            .filter(|rule| rule.pattern.matches_ref(&record.target_ref))
            .collect();
        let forbid_self = rules.iter().any(|rule| rule.forbid_self_approval);
        let required = rules
            .iter()
            .map(|rule| rule.required_approvals)
            .max()
            .unwrap_or(0)
            .max(1) as usize;
        let approvers: Vec<&str> = approved
            .approvals
            .iter()
            .filter(|a| a.verified && a.commit == head)
            .map(|a| a.actor.as_str())
            .collect();
        let counted: Vec<&str> = approvers
            .iter()
            .copied()
            .filter(|actor| !(forbid_self && *actor == record.author))
            .collect();
        if forbid_self && counted.is_empty() && !approvers.is_empty() {
            return Err(ControlError::FailedPrecondition(format!(
                "the protection on {} forbids self-approval, and the only verified approval \
                 of {} is the author's own ({}). An author's sign-off on their own work is \
                 not a review; somebody else has to look at it.",
                record.target_ref,
                &head[..12.min(head.len())],
                record.author
            )));
        }
        if counted.len() < required {
            return Err(ControlError::FailedPrecondition(format!(
                "the protection on {} requires {required} distinct verified approvals of {} \
                 and there {} ({}). Approvals by the same principal count once{}.",
                record.target_ref,
                &head[..12.min(head.len())],
                if counted.len() == 1 {
                    "is 1".to_owned()
                } else {
                    format!("are {}", counted.len())
                },
                if counted.is_empty() {
                    "nobody".to_owned()
                } else {
                    counted.join(", ")
                },
                if forbid_self {
                    ", and the author's own does not count here"
                } else {
                    ""
                }
            )));
        }

        // ── THE APPROVAL RULE FOR A MERGE COMMIT (GUN-MERGE-ENGINE) ──────────
        //
        // An approval names a commit, and a merge commit is a commit nobody has
        // approved: it does not exist until this function writes it. The rule:
        // **approvals of the head authorise merging exactly that head into the
        // target tip found here**, and nothing else — the merge commit is the
        // mechanical, conflict-free result of those two inputs, and it says so
        // (`Head:`, `Target:`, one `Approved-by:` per approver). A head that moved
        // has no approval (the gate above); a conflict is refused, never resolved
        // by the server; a target that moved is checked again from the top.
        let approvers: Vec<String> = counted.iter().map(|id| (*id).to_owned()).collect();
        let hash = source.kind();
        let plan = MergedRef {
            ref_name: record.target_ref.clone(),
            old_oid: target.to_string(),
            new_oid: String::new(),
            strategy: S::Unspecified,
            head_oid: source.to_string(),
            conflicts: Vec::new(),
            approvers: approvers.clone(),
            rechecked,
            contained_in: String::new(),
            closed: String::new(),
        };
        let inconclusive = |err: gunnar_policy::Error| {
            // Inconclusive is a refusal, never an allow — the same judgement
            // BranchProtectionGate makes.
            ControlError::FailedPrecondition(format!(
                "the ancestry walk could not be completed ({err}); refusing rather than guessing"
            ))
        };

        let fast_forward = gunnar_policy::ancestry::is_descendant_of(git, &source, &target, budget)
            .map_err(inconclusive)?;
        let strategy = choose_strategy(options.strategy, fast_forward, &policy.merge, &record)?;

        let principal = self
            .stores
            .auth()
            .principal(principal_id)
            .map_err(internal)?
            .ok_or_else(|| {
                // The caller authenticated and passed a grant check to get
                // here, so this is a table that changed underneath the
                // request. Refuse; a merge attributed to nobody is worse
                // than a merge that did not happen.
                ControlError::FailedPrecondition(format!(
                    "the principal {principal_id} is no longer in the identity table; \
                     refusing to move a protected reference for an identity that \
                     cannot be resolved"
                ))
            })?;

