runner_manager_agent/

lifecycle.rs

// owner: e3-jit-lifecycle-recovery

//! One ephemeral runner, from an allocation decision to a scrubbed runtime.
//!
//! The ordering in this module is intentional.  An attempt is written before
//! the package or GitHub is touched, the JIT value exists only in a restrictive
//! handoff, and a registration-timeout termination is journalled before the
//! process is signalled.  Recovery uses the same code as ordinary supervision;
//! startup merely supplies the first observation.

#[cfg(test)]
use std::collections::VecDeque;
use std::collections::{BTreeMap, BTreeSet, HashMap};
use std::ffi::OsStr;
use std::fmt;
use std::fs;
use std::io::Write;
use std::num::NonZeroU16;
use std::path::{Path, PathBuf};
use std::sync::{Arc, Mutex};
use std::time::Duration;

use async_trait::async_trait;
use runner_manager_domain::attempt::{
    AttemptOutcome, AttemptState, FailureReason, GithubRunnerObservation, IsolationProviderFailure,
    RecoveryDecision, RecoveryObservation, RecoveryTimeouts, RunnerAttempt, authorize,
    recovery_decision,
};
use runner_manager_domain::execution::{AttemptExecution, Backend, ImageReference};
use runner_manager_domain::model::{AttemptId, Clock, HostId, PolicyId, ScaleTarget};
use runner_manager_domain::path::LocalAbsolutePath;
use runner_manager_domain::policy::ScalePolicy;
use runner_manager_domain::store::{Store, StoreError};
use runner_manager_domain::workspace::{AttemptWorkspace, WorkspacePolicy};
use runner_manager_github::jit::{
    DEFAULT_WORK_FOLDER, EncodedJitConfig, JitError, JitGateway, JitRegistration, JitRunnerRequest,
};
use runner_manager_github::rest::{CancelToken, InventoryGateway};
use runner_manager_platform::process::{
    Adoption, ChildProcess, ProcessIdentity, RestrictiveHandoff, SpawnSpec, Termination,
};
use runner_manager_platform::runner_env::{self, RunnerEnv, RunnerPlatform};
use runner_manager_platform::runner_root::{
    self, RootOwner, RootPreflight, RunnerRootError, default_runner_root,
};
use secrecy::SecretString;

use crate::dependency_caches::DependencyCaches;
use crate::oci::OciProcesses;
use crate::package::{
    InstalledPackage, LastCheck, PackageCache, PackageContents, PackageError, RunnerVersion,
};
use crate::reconcile::{
    AllocationGuard, CleanBackoff, EventSink, LaunchFailure, LaunchRequest, LifecycleEvent,
    OutcomeKind, ReplacementIntent, ReservationWaits, RunnerLauncher, failure_reason_kind,
};

mod windows_hyperv;
pub use windows_hyperv::{WindowsHyperVContainers, WindowsHyperVHostState};

const IDENTITY_FILE: &str = ".runner-process.json";
const FALLBACK_IDENTITY_FILE: &str = ".runner-process.recovery.json";
const UNRESOLVED_PROCESS_FILE: &str = ".runner-process.unresolved";
const RUNNER_ID_FILE: &str = ".github-runner-id";
const TERMINATE_INTENT_FILE: &str = ".terminate-registration-timeout";
const MAX_POST_SPAWN_STOP_ATTEMPTS: usize = 3;

/// Slot-root names a cleaned persistent attempt must not have left behind.
///
/// This is not the rule — the rule is that *nothing* but a real `_work`
/// survives, and [`verify_slot_scrubbed`] enforces that by counting. This list
/// is the second, independent question asked of the same directory: each name
/// is stat-ed directly, so a scrub that skipped one is caught even if the
/// enumeration that was supposed to find it under-reported. Every entry is one
/// of the things `04-security-recovery.md` requires to be proven absent before a
/// slot is released; the encoded JIT handoff is the one exception, matched by
/// its published prefix in [`verify_slot_scrubbed`] because the rest of its name
/// is a UUID. Being compile-time constants, these are also the only entry names
/// a refusal message is allowed to print.
const SENSITIVE_SLOT_ENTRIES: &[&str] = &[
    // Runner binaries and the launchers beside them.
    "bin",
    "externals",
    "run.sh",
    "run.cmd",
    "config.sh",
    "config.cmd",
    // The registration identity GitHub's runner writes for itself, and the
    // per-run environment it reads back.
    ".runner",
    ".credentials",
    ".credentials_rsaparams",
    ".env",
    ".path",
    "_diag",
    // This agent's own process-identity and lifecycle sidecars.
    IDENTITY_FILE,
    FALLBACK_IDENTITY_FILE,
    UNRESOLVED_PROCESS_FILE,
    RUNNER_ID_FILE,
    TERMINATE_INTENT_FILE,
];
#[cfg(test)]
const TEST_LISTENER_READY: &str = ".test-listener-ready";

/// GitHub Runner v2.336.0 accepts JIT configuration for `run` through its
/// secret `ACTIONS_RUNNER_INPUT_JITCONFIG` input. The platform spawn boundary
/// supplies that input from the restrictive handoff; the listener command line
/// must contain only the supported `run` command.
///
/// The environment is the daemon's plus [`runner_env::platform_defaults`], then
/// the dependency caches (`caches`, from [`DependencyCaches::for_launch`]), then
/// the host's `runner.env`, which wins over either of the others.
/// The per-attempt temporary directory goes last and `runner.env` cannot name
/// it. On macOS a runner that still starts throttled is reported
/// ([`SpawnSpec::expect_normal_scheduling`]).
fn runner_listener_spec(
    program: PathBuf,
    runtime: &Path,
    caches: Vec<(&'static str, std::ffi::OsString)>,
    host_env: &RunnerEnv,
) -> SpawnSpec {
    let tmp = runtime.join("tmp");
    let _ = std::fs::create_dir_all(&tmp);
    let defaults = runner_env::platform_defaults(
        RunnerPlatform::current(),
        runtime,
        &runner_env::Inherited::current(),
        Path::exists,
    );
    // The Windows profile the defaults point at. Created even when
    // `runner.env` overrides part of it: it is inside the attempt, so it costs
    // nothing and goes with the attempt.
    for (name, dir) in &defaults {
        if runner_env::DIRECTORY_VARIABLES.contains(name) {
            let _ = std::fs::create_dir_all(dir);
        }
    }
    let mut spec = SpawnSpec::new(program)
        .arg("run")
        .working_dir(runtime)
        .expect_normal_scheduling();
    for (name, value) in runner_env::runner_environment(defaults, caches, host_env) {
        spec = spec.env(name, value);
    }
    spec.env("TMPDIR", &tmp).env("TEMP", &tmp).env("TMP", &tmp)
}

/// Retry bounds for failures that can resolve without operator action.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct RetryPolicy {
    pub max_attempts: u32,
    pub initial: Duration,
    pub maximum: Duration,
}

impl RetryPolicy {
    #[must_use]
    pub const fn bounded(max_attempts: u32, initial: Duration, maximum: Duration) -> Self {
        Self {
            max_attempts,
            initial,
            maximum,
        }
    }

    pub(crate) fn delay(self, failure_index: u32) -> Duration {
        let shift = failure_index.saturating_sub(1).min(31);
        self.initial
            .saturating_mul(1_u32 << shift)
            .min(self.maximum)
    }
}

/// Non-secret lifecycle evidence.  Payloads are identifiers and closed enums;
/// neither the encoded configuration nor child output can enter this type.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum AttemptEvent {
    State {
        attempt: AttemptId,
        state: AttemptState,
    },
    Retry {
        attempt: AttemptId,
        operation: &'static str,
        delay: Duration,
    },
    /// How long each step of a launch took, whether or not it started a
    /// runner, so a slow or failed start can be attributed to the wait for the
    /// allocation lock, the package copy, the JIT request, or the process start.
    Launched {
        attempt: AttemptId,
        started: bool,
        timings: LaunchTimings,
    },
    Adopted {
        attempt: AttemptId,
    },
    RemoteIdentityRecovered {
        attempt: AttemptId,
        runner_id: u64,
    },
    TerminateIntent {
        attempt: AttemptId,
    },
    Terminated {
        attempt: AttemptId,
    },
    /// The attempt's GitHub registration was removed by this agent. Carries the
    /// runner id because that is the identifier an operator sees in the
    /// target's runner settings, and the attempt id is not shown there.
    Deregistered {
        attempt: AttemptId,
        runner_id: u64,
    },
    Concluded {
        attempt: AttemptId,
        outcome: OutcomeKind,
    },
    Cleaned {
        attempt: AttemptId,
        outcome: OutcomeKind,
    },
    QuarantinedOwnedResource {
        attempt: AttemptId,
    },
}

pub trait AttemptEventSink: fmt::Debug + Send + Sync {
    fn emit(&self, event: AttemptEvent);
}

#[derive(Debug, Default)]
pub struct AttemptEventLog(Mutex<Vec<AttemptEvent>>);

impl AttemptEventLog {
    #[must_use]
    pub fn events(&self) -> Vec<AttemptEvent> {
        self.0
            .lock()
            .map(|events| events.clone())
            .unwrap_or_default()
    }
}

impl AttemptEventSink for AttemptEventLog {
    fn emit(&self, event: AttemptEvent) {
        if let Ok(mut events) = self.0.lock() {
            events.push(event);
        }
    }
}

#[derive(Debug, Clone, Copy, Default)]
pub struct NoAttemptEvents;

impl AttemptEventSink for NoAttemptEvents {
    fn emit(&self, _event: AttemptEvent) {}
}

/// Where one launch spent its time. A step the launch never reached is zero.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct LaunchTimings {
    /// Waiting for older launches of this host to reserve first.
    pub order_wait: Duration,
    /// Waiting for the host allocation lock, which another launch may hold, and
    /// for the rest of its pass to be reserved after it.
    pub lock_wait: Duration,
    /// Waiting for a turn to prepare: see [`preparation_turns`].
    pub turn_wait: Duration,
    pub materialize: Duration,
    /// Where `materialize` went.
    pub package: PackageTimings,
    /// The execution provider's preparation: its environment, and the checks
    /// of the host's runner environment and dependency caches.
    pub prepare: Duration,
    pub register: Duration,
    pub spawn: Duration,
}

impl LaunchTimings {
    #[must_use]
    pub fn total(&self) -> Duration {
        self.order_wait
            + self.lock_wait
            + self.turn_wait
            + self.materialize
            + self.prepare
            + self.register
            + self.spawn
    }
}

/// Where a launch's package step went, across its retries.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct PackageTimings {
    /// Waiting for another launch's install, or for copies an install must
    /// not run under.
    pub wait: Duration,
    /// Checking the catalog, and downloading and extracting a package.
    pub install: Duration,
    /// Fingerprinting the trees a copy may trust.
    pub verify: Duration,
    /// Copying or cloning the tree into the runner's runtime.
    pub copy: Duration,
    /// A package was downloaded for this launch.
    pub downloaded: bool,
}

#[derive(Debug, Clone, Copy)]
enum LaunchStep {
    Turn,
    Materialize,
    Prepare,
    Register,
    Spawn,
}

/// Times a launch's steps; beginning one ends the one before, so an early
/// return still leaves the step it failed in measured once [`Self::finish`]
/// runs.
#[derive(Debug)]
struct LaunchStopwatch {
    timings: LaunchTimings,
    running: Option<(LaunchStep, std::time::Instant)>,
}

impl LaunchStopwatch {
    fn new(waits: ReservationWaits) -> Self {
        Self {
            timings: LaunchTimings {
                order_wait: waits.order,
                lock_wait: waits.lock,
                ..LaunchTimings::default()
            },
            running: None,
        }
    }

    fn begin(&mut self, step: LaunchStep) {
        self.finish();
        self.running = Some((step, std::time::Instant::now()));
    }

    fn finish(&mut self) {
        if let Some((step, since)) = self.running.take() {
            let slot = match step {
                LaunchStep::Turn => &mut self.timings.turn_wait,
                LaunchStep::Materialize => &mut self.timings.materialize,
                LaunchStep::Prepare => &mut self.timings.prepare,
                LaunchStep::Register => &mut self.timings.register,
                LaunchStep::Spawn => &mut self.timings.spawn,
            };
            *slot = since.elapsed();
        }
    }
}

/// A launch slower than this is logged as a warning, with its steps.
///
/// A healthy launch is a few seconds; a queued job waits for all of it, and
/// the daemon's default filter drops the `info` line that times every launch.
const SLOW_LAUNCH: Duration = Duration::from_secs(60);

/// The daemon's sink for retries and launch timings; the other attempt events
/// already reach the log through the reconcile sink.
///
/// Every field name is on `d1`'s allow-list, or the redacting layer would log
/// `[redacted]` in its place; `tests::every_field_name_the_attempt_sink_emits_is_allowed`
/// keeps that true.
#[derive(Debug, Clone, Copy, Default)]
pub struct TracingAttemptEvents;

impl AttemptEventSink for TracingAttemptEvents {
    fn emit(&self, event: AttemptEvent) {
        match event {
            AttemptEvent::Retry {
                attempt,
                operation,
                delay,
            } => tracing::warn!(
                event = "attempt_retry",
                attempt_id = %attempt,
                reason = operation,
                retry_in_ms = millis(delay),
            ),
            AttemptEvent::Launched {
                attempt,
                started,
                timings,
            } => {
                macro_rules! launched {
                    ($level:ident, $name:literal) => {
                        tracing::$level!(
                            event = $name,
                            attempt_id = %attempt,
                            duration_ms = millis(timings.total()),
                            order_wait_ms = millis(timings.order_wait),
                            lock_wait_ms = millis(timings.lock_wait),
                            turn_wait_ms = millis(timings.turn_wait),
                            materialize_ms = millis(timings.materialize),
                            package_wait_ms = millis(timings.package.wait),
                            package_install_ms = millis(timings.package.install),
                            package_verify_ms = millis(timings.package.verify),
                            package_copy_ms = millis(timings.package.copy),
                            package_downloaded = timings.package.downloaded,
                            prepare_ms = millis(timings.prepare),
                            register_ms = millis(timings.register),
                            spawn_ms = millis(timings.spawn),
                        )
                    };
                }
                if !started {
                    launched!(warn, "attempt_launch_failed");
                } else if timings.total() >= SLOW_LAUNCH {
                    launched!(warn, "attempt_launch_slow");
                } else {
                    launched!(info, "attempt_launched");
                }
            }
            _ => {}
        }
    }
}

fn millis(duration: Duration) -> u64 {
    u64::try_from(duration.as_millis()).unwrap_or(u64::MAX)
}

/// Whether the demand that justified a retry still exists.
#[async_trait]
pub trait DemandPersistence: fmt::Debug + Send + Sync {
    async fn persists(&self, policy: PolicyId) -> bool;
}

#[derive(Debug, Clone, Copy, Default)]
pub struct PersistentDemand;

#[async_trait]
impl DemandPersistence for PersistentDemand {
    async fn persists(&self, _policy: PolicyId) -> bool {
        true
    }
}

#[async_trait]
pub trait RetryDelay: fmt::Debug + Send + Sync {
    async fn wait(&self, duration: Duration);
}

#[derive(Debug, Clone, Copy, Default)]
pub struct TokioRetryDelay;

#[async_trait]
impl RetryDelay for TokioRetryDelay {
    async fn wait(&self, duration: Duration) {
        tokio::time::sleep(duration).await;
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct JitRequestFailure {
    pub terminal: bool,
    pub reason: FailureReason,
    pub retry_after: Option<Duration>,
}

/// GitHub's authoritative runner state plus the identity returned by inventory.
/// The id is carried independently of the local sidecar so recovery can close
/// the crash boundary immediately after a successful remote registration.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct LifecycleGithubObservation {
    pub status: GithubRunnerObservation,
    pub runner_id: Option<u64>,
}

impl LifecycleGithubObservation {
    #[must_use]
    pub const fn unreachable() -> Self {
        Self {
            status: GithubRunnerObservation::Unreachable,
            runner_id: None,
        }
    }

    #[must_use]
    pub const fn not_registered() -> Self {
        Self {
            status: GithubRunnerObservation::NotRegistered,
            runner_id: None,
        }
    }

    #[must_use]
    pub const fn registered(runner_id: u64, busy: bool) -> Self {
        Self {
            status: GithubRunnerObservation::Registered { busy },
            runner_id: Some(runner_id),
        }
    }
}

/// The two GitHub views the lifecycle needs, combined so one fake can drive
/// registration and authoritative runner telemetry.
#[async_trait]
pub trait LifecycleGithub: fmt::Debug + Send + Sync {
    async fn register(
        &self,
        target: &ScaleTarget,
        request: &JitRunnerRequest,
        cancel: &CancelToken,
    ) -> Result<JitRegistration, JitRequestFailure>;

    async fn observe(
        &self,
        target: &ScaleTarget,
        attempt: AttemptId,
        cancel: &CancelToken,
    ) -> LifecycleGithubObservation;

    /// Remove one runner registration this agent created.
    ///
    /// Answers whether the registration is gone, and is deliberately not
    /// fallible in the `Result` sense: no caller may abandon a conclusion
    /// because GitHub was unreachable. See
    /// [`LifecycleLauncher::deregister_runner`].
    async fn deregister(&self, target: &ScaleTarget, runner_id: u64, cancel: &CancelToken) -> bool;
}

#[async_trait]
impl<T> LifecycleGithub for T
where
    T: JitGateway + InventoryGateway + fmt::Debug + Send + Sync,
{
    async fn register(
        &self,
        target: &ScaleTarget,
        request: &JitRunnerRequest,
        cancel: &CancelToken,
    ) -> Result<JitRegistration, JitRequestFailure> {
        self.generate_jit_config(target, request, cancel)
            .await
            .map_err(|error| {
                let reason = if matches!(&error, JitError::Forbidden { .. }) {
                    FailureReason::Other(
                        "GitHub refused JIT registration with 403; check the App's runner permission and runner-group access"
                            .into(),
                    )
                } else {
                    FailureReason::JitRequestFailed
                };
                JitRequestFailure {
                    terminal: error.is_terminal(),
                    reason,
                    retry_after: error
                        .rate_limited()
                        .map(|limit| limit.delay_from(self.now())),
                }
            })
    }

    async fn observe(
        &self,
        target: &ScaleTarget,
        attempt: AttemptId,
        cancel: &CancelToken,
    ) -> LifecycleGithubObservation {
        let expected_name = runner_name(attempt);
        match self.list_runners(target, cancel).await {
            Ok(inventory) => inventory
                .runners()
                .iter()
                .find(|runner| runner.name == expected_name)
                .map_or(LifecycleGithubObservation::not_registered(), |runner| {
                    LifecycleGithubObservation::registered(runner.id, runner.busy)
                }),
            Err(_) => LifecycleGithubObservation::unreachable(),
        }
    }

    async fn deregister(&self, target: &ScaleTarget, runner_id: u64, cancel: &CancelToken) -> bool {
        self.remove_runner(target, runner_id, cancel).await.is_ok()
    }
}

/// Package/cache operations used by one attempt.
#[async_trait]
pub trait RuntimePackages: fmt::Debug + Send + Sync {
    /// Copy the package into `attempt`'s runtime, adding where the time went
    /// to `timings`.
    async fn materialize(
        &self,
        attempt: &RunnerAttempt,
        timings: &mut PackageTimings,
    ) -> Result<RunnerVersion, FailureReason>;
    fn release(&self, attempt: AttemptId) -> Result<(), FailureReason>;
    fn prune_obsolete_guarded(
        &self,
        authority: PruneAuthority<'_>,
        attempts: &[RunnerAttempt],
    ) -> Result<(), FailureReason>;
}

/// Unforgeable evidence that pruning was reached through e1's launch request.
/// The type is public only because it appears in the public adapter trait; its
/// private field and constructor prevent callers from substituting a guard
/// acquired from an unrelated lock.
pub struct PruneAuthority<'a> {
    _guard: &'a AllocationGuard,
}

impl fmt::Debug for PruneAuthority<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("PruneAuthority")
    }
}

impl<'a> PruneAuthority<'a> {
    fn from_launch_request(guard: &'a AllocationGuard) -> Self {
        Self { _guard: guard }
    }

    #[cfg(test)]
    pub(crate) const fn for_test(guard: &'a AllocationGuard) -> Self {
        Self { _guard: guard }
    }
}

/// What every target of one daemon shares about the one package directory they
/// all use: which trees this process vouches for, and who may touch them.
///
/// Per target, one target's reinstall replaces the tree another target
/// recorded, whose next launch finds it changed and reinstalls in turn: on a
/// host serving two targets, every switch between them was a full download.
#[derive(Debug, Clone, Default)]
pub struct SharedPackages {
    /// Held shared to copy from a tree, exclusive to change one. A cache entry
    /// or seed is not replaced under a copy.
    trees: Arc<tokio::sync::RwLock<()>>,
    trusted: Arc<TrustedTrees>,
    last_check: LastCheck,
    /// The last install that failed, and when: the launches queued behind it
    /// get its answer. See [`CachedRuntimePackages::materialize`].
    failed_install: Arc<Mutex<Option<(std::time::Instant, FailureReason)>>>,
}

impl SharedPackages {
    /// Stops trusting a shared package, unless a later install has replaced the
    /// record this launch read: that one is another package's. The next launch
    /// prepares it again.
    fn discard(
        &self,
        root: &Path,
        origin: &Path,
        contents: &Arc<PackageContents>,
        reason: &'static str,
    ) {
        if self.trusted.forget_if_holding(root, contents) {
            tracing::warn!(
                event = "package_verify_failed",
                reason,
                "a shared runner package does not match its verified archive; it is discarded \
                 and prepared again"
            );
            self.trusted.forget(origin);
        }
    }

    /// What an install ended in, for the launches queued behind it. A terminal
    /// failure is not shared: it would close each of them, with no retry of its
    /// own, and one that succeeded clears the last failure.
    fn note_install(&self, result: Result<(), &FailureReason>) {
        *self
            .failed_install
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner) = result
            .err()
            .filter(|reason| !package_failure_is_terminal(reason))
            .map(|reason| (std::time::Instant::now(), reason.clone()));
    }

    /// What an install that failed while a launch queued since `queued` for it
    /// answered.
    fn install_failed_since(&self, queued: std::time::Instant) -> Option<FailureReason> {
        self.failed_install
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
            .as_ref()
            .filter(|(at, _)| *at >= queued)
            .map(|(_, reason)| reason.clone())
    }

    /// For each target's [`PackageCache`]: the published version is one fact,
    /// so one target's check spares the others theirs, and each check holds
    /// every copy on this host back.
    #[must_use]
    pub fn last_check(&self) -> LastCheck {
        self.last_check.clone()
    }
}

#[cfg(test)]
impl SharedPackages {
    pub(crate) async fn copying(&self) -> tokio::sync::RwLockReadGuard<'_, ()> {
        self.trees.read().await
    }

    /// Trusts `root`'s look as it is now, keeping what it must hold: what an edit
    /// no fingerprint can see leaves behind, as on Windows, or by a superuser.
    pub(crate) fn blind_to_edits_of(&self, root: &Path) {
        let contents = self.trusted.contents_of(root);
        self.trusted.record(root, contents).expect("recorded");
    }

    pub(crate) fn vouches_for(&self, root: &Path) -> bool {
        self.trusted.contents_of(root).is_some()
    }
}

/// Production package adapter.  It takes an e2 lease before returning, so a
/// cache entry can never look unused while its runtime is starting.
#[derive(Debug)]
pub struct CachedRuntimePackages {
    cache: Arc<PackageCache>,
    shared: SharedPackages,
}

/// Add how long `work` took to `slot`.
async fn timed<T>(slot: &mut Duration, work: impl std::future::Future<Output = T>) -> T {
    let began = std::time::Instant::now();
    let result = work.await;
    *slot += began.elapsed();
    result
}

impl CachedRuntimePackages {
    /// Run `work` against a package tree on the blocking pool: a fingerprint
    /// walks ~9,000 entries and a copy can take minutes.
    async fn blocking<T: Send + 'static>(
        &self,
        root: &Path,
        work: impl FnOnce(&TrustedTrees, &Path) -> T + Send + 'static,
    ) -> Result<T, FailureReason> {
        let trusted = Arc::clone(&self.shared.trusted);
        let root = root.to_path_buf();
        tokio::task::spawn_blocking(move || work(&trusted, &root))
            .await
            .map_err(|_| FailureReason::ProcessStartFailed)
    }

    /// One target's view of the package directory the targets of `shared` use.
    #[must_use]
    pub const fn new(cache: Arc<PackageCache>, shared: SharedPackages) -> Self {
        Self { cache, shared }
    }

    /// A copy that cannot be used: removed, and the trees it came from read to see
    /// whose fault it is. A runtime can be touched by a job, or sit on a disk with a
    /// fault, and that is no reason to download anything. A tree that differs is
    /// discarded, and prepared again by the next launch that needs it.
    async fn reject_copy(
        &self,
        attempt: &RunnerAttempt,
        root: &Path,
        origin: &Path,
        contents: &Arc<PackageContents>,
        timings: &mut PackageTimings,
    ) -> Result<(), FailureReason> {
        let (attempt_copy, checking, from) =
            (attempt.clone(), Arc::clone(contents), origin.to_path_buf());
        let differs = timed(
            &mut timings.verify,
            self.blocking(root, move |_, source| {
                let _ = remove_materialized_package(&attempt_copy);
                let shared = checking.verify(source, |_| false);
                shared.and_then(|()| {
                    if from == source {
                        Ok(())
                    } else {
                        checking.verify(&from, |_| false)
                    }
                })
            }),
        )
        .await?;
        if let Err(mismatch) = differs {
            self.shared
                .discard(root, origin, contents, mismatch.as_str());
        }
        Ok(())
    }

    /// The tree a runtime can be copied from right now, under nothing more than
    /// the shared hold: nothing to check for or install, and a tree still as
    /// this process left it.
    async fn ready(
        &self,
        destination: &Path,
        timings: &mut PackageTimings,
    ) -> Result<Option<(InstalledPackage, PathBuf)>, FailureReason> {
        let Some(installed) = self.cache.reusable().map_err(package_failure)? else {
            return Ok(None);
        };
        let destination = destination.to_path_buf();
        let verifying = self.blocking(installed.root(), move |trusted, source| {
            if trusted.holds(source) {
                copy_origin_ready(source, &destination, trusted)
            } else {
                None
            }
        });
        let origin = timed(&mut timings.verify, verifying).await?;
        Ok(origin.map(|origin| (installed, origin)))
    }

    /// Under the exclusive hold: a package installed and trusted, and the tree
    /// to copy it from.
    async fn install_trusted(
        &self,
        destination: &Path,
        timings: &mut PackageTimings,
    ) -> Result<(InstalledPackage, PathBuf), FailureReason> {
        let (mut installed, downloaded) = timed(
            &mut timings.install,
            self.cache.ensure_installed_reporting(),
        )
        .await
        .map_err(package_failure)?;
        timings.downloaded |= downloaded;
        // A cache entry this process did not install, or one that has changed
        // since, may hold a job's edits; replace it with one downloaded and
        // verified now. One this call just downloaded is trusted as it lands.
        // See `TrustedTrees`.
        let fresh = downloaded
            || !timed(
                &mut timings.verify,
                self.blocking(installed.root(), TrustedTrees::holds),
            )
            .await?;
        if fresh && !downloaded {
            // After a restart there is simply no record. With one, this is an edit.
            if self.shared.trusted.contents_of(installed.root()).is_some() {
                tracing::warn!(
                    event = "package_verify_failed",
                    reason = "changed",
                    "a shared runner package changed since it was prepared; it is discarded and \
                     prepared again"
                );
            }
            installed = timed(&mut timings.install, self.cache.reinstall())
                .await
                .map_err(package_failure)?;
            timings.downloaded = true;
        }
        let destination = destination.to_path_buf();
        let contents = installed.contents();
        let origin = timed(
            &mut timings.verify,
            self.blocking(installed.root(), move |trusted, source| {
                if fresh {
                    trusted.record(source, contents)?;
                }
                Ok::<_, std::io::Error>(copy_origin(source, &destination, trusted))
            }),
        )
        .await?
        .map_err(|_| FailureReason::ProcessStartFailed)?;
        Ok((installed, origin))
    }
}

#[async_trait]
impl RuntimePackages for CachedRuntimePackages {
    async fn materialize(
        &self,
        attempt: &RunnerAttempt,
        timings: &mut PackageTimings,
    ) -> Result<RunnerVersion, FailureReason> {
        let destination = attempt.runtime_path().to_path_buf();
        let trees = &self.shared.trees;
        // Only a launch that has something to change goes exclusive, and it lets
        // go before it copies, so the launches queued behind it do not wait for
        // its copy too. Once more if the tree still is not ready: a job edited
        // it meanwhile, or a seed cannot be made here. Then it copies under what
        // it just made, which no other launch can change.
        let mut installs = 0;
        let (hold, (installed, origin)) = loop {
            let queued = std::time::Instant::now();
            let hold = timed(&mut timings.wait, trees.read()).await;
            if let Some(ready) = self.ready(&destination, timings).await? {
                break (hold, ready);
            }
            drop(hold);
            // An install that failed while this launch queued for it answers
            // this launch too. Trying again at once, one queued launch after
            // another, would hold every copy of the package back for as many
            // stalled downloads as there are launches; the launch's own retry,
            // after its back-off, may try the download.
            let exclusive = timed(&mut timings.wait, trees.write()).await;
            if let Some(reason) = self.shared.install_failed_since(queued) {
                return Err(reason);
            }
            let installed = self.install_trusted(&destination, timings).await;
            self.shared.note_install(installed.as_ref().map(|_| ()));
            let ready = installed?;
            installs += 1;
            if installs == 2 {
                break (exclusive.downgrade(), ready);
            }
        };
        // Taken under the hold, so it is the record of the tree this copies. None
        // vouches for a tree with no record: before it is copied, not after.
        let Some(contents) = self.shared.trusted.contents_of(installed.root()) else {
            self.shared.trusted.forget(installed.root());
            return Err(FailureReason::ProcessStartFailed);
        };
        let copied_from = origin.clone();
        // Off the async thread: the daemon runs a current-thread runtime, and a
        // copy can take minutes on a busy disk.
        let copied = timed(
            &mut timings.copy,
            self.blocking(installed.root(), {
                let destination = destination.clone();
                move |trusted, source| {
                    copy_package_from(source, &origin, &destination, trusted)?;
                    // Checked again after the copy: an edit a job made while it ran
                    // moved the entry's print, and the runtime may hold it.
                    if trusted.holds(source) {
                        Ok(())
                    } else {
                        Err(std::io::Error::other(
                            "the runner package changed while copied",
                        ))
                    }
                }
            }),
        )
        .await?;
        if copied.is_err() {
            // Nothing a failed or tainted copy left may reach a retry's copy,
            // which lays out over the same runtime.
            drop(hold);
            self.reject_copy(attempt, installed.root(), &copied_from, &contents, timings)
                .await?;
            return Err(FailureReason::ProcessStartFailed);
        }
        if let Err(error) = self.cache.lease(attempt, installed.version()) {
            // Undoing the copy must not undo the *job* workspace: a persistent
            // slot's `_work` is retained across attempts, and this rollback
            // runs before the attempt that would have owned it ever started.
            drop(hold);
            self.reject_copy(attempt, installed.root(), &copied_from, &contents, timings)
                .await?;
            return Err(package_failure(error));
        }
        // Leased while still holding the trees, so a prune that gets the
        // exclusive hold finds this runtime's lease.
        drop(hold);
        // What runs is this copy, so this copy is what is checked, whatever
        // happened to the shared trees meanwhile: read in full against the
        // archive, under neither the host lock nor the trees' hold.
        let persistent = matches!(attempt.workspace(), AttemptWorkspace::PersistentSlot { .. });
        let checking = Arc::clone(&contents);
        let verified = timed(
            &mut timings.verify,
            self.blocking(installed.root(), move |_, _| {
                checking.verify(&destination, |name| persistent && is_work_folder(name))
            }),
        )
        .await?;
        if let Err(mismatch) = verified {
            let _ = self.cache.release(attempt.id);
            tracing::warn!(
                event = "package_copy_differs",
                attempt_id = %attempt.id,
                reason = mismatch.as_str(),
                "a runner's package copy does not match the package's verified archive; it is \
                 being removed and will not be used"
            );
            self.reject_copy(attempt, installed.root(), &copied_from, &contents, timings)
                .await?;
            return Err(FailureReason::ProcessStartFailed);
        }
        Ok(installed.version().clone())
    }

    fn release(&self, attempt: AttemptId) -> Result<(), FailureReason> {
        self.cache.release(attempt).map_err(package_failure)
    }

    /// Everything but the newest version, when nothing is using the trees: a
    /// copy from an older version, or an install in progress, makes this a
    /// no-op, and a later launch prunes what it left, which costs only disk.
    fn prune_obsolete_guarded(
        &self,
        _authority: PruneAuthority<'_>,
        attempts: &[RunnerAttempt],
    ) -> Result<(), FailureReason> {
        let Ok(_exclusive) = self.shared.trees.try_write() else {
            return Ok(());
        };
        let Some(current) = self.cache.newest_installed().map_err(package_failure)? else {
            return Ok(());
        };
        for installed in self.cache.installed().map_err(package_failure)? {
            if installed.version() != current.version() {
                match self.cache.prune(installed.version(), attempts) {
                    Ok(()) => self.shared.trusted.forget(installed.root()),
                    Err(PackageError::VersionInUse { .. }) => {}
                    Err(error) => return Err(package_failure(error)),
                }
            }
        }
        Ok(())
    }
}

fn package_failure(error: PackageError) -> FailureReason {
    error.failure_reason().unwrap_or(FailureReason::Other(
        "runner package cache operation failed".into(),
    ))
}

fn package_failure_is_terminal(reason: &FailureReason) -> bool {
    matches!(
        reason,
        FailureReason::RunnerPackageUnverified | FailureReason::RunnerVersionRejected
    )
}

/// How many hex characters of the attempt id name its workspace.
///
/// # Why this is not the whole identifier, and why the policy is not in the path
///
/// Windows refuses a path over `MAX_PATH`, and the runner writes deep inside
/// this directory: `_work/<repo>/<repo>/.git/objects/pack/pack-<40 hex>.keep`
/// is 100 characters on its own before the repository is named twice. The
/// layout used to add two full identifiers -- the policy's and the attempt's,
/// 74 characters between them -- and that was enough to put a real checkout
/// over the line. Measured, not guessed: this repository's own CI failed here
/// three times in a row at 264 characters against a limit of 260, with
/// `fatal: cannot write keep file ...: Filename too long`. A repository whose
/// name is ten characters longer would have missed by fourteen.
///
/// The policy identifier is simply redundant -- an attempt identifier is
/// unique on its own, and nothing reads the directory tree to find a policy's
/// attempts, because [`crate::lifecycle::LifecycleLauncher`] asks the journal.
/// Twelve hex characters of the attempt is 48 bits, which for the handful of
/// directories one host holds at once is not a collision anybody will see, and
/// the journal keeps the full identifier either way.
///
/// Together that is 61 characters returned to the repository name.
const WORKSPACE_NAME_LEN: usize = 12;

/// The directory name for one attempt's workspace.
fn workspace_name(id: AttemptId) -> String {
    let full = id.to_string();
    full.chars()
        .filter(|c| *c != '-')
        .take(WORKSPACE_NAME_LEN)
        .collect()
}

/// Where one attempt's files go, and which cleanup algorithm they are owed.
///
/// The pair travels together because journalling them apart is exactly the bug
/// `AttemptWorkspace` exists to prevent: a `runtime_path` under a persistent
/// root recorded as ephemeral would be removed whole, taking the retained job
/// workspace with it.
#[derive(Debug, Clone)]
struct Placement {
    runtime: PathBuf,
    workspace: AttemptWorkspace,
}

/// A runner-root refusal, rendered for the operator who has to fix it.
///
/// `RunnerRootError`'s `Display` already names the path, the relation and the
/// remediation command, and none of its variants can carry a credential — they
/// are paths, and `03-migration-rollout.md` requires the remediation command to
/// reach the operator verbatim.
fn root_failure(error: RunnerRootError) -> LifecycleError {
    // Logged here because here is the last place this is known at all. A launch
    // refused by the runner root fails *before* `record_allocation`, so no
    // attempt row is ever written: `b2` has nothing to carry the failure on and
    // `g2` has nothing to show it from. The lifecycle event keeps only
    // `reason=other`, by `failure_reason_kind`'s rule that no free text may
    // reach an event -- which left the whole refusal reading
    // `runner_start_failed reason=other`, once per poll, naming nothing.
    //
    // What travels is the *kind* and not the sentence, and that is forced rather
    // than chosen: `crate::logging` redacts every field it does not allow-list
    // and then scrubs anything path-shaped out of the ones it does, so a
    // rendered `RunnerRootError` -- which is mostly paths -- reaches the log as
    // `[redacted]`. `error_kind` is allow-listed and `RunnerRootError::kind` is
    // a closed vocabulary that survives the scrub, so this names which of a
    // dozen causes the operator has. The paths and the remediation reach them
    // through the command line, which is not redacted.
    tracing::warn!(
        error_kind = error.kind(),
        "the runner root refused this launch, so no attempt was created; the host will \
         retry every poll until the cause is resolved. Re-running `host set-runtime-root` \
         with the same path re-runs this check and prints the directory and the \
         remediation in full"
    );
    LifecycleError::Failed(FailureReason::Other(error.to_string()))
}

/// The lowest positive slot inside `ceiling` that no uncleaned attempt holds.
///
/// `leases` is the journal's answer to "which slots are leased"
/// (`Store::slot_leases_for_policy`), which deliberately includes a terminal
/// attempt whose cleanup has not finished: that attempt still owns its
/// directory, so its slot is not free even though it no longer counts against
/// host capacity. `None` means the ceiling is reached, which is a refusal and
/// not a reason to allocate `s(ceiling + 1)`.
fn lowest_free_slot(leases: &[RunnerAttempt], ceiling: NonZeroU16) -> Option<NonZeroU16> {
    let held: BTreeSet<u16> = leases
        .iter()
        .filter_map(|attempt| attempt.workspace().slot_number())
        .collect();
    (1..=ceiling.get())
        .find(|slot| !held.contains(slot))
        .and_then(NonZeroU16::new)
}

/// Create `<root>/sN`, or prove that what is already there is a real directory.
///
/// A symlink, junction or reparse point standing where the slot should be is
/// refused rather than followed: it is the one thing that could put an attempt's
/// files outside the root the operator configured, and
/// `04-security-recovery.md` requires that case to fail closed rather than to
/// be repaired here.
fn create_or_validate_slot(slot: &Path) -> Result<(), LifecycleError> {
    match fs::symlink_metadata(slot) {
        // [`is_link_like`] and not `is_symlink`, so that this is the same
        // question cleanup asks in [`slot_is_present`]: a reparse tag the
        // standard library has no name for is refused here rather than
        // allocated into and then quarantined forever by a cleanup that will
        // not scrub it.
        Ok(metadata) if is_link_like(&metadata) => Err(slot_refusal(
            slot,
            "is a symbolic link, junction or other reparse point, which could place runner \
             files outside the configured root",
        )),
        Ok(metadata) if !metadata.is_dir() => Err(slot_refusal(slot, "is not a directory")),
        Ok(_) => Ok(()),
        Err(error) if error.kind() == std::io::ErrorKind::NotFound => fs::create_dir(slot)
            .map_err(|source| slot_refusal(slot, format!("could not be created: {source}"))),
        Err(source) => Err(slot_refusal(
            slot,
            format!("could not be inspected: {source}"),
        )),
    }
}

/// Accept a slot for reuse only when it is empty or holds one real `_work`.
///
/// `02-target-architecture.md`: "Before materialization, a reusable slot must
/// contain only a valid real `_work` directory or be empty." Everything else —
/// a leftover `bin/`, a link-shaped `_work`, a stray file — is refused here
/// rather than cleaned, because deciding whether those bytes are safe is
/// cleanup's and recovery's job (`c3`), and quietly reusing them would hand one
/// repository's retained state to the next attempt without anybody choosing to.
///
/// The inspection is one level deep and uses `symlink_metadata`, so nothing is
/// followed while it is being judged.
fn accept_reusable_slot(slot: &Path) -> Result<(), LifecycleError> {
    let unreadable =
        |source: std::io::Error| slot_refusal(slot, format!("could not be read: {source}"));
    let entries = fs::read_dir(slot).map_err(unreadable)?;
    let mut refused: Vec<String> = Vec::new();
    for entry in entries {
        let entry = entry.map_err(unreadable)?;
        let name = entry.file_name();
        let metadata = fs::symlink_metadata(entry.path()).map_err(|source| {
            slot_refusal(
                slot,
                format!("entry {name:?} could not be inspected: {source}"),
            )
        })?;
        // The same predicate cleanup retains by, so a `_work` this accepts is
        // one [`scrub_slot_entries`] will keep rather than refuse: a link, a
        // junction or any other reparse point is not a job workspace to either
        // of them.
        if is_retainable_work_folder(&name, &metadata) {
            continue;
        }
        refused.push(name.to_string_lossy().into_owned());
    }
    if refused.is_empty() {
        return Ok(());
    }
    refused.sort();
    Err(slot_refusal(
        slot,
        format!(
            "holds {} that this attempt may not reuse: [{}]. A reusable slot is empty or holds \
             one real `{DEFAULT_WORK_FOLDER}` directory and nothing else; remove or move the \
             entries listed, or let cleanup and recovery resolve them",
            if refused.len() == 1 {
                "an entry"
            } else {
                "entries"
            },
            refused.join(", ")
        ),
    ))
}

fn slot_refusal(slot: &Path, detail: impl fmt::Display) -> LifecycleError {
    LifecycleError::Failed(FailureReason::Other(format!(
        "the persistent slot {} {detail}",
        slot.display()
    )))
}

/// Whether a directory entry names the retained job workspace.
///
/// The comparison folds case on Windows because the filesystem does: there
/// `_Work` and `_work` are one directory, so a case-sensitive test would let
/// [`scrub_slot_entries`] delete the very directory it exists to keep, let
/// [`accept_reusable_slot`] refuse a slot that holds nothing but a valid job
/// workspace, and let a package's top-level `_Work` merge itself into the
/// previous attempt's `_work`. Elsewhere the two names really are two
/// directories and only the exact one is the job workspace.
fn is_work_folder(name: &OsStr) -> bool {
    if cfg!(windows) {
        name.eq_ignore_ascii_case(DEFAULT_WORK_FOLDER)
    } else {
        name == OsStr::new(DEFAULT_WORK_FOLDER)
    }
}

/// Whether the operating system would follow this entry somewhere else.
///
/// `FileType::is_symlink` is the whole answer on Unix. On Windows it is not:
/// the standard library reports only the symlink and mount-point reparse tags,
/// and the substitution this has to refuse is *any* reparse point standing
/// where a real directory should be. So the attribute bit is the test there,
/// and a tag the standard library has no name for fails closed with the two it
/// does.
fn is_link_like(metadata: &fs::Metadata) -> bool {
    if metadata.file_type().is_symlink() {
        return true;
    }
    #[cfg(windows)]
    {
        use std::os::windows::fs::MetadataExt;

        const FILE_ATTRIBUTE_REPARSE_POINT: u32 = 0x0000_0400;
        metadata.file_attributes() & FILE_ATTRIBUTE_REPARSE_POINT != 0
    }
    #[cfg(not(windows))]
    false
}

/// Whether an entry is the retained job workspace and is safe to retain.
///
/// The two halves are one question. A `_work` that is a file, a symlink, a
/// junction or any other reparse point is not a job workspace, and it is also
/// the exact substitution a hostile workflow makes to send cleanup somewhere
/// else (`04-security-recovery.md`, "A workflow replaces `_work` with a
/// junction or symlink to escape cleanup").
fn is_retainable_work_folder(name: &OsStr, metadata: &fs::Metadata) -> bool {
    is_work_folder(name) && metadata.is_dir() && !is_link_like(metadata)
}

/// Undo one package materialization, dispatching on the journalled workspace.
///
/// The ephemeral half is what this always did: the directory is the attempt's
/// alone, so it goes whole. The persistent half removes the copy and nothing
/// else, because the slot's `_work` predates this attempt and outlives it
/// (`02-target-architecture.md`, "Persistent repository").
fn remove_materialized_package(attempt: &RunnerAttempt) -> std::io::Result<()> {
    match attempt.workspace() {
        AttemptWorkspace::Ephemeral => remove_runtime_tree(attempt.runtime_path()),
        AttemptWorkspace::PersistentSlot { .. } => scrub_slot_entries(attempt.runtime_path())
            .map_err(|quarantine| std::io::Error::other(quarantine.to_string())),
    }
}

/// Remove a disposable runner tree without opening workflow-created special files.
///
/// On Unix, `remove_dir_all` 1.0 can open a FIFO while walking a directory and
/// wait forever for its peer. The .NET runner routinely leaves diagnostic FIFOs
/// in its private `tmp`, so use the standard library's fd-relative Unix remover,
/// which unlinks non-directories without opening them. Keep the external remover
/// on Windows for its existing read-only and long-path handling; when it is
/// refused, [`unlink_reparse_points`] takes every link out of its way and it
/// runs once more.
fn remove_runtime_tree(path: &Path) -> std::io::Result<()> {
    #[cfg(windows)]
    {
        match remove_dir_all::remove_dir_all(path) {
            Err(error) if error.kind() == std::io::ErrorKind::PermissionDenied => {
                unlink_reparse_points(path);
                remove_dir_all::remove_dir_all(path)
            }
            other => other,
        }
    }
    #[cfg(not(windows))]
    {
        fs::remove_dir_all(path)
    }
}

/// Remove every symlink, junction and other reparse point under `dir` as a
/// link, without ever descending into one.
///
/// WinINet creates `…\INetCache\Content.IE5` as a junction whose own DACL denies
/// `Everyone` the right to list it, and a job that points `USERPROFILE` or
/// `LOCALAPPDATA` into its workspace gets one there. Both `remove_dir_all` 1.0
/// and `std::fs::remove_dir_all` then fail on the whole tree with
/// `ERROR_ACCESS_DENIED`, so the attempt could never be cleaned. Removing the
/// link itself is a different operation (`RemoveDirectoryW` on the reparse
/// point) that the deny entry does not cover, and once the links are gone the
/// tree is ordinary.
///
/// Only walked after a refusal, so an ordinary tree is traversed once. The
/// metadata comes from the directory listing itself, which on Windows
/// describes a reparse point without opening it.
///
/// Best effort: a failure here is not reported, because
/// [`remove_runtime_tree`]'s second `remove_dir_all` runs next and its result
/// is the authority on whether the tree went.
#[cfg(windows)]
fn unlink_reparse_points(dir: &Path) {
    let Ok(entries) = fs::read_dir(dir) else {
        return;
    };
    for entry in entries.flatten() {
        let path = entry.path();
        let Ok(metadata) = entry.metadata() else {
            continue;
        };
        if is_link_like(&metadata) {
            let _ = fs::remove_dir(&path).or_else(|_| fs::remove_file(&path));
        } else if metadata.is_dir() {
            unlink_reparse_points(&path);
        }
    }
}

// ---------------------------------------------------------------------------
// Persistent cleanup (`04-security-recovery.md`, "Safe path handling")
// ---------------------------------------------------------------------------

/// Why a persistent slot could not be proven safe to scrub.
///
/// A closed set rather than a formatted string, for two reasons that point the
/// same way. [`LifecycleEvent::AttemptCleanFailed`] takes a `&'static str` for
/// exactly the reason [`crate::reconcile::failure_reason_kind`] documents —
/// free text is the one shape that can carry a credential past a field
/// allow-list. And the entries under a slot root are *workflow-controlled*: a
/// job that writes a file named after a secret would publish it through any
/// message that echoed a directory listing, which is why nothing here ever
/// renders an entry name that did not come from this module's own constants.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum SlotRefusal {
    /// The journalled runtime path is not `<root>/sN` for the journalled slot.
    NotTheJournalledSlot,
    /// A policy that still exists names a different root than the journal does.
    PolicyRootDisagrees,
    /// The slot is not strictly inside its root once components resolve.
    Containment,
    /// The slot itself is a file, a link, or could not be inspected.
    SlotNotADirectory,
    /// The slot's direct entries could not be listed.
    Enumeration,
    /// `_work` is a file, a symlink, a junction or another reparse point.
    WorkNotADirectory,
    /// An entry that had to go could not be removed.
    Deletion,
    /// Something other than the job workspace survived removal.
    Residue,
}

impl SlotRefusal {
    /// The event field: a fixed vocabulary, never operator or workflow text.
    const fn class(self) -> &'static str {
        match self {
            Self::NotTheJournalledSlot => "slot_path_is_not_the_journalled_slot",
            Self::PolicyRootDisagrees => "slot_root_disagrees_with_policy",
            Self::Containment => "slot_escapes_its_root",
            Self::SlotNotADirectory => "slot_is_not_a_directory",
            Self::Enumeration => "slot_could_not_be_enumerated",
            Self::WorkNotADirectory => "retained_work_is_not_a_directory",
            Self::Deletion => "slot_entry_could_not_be_removed",
            Self::Residue => "slot_still_holds_runner_state",
        }
    }

    /// What the operator has to do, in one sentence and with no path in it.
    const fn remediation(self) -> &'static str {
        match self {
            Self::NotTheJournalledSlot | Self::PolicyRootDisagrees | Self::Containment => {
                "the attempt keeps its slot lease and nothing was removed; correct the \
                 repository's persistent workspace path, or remove the slot directory by hand \
                 once you have confirmed what is in it"
            }
            Self::SlotNotADirectory | Self::WorkNotADirectory => {
                "the attempt keeps its slot lease and nothing was removed; a job replaced the \
                 slot or its `_work` with a link, so inspect it before deleting anything and \
                 treat the retained workspace as untrusted"
            }
            Self::Enumeration | Self::Deletion | Self::Residue => {
                "the attempt keeps its slot lease and will be cleaned again on the next pass; \
                 release whatever is holding the files open, or remove the slot's contents by \
                 hand leaving only `_work`"
            }
        }
    }
}

/// A refusal that leaves one persistent slot quarantined.
///
/// `detail` is redacted by construction: it may hold paths this product
/// configured, `std::io::ErrorKind` values, counts, and names drawn from
/// [`SENSITIVE_SLOT_ENTRIES`] — and nothing that came out of a directory
/// listing.
#[derive(Debug, Clone, PartialEq, Eq)]
struct SlotQuarantine {
    refusal: SlotRefusal,
    detail: String,
}

impl SlotQuarantine {
    fn new(refusal: SlotRefusal, detail: impl Into<String>) -> Self {
        Self {
            refusal,
            detail: detail.into(),
        }
    }
}

impl fmt::Display for SlotQuarantine {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}; {}", self.detail, self.refusal.remediation())
    }
}

/// Steps 1 to 3: the journalled root, the journalled slot, and containment.
///
/// Everything comes from the two immutable allocation facts — the exact runtime
/// path and the slot number. Not from the filesystem: scanning a root to decide
/// which directories are "mine" is what invariant 6 forbids, and it is also
/// impossible for an attempt whose policy has since been deleted. `configured`
/// is therefore a *cross-check* and not a source. A policy that survives has to
/// agree; a policy that does not survive removes a check rather than the
/// ability to clean the directory the journal already names.
///
/// The name test comes before the parent is used, so `<root>/s1` for a journal
/// row that says `s2` — and anything at all that is not one `sN` component —
/// is refused before a root is derived from it.
fn verify_journalled_slot(
    runtime: &Path,
    slot: NonZeroU16,
    configured: Option<&LocalAbsolutePath>,
) -> Result<(), SlotQuarantine> {
    let mislaid = || {
        SlotQuarantine::new(
            SlotRefusal::NotTheJournalledSlot,
            format!(
                "the journalled runtime {} is not the slot s{slot} this attempt was allocated as",
                runtime.display()
            ),
        )
    };
    let local = |path: &Path| {
        path.to_str()
            .and_then(|raw| LocalAbsolutePath::new(raw).ok())
            .ok_or_else(mislaid)
    };

    let runtime_path = local(runtime)?;
    let root = local(runtime.parent().ok_or_else(mislaid)?)?;
    // Containment's lexical half, by construction: `derive_child` accepts one
    // component, so the equality below can only hold when the journalled path
    // really is this root's `sN` and nothing else.
    // The directory name comes from the domain that allocation named it with,
    // never from a second `s{n}` spelled out here: a convention with two
    // spellings would let cleanup refuse every slot the allocator created.
    let name = AttemptWorkspace::persistent_slot(slot)
        .slot_directory_name()
        .expect("a persistent workspace names its slot directory");
    let derived = runner_root::derive_child(&root, &name).map_err(|_| mislaid())?;
    if derived != runtime_path {
        return Err(mislaid());
    }
    if let Some(configured) = configured
        && configured != &root
    {
        return Err(SlotQuarantine::new(
            SlotRefusal::PolicyRootDisagrees,
            format!(
                "the journalled slot {} is not under the repository's configured persistent root \
                 {}",
                runtime.display(),
                configured.as_str()
            ),
        ));
    }
    // And containment's canonical half, which is what a junction planted inside
    // the root between allocation and cleanup has to get past.
    runner_root::verify_containment(&root, &derived).map_err(|source| {
        SlotQuarantine::new(
            SlotRefusal::Containment,
            format!("the journalled slot is not inside the root it was allocated from: {source}"),
        )
    })
}

/// Whether the slot is there to be scrubbed at all, before its entries are.
///
/// `Ok(false)` — the directory is gone — is not a refusal. There is nothing to
/// remove and nothing to prove absent, which is the same tolerance the
/// disposable arm has always had for a runtime that vanished under it.
///
/// A slot that is a file, a link, a junction or any other reparse point *is* a
/// refusal, and it is checked here rather than inside the enumeration so that
/// the reason an operator reads names the shape rather than reporting that a
/// directory could not be listed.
fn slot_is_present(slot: &Path) -> Result<bool, SlotQuarantine> {
    match fs::symlink_metadata(slot) {
        Err(error) if error.kind() == std::io::ErrorKind::NotFound => Ok(false),
        Err(source) => Err(SlotQuarantine::new(
            SlotRefusal::SlotNotADirectory,
            format!(
                "the slot {} could not be inspected: {:?}",
                slot.display(),
                source.kind()
            ),
        )),
        Ok(metadata) if !metadata.is_dir() || is_link_like(&metadata) => Err(SlotQuarantine::new(
            SlotRefusal::SlotNotADirectory,
            format!(
                "the slot {} is a link or a file rather than a real directory",
                slot.display()
            ),
        )),
        Ok(_) => Ok(true),
    }
}

/// Steps 4 to 6: list the slot's direct entries, keep one real `_work`, remove
/// every other one.
///
/// Every call is a literal filesystem API against a path built from the slot
/// root and one entry name — no glob, no shell string, no repository-controlled
/// fragment. Nothing is followed: `symlink_metadata` says what each entry *is*,
/// and a link-shaped entry is unlinked rather than descended into, so a junction
/// planted where `bin` used to be cannot take the deletion outside the slot.
///
/// A `_work` that is not a real directory is the one entry this refuses to act
/// on at all. Removing it could destroy an operator's data if the link were
/// theirs; keeping it would hand the next attempt a workspace pointing
/// anywhere. `04-security-recovery.md` requires that case to quarantine the
/// slot, so the whole scrub stops there with nothing removed after it.
fn scrub_slot_entries(slot: &Path) -> Result<(), SlotQuarantine> {
    let unreadable = |source: std::io::Error| {
        SlotQuarantine::new(
            SlotRefusal::Enumeration,
            format!(
                "the entries of {} could not be listed: {:?}",
                slot.display(),
                source.kind()
            ),
        )
    };
    for entry in fs::read_dir(slot).map_err(unreadable)? {
        let name = entry.map_err(unreadable)?.file_name();
        let path = slot.join(&name);
        // Nothing is assumed from an entry that vanished: `verify_slot_scrubbed`
        // asks the filesystem again afterwards and refuses if it is still there.
        let Some(metadata) = listed_entry_metadata(&path).map_err(unreadable)? else {
            continue;
        };
        if is_work_folder(&name) {
            if is_retainable_work_folder(&name, &metadata) {
                continue;
            }
            return Err(SlotQuarantine::new(
                SlotRefusal::WorkNotADirectory,
                format!(
                    "the retained `{DEFAULT_WORK_FOLDER}` in {} is a link or a file rather than a \
                     real directory",
                    slot.display()
                ),
            ));
        }
        remove_slot_entry(&path, &metadata).map_err(|source| {
            SlotQuarantine::new(
                SlotRefusal::Deletion,
                format!(
                    "an entry of {} could not be removed: {:?}",
                    slot.display(),
                    source.kind()
                ),
            )
        })?;
    }
    Ok(())
}

/// What a listed entry *is*, or `None` when it is no longer there.
///
/// An entry named by a listing and gone by the time it is stat-ed is absent,
/// which is a fact both passes over a slot want rather than an enumeration that
/// failed. Nothing is followed: `symlink_metadata` reports a link as a link.
fn listed_entry_metadata(path: &Path) -> std::io::Result<Option<fs::Metadata>> {
    match fs::symlink_metadata(path) {
        Ok(metadata) => Ok(Some(metadata)),
        Err(error) if error.kind() == std::io::ErrorKind::NotFound => Ok(None),
        Err(source) => Err(source),
    }
}

/// Remove one slot entry without following it.
///
/// An entry that is already gone is removed: the post-condition this serves is
/// "not there", and racing with whatever removed it first is not a refusal.
fn remove_slot_entry(path: &Path, metadata: &fs::Metadata) -> std::io::Result<()> {
    let removed = if is_link_like(metadata) {
        // A file symlink unlinks with `remove_file`; a directory symlink or a
        // Windows junction needs `remove_dir`. Neither follows the link.
        fs::remove_file(path).or_else(|_| fs::remove_dir(path))
    } else if metadata.is_dir() {
        remove_runtime_tree(path)
    } else {
        fs::remove_file(path)
    };
    match removed {
        Err(error) if error.kind() == std::io::ErrorKind::NotFound => Ok(()),
        other => other,
    }
}

/// Step 7: prove that nothing but the retained job workspace is left.
///
/// Two passes, deliberately independent, because the interesting failure is an
/// enumeration that under-reports. The first asks the directory what remains
/// and counts everything that is not a real `_work`. The second ignores the
/// listing entirely and stats the names an attempt is known to write — the
/// runner's binaries, the registration identity it stores beside them, the
/// process-identity sidecars and this agent's lifecycle marks — so a scrub that
/// silently skipped one is caught by a question that never consulted the
/// listing that skipped it.
///
/// Only the second pass names anything, and the encoded JIT handoff is reported
/// by its published prefix rather than by the UUID that follows it. A slot root
/// is workflow-writable, so a job that named a file after a secret would publish
/// it through any message that echoed the listing; the first pass therefore
/// reports a count.
fn verify_slot_scrubbed(slot: &Path) -> Result<(), SlotQuarantine> {
    let unreadable = |source: std::io::Error| {
        SlotQuarantine::new(
            SlotRefusal::Enumeration,
            format!(
                "the entries of {} could not be listed to verify the scrub: {:?}",
                slot.display(),
                source.kind()
            ),
        )
    };
    let mut residue = 0_usize;
    let mut named: Vec<String> = Vec::new();
    for entry in fs::read_dir(slot).map_err(unreadable)? {
        let name = entry.map_err(unreadable)?.file_name();
        // Absent is what this pass is here to establish. The named half below
        // stats every sensitive entry again, so an entry that only *looks*
        // absent to this listing is still caught.
        let Some(metadata) = listed_entry_metadata(&slot.join(&name)).map_err(unreadable)? else {
            continue;
        };
        if is_retainable_work_folder(&name, &metadata) {
            continue;
        }
        residue = residue.saturating_add(1);
        if name
            .to_string_lossy()
            .starts_with(RestrictiveHandoff::NAME_PREFIX)
        {
            named.push("an encoded JIT handoff".to_owned());
        }
    }
    named.extend(
        SENSITIVE_SLOT_ENTRIES
            .iter()
            .filter(|entry| fs::symlink_metadata(slot.join(entry)).is_ok())
            .map(|entry| format!("`{entry}`")),
    );
    if residue == 0 && named.is_empty() {
        return Ok(());
    }
    named.sort_unstable();
    named.dedup();
    Err(SlotQuarantine::new(
        SlotRefusal::Residue,
        residue_detail(slot, residue, &named),
    ))
}

/// Word a [`SlotRefusal::Residue`] refusal from the two facts that produced it.
///
/// Separate from [`verify_slot_scrubbed`] because the disagreement it has to
/// report — a listing that counted nothing and a filesystem that answered
/// otherwise — is a race no test can stage, and a message that contradicts
/// itself is exactly what an operator reads at three in the morning.
///
/// `named` is the sanitized half: entries this crate published the names of.
/// A name a workflow chose is only ever counted, never echoed.
fn residue_detail(slot: &Path, residue: usize, named: &[String]) -> String {
    if residue == 0 {
        // The whole reason the second pass ignores the listing: the listing
        // reported a clean slot and the filesystem disagrees. Saying "0
        // entries survived" here would report the under-count as the fact.
        format!(
            "the listing of {} reported nothing but `{DEFAULT_WORK_FOLDER}`, yet {} survived \
                 cleanup",
            slot.display(),
            named.join(", ")
        )
    } else {
        format!(
            "{residue} entr{} other than `{DEFAULT_WORK_FOLDER}` survived cleanup of {}{}",
            if residue == 1 { "y" } else { "ies" },
            slot.display(),
            if named.is_empty() {
                String::new()
            } else {
                format!(", including {}", named.join(", "))
            }
        )
    }
}

fn replacement_operation(outcome: &AttemptOutcome) -> Option<&'static str> {
    match outcome {
        AttemptOutcome::Failed {
            reason: FailureReason::JitExpired,
        } => Some("jit_expired_replacement"),
        AttemptOutcome::Failed {
            reason: FailureReason::ProcessExitedUnexpectedly,
        } => Some("exit_before_acceptance_replacement"),
        _ => None,
    }
}

/// Lay the verified runner package out *around* whatever the slot retains.
///
/// `02-target-architecture.md`: "The verified runner package is copied into the
/// slot for the attempt", beside a `_work` that survives every attempt. Two
/// properties make that safe, and both are structural rather than documented:
///
/// * the walk is of the **source** tree, so a retained `_work` in the
///   destination is never opened, never descended into, and cannot be followed
///   wherever it might point;
/// * a top-level source entry named `_work` is refused rather than copied, so a
///   package that ever grew one could not merge itself into, or replace, the
///   job workspace of the attempt before it. The refusal is top-level only,
///   because the retained directory is a direct child of the slot; a `_work`
///   nested inside the package's own tree is an ordinary name.
///
/// On Unix the copy is a copy-on-write clone where the filesystem offers one,
/// taken from a [`package_seed`] on the destination's own volume. A plain
/// byte copy of the ~9,000-file package across volumes took four minutes on a
/// host whose runner root shared a busy disk with a build, and a queued job
/// waits for every second of it.
/// The tree to copy `source` from, making a seed where one helps; a change to
/// a tree, so only under the exclusive hold of [`SharedPackages::trees`].
///
/// A seed that cannot be made is a slower launch, not a failed one. The seed
/// sits under the runner root, beside job runtimes, so the refusal is re-checked
/// on it; a seed that fails it is bypassed.
fn copy_origin(source: &Path, destination: &Path, seeds: &TrustedTrees) -> PathBuf {
    #[cfg(unix)]
    {
        package_seed(source, destination, seeds)
            .ok()
            .filter(|seed| refuse_work_folder(seed).is_ok())
            .unwrap_or_else(|| source.to_path_buf())
    }
    #[cfg(not(unix))]
    {
        let _ = (destination, seeds);
        source.to_path_buf()
    }
}

/// The tree to copy `source` from if it needs no change: `None` is a seed to
/// rebuild first.
fn copy_origin_ready(source: &Path, destination: &Path, seeds: &TrustedTrees) -> Option<PathBuf> {
    #[cfg(unix)]
    {
        match seed_location(source, destination) {
            Ok(None) => Some(source.to_path_buf()),
            Ok(Some(seeds_root)) => held_seed(source, &seeds_root, seeds)
                .ok()
                .flatten()
                .filter(|seed| refuse_work_folder(seed).is_ok()),
            Err(_) => None,
        }
    }
    #[cfg(not(unix))]
    {
        let _ = (destination, seeds);
        Some(source.to_path_buf())
    }
}

/// Copy the package at `source` into `destination`, from `origin`: itself or
/// its seed. Under the shared hold of [`SharedPackages::trees`].
fn copy_package_from(
    source: &Path,
    origin: &Path,
    destination: &Path,
    seeds: &TrustedTrees,
) -> std::io::Result<()> {
    refuse_work_folder(source)?;

    #[cfg(unix)]
    {
        clone_tree(origin, destination)?;
        // A seed a job edited during the clone no longer holds; the caller
        // re-checks the cache entry itself.
        if origin != source && !seeds.holds(origin) {
            return Err(std::io::Error::other(
                "the package seed changed while cloned",
            ));
        }
        Ok(())
    }
    #[cfg(not(unix))]
    {
        let _ = (origin, seeds);
        copy_package_entries(source, destination, true)
    }
}

fn refuse_work_folder(source: &Path) -> std::io::Result<()> {
    if source.join(DEFAULT_WORK_FOLDER).exists() {
        return Err(std::io::Error::new(
            std::io::ErrorKind::InvalidData,
            "a cached runner package contains a _work folder, which means it was used \
             to run a job before it was archived; the cache must only contain clean \
             extracts to prevent data leakage",
        ));
    }
    Ok(())
}

/// Where runtime copies of the package are cloned from, beside the runtimes.
#[cfg(unix)]
const PACKAGE_SEED_DIR: &str = ".runner-package";

/// A copy of the cache entry on the destination's volume, so that every
/// runtime after the first is a same-volume clone rather than a cross-volume
/// byte copy. Returns `source` itself when it already shares the volume.
///
/// The seed lives at `<runner root>/.runner-package/<version>` and is replaced
/// whenever its manifest stops matching the cache entry's, which covers both a
/// new version and a reinstalled one. Superseded versions and interrupted
/// stagings are removed on that same pass. A seed is only made under the
/// exclusive hold of [`SharedPackages::trees`], so no launch is cloning from it
/// while it is replaced.
///
/// The seed sits one `..` from every job's runtime and is owned by the account
/// jobs run as, so it is only reused while it is provably the tree this
/// process built: see [`TrustedTrees`].
///
/// Only on macOS, where the runner root is all but certainly APFS and a clone
/// is free. On a Linux filesystem without reflinks a seed would only move every
/// copy's reads onto the runner root's own, possibly busy, disk.
#[cfg(unix)]
fn package_seed(
    source: &Path,
    destination: &Path,
    seeds: &TrustedTrees,
) -> std::io::Result<PathBuf> {
    match seed_location(source, destination)? {
        Some(root) => refresh_package_seed(source, &root, seeds),
        None => Ok(source.to_path_buf()),
    }
}

/// Where `destination`'s seeds live, if copies to it use one.
#[cfg(unix)]
fn seed_location(source: &Path, destination: &Path) -> std::io::Result<Option<PathBuf>> {
    use std::os::unix::fs::MetadataExt as _;

    if !cfg!(target_os = "macos") {
        return Ok(None);
    }
    let root = destination
        .parent()
        .ok_or_else(|| std::io::Error::other("a runtime directory has no parent"))?;
    if fs::metadata(source)?.dev() == fs::metadata(root)?.dev() {
        return Ok(None);
    }
    Ok(Some(root.join(PACKAGE_SEED_DIR)))
}

/// The package trees this process built or installed: what each must hold, and
/// what each looked like right after. They are the cache entry runtimes are copied
/// from and the seeds they are cloned from.
///
/// Both are owned by the account jobs run as, so a job can edit any file in them,
/// and nothing on disk can say what they should hold: the published digest covers
/// the archive, not the extracted tree, and a record kept on disk could be
/// rewritten by the same account. So a tree without a record here, as every tree
/// has after a restart, is rebuilt before it is used.
///
/// Two checks, for two costs. [`PackageContents`] reads every file against the
/// verified archive, on every runtime a launch is about to run: that is the one
/// that decides. On Unix the tree's [`tree_fingerprint`] also spots a changed
/// tree cheaply before any of it is copied, since every edit, replacement or
/// rename moves the change time (`ctime`) of the entry or of its directory, and
/// only the superuser can set a change time.
#[derive(Debug, Default)]
pub(crate) struct TrustedTrees {
    trees: Mutex<HashMap<PathBuf, TrustedTree>>,
}

#[derive(Debug, Clone)]
struct TrustedTree {
    #[cfg(unix)]
    print: [u8; 32],
    contents: Option<Arc<PackageContents>>,
}

impl TrustedTrees {
    fn trees(&self) -> std::sync::MutexGuard<'_, HashMap<PathBuf, TrustedTree>> {
        self.trees
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
    }

    /// Whether `root` is a tree recorded here and, where that can be told, still
    /// looks as it did.
    fn holds(&self, root: &Path) -> bool {
        let Some(tree) = self.trees().get(root).cloned() else {
            return false;
        };
        #[cfg(unix)]
        {
            tree_fingerprint(root).is_ok_and(|current| current == tree.print)
        }
        #[cfg(not(unix))]
        {
            let _ = tree;
            true
        }
    }

    /// What `root` must hold.
    fn contents_of(&self, root: &Path) -> Option<Arc<PackageContents>> {
        self.trees()
            .get(root)
            .and_then(|tree| tree.contents.clone())
    }

    /// Trust `root` as it is now; called right after this process made it.
    fn record(&self, root: &Path, contents: Option<Arc<PackageContents>>) -> std::io::Result<()> {
        let tree = TrustedTree {
            #[cfg(unix)]
            print: tree_fingerprint(root)?,
            contents,
        };
        self.trees().insert(root.to_path_buf(), tree);
        Ok(())
    }

    /// Stops trusting `root` if `contents` is still what is recorded for it, and
    /// answers whether it did.
    fn forget_if_holding(&self, root: &Path, contents: &Arc<PackageContents>) -> bool {
        let mut trees = self.trees();
        let holding = trees
            .get(root)
            .and_then(|tree| tree.contents.as_ref())
            .is_some_and(|current| Arc::ptr_eq(current, contents));
        if holding {
            trees.remove(root);
        }
        holding
    }

    /// Stop trusting `root`: its next use rebuilds it.
    fn forget(&self, root: &Path) {
        self.trees().remove(root);
    }
}

/// A digest of every entry under `root`: its relative path, inode, size, mode,
/// owner and change time.
#[cfg(unix)]
fn tree_fingerprint(root: &Path) -> std::io::Result<[u8; 32]> {
    use sha2::{Digest as _, Sha256};
    use std::os::unix::fs::MetadataExt as _;

    fn walk(root: &Path, path: &Path, hasher: &mut Sha256) -> std::io::Result<()> {
        let metadata = fs::symlink_metadata(path)?;
        let relative = path.strip_prefix(root).unwrap_or(path);
        hasher.update(relative.as_os_str().as_encoded_bytes());
        hasher.update([0]);
        for field in [
            metadata.ino(),
            metadata.size(),
            u64::from(metadata.mode()),
            u64::from(metadata.uid()),
            u64::from(metadata.gid()),
        ] {
            hasher.update(field.to_le_bytes());
        }
        hasher.update(metadata.ctime().to_le_bytes());
        hasher.update(metadata.ctime_nsec().to_le_bytes());
        if metadata.is_dir() {
            let mut children = fs::read_dir(path)?
                .map(|entry| entry.map(|entry| entry.path()))
                .collect::<std::io::Result<Vec<_>>>()?;
            children.sort();
            for child in children {
                walk(root, &child, hasher)?;
            }
        }
        Ok(())
    }

    let mut hasher = Sha256::new();
    walk(root, root, &mut hasher)?;
    Ok(hasher.finalize().into())
}

#[cfg(unix)]
fn seed_path(source: &Path, seeds: &Path) -> std::io::Result<PathBuf> {
    let version = source
        .file_name()
        .ok_or_else(|| std::io::Error::other("a cache entry has no name"))?;
    Ok(seeds.join(version))
}

/// The seed of `source` under `seeds`, if its manifest matches the cache
/// entry's and its fingerprint the one this process recorded.
#[cfg(unix)]
fn held_seed(
    source: &Path,
    seeds: &Path,
    trusted: &TrustedTrees,
) -> std::io::Result<Option<PathBuf>> {
    use crate::package::MANIFEST_FILE;

    let seed = seed_path(source, seeds)?;
    let manifest = fs::read(source.join(MANIFEST_FILE))?;
    let held = fs::read(seed.join(MANIFEST_FILE)).is_ok_and(|held| held == manifest)
        && trusted.holds(&seed);
    Ok(held.then_some(seed))
}

/// The seed of `source` under `seeds`, rebuilt unless [`held_seed`] finds it.
#[cfg(unix)]
fn refresh_package_seed(
    source: &Path,
    seeds: &Path,
    trusted: &TrustedTrees,
) -> std::io::Result<PathBuf> {
    if let Some(seed) = held_seed(source, seeds, trusted)? {
        return Ok(seed);
    }
    let seed = seed_path(source, seeds)?;

    // Superseded versions, a stale seed and interrupted stagings all go.
    match remove_runtime_tree(seeds) {
        Err(error) if error.kind() != std::io::ErrorKind::NotFound => return Err(error),
        _ => {}
    }
    fs::create_dir_all(seeds)?;
    let staging = seeds.join(format!(".staging-{}", uuid::Uuid::new_v4()));
    fs::create_dir(&staging)?;
    // A half-made staging would hold the disk space the fallback copy needs.
    if let Err(error) = clone_tree(source, &staging).and_then(|()| fs::rename(&staging, &seed)) {
        let _ = remove_runtime_tree(&staging);
        return Err(error);
    }
    // After the rename, which itself moves the seed directory's change time.
    trusted.record(&seed, None)?;
    Ok(seed)
}

/// `cp -a`, asking for a copy-on-write clone where the platform's `cp` can.
///
/// macOS `cp -c` and GNU `--reflink=auto` both fall back to a byte copy across
/// volumes; a `cp` that does not know the flag at all gets a plain `cp -a`.
#[cfg(unix)]
fn clone_tree(source: &Path, destination: &Path) -> std::io::Result<()> {
    #[cfg(target_os = "macos")]
    const CLONE: &[&str] = &["-c"];
    #[cfg(target_os = "linux")]
    const CLONE: &[&str] = &["--reflink=auto"];
    #[cfg(not(any(target_os = "macos", target_os = "linux")))]
    const CLONE: &[&str] = &[];

    let from = format!("{}/.", source.display());
    let cp = |extra: &[&str]| {
        std::process::Command::new("cp")
            .arg("-a")
            .args(extra)
            .arg(&from)
            .arg(destination)
            .status()
    };
    if cp(CLONE)?.success() || cp(&[])?.success() {
        Ok(())
    } else {
        Err(std::io::Error::other("cp failed"))
    }
}

#[cfg(not(unix))]
fn copy_package_entries(source: &Path, destination: &Path, top_level: bool) -> std::io::Result<()> {
    fs::create_dir_all(destination)?;
    for entry in fs::read_dir(source)? {
        let entry = entry?;
        if top_level && is_work_folder(&entry.file_name()) {
            return Err(std::io::Error::new(
                std::io::ErrorKind::InvalidData,
                format!(
                    "the runner package holds a top-level `{DEFAULT_WORK_FOLDER}`; copying \
                     it would overwrite the job workspace a persistent slot retains"
                ),
            ));
        }
        let target = destination.join(entry.file_name());
        if entry.file_type()?.is_dir() {
            copy_package_entries(&entry.path(), &target, false)?;
        } else {
            fs::copy(entry.path(), target)?;
        }
    }
    Ok(())
}

/// Process operations are attempt-addressed so a recovered process and a child
/// started in this invocation are supervised through one port.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ProcessStartFailure {
    pub reason: FailureReason,
    /// False once a child existed: the one-shot JIT value may have been
    /// consumed, so retrying it could start a duplicate.
    pub retryable: bool,
    /// Set only when cleanup could not prove the spawned process dead.  The
    /// caller must journal `starting` and retain capacity/supervision.
    pub live_pid: Option<u32>,
}

impl ProcessStartFailure {
    pub(crate) fn before_spawn(reason: FailureReason) -> Self {
        Self {
            reason,
            retryable: true,
            live_pid: None,
        }
    }

    fn after_spawn_stopped() -> Self {
        Self {
            reason: FailureReason::ProcessStartFailed,
            retryable: false,
            live_pid: None,
        }
    }

    fn after_spawn_live(pid: u32) -> Self {
        Self::after_spawn_live_with_reason(pid, FailureReason::ProcessStartFailed)
    }

    fn after_spawn_live_with_reason(pid: u32, reason: FailureReason) -> Self {
        Self {
            reason,
            retryable: false,
            live_pid: Some(pid),
        }
    }
}

/// A credential-free capability report. An isolated policy never treats a
/// native-ready result as permission to launch.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ProviderCapability {
    Ready,
    Unsupported,
    NotInstalled,
    PermissionDenied,
    ImageUnavailableOrIncompatible,
    DiskQuotaUnavailable,
    Degraded,
}

impl ProviderCapability {
    #[must_use]
    pub const fn display_name(self) -> &'static str {
        match self {
            Self::Ready => "ready",
            Self::Unsupported => "unsupported",
            Self::NotInstalled => "not installed",
            Self::PermissionDenied => "permission denied",
            Self::ImageUnavailableOrIncompatible => "image unavailable or incompatible",
            Self::DiskQuotaUnavailable => "disk quota unavailable",
            Self::Degraded => "degraded",
        }
    }

    pub(crate) fn refusal(self) -> FailureReason {
        FailureReason::IsolationProvider(match self {
            Self::Ready | Self::Degraded => IsolationProviderFailure::Degraded,
            Self::Unsupported => IsolationProviderFailure::Unsupported,
            Self::NotInstalled => IsolationProviderFailure::NotInstalled,
            Self::PermissionDenied => IsolationProviderFailure::PermissionDenied,
            Self::ImageUnavailableOrIncompatible => {
                IsolationProviderFailure::ImageUnavailableOrIncompatible
            }
            Self::DiskQuotaUnavailable => IsolationProviderFailure::DiskQuotaUnavailable,
        })
    }
}

/// Only the closed isolation category may cross from an adapter into the
/// attempt journal or operator error. Arbitrary adapter text could echo JIT.
fn safe_isolation_reason(
    reason: FailureReason,
    fallback: IsolationProviderFailure,
) -> FailureReason {
    match reason {
        FailureReason::IsolationProvider(_) => reason,
        _ => FailureReason::IsolationProvider(fallback),
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct PreparedEnvironment {
    attempt: AttemptId,
    identity: Option<EnvironmentIdentity>,
    /// The target whose dependency-cache namespace a native runner uses:
    /// `prepare` sees the policy and `start` does not.
    cache_target: Option<runner_manager_domain::model::ScaleTarget>,
}

impl PreparedEnvironment {
    /// An adapter must return the identity independently recorded on its resource.
    #[must_use]
    pub fn isolated(attempt: AttemptId, identity: EnvironmentIdentity) -> Self {
        Self {
            attempt,
            identity: Some(identity),
            cache_target: None,
        }
    }

    #[must_use]
    pub fn identity(&self) -> Option<&EnvironmentIdentity> {
        self.identity.as_ref()
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ResolvedEnvironment {
    pub provider_kind: Backend,
    pub image: ImageReference,
}

/// Closed, non-secret provider diagnostics; adapters cannot attach arbitrary output.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ProviderDiagnostic {
    CapabilityUnavailable,
    ImageRejected,
    PrepareFailed,
    StartFailed,
    OwnershipMismatch,
    CleanupDeferred,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum EnvironmentIdentity {
    NativeProcess(u32),
    Isolated {
        host: HostId,
        attempt: AttemptId,
        provider_kind: Backend,
        environment_id: String,
        resolved_image: ImageReference,
        generation: String,
    },
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum EnvironmentState {
    Starting,
    Running,
    Exited,
    Missing,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ProviderStop {
    Stopped,
    StillRunning,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ProviderDestroy {
    Destroyed,
    Deferred(&'static str),
}

fn identity_matches_intent(
    host: HostId,
    attempt: &RunnerAttempt,
    identity: &EnvironmentIdentity,
) -> bool {
    identity_same_allocation(host, attempt, identity)
        && match (attempt.execution(), identity) {
            (
                AttemptExecution::Isolated { environment_id, .. },
                EnvironmentIdentity::Isolated {
                    environment_id: id, ..
                },
            ) => environment_id
                .as_ref()
                .is_none_or(|journal_id| journal_id == id),
            _ => false,
        }
}

fn identity_same_allocation(
    host: HostId,
    attempt: &RunnerAttempt,
    identity: &EnvironmentIdentity,
) -> bool {
    match (attempt.execution(), identity) {
        (
            AttemptExecution::Isolated {
                provider_kind,
                environment_id: _,
                resolved_image,
                generation,
            },
            EnvironmentIdentity::Isolated {
                host: owner,
                attempt: owner_attempt,
                provider_kind: kind,
                environment_id: _,
                resolved_image: image,
                generation: resource_generation,
            },
        ) => {
            *owner == host
                && *owner_attempt == attempt.id
                && provider_kind == kind
                && resolved_image == image
                && generation == resource_generation
        }
        _ => false,
    }
}

/// The JIT value can be passed into a provider start exactly once. It must never
/// become a provider identity, label, argument, persisted configuration or log field.
pub struct OneTimeJitHandoff<'a> {
    config: &'a EncodedJitConfig,
}

impl fmt::Debug for OneTimeJitHandoff<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("OneTimeJitHandoff([redacted])")
    }
}

impl<'a> OneTimeJitHandoff<'a> {
    pub(crate) fn new(config: &'a EncodedJitConfig) -> Self {
        Self { config }
    }

    /// Consuming the handoff prevents the same token being delivered twice by one call.
    pub fn consume(self) -> &'a EncodedJitConfig {
        self.config
    }
}

/// Provider lifecycle and native process supervision. The default lifecycle
/// methods adapt the existing native spawn/recovery implementation, and refuse
/// every isolated allocation. Future platform adapters must implement their
/// own prepare/start/inspect/stop/destroy paths rather than fall back here.
pub trait ExecutionProvider: fmt::Debug + Send + Sync {
    fn probe(&self, policy: &ScalePolicy) -> ProviderCapability {
        if policy.execution_policy().is_native() {
            ProviderCapability::Ready
        } else {
            ProviderCapability::Unsupported
        }
    }

    /// Resolve Auto and image identity before allocation or GitHub JIT. Native has no image.
    fn resolve(&self, policy: &ScalePolicy) -> Result<Option<ResolvedEnvironment>, FailureReason> {
        if policy.execution_policy().is_native() {
            Ok(None)
        } else {
            Err(FailureReason::Other(
                "execution provider unavailable".into(),
            ))
        }
    }

    fn prepare(
        &self,
        attempt: &RunnerAttempt,
        policy: &ScalePolicy,
    ) -> Result<PreparedEnvironment, FailureReason> {
        if !attempt.execution().is_native() || !policy.execution_policy().is_native() {
            return Err(FailureReason::Other(
                "execution provider unavailable".into(),
            ));
        }
        Ok(PreparedEnvironment {
            attempt: attempt.id,
            identity: None,
            cache_target: None,
        })
    }

    fn start(
        &self,
        prepared: PreparedEnvironment,
        attempt: &RunnerAttempt,
        handoff: OneTimeJitHandoff<'_>,
    ) -> Result<EnvironmentIdentity, ProcessStartFailure> {
        if prepared.attempt != attempt.id || !attempt.execution().is_native() {
            return Err(ProcessStartFailure::before_spawn(FailureReason::Other(
                "execution provider identity mismatch".into(),
            )));
        }
        self.spawn(attempt, handoff.consume())
            .map(EnvironmentIdentity::NativeProcess)
    }

    fn inspect(&self, attempt: &RunnerAttempt) -> Result<EnvironmentState, FailureReason> {
        if !attempt.execution().is_native() {
            return Err(FailureReason::Other(
                "execution provider unavailable".into(),
            ));
        }
        self.is_alive(attempt).map(|alive| {
            if alive {
                EnvironmentState::Running
            } else {
                EnvironmentState::Missing
            }
        })
    }

    fn stop(&self, attempt: &RunnerAttempt) -> Result<ProviderStop, FailureReason> {
        if !attempt.execution().is_native() {
            return Err(FailureReason::Other(
                "execution provider unavailable".into(),
            ));
        }
        self.terminate(attempt).map(|()| ProviderStop::Stopped)
    }

    fn destroy(&self, attempt: &RunnerAttempt) -> Result<ProviderDestroy, FailureReason> {
        if !attempt.execution().is_native() {
            return Err(FailureReason::Other(
                "execution provider unavailable".into(),
            ));
        }
        // Native termination is already settled by the existing recovery
        // decision before workspace cleanup. There is no separate sandbox
        // resource to destroy, and repeating an observation here changes the
        // established native cleanup behaviour.
        Ok(ProviderDestroy::Destroyed)
    }

    fn recover(&self, attempt: &RunnerAttempt) -> Result<EnvironmentState, FailureReason> {
        self.inspect(attempt)
    }

    fn enumerate_owned(&self, _host_id: HostId) -> Vec<EnvironmentIdentity> {
        Vec::new() // Native processes have no independent provider resources.
    }

    fn diagnostics(&self, _attempt: &RunnerAttempt) -> Vec<ProviderDiagnostic> {
        Vec::new() // No job or JIT output enters provider metadata.
    }

    /// Independent resource metadata must match the journal before destructive calls.
    fn owns(&self, attempt: &RunnerAttempt) -> Result<bool, FailureReason> {
        Ok(attempt.execution().is_native())
    }

    fn spawn(
        &self,
        attempt: &RunnerAttempt,
        config: &EncodedJitConfig,
    ) -> Result<u32, ProcessStartFailure>;
    fn is_alive(&self, attempt: &RunnerAttempt) -> Result<bool, FailureReason>;
    /// Durable identity observed for a process that spawned before the
    /// `starting` journal write survived.
    fn recovered_pid(&self, attempt: &RunnerAttempt) -> Result<Option<u32>, FailureReason>;
    /// True only for a child this invocation owned and reaped with a successful
    /// exit status.  A recovered process that is merely gone answers false.
    fn completed_successfully(&self, attempt: &RunnerAttempt) -> bool;
    fn record_terminate_intent(&self, attempt: &RunnerAttempt) -> Result<(), FailureReason>;
    fn has_terminate_intent(&self, attempt: &RunnerAttempt) -> bool;
    fn terminate(&self, attempt: &RunnerAttempt) -> Result<(), FailureReason>;
}

/// Compatibility name for existing native process tests and callers.
pub use ExecutionProvider as ProcessSupervisor;

/// Native process supervision.  The start token is stored beside the runtime;
/// recovery never trusts a recycled PID merely because SQLite contains it.
#[derive(Debug, Default)]
pub struct NativeProcesses {
    children: Mutex<BTreeMap<AttemptId, ChildProcess>>,
    successful_exits: Mutex<BTreeMap<AttemptId, bool>>,
    /// The host's `runner.env`, read at every launch so that `host env set`
    /// reaches the next runner without a daemon restart. `None` applies none.
    runner_env_file: Option<PathBuf>,
    /// Persistent dependency caches. `None` gives runners none.
    dependency_caches: Option<DependencyCaches>,
    docker_cleanup: Option<crate::docker_cleanup::DockerCleanup>,
    #[cfg(test)]
    post_spawn_faults: Mutex<VecDeque<PostSpawnBoundary>>,
    #[cfg(test)]
    post_spawn_reaps: std::sync::atomic::AtomicUsize,
    #[cfg(test)]
    post_spawn_stop_failures: std::sync::atomic::AtomicUsize,
    #[cfg(test)]
    use_long_lived_test_listener: std::sync::atomic::AtomicBool,
}

/// Production provider set. Native and isolated allocations are routed by the
/// immutable execution kind in the policy/journal; an unavailable isolated
/// backend can never fall through to native process launch.
#[derive(Debug)]
pub struct PlatformExecutionProvider {
    native: NativeProcesses,
    oci: OciProcesses,
    windows_hyper_v: WindowsHyperVContainers,
}

impl PlatformExecutionProvider {
    #[must_use]
    pub fn new(host_id: HostId) -> Self {
        Self {
            native: NativeProcesses::new(),
            oci: OciProcesses::new(host_id),
            windows_hyper_v: WindowsHyperVContainers::new(host_id),
        }
    }

    /// Applies the host's `runner.env` at `path` to every native runner.
    /// Isolated runners do not get it: their environment is the image's.
    #[must_use]
    pub fn with_runner_env_file(mut self, path: PathBuf) -> Self {
        self.native = self.native.with_runner_env_file(path);
        self
    }

    /// Gives every native runner persistent dependency caches. Isolated
    /// runners do not get them: their providers mount no host directory.
    #[must_use]
    pub fn with_dependency_caches(mut self, caches: DependencyCaches) -> Self {
        self.native = self.native.with_dependency_caches(caches);
        self
    }

    #[must_use]
    pub fn with_docker_cleanup(mut self, cleanup: crate::docker_cleanup::DockerCleanup) -> Self {
        self.native.docker_cleanup = Some(cleanup);
        self
    }

    fn isolated_provider(&self, backend: Backend) -> Option<&dyn ExecutionProvider> {
        match backend {
            Backend::Auto => {
                #[cfg(target_os = "windows")]
                {
                    Some(&self.windows_hyper_v)
                }
                #[cfg(not(target_os = "windows"))]
                {
                    Some(&self.oci)
                }
            }
            Backend::Oci => Some(&self.oci),
            Backend::WindowsHyperVContainer => Some(&self.windows_hyper_v),
            Backend::VirtualMachine => None,
        }
    }

    fn provider_for_attempt(&self, attempt: &RunnerAttempt) -> Option<&dyn ExecutionProvider> {
        match attempt.execution() {
            AttemptExecution::Native { .. } => Some(&self.native),
            AttemptExecution::Isolated { provider_kind, .. } => {
                self.isolated_provider(*provider_kind)
            }
        }
    }

    fn required_provider_for_attempt(
        &self,
        attempt: &RunnerAttempt,
    ) -> Result<&dyn ExecutionProvider, FailureReason> {
        self.provider_for_attempt(attempt)
            .ok_or_else(|| FailureReason::Other("execution provider unavailable".into()))
    }
}

impl ExecutionProvider for PlatformExecutionProvider {
    fn probe(&self, policy: &ScalePolicy) -> ProviderCapability {
        match policy.execution_policy() {
            runner_manager_domain::execution::ExecutionPolicy::Native => self.native.probe(policy),
            runner_manager_domain::execution::ExecutionPolicy::Isolated { backend, .. } => self
                .isolated_provider(*backend)
                .map_or(ProviderCapability::Unsupported, |provider| {
                    provider.probe(policy)
                }),
        }
    }

    fn resolve(&self, policy: &ScalePolicy) -> Result<Option<ResolvedEnvironment>, FailureReason> {
        match policy.execution_policy() {
            runner_manager_domain::execution::ExecutionPolicy::Native => {
                self.native.resolve(policy)
            }
            runner_manager_domain::execution::ExecutionPolicy::Isolated { backend, .. } => self
                .isolated_provider(*backend)
                .ok_or_else(|| FailureReason::Other("execution provider unavailable".into()))?
                .resolve(policy),
        }
    }

    fn prepare(
        &self,
        attempt: &RunnerAttempt,
        policy: &ScalePolicy,
    ) -> Result<PreparedEnvironment, FailureReason> {
        match policy.execution_policy() {
            runner_manager_domain::execution::ExecutionPolicy::Native => {
                self.native.prepare(attempt, policy)
            }
            runner_manager_domain::execution::ExecutionPolicy::Isolated { backend, .. } => self
                .isolated_provider(*backend)
                .ok_or_else(|| FailureReason::Other("execution provider unavailable".into()))?
                .prepare(attempt, policy),
        }
    }

    fn start(
        &self,
        prepared: PreparedEnvironment,
        attempt: &RunnerAttempt,
        handoff: OneTimeJitHandoff<'_>,
    ) -> Result<EnvironmentIdentity, ProcessStartFailure> {
        self.provider_for_attempt(attempt)
            .ok_or_else(|| {
                ProcessStartFailure::before_spawn(FailureReason::Other(
                    "execution provider unavailable".into(),
                ))
            })?
            .start(prepared, attempt, handoff)
    }

    fn inspect(&self, attempt: &RunnerAttempt) -> Result<EnvironmentState, FailureReason> {
        self.required_provider_for_attempt(attempt)?
            .inspect(attempt)
    }

    fn stop(&self, attempt: &RunnerAttempt) -> Result<ProviderStop, FailureReason> {
        self.required_provider_for_attempt(attempt)?.stop(attempt)
    }

    fn destroy(&self, attempt: &RunnerAttempt) -> Result<ProviderDestroy, FailureReason> {
        self.required_provider_for_attempt(attempt)?
            .destroy(attempt)
    }

    fn recover(&self, attempt: &RunnerAttempt) -> Result<EnvironmentState, FailureReason> {
        self.required_provider_for_attempt(attempt)?
            .recover(attempt)
    }

    fn enumerate_owned(&self, host_id: HostId) -> Vec<EnvironmentIdentity> {
        let mut owned = self.oci.enumerate_owned(host_id);
        owned.extend(self.windows_hyper_v.enumerate_owned(host_id));
        owned
    }

    fn diagnostics(&self, attempt: &RunnerAttempt) -> Vec<ProviderDiagnostic> {
        self.provider_for_attempt(attempt)
            .map_or_else(Vec::new, |provider| provider.diagnostics(attempt))
    }

    fn owns(&self, attempt: &RunnerAttempt) -> Result<bool, FailureReason> {
        self.required_provider_for_attempt(attempt)?.owns(attempt)
    }

    fn spawn(
        &self,
        attempt: &RunnerAttempt,
        config: &EncodedJitConfig,
    ) -> Result<u32, ProcessStartFailure> {
        if !attempt.execution().is_native() {
            return Err(ProcessStartFailure::before_spawn(FailureReason::Other(
                "native process launch refused for an isolated allocation".into(),
            )));
        }
        self.native.spawn(attempt, config)
    }

    fn is_alive(&self, attempt: &RunnerAttempt) -> Result<bool, FailureReason> {
        self.required_provider_for_attempt(attempt)?
            .is_alive(attempt)
    }

    fn recovered_pid(&self, attempt: &RunnerAttempt) -> Result<Option<u32>, FailureReason> {
        self.required_provider_for_attempt(attempt)?
            .recovered_pid(attempt)
    }

    fn completed_successfully(&self, attempt: &RunnerAttempt) -> bool {
        self.provider_for_attempt(attempt)
            .is_some_and(|provider| provider.completed_successfully(attempt))
    }

    fn record_terminate_intent(&self, attempt: &RunnerAttempt) -> Result<(), FailureReason> {
        self.required_provider_for_attempt(attempt)?
            .record_terminate_intent(attempt)
    }

    fn has_terminate_intent(&self, attempt: &RunnerAttempt) -> bool {
        self.provider_for_attempt(attempt)
            .is_some_and(|provider| provider.has_terminate_intent(attempt))
    }

    fn terminate(&self, attempt: &RunnerAttempt) -> Result<(), FailureReason> {
        self.required_provider_for_attempt(attempt)?
            .terminate(attempt)
    }
}

#[cfg(test)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum PostSpawnBoundary {
    HandoffDelete,
    IdentitySerialize,
    IdentityWrite,
    ChildMapInsert,
}

impl NativeProcesses {
    #[must_use]
    pub fn new() -> Self {
        Self::default()
    }

    /// Applies the host's `runner.env` at `path` to every runner launched.
    #[must_use]
    pub fn with_runner_env_file(mut self, path: PathBuf) -> Self {
        self.runner_env_file = Some(path);
        self
    }

    /// Gives every runner launched persistent dependency caches.
    #[must_use]
    pub fn with_dependency_caches(mut self, caches: DependencyCaches) -> Self {
        self.dependency_caches = Some(caches);
        self
    }

    /// The cache variables for `attempt`, when `prepare` named its target.
    fn cache_env(
        &self,
        attempt: &RunnerAttempt,
        target: Option<&runner_manager_domain::model::ScaleTarget>,
        host_env: &RunnerEnv,
    ) -> Vec<(&'static str, std::ffi::OsString)> {
        match (&self.dependency_caches, target) {
            (Some(caches), Some(target)) => {
                caches.for_launch(target, attempt.runtime_path(), host_env)
            }
            _ => Vec::new(),
        }
    }

    /// Starts `Runner.Listener` for `attempt`, with the dependency caches of
    /// `cache_target` when there is one.
    fn spawn_listener(
        &self,
        attempt: &RunnerAttempt,
        config: &EncodedJitConfig,
        cache_target: Option<&runner_manager_domain::model::ScaleTarget>,
    ) -> Result<u32, ProcessStartFailure> {
        let handoff = RestrictiveHandoff::create(
            attempt.runtime_path(),
            SecretString::from(config.expose().to_owned()),
        )
        .map_err(|_| ProcessStartFailure::before_spawn(FailureReason::ProcessStartFailed))?;
        #[cfg(windows)]
        let program = attempt
            .runtime_path()
            .join("bin")
            .join("Runner.Listener.exe");
        #[cfg(not(windows))]
        let program = attempt.runtime_path().join("bin").join("Runner.Listener");
        // Checked after the handoff exists on purpose: the error path below is
        // a real post-handoff launch failure, and unwinding must delete it.
        if !program.is_file() {
            return Err(ProcessStartFailure::before_spawn(
                FailureReason::ProcessStartFailed,
            ));
        }
        let host_env = self.host_env().map_err(ProcessStartFailure::before_spawn)?;
        let caches = self.cache_env(attempt, cache_target, &host_env);
        #[cfg(test)]
        let spec = if self
            .use_long_lived_test_listener
            .load(std::sync::atomic::Ordering::SeqCst)
        {
            SpawnSpec::new(program)
                .args([
                    "--ignored",
                    "--exact",
                    "lifecycle::tests::long_lived_native_listener_helper",
                    "--nocapture",
                ])
                .env(
                    "RUNNER_MANAGER_TEST_LISTENER_READY",
                    attempt.runtime_path().join(TEST_LISTENER_READY),
                )
                .working_dir(attempt.runtime_path())
        } else {
            runner_listener_spec(program, attempt.runtime_path(), caches, &host_env)
        };
        #[cfg(not(test))]
        let spec = runner_listener_spec(program, attempt.runtime_path(), caches, &host_env);
        let (spec, docker_proxy) = if let Some(cleanup) = &self.docker_cleanup {
            let repository = cache_target.map(ToString::to_string).unwrap_or_default();
            match cleanup.launch_environment(attempt.id, &repository, &host_env) {
                Ok(Some(endpoint)) => (
                    spec.env("DOCKER_HOST", endpoint),
                    Some(cleanup.root.join(attempt.id.to_string())),
                ),
                Ok(None) => (spec, None),
                Err(error) => {
                    tracing::warn!(attempt_id = %attempt.id, event = "docker_accounting_unavailable", reason = ?error.kind(), "native Docker accounting could not start");
                    if crate::docker_cleanup::Config::load(&cleanup.config).map_or(true, |config| {
                        config.mode == crate::docker_cleanup::Mode::Apply
                    }) {
                        return Err(ProcessStartFailure::before_spawn(
                            FailureReason::ProcessStartFailed,
                        ));
                    }
                    (spec, None)
                }
            }
        } else {
            (spec, None)
        };
        let child = spec
            .spawn_runner_with_handoff(&handoff)
            .map_err(|_| ProcessStartFailure::before_spawn(FailureReason::ProcessStartFailed))?;
        // The payload is gone before any state saying "starting" is persisted.
        #[cfg(test)]
        if self.faults_at(PostSpawnBoundary::HandoffDelete) {
            drop(handoff);
            return Err(self.abort_spawned_child(child, attempt, false));
        }
        if handoff.delete().is_err() {
            return Err(self.abort_spawned_child(child, attempt, false));
        }
        #[cfg(test)]
        if self.faults_at(PostSpawnBoundary::IdentitySerialize) {
            return Err(self.abort_spawned_child(child, attempt, false));
        }
        let identity = match serde_json::to_vec(child.identity()) {
            Ok(identity) => identity,
            Err(_) => {
                return Err(self.abort_spawned_child(child, attempt, false));
            }
        };
        if self.persist_identity(attempt, &identity).is_err() {
            return Err(self.abort_spawned_child(child, attempt, true));
        }
        if let Some(directory) = docker_proxy
            && crate::docker_cleanup::write_json(&directory.join("runner.json"), child.identity())
                .is_err()
        {
            return Err(self.abort_spawned_child(child, attempt, true));
        }
        let pid = child.pid();
        #[cfg(test)]
        if self.faults_at(PostSpawnBoundary::ChildMapInsert) {
            return Err(self.abort_spawned_child(child, attempt, true));
        }
        let mut children = self
            .children
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);
        children.insert(attempt.id, child);
        Ok(pid)
    }