        // ── THE MERGE (GUN-MERGE-ENGINE) ───────────────────────────────────
        //
        // Gunnar's own engine over `GitServe::read` (`crate::merge_engine`). It
        // writes nothing: the objects it makes are judged by every gate through
        // the overlay below, and stored only after.
        let mut made = crate::merge_engine::NewObjects::default();
        let engine = |err: crate::merge_engine::EngineError| {
            ControlError::FailedPrecondition(format!(
                "gunnar could not merge {} into {} ({err}); nothing was written",
                record.source_ref, record.target_ref
            ))
        };
        let result = match strategy {
            S::FastForward => source,
            S::MergeCommit | S::Squash => {
                let base = crate::merge_engine::merge_base(git, hash, &target, &source, budget)
                    .map_err(engine)?;
                let tree = |commit| crate::merge_engine::commit_tree(git, hash, commit);
                let (base_tree, ours, theirs) = (
                    tree(&base).map_err(engine)?,
                    tree(&target).map_err(engine)?,
                    tree(&source).map_err(engine)?,
                );
                let mut merger = crate::merge_engine::Merger::new(git, hash, repo_record.encrypted);
                let merged_tree = match merger
                    .merge_trees(Some(&base_tree), &ours, &theirs)
                    .map_err(engine)?
                {
                    crate::merge_engine::TreeMerge::Clean(tree) => tree,
                    crate::merge_engine::TreeMerge::Conflicts(conflicts) => {
                        let listed: Vec<String> =
                            conflicts.iter().map(ToString::to_string).collect();
                        if dry_run {
                            return Ok(MergeAttempt::Done(Box::new((
                                pull_out(path, record.clone()),
                                MergedRef {
                                    strategy,
                                    conflicts: listed,
                                    ..plan
                                },
                            ))));
                        }
                        return Err(ControlError::FailedPrecondition(format!(
                            "merge conflict: {} ({}) and {} ({}) both changed {} {}, and gunnar \
                             does not guess: {}. Nothing was written. Merge {} into {} locally, \
                             resolve them, push, and have the new head reviewed.",
                            record.source_ref,
                            &plan.head_oid[..12],
                            record.target_ref,
                            &plan.old_oid[..12],
                            listed.len(),
                            if listed.len() == 1 { "path" } else { "paths" },
                            listed.join("; "),
                            short_ref(&record.target_ref),
                            short_ref(&record.source_ref),
                        )));
                    }
                };
                made = merger.new;
                let parents = if strategy == S::MergeCommit {
                    vec![target, source]
                } else {
                    vec![target]
                };
                let message = self
                    .merge_message(strategy, &record, git, &source, &target, &approvers, budget);
                let when = std::time::SystemTime::now()
                    .duration_since(std::time::UNIX_EPOCH)
                    .map(|d| d.as_secs() as i64)
                    .unwrap_or(0);
                let bytes = crate::merge_engine::commit_bytes(
                    &merged_tree,
                    &parents,
                    &principal_ident(&principal),
                    &gunnar_ident(),
                    when,
                    &message,
                );
                // GUN-MERGE-SIGN: signed by gunnar's own merge-signing key (minted on the
                // box at first use, never handed out), so a repository that requires
                // signed commits takes the merge; the gates below verify it.
                let key = self
                    .stores
                    .merge_signing_key()
                    .map_err(|err| ControlError::Unavailable(format!("{err:#}")))?;
                let bytes = crate::merge_engine::sign_commit(&bytes, hash, &key).map_err(engine)?;
                made.add_commit(hash, bytes).map_err(engine)?
            }
            S::Unspecified => {
                return Err(ControlError::Internal(
                    "the merge strategy was not decided".to_owned(),
                ))
            }
        };
        let overlay = crate::merge_engine::Overlay::new(git, &made);