    /// The host's `runner.env`, read now.
    ///
    /// A file that cannot be read or parsed fails the launch rather than
    /// starting a runner without the environment the operator configured.
    /// [`ExecutionProvider::prepare`] asks first, before a JIT runner is
    /// registered, so a broken file costs no registration. The reason names
    /// the file and the line or variable, never a value.
    fn host_env(&self) -> Result<RunnerEnv, FailureReason> {
        let Some(path) = &self.runner_env_file else {
            return Ok(RunnerEnv::default());
        };
        RunnerEnv::load(path).map_err(|error| {
            tracing::warn!(
                reason = "runner_env_file_invalid",
                "runner.env could not be applied, so no runner starts until it is fixed: {error}"
            );
            FailureReason::Other(format!(
                "runner.env cannot be applied ({error}); fix it with `runner-manager host env`"
            ))
        })
    }

    #[cfg(test)]
    fn fail_post_spawn_at(&self, boundary: PostSpawnBoundary) {
        self.post_spawn_faults.lock().unwrap().push_back(boundary);
    }

    #[cfg(test)]
    fn faults_at(&self, boundary: PostSpawnBoundary) -> bool {
        let mut faults = self.post_spawn_faults.lock().unwrap();
        if faults.front() == Some(&boundary) {
            faults.pop_front();
            true
        } else {
            false
        }
    }

    #[cfg(test)]
    fn fail_post_spawn_stops(&self, count: usize) {
        self.post_spawn_stop_failures
            .fetch_add(count, std::sync::atomic::Ordering::SeqCst);
    }

    #[cfg(test)]
    fn fail_next_post_spawn_stop(&self) {
        self.fail_post_spawn_stops(1);
    }

    #[cfg(test)]
    fn use_long_lived_test_listener(&self) {
        self.use_long_lived_test_listener
            .store(true, std::sync::atomic::Ordering::SeqCst);
    }

    fn stop_spawned_child(&self, child: &mut ChildProcess) -> Result<(), FailureReason> {
        #[cfg(test)]
        if self
            .post_spawn_stop_failures
            .fetch_update(
                std::sync::atomic::Ordering::SeqCst,
                std::sync::atomic::Ordering::SeqCst,
                |left| if left > 0 { Some(left - 1) } else { None },
            )
            .is_ok()
        {
            return Err(FailureReason::Other("injected runner stop failure".into()));
        }
        child
            .stop(Duration::from_secs(1))
            .map(|_| ())
            .map_err(|_| FailureReason::Other("spawned runner process could not be stopped".into()))
    }

    fn abort_spawned_child(
        &self,
        mut child: ChildProcess,
        attempt: &RunnerAttempt,
        remove_identity: bool,
    ) -> ProcessStartFailure {
        let mut reaped = self.stop_spawned_child(&mut child).is_ok();
        if reaped {
            if remove_identity {
                Self::remove_identity_files(attempt);
            }
        } else {
            // A failed stop is not a failed attempt yet.  Persist enough truth
            // for crash recovery, and retain the owned child when possible.
            let identity_durable =
                serde_json::to_vec(child.identity())
                    .ok()
                    .is_some_and(|identity| {
                        self.persist_identity(attempt, &identity).is_ok()
                            || self.persist_fallback_identity(attempt, &identity).is_ok()
                    });
            if !identity_durable {
                // Returning a live PID as though recovery were complete would
                // make the next boot trust a recyclable PID. Reaping is bounded;
                // if it cannot finish, the durable `starting` journal entry is
                // deliberately unresolved on restart and blocks new launches.
                for _ in 1..MAX_POST_SPAWN_STOP_ATTEMPTS {
                    if self.stop_spawned_child(&mut child).is_ok() {
                        reaped = true;
                        break;
                    }
                }
                if !reaped {
                    // The attempt journal will durably record `starting` and
                    // its PID. Recovery treats a missing full identity as
                    // unresolved and starts nothing, so bounded stop failure
                    // cannot turn into either a hang or a duplicate runner.
                    let pid = child.pid();
                    let marker = write_durable_file(
                        &Self::unresolved_process_path(attempt),
                        pid.to_string().as_bytes(),
                    );
                    self.children
                        .lock()
                        .unwrap_or_else(std::sync::PoisonError::into_inner)
                        .insert(attempt.id, child);
                    let reason = if marker.is_ok() {
                        FailureReason::Other(
                            "spawn cleanup exhausted its bounded stop attempts; the live process remains under durable unresolved supervision"
                                .into(),
                        )
                    } else {
                        FailureReason::Other(
                            "spawn cleanup exhausted its bounded stop attempts and the unresolved-process marker could not be journalled"
                                .into(),
                        )
                    };
                    return ProcessStartFailure::after_spawn_live_with_reason(pid, reason);
                }
            } else {
                let pid = child.pid();
                self.children
                    .lock()
                    .unwrap_or_else(std::sync::PoisonError::into_inner)
                    .insert(attempt.id, child);
                return ProcessStartFailure::after_spawn_live(pid);
            }
        }
        #[cfg(test)]
        if reaped {
            self.post_spawn_reaps
                .fetch_add(1, std::sync::atomic::Ordering::SeqCst);
        }
        #[cfg(not(test))]
        let _ = reaped;
        ProcessStartFailure::after_spawn_stopped()
    }

    fn identity_path(attempt: &RunnerAttempt) -> PathBuf {
        attempt.runtime_path().join(IDENTITY_FILE)
    }

    fn fallback_identity_path(attempt: &RunnerAttempt) -> PathBuf {
        attempt.runtime_path().join(FALLBACK_IDENTITY_FILE)
    }

    fn unresolved_process_path(attempt: &RunnerAttempt) -> PathBuf {
        attempt.runtime_path().join(UNRESOLVED_PROCESS_FILE)
    }

    fn remove_identity_files(attempt: &RunnerAttempt) {
        let _ = fs::remove_file(Self::identity_path(attempt));
        let _ = fs::remove_file(Self::fallback_identity_path(attempt));
        let _ = fs::remove_file(Self::unresolved_process_path(attempt));
    }

    fn persist_identity(&self, attempt: &RunnerAttempt, bytes: &[u8]) -> std::io::Result<()> {
        self.persist_identity_at(&Self::identity_path(attempt), bytes)
    }

    fn persist_fallback_identity(
        &self,
        attempt: &RunnerAttempt,
        bytes: &[u8],
    ) -> std::io::Result<()> {
        self.persist_identity_at(&Self::fallback_identity_path(attempt), bytes)
    }

    fn persist_identity_at(&self, path: &Path, bytes: &[u8]) -> std::io::Result<()> {
        #[cfg(test)]
        if self.faults_at(PostSpawnBoundary::IdentityWrite) {
            return Err(std::io::Error::other("injected identity write failure"));
        }
        write_durable_file(path, bytes)
    }

    fn intent_path(attempt: &RunnerAttempt) -> PathBuf {
        attempt.runtime_path().join(TERMINATE_INTENT_FILE)
    }

    fn read_identity(attempt: &RunnerAttempt) -> Result<Option<ProcessIdentity>, FailureReason> {
        match Self::read_identity_at(&Self::identity_path(attempt))? {
            Some(identity) => Ok(Some(identity)),
            None => Self::read_identity_at(&Self::fallback_identity_path(attempt)),
        }
    }

    fn read_identity_at(path: &Path) -> Result<Option<ProcessIdentity>, FailureReason> {
        match fs::read(path) {
            Ok(bytes) => serde_json::from_slice(&bytes)
                .map(Some)
                .map_err(|_| FailureReason::Other("process identity journal is unreadable".into())),
            Err(error) if error.kind() == std::io::ErrorKind::NotFound => Ok(None),
            Err(_) => Err(FailureReason::Other(
                "process identity journal could not be read".into(),
            )),
        }
    }
}

impl ProcessSupervisor for NativeProcesses {
    fn destroy(&self, attempt: &RunnerAttempt) -> Result<ProviderDestroy, FailureReason> {
        if !attempt.execution().is_native() {
            return Err(FailureReason::Other(
                "execution provider unavailable".into(),
            ));
        }
        // Existing native reconciliation has already settled process termination
        // before this boundary. Capture before ephemeral workspace deletion.
        if let Some(caches) = &self.dependency_caches {
            caches.capture_git(attempt.runtime_path());
        }
        Ok(ProviderDestroy::Destroyed)
    }

    fn prepare(
        &self,
        attempt: &RunnerAttempt,
        policy: &ScalePolicy,
    ) -> Result<PreparedEnvironment, FailureReason> {
        if !attempt.execution().is_native() || !policy.execution_policy().is_native() {
            return Err(FailureReason::Other(
                "execution provider unavailable".into(),
            ));
        }
        self.host_env()?;
        // Asked here, before the JIT registration, for the reason `host_env`
        // is: a broken file must cost no registration.
        let cache_target = match &self.dependency_caches {
            Some(caches) => {
                caches.config()?;
                Some(policy.target.clone())
            }
            None => None,
        };
        Ok(PreparedEnvironment {
            attempt: attempt.id,
            identity: None,
            cache_target,
        })
    }

    fn start(
        &self,
        prepared: PreparedEnvironment,
        attempt: &RunnerAttempt,
        handoff: OneTimeJitHandoff<'_>,
    ) -> Result<EnvironmentIdentity, ProcessStartFailure> {
        if prepared.attempt != attempt.id || !attempt.execution().is_native() {
            return Err(ProcessStartFailure::before_spawn(FailureReason::Other(
                "execution provider identity mismatch".into(),
            )));
        }
        self.spawn_listener(attempt, handoff.consume(), prepared.cache_target.as_ref())
            .map(EnvironmentIdentity::NativeProcess)
    }

    fn spawn(
        &self,
        attempt: &RunnerAttempt,
        config: &EncodedJitConfig,
    ) -> Result<u32, ProcessStartFailure> {
        self.spawn_listener(attempt, config, None)
    }

    fn is_alive(&self, attempt: &RunnerAttempt) -> Result<bool, FailureReason> {
        let mut children = self
            .children
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);
        if let Some(child) = children.get_mut(&attempt.id) {
            return match child
                .try_exit_status()
                .map_err(|_| FailureReason::Other("runner process could not be observed".into()))?
            {
                None => Ok(true),
                Some(status) => {
                    if let Ok(mut exits) = self.successful_exits.lock() {
                        exits.insert(attempt.id, status.success());
                    }
                    Ok(false)
                }
            };
        }
        let Some(identity) = Self::read_identity(attempt)? else {
            if attempt.process_id().is_some() || Self::unresolved_process_path(attempt).is_file() {
                return Err(FailureReason::Other(
                    "runner process identity is missing; refusing recovery until the process is resolved"
                        .into(),
                ));
            }
            return Ok(false);
        };
        match identity.recheck() {
            Ok(Adoption::Live) => Ok(true),
            Ok(Adoption::Gone | Adoption::PidRecycled { .. }) => Ok(false),
            Err(_) => Ok(false),
        }
    }

    fn recovered_pid(&self, attempt: &RunnerAttempt) -> Result<Option<u32>, FailureReason> {
        Ok(Self::read_identity(attempt)?.map(|identity| identity.pid()))
    }

    fn completed_successfully(&self, attempt: &RunnerAttempt) -> bool {
        self.successful_exits
            .lock()
            .ok()
            .and_then(|exits| exits.get(&attempt.id).copied())
            .unwrap_or(false)
    }

    fn record_terminate_intent(&self, attempt: &RunnerAttempt) -> Result<(), FailureReason> {
        let path = Self::intent_path(attempt);
        write_durable_file(&path, b"registration-timeout\n")
            .map_err(|_| FailureReason::Other("terminate intent could not be journalled".into()))
    }

    fn has_terminate_intent(&self, attempt: &RunnerAttempt) -> bool {
        Self::intent_path(attempt).is_file()
    }

    fn terminate(&self, attempt: &RunnerAttempt) -> Result<(), FailureReason> {
        let mut children = self
            .children
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);
        if let Some(child) = children.get_mut(&attempt.id) {
            child
                .stop(Duration::from_secs(10))
                .map_err(|_| FailureReason::Other("runner process could not be stopped".into()))?;
            return Ok(());
        }
        let Some(identity) = Self::read_identity(attempt)? else {
            return Ok(());
        };
        match identity
            .terminate(Duration::from_secs(10))
            .map_err(|_| FailureReason::Other("runner process could not be stopped".into()))?
        {
            Termination::Terminated | Termination::AlreadyGone => Ok(()),
            Termination::RefusedPidRecycled { .. } => Err(FailureReason::Other(
                "runner PID was recycled; refusing to signal it".into(),
            )),
        }
    }
}

pub struct LifecyclePorts {
    pub store: Arc<dyn Store>,
    pub github: Arc<dyn LifecycleGithub>,
    pub packages: Arc<dyn RuntimePackages>,
    pub processes: Arc<dyn ExecutionProvider>,
    pub clock: Arc<dyn Clock>,
    pub demand: Arc<dyn DemandPersistence>,
    pub delay: Arc<dyn RetryDelay>,
    pub events: Arc<dyn AttemptEventSink>,
    pub reconcile_events: Arc<dyn EventSink>,
}

impl fmt::Debug for LifecyclePorts {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("LifecyclePorts")
            .field("store", &self.store)
            .field("github", &self.github)
            .field("packages", &self.packages)
            .field("processes", &self.processes)
            .finish_non_exhaustive()
    }
}

#[derive(Debug, thiserror::Error)]
pub enum LifecycleError {
    #[error("attempt journal operation failed")]
    Journal,
    #[error("attempt {0} is not in the journal")]
    Missing(AttemptId),
    #[error("attempt lifecycle transition was refused")]
    Transition,
    #[error("startup recovery has not completed")]
    RecoveryIncomplete,
    /// A persistent slot could not be proven safe to scrub, so the attempt keeps
    /// its uncleaned state and, with it, its slot lease.
    ///
    /// Separate from [`Self::Failed`] because the two demand opposite handling
    /// from the same call sites. A failure aborts the pass; a quarantine must
    /// not, or one stuck slot would stop the host launching anything at all —
    /// which is precisely what `04-security-recovery.md` rules out when it says
    /// such an attempt "does not count as active host capacity" and "recovery
    /// retries the same cleanup".
    #[error("the persistent slot was not cleaned: {detail}")]
    SlotQuarantined {
        /// The closed-vocabulary event field; never operator or workflow text.
        class: &'static str,
        detail: String,
    },
    /// An ephemeral runtime is still held by a late process. Its journal state
    /// remains unchanged and ordinary supervision retries it, but startup
    /// recovery must not take unrelated repositories offline because of it.
    #[error("{}", FailureReason::WorkspaceCleanupDeferred)]
    WorkspaceCleanupDeferred,
    #[error("isolated environment cleanup is deferred")]
    EnvironmentCleanupDeferred,
    #[error("runner lifecycle failed: {0}")]
    Failed(FailureReason),
}

impl LifecycleError {
    fn reason(&self) -> FailureReason {
        match self {
            Self::Failed(reason) => reason.clone(),
            Self::RecoveryIncomplete => FailureReason::Other("startup recovery incomplete".into()),
            Self::Journal => FailureReason::Other("attempt journal operation failed".into()),
            Self::Missing(_) => FailureReason::Other("attempt disappeared from the journal".into()),
            Self::Transition => FailureReason::Other("attempt transition was refused".into()),
            // Rendered through `Display` rather than a second copy of the same
            // sentence, so the two cannot drift apart.
            Self::SlotQuarantined { .. } => FailureReason::Other(self.to_string()),
            Self::WorkspaceCleanupDeferred => FailureReason::WorkspaceCleanupDeferred,
            Self::EnvironmentCleanupDeferred => FailureReason::Other(self.to_string()),
        }
    }
}

/// Production implementation of e1's launcher port.
#[derive(Debug)]
pub struct LifecycleLauncher {
    host_id: HostId,
    app_paths: runner_manager_platform::paths::AppPaths,
    diagnostics_root: PathBuf,
    runner_group_id: u64,
    timeouts: RecoveryTimeouts,
    retry: RetryPolicy,
    cancel: CancelToken,
    ports: LifecyclePorts,
    recovery_complete: Mutex<bool>,
    versions: Mutex<BTreeMap<AttemptId, RunnerVersion>>,
    pending_replacements: Mutex<BTreeMap<AttemptId, ReplacementIntent>>,
    /// Backoff for cleanups [`Self::supervise`] tolerates and retries, so a
    /// workspace that cannot be removed is not retried and reported on every
    /// pass.
    cleanup_retries: Mutex<CleanBackoff>,
    turns: Arc<tokio::sync::Semaphore>,
    /// The attempts reserved and not yet up or failed: their bring-up is writing
    /// their journal entries, and it runs while the target's pass supervises.
    bringing_up: Mutex<BTreeSet<AttemptId>>,
}

/// Takes an attempt out of [`LifecycleLauncher::bringing_up`], however its
/// bring-up ends.
struct BroughtUpOnDrop<'a> {
    attempts: &'a Mutex<BTreeSet<AttemptId>>,
    id: AttemptId,
}

impl Drop for BroughtUpOnDrop<'_> {
    fn drop(&mut self) {
        self.attempts
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
            .remove(&self.id);
    }
}

/// How many runners of one host prepare at once, whatever their target: a
/// quarter of its cores, at least two. A runner's package is ~9,000 files, and
/// on a disk jobs are using, more at once only make all of them slower. Fair,
/// so the ones waiting go in the order they were reserved.
#[must_use]
pub fn preparation_turns() -> Arc<tokio::sync::Semaphore> {
    let cores = std::thread::available_parallelism().map_or(1, std::num::NonZero::get);
    Arc::new(tokio::sync::Semaphore::new((cores / 4).max(2)))
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum ReconcileProgress {
    Reconciled,
    Deferred,
    Replacement {
        attempt: AttemptId,
        operation: &'static str,
    },
}

impl LifecycleLauncher {
    #[must_use]
    pub fn new(
        host_id: HostId,
        app_paths: runner_manager_platform::paths::AppPaths,
        diagnostics_root: impl Into<PathBuf>,
        runner_group_id: u64,
        timeouts: RecoveryTimeouts,
        retry: RetryPolicy,
        ports: LifecyclePorts,
    ) -> Self {
        Self {
            host_id,
            app_paths,
            diagnostics_root: diagnostics_root.into(),
            runner_group_id,
            timeouts,
            retry,
            cancel: CancelToken::new(),
            ports,
            recovery_complete: Mutex::new(false),
            versions: Mutex::new(BTreeMap::new()),
            pending_replacements: Mutex::new(BTreeMap::new()),
            cleanup_retries: Mutex::new(CleanBackoff::default()),
            turns: preparation_turns(),
            bringing_up: Mutex::default(),
        }
    }

    /// Takes turns to prepare with every launcher holding `turns`, rather than
    /// only with itself: the targets of one host.
    #[must_use]
    pub fn with_preparation_turns(mut self, turns: Arc<tokio::sync::Semaphore>) -> Self {
        self.turns = turns;
        self
    }

    /// Reconcile the entire journal before allowing a launch.  Unknown-policy
    /// attempts are left untouched rather than being acted on without an
    /// ownership proof.
    pub async fn recover_startup(
        &self,
        policies: &[ScalePolicy],
    ) -> Result<Vec<ReplacementIntent>, LifecycleError> {
        *self
            .recovery_complete
            .lock()
            .map_err(|_| LifecycleError::Journal)? = false;
        let by_id: BTreeMap<_, _> = policies.iter().map(|policy| (policy.id, policy)).collect();
        let attempts = self
            .ports
            .store
            .attempts()
            .map_err(|_| LifecycleError::Journal)?;
        let owned = self.ports.processes.enumerate_owned(self.host_id);
        for identity in &owned {
            if let EnvironmentIdentity::Isolated { attempt: id, .. } = identity
                && !attempts.iter().any(|attempt| {
                    attempt.state() != AttemptState::Cleaned
                        && identity_matches_intent(self.host_id, attempt, identity)
                })
            {
                // Enumeration is discovery, not authority to delete.
                self.ports
                    .events
                    .emit(AttemptEvent::QuarantinedOwnedResource { attempt: *id });
                tracing::warn!(host_id = %self.host_id, attempt_id = %id, reason = "owned_isolated_resource_without_matching_journal", "provider resource quarantined for operator review");
            }
        }
        let mut unresolved = false;
        for mut attempt in attempts {
            let Some(policy) = by_id.get(&attempt.policy_id) else {
                if attempt.counts_against_capacity() {
                    unresolved = true;
                }
                continue;
            };
            authorize(self.host_id, policy, &attempt).map_err(|_| LifecycleError::Journal)?;
            let allocation_resources = owned
                .iter()
                .filter(|identity| identity_same_allocation(self.host_id, &attempt, identity))
                .collect::<Vec<_>>();
            if allocation_resources.len() > 1 {
                self.ports
                    .events
                    .emit(AttemptEvent::QuarantinedOwnedResource {
                        attempt: attempt.id,
                    });
                tracing::warn!(attempt_id = %attempt.id, reason = "duplicate_isolated_resource_ownership", "provider resources quarantined for operator review");
            }
            if attempt.state() != AttemptState::Cleaned
                && matches!(
                    attempt.execution(),
                    AttemptExecution::Isolated {
                        environment_id: None,
                        ..
                    }
                )
                && allocation_resources.len() == 1
                && let Some(EnvironmentIdentity::Isolated { environment_id, .. }) =
                    allocation_resources.first().copied()
            {
                attempt
                    .prepared_environment(environment_id.clone())
                    .map_err(|_| LifecycleError::Transition)?;
                if attempt.state() == AttemptState::Preparing {
                    attempt
                        .mark_prepared(self.ports.clock.now())
                        .map_err(|_| LifecycleError::Transition)?;
                }
                self.record(&attempt)?;
            }
            match self.reconcile_one(policy, attempt).await? {
                ReconcileProgress::Deferred => {
                    if policy.execution_policy().is_native() {
                        unresolved = true;
                    }
                }
                ReconcileProgress::Replacement { attempt, operation } => {
                    self.pending_replacements
                        .lock()
                        .map_err(|_| LifecycleError::Journal)?
                        .insert(
                            attempt,
                            ReplacementIntent {
                                policy: policy.id,
                                previous_attempt: attempt,
                                operation,
                            },
                        );
                }
                ReconcileProgress::Reconciled => {}
            }
        }
        if unresolved {
            return Err(LifecycleError::RecoveryIncomplete);
        }
        *self
            .recovery_complete
            .lock()
            .map_err(|_| LifecycleError::Journal)? = true;
        Ok(self
            .pending_replacements
            .lock()
            .map_err(|_| LifecycleError::Journal)?
            .values()
            .copied()
            .collect())
    }

    /// Supervise all attempts of one policy during an ordinary poll.
    pub async fn supervise(
        &self,
        policy: &ScalePolicy,
    ) -> Result<Vec<ReplacementIntent>, LifecycleError> {
        let mut replacements = Vec::new();
        self.pending_replacements
            .lock()
            .map_err(|_| LifecycleError::Journal)?
            .retain(|_, intent| {
                if intent.policy == policy.id {
                    replacements.push(*intent);
                    false
                } else {
                    true
                }
            });
        // Read under the set a reservation joins before it is journalled, so
        // every attempt read here that a bring-up may write to is known to be
        // one: it has no process yet and no registration, which this pass would
        // read as a runner gone, and what was read of it is out of date at once.
        let attempts = {
            let bringing_up = self
                .bringing_up
                .lock()
                .map_err(|_| LifecycleError::Journal)?;
            let mut attempts = self
                .ports
                .store
                .attempts_for_policy(policy.id)
                .map_err(|_| LifecycleError::Journal)?;
            attempts.retain(|attempt| !bringing_up.contains(&attempt.id));
            attempts
        };
        for attempt in attempts {
            authorize(self.host_id, policy, &attempt).map_err(|_| LifecycleError::Journal)?;
            if let ReconcileProgress::Replacement { attempt, operation } =
                self.reconcile_one(policy, attempt).await?
            {
                replacements.push(ReplacementIntent {
                    policy: policy.id,
                    previous_attempt: attempt,
                    operation,
                });
            }
        }
        Ok(replacements)
    }

    async fn reconcile_one(
        &self,
        policy: &ScalePolicy,
        mut attempt: RunnerAttempt,
    ) -> Result<ReconcileProgress, LifecycleError> {
        if !attempt.execution().is_native() {
            return self.reconcile_isolated_one(policy, attempt).await;
        }
        if attempt.state() == AttemptState::Cleaned {
            // A child of Runner.Worker can outlive the runner process briefly.
            // If it recreates `_work` after `clean_attempt` removed the tree but
            // before the journal's final write, the journal truthfully reaches
            // `cleaned` and the directory appears again afterwards. Cleaned
            // attempts used to return here forever, making that late residue
            // invisible. The journalled ephemeral mode is the ownership proof:
            // retry the whole-tree removal, while a persistent slot deliberately
            // remains on disk with its retained `_work`.
            if matches!(attempt.workspace(), AttemptWorkspace::Ephemeral)
                && attempt.runtime_path().exists()
            {
                // The attempt is already terminal, has released its package
                // lease, and consumes no capacity. A late child may still hold
                // one of its recreated files open on Windows, so failure here
                // is residue to retry, not a reason to abort startup recovery
                // and take every unrelated repository offline.
                // Retried with backoff; the event is the one report, which the
                // event sink logs as a warning.
                let now = self.ports.clock.now();
                if !self.cleanup_retries().is_due(attempt.id, now) {
                    return Ok(ReconcileProgress::Reconciled);
                }
                match self.scrub_workspace(&attempt) {
                    Ok(()) => self.cleanup_retries().succeeded(attempt.id),
                    Err(LifecycleError::WorkspaceCleanupDeferred) => {
                        self.cleanup_retries().failed(attempt.id, now);
                        self.ports
                            .reconcile_events
                            .emit(LifecycleEvent::AttemptCleanFailed {
                                policy: attempt.policy_id,
                                attempt: attempt.id,
                                reason: "late_ephemeral_workspace_could_not_be_removed",
                            });
                    }
                    Err(error) => return Err(error),
                }
            }
            return Ok(ReconcileProgress::Reconciled);
        }
        if attempt.is_terminal() {
            self.clean_or_quarantine(&mut attempt)?;
            return Ok(ReconcileProgress::Reconciled);
        }
        let process_alive = self
            .ports
            .processes
            .inspect(&attempt)
            .map_err(LifecycleError::Failed)?
            == EnvironmentState::Running;
        let github = self
            .ports
            .github
            .observe(&policy.target, attempt.id, &self.cancel)
            .await;

        // If the agent died after GitHub accepted the registration but before
        // the non-secret runner-id sidecar landed, inventory closes the gap.
        // Persist it before making any state decision so a second crash moves
        // the boundary forward rather than repeating it.
        if let Some(runner_id) = github.runner_id
            && read_runner_id(attempt.runtime_path()).is_none()
        {
            write_runner_id(attempt.runtime_path(), runner_id)?;
            self.ports
                .events
                .emit(AttemptEvent::RemoteIdentityRecovered {
                    attempt: attempt.id,
                    runner_id,
                });
        }

        // The child identity is synced before `spawn` returns.  If the agent
        // crashed before the following `starting` journal write, recover that
        // exact PID and take the legal `jit_received -> starting` edge before
        // applying GitHub's authoritative idle/busy observation below.
        if attempt.state() == AttemptState::JitReceived
            && process_alive
            && let Some(pid) = self
                .ports
                .processes
                .recovered_pid(&attempt)
                .map_err(LifecycleError::Failed)?
        {
            attempt
                .started(pid, self.ports.clock.now())
                .map_err(|_| LifecycleError::Transition)?;
            self.record(&attempt)?;
        }

        // What the runner's own diagnostics say about whether it ran a job.
        // Read before anything below can conclude the attempt, because cleanup
        // deletes `_diag` with the rest of the runtime directory.
        // A one-shot child owned by this invocation exited successfully. This
        // concludes the *runner attempt*, never the workflow outcome; GitHub
        // remains authoritative for that. GitHub's inventory is a sampled
        // witness: a job of a few seconds starts and ends between two passes,
        // and an assignment GitHub shows can be one the runner never took up.
        // The runner's own diagnostics decide, read before cleanup deletes
        // them, and GitHub's sample only decides when they say nothing. Not
        // while GitHub is unreachable: a registration still listed there could
        // not be removed, and nothing visits a concluded attempt again.
        if !process_alive
            && github.status != GithubRunnerObservation::Unreachable
            && matches!(
                attempt.state(),
                AttemptState::Starting | AttemptState::Idle | AttemptState::Busy
            )
            && self.ports.processes.completed_successfully(&attempt)
        {
            let state = attempt.state();
            let outcome = match (state, JobEvidence::of(attempt.runtime_path())) {
                // Without a runner id there is no edge to `busy`; the recovery
                // path below concludes the attempt without one.
                (AttemptState::Starting | AttemptState::Idle, JobEvidence::RanAJob) => {
                    known_runner_id(&attempt, github.runner_id)
                        .map(|runner_id| (Some(runner_id), AttemptOutcome::CompletedJob))
                }
                (AttemptState::Busy, JobEvidence::RanAJob) => {
                    Some((None, AttemptOutcome::CompletedJob))
                }
                (AttemptState::Busy, JobEvidence::NoJob) => {
                    Some((None, AttemptOutcome::ExitedIdleWithoutWork))
                }
                (AttemptState::Busy, JobEvidence::Unknown)
                    if github.status == GithubRunnerObservation::NotRegistered =>
                {
                    Some((None, AttemptOutcome::CompletedJob))
                }
                _ => None,
            };
            if let Some((walk_to_busy, outcome)) = outcome {
                // An ephemeral runner leaves GitHub's list a little after its
                // process exits; one still listed is removed here rather than
                // left for GitHub to time out. First, so the journal's last
                // intermediate state and the conclusion are written back to back:
                // an agent that dies between them recovers from the state it was
                // in before this pass.
                if matches!(github.status, GithubRunnerObservation::Registered { .. }) {
                    self.deregister_runner(policy, &attempt).await;
                }
                let now = self.ports.clock.now();
                match (walk_to_busy, &outcome) {
                    (Some(runner_id), _) => {
                        self.transition(&mut attempt, |a| a.assigned_job(runner_id, now))?;
                    }
                    (None, AttemptOutcome::ExitedIdleWithoutWork) => {
                        self.transition(&mut attempt, |a| a.assignment_not_taken(now))?;
                    }
                    (None, _) => {}
                }
                self.conclude(&mut attempt, outcome)?;
                self.clean_or_quarantine(&mut attempt)?;
                return Ok(ReconcileProgress::Reconciled);
            }
        }

        // A live runner journalled `busy` that GitHub now shows waiting, and
        // whose diagnostics show no job: the assignment was never taken up.
        // Back to `idle`, where the idle timeout applies to it again; the
        // `busy` arm below would otherwise adopt it for as long as it runs.
        if process_alive
            && attempt.state() == AttemptState::Busy
            && github.status == (GithubRunnerObservation::Registered { busy: false })
            && JobEvidence::of(attempt.runtime_path()) == JobEvidence::NoJob
        {
            let now = self.ports.clock.now();
            self.transition(&mut attempt, |a| a.assignment_not_taken(now))?;
            return Ok(ReconcileProgress::Reconciled);
        }

        // This durable mark is more authoritative than a later observation
        // which cannot distinguish an agent kill from a crash.
        if self.ports.processes.has_terminate_intent(&attempt) && !process_alive {
            self.deregister_runner(policy, &attempt).await;
            self.conclude(
                &mut attempt,
                AttemptOutcome::failed(FailureReason::TerminatedAfterRegistrationTimeout),
            )?;
            self.clean_or_quarantine(&mut attempt)?;
            return Ok(ReconcileProgress::Replacement {
                attempt: attempt.id,
                operation: "registration_timeout_replacement",
            });
        }

        // A remote registration with no surviving process has lost its
        // one-shot JIT secret.  Walking it to `starting` would require inventing
        // a PID; retrying the same registration would require inventing the
        // secret.  Record the configuration as expired and let the bounded
        // replacement path request a fresh one only if demand remains.
        if matches!(
            attempt.state(),
            AttemptState::Allocated | AttemptState::JitReceived
        ) && !process_alive
            && matches!(github.status, GithubRunnerObservation::Registered { .. })
        {
            if attempt.state() == AttemptState::Allocated {
                attempt
                    .jit_received(self.ports.clock.now())
                    .map_err(|_| LifecycleError::Transition)?;
                self.record(&attempt)?;
            }
            self.deregister_runner(policy, &attempt).await;
            self.conclude(
                &mut attempt,
                AttemptOutcome::failed(FailureReason::JitExpired),
            )?;
            self.clean_or_quarantine(&mut attempt)?;
            return Ok(ReconcileProgress::Replacement {
                attempt: attempt.id,
                operation: "jit_expired_replacement",
            });
        }

        match recovery_decision(
            &attempt,
            RecoveryObservation {
                process_alive,
                github: github.status,
            },
            self.timeouts,
            self.ports.clock.as_ref(),
        ) {
            RecoveryDecision::Nothing | RecoveryDecision::Wait => Ok(ReconcileProgress::Reconciled),
            RecoveryDecision::Defer => Ok(ReconcileProgress::Deferred),
            RecoveryDecision::Adopt => {
                self.ports.events.emit(AttemptEvent::Adopted {
                    attempt: attempt.id,
                });
                Ok(ReconcileProgress::Reconciled)
            }
            RecoveryDecision::Clean => {
                self.clean_or_quarantine(&mut attempt)?;
                Ok(ReconcileProgress::Reconciled)
            }
            RecoveryDecision::Observe(state) => {
                let runner_id = known_runner_id(&attempt, github.runner_id)
                    .ok_or(LifecycleError::Transition)?;
                match state {
                    AttemptState::JitReceived => attempt
                        .jit_received(self.ports.clock.now())
                        .map_err(|_| LifecycleError::Transition)?,
                    AttemptState::Starting => {
                        let pid = attempt.process_id().ok_or(LifecycleError::Transition)?;
                        attempt
                            .started(pid, self.ports.clock.now())
                            .map_err(|_| LifecycleError::Transition)?;
                    }
                    AttemptState::Idle => attempt
                        .registered_idle(runner_id, self.ports.clock.now())
                        .map_err(|_| LifecycleError::Transition)?,
                    AttemptState::Busy => attempt
                        .assigned_job(runner_id, self.ports.clock.now())
                        .map_err(|_| LifecycleError::Transition)?,
                    _ => return Err(LifecycleError::Transition),
                }
                self.record(&attempt)?;
                Ok(ReconcileProgress::Reconciled)
            }
            RecoveryDecision::Conclude(outcome) => {
                let replacement = replacement_operation(&outcome);
                // Only when GitHub still holds one. Every other conclusion here
                // was reached *because* the observation was `NotRegistered`, and
                // spending a DELETE to be told so again would put a request per
                // concluded attempt on a budget `rest.rs` prices to the request.
                if matches!(github.status, GithubRunnerObservation::Registered { .. }) {
                    self.deregister_runner(policy, &attempt).await;
                }
                self.conclude(&mut attempt, outcome)?;
                self.clean_or_quarantine(&mut attempt)?;
                Ok(
                    replacement.map_or(ReconcileProgress::Reconciled, |operation| {
                        ReconcileProgress::Replacement {
                            attempt: attempt.id,
                            operation,
                        }
                    }),
                )
            }
            RecoveryDecision::Terminate(payload) => {
                // The mark is synced first, and what proves the process died is
                // the `is_alive` re-read below -- not the outcome recorded after
                // it. Which outcome that is depends on why the termination was
                // ordered, and only the payload knows: a `starting` runner that
                // never registered is a failure this agent then stopped, while
                // an `idle` one past its timeout is flow 2.7's surplus exit and
                // no failure at all. Hardcoding the first reason here labelled
                // the second as a registration timeout and asked the allocator
                // for a replacement to boot.
                let idle_exit = payload.is_idle_exit();
                self.ports
                    .processes
                    .record_terminate_intent(&attempt)
                    .map_err(LifecycleError::Failed)?;
                self.ports.events.emit(AttemptEvent::TerminateIntent {
                    attempt: attempt.id,
                });
                if self
                    .ports
                    .processes
                    .stop(&attempt)
                    .map_err(LifecycleError::Failed)?
                    == ProviderStop::StillRunning
                {
                    return Ok(ReconcileProgress::Deferred);
                }
                if self
                    .ports
                    .processes
                    .inspect(&attempt)
                    .map_err(LifecycleError::Failed)?
                    == EnvironmentState::Running
                {
                    return Ok(ReconcileProgress::Deferred);
                }
                self.ports.events.emit(AttemptEvent::Terminated {
                    attempt: attempt.id,
                });
                // The registration-timeout path keeps deriving its own reason
                // rather than applying the payload: on the pass that reads the
                // journalled mark back the process is dead, and
                // `TerminatedAfterRegistrationTimeout` is the reason that stays
                // true of a dead process. See `RecoveryDecision::Terminate`.
                let outcome = if idle_exit {
                    AttemptOutcome::ExitedIdleWithoutWork
                } else {
                    AttemptOutcome::failed(FailureReason::TerminatedAfterRegistrationTimeout)
                };
                self.deregister_runner(policy, &attempt).await;
                self.conclude(&mut attempt, outcome)?;
                self.clean_or_quarantine(&mut attempt)?;
                // A surplus runner is not replaced. It was stopped precisely
                // because the work it was started for went elsewhere; asking the
                // allocator for another one rebuilds it every idle timeout.
                if idle_exit {
                    Ok(ReconcileProgress::Reconciled)
                } else {
                    Ok(ReconcileProgress::Replacement {
                        attempt: attempt.id,
                        operation: "registration_timeout_replacement",
                    })
                }
            }
        }
    }

    async fn reconcile_isolated_one(
        &self,
        policy: &ScalePolicy,
        mut attempt: RunnerAttempt,
    ) -> Result<ReconcileProgress, LifecycleError> {
        if attempt.state() == AttemptState::Cleaned {
            return Ok(ReconcileProgress::Reconciled);
        }
        if attempt.is_terminal() {
            self.clean_or_quarantine(&mut attempt)?;
            return Ok(ReconcileProgress::Reconciled);
        }
        if matches!(
            attempt.state(),
            AttemptState::Allocated | AttemptState::Preparing | AttemptState::Prepared
        ) {
            // No JIT was requested yet. Restart can safely retire this attempt;
            // a matching owned resource is stopped by the durable cleanup path.
            self.conclude(
                &mut attempt,
                AttemptOutcome::failed(FailureReason::Other(
                    "isolated preparation interrupted".into(),
                )),
            )?;
            self.clean_or_quarantine(&mut attempt)?;
            return Ok(ReconcileProgress::Reconciled);
        }
        let Ok(provider_state) = self.ports.processes.recover(&attempt) else {
            return Ok(ReconcileProgress::Deferred);
        };
        if provider_state != EnvironmentState::Missing {
            let Ok(owned) = self.ports.processes.owns(&attempt) else {
                return Ok(ReconcileProgress::Deferred);
            };
            if !owned {
                self.ports
                    .events
                    .emit(AttemptEvent::QuarantinedOwnedResource {
                        attempt: attempt.id,
                    });
                tracing::warn!(attempt_id = %attempt.id, reason = "isolated_resource_ownership_mismatch", "provider resource quarantined for operator review");
                return Ok(ReconcileProgress::Deferred);
            }
        }
        let live = matches!(
            provider_state,
            EnvironmentState::Starting | EnvironmentState::Running
        );
        if attempt.state() == AttemptState::JitReceived && live {
            attempt
                .started_isolated(self.ports.clock.now())
                .map_err(|_| LifecycleError::Transition)?;
            self.record(&attempt)?;
        }
        let github = self
            .ports
            .github
            .observe(&policy.target, attempt.id, &self.cancel)
            .await;
        if let Some(runner_id) = github.runner_id
            && read_runner_id(attempt.runtime_path()).is_none()
        {
            write_runner_id(attempt.runtime_path(), runner_id)?;
        }
        // A successfully reaped one-shot listener is stronger evidence than a
        // missing registration. Recovered guests have no attached child and
        // still follow the conservative orphan path below.
        if attempt.state() == AttemptState::Busy
            && !live
            && github.status == GithubRunnerObservation::NotRegistered
            && self.ports.processes.completed_successfully(&attempt)
        {
            self.conclude(&mut attempt, AttemptOutcome::CompletedJob)?;
            self.clean_or_quarantine(&mut attempt)?;
            return Ok(ReconcileProgress::Reconciled);
        }
        match recovery_decision(
            &attempt,
            RecoveryObservation {
                process_alive: live,
                github: github.status,
            },
            self.timeouts,
            self.ports.clock.as_ref(),
        ) {
            RecoveryDecision::Nothing | RecoveryDecision::Wait => Ok(ReconcileProgress::Reconciled),
            RecoveryDecision::Defer => Ok(ReconcileProgress::Deferred),
            RecoveryDecision::Adopt => {
                self.ports.events.emit(AttemptEvent::Adopted {
                    attempt: attempt.id,
                });
                Ok(ReconcileProgress::Reconciled)
            }
            RecoveryDecision::Clean => {
                self.clean_or_quarantine(&mut attempt)?;
                Ok(ReconcileProgress::Reconciled)
            }
            RecoveryDecision::Observe(state) => {
                let runner_id = github
                    .runner_id
                    .or_else(|| read_runner_id(attempt.runtime_path()))
                    .ok_or(LifecycleError::Transition)?;
                match state {
                    AttemptState::Idle => attempt
                        .registered_idle(runner_id, self.ports.clock.now())
                        .map_err(|_| LifecycleError::Transition)?,
                    AttemptState::Busy => attempt
                        .assigned_job(runner_id, self.ports.clock.now())
                        .map_err(|_| LifecycleError::Transition)?,
                    _ => return Err(LifecycleError::Transition),
                }
                self.record(&attempt)?;
                Ok(ReconcileProgress::Reconciled)
            }
            RecoveryDecision::Conclude(outcome) | RecoveryDecision::Terminate(outcome) => {
                let replacement = replacement_operation(&outcome);
                if matches!(github.status, GithubRunnerObservation::Registered { .. }) {
                    self.deregister_runner(policy, &attempt).await;
                }
                self.conclude(&mut attempt, outcome)?;
                self.clean_or_quarantine(&mut attempt)?;
                Ok(
                    replacement.map_or(ReconcileProgress::Reconciled, |operation| {
                        ReconcileProgress::Replacement {
                            attempt: attempt.id,
                            operation,
                        }
                    }),
                )
            }
        }
    }

    /// Takes one domain edge and journals it.
    fn transition(
        &self,
        attempt: &mut RunnerAttempt,
        edge: impl FnOnce(
            &mut RunnerAttempt,
        ) -> Result<(), runner_manager_domain::attempt::AttemptError>,
    ) -> Result<(), LifecycleError> {
        edge(attempt).map_err(|_| LifecycleError::Transition)?;
        self.record(attempt)
    }

    fn record(&self, attempt: &RunnerAttempt) -> Result<(), LifecycleError> {
        self.ports
            .store
            .record_attempt(attempt)
            .map_err(|_| LifecycleError::Journal)?;
        self.ports.events.emit(AttemptEvent::State {
            attempt: attempt.id,
            state: attempt.state(),
        });
        Ok(())
    }

    /// Remove the GitHub registration an attempt is about to leave behind.
    ///
    /// # Why this is not fallible, and does not block the conclusion
    ///
    /// GitHub retires an ephemeral runner itself once that runner *completes a
    /// job*, and for the ordinary path that is the whole story. The paths that
    /// reach here are the ones where it does not: a runner stopped before it
    /// was ever assigned work, a registration whose process died still holding
    /// it, a JIT configuration that expired. Nothing else deletes those, and
    /// before this existed nothing did — they accumulated in the target's
    /// runner settings, one row per attempt, for the life of the repository.
    ///
    /// It returns `()` rather than a `Result` because the alternative is worse
    /// in both directions. The attempt is over: its process is gone and its
    /// slot has to come back, so a failed delete may not abort the conclusion
    /// or the host leaks capacity every time GitHub is unreachable. And a
    /// registration that outlives this call is not lost — it is exactly the
    /// `Registered` + dead-process observation that
    /// [`AttemptOutcome::Orphaned`] already names, which a later pass can still
    /// see. So a failure is logged and stepped over, deliberately.
    async fn deregister_runner(&self, policy: &ScalePolicy, attempt: &RunnerAttempt) {
        let Some(runner_id) = attempt
            .github_runner_id()
            .or_else(|| read_runner_id(attempt.runtime_path()))
        else {
            return;
        };
        if self
            .ports
            .github
            .deregister(&policy.target, runner_id, &self.cancel)
            .await
        {
            self.ports.events.emit(AttemptEvent::Deregistered {
                attempt: attempt.id,
                runner_id,
            });
        } else {
            tracing::warn!(
                attempt = %attempt.id,
                runner_id,
                "the runner registration could not be removed from GitHub; it will show in the \
                 target's runner settings until GitHub retires it or a later pass removes it"
            );
        }
    }

    fn conclude(
        &self,
        attempt: &mut RunnerAttempt,
        outcome: AttemptOutcome,
    ) -> Result<(), LifecycleError> {
        attempt
            .conclude(outcome.clone(), self.ports.clock.now())
            .map_err(|_| LifecycleError::Transition)?;
        self.record(attempt)?;
        self.ports.events.emit(AttemptEvent::Concluded {
            attempt: attempt.id,
            outcome: OutcomeKind::of(&outcome),
        });
        Ok(())
    }

    /// Clean a concluded attempt, tolerating a quarantined persistent slot.
    ///
    /// The quarantine is reported and stepped over rather than raised, because
    /// raising it aborts the whole pass: on the startup path that leaves
    /// `recovery_complete` false and stops the host launching anything, which is
    /// the opposite of `04-security-recovery.md`'s "it does not count as active
    /// host capacity" and "recovery retries the same cleanup". The attempt keeps
    /// its state, so it keeps its slot lease and its directory, and the next
    /// pass — [`crate::reconcile::Reconciler`]'s terminal sweep on every poll,
    /// or the next startup — attempts exactly the same cleanup again.
    ///
    /// A persistent-slot quarantine and an ephemeral directory still held by a
    /// late process are tolerated. A journal failure or a package lease that
    /// cannot be released still propagates: those are not one workspace's
    /// problem.
    ///
    /// A tolerated failure is retried with per-attempt backoff: until it is
    /// due again the attempt is skipped silently rather than re-tried and
    /// re-reported on every pass.
    fn clean_or_quarantine(&self, attempt: &mut RunnerAttempt) -> Result<(), LifecycleError> {
        let now = self.ports.clock.now();
        if !self.cleanup_retries().is_due(attempt.id, now) {
            return Ok(());
        }
        let reason = match self.clean_attempt(attempt) {
            Err(LifecycleError::SlotQuarantined { class, .. }) => class,
            Err(LifecycleError::WorkspaceCleanupDeferred) => {
                failure_reason_kind(&FailureReason::WorkspaceCleanupDeferred)
            }
            Err(LifecycleError::EnvironmentCleanupDeferred) => {
                "isolated_environment_cleanup_deferred"
            }
            other => {
                if other.is_ok() {
                    self.cleanup_retries().succeeded(attempt.id);
                }
                return other;
            }
        };
        self.cleanup_retries().failed(attempt.id, now);
        self.ports
            .reconcile_events
            .emit(LifecycleEvent::AttemptCleanFailed {
                policy: attempt.policy_id,
                attempt: attempt.id,
                reason,
            });
        Ok(())
    }

    fn cleanup_retries(&self) -> std::sync::MutexGuard<'_, CleanBackoff> {
        self.cleanup_retries
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
    }

    fn clean_attempt(&self, attempt: &mut RunnerAttempt) -> Result<(), LifecycleError> {
        if !attempt.execution().is_native() {
            return self.clean_isolated_attempt(attempt);
        }
        match self
            .ports
            .processes
            .destroy(attempt)
            .map_err(LifecycleError::Failed)?
        {
            ProviderDestroy::Destroyed => {}
            ProviderDestroy::Deferred(reason) => {
                return Err(LifecycleError::Failed(FailureReason::Other(reason.into())));
            }
        }
        let outcome = attempt
            .outcome()
            .cloned()
            .ok_or(LifecycleError::Transition)?;
        self.preserve_diagnostics(attempt, &outcome)?;
        self.scrub_workspace(attempt)?;
        self.ports
            .packages
            .release(attempt.id)
            .map_err(LifecycleError::Failed)?;
        attempt
            .clean(self.ports.clock.now())
            .map_err(|_| LifecycleError::Transition)?;
        self.record(attempt)?;
        let kind = OutcomeKind::of(&outcome);
        self.ports.events.emit(AttemptEvent::Cleaned {
            attempt: attempt.id,
            outcome: kind,
        });
        self.ports
            .reconcile_events
            .emit(LifecycleEvent::AttemptCleaned {
                policy: attempt.policy_id,
                attempt: attempt.id,
                outcome: kind,
            });
        Ok(())
    }

    fn clean_isolated_attempt(&self, attempt: &mut RunnerAttempt) -> Result<(), LifecycleError> {
        if attempt.state() != AttemptState::Destroying {
            attempt
                .begin_destroy(self.ports.clock.now())
                .map_err(|_| LifecycleError::Transition)?;
            self.record(attempt)?;
        }
        let provider = self.ports.processes.as_ref();
        let allocation_resources = provider.enumerate_owned(self.host_id);
        let matching_allocation = allocation_resources
            .iter()
            .filter(|identity| identity_same_allocation(self.host_id, attempt, identity))
            .collect::<Vec<_>>();
        if matching_allocation.len() > 1
            || matching_allocation
                .iter()
                .any(|identity| !identity_matches_intent(self.host_id, attempt, identity))
        {
            self.ports
                .events
                .emit(AttemptEvent::QuarantinedOwnedResource {
                    attempt: attempt.id,
                });
            tracing::warn!(attempt_id = %attempt.id, reason = "duplicate_or_mismatched_isolated_ownership", "provider resources quarantined for operator review");
            return Err(self.defer_environment_cleanup(attempt)?);
        }
        let has_identity = matches!(
            attempt.execution(),
            AttemptExecution::Isolated {
                environment_id: Some(_),
                ..
            }
        );
        if !has_identity
            && allocation_resources
                .iter()
                .any(|identity| identity_matches_intent(self.host_id, attempt, identity))
        {
            return Err(self.defer_environment_cleanup(attempt)?);
        }
        let current = if has_identity {
            provider.inspect(attempt)
        } else {
            // A prepare effect may have succeeded before its identity could be
            // journalled. Empty enumeration alone is not proof of absence.
            provider.recover(attempt)
        };
        let current = match current {
            Ok(state) => state,
            Err(_) => return Err(self.defer_environment_cleanup(attempt)?),
        };
        if !has_identity && current != EnvironmentState::Missing {
            return Err(self.defer_environment_cleanup(attempt)?);
        }
        if current != EnvironmentState::Missing {
            if !matches!(provider.owns(attempt), Ok(true)) {
                self.ports
                    .events
                    .emit(AttemptEvent::QuarantinedOwnedResource {
                        attempt: attempt.id,
                    });
                tracing::warn!(attempt_id = %attempt.id, reason = "isolated_resource_ownership_mismatch", "provider resource quarantined for operator review");
                return Err(self.defer_environment_cleanup(attempt)?);
            }
            if matches!(
                current,
                EnvironmentState::Starting | EnvironmentState::Running
            ) && !matches!(provider.stop(attempt), Ok(ProviderStop::Stopped))
            {
                return Err(self.defer_environment_cleanup(attempt)?);
            }
            if !matches!(provider.destroy(attempt), Ok(ProviderDestroy::Destroyed)) {
                return Err(self.defer_environment_cleanup(attempt)?);
            }
            if !matches!(provider.inspect(attempt), Ok(EnvironmentState::Missing)) {
                return Err(self.defer_environment_cleanup(attempt)?);
            }
        }
        if provider
            .enumerate_owned(self.host_id)
            .iter()
            .any(|identity| identity_same_allocation(self.host_id, attempt, identity))
        {
            return Err(self.defer_environment_cleanup(attempt)?);
        }
        let outcome = attempt
            .outcome()
            .cloned()
            .ok_or(LifecycleError::Transition)?;
        // Provider diagnostics are a closed vocabulary and bounded before they
        // can enter tracing, even if an adapter returns an unbounded vector.
        for diagnostic in provider.diagnostics(attempt).into_iter().take(32) {
            tracing::debug!(attempt_id = %attempt.id, provider_diagnostic = ?diagnostic, "provider lifecycle diagnostic");
        }
        self.preserve_diagnostics(attempt, &outcome)?;
        self.scrub_workspace(attempt)?;
        self.ports
            .packages
            .release(attempt.id)
            .map_err(LifecycleError::Failed)?;
        attempt
            .clean_isolated(self.ports.clock.now())
            .map_err(|_| LifecycleError::Transition)?;
        self.record(attempt)?;
        self.ports.events.emit(AttemptEvent::Cleaned {
            attempt: attempt.id,
            outcome: OutcomeKind::of(&outcome),
        });
        self.ports
            .reconcile_events
            .emit(LifecycleEvent::AttemptCleaned {
                policy: attempt.policy_id,
                attempt: attempt.id,
                outcome: OutcomeKind::of(&outcome),
            });
        Ok(())
    }

    fn defer_environment_cleanup(
        &self,
        attempt: &mut RunnerAttempt,
    ) -> Result<LifecycleError, LifecycleError> {
        attempt
            .defer_cleanup(self.ports.clock.now())
            .map_err(|_| LifecycleError::Transition)?;
        self.record(attempt)?;
        Ok(LifecycleError::EnvironmentCleanupDeferred)
    }

    /// Undo an attempt's placement by the algorithm its journalled workspace
    /// kind makes legal (`02-target-architecture.md`, "Cleanup and recovery").
    ///
    /// The dispatch is on the *journal*, never on what the directory looks like
    /// now. A slot whose `_work` was replaced by a junction is still scrubbed as
    /// a slot rather than removed whole, and a disposable directory that happens
    /// to contain a `_work` still goes whole rather than being spared: the
    /// workspace kind is immutable precisely so that the shape of a directory a
    /// workflow can write to cannot choose the algorithm applied to it.
    fn scrub_workspace(&self, attempt: &RunnerAttempt) -> Result<(), LifecycleError> {
        #[cfg(test)]
        {
            // The two contamination mutants `f1` drives the security gates with.
            // They sit in front of the dispatch rather than inside one arm so
            // that a skipped cleanup is equally observable in both modes.
            if matches!(
                std::env::var("RUNNER_MANAGER_TEST_MUTANT").as_deref(),
                Ok("skip_workspace_cleanup" | "reuse_job_workspace")
            ) {
                return Ok(());
            }
        }
        match attempt.workspace() {
            AttemptWorkspace::Ephemeral => match remove_runtime_tree(attempt.runtime_path()) {
                Ok(()) => Ok(()),
                Err(error) if error.kind() == std::io::ErrorKind::NotFound => Ok(()),
                Err(_) => Err(LifecycleError::WorkspaceCleanupDeferred),
            },
            AttemptWorkspace::PersistentSlot { slot } => self.scrub_persistent_slot(attempt, slot),
        }
    }

    /// Retain exactly `_work` and prove everything else is gone.
    ///
    /// The seven ordered checks of `04-security-recovery.md`, "Safe path
    /// handling": the journalled root and slot, a surviving policy's agreement,
    /// lexical and canonical containment, a literal enumeration, the one-entry
    /// allowlist, and a verification pass before the caller releases the package
    /// lease and marks the attempt cleaned. Any of them may refuse, and a
    /// refusal removes nothing after it.
    ///
    /// A slot directory that is already gone is not a refusal. There is nothing
    /// to scrub and nothing to prove absent, which is the same tolerance the
    /// disposable arm has always had for a runtime that vanished under it.
    fn scrub_persistent_slot(
        &self,
        attempt: &RunnerAttempt,
        slot: NonZeroU16,
    ) -> Result<(), LifecycleError> {
        // The policy is read from the journal, never inferred from the
        // directory tree, and its absence is legal: `Reconciler` cleans every
        // concluded attempt whether or not its policy still exists, and this
        // one's root is already journalled on the attempt itself.
        let configured = self
            .ports
            .store
            .policy(attempt.policy_id)
            .map_err(|_| LifecycleError::Journal)?
            .and_then(|policy| match policy.workspace_policy() {
                WorkspacePolicy::Persistent { root } => Some(root.clone()),
                WorkspacePolicy::Ephemeral => None,
            });
        let runtime = attempt.runtime_path();
        self.quarantine_on_refusal(
            attempt,
            verify_journalled_slot(runtime, slot, configured.as_ref())
                .and_then(|()| slot_is_present(runtime))
                .and_then(|present| {
                    if present {
                        scrub_slot_entries(runtime).and_then(|()| verify_slot_scrubbed(runtime))
                    } else {
                        Ok(())
                    }
                }),
        )
    }

    /// Turn a slot refusal into the error that keeps the attempt uncleaned.
    ///
    /// The warning is emitted here, at the one place a quarantine is minted, so
    /// that both routes out of cleanup carry it: the reconciler's terminal sweep,
    /// which receives the error through the launcher port, and
    /// [`Self::clean_or_quarantine`], which swallows it to keep the pass alive.
    /// Everything logged is either a path this product configured or a constant
    /// from this module — see [`SlotQuarantine`] for why that matters.
    fn quarantine_on_refusal(
        &self,
        attempt: &RunnerAttempt,
        outcome: Result<(), SlotQuarantine>,
    ) -> Result<(), LifecycleError> {
        let Err(quarantine) = outcome else {
            return Ok(());
        };
        let detail = quarantine.to_string();
        tracing::warn!(
            attempt = %attempt.id,
            policy = %attempt.policy_id,
            slot = attempt.workspace().slot_number(),
            refusal = quarantine.refusal.class(),
            "{detail}"
        );
        Err(LifecycleError::SlotQuarantined {
            class: quarantine.refusal.class(),
            detail,
        })
    }

    fn preserve_diagnostics(
        &self,
        attempt: &RunnerAttempt,
        outcome: &AttemptOutcome,
    ) -> Result<(), LifecycleError> {
        fs::create_dir_all(&self.diagnostics_root).map_err(|_| {
            LifecycleError::Failed(FailureReason::Other(
                "diagnostics directory could not be created".into(),
            ))
        })?;
        // Intentionally constructed from typed local facts, not runner output.
        // Raw child output can contain workflow secrets and is never copied.
        let reason_kind = match outcome {
            AttemptOutcome::Failed { reason } => failure_reason_kind(reason),
            _ => "none",
        };
        let diagnostic = format!(
            "attempt_id={}\npolicy_id={}\noutcome={}\nreason={}\n",
            attempt.id,
            attempt.policy_id,
            OutcomeKind::of(outcome).as_str(),
            reason_kind,
        );
        fs::write(
            self.diagnostics_root.join(format!("{}.log", attempt.id)),
            diagnostic,
        )
        .map_err(|_| {
            LifecycleError::Failed(FailureReason::Other(
                "redacted diagnostics could not be preserved".into(),
            ))
        })
    }

    async fn materialize_with_retry(
        &self,
        policy: &ScalePolicy,
        attempt: &RunnerAttempt,
        timings: &mut PackageTimings,
    ) -> Result<RunnerVersion, FailureReason> {
        let mut issued = 0_u32;
        loop {
            issued = issued.saturating_add(1);
            match self.ports.packages.materialize(attempt, timings).await {
                Ok(version) => return Ok(version),
                Err(reason)
                    if package_failure_is_terminal(&reason)
                        || issued >= self.retry.max_attempts.max(1) =>
                {
                    return Err(reason);
                }
                Err(reason) => {
                    if !self.ports.demand.persists(policy.id).await {
                        return Err(reason);
                    }
                    let delay = self.retry.delay(issued);
                    self.ports.events.emit(AttemptEvent::Retry {
                        attempt: attempt.id,
                        operation: "package_materialization",
                        delay,
                    });
                    self.ports.delay.wait(delay).await;
                    if !self.ports.demand.persists(policy.id).await {
                        return Err(reason);
                    }
                }
            }
        }
    }

    async fn register_with_retry(
        &self,
        policy: &ScalePolicy,
        attempt: AttemptId,
        request: &JitRunnerRequest,
    ) -> Result<JitRegistration, LifecycleError> {
        let mut issued = 0_u32;
        loop {
            issued = issued.saturating_add(1);
            match self
                .ports
                .github
                .register(&policy.target, request, &self.cancel)
                .await
            {
                Ok(registration) => return Ok(registration),
                Err(error) if error.terminal => {
                    return Err(LifecycleError::Failed(error.reason));
                }
                Err(error) => {
                    if issued >= self.retry.max_attempts.max(1)
                        || !self.ports.demand.persists(policy.id).await
                    {
                        return Err(LifecycleError::Failed(error.reason));
                    }
                    let delay = error
                        .retry_after
                        .unwrap_or_else(|| self.retry.delay(issued));
                    self.ports.events.emit(AttemptEvent::Retry {
                        attempt,
                        operation: "jit_request",
                        delay,
                    });
                    self.ports.delay.wait(delay).await;
                    if !self.ports.demand.persists(policy.id).await {
                        return Err(LifecycleError::Failed(error.reason));
                    }
                }
            }
        }
    }

    /// Where one attempt's files go, decided while the host allocation lock is
    /// held and before anything external happens.
    ///
    /// The branch is on the *repository's configured* workspace policy, so an
    /// organization policy and an ephemeral repository never reach slot
    /// selection at all: a persistent policy is unrepresentable for an
    /// organization target (D7, refused by `WorkspacePolicy::permitted_for` in
    /// both the constructor and the loader), and an ephemeral repository takes
    /// the disposable arm that existed before slots did.
    fn allocate_workspace(
        &self,
        policy: &ScalePolicy,
        id: AttemptId,
    ) -> Result<Placement, LifecycleError> {
        let placement = match policy.workspace_policy() {
            // Precedence (`02-target-architecture.md`): the repository's
            // persistent root is selected *before* the host root, which is why
            // this arm is first and why it never makes resolving the host
            // default a precondition of its own success.
            WorkspacePolicy::Persistent { root } => self.allocate_persistent_slot(policy, root),
            WorkspacePolicy::Ephemeral => self.allocate_disposable(policy, id),
        };
        // Here rather than inside the two arms, so that every path a root can
        // accept clears the record and none can be forgotten.
        if placement.is_ok() {
            self.root_accepted(policy.id);
        }
        placement
    }

    /// `Host.runner_root_override`, read from the journal.
    ///
    /// Separated from [`Self::effective_host_root`] so that the two failures it
    /// folds together stay apart: an unreadable or missing host row is a journal
    /// problem and is always fatal, while an unresolvable *platform default* is
    /// only fatal to a placement that actually needs the host root.
    fn configured_host_root(&self) -> Result<Option<LocalAbsolutePath>, LifecycleError> {
        let host = self
            .ports
            .store
            .host(self.host_id)
            .map_err(|_| LifecycleError::Journal)?
            .ok_or_else(|| LifecycleError::Failed(FailureReason::Other("host not found".into())))?;
        Ok(host.runner_root_override.clone())
    }

    /// `Host.runner_root_override`, or the platform default when that resolves;
    /// `None` when neither does. Unlike [`Self::effective_host_root`] it records
    /// no refusal, for callers to whom an unresolvable root is not a failure.
    fn resolvable_host_root(&self) -> Result<Option<LocalAbsolutePath>, LifecycleError> {
        Ok(self
            .configured_host_root()?
            .or_else(|| default_runner_root(&self.app_paths).ok()))
    }

    /// `Host.runner_root_override`, or the platform default standing in for it.
    ///
    /// Takes the policy because an unresolvable default is a refusal like any
    /// other, and the record it leaves is that policy's.
    fn effective_host_root(
        &self,
        policy: &ScalePolicy,
    ) -> Result<LocalAbsolutePath, LifecycleError> {
        match self.configured_host_root()? {
            Some(configured) => Ok(configured),
            None => default_runner_root(&self.app_paths).map_err(|error| {
                // No root resolved, so there is no path to name but the one the
                // platform would have produced.
                self.root_refused(policy.id, "the platform default runner root", error)
            }),
        }
    }

    /// Turns a runner-root refusal into a failure, and leaves the sentence
    /// somewhere an operator can read it.
    ///
    /// Per policy, because the policies on a host do not share a fate: one with
    /// its own persistent root places runners while another on a withheld
    /// volume places none, and a host-wide record would have the first clear
    /// the second's on the same pass.
    ///
    /// The recording is best-effort and its failure is deliberately swallowed:
    /// this runs on the path that is already failing, and a host that cannot
    /// write a diagnostic file must still report the refusal it came to report.
    /// `service status` says so itself when the file is unreadable.
    fn root_refused(&self, policy: PolicyId, root: &str, error: RunnerRootError) -> LifecycleError {
        let _ = runner_manager_platform::service::record_runner_root_refusal(
            &self.app_paths,
            &policy.to_string(),
            self.ports.clock.now(),
            error.kind(),
            root,
            &error.to_string(),
        );
        root_failure(error)
    }

    /// Clears that policy's record, because its root accepted a placement.
    ///
    /// Called on every successful placement rather than only after a failure:
    /// the daemon that recovers is often not the process that failed -- a
    /// self-update restarts it -- so "clear it if we wrote it" would leave a
    /// stale note on `service status` for as long as the host ran.
    fn root_accepted(&self, policy: PolicyId) {
        let _ = runner_manager_platform::service::clear_runner_root_refusal(
            &self.app_paths,
            &policy.to_string(),
        );
    }

    /// D3's disposable placement: a unique child of the effective host root,
    /// removed whole on cleanup. `c1`'s behaviour, moved behind the branch.
    fn allocate_disposable(
        &self,
        policy: &ScalePolicy,
        id: AttemptId,
    ) -> Result<Placement, LifecycleError> {
        let effective_root = self.effective_host_root(policy)?;
        RootPreflight::new(&self.app_paths)
            .check(&RootOwner::Host, &effective_root)
            .map_err(|error| self.root_refused(policy.id, effective_root.as_str(), error))?;
        let runtime = effective_root.as_path().join({
            #[cfg(test)]
            {
                if std::env::var("RUNNER_MANAGER_TEST_MUTANT").as_deref()
                    == Ok("reuse_job_workspace")
                {
                    "mutant-shared-workspace".to_owned()
                } else {
                    workspace_name(id)
                }
            }
            #[cfg(not(test))]
            {
                workspace_name(id)
            }
        });
        fs::create_dir_all(&runtime)
            .map_err(|_| LifecycleError::Failed(FailureReason::ProcessStartFailed))?;
        Ok(Placement {
            runtime,
            workspace: AttemptWorkspace::Ephemeral,
        })
    }

    /// D4/D5's persistent placement: the lowest free `sN` under the repository's
    /// configured root.
    ///
    /// Steps 1 to 6 of `02-target-architecture.md`, "Slot allocation", in order;
    /// step 7 is the journal write [`Self::record_allocation`] owns. All of them
    /// run under the host allocation lock, because [`Self::reserve_attempt`] is
    /// reachable only through a `LaunchRequest` and that carries the guard.
    ///
    /// **The filesystem is never consulted to decide which slots are taken**
    /// (invariant 6). The leases come from the journal; the directory is
    /// inspected only to decide whether *this* slot is safe to reuse.
    fn allocate_persistent_slot(
        &self,
        policy: &ScalePolicy,
        root: &LocalAbsolutePath,
    ) -> Result<Placement, LifecycleError> {
        // 1-4. The lowest positive slot no uncleaned attempt holds, refused
        // above the policy ceiling.
        let ceiling = policy.max_capacity().ok_or_else(|| {
            LifecycleError::Failed(FailureReason::Other(
                "a persistent workspace needs the policy's max_capacity to bound its slots"
                    .to_string(),
            ))
        })?;
        let leases = self
            .ports
            .store
            .slot_leases_for_policy(policy.id)
            .map_err(|_| LifecycleError::Journal)?;
        let slot = lowest_free_slot(&leases, ceiling).ok_or_else(|| {
            LifecycleError::Failed(FailureReason::Other(format!(
                "every persistent slot s1 to s{ceiling} for {} is leased by an attempt that has \
                 not been cleaned, so no slot is free; raise the repository's max capacity, or \
                 finish cleaning a concluded attempt",
                policy.target
            )))
        })?;
        let workspace = AttemptWorkspace::persistent_slot(slot);
        let name = workspace
            .slot_directory_name()
            .expect("a persistent allocation names its slot directory");

        // The operational preflight, for the reasons the host root gets one: a
        // root that is remote, unwritable, or overlapping application data has
        // to fail before a directory is created rather than after. The host
        // root is registered only as something *not* to overlap; a host default
        // that cannot be resolved is a host-root problem and does not block a
        // repository that configured a root of its own.
        //
        // Only *that* failure is tolerated. An unreadable host row is a journal
        // failure and propagates, because silently continuing would drop the
        // overlap check entirely and accept a repository root that sits inside
        // the host root — the pair `RootPreflight` exists to refuse.
        let host_root = self.resolvable_host_root()?;
        let mut preflight = RootPreflight::new(&self.app_paths);
        if let Some(host_root) = host_root {
            preflight = preflight.against(RootOwner::Host, host_root);
        }
        let checked = preflight
            .check(&RootOwner::Repository(policy.target.to_string()), root)
            .map_err(|error| self.root_refused(policy.id, root.as_str(), error))?;
        if let Some(leaf) = checked.leaf_to_create() {
            fs::create_dir(leaf).map_err(|source| {
                LifecycleError::Failed(FailureReason::Other(format!(
                    "the persistent workspace root {} could not be created: {source}",
                    leaf.display()
                )))
            })?;
        }

        // 5-6. `<root>/sN`, contained lexically by construction, then created or
        // validated, then contained canonically now that it resolves, and only
        // then accepted for reuse.
        let slot_path = runner_root::derive_child(root, &name)
            .map_err(|error| self.root_refused(policy.id, root.as_str(), error))?;
        create_or_validate_slot(slot_path.as_path())?;
        runner_root::verify_containment(root, &slot_path)
            .map_err(|error| self.root_refused(policy.id, root.as_str(), error))?;
        accept_reusable_slot(slot_path.as_path())?;
        Ok(Placement {
            runtime: slot_path.as_path().to_path_buf(),
            workspace,
        })
    }

    /// The first journal write of an attempt, where a duplicate slot lease is
    /// still possible and has to be reported as itself.
    ///
    /// [`Self::record`] flattens every store failure into
    /// [`LifecycleError::Journal`], which is right for a state transition and
    /// wrong here: the partial unique index
    /// `one_uncleaned_persistent_attempt_per_slot` is the final race fence
    /// (`04-security-recovery.md`, "two attempts use one slot concurrently"),
    /// and an operator who reaches it needs to read that rather than "attempt
    /// journal operation failed". Nothing was written, so the caller returns
    /// without concluding an attempt that is not in the journal.
    fn record_allocation(&self, attempt: &RunnerAttempt) -> Result<(), LifecycleError> {
        match self.ports.store.record_attempt(attempt) {
            Ok(()) => {
                self.ports.events.emit(AttemptEvent::State {
                    attempt: attempt.id,
                    state: attempt.state(),
                });
                Ok(())
            }
            Err(error @ StoreError::SlotAlreadyLeased { .. }) => Err(LifecycleError::Failed(
                FailureReason::Other(error.to_string()),
            )),
            Err(_) => Err(LifecycleError::Journal),
        }
    }

    /// Under the allocation lock: what no other launch may decide at the same
    /// time. The rest is [`Self::finish_attempt`], outside it.
    fn reserve_attempt(
        &self,
        policy: &ScalePolicy,
        allocation_guard: &AllocationGuard,
    ) -> Result<RunnerAttempt, LifecycleError> {
        // What a prune leaves costs only disk, and a tree it cannot remove is one
        // the launch's install may yet repair: not a reason to refuse the launch.
        if let Err(error) = self.prune_under_allocation_lock(allocation_guard) {
            tracing::warn!(
                event = "package_prune_failed",
                reason = failure_reason_kind(&error.reason()),
            );
        }
        self.allocate_attempt(policy)
    }

    async fn finish_attempt(
        &self,
        policy: &ScalePolicy,
        attempt: RunnerAttempt,
        waits: ReservationWaits,
    ) -> Result<RunnerAttempt, LifecycleError> {
        let id = attempt.id;
        let _bringing_up = BroughtUpOnDrop {
            attempts: &self.bringing_up,
            id,
        };
        let mut stopwatch = LaunchStopwatch::new(waits);
        let result = self.launch_steps(policy, attempt, &mut stopwatch).await;
        stopwatch.finish();
        self.ports.events.emit(AttemptEvent::Launched {
            attempt: id,
            started: result.is_ok(),
            timings: stopwatch.timings,
        });
        result
    }

    /// Place and journal a new attempt: everything before its first external
    /// effect, and so before there is anything to time.
    fn allocate_attempt(&self, policy: &ScalePolicy) -> Result<RunnerAttempt, LifecycleError> {
        if !*self
            .recovery_complete
            .lock()
            .map_err(|_| LifecycleError::Journal)?
        {
            return Err(LifecycleError::RecoveryIncomplete);
        }
        let capability = self.ports.processes.probe(policy);
        if capability != ProviderCapability::Ready {
            return Err(LifecycleError::Failed(capability.refusal()));
        }
        let resolved = self.ports.processes.resolve(policy).map_err(|reason| {
            LifecycleError::Failed(if policy.execution_policy().is_native() {
                reason
            } else {
                safe_isolation_reason(reason, IsolationProviderFailure::RuntimeOperationFailed)
            })
        })?;
        if policy.execution_policy().is_native() != resolved.is_none() {
            return Err(LifecycleError::Failed(FailureReason::Other(
                "provider resolution mismatch".into(),
            )));
        }
        if let Some(resolution) = &resolved {
            if resolution.provider_kind == Backend::Auto {
                return Err(LifecycleError::Failed(FailureReason::Other(
                    "provider resolution mismatch".into(),
                )));
            }
            AttemptExecution::Isolated {
                provider_kind: resolution.provider_kind,
                environment_id: None,
                resolved_image: resolution.image.clone(),
                generation: "generation-check".into(),
            }
            .validate()
            .map_err(|_| {
                LifecycleError::Failed(FailureReason::Other(
                    "resolved image is incompatible".into(),
                ))
            })?;
        }
        policy
            .routing_labels()
            .ok_or(LifecycleError::Failed(FailureReason::JitRequestFailed))?;
        let id = AttemptId::new_random();
        let placement = self.allocate_workspace(policy, id)?;
        let mut attempt = RunnerAttempt::allocate_in(
            id,
            policy.id,
            placement.runtime,
            placement.workspace,
            self.ports.clock.now(),
        );
        if let Some(resolution) = &resolved {
            attempt
                .allocate_execution(AttemptExecution::Isolated {
                    provider_kind: resolution.provider_kind,
                    environment_id: None,
                    resolved_image: resolution.image.clone(),
                    generation: uuid::Uuid::new_v4().to_string(),
                })
                .map_err(|_| LifecycleError::Transition)?;
        }
        // This is deliberately the first effect after directory allocation, and
        // for a persistent attempt it is also what makes the slot lease durable
        // before any package or GitHub effect
        // (`02-target-architecture.md`, "Slot allocation", step 7).
        self.bringing_up
            .lock()
            .map_err(|_| LifecycleError::Journal)?
            .insert(id);
        if let Err(error) = self.record_allocation(&attempt) {
            self.bringing_up
                .lock()
                .map_err(|_| LifecycleError::Journal)?
                .remove(&id);
            return Err(error);
        }
        Ok(attempt)
    }

    async fn launch_steps(
        &self,
        policy: &ScalePolicy,
        mut attempt: RunnerAttempt,
        stopwatch: &mut LaunchStopwatch,
    ) -> Result<RunnerAttempt, LifecycleError> {
        let id = attempt.id;
        let isolated = !attempt.execution().is_native();
        let Some(labels) = policy.routing_labels() else {
            return self.fail_launch(&mut attempt, FailureReason::JitRequestFailed);
        };
        stopwatch.begin(LaunchStep::Turn);
        // Never closed; held through the preparation below.
        let turn = self.turns.acquire().await.ok();
        stopwatch.begin(LaunchStep::Materialize);
        let package_timings = &mut stopwatch.timings.package;
        let version = match self
            .materialize_with_retry(policy, &attempt, package_timings)
            .await
        {
            Ok(version) => version,
            Err(reason) => return self.fail_launch(&mut attempt, reason),
        };
        self.versions
            .lock()
            .map_err(|_| LifecycleError::Journal)?
            .insert(id, version);

        if isolated {
            attempt
                .begin_prepare(self.ports.clock.now())
                .map_err(|_| LifecycleError::Transition)?;
            self.record(&attempt)?;
        }
        stopwatch.begin(LaunchStep::Prepare);
        // Off the async thread: a provider may pull an image, and every target
        // of this host shares that thread.
        let preparing = {
            let (processes, attempt, policy) = (
                Arc::clone(&self.ports.processes),
                attempt.clone(),
                policy.clone(),
            );
            tokio::task::spawn_blocking(move || processes.prepare(&attempt, &policy)).await
        };
        drop(turn);
        let prepared = match preparing.unwrap_or(Err(FailureReason::ProcessStartFailed)) {
            Ok(prepared) => prepared,
            Err(reason) => {
                let safe_reason = if isolated {
                    safe_isolation_reason(reason, IsolationProviderFailure::RuntimeOperationFailed)
                } else {
                    reason
                };
                return self.fail_launch(&mut attempt, safe_reason);
            }
        };
        if isolated {
            let Some(identity) = prepared.identity() else {
                return Err(LifecycleError::Failed(FailureReason::IsolationProvider(
                    IsolationProviderFailure::OwnershipMismatch,
                )));
            };
            if !identity_matches_intent(self.host_id, &attempt, identity) {
                return Err(LifecycleError::Failed(FailureReason::IsolationProvider(
                    IsolationProviderFailure::OwnershipMismatch,
                )));
            }
            let EnvironmentIdentity::Isolated { environment_id, .. } = identity else {
                unreachable!()
            };
            attempt
                .prepared_environment(environment_id.clone())
                .map_err(|_| LifecycleError::Transition)?;
            attempt
                .mark_prepared(self.ports.clock.now())
                .map_err(|_| LifecycleError::Transition)?;
            self.record(&attempt)?;
        }

        stopwatch.begin(LaunchStep::Register);
        let jit_request =
            JitRunnerRequest::for_policy(runner_name(id), self.runner_group_id, labels);
        let registration = match self.register_with_retry(policy, id, &jit_request).await {
            Ok(registration) => registration,
            Err(error) => return self.fail_launch(&mut attempt, error.reason()),
        };
        stopwatch.begin(LaunchStep::Spawn);
        let runner_id = registration.runner().id;
        write_runner_id(attempt.runtime_path(), runner_id)?;
        attempt
            .jit_received(self.ports.clock.now())
            .map_err(|_| LifecycleError::Transition)?;
        self.record(&attempt)?;
        let config = registration.into_config();
        if isolated {
            let started = self
                .ports
                .processes
                .start(prepared, &attempt, OneTimeJitHandoff::new(&config))
                .map_err(|failure| {
                    LifecycleError::Failed(safe_isolation_reason(
                        failure.reason,
                        IsolationProviderFailure::RuntimeOperationFailed,
                    ))
                })?;
            if !identity_matches_intent(self.host_id, &attempt, &started) {
                return Err(LifecycleError::Failed(FailureReason::IsolationProvider(
                    IsolationProviderFailure::OwnershipMismatch,
                )));
            }
            attempt
                .started_isolated(self.ports.clock.now())
                .map_err(|_| LifecycleError::Transition)?;
            self.record(&attempt)?;
            return Ok(attempt);
        }
        let mut issued = 0_u32;
        let pid = loop {
            issued = issued.saturating_add(1);
            match self.ports.processes.start(
                prepared.clone(),
                &attempt,
                OneTimeJitHandoff::new(&config),
            ) {
                Ok(EnvironmentIdentity::NativeProcess(pid)) => break pid,
                Ok(EnvironmentIdentity::Isolated { .. }) => {
                    // No isolated launch sequence is wired in this task. Keep
                    // the nonterminal JIT journal as a capacity fence rather
                    // than treating an unexpected resource as a native PID.
                    return Err(LifecycleError::Failed(FailureReason::Other(
                        "unexpected isolated environment identity".into(),
                    )));
                }
                Err(error) => {
                    if let Some(pid) = error.live_pid {
                        attempt
                            .started(pid, self.ports.clock.now())
                            .map_err(|_| LifecycleError::Transition)?;
                        self.record(&attempt)?;
                        return Err(LifecycleError::Failed(error.reason));
                    }
                    if !error.retryable
                        || issued >= self.retry.max_attempts.max(1)
                        || !self.ports.demand.persists(policy.id).await
                    {
                        return self.fail_launch(&mut attempt, error.reason);
                    }
                    let delay = self.retry.delay(issued);
                    self.ports.events.emit(AttemptEvent::Retry {
                        attempt: attempt.id,
                        operation: "process_start",
                        delay,
                    });
                    self.ports.delay.wait(delay).await;
                    if !self.ports.demand.persists(policy.id).await {
                        return self.fail_launch(&mut attempt, error.reason);
                    }
                }
            }
        };
        attempt
            .started(pid, self.ports.clock.now())
            .map_err(|_| LifecycleError::Transition)?;
        self.record(&attempt)?;
        Ok(attempt)
    }

    fn fail_launch<T>(
        &self,
        attempt: &mut RunnerAttempt,
        reason: FailureReason,
    ) -> Result<T, LifecycleError> {
        self.conclude(attempt, AttemptOutcome::failed(reason.clone()))?;
        Err(LifecycleError::Failed(reason))
    }

    /// e2's prune guard is invoked only with e1's allocation guard borrowed.
    /// The otherwise-unused argument is a compile-time witness of the ordering.
    fn prune_under_allocation_lock(&self, guard: &AllocationGuard) -> Result<(), LifecycleError> {
        let attempts = self
            .ports
            .store
            .attempts()
            .map_err(|_| LifecycleError::Journal)?;
        self.ports
            .packages
            .prune_obsolete_guarded(PruneAuthority::from_launch_request(guard), &attempts)
            .map_err(LifecycleError::Failed)?;
        #[cfg(target_os = "macos")]
        self.prune_abandoned_seeds(&attempts);
        Ok(())
    }

    /// Remove the package seed from every runner root this host once placed a
    /// runtime in and no longer does: a changed host root override, a removed
    /// persistent policy, or one that moved its workspace.
    ///
    /// The roots ever used are the parents of the journal's runtime paths; the
    /// roots in use are the effective host root and every persistent policy's
    /// root. When the effective host root cannot be resolved nothing is
    /// removed, because a seed still in use cannot then be told apart. No
    /// launch clones from a seed under a root no policy uses, and it is
    /// best-effort: a seed left behind costs disk, never a launch.
    #[cfg(target_os = "macos")]
    fn prune_abandoned_seeds(&self, attempts: &[RunnerAttempt]) {
        let Ok(policies) = self.ports.store.policies() else {
            return;
        };
        let Ok(Some(host_root)) = self.resolvable_host_root() else {
            return;
        };
        let in_use: BTreeSet<PathBuf> = policies
            .iter()
            .filter_map(|policy| match policy.workspace_policy() {
                WorkspacePolicy::Persistent { root } => Some(canonical_or_raw(root.as_path())),
                WorkspacePolicy::Ephemeral => None,
            })
            .chain(std::iter::once(canonical_or_raw(host_root.as_path())))
            .collect();
        // Distinct parents first: the journal keeps every attempt ever made.
        let used: BTreeSet<&Path> = attempts
            .iter()
            .filter_map(|attempt| attempt.runtime_path().parent())
            .collect();
        for root in used.into_iter().map(canonical_or_raw) {
            if !in_use.contains(&root) {
                let _ = remove_runtime_tree(&root.join(PACKAGE_SEED_DIR));
            }
        }
    }
}

#[cfg(target_os = "macos")]
fn canonical_or_raw(path: &Path) -> PathBuf {
    fs::canonicalize(path).unwrap_or_else(|_| path.to_path_buf())
}

#[async_trait]
impl RunnerLauncher for LifecycleLauncher {
    async fn host_capacity(
        &self,
        host: &runner_manager_domain::model::Host,
    ) -> Result<std::num::NonZeroU16, crate::reconcile::HostCapacityError> {
        self.ports
            .store
            .host(host.id)
            .map_err(|_| crate::reconcile::HostCapacityError::JournalUnreadable)?
            .map(|current| current.host_capacity)
            .ok_or(crate::reconcile::HostCapacityError::MissingHost)
    }

    async fn supervise(
        &self,
        policy: &ScalePolicy,
    ) -> Result<Vec<ReplacementIntent>, LaunchFailure> {
        LifecycleLauncher::supervise(self, policy)
            .await
            .map_err(|error| LaunchFailure::new(error.reason()))
    }

    async fn attempts(&self) -> Result<Vec<RunnerAttempt>, LaunchFailure> {
        self.ports.store.attempts().map_err(|_| {
            LaunchFailure::new(FailureReason::Other(
                "attempt journal could not be read".into(),
            ))
        })
    }

    async fn launch(&self, request: LaunchRequest<'_>) -> Result<RunnerAttempt, LaunchFailure> {
        self.reserve_attempt(request.policy, request.allocation_guard)
            .map_err(|error| LaunchFailure::new(error.reason()))
    }

    async fn finish_launch(
        &self,
        policy: &ScalePolicy,
        attempt: RunnerAttempt,
        waits: ReservationWaits,
    ) -> Result<RunnerAttempt, LaunchFailure> {
        self.finish_attempt(policy, attempt, waits)
            .await
            .map_err(|error| LaunchFailure::new(error.reason()))
    }

    async fn clean(&self, id: AttemptId) -> Result<(), LaunchFailure> {
        let mut attempt = self
            .ports
            .store
            .attempt(id)
            .map_err(|_| {
                LaunchFailure::new(FailureReason::Other(
                    "attempt journal could not be read".into(),
                ))
            })?
            .ok_or_else(|| {
                LaunchFailure::new(FailureReason::Other(
                    "attempt disappeared from the journal".into(),
                ))
            })?;
        self.clean_attempt(&mut attempt)
            .map_err(|error| LaunchFailure::new(error.reason()))?;
        self.cleanup_retries().succeeded(id);
        Ok(())
    }
}

/// The name an attempt's runner registers with GitHub, which a
/// `workflow_job` webhook's `runner_name` repeats.
#[must_use]
pub fn runner_name(attempt: AttemptId) -> String {
    format!("runner-manager-{attempt}")
}

/// How long reading a runner's diagnostics may take.
const EVIDENCE_DEADLINE: Duration = Duration::from_secs(2);

/// What a native runner's own diagnostics say about whether it ran a job.
///
/// `Runner.Listener` writes `_diag/Runner_*.log` when it starts, and starts
/// `Runner.Worker` -- which writes `_diag/Worker_*.log` -- only for a job it has
/// acquired. So a worker log is proof a job ran, and a listener log without one
/// is proof none did. With neither, the directory is not where the listener
/// wrote, and nothing is concluded from it. `_diag` is scrubbed with the rest of
/// the runtime after every attempt, persistent slots included, so a log found
/// here belongs to this attempt.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum JobEvidence {
    RanAJob,
    NoJob,
    Unknown,
}

impl JobEvidence {
    fn of(runtime: &Path) -> Self {
        let diag = runtime.join("_diag");
        // Bounded: the daemon's loop runs on one thread, and a runtime on a
        // volume that does not answer (a hung disk, a pending macOS question)
        // must not stall it for longer than this.
        if runner_manager_platform::host_fitness::directory_responds(&diag, EVIDENCE_DEADLINE)
            != runner_manager_platform::host_fitness::Responsiveness::Responds
        {
            return Self::Unknown;
        }
        let Ok(entries) = fs::read_dir(diag) else {
            return Self::Unknown;
        };
        let mut listener = false;
        for entry in entries.flatten() {
            let name = entry.file_name();
            let name = name.to_string_lossy();
            if !name.ends_with(".log") {
                continue;
            }
            if name.starts_with("Worker_") {
                return Self::RanAJob;
            }
            listener |= name.starts_with("Runner_");
        }
        if listener { Self::NoJob } else { Self::Unknown }
    }
}

/// The attempt's GitHub runner id: journalled, observed, or from the sidecar
/// written at registration.
fn known_runner_id(attempt: &RunnerAttempt, observed: Option<u64>) -> Option<u64> {
    attempt
        .github_runner_id()
        .or(observed)
        .or_else(|| read_runner_id(attempt.runtime_path()))
}

fn read_runner_id(runtime: &Path) -> Option<u64> {
    fs::read_to_string(runtime.join(RUNNER_ID_FILE))
        .ok()?
        .trim()
        .parse()
        .ok()
}

fn write_runner_id(runtime: &Path, runner_id: u64) -> Result<(), LifecycleError> {
    let target = runtime.join(RUNNER_ID_FILE);
    if let Some(existing) = read_runner_id(runtime) {
        return (existing == runner_id)
            .then_some(())
            .ok_or(LifecycleError::Journal);
    }
    let temporary = runtime.join(format!("{RUNNER_ID_FILE}.{}.tmp", uuid::Uuid::new_v4()));
    write_durable_file(&temporary, runner_id.to_string().as_bytes())
        .map_err(|_| LifecycleError::Journal)?;
    match fs::rename(&temporary, &target) {
        Ok(()) => sync_directory(runtime).map_err(|_| LifecycleError::Journal),
        Err(error) if error.kind() == std::io::ErrorKind::AlreadyExists => {
            let _ = fs::remove_file(&temporary);
            (read_runner_id(runtime) == Some(runner_id))
                .then_some(())
                .ok_or(LifecycleError::Journal)
        }
        Err(_) => {
            let _ = fs::remove_file(&temporary);
            Err(LifecycleError::Journal)
        }
    }
}

fn write_durable_file(path: &Path, bytes: &[u8]) -> std::io::Result<()> {
    let mut file = fs::OpenOptions::new()
        .create(true)
        .truncate(true)
        .write(true)
        .open(path)?;
    file.write_all(bytes)?;
    file.sync_all()?;
    let parent = path.parent().ok_or_else(|| {
        std::io::Error::new(
            std::io::ErrorKind::InvalidInput,
            "file has no parent directory",
        )
    })?;
    sync_directory(parent)
}

#[cfg(unix)]
fn sync_directory(path: &Path) -> std::io::Result<()> {
    fs::File::open(path)?.sync_all()
}

#[cfg(windows)]
fn sync_directory(path: &Path) -> std::io::Result<()> {
    use std::os::windows::fs::OpenOptionsExt;

    const FILE_FLAG_BACKUP_SEMANTICS: u32 = 0x0200_0000;
    const FILE_SHARE_ALL: u32 = 0x0000_0007;
    const GENERIC_WRITE: u32 = 0x4000_0000;
    fs::OpenOptions::new()
        .access_mode(GENERIC_WRITE)
        .share_mode(FILE_SHARE_ALL)
        .custom_flags(FILE_FLAG_BACKUP_SEMANTICS)
        .open(path)?
        .sync_all()
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::collections::BTreeSet;
    use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};

    use crate::reconcile::{AllocationLock, InProcessAllocationLock};
    use runner_manager_domain::model::{Elapsed, TargetScope};
    use runner_manager_domain::store::SqliteStore;
    use runner_manager_github::jit::JitRunner;
    use runner_manager_testkit::clock::FakeClock;
    use runner_manager_testkit::fixtures;

    #[test]
    fn production_provider_set_routes_every_implemented_isolated_backend() {
        let providers = PlatformExecutionProvider::new(HostId::from_u128(1));
        assert!(providers.isolated_provider(Backend::Auto).is_some());
        assert!(providers.isolated_provider(Backend::Oci).is_some());
        assert!(
            providers
                .isolated_provider(Backend::WindowsHyperVContainer)
                .is_some()
        );
        assert!(
            providers
                .isolated_provider(Backend::VirtualMachine)
                .is_none()
        );
    }

    /// One event's fields, in the order they were recorded.
    type CapturedFields = Vec<(String, String)>;

    /// Keeps the `(name, value)` fields of every `tracing` event emitted while
    /// it is installed.
    ///
    /// The names are kept and not just the rendered line, so a test can hold the
    /// event to `crate::logging`'s two rules -- the field allow-list and the
    /// value scrub -- instead of asserting that some string was passed to a
    /// macro.
    #[derive(Clone, Default)]
    struct CapturedEvents(std::sync::Arc<std::sync::Mutex<Vec<CapturedFields>>>);

    impl<S: tracing::Subscriber> tracing_subscriber::Layer<S> for CapturedEvents {
        fn on_event(
            &self,
            event: &tracing::Event<'_>,
            _context: tracing_subscriber::layer::Context<'_, S>,
        ) {
            struct Collect(Vec<(String, String)>);
            impl tracing::field::Visit for Collect {
                fn record_debug(
                    &mut self,
                    field: &tracing::field::Field,
                    value: &dyn std::fmt::Debug,
                ) {
                    // `{value:?}` on a `&str` field would keep the quotes, and
                    // the redaction rules are about the value, not its literal.
                    self.0.push((
                        field.name().to_owned(),
                        format!("{value:?}").trim_matches('"').to_owned(),
                    ));
                }
            }
            let mut collected = Collect(Vec::new());
            event.record(&mut collected);
            self.0
                .lock()
                .expect("the capture mutex is not poisoned")
                .push(collected.0);
        }
    }

    /// The regression behind a three-hour outage that showed nothing an operator
    /// could act on.
    ///
    /// A root the daemon cannot use refuses the launch *before*
    /// `record_allocation`, so no attempt row is ever written: `b2` has nothing
    /// to carry the failure on and `g2` has nothing to show it from. The
    /// lifecycle event keeps only the variant -- `failure_reason_kind` allows no
    /// free text on an event -- so the whole failure read
    /// `runner_start_failed reason=other`, once per poll, for hours.
    ///
    /// The assertion is deliberately made against the **production redaction
    /// rules** and not merely against what was emitted. An earlier attempt at
    /// this fix logged the rendered error on a `detail` field and passed a test
    /// exactly like this one, while shipping `detail="[redacted]"`: the field
    /// was not allow-listed, and had it been, the value is mostly paths and
    /// would have been scrubbed to `[path]`. A test that does not ask
    /// `crate::logging` what survives is a test that proves nothing.
    #[test]
    fn a_launch_the_runner_root_refused_names_the_cause_in_the_log_that_ships() {
        use runner_manager_platform::logging;
        use tracing_subscriber::layer::SubscriberExt as _;

        let captured = CapturedEvents::default();
        let error = RunnerRootError::DeniedByPrivacyPolicy {
            requested: PathBuf::from("/Volumes/NVME/runners"),
            refused: PathBuf::from("/Volumes/NVME"),
            remediation: RootOwner::Host.remediation(),
        };
        let kind = error.kind();

        let failure = tracing::subscriber::with_default(
            tracing_subscriber::registry().with(captured.clone()),
            || root_failure(error),
        );

        // The reason still carries the whole sentence. Nothing on *this* path
        // renders it -- there is no attempt row, and the event carries only the
        // variant -- so this is a guard against a refactor that drops the detail
        // before some future surface can show it, and not a claim that one does.
        assert!(
            matches!(
                &failure,
                LifecycleError::Failed(FailureReason::Other(detail))
                    if detail.contains("/Volumes/NVME/runners")
                        && detail.contains("Full Disk Access")
            ),
            "the reason must still carry the detail: {failure:?}"
        );

        let events = captured
            .0
            .lock()
            .expect("the capture mutex is not poisoned")
            .clone();
        let event = events
            .iter()
            .find(|fields| fields.iter().any(|(_, value)| value.contains(kind)))
            .unwrap_or_else(|| panic!("the refusal did not name its cause: {events:?}"));

        // Held to the rules the real sink applies, by name and by value. An
        // earlier fix put the rendered error on an unlisted `detail` field and
        // shipped `[redacted]`; asserting only that something was emitted would
        // have passed then too.
        for (name, value) in event {
            assert!(
                logging::is_field_allowed(name),
                "`{name}` is not allow-listed, so it ships as `{}`: {event:?}",
                logging::REDACTION
            );
            assert_eq!(
                &logging::redact(value),
                value,
                "`{name}` does not survive value-shape scrubbing: {event:?}"
            );
        }
    }

    /// A slot number, for the tests that name one.
    fn nz(slot: u16) -> NonZeroU16 {
        NonZeroU16::new(slot).expect("a positive slot")
    }

    const JIT: &str = "eyJzZWNyZXQiOiJnaHBfRE9fTk9UX0xFQUsifQ==";

    #[derive(Debug, Default)]
    struct FakeGithubLifecycle {
        registration_failures: Mutex<VecDeque<bool>>,
        observations: Mutex<VecDeque<LifecycleGithubObservation>>,
        registrations: AtomicUsize,
        remaining_runners: AtomicUsize,
        /// Every runner id `deregister` was asked to remove, in order. A count
        /// would not do: the assertions worth making are that the *right*
        /// registration was deleted and that it was deleted once.
        deregistrations: Mutex<Vec<u64>>,
        /// Set to make `deregister` answer `false`, standing for a GitHub that
        /// could not be reached at the moment the attempt concluded.
        deregistration_fails: AtomicBool,
        /// The journal to read *during* a registration, for the ordering
        /// assertion `02-target-architecture.md` makes: the slot lease is
        /// written "before package or GitHub effects". Reading it afterwards
        /// would pass even if the write happened second.
        journal: Mutex<Option<Arc<SqliteStore>>>,
        /// One entry per registration, in order.
        registration_facts: Mutex<Vec<RegistrationFact>>,
    }