        // ── THE GATES, on the merge RESULT ─────────────────────────────────
        //
        // GUN-004: branch protection, the same gate the push path runs —
        // `allowed_principals` and `require_signature` live in the same
        // `ProtectionRule` as the review fields above, and the merge path once
        // skipped them. GUN-MERGE-ENGINE: and the other gates that judge COMMITS
        // (signed commits, the machine-attribution trailer) — a merge commit is a
        // new commit and is judged like one. Over the overlay, so a merge commit
        // that does not exist yet is judged exactly as it will be stored.
        //
        // Not `LimitsGate`, `PushOptionsGate` or `RefNameGate`: a merge has no pack
        // a client sent, no push options and no reference name a client chose.
        let policy_principal = gunnar_policy::Principal {
            id: principal.id.clone(),
            name: principal.name.clone(),
            kind: crate::transport::policy_principal_kind(principal.kind),
        };
        let repo_id = gunnar_policy::RepoId::new(&path.namespace, &path.repo);
        // What this ref move ADDS: the range `target..result`, never an empty
        // pack set (which would make `require_signature` pass by having nothing
        // to look at); see `ancestry::commits_between`.
        let introduced = gunnar_policy::ancestry::commits_between(
            &overlay, &result, &target, budget,
        )
        .map_err(|err| {
            ControlError::FailedPrecondition(format!(
                "the commits this merge would add could not be enumerated ({err}); \
                         refusing rather than running branch protection over an empty set"
            ))
        })?;
        let updates = [gunnar_policy::RefUpdate::from_wire(
            record.target_ref.clone(),
            target,
            result,
        )];
        let keys = crate::transport::key_directory(&self.stores);
        let ctx = gunnar_policy::PushContext::new(
            &policy_principal,
            &repo_id,
            &updates,
            &introduced,
            &overlay,
            &keys,
        );
        let mut gates: Vec<(&str, Box<dyn gunnar_policy::Gate>)> = vec![(
            "branch protection",
            Box::new(gunnar_policy::BranchProtectionGate::new(
                policy.protection.clone(),
            )),
        )];
        if policy.signatures.required {
            gates.push((
                "the signed-commits policy",
                Box::new(gunnar_policy::SignedCommitsGate::new(
                    policy.signatures.clone(),
                )),
            ));
        }
        if policy.ai_trailers.refuse {
            gates.push((
                "the attribution-trailer policy",
                Box::new(gunnar_policy::AiTrailerGate::new(
                    policy.ai_trailers.clone(),
                )),
            ));
        }
        for (label, gate) in &gates {
            match gate.check(&ctx) {
                Ok(gunnar_policy::Verdict::Allow) => {}
                Ok(verdict) => {
                    return Err(ControlError::FailedPrecondition(format!(
                        "{label} refuses this merge: {}",
                        verdict.reason().unwrap_or_default()
                    )));
                }
                // A gate that could not decide refuses, exactly as it does on
                // the push path.
                Err(err) => {
                    return Err(ControlError::FailedPrecondition(format!(
                        "{label} could not decide this merge ({err}); refusing rather \
                         than guessing"
                    )));
                }
            }
        }

        // The check stops here: every gate has answered, nothing is written and
        // the record stays open.
        if dry_run {
            let new_oid = if strategy == S::FastForward {
                result.to_string()
            } else {
                String::new()
            };
            return Ok(MergeAttempt::Done(Box::new((
                pull_out(path, record.clone()),
                MergedRef {
                    strategy,
                    new_oid,
                    ..plan
                },
            ))));
        }

        // ── THE WRITE: the objects, then the ref through the store's CAS ──
        if let Some(pack) = made.pack(hash, git).map_err(engine)? {
            git.put_pack(&pack).map_err(|err| {
                ControlError::Internal(format!(
                    "storing the merge of pull request #{number}: {err:#}; no ref moved"
                ))
            })?;
        }
        if let Err(err) = git.update_ref(
            &record.target_ref,
            Some(target.as_bytes()),
            Some(result.as_bytes()),
        ) {
            // Moved under us: check everything again against the new tip. Not
            // moved: a real failure, said as one.
            let now = RefSnapshot::read(git)
                .map_err(wire_error)?
                .resolve(&record.target_ref)
                .map_err(wire_error)?;
            if now != Some(target) {
                return Ok(MergeAttempt::TargetMoved);
            }
            return Err(ControlError::FailedPrecondition(format!(
                "the target ref could not be moved ({err}); no ref moved — retry"
            )));
        }
        let merged = self.mark_merged(&pulls, &key, number, &result.to_string())?;
        Ok(MergeAttempt::Done(Box::new((
            pull_out(path, merged),
            MergedRef {
                strategy,
                new_oid: result.to_string(),
                ..plan
            },
        ))))
    }