    /// What one JIT registration saw of the world at the moment it was issued.
    ///
    /// `runner_name` is what ties the other two fields to *one* attempt: with
    /// two allocators racing, "some slot was journalled" is a much weaker claim
    /// than "the slot this very request belongs to was journalled", and only the
    /// name distinguishes them.
    #[derive(Debug, Clone)]
    struct RegistrationFact {
        /// The persistent slots the journal already held.
        leased_slots: Vec<u16>,
        /// The `work_folder` the request carried.
        work_folder: String,
        /// The runner name the request carried, i.e. [`runner_name`] of the
        /// registering attempt.
        runner_name: String,
        journal_states: Vec<AttemptState>,
    }

    impl FakeGithubLifecycle {
        fn fail(mut self, terminal: bool) -> Self {
            self.registration_failures
                .get_mut()
                .expect("unpoisoned")
                .push_back(terminal);
            self
        }

        fn watch_journal(&self, store: Arc<SqliteStore>) {
            *self.journal.lock().unwrap() = Some(store);
        }

        fn registration_facts(&self) -> Vec<RegistrationFact> {
            self.registration_facts.lock().unwrap().clone()
        }

        fn observe(&self, observation: GithubRunnerObservation) {
            let observation = match observation {
                GithubRunnerObservation::Unreachable => LifecycleGithubObservation::unreachable(),
                GithubRunnerObservation::NotRegistered => {
                    LifecycleGithubObservation::not_registered()
                }
                GithubRunnerObservation::Registered { busy } => {
                    LifecycleGithubObservation::registered(73, busy)
                }
            };
            self.observations.lock().unwrap().push_back(observation);
        }
    }

    #[async_trait]
    impl LifecycleGithub for FakeGithubLifecycle {
        async fn register(
            &self,
            _target: &ScaleTarget,
            request: &JitRunnerRequest,
            _cancel: &CancelToken,
        ) -> Result<JitRegistration, JitRequestFailure> {
            self.registrations.fetch_add(1, Ordering::SeqCst);
            if let Some(store) = self.journal.lock().unwrap().as_ref() {
                let attempts = store.attempts().expect("the journal is readable");
                let slots = attempts
                    .iter()
                    .filter_map(|attempt| attempt.workspace().slot_number())
                    .collect();
                self.registration_facts
                    .lock()
                    .unwrap()
                    .push(RegistrationFact {
                        leased_slots: slots,
                        work_folder: request.work_folder().to_string(),
                        runner_name: request.name().to_string(),
                        journal_states: attempts.iter().map(RunnerAttempt::state).collect(),
                    });
            }
            if let Some(terminal) = self.registration_failures.lock().unwrap().pop_front() {
                return Err(JitRequestFailure {
                    terminal,
                    reason: if terminal {
                        FailureReason::Other("GitHub refused JIT registration with 403".into())
                    } else {
                        FailureReason::JitRequestFailed
                    },
                    retry_after: None,
                });
            }
            self.remaining_runners.store(1, Ordering::SeqCst);
            Ok(JitRegistration::new(
                EncodedJitConfig::new(JIT),
                JitRunner {
                    id: 73,
                    name: request.name().to_string(),
                    os: "windows".into(),
                    status: "offline".into(),
                    busy: false,
                    runner_group_id: Some(1),
                    labels: request.labels().to_vec(),
                },
            ))
        }

        async fn observe(
            &self,
            _target: &ScaleTarget,
            _attempt: AttemptId,
            _cancel: &CancelToken,
        ) -> LifecycleGithubObservation {
            let observation = self
                .observations
                .lock()
                .unwrap()
                .pop_front()
                .unwrap_or(LifecycleGithubObservation::not_registered());
            if observation.status == GithubRunnerObservation::NotRegistered {
                self.remaining_runners.store(0, Ordering::SeqCst);
            }
            observation
        }

        async fn deregister(
            &self,
            _target: &ScaleTarget,
            runner_id: u64,
            _cancel: &CancelToken,
        ) -> bool {
            self.deregistrations.lock().unwrap().push(runner_id);
            if self.deregistration_fails.load(Ordering::SeqCst) {
                return false;
            }
            self.remaining_runners.store(0, Ordering::SeqCst);
            true
        }
    }

    #[derive(Debug)]
    struct FakePackages {
        version: RunnerVersion,
        leases: Mutex<BTreeSet<AttemptId>>,
        materializations: AtomicUsize,
        materializing: AtomicUsize,
        peak_materializing: AtomicUsize,
        materialization_failures: AtomicUsize,
        release_failures: AtomicUsize,
        releases: AtomicUsize,
        prunes: AtomicUsize,
    }

    impl Default for FakePackages {
        fn default() -> Self {
            Self {
                version: RunnerVersion::parse("2.330.0").unwrap(),
                leases: Mutex::new(BTreeSet::new()),
                materializations: AtomicUsize::new(0),
                materializing: AtomicUsize::new(0),
                peak_materializing: AtomicUsize::new(0),
                materialization_failures: AtomicUsize::new(0),
                release_failures: AtomicUsize::new(0),
                releases: AtomicUsize::new(0),
                prunes: AtomicUsize::new(0),
            }
        }
    }

    impl FakePackages {
        fn fail_materializations(&self, count: usize) {
            self.materialization_failures.store(count, Ordering::SeqCst);
        }

        fn fail_releases(&self, count: usize) {
            self.release_failures.store(count, Ordering::SeqCst);
        }
    }

    #[async_trait]
    impl RuntimePackages for FakePackages {
        async fn materialize(
            &self,
            attempt: &RunnerAttempt,
            _timings: &mut PackageTimings,
        ) -> Result<RunnerVersion, FailureReason> {
            self.materializations.fetch_add(1, Ordering::SeqCst);
            let now = self.materializing.fetch_add(1, Ordering::SeqCst) + 1;
            self.peak_materializing.fetch_max(now, Ordering::SeqCst);
            for _ in 0..5 {
                tokio::task::yield_now().await;
            }
            self.materializing.fetch_sub(1, Ordering::SeqCst);
            if self
                .materialization_failures
                .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |left| {
                    if left > 0 { Some(left - 1) } else { None }
                })
                .is_ok()
            {
                return Err(FailureReason::Other(
                    "runner package materialization failed transiently".into(),
                ));
            }
            fs::create_dir_all(attempt.runtime_path()).unwrap();
            fs::write(attempt.runtime_path().join("runner-package"), b"verified").unwrap();
            self.leases.lock().unwrap().insert(attempt.id);
            Ok(self.version.clone())
        }

        fn release(&self, attempt: AttemptId) -> Result<(), FailureReason> {
            if self
                .release_failures
                .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |left| {
                    if left > 0 { Some(left - 1) } else { None }
                })
                .is_ok()
            {
                return Err(FailureReason::Other(
                    "runner package lease could not be released".into(),
                ));
            }
            self.leases.lock().unwrap().remove(&attempt);
            self.releases.fetch_add(1, Ordering::SeqCst);
            Ok(())
        }

        fn prune_obsolete_guarded(
            &self,
            _authority: PruneAuthority<'_>,
            _attempts: &[RunnerAttempt],
        ) -> Result<(), FailureReason> {
            self.prunes.fetch_add(1, Ordering::SeqCst);
            Ok(())
        }
    }

    #[derive(Debug, Default)]
    struct FakeProcesses {
        alive: AtomicBool,
        completed_successfully: AtomicBool,
        spawns: AtomicUsize,
        spawn_failures: AtomicUsize,
        live_spawn_failure: AtomicBool,
        terminations: AtomicUsize,
        intent: AtomicBool,
        intent_failure: AtomicBool,
        actions: Mutex<Vec<&'static str>>,
        saw_secret: AtomicBool,
    }

    impl FakeProcesses {
        fn fail_spawns(&self, count: usize) {
            self.spawn_failures.store(count, Ordering::SeqCst);
        }

        fn fail_spawn_with_live_child(&self) {
            self.live_spawn_failure.store(true, Ordering::SeqCst);
        }

        fn set_alive(&self, alive: bool) {
            self.alive.store(alive, Ordering::SeqCst);
        }

        fn finish_successfully(&self) {
            self.completed_successfully.store(true, Ordering::SeqCst);
            self.alive.store(false, Ordering::SeqCst);
        }

        fn fail_intent(&self) {
            self.intent_failure.store(true, Ordering::SeqCst);
        }
    }

    impl ProcessSupervisor for FakeProcesses {
        fn spawn(
            &self,
            attempt: &RunnerAttempt,
            config: &EncodedJitConfig,
        ) -> Result<u32, ProcessStartFailure> {
            self.spawns.fetch_add(1, Ordering::SeqCst);
            // Model the production handoff on both paths: the sensitive file is
            // scoped to this call and absent when it returns.
            let handoff = RestrictiveHandoff::create(
                attempt.runtime_path(),
                SecretString::from(config.expose().to_owned()),
            )
            .unwrap();
            self.saw_secret
                .store(config.expose() == JIT, Ordering::SeqCst);
            let handoff_path = handoff.path().to_path_buf();
            let failing = self
                .spawn_failures
                .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |left| {
                    if left > 0 { Some(left - 1) } else { None }
                })
                .is_ok();
            drop(handoff);
            assert!(!handoff_path.exists(), "handoff must be absent on return");
            if self.live_spawn_failure.swap(false, Ordering::SeqCst) {
                self.alive.store(true, Ordering::SeqCst);
                return Err(ProcessStartFailure::after_spawn_live(4242));
            }
            if failing {
                return Err(ProcessStartFailure::before_spawn(
                    FailureReason::ProcessStartFailed,
                ));
            }
            self.alive.store(true, Ordering::SeqCst);
            Ok(4242)
        }

        fn is_alive(&self, _attempt: &RunnerAttempt) -> Result<bool, FailureReason> {
            self.actions.lock().unwrap().push("observe_process");
            Ok(self.alive.load(Ordering::SeqCst))
        }

        fn recovered_pid(&self, _attempt: &RunnerAttempt) -> Result<Option<u32>, FailureReason> {
            Ok(self.alive.load(Ordering::SeqCst).then_some(4242))
        }

        fn completed_successfully(&self, _attempt: &RunnerAttempt) -> bool {
            self.completed_successfully.load(Ordering::SeqCst)
        }

        fn record_terminate_intent(&self, _attempt: &RunnerAttempt) -> Result<(), FailureReason> {
            self.actions.lock().unwrap().push("terminate_intent");
            if self.intent_failure.load(Ordering::SeqCst) {
                return Err(FailureReason::Other(
                    "terminate intent directory sync failed".into(),
                ));
            }
            self.intent.store(true, Ordering::SeqCst);
            Ok(())
        }

        fn has_terminate_intent(&self, _attempt: &RunnerAttempt) -> bool {
            self.intent.load(Ordering::SeqCst)
        }

        fn terminate(&self, _attempt: &RunnerAttempt) -> Result<(), FailureReason> {
            assert!(
                self.intent.load(Ordering::SeqCst),
                "the durable intent must exist before signalling"
            );
            self.actions.lock().unwrap().push("terminate");
            self.terminations.fetch_add(1, Ordering::SeqCst);
            self.alive.store(false, Ordering::SeqCst);
            Ok(())
        }
    }

    #[derive(Debug, Default)]
    struct FakeIsolatedProvider {
        resources: Mutex<BTreeMap<AttemptId, (EnvironmentIdentity, EnvironmentState)>>,
        extra_resources: Mutex<Vec<EnvironmentIdentity>>,
        unsupported_host: AtomicBool,
        permission_denied: AtomicBool,
        incompatible_image: AtomicBool,
        prepare_failure: AtomicBool,
        recovery_unavailable: AtomicBool,
        destroy_deferred: AtomicBool,
        handoffs: AtomicUsize,
        completed_successfully: AtomicBool,
        native_calls: AtomicUsize,
        actions: Mutex<Vec<&'static str>>,
    }

    impl FakeIsolatedProvider {
        fn identity(attempt: &RunnerAttempt, host: HostId) -> EnvironmentIdentity {
            let AttemptExecution::Isolated {
                provider_kind,
                resolved_image,
                generation,
                ..
            } = attempt.execution()
            else {
                panic!("isolated intent required")
            };
            EnvironmentIdentity::Isolated {
                host,
                attempt: attempt.id,
                provider_kind: *provider_kind,
                environment_id: format!("environment-{}", attempt.id),
                resolved_image: resolved_image.clone(),
                generation: generation.clone(),
            }
        }

        fn resource_count(&self) -> usize {
            self.resources.lock().unwrap().len()
        }
    }

    impl ExecutionProvider for FakeIsolatedProvider {
        fn probe(&self, policy: &ScalePolicy) -> ProviderCapability {
            if self.unsupported_host.load(Ordering::SeqCst) {
                ProviderCapability::Unsupported
            } else if self.permission_denied.load(Ordering::SeqCst) {
                ProviderCapability::PermissionDenied
            } else if policy.execution_policy().is_native() {
                ProviderCapability::Unsupported
            } else {
                ProviderCapability::Ready
            }
        }

        fn resolve(
            &self,
            policy: &ScalePolicy,
        ) -> Result<Option<ResolvedEnvironment>, FailureReason> {
            let runner_manager_domain::execution::ExecutionPolicy::Isolated { image, .. } =
                policy.execution_policy()
            else {
                return Err(FailureReason::Other("isolated policy required".into()));
            };
            Ok(Some(ResolvedEnvironment {
                provider_kind: Backend::Oci,
                image: if self.incompatible_image.load(Ordering::SeqCst) {
                    ImageReference::new("vm-version:wrong-provider")
                        .expect("valid but incompatible")
                } else {
                    image.clone()
                },
            }))
        }

        fn prepare(
            &self,
            attempt: &RunnerAttempt,
            policy: &ScalePolicy,
        ) -> Result<PreparedEnvironment, FailureReason> {
            assert_eq!(
                attempt.state(),
                AttemptState::Preparing,
                "intent must be durable before provider effect"
            );
            self.actions.lock().unwrap().push("prepare");
            let identity = Self::identity(attempt, policy.host_id);
            self.resources
                .lock()
                .unwrap()
                .insert(attempt.id, (identity.clone(), EnvironmentState::Starting));
            if self.prepare_failure.swap(false, Ordering::SeqCst) {
                return Err(FailureReason::Other("provider-secret-needle".into()));
            }
            Ok(PreparedEnvironment::isolated(attempt.id, identity))
        }

        fn start(
            &self,
            prepared: PreparedEnvironment,
            attempt: &RunnerAttempt,
            handoff: OneTimeJitHandoff<'_>,
        ) -> Result<EnvironmentIdentity, ProcessStartFailure> {
            assert_eq!(prepared.attempt, attempt.id);
            assert_eq!(attempt.state(), AttemptState::JitReceived);
            assert_eq!(handoff.consume().expose(), JIT);
            self.handoffs.fetch_add(1, Ordering::SeqCst);
            self.actions.lock().unwrap().push("start");
            let mut resources = self.resources.lock().unwrap();
            let (identity, state) = resources.get_mut(&attempt.id).expect("prepared resource");
            *state = EnvironmentState::Running;
            Ok(identity.clone())
        }

        fn inspect(&self, attempt: &RunnerAttempt) -> Result<EnvironmentState, FailureReason> {
            self.actions.lock().unwrap().push("inspect");
            Ok(self
                .resources
                .lock()
                .unwrap()
                .get(&attempt.id)
                .map_or(EnvironmentState::Missing, |(_, state)| *state))
        }

        fn recover(&self, attempt: &RunnerAttempt) -> Result<EnvironmentState, FailureReason> {
            if self.recovery_unavailable.load(Ordering::SeqCst) {
                return Err(FailureReason::Other(
                    "provider discovery unavailable".into(),
                ));
            }
            self.inspect(attempt)
        }

        fn owns(&self, attempt: &RunnerAttempt) -> Result<bool, FailureReason> {
            Ok(self
                .resources
                .lock()
                .unwrap()
                .get(&attempt.id)
                .is_some_and(|(identity, _)| {
                    identity_matches_intent(attempt_host(identity), attempt, identity)
                }))
        }

        fn stop(&self, attempt: &RunnerAttempt) -> Result<ProviderStop, FailureReason> {
            assert!(self.owns(attempt)?);
            self.actions.lock().unwrap().push("stop");
            if let Some((_, state)) = self.resources.lock().unwrap().get_mut(&attempt.id) {
                *state = EnvironmentState::Exited;
            }
            Ok(ProviderStop::Stopped)
        }

        fn destroy(&self, attempt: &RunnerAttempt) -> Result<ProviderDestroy, FailureReason> {
            assert!(self.owns(attempt)?);
            self.actions.lock().unwrap().push("destroy");
            if self.destroy_deferred.load(Ordering::SeqCst) {
                return Ok(ProviderDestroy::Deferred("provider busy"));
            }
            self.resources.lock().unwrap().remove(&attempt.id);
            Ok(ProviderDestroy::Destroyed)
        }

        fn enumerate_owned(&self, host: HostId) -> Vec<EnvironmentIdentity> {
            let mut owned = self
                .resources
                .lock()
                .unwrap()
                .values()
                .filter(|(identity, _)| attempt_host(identity) == host)
                .map(|(identity, _)| identity.clone())
                .collect::<Vec<_>>();
            owned.extend(
                self.extra_resources
                    .lock()
                    .unwrap()
                    .iter()
                    .filter(|identity| attempt_host(identity) == host)
                    .cloned(),
            );
            owned
        }

        fn diagnostics(&self, _attempt: &RunnerAttempt) -> Vec<ProviderDiagnostic> {
            vec![ProviderDiagnostic::CleanupDeferred; 40]
        }

        fn spawn(
            &self,
            _attempt: &RunnerAttempt,
            _config: &EncodedJitConfig,
        ) -> Result<u32, ProcessStartFailure> {
            self.native_calls.fetch_add(1, Ordering::SeqCst);
            panic!("isolated provider must never spawn natively")
        }
        fn is_alive(&self, _attempt: &RunnerAttempt) -> Result<bool, FailureReason> {
            panic!("native fallback")
        }
        fn recovered_pid(&self, _attempt: &RunnerAttempt) -> Result<Option<u32>, FailureReason> {
            panic!("native fallback")
        }
        fn completed_successfully(&self, _attempt: &RunnerAttempt) -> bool {
            self.completed_successfully.load(Ordering::SeqCst)
        }
        fn record_terminate_intent(&self, _attempt: &RunnerAttempt) -> Result<(), FailureReason> {
            panic!("native fallback")
        }
        fn has_terminate_intent(&self, _attempt: &RunnerAttempt) -> bool {
            false
        }
        fn terminate(&self, _attempt: &RunnerAttempt) -> Result<(), FailureReason> {
            panic!("native fallback")
        }
    }

    fn attempt_host(identity: &EnvironmentIdentity) -> HostId {
        let EnvironmentIdentity::Isolated { host, .. } = identity else {
            panic!("isolated identity")
        };
        *host
    }

    #[derive(Debug, Default)]
    struct FakeDemand {
        answers: Mutex<VecDeque<bool>>,
    }

    impl FakeDemand {
        fn answering(answers: impl IntoIterator<Item = bool>) -> Self {
            Self {
                answers: Mutex::new(answers.into_iter().collect()),
            }
        }
    }

    #[async_trait]
    impl DemandPersistence for FakeDemand {
        async fn persists(&self, _policy: PolicyId) -> bool {
            self.answers.lock().unwrap().pop_front().unwrap_or(true)
        }
    }

    #[derive(Debug, Default)]
    struct FakeDelay(Mutex<Vec<Duration>>);

    #[async_trait]
    impl RetryDelay for FakeDelay {
        async fn wait(&self, duration: Duration) {
            self.0.lock().unwrap().push(duration);
        }
    }

    #[tokio::test]
    async fn live_capacity_reads_the_updated_sqlite_host_and_rejects_a_missing_host() {
        let mut harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        let path = harness._root.path().join("live-capacity.sqlite3");
        harness.store = Arc::new(SqliteStore::open(&path).unwrap());
        harness.store.put_host(&harness.host).unwrap();
        harness.launcher = harness.restart();
        assert_eq!(
            harness.launcher.host_capacity(&harness.host).await.unwrap(),
            harness.host.host_capacity
        );
        // A separate CLI/TUI connection updates the journal while the existing
        // launcher keeps its original store connection and startup host.
        let writer = SqliteStore::open(&path).unwrap();
        let mut updated = harness.host.clone();
        updated.host_capacity = std::num::NonZeroU16::new(12).unwrap();
        writer.put_host(&updated).unwrap();
        assert_eq!(
            harness
                .launcher
                .host_capacity(&harness.host)
                .await
                .unwrap()
                .get(),
            12
        );

        updated.host_capacity = std::num::NonZeroU16::new(2).unwrap();
        writer.put_host(&updated).unwrap();
        assert_eq!(
            harness
                .launcher
                .host_capacity(&harness.host)
                .await
                .unwrap()
                .get(),
            2
        );

        let mut missing = harness.host.clone();
        missing.id = HostId::from_u128(999);
        assert_eq!(
            harness.launcher.host_capacity(&missing).await,
            Err(crate::reconcile::HostCapacityError::MissingHost)
        );
    }

    struct Harness {
        _root: tempfile::TempDir,
        app_paths: runner_manager_platform::paths::AppPaths,
        launcher: LifecycleLauncher,
        demand: Arc<dyn DemandPersistence>,
        store: Arc<SqliteStore>,
        github: Arc<FakeGithubLifecycle>,
        packages: Arc<FakePackages>,
        processes: Arc<FakeProcesses>,
        clock: Arc<FakeClock>,
        events: Arc<AttemptEventLog>,
        reconcile_events: Arc<crate::reconcile::EventLog>,
        delay: Arc<FakeDelay>,
        host: runner_manager_domain::model::Host,
        policy: ScalePolicy,
        allocation_lock: InProcessAllocationLock,
        /// The repository persistent root, once one is configured.
        workspace_root: Option<LocalAbsolutePath>,
    }

    impl Harness {
        fn new(github: FakeGithubLifecycle, demand: Arc<dyn DemandPersistence>) -> Self {
            let root = tempfile::tempdir().unwrap();
            let paths = runner_manager_platform::paths::AppPaths::rooted_at(root.path());
            paths.create_all().unwrap();
            let policy = fixtures::policy()
                .repository("octo/repo")
                .autoscale("home", 2)
                .active()
                .build();
            // A unit harness must never inspect or write the workstation's
            // production runner root. On Windows that is C:\rman, which is
            // intentionally inaccessible to an ordinary account after a boot
            // service is installed. Using it made the same suite pass on a
            // clean CI image and fail on a correctly secured developer host.
            let host_root = root.path().join("host-root");
            fs::create_dir_all(&host_root).unwrap();
            let mut host = fixtures::host().build();
            host.runner_root_override = Some(
                LocalAbsolutePath::new(host_root.to_str().expect("a UTF-8 temporary path"))
                    .expect("a local absolute host root"),
            );
            let store = Arc::new(SqliteStore::open_in_memory().unwrap());
            store.put_host(&host).unwrap();
            let github = Arc::new(github);
            let packages = Arc::new(FakePackages::default());
            let processes = Arc::new(FakeProcesses::default());
            let clock = Arc::new(FakeClock::default());
            let events = Arc::new(AttemptEventLog::default());
            let reconcile_events = Arc::new(crate::reconcile::EventLog::new());
            let delay = Arc::new(FakeDelay::default());
            let ports = LifecyclePorts {
                store: Arc::clone(&store) as Arc<dyn Store>,
                github: Arc::clone(&github) as Arc<dyn LifecycleGithub>,
                packages: Arc::clone(&packages) as Arc<dyn RuntimePackages>,
                processes: Arc::clone(&processes) as Arc<dyn ProcessSupervisor>,
                clock: Arc::clone(&clock) as Arc<dyn Clock>,
                demand: Arc::clone(&demand),
                delay: Arc::clone(&delay) as Arc<dyn RetryDelay>,
                events: Arc::clone(&events) as Arc<dyn AttemptEventSink>,
                reconcile_events: Arc::clone(&reconcile_events) as Arc<dyn EventSink>,
            };
            let launcher = Self::launcher_over(policy.host_id, &paths, ports);
            Self {
                _root: root,
                app_paths: paths,
                launcher,
                demand,
                store,
                github,
                packages,
                processes,
                clock,
                events,
                reconcile_events,
                delay,
                host,
                policy,
                allocation_lock: InProcessAllocationLock::new(),
                workspace_root: None,
            }
        }

        /// Put disposable attempts under a host root of this harness's own.
        ///
        /// Without it the launcher resolves the *platform* default, which on
        /// Windows is `%SystemDrive%\rman` — a real directory on the machine
        /// running the suite. Every test added by `c2` places its files inside
        /// its own temporary directory instead.
        fn with_host_runner_root(mut self) -> Self {
            let host_root = self.host_root();
            fs::create_dir_all(&host_root).unwrap();
            self.host.runner_root_override = Some(
                LocalAbsolutePath::new(host_root.to_str().expect("a UTF-8 temporary path"))
                    .expect("a local absolute host root"),
            );
            self.store.put_host(&self.host).unwrap();
            self
        }

        /// Opt this harness's repository into a persistent workspace (D4).
        fn with_persistent_workspace(mut self, capacity: u16) -> Self {
            self = self.with_host_runner_root();
            let root = self._root.path().join("persist");
            let root = LocalAbsolutePath::new(root.to_str().expect("a UTF-8 temporary path"))
                .expect("a local absolute workspace root");
            self.policy = fixtures::policy()
                .repository("octo/repo")
                .autoscale("home", capacity)
                .active()
                .build();
            self.policy
                .set_workspace_policy(
                    WorkspacePolicy::persistent(root.clone(), TargetScope::Repository)
                        .expect("a repository may be persistent"),
                )
                .expect("a repository may be persistent");
            self.workspace_root = Some(root);
            // The journal's copy, so that cleanup's cross-check against a
            // surviving policy is exercised rather than skipped.
            self.store.insert_policy(&self.policy).unwrap();
            self
        }

        fn workspace_root(&self) -> &LocalAbsolutePath {
            self.workspace_root
                .as_ref()
                .expect("this harness configured a persistent workspace")
        }

        fn slot_path(&self, slot: u16) -> PathBuf {
            self.workspace_root().as_path().join(format!("s{slot}"))
        }

        fn host_root(&self) -> PathBuf {
            self._root.path().join("host-root")
        }

        fn attempt(&self, id: AttemptId) -> RunnerAttempt {
            self.store
                .attempt(id)
                .unwrap()
                .expect("the attempt is journalled")
        }

        /// Conclude an attempt and run the real cleanup over it.
        fn conclude(&self, id: AttemptId) -> RunnerAttempt {
            let mut attempt = self.attempt(id);
            attempt
                .conclude(
                    AttemptOutcome::failed(FailureReason::ProcessExitedUnexpectedly),
                    self.clock.now(),
                )
                .unwrap();
            self.store.record_attempt(&attempt).unwrap();
            attempt
        }

        async fn cleanup_retaining_work(&self, id: AttemptId) {
            self.conclude(id);
            self.launcher
                .clean(id)
                .await
                .expect("the slot is scrubbed and the lease released");
        }

        /// The launcher configuration every launcher in this harness shares, so
        /// that the one a restart mints cannot drift from the original.
        fn launcher_over(
            host: HostId,
            paths: &runner_manager_platform::paths::AppPaths,
            ports: LifecyclePorts,
        ) -> LifecycleLauncher {
            LifecycleLauncher::new(
                host,
                paths.clone(),
                paths.logs_dir(),
                1,
                RecoveryTimeouts::new(
                    Elapsed::seconds(10),
                    Elapsed::seconds(10),
                    Elapsed::seconds(10),
                ),
                RetryPolicy::bounded(3, Duration::from_millis(10), Duration::from_millis(25)),
                ports,
            )
        }

        /// The same journal, the same directories, a launcher that remembers
        /// nothing — which is what a daemon restart is.
        fn restart(&self) -> LifecycleLauncher {
            Self::launcher_over(
                self.policy.host_id,
                &self.app_paths,
                LifecyclePorts {
                    store: Arc::clone(&self.store) as Arc<dyn Store>,
                    github: Arc::clone(&self.github) as Arc<dyn LifecycleGithub>,
                    packages: Arc::clone(&self.packages) as Arc<dyn RuntimePackages>,
                    processes: Arc::clone(&self.processes) as Arc<dyn ProcessSupervisor>,
                    clock: Arc::clone(&self.clock) as Arc<dyn Clock>,
                    demand: Arc::clone(&self.demand),
                    delay: Arc::clone(&self.delay) as Arc<dyn RetryDelay>,
                    events: Arc::clone(&self.events) as Arc<dyn AttemptEventSink>,
                    reconcile_events: Arc::clone(&self.reconcile_events) as Arc<dyn EventSink>,
                },
            )
        }

        async fn ready(&self) {
            self.launcher
                .recover_startup(std::slice::from_ref(&self.policy))
                .await
                .unwrap();
        }

        async fn launch(&self) -> RunnerAttempt {
            self.launch_result().await.unwrap()
        }

        async fn launch_result(&self) -> Result<RunnerAttempt, LaunchFailure> {
            self.launch_after_waiting(Duration::ZERO).await
        }

        async fn launch_after_waiting(
            &self,
            lock_wait: Duration,
        ) -> Result<RunnerAttempt, LaunchFailure> {
            let reserved = self.reserve().await?;
            self.launcher
                .finish_launch(
                    &self.policy,
                    reserved,
                    ReservationWaits {
                        lock: lock_wait,
                        order: Duration::from_secs(2),
                    },
                )
                .await
        }

        /// A whole launch through `launcher`, as a reconciliation pass makes it.
        async fn launch_through(
            &self,
            launcher: &LifecycleLauncher,
        ) -> Result<RunnerAttempt, LaunchFailure> {
            let reserved = self.reserve_through(launcher).await?;
            launcher
                .finish_launch(&self.policy, reserved, ReservationWaits::default())
                .await
        }

        async fn reserve(&self) -> Result<RunnerAttempt, LaunchFailure> {
            self.reserve_through(&self.launcher).await
        }

        async fn reserve_through(
            &self,
            launcher: &LifecycleLauncher,
        ) -> Result<RunnerAttempt, LaunchFailure> {
            let guard = self.allocation_lock.acquire().await.unwrap();
            launcher
                .launch(LaunchRequest {
                    host: &self.host,
                    policy: &self.policy,
                    allocation_guard: &guard,
                })
                .await
        }

        fn only_attempt(&self) -> RunnerAttempt {
            self.store.attempts().unwrap().into_iter().next().unwrap()
        }
    }

    fn isolated_harness() -> Harness {
        use runner_manager_domain::execution::{ExecutionPolicy, ResourceLimits};
        let mut harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_host_runner_root();
        let image =
            ImageReference::new(format!("registry.example/runner@sha256:{}", "a".repeat(64)))
                .expect("pinned image");
        harness
            .policy
            .set_execution_policy(ExecutionPolicy::Isolated {
                backend: Backend::Oci,
                image,
                resources: ResourceLimits {
                    cpu_millis: 1000,
                    memory_mib: 1024,
                    disk_mib: 4096,
                },
            })
            .expect("isolated policy");
        harness.github.watch_journal(Arc::clone(&harness.store));
        harness
    }

    fn launcher_with_isolated(
        harness: &Harness,
        provider: Arc<FakeIsolatedProvider>,
    ) -> LifecycleLauncher {
        Harness::launcher_over(
            harness.policy.host_id,
            &harness.app_paths,
            LifecyclePorts {
                store: Arc::clone(&harness.store) as Arc<dyn Store>,
                github: Arc::clone(&harness.github) as Arc<dyn LifecycleGithub>,
                packages: Arc::clone(&harness.packages) as Arc<dyn RuntimePackages>,
                processes: provider as Arc<dyn ExecutionProvider>,
                clock: Arc::clone(&harness.clock) as Arc<dyn Clock>,
                demand: Arc::clone(&harness.demand),
                delay: Arc::clone(&harness.delay) as Arc<dyn RetryDelay>,
                events: Arc::clone(&harness.events) as Arc<dyn AttemptEventSink>,
                reconcile_events: Arc::clone(&harness.reconcile_events) as Arc<dyn EventSink>,
            },
        )
    }

    #[tokio::test]
    async fn isolated_policy_and_journal_never_enter_native_provider_or_jit() {
        use runner_manager_domain::execution::{
            AttemptExecution, Backend, ExecutionPolicy, ImageReference, ResourceLimits,
        };

        let mut harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_host_runner_root();
        let image =
            ImageReference::new(format!("registry.example/runner@sha256:{}", "a".repeat(64)))
                .expect("pinned image");
        harness
            .policy
            .set_execution_policy(ExecutionPolicy::Isolated {
                backend: Backend::Oci,
                image: image.clone(),
                resources: ResourceLimits {
                    cpu_millis: 1000,
                    memory_mib: 1024,
                    disk_mib: 4096,
                },
            })
            .expect("valid isolated profile");

        harness.ready().await;
        assert_eq!(
            harness.processes.probe(&harness.policy),
            ProviderCapability::Unsupported
        );
        let failure = harness
            .launch_result()
            .await
            .expect_err("provider is unavailable");
        assert_eq!(
            failure.reason,
            FailureReason::IsolationProvider(IsolationProviderFailure::Unsupported)
        );

        let runtime = harness.host_root().join("isolated-owned-environment");
        fs::create_dir_all(&runtime).expect("provider resource fixture");
        fs::write(runtime.join("owned-marker"), "non-secret").expect("fixture marker");
        let mut attempt = RunnerAttempt::allocate(
            AttemptId::from_u128(0x123),
            harness.policy.id,
            runtime.clone(),
            harness.clock.now(),
        );
        attempt
            .allocate_execution(AttemptExecution::Isolated {
                provider_kind: Backend::Oci,
                environment_id: None,
                resolved_image: image,
                generation: "generation-123".into(),
            })
            .expect("isolated intent");
        attempt
            .prepared_environment("environment-123".into())
            .expect("prepared identity");
        harness
            .store
            .record_attempt(&attempt)
            .expect("durable isolated journal");

        harness
            .launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("unsupported isolated cleanup is profile-local");
        let failure = harness
            .launch_result()
            .await
            .expect_err("provider unavailable for this policy");
        assert_eq!(
            failure.reason,
            FailureReason::IsolationProvider(IsolationProviderFailure::Unsupported)
        );
        harness
            .launcher
            .supervise(&harness.policy)
            .await
            .expect("unavailable attempt is deferred");
        assert!(harness.launcher.clean(attempt.id).await.is_err());
        assert_eq!(
            harness.store.attempt(attempt.id).unwrap().unwrap().state(),
            AttemptState::CleanupDeferred
        );
        assert!(matches!(
            harness.launcher.recover_startup(&[]).await,
            Err(LifecycleError::RecoveryIncomplete)
        ));
        assert!(
            runtime.join("owned-marker").is_file(),
            "native cleanup touched the isolated environment"
        );
        assert!(
            harness.processes.actions.lock().unwrap().is_empty(),
            "native recovery inspected an isolated identity"
        );
        assert_eq!(harness.processes.spawns.load(Ordering::SeqCst), 0);
        assert_eq!(harness.github.registrations.load(Ordering::SeqCst), 0);
        assert_eq!(harness.packages.materializations.load(Ordering::SeqCst), 0);
    }

    #[tokio::test]
    async fn isolated_prepare_is_durable_before_jit_and_start_uses_one_handoff() {
        let harness = isolated_harness();
        let provider = Arc::new(FakeIsolatedProvider::default());
        let launcher = launcher_with_isolated(&harness, Arc::clone(&provider));
        launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("ready");
        let attempt = harness
            .launch_through(&launcher)
            .await
            .expect("isolated launch");
        assert_eq!(attempt.state(), AttemptState::Starting);
        assert_eq!(provider.resource_count(), 1);
        assert_eq!(provider.handoffs.load(Ordering::SeqCst), 1);
        assert_eq!(provider.native_calls.load(Ordering::SeqCst), 0);
        assert_eq!(harness.github.registrations.load(Ordering::SeqCst), 1);
        let fact = harness
            .github
            .registration_facts()
            .pop()
            .expect("JIT registration");
        assert_eq!(
            fact.journal_states,
            vec![AttemptState::Prepared],
            "provider readiness preceded GitHub JIT"
        );
        assert_eq!(
            harness
                .events
                .events()
                .into_iter()
                .filter_map(|event| match event {
                    AttemptEvent::State { state, .. } => Some(state),
                    _ => None,
                })
                .collect::<Vec<_>>(),
            vec![
                AttemptState::Allocated,
                AttemptState::Preparing,
                AttemptState::Prepared,
                AttemptState::JitReceived,
                AttemptState::Starting
            ]
        );
        let restarted = launcher_with_isolated(&harness, Arc::clone(&provider));
        restarted
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("adopt live sandbox");
        assert_eq!(provider.resource_count(), 1);
        assert_eq!(
            harness.github.registrations.load(Ordering::SeqCst),
            1,
            "restart cannot issue duplicate JIT"
        );
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: true });
        restarted
            .supervise(&harness.policy)
            .await
            .expect("job observed");
        assert_eq!(
            harness.store.attempt(attempt.id).unwrap().unwrap().state(),
            AttemptState::Busy
        );
        provider
            .resources
            .lock()
            .unwrap()
            .get_mut(&attempt.id)
            .unwrap()
            .1 = EnvironmentState::Exited;
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        restarted
            .supervise(&harness.policy)
            .await
            .expect("terminal cleanup");
        assert_eq!(provider.resource_count(), 0);
        assert_eq!(
            harness.store.attempt(attempt.id).unwrap().unwrap().state(),
            AttemptState::Cleaned
        );
    }

    #[tokio::test]
    async fn attached_isolated_job_exit_is_recorded_as_completed() {
        let harness = isolated_harness();
        let provider = Arc::new(FakeIsolatedProvider::default());
        let launcher = launcher_with_isolated(&harness, Arc::clone(&provider));
        launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .unwrap();
        let attempt = harness.launch_through(&launcher).await.unwrap();
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: true });
        launcher.supervise(&harness.policy).await.unwrap();
        provider
            .resources
            .lock()
            .unwrap()
            .get_mut(&attempt.id)
            .unwrap()
            .1 = EnvironmentState::Exited;
        provider
            .completed_successfully
            .store(true, Ordering::SeqCst);
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        launcher.supervise(&harness.policy).await.unwrap();
        let cleaned = harness.store.attempt(attempt.id).unwrap().unwrap();
        assert_eq!(cleaned.outcome(), Some(&AttemptOutcome::CompletedJob));
        assert_eq!(cleaned.state(), AttemptState::Cleaned);
    }

    #[tokio::test]
    async fn isolated_prepare_failure_stays_local_and_crash_gap_recovers_owned_resource() {
        let harness = isolated_harness();
        let provider = Arc::new(FakeIsolatedProvider::default());
        provider.prepare_failure.store(true, Ordering::SeqCst);
        let launcher = launcher_with_isolated(&harness, Arc::clone(&provider));
        launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("ready");
        let failure = harness
            .launch_through(&launcher)
            .await
            .expect_err("prepare failed after creating resource");
        assert_eq!(
            failure.reason,
            FailureReason::IsolationProvider(IsolationProviderFailure::RuntimeOperationFailed)
        );
        assert_eq!(provider.resource_count(), 1);
        assert_eq!(harness.github.registrations.load(Ordering::SeqCst), 0);
        assert!(
            !harness
                .store
                .dump_text()
                .unwrap()
                .contains("provider-secret-needle")
        );
        let id = harness.store.attempts().unwrap()[0].id;
        assert_eq!(
            harness.store.attempt(id).unwrap().unwrap().outcome(),
            Some(&AttemptOutcome::failed(FailureReason::IsolationProvider(
                IsolationProviderFailure::RuntimeOperationFailed
            )))
        );
        let restarted = launcher_with_isolated(&harness, Arc::clone(&provider));
        restarted
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("profile-local recovery");
        assert_eq!(
            provider.resource_count(),
            0,
            "the exact owned resource was destroyed once"
        );
        assert_eq!(
            harness.store.attempt(id).unwrap().unwrap().state(),
            AttemptState::Cleaned
        );
        let diagnostic =
            fs::read_to_string(restarted.diagnostics_root.join(format!("{id}.log"))).unwrap();
        assert!(diagnostic.contains("reason=isolation_runtime_operation_failed"));
        assert!(!diagnostic.contains("provider-secret-needle"));
        assert_eq!(
            provider
                .actions
                .lock()
                .unwrap()
                .iter()
                .filter(|action| **action == "destroy")
                .count(),
            1
        );
        assert_eq!(provider.native_calls.load(Ordering::SeqCst), 0);
    }

    #[test]
    fn isolation_capability_and_adapter_failures_keep_closed_categories() {
        let cases = [
            (
                ProviderCapability::NotInstalled,
                IsolationProviderFailure::NotInstalled,
            ),
            (
                ProviderCapability::PermissionDenied,
                IsolationProviderFailure::PermissionDenied,
            ),
            (
                ProviderCapability::ImageUnavailableOrIncompatible,
                IsolationProviderFailure::ImageUnavailableOrIncompatible,
            ),
            (
                ProviderCapability::DiskQuotaUnavailable,
                IsolationProviderFailure::DiskQuotaUnavailable,
            ),
            (
                ProviderCapability::Degraded,
                IsolationProviderFailure::Degraded,
            ),
        ];
        for (capability, category) in cases {
            assert_eq!(
                capability.refusal(),
                FailureReason::IsolationProvider(category)
            );
        }
        let raw = FailureReason::Other("ghp_secret_from_provider".into());
        let safe = safe_isolation_reason(raw, IsolationProviderFailure::RuntimeOperationFailed);
        assert_eq!(
            safe,
            FailureReason::IsolationProvider(IsolationProviderFailure::RuntimeOperationFailed)
        );
        assert!(!safe.to_string().contains("ghp_secret"));
        assert_eq!(
            safe_isolation_reason(
                FailureReason::IsolationProvider(IsolationProviderFailure::PermissionDenied),
                IsolationProviderFailure::RuntimeOperationFailed,
            ),
            FailureReason::IsolationProvider(IsolationProviderFailure::PermissionDenied)
        );
    }

    #[tokio::test]
    async fn isolated_permission_and_image_failures_stop_before_jit_without_native_fallback() {
        for image_failure in [false, true] {
            let harness = isolated_harness();
            let provider = Arc::new(FakeIsolatedProvider::default());
            provider
                .permission_denied
                .store(!image_failure, Ordering::SeqCst);
            provider
                .incompatible_image
                .store(image_failure, Ordering::SeqCst);
            let launcher = launcher_with_isolated(&harness, Arc::clone(&provider));
            launcher
                .recover_startup(std::slice::from_ref(&harness.policy))
                .await
                .unwrap();
            let error = harness
                .launch_through(&launcher)
                .await
                .expect_err("pre-JIT refusal");
            let expected = if image_failure {
                "resolved image is incompatible"
            } else {
                "permission denied"
            };
            assert!(error.reason.to_string().contains(expected));
            assert!(
                harness.store.attempts().unwrap().is_empty(),
                "no allocation was journalled"
            );
            assert_eq!(harness.github.registrations.load(Ordering::SeqCst), 0);
            assert_eq!(provider.handoffs.load(Ordering::SeqCst), 0);
            assert_eq!(provider.native_calls.load(Ordering::SeqCst), 0);
        }
    }

    #[tokio::test]
    async fn unsupported_host_stops_before_jit_without_allocation_or_native_fallback() {
        let harness = isolated_harness();
        let provider = Arc::new(FakeIsolatedProvider::default());
        provider.unsupported_host.store(true, Ordering::SeqCst);
        let launcher = launcher_with_isolated(&harness, Arc::clone(&provider));
        launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .unwrap();
        let error = harness
            .launch_through(&launcher)
            .await
            .expect_err("unsupported host must be refused before JIT");

        assert_eq!(
            error.reason,
            FailureReason::IsolationProvider(IsolationProviderFailure::Unsupported)
        );
        assert!(harness.store.attempts().unwrap().is_empty());
        assert_eq!(harness.github.registrations.load(Ordering::SeqCst), 0);
        assert_eq!(provider.handoffs.load(Ordering::SeqCst), 0);
        assert_eq!(provider.native_calls.load(Ordering::SeqCst), 0);
        assert!(provider.actions.lock().unwrap().is_empty());
    }

    #[tokio::test]
    async fn no_journalled_environment_id_waits_for_provider_absence_proof() {
        let harness = isolated_harness();
        let provider = Arc::new(FakeIsolatedProvider::default());
        let launcher = launcher_with_isolated(&harness, Arc::clone(&provider));
        let runtime = harness.host_root().join("prepare-without-identity");
        fs::create_dir_all(&runtime).unwrap();
        let mut attempt = RunnerAttempt::allocate(
            AttemptId::from_u128(0x9191),
            harness.policy.id,
            runtime,
            harness.clock.now(),
        );
        let runner_manager_domain::execution::ExecutionPolicy::Isolated { image, .. } =
            harness.policy.execution_policy()
        else {
            unreachable!()
        };
        attempt
            .allocate_execution(AttemptExecution::Isolated {
                provider_kind: Backend::Oci,
                environment_id: None,
                resolved_image: image.clone(),
                generation: "prepare-generation".into(),
            })
            .unwrap();
        attempt.begin_prepare(harness.clock.now()).unwrap();
        attempt
            .conclude(
                AttemptOutcome::failed(FailureReason::Other("prepare interrupted".into())),
                harness.clock.now(),
            )
            .unwrap();
        harness.store.record_attempt(&attempt).unwrap();

        provider.recovery_unavailable.store(true, Ordering::SeqCst);
        launcher
            .clean(attempt.id)
            .await
            .expect_err("absence unproven");
        let deferred = harness.store.attempt(attempt.id).unwrap().unwrap();
        assert_eq!(deferred.state(), AttemptState::CleanupDeferred);
        assert!(deferred.counts_against_capacity());

        provider.recovery_unavailable.store(false, Ordering::SeqCst);
        launcher.clean(attempt.id).await.expect("absence proven");
        assert_eq!(
            harness.store.attempt(attempt.id).unwrap().unwrap().state(),
            AttemptState::Cleaned
        );
    }

    #[tokio::test]
    async fn isolated_terminal_capacity_waits_for_confirmed_absence_and_generation_matches() {
        let harness = isolated_harness();
        let provider = Arc::new(FakeIsolatedProvider::default());
        let launcher = launcher_with_isolated(&harness, Arc::clone(&provider));
        launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("ready");
        let mut attempt = harness.launch_through(&launcher).await.expect("launch");
        attempt
            .conclude(
                AttemptOutcome::failed(FailureReason::ProcessStartFailed),
                harness.clock.now(),
            )
            .unwrap();
        harness.store.record_attempt(&attempt).unwrap();
        provider.destroy_deferred.store(true, Ordering::SeqCst);
        launcher
            .clean(attempt.id)
            .await
            .expect_err("provider deferred destroy");
        let deferred = harness.store.attempt(attempt.id).unwrap().unwrap();
        assert_eq!(deferred.state(), AttemptState::CleanupDeferred);
        assert!(deferred.counts_against_capacity());
        assert_eq!(provider.resource_count(), 1);
        provider.destroy_deferred.store(false, Ordering::SeqCst);
        let restarted = launcher_with_isolated(&harness, Arc::clone(&provider));
        restarted
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("retry cleanup");
        assert_eq!(provider.resource_count(), 0);
        assert!(
            !harness
                .store
                .attempt(attempt.id)
                .unwrap()
                .unwrap()
                .counts_against_capacity()
        );

        // A reused runtime name with a different generation is not ours to delete.
        let second_id = AttemptId::from_u128(0x9999);
        let second_runtime = harness.host_root().join("generation-mismatch");
        fs::create_dir_all(&second_runtime).unwrap();
        let mut terminal = RunnerAttempt::allocate(
            second_id,
            harness.policy.id,
            second_runtime,
            harness.clock.now(),
        );
        let runner_manager_domain::execution::ExecutionPolicy::Isolated { image, .. } =
            harness.policy.execution_policy()
        else {
            unreachable!()
        };
        terminal
            .allocate_execution(AttemptExecution::Isolated {
                provider_kind: Backend::Oci,
                environment_id: None,
                resolved_image: image.clone(),
                generation: "expected-generation".into(),
            })
            .unwrap();
        let mut stranger = FakeIsolatedProvider::identity(&terminal, harness.policy.host_id);
        let EnvironmentIdentity::Isolated { environment_id, .. } = &stranger else {
            unreachable!()
        };
        terminal.begin_prepare(harness.clock.now()).unwrap();
        terminal
            .prepared_environment(environment_id.clone())
            .unwrap();
        terminal.mark_prepared(harness.clock.now()).unwrap();
        terminal.jit_received(harness.clock.now()).unwrap();
        terminal.started_isolated(harness.clock.now()).unwrap();
        terminal
            .conclude(
                AttemptOutcome::failed(FailureReason::ProcessStartFailed),
                harness.clock.now(),
            )
            .unwrap();
        harness.store.record_attempt(&terminal).unwrap();
        let EnvironmentIdentity::Isolated { generation, .. } = &mut stranger else {
            unreachable!()
        };
        *generation = "another-generation".into();
        provider
            .resources
            .lock()
            .unwrap()
            .insert(second_id, (stranger, EnvironmentState::Running));
        restarted
            .clean(terminal.id)
            .await
            .expect_err("ownership mismatch quarantined");
        assert_eq!(provider.resource_count(), 1);
        assert_eq!(
            harness.store.attempt(terminal.id).unwrap().unwrap().state(),
            AttemptState::CleanupDeferred
        );
        assert_eq!(provider.native_calls.load(Ordering::SeqCst), 0);
    }

    #[tokio::test]
    async fn isolated_restart_at_each_transition_adopts_or_destroys_one_resource() {
        for stage in [
            AttemptState::Allocated,
            AttemptState::Preparing,
            AttemptState::Prepared,
            AttemptState::JitReceived,
            AttemptState::Starting,
            AttemptState::Idle,
            AttemptState::Busy,
            AttemptState::Finished,
            AttemptState::Failed,
            AttemptState::Orphaned,
            AttemptState::Destroying,
            AttemptState::CleanupDeferred,
        ] {
            let harness = isolated_harness();
            let provider = Arc::new(FakeIsolatedProvider::default());
            let launcher = launcher_with_isolated(&harness, Arc::clone(&provider));
            let id = AttemptId::from_u128(0x1000 + stage as u128);
            let runtime = harness.host_root().join(format!("phase-{stage}"));
            fs::create_dir_all(&runtime).unwrap();
            let mut attempt =
                RunnerAttempt::allocate(id, harness.policy.id, runtime, harness.clock.now());
            let runner_manager_domain::execution::ExecutionPolicy::Isolated { image, .. } =
                harness.policy.execution_policy()
            else {
                unreachable!()
            };
            attempt
                .allocate_execution(AttemptExecution::Isolated {
                    provider_kind: Backend::Oci,
                    environment_id: None,
                    resolved_image: image.clone(),
                    generation: format!("generation-{stage}"),
                })
                .unwrap();
            if stage != AttemptState::Allocated {
                attempt.begin_prepare(harness.clock.now()).unwrap();
            }
            let identity = FakeIsolatedProvider::identity(&attempt, harness.policy.host_id);
            if stage != AttemptState::Allocated {
                let resource_state = if matches!(
                    stage,
                    AttemptState::Finished
                        | AttemptState::Failed
                        | AttemptState::Orphaned
                        | AttemptState::Destroying
                        | AttemptState::CleanupDeferred
                ) {
                    EnvironmentState::Exited
                } else {
                    EnvironmentState::Running
                };
                provider
                    .resources
                    .lock()
                    .unwrap()
                    .insert(id, (identity.clone(), resource_state));
            }
            if !matches!(stage, AttemptState::Allocated | AttemptState::Preparing) {
                let EnvironmentIdentity::Isolated { environment_id, .. } = &identity else {
                    unreachable!()
                };
                attempt
                    .prepared_environment(environment_id.clone())
                    .unwrap();
                attempt.mark_prepared(harness.clock.now()).unwrap();
            }
            if matches!(
                stage,
                AttemptState::JitReceived
                    | AttemptState::Starting
                    | AttemptState::Idle
                    | AttemptState::Busy
                    | AttemptState::Finished
                    | AttemptState::Failed
                    | AttemptState::Orphaned
                    | AttemptState::Destroying
                    | AttemptState::CleanupDeferred
            ) {
                attempt.jit_received(harness.clock.now()).unwrap();
            }
            if matches!(
                stage,
                AttemptState::Starting
                    | AttemptState::Idle
                    | AttemptState::Busy
                    | AttemptState::Finished
                    | AttemptState::Failed
                    | AttemptState::Orphaned
                    | AttemptState::Destroying
                    | AttemptState::CleanupDeferred
            ) {
                attempt.started_isolated(harness.clock.now()).unwrap();
            }
            if matches!(
                stage,
                AttemptState::Idle | AttemptState::Busy | AttemptState::Finished
            ) {
                attempt.registered_idle(73, harness.clock.now()).unwrap();
            }
            if matches!(stage, AttemptState::Busy | AttemptState::Finished) {
                attempt.assigned_job(73, harness.clock.now()).unwrap();
            }
            if matches!(
                stage,
                AttemptState::Finished
                    | AttemptState::Failed
                    | AttemptState::Orphaned
                    | AttemptState::Destroying
                    | AttemptState::CleanupDeferred
            ) {
                let outcome = match stage {
                    AttemptState::Finished => AttemptOutcome::CompletedJob,
                    AttemptState::Orphaned => AttemptOutcome::Orphaned,
                    _ => AttemptOutcome::failed(FailureReason::ProcessStartFailed),
                };
                attempt.conclude(outcome, harness.clock.now()).unwrap();
            }
            if matches!(
                stage,
                AttemptState::Destroying | AttemptState::CleanupDeferred
            ) {
                attempt.begin_destroy(harness.clock.now()).unwrap();
            }
            if stage == AttemptState::CleanupDeferred {
                attempt.defer_cleanup(harness.clock.now()).unwrap();
            }
            harness.store.record_attempt(&attempt).unwrap();
            launcher
                .recover_startup(std::slice::from_ref(&harness.policy))
                .await
                .unwrap_or_else(|error| panic!("restart from {stage}: {error}"));
            let resumed = harness.store.attempt(id).unwrap().unwrap();
            if matches!(
                stage,
                AttemptState::Allocated
                    | AttemptState::Preparing
                    | AttemptState::Prepared
                    | AttemptState::Finished
                    | AttemptState::Failed
                    | AttemptState::Orphaned
                    | AttemptState::Destroying
                    | AttemptState::CleanupDeferred
            ) {
                assert_eq!(
                    resumed.state(),
                    AttemptState::Cleaned,
                    "{stage} must retire after restart"
                );
            } else {
                assert!(resumed.counts_against_capacity(), "live {stage} is adopted");
                assert_eq!(provider.resource_count(), 1);
                provider.resources.lock().unwrap().get_mut(&id).unwrap().1 =
                    EnvironmentState::Exited;
                launcher.supervise(&harness.policy).await.unwrap();
                assert_eq!(
                    harness.store.attempt(id).unwrap().unwrap().state(),
                    AttemptState::Cleaned
                );
            }
            assert_eq!(
                provider.resource_count(),
                0,
                "{stage} resource cleaned exactly once"
            );
            let destroyed = provider
                .actions
                .lock()
                .unwrap()
                .iter()
                .filter(|action| **action == "destroy")
                .count();
            assert_eq!(
                destroyed,
                usize::from(stage != AttemptState::Allocated),
                "{stage} destroy count"
            );
            assert_eq!(
                harness.github.registrations.load(Ordering::SeqCst),
                0,
                "restart from {stage} cannot duplicate JIT"
            );
            assert_eq!(provider.native_calls.load(Ordering::SeqCst), 0);
        }
    }

    #[tokio::test]
    async fn duplicate_provider_ownership_is_quarantined_until_unambiguous() {
        let harness = isolated_harness();
        let provider = Arc::new(FakeIsolatedProvider::default());
        let launcher = launcher_with_isolated(&harness, Arc::clone(&provider));
        let id = AttemptId::from_u128(0x7777);
        let runtime = harness.host_root().join("duplicate-provider-ownership");
        fs::create_dir_all(&runtime).unwrap();
        let mut attempt =
            RunnerAttempt::allocate(id, harness.policy.id, runtime, harness.clock.now());
        let runner_manager_domain::execution::ExecutionPolicy::Isolated { image, .. } =
            harness.policy.execution_policy()
        else {
            unreachable!()
        };
        attempt
            .allocate_execution(AttemptExecution::Isolated {
                provider_kind: Backend::Oci,
                environment_id: None,
                resolved_image: image.clone(),
                generation: "duplicate-generation".into(),
            })
            .unwrap();
        attempt.begin_prepare(harness.clock.now()).unwrap();
        harness.store.record_attempt(&attempt).unwrap();
        let first = FakeIsolatedProvider::identity(&attempt, harness.policy.host_id);
        let mut second = first.clone();
        let EnvironmentIdentity::Isolated { environment_id, .. } = &mut second else {
            unreachable!()
        };
        *environment_id = "another-environment".into();
        provider
            .resources
            .lock()
            .unwrap()
            .insert(id, (first, EnvironmentState::Running));
        provider.extra_resources.lock().unwrap().push(second);
        launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("duplicate is local");
        let deferred = harness.store.attempt(id).unwrap().unwrap();
        assert_eq!(deferred.state(), AttemptState::CleanupDeferred);
        assert!(deferred.counts_against_capacity());
        assert_eq!(provider.resource_count(), 1);
        assert_eq!(
            provider
                .actions
                .lock()
                .unwrap()
                .iter()
                .filter(|action| **action == "destroy")
                .count(),
            0
        );
        provider.extra_resources.lock().unwrap().clear();
        // A tolerated cleanup failure is retried after its backoff delay.
        harness.clock.advance_secs(31);
        launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("single identity recovered");
        assert_eq!(provider.resource_count(), 0);
        assert_eq!(
            harness.store.attempt(id).unwrap().unwrap().state(),
            AttemptState::Cleaned
        );
    }

    #[tokio::test]
    async fn provider_resource_without_live_journal_is_surfaced_but_never_deleted() {
        let harness = isolated_harness();
        let provider = Arc::new(FakeIsolatedProvider::default());
        let launcher = launcher_with_isolated(&harness, Arc::clone(&provider));
        let id = AttemptId::from_u128(0x8888);
        let runtime = harness.host_root().join("orphan-provider-resource");
        fs::create_dir_all(&runtime).unwrap();
        let mut attempt =
            RunnerAttempt::allocate(id, harness.policy.id, runtime, harness.clock.now());
        let runner_manager_domain::execution::ExecutionPolicy::Isolated { image, .. } =
            harness.policy.execution_policy()
        else {
            unreachable!()
        };
        attempt
            .allocate_execution(AttemptExecution::Isolated {
                provider_kind: Backend::Oci,
                environment_id: None,
                resolved_image: image.clone(),
                generation: "orphan-generation".into(),
            })
            .unwrap();
        let identity = FakeIsolatedProvider::identity(&attempt, harness.policy.host_id);
        provider
            .resources
            .lock()
            .unwrap()
            .insert(id, (identity, EnvironmentState::Running));
        launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("orphan cannot block host");
        assert_eq!(provider.resource_count(), 1);
        assert!(
            harness
                .events
                .events()
                .contains(&AttemptEvent::QuarantinedOwnedResource { attempt: id })
        );
        assert_eq!(
            provider
                .actions
                .lock()
                .unwrap()
                .iter()
                .filter(|action| **action == "destroy")
                .count(),
            0
        );

        let EnvironmentIdentity::Isolated { environment_id, .. } = provider
            .resources
            .lock()
            .unwrap()
            .get(&id)
            .unwrap()
            .0
            .clone()
        else {
            unreachable!()
        };
        attempt.begin_prepare(harness.clock.now()).unwrap();
        attempt.prepared_environment(environment_id).unwrap();
        attempt.mark_prepared(harness.clock.now()).unwrap();
        attempt.jit_received(harness.clock.now()).unwrap();
        attempt.started_isolated(harness.clock.now()).unwrap();
        attempt
            .conclude(
                AttemptOutcome::failed(FailureReason::ProcessStartFailed),
                harness.clock.now(),
            )
            .unwrap();
        attempt.begin_destroy(harness.clock.now()).unwrap();
        attempt.clean_isolated(harness.clock.now()).unwrap();
        harness.store.record_attempt(&attempt).unwrap();
        launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("cleaned row cannot authorize deletion");
        assert_eq!(provider.resource_count(), 1);
        assert_eq!(
            provider
                .actions
                .lock()
                .unwrap()
                .iter()
                .filter(|action| **action == "destroy")
                .count(),
            0
        );
    }

    /// The wiring the three-hour outage needed and did not have.
    ///
    /// A root that refuses a launch does so before `record_allocation`, so no
    /// attempt row carries it, and the daemon's log scrubs the paths out of the
    /// sentence. The record this asserts is the only surface left, and
    /// `service status` reads it -- so if this wiring is ever dropped, the
    /// failure goes back to reading `runner_start_failed reason=other` once per
    /// poll and nothing else.
    #[tokio::test]
    async fn a_root_that_refuses_a_launch_is_recorded_and_cleared_when_one_succeeds() {
        use runner_manager_platform::service::{clear_runner_root_refusal, runner_root_refusals};

        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_host_runner_root();
        harness.ready().await;

        // A root under two directories that do not exist: refused by the
        // preflight, for a reason that has nothing to do with this platform, so
        // the assertion holds on all three.
        let unusable = harness
            ._root
            .path()
            .join("absent")
            .join("deeper")
            .join("runners");
        let mut host = harness.host.clone();
        host.runner_root_override = Some(
            LocalAbsolutePath::new(unusable.to_str().expect("a UTF-8 temporary path"))
                .expect("a local absolute host root"),
        );
        harness.store.put_host(&host).unwrap();

        let failure = harness
            .launch_result()
            .await
            .expect_err("a root whose parents are missing cannot hold a runner");
        assert!(
            matches!(failure.reason, FailureReason::Other(_)),
            "{failure:?}"
        );

        let refusals = runner_root_refusals(&harness.app_paths).expect("readable");
        let refusal = refusals
            .first()
            .expect("the refusal reached the one surface that can hold it");
        assert_eq!(refusal.policy, harness.policy.id.to_string());
        assert_eq!(refusal.kind, "missing_parents");
        assert!(
            refusal.root.contains("runners") && refusal.detail.contains("runners"),
            "the directory must be named in full: {refusal:?}"
        );

        // And a root that works clears it, so a host that has been fixed stops
        // reporting a fault it no longer has.
        harness.store.put_host(&harness.host).unwrap();
        harness.launch().await;
        assert!(
            runner_root_refusals(&harness.app_paths)
                .expect("readable")
                .is_empty(),
            "a successful placement clears that policy's record"
        );

        clear_runner_root_refusal(&harness.app_paths, &harness.policy.id.to_string())
            .expect("cleanup");
    }

    #[tokio::test]
    async fn a_launch_reports_how_long_each_step_took() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let started = harness.launch().await;
        let events = harness.events.events();
        let launched = events
            .iter()
            .position(|event| matches!(event, AttemptEvent::Launched { attempt, .. } if *attempt == started.id))
            .expect("a successful launch reports its step timings");
        let starting = events
            .iter()
            .position(|event| matches!(event, AttemptEvent::State { attempt, state: AttemptState::Starting } if *attempt == started.id))
            .unwrap();
        assert!(starting < launched, "timings follow the start: {events:?}");
    }

    #[tokio::test]
    async fn a_failed_launch_still_reports_its_step_timings() {
        let harness = Harness::new(
            FakeGithubLifecycle::default().fail(true),
            Arc::new(PersistentDemand),
        );
        harness.ready().await;
        let failed = harness.launch_after_waiting(Duration::from_secs(90)).await;
        assert!(failed.is_err());

        let timings = harness
            .events
            .events()
            .into_iter()
            .find_map(|event| match event {
                AttemptEvent::Launched {
                    started: false,
                    timings,
                    ..
                } => Some(timings),
                _ => None,
            })
            .expect("a launch that failed at registration reports its timings");
        assert_eq!(timings.lock_wait, Duration::from_secs(90));
        assert_eq!(timings.order_wait, Duration::from_secs(2));
        assert_eq!(timings.spawn, Duration::ZERO, "spawn was never reached");
        assert!(timings.total() >= Duration::from_secs(92));
    }

    #[cfg(target_os = "macos")]
    #[tokio::test]
    async fn a_launch_removes_the_seed_of_a_root_no_longer_in_use() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;

        // A runtime this host once placed under a root it no longer uses.
        let old_root = harness._root.path().join("old-root");
        let old_runtime = old_root.join("abandoned");
        fs::create_dir_all(old_root.join(PACKAGE_SEED_DIR).join("2.335.0")).unwrap();
        fs::create_dir_all(&old_runtime).unwrap();
        let old = RunnerAttempt::allocate(
            AttemptId::new_random(),
            harness.policy.id,
            &old_runtime,
            harness.clock.now(),
        );
        harness.store.record_attempt(&old).unwrap();
        let kept = harness.host_root().join(PACKAGE_SEED_DIR);
        fs::create_dir_all(kept.join("2.336.0")).unwrap();

        harness.launch().await;

        assert!(
            !old_root.join(PACKAGE_SEED_DIR).exists(),
            "the abandoned root's seed is removed"
        );
        assert!(old_runtime.exists(), "only the seed is touched");
        assert!(kept.exists(), "the host root's own seed is kept");
    }

    #[tokio::test]
    async fn a_job_walks_every_state_and_cleans_every_artifact() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let started = harness.launch().await;
        assert_eq!(started.state(), AttemptState::Starting);
        assert_eq!(read_runner_id(started.runtime_path()), Some(73));

        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: false });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(harness.only_attempt().state(), AttemptState::Idle);

        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: true });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(harness.only_attempt().state(), AttemptState::Busy);

        harness.processes.finish_successfully();
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        harness.launcher.supervise(&harness.policy).await.unwrap();
        let cleaned = harness.only_attempt();
        assert_eq!(cleaned.state(), AttemptState::Cleaned);
        assert_eq!(cleaned.outcome(), Some(&AttemptOutcome::CompletedJob));
        assert!(!started.runtime_path().exists());
        assert_eq!(harness.packages.releases.load(Ordering::SeqCst), 1);
        assert_eq!(harness.github.remaining_runners.load(Ordering::SeqCst), 0);

        let states: Vec<_> = harness
            .events
            .events()
            .into_iter()
            .filter_map(|event| match event {
                AttemptEvent::State { state, .. } => Some(state),
                _ => None,
            })
            .collect();
        assert_eq!(
            states,
            vec![
                AttemptState::Allocated,
                AttemptState::JitReceived,
                AttemptState::Starting,
                AttemptState::Idle,
                AttemptState::Busy,
                AttemptState::Finished,
                AttemptState::Cleaned,
            ]
        );
    }

    #[tokio::test]
    async fn a_cleaned_ephemeral_attempt_reaps_a_directory_recreated_after_cleanup() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let started = harness.launch().await;
        let runtime = started.runtime_path().to_path_buf();

        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: true });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        harness.processes.finish_successfully();
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        harness.launcher.supervise(&harness.policy).await.unwrap();

        assert_eq!(harness.attempt(started.id).state(), AttemptState::Cleaned);
        assert!(!runtime.exists());
        assert_eq!(harness.packages.releases.load(Ordering::SeqCst), 1);

        // Reproduce a late orphan creating output after the successful removal
        // and journal transition. The next ordinary policy supervision must
        // remove it without replaying package release or another state change.
        let residue = runtime.join("_work").join("late-node-process");
        fs::create_dir_all(&residue).unwrap();
        fs::write(residue.join("node_modules.lock"), b"late residue").unwrap();

        harness.launcher.supervise(&harness.policy).await.unwrap();

        assert!(!runtime.exists(), "late ephemeral residue is reaped");
        assert_eq!(harness.attempt(started.id).state(), AttemptState::Cleaned);
        assert_eq!(
            harness.packages.releases.load(Ordering::SeqCst),
            1,
            "reaping residue does not release the package lease twice"
        );
    }

    #[tokio::test]
    async fn locked_late_residue_never_blocks_startup_recovery() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let started = harness.launch().await;
        let runtime = started.runtime_path().to_path_buf();

        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: true });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        harness.processes.finish_successfully();
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(harness.attempt(started.id).state(), AttemptState::Cleaned);

        let held = runtime.join("_work").join("late-node-process");
        fs::create_dir_all(&held).unwrap();
        fs::write(held.join("node_modules.lock"), b"late residue").unwrap();
        let Some(block) = BlockedDeletion::inject(&held) else {
            eprintln!(
                "skipped: this account cannot be refused a deletion, so locked late residue cannot be injected"
            );
            return;
        };

        let restarted = harness.restart();
        restarted
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("late residue cannot take the daemon offline");
        assert!(runtime.exists(), "the locked residue remains for a retry");
        assert!(
            harness
                .reconcile_events
                .events()
                .iter()
                .any(|event| matches!(
                    event,
                    LifecycleEvent::AttemptCleanFailed {
                        attempt,
                        reason: "late_ephemeral_workspace_could_not_be_removed",
                        ..
                    } if *attempt == started.id
                )),
            "the non-blocking cleanup failure remains visible"
        );

        block.release();
        // A tolerated cleanup failure is retried after its backoff delay.
        harness.clock.advance_secs(31);
        restarted
            .supervise(&harness.policy)
            .await
            .expect("the ordinary retry succeeds after the lock is released");
        assert!(!runtime.exists(), "the retry removes the late residue");
        assert_eq!(harness.attempt(started.id).state(), AttemptState::Cleaned);
        assert_eq!(
            harness.packages.releases.load(Ordering::SeqCst),
            1,
            "retrying residue never releases the package lease twice"
        );
    }

    #[tokio::test]
    async fn mixed_locked_cleanup_residue_isolated_from_the_whole_startup_pass() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;

        // The first attempt is terminal but its initial cleanup cannot finish.
        // This is the state left by the original failed job on the affected
        // workstation.
        let terminal = harness.launch().await;
        let terminal_runtime = terminal.runtime_path().to_path_buf();
        harness.conclude(terminal.id);
        let Some(terminal_block) = BlockedDeletion::inject(&terminal_runtime.join("late-child"))
        else {
            eprintln!("skipped: this account cannot inject the two independent deletion refusals");
            return;
        };

        // The second attempt was cleaned successfully, then a child recreated
        // part of `_work`. Both real-world residue shapes existed together in
        // the incident, and neither may short-circuit recovery of the other.
        let cleaned = harness.launch().await;
        let cleaned_runtime = cleaned.runtime_path().to_path_buf();
        harness.conclude(cleaned.id);
        harness
            .launcher
            .clean(cleaned.id)
            .await
            .expect("the second attempt initially cleans");
        let Some(cleaned_block) =
            BlockedDeletion::inject(&cleaned_runtime.join("_work").join("late-child"))
        else {
            terminal_block.release();
            eprintln!("skipped: this account cannot inject the two independent deletion refusals");
            return;
        };

        let restarted = harness.restart();
        for _ in 0..2 {
            restarted
                .recover_startup(std::slice::from_ref(&harness.policy))
                .await
                .expect("repeated recovery remains ready while both residues are locked");
        }
        assert_ne!(
            harness.attempt(terminal.id).state(),
            AttemptState::Cleaned,
            "the journal does not claim the terminal workspace was removed"
        );
        assert_eq!(
            harness.attempt(cleaned.id).state(),
            AttemptState::Cleaned,
            "late residue does not undo an already durable cleaned transition"
        );
        assert!(terminal_runtime.exists());
        assert!(cleaned_runtime.exists());
        assert_eq!(
            harness.packages.releases.load(Ordering::SeqCst),
            1,
            "repeated recovery neither loses nor duplicates package leases"
        );

        terminal_block.release();
        cleaned_block.release();
        // A tolerated cleanup failure is retried after its backoff delay.
        harness.clock.advance_secs(31);
        restarted
            .supervise(&harness.policy)
            .await
            .expect("one ordinary pass clears both residues after their locks disappear");
        assert!(!terminal_runtime.exists());
        assert!(!cleaned_runtime.exists());
        assert_eq!(harness.attempt(terminal.id).state(), AttemptState::Cleaned);
        assert_eq!(harness.attempt(cleaned.id).state(), AttemptState::Cleaned);
        assert_eq!(harness.packages.releases.load(Ordering::SeqCst), 2);
    }

    #[tokio::test]
    async fn a_terminal_attempt_whose_runtime_is_already_gone_recovers_cleanly() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let attempt = harness.launch().await;
        let runtime = attempt.runtime_path().to_path_buf();
        harness.conclude(attempt.id);
        fs::remove_dir_all(&runtime).unwrap();

        harness
            .restart()
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("an already absent disposable runtime is successful cleanup");

        assert_eq!(harness.attempt(attempt.id).state(), AttemptState::Cleaned);
        assert_eq!(harness.packages.releases.load(Ordering::SeqCst), 1);
    }

    #[tokio::test]
    async fn a_non_workspace_cleanup_failure_still_fails_closed_and_can_retry() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let attempt = harness.launch().await;
        let runtime = attempt.runtime_path().to_path_buf();
        harness.conclude(attempt.id);
        harness.packages.fail_releases(1);

        let restarted = harness.restart();
        let failure = restarted
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect_err("a package-accounting failure is not safe to downgrade to residue");
        assert!(
            failure
                .reason()
                .to_string()
                .contains("package lease could not be released")
        );
        assert!(
            !runtime.exists(),
            "workspace removal completed before release failed"
        );
        assert_ne!(harness.attempt(attempt.id).state(), AttemptState::Cleaned);

        restarted
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("the same journal entry retries safely after the transient failure");
        assert_eq!(harness.attempt(attempt.id).state(), AttemptState::Cleaned);
        assert_eq!(harness.packages.releases.load(Ordering::SeqCst), 1);
    }

    #[tokio::test]
    async fn startup_never_scrubs_a_cleaned_persistent_work_directory() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_persistent_workspace(1);
        harness.ready().await;
        let attempt = harness.launch().await;
        let retained = attempt.runtime_path().join("_work").join("checkout-marker");
        fs::create_dir_all(retained.parent().unwrap()).unwrap();
        fs::write(&retained, b"persistent checkout").unwrap();
        harness.cleanup_retaining_work(attempt.id).await;

        harness
            .restart()
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("a cleaned persistent slot is already reconciled");

        assert_eq!(fs::read(&retained).unwrap(), b"persistent checkout");
        assert_eq!(harness.packages.releases.load(Ordering::SeqCst), 1);
    }

    #[tokio::test]
    async fn an_idle_exit_is_not_a_failure_in_the_journal_or_events() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let started = harness.launch().await;
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: false });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        harness.clock.advance_secs(11);
        harness.processes.set_alive(false);
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        harness.launcher.supervise(&harness.policy).await.unwrap();

        let cleaned = harness.only_attempt();
        assert!(cleaned.outcome().unwrap().is_idle_exit());
        assert!(!cleaned.outcome().unwrap().is_failure());
        assert!(!started.runtime_path().exists());
        assert!(
            harness
                .reconcile_events
                .events()
                .iter()
                .any(|event| matches!(
                    event,
                    LifecycleEvent::AttemptCleaned {
                        outcome: OutcomeKind::IdleExit,
                        ..
                    }
                ))
        );
        assert!(!harness.events.events().iter().any(|event| matches!(
            event,
            AttemptEvent::Concluded {
                outcome: OutcomeKind::Failed,
                ..
            }
        )));
    }

    #[tokio::test]
    async fn handoff_is_absent_after_success_and_every_failed_spawn_retry() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.processes.fail_spawns(2);
        harness.ready().await;
        let attempt = harness.launch().await;
        assert_eq!(harness.processes.spawns.load(Ordering::SeqCst), 3);
        assert!(harness.processes.saw_secret.load(Ordering::SeqCst));
        let names: Vec<_> = fs::read_dir(attempt.runtime_path())
            .unwrap()
            .map(|entry| entry.unwrap().file_name())
            .collect();
        assert!(
            names.iter().all(|name| {
                !name
                    .to_string_lossy()
                    .starts_with(RestrictiveHandoff::NAME_PREFIX)
            }),
            "JIT artifact survived: {names:?}"
        );
        assert_eq!(
            *harness.delay.0.lock().unwrap(),
            vec![Duration::from_millis(10), Duration::from_millis(20)]
        );
    }

    #[tokio::test]
    async fn jit_retry_stops_with_demand_and_a_terminal_403_never_retries() {
        let gone = Harness::new(
            FakeGithubLifecycle::default().fail(false),
            Arc::new(FakeDemand::answering([false])),
        );
        gone.ready().await;
        assert!(gone.launch_result().await.is_err());
        assert_eq!(gone.github.registrations.load(Ordering::SeqCst), 1);
        assert!(gone.delay.0.lock().unwrap().is_empty());

        let forbidden = Harness::new(
            FakeGithubLifecycle::default().fail(true),
            Arc::new(PersistentDemand),
        );
        forbidden.ready().await;
        assert!(forbidden.launch_result().await.is_err());
        assert_eq!(forbidden.github.registrations.load(Ordering::SeqCst), 1);
        assert!(forbidden.delay.0.lock().unwrap().is_empty());
        assert!(matches!(
            forbidden.only_attempt().outcome(),
            Some(AttemptOutcome::Failed {
                reason: FailureReason::Other(action)
            }) if action.contains("403")
        ));

        let transient = Harness::new(
            FakeGithubLifecycle::default().fail(false).fail(false),
            Arc::new(PersistentDemand),
        );
        transient.ready().await;
        transient.launch().await;
        assert_eq!(transient.github.registrations.load(Ordering::SeqCst), 3);
        assert_eq!(
            *transient.delay.0.lock().unwrap(),
            vec![Duration::from_millis(10), Duration::from_millis(20)]
        );
    }

    /// The layout has to leave room for what the runner writes underneath it.
    ///
    /// Windows refuses a path over `MAX_PATH`, and this product's own CI hit
    /// that: 264 characters against a limit of 260, failing three checkout
    /// retries with `Filename too long`. The two identifiers in the old layout
    /// cost 74 characters between them for no benefit -- an attempt id is
    /// unique on its own.
    #[test]
    fn a_workspace_leaves_room_for_the_deepest_path_a_checkout_writes() {
        const MAX_PATH: usize = 260;
        // The real root on the machine this was found on.
        let root = r"C:\Users\IvanD\AppData\Local\IvanMurzak\runner-manager\data\runtime";
        // What `actions/checkout` writes at its deepest: the work directory,
        // the repository named twice, and a pack keep-file with a 40-character
        // object name.
        let repo = "GitHub-Runner-Scaler-UI";
        let deepest = format!(
            r"_work\{repo}\{repo}\.git\objects\pack\pack-{}.keep",
            "0".repeat(40)
        );

        let name = workspace_name(AttemptId::new_random());
        assert_eq!(name.len(), WORKSPACE_NAME_LEN, "{name}");
        assert!(
            name.chars().all(|c| c.is_ascii_hexdigit()),
            "a directory name must not carry the identifier's dashes: {name}"
        );

        let full = format!(r"{root}\{name}\{deepest}");
        assert!(
            full.len() < MAX_PATH,
            "the deepest path a checkout writes must fit: {} characters, limit {MAX_PATH}",
            full.len()
        );

        // The discriminator: the layout this replaced does not fit, so a test
        // that passed for both would be proving nothing.
        let old = format!(
            r"{root}\{}\{}\{deepest}",
            PolicyId::new_random(),
            AttemptId::new_random()
        );
        assert!(
            old.len() > MAX_PATH,
            "the old layout is supposed to be the thing that did not fit: {} characters",
            old.len()
        );
    }

    #[tokio::test]
    async fn two_attempts_never_share_a_workspace_even_after_failure() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let first = harness.launch().await;
        fs::write(first.runtime_path().join("hostile-leftover"), b"first job").unwrap();
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: false });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        harness.clock.advance_secs(11);
        harness.processes.set_alive(false);
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert!(!first.runtime_path().exists());

        let second = harness.launch().await;
        assert_ne!(first.runtime_path(), second.runtime_path());
        assert!(!second.runtime_path().join("hostile-leftover").exists());

        fs::write(
            second.runtime_path().join("hostile-on-failure"),
            b"second job",
        )
        .unwrap();
        harness.processes.set_alive(false);
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert!(
            !second.runtime_path().exists(),
            "failed workspace was retained"
        );
    }

    #[tokio::test]
    async fn a_runner_that_never_gets_a_job_is_stopped_deregistered_and_not_replaced() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let attempt = harness.launch().await;

        // Registered and waiting, which is where it stays: the fake keeps
        // answering the same observation, exactly as GitHub does for a runner
        // nobody assigns work to.
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: false });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(harness.only_attempt().state(), AttemptState::Idle);

        // One second inside the ten-second idle timeout nothing happens, which
        // is what keeps this from being a test that would pass on any clock.
        harness.clock.advance_secs(9);
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: false });
        let none_yet = harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(harness.only_attempt().state(), AttemptState::Idle);
        assert!(none_yet.is_empty());
        assert_eq!(harness.processes.terminations.load(Ordering::SeqCst), 0);

        // Past it, the agent ends the runner itself.
        harness.clock.advance_secs(1);
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: false });
        let replacements = harness.launcher.supervise(&harness.policy).await.unwrap();

        let concluded = harness.store.attempt(attempt.id).unwrap().unwrap();
        assert_eq!(
            concluded.outcome(),
            Some(&AttemptOutcome::ExitedIdleWithoutWork),
            "a surplus runner did not fail; recording one as a failure sends an operator \
             hunting a fault that does not exist"
        );
        assert_eq!(concluded.state(), AttemptState::Cleaned);
        assert_eq!(harness.processes.terminations.load(Ordering::SeqCst), 1);
        assert!(!attempt.runtime_path().exists());

        // The registration goes with it. Without this the runner stays listed
        // in the target's runner settings after the process it named is gone.
        assert_eq!(
            *harness.github.deregistrations.lock().unwrap(),
            vec![73],
            "the attempt's own runner id, deleted exactly once"
        );

        // And nothing is started in its place: the work it was launched for went
        // elsewhere, so a replacement would rebuild it every idle timeout.
        assert!(
            replacements.is_empty(),
            "a surplus exit must not request a replacement"
        );
    }

    #[tokio::test]
    async fn a_registration_github_will_not_delete_still_concludes_the_attempt() {
        // The delete is best-effort by construction: the process is gone and the
        // slot has to come back. Holding the conclusion until GitHub cooperates
        // would leak a capacity slot on every unreachable moment.
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let attempt = harness.launch().await;
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: false });
        harness.launcher.supervise(&harness.policy).await.unwrap();

        harness
            .github
            .deregistration_fails
            .store(true, Ordering::SeqCst);
        harness.clock.advance_secs(11);
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: false });
        harness.launcher.supervise(&harness.policy).await.unwrap();

        assert_eq!(
            *harness.github.deregistrations.lock().unwrap(),
            vec![73],
            "the delete was attempted"
        );
        let concluded = harness.store.attempt(attempt.id).unwrap().unwrap();
        assert_eq!(
            concluded.outcome(),
            Some(&AttemptOutcome::ExitedIdleWithoutWork),
            "the attempt concluded anyway"
        );
        assert_eq!(concluded.state(), AttemptState::Cleaned);
        assert!(!attempt.runtime_path().exists());
    }

    #[tokio::test]
    async fn exit_before_acceptance_returns_replacement_intent_without_launching() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let first = harness.launch().await;
        harness.processes.set_alive(false);
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        let replacements = harness.launcher.supervise(&harness.policy).await.unwrap();
        let failed = harness.store.attempt(first.id).unwrap().unwrap();
        assert!(matches!(
            failed.outcome(),
            Some(AttemptOutcome::Failed {
                reason: FailureReason::ProcessExitedUnexpectedly
            })
        ));
        assert!(!first.runtime_path().exists());

        assert_eq!(
            replacements,
            vec![ReplacementIntent {
                policy: harness.policy.id,
                previous_attempt: first.id,
                operation: "exit_before_acceptance_replacement",
            }]
        );
        assert_eq!(harness.store.attempts().unwrap().len(), 1);
        assert_eq!(harness.github.registrations.load(Ordering::SeqCst), 1);
        assert_eq!(harness.processes.spawns.load(Ordering::SeqCst), 1);
        assert!(harness.delay.0.lock().unwrap().is_empty());
    }

    /// Writes the runner's own diagnostics: always the listener's log, and the
    /// job worker's when `ran_a_job`. `Runner.Listener` starts `Runner.Worker`
    /// only for a job it has acquired.
    fn write_runner_diagnostics(runtime: &Path, ran_a_job: bool) {
        let diag = runtime.join("_diag");
        fs::create_dir_all(&diag).unwrap();
        fs::write(diag.join("Runner_20261007-211941-utc.log"), b"listener").unwrap();
        if ran_a_job {
            fs::write(diag.join("Worker_20261007-211950-utc.log"), b"worker").unwrap();
        }
    }

    /// The macOS field case: a job of a few seconds starts and ends between two
    /// passes, so GitHub was never seen reporting the runner busy -- the attempt
    /// is still `starting` -- and the registration is already gone. It used to be
    /// recorded `process_exited_unexpectedly`, with a replacement runner.
    #[tokio::test]
    async fn a_job_too_short_to_be_seen_busy_is_recorded_as_completed() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let started = harness.launch().await;
        assert_eq!(started.state(), AttemptState::Starting);
        write_runner_diagnostics(started.runtime_path(), true);
        harness.processes.finish_successfully();
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);

        let replacements = harness.launcher.supervise(&harness.policy).await.unwrap();

        let cleaned = harness.only_attempt();
        assert_eq!(cleaned.outcome(), Some(&AttemptOutcome::CompletedJob));
        assert_eq!(cleaned.state(), AttemptState::Cleaned);
        assert_eq!(cleaned.github_runner_id(), Some(73));
        assert!(
            replacements.is_empty(),
            "a finished job needs no replacement"
        );
        let busy_seen = harness.events.events().into_iter().any(|event| {
            matches!(
                event,
                AttemptEvent::State {
                    state: AttemptState::Busy,
                    ..
                }
            )
        });
        assert!(busy_seen, "the journal walks the diagram to `busy` first");
    }

    /// The same from `idle`: seen registered and waiting once, then gone.
    #[tokio::test]
    async fn a_job_taken_between_two_passes_after_idle_is_recorded_as_completed() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let started = harness.launch().await;
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: false });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(harness.only_attempt().state(), AttemptState::Idle);

        write_runner_diagnostics(started.runtime_path(), true);
        harness.processes.finish_successfully();
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        let replacements = harness.launcher.supervise(&harness.policy).await.unwrap();

        assert_eq!(
            harness.only_attempt().outcome(),
            Some(&AttemptOutcome::CompletedJob)
        );
        assert!(replacements.is_empty());
    }

    /// The reverse error, from the same sampling: GitHub showed the runner
    /// assigned, the runner never started the job (no worker log), and it exited
    /// 0. That is not a completed job.
    #[tokio::test]
    async fn an_assignment_the_runner_never_took_up_is_not_a_completed_job() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let started = harness.launch().await;
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: true });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(harness.only_attempt().state(), AttemptState::Busy);

        write_runner_diagnostics(started.runtime_path(), false);
        harness.processes.finish_successfully();
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        harness.launcher.supervise(&harness.policy).await.unwrap();

        let cleaned = harness.only_attempt();
        assert_eq!(
            cleaned.outcome(),
            Some(&AttemptOutcome::ExitedIdleWithoutWork)
        );
        assert_eq!(cleaned.state(), AttemptState::Cleaned);
    }

    /// The mirror case: the runner really ran its job and exited 0 before GitHub
    /// took it off the list. It used to be recorded `orphaned`.
    #[tokio::test]
    async fn a_finished_job_still_listed_at_github_is_completed_and_deregistered() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let started = harness.launch().await;
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: true });
        harness.launcher.supervise(&harness.policy).await.unwrap();

        write_runner_diagnostics(started.runtime_path(), true);
        harness.processes.finish_successfully();
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: true });
        harness.launcher.supervise(&harness.policy).await.unwrap();

        assert_eq!(
            harness.only_attempt().outcome(),
            Some(&AttemptOutcome::CompletedJob)
        );
        assert_eq!(*harness.github.deregistrations.lock().unwrap(), vec![73]);
    }

    /// A live runner journalled `busy` whose assignment GitHub withdrew goes
    /// back to `idle`, where the idle timeout holds it again.
    #[tokio::test]
    async fn a_live_runner_whose_assignment_was_withdrawn_goes_back_to_idle() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let started = harness.launch().await;
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: true });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(harness.only_attempt().state(), AttemptState::Busy);

        write_runner_diagnostics(started.runtime_path(), false);
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: false });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(harness.only_attempt().state(), AttemptState::Idle);

        // A runner that did start its job keeps `busy` whatever GitHub says.
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: true });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        write_runner_diagnostics(started.runtime_path(), true);
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: false });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(harness.only_attempt().state(), AttemptState::Busy);
    }

    /// While GitHub cannot be reached nothing is concluded, so a registration
    /// still listed there is removed once it answers.
    #[tokio::test]
    async fn a_clean_exit_waits_for_github_to_answer() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let started = harness.launch().await;
        write_runner_diagnostics(started.runtime_path(), true);
        harness.processes.finish_successfully();
        harness.github.observe(GithubRunnerObservation::Unreachable);
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(harness.only_attempt().state(), AttemptState::Starting);

        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(
            harness.only_attempt().outcome(),
            Some(&AttemptOutcome::CompletedJob)
        );
    }

    /// A runner id nobody can name is not a reason to stop supervising the
    /// policy: the attempt is concluded the way it was before, without one.
    #[tokio::test]
    async fn a_short_job_with_no_runner_id_still_concludes() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let started = harness.launch().await;
        fs::remove_file(started.runtime_path().join(RUNNER_ID_FILE)).unwrap();
        write_runner_diagnostics(started.runtime_path(), true);
        harness.processes.finish_successfully();
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        harness
            .launcher
            .supervise(&harness.policy)
            .await
            .expect("supervision goes on");
        assert!(harness.only_attempt().is_terminal());
    }

    /// Without the runner's diagnostics nothing changes: a clean exit seen only
    /// at `starting` is still a runner that exited before taking a job.
    #[tokio::test]
    async fn without_runner_diagnostics_an_early_exit_is_still_a_failure() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        harness.launch().await;
        harness.processes.finish_successfully();
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert!(matches!(
            harness.only_attempt().outcome(),
            Some(AttemptOutcome::Failed {
                reason: FailureReason::ProcessExitedUnexpectedly
            })
        ));
    }

    #[tokio::test]
    async fn expired_jit_is_removed_and_does_not_reregister_after_demand_disappears() {
        let harness = Harness::new(
            FakeGithubLifecycle::default(),
            Arc::new(FakeDemand::answering([false])),
        );
        let id = AttemptId::new_random();
        let runtime = harness
            .launcher
            .app_paths
            .runtime_dir()
            .join(harness.policy.id.to_string())
            .join(id.to_string());
        fs::create_dir_all(&runtime).unwrap();
        let mut attempt =
            RunnerAttempt::allocate(id, harness.policy.id, &runtime, harness.clock.now());
        attempt.jit_received(harness.clock.now()).unwrap();
        harness.store.record_attempt(&attempt).unwrap();
        harness.clock.advance_secs(11);
        let replacements = harness
            .launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .unwrap();
        assert_eq!(
            replacements,
            vec![ReplacementIntent {
                policy: harness.policy.id,
                previous_attempt: id,
                operation: "jit_expired_replacement",
            }]
        );

        let cleaned = harness.store.attempt(id).unwrap().unwrap();
        assert_eq!(cleaned.state(), AttemptState::Cleaned);
        assert!(matches!(
            cleaned.outcome(),
            Some(AttemptOutcome::Failed {
                reason: FailureReason::JitExpired
            })
        ));
        assert!(!runtime.exists());
        assert_eq!(harness.github.registrations.load(Ordering::SeqCst), 0);
        assert!(harness.delay.0.lock().unwrap().is_empty());
    }

    #[tokio::test]
    async fn expired_jit_returns_intent_but_never_launches_inside_lifecycle() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        let id = AttemptId::new_random();
        let runtime = harness
            .launcher
            .app_paths
            .runtime_dir()
            .join("expired-with-demand");
        fs::create_dir_all(&runtime).unwrap();
        let mut attempt =
            RunnerAttempt::allocate(id, harness.policy.id, &runtime, harness.clock.now());
        attempt.jit_received(harness.clock.now()).unwrap();
        harness.store.record_attempt(&attempt).unwrap();
        harness.clock.advance_secs(11);
        let replacements = harness
            .launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .unwrap();

        let attempts = harness.store.attempts().unwrap();
        assert_eq!(attempts.len(), 1);
        assert_eq!(
            attempts
                .iter()
                .find(|attempt| attempt.id == id)
                .unwrap()
                .state(),
            AttemptState::Cleaned
        );
        assert_eq!(
            replacements,
            vec![ReplacementIntent {
                policy: harness.policy.id,
                previous_attempt: id,
                operation: "jit_expired_replacement",
            }]
        );
        assert_eq!(harness.github.registrations.load(Ordering::SeqCst), 0);
        assert_eq!(harness.processes.spawns.load(Ordering::SeqCst), 0);
        assert!(harness.delay.0.lock().unwrap().is_empty());
    }

    #[tokio::test]
    async fn package_materialization_retries_are_bounded_and_demand_adjacent() {
        let persistent = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        persistent.packages.fail_materializations(2);
        persistent.ready().await;
        persistent.launch().await;
        assert_eq!(
            persistent.packages.materializations.load(Ordering::SeqCst),
            3
        );
        assert_eq!(
            *persistent.delay.0.lock().unwrap(),
            vec![Duration::from_millis(10), Duration::from_millis(20)]
        );

        let gone_before_wait = Harness::new(
            FakeGithubLifecycle::default(),
            Arc::new(FakeDemand::answering([false])),
        );
        gone_before_wait.packages.fail_materializations(3);
        gone_before_wait.ready().await;
        assert!(gone_before_wait.launch_result().await.is_err());
        assert_eq!(
            gone_before_wait
                .packages
                .materializations
                .load(Ordering::SeqCst),
            1
        );
        assert!(gone_before_wait.delay.0.lock().unwrap().is_empty());

        let gone_during_wait = Harness::new(
            FakeGithubLifecycle::default(),
            Arc::new(FakeDemand::answering([true, false])),
        );
        gone_during_wait.packages.fail_materializations(3);
        gone_during_wait.ready().await;
        assert!(gone_during_wait.launch_result().await.is_err());
        assert_eq!(
            gone_during_wait
                .packages
                .materializations
                .load(Ordering::SeqCst),
            1
        );
        assert_eq!(
            *gone_during_wait.delay.0.lock().unwrap(),
            vec![Duration::from_millis(10)]
        );
    }

    #[tokio::test]
    async fn replacement_is_intent_only_and_never_launches_inside_lifecycle() {
        let harness = Harness::new(
            FakeGithubLifecycle::default(),
            Arc::new(FakeDemand::answering([true, false])),
        );
        harness.ready().await;
        let first = harness.launch().await;
        harness.processes.set_alive(false);
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        let replacements = harness.launcher.supervise(&harness.policy).await.unwrap();

        assert_eq!(harness.store.attempts().unwrap().len(), 1);
        assert_eq!(harness.github.registrations.load(Ordering::SeqCst), 1);
        assert_eq!(harness.processes.spawns.load(Ordering::SeqCst), 1);
        assert!(harness.delay.0.lock().unwrap().is_empty());
        assert_eq!(
            replacements,
            vec![ReplacementIntent {
                policy: harness.policy.id,
                previous_attempt: first.id,
                operation: "exit_before_acceptance_replacement",
            }]
        );
        assert_eq!(
            harness.store.attempt(first.id).unwrap().unwrap().state(),
            AttemptState::Cleaned
        );
    }

    #[tokio::test]
    async fn startup_adopts_a_live_process_and_refuses_launch_before_recovery() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        let before = harness.launch_result().await;
        assert!(before.is_err());
        assert_eq!(harness.processes.spawns.load(Ordering::SeqCst), 0);

        let id = AttemptId::new_random();
        let runtime = harness.launcher.app_paths.runtime_dir().join("adopt");
        fs::create_dir_all(&runtime).unwrap();
        let mut attempt =
            RunnerAttempt::allocate(id, harness.policy.id, runtime, harness.clock.now());
        attempt.jit_received(harness.clock.now()).unwrap();
        attempt.started(4242, harness.clock.now()).unwrap();
        harness.store.record_attempt(&attempt).unwrap();
        harness.processes.set_alive(true);
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        let replacements = harness
            .launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .unwrap();
        assert!(replacements.is_empty());
        assert_eq!(harness.processes.spawns.load(Ordering::SeqCst), 0);
        assert!(
            harness
                .events
                .events()
                .contains(&AttemptEvent::Adopted { attempt: id })
        );
    }

    #[tokio::test]
    async fn spawn_before_starting_crash_recovers_pid_then_completes_and_cleans() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        let id = AttemptId::new_random();
        let runtime = harness
            .launcher
            .app_paths
            .runtime_dir()
            .join("spawn-before-starting");
        fs::create_dir_all(&runtime).unwrap();
        let mut attempt =
            RunnerAttempt::allocate(id, harness.policy.id, &runtime, harness.clock.now());
        attempt.jit_received(harness.clock.now()).unwrap();
        harness.store.record_attempt(&attempt).unwrap();
        harness.processes.set_alive(true);
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: true });

        let replacements = harness
            .launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .unwrap();
        assert!(replacements.is_empty());
        let recovered = harness.store.attempt(id).unwrap().unwrap();
        assert_eq!(recovered.state(), AttemptState::Busy);
        assert_eq!(recovered.process_id(), Some(4242));
        assert_eq!(recovered.github_runner_id(), Some(73));
        let events = harness.events.events();
        let starting = events
            .iter()
            .position(|event| matches!(event, AttemptEvent::State { attempt, state: AttemptState::Starting } if *attempt == id))
            .unwrap();
        let busy = events
            .iter()
            .position(|event| matches!(event, AttemptEvent::State { attempt, state: AttemptState::Busy } if *attempt == id))
            .unwrap();
        assert!(starting < busy, "recovery skipped a legal edge: {events:?}");

        harness.processes.finish_successfully();
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        assert!(
            harness
                .launcher
                .supervise(&harness.policy)
                .await
                .unwrap()
                .is_empty()
        );
        let cleaned = harness.store.attempt(id).unwrap().unwrap();
        assert_eq!(cleaned.state(), AttemptState::Cleaned);
        assert_eq!(cleaned.outcome(), Some(&AttemptOutcome::CompletedJob));
        assert!(!runtime.exists());
    }

    #[tokio::test]
    async fn failed_post_spawn_stop_keeps_capacity_until_supervision_proves_death() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.processes.fail_spawn_with_live_child();
        harness.ready().await;
        assert!(harness.launch_result().await.is_err());

        let attempt = harness.only_attempt();
        assert_eq!(attempt.state(), AttemptState::Starting);
        assert_eq!(attempt.process_id(), Some(4242));
        assert!(attempt.outcome().is_none());
        assert!(attempt.state().counts_against_capacity());
        assert_eq!(harness.processes.spawns.load(Ordering::SeqCst), 1);
        assert!(harness.delay.0.lock().unwrap().is_empty());

        harness.processes.set_alive(false);
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        let replacements = harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(replacements.len(), 1);
        assert_eq!(
            harness.store.attempt(attempt.id).unwrap().unwrap().state(),
            AttemptState::Cleaned
        );
    }