    /// ★ SEC-G1: **the principals whose verified approvals of `head` satisfy the review
    /// policy on the pull request's target** — the review gate's rule (a verified approval
    /// names exactly this commit) and the policy's (`forbid_self_approval`,
    /// `required_approvals`, at least one) — or `None` when they do not.
    fn approvals_enough(
        &self,
        key: &str,
        number: u64,
        record: &gunnar_core::PullRecord,
        repo_record: &gunnar_core::Repo,
        head: &str,
    ) -> ControlResult<Option<Vec<String>>> {
        let signed = self.forge_events()?;
        let events: Vec<gunnar_core::ForgeEvent> = signed
            .iter()
            .filter(|s| s.event.repo == key)
            .map(|s| s.event.clone())
            .collect();
        let review = gunnar_core::forge::fold(number, &events);
        let approved = self.review_state(key, &review, &signed)?;
        let policy = self.policy_of(repo_record)?;
        let rules: Vec<&gunnar_policy::ProtectionRule> = policy
            .protection
            .iter()
            .filter(|rule| rule.pattern.matches_ref(&record.target_ref))
            .collect();
        let forbid_self = rules.iter().any(|rule| rule.forbid_self_approval);
        let required = rules
            .iter()
            .map(|rule| rule.required_approvals)
            .max()
            .unwrap_or(0)
            .max(1) as usize;
        let counted: Vec<String> = approved
            .approvals
            .iter()
            .filter(|a| a.verified && a.commit == head)
            .filter(|a| !(forbid_self && a.actor == record.author))
            .map(|a| a.actor.clone())
            .collect();
        Ok((counted.len() >= required).then_some(counted))
    }

    /// Mark the record merged at `oid`, after the ref has moved.
    fn mark_merged(
        &self,
        pulls: &gunnar_core::Pulls,
        key: &str,
        number: u64,
        oid: &str,
    ) -> ControlResult<gunnar_core::PullRecord> {
        match pulls.mark_merged(key, number, oid).map_err(internal)? {
            gunnar_core::PullTransition::Done(record) => Ok(record),
            // The ref HAS moved; a racing close between our CAS and this write
            // must be reported loudly, not papered over.
            other => Err(ControlError::Internal(format!(
                "the ref moved to {oid} but the record could not be marked merged \
                 ({other:?}); the repository is correct, the record is not"
            ))),
        }
    }

    /// **The merge commit's message**: what was merged, and what authorised it, as
    /// trailers a person (and `git interpret-trailers`) can read — `Pull-request:`,
    /// `Head:`, `Target:` and one `Approved-by:` per approver. A squash also lists the
    /// subjects of the commits it squashed.
    #[allow(clippy::too_many_arguments)]
    fn merge_message(
        &self,
        strategy: gunnar_proto::MergeStrategy,
        record: &gunnar_core::PullRecord,
        git: &dyn GitServe,
        source: &gix_hash::ObjectId,
        target: &gix_hash::ObjectId,
        approvers: &[String],
        budget: usize,
    ) -> String {
        let title = record.title.lines().next().unwrap_or("").trim();
        let mut message = if strategy == gunnar_proto::MergeStrategy::Squash {
            let mut out = format!(
                "{} (#{})\n\nSquashed pull request #{} from {} into {}",
                if title.is_empty() {
                    "Squashed changes"
                } else {
                    title
                },
                record.number,
                record.number,
                short_ref(&record.source_ref),
                short_ref(&record.target_ref),
            );
            let mut commits = gunnar_policy::ancestry::commits_between(git, source, target, budget)
                .unwrap_or_default();
            commits.reverse();
            let subjects = crate::merge_engine::subjects(git, source.kind(), &commits);
            if !subjects.is_empty() {
                out.push_str(":\n");
                for subject in subjects.iter().take(100) {
                    out.push_str(&format!("\n* {subject}"));
                }
            }
            out
        } else {
            let mut out = format!(
                "Merge pull request #{} from {} into {}",
                record.number,
                short_ref(&record.source_ref),
                short_ref(&record.target_ref),
            );
            if !title.is_empty() {
                out.push_str(&format!("\n\n{title}"));
            }
            out
        };
        message.push_str(&format!(
            "\n\nPull-request: #{}\nHead: {source}\nTarget: {target}",
            record.number
        ));
        for id in approvers {
            let ident = match self.stores.auth().principal(id) {
                Ok(Some(p)) => principal_ident(&p),
                _ => crate::merge_engine::Ident {
                    name: id.clone(),
                    email: format!("{id}@gunnar.invalid"),
                },
            };
            message.push_str(&format!("\nApproved-by: {}", ident.line()));
        }
        message.push('\n');
        message
    }
}