    #[tokio::test]
    async fn remote_runner_identity_closes_both_sides_of_the_registration_crash_boundary() {
        for sidecar_already_present in [false, true] {
            let harness = Harness::new(
                FakeGithubLifecycle::default(),
                Arc::new(FakeDemand::answering([false])),
            );
            let id = AttemptId::new_random();
            let runtime =
                harness
                    .launcher
                    .app_paths
                    .runtime_dir()
                    .join(if sidecar_already_present {
                        "after-id-sidecar"
                    } else {
                        "before-id-sidecar"
                    });
            fs::create_dir_all(&runtime).unwrap();
            let mut attempt =
                RunnerAttempt::allocate(id, harness.policy.id, &runtime, harness.clock.now());
            if sidecar_already_present {
                write_runner_id(&runtime, 73).unwrap();
                attempt.jit_received(harness.clock.now()).unwrap();
            }
            harness.store.record_attempt(&attempt).unwrap();
            harness.processes.set_alive(true);
            harness
                .github
                .observe(GithubRunnerObservation::Registered { busy: false });
            harness
                .launcher
                .recover_startup(std::slice::from_ref(&harness.policy))
                .await
                .unwrap();

            assert_eq!(read_runner_id(&runtime), Some(73));
            assert!(
                harness
                    .store
                    .attempt(id)
                    .unwrap()
                    .unwrap()
                    .outcome()
                    .is_none()
            );
            let events = harness.events.events();
            let recovered = events.iter().position(|event| {
                matches!(
                    event,
                    AttemptEvent::RemoteIdentityRecovered {
                        attempt,
                        runner_id: 73
                    } if *attempt == id
                )
            });
            assert_eq!(recovered.is_some(), !sidecar_already_present);
            if let Some(recovered) = recovered {
                let adopted = events
                    .iter()
                    .position(|event| matches!(event, AttemptEvent::Adopted { attempt } if *attempt == id))
                    .unwrap();
                assert!(
                    recovered < adopted,
                    "identity was not durable before adoption: {events:?}"
                );
            }
            assert!(runtime.exists());
        }
    }

    #[tokio::test]
    async fn recovery_stays_closed_for_unknown_policy_and_unreachable_attempts() {
        let unknown = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        let unknown_attempt = RunnerAttempt::allocate(
            AttemptId::new_random(),
            PolicyId::from_u128(0xfeed),
            unknown
                .launcher
                .app_paths
                .runtime_dir()
                .join("unknown-policy"),
            unknown.clock.now(),
        );
        unknown.store.record_attempt(&unknown_attempt).unwrap();
        let expired_id = AttemptId::new_random();
        let expired_runtime = unknown
            .launcher
            .app_paths
            .runtime_dir()
            .join("expired-beside-unknown");
        fs::create_dir_all(&expired_runtime).unwrap();
        let mut expired = RunnerAttempt::allocate(
            expired_id,
            unknown.policy.id,
            expired_runtime,
            unknown.clock.now(),
        );
        expired.jit_received(unknown.clock.now()).unwrap();
        unknown.store.record_attempt(&expired).unwrap();
        unknown.clock.advance_secs(11);
        assert!(matches!(
            unknown
                .launcher
                .recover_startup(std::slice::from_ref(&unknown.policy))
                .await,
            Err(LifecycleError::RecoveryIncomplete)
        ));
        assert!(unknown.launch_result().await.is_err());
        assert_eq!(unknown.processes.spawns.load(Ordering::SeqCst), 0);
        let recovered_policy = fixtures::policy()
            .id(PolicyId::from_u128(0xfeed))
            .repository("octo/repo")
            .autoscale("home", 2)
            .active()
            .build();
        let pending = unknown
            .launcher
            .recover_startup(&[unknown.policy.clone(), recovered_policy])
            .await
            .unwrap();
        assert_eq!(
            pending,
            vec![ReplacementIntent {
                policy: unknown.policy.id,
                previous_attempt: expired_id,
                operation: "jit_expired_replacement",
            }]
        );
        assert_eq!(unknown.processes.spawns.load(Ordering::SeqCst), 0);

        let unreachable = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        let id = AttemptId::new_random();
        let runtime = unreachable
            .launcher
            .app_paths
            .runtime_dir()
            .join("unreachable");
        fs::create_dir_all(&runtime).unwrap();
        unreachable
            .store
            .record_attempt(&RunnerAttempt::allocate(
                id,
                unreachable.policy.id,
                runtime,
                unreachable.clock.now(),
            ))
            .unwrap();
        unreachable
            .github
            .observe(GithubRunnerObservation::Unreachable);
        assert!(matches!(
            unreachable
                .launcher
                .recover_startup(std::slice::from_ref(&unreachable.policy))
                .await,
            Err(LifecycleError::RecoveryIncomplete)
        ));
        assert!(unreachable.launch_result().await.is_err());
        assert_eq!(unreachable.processes.spawns.load(Ordering::SeqCst), 0);
    }

    #[tokio::test]
    async fn a_dead_busy_process_unknown_to_github_is_orphaned_and_cleaned() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        let id = AttemptId::new_random();
        let runtime = harness.launcher.app_paths.runtime_dir().join("orphan");
        fs::create_dir_all(&runtime).unwrap();
        let mut attempt =
            RunnerAttempt::allocate(id, harness.policy.id, &runtime, harness.clock.now());
        attempt.jit_received(harness.clock.now()).unwrap();
        attempt.started(4242, harness.clock.now()).unwrap();
        attempt.assigned_job(73, harness.clock.now()).unwrap();
        harness.store.record_attempt(&attempt).unwrap();
        harness.processes.set_alive(false);
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        harness
            .launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .unwrap();
        let cleaned = harness.store.attempt(id).unwrap().unwrap();
        assert_eq!(cleaned.state(), AttemptState::Cleaned);
        assert_eq!(cleaned.outcome(), Some(&AttemptOutcome::Orphaned));
        assert!(!runtime.exists());
    }

    #[tokio::test]
    async fn registration_timeout_journals_intent_stops_then_concludes_with_dead_reason() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let id = AttemptId::new_random();
        let runtime = harness.launcher.app_paths.runtime_dir().join("timeout");
        fs::create_dir_all(&runtime).unwrap();
        let mut attempt =
            RunnerAttempt::allocate(id, harness.policy.id, runtime, harness.clock.now());
        attempt.jit_received(harness.clock.now()).unwrap();
        attempt.started(4242, harness.clock.now()).unwrap();
        harness.store.record_attempt(&attempt).unwrap();
        harness.clock.advance_secs(11);
        harness.processes.set_alive(true);
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        let replacements = harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(
            replacements,
            vec![ReplacementIntent {
                policy: harness.policy.id,
                previous_attempt: id,
                operation: "registration_timeout_replacement",
            }]
        );

        assert_eq!(harness.processes.terminations.load(Ordering::SeqCst), 1);
        assert!(!harness.processes.alive.load(Ordering::SeqCst));
        let actions = harness.processes.actions.lock().unwrap().clone();
        let intent = actions
            .iter()
            .position(|action| *action == "terminate_intent")
            .unwrap();
        let signal = actions
            .iter()
            .position(|action| *action == "terminate")
            .unwrap();
        assert!(
            intent < signal,
            "intent was not durable before signal: {actions:?}"
        );

        let cleaned = harness.store.attempt(id).unwrap().unwrap();
        assert!(matches!(
            cleaned.outcome(),
            Some(AttemptOutcome::Failed {
                reason: FailureReason::TerminatedAfterRegistrationTimeout
            })
        ));
        let events = harness.events.events();
        let intent = events
            .iter()
            .position(|event| matches!(event, AttemptEvent::TerminateIntent { .. }))
            .unwrap();
        let stopped = events
            .iter()
            .position(|event| matches!(event, AttemptEvent::Terminated { .. }))
            .unwrap();
        let concluded = events
            .iter()
            .position(|event| matches!(event, AttemptEvent::Concluded { .. }))
            .unwrap();
        assert!(intent < stopped && stopped < concluded, "{events:?}");
    }

    #[tokio::test]
    async fn timeout_crash_recovery_returns_the_same_replacement_intent() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        let id = AttemptId::new_random();
        let runtime = harness
            .launcher
            .app_paths
            .runtime_dir()
            .join("timeout-after-crash");
        fs::create_dir_all(&runtime).unwrap();
        let mut attempt =
            RunnerAttempt::allocate(id, harness.policy.id, runtime, harness.clock.now());
        attempt.jit_received(harness.clock.now()).unwrap();
        attempt.started(4242, harness.clock.now()).unwrap();
        harness.store.record_attempt(&attempt).unwrap();
        harness.processes.intent.store(true, Ordering::SeqCst);
        harness.processes.set_alive(false);
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);

        let replacements = harness
            .launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .unwrap();
        assert_eq!(
            replacements,
            vec![ReplacementIntent {
                policy: harness.policy.id,
                previous_attempt: id,
                operation: "registration_timeout_replacement",
            }]
        );
        let consumed = RunnerLauncher::supervise(&harness.launcher, &harness.policy)
            .await
            .unwrap();
        assert_eq!(consumed, replacements);
        assert!(
            RunnerLauncher::supervise(&harness.launcher, &harness.policy)
                .await
                .unwrap()
                .is_empty(),
            "startup replacement evidence must be consumed exactly once by e1"
        );
        assert!(matches!(
            harness.store.attempt(id).unwrap().unwrap().outcome(),
            Some(AttemptOutcome::Failed {
                reason: FailureReason::TerminatedAfterRegistrationTimeout
            })
        ));
    }

    #[tokio::test]
    async fn terminate_intent_sync_failure_prevents_signal_and_conclusion() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        let id = AttemptId::new_random();
        let runtime = harness
            .launcher
            .app_paths
            .runtime_dir()
            .join("timeout-sync-failure");
        fs::create_dir_all(&runtime).unwrap();
        let mut attempt =
            RunnerAttempt::allocate(id, harness.policy.id, &runtime, harness.clock.now());
        attempt.jit_received(harness.clock.now()).unwrap();
        attempt.started(4242, harness.clock.now()).unwrap();
        harness.store.record_attempt(&attempt).unwrap();
        harness.clock.advance_secs(11);
        harness.processes.set_alive(true);
        harness.processes.fail_intent();
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);

        assert!(
            harness
                .launcher
                .recover_startup(std::slice::from_ref(&harness.policy))
                .await
                .is_err()
        );
        assert_eq!(harness.processes.terminations.load(Ordering::SeqCst), 0);
        assert!(harness.processes.alive.load(Ordering::SeqCst));
        assert_eq!(
            harness.store.attempt(id).unwrap().unwrap().state(),
            AttemptState::Starting
        );
        assert!(!harness.events.events().iter().any(|event| matches!(
            event,
            AttemptEvent::Terminated { attempt } | AttemptEvent::Concluded { attempt, .. }
                if *attempt == id
        )));
    }

    #[tokio::test]
    async fn diagnostics_survive_cleanup_without_the_jit_or_a_token() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let attempt = harness.launch().await;
        harness
            .github
            .observe(GithubRunnerObservation::Registered { busy: false });
        harness.launcher.supervise(&harness.policy).await.unwrap();
        harness.clock.advance_secs(11);
        harness.processes.set_alive(false);
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);
        harness.launcher.supervise(&harness.policy).await.unwrap();
        let diagnostic = fs::read_to_string(
            harness
                .launcher
                .diagnostics_root
                .join(format!("{}.log", attempt.id)),
        )
        .unwrap();
        assert!(diagnostic.contains("exited_idle_without_work"));
        assert!(!diagnostic.contains(JIT));
        assert!(!diagnostic.contains("ghp_"));
        assert!(!attempt.runtime_path().exists());
    }

    #[test]
    fn native_process_listing_never_contains_jit_and_handoffs_never_survive() {
        let root = tempfile::tempdir().unwrap();
        let policy = fixtures::policy()
            .repository("octo/repo")
            .autoscale("home", 1)
            .active()
            .build();
        let runtime = root.path().join("successful");
        fs::create_dir_all(&runtime).unwrap();
        let processes = NativeProcesses::new();
        let config = EncodedJitConfig::new(JIT);
        let handoff =
            RestrictiveHandoff::create(&runtime, SecretString::from(config.expose().to_owned()))
                .unwrap();
        let mut child = native_inspection_spec()
            .spawn_runner_with_handoff(&handoff)
            .expect("native child starts");
        let pid = child.pid();
        handoff.delete().unwrap();
        let command_line = native_command_line(pid);
        assert!(
            !command_line.contains(JIT),
            "the encoded JIT configuration appeared in the native process listing"
        );
        assert_no_jit_file(&runtime);
        child
            .stop(Duration::from_secs(1))
            .expect("native child stops");

        let failed_runtime = root.path().join("failed");
        fs::create_dir_all(&failed_runtime).unwrap();
        let failed = RunnerAttempt::allocate(
            AttemptId::new_random(),
            policy.id,
            &failed_runtime,
            FakeClock::default().now(),
        );
        assert!(
            processes
                .spawn(&failed, &EncodedJitConfig::new(JIT))
                .is_err(),
            "a runtime with no runner executable must fail"
        );
        assert_no_jit_file(&failed_runtime);
        processes
            .record_terminate_intent(&failed)
            .expect("the intent file and its directory entry are durably synced");
        assert_eq!(
            fs::read(NativeProcesses::intent_path(&failed)).unwrap(),
            b"registration-timeout\n"
        );
    }

    #[test]
    fn post_spawn_boundaries_are_bounded_durable_and_never_retry_jit() {
        let root = tempfile::tempdir().unwrap();
        let policy = fixtures::policy()
            .repository("octo/repo")
            .autoscale("home", 1)
            .active()
            .build();
        let processes = NativeProcesses::new();
        processes.use_long_lived_test_listener();
        for (index, boundary) in [
            PostSpawnBoundary::HandoffDelete,
            PostSpawnBoundary::IdentitySerialize,
            PostSpawnBoundary::IdentityWrite,
            PostSpawnBoundary::ChildMapInsert,
        ]
        .into_iter()
        .enumerate()
        {
            let runtime = root.path().join(format!("post-spawn-{index}"));
            let bin = runtime.join("bin");
            fs::create_dir_all(&bin).unwrap();
            #[cfg(windows)]
            let listener = bin.join("Runner.Listener.exe");
            #[cfg(not(windows))]
            let listener = bin.join("Runner.Listener");
            fs::copy(std::env::current_exe().unwrap(), &listener).unwrap();
            let attempt = RunnerAttempt::allocate(
                AttemptId::new_random(),
                policy.id,
                &runtime,
                FakeClock::default().now(),
            );
            processes.fail_post_spawn_at(boundary);
            let failure = processes
                .spawn(&attempt, &EncodedJitConfig::new(JIT))
                .expect_err("fault must cross the post-spawn cleanup path");
            assert!(!failure.retryable, "{boundary:?} allowed duplicate retry");
            assert!(
                !processes.is_alive(&attempt).unwrap(),
                "{boundary:?} left a child"
            );
            assert!(!NativeProcesses::identity_path(&attempt).exists());
            assert_no_jit_file(&runtime);
        }
        assert_eq!(processes.post_spawn_reaps.load(Ordering::SeqCst), 4);

        let runtime = root.path().join("identity-and-stop-fail");
        let bin = runtime.join("bin");
        fs::create_dir_all(&bin).unwrap();
        #[cfg(windows)]
        let listener = bin.join("Runner.Listener.exe");
        #[cfg(not(windows))]
        let listener = bin.join("Runner.Listener");
        fs::copy(std::env::current_exe().unwrap(), &listener).unwrap();
        let attempt = RunnerAttempt::allocate(
            AttemptId::new_random(),
            policy.id,
            &runtime,
            FakeClock::default().now(),
        );
        // The first fault rejects the normal identity write; the second rejects
        // its retry after the first stop fails. The fallback sidecar must make
        // the live-child result durable without an unbounded reap loop.
        processes.fail_post_spawn_at(PostSpawnBoundary::IdentityWrite);
        processes.fail_post_spawn_at(PostSpawnBoundary::IdentityWrite);
        processes.fail_next_post_spawn_stop();
        let failure = processes
            .spawn(&attempt, &EncodedJitConfig::new(JIT))
            .expect_err("the identity boundary must fail closed");
        assert!(failure.live_pid.is_some());
        assert_long_lived_listener_ready(&processes, &attempt);
        assert!(processes.is_alive(&attempt).unwrap());
        assert!(!NativeProcesses::identity_path(&attempt).exists());
        assert!(NativeProcesses::fallback_identity_path(&attempt).is_file());
        assert_eq!(processes.post_spawn_reaps.load(Ordering::SeqCst), 4);
        processes.terminate(&attempt).unwrap();

        let runtime = root.path().join("persistent-stop-and-identity-failures");
        let bin = runtime.join("bin");
        fs::create_dir_all(&bin).unwrap();
        #[cfg(windows)]
        let listener = bin.join("Runner.Listener.exe");
        #[cfg(not(windows))]
        let listener = bin.join("Runner.Listener");
        fs::copy(std::env::current_exe().unwrap(), &listener).unwrap();
        let mut unresolved = RunnerAttempt::allocate(
            AttemptId::new_random(),
            policy.id,
            &runtime,
            FakeClock::default().now(),
        );
        for _ in 0..3 {
            processes.fail_post_spawn_at(PostSpawnBoundary::IdentityWrite);
        }
        processes.fail_post_spawn_stops(MAX_POST_SPAWN_STOP_ATTEMPTS);
        let failure = processes
            .spawn(&unresolved, &EncodedJitConfig::new(JIT))
            .expect_err("bounded cleanup must return even when every stop errors");
        let pid = failure
            .live_pid
            .expect("the owned child remains supervised in this invocation");
        assert!(matches!(failure.reason, FailureReason::Other(_)));
        assert_long_lived_listener_ready(&processes, &unresolved);
        unresolved.jit_received(FakeClock::default().now()).unwrap();
        unresolved.started(pid, FakeClock::default().now()).unwrap();
        let journal = SqliteStore::open_in_memory().unwrap();
        journal.record_attempt(&unresolved).unwrap();
        let recovered = journal.attempt(unresolved.id).unwrap().unwrap();
        assert_eq!(recovered.process_id(), Some(pid));
        assert_eq!(recovered.state(), AttemptState::Starting);
        assert!(processes.is_alive(&unresolved).unwrap());
        assert!(!NativeProcesses::identity_path(&unresolved).exists());
        assert!(!NativeProcesses::fallback_identity_path(&unresolved).exists());
        assert_eq!(
            fs::read_to_string(NativeProcesses::unresolved_process_path(&unresolved)).unwrap(),
            pid.to_string(),
            "bounded cleanup must leave durable unresolved-process evidence before returning"
        );
        assert!(
            NativeProcesses::new().is_alive(&recovered).is_err(),
            "restart must fail closed on the durable starting/PID journal rather than trust a bare PID"
        );
        processes.terminate(&unresolved).unwrap();

        let runtime = root.path().join("post-spawn-stop-failed");
        let bin = runtime.join("bin");
        fs::create_dir_all(&bin).unwrap();
        #[cfg(windows)]
        let listener = bin.join("Runner.Listener.exe");
        #[cfg(not(windows))]
        let listener = bin.join("Runner.Listener");
        fs::copy(std::env::current_exe().unwrap(), &listener).unwrap();
        let attempt = RunnerAttempt::allocate(
            AttemptId::new_random(),
            policy.id,
            &runtime,
            FakeClock::default().now(),
        );
        processes.fail_post_spawn_at(PostSpawnBoundary::ChildMapInsert);
        processes.fail_next_post_spawn_stop();
        let failure = processes
            .spawn(&attempt, &EncodedJitConfig::new(JIT))
            .expect_err("the injected stop failure must preserve supervision");
        let live_pid = failure
            .live_pid
            .expect("live PID is returned to the journal");
        assert!(!failure.retryable);
        assert_long_lived_listener_ready(&processes, &attempt);
        assert!(NativeProcesses::identity_path(&attempt).is_file());
        assert_eq!(
            NativeProcesses::read_identity(&attempt)
                .unwrap()
                .unwrap()
                .pid(),
            live_pid
        );
        assert_eq!(processes.post_spawn_reaps.load(Ordering::SeqCst), 4);
        processes.terminate(&attempt).unwrap();
    }

    #[test]
    #[ignore = "spawned only as the platform-stable native listener fixture"]
    fn long_lived_native_listener_helper() {
        let ready = std::env::var_os("RUNNER_MANAGER_TEST_LISTENER_READY")
            .map(PathBuf::from)
            .expect("the parent supplies the readiness path");
        // Atomically: the parent polls for the file and must never read it
        // created but not yet written.
        runner_manager_platform::host_fitness::write_atomically(&ready, b"ready\n")
            .expect("the listener publishes readiness");
        std::thread::sleep(Duration::from_secs(30));
    }

    fn assert_long_lived_listener_ready(processes: &NativeProcesses, attempt: &RunnerAttempt) {
        let ready = attempt.runtime_path().join(TEST_LISTENER_READY);
        let deadline = std::time::Instant::now() + Duration::from_secs(5);
        loop {
            if ready.is_file() {
                assert_eq!(fs::read(&ready).unwrap(), b"ready\n");
                return;
            }
            assert!(
                processes.is_alive(attempt).unwrap(),
                "the native listener exited before publishing readiness"
            );
            assert!(
                std::time::Instant::now() < deadline,
                "the native listener stayed alive but never published readiness"
            );
            std::thread::sleep(Duration::from_millis(10));
        }
    }

    #[tokio::test]
    async fn a_reservation_is_journalled_before_any_effect_and_holds_its_slot() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;

        let reserved = harness.reserve().await.unwrap();

        assert_eq!(reserved.state(), AttemptState::Allocated);
        assert!(reserved.counts_against_capacity());
        let journalled = harness.store.attempt(reserved.id).unwrap().unwrap();
        assert_eq!(journalled.state(), AttemptState::Allocated);
        assert_eq!(harness.packages.materializations.load(Ordering::SeqCst), 0);
        assert_eq!(harness.github.registrations.load(Ordering::SeqCst), 0);

        let started = harness
            .launcher
            .finish_launch(&harness.policy, reserved, ReservationWaits::default())
            .await
            .unwrap();
        assert_eq!(started.state(), AttemptState::Starting);
    }

    /// A launch runs beside its target's pass: the pass does not read a runner
    /// still coming up as one that is gone. It has no process and no registration
    /// yet, and the bring-up is writing its journal entry.
    #[tokio::test]
    async fn a_pass_leaves_a_runner_coming_up_alone_and_supervises_it_once_up() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let reserved = harness.reserve().await.unwrap();
        let looks_left = || harness.github.observations.lock().unwrap().len();
        harness
            .github
            .observations
            .lock()
            .unwrap()
            .push_back(LifecycleGithubObservation::not_registered());

        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(looks_left(), 1, "it did not look");
        let journalled = harness.store.attempt(reserved.id).unwrap().unwrap();
        assert_eq!(journalled.state(), AttemptState::Allocated);

        harness
            .launcher
            .finish_launch(&harness.policy, reserved, ReservationWaits::default())
            .await
            .unwrap();
        assert!(harness.launcher.bringing_up.lock().unwrap().is_empty());

        harness.launcher.supervise(&harness.policy).await.unwrap();
        assert_eq!(looks_left(), 0, "up, it is this pass's to supervise");
    }

    /// A daemon that dies between the reservation and the process: the
    /// journalled attempt is what recovery finds, and the slot comes back.
    #[tokio::test]
    async fn a_crash_between_reservation_and_spawn_recovers_the_slot() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let reserved = harness.reserve().await.unwrap();
        harness.clock.advance_secs(31);

        harness
            .launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .unwrap();

        let recovered = harness.store.attempt(reserved.id).unwrap().unwrap();
        assert!(
            !recovered.counts_against_capacity(),
            "the slot is free again: {:?}",
            recovered.state()
        );
    }

    /// A crash once the package is there, before the process: same result.
    #[tokio::test]
    async fn a_crash_after_the_package_is_copied_recovers_the_slot() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let reserved = harness.reserve().await.unwrap();
        harness
            .packages
            .materialize(&reserved, &mut PackageTimings::default())
            .await
            .unwrap();
        harness.clock.advance_secs(31);

        harness
            .launcher
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .unwrap();

        let recovered = harness.store.attempt(reserved.id).unwrap().unwrap();
        assert!(!recovered.counts_against_capacity());
    }

    #[tokio::test]
    async fn runners_prepare_at_once_within_the_bound() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let turns = harness.launcher.turns.available_permits();
        harness.launcher.turns.forget_permits(turns - 2);
        let mut reserved = Vec::new();
        for _ in 0..4 {
            reserved.push(harness.reserve().await.unwrap());
        }

        let finished = futures::future::join_all(reserved.into_iter().map(|attempt| {
            harness
                .launcher
                .finish_launch(&harness.policy, attempt, ReservationWaits::default())
        }))
        .await;

        assert!(finished.iter().all(Result::is_ok));
        assert_eq!(
            harness.packages.peak_materializing.load(Ordering::SeqCst),
            2
        );
    }

    #[tokio::test]
    async fn every_production_launch_prunes_under_the_same_allocation_guard() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        assert_eq!(harness.packages.prunes.load(Ordering::SeqCst), 0);
        harness.launch().await;
        assert_eq!(harness.packages.prunes.load(Ordering::SeqCst), 1);
    }

    fn copy_package_tree(
        source: &Path,
        destination: &Path,
        seeds: &TrustedTrees,
    ) -> std::io::Result<()> {
        let origin = copy_origin(source, destination, seeds);
        copy_package_from(source, &origin, destination, seeds)
    }

    fn assert_no_jit_file(runtime: &Path) {
        for entry in fs::read_dir(runtime).unwrap() {
            let path = entry.unwrap().path();
            if path.is_file() {
                let bytes = fs::read(&path).unwrap();
                assert!(
                    !bytes
                        .windows(JIT.len())
                        .any(|window| window == JIT.as_bytes()),
                    "a JIT payload survived in a runtime file"
                );
            }
        }
    }

    #[test]
    fn production_listener_command_uses_the_supported_jit_contract() {
        let runtime = Path::new("runtime");
        let spec = runner_listener_spec(
            PathBuf::from("Runner.Listener"),
            runtime,
            Vec::new(),
            &RunnerEnv::default(),
        );
        let arguments: Vec<_> = spec
            .arguments()
            .iter()
            .map(|argument| argument.to_string_lossy().into_owned())
            .collect();

        assert_eq!(arguments, ["run"]);
        assert!(
            !arguments
                .iter()
                .any(|argument| argument == "--jit-config-file"),
            "the obsolete file option would be rejected by Runner.Listener 2.336.0"
        );
    }

    /// What a production runner starts with: the platform defaults, the host's
    /// `runner.env` over them, the attempt's own temporary directory, and
    /// normal scheduling.
    #[test]
    fn production_listener_layers_runner_env_over_the_platform_defaults() {
        let root = tempfile::tempdir().unwrap();
        let runtime = root.path().join("attempt");
        let host_env =
            RunnerEnv::parse("ELECTRON_CACHE=/cache/electron\nHOME=/operator/chose/this\n")
                .unwrap();
        let caches = vec![
            (
                "ELECTRON_CACHE",
                std::ffi::OsString::from("/rman/_cache/o/r/electron"),
            ),
            (
                "npm_config_cache",
                std::ffi::OsString::from("/rman/_cache/o/r/npm"),
            ),
        ];
        let spec = runner_listener_spec(
            PathBuf::from("Runner.Listener"),
            &runtime,
            caches,
            &host_env,
        );
        let env = |name: &str| spec.configured_env(name).map(PathBuf::from);

        assert!(spec.expects_normal_scheduling());
        assert_eq!(
            env("ELECTRON_CACHE"),
            Some(PathBuf::from("/cache/electron")),
            "runner.env must win over a dependency cache of the same name"
        );
        assert_eq!(
            env("npm_config_cache"),
            Some(PathBuf::from("/rman/_cache/o/r/npm"))
        );
        assert_eq!(
            env("HOME"),
            Some(PathBuf::from("/operator/chose/this")),
            "runner.env must win over a platform default of the same name"
        );
        for tmp in ["TMPDIR", "TEMP", "TMP"] {
            assert_eq!(env(tmp), Some(runtime.join("tmp")), "{tmp}");
        }

        let home = runtime.join(runner_env::RUNNER_HOME_DIR);
        if cfg!(windows) {
            // Each runner's own profile, created inside its attempt, so that
            // concurrent jobs stop sharing the service account's.
            assert_eq!(env("USERPROFILE"), Some(home.clone()));
            assert_eq!(env("APPDATA"), Some(home.join(r"AppData\Roaming")));
            assert_eq!(env("LOCALAPPDATA"), Some(home.join(r"AppData\Local")));
            assert!(home.join(r"AppData\Roaming").is_dir());
            assert!(home.join(r"AppData\Local").is_dir());
        } else {
            // Unix keeps the account's own profile.
            assert_eq!(env("USERPROFILE"), None);
            assert!(!home.exists());
        }
    }

    /// Every step shell a runner starts inherits PowerShell's telemetry
    /// opt-out from the listener, unless the daemon or `runner.env` decided
    /// otherwise; see [`runner_env::POWERSHELL_TELEMETRY_OPTOUT`].
    #[test]
    fn production_listener_opts_powershell_out_of_telemetry() {
        let root = tempfile::tempdir().unwrap();
        let runtime = root.path().join("attempt");
        let listener = |host_env: &RunnerEnv| {
            runner_listener_spec(
                PathBuf::from("Runner.Listener"),
                &runtime,
                Vec::new(),
                host_env,
            )
        };
        let optout = |spec: &SpawnSpec| {
            spec.configured_env(runner_env::POWERSHELL_TELEMETRY_OPTOUT)
                .map(OsStr::to_os_string)
        };

        let spec = listener(&RunnerEnv::default());
        if std::env::var_os(runner_env::POWERSHELL_TELEMETRY_OPTOUT)
            .is_some_and(|value| !value.is_empty())
        {
            // The daemon's own value is inherited as it is.
            assert_eq!(optout(&spec), None);
        } else {
            assert_eq!(
                optout(&spec),
                Some(runner_env::POWERSHELL_TELEMETRY_OPTOUT_VALUE.into())
            );
        }

        let operator = RunnerEnv::parse("POWERSHELL_TELEMETRY_OPTOUT=0\n").unwrap();
        assert_eq!(
            optout(&listener(&operator)),
            Some("0".into()),
            "runner.env must win over the telemetry opt-out"
        );
    }

    #[test]
    fn an_invalid_runner_env_fails_the_launch_without_echoing_a_value() {
        let root = tempfile::tempdir().unwrap();
        let path = runner_env::path_in(root.path());
        fs::write(&path, "GOOD=1\nghp_notarealtokenbutshapedlikeone\n").unwrap();
        let processes = NativeProcesses::new().with_runner_env_file(path.clone());
        let failure = processes.host_env().unwrap_err().to_string();
        assert!(
            failure.contains("runner.env") && failure.contains("line 2"),
            "{failure}"
        );
        assert!(
            !failure.contains("ghp_"),
            "the failure echoed a value: {failure}"
        );

        // `prepare` runs before the JIT registration, so a broken file is
        // refused there, before GitHub is asked for anything.
        let policy = fixtures::policy()
            .repository("octo/repo")
            .autoscale("home", 1)
            .active()
            .build();
        let attempt = RunnerAttempt::allocate(
            AttemptId::new_random(),
            policy.id,
            root.path(),
            FakeClock::default().now(),
        );
        assert!(processes.prepare(&attempt, &policy).is_err());

        fs::write(&path, "GOOD=1\n").unwrap();
        assert!(processes.prepare(&attempt, &policy).is_ok());
        assert_eq!(processes.host_env().unwrap().get("GOOD"), Some("1"));
        assert!(NativeProcesses::new().host_env().unwrap().is_empty());
    }

    /// The wiring from `prepare` (which sees the policy) to `spawn` (which
    /// does not): the policy's repository decides the namespace, and a broken
    /// `caches.toml` is refused before GitHub is asked for anything.
    #[test]
    fn prepare_hands_the_policys_cache_namespace_to_the_launch() {
        let root = tempfile::tempdir().unwrap();
        let runner_root = root.path().join("rman");
        let runtime = runner_root.join("a1");
        fs::create_dir_all(runtime.join("bin")).unwrap();
        let config = runner_manager_platform::dependency_cache::config_path_in(root.path());
        let source_root = runner_root.clone();
        let processes = NativeProcesses::new().with_dependency_caches(DependencyCaches::new(
            config.clone(),
            Arc::new(move || Some(source_root.clone())),
            None,
        ));
        let policy = fixtures::policy()
            .repository("Octo/Repo")
            .autoscale("home", 1)
            .active()
            .build();
        let attempt = RunnerAttempt::allocate(
            AttemptId::new_random(),
            policy.id,
            &runtime,
            FakeClock::default().now(),
        );
        assert!(
            processes
                .cache_env(&attempt, None, &RunnerEnv::default())
                .is_empty(),
            "a launch with no prepared target, such as a bare `spawn`, has no cache"
        );
        let prepared = processes.prepare(&attempt, &policy).unwrap();
        let variables = processes.cache_env(
            &attempt,
            prepared.cache_target.as_ref(),
            &RunnerEnv::default(),
        );
        let npm = variables
            .iter()
            .find(|(name, _)| *name == "npm_config_cache")
            .map(|(_, value)| PathBuf::from(value));
        assert_eq!(
            npm,
            Some(
                runner_root
                    .join("_cache")
                    .join("octo")
                    .join("repo")
                    .join("npm")
            )
        );

        fs::write(&config, "[tools]\nnot-a-tool = true\n").unwrap();
        let refused = processes
            .prepare(&attempt, &policy)
            .unwrap_err()
            .to_string();
        assert!(refused.contains("caches.toml"), "{refused}");
    }

    #[cfg(windows)]
    fn native_inspection_spec() -> SpawnSpec {
        SpawnSpec::new("powershell.exe").args([
            "-NoProfile",
            "-NonInteractive",
            "-Command",
            "Start-Sleep -Seconds 30",
        ])
    }

    #[cfg(unix)]
    fn native_inspection_spec() -> SpawnSpec {
        SpawnSpec::new("/bin/sh").args(["-c", "sleep 30"])
    }

    #[cfg(windows)]
    fn native_command_line(pid: u32) -> String {
        let output = std::process::Command::new("powershell.exe")
            .args([
                "-NoProfile",
                "-NonInteractive",
                "-Command",
                &format!("(Get-CimInstance Win32_Process -Filter 'ProcessId = {pid}').CommandLine"),
            ])
            .output()
            .expect("PowerShell can inspect the native child");
        assert!(output.status.success(), "native process inspection failed");
        String::from_utf8(output.stdout).expect("Windows command lines are Unicode")
    }

    #[cfg(target_os = "linux")]
    fn native_command_line(pid: u32) -> String {
        fs::read(format!("/proc/{pid}/cmdline"))
            .map(|bytes| String::from_utf8_lossy(&bytes).replace('\0', " "))
            .expect("/proc exposes the native child command line")
    }

    #[cfg(target_os = "macos")]
    fn native_command_line(pid: u32) -> String {
        let output = std::process::Command::new("ps")
            .args(["-o", "command=", "-p", &pid.to_string()])
            .output()
            .expect("ps can inspect the native child");
        assert!(output.status.success(), "native process inspection failed");
        String::from_utf8(output.stdout).expect("the command line is UTF-8")
    }

    // -- c2: persistent slot allocation -------------------------------------

    #[tokio::test]
    async fn a_persistent_repository_leases_s1_and_journals_it_before_any_github_effect() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_persistent_workspace(2);
        harness.github.watch_journal(Arc::clone(&harness.store));
        harness.ready().await;

        let attempt = harness.launch().await;

        assert_eq!(
            attempt.workspace(),
            AttemptWorkspace::persistent_slot(nz(1)),
            "the lowest free slot is leased"
        );
        assert_eq!(attempt.runtime_path(), harness.slot_path(1));
        assert!(attempt.holds_slot_lease());
        // The exact runtime path is journalled, not re-derived later.
        assert_eq!(
            harness.attempt(attempt.id).runtime_path(),
            harness.slot_path(1)
        );

        // Step 7 of "Slot allocation": the lease exists before GitHub is asked
        // for anything, and the runner's work folder stays the relative `_work`
        // the slot root is laid out around.
        let facts = harness.github.registration_facts();
        assert_eq!(facts.len(), 1);
        assert_eq!(
            facts[0].leased_slots,
            vec![1],
            "the lease was journalled first"
        );
        assert_eq!(facts[0].work_folder, DEFAULT_WORK_FOLDER);
    }

    #[tokio::test]
    async fn a_terminal_but_uncleaned_attempt_keeps_its_slot_without_holding_capacity() {
        let harness = Harness::new(
            FakeGithubLifecycle::default().fail(true),
            Arc::new(PersistentDemand),
        )
        .with_persistent_workspace(2);
        harness.ready().await;

        // A terminal JIT refusal concludes the attempt without cleaning it.
        harness.launch_result().await.unwrap_err();
        let first = harness.store.attempts().unwrap().remove(0);
        assert_eq!(first.state(), AttemptState::Failed);
        assert!(
            !first.state().counts_against_capacity(),
            "a concluded attempt is invisible to host capacity"
        );
        assert!(
            first.holds_slot_lease(),
            "and still owns its directory, so its slot is not free"
        );

        let second = harness.launch().await;
        assert_eq!(second.workspace(), AttemptWorkspace::persistent_slot(nz(2)));
        assert_eq!(second.runtime_path(), harness.slot_path(2));
        assert_eq!(
            harness
                .store
                .slot_leases_for_policy(harness.policy.id)
                .unwrap()
                .len(),
            2
        );
    }

    #[tokio::test]
    async fn two_sequential_allocations_at_capacity_one_reuse_s1_and_its_retained_work() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_persistent_workspace(1);
        harness.ready().await;

        let first = harness.launch().await;
        assert_eq!(first.runtime_path(), harness.slot_path(1));

        // What a job leaves behind, at the path the runner writes it to.
        let checkout = harness.slot_path(1).join(DEFAULT_WORK_FOLDER).join("repo");
        fs::create_dir_all(&checkout).unwrap();
        fs::write(checkout.join("checkout.txt"), b"from the first job").unwrap();

        harness.cleanup_retaining_work(first.id).await;

        let second = harness.launch().await;
        assert_ne!(second.id, first.id);
        assert_eq!(
            second.workspace(),
            AttemptWorkspace::persistent_slot(nz(1)),
            "a released slot is leased again rather than skipped"
        );
        assert_eq!(
            second.runtime_path(),
            first.runtime_path(),
            "the same slot is the same exact path"
        );
        assert_eq!(
            fs::read_to_string(checkout.join("checkout.txt")).unwrap(),
            "from the first job",
            "the retained job workspace survived the second allocation"
        );
        // The attempt's own runner material was recreated for this attempt.
        assert!(harness.slot_path(1).join("runner-package").exists());
    }

    #[tokio::test]
    async fn lowering_capacity_leaves_higher_slots_alone_and_raising_it_permits_them_again() {
        let mut harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_persistent_workspace(2);
        harness.ready().await;

        let first = harness.launch().await;
        let second = harness.launch().await;
        assert_eq!(second.runtime_path(), harness.slot_path(2));
        let kept = harness
            .slot_path(2)
            .join(DEFAULT_WORK_FOLDER)
            .join("kept.txt");
        fs::create_dir_all(kept.parent().unwrap()).unwrap();
        fs::write(&kept, b"s2 was here").unwrap();
        harness.cleanup_retaining_work(second.id).await;

        // The operator lowers the ceiling while s1 is still leased.
        harness.policy.set_max_capacity(nz(1)).unwrap();
        let refusal = harness.launch_result().await.unwrap_err().to_string();
        assert!(
            refusal.contains("s1 to s1"),
            "the refusal names the ceiling it reached: {refusal}"
        );
        assert!(
            harness.slot_path(2).exists() && kept.exists(),
            "lowering capacity deletes nothing; the higher slot is merely unusable"
        );

        // Raising it again makes the free higher slot available.
        harness.policy.set_max_capacity(nz(2)).unwrap();
        let third = harness.launch().await;
        assert_eq!(third.workspace(), AttemptWorkspace::persistent_slot(nz(2)));
        assert_eq!(third.runtime_path(), harness.slot_path(2));
        assert_eq!(fs::read_to_string(&kept).unwrap(), "s2 was here");
        assert!(first.holds_slot_lease(), "s1 was never disturbed");
    }

    #[tokio::test]
    async fn organization_and_ephemeral_policies_never_enter_slot_allocation() {
        for policy in [
            fixtures::policy()
                .organization("octo")
                .autoscale("home", 2)
                .active()
                .build(),
            fixtures::policy()
                .repository("octo/repo")
                .autoscale("home", 2)
                .active()
                .build(),
        ] {
            let mut harness =
                Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
                    .with_host_runner_root();
            assert_eq!(policy.workspace_policy(), &WorkspacePolicy::Ephemeral);
            harness.policy = policy;
            harness.ready().await;

            let attempt = harness.launch().await;
            assert_eq!(attempt.workspace(), AttemptWorkspace::Ephemeral);
            assert_eq!(attempt.workspace().slot_number(), None);
            assert!(!attempt.holds_slot_lease());
            assert_eq!(
                attempt.runtime_path().parent().unwrap(),
                harness.host_root(),
                "a disposable attempt is a child of the host root, never of a slot"
            );
            assert!(
                harness
                    .store
                    .slot_leases_for_policy(harness.policy.id)
                    .unwrap()
                    .is_empty()
            );
        }
    }

    #[tokio::test]
    async fn two_concurrent_allocations_never_share_a_slot() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_persistent_workspace(2);
        harness.github.watch_journal(Arc::clone(&harness.store));
        harness.ready().await;

        // Both allocators race for the same host allocation lock, which is what
        // orders slot *selection*; each one then journals its lease before it
        // asks GitHub for anything.
        let (first, second) = tokio::join!(harness.launch_result(), harness.launch_result());
        let first = first.unwrap();
        let second = second.unwrap();

        let slots: BTreeSet<u16> = [&first, &second]
            .iter()
            .map(|attempt| {
                attempt
                    .workspace()
                    .slot_number()
                    .expect("a persistent attempt leases a slot")
            })
            .collect();
        assert_eq!(slots, BTreeSet::from([1, 2]), "one slot each, never shared");
        assert_ne!(first.runtime_path(), second.runtime_path());
        assert_eq!(
            harness
                .store
                .slot_leases_for_policy(harness.policy.id)
                .unwrap()
                .len(),
            2
        );

        // Every registration saw *its own* lease already in the journal. Reading
        // the whole journal and asking only that it be non-empty would pass on
        // the other allocator's lease, which is precisely the ordering bug this
        // test exists to exclude.
        let facts = harness.github.registration_facts();
        assert_eq!(facts.len(), 2);
        for fact in facts {
            let attempt = [&first, &second]
                .into_iter()
                .find(|attempt| runner_name(attempt.id) == fact.runner_name)
                .expect("every registration belongs to one of the two attempts");
            let slot = attempt
                .workspace()
                .slot_number()
                .expect("a persistent attempt leases a slot");
            assert!(
                fact.leased_slots.contains(&slot),
                "a JIT request never precedes its own lease: s{slot} not in {:?}",
                fact.leased_slots
            );
            assert_eq!(fact.work_folder, DEFAULT_WORK_FOLDER);
        }
    }

    #[tokio::test]
    async fn the_database_is_the_final_fence_against_two_attempts_in_one_slot() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_persistent_workspace(2);
        harness.ready().await;
        let first = harness.launch().await;

        // What a second allocator that lost the race would write: the lock
        // orders selection, and this index is what catches a writer the lock
        // could not see.
        let clash = RunnerAttempt::allocate_in(
            AttemptId::new_random(),
            harness.policy.id,
            first.runtime_path(),
            AttemptWorkspace::persistent_slot(nz(1)),
            harness.clock.now(),
        );
        assert!(matches!(
            harness.store.record_attempt(&clash).unwrap_err(),
            StoreError::SlotAlreadyLeased { slot: 1, .. }
        ));

        // And the launcher reports it as itself rather than as a generic
        // journal failure, so the operator reads what actually happened.
        let error = harness.launcher.record_allocation(&clash).unwrap_err();
        let rendered = error.to_string();
        assert!(rendered.contains("slot s1"), "{rendered}");
        assert!(rendered.contains("nothing was written"), "{rendered}");
        assert_eq!(
            harness.store.attempts().unwrap().len(),
            1,
            "the losing allocator journalled nothing"
        );
    }

    #[test]
    fn slot_selection_fills_the_lowest_gap_and_stops_at_the_ceiling() {
        let leased = |slots: &[u16]| -> Vec<RunnerAttempt> {
            slots
                .iter()
                .map(|slot| {
                    RunnerAttempt::allocate_in(
                        AttemptId::new_random(),
                        fixtures::POLICY_ID,
                        format!("/srv/rman/acme/s{slot}"),
                        AttemptWorkspace::persistent_slot(nz(*slot)),
                        fixtures::created_at(),
                    )
                })
                .collect()
        };

        assert_eq!(lowest_free_slot(&[], nz(1)), Some(nz(1)));
        assert_eq!(lowest_free_slot(&leased(&[1]), nz(4)), Some(nz(2)));
        // The gap a released middle slot leaves is filled before the tail.
        assert_eq!(lowest_free_slot(&leased(&[1, 3]), nz(4)), Some(nz(2)));
        // The ceiling is a refusal, never a reason to allocate past it.
        assert_eq!(lowest_free_slot(&leased(&[1]), nz(1)), None);
        assert_eq!(lowest_free_slot(&leased(&[1, 2]), nz(2)), None);
        // An ephemeral attempt holds no slot and cannot block one.
        let ephemeral = vec![RunnerAttempt::allocate(
            AttemptId::new_random(),
            fixtures::POLICY_ID,
            "/srv/rman/host/abc",
            fixtures::created_at(),
        )];
        assert_eq!(lowest_free_slot(&ephemeral, nz(1)), Some(nz(1)));
    }

    #[test]
    fn a_slot_is_reusable_only_when_it_is_empty_or_holds_one_real_work_directory() {
        let root = tempfile::tempdir().unwrap();
        let slot = root.path().join("s1");
        fs::create_dir(&slot).unwrap();
        accept_reusable_slot(&slot).expect("an empty slot is reusable");

        fs::create_dir(slot.join(DEFAULT_WORK_FOLDER)).unwrap();
        accept_reusable_slot(&slot).expect("a retained job workspace is reusable");

        // Runner material a previous attempt left behind is refused rather than
        // reused or removed: deciding those bytes are safe is cleanup's job.
        fs::create_dir(slot.join("bin")).unwrap();
        fs::write(slot.join(".github-runner-id"), b"73").unwrap();
        let refusal = accept_reusable_slot(&slot).unwrap_err().to_string();
        assert!(refusal.contains("bin"), "{refusal}");
        assert!(refusal.contains(".github-runner-id"), "{refusal}");

        // A `_work` that is not a real directory is not a job workspace.
        let file_work = root.path().join("s2");
        fs::create_dir(&file_work).unwrap();
        fs::write(file_work.join(DEFAULT_WORK_FOLDER), b"not a directory").unwrap();
        assert!(accept_reusable_slot(&file_work).is_err());
    }

    #[cfg(unix)]
    #[test]
    fn a_link_shaped_work_directory_is_refused_rather_than_followed() {
        // Windows needs a privilege to create either kind of link, so the
        // link-shaped cases are asserted here; the rule itself is
        // platform-independent because it is `symlink_metadata`'s answer.
        let root = tempfile::tempdir().unwrap();
        let elsewhere = root.path().join("elsewhere");
        fs::create_dir(&elsewhere).unwrap();

        let slot = root.path().join("s1");
        fs::create_dir(&slot).unwrap();
        std::os::unix::fs::symlink(&elsewhere, slot.join(DEFAULT_WORK_FOLDER)).unwrap();
        assert!(accept_reusable_slot(&slot).is_err());

        let linked_slot = root.path().join("s2");
        std::os::unix::fs::symlink(&elsewhere, &linked_slot).unwrap();
        assert!(create_or_validate_slot(&linked_slot).is_err());
    }

    #[test]
    fn a_slot_standing_where_a_file_is_refuses_rather_than_replacing_it() {
        let root = tempfile::tempdir().unwrap();
        let occupied = root.path().join("s1");
        fs::write(&occupied, b"an operator's file").unwrap();
        let refusal = create_or_validate_slot(&occupied).unwrap_err().to_string();
        assert!(refusal.contains("is not a directory"), "{refusal}");
        assert_eq!(fs::read_to_string(&occupied).unwrap(), "an operator's file");

        let fresh = root.path().join("s2");
        create_or_validate_slot(&fresh).expect("a missing slot is created");
        assert!(fresh.is_dir());
        create_or_validate_slot(&fresh).expect("an existing directory is accepted");
    }

    #[test]
    fn the_retained_work_directory_is_matched_the_way_the_filesystem_matches_it() {
        assert!(is_work_folder(OsStr::new(DEFAULT_WORK_FOLDER)));
        assert!(!is_work_folder(OsStr::new("_work2")));
        // A Windows filesystem is case-insensitive, so `_Work` *is* the retained
        // job workspace there and must never be removed as a leftover; on a
        // case-sensitive filesystem it is a different directory entirely.
        assert_eq!(is_work_folder(OsStr::new("_Work")), cfg!(windows));
    }

    #[test]
    fn package_materialization_never_overwrites_or_follows_a_retained_work_directory() {
        let root = tempfile::tempdir().unwrap();
        let package = root.path().join("package");
        fs::create_dir_all(package.join("bin")).unwrap();
        fs::write(package.join("bin").join("Runner.Listener"), b"binary").unwrap();
        // A nested `_work` inside the package's own tree is an ordinary name.
        fs::create_dir_all(package.join("externals").join(DEFAULT_WORK_FOLDER)).unwrap();

        let slot = root.path().join("s1");
        let retained = slot.join(DEFAULT_WORK_FOLDER).join("repo");
        fs::create_dir_all(&retained).unwrap();
        fs::write(retained.join("checkout.txt"), b"from the first job").unwrap();

        copy_package_tree(&package, &slot, &TrustedTrees::default())
            .expect("the package lays out around `_work`");
        assert!(slot.join("bin").join("Runner.Listener").exists());
        assert!(
            slot.join("externals").join(DEFAULT_WORK_FOLDER).is_dir(),
            "the guard is top-level only"
        );
        assert_eq!(
            fs::read_to_string(retained.join("checkout.txt")).unwrap(),
            "from the first job"
        );

        // A package that ever grew a top-level `_work` is refused, not merged.
        fs::create_dir(package.join(DEFAULT_WORK_FOLDER)).unwrap();
        let error = copy_package_tree(&package, &slot, &TrustedTrees::default()).unwrap_err();
        assert_eq!(error.kind(), std::io::ErrorKind::InvalidData);
        assert_eq!(
            fs::read_to_string(retained.join("checkout.txt")).unwrap(),
            "from the first job"
        );
    }

    #[test]
    fn rolling_back_a_materialization_keeps_a_slot_but_removes_a_disposable_directory() {
        let root = tempfile::tempdir().unwrap();

        let slot = root.path().join("s1");
        let retained = slot.join(DEFAULT_WORK_FOLDER);
        fs::create_dir_all(retained.join("repo")).unwrap();
        fs::write(retained.join("repo").join("checkout.txt"), b"kept").unwrap();
        fs::create_dir_all(slot.join("bin")).unwrap();
        fs::write(slot.join(".github-runner-id"), b"73").unwrap();
        let persistent = RunnerAttempt::allocate_in(
            AttemptId::new_random(),
            fixtures::POLICY_ID,
            &slot,
            AttemptWorkspace::persistent_slot(nz(1)),
            fixtures::created_at(),
        );

        remove_materialized_package(&persistent).unwrap();
        assert!(slot.is_dir(), "the slot itself is not removed");
        assert!(!slot.join("bin").exists());
        assert!(!slot.join(".github-runner-id").exists());
        assert_eq!(
            fs::read_to_string(retained.join("repo").join("checkout.txt")).unwrap(),
            "kept"
        );

        let disposable_path = root.path().join("abcdef012345");
        fs::create_dir_all(disposable_path.join(DEFAULT_WORK_FOLDER)).unwrap();
        let disposable = RunnerAttempt::allocate(
            AttemptId::new_random(),
            fixtures::POLICY_ID,
            &disposable_path,
            fixtures::created_at(),
        );
        remove_materialized_package(&disposable).unwrap();
        assert!(
            !disposable_path.exists(),
            "a disposable directory is still removed whole"
        );
    }

    // -- c3: persistent cleanup and recovery --------------------------------

    /// The runner state one attempt leaves at a slot root, as a real attempt
    /// leaves it: binaries, registration identity, a JIT handoff that outlived
    /// its process, and this agent's own lifecycle sidecars.
    ///
    /// Driven by [`SENSITIVE_SLOT_ENTRIES`] rather than by a second copy of it,
    /// so a name added to the thing cleanup must prove absent is a name every
    /// test here starts leaving behind.
    fn litter_the_slot(slot: &Path) {
        for directory in ["bin", "externals", "_diag"] {
            fs::create_dir_all(slot.join(directory)).unwrap();
        }
        fs::write(slot.join("bin").join("Runner.Listener"), b"binary").unwrap();
        for file in SENSITIVE_SLOT_ENTRIES
            .iter()
            .filter(|entry| !slot.join(entry).is_dir())
        {
            fs::write(slot.join(file), b"runner state").unwrap();
        }
        // A handoff whose owning process died before `Drop` could delete it.
        fs::write(
            slot.join(format!(
                "{}0f1e2d3c-4b5a-6978-8796-a5b4c3d2e1f0.tmp",
                RestrictiveHandoff::NAME_PREFIX
            )),
            JIT.as_bytes(),
        )
        .unwrap();
    }

    /// A marker under `_work` of the kind a job leaves for the next one.
    fn retain_under_work(slot: &Path) -> PathBuf {
        let checkout = slot.join(DEFAULT_WORK_FOLDER).join("repo").join("target");
        fs::create_dir_all(&checkout).unwrap();
        let marker = checkout.join("build-output.bin");
        fs::write(&marker, RETAINED).unwrap();
        marker
    }

    /// What a job leaves under `_work` for the next job to reuse.
    const RETAINED: &str = "a Git-ignored build output the next job reuses";

    /// Every direct entry of a directory, sorted, as plain strings.
    fn entries_of(directory: &Path) -> Vec<String> {
        let mut names: Vec<String> = fs::read_dir(directory)
            .unwrap()
            .map(|entry| entry.unwrap().file_name().to_string_lossy().into_owned())
            .collect();
        names.sort();
        names
    }

    /// The one entry a cleaned slot is allowed to hold.
    fn only_the_job_workspace() -> Vec<String> {
        vec![DEFAULT_WORK_FOLDER.to_owned()]
    }

    #[cfg(unix)]
    #[test]
    fn disposable_tree_removal_does_not_open_a_dotnet_diagnostic_fifo() {
        use std::sync::mpsc;

        let temporary = tempfile::tempdir().unwrap();
        let tree = temporary.path().join("attempt");
        let diagnostic = tree.join("tmp/clr-debug-pipe-runner-in");
        fs::create_dir_all(diagnostic.parent().unwrap()).unwrap();
        assert!(
            std::process::Command::new("mkfifo")
                .arg(&diagnostic)
                .status()
                .unwrap()
                .success()
        );

        let (finished, result) = mpsc::channel();
        std::thread::spawn(move || {
            let removed = remove_runtime_tree(&tree);
            let _ = finished.send(removed);
        });

        result
            .recv_timeout(Duration::from_secs(2))
            .expect("runtime deletion must not wait for a FIFO peer")
            .unwrap();
        assert!(!diagnostic.exists());
    }

    /// The junction WinINet leaves in a job's profile, reproduced: its own DACL
    /// denies `Everyone` the right to list it.
    #[cfg(windows)]
    #[test]
    fn disposable_tree_removal_unlinks_a_junction_nobody_may_list() {
        let temporary = tempfile::tempdir().unwrap();
        let tree = temporary.path().join("attempt");
        let cache = tree.join(r"tmp\home\AppData\Local\Microsoft\Windows\INetCache");
        let outside = temporary.path().join("outside");
        fs::create_dir_all(&cache).unwrap();
        fs::create_dir_all(&outside).unwrap();
        fs::write(outside.join("keep.txt"), b"not the attempt's").unwrap();
        fs::write(tree.join("tmp").join("job.log"), b"job output").unwrap();
        let junction = cache.join("Content.IE5");
        let created = std::process::Command::new("cmd")
            .arg("/C")
            .arg("mklink")
            .arg("/J")
            .arg(&junction)
            .arg(&outside)
            .output()
            .unwrap();
        assert!(created.status.success(), "{created:?}");
        // `/L` puts the entry on the junction itself, as WinINet does, rather
        // than on the directory it points at. `*S-1-1-0` is `Everyone` in every
        // display language.
        let denied = std::process::Command::new("icacls")
            .arg(&junction)
            .args(["/L", "/deny", "*S-1-1-0:(RD)"])
            .output()
            .unwrap();
        assert!(denied.status.success(), "{denied:?}");

        // The control: without the fix the tree cannot be removed at all.
        let unfixed = remove_dir_all::remove_dir_all(&tree)
            .expect_err("the fixture no longer reproduces the WinINet junction");
        assert_eq!(unfixed.kind(), std::io::ErrorKind::PermissionDenied);
        assert!(junction.symlink_metadata().is_ok());

        remove_runtime_tree(&tree).expect("a tree holding a deny-list junction is removed");
        assert!(!tree.exists(), "the attempt tree survived");
        assert_eq!(
            fs::read(outside.join("keep.txt")).unwrap(),
            b"not the attempt's",
            "removing the junction followed it into the directory it points at"
        );
    }

    /// One slot entry that refuses to be removed, and the undo that lets the
    /// temporary directory be torn down afterwards.
    ///
    /// The two operating systems refuse for different reasons and there is no
    /// portable third. Windows will not open a file for deletion while a handle
    /// with share mode zero is held on it; Unix will not unlink from a directory
    /// the caller cannot write. Both are states a real machine reaches -- a
    /// scanner holding a file open, a job that left a directory read-only -- so
    /// the injection is a filesystem fact rather than a seam cut into the
    /// product for a test to pull.
    ///
    /// The Unix half is a permission, and permissions do not apply to `root`.
    /// [`Self::inject`] proves the block on a throwaway directory before
    /// claiming it, so a suite running as `root` says it could not inject rather
    /// than asserting nothing and passing.
    struct BlockedDeletion {
        directory: PathBuf,
        #[cfg(windows)]
        _handle: fs::File,
    }

    impl BlockedDeletion {
        const HELD: &'static str = "held-open";

        /// Fill `directory` with a file that cannot be removed, or answer `None`
        /// when this account cannot be stopped from removing anything.
        fn inject(directory: &Path) -> Option<Self> {
            #[cfg(unix)]
            if !Self::refusal_is_possible() {
                return None;
            }
            fs::create_dir_all(directory).unwrap();
            fs::write(
                directory.join(Self::HELD),
                b"a file the scrub cannot remove",
            )
            .unwrap();
            #[cfg(windows)]
            let handle = {
                use std::os::windows::fs::OpenOptionsExt;

                fs::OpenOptions::new()
                    .read(true)
                    .share_mode(0)
                    .open(directory.join(Self::HELD))
                    .expect("the blocking handle opens")
            };
            #[cfg(unix)]
            Self::set_mode(directory, 0o555);
            Some(Self {
                directory: directory.to_path_buf(),
                #[cfg(windows)]
                _handle: handle,
            })
        }

        fn release(self) {
            drop(self);
        }

        #[cfg(unix)]
        fn refusal_is_possible() -> bool {
            let probe = tempfile::tempdir().unwrap();
            let directory = probe.path().join("probe");
            fs::create_dir(&directory).unwrap();
            fs::write(directory.join("file"), b"probe").unwrap();
            Self::set_mode(&directory, 0o555);
            let refused = fs::remove_dir_all(&directory).is_err();
            Self::set_mode(&directory, 0o755);
            refused
        }

        #[cfg(unix)]
        fn set_mode(directory: &Path, mode: u32) {
            use std::os::unix::fs::PermissionsExt;

            let mut permissions = fs::metadata(directory).unwrap().permissions();
            permissions.set_mode(mode);
            fs::set_permissions(directory, permissions).unwrap();
        }
    }

    impl Drop for BlockedDeletion {
        fn drop(&mut self) {
            #[cfg(unix)]
            Self::set_mode(&self.directory, 0o755);
            #[cfg(not(unix))]
            let _ = &self.directory;
        }
    }

    #[tokio::test]
    async fn two_sequential_jobs_keep_the_checkout_and_start_without_the_earlier_runner_state() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_persistent_workspace(1);
        harness.ready().await;

        let first = harness.launch().await;
        let slot = harness.slot_path(1);
        assert_eq!(first.runtime_path(), slot);
        assert_eq!(
            read_runner_id(&slot),
            Some(73),
            "the attempt registered, so its identity is on disk"
        );
        let marker = retain_under_work(&slot);
        litter_the_slot(&slot);

        harness.cleanup_retaining_work(first.id).await;

        // The allowlist is exactly one entry, so this assertion is the security
        // property in full: what is retained, and that nothing else is.
        assert_eq!(entries_of(&slot), only_the_job_workspace());
        assert_eq!(fs::read_to_string(&marker).unwrap(), RETAINED);
        assert_eq!(
            read_runner_id(&slot),
            None,
            "the first attempt's registration identity is gone before the second starts"
        );
        assert_eq!(harness.attempt(first.id).state(), AttemptState::Cleaned);
        assert!(!harness.attempt(first.id).holds_slot_lease());

        let second = harness.launch().await;
        assert_ne!(second.id, first.id);
        assert_eq!(second.workspace(), AttemptWorkspace::persistent_slot(nz(1)));
        assert_eq!(
            second.runtime_path(),
            slot,
            "the same slot, so the same retained `_work`"
        );
        assert_eq!(fs::read_to_string(&marker).unwrap(), RETAINED);
    }

    #[tokio::test]
    async fn cleaning_a_persistent_slot_needs_no_policy_and_scans_no_directory_for_ownership() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_persistent_workspace(1);
        harness.ready().await;
        let attempt = harness.launch().await;
        let slot = harness.slot_path(1);
        let marker = retain_under_work(&slot);
        litter_the_slot(&slot);
        harness.conclude(attempt.id);

        // A repository removed from the product between the attempt concluding
        // and the sweep reaching it. The journalled runtime path and slot are
        // the only facts left, and `04-security-recovery.md` requires them to be
        // enough: the alternative is scanning a root to work out which
        // directories were ours, which invariant 6 forbids.
        harness
            .store
            .remove_policy(harness.policy.id, harness.policy.revision())
            .unwrap();
        assert!(harness.store.policy(harness.policy.id).unwrap().is_none());

        harness
            .launcher
            .clean(attempt.id)
            .await
            .expect("journal facts alone are enough to clean the slot");

        assert_eq!(entries_of(&slot), only_the_job_workspace());
        assert!(marker.exists());
        assert_eq!(harness.attempt(attempt.id).state(), AttemptState::Cleaned);
    }

    #[tokio::test]
    async fn an_injected_partial_deletion_quarantines_the_slot_across_a_restart() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_persistent_workspace(2);
        harness.ready().await;
        let first = harness.launch().await;
        let slot = harness.slot_path(1);
        let marker = retain_under_work(&slot);
        litter_the_slot(&slot);
        harness.conclude(first.id);

        let Some(block) = BlockedDeletion::inject(&slot.join("bin")) else {
            eprintln!(
                "skipped: this account cannot be refused a deletion, so no partial deletion can \
                 be injected"
            );
            return;
        };

        let refusal = harness
            .launcher
            .clean(first.id)
            .await
            .expect_err("a deletion that failed may not report a cleaned slot");
        let rendered = refusal.reason.to_string();
        assert!(rendered.contains("could not be removed"), "{rendered}");

        let held = harness.attempt(first.id);
        assert_eq!(held.state(), AttemptState::Failed, "still not cleaned");
        assert!(held.holds_slot_lease(), "so the slot is still leased");
        assert!(
            !held.state().counts_against_capacity(),
            "and a concluded attempt still costs the host no capacity"
        );

        // The same journal and the same directories, under a launcher that
        // remembers nothing. Recovery must complete: a host that can launch
        // nothing at all because one slot is stuck is not what "does not count
        // as active host capacity" means.
        let restarted = harness.restart();
        restarted
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("one quarantined slot does not stop the host recovering");
        assert_eq!(
            harness.attempt(first.id).state(),
            AttemptState::Failed,
            "the quarantine survived the restart"
        );
        assert!(
            harness
                .reconcile_events
                .events()
                .iter()
                .any(|event| matches!(
                    event,
                    LifecycleEvent::AttemptCleanFailed {
                        reason: "slot_entry_could_not_be_removed",
                        ..
                    }
                )),
            "the refusal is reported rather than retried in silence"
        );

        // Capacity two, slot one quarantined: the next attempt goes to s2 and
        // never to the slot still holding runner state.
        let second = harness
            .launch_through(&restarted)
            .await
            .expect("the host can still launch");
        assert_eq!(second.workspace(), AttemptWorkspace::persistent_slot(nz(2)));

        // And the same cleanup succeeds once the obstruction is gone, which is
        // what "retry through normal recovery" has to mean.
        block.release();
        restarted
            .clean(first.id)
            .await
            .expect("the retried cleanup completes");
        assert_eq!(entries_of(&slot), only_the_job_workspace());
        assert!(marker.exists());
        assert_eq!(harness.attempt(first.id).state(), AttemptState::Cleaned);
    }

    /// The disposable half of the same injection, which had no test of its own.
    ///
    /// `scrub_workspace`'s ephemeral arm turns a failed `remove_dir_all` into
    /// `"attempt workspace could not be removed"`, and until now that branch was
    /// only reachable in theory: every injected-deletion test drove a persistent
    /// slot. The property is the same one and matters for the same reason --
    /// `04-security-recovery.md`'s "Cleanup partly fails and the slot is reused
    /// anyway" -- but the disposable guarantee is stronger, so a cleanup that
    /// reported success over a directory it had not removed would be the
    /// contamination gate failing silently rather than a slot being held.
    #[tokio::test]
    async fn an_injected_deletion_failure_leaves_a_disposable_attempt_uncleaned() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let attempt = harness.launch().await;
        let runtime = attempt.runtime_path().to_path_buf();
        assert_eq!(attempt.workspace(), AttemptWorkspace::Ephemeral);
        harness.conclude(attempt.id);

        let Some(block) = BlockedDeletion::inject(&runtime.join("held-open-subdirectory")) else {
            eprintln!(
                "skipped: this account cannot be refused a deletion, so no partial deletion can be injected"
            );
            return;
        };

        let refusal = harness
            .launcher
            .clean(attempt.id)
            .await
            .expect_err("a deletion that failed may not report a removed workspace");
        let rendered = refusal.reason.to_string();
        assert!(
            rendered.contains("could not be removed"),
            "the refusal names what happened: {rendered}"
        );
        assert_ne!(
            harness.attempt(attempt.id).state(),
            AttemptState::Cleaned,
            "an attempt whose directory is still on disk is not cleaned"
        );
        assert!(
            runtime.is_dir(),
            "the directory the removal could not finish is still there, which is the fact the journal must keep agreeing with"
        );

        let restarted = harness.restart();
        restarted
            .recover_startup(std::slice::from_ref(&harness.policy))
            .await
            .expect("one locked ephemeral workspace does not stop startup recovery");
        assert!(
            harness
                .reconcile_events
                .events()
                .iter()
                .any(|event| matches!(
                    event,
                    LifecycleEvent::AttemptCleanFailed {
                        attempt: failed_attempt,
                        reason: "ephemeral_workspace_could_not_be_removed",
                        ..
                    } if *failed_attempt == attempt.id
                )),
            "the deferred cleanup remains visible while the daemon keeps running"
        );

        // And the ordinary retry -- the reconciler's next terminal sweep --
        // finishes it once the obstruction is gone.
        block.release();
        harness
            .launcher
            .clean(attempt.id)
            .await
            .expect("the retried cleanup completes");
        assert!(!runtime.exists(), "the whole attempt directory goes");
        assert_eq!(harness.attempt(attempt.id).state(), AttemptState::Cleaned);
    }

    /// Supervision retries a workspace it cannot remove with per-attempt
    /// backoff, so a stuck workspace is reported once per delay rather than on
    /// every pass.
    #[tokio::test]
    async fn supervision_backs_off_a_workspace_it_cannot_remove() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand));
        harness.ready().await;
        let attempt = harness.launch().await;
        let runtime = attempt.runtime_path().to_path_buf();
        harness.conclude(attempt.id);
        let Some(block) = BlockedDeletion::inject(&runtime.join("held-open-subdirectory")) else {
            eprintln!(
                "skipped: this account cannot be refused a deletion, so no partial deletion can be injected"
            );
            return;
        };
        let failures = || {
            harness
                .reconcile_events
                .events()
                .iter()
                .filter(|event| {
                    matches!(
                        event,
                        LifecycleEvent::AttemptCleanFailed { attempt: failed, .. }
                            if *failed == attempt.id
                    )
                })
                .count()
        };
        let supervise = async || {
            harness
                .launcher
                .supervise(&harness.policy)
                .await
                .expect("a stuck workspace does not fail supervision");
        };

        supervise().await;
        assert_eq!(failures(), 1);
        supervise().await;
        assert_eq!(
            failures(),
            1,
            "the failed cleanup was retried on the very next pass"
        );
        harness.clock.advance_secs(31);
        supervise().await;
        assert_eq!(
            failures(),
            2,
            "the cleanup was not retried once its delay passed"
        );

        block.release();
        harness.clock.advance_secs(61);
        supervise().await;
        assert!(
            !runtime.exists(),
            "the retry removes the workspace once it can"
        );
        assert_eq!(harness.attempt(attempt.id).state(), AttemptState::Cleaned);
    }

    #[tokio::test]
    async fn changing_a_repository_back_to_ephemeral_leaves_every_old_slot_untouched() {
        let mut harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_persistent_workspace(1);
        harness.ready().await;
        let first = harness.launch().await;
        let slot = harness.slot_path(1);
        let marker = retain_under_work(&slot);
        harness.cleanup_retaining_work(first.id).await;

        // Every attempt for this policy is cleaned, so the mutation is allowed
        // (`04-security-recovery.md`, "Recovery rules"). What it must not do is
        // move or delete anything the operator still owns.
        harness
            .policy
            .set_workspace_policy(WorkspacePolicy::Ephemeral)
            .unwrap();

        let second = harness.launch().await;
        assert_eq!(second.workspace(), AttemptWorkspace::Ephemeral);
        assert_eq!(
            second.runtime_path().parent().unwrap(),
            harness.host_root(),
            "a disposable attempt is a child of the host root"
        );
        assert!(slot.is_dir(), "the old slot is left where it stands");
        assert_eq!(fs::read_to_string(&marker).unwrap(), RETAINED);

        // And cleaning the disposable attempt removes its own directory whole
        // without reaching the retained slot beside it.
        harness.conclude(second.id);
        harness.launcher.clean(second.id).await.unwrap();
        assert!(!second.runtime_path().exists());
        assert!(marker.exists());
    }

    #[tokio::test]
    async fn a_persistent_slot_is_scrubbed_only_after_the_process_is_signalled_and_gone() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_persistent_workspace(1);
        harness.ready().await;
        let slot = harness.slot_path(1);
        fs::create_dir_all(&slot).unwrap();
        let marker = retain_under_work(&slot);
        litter_the_slot(&slot);

        let id = AttemptId::new_random();
        let mut attempt = RunnerAttempt::allocate_in(
            id,
            harness.policy.id,
            &slot,
            AttemptWorkspace::persistent_slot(nz(1)),
            harness.clock.now(),
        );
        attempt.jit_received(harness.clock.now()).unwrap();
        attempt.started(4242, harness.clock.now()).unwrap();
        harness.store.record_attempt(&attempt).unwrap();
        harness.clock.advance_secs(11);
        harness.processes.set_alive(true);
        harness
            .github
            .observe(GithubRunnerObservation::NotRegistered);

        harness.launcher.supervise(&harness.policy).await.unwrap();

        // The identity and termination ordering `e3` established is unchanged by
        // the workspace kind: the intent is durable before the signal, and the
        // slot is scrubbed only once the process is gone.
        let actions = harness.processes.actions.lock().unwrap().clone();
        let intent = actions
            .iter()
            .position(|action| *action == "terminate_intent")
            .unwrap();
        let signal = actions
            .iter()
            .position(|action| *action == "terminate")
            .unwrap();
        assert!(intent < signal, "{actions:?}");
        assert!(!harness.processes.alive.load(Ordering::SeqCst));

        let cleaned = harness.attempt(id);
        assert_eq!(cleaned.state(), AttemptState::Cleaned);
        assert!(matches!(
            cleaned.outcome(),
            Some(AttemptOutcome::Failed {
                reason: FailureReason::TerminatedAfterRegistrationTimeout
            })
        ));
        assert_eq!(entries_of(&slot), only_the_job_workspace());
        assert!(marker.exists());
    }

    #[test]
    fn a_scrub_retains_one_real_work_directory_and_removes_every_other_entry() {
        let root = tempfile::tempdir().unwrap();
        let slot = root.path().join("s1");
        fs::create_dir(&slot).unwrap();
        let marker = retain_under_work(&slot);
        litter_the_slot(&slot);
        fs::write(slot.join("runner-package"), b"verified").unwrap();

        scrub_slot_entries(&slot).expect("a slot of ordinary runner state scrubs");
        verify_slot_scrubbed(&slot).expect("and proves it afterwards");

        assert_eq!(entries_of(&slot), only_the_job_workspace());
        assert!(marker.exists());
    }

    #[test]
    fn a_residue_refusal_never_reports_the_under_count_as_the_fact() {
        let slot = Path::new("/runners/s1");

        // The ordinary case: the listing counted, so the count is the fact and
        // the published names qualify it.
        let counted = residue_detail(slot, 2, &["`bin`".to_owned()]);
        assert!(counted.contains("2 entries other than"), "{counted}");
        assert!(counted.contains("including `bin`"), "{counted}");
        assert_eq!(
            residue_detail(slot, 1, &[]),
            format!(
                "1 entry other than `{DEFAULT_WORK_FOLDER}` survived cleanup of {}",
                slot.display()
            )
        );

        // The race the second pass exists for: the listing saw nothing and the
        // filesystem answered otherwise. Saying "0 entries survived" here would
        // state the under-count as the fact and contradict the rest of the
        // sentence.
        let raced = residue_detail(slot, 0, &["`.credentials`".to_owned()]);
        assert!(!raced.contains('0'), "{raced}");
        assert!(raced.contains("reported nothing but"), "{raced}");
        assert!(raced.contains("`.credentials` survived cleanup"), "{raced}");
    }

    #[test]
    fn verification_asks_the_filesystem_rather_than_the_listing_that_missed_an_entry() {
        let root = tempfile::tempdir().unwrap();
        let slot = root.path().join("s1");
        fs::create_dir(&slot).unwrap();
        fs::create_dir(slot.join(DEFAULT_WORK_FOLDER)).unwrap();
        verify_slot_scrubbed(&slot).expect("only `_work` is a clean slot");

        // Runner binaries, registration identity, process identity and this
        // agent's lifecycle marks, one at a time, so a scrub that skipped
        // exactly one is still caught.
        for survivor in ["bin", ".credentials", IDENTITY_FILE, RUNNER_ID_FILE] {
            fs::write(slot.join(survivor), b"left behind").unwrap();
            let quarantine = verify_slot_scrubbed(&slot).unwrap_err();
            assert_eq!(quarantine.refusal, SlotRefusal::Residue);
            assert!(
                quarantine.detail.contains(&format!("`{survivor}`")),
                "{quarantine}"
            );
            fs::remove_file(slot.join(survivor)).unwrap();
        }

        // A handoff is named by its published prefix, never by the UUID that
        // follows it, and never by the payload it holds.
        let handoff = slot.join(format!("{}whatever.tmp", RestrictiveHandoff::NAME_PREFIX));
        fs::write(&handoff, JIT.as_bytes()).unwrap();
        let quarantine = verify_slot_scrubbed(&slot).unwrap_err();
        assert!(
            quarantine.detail.contains("an encoded JIT handoff"),
            "{quarantine}"
        );
        assert!(!quarantine.detail.contains(JIT), "{quarantine}");
        fs::remove_file(&handoff).unwrap();

        // A name a workflow chose is counted and never echoed: a slot root is
        // writable by the job, so a file named after a secret would be published
        // by any message that repeated the listing.
        fs::write(slot.join("ghp_DO_NOT_LEAK"), b"named by the job").unwrap();
        let quarantine = verify_slot_scrubbed(&slot).unwrap_err();
        assert!(
            quarantine.detail.contains("1 entry other than"),
            "{quarantine}"
        );
        assert!(
            !quarantine.detail.contains("ghp_DO_NOT_LEAK"),
            "{quarantine}"
        );
    }

    #[test]
    fn a_slot_is_derived_from_the_journal_and_refused_when_it_disagrees() {
        let root = tempfile::tempdir().unwrap();
        let configured =
            LocalAbsolutePath::new(root.path().to_str().unwrap()).expect("a local absolute root");
        let slot = configured.as_path().join("s1");
        fs::create_dir(&slot).unwrap();

        verify_journalled_slot(&slot, nz(1), Some(&configured))
            .expect("the journalled slot agrees");
        verify_journalled_slot(&slot, nz(1), None)
            .expect("and a policy that is gone removes a check, not the ability to clean");

        // The journalled slot number is what names the directory. `s1` recorded
        // as slot two is corrupt state, not a slot to clean.
        assert_eq!(
            verify_journalled_slot(&slot, nz(2), None)
                .unwrap_err()
                .refusal,
            SlotRefusal::NotTheJournalledSlot
        );
        for stray in ["s1/nested", "not-a-slot", "s01"] {
            let path = configured.as_path().join(stray);
            assert_eq!(
                verify_journalled_slot(&path, nz(1), None)
                    .unwrap_err()
                    .refusal,
                SlotRefusal::NotTheJournalledSlot,
                "{}",
                path.display()
            );
        }

        // A surviving policy that names a different root does not get to have
        // its disagreement resolved by deleting something.
        let elsewhere = tempfile::tempdir().unwrap();
        let other =
            LocalAbsolutePath::new(elsewhere.path().to_str().unwrap()).expect("a second root");
        assert_eq!(
            verify_journalled_slot(&slot, nz(1), Some(&other))
                .unwrap_err()
                .refusal,
            SlotRefusal::PolicyRootDisagrees
        );
    }

    #[cfg(unix)]
    #[test]
    fn a_substituted_work_directory_quarantines_the_slot_and_deletes_nothing_outside_it() {
        // Windows needs a privilege to create a junction or a symlink, so the
        // substitution is made here; the rule is platform-independent because it
        // is `symlink_metadata`'s answer plus the reparse attribute.
        let root = tempfile::tempdir().unwrap();
        let outside = root.path().join("operator-data");
        fs::create_dir(&outside).unwrap();
        let sentinel = outside.join("do-not-delete.txt");
        fs::write(
            &sentinel,
            b"an operator's data, outside every approved root",
        )
        .unwrap();

        let slot = root.path().join("s1");
        fs::create_dir(&slot).unwrap();
        fs::create_dir(slot.join("bin")).unwrap();
        std::os::unix::fs::symlink(&outside, slot.join(DEFAULT_WORK_FOLDER)).unwrap();

        let quarantine = scrub_slot_entries(&slot).unwrap_err();
        assert_eq!(quarantine.refusal, SlotRefusal::WorkNotADirectory);
        assert!(
            sentinel.exists(),
            "the deletion followed the link out of the slot"
        );
        assert!(outside.is_dir());
        assert!(
            slot.join(DEFAULT_WORK_FOLDER).symlink_metadata().is_ok(),
            "the substituted link is left for the operator, never unlinked as if it were ours"
        );

        // A `_work` that is a plain file is the same refusal for the same
        // reason: it is not a job workspace, and this is not the code that
        // decides what to do about it.
        let file_work = root.path().join("s2");
        fs::create_dir(&file_work).unwrap();
        fs::write(file_work.join(DEFAULT_WORK_FOLDER), b"not a directory").unwrap();
        assert_eq!(
            scrub_slot_entries(&file_work).unwrap_err().refusal,
            SlotRefusal::WorkNotADirectory
        );
    }

    #[cfg(unix)]
    #[test]
    fn a_slot_replaced_by_a_link_out_of_its_root_is_refused_before_anything_is_read() {
        let root = tempfile::tempdir().unwrap();
        let outside = root.path().join("operator-data");
        fs::create_dir(&outside).unwrap();
        let sentinel = outside.join("do-not-delete.txt");
        fs::write(
            &sentinel,
            b"an operator's data, outside every approved root",
        )
        .unwrap();

        // The lexical half of containment passes -- the name is right and the
        // parent is right -- and canonical resolution is what catches it.
        let inside = root.path().join("inside");
        fs::create_dir(&inside).unwrap();
        let slot = inside.join("s1");
        std::os::unix::fs::symlink(&outside, &slot).unwrap();

        assert_eq!(
            verify_journalled_slot(&slot, nz(1), None)
                .unwrap_err()
                .refusal,
            SlotRefusal::Containment
        );
        assert!(sentinel.exists());
        assert!(
            slot.symlink_metadata().is_ok(),
            "the link is left for the operator rather than removed as if it were ours"
        );
    }

    /// The Windows half of the case above.
    ///
    /// Containment was proven only on Unix, and a symbolic link is the wrong
    /// instrument to prove it with on Windows: creating one needs a privilege an
    /// ordinary workflow does not have, so it is not the substitution an
    /// attacker would reach for. A **junction** needs none, which makes it both
    /// the realistic attack and the one this repository must refuse -- and
    /// `04-security-recovery.md` names it in the same breath as the symlink for
    /// exactly that reason.
    #[cfg(windows)]
    #[test]
    fn a_slot_root_replaced_by_a_junction_is_refused_before_anything_is_read() {
        let root = tempfile::tempdir().unwrap();
        let outside = root.path().join("operator-data");
        fs::create_dir(&outside).unwrap();
        let sentinel = outside.join("do-not-delete.txt");
        fs::write(
            &sentinel,
            b"an operator's data, outside every approved root",
        )
        .unwrap();

        // The lexical half of containment passes -- `s1` under the root the
        // journal names -- and canonical resolution is what catches it.
        let inside = root.path().join("inside");
        fs::create_dir(&inside).unwrap();
        let slot = inside.join("s1");
        let Some(()) = plant_junction(&slot, &outside) else {
            eprintln!("skipped: this machine would not create a directory junction");
            return;
        };

        assert_eq!(
            verify_journalled_slot(&slot, nz(1), None)
                .unwrap_err()
                .refusal,
            SlotRefusal::Containment
        );
        assert!(
            sentinel.exists(),
            "the refusal resolved the junction and reached the operator's data"
        );
        assert!(
            slot.symlink_metadata().is_ok(),
            "the junction is left for the operator rather than removed as if it were ours"
        );
    }

    /// Plant a directory junction at `link` pointing at `target`.
    ///
    /// A junction is the Windows substitution this has to refuse, and unlike a
    /// symbolic link it needs no privilege — which is exactly why it is the one
    /// an unprivileged workflow would reach for. `mklink` is a `cmd` builtin, so
    /// there is no binary to find and nothing to install; `None` means this
    /// machine would not make one and the caller says so rather than asserting
    /// nothing.
    #[cfg(windows)]
    fn plant_junction(link: &Path, target: &Path) -> Option<()> {
        let made = std::process::Command::new("cmd")
            .arg("/C")
            .arg("mklink")
            .arg("/J")
            .arg(link)
            .arg(target)
            .output()
            .ok()?;
        (made.status.success() && link.symlink_metadata().is_ok()).then_some(())
    }

    /// The dependency caches live beside attempts, under `<runner root>/_cache`,
    /// and jobs link into them (pnpm hard-links from its store; a workflow may
    /// symlink or junction a cache into its workspace). Removing an ephemeral
    /// attempt must take the links and never what they point at.
    #[test]
    fn removing_an_attempt_never_reaches_into_the_dependency_caches_it_linked() {
        let root = tempfile::tempdir().unwrap();
        let cache = root.path().join("_cache").join("o").join("r").join("npm");
        fs::create_dir_all(&cache).unwrap();
        let cached = cache.join("package.tgz");
        fs::write(&cached, b"kept between jobs").unwrap();
        let attempt = root.path().join("0123456789abcdef");
        let work = attempt.join("_work").join("repo");
        fs::create_dir_all(&work).unwrap();
        fs::hard_link(&cached, work.join("hard-linked.tgz")).unwrap();
        #[cfg(unix)]
        std::os::unix::fs::symlink(&cache, work.join("linked-cache")).unwrap();
        #[cfg(windows)]
        if plant_junction(&work.join("linked-cache"), &cache).is_none() {
            eprintln!("this machine would not create a junction; the hard link is still checked");
        }

        remove_runtime_tree(&attempt).unwrap();
        assert!(!attempt.exists());
        assert_eq!(fs::read(&cached).unwrap(), b"kept between jobs");
    }

    #[cfg(windows)]
    #[test]
    fn a_work_directory_replaced_by_a_junction_fails_closed_and_deletes_nothing_beyond_it() {
        let root = tempfile::tempdir().unwrap();
        let outside = root.path().join("operator-data");
        fs::create_dir(&outside).unwrap();
        let sentinel = outside.join("do-not-delete.txt");
        fs::write(
            &sentinel,
            b"an operator's data, outside every approved root",
        )
        .unwrap();

        let slot = root.path().join("s1");
        fs::create_dir(&slot).unwrap();
        fs::create_dir(slot.join("bin")).unwrap();
        let Some(()) = plant_junction(&slot.join(DEFAULT_WORK_FOLDER), &outside) else {
            eprintln!("skipped: this machine would not create a directory junction");
            return;
        };

        // The reparse point is what `is_link_like` answers on, so a junction is
        // refused for the same reason a symbolic link is and neither is
        // descended into.
        let work = fs::symlink_metadata(slot.join(DEFAULT_WORK_FOLDER)).unwrap();
        assert!(is_link_like(&work), "a junction is a reparse point");
        let quarantine = scrub_slot_entries(&slot).unwrap_err();
        assert_eq!(quarantine.refusal, SlotRefusal::WorkNotADirectory);
        assert!(
            sentinel.exists(),
            "the deletion followed the junction out of the slot"
        );
        assert!(outside.is_dir());

        // A junction standing where an ordinary entry was is unlinked rather
        // than followed, so the removal still cannot reach through it.
        let elsewhere = root.path().join("s2");
        fs::create_dir(&elsewhere).unwrap();
        fs::create_dir(elsewhere.join(DEFAULT_WORK_FOLDER)).unwrap();
        if plant_junction(&elsewhere.join("externals"), &outside).is_some() {
            scrub_slot_entries(&elsewhere).expect("an ordinary entry is removed, junction or not");
            verify_slot_scrubbed(&elsewhere).expect("and the slot verifies");
            assert!(sentinel.exists(), "the junction was followed, not unlinked");
            assert_eq!(entries_of(&elsewhere), only_the_job_workspace());
        }
    }

    #[cfg(unix)]
    #[tokio::test]
    async fn a_substituted_work_directory_leaves_the_attempt_uncleaned_and_still_leased() {
        let harness = Harness::new(FakeGithubLifecycle::default(), Arc::new(PersistentDemand))
            .with_persistent_workspace(2);
        harness.ready().await;
        let first = harness.launch().await;
        let slot = harness.slot_path(1);
        harness.conclude(first.id);

        let outside = harness._root.path().join("operator-data");
        fs::create_dir_all(&outside).unwrap();
        let sentinel = outside.join("do-not-delete.txt");
        fs::write(&sentinel, b"outside every approved root").unwrap();
        std::os::unix::fs::symlink(&outside, slot.join(DEFAULT_WORK_FOLDER)).unwrap();

        harness
            .launcher
            .clean(first.id)
            .await
            .expect_err("a slot whose `_work` was substituted is quarantined");
        assert!(sentinel.exists());

        let held = harness.attempt(first.id);
        assert_eq!(held.state(), AttemptState::Failed);
        assert!(held.holds_slot_lease());

        // The quarantined slot is not silently chosen again.
        let second = harness.launch().await;
        assert_eq!(second.workspace(), AttemptWorkspace::persistent_slot(nz(2)));
    }

    #[test]
    fn a_slot_that_is_a_file_is_refused_and_a_slot_that_is_gone_is_not() {
        let root = tempfile::tempdir().unwrap();
        let occupied = root.path().join("s1");
        fs::write(&occupied, b"an operator's file").unwrap();
        // The journal check passes -- it is the right name under the right root
        // -- and the shape check is what refuses.
        verify_journalled_slot(&occupied, nz(1), None).expect("the path is the journalled slot");
        assert_eq!(
            slot_is_present(&occupied).unwrap_err().refusal,
            SlotRefusal::SlotNotADirectory
        );
        assert_eq!(fs::read_to_string(&occupied).unwrap(), "an operator's file");

        // A directory that is simply not there leaves nothing to remove and
        // nothing to prove absent, so it is not a refusal.
        assert!(!slot_is_present(&root.path().join("s2")).unwrap());
        let present = root.path().join("s3");
        fs::create_dir(&present).unwrap();
        assert!(slot_is_present(&present).unwrap());
    }

    #[test]
    fn cleanup_dispatches_on_the_journalled_kind_and_not_on_what_the_directory_holds() {
        let root = tempfile::tempdir().unwrap();

        // A disposable directory that happens to contain a `_work` still goes
        // whole: the workspace kind is immutable so that the shape of a
        // directory a workflow can write to cannot choose its own algorithm.
        let disposable = root.path().join("abcdef012345");
        fs::create_dir_all(disposable.join(DEFAULT_WORK_FOLDER).join("repo")).unwrap();
        let ephemeral = RunnerAttempt::allocate(
            AttemptId::new_random(),
            fixtures::POLICY_ID,
            &disposable,
            fixtures::created_at(),
        );
        remove_materialized_package(&ephemeral).unwrap();
        assert!(!disposable.exists());

        // And a slot keeps its `_work` with the same contents beneath it.
        let slot = root.path().join("s1");
        fs::create_dir_all(slot.join(DEFAULT_WORK_FOLDER).join("repo")).unwrap();
        fs::create_dir_all(slot.join("bin")).unwrap();
        let persistent = RunnerAttempt::allocate_in(
            AttemptId::new_random(),
            fixtures::POLICY_ID,
            &slot,
            AttemptWorkspace::persistent_slot(nz(1)),
            fixtures::created_at(),
        );
        remove_materialized_package(&persistent).unwrap();
        assert_eq!(entries_of(&slot), only_the_job_workspace());
        assert!(slot.join(DEFAULT_WORK_FOLDER).join("repo").is_dir());
    }

    #[test]
    fn every_slot_refusal_names_a_distinct_event_class_and_keeps_the_lease() {
        let refusals = [
            SlotRefusal::NotTheJournalledSlot,
            SlotRefusal::PolicyRootDisagrees,
            SlotRefusal::Containment,
            SlotRefusal::SlotNotADirectory,
            SlotRefusal::Enumeration,
            SlotRefusal::WorkNotADirectory,
            SlotRefusal::Deletion,
            SlotRefusal::Residue,
        ];
        let classes: BTreeSet<&str> = refusals.iter().map(|refusal| refusal.class()).collect();
        assert_eq!(
            classes.len(),
            refusals.len(),
            "an event class shared by two refusals tells an operator less than it appears to"
        );
        for refusal in refusals {
            // The event field is a closed vocabulary, so it has to look like
            // one: `d1`'s sink allows the name verbatim.
            assert!(
                refusal
                    .class()
                    .chars()
                    .all(|c| c.is_ascii_lowercase() || c == '_'),
                "{}",
                refusal.class()
            );
            assert!(
                refusal.remediation().contains("slot lease"),
                "every refusal has to say the lease is still held: {}",
                refusal.class()
            );
        }
    }

    #[test]
    fn copy_package_tree_copies_files_and_preserves_paths_with_spaces() {
        let root = tempfile::tempdir().unwrap();
        let source = root.path().join("source with spaces");
        let dest = root.path().join("dest with spaces");

        fs::create_dir_all(&source).unwrap();
        fs::write(source.join("file1.txt"), b"hello").unwrap();

        let nested = source.join("nested dir");
        fs::create_dir_all(&nested).unwrap();
        fs::write(nested.join("file2.txt"), b"world").unwrap();

        // This is not a top-level `_work`, so it should be allowed
        let nested_work = nested.join(DEFAULT_WORK_FOLDER);
        fs::create_dir_all(&nested_work).unwrap();
        fs::write(nested_work.join("allowed.txt"), b"allowed").unwrap();

        copy_package_tree(&source, &dest, &TrustedTrees::default()).unwrap();

        assert_eq!(fs::read_to_string(dest.join("file1.txt")).unwrap(), "hello");
        assert_eq!(
            fs::read_to_string(dest.join("nested dir").join("file2.txt")).unwrap(),
            "world"
        );
        assert_eq!(
            fs::read_to_string(
                dest.join("nested dir")
                    .join(DEFAULT_WORK_FOLDER)
                    .join("allowed.txt")
            )
            .unwrap(),
            "allowed"
        );
    }

    #[test]
    fn every_field_name_the_attempt_sink_emits_is_allowed() {
        use runner_manager_platform::logging::is_field_allowed;

        // Kept beside the sink rather than derived from it, as in `reconcile`.
        for field in [
            "event",
            "attempt_id",
            "reason",
            "retry_in_ms",
            "duration_ms",
            "order_wait_ms",
            "lock_wait_ms",
            "turn_wait_ms",
            "materialize_ms",
            "package_wait_ms",
            "package_install_ms",
            "package_verify_ms",
            "package_copy_ms",
            "package_downloaded",
            "prepare_ms",
            "register_ms",
            "spawn_ms",
        ] {
            assert!(
                is_field_allowed(field),
                "`{field}` would be logged as `[redacted]`"
            );
        }
    }

    #[cfg(unix)]
    fn package_entry(root: &Path, version: &str, manifest: &str) -> PathBuf {
        let entry = root.join("packages").join(version);
        fs::create_dir_all(entry.join("bin")).unwrap();
        fs::write(entry.join(crate::package::MANIFEST_FILE), manifest).unwrap();
        fs::write(entry.join("bin").join("Runner.Listener"), version).unwrap();
        entry
    }

    /// The seed's binary's inode: a rebuilt seed holds a new file.
    #[cfg(unix)]
    fn listener_inode(seed: &Path) -> u64 {
        use std::os::unix::fs::MetadataExt as _;
        fs::metadata(seed.join("bin").join("Runner.Listener"))
            .unwrap()
            .ino()
    }

    #[cfg(unix)]
    #[test]
    fn a_package_seed_is_built_once_and_reused_while_untouched() {
        let root = tempfile::tempdir().unwrap();
        let source = package_entry(root.path(), "2.336.0", "{\"digest\":\"a\"}");
        let seeds = root.path().join("runners").join(PACKAGE_SEED_DIR);
        let trusted = TrustedTrees::default();

        let seed = refresh_package_seed(&source, &seeds, &trusted).unwrap();
        assert_eq!(seed, seeds.join("2.336.0"));
        assert_eq!(
            fs::read_to_string(seed.join("bin").join("Runner.Listener")).unwrap(),
            "2.336.0"
        );

        let built = listener_inode(&seed);
        assert_eq!(
            refresh_package_seed(&source, &seeds, &trusted).unwrap(),
            seed
        );
        assert_eq!(listener_inode(&seed), built, "an untouched seed is reused");
    }

    #[cfg(unix)]
    #[test]
    fn a_tampered_or_unrecorded_seed_is_rebuilt() {
        let root = tempfile::tempdir().unwrap();
        let source = package_entry(root.path(), "2.336.0", "{\"digest\":\"a\"}");
        let seeds = root.path().join("runners").join(PACKAGE_SEED_DIR);
        let trusted = TrustedTrees::default();
        let seed = refresh_package_seed(&source, &seeds, &trusted).unwrap();

        // A job rewrites the binary in place and leaves the manifest alone.
        fs::write(seed.join("bin").join("Runner.Listener"), b"planted").unwrap();
        refresh_package_seed(&source, &seeds, &trusted).unwrap();
        assert_eq!(
            fs::read_to_string(seed.join("bin").join("Runner.Listener")).unwrap(),
            "2.336.0",
            "a seed whose print moved is rebuilt from the cache entry"
        );

        // A restarted daemon has no print of a seed it did not build.
        // Keep the old inode allocated until the replacement is complete;
        // otherwise the filesystem may immediately reuse its number.
        let old_listener = fs::File::open(seed.join("bin").join("Runner.Listener")).unwrap();
        let built = listener_inode(&seed);
        refresh_package_seed(&source, &seeds, &TrustedTrees::default()).unwrap();
        assert_ne!(
            listener_inode(&seed),
            built,
            "an unrecorded seed is rebuilt"
        );
        drop(old_listener);
    }

    #[cfg(unix)]
    #[test]
    fn a_package_seed_is_rebuilt_for_a_new_entry_and_drops_every_other() {
        let root = tempfile::tempdir().unwrap();
        let seeds = root.path().join("runners").join(PACKAGE_SEED_DIR);
        let trusted = TrustedTrees::default();
        let old = package_entry(root.path(), "2.335.0", "{\"digest\":\"old\"}");
        refresh_package_seed(&old, &seeds, &trusted).unwrap();
        fs::create_dir_all(seeds.join(".staging-interrupted")).unwrap();
        fs::write(seeds.join("stray"), b"").unwrap();

        let new = package_entry(root.path(), "2.336.0", "{\"digest\":\"new\"}");
        let seed = refresh_package_seed(&new, &seeds, &trusted).unwrap();

        let mut left: Vec<_> = fs::read_dir(&seeds)
            .unwrap()
            .map(|entry| entry.unwrap().file_name().into_string().unwrap())
            .collect();
        left.sort();
        assert_eq!(left, ["2.336.0"]);

        // A reinstalled entry of the same version has a different manifest.
        fs::write(
            new.join(crate::package::MANIFEST_FILE),
            "{\"digest\":\"again\"}",
        )
        .unwrap();
        refresh_package_seed(&new, &seeds, &trusted).unwrap();
        assert_eq!(
            fs::read_to_string(seed.join(crate::package::MANIFEST_FILE)).unwrap(),
            "{\"digest\":\"again\"}",
            "a stale seed is rebuilt from the changed entry"
        );
    }

    #[cfg(unix)]
    #[test]
    fn a_package_on_the_runtime_volume_is_its_own_seed() {
        let root = tempfile::tempdir().unwrap();
        let source = package_entry(root.path(), "2.336.0", "{}");
        let runtime = root.path().join("runners").join("attempt");
        fs::create_dir_all(&runtime).unwrap();

        let trusted = TrustedTrees::default();
        assert_eq!(package_seed(&source, &runtime, &trusted).unwrap(), source);
        copy_package_tree(&source, &runtime, &trusted).unwrap();
        assert!(runtime.join("bin").join("Runner.Listener").exists());
        assert!(!root.path().join("runners").join(PACKAGE_SEED_DIR).exists());
    }

    #[test]
    fn copy_package_tree_refuses_top_level_work_folder() {
        let root = tempfile::tempdir().unwrap();
        let source = root.path().join("source");
        let dest = root.path().join("dest");

        fs::create_dir_all(&source).unwrap();
        fs::write(source.join("file1.txt"), b"hello").unwrap();

        // Top-level `_work` should be refused
        let top_work = source.join(DEFAULT_WORK_FOLDER);
        fs::create_dir_all(&top_work).unwrap();

        let err = copy_package_tree(&source, &dest, &TrustedTrees::default()).unwrap_err();
        assert_eq!(err.kind(), std::io::ErrorKind::InvalidData);
    }
}